CIHM 
Microfiche 
Series 
(■Monographs) 


ICMH 

Collection  de 
microfiches 
(monographies) 


Canadian  Inttituta  for  Historical  Microraproductions  /  InstHut  Canadian  da  microraproductions  hiatoriquat 


Technical  and  Bibliographic  Notaa/Notas  tachniquaa  at  bibliographiquaa 


Tha  Instituta  haa  anamptad  to  obtain  tha  baat 
original  copy  availabia  for  filming.  Faaturaa  of  thia 
copy  which  may  ba  bibliographically  uniqua, 
which  may  altar  any  of  tha  imagaa  in  tha 
reproduction,  or  which  may  significantly  changa 
tha  usual  method  of  filming,  are  chocked  below. 


D 
D 
D 
□ 
D 


Coloured  covers/ 
Couverture  do  couleur 

Covers  damaged/ 
Couverture  endommagto 

Covers  restored  and/or  laminated/ 
Couverture  restaurie  at/ou  pellicula 

Cover  title  missing/ 

La  titra  da  couverture  manque 

Coloured  mapa/ 

Cartea  gAographiques  en  couleur 


0    Coloured  ink  (i.e.  other  then  blue  or  black)/ 
Encre  de  couleur  (i.e.  autre  que  bleue  ou  noirel 

rri    Coloured  platas  and/or  illuatrations/ 


D 


Planchea  at/ou  illuatrations  tn  couleur 

Bound  with  other  material/ 
Rali*  avec  d'autras  documents 


r~7]    Tifl'ft  binding  may  cause  shadows  or  distortion 


D 


along  interior  margin/ 

La  re  liure  serrAe  peut  causer  de  I'ombre  ou  de  la 

distorsion  la  long  da  la  marga  intirioura 

Blank  leaves  added  during  restoration  may 
appear  within  tha  text.  Whenever  possible,  these 
have  been  omitted  from  filming/ 
II  se  peut  que  certaines  pages  blanches  ajout*as 
lore  dune  restauration  apparaissant  dana  la  texte. 
mais,  lorsque  cela  Atait  possible,  ees  pages  n'ont 
pas  *t*  filmtes. 


L'Institut  a  microfilm*  la  mailleur  exemplaire 
qu'il  lui  a  At*  possible  de  se  procurer.  Las  details 
da  eat  exemplaire  qui  sont  paut-*tre  uniques  du 
point  de  vue  bibliographiqua.  qui  peuvent  modifier 
une  image  reproduite.  ou  qui  peuvent  axiger  una 
modification  dans  la  m*thoda  normala  de  fllmaga 
sent  indiquAs  ci-dessous. 


r~n   Coloured  pages/ 


Pagea  de  couleur 

Pagaa  damaged/ 
Pages  endommag*as 

Pages  restored  and/oi 

Pages  restaur*as  et/ou  pellicul*es 

Pages  discoloured,  stained  or  foxei 
Pages  d*color*es.  tachatAes  ou  piqu*os 

Pages  detaclied/ 
Pages  d*tacha*s 

Showthrough/ 
Transparence 

Quality  of  prin 

Qualit*  inAgala  de  {'impression 

Includes  supplementary  materii 
Comprend  du  matArial  suppl*mentaira 

Only  edition  available/ 
Seule  Edition  disponible 


rri  Pagaa  damaged/ 

I      I  Pages  restored  and/or  laminated/ 

rT\  Pages  discoloured,  stained  or  foxed/ 

rri  Pages  detaclied/ 

("71  Showthrough/ 

r~~|  Quality  of  print  varies/ 

r~j  Includes  supplementary  material/ 

r~|  Only  edition  available/ 


^ 


n 


r^    Additional  comments:/ 


Commentaires  supplAmantairas; 


Pagination  is 
La  pagination 


Pages  wholly  or  partially  obscured  by  arrata 
slips,  tissues,  ate.  have  been  rafilmad  to 
ensure  tha  bast  possible  image/ 
Lea  pagaa  totalamant  ou  partiellamant 
obscurcias  par  un  fauillet  d'crrata.  una  palura. 
etc..  ont  At*  film**s  *  nouveau  da  facon  * 
obtanir  la  meilleure  image  possible 


as  followa:    p.    [i)-xi,    996-2088. 
eat  conuna  suit:   p.    (ij-xi,    996-2088. 


This  item  is  filmed  at  tha  reduction  ratio  chocked  below/ 
Ca  document  est  film*  au  taux  da  r*duction  indiqu*  ei-dassous. 
10X  14X  1IX  22X 


2ex 


30X 


/ 


12X 


IfX 


aox 


24X 


ax 


32X 


Th«  copy  film«d  h«r«  hM  b««n  niproduc«d  thanks 
to  tho  gonoroslty  of: 

Academy  of  Medicine  Collection 
The  Toronto  Hospital 

Tho  imagoo  appoaring  horo  aro  tho  boat  quality 
possiblo  eonsidoring  tho  condition  and  lagibility 
of  tha  originai  copy  and  In  Icaoping  with  tho 
filming  contract  apadfieationa. 


Originai  copiaa  in  printad  popor  eovara  ara  fltmod 
baginning  with  tho  front  covor  and  anding  on 
tha  last  paga  with  a  printad  or  illuatratad  impraa- 
sion.  or  tho  bacit  covor  whon  appropriato.  All 
othor  original  coploa  ara  filmod  boginning  on  tho 
first  paga  with  a  printad  or  illuatratad  improa- 
sion.  and  anding  on  tho  laat  paga  with  a  printad 
or  illuatratad  impraasion. 


Tha  laat  racordod  frama  on  ooch  microfieho 
shaH  contain  tho  symbol  «^  (moaning  "CQN> 
TINUED").  or  tho  symbol  ▼  (moaning  "END"), 
whiehavor  appliaa. 

Mapa.  plataa.  charts,  ate.,  may  ba  Tlimad  at 
diffaront  reduction  ratios.  Thoso  too  larga  to  bo 
ontlraly  included  in  ono  axpoouro  ara  fNmad 
baginning  in  tha  uppar  laft  hand  eomor.  loft  to 
right  and  top  to  bottom,  as  many  framaa  aa 
raquirod.  Tha  following  diagrams  illustrata  ttia 
mathod: 


L'oxamplaira  film*  fut  raproduit  grica  i  la 
g*n4rosit4  do: 

Academy  of  Medicine  Collection 
The  Toronto  Hospital 

Las  imagos  suivantss  ont  *tt  raproduitas  avac  la 
plus  grand  soin.  compta  tanu  da  la  condition  at 
da  la  nattat*  da  I'axamplaira  film*,  at  an 
conformity  avac  las  conditions  du  contrat  da 
fUmaga. 

Laa  OKompiairoa  originaux  dont  la  couvartura  an 
papiar  ast  imprim4a  sont  filmte  un  comman9ant 
par  la  pramiar  plat  at  an  tarminant  soit  par  la 
darnlAra  paga  qui  eomporto  una  amprainta 
d'impraasion  ou  d'illustration.  soit  par  la  second 
plat,  salon  io  caa.  Toua  las  autras  exemplairas 
originaux  sont  fiimte  en  common^ ant  par  la 
premiere  page  qui  comporte  une  empreinte 
dimpreeaion  ou  dINuatration  at  an  tarminant  par 
la  darniire  page  qui  comporte  une  telle 
empreinte. 

Un  dee  symbolee  suivants  sppareltre  sur  le 
derniire  imege  do  cheque  microfiche,  selon  le 
ces:  le  symbole  — ^  signifie  "A  SUIVRE".  le 
symbole  ▼  eignifie  "FIN". 

Les  cortee.  plenchee.  tebleeux.  etc..  peuvent  Atre 
filmie  A  doe  teux  do  reduction  diff*rents. 
Lorsque  le  document  est  trop  grend  pour  *tre 
reproduit  en  un  soul  clich*.  it  est  film*  *  psrtir 
do  i'engie  supArieur  geuche.  do  gauche  i  droite. 
et  do  heut  en  bas.  en  prenent  le  nombre 
d'imegee  n^ceesoire.  Les  diagrammes  suivants 
illustrent  la  mtthode. 


12  3 


1 

2 

3 

4 

5 

6 

I J 


m 


mtm 


mmmmmmm 


Human  Anatomy 


/^n^' 


^mmiHmKmmmmmmm 


HUMAN  ANATOMY 

INCLUDING  STRUCTURE  AND  DEVELOPMENT 


AND 


PRACTICAL  CONSIDERATIONS 


BY 


THOMAS  DWIGHT.  M.D..  LL.D. 
PAttHAit  nopmoii    or    anatomy    in    iia«vabd 

UNIVEWTV 

CARL  A.  HAMANN,  M.D. 

novnaoi   ot   amatomv   m   wnrBUM    unuvs 
imivsasiTV 


J.  PLAYFAIR  McMURRICH.  PH.D. 

PKOPmnK  or  anatohv  in  the  UNIVnSITT  o 

MICHIGAN 

GEORGE  A.  PIERSOL,  M.D..  SC.D. 
norKuoii  or  anatomy  in  the  umvEEarrr    < 

PENNSYLVANIA 


J.  WILLIAM  WHITE,  M.D..  PH.D..  LL.D. 

•   EAETOH  PEOPEMOE  Or  SUEGBKY  IN  THE  UNIVBEIITT  Or  PEMMSVLVAMIA 


TH   SEVENTEEN   HUNDRED  AND  THIRTY-FOUR    ILLUSTRATIONS. 
OF  WHICH    FIFTEEN   HUNDRED  AND  TWENTY-TWO  ARE  ORIGINAL 
AND  LARGELY  FROM  DISSECTIONS  BY 

JOHN  C.  HEISLER.  M.D. 

P^OrEMOE  or  ANATOMY  IN  THE  MBOICO-CHIEUKOICAL  <  Ol  LEGE 


EDITED  BY 

GEORGE  A.  PIERSOL 


VOL.   II. 


PHILADELPHIA  &  LONDON  /      / 

J.  B.  LFPPINCOTT  COMPANY 


.Id  OS] 


€,'! 


wmmmm 


pnppMP«fi»«iiip 


Copyright,  1906,  by  J.  B.  Lippincott  Company. 
Copyright,  1907,  by  ].  B.  Lippincott  Company. 


Copyright,  1908,  by  ].  B.  Lippincott  Company. 


Entered  at  Stationers'  Hall,  London,  England. 


All  fiiffhts  RfSfrved^ 


IHeTMTTnD  AND  niNTID  IT  i.  ■.  IIWIMOTT  COWMV ,  rHILAHirHI*,  U.IA 


tjm-':^  • 


CONTENTS. 

VOL.   II. 


THE   NERVOIS   SYSTEM. 


General  Considerations 

The  Nervous  Tissues 

The  Ner\e-Cells 

The  Nerve-Fibres 

Neur(M;lia 

The  Nerve-Trunks 

The  Ganglia 

Development  of  th.-  Nervous  Tis.sues  . .  . 
Nerve-Terminations 

Motor  Endings 

Sensory  Endings 

The  Ckntral  Nervous  System. 

The  Spi.nai.  Cord 

Membranes 

Cord-Segments 

Form  of  the  Spinal  Cord 

Columns  of  the  Cord 

Gray  Matter 

Central  Canal 

Microscopical  Structure 

White  Matter 

Fibre  Tracts 

Blood- Vessels  of  Spinal  Cord 

Development  of  Spmal  Cord 

Practical  Considerations  :  Spina'    "oril.  . 

Malformations 

Injuries 

Localization  of  Lesions 

The  Brain 

General  Description 

General  Development 

Derivatives  from  the  Khombencephiilon 

The  Medulla  Oblongata 

Internal  Structure 

The  Pons  Varolii 

Internal  .Structure 

The  Cerebellum 

Lobes  and  Fissures 

Architecture 

Internal  Nuclei 

Cerebellar  Cortex 

Ceret)ellar  Peduncles 

The  Fourth  Ventricle 

Development     of    the    Hind-Brain 

Derivatives 

The  Medulla 

The  Pons 

The  Cerebellum 

The  Mesencephalon 

The  Cor|K>ra  Ouadrigemina 

The  Cerebral  Peduncles 

The  Sylvian  Aqueduct 

Internal  Structure  of  the  Mid-Brain 

The  Tegmentum 

The  Cnista .  .    . 

The  Median  Fillet 

The  Posterior  longitudinal  Fas- 
ciculus  


996 
997 
997 
1000 
1003 
1006 
1007 
IU09 
1014 
1014 
lojc 


IU2I 
IU22 
1024 
IU26 
1027 
1028 
1030 
1030 
1036 

J039 
1047 
1049 
I051 
105 1 
1052 
1053 
i'>55 
1056 
1058 
1063 
1063 
1068 
1077 
1078 
1082 
1084 
1088 
uxS8 
109U 

■09.? 
1096 

tloo 
I  lot    1 

>>o3  : 
1 103   ' 

"05   I 

1106  ■ 

1 107  I 

I  108      ; 
III2     ! 


III3 

III5 
III5 

III6 


The  Mesencephalon — Omtinued 

Development  of  Mi<l-Brain 1 117 

The  Fore-Brain 11 19 

The  Diencephalon 1 119 

The  Thalamus 1 1 19 

Structure 1 120 

Connections 1121 

The  Epithalamus 1 123 

The  Trigonum  Habemilu; 1 123 

The  Pineal  BtKly 1 124 

The  Posterior  Commissure.    ...   1125 

The  Metathalamus 11 26 

The  Hypothalamus 1 127 

The  Subthalamic  Region 11 27 

The  Corpora  Mammillaria 1128 

The  Pituitary  Body 1 1 29 

The  Third  Ventricle 1 131 

The  Telencephalon 1 132 

The  Cerebral  Hemispheres    1 133 

Cerebral   Lobes  and  Interlobar 

Fissures 1 135 

Lobes  of  the  Hemispheres 1 139 

P'rontal  Lobe 1 139 

Parietal  Lobe 1 143 

Occipital  Lobe 1 145 

Temporal  LoIh- 1 147 

Insula 1 149 

Limbic  Lobe  .  . .  , 1 150 

The  Khinencephalon 1151 

The  Olfactory  Lobe .    1 151 

Architecture  of  the  Hemispheres 1155 

The  Corpus  Callosum .  1155 

The  Fornix 1 158 

The  Septum  Lucidum 1 159 

The  Lateral  Ventricles 1 160 

Internal  Nuclei  of  the  Hemisphere   .....   1 169 

The  Caudate  Nucleus 1 169 

The  Lenticular  Nucleus 1 169 

The  Claustrum 1172 

The  Amygdaloid  Nucleus 1172 

The  Internal  Capsule 1 173 

Structure  of  the  Cerebral  Cortex 1 175 

The  Nerve-Cells  of  Cortex 1 176 

The  Nerve-Fibres  of  Cortex 1 179 

\'ariations  in  Cerebral  Cortex 1180 

White  Centre  of  the  Hemisphere 1182 

The  Association  Fibres 1 182 

The  Commissural  Fibres 1 184 

The  Projection  Fibres 1187 

Development  of  the  Derivatives  of  Fore- 
Brain  1 189 

The  Pallium riSg 

The  Sulci  and  Gyri 1 190 

Histogenesis  of  Cer>  !>ral  Corte-        .   1192 

the  Khinencephak.m 1 193 

The  Corpus  Striatum 1 193 

The  Diencephalon 1193 

The  Cerebral  Commissures 1 194 

Measurements  of  the  Brain 1 195 

V 


^1« 


CONTENTS. 


// 


rAns 

The  Membranes  of  the  Brain 1 197 

The  Dura  Mater 119**  ! 

The  I'ia  Mater "oa 

The  Arachnoid 1*03  ] 

The  Pacchionian  Bodies 1  Jos 

The  Blood-Vessels  of  the  Brain 1206 

Prainical  Considerations :  The  Brain  and 

Its  Membranes 1*07  | 

Congenital  Errors  of  Development  .  iao7  ; 

The  Meninges >«>8 

Cerebral  Hemorrhage 1*09  , 

Cerebral  l^ocalization 1210 

Cranio-Cerebral  Topography 1214 

The  Peripherai.  Nervous  Svstbsi. 

The  Cranial  Nerves lajo 

The  Olfactory  Nerve i  J»o 

The  Optic  Nerve 1223 

The  Oculomotor  Nerve 1225  , 

The  Trochlear  Nerve 1228 

The  Trigeminal  Nerve 1230 

The  Gasserian  Ganglion 1232 

The    Ophthalmic     Nerve    and 

Branches 1233 

The  Ciliar>-  Ganglion 1236 

The  Maxillary 'Ner\-e  and 

Branches 1237 

The  Spheno-Palatine  Gang- 
lion     124" 

The     Mandibular     Nerve    and 

Branches 1242 

The  Otic  Ganglion >246 

The  Submaxillary  Ganglion  1247 
Practical  Considerations:   The  Tri- 
geminal Nerve 1248 

The  Abducent  Nerve 1249 

The  Facial  Ner\e 1250 

Practical  Considerations 1254 

The  Auditory  Nerve '256 

The  Glosso-Pharyngeal  Nerve 1260 

The  Vagus  or  Pneumogastri''  Nerve  1265 

Practical  Considerations 1272 

The  Spinal  Accessory  Nerve 1274 

Practical  Considerations 1275 

The  Hypoglossal  Nerve 1275 

Practical  Considerations 1277 

The  Spinal  Nerves 127S 

The  Posterior  Primary  Divisions 1279 

The  Cervical  Nerves 1281 

The  Thoracic  Nerves 1282 

The  Lumbar  Nerves 1282 

The  Coccvgeal  Nerve 1284 

The  Anterior  Primary  Divisions  1284 

The  Cervical  Nerves 1285 

The  Cervical  Plexus  and  Branches 1286 

The  Phrenic  Nerve >290 

Practical  Considerations 1292 

The  Brachial  Plexus  and  Branches 1292 

The    External    Anterior    Thoracic 

Ntrve "97 

The  Mus<  ulo-Cutaneous  Ner\'e 1298 

The  Me<tian  Nerve 1298 


PACK 

The  Brachial  Plexi's  and  Branches— r»«//»riKrrf 

Practical  Coasiderations 1301 

The     Internal     Anterior    Thoracic 

Nerve 1303 

The     Lesser     Internal     CuUineoas 

Nerve >3o3 

The  Internal  Cutaneous  Nerve 1303 

The  Ulnar  Ner\e 1303 

Practical  Considerations 1306 

The  Subscapular  Nerves 1306 

The  Circumflex  Nerves 1307 

Practical  Considerations 1308 

The  Musculo-Spiral  Nerve 1308 

Practical  Considerationf 1314 

The  Thoracic  Nerves I3»4 

Practical  Considerations 1318 

The  Lumbar  Plexus  and  Branches 1319 

The  llio-Hypopastric  Ner\'e 1320 

The  Ilio-Inguinal  Nerve 1321 

The  (;enito-Crural  Nerve 1322 

The  pxtemal  Cutaneous  Nerve 1324 

The  Obturator  Nerve 1324 

The  Accessory  Obturator  Ner>e 1324 

Thf  Anterior  Crural  Nerve 1327 

Practical  Considerations :  Lumbar  Plexus  1330 

The  Sacral  Plexus  and  Branches 1331 

The  Great  Sciatic  Nerve i335 

The  External  Popliteal  Nerve 1336 

The  Anterior  Tibial  Nerve 1336 

The  Musculo-Cutaneous 1338 

The  Internal  Popliteal  Nerve 1339 

The  Posterior  Tibial  Nerve 1342 

The  Pudendal  Pleyusand  Branches 1345 

The  Smai  Sc'    ic  Nerve 1348 

The  Pudi<    Ntn.; 1349 

The  Coc  ygeal  plexus 1352 

Practical  Considerations:  Sacral  Plexus  1352 

The  Svmpathetic  Nerves 1353 

General  Constitution  and  Arrange- 
ment    »355 

The  Gangliated  Cord 1356 

Rami  Communicantes 135* 

Cer\iro-Cephalic  Portion  of  Gangliated 

Cord 1358 

The  Superior  Cervical  Ganglion 1359 

The  Middle  Cervical  Ganglion 1362 

The  Inferior  Cervical  Ganglion 1362 

Thoracic  Portion  of  Gangliated  Cord 1364 

The  Splanchnic  Nerves 13*4 

Lumbar  Portion  of  Gangliated  Cord 1366 

Sacral  Portion  of  Gangliated  Cord 1367 

The  Plexuses  of  the  Sympathetic  Nerves  1367 

The  Cardiac  Plexus 1367 

The  Solar  Plexus 1368 

Subsidiary  Plexuses 13*9 

The  Hypogastric  Plexus 1374 

Subsidiary  Plexuses 1374 

Practical  Considerations:   The    Sympa- 
thetic Nerves 1375 

Development  of  the  Peripheral  Nerves. .  1375 


THE  ORGA         OF   SENSE. 


The  Skin. 

General  Description I38« 

Structure >3»» 

The  Hairs '389 

•-itnictHrf '39' 


The  Nails 1394 

The  Cutaneous  Glands I397 

The  Sebaceous  Glands i397 

The  Sweat  Glands 1398 

Development  of  the  Skin  and  its  Append- 
ages    1400 


CONTENTS. 


ve 


PAGII 

The  Nose. 

The  Outer  Ncsf 140 

Cartilazes  o(  the  Nose I4r 

Practical  Considerations :   The  ExN  mal 

Nose ,07 

The  Nasal  Fossie 1409 

The  Vestibule 1409 

The  Septiin 14 10 

The  Lateral  Wall. 1410 

The  Nasal  Mucous  Membrane 1413 

The  Olfactory  Region 1413 

The  Respiratory  Region 1415 

Jacobson's  Organ 1417 

Practical   Considerations :     The    Nasal 

Cavities 1417 

The  Accessory  Air- Spaces 1421 

The  Maxillary  Sinus 142: 

The  Frontal  Sinus 1423 

The  Ethmoidal  Air-Cells 1424 

The  Sphenoidal  Sinus 1425 

Practical  Considerations :  The  Accessory 

Air-Spaces 1426 

Development  of  the  Nose 1429 

The  Okoan  op  Taste 

The  Taste-Buds 1433 

Structure 1434 

Development 1436 

The  Eve. 

The  Orbit  and  its  Fasc  _  1436 

Practical  Considerations 1438 

The  Eyelids  and  Conjunctiva 144 1 

Practical  Considerations 1446 

The  Eyeball 1447 

Practical  Considerations 1448 

The  Fibrous  Tunic 1449 

The  Sclera 1449 

The  Cornea 1450 

Practical  Considerations 1453 

The  Vascular  Tunic 1454 

The  Choroid 1455 

The  Ciliary  Body 1457 

Practical  Considerations 1459 

The  Iris 1459 

Practical  Consideratioas 146 1 

The  Nervous  Tunic 1462 


The  Nervous  Tunic— £0«A««/-(/ 

Tlie  Retina 1462 

Practical  Consideratlbiis 1468 

The  Optic  Ner\e 1469 

Practical  Considerations 1470 

The  Cr)-stalline  Lens 1471 

Practical  Considerntion'^    1473 

The  Vitreous  Body 1473 

Practical  Consideration^ 1474 

The  Suspensory  Apparatus  of  the  Leii«.  .  '475 

The  Aqueous  Humor  and  its  Chamlwr. .  1476 

Practical  Considerations 1476 

The  I^chr>'mal  Apparatus 1477 

The  Ijichr\mal  Ctland 1477 

The  lachrymal  Pass-iges 1478 

Practical  Considerations 1479 

Development  of  the  Eye 1480 

The  Ear. 

The  F     'mal  Eiir 1484 

Tht      'ricle 1484 

The  External  Audito,        mal 148; 

Practical  Co^isideratic        1490 

The  Middle  Ear   149a 

The  T'.  nin  iiiic  C.;vity 1492 

The  M;>.iibr:'.na  Tympani 1494 

The  A.:  't^ry  Ossicles 1496 

The  Mu'  ).i~  Moiiibrane 1500 

'  ie  Eustachir.  Tube 1501 

;  ne  Ma.stoid  Cells 1504 

Pract.  Consid. :    The  Middle  Ear 1504 

The  TympiHiic  Cavity 1504 

The  Tympanic  Membrane 1505 

The  Eustachian  Tube 1507 

The  Ma.stoid  Process  and  Cells 1508 

The  Internal  Ear 1510 

The  Os-seous  Labyrinth 1311 

The  Vestibule 1511 

The  Semicircular  Canals 15 12 

The  Cochlea 1513 

The  Membranous  Ijibyxinth 1514 

The  Utricle 1514 

The  Saccule 1515 

The  Semicircular  Canals 1515 

The  Cochlear  Duct 1517 

The  Nerve   of  the  Cochlea 1521 

Developni.;nt  of  the  Ear 1523 


THE  GASTRO-PULMONARY   SYSTEM. 


General  Considerations 1527 

Mucous  Membranes 1528 

Structure 1528 

Glands 1531 

T\-pes  of  Glands 1531 

Simple  Tubular  Glands 1532 

Compound  Tubular  Glands  ....  1532 

Tubo-Alveolar  Glands 153a 

Serous  Glands 1534 

Mucous  Glands 1534 

Simple  Alveolar 1535 

Compound  Alveolar  Glands.  . .  .  1535 

Development  of  Glands 1537 

The  Alimentary  Canal. 

The  Mouth 1538 

The  Lips,  Cheeks  and  Vestibule 1538 

The  Teeth 1542 

Description  of  Individual  Forms.  . . .  1543 

Structure  of  the  Teeth 1548 

The  Enamel 1548 

The  Dentine 1550 


The  Teeth— CofUinueJ 

The  Cementum 1552 

The  Alveolar  Periosteum 1553 

Implantation  and  Relations  of   the 

Teeth 1554 

Development  of  the  Teeth 1556 

First  and  Second  Dentition 1564 

The  Gums 1567 

The  Palate .'  .  1567 

The  Hard  Palate 1567 

The  Soft  Pali     1568 

The  Tongue    1573 

General  Description 1573 

The  Glands  of  the  Tongue 1575 

The  Muscles  of  the  Tongue 1.^77 

The  Sublingual  Space 1581 

The  Salivary  Glands '.  1582 

The  Parotid  Gland 1582 

The  Submaxillary  Gland 1583 

The  Sublingual  Gland 1585 

Structure  of  the  Salivary  Glands. ...  1585 

Development  of  the  Oral  Glands.  ...  1589 


"PMNM 


*«Milii 


VIH 


CONTENTS. 


// 


Practical  Considerations :  The  Month  . .  .  1589 
Malformations:    Harelip   and   Cleft 

Palate' 1589 

The  Lips 159° 

The  Gums 159° 

The  Teeth 1591 

The  Roof  of  the  Mouth 1593 

The  Floor  of  the  Mouth 1593 

TheCHeeks i594 

The  Tongue i594 

The  Pharynx 1596 

The  Naso-Pharynx 1598 

The  Oro-Pharynx 1598 

The  Laryngo-Pharynx 1598 

The  Lymphoid  Structures 1599 

The  Faucial  Tonsils 1600 

The  Pharyngeal  Tonsil 1601 

Relations  of  the  Pharynx 1601 

Development  and  Growth  of  Pharynx  1603 

Muscles  of  the  Pharynx 1604 

Practical  Considerations :  The  Pharynx . .  1606 

The  CEsophagus 1609 

General  Description 1609 

Course  and  Relations 1609  ^ 

Structure 1611   1 

Practical  Considerations :  C£sophagus  .  .  1613  j 

Congenital  Malformations 1613  ' 

Foreign  Bodies 1613  < 

Strictures 1614  ; 

Carcinoma 1614 

Extrinsic  Disease 1614 

Diverticula 1614 

The  Abdominal  Cavity 1615 

The  Stomach 1617 

General  Description 1617 

Peritoneal  Relations 1619 

Position  and  Relations 1619  ; 

Structure 1621 

Growth 1629 

Variations  1629 

Practical  Considerations :  The  Stomach  1619 

Congenital  Malformations 1629 

Injuries  of  the  Stomach 1630 

Ulcers  and  Cancer 1631 

Dilatation  and  Displacement 1631 

Operations  on  the  Stomach 1632 

The  Small  Intestine 1633 

General  Description 1633 

Structure 1634 

The  Duodenum 1644 

Ouodeno-Jejunal  Fossa; 1647 

Interior  of  the  Duodenum 1648 

The  lejuno-Ileum 1649 

The  Slesentery  and  Topography  ....   1650 

Meckel's  Diverticulum 165a 

Practical  Considerations:  The  Small  In- 
testine    1652 

The  Peritoneal  Coat 1652 

The  Muscular  Coat 1653 

The  Mucous  and  Submucous  CohIs  1653 

Ulcers  of  the  Duodenum 1653 

Infection 1654 

Typhoid  Ulcers 1654 

Contusion  and  Rupture 1654 

Obstruction ifjj 

Operations 1656 

The  Large  Intestine 1657 

General  Description 1657 

Structure 1657 

The  Ca.H-um i66o 

The  Vermiform  Appendix 1664 

Peritoneal  Relations !66.s 

Pericaecal  Fosss 1666 


PAGB 

The  Large  Intestine— r<w»/i»«««rf 

Retro-Colic  Fossk 1667 

The  Colon 1668 

General  Description 1668 

Peritoneal  Relations 1670 

The  Sigmoid  Flexure 1671 

Uevelopment  and  Growth 1671 

The  Rectum 1672 

The  Anal  Canal 1673 

The  Anus 1673 

Muscles  and  Fasciae  of  Rectum  and 

Anus 1675 

The  Ischio-Rectal  Fossa 1678 

Pract.  Consid. :    The  Large  Intestine  . . .  1680 

The  Caecum 1680 

The  Vermiform  Appendix 1681 

Etiology  of  Appendicitis 1681 

Anatomical  Pomts  relating  to  the 
Symptoms  and  to  the  Treat- 
ment of  Appendicitis 1683 

Operations  for  Appendicitis  ....  168c 
The  Colon  and  Sigmoid  Flexure.  . .  .  1685 

Distention  and  Rupture 1686 

Displacements 1686 

Obstruction  and  Stricture 1687 

Wounds 168.S 

Operations 1688 

The  Rectum  and  Anal  Canal 1689 

Development  of  the  Alimentary  Canal  .  .  1694 

Formation  of  the  Mouth 1694 

Formation  of  the  Anus 1695 

Differentiation  of  the  Body-Cavity  . .  1700 
Development  of  the  Peritoneum. ...  1702 

The  Liver 1705 

General  Description 1705 

Borders  and  Surfaces 1707 

Blood- Vessels 1709 

Structure 171* 

The  Hepatic  Duct i7'8 

The  Gall-Bladder 1719 

The  Common  Bile-Duct 1720 

Peritoneal  Relations  of  the  Liver  .  . .   1721 

Position  of  the  Liver 1722 

Development  and  Growth 1723 

Practic.il   Considerations :    The    Biliary 

Apparatus 1726 

,  Anomalies  in  Form  and  Position  of 

the  Liver 1726 

Hepatoptosis  and  Hepatopexy 1726 

!  Obstruction  of  Hepatic  Circulation.  .  1727 

Wounds  and  Hepatic  Abscess 1727 

i  Malformations  of  Gall-Bladder 17*9 

Wounds  and  Rupture 1729 

Distention  and  Cholecystitis 1729 

TheCystic  and  Common  Bile-Ducts.   1731 
Operations  on  Gall-Bladder  and  Bili- 
ary Ducts ijii 

The  Pancreas 173* 

General  Description 1732 

Structure i734 

Pancreatic  Ducts 1736 

Development 1737 

Practical  Considerations  :  The  Pancreas.   1738 

Malformations 1 738 

Injuries 1738 

Pancreatitis 1739 

The  Peritoneum J740 

General  Considerations 1740 

The  Anterior  Parietal  Peritoneum  .  .  1742 

j  The  Anterior  Mesentery 1744 

!  The  Posterior  Mesentery :  Part  I  .  . .   1746 

!  The  Posterior  Mesentery  :  Part  II         1751 

j  The  Posterior  Mesentery  :  Part  111.  .  1753 


CONTENTS. 


IX 


Practical    Considerations :    The   Perito- 
neum    1754 

Anatomical  Routes  for  Infections. . .   1754 
Peritonitis  anatomically  considered . .  1 756 

Abdominal  Hernia 1759 

General  Considerations 1759 

Predisposing  anatomical  conditions.   1759 

Inguinal  Hernia 1763 

Anatomy  of  Inguinal  Canal 1763 

Anatomy   of   Indirect    Inguinal 

Hernia 1766 

Varieties  of  Inj^inal  Hernia. ..  .  1767 
Anatomy  of  Direct  Inguinal  Her- 
nia    1770 

Anatomical    Considerations    of 

Treatment 1770 

Femoral  Hernia 1773 

Anatomy  of  Femoral  Canal. . . .  1773 
Anatomical    Considerations 

Treatment 1774 

Umbilical  Hernia 1775 

Ventral  Hernia 1776 

Lumbar  Heniia 1777 

Obturator  Hernia 1777 

Sciatic  Hemiae 1778 

Perineal  Hemix 1778 

Diaphragmatic  Hernia'  1778 

Intraabdominal  Hernia- 1779 

AccEssoRv  Organs  of  Nutrition. 

The  Spleen 1781  i 

General  Description 1781  1 

Structure '..'...  1783 

Peritoneal  Relatiuns ..'..'.  1785 

Development  and  Growth 1787 

Accessory  Spleens 1787 

Practical  Considerations:  The  Splec-ii.  .    .  1787 

The  Thyroid  Body 1789 

General  Description 1789  '• 

Structure '  179,  ! 

Development 1793  I 

Accessory  Thyroids 1793  ' 

Practical  Considerations  :    The  Thyroid 

Body 1794 

The  Parathyroid  Bodies 1795 

General  Description 1795 

Structure ;;;  ,795 

The  Thymus lygg 

General  Description 1796 

Structure "  '  ,798 


The  Thymus— CoH/tNHi-d 

Development  and  Changes 1800 

The  .Suprarenal  Bodies 1801 

General  Description ]  1801 

J  Structure '  iSoj 

Development  and  Growth   .......   .  1804 

Accessory  Suprarenals 1805 

Practical  Con.siderations:  The  Suprarenai 

Bodies ,806 

The  Anterior  Lobe  of  the  Pituitary  Body.  1807 

Development 1808 

The  Carotid  Bodv 1809 

The  Coccygeal  Bodv 1811 

The  Aortic  Bodies  .' 1812 

The  Orc;.\ns  ok  Kesi'ikation. 

The  Larynx ix, j 

Cartilages,  Joints  and  Ligaments.  . .  '.  1813 
Form  of  Larynx  and  Mucous  Mem- 
brane       ,818 

Muscles  of  the  Larynx 1825 

Changes  with  Age  and  Sex. ...... .   1828 

Practical  Considerations  :  The  Larynx..   1828 

The   Mediastinal   Space 1832 

Practical  Considerations  i8t» 

The  Trachea '.'.'.'.'..'.  1834 

General  I)escripti(iii '   1835 

Structure '    1835 

Relations '    ;'  '  ,836 

Growth  and  Subsei|uent  Changes  18^7 
Bifurcation  of    Trachea    and    Roots 

_.       "'Lungs ,837 

The  Bronchi 1838 

Practical  Considerations :    The  Air-Piis- 

_,      ,     «»K'^s 1840 

The  Lungs ,^j 

General  Description 1843 

Lobes  and  Fissures 1845 

Physical  Characteristics ..'.  1846 

The  Bronchial  Tree 1847 

The  Lung  Lobule 1849 

Structure 1851 

Blood-Vessels ]    '  1853 

Relations  to  Thoracic  Walls.  .  1855 

The  Pleur.-e 1858 

General  Description .,[  1858 

Relations  to  the  Surface 1859 

Structure '  i860 

Development  of  the  Respiratory  Tract  1861 
Practical  Considerations  :  The  Lungs  and 

PleiTie 1864 


THE  URO-GENITAL   .SYSTEM. 


The  Urinary  Organs. 
The  Kidneys 

General  Description 

Position  and  Fixation 

Relations  

Architecture 

Stnicture ..!!!!!!] 

Practical  Considerations:  The  kidneys  . . 

Anomalies  of  Form,  Size  or  Num- 
ber   

Anomalies  of  Position 

Renal  Calculus 

Injuries  and  Tumors ....'..'. 

Operations 

The  Renal  Ducts 

Pelvis  of  the  Kidney 

The  Ureter  , 

Structure 


1869 
1869 
1870 
1873 
«87S 
1877 
1887 

1887 
1887 
1890 
1893 
•893 
1894 
1894 

\^ 


Practical  Considerations:  The  Ureters  .  .   1898 

Congenital  Anomalies 1898 

Ureteral  Calculus .'.'.'  1899 

Wounds '....'.  1900 

Operations ,~„ 

The  Bladder '..'.'.'.'.'.'.'.'.'."  1901 

General  I  )escription [  igoi 

Peritt)neal  Relations 1904 

Fixation  and  Relations '  1905 

.Structure 1908 

Practical  Considerations:  The  Bladder  \   1910 

Congenital  Anomalies 1910 

F^ffects  of  Distention 191 1 

Retention  of  Urine ..  .  1912 

■  Rupture  and  Wounds 1913 

Cjrstitis  and  Vesical  Calculus 1914 

""   ~  i9«5 


The  Male  Perinei---- 


The  Triangles ,9,6 


■^ 


■■•"^.f  iwiii  I  iiii.niu!J!W|iiiHpiisiq|ippt 


CONTENTS. 


Pract.  Consid  :  The  Bladder- GwrtiWrf  '"" 

The  Penneal  Interspaces iq,6 

Landmarks ,2i« 

lateral  Lilhotomy . .         J' „ 

Median  Lithotomy     J'!? 

Suprapubic  Lithotomy  ;:.':: 11" 

The  Female  Bladder*. . .       J|" 

The  Urethra  ...  J'*' 

The  Prostatic  Portion '.'.'.'..'. J'?' 

The  Membranous  Portion  ....■..■"     ig„ 

The  Spongy  Portion "  ,^j^ 

The  Female  Urethra..  ,12 

Stnicture [^ 

Practical  Considerations:  MaleUreihri' '  iIjt 

Congenita   Abnonnalities '*Z 

Chnical  Division  of  Urethra              '  ,^8 
Rupture  of  Urethra...        2!^ 


Anatomical   Conk?deration '  of  •(;,«:  ''^° 
tnntis  ... 

Stricture  of  Urethra'.  V. '. J'f? 

Urethral  Instrumentation ..'. ,o« 

The  Bladder  and  Urethra    ......     .'  jgjg 

The  Male  Reprodictivk  Organs. 

The  Testes 

General  D^i^ription  .' . .' ,'** J 

Architecture  .  J94i 

Stnicture J94» 

Spermatogenesis  . . .' .^ 

The  EpidTSp.^rr"''"  ••••■•■■ -j^ 

General  Description  .■..■.::; J'JJ  | 

Structure  '9*'   ' 

The  AppendaKe's;  of  the  Testicle  .  i .' \^l 

The  AppendLx  Testis '       i2;2 

The  Appendix  Epididymidis. '.'.'..,"  ,Zl 
The  Paradidymis  .  ,  J*^ 

TheVasaA^errantia;;: \t^ 

ITactical   Considerations:     The   Tm  " 
tides  .  . 

Congenital  Aiiomal'ies. .  ] .' ]l^ 

Orchitis '95° 

Epididymo-Orchit'is.' l^l 

Castration  ...  J'?* 

^^   Hydrocele ]: HI' 

The  Sprmat'    Ducts  . .       tj^X 

TheVas  IMerens f^M 

The  Ejaculatory  Duct.     ,''; 

Th.lL""i*"';^?^  Spennatic  Duci.  . . . .'  HH 

The  Seminal  Vesicles  f  ~? 

General  Description'.  , '. '. J"? 

Structure  '95° 

Practical  ConsideraHonsV  The' Seminal  ''' 
„.  Vesicles ... 

The  Spermatic  Cord  .      l^ 

Practical  Considerations:  the  Spermatic    ^ 

The  Scrotum^.'.' '96' 

General  Description,    l^l 

Coverings  of  the  Testicle ,S; 

The  Penis  "''""'•  ^he  Scrotum  .  I^ 

General  iiescription'  '.'.'. |9*5 

The  Corpora  Cavernosa .  .  jSg 

The  Corpus  Spongiosum ,^ 

The(.lans  Penis  ..  l^ 

Structure  ..  '9M 

Practical  Considerations': '  The  Penis.  .    [  ,2^ 


Pract.  Consid.:  Jhe  Penis-aw»/iV.«rrf 

Circumcision ' 

Contusions  and  Wounds  .llj 

Amputation '974 

The  Prostate  Gland      '975 

General  Description  .' ' , '^f 

Position  and  Relations  ,      io7fi 

Structure '    97o 

Development.  '.'. '977 

'ReS^^'i^    The  Prostate  (iiand.  ,  ,'^^ 
InjiriS         ^'^"'^""v«  System  ....  i|f| 

Hypertrophy::::::::::::: J2S 

Operations  .  '9«> 

Thedl-ndsofCowper f^f? 

General  Description: If^ 


Strllrture^r^'""'"" '984 

Development ::::::::::'  J^ 

i         The  Female  REPRODtcrivE  Organs. 

'  The  Ovaries „ 

General  Description:::': \^l 

Position  and  Fixation ...    J^ 

Structure  '9* 

Follicles  and  Ova: ,'^2 

The  Human  Ovum  . : ,^ 

Corpus  Luteum l^ 

Development.  99° 

Variations  '993 

i  The  Fallopian  Tubes  "vanes.  .  1995 

General  Description  ; : J'S 

Course  and  Relations. ,3 

Structure '997 

Development 'and  Changes. JS^ 

Variations..  '999 

Practical  Conaderations :'  the  Faliopjan  '^ 

Rudimentary"  ojaas': ;:  ^999 

The  Epoophoron !~° 

Gartner's  Duct  ^°" 

The  Paroophoron: : ???' 

Thete'"^'''""'''^^'-'-----'--''-'^^^ 

Generai  biesinption . : : : !^f 

Attachments   and   Peritoneal" Rela-       ' 
tions «.^ 

The  Round  Ligament ....  jnol 

Position  and  Relations.  . .     ^ 

Structure. .  ""z 

Development  'andChan^." : : ; ^ 

PracticT  r  «l'i»n-'l!llP''^^cy  •     ' ' ' 


Considerations : 


't"'"'"e™ions :     Utenis   and 
Attachments  . . . 


30I2 


Congenital  Abnormalities 


1 97  J 


Compartments  of  Pelvii: : ^J? 

frfrdTi^aenr'-'''--- •■  i 

Thel^ali^^''^'-----^-^-..-^ 

Gej^«.De;.ription';::::::::::::::-;| 

Structure  *°'^ 

Development: *"7 

Variations.  *'"' 

Practicil  .Considerations:   the  Vagina     Mm 
Rela^mnstoUterineCervix™;^,'! 

The  Labia  a/id'  ihe'Vwtibul'e : : : ^^ 

The  Labia  Ma  ora  .. .         ??" 

The  Mons  Pubis       "" 

The  Labia  Minora': !??! 

The  VMttbHle  *°" 

Joaj 


CONTENTS. 


The  Clitoris joa4 

The  Bulbus  Vestibuli aoas 

The  Glands  of  Bartholin 2026 

Pract  Consid.:  The  External  Genitals  .  .  J027 

The  Mammary  Glands J027 

General  Description 2027 

Structure 2029 

Milk  and  Colostrum 2030 

Development 2032 

Variadons  2033 

Practical  Considerations :  The  Mammary 

Glands 2033 

The  Nipple J033 

Paths  of  Infection. 2034 

Carcinoma 2035  | 


Practical  Considerations  :  The  Mammary 
Glands —  ContiHued 

Removal  of  the  Breast 2036 

Development  of  Reproductive  Organs.    .  2037 

General  Consiclerations 2037 

The  Indifferent  Stage 2o3« 

Differentiation  of  the  Male  Type.  2038 

Descent  of  the  Testis 2040 

Differentiation  of  the  Female  Type  2042 

Descent  of  the  Ovary 2041 

The  External  Organs 2043 

In  the  Female 2044 

In  the  Male WW,  joJJ 

Summary  of  Development 2045 

The  Female  Perineum ]  2046 


/,/ 


4' 


VOLUME  II. 


THE  CENTRAL  NERVOUS  SYSTEM 

THE  NERVOUS  TISSUES  THE  SPINAL  CORD  THE  BRAI!* 

THE   PERIPHERAL   NERVOUS  SYSTEM  ' 

THE  CRANIAL.  SPINAL  AND  SYMPATHETIC  NERVES 

THE  ORGANS  OF  SENSE 
THE  GASTRO-PULMONARY  SYSTEM 

THE  ALWENTARy  CANAL  AND  ITS  GLANDS 

THE  ACCESSORY  ORGANS  OF  NUTRITION  OR  THE  DUCTLESS  GLANDS 

THE  RESPIRATORY  ORGANS 

THE  URO-GENITAL  SYSTEM 


// 


■; 


-m; 


Fro.  834. 


THE  NERVOUS  SYSTEM. 

The  nervous  system — the  complex  apparatus  by  which  the  organism  is  brought 
into  relation  with  its  surroundings  and  by  which  its  various  p4rts  are  united  into  one 
coordinated  whole — consists  essentially  of  structural  units,  the  neurones,  held  together 
by  a  special  sustentacular  tissue,  the  neuroglia,  assisted  by  ingrowths  of  connective 
tissue  from  the  investing  membrane,  the  p<a  mater. 

The  neurone,  the  morphological  unit  of  the  nervous  system,  includes  a 
nucleated  protoplasmic  accumulation,  the  cell-body,  and  the  processes.  The  former, 
usually  spoken  of  as  the  nerve-cell,  presides  over  the  nutrition  of  the  neurone  and  is 
the  seat  of  the  subtle  changes  giving  rise  to  nervous  impulse.  The  processes  arise 
as  outgrowths  from  the  cell-body  and  provide  the  paths  along  which  impulses  are 
conveyed.  They  are  very  variable  in  length,  some  extending  only  a  fraction  of  a 
millimeter  beyond  the  cell-body,  while  others  continue  for  many  centimeters  to 
distant  parts  of  the  body.  The  longer  processes,  which  usually  acquire  protecting 
sheaths,  are  known  as  the  nerve-fibres,  and  these,  associated  in  bimdles,  constitute 
the  nerve-trunks  that  pass  to  the  muscles  and  various  other  organs. 

Reduced  to  its  simplest  terms,  the  nervous  system  consists  of  the  two  parts  rep- 
resented in  the  accompanying  diagram  (Fig.  834).     The  one,  the  sensory  neurone, 

{A)  takes  up  the  stimulus  received  u[>on  the 
integument  or  other  sensory  surface  and,  by  means 
of  its  procec  (nerve-fibre),  conveys  such  impulse 
from  the  periphe./  towards  the  central  aggregations 
of  nerve-cells  that  commonly  lie  in  the  vicinity  of  the 
body-axis.  Functionally,  such  a  path  constitutes  a 
centripetal  Qfc  ajferent  fibre  (a).  The  impressions 
thus  carried  are  transferred  to  the  second  element, 
the  motor  neurone  {B),  which  in  response  sends 
out  the  impulse  originating  within  the  cell-body 
(nerve-cell)  along  the  process  known  as  the  centri- 
fugal or  efferent  fibre  {e),  to  the  muscle-cell 
and  causes  contraction.  The  simple  relations  of 
the  foregoing  apparatus  are,  in  fact,  superceded 
by  much  greater  complexity  in  consequence  of  the 
introduction  of  additional  neurones  by  which  the 
afferent  impressions  are  distributed  to  nerve-cells 
situated  not  only  in  the  immediate  vicinity  of  the 
first  neurone,  but  at  different  and  often  distant  levels. 

Although  very  exceptionally  the  relation  between  the  neurones  may  perhaps  be 
that  of  actual  continuity  in  consequence  of  a  secondary  union  of  their  processes 
(Held),  the  view  concerning  the  constitution  of  the  nervous  system  most  worthy  of 
confidence,  notwithstanding  the  bitter  attacks  by  certain  histologists,  regards  the 
neurones  as  separate  and  distinct  units.  While  chained  together  to  form  the  various 
paths  of  conduction,  they  are  probably  seldom,  if  ever,  actually  united  to  one  another 
but  only  intimately  related,  sir  their  processes,  although  in  close  contact,  are  not 
directly  continuous, — contigui        ut  not  continuity  being  the  ordinary  relation. 

During  the  evolution  of  ihe  nerx'ous  system  from  the  simpler  type,  the  cell- 
bodies  of  the  neurones  forsake  their  primary  superficial  position  and  recede  from  the 
periphery.  In  vertebrates  this  recession  is  expressed  in  the  axial  accumulation  of 
cell-bodies  either  within  the  wall  or  in  the  immediate  vicinity  of  the  neural  tube 
(brain  and  spinal  cord),  from  or  to  which  the  processes  pass.  The  nervous  system 
is  often  divided,  therefore,  into  a  central  AnA  a  peripheral  portion.  The  former,  also 
known  as  the  ccrrbro- spinal  axis,  includes  the  brain  and  spinal  cord  and  contains 
the  chief  axial  collections  of  nerve-cells  ;  the  peripheral  portion,  on  the  contrary, 
996 


Diaffnm  showing  fundamental  units 
<rf  nervous  s>-stem.  A,  sensory  neurone, 
conducting  afferent  impulses  hv  its  pro- 
cess (a)  from  periphery  [S);  B,,  motor 
neurone  sending  efferent  impulses  by  its 
process  {e)  to  muscle. 


THE  NERVOUS  TISSUES. 


997 


contains  the  nerve-cells  of  the  sensory  ganglir  and  is  principally  composed  of  the 
nerve-fibres  that  pass  to  and  from  the  end-organs.  Intimately  associated  with  and 
in  fact  a  part  of  the  peripheral  nervous  system,  but  at  the  same  time  possessing  a 
certain  degree  of  independence,  stands  the  sympathetic  system,  which  provides  for 
the  innervation  of  the  involuntary  muscle  and  glandular  tissue  throughout  the  body 
and  the  muscle  of  the  heart. 

When  sectioned,  the  fresh  brain  and  spinal  cord  do  not  present  a  uniform  appear- 
ance, but  are  seen  to  be  made  up  of  a  darker  and  a  lighter  substance.  The  former, 
the^rav  matUr,  owes  its  reddish  brown  color  not  only  to  the  numerous  nerve-cells 
that  it  contains,  but  also  to  its  greater  vascularity  ;  the  hue  of  the  lighter  substance, 
X\x  white  matter,  is  due  to  its  chief  constituents,  the  medullated  nerve-fibres,  in 
conjunction  with  its  relatively  meagre  vascular  supply. 

THE  NERVOUS  TISSUES. 
The  Neurones — The  neurones,  the  essential  morphological  units  of  the 
nervous  system,  consist  of  the  cell -body  and  the  processes.  The  latter,  as  seen  in 
the  case  of  a  typical  motor  neurone  f  Fig.  835 j,  are  of  two  kinds  :  (a)  the  branched 
protoplasmic  extensions,  the  dendrites,  which  may  be  multiple  and  form  elaborate 
arborescent  ramifications  that  establish  relations  with  other  neurones,  and  (b)  the 
single  unbranched  axone  (neuraxis,  neurite)  that  ordinarily  is  prolonged  to  form  the 
axis-wlinder  of  a  nerve-fibre,  and,  hence,  is  often  termed  the  axis-cylinder  process. 
The  dendrites  are  usually  uneven  in  contour  and  relatively  robust  as  they  leave 
the  cell-body,  but  rapidly  become  thinner,  due  to  their  repeated  branching,  until 

they  are  reduced  to  delicate  threads  that  con- 
stitute the  terminal  arborizations,  the  telodendria, 
formed  by  the  end-branches.  The  latter  are 
beset  with  minute  varicosities  and  finally  end  in 
terminal  bead-like  thickenings.  The  axones, 
slender  and  smooth  and  of  uniform  thickness, 
are  much  less  conspicuous  than  the  dendrites. 
They  may  be  short  and  only  extend  to  nearby 
cells  ;  or  they  may  be  of  great  length  and  con- 
nect distant  parts  that  lie  either  wholly  within  the 


Fig.  835. 


Dendritn 


Collaleral 


Fig.  836. 


Dendritn 


Telodcndrioii 
IMagram  of  tv-plcal  neurone. 


Arburintion 

of  axone 


Diarrem  of  nerve-cell  of  type 
if,  in  which  axone  fa  not  prolonged 
.IS  ner\-e-nbre. 


cerebro-spinal  axis  (as  from  the  brkin-cortex  to  the  lower  part  of  the  spinal  cord)  or 
extend  beyond  (as  from  the  lower  part  of  the  cord  to  the  plantar  musclw  of  the  foot ). 


998 


HUMAN  ANATOMY. 


/; 


^^  '  ! 


ill  1  I 


Fig, 


ScniidiagtHmnntic  represenution  of 
structure  f)f  neurone :  u,  axone. 


On  reaching  their  destination  the  axones  terminate  in  end-arborizadons  (telodendria) 
of  various  forms,  in  a  manner  similar  to  the  dendrites.     According  to  the  distribution 

of  their  axones,  the  neurones  are  divided  into  two 
classes.  In  those  of  the  first,  known  as  fe//s  of  type  / 
the  axone  is  continued  as  a  nerve-fibre  and  is,  therefore, 
relatively  long.  Soon  after  leaving  the  cell-body  such 
axones  give  off  delicate  lateral  processes,  the  collaterals, 
which,  after  a  longer  or  shorter  course,  break  up  into 
arborizations  ending  in  relation  with  other  and  often 
remote  neurones.  Neurones  of  the  second  and  much 
less  fa-equent  class,  cells  of  type  II,  possess  short  axones 
that  are  not  continued  is  ner\e-fibres,  but  almost 
immediately  break  up  into  complex  end-arborizations 
or  neuropodia  (Kolliker),  limited  to  the  gray  matter. 
The  processes  of  the  sensory  neurones,  as  in  the 
case  of  those  constituting  the  spinal  and  other  ganglia 
connected  with  afferent  nerves,  are  so  modified  during 
development  (Fig.  839)  that  later  both  dendrites  and 
axones  arise  in  common  from  the  single  robust  stalk  of 
an  apparendy  unipolar  cell.  Branching  T-like,  one 
process  (the  dendrite)  passes  towards  the  periphery 
and  the  other  (the  axone)  extends  to  and  into  the 
cerebro-spinal  axis. 

The  nerve-cells,  as  the  bodies  of  the  neurones 
are  called,  possess  certain  structural  details  in  common, 
although  in  some  instances  they  present  characteristics 
that  suffice  to  identify  them  as  belonging  to  particular  localities.  Nerve-cells  are 
relatively  large  elements,  those  in  the  anterior  horns  of  the  spinal  cord  measuring 
from  .070-.  150  mm.  in  diameter,  and  contain  a  large  spherical  nucleus,  poor  in 
chromatin  but  usually  pro- 
vided with  a  conspicuous  pic.  838. 
nucleolus.  Their  ry/i^Aww 
varies  in  appearance  with 
the  method  of  fixation  and 
staining  to  such  an  extent 
that  considerable  uncertain- 
ty exists  as  to  the  relation 
of  many  described  details  to 
the  actual  structure  of  the 
jUs.  It  may  be  accepted 
as  established,  however, 
that  the  cell-body  of  the 
neurone  consists  ol  Aground 
substance,  homogeneous  or 
finely  jfranular,  in  which 
delicate y?*/-///<r  and  masses 
of  rhromatophilk  granules 
art'  tinbedded  :  in  addition, 
a  variable  amount  of  brown 
or  blackish  pigment  is  com- 
monly present  in  the  vicin- 
ity of  the  nucleus.  The 
presence  of  the  fibrillae 
within  the  nerve-cell,  long 
ago  niaintainetl  by  Max 
Schult/e  but  later  disre- 
garded, has  been  placed 
beyond  question  by  the  researches  of  Apdthy,  Bethe,  Cajal  and  others.  The  signifi- 
cance and  relations  of  the  fibrill.e  to  the  nerve-cell,  however,  have  given  rise  to  warm 


Ncrve-celLs  of  humtn  ipinal  cord  stained  to  show  Niul  bodies ;  IJ,  dendrites ; 
.-<.  axones;  C,  implantation  rone ;  .V,  nucteiMi  jV,  nucleolus,    v  4go. 


II 


THE  NERVOUS  TISSUES. 


999 


discussion.  The  observations  based  upon  the  improved  methods  of  silver-staininK 
mtroduced  by  Cajal  have  contributed  much  towards  the  solution  of  these  questions, 
and.  at  present,  the  most  experienced  histologists  incline  towards  the  view  that  the 
hbnllae  demonstrable  within  the  nerve-cell  are  limited  to  the  body  and  processes  of 
that  particular  neurone  and  do  not  unite  with  the  fibrill*  of  other  neurones.  When 
adequately  differentiated  by  successful  staining,  the  fibrill*  form  an  intracellular 
net-work  within  the  cell-body,  from  which  they  are  continued  into  the  dendrites  and 
axone  and  in  all  cases  end  free  in  the  terminal  arborizations  (Retzius). 

After  special  staining  with  methylene  blue,  or  other  basic  anilim.-s.  the  chrom- 
atophihc  granules  appear  deeply  colored  and  arranged  in  groups  or  masses  of  vary- 
ing fonn  and  size.  Such  aggregations,  known  as  Nissl  bodies,  after  the  German 
histologist  whose  elaborate  studies  and  theories  concerning  the  structure  of  the  nerve- 
cell  have  given  prominence  to  these  masses  of  "stainable  substonce,"  are  usually 
most  conspicuous  in  the  vicinity  of  the  nucleus.  Collectively,  they  constitute  the 
''C^'Cl*'*^''"^''  °^  Lenhoss6k  and  are  least  marked  at  the  periphery  of  the  nerve- 
cell.  They  are  continued  into  the  dendrites  as  elongated  flakes  or  poii '<  d  rod-like 
tracts  that  finally  are  resolved  into  scattered  granules  along  the  processis  The 
axone.  on  the  contrary,  is  not  invaded  by  the  Nissl  bodies,  and  usually  joins  the 
nerve-cell  at  an  area  free  from  the  stainable  substance,  the  axis-cylinder  process  com- 
monly arising  from  a  slight  elevation  known  as  the  implanlation  cone.  Exception- 
ally, the  axone  may  arise  from  one  of  the  dendrites,  either  at  its  base  or  at  a  ooint 
some  distance  from  the  cell-body.  "^ 

Notwithstanding  the  elaborate  classification  of  nerve-cells  and  the  theories  based  upon  the 
NissI  bodies  their  significance  is  still  debatable,  although  in  the  light  of  the  more  recent^dies 
by  earner.  Holmes  and  others  it  seems  probable  that  they  are  normal  constituents  of  the  cell 
and  are  directly  related  to  functional  activity,  undergoing  increase  und^r  unusual  stimulus 

The  intracellular  canals  described  by  Holmgren  as  existing  in  nerve-cells,  in  connection 
with  a  reticulum  {trophospongium)  that  appears  after  certain  treatment,  have  been  van^y 
I!lnT  l^-n  ''.""^.u"  •***  ^^l  ?•*  '"^^^^  ^  artefacts,  or  at  least  dependent  upon  the  intn.- 
cellular  fibnite  for  their  exhibition.  Pewsner-Neufeld,  however,  believes  them  to  be  lymph- 
clefts  withm  the  cytoplasm  that  directly  communicate  with  lymph-spaces  which  surround  the 
iierve^ell  and  thus  provide  a  means  for  the  rapid  removal  of  waste  products  from  the  neurone. 

Every  neurone  possesses  at  least  one  process,  which  is  then  an  axone,  although 
usually  provided  with  both  dendrites  and  axone.    Very 
rarely  more  than  a  single  axone  is  present.     Depend- 
ing upon  the  number  of  their  processes,  nerve-cells  are 
described  as  unipolar,  bipolar,  or  multipolar.     The 
unipolar  condition  is  often  secondary,  since  two 
processes  may  be  so  blended  for  part  of  their  course 
that  they  form  a  single  process.    Conspicuous  examples 
of  such  relation  are  seen  in  the  spherical  ner\'e-cells 
imposing  the  spinal  and  other  ganglia  connected  with 
the  sensory  nerves.     Primarily  such  neurones  possess 
an  axone  and  a  dendrite  that  arise  from  opposite  ends 
of  what  IS  for  a  time  a  spindle-shaped  bipolar  cell 
During  development,  however,  the  unilateral  growth 
ot  the  cell-body  towards  the  surface  of  the  ganglion 
brings  about  the  gradual  approximation  of  the  two 
procMses  until  they  hise  in  the  single  extension  into 
which  the  spherical  or  flask-like  cell  is  prolonged 
This  process  sooner  or  later  undergoes  a  Y-  or  T-  like 
division,  one  process,  usually  identified  as  the  dendrite 
IKWsing  to  the  periphery  to  end  in  the  free  terminal 
arbonzation,    whilst    the    other,    the    axone,    passes 
centrally    to    end    in    an    arborization    around    the 
neurones  lying  within  the  cerebro-spinal  axis. 

ODD  Jte  Tidt  o/  th^'^K'  ■*?"«?•.'"  ^^'""^  '^^  ^^"'l"*^  •■>"'»  ^"""^  P»^  from 
opposite  sides  of  the  spherical  cell-body,  are  found  in  the  retina  and  the  ganglia 


Dtacram  ahowini;  transfornwtiun 
of  young  bipolar  Hnwry  neurone  into 
one  of  unipniar  tvpr 


lOOO 


HUMAN  ANATOMY. 


connected  with  the  acoustic  nerve.     An  interesting  modification  of  bipolar  neurones 
is  presented  by  the  olfactory  cells,  whose  dendrites  are  represented  by  the  extremely 

short  processes  embedded  within  the  nasal  mucous 
Fig.  840.  membrane,  whilst  the  axones  are  prolonged  as  the 

1  fibres  of  the  olfactory  nerves  into  the  cranial  cavity 

to  end   in  lelodendria  within  the  glomeruli  of  the 
olfactory  bulb. 
The  cell-bodies  of  the  multipolar  neurone*, 
\?  which  possess  one  axone  and  several  dendrites,  vary 

T  in  form  (Fig.  841).     Some,  as  those  within  the  sym- 

S  pathetic  ganglia,  are  approximately  spherical  and  of 

moderate  size,  with  short  delicate  dendrites ;  many 
are  of  large  size  and  irregularly  stellate  form,  the 
dendrites  passing  out  in  all  directions,  as  seen  in  the 
conspicuous  motor  neurones  within  the  gray  matter 
of  the  spinal  cord  ;  others  possess  a  regular  and 
characteristic  form,  as  the  flask-shaped  cells  of  Purkinje 
within  the  cerebellum,  or  the  pyramidal  cells  of  the 
cerebral  cortex.  Certain  multipolar  neurones  within 
i!u-  cerebral  cortex,  and  especially  those  constituting 
the  chief  components  of  the  granule  layer,  of  the 
cerebellum,  are  distinguished  by  the  small  size  of 
their  cell-bodies  and  the  peculiar  ramifications  and  claw-like  telodendria  of  their 
dendrites  (Fig.  945J.    Within  the  cerebellar  cortex  are  likewise  found  examples  of 


A 


Bipolar  neurones;  a.fromolfactory 
mucous  membrane — dendrite  is  above; 
*,  from  retina.    (Atodi/ird/rom  Cajal.^ 


KlO.  841. 


Si 

1} 


Multipolar nerve-celli of  various  forms ^  ^,  from  spinal  cord;  A,  from  cerebral  cortex;  C  from  cerebellar  cortex 
(Purkmjecell) ;  a,  axone;  c,  implantation  cune. 


the  multipolar  neurones  of  Goljji's  type  II,  whose  a-vones  almost  iniinediately 
undergo  elaborate  branching  within  the  gray  matter  to  which  they  are  confined. 
The  Nerve-Fibres. — From  the  foregoing  considerations  it  is  evident  that  the 
nerve-fibres  are  not  independent  elements,  but  that  all  ai  e  the  processes  of  neurones 
— either  the  axones  of  those  that  are  prolonged  into  fibres  ( type  I;,  or  the  dendrites 
of  those  situated  within  the  spinal  and  other  sensory  peripheral  ganglia.  Although 
neurones  exist  which  are  not  continuetl  as  nerve-fibres,  the  latter  are  always  connected 


THE  NERVOI.S  TISSUES. 


loui 


Fio.  84J. 


Axi!t.c>  limlcrs 


Axolctnmu 


Medullary  shivtli 


NfMieof  ki«ii\it-r 


N'enrileniinff 


Medullatcd  iicrve-Hhrt^,  ms  mi-ii  in  IuhkI- 
tudinal  sections  of  spinal  nerve.     •:  *pn. 


with  neurones.  Recognizing,  therefore,  that  the  nerve-Abres  are  only  procc-s.-M»  <  if 
neurones,  their  separate  description  is  iustified  only  as  a  matter  of  convtiiience. 
The  fundamental  part  of  every  nerve-fibre  is  the  central  cord,  commonly  know  n 
as  the  axis-cylinder,  which  is  composed  of  threads  of  great  <klicacy,  the  axis- 
fibrilla,  prolonged  from  the  nerve-cell  and  embedded  within  a  seiniriuid'intcrtibrillar 
substance,  the  neuroplasm,  the  entire  cord  so  con- 
stituted being  enclosed  by  a  delicate  structureless 
sheath,  the  axolemma.  The  existence  of  the 
axolemma  as  a  distinct  sheath,  however,  is  ques- 
tionable, the  appearance  of  such  investment  not 
improbably  being  due  to  a  local  condensation  of 
the  framework  of  the  medullary  coat  immediately 
around  the  axis-cylinder. 

In  the  case  of  the  typical  fibres,  such  as  form 
the  chief  constituents  of  ^the  peripheral  nerves 
distributed  to  various  parts  of  the  body,  the  axis- 
cylinder  is  surrounded  by  a  relatively  thick  coat, 
known  as  the  nudullary  sheath,  outside  of  which 
lies  a  thin  structureless  envelope,  the  neurilemma 
or  sheath  of  Schwann,  that  invests  the  entire 
nerve-fibre.  In  the  case  of  fibres  proceeding  from 
neurones  composing  the  sensory  ganglia,  the 
neurilemma  is  continuous  with  the  nucleated 
sheath  enclosing  the  individual  ganglion-cells. 
The  medullary  sheath  consists  of  two  parts, 
a  delicate  xeacwXM  framework  and  a  fatty  substance,  the  mvelin,  that  fills  the  nu-slus 
of  the  supporting  reticulum.  The  latter,  arranged  for  the  most  part  as  anastomosing 
membranous  lamellse,  that  in  transverse  sections  of  the  ner\e-fibre  appear  as  faint 
concentric  lines,  resists  pancreatic  digestion  and  fat-dissolving  reagents,  and  was 
regarded  by  Ewald  and  Kiihne  as  possessing  properties  similar  to  the  keratin  of 
homy  substances  and,  hence,  was  named  by  them  neurokeratin.  The  blackening 
after  treatment  with  osmic  acid  and  other  reactions  exhibited  by  myelin  indicate  its 
fatty  nature,  and  it  is  probable  that  this  substance  exists  during  life  in  the  form  of  a 
fine  emulsion  supported  by  the  framework.  When  fresh,  myelin  appears  highly 
refracting  and  homogeneous,  and  confers  upon  the  niedullated  ner\e-fibres  their 
chru^cteristic  whitish  color.  It  is,  however,  prone  to  post-mortem  changes,  .so  that 
after  death  it  loses  its  former  uniformity  and  presents  irregular  contractions  and 
collections,  or  at  the  broken  end  of  the  fibre  extrudes  in  irregular  globules,  <liie 
probably  to  fusion  of  the  normal  individual  minute  droplet?  into  larger  masses. 

The  medullary  sheath  b  not  uniformly  continuoi"  ,  nost  completely  inter- 

rupted at  regular,  although  in  different  fibres  variabi  '■%  marked  by  annular 

constrictions.  ..  constrictions,  the  nodes 

of  Ranvier,  correspond  to  narrow  zones  at 
which    the    medullary   sheath    is    practically 
wanting  and  the  neurilemma  dips  in  and,  s'-ine- 
what  thickened,  lies  in  close  relation  wit.'i  I'le 
axis-cylinder.     According  to  Hardesty '  the 
medullary  sheath  does   not   suffer  complete 
suppression  at  the  nodes,  but  is  represented 
by  part  of  its  reduced  framework  which  trans- 
verses   the   constriction,  a   conclusion  which 
we  can  confirm.     The  nodes  occur  at  regular 
inter\als  along  the  fibre,  which  they  thus  divide 
In  general,  the  latter  are  longer  in  large  fibres, 
mm. ,  and  shorter  in  those  of  small  diameter,  in 
The  axis-cylinder  passes  uniiittr- 


Fic. 


Axis-cylinder 

Neurilemma 
Medullar}'  sheatli 

Medullated  nerve-Abres  in  transverse 
section,    x  550. 


into  a  series  of  internodal  segments. 
where  they  have  a  length  of  about 

which  they  may  mea.sure  .  i  mm.  or  less  in 'length ...., ^_.  „....„,, . 

niptedly  across  the  nodes,  although  it  often  presents  a  slight'  fusiform  enlargement 


'Amer  Journal  of  Anatomy,  vol.  iv.,  1905. 


I003 


HUMAN  ANATOMY. 


opposite  each  constriction  (Ranvier).     The  neurilemma  also  Millers  no  break  at 

the  nodes,  but  is  continuous  from  one  segment  to  the  other. 

In  addition  to  the  partial  interruptions  at  the 
nodes,  the  medullary-  sheath  after  treatment  with 
osmic  add  frequently  app«irs  broken  by  clear 
narrow  clefts  that  extend  obliquely  from  the  neuri- 
lemma to  the  a.xolemma  and  thus  subdivide  each 
intemodal  segment  into  a  number  of  smaller 
tracts,  known  as  the  Schmidt- Lantermann  segments 
(Fig.  844).  The  oblique  clefts  do  not  all  extend 
in  the  same  direction,  even  within  the  same  inter- 
nodal  se^ent,  since  they  are  usually  directed  from 
without  mward  and  towards  the  nodal  constrictions 
and,  therefore,  have  an  opposed  disposition  at  the 
ends  of  the  same  as  well  as  of  the  adjoining  seg- 
ments. The  significance  of  this  subdivision  is  un- 
certain ;  many  regarding  the  details  as  artebcts. 
According  to  Capparelli',  however,  the  apparent 
clefts  are  in  reality  unstained  membraneous  septa 
that  pass  obliquely  from  the  axolemma  to  the  inner 
■surface  of  the  neurilemma  and  serve  to  hold  the 
axis-cylinder  in  place  and  to  enclose  the  myelin. 
The  studies  of  Hatai^  on  the  arrangement  of  the 
neurokeratin  seem  to  support  these  conclusions. 
Within  each  intemodal  segment,  beneath  the  sheath 
of  Schwann,  lies  a  single  (sometimes  more  than 
one)  small  tteiiri/emma-cell  which  consists  of  an 
elongated  oval  nucleus  surrounded  by  a  meagre 
amount  of  cytoplasm.     These  cells  represent  the 

remams  of  the  mesoblastic  elements  {shfath-cells)  that  during  the  growth  of  the 

nerve-fibre  were  active  in  providing  its  envelope  (page  loii). 

Fig.  845. 


■Hodc  of  Ranvier 


Medullatcd  ocrve-librcs  after  treatment 
with  osmic  acid:  A,  fibre  showing  reticu- 
lum within  mcdiillary  coat;  ^.oneahowing 
same  coal  divided  into  segments,    x  s<x>. 


Medullated  ner\-e-fibres  becoming  nonmedullated  oti  approaciiing 
tiieir  termination.     ''.  335. 

Dependinjr  upon  the  presence  or  absence  of  the  medullar}'  .she.ith  throughout 
the  greater  part  of  their  course,  nerve-fibres  are  distinguished  as  medullated  or  non- 

'  .\rchiv  f.  mikros.  Anat  u.  Entwick.,  Bd.  66,  1905. 
•  Journal  of  Comparative  Neurology,  vol.  xiii.,  1903. 


. 


THE   NERVOUS  TISSUES. 


1003 


■^  :)ninedullatcd   

fibre!*  Ill  kmgitudiiialiection 
of  iplenic  iwn-e.     <  310. 


meduUated.  The  meduUated  fibres  constitute  the  jjpeat  majority  of  th<»se  making; 
up  the  peripheral  nerves  and  the  tracts  of  the  cerebro-spinal  axis  ;  the  component 
fibres  of  the  latter,  however,  while  medullated  are  without  the  neurilemma.  The 
nonmedfillated  fibres,  on  the  other  hand,  are  chiefly  prolongations  ( uxones )  fr<»m 
the  ganglion  cells  of  the  sympathetic  system,  although  in  the  case  of  the  olfactory 
nerves  the  fibres  are  also  without  a  myelin-coat.  The  dis- 
tinction between  these  two  classes  of  fibres  is  relative  rather  than  Fiu.  846. 
absolute,  sine?  every  medullated  ner\e-fibre  becomes  nonmed- 
ullated  before  reaching  its  termination,  central  or  peripheral. 

Medullary  nerve-fibres  vary  greatly  in  thickness,  the  smallest  hav- 
ing a  diameter  of  only  .001  mm.,  whilst  the  largest  may  measure  as 
much  as  .030  mm.  According  to  their  diameter,  sa  determined  by 
Kolliker,  the  medullated  fibres  may  be  grouped  as  fine  (.002-.004 
mm.),  medium  (.aoj-.oo9  mm.),  and  coarse  (.010-.020  mm.).  In 
general,  the  thicker  fibres  are  the  longer  and  are  the  processes  of  large 
nerve-cells  ;  conversely,  the  finer  have  shorter  courses  and  belong  to 
small  cells.  Although  !;ubject  to  many  exceptions,  die  motor  fibres 
are  usually  the  thicker  and  the  sensory  the  smaller. 

Since  there  are  many  more  nerv-e-fibres  ihan  nerve-cells,  it  is  evi- 
dent that  die  fomier  must  undei^go  division  along  their  course.  Such 
doubling  always  ocnirs  at  a  point  corresponding  to  a  node  of  Ranvier, 
never  within  the  intcrnodal  segment,  the  sheaths  being  continued  over 
the  two  resulting  fibres.  On  approadiing  their  peripheral  termination 
the  l>ranching  becomes  more  frequent  and  the  medullary  sheath  thinner 
until  it  ends,  after  which  the  axis-cylinder  continues  invested  with  only 
the  attenuated  neurilemma.  The  latter,  now  reduced  to  an  extremely 
delicate  covering  beset  with  occasional  nuclei,  soo.t^  or  later  disappears,  the  naked  axis-cylinder 
alone  being  prolonged  to  end  finally  in  the  varicose  threads  of  the  telodendrion. 

The  nonmcduUditd  nerve-fibres  proper,  also  termed  pale  fibres  ox  fibres  ofReinak,  include 
those  that  are  without  the  myelin  sheath  throughou'  -ir  course.  They  are  chiefly  the  axones 
of  sympathetic  neurones.  Devoid  of  medullary  sheath,  these  fibres,  often  .oca  mm.  or  less  in 
diameter,  consist  of  only  the  ax:s<ylinder  and  the  neurilemma,  the  latter  being  thinner  and 
more  delicate  than  on  the  medullated  fibres.  Like  the  latter,  the  pale  fibres  end  in  tekxlendria 
composed  of  naked  a.xis-cylinders,  bearing  irregular  varicosities. 

Neuroglia.— The  neurones  ('ner\'e-cells  and  fibres)  within  the  cerebro-spinal 
axis  are  everv-where  held  together  by  a  sjiecial  supportinj^y  tissue  known  as  neuroglia. 

The  latter  is  primarily  derivod  from  the  invagi- 
naled  ectoblast  lining  the  nei>ral  tube,  certain 
elements,  the  spongioblaits,  being  devoted  to  the 
production  of  the  neuroglia,  whili  others,  the 
neuroblasts,  give  rise  to  the  neurones.  At  first 
the  supporting  tissue  is  represented  by  greatly 
elongated,  radially  disposed  fibre-cells  that  often 
extend  the  entire  thickness  of  the  wall  of  the 
neural  canal.  Later,  the  neurogliar  elements 
become  differentiated  into  (a)  those  bordering 
the  lumen  of  the  canal,  which  are  partly  retained 
as  the  ependymal  cells,  and  ( b^  those  w  hich  have 
early  migrated  to  more  peripheral  locations  and 
gi\en  rise  to  stellate  cells  that  are  converted 
into  spider-like  elements,  the  astrocytes.  Seen 
in  chrome-silver  preparations  (Fig.' 847)  these 
appear  as  irregular  triangular  or  quadrilateral 
cells  from  whose  angles  numerous  delicate 
fibrillae  extend  lietween  the  surrounding  nerxous 
elements.  According  to  Rubaschkin, '  the  astro- 
cytes ..  transformations  from  larger  branched  gliogenetic  cells,  by  the  conversion  of 
wh.    ■  r  bust  protoplasmic  processes  the  delicate  _/fM7/tf-  that  later  form  the  chief 

'  Archiv  f.  inikros.  Anat.  u.  Entwick.,  Bd.  64,  1904. 


Youiijf  neuroKlia  cells;  uirocytes.  from  brain 
of  child.    X  300. 


I004 


HUMAN  ANATOMY. 


i 


Fig.  848. 


constituents  of  the  neuroglia  arise.  So  long  as  neuroglia  is  being  produced,  as  in 
the  nervous  axis  of  young  animals,  the  large  gliogenetic  cells  are  present  and  directly 
concerned  in  the  production  of  additional  fibrillae,  their  cytoplasm  becoming  pro- 
gressively less  granular  and  reduced  through  the  various  transition  phases  until  in 
«ie  hnal  condition,  as  the  small  g^/ta  cells,  little  more  than  the  nucleus  remains 
During  these  changes  very  many  fibrillie  lose  their  connection  with  the  cells  and  in 
conjuncuon  with  the  glia  threads  still  attached  to  the  astrocytes,  form  an  elaborate 
interlacement  in  which  the  neuroglia  cells,  now  reduced  and  for  the  most  part  devoid 
of  processes,  he  scattered  at  uncertain  intervals. 

In  all  parts  of  the  central  nervous  system  the  mature  neuroglia  consists  of 
essentially  the  same  tissue,  the  differences  presented  in  certain  localities  depending 
largely  upon  vanations  in  its  compactness.  Everywhere  the  chief  part  of  the  sup- 
porting tissue  consists  of  the  intricate  felt-work  of  fibriUa?,  glia-fibres,  as  they  are 
called,  which  are  usually  free  but  to  some  extent  connected  with  the  spider-cells  or 
astrocytes.  Where,  however,  the  neuroglia  borders  the  neural  tube  (the  ventricles 
ot  the  brain  and  the  central  canal  of  the  spinal  cord )  as  the  ependymal  layer  its 
arrangement  exhibits  peculiarities  that  call  for  later  special  mention. 

In  the  immediate  vicinity  of  the  neurones  the  felt-work  of  the  fibrillK  is  unusually  close  so 
that  the  cell-lKxIies  and  the  r.xrts  of  the  processes  are  surrounded  by  a  protecting  sheath,  the 
g/ta-cafisu/e.  This  diminishes  along  the  dendrites,  and  after  these  begin  to  branch  the  neuroglia 
no  longer  forms  a  complete  special  investment.  The  medullated  nerve-fibres  within  the  brain 
and  spinal  cord  ;,  ■  also  provided  with  delicate  neurogliar  sheaths  which  replace  the  neurilemma 
which  on  these  fibres  is  «  anting.     These  sheaths  are  prolonged  for  some  distance  on  the  fibres 

of  the  roots  of  the  spinal  nerves.  The  fibres  of  the  optic 
nerve  and  of  the  olfactor>-  tract  are  accompanied  through- 
out their  length  by  neurogliar  sheaths,  those  of  the 
remaining  cranial  nerves  losing  these  envelopes  shortly 
after  leaving  the  brain  (Rubiischkin). 

Beneath  the  pia  mater  the  neuroglia  is  especially 
dense  and  forms  the  external  subpial  layer  that  every- 
where in\ests  thener\ous  mass,  following  all  the  inequali- 
ties of  its  surface.  In  this  manner  the  pia  mater  is  excluded 
and,  except  where  its  connective-tis.sue  strands  accompany 
the  bhxKl-vessels  that  enter  the  nervous  mass,  takes  no 
part  in  the  make-up  of  the  supporting  stroma.  Thi 
subpial  layer  consists  of  a  dense  felt-work  of  glia-fibres. 
disposed  in  various  planes,  which  are  partly  free  and  partly 
the  processes  of  spider  cells.  Internally  the  layer  fades 
into  the  adjoining  difTuse  neuroglia  without  demarcation. 
At  the  periphery  the  fibres  often  exhibit  a  radial  disposi- 
tion, their  outer  ends  usually  l)eing  somewhat  expanded. 
Within  the  white  matter  the  neuroglia,  both  in  its  distri- 
bution and  density,  is  fairly  uniform,  although  special 
tracts  often  separate  the  larger  bundles  of  nerve-fibres. 
Its  arrangement  within  the  gray  matter  presents  less 
uniformity,  since  more  or  less  marked  condensations 
cKcur  where  the  nerve-cells  are  collected  into  nuclei,  as 
conspicuously  seen  in  the  interior  olive. 

Where  the  neuroglia  lH>rders  the  neural  tube 
>  especially  the  central  canal  of  the  spinal  cord)  it 
F.p«iid>mjii  leiis  uiid  •.ijaceut  iieurn-     constitutes  the  ependvmal  layer,  the  neculiari- 

Klia   smrouiHlhiK  central    canal  of   spinal       .•  ,       ,.    ,         ,,',  '     .    ,      "~7  7* '    !"<-    1'i.v-uiiaii 

coniofcat.       75.   (A'i<*iijiA*/ii.j  ties  of  Which  call  tor  special  mention.      1  he  imme- 

diate lining  of  the  tube  consists  of  a  sin>;le  layer  of 
pyramidal  epithelial  elements,  the  <f>,iidyinaf  cil/s.  whose  free  surfaces  or  bases  look 
towards  the  lumen,  and  the  ajiices  towards  the  surrounding  nervous  tissue.  At  least 
during  the  earlier  years  in  man,  and  throughout  life  in  inany  lower  mammals,  tlu' 
free  surface  of  each  cell  is  beset  with  a  niimlx'r  of  hair-like  jirocesses  that  in  their 
relations  with  the  ''yto|)lasin  correspond  to  ordinary  cilia.  The  pointed  distal  end  of 
the  ependymal  cell  is  prolonged  into  a  conical  jirocess  that  is  directly  continued 
into  usually  a  single  neurogliar  fibre  which,  after  a  course  of  uncertain  length  becomes 


THE  NERVOUS  TISSUES. 


1005 


lost  in  the  surrounding  complex  of  glia-fibres.  In  young  tissue  the  apical  processes 
often  exhibit  evidences  of  breaking  up  into  a  number  of  fine  fibrillie.  Where  the 
processes  enter  robust  tracts  of  neuroglia,  as  in  the  posterior  longitudinal  septum  of 
the  spinal  cord,  they  are  of  unusual  length.  In  addition  to  the  radially  directed 
fibres  connected  with  the  ependymal  cells,  the  tibre-complex  of  the  ependymal  zone 
includes  many  fibrillx  that  are  circularly  and  longitudinally  disposed.  Scattered 
glia  cells,  some  stellate  but  mosdy  small,  are  also  present  and  represent  the  elements 
from  which  the  neuroglia-fibrillje  have  been  derived. 

In  the  preceding  account  of  the  elements  composing  the  nervous  tissues  the  neurones  have 
been  regarded  as  the  morphological  units,  each  retaining  its  individual  ana'omical  inde|)en- 
dence,  although  functionally  closely  related  with  other  similar  units.  This  conception,  com- 
moply  referred  to  as  the  Neurone  Doctrine  and  strikingly  formulated  by  VValdeyer  in  1891, 
stands  in  contrast  to  the  prior  views  by  which  actual  continuity  was  attributed  to  the  nerve-cells 
by  means  of  the  union  assumed  to  exist  within  tlie  terminal  net-works  of  tlieir  processes.  The 
independence  and  true  relation  of  the  neurone  was  established  largely  through  the  convincing 
embryological  investigations  of  His  and  the  renewed  study  of  the  ner\e-cells  as  denionstmted 
by  the  improved  applications  of  the  Golgi  silver-impregnations,  supplemented  by  the  inethrK] 
of  vital  staining  by  methylene  blue  introduced  by  Ehrlich.  The  Neurone  Doctrine  has  gained 
wide  acceptance  and  the  sup|X)rt  of  the  most  distinguished  anatomists,  among  those  who  have 
materially  strengthened  its  position  being  K<)lliker,  Ram6n  y  Cajal,  Retzius,  LenhossC-k, 
Waldeyer,  van  Gehuchten,  and  Edinger. 

The  neurone  conception,  securely  founded  as  it  is  upon  a  vast  mass  of  evidence  collected 
from  a  wide  field  by  the  most  painstaking  and  accurate  observation,  has  not  escaped  challenge, 
and  at  present  is  assailed  by  a  group  of  histologists  headed  by  Apdthy  and  Bethe,  who  not  only 
bitterly  oppose  the  integrity  of  the  neurone  as  an  independent  unit,  but  also  strive  to  depose  the 
nerve-cell  from  its  dignity  as  the  fundamental  physiological  factor.  In  1897  Ap.^thy'  published 
his  observations  on  the  structure  of  the  ganglia  of  certain  invertebrates,  iis  revealed  by  a  new 
mercuric  gold-chloride  method,  and  thereby  established  the  important  fact  that  the  cell-body 
and  processes  of  the  neurone  are  pervaded  by  fine  neurofibrilUe,  thus  confirming  the  fibrill.ir 
structure  of  the  nerve-cell  advanced  by  Max  .Schultze  more  than  a  ciuarter  of  a  century  bf  fore. 
Following  ApSthy,  Bethe»  investigated  the  tissues  of  the  higher  animals  and  succeeded  in  dem- 
onstrating the  existence  of  the  neurofibrillce  within  the  neurones  of  man.  According  to  these 
observers,  the  neiirofibrilte,  although  interlaced  without  junction  within  the  cell-l)odies,  are 
independent  threads,  that  are  not  confined  to  the  neurones  but  pass  Ijeyond  and  unite  with 
fibres  from  other  sources.  The  neurofibrill.-e,  therefore,  and  not  the  nerve-cells,  are  the  essen- 
tial elements  of  the  nervous  system,  the  cells  being  only  intenxised  along  the  path  of  conduc- 
tion. Indeed,  according  to  these  views,  the  neurofibrillx  are  independent  of  and,  in  a  sense, 
foreign  to  the  nerve-cells,  leaving  or  entering  the  latter  at  pleasure  and  oonstltutinf.  by  their 
union  a  continuous  path  of  conduction  from  the  receptive  element  to  the  muscle-fibre.  Ap.'lthy, 
moreover,  assumes  the  existence  throughout  the  central  nervous  system  of  a  fibrillar  net-work 
formed  outside  and  between  the  nerve-cells  by  the  nenrofibrilla?  from  which  the  axones  may 
arise  independently  of  the  nerve-cells.  It  is  evident  that  it  such  lie  the  case  the  conception  of 
the  neurone  as  an  individual  unit  falls. 

The  criticism  made  by  the  newer  school,  that  the  supporters  of  the  neurone  theory  relied 
upon  methods  which  inadequately  demonstrated  the  ultimate  terminal  relations  (the  assumed 
union  in  net-works)  has  bten  met  by  the  introduction  of  the  still  newer  methods  of  Beil.schow- 
sky  and  especially  of  C.ijal,  which  have  yielded  preparations  that  demonstrate  that  the  neuro- 
fibrilk-e  everywhere  form  net-works  jvithhi  the  cell-bodies  of  the  neurones,  are  confined  to  their 
processes,  .ind  even  in  their  ultiiuate  endings  form  ununited  terminal  arborizations.  It  seems, 
indeed,  that,  at  present  at  least,  the  defenders  of  the  neurone  t'neory  mav  with  justice  charge 
their  opiHinents  in  turn  with  depending  upon  methods  thai  only  partial Iv  show  the  relations  of 
the  iieurofibrillie  within  the  neurones.  Retzius.  than  whom  no  niore  experienced  an<l  i-om|)eient 
authority  in  this  difficult  field  of  research  can  be  consulted,  has  recently  reviewed  the  entire 
question  and  presented »  most  convincingly  the  facts  th.U  enable  him,  as  well  as  the  most 
distinitiiished  anatomists  of  to-day,  still  vigorously  to  champion  the  Neurone  Doctrine.  After 
a  critical  and  scientific  discussion  of  the  arguments  advanced  bv  .'\i).1thy,  Hethe  and  Nissl, 
Retzius  rests  his  case  with  little  concern  as  to  the  verdict  of  those  to  whom  facts  and  not 
speculation  most  appeal. 

'Mitteihmgen  aus  d.  /.oolog.  Station  zn  Neapel.  Bd.  xii.,  1897. 
•AllKemeine  Anar.  u.  riiysiol.  des  Nervensvstoms,  1903. 
•Biologische  rntersuchunvren.  N.  I'"..  lUl.  xii.,  1905. 
•Die  Neuronenlehre  und  ihre  Anhiinger,  1901. 


■■■■Ma 


ioo6 


HUMAN   ANATOMY. 


fll! 


I 


Ir 


The  Nerve-Trunks.— The  fibres  composing  the  peripheral  nervous  svstem  ar* 
grouped  into  the  larger  and  smaller  nerve-tnlX  fhich  extend  to  !Zu"^i  the 
body^  In  the  make-up  of  those  that  supply  both  muscles  and  sensoJyTurfacS 
(  ntegument  or  mucous  membranes),  as.  for  example,  the  median  or  thethWdSo^ 
of  the  trigeminal  nerve,  three  sets  of  fibres  are  included :  (i)  the  efferent  axon«  o^ 
Xr  r  h"™-?  >  ^'T  "*"-'^'"=" ""''  ''''"'"''^  ^"hin  the  spinal  ..ord  Tb^L  !  ( T)  the 
f H^r^  fh  «'""  ?'  ^'^'^,  "^"'■"""^  *'»*"'"  '^^  'P^  «"d  other  sensory  ganil  J 
and  (3)  the  efferent  axones  o  neurones  within  the  sympathetic  ganglia  that  accomlanv 
musc'StSn^  ""^  periphery  and  serve  for  the  innervadon^f  the  involun^ 
muscle  of  the  blood-vessels  and  of  the  skin  and  the  glands  " 

The  nerve-fibres,  the  various  kinds  usually  more  or  less  intermingled  are 
Ttri'f  A"'*''';'''"^  ^Tf''  l^''^  '^•"^^  '"  ""'"'^^  *"d  diameter  a?co;drng 
defin^teXl  f  A  '^  "^"^  ^^'  '^^^  '"""•  ^'^  '""'*^"1»«  «  surrounded  by  a 
definite  sheath  of  dense  connective  tissue,  the  perineurium,  which  is  directly  con- 
unuous  with  the  delicate  fibro-el^tic  tissue  prolonged  between  the  individual  ner^e- 
fibres  as  the  endoruurmm  When  well  represented,  the  sheath  of  the  hinicdus 
consists  of  concentric  lamellae  of  fibrous  tissue  which  enclose  perineuria!  lymph^^s. 

Fig.  849. 

^^^'^^':>  ■  .      ;a 


Epineurium 


'  Blood-vcnels 


— •'.   "'wr ,■■■■ — ■ Peniieurium 


Transverse  teclion  of  small  nerxe-trunk  composed  o(  looMly  uniteJ  funiculi,    y  ». 

The  latter,  lined  by  flattened  connectivc-tissuf  plates,  are  in  relation  with  the  clefts 
between  the  nerve-fiores.  on  the  one  hand,  and  with  the  lymphatics  with  n  the  inter 

t-vl^r'""  ""/''"  ."'^'■-  .^'^^^'■"'  -'^  "''"■■»'•  "^^  neA-eiscomposS  of  several 
funiculi,  these  are  loosely  Ixiund  togetiier  and  the  entire  trunk  .so  formed  is  investS 

and^S"  •       "^  Tr"'  '"""f"^'"^'  ^h*^//''"""''"'".  in  which  course  the  blood-vSels 
and  lymphatics.     These  enve  opes  of  the  nerve-trunk  are  c.ntinued  over  its  branch^ 
even  onto  its  sma lest   suMivisions.     The   last    representative   of   thLe   coverines 
is  seen  on  the  mdividual  fibres  as  the  sheath  of  Henle,  that  surrounds  the  fib?e 
neurZmt         '"'""^  ""^  ''"'  '''''''''  ''^'''''"^^  "'  '""""-"-  ti'ue  ....Li^le  die 

„,pH,Il'^r'r"'"'''''yr  "'  "'^  "^■'■^'-funk  (Fig.  850),  the  transverselv  cut  individual 
medullated  nerve-hbres  apjvar  as  small  ciicles,  sharply  defined  bv  a  fine  outZeTthe 
neunlemma  ,  each  enclosing  a  deeply  stained  doi  (the  axis-cyiinder  i.  mi  on , 
The  interval  between  the  latter  and  the  neurilemma,  corresponding  t  the  'mce 
occupied  by  the  mye^n,  usually  appears  dear  and  unstained  with  the  exception  0^ 
delicate  and  uncertain  suggestions  of  „„.n,branous  septa.  In  contrast  wh  1. 
unstained  appearance  m  sect  ons  tinge.1  with  carmine,  aft'er  the  action  of  osmicncid 
or  special  hem.itoxyl,n  staining  (VVeigert)  the  med.illarv  substance  exhibits  a  chk 
color  and  the  axis-cyl.nder  appears  surrounded  bv  a  d..p!v  tint«l  rin^      The  neu  i- 


THE  NERVOUS  TISSUES.  ,007 

lemma  nuclei  are  o^ionally  seen  as  deeply  stained  crescentic  figures  that  partially 
embrace  the  nerve-fibre,  lymg  beneath  the  neurilemma  within  depressions  in  the 
medullary  substance. 

Fig.  850. 


Pcriiicuriuia 


Nervt-fibre 


Epinmrium 


Blood-vcsKi 

Tr.nsver«  .otion  of  '•"•«»l»»«"e««d of  «rv,sfibr«  held  tog«h,r  by  endoneurium  .nd 
sunounded  by  perineurium,     x  175. 

J'^*^  '"  o-oss-section.  the  nonmedullated  fibres  appear  as  small  irregularly 

round  figure  arranged  m  groups  that  correspond  to  bundles  (Fig.  851).     When 
numerous,  the  latter  are  aggregated  v    k-    3«^ 

into  seconr'iry  bundles  between 
which  extend  delicate  connective- 
tissue  septa,  continuous  with  the 
general  envelope  investing  the  nerve- 
trunk.  The  medullary  substance 
being  wanting,  the  pale  fibres  are 
of  small  size  and  often  possess  a 
diameter  of  less  than  .001  mm. 

The  Ganglia The  cell- 
bodies  of  the  neurones  that  consti- 
tute the  sensory  pathways  within  the 
peripheral  nerves  and  of  tho  neu- 
rones  of  the  sympathetic  system 
are  collected  at  various  points  into 
aggregations  known  as  ganglia. 
Fam".  examples  of  t'le  latter  are 
thr  .,pinal  ganglia  on  the  posterior 
roots  of  the  spinal  nerves,  certain 
cranial  ganglia  (as  the  frtsserian 
connected  with  the  fifth  nerve,  the 
Voustic  with  the  eighth,  and  those  on  the  tnmks  of  the  seventh,  ninth  and  tenth 
cranial  nerves),  and  the  .sympathetic  ganglia  along  the  gangliated  cords  and  within 
various  plexuses  of  the  sympathetic-. 

A  longitudinal  section  of  a  spinal  ganglion  (Fig,  852),  which  niav  be  taken 
as  a  type  of  such  collections,  shows  the  entire  ovoid  mass  to  be  enclosed  bv  a  fibrom 
capsule  continuous  with  that   ensheathing  the  nerves.      Immediately  bi^neath   the 
capsule  the  ganglion-cells  are  arranged  in  a  fairh  continim,!*  lavor  ofvarvincr  thick 
ness,  while  tlie  cells,  more  deeply  placed,  are  broken  up  into  groups  by  the  tracts  of 


Inter-fascicular 
septum 


Transverae  section  of  small  splenic  nrrve  consisting  chiefly  of 
nonmedullated  fibres.    :■  aoo. 


UHW 


WW1 


1008 


HUMAN   ANATOMY. 


intervening  nerve-fibres,  a  small  amount  of  connective  tissue  prolonged  from  the 
endoneurium  of  the  nerve-bundles  and  accompanying  the  blood-vessels  being  also 


5 


KiG.  852. 


Posterior  root  (Kraory) 


Spinal  cord 


Spinal  ganglion 


Fig.  853. 

Nerve-6bre8,  cut  transversely 
Nerve-cell 


Anterior  (motor)  root 

Common  trunk  of  spinal  nerve 
Anterior  division 

Section  of  spinal  nerve,  showinn  its  roots,  jtanxliun.  common  trunk  and  primar>  divisiuns.    X  10. 

present.     The  cliief  ganglion-cells  are  from  .060-.080  mm.  in  diameter,  but  some 
measure   as   much   as  .170   mm.   and   others  as   little   as  .025  mm.     In   sections 

(Fig.  853)  they  usually  appear  round  or  oval, 
since  only  exceptionally  are  their  processes  to 
l5e  seen.  Each  cell  is  enclosed  by  a  richly 
nucleated  capsule  which  is  continuous  with  the 
sheath  of  the  ner\'e-fibres.  Mci  of  the  many 
other  oval  nuclei  that  are  conspicuous  in  sections 
of  the  ganglia  belong  to  the  neurilemiiu  of  the 
ner\'e-fibres  and,  hence,  are  seen  as  chains  e.x- 
tending  in  different  planes.  Although  by  far 
the  greater  number  of  the  ner\'e-cells  within 
the  spinal  ganglia  are  (a)  the  cell-bodies  c)f 
the  sensory  neurones,  whose  processes  course 
within  the  spinal  ncr\ ts,  additional  ner\()us  ele- 
ments are  also  present.  According  to  Dogiel ' 
among  these  are  ib)  cells  of  type  J/,  which, 
while  closely  resembling  tht  chief  neurones  in 
the  form  and  appearance  of  their  cell-bodies, 
differ  from  them  in  possessing  processes  that 
are  confined  to  the  ganglion  and  end  in  fine 
ramifications  over  or  beneath  the  capsules  of  other  ganglion -cells.  The  cell-bodies 
of  the  neurones  of  type  II  are  in  turn  surrounded  by  end-ple.xuses  of  probabl>- 

'  Anatomischer  Anzeiger,  Ud.  xii.,  1896. 


Cainule 


Ner\e(ibres 


Section  of  spinal  KtinKlion,  showing  tierve-ceth 
surrounded  by  nucleated  capsules.    >. 


^^  i 


Dwgram  ol  conMilueiiU  of  spinal  nnglion ;  bloc  lines  reorr- 

SSJ?H!.r"rS^V'''JTB'A''"'^"*''™"j  '*f'PH,  anterior  and 
postcnor  roots;  AD.  PI>.  anterior  and  posterior  primary  divi- 
sions ol  spinal  nerve;  «C,  ramus  commuiiicans.  "•»'>•"" 


DEVELOPMENT  OF  THE  NERVOUS  TISSUES.  1009 

in^t^L  ^^  (^«"-,  f'"a"y  (^)  a  few  multipolar  nenv<ells  are  usually 
ot  the  sympathetic  neurones.  -^v*"-;. 

The  sympaihetugangjia  are  represented  by  those  of  ti.»  great  Kangliated  cords 
SlTtr^if*  ^'*^''*  ^''f^'  .^Pheno-palatine:  otic,  and  submaxillf^f  thrgangiia 
within  the  three  prevertebral  plexuses,  and  the  innumerable  small  and  often  mifro- 
scopic  ganglia  associated  with  the  muscular  tissue  of  the  digestive  respirato^aiTd 
iiro-gemtal  tracts,  in  the  heart  and  in  the  various  glands     '"^^'"'*''  '"P'^^tory  and 

with  thi'lfnLT^'^'  '*"J''"''^  the  sympathetic  ganglia  are  similar  to  ihose  connected  • 
with  the  spinal  nerves,  forming  definite  masses  enclosed  by  a  fibrous  capsule   from 

Tnd     sZr.T''^""T"\P'^"^"'  P^  •"'''  '^^  '"'^""^  °f  the  ganglion  foTtL  sup^rt 
and     separation     of    the    nervous  vv^tf- 

elements.     The  individual    gangli-  Fic;   S54 

on-cells— unipolar,  bipolar  or  multi- 
polar— are  ensheathed  by  nucleated 
capsules  continuous  with  the  neuri- 
lemma of  the  nerve-fibres.  The 
sympathetic  ganglion-cells  are  vari- 
ously related  to  the  terminal  ramifi- 
cations of  (a)  other  sympathetic 
neurones  and  of  {b)  the  neurones 
of  the  central  nervous  system  (by 
way  of  the  white  rami  fibres  or  their 
equivalents).  In  both  cases,  the 
ramification  of  the  nonmedullated 
and  fine  fibre  in  the  one  and  of  the 
medullated  fibre  in  the  other,  a 
pericellular  plexus,  commonly  en- 
doses  the  cell-body.     In  the  lower 

thf  !-^"i'^  (amphibians  and  reptiles),  the  spinal  fibre  frequently  winds  spirally  around 
( Hurf^  '"■t^hI^h"  8*"S  !on-cell  before  breaking  ^  into  the  pericelluhr  pTexus 
(Huber  ).  The  broader  relations  of  the  component  nervous  elements  of  the  spinal 
ganglia  are  considered  in  connection  with  the  Sympathetic  System  (p^e  1354)!^ 

DEVELOPMENT  OF  THE  NERVOUS  TISSUES. 

TecalUhIZ1?hI?»h!'"^°T'  °'  ♦»'^««'•^y  development  of  the  nervous  system  (page  26)  will 
recall  the  fact  that  the  neural  groove,  later  the  net-  al  tube,  is  lined  by  invaginated  .^^icken«l 

ecttiblast  from  which  the  essential  nervous  ti.ssues  are 
derived.  For  the  fundamental  facts  concerning  the  histo- 
genesis of  these  tissues  we  are  in  large  measure  indebted 
to  the  lahors  of  His,  whose  account,  supplemented  by  the 
important  contributions  of  Kolliker,  Cajal,  Lenhoss^k, 
Sch,- .  <r  tnd  others,  forms  the  l>asis  of  our  knowledge 
conct.  ig  these  proces.ses.  Although  in  its  principal 
features  the  histogenesis  is  similar  in  all  parts  of  the 
neural  tube,  in  that  portion  which  becomes  the  spinal 
cord  the  changes  are  most  typical  and  will,  therefore,  be 
here  described. 

During  the  approximation  and  closure  of  the  neural 
tube  the  cells  composing  its  wall  undergo  active  prolife- 
ration, whereby  the  wall,  at  first  composed  of  only  one 
or  two  rows  of  definitely  outlined  cells,  is  converted  into 
a  multinucleated  tract  in  w  hich  the  cell  boundaries  dis- 
appear and  the  nuclei  lie  embedded  within  a  general 
protoplasmic  sheet  or  symrfwrn  (Hardesty»).  The 
large  dividing  elemenU  within  the  latter,  the  germinal 
<;«.~-      J  •.     .    .    .  '"'"'''■' °'H'*' *re  conspicuous  on  account  of  their  mitotir 

figures  and  are  situated  close  to  the  lumen  of  the  neural  tube.     His  regarded  thVrn  m  ^TZ\ 
cell,  directly  concerned  in  the  prtxluction  of  the  neurones,  a  conclusioM^wevir  t^aThX^^I 
'  Jouriidt  of  Morpliologj-,  1099. 
'Amer.  Journal  of  Ana'tomy,  vol.  iii..  1904 
64 


ilm 
Segment  from  lateral  wall  ot  neural  tube 
of  p^  embryo  of  5  mm  ■  syncytium  replacinK 
dlsllhctlv  outlineil  lells.  a.  inner  .one;  / 
^rminal  cells;  ilm.  Internal  limllinir  mein- 
jrane;  w,  peripheral  zone ;  r.  radial  strands 
of  cytoplasm.     <  &»,.    (ffardrslr.) 


f?, 


lOtO 


HUMAN  ANATOMY. 


teen  sustained  (koUiker,  Schaper  and  others)  since  the  primary  germinal  cells  probably  only 
represent  proliferating  elements  engaged  in  forming  what  for  a  time  is  an  undifferentiated  tissue. 
The  cells  composing  the  neural  wall  are  at  first  in  close  contact,  their  blended  cytoplasm 
(synotiumj  forming  an  almost  unbroken  sheet.  Soon,  however,  this  continuity  is  internipted 
in  consequence  of  the  longitudinal  expansion  of  the  tissue  and  the  appearance  of  spaces,  a.  id  the 

r^nrn^"''f  .!f  '*'"  ■"*  ',"*°  "  '■'^''"'^  reticulum,  the  myelospongium  of  His,  which  b,:comes 
condensed  at  the  inner  and  outer  margins  of  the  wall  of  the  neural  tube  into  the  intental  and 
external  Itmiling  tnemorane. 

The  meshes  of  the  reticulum  enlarge,  the  intervening  nucleated  tracts  of  cytoplasm  elongate 
.  and  the  increasing  nuclei  become  radially  disposed.     By  reason  of  these  changes  the  elemfnts 

^  T^D       ,     ','J^  ^"""^  '  ™''"""»'-  'o™  and  radial  arrangement  and  become  the 

primary  ependymal  cells.  The  remaining  elements,  appropriately  named  the  indifferent  cells 
^^^?^^  >l1""^^*  '"  """!!*'  >n  consequence  of  the  continued  division  of  the  germinal  cells  and 
gradually  become  collected  as  the  nuclear  layer  at  some  distance  beyond  the  ependymal  zone. 
theomr^rH  r"f  r'^^"'^'*"?,  P^^'Ph^al  portion  of  the  supporting  framework  adjoining 
the  outer  border  of  the  neural  wall  becomes  denser  and  free  from  nuclei  and  is  converted  into 

p       o  ,  the»Mr^j»a/s«»«<-{Randschleierof 

elm  •     5  •  His),  that  is  continuous  with  the 

delicate  reticulum  per\-ading  the 
other  parts  of  the  wall.  The  in- 
different cells  later  differentiate 
into  (a)  the  spongioblasts  from 
which  the  characteristic  constitu- 
.      ,„^,  .^^^^^      ^^^^ .      ^."^^   of    the   definite   supporting 

fSHFr-4's;^SJij^^^^^^JS£^^^^^^^S^St     tissue,  the  neuroglia,  are  derived, 
iw,,ri.t-^  >\TV^as»*SiSi'^iS— -«5&'^<Sa^^g^     and   (b)  the  ««<»-o4/(uA  that  are 
*         "  *  directly  converted   into  the  neu- 

rones.   Within  the  resulting  cell- 
complex  that  for  a  time  occupies 
the  greater  part  of  the  wall   of 
J-  ..       ■  ,.     .,.  .       .  the  neural  tube,  it  is  difficult  to 

distinguish  with  certainty  between  the  neuroglia  and  neuron-producing  elements,  since  botii 
are  often  elongated  m  shape  and  prolonged  into  processes 

/K  .I^"i°*'?"-'  °^  *'  **'"~«"!t'"  ^^^^^  to  the  extension,  condensation  and  moulding 
(by  the  developing  nerve-cells  and  fibres)  that  die  primary  syncytial  meshwork  undergoes 

Fig.  857. 


p  m  b 

Segment  of  wall  of  neural  tube  of  pig  embryo  of  10  mm 

randit  Irl  nf  ■viicvttiin,  sMrl  .4l0_ran*;..*:«..  „< i _>    ^    . 


"■?"    4  ''■*  ^•"''I'^y""'?  ""1  "'■""entiation  of  ependymal  (a) ,  ,.„t,cr 
...  i/»»,  Wm,  internal  and  external  limiting 


(*)  and  marginal  (»i)  layers; 
membrane ;  g,  dividing  cell ;  p,  pia  mater. 


,  radial 
nuclear 


690-     {//at  drily.) 


IJ 


IH 


I 
f 


^S^^j?s^^zS^;i?^S3Sss?is 


(Hardestyl,  the  gradual  transformation  of  the  spongioblasts  and  their  descendants  into  fibrill* 
establishes  a  more  definite  framework  that  replaces  the  primar%-  net-work  f  myelosponfrium ^  ind 
eventually,  ii>  conjuntlion  with  the  fibriila;  derived  from  the  processes  of  the  ependymal  Mils 


i 


DEVELOPMENT  OF  THE  NERVOUS  TISSUES.  loii 

gives  rise  to  the  definite  supporting  tissue,  the  neuroglia.  According  to  Hardesty  the  irlia-fibres 
ar.se  w.th.n  the  syncytial  tissue  independently  of  the  neuroglia  cells  a  view  i^K  op^kb^ 
totheobservaionsof  Rubaschkin,  who  attributes.to  the  descendants  of  the"  pii^LbE  h" 
gUagenetic  ceUs.  a  positive  role  in  the  production  of  the  fibres.  Accepting  th^  Sticks  ^ 
he  last-named  investigator,  the  successive  stages  of  the  cells  concerned  in  the  prXuon  C 
the  general  neurog liar  tissue  are  represented  by  the  spongioblasts,  the  glwge,utk^^stvL 
"Jtrocytes.  and,  finally,  the  gtia  cells.  The  primary  e^Jy,Hal  ele\nents  fre  ^c^^  by  he 
epi  hehum  which  lines  the  ventricles  and  the  central  canal  of  the  spinal  cord.  Theh^peri X 
n,^^  f  i"'"'^*^  "■;?  '"  ^"^.V^  transformed  into  glia-fibres  and  thus,  along  «^le 
processes  of  the  spider  cells,  contribute  to  the  formation  of  the  neurogliar  elt-work  The 
accompanying  illustration  (Fig.  857),  taken  from  Hardestys  paper,  affords  an  histrucive 
re«'^^r'?r  h"",^  ='PP^r"«  ^  ^^^  >??"«  supporting  tissue'after  Jn,;  staining  ^th  a p^ov^^ 
reagents  (Benda)  and  after  silver  precipitation  methods  (Golgi)  upon  which  so  much  reliant 
e„"^r^h"  P""*"-  The  silver  picture  shows  the  classic  long  „eu'^lia?fibr«  Txtendinnhe 
entire  thickness  bu  fails  to  reveal  the  wealth  of  supporting  tis.sJe  and  nuclei.  To  what 
extent  the  mesoblastic  ingrowths  that  follow  the  penetrating  young  blood-vesseU  in  to  the  nlr^ 
wall  Uke  ^rt  in  the  production  of  the  distinctive  neurogliar  f'^amewor^s  aZi tt^  y  difficuTtTo 
erem™rii"'rSr^ '  ''''  '"'^'  '""''  '°"^^^''  '^""'"''"^  '"  '"^  support'^^fr'S^l'oi: 
Histogenesis  of  the  Neurones.— The  neuroblasts  are  distinguishable  with  certeintv  from  th^ 

gSftrthr^i^teranT  "-^''"^  *''"  — P— •     THe  -7 TpSTot 
peripherally  directed  ends  of  the  f       «  s 

developing  nerve-cells,  invade  the  "''    ' 

marginal  zone,  and  later  emerge 
from  the  wall  of  the  immature 
cord  as  the  ventral  or  anterior 
root-fibres  of  the  spinal  nerves 
(Fig.  858).  The  deeper  tint  of 
their  distal  ends  after  staining, 
their  tendency  to  collect  in  con- 
verging groups,  and  the  uniform 
width  of  the  '>utgrowing  nerve- 
processes  are  distinctive  charac- 
teristics of  the  neuroblasts  ( His ' ). 
The  first,  and  for  a  considerable 
time  the  only  proces.ses  with  which 
the  neurones  are  provided  cor- 
respond to  the  axones  that  be- 
come the  axis-cylinders  of  the 
efferent  (motor)  nerves.  Subse- 
quently other  processes,  the  den- 
drites, grow  out  in  various  direc- 
tions from  the  cell-bodies  of  the 
young  neurones. 

Sthecmn^ite  A^i^.TtK  fi^^^u''''^''^"*^*^^  investigations,  and  the  findings  upon 
ReUius)    "'""P""*'  "'•=°^  "^  'he  fibre  is  based  are  open  to  different  interpretation  (K.illiker, 

The  morr'SoblSs'^a'nd 'ti^/  development  of  the  peripheral  spinal  ner^.es  is  briefly  as  follows: 
th^k^^s  aM  of  S  ZL  h!  ^T^-  *"'"'''  >f«»K"°"-«"''  ^^^  out  pr<Kesses  of  considerable 
n^reasTin  hickne^  a^  le^T  /■'"  '""^  "*  "'^  »''"■■«"'"'<-•''  '"  K^""l«  of  fibritUr,  which 
fibrik      A^  fir^f  .h  T-^  "I''-  '"  '""■"•  «'  *heir  extremities  give  rise  to  new  groups  of 

of  m^sobistic  orS^h^h'fhr  "'''^'''  '"'."^"^''•.  *•"'  """  "^'^^^  surrounded  with  slZk^el 

0  Sr    Af  e  Tne^^  hi  iT^  "'^'-''^  •'^"!:  "^•"*'^o"i'-  "erve,  that  may  contain  hundreds 

pLliferatinir  V^eTth  cenX!^r„  .  "!f  ^T'"^'^  ^^  '"«^°«"^  "'  ""^^  ^''^Is  from  Ix^hind,  the 
proiiitratmg  sheath  tells  begin  to  wander  from  the  periphery  in  amone  the  fihrilla.  nnd  .riv..  ri« 

0I  Lrr^bu  d  eT  "Trrra? ''  -r  ^^!•'«^-Ls7he  .s  t^:^:^^z:^ 

01  secondary  bundles.     The  intrafascicular  cells  increase  rapidly,  the  process  of  subdivision 

I?''  EmwickeUing  des  menschlichen  f.ehirns.  1004 
Amer.  Journal  of  Anatomy,  vol.  ii.,  1903. 


Neuroblans 


Efierent  axones 


v.n.'^lSIILlf.*?,'"*'  ™''<'.<''  liumsn  embryo,  ahowing  development  oT 
u!»"^)  "  '""«™«'"  '■■o"  ventrml  neukibluui.     X  joo. 


IOI2 


HUMAN  ANATOMY. 


I>e\ elcpiiiK   iiileii'uslal    nerve   u(    pig 
*".>.?"'  ""n"'-.;  lipof  nerve  is  composed 


-;"--j :  lipof  nerveisco 

otSbrils  surrounded  by  sheath-cells,   x  360 


(Bard fen.) 


^?,^J^  K  "'*''*  "*  "•'""f  •*«*'»*  P'«P««^ve!y  tmaller  and  more  compact  unUI. 

fib^  enHn^  h'^.k"""""  f""'  ""ey  correspond  to  the  axis-cylindrrs  of  the  individ\i.l  nerve! 
hbrps,  enclosed  by  the  »w*n/m»«a  and  its  cells.    The  endonfuriMtn  appears  comparatively  late 

and,  like  the  neurilemma,  is  a  product  of  the  mesoblast. 
Later,  condensations  of  the  mesoblast  around  the  definite 
bundles  of  nerve-fibres  and  about  the  entire  nerve-trunk 
provide  the  periiteurium  and  the  epineurium  respectively. 
During  its  course  to  the  periphery  the  young  nerve  gives 
rise  to  numerous  branches,  the  points  of  outgrowth  being 
indicated  by  a  preparatory  increase  of  the  peripheral  cells 
which  often  form  a  tubular  projection  into  which  the  nerve- 
librillx  grow.  The  proximal  plexuses  (such  as  the 
brachial  or  lumbar)  are  formed  during  the  outgrowth  of 
the  nerves  from  the  region  of  the  central  nervous  system ; 
the  coarser  distal  plexuses  arise  during  the  extension  of 
.  . -,      .     „  ""^  branches  to  the  various  parts  for  which  they  are 

destmed  ;  whilst  the  finer  tertninal plexuses  are  established  during  the  development  of  functional 

unity  between  the  nerve-fibres  and  the  structures  to  which  they  are  distributed. 

The  tnedullary  sheath  is  a  comparatively  late  acquisition,  since  it  does  not  appear  until 

about  the  fourth  month  of  ftetal  life.     Within  the  central  nervous  system  the  tracts  of  nerve- 
fibres  obtain  their  medullary  coat  at  different  times  (some  not  until  after  birth),  a  variation  that 

IS  of  niuch  service  in  enabling  the  anatomist  to  trace  the  course  of  the  individual  paths  of  con- 
duction.   The  origin  and  method  of  formation  of  the  medullary  substance  has  been,  and  in  fact 

still  IS,  a  subject  of  discussion.     It  is,  however,  certain  that  its  production  is  not  dependent 

upon  the  neurilemma,  since  the  medullated  fibres  within  the 

cerebro-spinal  a.xis  are  devoid  of  this  sheath,  and.  further, 

that  the  myelin  sometimes  appears  before  the  neurilemma 

( Kolster,  Bardeen ).    While  it  is  doubtful  whether  the  myeHn 

is  directly  formed  from  the  outer  part  of  the  axis-cylinder, 

as  suggested  by  Kiilliker,  it  is  probable  that  this  structure 

exerts  some  influence  resulting  in  the  deposit  of  the  myetin- 

droplets  either  from  the  blood  (Wlassak),  or  from  the 

apparently  fluid  substance  that  after  a  time  surrounds 

the  axis-cylinder  (Bardeen).     Regarding  the  formation  of 

\heframeuiori  supporting  the  droplets  of  myelin,  Hardesty' 

inclines  to  the  view  that  certain  sheath  cells,  which  appear 

during  mediillation,  are  probably  concerned.    From  the 

foregoing  account  it  is  evident  that  the  axis-cylinder  is 

derived  from  the  ectoblast  and  the  neurilemma  from  the 

mesoblast;  the  origin   of  the   medullary  sheath   is  still 

undetermined,  but  most  probably  is  mesoblastic. 

Development  of  the  Oanglia.— The  origin  of  the  afferent 

(sensorj)  neurones,  whose  cell-bodies  are  situated  within 

the  spinal  and  other  ganglia,  is  entirely  different  from  that 

of  the  efferent  (motor)  ones  above  described.     In  the  case 

of  the  spinal  ner\es,  the  development  of  the  ganglia  pro- 
ceeds from  a  group  of  ectoblastic  cells  that  form  a  ridge,  the 

ganglion-crest,  on  the  margin  of  either  lip  of  the  still  open 

neural   tube    (Fig.  860),  just  where  the  general  ectoblast 

passes  into  that  lining  the  groove.     On  approximation  of 

the  lips  of  the  latter,  the  cells  of  the  ganglion-crests  fuse 

into  a  wedge-shaped  mass  that  completes  the  closure  of  the 

neural  tube  and  constitutes  a  centre  of  proliferation  from 

which  the  cells  migrate  outward  over  the  dorsolateral  wall 

of  the  tube.    The  proliferation  is  not  uniform  but  most 

marked    at   points   that   correspond    to   the   mesoblastic 

somites,  in  consequence  of  which  a  series  of  segmentally 

arranged   cell-aggregations  appears  on  each  side  of  the 

neiinil    tulie.     These   collections   are   the  anlages  of   the 

spinal  ganglia.     Within  them  certain  cells  soon  become  fusiform  and,  a.ssuming  the  r61e  of 

«eiirohlasts,  seiul  out  a  process  from  either  end.     One  process— the  axone-grows  centrally, 

while  the  other— the  dendrite— extends  peripherally  and  becomes  the  chief  part  of  a  sensory 

nerve-fibre.    The  subsequent  growth  of  the  neurone  is  not  svmmetrical,  but  to  one  side,  and  so 


TraiiftverM  sections  o!  dorsal  reKton 
of  human  embryos,  showing  early  differ- 
eiitjation  of  spinal  RanBlion;  ^,  ^.neural 
tube  still  open;  C,  D,  tube  closeo  i  a, 
KanKlion-riclf^s;  A,  fused  ridaes;  r.  out- 
growth (o  form  KEittglioit :  a.  ectoblast. 
'^  a.v>.     (LemkossH.)  • 


'  Amer.  Journal  of  Anatomy,  vol.  iv.,  1905. 


Fig. 


DEVELOPMENT  OF  THE   NERVOUS  TISSUES.  ,013 

ordered  that  the  two  processes  are  approximated  and  finallv  joined  to  th»  r.11  k^i„  k., 
common  stalk  (Fig  839).  the  neurone  being  thus  conve.JI^'^in'^":^  unij^ar  "n^oV/ell 
The  centrally  direaed  processes,  the  later  posterior  "nipoi.Tr  ganglion-cell, 

root-fibres  of  a  spinal  nerve,  grow  into  the  develop- 
ing cord  and  enter  the  peripheral  zone  (later  the 
white  matter)  to  end,  when  their  development  is 
completed,  at  various  levels  in  relation  with  neu- 
rones formed  within  the  neural  axis.  The  peri- 
pherally directed  processes  of  the  spinal  sensory 
neurones,  on  the  other  hami,  mingle  with  the 
axones  from  the  motor  neurones  to  form  the  mixed 
nerves  distributed  to  the  various  parts  of  the  body. 
The  essential  parts  of  the  sensory  neurones,  the 
cell-body  and  the  processes,  are  derived  from 
ectoblastic  elements,  whilst  the  sheaths,  whether 

of  the  nerve-cells,  of  the  fibres  or  of  the  entire 

ganglion,  are  contributed  by  the  mesoblast. 

The  development  of  the  sympathetic  ganglia, 

which  include  essentially  three  sets— those  of  the 

ganghated  cords,  those  of  the  prevertebral  plexuses 

(cardiac,  solar  and  hypogastric),  and  the  terminal 

—has  given  rise  to  much  discussion.    According 

to  one  view,  the  sympathetic  neurones  have  an 

independent  origin  and  cily  s.  condarily  form  con- 
nections with  the  cerebro-spinal  nerves.     The  other 

view,   on   the  contrary,    regards  the  sympathetic 

neurones  as  the  direct  descendents  of  neurogenetic 

elements  derived  from  the  developing  spinal  nerves 

The  evidence  in  support   of  the   last   view  is  so 

convincing  that  there  is  little  question  as  to  the 

correctness  of  its  principle,  although  many  details 

of  the  process,   as  relating  to  man,  are  still  to 

be  studied.     It  is,  however,  equally  true  that  the 

sympatnetic  ganglia  are  neither  produced  by  constriction  and  isolation  of  parts  of  the  spinal 
Fig.  862.  KaiRlia,  as  sometimes  assumetl. 


.-.t*-™*^,.'**^'''"  ".'  P"'*  "'  'lofsal  reRioii  t,(  human 
embryo,  showing  developinK  s|'">al  fpmgUoii;   rf.-, 

°oM  sl        '">•«■  'P'"*'  8«nitlion  on  dor«l 


nor  by  the  migration  of  fully 
difTerentiateil     ganglion  -  cells, 
but,    as  eniph.-isized    by   N'eu- 
mayer.    from    iinditTerentiated 
neuroblasts  which  unilergo  in 
loco  their  development.     The 
earliest  suggestions  of  definite 
synip.ithetic     ganglia     in     the 
human  embrjo  apiie.ir  aliout 
the    beginning  of    the  soond 
filial  mtMith  as  aggregatii ms  of 
cells  .It  the  distal  ends  of  the 
visceral  r.inii  of  the  developing 
spinal  nerves.    Frrnn  these  itlls 
art-  derived  the  derinite  sympa- 
thetic neiironesofthegaiigliated 
cord,   as  well   as   those  which 
loJNnv  the  mesial  Ingrowth  of 
the  spinal   fibres  for  the   pro- 
fhution  of  the  prevertebral  and 
termin.il  ganglia.     The  lateral 
g-inglia  thus  fomud  c-onstitiiti- 
for  a  time  a  series  of  isol.ited 
nixies  :  snl)seqM  nllv  fhisc  are 
connected  bvtlie  differentiation 
of   sympathetic    axones    uliicb 

efferent  splanchnic  nerves,  whilst  'Ctt^^f^l:^^ 'T^^^:^::::: 


^'•^K^^i.-Krtr^r^'iii.— S^y-'p^^-^ 


IOI4 


HUMAN  ANATOMY. 


NERVE-TERMINATIONS. 
The  terminations  of  the  fibres  composing  the  peripheral  nerves — the  axones  of 
certain  motor  neurones  situated  within  the  cerebro-spinal  axis  and  the  sympathetic 
system  and  the  dendrites  of  the  neurones  of  the  sensory  ganglia — supply  the  means 
by  which  the  various  structures  of  the  body  are  brought  into  intimate  relation 
with  the  nervous  system.  Some  of  these  terminations  transfer  impulses  resulting  in 
muscular  contractions  ;  others  conve]'  impressions  that  produce  various  sensations 
„      -^  (pain,  pressure,  muscle-sense, 

**'°'  "^  temperature).      The    nerve- 

terminations,  therefore,  may 
be  grouped  according  to  func- 
tion into  motor  and  sensory 
endings. 

Motor  NERVE-ENDmcs. 
The  motor  endings  in- 
clude (a)  terminations  of  the 
axones  of  neurones  situated 
within  the  motor  nuclei  of 
the  spinal  cord  and  brain- 
stem that  pass  to  voluntary 
muscle  ;  (3)  terminations  of 
sympathetic  neurones  that 
end  in  involuntary  muscle  and 
(f)  in  cardiac  muscle. 

Endings  in  Voluntary 
Muscle. — On  approaching 
their  peripheral  destination 
the  medullated  nerve-fibres 
branch  repeatedly,  each  fibre 
in  this  manner  coming  into 
relation  with  a  number  of  mus- 
cle-fibres. When  the  med- 
ullated nerve-fibre  reaches  the 


.End- 
plate 


Fig.  864. 


Motor  mrve-cndings  in  voluntary  muscle ;  bundle  of  nerve-fibres  is 
seen  separating  to  supply  the  individual  muscle-fibres.    X  l6o. 

....  ...  ,  "»»<»icu  iici  vc-iiure  reacnes  me 

muscle-fibre  which  it  supplies,  its  medullary  sheath  abruptly  ends  and  the  neurilemma 
becomes  inseparably  fused  with  the  sarcolemma,  whilst  the  axis-cylinder  passes  beneath 
this  sheath  to  terminate  in  an  end-plate.  The  latter  appears  as  an  oval  area,  from 
.  040-.  060  mm.  in  its  greatest  diameter,  which  is  applied 
to  the  muscle-substance  ;  in  profile  it  shows  a  slight 
projection  beyond  the  contour  of  the  muscle-fibre, 
known  as  the  eminence  of  Doye^e.  Embedded  within 
a  general  nucleated  sheet  of  granular  protoplasm,  the 
sole-plate,  lie  the  brush-like  terminal  arborizations  of  the 
axis-cylinder  formed  of  irregular  varicosites  and  club- 
shaped  ends.  From  the  details  of  the  development  of 
the  motor  end  plates,  as  described  by  Bardeen,  it  is 
probable  that  the  granular  sole-plate  and  its  nuclei  are 
differentiated  from  the  sarcoplasm  and  the  nuclei  of  the 
muscle-fibre  respectively.  The  much  discussed  relation 
of  the  end-plate  to  the  sarcolemma — whether  outside  or 
beneath— seems  to  be  decided  in  favor  of  a  subsarco- 
lemmal  position,  since  the  muscle-sheath  appears  sub- 
sequently to  the  formation  of  the  motor-ending,  a  fact 
that  explains  the  apparent  piercing  of  the  sarcolemma 
by  the  axis-cylinder.  I'sually  each  muscle-fibre  is  pro- 
vided with  a  single  motor  end-plate,  which  may  lie  at  an 

equal  or  unequal  distance  from  the  ends  of  the  fibre.     Exceptionally  two  end-plates 
may  be  found  on  one  muscle-fibre,  in  which  case  the  endings  lie  near  each  other. 


Motor  ner\'e.endinr  in  voluntarv 
muRcle;  a,  axone  terminating:  in  enc{- 
plate  ;   fi,  neurilemma  ;   *,  sole-plaie. 

x  400. 


NERVE-TERM  I  NATIONS. 


1015 


Fit;.  ,S65. 


Ncnrr-cndinx  in  involununr 
niucl«.     {//mirr.) 


Endings  m  Involuntary  liuicle.— The  terminations  of  the  a.xoncs  of  the 
sympatheUc  neurones  supplying  the  nonstriatsd  muscle  are  comparatively  simple 
The  neuroncii  contributrng  the  immediate  fibres  of  distribution 
usually  occupy  the  nodal  points  of  plexuses  from  which  bundles 
of  nonmedullated  nerve-fibres  extend  to  and  enclose  the  muscle 
fasciculi.  Entering  the  latter  the  nerve-fibres  divide  into 
delicate  varicose  threads  that  pass  between  the  muscle-cells, 
parallel  with  their  long  axes.  As  they  course  within  the 
mtercdlular  substance,  the  varicose  fibrils  give  off  short  lateral 
branches  that  end,  as  does  also  the  parent  fibre,  in  minute 
terminal  knots  on  the  surface  of  the  muscle-cells,  often  in  the 
vicinity  of  the  nucleus.  Probably  by  no  means  every  muscle- 
cell  individually  receives  a  nerve-ending,  a  longitudinal  group 
including  three  or  four  rows  of  muscle-cells  lying  between 
two  adjoining  terminal  ner\e-fibriU      luber). 

Endings  in  Cardiac  Muscle.— These,  also  the  termi- 
nauonsof  sympathetic  neurones,  have  been  stud.ed  by,  among 
others,  Cajal,  Retzius,  Berkley  and  Huber.  According  to 
the  last-named  investigator,  the  varicose  ner\'e-fibrils  may  be 
followed  between  the  muscle-cells,  during  which  course  side  branches  arise  that,  as 
well  as  the  mam  fibnl,  termmate  on  the  muscle  elements  in  endings  of  varying  com- 
plexity. In  some  cases  these  are  merelv  minute  simple  end-knots,  resembling  those 
found  m  mvoluntary  muscle  ;  in  other  cases  they  are  more  elaborate  and  consist  of  a 
group  of  secondary  fibnllae  bearing  nodular  endings,  the  whole  recalling  somewhat 
the  motor  end-plates  m  striped  muscle.  It  is  probable  that  most  of  the  cardiac 
muscle-cells  are  m  direct  relation  with  nerve-endings  (Huber). 

Sensory  Nerve-Endings. 
Since  the  sensory  endings  are  the   peripheral   terminal   arborizations  of   the 
neurones  whose  cell-bodies  he  in  the  spinal  and  other  sensory  ganglia,  such  teloden- 
dna  are  functionally  the  beginnmgs  of  the  paths  conducting  the  sensory  stimuli  to 
the  central  nervous  system.     According  to  their  relations  to  the  surrounding  tissue 
the  sensory  endings  are  broadly  grouped  into  free  and  encapsulated. 

Free  Sensory  Endings.— These  endings  include  vast  numbers  of  nerve- 
terminations  found  in  the  skin  and  the  mucous  membranes,  chiefly  within  the 
epithelium  but  to  some  extent  also  within  the  connective  tissue  strata.  As  a  rule 
the  sensory  '^ afferent)  ner\'e-fibrcs  do  not  branch  to  any  extent  until  near  their 
peripheral  o  tination,  where  they  undergo  repeated  divisions,  always  at  a  node  of 
Kanvier  and  in  various  directions.  The  medullary  sheath  of  the  main  fibre  is 
retained  unti  close  to  its  termination,  although  some  of  its  branches  may  course 
as  nonmedullated  fibres  for  a  considerable  distance  before  ending  or  entering  the 
epithelium,,  in  the  .:'.  --and  the  same  general  plan  applies  to  the  mucous  mem- 
branes—the fibres  de:.  irted  for  the  epidermis  lose  their  myelin  coat  beneath  the 
basement  membrane  and  enter  the  epithelium  as  vertically  coursing  nonmedullated 

fibrils.  Within  the  epidermis  they  break  up  into 
numerous  delicate  fibrils  which  undergo  further  divi- 
sion into  still  finer  varicose  threads  that  ramify 
between  the  cells  of  the  stratum  germinativum  and 
terminate  in  minute  free  end-knobs  (Fig.  866). 
Although  an  intracellular  position  of  these  nerve- 
endings  has  been  described  by  various  writers,  it 
is  probable  that  the  endings  are  extracellular  and  lie 
upon  the  surface  of  and  not  within  the  epithelial 
elements.  Similar,  but  far  less  numerous,  free  end- 
ings, varicose  and  dub-like  in  form,  occur  within 
,     .  .       ,  t'»*^  connective  tissue  layers  of  the  skin  and  the 

tunica  propria  of  mucous  membranes.  Within  the  integument,  conspicuous  end- 
ramihcations  of  sensory  neurones  surround  the  hair  follicles,  lying  upon  the  outer 
surface  of  the  glassy  membrane.  /    »     r 


Fio.  866. 


Free  sensory  endines  within  epidermis 
01  rabbit ;  in  several  places  ner\e-fibrilli 
terminate  in  end-knobs.    (Doxirl.^ 


ioi6 


HUMAN  ANATOMY. 


Fig.  .S67. 


in!^"L.^.''i'',  "'  ^'^'V  '>'"«  "l">in  inter- 


Junction  of  cpithclmm  and    connective  tiuue 
(»'erMiM«'^*  P«Ming  into  epithelium.    X  160. 


Fig.  «68. 


«r.  ^*";  **'^*"'  'if"'  "'  *««'kel,  found  in  the  deeper  layers  of  the  epidermb. 

represent  a  scmewhat  more  differentiated  form  of  inn^ithelial  termina^ST^ 

suggest  transitions  to  the  more  specialized  end- 
organs.  In  these  endings  the  nerve-fibrils, 
terminate  in  cup-shaped  expansions  or  menisci, 
against  which  rest  the  modified  epithelial  cells. 
The  latter  may  be  regarded  as  an  imperfectly 
differentiated  neuroepilhelium,  examples  of 
which  are  seen  in  the  gustatory  cells  in  the 
taste  buds  and  in  the  highly  specialized  visual 
and  auditory  cells  in  the  retina  and  in  the 
oi^n  of  Corti  respectively. 

Encapsulated  Sensory  Endings.— In 
their  most  highly  developed  forms  these  end- 
mgs  (corpuscula  nervomin  tcnninalia)  arc 
represented  by  relatively  lai^e  special  end- 
organs  in  which  the  terminations  of  the  axis- 
cylinder  are  enclosed  within  an  elaborate 
laminated  capsule.  The  latter,  however,  is 
more  often  present  as  a  much  simpler  and 
thinner  envelope  consisting  of  strands  of  fibrous 

mor7l^^!'\°"J''""*  ^*r^'i  the  intraepiihelial  tactile  cells  above  noted  and  the 

^rinThetrS.!?.?^/^'''''/"^"'^."^'  ^^'^^^  *"''"'  '^^  ^"""^^'ve  tissue,  Tr. 
seen  in  the  corpuscles  of  Grandry  (no    found  in  man 

but  conspicuous  in  the  skin  covering  th  •  *  iil  and  in 
the  tongue  of  many  water-fowl),  in  whi.U  the  nerve 
ends  in  a  disc-like  expansion  enclosed  btlN^een  largt- 
modified  epithelial  cells  and  the  neuromuscular  ami 
neurotendinous  end-organs,  presently  to  be  descrilml 
(page  1020). 

•  ,  T''^  J^''°"P  °'  simpler  encapsulated  endings 
mc  udes  three  well-known  examples  :  the  end-lnilbs 
and  the  genital  corpuscles  of  A'rausc  and  the  cor- 
puscles of  Meissuer,  all  of  which  possess  a  common 
strijctural    plan— interwoven    telodendria   emliedded 

withm  a  semifluid  interfibrillar  substance  ar.d  surrounded  by  a  thin  fibrous  envelope 

The  End-Bulbs  of  Krause.— These  endings 
include  a  variety  of  irregularly  spherical  or  ellipsoidal 
bodies  found  in  the  edge  of  the  eyelid,  the  conjunctiva 
and  corneal  margin,  the  lips  and  the  oral  mucous 
membrane,  the  glans  penis  and  clitoridis  and  probably 
other  parts  of  the  integument  hijihiy  endowed  with 
sensibility.  Within  the  conjunctiva,  as  described  bv 
Dogiel  ,  they  he  superficially  placed  within  the  con- 
nective tissue  near  the  summit  of  the  papilla  and 
folds,  when  such  elevations  e.xist,  but  always  close 
beneath  the  epithelium.  They  vary  considerably  in 
size,  often  being  small  (.002-.004  mm.),  but  some- 
times measuring  from  .05-10  mm.  in  diameter, 
l  sually  a  single  ner\  e-fibre,  exceptionally  two  or  even 
more,  enters  each  bull),  losing  its  medullary  she:ith  as 
it  pierces  the  thin  fibrous  capsule  Within  the  latter 
the  nerve,  now  represented  bv  the  naked  axis-cylinder, 
divides  into  from  two  to  four  branches,  which,  after 
c,    .,      ,  .  desrribine:   several   ann^!l.^r  or  spiral  turns    ^ive  off 

iTs^Ttricatfj';''  ">K-''^t  further  division,  the  terminal  threads  forn^ing  a  more  or 
less  intricate  maze  within  the  semifluid  substance  enclosed  by  the  fibrous  capsule. 
'Archivf.  mik.  Anat.,  B<l.  xliv.,  1S95. 


Two  corpuscles  ol  Granilry  froi, 
bill  of  duck;  nerve  is  seen  enterini: 
corpuscle  on  ri|tht.     X  J«5. 


Fig.  869. 


>  cnd-bulhs  of  Krause  from  human 
conjuTiitiv.T.     iDogiW.t 


I 


Fig.  871 


G«niul  corpudTlr  from  interunwnt 
01  peni* ;  nerve  divides  before  piercinc 
capsule  and  lerminates  in  inlricale  eiid- 
windings.    ( Dofirl. ) 


Gcniul  rotpuscle  from  Inieg- 
umeiil  ul  human  i  litoris.     .    iQ, 


NERVE-TERMINATIONS.  ,0,7 

to  »hJ5,!.?*"*-n-'  Corpu.clet^These  endings,  most  numerous  (from  on.  to  lour 
InH  Tf^""  millimeter)  m  the  deeper  strata  of  tl,e  corium  covering  t»,e  glans  penis 

rr"r4utl!i  t'STeS^*^  '"  ^"^  ""«•''-""«  ^  ^'  »'''«--•«•  ^  ^ 
oudine  an  J  from  .02  to  .35  F'c-  8to. 

mm.  in  diameter.  They 
present  the  same  general 
architecture  as  the  end- 
bulbs,  but  are  of  larger  size, 
possess  a  somewhat  thicker 
capsule,  and  contain  a  more 
intricate  interlacement  of 
the  termi.nal  nerve-fibrillie. 
The  latter  are  derived  from 
the  subdivision  of  two  or 
three  medullated  fibres  that 
enter  near  the  base  nf  the 
corpuscle  and  are  beset  with 
varicosities  and  club-shaped 
terminal  enlargements. 

t™lf  ^TJJ"  '^P'"'*.'  5°"»«''"S  °[  *^v«"'  connective  tissue  lamell*  possessing  flat- 
whS.  h  "T  "J!^'-*'  ^"'^'"^  the  semifluid  or  granular  interfibrilbr  substance  in 
which  the  cnd-arbonzations  are  embedded. 

roH„I*!ff  !;°T"*''"°^**u  ".*"*'— '"   '"^"    ""^«=   ^'^  niost   numerous   in   the 
conum  of  the  skin  covering  the  flexor  surface  of  the  fingers  and  toes.     Thev  are  also 
found  m  other  regions  possessing  sensibility  in  a  high  degree,  such  as   the  £ 
margin  of  the  eyelid,  nipple,  penis  and  clitoris,  as  well  Is  onThe  dorsum  of  the  ha^d 

and  foot  and  the  radial  surface  of  the  forearm 
On  the  volar  surface  of  the  distal  phalan.x  of  the 
fingers,  where  they  occur  in  greatest  numbers, 
*^^  twenty  are  found  to  the  square  millimeter 
(Meissner).  The  corpuscles  occupy  the  summit 
of  the  papillae  and  ridges  of  the  connective  tissue 
stratum  of  the  skin,  and  lie  close  beneath  the 
cuUcle.  with  their  long  axes  perpendicular  to  the 

ir^'^-j'"  ^^^'^   ^^^^  ■'"■^   elongated    irregular 
ellipsoids,   often   somewhat   sinuous   in    outline 
and  in  the  larger  papilla-  mav  be  joined  at  the 
deeper  end  with   others   to   form    a   compound 
corpuscle.     They  are  relatively  large,  l)eing  from 
.12-  18  mm.  long  and  about  one-third  as  wide 
Depending  upon  the  size,  each  corpuscle  is  sup- 
plied by  one  or  more  nerve-fibres  which  enter  in 
the  vicinity  of  the  base,  as  the   deeper  end   is 
called,  and,  on  piercing  the  cajjsiile  and  losing 
the  medullary  sheath,  divide  into  a  nuinlKr  of 
naked    axis-cylinders.      These    pass    across   the 
corpuscle  in  parallel  or  spiral  windings  and  are 
beset   with    fusiform    and    pvriform    v.iricnsities 
similar  enlargements  marking   the   ends  of   the 
temiin.il  threads.     The  entire  fibrillar  interlace- 
ment IS  cmbeddetl  within  a  semifluid  substance 
and  enclosed  by  a  thin  nucleated  fibrous  capsule. 

I      r        1     . . .      .  '^^^  Corpuscles  of  Ruffini  — These  emi- 

ings  are  also  found  with  n  the  skin  but  if  Hrr-t^r  U,-^!=    „  ,m       i  '"^^e  emi 

the  subro'ium      Thp„  ,r„    ^  1  "*""•  .  ^  ^^  ncepor  levels,  near  and  sometimes  wiilim 
n  len^h^^^.i     f     ^  x  '"Y^*'  T""'  sometimes  measuring  as  much  as  1.  ,,  mm. 

in  length    and  o    an  elongated  fusifqrm  contour.     The  iien'e-fibres    often  tAvon; 

t^m;:!^.'!!  r"T"rJf "  "^^  ^'^j?^"'^  °"  '^^  '^^''  '-«  '^^^^^^^hr  near  ^ne  end     e  a  in 
the  medullary  sheath  for  some  distance  after  penetrating  'the  capsule  and  throughou" 


Fig.  872. 


Corpuscle  of  Meissner  lying  within  papilla 
pi  conum  of  skrii  from  fiiiRer;  only  deeper 
layers  of  overlying  epidermis  are  shown ;  », 
enleriiii;  iierve-hbre.     <  370. 


IOI8 


HUMAN  ANATOMY. 


Fig. 


Cylindrical  end-bulh  Irom  con- 
nective tiuue  layer  of  skin.  X  180. 
iSiymoMowicx.) 


a  number  of  bold  curves  and  twistings.  After  the  disappearance  of  their  sheaths, 
the  naked  axis-cylinders  undergo  repeated  divisions,  the  resulting  tibrilia;  becoming 

varicose  and   intertwined  and   ending  in  free  terminal 
knob-like  enlargements. 

In  contrast  to  the  foregoing  end-organs,  in  which 
the  axis-cylinder  subdivides  into  numerous  terminal 
threads  disposed  as  more  or  less  elaborate  inter  rvtinings, 
a  second  group  is  distinguished  by  the  possession  of  a 
thick  lamitMted  capsule  that  encloses  a  cylindrical  core  or 
inner  bulb  containing  the  slightly  branched  axis-cylinder. 
These  endings,  of  which  the  Pacinian  corpuscle  is  repre- 
sentative, are  relatively  large  and  ellipsoidal. 

A  transitional  form,  connecting  them  with  the 
spherical  end-bulbs,  is  presented  by  the  cylindrical 
end-bulbs  of  Krause.  These  are  found  in  various 
parts  of  the  corium,  the  oral  mucous  membrane  and 
between  the  bundles  of  striped  muscle  and  of  tendon. 
,       ,  ...      ^^^y  ^^^  irregularly  cylindrical  in  form,  often  more  or 

ICM  bent,  and  consist  of  a  thin  laminated  capsule  that  encloses  a  core  of  semifluid 
substance  in  which  lies  the  centrally  placed  axis-cylinder.  The  latter,  after  losing 
the  medullary  sheath  on  entering  at  the  proximal  end  of  the  capsule,  traver^ss  the 
core  without  branching  until  near  the  distal  pole,  where  it  ends  in  a  single  or  sliehtly 
subdivided  terminal  enlargement. 

The  Vater-Pacinian  Corpuscles.— These  structures,  the  most  highly  special- 
ized sensory  end-organs,  are  relatively  large  ellipsoidal  bodies,  from  .05-.  15  mm  in 
length  and  about  one-third  as  much  in  breadth,  situated  within  the  connective  tissue 
m  many  parts  of  the  body. 

In  man  they  are  found  in  Fig.  874. 

the  deeper  layers  of  the  '* 

connective  tissue  layer  of 
the  skin,  especially  on  the 
palmar  and  plantar  aspects 
of  the  fingers  and  toes,  in 
the  connective  tissue  in  the 
vicinity  of  the  joints,  in 
tendons,  in  the  sheath  of 
muscles,  in  the  periosteum 
and  in  the  tunica  propria 
of  the  serous  membranes, 
the  peritoneum,  pleura  and 
pericardium.  They  are 
particularly  large  in  the 
mesentery  of  the  cat,  where 
they  may  be  readily  de- 
tected with  the  unaided  eye 
as  oval  pearly  bodies  some- 
times two  millimeters  or 
more  in  length. 

The  most  conspicuous 
part  of  the  Pacinian  body 
IS  the  robust  capsule  that 
constitutes  almost  the  en- 
tire bulk  of  the  corpuscle 
and  consists  of  from  one 
to  three  dozen  thin  con- 
centric hmella'  i>f  fijiroiis 
tissue.     The  surfac  es  of  the 

lamellae  .lie  covered  with  endothelial  plates  whose  nuclei  appear  as  fusiform  thicken- 
ings, along  the  concentric  stria-  of  the  corpuscle.     The  axis  of  the  Pacinian  body 


Vater-Pacinian  corpuKles  Irom  titin  of  child'a  finiter 
Iranavertc  wction '  -  ' ' 


.  ._...  ., _  .  ..,.,,, ,   A.  lonrttndlnal 

nerve  entering  capsule  to  reach  inner  bulb. 


1 8s- 


NER  V  E-  i  £r_ 


VTIONS. 


1019 


tl,«  n*^!?  ^T"*^K^  "'■"^I'V^'  Po'e  of  the  corpuscle,  the  fibrous  (Henle's)  sheath  of 
the  nerve-hbre  blends  w.th  the  outer  lamella,  of  the  capsule,  while  the  medu  larv 
coat  ,s  retained  during  the  somewhat  tortuous  path  of  the  tibre  through  the  capS 


Fig.  875. 


t^^SSS'^S^''^^'^^'^^^^^^ 


through  the  core,   being  as 
the  naked  axis-cylinder.     At 
a  variable  distance  but  often 
just  before  gaining  the  distal 
poi'    of  the  core,  the  axis- 
cylinder   divides    into    from 
two  to  four  branches,  each  of 
which  terminates  in  a  slightly 
expanded  end-knot.     Some- 
times shortly  after  penetrat- 
ing the  capsule,  the  nerve- 
fibre  splits  into  two  or  more 
axis-cylinder      which     then 
share  the  common  envelope 
of  semifluid  axial  suh»tance. 
Similar  end-organs,  the 
corpuscles  of  Herbst, 
occur   in    the   velvety  skin 
covering  the  bill  and  in  the 
tongue  of  wa^er-fowl.     They 
closely  resemble  the  Pacinian 
bodies  of  mammals,  but  differ 
in  being  generally  smaller,  relatively  broader,  and  in  exhibiting  a  row  of  cubic-,1  cell, 
withm  the  core  and  around  the  axis-cylinder.     These  cells  are  regard Lh, J 

'""'T^Gc^ii  M*^^  ^^"-^  ^"^'"^'"^  '^^  tactile  JjsT^inlKrSt  CO  p^^^^^ 
.f  ^  J  fi  Golg'-Mazroni  corpuscles,  found  in  the  subcutaneous  tiLsue  o^the  nuTn 
fro^  ^h  f  .?•  ^-^  '""'»"'«''«"«  of  'he  ordinary  Pacinian  end-organs  ThevC 
LTanchedSs!yindT'"^'"^  ''^''  '^'"^"*'  ^  ^'^^'-'^  '^^^  --  aS^i  ZT. 
NeuromuBcuJsir  Endiiigs.-First  described  by  Kblliker  and  bv  K,lhn„ 
although  previously  seen  by  Weissmann.  these  end-o^rgalis  Sen  termid  ^t^.' 
^dUs,  are  now  regarded  as  sensory  endings  that  are  prSly  c^"cJrnTd1n^fford" 
ing  impressions  as  to  tens  on  or  "  mnsrlp  «»t,c-»  ••      xu     T  ^  ^Y.      "      "'  ^nord- 

Undtnoits)  end-organs  have  been  demonstrated  ^  ^  """^^ 

»  may  a.  tw™,y.  ..riped  m^&uS,.  mSSttSTnt  blS-i™;^  "nTSr 
spersed  connective  t  ssue.     These  intrafusal  ifA^^r    L»  .iT  if^     .^P    '"'^'^" 

tUe  of  the  surrounding  muscTe  irSr^rT  ,'„,=li       ''  ![-^  ""'=''•  ^"^"  f^'"" 

equah)nal  region  than  near  the  poles  of  the  spindle  ^  diameter  m  the 

The  intrafusal  fibres  collectively  are  surrounded  hv  a  thin  .,,-^i,i 
t.„„,  ^,.„„p,.  ,He  a.rial  sHcaih,  b/twe.n  wh^a^d  Se  L'X  Shr;"riS 


t030 


HUMAN  ANATOMY. 


Nerve-Abn 


Capsule 


lymph-space.  Each  spindle  receives  usually  severa!  medullated  nerve-fibres,  which, 
after  incorporation  of  their  sheaths  of  Henle  with  the  capsule,  pierce  the  latter  at 
various  points  and  proceed  to  the  individual  muscle-fibres.  The  terminal  relations 
of  the  nerves  to  the  intrafusal  fibres  have  been  studied   by  means  of  the  newer 

methods  especially  by  Ruffini, 
Huberand  DeWittand  Dogiel. 
After  repeated  division  during 
their  course  through  the  cap- 
sule and  periaxial  space,  the 
ner^'e-fihres  pierce  the  axial 
sheath,  lose  their  medullary 
coat  and  terminate  either  as 
one  or  more  ribbon-like 
branches  that  encircle  the  mus- 
cle-fibres in  annular  or  spiral 
windings,  or,  after  further 
subdivision,  as  branched  telo- 
dendria  in  which  the  ultimate 
fibrils  end  in  irregular  spherical 
or  pyriform  enlargements. 

Neurotendinous  End- 
ings.— These  end-organs, 
described  by  Golgi  and  sub- 
sequently more  fully  investi- 
gated by  Kolliker,  Ciaccio,  and 
Huber  and  DeWitt,  in  their 
general  architecture  resemble 
closely  the  sensory  endings  in 
muscle.  They  lie  embedded 
within  the  intrafascicular  con- 
nective tissue  and  are  usually 
found  in  the  vicinity  of  the 
junction  of  muscle  and  tendon. 
Like  the  neuromuscular  end- 
ings, the  tendon-spindles  are 
long  fusiform  structures,  from 
I. -1. 5  mm.  in  length,  sur- 
roimded  by  a  fibrous  capsule. 
The  latter  encU)ses  a  group  of 
from  eight  to  twenty  intrafusal 
tendon  fasciculi,  which  are 
smaller  and  apparently  less 
niaturi-  than  those  of  the  sur- 
rounding tendon-tissue.  The 
intrafus;ii  fasciculi  are  invested 
by  a  fibrous  axial  sheath  be- 
tween which  and  the  capsule 
\\w<  a  periaxial  lymph-space. 

On  reaching  the  spindle, 
after  repeated  branching,  the 
medullated  nerve-fibres  pene- 
trate the  capsule,  with  which 
their  fibrous  ( Henle's )  sheaths 
blend,  and  undergo  further 
division.  The  medullary  coat  is  lost  after  they  pierce  the  axial  sheath,  the  naked  axis- 
cylinders  breaking  up  into  smaller  fibrils  that  extend  along  the  intrafusal  fasciculi.  The 
terminal  ramifications,  applied  to  the  surface  of  the  fasciculi,  vary  in  details  (Huber). 
Some  arise  as  short  lateral  branches  that  partly  encircle  the  fasciculi  and  end  in 
irregular  plate-like  expansions,  while  other's  terniinatc  between  the  smaller  fasciculi. 


Nerve-fibre 


A,  neiironili!ii:ular  endirii;;  B,  iicnoteMdltiMUs  emlliiK  in  tnnKitudi- 
nal  wi'tlnn,  mrlhyliMichluestainiiii;  .■'lo.  (  Drawn  (rum  (ircpiinUoii 

niadt'  iiy  Professor  Ihiliei   i 


THE  CENTRAL  NERVOUS  SYSTEM. 

.    theJn.^T^y'l  "^'°"'  T'J""  '"^'"'^'^  "'^  ''P'"^'  '^"'■'l  «"d  'h*-  brain.   In  principle 
these  parts  are  to  be  regarded  as  the  walls  of  the  primary  neura/  tube   niodirted  bv 

rir\hT;:in"'orr'?°".'  """'  --  nfter'acqui^g  their  dt^nr'r'etu l.ns 
enclose  the  remains  o  the  canal,  as  represented  l)v  the  system  of  ventricular  si.  ires 
In  contrast  to  the  spinal  segment  of  the  neural  tube,  which  always  en^^s  TX 
tiv^'y  simple  cylinder  the  spinal  cord,  the  cephalic  segment  earlydilTere  ttes  i  o 
three /r/«,ar,-  cerebral  vesicles,  the  anterior  and  posterior  of  which  subdivide  ^.^ 
hve  secondary  brain-vesicles  are  present.  Coincidendy  marked  flex  ire  o  lu 
cephalic  segment  occurs  at  certain  points  and  in  consequence  this  ilrt^^f  the  neurd 
tube  becomes  bent  upon  itself  to  such  a  degree  that  the  a.xis  of  the  anterior  es  cle 
lies  almost  parallel  with  that  of  the  spinal  segment  (Fig.  9,2  F  om  heT^' 
r  WdetS  t  '^  ^  •'*  sinuously int  ceUalic Lgment  of  "h™^^ 

uescnoea  ( page  1060)  whiU  .  relatively  straight  sp  nal  segment  proceeds  the 

?he  oriS llln'  '"^r^::-  '"  ^'^''^^  P™'^^  grcfwth':.nd  diffemuE  ctv 'r 
Ilir^  •  ^'  "''"-^»"«'  t"l^  '"t»  •'«n  almost  solid  cylinder,  the  minute  central  cina 
alone  remaining  as  the  representative  of  the  once  conspicuous  lumen 

THE  SPINAL  CORD. 

cerebm-sDtd*'axl'''^aS"r'*  "PI"-"''^ '^  ^^at  part  of  the  central  ner^•ous  system,  or 
cereoro-spina^  axis,  which  lies  within  the  vertebra  canal.  Its  UDoer  limit  wher..  if 
becomes  continuous  with  the  medulla  oblongata,  is  in  a  meite'^'^nvSnal  sCicl 
AcrnrLfT  '*^'"^''^^*'°"  «"  '^^  «^«rd  itself  to  indicate  exacdy  its  junc^n  wShe'brLin 

posterior  arch  of  the  atlas.  For  practical  purposes,  however  the  lower  marain  ot 
cord  rr  •"«?""■".  ^f"^,*"h  sufficient  ac^y  the  upp^  hmn  t^rSna 
cord.     Below,    he  spinal  cord  terminates  somewhat  abruptly  in  a  no  nted  en7 Thj 

fuXr'^^S:"  The  levl'r  -?^«Pr''^'•'^  ^^  betE Ve  K'fnd'loJd 
uimDar\ertebr».     The  level  to  which  the  cord  extends  inferiorlv  however  ii  s..hi...f 

astTot^c^meT^  rSi  ^T  T'y  •"'T  «''  '^'«''  ^  '''^^^^^  of  th^^y  JK 
tht  luX  Jerteb^^V  W°a!;S  "j"  ^'T  -  ^  "RP^r  border  of  the  b<Kl^f  the 
absolutely  shorter  thin  in  »K*^^i  \  '^'"'*'^  '"''J^'''  "«^  "?'"'»'  ^^^^'  although 

can^  V^^Trk^H  L  .^"  '*'1'"«'^  *'''te"ds  to  a  relatively  lower  level  in  the  vertebral 
co?c1  duKJo^J'fll"?  °'  "'"  'P'""-  P,''^"""  ^'*'''  ^\xLr:^or.^  in  the  position  dtS 
rX  i',.n  T/k         f       i°"  ""  »PP'"e<^"»t     iiscent  of  the  lower  end  taking  place     The 

nil  roH^nl  I^^^^^  ctr"''"''^'  '^r'  ^^"•".'''  ^'"^^•^"^  periods.  Suhe  thi  d 
Sumo  th!  more  .l^i  n      ^^"P"-"^  the  entire  length  of  the  canal,  but  subsequently. 

«  7  cm   (17  H   n  )   in  LTh  L        1  ""^  ^'^"•^'^  °'  '♦S  cm.  ( 17}^  in. ).  and  in  the  fcM.mIe  of 

lion  to  stature,  althoueh  in  a  «neral  w«J^im' h-  "J'  1  <^°f''-''^"f<»h  Inars  no  consta.u  rela- 
"f  the  spinal  cord  stripped  of  hsmZf^rlJ  '"'"T''"'''''  •"!">■  P**^**^^  '""«  '•>'"''*•  The  w.iKhl 
(.  o«.).  or  about  .-^^^KCvwH^hritrn^  somethInK  less  than  30  grammes 

When  tresh  th.  spina,  «.rd  ^^^^  c;;^^*^i^i;;:tu';;^i,c!fi;!"S;  !^  '^^. 

lOJI 


I022 


HUMAN   ANATOMY. 


Fig.  877. 

JH^-^^Jx'       Medulla 


Pedicles,  cut . 


'.^M 


•Lamina;,  cut 


to  Transverse 

processes 


Pedicle** 


-Dural  iheath 


C^ 


If'^ 


XII  T- 


-//■ 


Pedlcles< 


.  End  of 

dural  sheath 


Posterior 
divisions  of 
sacral  nerves  4 


Sheath  of  filuni  - 


End  of  filuni 


-Coccyx 


Si.injil  cord  encloM.1  in  unopened  duml  sheath  lyine  within 

™h  Liu'^'n""!"  .'  ;■•""'  ""'r  ™,n'l'l«'l>  re>novedonriShls,le, 
partialiy  on  left,  to  c«|)os<-  dorsal  aspect  of  dura:  first  and  last 

netAvsofcervical.lhoracic.lun,h,rnnd.acr!!U.-,>,,=  =rrindir,i«t 
b>  Italic  fiKuresi   corresponding  vrrtebnr  by  Roman  numerals 


Th^  Membranes  of  the 
Cord. — The  spinal  cord,  together 
with  the  roots  of  the  thirty-one  pairs 
of  spinal  nerves,  lies  within  the 
vertebral  canal  enclosed  by  three 
protecting  membranes,  ormeninges, 
which,  from  without  inward,  are  (i ) 
the  dura  mater,  (2)  the  aracAnoidea, 
and  (3 )  the  pia  mater,  all  of  which 
are  directly  continuous  through  the 
foramen  magnum  with  the  corres- 
ponding coverings  of  the  brain. 
The  external  sheath,  or  theea,  formed 
by  the  dura,  is  a  robust  fibro-elastic 
tubular  envelope,  much  longer  and 
considerably  wider  than  the  cord, 
that  does  not  lie  against  the  wall  of 
the  vertebral  canal,  but  is  separated 
by  an  interval  containing  thin-walled 
plexiform  veins  and  loose  fatty  con- 
nective tissues  (Fig.  879). 

The  dural  sheath,  about  .5 
mm.  in  thickness,  extends  to  the 
level  of  the  second  sacral  vertebra 
and  is,  therefore,  considerably  longer 
than  the  spinal  cord.  The  part  of 
the  sac  not  occupied  by  the  cord 
encloses  the  longitudinal  bundles 
of  root-fibres,  that  pass  obliquely  to 
the  levels  at  which  the  correspond- 
ing ner\es  leave  the  vertebral  canal, 
and  a  fibrous  strand,  the //urn  ter- 
minate, prolonged  from  the  cord  to 
the  lower  end  of  the  spine. 

The  pia  constitutes  the  imme- 
diate investment  of  the  cord  and 
supports  the  blood-vessels  destined 
for  the  nutrition  of  the  enclosed 
ner\ous  cylinder.  The  pial  sheath 
is  composed  of  an  outer  fibrous 
and  an  inner  vascular  layer,  the 
connective  tissue  of  the  latter  ac- 
companying the  blood-vessels  into 
the  substance  of  the  cord. 

The  arachnoid,  a  delicate  veil- 
like structure  made  up  of  interfacing 
bundles  of  fibro-elastic  tissue,  lies 
between  the  other  two  membranes 
anil  invests  loosely  the  inner  surface 
of  the  dura  and  closely  the  outer 
surface  of  the  pia.  It  effectually 
subdivides  the  considerable  space 
between  the  external  and  internal 
sheaths  into  two  compartments,  the 
one  beneath  the  dura,  the  subdural 
spate,  being  little  more  than  a  capil- 
lary cleft  filled  with  modified  lymph, 
and  the  other,  the  sutnirar/inoid 
space,  between  the  arachnoid  and 


THE   CENTRAL   NERVOUS   SYSTEM. 


loaa 


The  spinal   cnrcl.    therefore,    haiurs 


Fig. 


Arachnoid 

\'ertehral 
artery 

Molulla 


the  pia,  containinjr  the  cerebrospinal  fluid. 
suspended  within  the  tube  of  dura, 
surrounded  by  a  cushion  of  fluid— 
an  arrangement  well  adapted  to  insure 
the  nervous  cylinder  against  the  inju- 
rious effects  of  shocks  and  of  undue 
pressure  during  changes  in  the  position 
of  the  spine.  Both  spaces,  but  par- 
ticularly the  subarachnoid,  are  crossed 
by  fibrous  trabecule  and  thus  imper- 
fectly subdivided  into  secondary  com- 
partments, all  of  which  are  lined  with 
endothelium. 

The  spinal  cord  is  fixed  within  the 
loose  dural  sheath  not  only  by  the  root- 
fibres  of  the  spinal   nerves   that   pass 
between  the  cord  and  the  outer  envelope 
but  also  by  two  lateral  fibrous  bands,  the 
ligatnenta  denticulcUa,  that  are  continu- 
ous with  the  pia  along  the  cord,  one  on 
each  side.     Mesially  they  are  attached 
between  the  anterior  and  posterior  root- 
fibres  and  externally  to  the  inner  surface 
of  the  dura  by  the  tips  of  pointed  pro- 
cesses,  about  twenty-one  in  all,    that 
stretch  across  the  subarachnoid  space 
which   they  imperfectly  divide  into  a 
general  anterior  and  a  posterior  com- 
partment.    The  ligaments,  covered  by 
prolongations  of  the  arachnoid,  extend 
the  entire  length  of  the  cord,  the  first  pro- 
cess being  attached  to  the  margin  of  the 
foramen   magnum,   immediately  above 
the  vertebral  artery  as  it  pierces  the  dura. 
The  succeeding   ones   meet   the  dura 
between  the  pairs  of  spinal  nerves,  the 
lowest  process  lying  between  the  last 
thoraac  and  the   first  lumbar    nerve. 

In  the  cervical  and  thoracic  region,  a  — ^  r-».  >.u,».,u  lu  aiirm. 

median  fibrous  band,  the  septum  posticum,  connects  the  posterior  surface  of  the  cord 

Fig.  879. 

jjgi,_  Spliwl  cord 

*  '  Potterior  root 


Spinal  coni, 
covered  with 
arachnoid 
and  pia 

1,.   l!?'*''  I*"^  P'  'P'™'  «"•<!  within  dural  shrath  which 


Dural  aheath 
PerioMeum 


Ligamcntum 
denliculatum 


Extradural 

areoLir  tlsiuc 


Anterior  root 


i^pinal  ganitlion 


Spinal  I 


Vertehral  artery . 

Bo<ly  of  fourth  ccrvic  il  vertebra  ^  ._         - ,^ 

Tranave:  be  aFctiim  r»f  ^'^rtehral  -ana!  ai  •       •  *  *  r        i.  .     . 

""  •"™'  "  "•'^'  °f  fnonh  cervical  vertebra,  •pinai  conl  ir  poaitloi, 

With  the  dura  and  partially  subdivides  the  subarachnoid  space.    Lower,  thi.  partition, 


I034 


HUMAN  ANATOMY. 


Flu. 

880. 
i 

Skull— ^ 
V^rtebnil  artery— -j 

it^^» 

^Medulla 
— --/  en 

Spinal           'C-^ 
accessory  nerve 

Pedicle*,  cut  <;^ 

i 

^"Spinal  accessoo' 

-;,Edg,of       "'"<= 
•^     cut  dural  sheath 

V  en  — 

^i\ 

E 

— Spinal  cord 

XCM 

IT  — 

1  In  — 

M 

^K^^=: 

l-IT 
— itii 

Pedicles  < 


Pediclea- 


Sln^ 


-Edge  of  cut 

dural  bheath 


•  Spinal  cord 


-End  of  conus 

niedullaris 


-Filum  terminale 


Posterior 
divisions    of  . 
aacral  nerves  V 


1' 


End  of  dural 
sheath 

.  J  sn 


-Filum  externum 
-Oi 


Posterior  »-all  of  vertehral  canal  hat  h<-en  removed  and 
aural  sheiilh  opened  to  expose  spinal  cord  atirt  cl„r«al  rooj. 
otaiuihetl  iieiveni/  < «,  I  C.  firni  cervical  nerve  and  vctttbra 
rwiwilivelyi  Cn,  coccyxeal  tiervea. 


which  may  transmit  blood-vessels,  is 
imperfect  or  altogether  absent.  As 
they  cross  the  subarachnoid  space  the 
bundles  of  root-fibres  of  the  spinal 
nerves  are  enclosed  by  prolongations 
of  the  pia  and  arachnoid.  These 
sheaths  are  retained  by  the  nerves  for 
only  a  short  distance  after  the  latter 
receive  an  additional  investment  froni 
the  dura  as  they  leave  the  vertebral 
canal.  The  dural  sheath  becomes 
continuous  with  the  epineurium  of  the 
spinal  nerves. 

The      Cord-Segments.— 
Although  no  suggestion  of  such  sub- 
division is  to  be  seen  as  constrictions 
on  its  surface,  in  principle  the  spinal 
cord  consists  of  a  series  of  segments, 
each   of   which   gives  origin    to   the 
anUnor  {motor)  and  receives  t\\e pos- 
terior   (sensor}-)   root-fibres    of    one 
pair  of  spinal  nerves.     These  ner\es, 
usually  thirty-one  pairs   in    number, 
are  classified  as  eight  cervical,  twelve 
thoracic,  five  lumbar,  five  sacral,  and 
one  coccygeal.    Corresponding   to  the 
attachment  of  the  nerves  the  cord  is 
conventionally  divided  into  cervical, 
thoracic,  lumbar,  and  scural  regions. 
Of  the  entire  length  of  a  cord  measur- 
ing 43  cm.,  approximately  10  cm.,  or 
about  23.5  per  cent.,  belonged  to  the 
cervical  region;  24  cm.,  or  55.5  per 
cent.,  to  the  thoracic;  6  cm.,  or  14 
per  cent.,  to  the  lumbar;  and  3  cm., 
or  7  per  cent.,  to  the  sacral  region. 
The  spinal   ner\es  are  attached 
to  the  lateral  surfaces  of  the  cord  by 
fan-shaped  groups  of  anterior  and  pos- 
terior root-fibres  that  are  gathered  into 
compact  strands  as  they  converge  to 
form   a  common   trunk    (Fig.  884). 
The  portion  of  the  spinal  cord  with 
which  the  root-fibres  of  a  spinal  nerve 
are  connected  constitutes   its  cord- 
segment,  the  limits  of  which  lie  in  the 
inter\'al  separating  the  extreme  fibres 
of  the  ner\'e  and  those  of  the  adjacent 
nerves.     In  the  thoracic  cord   these 
intervals  are  very  evident,  since  the 
segments  are  relatively  long  ;  in  the 
cervical  and  lumbar  regions,  on  the 
contrary,    the   groups   of   root-fibres 
are  so  crowded  that  they  form  almost 
unbroken  rows. 

The  leiiRth  of  the  individual  cord- 
segments  varies;  thus,  according  to  the 
tiicrtsurcmcnts  of  Liiderit/,  lliose  of  tiie 
cervical  region,  are  from  11-13.5  mm.; 


THE  CENTRAL  NERVOUS  SYSTEM. 


1025 


Fio.  881. 


those  of  the  thoracic  re- 
gion from  12-26  mm.,  the 

longest  belonging  to  the 

V-VII    thoracic  nerves; 

those  of  the  lumbar  region 

rapidly  decrease  from  15.5 

-5.5  cm.,   followed   by  a 

more  gradual  diminution 

to  less  than  4  cm.  in  the 
sacral  region. 

In  consequence  of  the 
disproportion  between  the 
length  of  the  spinal  cord 
and  that  of  the  vertebral 
canal,  the  discrepancy  be- 
tween the  level  at  which 
the  nerves  are  attached 
to  the  cord  and  that  of 
the  intervertebral  foramina 
through  which  they  leave 
the  canal  becomes  more 
marked  towards  the  lower 
end   of    the  series.    The 

growth  of  the  cord,  how- ,„„,„ 

ever,  is  not  unifom,  since,  as  shown  by  Pfitzner.  during  the  later  years  of  childhood  elongation 


Bundles  nt 

nerve- fibres 

Duial  sheath 

Extradural 
areolar  tissue 


vert5ira"'m^i'J"i?'!  2l  *«"«''™'  '?'«'"■  «t  level  of  middle  of  first  lumhar 
w'Ih1S"i2|ThMth  medull.ri.),su:  rounded  by  nerve-bundl™,  i.^n 


Fig.  882. 


~Conu8 


Riedullaris 


•Descending 
spinal  nerves 

Front  wall  of 

dural  sheath 
■Filum  internum 


•Coccyx 

End  of  spinal  cord  with  roots  of  lower  nervo  ■■•»...  j 
'  S  i»,  1-3  "•,  CH,  lumbar,  aacral  and  cocc>|«al  netv«. 


of  the  thoracic  region  occurs  to  such  an  extent 
that  this  part  of  the  cord  once  more  equals, 
if  indeed  not  exceeds,  the  corresponding 
portion  of  the  spine.  While  the  cervical  cord 
keeps  fairly  abreast  the  cervical  portion  of 
the  vertebral  LX>lumn,  the  lumbar  and  sacral 
segments  are  left  far  behind.  The  results  of 
these  changes  are  seen  in  the  course  of  the 
root-fibres,  which  in  the  neck,  below  the  third 
nerve,  run  somewhat  downward  to  their  points 
of  emergence,  and  in  the  thoracic  region  pass 
more  horizontally,  while  those  of  the  lumbar 
and  sacral  nerves  descend  almost  vertically 
for  a  considerable  distance— in  the  case  01  the 
last  sacral  nerve  28  cm.  (Testut)— before 
reaching  their  appropriate  levels. 

The  large  and  conspicuous  leash  of 
descending  root-fibres,  seen  upon  open- 
ing  the   dural    sheath,    constitutes   the 
Cauda  equina,  in  the  midst  of  which 
the  glistening  silvery  filum  terminale 
is  distinguishable.      It  is  evident,  there- 
fore, that  in  most  cases  the  level  of  the 
cord-segment  and  that  of  the  vertebra 
bearing  the  same  designation   do  not 
correspond.     likewise,  it  must   be  re- 
membered that,  although  in  general  the 
spinal  nerves  are  named  in  accordance 
with    th'    vertebrjE  immediately   below 
which  they  escape,   in  the   neck  there 
are    eight    cervical    spinal    nerves    and 
only  seven  vertebrae,  the  first  or  sub- 
occipital  nerve  emerging   between   the 
atlas   and    the   skull,   and    the  eighth 
between  the  last  cervical  and  first  thoracic 
vertebra ;  hence,  except  the  last  one,  they 
correspond  with  the  vertebra  below. 


I026 


HUMAN  ANATOMY. 


Form  of  the  Cord — After  removal  of  its  membranes  and  the  root-fibres,  the 


Fig.  883. 


Medulla 


Cervical 


Thoracic 


Lumbar 


f-acral 


CcKCVKWll 


Filum 


spinal  cord  is  seen  to  differ  from  a  simple  cylinder  in 
the  following  respects.     It  is  somewhat  flattened  in  the 
antero-posterior  direction,  so  that  the  sagittal  diameter  is 
always  less  than  the  transverse  diameter,  and  its  oudine 
in  cross-sections,  therefore,  is  not  circular  but  mpre  or 
less  oval  ;   its  width  is  not  uniform  on  account  of  two 
conspicuous  swellings  that  are  associated  with  the  origin 
and  reception  of  the  large  nerves  supplying  the  limbs. 
The  upper  or   cervical   enlargement   ( intumescentia 
cervicalis)  begins  just  below  the  upper  end  of  the  cord 
and  ends  opposite  the  second  thoracic  vertebra,  having 
Its  greatest  expansion  at  the  level  of  the  fifth  and  sixth 
cervical  vertebrae,  where  the  sagittal  diameter  is  about 
9  mm.  and  the  transverse  from  13-14  mm.     The  lower 
or  lumbar  enlargement  (intumescentia  lumbalis)  begins 
opposite  the  tenth  thoracic  vertebra,  slightly  above  the 
origin  of  the  first  lumbar  nerve,  and  fades  away  in  the 
conus  medullaris  below.     It  appears  very  gradually 
and  reaches  its  maximum  opposite  the  twelfth  thoracic 
vertebra,  where  the  cord  has  a  sagittal  diameter  of  8. 5  mm. 
and  a  transverse  diameter  of  from  1 1-13  mm.  (Ravenel). 
The   lumbar  enlargement   is  associated  with  the  great 
nerve-trunks  supplying   the   lower   limbs.     The    inter- 
vening part  of  the  thoracic  region  is  the  smallest  and  most 
uniform  portion  of  the  cord  and  is  almost  circular  in  out- 
line.   Where  least  expanded,  opposite  the  middle  of  the 
thoracic  spine,  the  cord  measures  8  mm.  in  its  sagittal 
and  10  mm.  in  its  transverse  diameter.     These  enlarge- 
ments appear  coincidentiy  with  the  formation  of  the  limbs, 
are  relatively  small  during  foetal  life,  and  acquire  their 
full  dimensions  only  after  the  limbs  have  attained  their 
definite  growth.     In  a  general  way,   a  similar  relation 
between  the  size  of  the  enlargements  and  the  degree  of 
development  of  the  limbs  is  obser\'ed  in  the  lower  animals. 
At  the  tip  of  the  conus  medullaris  the  spinal  cord 
is  prolonged  into  a  delicate  tapering  strand,  the  filum 
terminate,  that  consists  chiefly  of  fibrous  tissue  con- 
tinued from  the  pia  mater  and  invested  by  arachnoid. 
It  extends  to  the  bottom  of  the  pointed  and  closed  end 
of  the  dural  sac,  which  it  pierces  at  the  level  of  the  second 
sacral  vertebra  and,  ensheathed  by  a  prolongation  of  dura 
(vaj^ina  terminalis),   as  the  Jilum  terminate  externum, 
proceeds  downward  through  the  lower  end  of  the  sacral 
canal  for  a  distance  of  about  8  cm.  (3^  in.),  finally  to 
be  attached  to  the   periosteum  covering  the  posterior 
surface  of  the  coccyx.     The  part  within  the  dural  sac, 
they?/«w  terminate  internum,  is  about  16  cm.  (6«^  in.) 
in  length  and  surrounded  by  the  ner\e-bundles  of  the 
Cauda  equina  (Fig.   882),  from  which  it  is  readily  dis- 
tinguished by  its  glistening  silvery  appearance. 

The  upper  half  or  less  of  the  internal  filum  contains  the 
ferminal  part  of  the  central  canal  of  the  spinal  cord  walled  by 
a  thin  and  variable  layer  of  nervous  sulwtance  in  which  small 
nerve-cells  are  usually  present.  The  minute  bundles  of  nerve- 
fibres  often  found  adhering  to  the  filum,  which  sometimes  may  be 
fnllnwed  to  and  even  thmuiih  the  dural  sheath,  are  lenardeU  by 
Rauber  as  representing  one  or  two  additional  (second  and  third) 
coccygeal  nerves,  homologous  with  the  caudal  nerv  es  of  the  lower  animals. 


V 


spinal  rtird  denuded  of  mem- 
branes and  nerves,  showinK  pro- 
portions of  its  leiiKth  rnntributed 
ny  flifTer?nt  reKJim*-  and  position 
and  relaHvesizeof  cnlarftcments.as 
viewed  from  before ;  semidiaKram- 
niaiir.  ha«ed  on  measurements : 
one-third  actual  size. 


THE  CENTRAL   NERVOUS  SYSTEM.  ,027 

The  Columns  of  the  Cord. -Inspection  of  the  surface  and  particularly  of 
cross-sections  of  the  spinal  cord  (Fig.  885)  shows  the  latter  to  be  pallially  divided 

m  H  H„?l!lh^';?'^T^''\T'*  u^  ^^  ^y  "  •""*^"  *^'*f»  •"  '^«"'  ""d  a  partition  in  the 
midline  behind.  The  cleft,  the  anterior  median  fissure  (essura  m^iana  anterior) 
e.xtends  the  enure  length  of  the  cord,  and  is  continued  on  the  upper  part  of  the 
filum  tenninale.  It  is  mirrow,  from  2-3.5  mm.  in  depth,  penetrating  for  less  than 
one-third  of  the  ventrodorsal  diameter  of  the  cord,  and  occupied  by  a  process  of 
pia  mater.  Along  its  floor,  which  lies  immediately  in  front  of  the  white  commissure. 
It  is  frequently  deflected  to  one  side  of  the  mid-line  and  presents  a  slight  expansion 
The  separation  into  halves  is  completed  by  the  posterior  median  septum 
(septum  mediaaum  posterlus),  the  so-called  posterior  inedian  fissure  With  the  ex 
cepdon  of  a  shallow  groove  in  the  upper  cervical  cord,  the  lumbar  enlargement  and 
the  conus  medullans,  no  fissure  exists,  but  in  its  place  a  dense  partition  extends  from 
the  posterior  surface  to  the  middle  of  the  interior  of  the  cord,  ending  inclose  relation 
to  the  gray  commissure. 

.!=»■  ^*  '*ar»'^«''  °f  the  septum  is  a  subject  of  dispute,  according  to  some  anatomists  con- 
sisting excliBiyely  of  condensed  neur^lU,  while  others  regard  it  a.s  composed  of  pial  ti™ue 
blended  with  the  neuroglia  and.  therefore,  of  both  mesoblastic  and  ectoblas^c  origin  The 
latter  view  is  substaiiuated  by  the  mode  of  development  of  the  posterior  septum,  the  immature 
pial  covering  of  the  deve  oping  blood-vessels  being  imprisoned  within  and  fused  with  ThVneC! 
n^har  partition  denved  from  the  expanding  dorsal  halves  of  the  developing  cord  (page  loso) 
The  application  of  differential  stains  also  demonstrates  the  composite  nature  of  the  septum. 

E^ch  half  of  the  spinal  cord  is  further  subdivided  by  the  lines  along  which  the 
root-fibres  of  the  spinal  nerves  are  attached.  The  root-line  of  the  dorsal  (sensory) 
fibres  is  relatively  straight  and  narrow,  and  marked  by  a  slight  hirrow.  the  postero- 
lateral  sulcus  (mIcim  lateralis  posterior)  that  lies  from  2.5-3.5  mm.  lateral  to  thr- 
posterior  septum  and  is  evident  even  on  the  intereegmentol  intervals  where  the  root- 
fibres  are  practi«lly  absent.  The  ventral  root-line,  marking  the  emergence  of  the 
antenor  (motor)  fibres,  is  much  less  certain,  since  the  bundles  of  fibres  of  the  indi- 
vidual nerves  do  not  emei^e  in  the  same  vertical  plane,  but  overlie  one  another  to 
some  extent,  so  that  each  group  occupies  a  crescentic  area,  whose  greatest  width  cor- 
responds in  a  general  way  with  that  of  the  subjacent  ventral  horn  of  gray  matter 
The  anterior  root-line,  which  lies  from  2-4  mm.  lateral  to  the  median  fissure  is 
neither  indicated  by  a 

distinct  furrow  nor  con-        -  Fio.  884. 

tinuous. 

In  this  manner  two 
longitudinal  xxi    s,  the 
posterior     columns 
(fuaiculi  posteriores)  are 
marked     off    between 
the    posterior    median 
septum  and   the  sulci 
of  the  posterior  root- 
lines.     These  columns 
include  something  less 
than   one-third  of    the 
circumference    of    the 
cord,    and    are   about 
6  mm.  in  width  in  the 
thoracic  cordand  8  mm. 
and  7  mm.  in  the  cervi- 
cal and  lumbar  enlarge- 
ments   respectively. 
The     tracts     included 


■Medulla 


on  4  nerve 


l>i)tsiil  rcxrts  of  5  cerv.  ner\'e 

.l,-.ViPP*-5J''  "'  'P'.""'  "f"! viewed  (rom  behind  .fler  partial  removal  of  dnral 
S^«KV.?."ltT?"f*""  *Jf  '"dicmted  bv  group,  of  convergViK  bun.lle,  of  port,r"r 
IS^.^.^.IiJEL"'''  *■".«"*  •"  '•'J.  ">''"«  *'"''''  '••«  int"venebfal  foramina; 
•pinal  accenory  nerve  ia  seen  aacending  on  each  aide. 

between  the  dorsal  and  ventral  root-linos  constitute  the  lateral  columns  (funiculi 
laterales)  and  those  between  the  ventral  root-lines  and  anterior  median  fissure  are  the 
antenor  columns  (funiculi  anteriores).     Such  subdivision  into  anterior  and  lateral 


I 


I038 


HUMAN  ANATOMY. 


riefi'nite^Hi'r^T"  V^  """l"^'  ^"^^  "'''»^"  superficiaUy  nor  internally  is  there 

reeLd^  f^ToS  "  ^'*^"  ''"^  "■''^'"-  'T'^^y  "«y  ^'  therefore,  conven=-nUy 
regarcled  as  forming  a  common  antero-lateral  column  that  on  each  ^iH^  P^mK.^-3 
something  more  than  two-thirds  of  the  semicircumf"7ence  of  the  cord  In  th^  1^^ 
Z:'^\Tfy^r  '''°"'"'  '^"^'^l  ^'"^  I^'^rior  colunm  is  suW.Vided  by  I  shSw 
ZrTrJ^A-  ?'"  '5-^  """•  '»'«-■'•»'  to  the  posterior  medium  septum      Thifth^ 


Fig.  885. 


■Pwterior  median  Mptum 


Anterior  median  fiaanre       Anterior  column 


Anterior  white  commiuure 


matter  forms  a  comma-shaped  area,  the  broader  end  of  which  lies  in  front  and  the 
narrower  behind,  with  the  concavity  directed  laterally.  The  convex  surfaces  of  the 
tracts  of  the  two  sides,  which  look  towards  each  other  and  the  mid-l.ne  ^re  crnnected 
extend^ ■^"^^"^•^^?^*y  "^T'  '^^  K^ay  Commissure  (commisLra  griS  that 
d^«m.tr  '■°!f  '^^'"«l-»'f  •  "«.»«"y  somewhat  in  advance  of  the  middTof  fKg  tt^ 
diameter,  and  encloses  the  minute  central  canal  of  the  cord  Bv  th.r™^?;^ 
connecting  band,  or  central  gray  matter,  is  divided  into  a  doiSi  an/a  ven^TLrt 
tK^l'^TivTly.  '  "'^"'■^'■''■y  ^-'-■--.  which  lie  behind  and  in  fronToHS' 
.     While  the  posterior  median  septum  reaches  the  dorsal  surface  of  th^  ot^«  nr.^ 


*^ 


Fk;.  8X6. 


THE  CENTRAL  NERVOUS  SYSTEM.  ,029 

Each  crescent  of  gray  matter  is  divisible  into  three  parts— the  ventral  and  the 
dorsal  extremity,  that  project  beyond  the  transverse  gray  commissure  and  constitute 
the  anienor  Md  posterior  horns  or  comua  of  the  gray  matter  (columnae  eriseae)  and 
the  iHtermediateportion  (pars  iotermedia)  that  connects  the  cornua  and  receiv^  the 
commissure  The  two  horns  differ  markedly  from  each  other  and.  although  varyine 
in  details  in  different  levels,  retain  their  distinctive  features  throughout  the  cord 

The  anterior  cornu  (columna  urisea  anterior)  is  short,  thick  and  rounded"  and 
separated  by  a  considerable  layer  of  white  matter  from  the  surface  of  the  cord  throuirh 
which  the  ventral  root-fibres  proceed  to  their  points  of  emergence  in  the  root-arei 
Ihe  blunt  tip  of  the  antenor  horn  is  known  as  the  caput  cornu,  r,nd  the  dorsal  por- 
Uon  by  which  it  joins  the  commissure  and  the  pars  intermedia  c^s  the  basis  cornu 

The  posterior  cornu  (columna  grisca  posterior)  presents  a  marked  contrast  in 
Ijeing  usually  relatively  long,  narrow  and  pointed,  and 
in  extending  peripherally  almost  to  the  postero-lateral 

sulcus.     The  tip  or  apex  of  the  dorsal  horn  is  formed 

of  a  A-shaped  stratum  of  peculiar  character,  the  sub- 

sUntia  gelatinosa  Rolandi,  that  appears  lighter  in 

tint  (Fig.  885)  and  somewhat  less  opaque  than  the 

subjacent  and  broader  portion  of  the  horn,  caput  cornu, 

which  it  covers  as  a  cap.     More  ventrally  the  posterior 

horn  is  usually  somewhat  contracted,  to  which  portion 

the  term,  cen>ix  cornu  (cervix  columnae  posterioris)  is 

applied.     In  the  lower  thoracic  cord,  however,   this 

constriction  is  replaced  by  a  slight  bulging  located  on 

the  mesial  side  of  the  junction  of  the  posterior  cornu 

with  the  gray  commissure.  This  enlargement  corres- 
ponds to  the  location  of  a  longitudinal  group  of  nerve- 
cells  constituting  the  column  of  Qarke. 

The  fairly  sharp  demarcation  between  the  gray 

and  white  matter  is  interrupted  along  the  lateral  border 

of  the  crescent  by  delicate  prolongations  of  gray  matter 

into  the  surrounding  lateral  column  (Fig.  888).     The 

subdivisions  of  these  processes  unite  to  form  a  reticulum 

of  gray  matter,  the  meshes  of  which  are  occupied  by 

longitudinally  coursing  nerve-fibres,  the  whole  giving 

rise  to  an  interlacement  known  as  \\\^  processus  -r  for- 

matio  reticularis.     Although  to  some  extent  present 

in  the  greater  part  of  the  cord,  this  structure  is  most 

marked  in  the  upper  cervical  region,  where  it  exists  as 

a  conspicuous  net-work  filling  the  recess  that  indenu 

the  lateral  border  of  the  pars  intermedb  and  the  neck 

of  the  posterior  horn  of  the  grav  crescent.     In  the 

thoracic  and  upper  parts  of  the  cervical  cord,  therefore 
in  regions  in  which  the  enlargements  are  wanting,  the 
formatio  reticularis  is  condensed  into  a  compact  process 
of  gray  matter  that  is  directed  outward  (Fig.  885)  and 
known  as  the  lateral  cornu  (columna  latc-ralis). 


Diagram  showing   amount  of 
and  while  Rialtcr  in  rrla.iun  In  i 


Taken  as  a  whole,  the  gray  matter,  which  in  cross-sections 
appears  as  the  H-shaped  area  fomied  bv  the  two  crescents 
and  tfie  commissure,  constitutes  a  continuous  column  whose 
irregular  contour  depends  not  only  upon  the  peculiar  disposi- 
tion of  the  p;ay  matter,  but  also  upon  the  variations  in  its 
amount  at  Different  levels  of  the  cord.  Thus,  at  the  level  of 
the  third  cervical  nerve  the  gray  matter  constitutes  somewhat 
more  than  one-fourth  of  the  entire  area  of  the  rord :  at  that  of 
the  seventh  nerve  about  one-third,  while  in  the  thoracic  region 
between  the  seojnd  and  eleventh  nerves,  it  is  reduced  to  abiut  one-sixth     At  the  hst  thoracic 

^■;"ctL^^Xs^r«S^S:'rer         ^^'^  ^'l  «"^  '-bar^wolfiffhltJ-Thrt^S 
respectively,     in  the  sacral  cord  the  relative  amount  of  gray  matter  increases  until,  at  the  level 


Kray 

■■--.' 7 —  .—  ■^.— ■"..  ...  entire 

area  ol  cotil,  an>l  relative  lenifths  oi 
aird-segmcnn;  the  latter  are  iriilicated 
by  divisions  on  left  margin  of  figure— 
'  C,  IT,  I  L.  1  S,  first  seKmenl  ofcer\  i- 
ral,  thorac'c,  lumbar  and  sacral  rej(ions 
respectively;  itark  lone  nex»  left  bor- 
der represents  the  gray  matter,  light 
lOne  the  white  matter,  outer  dark  loni- 
the  entire  area  of  cord.    IDoKa.'Js.m.i 


I030 


HUMAN   ANATOMY. 


« ith^^  .hi  ^  nerve  It  reaches  three-fourths.  The  absolute  amount  of  gray  matter  is  neatest 
^^«  sun^^r  K™*.'";::^'^''''^"'™"'  °*  '^  '°"^'  ^^"^  *»  '*  ^irec^y  delated  to  thelai^e 
fo^r^!^  ,?^  '^T^  *^'  u'".'^-  ^  co-nparing  the  tracts  ol  white  matter  and  the  gray  column  it 
^ tw  .h  "^  "^''V"  ^  '"*"  '^'"^  °^  ^^  '""''«^  ~'<1  'hese  are  of  approximately  eW^  area 
h!^  .h  LT'  ""^  ^^"^  """"''  ^''°*^"'  "^  *»"««•  '"  'h«  '«maining\egions  on  rt^  othe; 
f,^m  "f  ™rf 'f  Tn  '  P;.'^""!'"*"^'  '"  ""^  K^^'"^'  "•■•«  "'  'he  thoracic  L^exceerng  tL  Jray 
Jrom  four  to  five  fold  and  m  the  cervical  cord  bemg  from  two  to  Uiree  times  greater. 

tr«luT*'fK^'"*"*  Canal—Where  well  represented,  the  central  canal  (canalis  cen- 
trails),   the  remains   of   the  once  conspicuous  neural    tube,  appears  L  a   minme 
opening  ,n  the  gray  commissure,  about  .2  mm.  in  diameter  and  hard  vvisiblTSh 
the  unaided  eye      In  the  child  it  extends  the  entire  length  of  the  cord  and  tlow 
ends  bhndly  m  the  upper  half  of  the  filum  terminale.     aSvc.  it  o^ns Tnto  the  lo^er 

hdf  o    thet'^nir"^;''''  ''°'"  ^^'l^  "  ?^  P'-°'°"^«'  downward^hrough  the  K^ 
slwL   K  •  °^'°"»^^  '"^".the  spinal  cord.     In  not  over  one-fifth  of  adult 

subjects,  however,  is  the  canal  retained  as  a  pervious  tube  throughout  the  cord   its 
umen  usually  being  partially  or  completely  obliterated  for  'onger  or  shorter  stretches 
the  lumen  l^t  disappearing   in    the  lower  part   of   the   cord.     Within   the  conus 
tw"i^*'  *'^* ''^"H;*'  ^'Pa'  regularly  e-xhibits  an  expansion,  the  sinus  terminalis 
i.,o^'"^  ^u"^  the  ongin  of  the  coccygeal  nerve  and  extends  caudally  for  from 
«-io  mm.,  with  a  maximum  frontal  diameter  of  i  mm.  or  over. 

middIHrfe°™l'ri,°!  't  ''^"'SL"'"''  ~'"P'f'^'"  "«»"'  50  per  cent,  of  subjects  beyond 
U  effi^,-H  K^^  f  *•  °  ^  '^^"^^  ""  a  physiological  accompaniment  of  advancing  age.  It 
don  ^  MnX^^f  7Tif "'  '""^  P™  ""«"°"  of  the  ependyma-cells  limng  the  canal,  in  c^njunc- 
^n  in  cr^^^tlnl  U^  ^"""•"^^"K  neurogliar  fibres  ( Weigert).  The  form  of  the  canal,  as 
^h  Jh  "P»^-f  Stj"""' 's  veO'  variable  and  uncertain  owing  to  the  changes  incident  to  the  use 
smaneJr.Lt"hoLiir  •'^'■"""'  *''^  "^"  well  preserved  the  lumen  is  round  or  ovafand 
e^an^m^n  ?.^T  ^'T  \ '"  ^""^  ^^'""^'  "^  '"  ""e  upper  cervical  cord  and  in  the  lumbar 
miv^^M  f  laiKer  and  often  appears  pentagonal  in  outline,  whilst  in  others  the  calibre 
X,i^  ^.1,  V  f^'-'j^l'""- .  The  position  of  the  cemral  canal  varies  at  different  levX  n 
rela  ion  to  the  ventral  and  dorsal  surfaces  of  the  cord.  In  the  middle  of  the  lumbar  reefon  i" 
occupies  approximately  the  centre  of  the  cord,  but  above,  in  the  thoracic  and  cervicalsegments 

Hn^l  w  "^T:  '^  ^^"'"'  '^^"  ""=  '^°'^'  ='"^»"-  ^hile  below  it  gradually  app  oaXsle 
dorsal  surface,  but  always  remains  closed.  FP'"-"^"e*  me 

»™,  JJe"«'"n  may  be  made  of  a  remarkable  structure  named  Reusne^'s  fibre,  after  ite  discov- 
erer that  as  a  longitudinal  thread  of  great  delicacy  lies  free  within  the  cental  can  Jo   iheTord 

r  lowJsT^rt  of  Tht."'  f^  '"f  lir '^"'?i-"J^  '^^  "«=  "^"y  "'  '"e  mesencephalon  ab^ve  o 
L^Jh!^  T"  he  cord-canal  below.  The  interpretation  of  this  structure  as  an  artefact 
which  considering  its  extraordinary  position  is  most  natural,  seems  untenable  in  view  of  the 
positive  testimony  confirming  its  existence  as  a  preformed  and  true  structure  in  n.anv 
vertebrates,  given  by  several  subsequent  observers  and  especially  by  Sargent  -  Its  na  ure  and 
significance  are  probtematic.  Although  the  existence  of  thiTfibre  has  l*en  eubl  shed  i,  many 
vertebrates,  even  in  birds,  it  has  not  yet  been  discovered  in  man.  * 

MICROSCOPICAL  STRLCTIRE  OF  THE  SPINAL  CORD. 

The  three  chief  components  of  the  spinal  cord— the  nerxe-cclls,  the  iktv e-fibres 
and  the  neuroglia— vary  in  proportion  and  disposition  in  the  white  an.i  gray  matter 
It  IS   therefore   desirable  to  consider  the  general  structure  of  the  cord  Wore  describ- 
ing Its  detailed  characteristics  at  different  levels. 

//T**/*  °'"*^  Matter.--Tlie  most  distinctive  elements  of  the  ywiv  n.atter  are  the 
multipolar ner-.e-cells  which  he  embedded  within  a  coi..,,lex  sponge-like  rnatri.^  formed 
by  the  various  p.ocesses— dendrites,  axones  and  collaterals— from  other  i-.eurones  the 
supporting  neuroglia  and  the  blood-vessels.  In  two  loc^Iities-immdi  .teK  around  the 
central  canal  and  capping  the  dorsal  cornu— the  grav  matter  vari.-s  in  its  anpeanince 
and  constitution  and  exhibits  the  modifications  peculiar  to  the  central  and  Rolandic 
substantia  gelatmosa    the  details  of  which  call  for  later  description    page  10^4) 

The  nerve-cells  of  the  anterior  horn  are  multipolar,  in  .-rnss-sections  the 
cell-ixxlies  appe  iring  irregularly  polygonal  and  in  longitudinal  section.-;  fusiform  in  out- 


'  Bulletin  of  Harvard  Museum  of  Comp.  Zoology,  vol   xl\ 


1904. 


MICROSCOPICAL  STRirTlRK    OF  SPINAL   CORU.  ,03. 

line.  They  may  vary  from  .065-.  1^=,  i„  .iuineter,  unless  unusually  small  when  thev 
measure  from  .030-.080  mm.  (  K..ll.ker  1.  Ju  a  typical  e.xample,  as  rer.resented  bv 
one  of  the  ventral  radicular  celU  jriving;  orifiin  to  anterior  root-fibres,  from  three 
to  ten  dendritic  processes  radiate  in  various  planes,  divide  dichotomouslv  with 
decreasing  width  and  hnally  end  in  terminal  arljorizations.  In  contrast  to  therobust 
dendrites  beset  with  spines,  th^  i.xone  is  smooth,  slender  and  directly  continuous 
with  the  axB-cyhnder  of  a  r»i.,.  i  bre  of  a  spinal  nerve  and  unbranched,  with  the 
exceptions  of  delicate  lateral  pr.Kesses  that  are  given  off  almost  at  rij;ht  anules  These 
processes,  the  collaterals,  arise  at  a  variable  distance  from  the  cell-b.jdy,  but' usual! v 
close  to  the  latter  and  always  before  leaving  the  gray  matter.  They  rcix-atedly 
divide  and  follow  a  recurrent  course  within  the  anterior  horn.  After  apt)r<>i)riate 
staining  the  cytopUsm  of  the  nerxe-cells  exhibits  conspicuous  accumulations  of  the 
deeply  staining  tigroid  substance  that  lie  within  the  meshes  of  the  reticulum  formed  bv 
delicate      neurofibnlla-,  ' 

the   cell-body  but  also 
extend  into  the  various 
processes.    The  fibrillie, 
however,    do   not   pass 
beyond  the  limits  of  the 
neurone  to  which  they 
belong  (Retzius).    Each 
nerve-cell    possesses    a 
spherical   or  ellipsoidal 
nucleus,    from  .010  to 
.020  mm.  in  its  greatest 
diameter,   which  is  en- 
closed    by    a    distinct 
nuclear  membrane  and 
usually  contains  a  single 
nucleolus,  exceptionally 
two  or  three.     Within 
the  cytoplasm  an  accu- 
mulation   of    brownish- 
yellow  pigment  granules 
is  usually  present  near 
one  pole,    often   in  the 
vicinity  of  the  implanta- 
tion   cone    from   which 
the  axone  springs. 

In  addUion  to  the  con- 
spicuous ventral  radicular 
cells  above  described,  the 
anterior  horn  contains 
other  ner\'ous  elements, 
some  of  which,  the  com- 
missural cells,  send   their 

XrlheTLrf!.,/r''"°'™'""''r'*l''*''^°P''°''''^  ■''"•■  "'  'he  cord,  while  the  axones  of 
opS  side  "'''  '"'"  *'"'  ''°'""'"'    °'  ^^'"^^  ""•""  "f  ^^"^  *""'^'  '""  frequentU 

,„.    •^''t  """"'""f*'  .««"».  which  with  few  exceptions  occupy   the  median  portion  of  tho 
anlenor  honj,  resemble  m  size  and  contour  the  radicular  cells,  but  differ  from  thnXr  i  V  s- 

^C^lx^^^rZt)-     ^■'^  '"'•''^"•^  "'  '•"^  '''■"''"«"  -^^  ^i^^""^''  '"^"^'''^  the  inner    .a  . "  , 
whif.  mllr     Th         """^  ^^^  '"'    "-^^  ^'■''  ^"-"missure  and  a  few  end  within  the  adjacent 
white  matter.     The  axones  traverse  the  anterior  white  commissure  to  gain  the  vt  ..r.,I  column 
'he  opposite  s,rle.  in  which  they  e-.-,.r  divi.-fe  T-Hk-  ^-Ho  a.cr:.uinK  .ind  descent  Ue   ™ 

undivided  turn  brainward.  "         "«-.steii.  on-.  „r 

snarin^v   r!!^r^  ?!i''  ""."i"'''*  '"■'""'  ^""-^         "'an  the  root-celi  ,   are  only 

spanngly  represented  in  the  anterio  iist.n^-u.shed  bv  the  course  of  their 

axones,  which  usually  pass  to  the  ant  .,n,e  si.le.     In  some  cases,  however 


Nerve-fihrcs  of  whitt*  matter 


Anierior  root-fibres 


Portion  of  anierior  u.rnu  of  ijray  matter,  showing  multiiM)lar 
nerve-cells,      ■    120. 


1033 


HUMAN   ANATOMY, 


i^ 


] 


I 


I 


the  axone  divides  into  two,  rarely  three,  fibres,  one  of  which  crosses  by  way  of  the  anterior 
white  commissure  to  the  opposite  ventral  column,  while  the  othe:  passes  to  the  ventral 
column  of  the  same  side. 

As  well  seen  in  cross-sections,  although  the  nerve<ells  of  the  anterior  horn  are  widely 
scattered  they  are  not  uniformly  distributed  through  the  gray  matter,  but  are  collected  into 
more  or  less  definite  groups  that  recur  in  consecutive  sections.  It  is  evident,  therefore,  that  the 
cell-groups  are  not  limited  to  a  ling^e  plane,  but  are  continuous  as  longitudinal  tracts  or 
columns  for  longer  or  shorter  stret^..ss  within  the  core  of  gray  matter  of  the  cord. 

The  grouping  of  the  nerve-cells  of  the  anterior  horn  includes  two  general 
collections,  a  mesial  group,  containing  many  commissural  cells,  and  a  lateral  group 
composed  chiefly  of  ventral  radicular  cells.  These  collections,  however,  vary  in 
extent  and  definition  in  different  parts  of  the  cord  and,  where  well  marked,  are  often 


.'s 


Fig.  888. 


A  A, 


\  Cdlii  of  subManlia 

(clatinoM  Rolandi 


*r—  Pcntcrior  born  cells 


Accessory  dorso- 
lateral groups 


Dorso-lateral  group 


,                              „-,,  ,  Ventro>laleral  group 

Mesial  group  "    -        - -^       "^ 

Transverse  section  ol  lower  cervical  cord,  showing  grouping  of  iwrv»<-ells ;  Nisal  staining,    x  so. 

made  up  of  more  than  a  single  aggregation  of  cells.  This  feature  is  particularly  evi- 
dent in  the  lateral  collection,  in  which  an  anterior  and  a  posterior  subdivision  are 
recognized  as  the  veniro-laleral  and  the  dorso-lateral  group  that  occupy  the  corre- 
sponding angles  of  the  anterior  horn.  The  mesial  collection,  situated  within  the 
ventral  angle,  is  likewise,  but  much  less  clearly,  divisible  into  a  ventro-nusial  and  a 
dor  so-mesial  group,  of  which  the  latter  is  variable  and  at  many  levels  wanting.  In  a 
general  way  the  pronounced  presence  of  these  cell-groups  influences  the  outline  of 
the  anterior  horn,  so  that  corresponding  projections  of  the  gray  matter  mark  their 
position.  This  relation  is  conspicuously  exemplified  in  the  cer\ical  and  lumbo-sacral 
enlargements,  in  which  the  presence  of  lar^e  lateral  cell-groups  is  directly  associated 
with  a  marked  increase  in  the  transverse  diameter  of  the  anterior  horn.  Conversely, 
when  these  cell-columns  become  smaller  or  disappear,  the  corresponding  elevations 
on  the  surface  of  the  anterior  horn  diminish  or  are  absent.  Owing  to  such  variations 
the  contours  of  the  gray  core  are  subject  to  constant  and  sometimes  abrupt  change, 


MICROSCOPICAL   STRUCTURE   OF   SPINAL  CORD. 


1033 


The  TWittD-fnediao  cell-column  is  the  most  constant,  since,  as  emphasized  by  the  pains- 
taking studies  of  Bruce,'  it  is  interrupted  only  between  the  levels  of  the  fifth  lumbar  and  first 
sacral  nerve  in  its  otherwise  unbroken  course  through  the  length  of  tlie  cord,  as  far  as  the  level 
of  the  fifth  sacral  nerve.  An  augmentation  of  this  tract  in  the  fourth  and  fifth  cervical  segments 
is  probably  associated  with  the  spinal  origin  of  the  phrenic  nerve  (Bruce). 

The  dono-mesial  cell-column  is  much  less  constant,  being  represented  only  in  the  thoracic 
region,  in  a  few  cervical  segments  and  at  the  level  of  the  first  lumbar  nerve.  In  agreement 
with  van  Gehuchten  and  others,  Bruce  regards  the  continuity  of  the  mesial  group  as  presump- 
tive evidence  of  its  close  relation  to  the  dorsal  extensor  muscles  of  the  trunk. 

The  ventro-Iateral  cell-column  appears  first  at  the  level  of  the  fourth  cervical  nerve, 
increases  rapidly  in  the  succeeding  segments  and  fades  away  at  the  lower  part  of  the  eighth 
cervical  seg^ment  It  reappears  in  the  lumbar  enlargement,  reaching  its  maximum  at  the  level 
of  the  first  sacral  nerve  and,  diminishing  rapidly  through  the  upper  part  of  the  second, 
disappears  before  the  third  sacral  segment  is  reached. 

The  dorao-lateral  cell-column,  in  places  the  most  conspicuous  collection  of  the  anterior 
horn,  begins  above  at  the  lower  part  of  the  fourth  cervical  segment  and,  increasing  rapidly, 
attains  its  greatest  development  in  the  neck  in  the  fifth  and  sixth  segments.  It  suffers  a  marked 
reduction  at  the  level  of  the  seventh  cervical  nerve,  which  is  followed  by  a  sudden  increase  in 
the  next  segment  in  which  the  column  presents  an  additional  collection  of  ner\'e-cells  known  as 
the  accessory  dorso-lateral  or  post-postero- lateral  group.  Below  the  level  of  the  second  thoracic 
nerve  the  dorso-lateral  cell-column  is  unrepresented  as  far  as  the  second  sacral  segment  where 
it  reappears,  somewhat  abruptly,  and  attains  its  maximum  size  in  the  fourth  and  fifth  lumbar 
segments.  The  column  then  diminishes  and  ceases  at  the  lower  part  of  the  third  sacral  seg- 
ment Within  the  sacral  cord,  between  the  levels  of  the  first  and  third  nerve  inclusive,  the 
dorso-lateral  cell-group  is  augmented  by  an  accessory  group.  From  the  third  lumbar  to  the 
sacral  nerve-levels,  an  additional  compact  collection  of  nerve-cells  occupies  a  more  median 
position  in  the  anterior  horn  and  constitutes  the  central  group. 

From  the  position  of  the  greatest  expansions  of  the  lateral  cell-columns — within  the  cervical 
and  lumbo-sacral  enlargements — it  is  evident  that  they  are  associated  with  the  large  nerves  sup- 
plying the  muscles  of  the  limbs.  Further,  according  to  Bruce,  in  a  general  way  the  size  of  the 
radicular  cells  bears  a  relation  to  that  of  the  muscles  supplied,  the  smaller  dimensions  of  the 
cervical  cells,  as  compared  with  those  of  the  lumbo-sacral  reg.on,  corresponding  with  the  smaller 
size  of  the  upper  limb  in  comparison  with  that  of  the  lower  one. 

In  addition  to  the  nerve-cells  assembled  within  the  foregoing  more  or  less  well  defined 
groups,  some  scattered  cells  are  irregularly  distributed  through  the  anterior  horn  and  do  not 
strictly  belong  to  any  of  the  groups. 

Below  the  level  of  the  first  coccygeal  nerve,  the  cells  of  the  anterior  horn  become  so 
diminished  in  number,  that  they  are  no  longer  groiiped  with  regularity,  but,  reduced  in  size,  lie 
uncertainly  distributed  within  the  gray  matter  as  far  as  the  lower  limits  of  the  conus  medullaris. 

The  nerve-cells  of  the  posterior  horn  are  neither  as  large  nor  as  regularly 
disposed  as  the  anterior  horn  cells.  Only  in  one  locality,  along  the  median  border 
of  the  base  of  the  posterior  horn,  are  they  collected  into  a  distinct  tract,  the  column  of 
Clarke  ;  otherwise  they  are  scattered  without  order  throughout  the  gray  matter  of  the 
posterior  comu.  Since,  however,  the  latter  comprises  certain  areas,  the  cells  of 
the  posterior  horn  may  be  divideid  into  (i)  the  cells  of  Clarke' s  column,  (2)  the 
cells  of  the  substantia  gelatinosa  Rolandi,  and  (3)  the  mner  cells  of  the  caput  comu. 

The  cells  of  CUrke'e  column  form  a  very  conspicuous  collection  which  extends  from  the  level 
of  the  seventh  cervical  nerve  to  that  of  the  second  lumbar  m.-rve  and  is  best  developed  in  the 
lower  thoracic  region  of  the  cord.  Although  confined  chiefly  to  the  dorsal  portion  of  the  cord, 
and  hence  sometimes  designated  as  the  "dorsal  nucleus,"  Clarke's  column  is  represented  to  a 
slight  degree  in  the  sacral  and  upper  cervical  regions  (sacral  and  cervical  nuclei  of  Stilling) .  In 
cross-sections  the  cell-column  appears  an  a  group  of  multipolar  cells  that  occupy  the  mesial 
border  of  the  base  of  the  posterior  horn  and,  where  the  column  is  best  developed  (opposite  the 
oiigin  of  the  twelfth  thoracic  nerve),  correspond  to  an  elevation  on  the  surface  of  the  gray 
matter.  The  cells  usually  are  about  .030  mm.  In  diameter,  pfilygonal  in  outline  and  possess  a 
relatively  large  number  of  richly  branched  dendrites  that  radiate  chiefly  within  the  limits  of  the 
group  (Cajal).  The  axones  commonly  spring  from  the  anterior  or  taternl  margin  of  the  cells 
and  course  ventrally  for  a  considerable  distance  before  bending  outward  toward  the  lateral 
column  of  white  matter  within  which,  as  constituent  fibres  of  the  direct  cerebellar  tract 
(page  1044),  they  turn  brainward. 


'  TopOKfrtphlcai  Atlas  of  ihe  .Spinal  Cord,  1901, 


»034 


HUMAN   ANATOMY. 


f 


(^ 


I  5-; 


The  nerve-eelU  of  the  aubaUntia  relatinosa  Rolandi,  also  known  as  Gierke's  cells,  include 
innumerable  small  stellate,  less  frequently  fusiform  or  pear-shaped  elements  that  measure  only 
from  .006-.020  mm.,  although  exceptionally  of  larger  size.  Their  numerous  short  dendrites  are 
irregularly  disposed  and  branched.  The  axones,  which  always  arise  from  the  dorsal  pole  of  the 
cell,  are  continued  partly  to  the  white  matter  of  the  posterior  column,  within  which  they  divide 
into  ascending  and  descending  limbs,  and  partly  to  the  gray  matter  itself,  within  which  they  run 
as  longitudinal  fibres.  Under  the  name  of  the  marginal  cella  are  described  the  much  larger 
(035-055  """• )  ner\e-cells  which  occupy  the  border  of  the  substantia  gelatinosa.  They  are 
spindle-shaped  or  pyramidal  in  form,  their  long  axes  lying  parallel  or  the  apices  directed  towards 
the  Rolandic  substance  respectively,  and  constitute  a  one-celled  layer  enclosing  the  substantia 
gelatinosa,  into  which  many  of  their  tangentially  coursing  dendrites  penetrate.  Their  axones 
pass  through  the  substantia  gelatinosa  and  probably  continue  for  the  most  part  within  the  lateral 
column,  although  some  enter  the  posterior  column  (Cajal,  Kolliker). 

The  inner  cella  of  the  posterior  horn  are  intermingled  with  niunerous  nervous  elements  of 
small  size  irregulariy  distributed  within  the  head  of  the  dorsal  comu.  The  inner  cells  proper 
are  triangular  or  spindle-shaped  in  form  and,  on  an  average,  measure  about  .050  mm.;  they 
are,  therefore,  larger  than  the  ordinary  cells  of  the  Rolandic  :,ubstance.    The  dendrites  arise 

Fig.  889. 


White  nwUet  of 

poMcrior  column 


C»llt  of  Clarke's  column 

Subilanlia  geUtinoaa  cenlrali* 


Central  canal 
Part  of  craaa-iection  of  cord,  ahowinK  cella  of  Clarke's  column  in  base  of  poalerior  hom.    X  1 10. 

from  the  angles  or  ends  of  the  cells  and  diverge  in  all  directions.  The  axones  pas.<t,  either 
directly  or  in  curves,  mostly  into  the  lateral  column  of  the  same  side ;  some,  however,  have 
been  followed  into  the  posterior  or  anterior  columns  of  the  same  side  (Kolliker),  and,  rarely,  into 
the  opposite  anterior  column  (Cajal).  Exceptionally  type  II  cells— those  in  which  the  axone  is 
"°'Pfo'''"f?ed.as  the  axis<ylinder  of  a  nerve-fibre,  but  soon  breaks  up  into  an  elaborate  end 
arborization  confined  to  the  gray  matter— are  found  within  the  gray  matter  of  the  posterior  hom. 
Their  number  is,  however,  much  less  than  often  assumed  (Ziehen). 

The  nervous  character  of  most  of  the  cells  seen  within  the  substantia  gelatinosa  Rolandi  has 
l)een  established  only  since  the  introduction  of  the  Oolgi  methods  of  silver-impregnation. 
Previously,  these  elements  were  regarded  as  glia  cells,  an  exceptionally  large  amount  of 
neuroglia  in  general  being  attributed  to  the  Rolandic  substance.  It  is  now  admitted  that 
instead  of  such  being  the  case,  this  region  of  the  gray  matter  is  relatively  poor  in  neurogliar 
elements  and  numerically  rich  in  nerve-cells. 

The  nerve-cellt  of  the  pars  intermediate  of  the  (fray  matter,  which  connects 
the  dorsal  and  ventral  horns  and  lies  opposite  the  Rray  commissure,  may  be  broadly 
divided  into  two  clas!«es,  the  lateral  and  the  middle  cells,  that  occupy  respectively  the 
outer  border  and  the  more  central  area  of  this  j>art  of  the  gray  inalter  ol  the  cord 


MICROSCOPICAL    STRUCTURE   OF    SPINAL  CORD. 


«o35 


Those  of  the  first  class,  or  intcnncdio-Uteral  cells,  are  associated  with  the  forniatio  reticu- 
laris and  its  condensation,  the  lateral  horn,  and  hence  are  often  spoken  of  as  the  group  or 
column  of  the  lateral  horn.  These  cells  form  a  slender  tract  of  small  closely  packed  elements 
that  is  represented  through  almost  the  entire  length  of  the  cord,  although  best  marked  in  the 
upper  third  of  the  thoracic  region  and  partially  interrupted  in  the  cervical  and  lumbo-sacral 
segments.  Where  the  forniatio  reticuliiris  is  condensed  with  a  distinct  lateral  horn,  as  in  the 
thoracic  region,  the  cells  occupy  the  projection,  but  elsewhere  lie  within  the  base  of  the  gray  net- 
work. As  a  continuous  cell-column  the  tract  extends  from  the  lower  part  of  the  eighth  cervical 
segment  to  the  upper  part  of  the  third  lumbar.being  most  conspicuous  at  the  level  of  the  third  and 
fourth  thoracic  nerves  (Bruce).  Practically  suppressed  in  the  cer\ical  region  between  the  eighth 
and  third  s^ments,  above  the  latter  the  column  reappears  along  with  the  formatio  reticularis. 
Below,  it  is  again  seen  within  the  third  and  fourth  sacral  segments.  Tlie  nerv  <:el!s  are  multi- 
polar or  fusiform  in  outline,  from  .015-.045  mm.  in  their  longest  diameter,  conUi.i  little  pigment, 
and  are  provided  with  a  variable  number  of  dendrites,  of  which  two  are  usually  larger  than  the 
others.  These  arise  from  opposite  poles  of  the  cell  and  send  branches,  for  the  most  part,  into  the 
adjacent  white  matter.  The  axones  pass  directly  into  the  lateral  columns  and  become  ascending 
or  descending  fibres  ;  a  few  axones,  however,  enter  the  anterior  column  of  the  same  side  (Ziehen) . 

The  cells  of  the  second  class,  or  intermediate  cells,  are  irregularly  disposed  and  only  in  the 
upper  part  of  the  cord  present  a  fairly  distinct  middle  group  (VValdeyer).  They  are  polygonal 
or  fusiform  in  outline,  small  in  size  (seldom  exceeding  .035  mm.)  and  provided  with  irregular 
dendrites.  The  axones  are  continued  chiefly  within  the  lateral  cr  *'imn  of  the  same  side,  although 
some  pass  to  the  anterior  column  and  a  few  probably  cross  to  the  opposite  side. 

A  small  number  of  isolated  nerve-cells  are  usually  to  be  found  within  the  white  matter,  out- 
side but  in  the  neighborhood  of  the  gray  core.  These,  the  outlying  celU  of  Sherrington,"  by 
whom  they  have  been  studied,  occur  most  frequently  in  the  vicinity  of  the  more  superficially 
placed  cell-columns.  Within  the  anterior  columns  they  lie  in  'he  paths  of  the  fibres  proceeding 
to  the  anterior  white  commissure ;  in  the  lateral  columns  they  are  in  proximity  to  the  intermedio- 
lateral  group  of  the  lateral  horn  and  formatio  reticularis  and  to  the  cells  of  the  .substantia 
Rolandi ;  an:*  in  the  posterior  columns,  where  they  are  relatively  numerous,  they  are  associated 
wi.h  the  "■  J«cts  leading  to  the  column  of  Clarke.  The  outlying  cells  are  regarded  as 
eleme'  .   d  from  their  usual  position  during  the  course  of  the  differentiation  and  growth 

of  thi  M  .  gray  matter.  Similar  displacement  sometimes  affects  the  cells  of  the  spinal 
gangli        '        then  may  be  encountered  within  the  cord. 

T  ,  .  tiuroglia  of  the  Gray  Matter. — As  in  other  parts  of  the  cord,  so  in 
the  gray  matter  the  neuroglia  is  everywhere  present  as  the  supporting  framework  of 
the  nervous  elements,  the 

cells  and  fibres.  The  gen-  '^'^ 

eral  structureof  neuroglia 
having  been  described 
(page  1004),  it  only  re- 
mains to  note  here  the 
special  features  of  its 
arrangement  within  the 
gray  matter.  In  general, 
the  felt-work  of  the  neu- 
rogliar  fibrils  is  more 
compact  than  that  per- 
meating the  white  matter, 
being  somewhat  denser 
at  the  periphery  than  in 
the  deeper  parts  of  the 
pray  matter.  There  is, 
however,  no  hard  boun- 
dary between  the  sup- 
porting tissue  of  the  two, 
since  numerousgiiii  fibrils 
extend  outward  from  the 
frame-work  of  the  gray  matter  to  be  lost  between  the  nerve  fibres  of  the  adjoinins 
columns.  This  feature  is  marked  in  the  anterior  horn,  where  the  glia  fibrils  form 
septa  of  considerable  thickness  that  diverge  into  the  surrounding  columns  ;  further 

'  Proceedings  Royal  Society,  vol.  30,  1890. 


Poitcrior  nMdian 
nepluin 

Paramedian  nptum 
■uhdividing 
poucrior  column 


Anterior  median  fiuure 


Anterior  column 


Transverte  section  of  cord  allKhtly  ma)(nifi«t,  lihowing  Kvneral  nrnmnenient 
of  neuroKlia.     ^   10. 


I036 


HUMAN  ANATOMY. 


i' 


^% 


If 


i 


Fig.  891. 


the  conspicuous  processes  of  the  formatio  reticularis  and  the  projecting  lateral  horn 
consist  largely  of  neuroglia.  The  larger  nerve-cells  and  their  robust  processes  are 
ensheathed  by  interlacements  of  neuroglia  fibrilke. 

In  the  several  parts  of  the  posterior  horn  the  amount  of  neuroglia  varies. 
Thus,  the  apex  consists  almost  exclusively  of  glia  tissue,  while  within  the  Rolandic 
substance  the  number  of  glia  fibres  and  cells  is  unusually  small.  Within  the 
caput  and  remaining  parts  of  the  posterior  horn  the  neurogliar  elements  are  similar 
m  quantity  and  disposition  to  th<we  in  the  anterior  horn. 

The  ependyma  eeUs  lining  the  central  canal  of  the  cord  are  the  direct  descendents  of  the 
radially  arranged  embryonal  supporting  elements  (page  1004) ;  they  may,  therefore,  be  regarded 
as  specialized  neuroglia  cells.  Althcugh  most  advantageously  studied  in  the  ftetus  and  the 
chiUl,  in  favorable  preparatioas  f-om  adult  cords  they  are  seen  as  a  single  row  of  pyramidal 
cells,  from  .ojo-.ojo  mm.  loi.f  and  from  one-fourth  to  one-third  as  broad,  whose  bases  are 
directed  towards  the  lumen  ci  the  canal  and  beset  with  cilia.  Their  pointed  distal  ends,  or 
apices,  are  prolonged  into  a  long  delicate  ependymal  fibre,  that  in  the  adult  is  soon  lost  in  the 
surrounding  neuroglia,  but  in  the  foetus  extends  through  the  entire  thickness  of  the  cord.  The 
ependyma  cells  are  not  all  of  equal  size,  those  occupying  the  ventral  mid-line,  especially  in  the 
cervical  region,  being  about  twice  as  long  as  those  on  the  opposite  wall  of  the  canal.  The  epen- 
dymal  fibres  proceeding  from  these  cells  are  of  special  length  and  thickness,  ;he  ventral  ones  con- 
verging to  form  a  wedge-shaped  mass  that  in  the  young  subject  continues  as  far  forward  as  the 
bottom  of  the  antenor  median  fissure.  Tht  dorsal  ependymal  fibres  are  prolonged  through  the 
gray  commissure  into  the  posterior  median  septu.-n,  some  diverging  into  the  columns  of  GoH. 

Substantia  gelatinosa  centralis  is  the  name  given  to  a  zone  of  peculiar  trans- 
lucency  that  immediately  surrounds  the  central  canal.     This  annular  area  consists  of 

modified  neuroglia  in  which  radial  ependymal  fibers  are 
interwoven  with  circularly  disposed  neurogliar  fibrillse, 
the  whole  giving  rise  to  a  compact  stratum,  interspersed 
with  an  unusual  number  of  glia  cells,  upon  which  arrange- 
ment, in  conjunction  with  the  absent,  of  nerve-fibres, 
the  characteristic  appearance  of  the  gelatinous  substance 
depends.  In  addition  to  the  branched  glia  elements,  a 
number  of  radially  directed  spindle  cells  are  present  in 
this  zone  ;  they  send  delicate  processes  between  the 
ependyma  cells,  of  which  they  are  probably  outwardly 
displaced  members.  In  marked  contrast  with  the  Ro- 
landic substance,  which  caps  the  posterior  horn,  the 
substantia  gelatinosa  centralis  contains  no  nerve-cells  but 
only  glia  elements,  in  recognition  of  which  the  term,  sub- 
stantia gliosa  centralis^  has  been  proposed  by  Ziehen. 
The  Nerve-Fibres  of  the  Gray  Matter.— 
Within  all  portions  of  the  gray  core  a  considerable  part 
of  the  intricate  ground-work  in  which  the  nerve-cells  lie 
embedded  is  contributed  by  the  processes  of  neurones 
situated  at  the  same,  different  or  even  remote  levels. 
These  processes,  which  constitute  the  nerve-fibres, 
medullated  and  nonmeduUated,  that  are  seen  traversing 
thegraymatterinalldirections,include:( I)  the  collate- 
rals and  the  terminal  branches  of  the  dorsal  root-fibres  that  enter  the  gray  matter  ; 
(2)  nerve-fibres  of  the  descending  tracts  that  terminate  in  relation  with  the  ventraj 
(motor)  horn  cells  ;  (3)  the  axones  and  collaterals  given  off  by  the  numerous  pos- 
terior horn  cells,  that  traverse  the  gray  matter  to  and  from  the  respective  columns  into 
which  they  pass.  The  dendritic  processes,  as  well  as  the  axones  of  the  type  II  cells 
also  contribute  to  the  sum  of  nervous  fibrilljc  encountered  within  the  irray  matter  of 
the  cord. 

WHITE  MATTER  OF  THE  SPINAL  CORD. 

The  predominating  components  of  the  white  substance  being  the  longitudinal 
nerve-fibres  which  pa.ss  for  n  Innper  or  shorter  distance  up  and  down  in  the  column^  of 
the  cord,  in  cross-sections  the  outer  field,  between  the  gray  core  and  the  periphery 


Central  canal  and  aurroundint 
■ubslantia  Rclattnoaa  ccntnilla,  from 
child'a  cord ;  canal  is  lined  wllh 
ependyma  celli.  outaide  of  which 
liea  neuroglia  with  glia  cella.    y  i^. 


WHITE  MATTER  OF  THE  SPINAL  CORD. 


1037 


of  the  cord,  appears  to  be  composed  of  innumerable,  closely  set,  small  cells,  held 
together  by  delicate  supporting  tissue.  These  apparent  cells  are  the  meduilated 
nerve-fibres  cut  transversely,  in  which  the  section^  axis-cylinders  show  as  deeply 
stained  dots,  that  commonly  lie  somewhat  eccentrically  and  are  surrounded  by  deli- 
cate irregularly  annular  striations  representing  the  framework  of  the  medullary  coat. 
The  nerve-fibres  of  the  cerebro-spinal  axis  are  without  neurilemma,  the  lack  of  this 
sheath  being  compensated  by  a  slight  condensation  of  the  neuroglia  around  the 
fibres.  Seen  in  faivsverse  sections  this  investment  appears  as  the  ring  that  gives 
a  definite  outline  to  the  fibie. 

The  individual  nerve-fibres  vary  greatly  in  size,  even  within  the  same  tract  large  and  small 
fibres  often  lying  side  by  side.  The  smallest  may  be  less  than  .005  mm.  and  the  largest  over 
.025  mm.     In  a  general  way,  the  diameter  of  the  fibre  bears  a  direct  relation  to  its  length,  those 

Fig.  892. 


Tnbectila  uf  neuroglia 


Blood-vesael  in  pia 


M  ir  ."^ti 

■i  ■     (  '  •>^  Suhpial  tayet 

.l!Vr'  "»"    ' o(  neuroglia 


Peripheral  part  of  trannrene  lectlon  of  spliul  cord,  thowliit  nerve-Rbtc*  rabdividcd  Into  ini>ups  by  inKTowth  of 

•ttbplal  layer  of  neuroclia.    X  i]o. 

having  an  extended  course  being  larger  than  shorter  ones  ;  it  follows  that  the  fibres  occupying 
the  peripheral  parts  of  the  white  matter,  particularly  in  the  lateral  columns,  are  more  frequently 
of  large  diameter  than  those  near  the  gray  matter. 

The  immediate  surface  of  the  white  substance  beneath  the  pia  mater  is  formed  by  a  con- 
densed tract  of  neuroglia,  the  tubpial  lajrtr,  from  .0J0-.040  mm.  in  thickness,  that  is  devoid  of 
nervous  elements  and  forms  the  definite  outer  boundary  of  the  cord.  This  lone  consists  of  a 
dense  interlacement  of  circular,  longitudinal  and  radial  neuroglia  fibrils  among  which  numer- 
ous glia  cells  are  embedded.  From  the  deeper  surface  of  this  ensheathing  layer  numerous 
bundles  of  fibrillae  penetrate  between  the  subjacent  nerve-fibres  to  become  lost  in  the  general 
supporting  ground-work.  At  certain  places  the  bundles  are  replaced  by  robust  septa  by  which 
the  nerve-fibres  are  imperfectly  divided  into  groups  or  tracts,  as  conspicuously  seen  in  the  pos- 
terior column  where  the  paramedian  septum,  effects  an  imperfect  subdivision  into  the  tract  of 
Goll  and  of  Rurdach.  The  blood-vessels  that  enter  the  nervous  substance  from  the  pia,  accom- 
panied by  connective  tiMue,  i»re  surrounded  by  tubular  iiheat*<s  of  neuroglia,  and  the  same  is 


9S 


1038 


HUMAN  ANATOMY, 


y, 


p 


true  of  the  bundles  of  root-fibres  of  the  spinal  nerves.  But  apart  from  the  connective  tissue  that 
enters  with  the  blood-vessels,  the  amount  of  mesoblastic  tissue  concerned  in  the  supporting 
framework  of  the  cord  is  inconsiderable,  according  to  some  histologists,  indeed,  beine 
practically  nothing.  •      >  >        -• 

Fibre-Tracts  of  the  White  Matter.— Although  microscopical  examination 
of  ordinary  sections  of  the  cord  aflords  slight  indication  of  a  subdivision  of  the 
columns  of  white  matter  into  areas  corresponding  with  definite  fibre-tracts,  yet  the 
combined  evidence  of  anatomical,  pathological,  embryological  and  experimental 
investigauon  establishes  the  existence  of  a  number  of  such  paths  of  conduction. 
With  few  exceptions,  they  are,  however,  without  sharp  boundaries  and  illy  defined 
adjoining  tracts  often  overlapping,  and  depend  for  their  presence  upon  the  fact  that 
nerve-fibres  having  the  same  function  and  destination  proceed  in  company  from  the 
same  group  of  nerve-cells  ( nucleus  )  along  a  similar  course.  In  addition  to  being  pro- 
vided with  paths  of  conduction  necessary  for  the  performance  of  its  function  as  a  centre 
for  independent  (reflex)  impulses  in  response  to  external  stimuli,  the  cord  contains 
tracts  that  connect  it  with  the  brain,  as  well  as  those  that  bring  the  various  levels  of 
the  cord  itself  into  as  sociation.  The  white  matter,  therefore,  contains  three  classes  of 
fibres  :  ( i )  those  entering  the  cord  from  the  periphery  and  other  parts  of  the  body  ; 
(  2  )  those  entering  it  from  the  brain ;  and  (  3  )  those  arising  from  the  nerve-cells  situated 
withm  the  cord  itself.  The  first  two  constitute  the  exogenous,  the  last  the  endogenous 
tracts.  It  IS  evident  that  some  of  these  fibres  constitute  pathways  for  the  transmission 
of  impulses  from  lower  to  higher  levels  and  hence  form  ascending  tracts,  while  others, 
which  conduct  impulses  in  the  opposite  direction,  form  descending  tracts. 

Since  it  is  impossible  to  distinguish  between  these  fibres  by  mere  inspection  of  sections  of 
the  adult  normal  cord,  and,  moreover,  extremely  difficult  and  practically  impossible  to  follow 
in  such  preparations  the  longer  fibres  throughout  their  course,  advantage  is  taken  of  other 
means  by  which  differentiation  of  individual  tracts  is  feasible.  Such  means  include  chiefly 
the  experimental  and  embryological  methods. 

The  experimental  method  depends  upon  the  law  discovered  by  Waller,  more  than  h.ilf  a 
century  ago,  that  when  the  continuity  of  a  nerve-fibre  is  destroyed,  either  by  a  pathological 
lesion  or  by  the  experimenter's  knife,  the  portion  of  the  nerve-fibre  (the  axone  of  a  neurone) 
beyond  the  break,  and  therefore  isolated  from  the  presiding  nerve-cell,  undergoes  secondary 
degeneration,  while  the  portion  remaining  connected  with  the  cell  usually  undergoes  little  or 
no  change.  It  should  be  pointed  out,  however,  that  occasionally  the  connected  portion  of  the 
fibre,  and  even  the  nerve-cell  itself,  undoubtedly  exhibits  changes  known  as  retrograde  degen- 
eration, which,  although  uncertain  as  to  occurrence  and  cause,  may  at  times  prove  a  source  of 
error  in  deducing  conclusions.  If  a  lateral  section  of  one-half  of  the  cord  of  a  living  animal  be 
made,  and,  after  the  expiration  of  from  three  to  four  weeks,  transverse  sections  be  cut  and 
appropriately  prepared  (by  the  methods  of  Marschi  or  of  Weigert),  certain  groups  of  nerve- 
fibres  will  present  degenerative  changes.  It  will  be  seen,  however,  that  the  degenerated  tracu 
in  sections  taken  from  above  the  lesion  are  not  the  same  as  those  in  sections  from  below  the 
division,  showing  that  certain  fibres  have  been  involved  in  opposite  directions,  those  arising 
from  ner  e-cells  lying  below  the  lesion  being  affected  with  a.scending  deKeneration,  and  those 
from  cells  situated  above  with  descending  degeneration.  In  this  manner,  by  careful  study  of 
consecutive  sections,  much  valuable  information  has  been  gained  as  to  the  origin,  course,  ter- 
mination and  function  of  many  fibre-tracts  within  the  central  nervous  system. 

The  embryological  method,  also  productive  of  important  advances  in  our  knowledge  of 
the  nervous  pathways,  is  based  on  the  fact,  first  demonstrated  by  Meckel,  that  the  nerve-fibres 
of  the  central  nervous  system  do  not  all  acquire  their  medullary  sheath  at  the  same  time. 
Taking  advantage  of  such  variation,  as  suggested  by  Meynert  and  later  extensively  carried  out 
by  I'lechsig  and  others,  upon  staining  sections  of  embryonal  tis.sue  with  reagents  that  color 
especially  the  medullary  substance,  it  is  possible  to  differentiate  and  follow  certain  fibre-tracts ' 
In  the  ffttal  cord  with  great  clearness,  since  only  those  tracts  are  stained  in  which  the  myelin  is 
already  formed.  It  is  of  interest  to  note  that,  in  a  general  way,  the  order  in  which  the  different 
strands  of  the  cord  acquire  their  medullary  coat  accords  with  the  sequence  in  which  nervous 
function  is  assumed  by  the  fcctus  and  child.  Thus,  the  paths  required  for  spinal  reflexes  (the 
posterior  and  anterior  root-fibres)  are  first  to  become  medullated  (fourth  and  fifth  feetel 
months);  those  bringing  into  association  the  different  segments  of  the  cord  next  (from  the 
fifth  to  the  seventh  month )  acquire  myelin  ;  those  ronnertinK  thr  mrd  with  the  cerebellum 
follow  somewhat  later,  while  those  establishing  relations  with  the  cerebral  cortex  are  last  and 
do  not  begin  to  medullate  until  shortly  before  birth. 


.^~?"^ 


WHITE  MATTER  OF  THE  SPINAL  CORD. 


1039 


Baaed  on  the  collective  evidence  contributed  by  these  methods — ^anatomical, 
physiological,  and  developmental — it  is  possible  to  locate  and  trace  with  fair  accuracy 
a  number  of  fibre-tracts  in  the  cerebro-spinal  axis.  Since  they  are  undergoing 
continual  augmentation  or  decrease,  their  actual  area  and  position  are  subject  to 
variation,  so  that  the  detailed  relations  in  one  region  of  the  cord  differ  from  those 
at  other  levels.  Tne  accompanying  schematic  figure,  therefore,  must  be  regarded 
as  showing  only  the  general  relations  of  the  most  important  paths  of  the  cord, 
and  not  as  accurately  representing  the  actual  form  and  size  of  the  fibre-tracts. 
It  must  also  be  appreciated  that  the  definite  limits  of  these  tracts  in  such  diagrammatic 

Fig.  893. 


Awociation  tracts 


Rubrotpinal 

tract 
VcitibulO'Spinal 

tract 
SpiiHHiulainic 

tract 


Spinoolivan' 
tract  (Hclwrg) 


Ccrcbitxpinal  tract 


Veitibulo-ipinal  tract 
Tecto-spinal  tract 


Diagram  of  •piiul  cord,  ahowins  poahion  of  chief  tracts  and  relation  1  of  their  component  flbres  to  ner\-e~cellt ; 
1-5.  poMerior  rool-fibrea  enterina  root-nme  (R.Z.)  and  Liaaauer'i  tract  (L.).  open  drclea  (0)  indicate  that  fihi«  pau 
upand  down;  c.c.collateraU  from  lonaaacendlna  tracu  (1,  >)  to  anterior  root^cella;  3.  fibrea  emlinf;  around  rella 
•  .ilS^'i  ">'"">" :  *.  nbrea  forming  direct  cerebellar  tract ;  7. 8,  abrei  formina  t^owera'  tract ;  9, 10,  fibres  from 
tataral  and  direct  pyramidal  tracta ;  ii,  11,  anterior  root-libm ;  V.F.,  ventral  Oeld :  O.F.,  oval  Seld :  C.B.,  comma 
Dunale. 

representations  seldom  exist  in  reality,  since  the  fibres  of  the  adjacent  paths  in 
most  cases  overlap,  or,  indeed,  extensively  intermingle,  so  that  the  fields  seen  in 
cross-sections  may  be  shared  by  strands  belonging  to  different  fibre-systems. 

The  Fibre-Tracts  of  the  Posterior  Column. — The  subdivision  of  the 
posterior  column  of  white  matter  by  the  paramedian  septum  into  two  general 
parts  has  been  noted  (page  loaS).  Of  these  the  inner  one  is  the  postero-median 
fasciculus,  or  tract  of  GoU  (fosciculus  gracilis),  and  the  outer  one  is  the  postero- 
lateral fasciculus  or  tract  of  Burdach  (fasciculus  cnneatus).  These  tracts  are 
so  intimately  associated  with  the  fibres  entering  by  the  posterior  roots  of  the  spinal 
nerves,  that  the  general  relations  and  behavior  of  these  fibres  must  be  considered 
in  order  to  understand  the  composition  of  the  posterior  columns,  as  well  as  that 
of  certain  secondary  paths. 

All  sensory  impulses  that  enter  the  spinal  cord  do  so  by  way  of  the  posterior 
root-fibres.  The  latter  are  the  centrally  directed  processes  (axones)  of  the  neuror . 
whose  cell-bodies  lie  within  the  spinal  ganglia  situated  on  the  dorsiti  nrnts  of  tV 
spinal  nerves.  They  convey  to  the  cord  the  various  impulses  collected  ^^  tho 
peripherally  directed  processes  (the  sensory  ner\es)  from  the  integument,  mucous 
membranes,  muscles,  tendons  and  joints  from  .ill  parts  of  the  body,  with  the 
exception  of  those  served  by  the  cranial  nerves.  The  impulses  thus  conducted  are 
transformed  into  the  impressions  of  touch,  muscle-sense,  heat,  cold  and  pain. 
The  .ast  ht'u\)i  |..<ibably  the  result  of  excessive  stimulation  that  by  its  intensity 
causes  discomfort  in  various  degrees,  the  existence  of  special  paths  for  the  conduc- 
tion of  painful  impressions  is  unlikely.      It  is  evident  that  the  larger  part  of  the 


1040 


HUMAN  ANATOMY. 


i 


(' 


Fig.  894. 


sensory  neurones  lies  outside  the  spinal  cord  ;  it  is,  however,  with  the  intraniedullar>' 
portion  of  these  neurones,  as  constituents  of  paths  within  the  cord,  that  we  are  here 
concerned. 

On  entering  the  spinal  cord  along  the  postero-lateral  groove,  the  dorsal  root- 
hbres  for  the  most  part  penetrate  the  tract  of  Burdach,  close  to  the  inner  side  of  the 
posterior  Ijorn.  Some  of  the  more  external  root-fibres,  however,  do  not  enter  Bur- 
dach s  tract,  but  form  a  small  adjoining  field,  the  tract  of  Lissauer.  that  lies  im- 
medately  dorwl  to  the  apex  of  the  posterior  horn.  Soon  after  gaining  the  posterior 
column,  with  few  exceptions,  each  dorsal  root-fibre  undergoes  a  >-  or  I-  like  divi- 
sion into  an  ascending  and  a  descending  limb,  which  assume  a  longitudinal  course 
and  pass  upward  and  downward  in  the  cord  for  a  variable  distance,  the  descending 
limb  being  usually  the  shorter.  During  their  course  from  both,  but  particularly  from 
the  descending  limb  and  from  the  proximal  part  of  the  ascending  fibre,  collateral 

branches  are  given  of!  which  bend  sharply 
inward  and  pass  horizontally  into  the  gray 
matter  to  end  chiefly  in  relation  with  the 
neurones  of  the  posterior  horn,  from  which 
cells  secondary  paths  arise.  Not  only  the 
collaterals,  but  also  the  main  stem-fibres  of 
the  descending  and  shorter  ascending  limbs 
end  in  the  manner  just  described.  In  addi- 
tion to  the  short  collaterals  destined  for  the 
cells  of  the  dorsal  horn,  others,  the  ventral 
reflex  collaterals,  pursue  a  sigmoid  course, 
traversing  the  substantia  gelatinosa  Rolandi 
and  the  remaining  parts  of  the  posterior 
horn  and  the  intermediate  gray  matter,  to 
end  in  arborizations  around  the  radicular 
cells  of  the  anterior  horn,  and  thus  complete 
important  reflex  arcs,  by  which  impulses 
transmitted  through  the  dorsal  roots  directly 
impress  the  motor  neurones.  The  latter  are 
usually  of  the  same  side,  but  some  collaterals 
cross  by  way  of  the  anterior  commissure  to 
terminate  in  relation  with  the  anterior  horn 
cells  of  the  opposite  side.  It  is  probable 
that  a  considerable  number  of  such  anterior 
fiK,     ju  »  J        u    I  ,   .  ^^^^  ^^^^^  collaterals  are  given  off  from  the 

hbres  (hat  ascend  in  the  long  tracts  of  the  posterior  column  to  the  medulla  oblongata 
**  ith  possibly  the  exception  of  certain  fibres  which  pass  direcdy  to  the  cerebellum 
( Hoche),  all  the  sensory  root-fibres  (axones  of  neurones  of  the  I  order)  end  afound 
the  neurones  situated  either  within  the  gray  matter  of  the  spinal  cord  or  within  the 
nuclei  of  the  medulla  ;  thence  the  impressions  are  conveyed  by  the  axones  of  these 
neurones  of  the  II  order  to  higher  centers,  to  be  taken  up,  in  turn,  bv  neurones  of 
the  III  or  even  higher  order,  in  the  sequence  of  the  chain  required  to  complete  the 
path  lor  the  conduction  and  distribution  of  the  impulse. 

The  most  important  groups  of  the  collaterals  and  stem-fibres  of  the  posterior 
roots  are:  ' 

'■  lu^  Lf  ^  ascending  tracts  passing  chiefly  to  the  nuclei  of  the  medulla. 

2.  The  fibres  passing  to  the  cells  of  the  column  of  Clarke. 

3.  The  collaterals  passing  to  the  anterior  horn  cells. 

4-  The  fibres  entering  the  posterior  horn  from  the  tract  of  Burdach  and  of 
Lissauer  to  end  about  the  neurones  of  the  II  order  situated  within  the  gray  matter 
of  tfie  posterior  horn  and  the  intermediate  gray  matter. 

The  direct  ascending  posterior  tract  includes  the  dor^  root-fibres  that 
paiw  uninterruptedlyr  upward  within  the  posterior  column  as  far  as  the  nuclei  of  the 
medulla.  On  entering  the  cord  they  lie  at  first  within  the  tract  of  Burdach,  but  in 
their  ascent  are  gradually  displaced  medianly  and  dorsally  by  the  continued  addition 
of  other  root-fibres  from  the  succeeding  higher  nerves.     In  consequence,  in  cross 


niajtram  showinK  division  of  poMerior  root-fibm 
inio  asccndiDK  and  descnidinK  hranches:  lonit  fibre 
sends  collaterals  ti.  anlt-rior  rool  cells:  other  fibres 
end  at  diflerent  levels  aro.ind  cells  in  grav  matter  of 
posterior  Irorn  ;  S.  G.,  spinal  ganglion* 


WHITE  MATTER  OF  THE  SPINAL  CORD.  1041 

sections  of  the  cord  in  the  cervical  region  the  long  fibres  entering  by  the  lower 
nerve-roots  occupy  the  inner  part  of  GoU's  column,  but  are  excluded  from  the  median 
septum,  except  behmd,  by  a  narrow  hemiellipucal  area,  which  with  its  mate  of  the 
opposite  side  forms  the  oval  field  of  Flechsig.  The  fibres  entering  by  the  lower 
thoracic  nerves  he  more  laterally,  while  those  entering  by  the  upper  thoracic  and 
cervical  nerv«  appropriate  the  adjoining  part  of  Burdach's  tract,  the  lateral  area  of 
which,  next  the  posterior  horn,  is  occupied  chiefly  by  the  posterior  root-hbres. 

It  must  be  understood  that  while  in  a  general  way  the  fibres  of  the  long  ascendine  tracts 
have  the  disp«BUon  just  indicated,  they  are  so  intertwined  and  mingled  with  ^  strands  t«»sing 
to  and  from  the  gray  matter  that  the  definite  outlines  of  their  conventional  area,  as  reprinted 
in  diagrams,  are  wanting.    Collectively  the  "<="icu 

fibres  composing  this  tract  are  of  medium  or  pm  g,^, 

small  size,  but  acquire  their  medullary  coat  ' 

very  early,  myelination  beginning  about  the 
fourth  fcetal  month,  although  not  completed 
until  the  ninth  (Bechterew). 

The  termination  of  the  long  ascend- 
ing fibres  is  chiefly  in  relation  with  the 
neurones  within  the  lower  part  of  the 
medulla — the  fibres  of  GoU's  tract  end- 
ing about  the  cells  of  the  nucleus  gracilis 
and  those  of  Burdach's  tract  about  the 
cells  of  the  nucleus  cuneatus.  From 
these  stations  paths  of  the  II  order 
convey  the  impulses  to  the  cerebel- 
lum, by  way  of  the  inferior  cerebelkr 
peduncle,  and  to  the  higher  sensory 
centres  by  way  of  the  mesial  fillet,  as 
later  described  (page  1115).  Whether 
certain  of  the  component  fibres  of  these 
ascending  tracts  are  directly  continued 
to  the  cerebellum,  and  perhaps  to  the 
mesial  fillet,  without  undergoing  inter- 
ruption in  the  nudei  of  the  meduUa  is  stUI  uncertain,  although  supported  by  the 
Statements  of  Hoche,  Kolliker,  Solder  and  others  f>        ff  J 

^rt  ^I'n  ~°»:?>>f«*P*"»inK  to  Clarke's  column  occupy  the  middle  and  median 
part  of  Burdach  s  tract,  mingled  with  those  of  the  long  ascending  paths.  After  cours- 
ing longitudinally,  usually  for  some  distance,  within  the  posterior  column,  they  bend 
outward,  and,  sweeping  m  graceful  curves,  enter  the  gray  matter  to  end  about 
Clarke  s  cells.  It  is  noteworthy  that  the  level  at  which  they  end  is  often  considerably 
higher  than  hat  at  which  the  root-fibres  enter  the  cord,  an  arrangement  which 
explains  the  fact  that  lesions  of  the  lowermost  of  these  strands  may  be  followed  as 
^cending  degenerations  into  the  thoracic  region  (Mayer).  On  entering  the  gray 
matter  the  terminal  arborization  of  a  single  root-fibre  usually  ends  in  relation  with 
several  neurones  of  Clarke's  column  (Lenhoss^k).  The  imj^ortant  sensory  path  of 
2  thL'^'ifeuron^.*"  ^  cerebellar  iract  (page  1044).  arises  as  the  kxones 

^tinnlol  rh"**r*°'/if^**,*'^?"  *''  "'^  ^^"""^'  •'*"■"  «^«  «"  collaterals,  not  continu- 
ations of  the  stem-hbres,  far  the  greater  part  of  which  come  from  the  fibres  of  the 

SiI^^?k'"^  '^''^Ty^'^*-.  V"^  collaterals  penetrate  the  gray  matter  princi- 
pally at  the  median  border  of  the  head  of  the  posterior  horn,  behind  Clarke's 
column  but  partly  also  through  the  substantia  Rolandi,  and  thence  pass  ventrally  or 
ventro-laterally  _  with  a  shghdy  curved  or  sigmoid  course,  towards  thVanterior  horn. 
As  they  enter  the  latter  the  collaterals  diverge  more  and  more  and  are  distributed 
to  the  vanous  groups  of  the  anterior  horn  cells,  chiefly  in  relation  with  the  lateral 
groups  of  radicular  cells  from  which  the  ventral  root-fibres  ari.se  ;  they  thus  establish 

rl  ^if"  ^}      ^y  *'*"'''  ^^^"y  '•"?">««  conveyed  by  the  posterior  root-fibres 

impress  the  motor  neurones,  while,  at  the  same  time,  these  impulses  are  transmitted 

£6 


Section  of  spinal  cord  u  Umi  o(  aecond  cervical  •••• 
nwnt;  fomiatio  rrticttlaris  filli  bay  between  posterior  and 
antenor  comna;  subauntia  aelatinoaa  caps  apex  o«  pos- 
terior comu.  Drawn  from  Weij —  '^"  -—-—-.  "^^ 
by  Professor  Spiller.    X  6. 


Kia.iifUB«   VMps    BfJCX   Ol    pOS' 

Weisert-nal  preparation  made 


I 


II 


1043 


HUMAN  ANATOMY. 


cornua..^  ,v. 
pottero-UtenI 


^U  «!^#  !u  ^  *•""  ascendinfr  stem-fibres.  Although  the  anterior  reflex  collat- 
oau  are,  for  the  most  psut  m  relation  with  the  cells  of  the  same  side,  it  is  probaWe 
hridcr^  t^.^'t^  ^  ^'y.^'  ^^  posterior  commissure,  and  possibly  also  by  the  an.  ^r 
wh&r  l£  7^^^  ventral  horn  cells.  It  is  doubtful,  on  the  other  hand. 
S^or  ^t  T^^Tu°'  "^^^"^"^  of  the  posterior  roots  pass  directly  to  th^ 
antenor  column  other  of  the  same  or  opposite  sides  ( Ziehen). 

t«t.  ^i!  ?,?!■♦?  J^'DPr"!"'  .*?  *•**  posterior  horn  include  those  which  pene- 
trate the  substantia  Rolandi,  either  as  collateraU  or  stem-fibres  of  Bunlach^  or 

of  Lissauer's  tracts,  to  end 
Ho.  896.  about  the  neurones  within 

the  Rolandic  substance  or 
within  the  head  of  the  pos- 
terior horn.  Their  longitudi- 
nal course  within  Burdach's 
tract  is  ordinarily  short ; 
they  then  bend  horizontally 
and  enter  the  gray  matter 
of  the  fMMterior  horn,  within 
which  they  soon  terminate 
in  end-arborizations  around 
the  neurones  of  the  II  order. 
Some  fibres,  however,  do 
not  undergo  T-division  until 
after  entering  the  posterior 
SMi«.  nf  «^..i  --«• ..  1     .    .   .  ^       ,   .  horn,  where,  within  the  Ro- 

?S^I~-=1^'''«'L^4^"'^^^^  '^"*^'*^  ^"•^^"'^e  or   caput 

..ro.uuer.i«.icu..  Pr.p.r.tU  by  ProTe-or  ^Hiter.  X  6.  comu,  they  then  bihircate, 

.•    .  ...  in  some  cases  the  ascendin? 

limbs  pursuing  a  verticd  course  within  the  gray  matter,  particulariy  of  the  caput 
cornu,  for  some  distance  before  ending  about  the  head-cells  of  the  posterior  horn 

1  he  tract  of  Lissauer,  or  marginal  zone,  situated  immediately  behind  the 
apex  of  the  dorsal  horn,  receives  the  lateral  group  of  the  posterior  root-fibres.  These 
are  all  of  unusuaUy  small  size  and,  after  a  short  longitudinal  course  in  which  the 
descending  limbs  predominate,  they  turn  h  Izontally  and,  both  as  collaterals  and 
stem-fibres,  penetrate  the  substantia  Rolant  about  whose  cells  and  those  of  the 
caput  comu  they  end. 

From  the  foregoing  description,  it  is  evident  that  the  dorsal  root-fibres  destined 
for  the  postenor  horn  terminate  in  relation  with  neurones  of  the  II  order  represented 
chiefly  bjr  the  cells  of  the  substantia  gelatinosa  Rolandi,  including  the  marginal  cells 
and  the  inner  cells  of  the  caput  comu. 

The  ^ndary  or  endogenout  tracts  of  the  posterior  column  arise  as  axones  from  the 
neurones  of  the  11  order  (the  marginal  cells,  the  cells  of  the  substantia  Rolandi  and  the  head- 
cells)  situated  withm  the  posterior  horn  and  include  ascending  and  descending  paths. 

n  7"^  ••'=«°<**n«  seconjUry  tract  is  composed  of  the  axones  derived  from  the  posterior  horn 
cells  of  the  same  and,  by  way  of  the  posterior  commissure,  opposite  side,  which  pass  into  the 
postenor  column.  In  a  general  way,  they  occupy  the  ventral  field,  although  sharing  it  with 
ftcattered  strands  of  root-fibres  and  of  descending  endogenous  fibres.  The  destination  of  the 
fibres  of  this  pending  tract  is  uncertain,  some  fibres  pursuing  a  short  and  others  a  longer 
course  within  the  postenor  column  before  entering  the  gray  matter  at  higher  levels  to  end  in 
relation  w.th  the  postenor  horn  cells,  or,  perhaps,  in  some  cases,  with  the  neurones  within 
the  nuclei  of  the  medulla  (Rothmann). 

The  descending  secondary  tracts,  as  shown  by  degenerations  following  lesions  involvine 
the  postenor  coluinn,  occupy  varying  but  fairiy  well  differentiated  areas.  In  the  cervical  and 
upper  thoracic  cord  they  are  collected  into  the  comma  bundle  of  SchulUe,  which  extends  from 
near  the  neck  of  the  posterior  horn  dorsally  along  the  median  margin  of  Burdach's  tract  In 
the  lower  thoracic  and  lumbar  cord  they  fonn  an  elongated  half-ellipse  along  the  posterior 
median  septum  which  with  the  con^sponding  bundle  of  the  opposite  side,  produces  the  oval 
Beld  of  FlrchsiK.  Still  lower,  in  the  sacral  cord,  they  lie  at  the  junction  of  the  median  septum 
and  the  posterior  surface  of  the  cord  as  the  medio-donal  triangular  bundle  of  Gombault  and 
fhilippe.    Additional  descending  endogenous  fibres  are  .scattered  in  the  ventral  field     It  is 


co™5?i!!?Lff  *?!.™'  "^  ■'  •«»»'  »'  •««nU>  «rvic«l  •Cdnenl :  anterior 


WHITE  MATTER  OF  THE  SPINAL  CORD.  ,043 

likely  that  these  areas  represent  the  principal  aggregations  of  the  downward  coursing  limbs  of 

the  axones,  after  their  T-like  branching,  oerived  from  the  posterior  horn  cells  of  the  same  and 

opposite  sides.    In  the  cervical  ^^ 

region  these  axones  are  col-  p|Q_  gg. 

lected  into  bundles  which  ap-  ' 

pear  as  the  comma  tract ;  in 

the  lower  thoracic  curd  these 

are  replaced  by,  without  being 

directly  continuous  with,  those 

forming  the  oval   field,  and 

these  in  turn  by  the  axones  of 
the  triangular  bundle.  No  one 
of  these  fields  is  exclusively 
devoted  to  the  descending 
limbs  of  endogenous  fibres, 
since  in  all  the  presence  of 
exogenous  posterior  root- 
fibres  has  been  demonstrated. 

"^Kc  Fibre -Tracts 
of  the  Lateral  Column. 

— These  include:  (i)  the 
lateral  pyramidal,  (2)  the 
direct  cerebellar,  (3)  the 
ascending  antero-lateral, 
and  (4)  the  lateral  ground- 
bundle. 

for^Jll*  ^*K*f'*  ?u  Z'°*^i  pyramidal  tract  (fasciculus  cerebrospinalis  lateralis) 
forms  the  chief  path  by  which  motor  impulses  originating  in  the  cerebral  cortex  are 
conveyed  to  the  spinal  cord.     It  stands  in  close  relation  with  the  direct  pJ^ZZ 

™tt  if  th^Tj^^n  ""k.""-  ^'^."^  continuations  of  the  conspicuous  pyramidal 
paths  of  the  medulla  oblongata  and  may  be  followed  upward  through  the  ventral 
Slebll  hlmS'"'  '''"r"'  and  the  cerebral  peduncles  into  the  white  matter  o?the 
^HJ?nJ^T  ,?  !r  S"1  «".t°  '•'^  '^«'?«=*'  «'^y  '»»"^'-  ^^^'^'  in  the  motor  areas 
S^rl^rii      TK^*^^«^'''*"u"=  'l'""'^'  "^  '^^  nerve-cells  from  which  th.-  pyramiSj 

!nrlT  •  '"'^[™P"°?  '■•on'  the  superficial  gray  matter  of  the  cerebral  hemi- 
motrTtr^oJ^T  '^''^i^  '"  the  cord,  constituting  long  descending  (corticifugTl) 
rnotor  tracts.  On  reaching  the  lower  part  of  the  medulla,  from  80^0  per  cent  of 
the  component  fibres  of  each  pyramid  cross  to  the  opposite  sideX  way  of  the 

f«^Tl^''•H'l^P''^'^'  'P^^*^  '"^5)  and,  entering  die  cord,  d^cTnd  as  the 
latend  pyramidal  tract;  the  remaining  fibres  (on  an  average,  ab<^ut  irSer  cent  ) 
pass  downward  into  the  ventral  column  of  the  cord  as  the  difect  pyi^m  daftract! 
..I..J^„^  ^^"^T^u  '^l^""^^  pyramidal  tract  passes  outward  to  enter  the  kteral 
bradel^»n^  •  ^''r^  «^«^hanging  its  former  median  and  superficia  ToS 
ZLrf^  !i  K  °'^  Uteral  one.  Since  its  fibres  are  continually  entering  the  gray 
matter  to  end  about  the  radicular  cells  from  which  the  anterior  root-fibres  of  the 

hTltdrthe"fourth'r*=7''"^""'^^'y  '""'^  '"  ^'^^  -  ''  ^-^-ds"  intS  It  aUu 
tne  level  of  the  fourth  sacral  nerve,  it  ceases  to  ex  st  as  a  distinct  strand   although 

^elT^'^K^^'™'^'  '^"^"^  ''""^'^'^  "f  fib'-*^  »«  '»^  =»«  the  orison  of  the'cocS 
Sss  ilni'ore  mark^";^  ""*,  ''^''''  ^'"'^^  '"  '^'  ^''''^  ^"^^  ^"^^^  e.largemS 
fo  tll:T4eToto7lSne^"es''""'"^^  °"  *'='^°""'  "' ''''  ''^'^''"^  «'  '"^^  '^^'-^"^'^ 

seen  Kr^tfon^nT.h  '"  "'^^  fu  "'^>*""'  P''^^"''''^'  '""='  ^'^^^  ■■"  different  levels.  As 
^sider^b^  sis  ?hL  m«L?T'  *°-''^'^  u'*^°"  °'  *e  cord,  the  tract  occupies  an  area  of 
f^I^f^         ill',  "nesially  lies  again.st  the  posterior  horn  and  laterally  is  in  contact  with 

the  direc   cerebellar  tract,  by  which  it  is  excludedfr-.m  the  peripher%'     I„  fron     uh,  rr  iK  lim" 

^«  of  "heT^  ce^befc™J     if^^^^  "^'''^  '^^  diminution  and  disap,War- 

a^^ro^ches  andTfinaHv  reLr^^K  i'"  ""=  1°"'."  H"""""^  °^  '^e  cord,  the  pyramidal  field 
approacnes  ana  hnally  reaches  the  surface,  which  relation  it  retains  as  it  grows  smaller,  the 


'i^m 


1044 


-  T*g%^-'^ 


HUMAN  ANAluNfY. 


reduction  affecting  the  more  deeply  placed  fibres. 
o{  the  pyramidal  tract  in  cross-section  changes  fr 

lyi., 
Fig.  898. 


Section  ci  spinal  enrd  at  level  of  sixth  thoracic 
segment ;  slender  itostcrior  cnrnua  covered  with  sub- 
stantia gelalinosa ;  pfistero-lateral  angle  marks  greatest 
width  of  anterior  comit.  X  6.  Preparation  hv  Pro- 
fessor Spiller. 


oasequun  :e  c!  these  variatioas,  the  form 
I  wedge-sh.i; le  to  'liangular,  with  the  base 
a'  the  ;)••'  i.htr;  and  o  apex  dirvtted 
uiw.irl.  Durit",  I  '  Mr  descent  the  fibres  t)f  the 
pyriimi  !?1  tract  j,  .  ■  off  at  different  levels  col- 
tatemls  which  i'cii<l  horizontally  inward  and 
forward,  enter  llit  .;iay  ii.itter,  .uid  end  in  rela- 
tion with  the  anteri'jr  lom  ct  its.  A  similar 
course  is  loUowtsi  by  the  (larent  fibres  on  reach- 
ing the  segment  for  which  the\  are  destined,  the 
terminal  part  <>f  the  indi\  i  lal  fibres  ^wt^ping 
in  short  curves  through  th^  iiterveniiiK  ground- 
bundle  of  the  lateral  column  to  gain  the  radicular 
cells  around  which  thi  >  end.  By  means  of  its 
collaterals,  each  pyramidal  fibre  establishes  rela- 
tion with  several  cord-segments.  The  fibres  of 
this  tract  are  relatively  tardy  in  acquiring  Iheir 
medullary  coat,  which  proce^s  dots  not  bejjin 
until  the  last  month  of  fcetal  lii<  and  is  not  com- 
pleted until  after  the  seconu  year. 


The  direct  cerebellar  tract  (fas* 
ciculus  cerebellttsptnalis).  is  an  important 
ascending  path  of  the  second  order  that 
establishes  communication  between  the  reception  sensory  cord-nucleus  formed  by 
Clarke's  cells  and  the  cerebellum.  In  cross-sections  of  the  thoraci<  legion,  the  tract 
forms  a  superfiLial  flattened  comet-shaj)ed  field  that  occupies  the  dorsiil  halt  of  the  lateral 
column,  extending  froni  the  ajje.x  of  the  posterior  horn  forward  along  the  periphery 
of  the  cord,  to  the  outer  side  of  the  lateral  pyramidal  tract,  to  about  the  .interior 
plane  of  the  gray  commissure.  Its  ventral  end,  particularly  in  the  lower  cer\ical 
region,  is  broadest  and  projects  somewhat  into  the  lateral  column  in  advance  of  the 
lateral  pyramidal  field.  Although  as  a  compact  strand  the  direct  cerebellar  tract 
begins  at  the  tenth  thoracic  segment,  it  is  represented  by  isolated  nores  in  the  lumbo- 
sacral region.  The  fibres  collectively  are  large  and  become  niedullated  about  the  sixth 
fcetal  month  (Bechterew).  In  a  general  way  the  fibres  having  the  longest  course 
occupy  the  dorsal  part  of  the  tract  and  those  having  the  shortest  the  ventral  (Flatau). 

Arising  as  the  axones  of  the  cells  of  Clarke's  column,  the  components  of  the 
tract  pass  in  curves  almost  horizontally  outward  through  the  gray  matter  ami  lateral 
column  to  the  peripheral  field,  on  gaming  which  they  bend  sharply  brainu  ird  and 
ascend  without  interruption  to  the  medulla.  Their  further  course  includes 
sage  through  the  dorso-lateral  field  of  the  medulla  as  far  as  the  inferior  < 
peduncle,  by  which  the  fibres  reach  the  cerebellum  to  end  in  relation  with  the 
worm,  on,  probably,  both  the  same  and  the  opf)osite  sides. 

The  tract  of  Gowers  (fasciculus  anterolatcralis  ^nperficialis)  constitutes  another 
pathway  of  the  II  order,  which  connects  the  cord  r     h  the  cerebellum  an  1  probably 
also  establishes  relations  with  the  cerebrum.      In  cross-sections  the  tract    ippcars 
somewhat  uncertainly  defined  owing  to  the  intermingling  of  its  fibre-     ith 
adjoining  strands,  but  in  the  main  it  includes  a  superticial  crescentic  fi<„       h.. 
the  direct  cerebellar  and  lateral  pyramidal  tracts  bel md.  extends  alon>;  ;ii> 
of  the  cord  for  a  variable  distance,  and  usually  ends  in  front  in  the  viciit 
ventral  nerve-roots.     The  inner  btjundary.  separating  the  tract  in  questii 
lateral  ground-bundle,  lacks  in  sharpness  and  is  overlaid  by  the  adjoinin 
Below,  the  tract  appears  about  tlu;  middle  of   the  lumbar  region  and 
throughout  the  remainder  of  the  cord.     As  Gowers'  tract  ascends,  it  fai! 
the  considerable  increase  in  size  that  might  be  expected  in  view  of  thi 
additions  that  it  receives.     In  explanation  of  this,  the  pnbahlo  mingling  oi  -.mie 
its  fibres  with  those  of  the  direct  cerebellar  tract,  rather  ihan  their  ending  in  t! 
curd,  seems  the  iiuwt  plausible  (Ziehen). 

The  exact  origin  of  the  constituents  of  Ciowers'  tract  is  st  i  uncertain,  but  it  i- 
verj-  likely  that  its  fibres  are  chiefly  the  axones  of  the  neurones  marginal  and  inner 
cells)  situated  within  the  posterior  horn,  partly  frosn  the  same  and  partlv  from  the 


if  pas- 

bellar 

iiuerior 


lose  of 
;•  inches 
margin 
of  th- 
om  th 
-trantis. 
itinues 
)  show 
litii 'sal 


WHlTt  MATTER  OF  THK  SPINA      CORD. 


«o45 


opposite  sKk^,  with  contributions,  |X)s?iib!y,  in 
mattt-r.      A  ter  traver>inK  tht-  cord,  the  lateral  ft 
portion  of     he  pons,    the  tnct  ascends  the 
brain  stem  to  the  vicinity  ol    he  inferior  cor- 
pora quadrigeinina.      Here  ti  ,f  major  part  ui 
the  fibres  turn  backward  anti    ' 
superior  cerebellar  peduncle  a 
medullaiy  velum,   reach    the 
end  mostly  in  th     supert<  >r  » 
the  same  side  a 
Possibly  .1  part 


'  t!      cells  of  the  intermediate  gray 
.li  vi  the  m<-<lulia,  and  the  tegmental 


Fig.  >i99 


by  way  of  the 
1  the  supi    ior 
•rebellii'      to 
,  -  im,  par'U      n 

partly  cro»*ed   (Hirhi  j. 
■t  the  cerelieli-  T  conttrigent 


m.iy  share  the  j.  .th  of  tlv    dir     t  nuii^ar 

tract    md    in  this  way  rea<  li  the  certoeilum 

by    its    inie  ri'ir    peduncle      Ziehen  1:    is 

probable  that  .ill  fibres  from  Gowers    tract  <lo 

not  pass  to  the       rchellum,   but   '!i;;:   some 

continue  upward  t.i  •     mmate  in  reiaiHm  with 

the  neurones  of  the  ~     .erior  co-  K»ra    luadri- 

geinina  and    ol    the    optic    thal.mus      The 

fibres    of   the    t:,cct    acquire    tht     medullary 

CO.  '  about  the  beginning  of     le     ighth  n    nth  of  foetal  life  (Bechterew). 
The  lateral  ground-bui  die    fasi  .uh     'iteralis  proprius)  of  Flechsig 

th     remaimier  of  thf  lateral  cohinn.      Mi        uncertainty  prevails  as  to  its  u 

paths.  biK  bevond  .luestion  the  compositio       '  the  ground-bundie  is  ver  >■  co 

and  onprisfs  a  numVx  r  of  1'  nfr  exogenous  paths  that  descend  from  the  br 

as  f       lonp  iirendin     md  mar     shorter  endogenous  strands,  both  asc 

de^  ..-diiig.      These  ...     ' /mrff    .xury  chiefly  the  central  parts  of  the  lat 

anci.  Ill  a  gener;»   way,      ■  dose  to  the  gray  matter,  within  an  are;.      twi 

id  postern  r  horn     kwwn    ^  the  boundary  zone.     They  1       .» 

is  tield,  as       -  a  tt  .»   of  th.  ir  fibres  lie  scattered  ai 
icts  occupvi        he  i,  ..re  lateral  portions  of  the  ground 


limite<:  to 
exogenous  t 


Section  of  spinal  cord  at  "I  of  I'-wt^r  per 
Mth  Jumtiar  segment;  gray  n,  n-r  rtlaf  Iv  I 
in  amount ;  anterior  comua  bulky.  Pr'  .itio.^ 
Profeuor  Spiller.     x  6. 


wel' 

an( 

viiumn 

f  ante- 

c\         lot 

he  I  ..^'er 


the  rilires  of 
just  medial 
ers  (tractus 

whi<h  arise  as 


One  lonu  endogenous  lu.  ^pmo-thalamic  tract,  is  of  unusual  import.an.o  since  it  estab- 

lishes a  direct  sensory  hnk  be.  the  cord  .  nd  hiRher  centres.     This  tract  arises  from  the 

cells  of  tf>e  postenor  horn  of  the  .,,.:. -site  side,  the  a.xones  crossing  in  the  ant.    ior  commissure 
to  pursue  a  course  bramward  within  the  antero-lateral  ground-bundle     Alth. 
this  tTr.  <     e  scattered  and  not  collected  into  a  compact  strand,  their  chief  !<Kfi 
to  Gowrs  tract    Associated  with  the  fibres  destined  for  the  optic  thalan-.K 
ipmo-lr,     '»t)  that  end  in  the  region  of  the  corpora  quadrigemina. 

.ort  endogenous  tracts  include  both  ascending  and  descending 
thr-  A  chiefly  of  the  marginal  and  inner  cells  of  the  posterior  horn,  s..i.ie  cominK  from  the 

opposite  side  by  way  of  the  posterior  intracentral  commissure. 
Entering  the  lateral  column  the  axones  underj,")  T-like  iivision 
with  ascending  and  descending  limbs.  The  fornier  pas-  upward 
for  a  distance  that  usually  includes  only  from  one  to  wrt-^ 
segments,  then  bend  inward  and  enter  the  gray  matter  to  »- . ' 
probably  in  relation  with  other  posterior  hom  cells.  The  dou  n- 
wardly  directed  limbs  form  the  descendtne  endogenous  fibres 
which,  in  addition  to  occupying  the  Ix^'indarv  ...ne  are  also 
scattered  among  the  longer  tracts  ,r  the  grtMimi-hujidU  .\fter 
a  relatively  long  course,  the  .-nte  t!  wjy  matter  «o  end 
probably  in  relation  with  th«-  ''^kmnr.^  =  .-^f}*  TVs^-  are, 
therefore,  regarded  as  est»'  -hi-;  reftrs'paffhs.  Since  these 
endogenous  .itrands  lint  .  ,^  -  .r»OB«  levels  of  the  cord  ?hev 
are  often  collectively  te  fi  iEwTseym«it«l  a»4KKUtion  Mwa. 
Th»  exogenous  tracts  t  th-  .^ral  %u  H>3..i-<u  wV.v  are  ck**). 
related  with  those  fniirirl  m  th.  .^..nn^-K.,.aia~  ^  .},_..  3;,._-..^ 
column  and  what  tray  i-  «jid  -f  the  torm<-  \m^\-^  applies  t< 
.      ,  .  .  .'"«  'att"""-     Notwithstan««ti(.    th.    studv  that  rlte«c   tracts  hav. 

receivedl  much  uncertainty  exists  as  to  their  exact  origin  and  !»    nination  ;  it  may  Instated  in 

L!Hnnr^;h^*'^'"'r  i^  ""^^l  ^"^""^  ^^  ^'^"^  ^""^"^^    '™'  coordinating  centres  in,. 
relation  with  the  spinal  cord   and  constitute,    there.  •       .'^^ding  paths  other  than  the 


Seciloli  of  ipinal  rord  at  level 
of  tliird  aacral  sejpnent ;  posterior 
cornua  witli  lubiumia  gelatinosn 
are  relatively  bulky.  PiVparation 
by  Piotessor  Spillcr.     a  8. 


1046 


HUMAN   ANATOMY. 


(/ 


( 


3. 
3- 

4- 
5- 


pyramidal  tracts.     Amon^  those  whose  existence  within  the  antero-lateral  ground-bundle 
may  be  considered  as  established,  or  at  least  probable,  are  the  following : 

I.    Rubro-ipinal  fibres  from  the  cells  of  the  red  nucleus  within  the  cerebral  peduncles. 
Teclo-^nal fibres  from  the  cells  of  the  anterior  corpora  quadrlgemina. 
VesHbtUo-spimU fibres  from  the  celk  of  the  lateral  vestibular  (loiters')  nucleus. 
MetiuUo-sfinal fibres  from  tlie  cells  of  the  formatio  reticularis,  arcuate  and  lateral  nuclei. 
Olivospinal  fibres  from  the  cells  of  the  inferior  olivary  nucleus. 
Of  these  strands,  those  from  the  red  nucleus,  corpora  quadrigemina,  and  vestibular  nucleus, 
descend  chiefly  within  the  lateral  grotmd-bundle,  whilst  those  from  the  medulla  are  particularly 

within  the  anterior  ground-bundle.  Although  the  latter  includes 
the  greater  part  of  the  descendinc;  cerebello-rubro-spinal  fibres 
in  the  narrow  peripheral  sulcu-marginal  zone  of  Marie,  other 
fibres  are  probably  distributed  within  the  lateral  column  in 
front  of  the  direct  pyramidal  tract  These  descending  indirect 
cerebellar  fibres  are  often  collectively  known  as  the  tract  of 
Marchi-Lowenthal.  For  the  most  part  the  exogenous  strands 
are  so  intermingled  and  scattered  that  they  are  without  definite 
outlines ;  an  exception  to  this  is  presented  by  the  olivary  fibres, 
which  are  sometimes  seen  as  a  fairly  distinct  triangular  bundle, 
just  behind  the  anterior  root-fibres  at  the  periphery  of  the  cord, 
known  as  Helweg's  tract.  Concerning  the  exact  ending  of 
these  descending  paths  little  is  known,  but  it  is  reasonable  to 
assume  that  they  terminate  at  various  levels  in  relation  with  the 
ventral  horn  cells  which  are  thus  brought  under  the  coordinating  influence  of  the  higher  centres. 


Section  of  spinal  cord  at  level  of 
fifth  lacral  segment ;  anterior  curnna 
small  and  inconspicuous.  Prepara- 
tion by  Professor  Spiller.    X  8. 


Fig.  902. 


The  Fibre-Tracts  of  the  Anterior  Column. — According  to  the  simplest 
classification  the  anterior  column  includes  two  subdivisions  :  ( i )  the  anterior  pyra- 
midal tract  and  (3)  the  anterior  ground-bundle. 

The  anterior  pyramidal  tract  (fasciculns  cerebrospinalis  anterior),  also  called 
the  uncrossed  or  direct  pyramidal  tract,  stands  in  complemental  relation  with  the  lat- 
eral pyramidal  fasciculus,  being  comfwsed  of  the  pyramidal  fibres  that  do  not  undergo 
decussation  in  the  medulla  oblongata.  It  usually  contains  about  15  per  cent,  of  the 
pyramidal  fibres,  but  may  include  a  much  larger  proportion ;  on  the  other  hand,  it 
may  be  entirely  suppressed  when,  as  rarely  happens,  total  crossing  occurs. 

The  direct  pyramidal  tract  occupies  the  inner  part  of  the  anterior  column, 
forming  a  narrow  arra  along  the  median  fissure  that  extends  from  the  white  commis- 
sure behind  to  near  the  ventral  margin  of  the  cord.  Ordinarily  the  tract  ends  below 
about  the  middle  of  the  thoracic  cord,  but  in  exceptional  cases,  when  a  larger  pro- 
portion of  the  pyramidal  fibres  than  usual  is  included  in  the  tract,  it  may  extend  as 
tar  as  the  middle  of  the  lumbar  enlargement,  with  corres- 
ponding increase  in  its  cross  area.  If,  on  the  other  hand, 
the  number  of  uncrossed  fibres  is  unusually  small,  the  tract 
may  reach  only  as  far  as  the  cervical  enlargement,  with  a 
reduction  of  its  sagittal  dimension.  Although  often  spoken 
of  as  the  "uncrossed"  pyramidal  tract,  this  characteristic 
applies  only  to  the  relation  of  the  fibres  at  the  decussation 
in  the  medulla,  since  in  their  downward  journey  in  the  cord 
the  great  majority  of  the  fibres  traverse  the  anterior  white 
commissure  at  appropriate  levels  to  end  in  arborizations 
about  the  ventral  root-cells  of  the  anterior  horn  of  the 
opposite  side.  It  is  highly  probable,  however,  that  some  fibres  do  not  undergo 
decussation,  but  terminate  about  the  radicular  cells  of  the  same  side. 

The  anterior  ground-bundle  (fasciculus  anCorior  proprius),  .'ollowing  the  divi- 
sion of  Flechsig,  includes  the  remainder  ol  the  ventral  column.  In  front,  where  its 
lateral  limits  are  uncertain,  it  is  continuous  with  the  ground-bundle  of  the  lateral  col- 
umn, the  two  together  Ix-ing  often  with  advantage  regarded  as  constituting  a  single 
antero-lateral  tract.  What  has  been  said  concerning  the  constitution  of  the  lateral 
ground-bundle  applies  in  the  main  to  that  of  the  anterior  column,  since,  here  as  there, 
the  region  bordenng  the  gray  matter  contains  chiefly  the  shvirt  endogenous  strands, 
while  the  more  porif  heral  jwrt*  r>f  the  groimd-himdle  .nre  orcupieH  by  the  lone 
exogenous  paths,  int'.'rmingled,  however,  with  the  longer  intrinsic  fibres. 


Section  of  spinal  cord  at 
level  of  lower  part  of  cuccyf;eal 
segment^  dilleretiliation  of  ror- 
nua  is  uncertain.  Preparation 
by  Professoi  Spiller.     v  g. 


WHITE  MATTER  OF  THE  SPINAL  CORD. 


1047 


The  endoftitous  fibie*  arise  as  the  axones,  chiefly  of  the  inner  cells  of  the  posterior  horn, 
as  well  as  froin  <Jie  celts  of  the  iiitemiediate  gray  matter  (Ziehen),  and  in  great  measure  cross 
by  way  of  the  anterior  white  commissure  to  the  opposite  anterior  column.  After  undergoing 
T-division,  their  upwanlly  directed  limbs  constitute  the  ascending  paths  and  those  coursing 
downward  the  descending  ones.  While  both  sets  of  fibres  for  the  most  part  pursue  only  a  short 
path,  that  of  the  descending  limbs  is  usually  the  longer,  the  fibres  entering  the  gray  matter  to 
end  in  relation  with  the  anterior  hom  cells  of  lower  levels.  They  are,  therefore,  regarded  as 
secondary  reflex  paths.  The  termination  of  the  ascending  limbs  is  uncertain,  but  probably  is 
within  the  gray  matter  of  the  posterior  hom. 

The  exof  enoua  tracts  of  the  anterior  ground-bundle,  have  been  mentioned  in  connection 
with  those  of  the  lateral  column.  The  investigations  of  Luwenthal,  Marchi,  Bechterew,  Thomas 
and  others,  support  the  presence  within  the  anterior  ground-bundle,  also  within  the  lateral 
column,  of  long  efferent  (cortifugal)  paths  that  arise,  at  least  indirectly,  from  neurones  within 
the  cerebellum,  and  end  ui  relation  to  the  anterior  hom  cells.  These  paUis,  collectively  known 
as  the  descending  cerebeUo-spinal  tract,  or  tract  of  Marchi-Lowenthal,  are  of  uncertain  extent 
and  outline,  and  more  or  less  mingled  with  the  constituents  of  other  strands.  In  a  general  way 
the  descending  cercbello-spinat  fibres  occupy  a  narrow  crescentic  field  that  appropriates  the 
periphery  of  the  cord  for  a  variable  distance  both  mesially  .iid  laterally.  In  the  anterior  column 
the  tract  includes  the  anterior  marginal  bundle,  probably  from  the  nucleus  fastigii  of  the 
cerebellum  of  the  same  and  opposite  side,  and  mesially  mingles  with  fibres  from  the  corpora 
quadrigemina  as  constituents  of  the  visual  reflex  paths.  The  termination  of  these  descending 
paths  is  assumed  to  be  in  relation  with  the  anterior  hom  cells,  which  in  this  manner  are  brought 
under  the  influence  of  the  higher  coordinating  and  reflex  centres. 

In  recapitulation  the  chief  ftbrc-tracts  of  tlie  spinal  cord  may  be  grouped  as  follows: 

I.    Within  the  Posterior  Column— 
Ascending  Paths  : 

Direct  ascending  posterior  root-fibres. 

Ascending  endogenous  fibres. 
Descending  fbths  : 

Descend.ng  posterior  root-fibres. 

Descending  endogenous  fibres. 

II.    Within  the  lateral  Column— 
Ascending  Paths  : 

Direct  cerebellar  tract. 
Gowers'  tract. 
Spino-thalamic  tract. 
Short  endogenous  fibres. 
Descending  Pat /is  : 

Lateral  pyramidal  tmct. 

Indefinite  exogenous  tracts  (including  the  mbro-spinal,  quadri- 
gemino-spinal,  vestibulo-spinal,  cerebello-spinal  and  olivo- 
spinal). 
Descending  endogenous  fibres. 

III.    Within  the  Anterior  Column  - 
Ascending  /btAs . 

Ascending  endogenous  fibres  from  posterior  hom  cells. 

Ascending  endogenous  fibres  from  anterior  hom  cells. 
Descending  Paths  : 

Direct  pyramidal  tract. 

Descending  cerebello-spinal  fibres. 

Tegmento-spiiiiil  fibres. 

Blood- VesselB  of  the  Spinal  Cord — The  arteries  supplying  the  cord  are 
from  many  sources — the  vertebral,  deet)  cervical,  intercostal,  hinibar,  ilio-lumbar  and 
lateral  sacral  of  the  two  sides — since  the  vascular  net-work  within  the  pia  accompanies 
the  nervous  cylinder  throughout  its  length.  Above  and  within  the  skull,  the  verte- 
bial  arteries  give  of|  the  two  anterior  and  the  two  posterior  spinal  arteries,  of  which 
the  latter  retain  their  independence  and  descend  upon  the  dorso-Iateral  surface  of  the 
cord,  one  on  each  side,  in  front  of  the  posterior  nerve-roots.  The  two  anterioi 
spinal  arteries,  on  the  other  hand,  soon  unite  (somewhere  above  the  level  of  the 
third  cervical  nerve )  into  a  single  trunk,  which  descends  along  the  ventral  surface  of 
the  cord,  just  in  front  of  the  anterior  median  fissure. 


MM 


(/ 


1048 


HUMAN  ANATOMY. 


As  these  stems  pass  downward,  they  are  joined  and  reinforced  by  the  segmental 
sptnaJ  branches  given  of!  by  the  vertebral,  intercostal,  lumbar  and  lateral  sacral 
arteries,  which  enter  the  spinal  canal  through  the  intervertebral  foramina  and,  after 
pierang  the  dura  and  giving  oS  small  radicular  branches  to  the  nerve-roots  them- 
selves, divide  into  ventral  and  dorsal  branches  that  follow  the  respective  nerve-roots 
to  the  cord,  where  they  join  with  the  longitudinal  trunks  which  they  thus  assist  in 
maintaining.  By  the  junction  of  horizontal  branches  arising  from  these  arteries,  a 
sen«  of  complete  annular  anastomoses  is  formed  around  the  cord,  which  is  still 
further  enclosed  by  additional  vertical  stems  resulting  from  the  union  of  upward  and 
downward  coursing  twigs.  In  this  manner,  in  addition  to  the  large  single  anterior 
spinal  trunk  {Iractus  arteriosus  spinalis  anteric)  in  the  mid-line  in  front  and  the 
paired  postero-lateral  trunk  (tractus  arteriosus  postero-lateralis  spinalis)  just  in 
advance  of  the  dorsal  nerve-roots,  smaller  longitudinal  arteries  are  formed  at  the 
side  and  in  the  vicinity  of  the  nerve-roots. 

From  the  arterial  net- work  within  the  pia,  the  nervous  tissue  is  supplied  by  pene- 
trating twigs  that  enter  the  surface  of  the  cord  at  various  points. 

The  gray  matter  receives  its  principal  blood-supply  from  the  series  of  anterior 

fissural  arteries,  over  two  hundred  in  number,  which  pass  from  the  anterior  spinal 

trunk  backward  within  the  median  fissure  to  its  bottom  and  there  divide  into  right 

P  and  left  branches,  which  traverse  the 

j^^erior  •uical  ^^'  anterior  white  commissure  to  gain  the 

VI  p.      1   I  gray  matter  on  either  side  of  the  central 

V's'\7vifi\uV><C''"  '^""^'-     '^''^  vessels,  the  suko-mar- 

iK  'r     1^  '^"^X.       ^PMtero-tatenti        ginal  arteries,  divide  into  ascending 

\^  \V'*K:'  r    'Jr^^L      Pentiniiiig         and  descending  branches  that  provide 
\    nt^l   "^'^''T  /i^>%v  /"^"^  '*"'  ^^^  ^"'•''^  ^"^y  matter  with  the 

T  vX  A  \'  /  K\LMIBi/7  fTVA  exception  of  the  most  peripheral  zone. 

i  ,    'VV"'  >*  JB-^  ^i3^\  ^^^  \a'»ac,  toj|;ether  with  the  white 

I't  ^  S|'  tl^^^W  ■v>^;r!;ir\  matter,    receives    its   supply    from 

*</. -,i   (^^HT'jJ^V— ^--.rj  t\\K  penetrating  branches  that  come 

from  the  surrounding  intrapial  trunks 
and  enter  the  surface  of  the  cord. 
Unpaired  horizontal  twigs,  the  pos- 
terior sulcal  arteries,  follow  the 
posterior  median  septum  at  different 
levels  for  some  distance,  but  before 
reaching  the  posterior  commissure 
usually  break  up  into  terminal  ramifi- 
cations, some  of  whicn  pass  to  the 
gray  matter  of  the  posterior  horns. 
Communications  exist  between  the 
penetrating  twigs  of  the  radicular 
^„,    .      r         ,       .^  .        .  arteries  and  the  lateral  branches  of  the 

anterior  fissural  After  entenng  the  nervous  tissue,  however,  each  artery  provides 
the  sole  supply  for  some  definite  part  of  the  cord  ;  they  are  therefore  "end-arteries," 
a  tact  which  explains  the  extensive  and  elaborate  system  of  vessels  necessary  to 
maintain  the  nutrition  of  the  cord. 

The  plexiform  veins  within  the  spinal  pia  are  formed  by  the  union  of  the  small 
radicles  that  collect  the  blood  from  the  intraspinal  capillaries  and,  after  an  independ- 
ent course  similar  to  that  of  the  arteries  but  not  accompanying  them,  emerge  at  the 
surface  of  the  cord.  From  the  venous  net-work  within  the  pia  six  main  longitudinal 
trunks  are  differentiated.  These  are  :-the  unpaired  anterior  median  vein,  in  front  of 
the  corresponding  fissure  ;  the  paired  antero-lateral  veins,  just  liehind  the  ventral 
nenc-roots— these  two  sets  receiving  the  tributaries  emerging  from  the  median  fissure 
and  in  the  vicinity  of  the  anterior  root-fibres  ;  the  unpaired  posterior  median  vein, 
behind  in  the  mid-line  ;  and  the  paired  posterolateral  veins,  just  behind  the  dorsal 
roots.  I  he  blood  is  conveyed  from  these  intrapial  channels  chiefly  by  the  radicular 
trw.  following  the  nerxe-ronts,  which  rommunieatc  with  or  terminate  in  the  aiUeiior 
and  posterior  long-tudinal  spinal  veins  within  the  vertebral  canal,  from  which  the 


PenetntInK 
arter)' 


Anterior 

fiHural      Anterior    AKending  branch 
•pinal  arter)' 

Part  of  tianiveiM  lectlon  of  inJectH  spinal  cord  showing 
vaacular  supply  o(  white  and  »ray  matter.    >  10. 


WHITE  MATTER  OF  THE  SPINAL  CORD.  1049 

intervertebral  efferents  carry  the  Wood  into  the  vertebral,  intercostal,  lumbar  and 
lateral  sacral  veins.  A  part  of  the  blood  from  the  intrapial  ple.xus  is  conducted 
upward  by  the  anterior  and  posterior  median  veins  into  the  venous  net-work  covering 
the  pons  and  thence  into  the  lower  dural  sinuses. 

Definite  lymphatic  vessels  within  the  spinal  cord  are  unknown. 

Development  of  the  Spinal  Cord.— A  sketch  of  the  general  histogenetic  processes  leading 
to  the  differentiation  of  the  neurones  and  the  neuroglia  has  been  tg:  r>n  (page  1009) ;  it  remains, 
therefore,  to  consider  here  the  changes  in  the  neural  tube  by  which  the  definite  spinal  cord  is 
evolved.  From  the  time  of  its  closure,  probably  aboiii  the  end  of  the  second  week  of  fittal 
life,  the  neural  tube  presents  three  regions :— the  relatively  thick  laUral  ivalls  and  the  thin  ven- 
tral and  dorsal  intervening  bridges,  the >?oor-  and  roof-plates,  that  in  front  and  behind  complete 
the  boundaries  of  the  canal  in  the  mid-line.  By  the  fifth  week  the  lateral  walls  exhibit  a  distinct 
differentiation  into  three  zones— the  inner  ependymat  layer,  the  middle  nutlear  layer  and  the 
outer  marginal  layer,  surroimded  by  the  external  limUing  membrane.  In  contrast  to  the  other 
two,  the  marginal  zone  is  almost  devoid  of  nuclei  and,  beyond  affording  support  and  perhaps 
assisting  m  providing  a  medullary  coat,  plays  a  passive  r6le  in  the  production  of  the  nervous 
elements. 

By  this  time  the  bmr-T  general  oval  contour  of  the  developing  cord,  as  seen  in  cross-sec- 
tions, has  become  modified  by  the  conspicuous  thickening  of  the  antero-lateral  area  of  the  nuclear 
layer  into  a  prominent  mass  on  each  side,  whereby  the  reticular  marginal  layer  is  pushed  out- 


FiG.  904. 
Roof-plaw 


Fig.  905. 

Roof'i>Utc 


Ooraaliom 


Epntdynwl 
laj'cr 


Vmtnil 
root-fibres 


Ncurobluu 


<■  Floor-plate 


Developing  iplruil  cord  o(  (bout  lour 
week*.    X  100.    (M».) 


Ploor-plaie 


Ventral  root-fibm 


Oevelopinc  "plnal  cord  of  about  five  weeki. 

X  60.    (Mj.) 


ward  With  corresponding  Increase  in  the  width  of  the  entire  ventral  part  of  the  cord  which  is 
now  broadest  in  front.  Within  this  thickened  ventro-lateral  part  of  the  nuclear  layer'  later  the 
antenor  horn  of  gray  matter,  as  early  as  the  fourth  week  young  neurones  are  seen  :rom  which 
axones  grow  outward  through  the  marginal  zone  and  pierce  the  external  limiting  membrane  as 
the  representatives  of  the  antenor  root-fibres  of  the  spinal  neives.  Postero-laterally  the  thin 
nuclear  layer  to  covered  by  a  somewhat  projecting  thickened  area  within  the  marginal  layer 
known  as  the  oval  bundle,  whose  presence  ii.  due  to  the  ingrowth  of  the  developing  tlorsal  root- 

e^f  the"'fdurth*S(H,"r*'  °'  '*"  '"'""'  '^"''"""'  ^^'''^  ^^^  begins  as  early  as  the 
^  .'!lf^'"'"'  *','*'  '^"f*  "Changes,  the  lumen  of  the  cord  becomes  he^rt-shaped  inconsequence 
UtTaTIL'iJl^T.i?^'''  '""*"«,"''«»  transver^,  diameter,  with  corresponding  bulging  of  the 
Irl^ff  ^".1  II^*?'!  ""'""*■■  "  '«'K«'"dlnal  furrow  appears  by  which  the  side  iails  of  the  tul« 
HT,r  ^.  t^"-°i  "^  '"f"'  *''■?  f*^^"/""''  «he  zrntral tones  (the  alar  and  basal  lamina-  of 
rlrtlln,J?.^  .u  K  •  "  ''  °'  T*'^  importance,  since  in  the  cord-segment,  and  also  with  less 
^fiKll   the  brain-segment  of  the  neural  tube,  these  tracts  are  definitely  connected  with  the 

^~  ,^  ^'  "5'""  "•''^''!!'  «"  '^^'  '""*  ^"''  "'«  '*"'«'^-  ""'1  »he  ventral  zone  with  the 
m^w  roots  In  advance  01  the  fto.,r-plale  the  venlrafly  protruding  halves  o(  Ok-  corti  include  a 
tm>ad  and  sMIow  furrow  which  marks  the  position  of  the  anterior  median  fissure.  During  the 
sixth  week  the  form  of  the  tube-lumen  becomes  further  modified  by  the  elongation  and  narrow- 


I050 


HUMAN  ANATOMY. 


mg  of  the  dorsal  part  o£  the  canal  in  consequence  of  the  approximation  of  its  walls,  which  in  the 
course  of  the  seventh  week  is  closer  and,  by  the  end  of  the  second  month  is  completed  by  the 
meeung  and  fusion  of  the  adjacent  inner  layers,  with  obliteration  of  the  intervening  cleft 
and  the  proouction  of  the  posterior  median  septum  in  its  place.  Since  the  partition  is  formed 
by  the  union  of  the  inner  (epeiidymal)  layers,  it  is  probable  that  the  septum  is  to  be  regarded 
as  e^ntially  neurogliar  in  origin  and  character.  It  must  be  remembered,  however,  that  a 
certain  amount  of  mesoblastic  tissue  may  be  later  introduced  in  company  with  the  blood-vessels 
which  subsequently  invade  the  septum.  The  remaining  and  un-.losed  part  of  the  lumen  for 
a  time  resembles  m  ouUine  the  conventional  spade  of  the  playing  card,  with  the  s.em  directed 
ventrally ;  but  later  gradually  diminUhes  in  size  and  acquires  the  •  ontour  of  the  definite  central 
canal. 

During  these  alterations  in  the  extent  and  form  of  its  lumen,  the  gray  maUer  of  the  develop- 
ing cord  markedly  increases,  especially  behind  where  the  posterior  horn  appears  as  a  projection 
beneath  the  broadening  mass  of  the  ingrowing  dorsal  root-fibres.  As  the  posterior  horn  becomes 
better  defined,  the  rootrbundle  becomes  meso-laterally  displaced,  lying  behind  the  horn  and 
then  constitutes  the  tract  of  Burdach.  Goll's  tract  is  formed  somewhat  later  and  at  about  the 
third  month  appears  as  a  narrow  wedge-shaped  area  that  is  introduced  between  the  mid-line  and 
Burdach  s  tract.  Towards  the  erfd  of  the  second  month,  the  anterior  white  commissure  is 
indicated  by  the  oblique  transverse  ingrowth  of  axones  into  the  most  ventral  part  of  the  floor- 
plate  as  they  make  their  way  to  the  opposite  side.    Meanwhile  the  anterior  median  fiaiure  has 


Fig.  907. 


GoU'i  tnct 

BunUch's  tnct 


Pia  nialer 


Anterinr  columii 


Developing  spinal  con]  of  about  acven  and  one-half 
weeks.     K^^.    {His.) 


wHh  |4a]  procca         column 

Developing  aijinal  cord  of  about  three  months.    Xjo.   (Mi.) 


become  deeper  and  narrower  in  consequence  of  the  increased  bulk  of  medio-ventral  parts  of  the 
cord.  As  the  fissure  is  thus  differentiated  the  process  of  mesoblastic  tis.sue,  which  from  the 
earheit  suggestion  of  the  groove  occupies  the  depres.sion,  is  correspondingly  elongated  and 
affords  a  passage  for  the  blood-vessels  destined  for  the  nutrition  of  the  interior  of  the  cord 
Until  the  third  month  the  gray  matter,  derived  from  the  nuclear  layer,  is  much  more  voluminoui 
than  the  surrounding  marginal  layer,  whkrh,  so  far  as  the  contribution  of  nervous  elements  is 
concerned,  is  (lassive,  since  ite  conversion  into  the  white  matter  depends  upon  the  ingrowth 
of  axones  from  the  neurones  situated  either  within  or  outside  the  cord. 

The  development  of  the  individual  fibrf  tracts  includes  two  stages,  between  the  comole- 
tion  of  which  a  considerable,  and  sometimes  a  lone,  period  intervenes.  The  first  marks  the 
invasion  of  the  supporting  tissue  of  the  marginal  mne  by  the  ingrowing  axones  as  naked  axis- 
cylinders  ;  the  second  witnesses  the  clothing  of  these  fibres  with  myelin.  The  period  between 
the  appearance  of  the  tract  and  the  development  of  the  medullary  coat  is  variable  In  some 
cases,  as  in  the  great  cerebro-spinal  motor  paths,  although  the  fibres  gro-.v  into  the  cord  durint 
the  fifth  month  of  fietal  life,  myelination  does  not  begin  until  shortly  before  birth  and  is  not 
completed  until  after  the  second  year.  In  other  cases,  as  in  the  direct  cerebellar  a  period  of 
three  months,  from  the  third  to  the  sixth,  elapses.  It  is  probable  that  the  acquisition  of  the 
medullary  coat  commences  before  the  functional  activity  of  the  fibres  hegln-i  although  su<;h 
stimulation  undoubtedly  assists ;  further  myelination  proceeds  gradually  along  the  course  of 
the  fibres  and  in  the  direction  of  conduction. 


PRACTICAL  CONSIDERATIONS:    SPINAL  CORD.  105 1 

Based  on  the  observations  of  Flechsig,  His,  Bechterew,  and  otliers,  the  time  of  the 
appearance  and  of  the  development  of  the  medullary  coat  of  some  of  the  fibres  within  the 
spinal  cord  may  be  given. 


Pibm  of 

Anterior  root 
Burdach's  tract 
GoU's  tract 
Pyramidal  tracts 
Direct  cerebellar  tract 
Cowers'  tract 


Appear 

about  4th  week 
during  4th  week 
about  9th  week 
end  of  5th  month 
beginning  of  3rd  month 
<iuring  4th  month 


Myelinate 

during  5th  month 
end  of  6th  month 
beginning  of  7th  month 
9th  month  to  snd  year 
about  6th  month 
during  6th  month 


The  presence  of  the  simu  terminalis  (page  1030)  in  the  cord  at  uirth  depends  partly  upon 
the  persistence  of  the  lumen  of  the  central  canal  at  the  lower  end  of  the  conus  medullaris  and 
partly  upon  a  proliferation  of  the  wall-cells  of  the  subjacent  segment,  followed  by  secondary 
dilatation  shortly  before  birth. 

During  the  early  weeks  of  development,  the  neural  tube  extends  to  the  lowermost  limits  of 
the  series  of  somites  ;  but  after  differentiation  of  the  root-fibres  begins,  the  segment  of  the  cord 
below  the  le-  el  of  origin  of  the  first  coccygeal  nerves  Is  marked  by  feeble  proliferation,  the 
effects  of  which  are  soon  manifest  in  the  rudimentary  condition  of  the  caudal  end  of  the  cord. 
With  the  subsequent  development  of  the  other  regions,  this  histological  contrast  becomes  more 
evident,  to  which  is  sc<on  added  the  conspicuous  attenuation  caused  by  the  attachment  of  the 
lower  end  of  the  cord  to  the  caudal  pole  of  the  spine,  which  elongates  with  greater  rapidity 
than  the  contained  nervous  cylinder.  In  this  manner  the  lowest  segment  of  the  cord,  with  its 
mesoblastic  envelope,  is  converted  into  the  delicate  thread-like  JUum  ttrminiUe,  within  whose 
upper  half  are  found  the  remains  of  the  rudimentary  nervous  tissue. 

PRACTICAL  CONSIDERATIONS :  SPINAL  CORD. 

Congenital  Errors  in  Development.— TYie  spinal  cord  may  bo  absent  {amyelia), 
or  it  may  be  defective  in  a  certain  portion  {cUeomyelia).  In  such  conditions,  however! 
the  patient  cannot  live.      The  cord  may  be  double  from  bifurcation  {diplomyelia). 

A  spina  bifida  is  a  congenital  condition  due  to  a  deficiency  in  the  vertebra, 
almost  always  of  the  laminae  and  spinous  processes.  There  is  usually  a  protrusion 
of  the  contents  of  the  spinal  canal,  although  in  some  cases  there  is  no  protrusion,  and 
in  others  the  vertebral  canal,  or  even  the  central  canal  of  the  cord  may  be  open  to 
the  surface.  Three  varieties  of  tumors  are  described  according  to  their  contents.  If 
the  meninges  only  protrude  from  the  canal  in  the  form  of  a  sac  containing  cerebro- 
spinal fluid,  it  is  called  a  meningocele;  if  the  sac  contains  a  portion  of  the  cord  also 
It  IS  called  a  meningo-myelocele.  In  the  third  variety,  syringo-myeloceU,  the  cavity 
of  the  tumor  is  found  to  consist  either  of  the  dilated  canal  of  the  cord,  so  that  the 
thinned-out  substance  of  the  cord  is  in  the  wall  of  the  sac,  or  of  a  cavity  in  the  cord 
tissue  itself.     This  is  the  least  common  of  the  three  forms. 

In  the  meningo-myeloeele,  which  is  the  most  common  form,  the  cord  becomes 
flattened  out  and  attached  to  the  posterior  wall  of  the  sac,  but  still  has  its  central 
canal  intact.  The  spinal  nerves  cross  the  sac  to  their  corresponding  intervertebral 
foramina.  In  this  and  in  the  syringo-myelocele  there  is  frequently  some  d^ree  of 
paralysis  in  the  parts  below  from  disturbance  of  the  cord  at  the  seat  of  the  tumor. 
The  most  common  seat  of  the  defect  is  in  the  lumbo-sacral  region.  It  is  rare  in 
other  parts  of  the  spine.  Therefore,  the  bowels,  bladder,  and  lower  extremities  are 
the  parts  most  frequendy  affected.  If  the  lesion  is  confined  to  the  lower  part  of  the 
sacral  region,  the  extremities  usually  escape.  Paralytic  talipes  is  comparatively 
common. 

.^'^-u  '*."*'.  "^T  ''"*  "'  demarcation  between  the  medulla  oblongata  and  the 
cord.  The  beginning  of  the  latter  is  variously  given  as  at  the  origin  of  the  first 
cervical  nerve,  the  lower  margin  of  the  foramen  magnum,  or  the  decussation  of  the 
pynimids,  the  last  being  the  more  generally  accepted. 

Since  in  the  adult,  the  spinal  cord  ends  below  usually  at  the  level  of  the  disc 
between  the  first  and  second  lumbar  vertebrae,  injuries  of  the  spine  below  the  second 
lumbar  vertebra  do  not  involve  the  cord.     The  membranes  of  the  cord,  however 
containing  cerebro-spinal  fluid  extend  as  far  aS  the  second  or  third  sacral  vertebra, 
so  that  at  this  level  injuries  with  infection  may  cause  faul  meningitis. 


1052 


HUMAN  ANATOMY. 


The  bony  canal  is  lined  with  penosteum,  unlike  the  cranium,  in  which  the 
external  layer  of  the  dura  mater  serves  that  purpose.  The  spinal  dura  is  separated 
from  the  postenor  common  ligament,  the  ligamenta  subflava,  and  the  periosteum  by  a 
fatty  areolar  tissue  containing  a  plexus  of  veins.  Extensive  extradural  hemorrhage 
may,  therefore  occur  without  serious  pressure  on  the  cord.  The  blood  tends  to  sink 
.nf^T^'  A  r  ""^y  Pi"**  u";^  symptoms  of  compression.  The  dura  is  thick 
and  strong  and  offers  considerable  resistance  to  the  invasion  of  disease  from  with- 

^thirfhl  v.^"^'*'    Tr.**"  ^"'"^  ?f  *\^  ^^"*'"'*'  «■■ '°  "lalignant  tumors  arising 
within  the  vertebrae.      Infections  outside  the  spinal  column,  as  in  abscess  of  the  back 

oL^  ^T'  ""u^"  ^"'^"'^  ^°?^  the-communicating  veins,  giving  rise  to  extradural 
abscess  and  perhaps  to  extensive  meningitis.  •  8       s 

The  spinal  cord,  surrounded  by  cerebro-spinal  fluid,  hangs  loosely  within  the 
dura  being  attached  to  it  only  by  the  roots  of  the  spinal  n;rves  which  receTve  in vit 
ZwlTr  %  f  thy  .pass  outward,  by  the  ligamenta  denticulata.  and  by  the 
delicate  fibres  of  arachnoid  tissue  extending  from  the  pia  to  the  dura.  The  cord  is 
therefore  not  frequently  injured  from  external  violence"^  The  numerous  arti<Xtio^ 
^h.  HuTr  W*  ^""f  '•'^  plasticity  of  the  ligaments  and  of  the  intervertebral  discs  pemi? 
the  distribution  of  much  of  the  force  applied  to  the  spine  before  it  reaches  the  cord. 
«„,.        K^K  P^"^"^  '^'l  cerebro-spinal  fluid  is  contained  in  the  subarachnoid 

space,  which  communicates  freely  with  the  same  space  in  the  cranium,  ind  is  con 
tmuous  with  the  ventricular  fluid  through  the  foramen  of  Majendie 
»^l,i  AU,      '^  e-j'PO'e^  to  the  danger  of  penetration  by  sharp  instruments  only  from 
behind,  bu    even  here  the  overlapping  of^the  lamin*  and  spinous  processes  offera 

and  the  nsk  there  from  such  wounds  is  correspondingly  greater.  At  lower  levels  in 
order  that  the  canal  may  hs  reached,  the  vuln^ating  insSment  must  b^  d  r«:ted  n 

tte  nTn  f3'  °"T*^  °'  '?"  >■"•".*•  ^^^^  *'"  W  in  the  different  poS  of 
the  spine,  being  greatest  m  the  dorsal  region.  ^ 

lesion^f'Vi"!^''*!?!"^  1"''  molecular  disturbance  and  without  obvious  gross 
T^^  "*•  although  more  frequent  than  has  been  supposed,  is  rare  because 

of  (a)  the  arrangement  of  the  different  constituents  of  the  vertebral  column  wSb^ 
means  of  its  curves,  the  elastic  intervertebral  discs,  its  numerous  joh^l  and  the 
large  amount  of  cancellous  tissue  in  the  vertebral  bodies,  is  able  to  bSe  up  and 

fnT^ln^'^''";'^'''  '?■■'"  °'  r*"^  ^^u*^^  "'  ^•'«'*^"'=^  ••  ('^  the  situatioS^f'thrcorS 
in  the  centre  of  the  column,  where,  as  the  most  frequent  serious  injuries  to  the  spine 
are  caused  by  extreme  forward  flexion,  it  is  somewhat  removed  fr^m  dange?  "n 
accordance  with  a  aw  of  mechanics  that  "when  a  beam,  as  of  timber. TexS  to 
breakage  and  the  force  does  not  exceed  the  limits  of  the  strength  o  the  KiaT 
one  division  resists  compression,  another  laceration  of  the  particles,  while  thlthS' 
between  the  two,  is  in  a  negative  condition"  (Jacobson)  ;  Or)  the  suspension  of  th^ 
cord  m  the  surrounding  cferebro-spinal  fluid  (-like  a  cate^ liar  hung  by  a  thread 
m  a  phial  of  water' •-Treves)  by  its  thecal  attachments  and  nerN-e-roots  (rf)  S 
connection  above  with  the  cerebellum,  itself  resting  on  ,,n  elastic  ^^^ieW' 
which  minimizes  the  transmission  downward  of  violence  applied  to  the  craniS 
SeTgr'oi^Ie -r  ;rffctl^  ^''"^"'''°"  ^^  undoubtedly^'Sue  to  hemorrhTgHr 
Th.  2li"/""'  "' '^'^  f"^*^  may  occur  from  sprains,  as  in  forced  flexion  of  the  spine 

S.  ^  ''"^H^;!!''"'*  """"  *^7''"'  "'^  ""'^  '^"^  d"«  to  fracture-dislocations  o?  the 
spine,  the  cord  being  more  or  less  crushed  between  the  upper  and  lower  fragments 
It  IS  so  delicate  a  structure  that  it  may  be  thoroughly  disorganized  without  evrdeni 
mjury  to  the  membranes  or  alteration  of  its  internal  foAn.  tL  paral^ss  of  the  parti 
bdow  will  be  complete  or  partial  according  to  whether  the  whole  or^nly  ..  ^rt^l 
he  ransverse  section  of  the  cord  at  the  seat  of  injury  is  destroyed.  Since  when 
he  lesion  IS  complete  everything  supplied  by  the  conf  below  the  seat  of  the  Sn 
»  paralyzed  the  higher  the  injurv  to  the  cord  the  greater  the  gravity  of  the^ 
When  the  atlas  or  axis  is  fractured  and  displaced  the^ital  centres^n  the  meSilla^ 

Z^tr  ■]  ±'*'''  "•'*y,  '■'=''""  '"""«J'«ely.  The  phrenic  nerves  which  ar^e  chieiw 
from  the  fourth  cervical  segment,  but  partly  from  the  third  and  fifth  ™J^Jf 
are  also  paralyzed  and  respiration  ceases.  scgmenis. 


PRACTICAL  CONSIDERATIONS:  SPINAL  CORD.  1053 

la/raciure-dislocations  of  the  spine  it  is  the  body  of  the  vertebra  which  is  most 
frequenUy  fractured,  the  hgaments  yielding  posteriorly  and  permitting  the  dislocation, 
rhe  fractured  edges  of  bone  are.  therefore,  in  front  of  the  cord ;  and,  as  the  upper 
fragment  passes  forward,  the  anterior  or  motor  portion  of  the  cord  is  pressed 
and  crushed  agamst  the  sharp  upper  edge  of  the  lower  fragment  In  partial 
transverse  lesions  of  die  cord  the  paralysis  below  the  lesions  affects,  therefore  the 
motor  columns  of  the  cord  more  than  the  sensory  columns  which  are  in '  part 
posterior.  ^ 

The  most  frequent  seat  of  fracture-dislocation  of  the  spine  is  in  the  thoraco- 
lumbar region  (page  145).  Fortunately,  it  U  this  variety  which  offers  the  best 
prognosis,  since  the  cord  ends  usually  just  below  the  lower  border  of  the  first 
lumbar  vertebra,  and  the  cauda  equina  being  more  movable  and  tougher  than  the 
cord  Itself,  it  can  better  evade  the  encroachment  on  the  canal,  although  in  spite  of 
these  facts,  it  is  not  infrequendy  injured  in  such  lesions.  The  bodies  of  the  lumbar 
vertebra  are  the  largest  and  most  cancellous,  the  intervertebral  discs  the  thickest 
and  most  elastic,  so  that  crushing  of  them  occurs  with  less  tendency  to  invade  the 
canal  and  injure  the  cord  than  in  any  other  portion  of  the  spine. 

In  caries  <A  the  spine  (Pott's  disease^  the  lesion  is  situated  in  the  bodies  of  the 
vertebrae,  and  therefore,  m  front  of  the  cord.     As  the  inflammatory  exudate  extends 
it  will  invade  the  spinal  canal  anterioriy,  often  producing  an  external  pachymeningitis 
The  untation  and  pressure  resulting  will  again  affect  the  motor  portion  of  the  cord 
first  producing  a  paralysis  of  motion  in  the  parts  below,  varying  in  degree  according 
to  the  amount  of  pressure  on  the  cord.     If  sensation  is  impaired  it  is  a  later 
phenomenon  and  is  due  to  greater  pressure  upon  the  cord,  and  in  some  cases  to 
myehtis.     The  loss  of  motion  is  often  the  only  effect  produced.     If  the  lower  cervical 
region  is  involved  by  the  lesion  the  phrenic  nerves  will  escape  paralysis,  but  the 
arms,  trunk,  bladder,  rectum,  and  lower  extremities  will  be  affected.     Since  the 
intercostal  and  abdominal  muscles  are  involved  in  the  paralysis,  breathing  will  be 
difficult  and  will  depend  upon  the  action  of  the  diaphragm  only.     Thus  as  the  lesion 
occura  at  successively  lower  levels,  the  highest  limits  of  the  paralyzed  area  descend 
and  the  expectation  of  life  increases. 

In  the  cervical  and  thoraco-lumbar  regions  where  the  injuries  to  the  spine  and 
the  cord  are  most  frequent,  are  situated  the  two  enlargements  of  the  cord  The 
cervical  begins  at  the  fourth  cervical  vertebra,  gradually  reaches  its  largest  diameter 
opposite  the  fifth  and  sixth  vertebra,  and  then  gradually  decreases  to  the  first 
thoracic,  where  it  merges  into  the  thoracic  portion  of  the  cord.  Only  the  thoracic 
region  does  the  arcumference  of  the  cord  remain  the  same  throughout.  The  lumbar 
enlargement  is  shorter  than  the  cervical  and  begins  opposite  the  tenth  thoracic 
vertebra,  gradually  increases  to  the  twelfth  thoracic,  after  which  it  gradually  decreases 
to  the  conus  meduUaris. 

The  localization  of  lesions  of  the  cord,  producing  symptoms  of  paralysis,  will  depend 
upon  the  height  and  e.ttent  of  the  paralyzed  areas.  It  must  be  borne  in  mind  that  the 
nerve-roots  arise  from  the  cord  usually  at  a  level  higher  than  the  foramina  through 
which  they  «cape  from  the  spinal  canal.  The  first  and  second  cervical  ner\e-roots 
pass  out  of  the  canal  almost  horizontally.  The  intraspinal  course  of  the  succeeding 
"if"^*""*?^  increases  gradually  in  obliquity  so  that  the  spinous  processes  of  the  second 
third  and  fourth  vertebne  correspond  approximately  to  the  level  of  the  third,  fourth 
and  fifth  cervical  nerve-roots.  The  seventh  cervical  spine  corresponds  to  the  first 
thoracic  nerve-root.  The  spinous  process  of  the  fifth  thoracic  vertebra  is  on  a 
level  with  the  seventh  thoracic  nerve,  and  the  spine  of  the  tenth  thoracic  vertebra 
with  the  origin  of  the  second  lumbar  nerve.  The  first  lumbar  ner\'e  arises  just  below 
the  ninth  thoracic  spine,  the  second  lumbar  nerve  opposite  the  tenth  thoracic 
spine  the  third  and  fourth  lumbar  nerves  opposite  the  eleventh  spine,  and  the 
hfth  lumbar  and  the  first  sacral  nerves  between  the  eleventh  and  twelfth  thoracic 
spines. 

•  P^"^  *u^  spinous  prnrpfwes  ran  he  our  surface  guides,  and  it  must  be  borne  in 
mind  that  thw  are  not  always  on  the  level  of  their  corresponding  vertebrte.  Briefly, 
It  may  be  said  that  the  eight  cervical  nerves  arise  from  the  cord  between  the  lower 
maiifin  of  the  foramen  magnum  and  the  sixth  cervical  spine,  the  first  six  thoracic 


J054 


HUMAN  ANATOMY. 


-<i 


Fig.  908. 


Firat  Ihoricic  ipin 


nenes  between  the  latter  spine  and  the  fourth  thoracic,  the  lower  six  thoracic  nerves 
between  the  fourth  and  ninth  dorsal  spines,  the  five  lumbar  nerves  opposite  the 

ninth,  tenth  and  eleventh  spines, 
and  the  five  sacral  nerves  opposite 
the  twelfth  thoracic  and  the  first 
lumbar  spine. 

A  convenient  rule  to  locate  the 
levels  of  origin  of  the  nerve-roots, 
applicable  to  the  prelumbar  ner\'es, 
is  given  by  Ziehen  as  follows  : — 
For  the  cervical  nerves,  subtract  one 
from  the  number  of  the  nerve,  the 
remainder  indicating  the  correspond- 
ing spinous  process  ;  for  the  upper 
( I-V)  thoracic  nerves  subtract  two ; 
for  the  lower  (VI-XII)  thoracic 
nerves  subtract  three.  All  the  cer- 
vical nerves  pass  out  through  the 
intervertebral  foramina  above  the 
vertebra;  after  which  they  are  named, 
except  the  eighth  cervical,  which 
emerges  between  the  seventh  cer- 
vical and  the  first  dorsal  vertebrse. 
All  the  other  spinal  nerves  escape 
below  the  vertebrae  from  which  they 
are  named.  Since  the  nerve-roots 
pass  a  considerable  distance*  down- 
ward within  the  spinal  canal  before 
leaving  it,  it  follows  that  a  lesion  of 
the  co/d  at  a  given  level  as  from 
a  fracture-dislocation  01  the  spine, 
may  be  associated  with  a  paralysis 
of  the  nerve-roots  passing  out  at 
or  below  that  level,  and  arising 
from  the  cord  at  a  higher  point. 
This  must  be  taken  into  account  in 
determining  the  seat  of  the  lesion, 
since  when  the  nerve-roots  are  not 
involved  the  lesion  will  be  as  much 
higher  than  its  corresponding  inter- 
vertebral foramina  (as  indicated  by 
the  upper  limits  of  the  paralyzed 
area)  as  the  length  of  the  intraspinal 
course  of  the  corresponding  nerve- 
roots. 

Elach  root-cell  in  the  anterior 
horn  of  gray  matter  is  connected 
with  a  motor  fibre,  which  passes 
out  in  the  anterior  root  of  a  spinal 
nerve  to  its  muscle.  M  otor  impulses 
originating  in  the  cortex  of  the  brain, 
pass  downward  along  the  antero- 
lateral columns  of  the  cord,  chiefly 
in  the  lateral  pyramidal  tract.  They 
first  traverse  the  ganglion  cells  of 
the  anterior  horns  before  passing 
out  in  the  anterior  or  motor  roots 
to  their  destination.  These  ganglion  cells  constitute,  at  least  functionally,  the  trophic 
centres  for  the  muscles.     Lesions  of  the  anterior  horns,  therefore,  besides  causing 


First  lumbar 
vertebra 


lumbar  spine 


Sacrum 


First  sacral  vertebra 


DiaKram,  hascti  on  troxen  siclitni.  siitiwing  relatione  d 
hxtUrs  ami  spines  uf  vertebrw  to  levels  at  which  .:>inal  nerves 
escape  troni  vertcbnil  cututl. 


THE   BRAIN. 


1055 


r 


paralysis  (poiio-myelitis),  will  lead  to  atrophy  of  the  corresponding  muscles.     The 
vasomotor   centres  are  also  in  the  anterior  horns,  probably  in  the  intermedio-lateral 

tnict.  til  J 

Sensory  impulses  pass  to  the  posterior  horns  through  the  posterior  roots,  and 
some  of  them  soon  cross  to  the  opposite  side  of  the  cord,  others  ascending  in  the 
posterior  column.  The  lemniscus  is  probably  the  chief  sensory  tract  in  the  medulla 
oblongata,  pons,  and  cerebral  peduncles. 

Every  segment  of  the  spinal  cord  contains  centres  for  certain  group  of  muscles, 
and  for  reflex  movements  associated  with  them.  A  reflex  begins  in  the  stimulation 
of  a  sensory  nerve.  The  impulse  thus  created  passes  to  a  centre  in  the  cord  and 
thence  is  transmitted  to  a  motor  nerve,  thus  producing  a  contraction  of  the  muscle 
supplied  by  that  nerve.  The  complete  path  of  this  impulse  is  called  a  reflex  arc. 
The  sensory  impulse  may  be  transmitted  to  different  segments  of  the  cord  and  thence 
out  through  the  corresponding  motor  roots.  Thus  a  complicated  reflex  arc  is 
produced.  It  is  to  be  assumed,  however,  that  the  impulse  will  take  the  shortest 
route,  so  that  simple  reflexes  will  have  their  reflex  arc  chiefly  in  those  segments  of 
the  cord  in  which  the  posterior  root  enters. 

Each  segment  of  the  cord  is  connected  with  fibres  from  the  brain  to  which  must 
be  ascribed  the  hmctinn  of  reflex  inhibition.  If  the  inhibitory  fibres  are  irritated,  the 
reflexes  are  impaired  from  stimulation  of  inhibition.  If  the  conductivity  of  these 
fibres  is  destroyed,  the  reflexes  are  increased;  but  if  the  reflex  arc  is  broken  at  any 
point,  the  reflexes  are  lost  Among  the  most  important  of  these  are  the  skin  and 
tendon  reflexes.  . 

The  centres  for  the  bladder,  rectum,  and  ^xual  apparatus,  are  located  in  the 
sacral  segment  of  the  spinal  cord  at  and  below  the  third  sacral  segment.  They 
regulate  the  functions  of  these  or^ns  and  are  associated  in  some  unknown  way  with 
the  brain.     (See  mechanics  of  urination,  ps^e  1914). 

Htemalo-rhachis,  or  hemorrhage  into  the  membranes  of  the  cord  (e.\tramedullary 
hemorrh^e),  may  result  from  an  injury  to  the  spinal  column,  as  a  fracture  or  a  severe 
sprain.  The  bleeding  inay  be  from  the  plexus  of  veins  between  the  dura  and  bony 
wall  of  the  canal  (most  frequent),  or  from  the  vessels  between  the  dura  and  the  cord. 
In  either  case  the  symptoms  will  be  much  the  same.  There  will  be  a  sudden  and 
severe  pain  in  the  region  of  the  spine,  diffused  some  distance  from  the  seat  of  the  in- 
jury, due  to  irritation  of  the  meninges,  and  pain  transferred  along  the  distribution  of 
the  sensory  ner\'es  coming  from  the  affected  segments  of  the  cord,  accompanied  by 
abnormal  sensations,  as  tingling  and  hyperiesthesia.  In  the  motor  distribution  there 
will  be  muscular  spasm,  or  sometimes  a  persistent  contraction  of  the  muscles.  Gen- 
eral convulsive  movements,  retention  of  urine,  and,  later,  symptoms  of  paralysis  may 
appear,  but  .is  a  rule  the  latter  is  not  complete. 

Hamalo-myelia,  or  hemorrhage  into  the  substance  of  the  cord  (intramedullary 
hemorrhage)  from  traumatism,  usually  occurs  between  the  fourth  cervical  segment 
of  the  cord  and  the  first  dorsal  (Thorburn),  and  is  commonly  due  to  forced  flexion 
of  the  spine,  which  is  most  marked  in  this  region,  as  in  falls  on  the  head  and  neck. 
The  cord  has  been  crushed  in  such  accidents  without  fracture  of  the  spine  and  with 
only  temporary  dislocation.  The  hemorrhage  is  usually  chiefly  in  the  gray  matter 
and  may  be  only  punctate  in  size,  or  may  Ut  large  enough  to  extend  far  into  the 
white  matter,  or  even  outside  the  cord  into  'a.c  sulKirachnoid  Space.  The  symptoms 
usually  .ippear  immediately  after  the  injury  and  are  bilateral,  suggesting  a  total 
transverst;  U^sion.  There  will  be  much  pain  in  the  back,  occasionally  extending  along 
the  a.-ms  </i  around  the  thorax.  Spasms,  rigidity,  and  paralysis  rapidly  ensue,  with 
loss  of  the  retle-ves  in  the  segment  of  the  cord  involved.  There  may  be  the  same 
dissociH'Jon  of  sensation  as  in  syringomyelia  when  the  hemorrhage  is  confined  to  the 
centre  of  the  cord. 

THE  BRAIN. 

The  brain, or  the  encephalon,  is  the  part  of  the  cerebro-spinal  axis  that  lies  within 
the  skull.  It  is  produced  by  the  difierenti.itioii  of  the  cephalic  segment  of  the  ncunil 
tube.  Although  the  brain  is  often  of  great  relative  bulk  and  high  complexity,  as  in 
man  and  some  other  mammals,  it  must  Jiot  be  forgotten  that  the  spinal  cord  is  the 


1056 


HUMAN  ANATOMY. 


fundamental  and  essential  part  of  the  nervous  axis  and  that  the  degree  to  which  the 
brain  is  developed  is,  in  a  sense,  accidental  and  dependent  upon  the  necessities  of  the 
animal  in  relaUon  to  the  exercise  of  the  higher  nervous  functions.  In  the  lowest 
vertebrates,  the  fishes  in  which  assocUtion  of  the  impressions  received  from  the 
omer  world  «  only  feebly  exer«^,  those  parts  of  the  brain  rendering  such  functions 
p^ible,  as  the  cerebral  hemispheres,  are  very  imperfectiy  represlnted.  On  the 
other  hand,  in  man,  in  whom  the  capacity  for  the  exercise  of  the  higher  nervous 
functions  involving  association  is  conspicuous,  the  antero-superior  parts  of  the  brain 
the  HItum  as  the  regions  particularly  concerned  are  called,  are  so  enormousl^ 
developed  that  the  human  brain  is  thereby  distinguished  from  all  others.  Whether  of 
low  or  high  development,  all  brains  are  evolved  from  certain  fundamental  parts  the 
bratn-vestcUs,  differentiated  in  the  head-end  of  the  embryonic  neural  canal  •'  the 
underlying  conception  of  the  brain,  therefore,  is  that  of  a  tube,  bent  and  modified  to  a 
variable  degree  by  the  thickening,  unequal  growth  and  expansion  of  its  walk  Even 
when  most  complex,  as  m  man,  the  adult  organ  exhibits  unmistakable  evidences  of 
subdivision  corresponding  more  or  less  closely  with  the  primary  brain-vesicles  and 
contains  spaces,  the  ventricles,  that  represent  the  modified  lumen  of  these  segments 


Fig.  909. 


OrbiUl  lutficc  ol 
fnmul  lobe 


Optic  commiMure 

Uptic  tract 

Cerebral  peduncle 

interpeduncular  space 


OUactorjr  tract 

Sulk  of  pituitary  body 

Tuber  ctnereum 
Mamraillary  bodies 
Cerebral  peduncle 
Temporal  lobe 
Pons 


Cerebellum 


Occipital  lobe 


Spinal  cord 


Simplified  drawing  of  brain  „,  .««,  from  below,  showin,  relations  of  brain-stem  to  spinal  cord  an.l  . ,  rebrum. 


r„  ll^\f    T^'a  '  '"'^f"^  VP°"  ^  description  of  the  hilly  formeti  brain,  it  is  desirable 

o  conbider  briefly  the  i,rr«d  plan  according  to  which  the  organ  is  laid  down  and 

the  general  lines  along  which  its  evolution  proceeds.     Before  doing  so,  however   it 

cdm.irngr'.LTn.''''"  ''  ^^"'^"'  ^"""^^ ''^  '""^  ^'"''^'''•"^  «'  '""^  several  divisions 

fr^.«  K?"'*^^"'  '^  investing  membranes  and  the  attached  cranial  nerves,  and  viewed 
rom  bel..w  (Fig.  909),  the  encephalon  is  seen  to  consist  of  a  median  brain-stem,  that 
inttnorl\  is  directly  continuous  with  the  spinal  cord  through  the  foramen  magnum 
and  above  divi-les  into  two  diverging  arms  that  disappear  within  the  large  overHang- 
LhiT'^'ir  V  ^;r  ."""  '^^^  brain-stem  includes  thr.-e  divisions,  the  inferior  of 
Ir^  .?'*  ™".'' f'<?**Sat',,  IS  the  uninterrupted  upward  prolongation  of  the  spinal 
cord  and  above  ,s  limited  by  the  projecting  lower  border  of  the  quadrilateral  mass 


THE  BRAIN. 


"057 


of  the  next  division,  the  pons  Varolii.  Beyond  the  upper  man^n  of  the  pons  the 
brain-stem  is  represented  by  a  third  division  that  ventraliy  Ls  separated  by  a  deep 
recess  into  two  diverging  limbs,  the  cerebrtU  peduncles,  or  crura  cerebri,  to  corre- 
spond with  the  halves  or  hemispheres  of  the  cerebrum,  each  of  which  receives  one 
of  the  crura  and  in  this  manner  is  connected  with  the  lower  levels  of  the  cerebro- 
spinal axis.  The  greater  part  of  the  medulla  and  pons  is  covered  dorsally  by  the 
cerebellum,  whose  large  lateral  expansions,  or  hemispheres,  project  on  either  side 
as  conspicuous  masses,  distinguished  by  the  closely  set  plications  and  intervening 
fissures  that  mark  their  surface.  Of  the  five  component  parts  of  the  brain — medulla, 
pons,  cerebral  peduncles,  cerebrum,  and  cerebellum — the  last  two  are  coated  with 
the  cortical  gray  matter,  in  which,  broadly  speaking,  are  situated  the  neurones 
that  constitute  the  end-stations  for  the  sensory  impulses  conveyed  by  the  various 
conicipetal  paths  and  the  centres  controlling  the  lower-lying  nuclei  of  the  motor 
ner\'es.  The  brain-stem,  on  the  other  hand,  whilst  containing  numerous  stations 
for  the  reception  and  distribution  of  sensory  impulses,  is  primarily  the  great  pathway 
by  which  the  cerebrum  and  the  cereljcUuin  are  connected  with  each  other  and  with 
the  spinal  cord. 

Viewed  in  a  mesial  s^ittal  section  ( Fig.  910),  each  of  these  divisions  is  seen  to 
be  related  to  some  part  of  the  system  of  communicating  spaces  that,  as  the  lalcra/ 
and  third  ventricles,  the  aqueduct  of  Sylvius  and  the  fourth  ventricle,  extend  from 
the  cerebral  hemispheres  above,  through  the  brain-stem  and  beneath  the  cerebellum, 
to  the  central  canal  of  the  spinal  cord  below.  Since  the  lateral  ventricles  are  two  in 
number,  in  correspondence  with  the  cerebral  hemispheres  in  which  they  lie,  their 
position  is  lateral  to  the  mid-plane  and  hence  only  one  of  the  openings,  >i\tforamina 
of  Monro,  by  which  they  communicate  with  the  unpaired  and  mesially  placed  third 
ventricle,  is  seen  in  sagittal  sections. 

Both  the  roof  and  the  floor  of  the  irregular  third  ventricle  are  thin,  whilst  its 
lateral  wails  are  formed  by  two  robust  masses,  the  optic  thalami,  the  mesial  surface 


Corpus  cilkMum 
liKldufn 


Fig.  910. 


Frontal  lobt,  mnUl  «uf&ce. 


Anterior  comnlMUM 

Foranira  of  Monro 

I.Aiiiim  cincrcs' 


Optic  commlwui 


FI«or  .if  tMr.1  vcwridc 

MammflUry  body 

Ailuc«1uct  at  SylvluC' 

Poaft< 


Simplified  drawing  of  brain  u  i 


0|)tic  ttujamuft.  donal  surface 


l.atcnl  wall  of  third 
VMttlclc  {o|Mk  thalamua) 


Cnvtinl  ptdundt 

Hoof  of  Syh  Un  •<|ueiltKt 

Icdplul :  <l« 
.Superior  nieitiillary  tcluR 

Whit*  tfift  of  crrH«llum 
Inferior  uirdiillarjr  trlum 


ia  mesial  scctiiMi,  shnwinx  rrlalion  ol  brain-stem,  cerebrum  and  cerebellum, 
and  ventricular  spaces. 

of  one  of  which  forms  the  background  of  the  space  when  viewed  in  sagittal  section. 
The  roofai  the  ventricle  is  very  ihin  and  consists  of  the  delicate  layer  of  ependytna, 
as  the  immediate  lining  of  the  ventricular  spaces  is  designated,  supported  by  the 
closely  adherent  fold  of  pia  mater  which  in  this  situation  pushes  before  it  the  neural 
wall  and  contains  within  its  lateral  border  a  thickened  fringe  of  blood-vessels,  the 

67 


V 


'   f 


1058 


HUMAN   ANATOMY. 


choroid  plexus.  The  two  structures,  the  ependyma  and  the  pia  mater  topjether, 
constitute  the  membranous  velum  inlerpoiitum  that  forms  the  roof  of  tiic  ventricle 
and  lies  beneath  the  triangular /<»r»Mjr,  whose  vaulted  form  is  suggested  by  the  arching 
ridge  that  descends  in  front  of  the  thalamus  and  marks  the  position  of  the  anterior 
pillar  of  the  fornix.  Behind,  just  over  the  upper  end  of  the  Sylvian  aqueduct,  lies 
the  cone-shaped  pineal  body  that  belongs  to  the  third  ventricle,  from  which  it  is  an 
outgrowth.  TheyKiw  of  the  ventricle  is  also,  for  the  most  part,  relatively  thin  and 
irregular  in  contour.  It  corresponds  to  the  median  part  of  the  lozenge-shaped  area, 
the  interpeduncular  space,  which,  seen  on  the  inferior  surface  of  the  brain,  is  bounded 
btihind  by  the  anteriorly  diverging  cerebral  peduncles  and  in  front  by  the  opHc  chiasm 
and  the  posteriorly  diverging  optic  tracts.  The  posterior  hMlf  of  this  area  includes 
the  deep  triangular  rf  cess  at  the  bottom  of  which  is  seen  the  numerous  minute  open- 
ings of  the  posterior  perforated  space  through  which  small  branches  of  the  posterior 
cerebral  arteries  pass  to  the  optic  thalamus  and  the  crura.  Passing  forward,  the 
paired  corpora  mammillaria,  the  tuber  cinereum,  \\\c  stalk  of  the  pituitary  body 
occupy  successively  the  interpeduncular  space.  Anteriorly,  between  the  trans- 
versely cut  optic  chiasm  below  and  the  recurved  portion  of  the  great  arching  com- 
missure, the  corpus  callosum,  above,  the  third  ventricle  is  closed  by  a  thin  sheet  oi 
nervous  substance  known  as  the  lamina  cinerea. 

Through  the  foramina  of  Monro  the  lateral  ventricles  open  into  the  third,  and 
the  latter  communicates  with  the  fourth  ventricle  by  way  of  the  Sylvian  aqueduct. 
This  narrow  canal  is  surrounded  below  and  laterally  by  the  dorsal  part  or  tegmentum 
of  the  cerebral  peduncles  ;  above  it  lies  a  plate  of  some  thickness  the  dorsal  surface 
of  which  is  modelled  into  two  pairs  of  rounded  elevations,  the  superior  and  inferior 
corpora  quadrigemina. 

In  sagittal  section,  the  fourth  ventricle  appears  as  a  triangular  space,  the 
anterior  or  basal  wall  being  formed  by  the  dorsal  surface  of  the  pons  and  medulla  and 
the  posteriorly  directed  apex  lying  beneath  the  cerebellum.  The  upper  half  of  tht 
thin  tent-like  roof  of  the  ventricle  is  formed  by  the  superior  medullary  velum,  a  thin 
layer  of  white  matter  that  stretches  from  beneath  the  inferior  corpora  quadrigemina 
to  the  cerebellum.  A  similar  lamina,  the  inferior  medullary  velum  extends  from  the 
cerebellum  downward,  but  before  reaching  the  dorsal  surface  of  the  medulla  becomes 
so  attenuated  that  this  part  of  the  ventricular  roof,  known  as  the  tela  chorioidea, 
consists  practically  of  the  pia  mater,  although  the  ependyma  excludes  the  vascular 
membrane  from  actual  entrance  into  the  ventricle.  The  pia,  however,  pushes  in  the 
epondymal  layer  and  in  this  manner  produces  the  vascular  fringes  known  as  the 
choroid  plexus  of  the  fourth  ventricle.  When  viewed  from  behind,  the  ventricle 
exhibits  a  rhomboidal  oudine,  the  lateral  boundaries  above  being  formed  by  two 
arms,  the  superior  cerebellar  peduncles,  that  divergingly  descend  from  the  sides  of  the 
corpora  quadrigemina  to  the  cerebellum.  Similar  bands,  the  inferior  cerebellar 
peduncles,  convergingly  descend  from  the  cerebellar  hemispheres  to  the  posterior 
columns  of  the  medulla  and  form  the  lower  lateral  boundaries  of  the  fourth  ventricle. 
Seen  from  directly  above  (Fig.  984),  the  cerebrum,  divided  into  its  hemi- 
spheres by  the  deep  satriltal  fissure,  is  the  only  part  of  the  brain  visible,  the  other  four 
divisions  being  masked  by  the  enormously  developed  overhanging  cerebral  mantle. 
The  effects  of  this  expansion  in  displacing  base-ward  parts  which,  temporarily  in  man 
and  permanently  in  the  lower  vertebrates,  occupy  a  superior  position,  are  conspicuous 
when  the  sagittal  section  of  the  developing  (Fig.  913)  and  that  of  the  fully  formed 
human  brain  (Fig.  910)  are  compared.  It  should  be  noted,  that  although  in  the 
latter  the  brain-stem  and  the  cerebellum  are  completely  overhung  by  the  cerebral 
hemispheres,  they  still  are  in  relation  with  the  free  surface  of  the  brain,  and  by 
passing  beneath  the  posterior  part  of  the  cerebrum  the  dorsal  surface  of  the  cerebellum 
and  of  the  brain-stem  may  be  reached  without  mutilation  of  the  nervous  tissue. 

THE  GENERAL  DEVELOPMENT  OF  THE  BRAIN. 

Even  before  complete  closure  of  the  anterior  end  of  the  neural  tube,  which 
takes  place  probably  shortly  after  the  end  of  the  second  week  of  foetal  life,  the 
cephalic  region  of  this  tube,  slightly  flattened  from  side  to  side,  exhibits  the  results 


■MHHiyKiiitta^ 


GENEKAL   DEVKLOFMKNT   (Jh    JlH»    imO^K. 


1059 


of  unequal  growth  in  two  slight  constrictiiHis  atepHMMf  tbr«-(>  ijikutioiw  Wimmmi  - 
the  primary  brain -vesicles.  The  positeriur  uf  liiHe.  the  JHed-brain.'  jji  1 
the  longer,  exceeding  the  combined  lei%;th  at  the-  ii^ter  cso  >  Mtc.-  911  alter  a  sbtM^ 
time  when  viewed  from  behind  it  presents  ^i  eiongaOitd  luz<nif«d;-shafH<l  tomi  awt, 
hence,  is  also  called  the  rhombencephakxi.  The  vmdiMe  \mwU-.  tiR-  mid-bnua, 
or  mescncepbalon,  is  conspicuous  on  account  ui  n»  roiMided  torm  iino  promineiH 
position,  lying,  as  it  does,  over  the  marked  primary  liexure  which  tht-  iMstd-end  oi 
the  neural  tube  very  early  exhibits. 

The  anterior  vesicle,  known  as  the  forc-orain     "  prosencepltalap    at  tir»t  is 
small  and  rounded,  but  soon  becomes  muditied  by  tin  appear.iiut-    .m  riiiier  side, 
of  a  hcdlow  protuberance,  the  optic  vesicif,  that  i>ui^e>  out  troin  tb«-  lciw<-r  lattrcal 
wall.     For  a  time  the  optic  vesicle  communicatee  wrtli  lim'  main  ^aviiy  of    lie  forv- 
brain  by  a  wide  opening.     This  gradually  becomes  rv<\^<sm\  awl  cunstfKted  until  tin" 


Forf-bimm 


ic  vesicle 


Fic;.  911. 


Focv-brain 


Pallium 


Mi<|.|>raiR 


Himl-brvin 


Reconitnictioii  ol  bf^iii  of  human  embr^  ;  uf  about  Iwc  wevlH(j.a  mm.);  w4, outer  surface;  S,  inner  surface; 
HP.  neural  pore,  wbere  fore-brain  ia  still  open  ;  ci,  aniagc  oi  corpus  striatum ;  or,  uptic  reccas  leailinc  into  optic 
vesicle  ;*/,  hypothalamic  region.    (Mu.) 

evagination  is  attached  by  a  hollow  stem,  the  optic  stalk,  which  later  takes  part  in 
the  formation  of  the  optic  nerve  that  connect-,  the  eye  with  the  brain,  the  vesicle 
itself  giving  rise  (page  1482)  to  the  iier\'ous  coat  «f  the  eye,  the  retina.  By  the 
time  the  optic  ev^nation  is  formed,  the  front  part  i>f  the  fore-brain  shows  a  slight 
bulging,  narrow  below  and  broader  and  rounded  above,  and  separated  from  the 
optic  outgrowth  by  a  slight  furrow.  This  is  the  first  suggestion  of  the  anlage  of  the 
hemisphere  or /<i//t«m  (His).  The  latter  soon  jjjives  rise  to  two  rounded  hollow 
protrusions,  one  on  either  side  of  the  fore-brain,  that  rapidly  ex|>and  into  the 
conspicuous  primary  cerebral  hemispheres.  The  lower  ]iart  of  the  fore-brain  includes 
the  region  that  later,  after  differentiation  and  outgrowth  from  the  hemisph»Tc, 
receives  the  nerves  of  smell  and  is  known  as  the  rhinencephalon. 

A  slight  ridge  (Fig.  911,  ^),  projecting  inward  from  the  roof  of  the  fore-brain, 
suggests  a  subdivision  of  the  general  space  into  a  posterior  and  an  anterior  region. 

'This  Use  trf  the  trrm  hindhrain  is  at  variance  with  its  oldci  siKnifiCiiiCr,  .still  reUiiicii  j.y 
some  German  writers,  as  indtcatinK  the  upper  division  fmetencephalon)  of  the  posterior 
primary  vesicle.  In  view,  however,  of  the  now  t^neral  application  of  fore-brain  and  mid-tirain 
to  the  other  primarj,-  vesicles,  it  seems  more  consistent  fo  include  hind-brain  in  the  series,  as  h.i5 
been  done  by  Cunningham,  with  a  distinct  gain  not  only  in  convenience,  but  in  avoiding  terms 
which  in  their  Anfflinsed  form  are  at  best  awkward  and  tmncces.sarv. 


i  ) 

!     t 


1060 


HUMAN  ANATOMY. 


The  latter,  the  outwardly  bulging  pallium  or  hemisphere-anlage,  is  limited  below  by 
the  optic  recess,  the  entrance  into  the  optic  vesicle,  and,  farther  front,  by  a  flattened 
triangular  elevation  that  marks  the  earliest  rudiment  of  the  cor^s  slrialuw.  The 
posterior  or  thalamic  region  extends  backward  to  the  mid-bram,  from  which  it  is 
separated  by  the  slight  external  constriction  and  corresponding  internal  ridge. 
During  the  fourth  week  the  demarcations  just  noted  become  more  definite,  so  that 
the  primar)'  anterior  vesicle  is  imperfectly  subdivided  into  two  secondary  compart- 
mc-nts,  the  telencephalon,  conveniently  calletl  the  end-brain,  and  the  dienceph- 
alon.  Considered  with  regard  to  the  details  presented  by  the  interior  of  the  fore- 
brain,  the  four  areas  recognized  by  His  are  evident.  These  are  (Fig.  912)  the 
region  of  the  pallium  and  of  the  corpus  striatum,  respectively  above  and  below  in 
the  telencephalon,  and  the  region  of  the  thalamus  and  of  the  hypothalamus  ri-spec- 
tively  above  and  below  in  the  diencephaion.  Between  the  protruding  hemispheres, 
the  telencephalon  is  closed  in  front  and  below  by  a  thin  and  narrow  wall,  the  lamina 
termiiialis,  which  defines  the  anterior  limit  of  the  brain-tube. 

While  the  more  detailed  account  of  the  further  c'exelopment  of  these  regions 
will  be  given  in  connection  with  the  description  of  the  several  divisions  of  the  brain. 


MUl-brain 


F>';.  9Ii. 

Diencephaion  Thalxmeiicephalan 

Telencenhmlun 
Pcllium 


Mitl-hrain 


Sptnal  <orc1 


CoilMi 
strimtum  / 


Spinal  (x>rct 


Kei-niiMructiiin  o(  brain  of  human  rmbr\o  iil  about  four  weeka  (ft.'i  mm.);  A.  r.uler  Mtrfare;  B,  inner  i.urfac(; 
/,  iMhmm  ;  <«.  a|>crturi-  of  opilc  atalk  ;  •  ^.  ccrrbral  |ie<luncle ;  ci.  ier> Iral  flraurr :  M,  cefilialic  flexure.  Krnw n  trom 
Hi»  miKlct. 

it  iii.iy  Ik-  piiintid  out  here,  in  a  miieral  way,  that  the  pallium  gives  ri.se  to  the  cim- 
spiiiious  ci  rebral  lieinisphires,  which,  joinc*!  IhIow  bv  a  onmmon  lamina,  ex|)und  out- 
ward, upward  and  iKickward  and  rapidly  dwarf  ihe  other  jwrts  of  the  brain -tube  which 
arc  thus  gratlually  roverejl  «i\tr.  Thestri.ite  area  thickens  into  the  i<«rj>us  striatum, 
wli'ch  appears  as  a  sfiking  prc>ininen<e  on  the  outer  and  lower  wall  of  each  lateral 
viiitricle.  The  latter  represents  a  swondary  extension  of  the  ori>;ii)al  cavity  of  the 
li)rc-hrain  enclosed  by  the  dodopinjr  cerebral  lu  inisphcrc,  atiil  at  first  is  large  and 
thin-walled  and  comiiiunicates  by  a  wide  o|)ening  with  the  remainder  of  the  braiti- 
vesiclc.  The  uiie(iual  growth  and  thickening,  which  sulwequently  nKxIily  the 
burrounding  walls,  reduce  this  large  aperture  until  it  persists  as  the  small  foramen 
of  Monro,  bv  which  the  lateral  ventricle  communicati-s  with  the  third  vetitricle.  The 
latter  represents  what  is  l<ft  of  the  cavity  of  the  fore-brain  and,  therefore,  the  com- 


GENERAL  DEVELOPMENT  OF  THE  BRAIN. 


1061 


bined  contribution  of  the  telencephalon  and  diencephalon.  Durinjj  the  fifth  week 
the  diencephalon  expands  into  a  relatively  large  irregular  space  (Fig.  <ji^),  whose 
roof  and  noor  are  thin  and  whose  lateral  walls  are  thickened  by  the  niiisses  of  the 
developing  thalami.  The  hypothalamic  region  becomes  the  most  dependent 
part  of  the  fore-brain  and  gives  rise  to  the  structures  that  later  cx-cupy  the  inter- 
peduncular space  on  the  bsJse  of  the  brain.  The  roof  of  the  diencephalon  remains 
thin,  does  not  produce  nervous  tissue  and,  in  conjunction  with  the  ingrowth  of  the 
vascular  pia  mater,  forms  the  velum  interpositum  and  its  choroid  plexuses.  The 
pineal  body  and  the  posterior  lobe  of  the  pituitary  body  arise  as  outgrowths  from  the 
roof  and  floor  of  the  diencephalon  respectively. 

The  mid-brain,  or  mesencephalon,  at  first  large  and  conspicuous  on  account 
of  its  elongation  and  prominent  position  at  the  summit  of  the  brain-tube,  does  ni>t 
keep  pace  with  the  adjoining  vesicles,  and  in  the  fully  formed  brain  is  representeti  by 
the  parts  surrounding  the  aqueduct  of  Sylvius.  Neither  does  it  subdivide,  but,  w  hile 
its  entire  wall  is  converted  into  nervous  tissue,  retains  its  primary  simplicity  to  a 
greater  dqrree  than  any  of  the  other  brain-segments.  The  lateral  and  ventral  walls 
of  the  mkl-brain  contribute  the  cerebral  peduncles  ;  its  roof  gives  rise  to  the  corpora 
quadrigemina  ;  and  its  cavity  persists  as  the  narrow  canal,  the  aqueduct  of  .Sylvius, 
that  connects  the  third  and  fourth  ventricles. 

The  posterior  vesicle,  the  hind-brain,  or  rhombencephalon,  the  largest  of 
the  primary  brain-segments,  is  the  seat  of  striking  changes.  These  include  thicken- 
ing and  sharp  forward  flexion  of  the  ventro-lateral  walb,  in  consequence  of  which  the 
floor  of  the  space  becomes  broadened  out  opposite  the  bend  and  as-sumes  a  lozenge- 
shaped  outline.  The  hind-brain  Ls  conventionally  subdivided  (Fig.  013)  into  a 
superior  part,  the  metencephalon,  and  an  inferior  part,  the  myelencephalon> 
Its  cavity,  common  to  both  subdivisions,  persists  as  the  fourth  ventricle. 

The  extreme  upper  part  ot  the  metencephalon,  where  it  joins  the  mid-brain, 
early  exhibits  a  constriction,  which  by  His  has  been  termed  the  inthmun  rhom- 
bcncephali  and  regarded  as  a  distinct  division  of  the  brain  tube.  In  the  fully  formed 
brain,  the  isthmus  corresponds  to  the  uppermost  part  of  the  fourth  ventricle,  just  below 
the  Sylvian  aqueduct,  roofed  in  L^  the  Sijperior  medullary  velum  that  stretches 
between  the  superior  cerebellar  peduncles.  The  thickened  and  markedly  bent  \entro- 
lateral  wall  of  the  metencephalon  gives  rise  to  the  pons  Varolii,  whilst  in  the  roof  of 
the  ventricle  appears  a  new  mass  of  nervous  tissue,  the  cerebellum. 

The  myelencephalon,  soon  limited  lx;low  by  the  cervical  flexure,  shares  in  the 
ventral  thickening  seen  in  the  preceding  division.  Its  floor  and  particularly  its  sides, 
the  latter  at  the  same  time  spreading  apart,  form  the  medulla  oblongata,  which 
below  gradually  tapers  into  the  spinal  cord.  Its  roof,  in  which  thinness  is  always 
a  prominent  feature,  becomes  more  attenuated  as  development  proceeds  and  is 
converted  into  the  inferior  medullary  \  elum  and  the  tela  chorioidea  that  close  in  this 
l>art  of  the  fourth  ventricle.  The  subsequent  invagination  of  this  membranous 
portion  of  the  ventricular  roof  by  the  pia  mater  brings  about  the  production  of  a 
choroid  plexus  similar  to  that  seen  in  the  roof  of  the  third  ventricle. 

From  the  foregoing  sketch  of  the  changes  affecting  the  embryonic  brain-tulx',  it 
is  evident  that  the  anterior  and  tKisterior  primary  vesicles  undergo  subdivision,  «hile 
the  mid-brain  remains  undivided,  five  secondary  brain-vesicles — the  telencepha- 
lon, the  diencephalon,  the  mesencephalon,  the  metencephalon  and  the  myelencepha- 
lon— replacing  the  three  primary  ones. 

In  consetjuence  of  the  unequal  growth  of  various  parts  of  the  cejihalic  segment 
of  the  neural  tube,  the  latter  becomes  bent  in  the  sagittal  plane  at  certain  jHiints, 
so  ihat,  when  viewed  from  the  side,  the  axis  of  the  developing  human  l.niin 
ilescribes  an  S-like  curve  (Fig.  912).  These  flexures,  to  which  mcidental  reference 
has  been  made,  bring  about  a  disturbance,  for  the  mcwt  part  temporary,  in  the 
relations  of  the  brain-segments,  which  in  the  lower  vertebrates  follow  in  regular  <  irder 
along  an  axis  practicallv  straight.  In  the  developing  human  bniin,  in  which  they 
.ire  most  conspicuous,  tliere  are  three  flexures — the  cephalic,  cervical,  and  |M)nlin( . 

The  first  of  these,  the  cephalic  flexure  which  appears  towards  the  end  <>f 
the  second  week  and  before  the  neural  tube  has  completely  closetl,  is  firimary  and 
involves  the  entire  head.     It  takes  place  in  the  region  of  the  mid-brain  anci  lies 


I 


1062 


HUMAN   ANATOMY. 


Mnracephalon 


Tdcnccphftlon 


Cotpat  ftriMum 
Optic 


Mctcnccphalon 


Myeknccphaloii 


above  the  anterior  end  of  the  primary  gut-tube  and  of  the  notochord.     At  first  the 
axis  of  the  fore-brain  lies  about  at  right  angles  with  that  of  the  rhombencephalon, 

(P'ig.  911)  but,  with  the  in- 

FiG.  913,  creasing  size  of  the  middle 

Dienceptaion  ^„^  anterior  vesicles,    the 

angle  of  the  flexure  becomes 
more  acute  until  the  long 
axis  of  the  fore-brain  and 
of  the  rhombencephalon  are 
almost  parallel  (Fig.  912). 
During  the  fourth  week 
a  second  ventral  bend,  the 
cervical  flexure,  appears 
at  the  lower  end  of  the  hind- 
brain  and  marks  the  separa- 
tion of  the  encephalic  from 
the  spinal  portion  of  the 
neural  tube.  The  cer\ical 
flexure,  which  also  involves 
the  head,  is  most  evident 
at  the  close  of  the  fourth 
week,  when  it  is  almost  a 
right  angle  (  Fig.  912):  after 
this  it  becomes  less  pronounced  in  consequence  of  the  elevation  of  the  head  which 
succeeds  the  period  when  I'.ie  embryonic  axis  is  most  bent. 

The  third  flexure  appears  about  the  fifth  week  in  the  part  of  the  metencephalon 
in  which  the  pons  is  later  developed  and,  hence,  is  termed  the  pontine  flexure. 
It  concerns  chiefly  the  ventral  wall,  which  is  in  consequence  for  a  time  ventrally 
doubled  on  itself ;  subsequently  this  flexure  almost  entirely  disappears.  In  contrast 
to  the  preceding  bends,  this  flexure  is  only  partial  and  involves  chiefly  the  ventral 
and  only  slightly  the  dorsal  wall  of  the  neural  tube  ;  on  the  exterior  of  the  embryo  its 
presence  is  not  detectable. 

The  developmental  relations  of  the  chief  party  of  the  fully  formed  brain  to  the 
embryoiiic  brain-vesicles  are  shown  in  the  accompanying  table. 

'1'ABUi  Showing  Relations  op  Rrain-Vbsiclbs  and  Thuk  DBRiXATrvxa. 


Ventral  Don$i\ 

xonc  ai  brain-wall 

tHacnm  ihowiuc  five  cerebral  vnicle*  ■nd  doraal  and  veiilral  loncs  ••( 
their  wall ;  faaieil  on  brain  of  cmbr>'o  o(  (our  and  one-half  weeka.  ( Hti. ) 


PaiMAav  Skcmrnt      Suci.NriAKV  Skumknt 


DKaivATivna 


Allleri-tr  vnicle 
Proaencaphaleo 


Tvlencrptmltiii 


[)icncr|thalt>n 


Cerebral  hemispheres 
Ollactory  lobes 
Corpura  striuta 

OlHic  llialanii 
Optic  nerves  and  Ira.-Ii* 
Suhthalamiv  tCKnicntn 
lnter|iediniculHr  Ktniclurrft 
Pineal  and  pituitary  btMlifs 


lateral  ventricles  \  __,,,■-_. 
K<>r»mina<.(  Monro  /  "*"""'> 
Anterior  |»art  of  Ihira  I'entricic 


Posterior  part  of  third  venirici* 


Mid.ll-\<ii,l< 
ll«aen..<phalan 


McHtiicrphaion 


Cerebral  (letlunvics 
Coi|iora  i|Ufl>lriKeniinA 


A'|i»'»t(ii  t  i»l  S)lvtu«t 


PilSliTli.I   \.  -!■  If 

Rhombsnkephalttn 
or 

lllnd-ltiiihi 


M.lill.  .-plLil., 


M\<  U  it>  <  |<it  tl-iti 


Sublet  lor  ctTi'bcIliir  |Htlini(li 
Su|ieiliir  nuilii)l.(t\  wlutn 

PlIIIX 

l'cit)>e!luni 


hiii-riiir  iiii'tttillarv  velum 


Kiturth  ventricle 


Notwitlistiiin'iii]^  the  great  •  lian'^fH  in  jHwition  aiul  n'liition  which  inaiiy  |>art»  of 
the  human  hniin  siiflir  iliirinif  <li'\''ii|inii'iit.  chiefly  in  coiiwquencc  of  the  cnornnMis 
exfiansion  ril  the  palliiuii  and  the  ciirrtt^ixmdingly  large  size  of  its  cmninissiirf.  the 


GENERAL   DEVELOPMENT  OF  THE   BRAIN. 


1063 


corpus  callosuni,  the  fundamental  relationships  indicated  by  embryology  are  of  such 
value  that,  even  in  the  description  of  the  adult  organ,  grouping  of  the  various  parts 
of  the  brain  upon  a  develop- 

FiG.  914. 

Epithalamus 
Thalamiu  /  ^Mcuthalamus 

Pars  maminillarit  hypothalami 


mental  basis  is  found  advan- 
tageous. Although  strict 
adherence  to  such  a  plan 
would  be  at  times  inconven- 
ient, and,  therefore,  will  not 
be  followed,  constant  refer- 
ence to  primary  relations  is 
imperative.  It  will  be  con- 
venient, therefore,  at  this 
place,  to  call  attention  to 
the  accompanying  outline 
diagrams  which  illustrate 
the  principles  established  by 
His  in  hb  epoch-making 
studies  of  the  human  brain. 
In  addition  to  showing  the 
five  cerebral  vesicles,  Fig. 
913  indicates  the  relative 
position  and  extent  of  the 
two  fundamental  subdivisions  of  the  lateral  walls  of  the  neural  tube,  the  dorsal 
or  aiar  and  the  ventral  or  basai  laminz,  which  play  such  important  r6les  in  the 
differentiation  of  the  various  parts  of  the  brain-stem.  Fig.  914  shows  a  later 
stage,  in  which  the  genetic  relations  of  all  the  more  important  parts  of  the  brain  may 
be  recognized.  The  greatest  complexity  is  presented  in  the  development  of  the 
derivations  of  the  fore-brain,  |.articularly  of  those  which  are  differentiated  from  the 
diencephalon  and  later  are  found  connected  with  the  third  ventricle.  In  order  to 
set  forth  the  developmental  relations  of  the  fore-brain,  the  following  table  from  His, 
slighdy  modified,  will  be  of  service  : 


Khlnencephal 


hypolh 


cienccphalon 

Prdunculi  cerebri 
Isthmus 
'Cerebellum 
Pons 

Medulla 


Dorsal  tone 
Ventral  sone 


INacrmin  showing  chief  derivatives  from  cerebral  visicles  ; 
brain  of  embryo  of  third  month.    {Hit.) 


based  on 


Fara-Brain 


Proaaaaaphalaa 


(Pallium 

(  Hemlspluerlum '  Carpus  striatum 

( TKi.BNCKniALON'<  ( Rhinencephalon 

1  Pars  optica  hypothalami 


DlKKCKrH*I.ON 


Pars  mammillaris  hvpothalsmi 

f  Thalamus 
Epithalamus 
Habenula 
Corpus  pinealc 
ICommissura  post. 
Mclalhalamus 
Cgrpen  ganiculata 


Parts  of  thk  Brain  deriveu  from  the  Rhombencephalon. 
THE  MEDULLA  OBLONGATA. 

The  medulla  oblongata,  sometimes  called  the  bulb  and  usually  designated  by  the 
ctjnvenicnt  but  indefinite  name  "  medulla,"  is  the  direct  upward  prolongation  of  the 
spinal  cord.  It  In^gins  at  the  decussation  of  the  pyramids  below,  about  on  a  level 
with  the  lower  Ixirtlcr  of  the  foramen  inagniiin,  and  ends  at  the  lower  margin  of  tin; 
|x)ns  .tbove  and  is  approximately  2.5  cm.  (1  in)  in.  length.  Its  general  form  is 
ta|KTing,  increasing  in  breadth  from  the  transverse  diameter  of  the  cord  (  10  inm. ) 
below,  to  almost  twice  as  much  ( 18  mm.  )  alx)ve,  and  in  the  antero-posturior  diiiu'n- 
sion  from  H-15  mm.  Its  long  axis  cnrresiMinds  very  closely  with  that  of  the  coril  and 
is.  therefore,  approximately  vertifat.  Tiie  me<luila,  surrounded  by  the  pia  and  arach- 
noid, lies  behind  the  concave  surface  of  tl  e  basilar  |>ortion  of  the  occipital  lM)ne,  willi 
its  dorsiil  surface  within  the  vallecula  In'twecn  the  hemispheres  of  the  cerelH'JUini. 

.Superficially,  in  many  respects  the  medulla  appears  to  Ik-  the  direct  continuation 
of  the  spinal  conl.  Thus,  it  is  dividetl  into  lateral  halves  l>y  the  prolongation  of  the 
anterior  and  jxisterior  metiian  fissures  :  each  half  is  sulKlivided  bv  a  ventro-lateral 
and  a  dorst)-iati'ral  line  of  nerve-n)ots  into  tracts  that  seemingly  are  continuations  of 


. 

I 

1 

i 

j 

! 

1064 


HUMAN  ANATOMY. 


the  anterior,  lateral  and  posterior  columns  of  the  cord.  This  correspondence,  how- 
ever, is  incomplete  and  only  superficial,  since,  as  will  be  evident  after  studying  the 
internal  structure  of  the  medulla,  the  components  of  the  cord,  both  gray  and  white 
matter,  are  rearranged  or  modified  to  such  an  extent  that  few  occupy  the  same  posi- 
tion in  the  medulla  as  they  do  in  the  cord. 

The  anterior  median  fiaiure  is  interrupted  at  the  lower  limit  of  the  medulla, 
for  a  disUnce  of  from  '1-7  mm. ,  by  from  five  to  seven  robust  strands  of  nerve-fibres 
that  pass  obliquely .  dss  the  hirrow,  interlacing  as  they  jiroceed  from  the  t»o  sides. 
These  strands  constitute  the  decussation  of  the  pyramids  (decnssatio  pyramidum), 
whereby  the  greater  number  of  the  fibres  of  the  important  motor  paths  pass  to  the 
opposite  sides  to  gain  the  lateral  columns  of  the  coixl,  in  which  they  descend  as  the 
lateral  pyramidal  tracts.  The  fibres  that  remain  uncrossed  occupy  the  lateral  por- 
tions of  the  pyramids  and,  converging  towards  the  median  fissure,  descend  on  either 
side  of  the  latter  within  the  anterior  columns  as  the  direct  pyramidal  tracts.     The 


Optic  tract 
MammilUry  body 


Poni  (faasilar  groove) 


Middle  cereliellar  pedmcli 


Anterior  mcdimii  iiMure' 


Orrbellum' 


Roil  bundle*  n<  ninth 
and  tenth  nert'e!* 


InlmdibaluB-. 

Cerebral  peduncle 


Interpeduncular  apace 


Tiigcninal  nerve 

Middle  cerebellar  peduncle 


Inl«rk>r  cerebellar  peduncle 
(Realilomboay) 

Olivary  eminenc* 


Arcuate  fibre* 
PytBmidal  decvaaation 


RoiH  bundle*  ol  twelfth  nerve  /' 

Anterior  root*  o(  firat  •|>inal  nervt 
Hrainstem  viewed  iron  in  iront,  showinc  ventral  aapcct  of  medulla,  pom  and  mid-brain. 

decussation  varies  in  distinctness,  sometimes  the  component  strands  being  so  buried 
within  the  fissure  that  they  are  scarcely  evident,  or  even  not  at  all  apparent,  on  the 
surface  and  can  be  satisfactorily  seen  only  when  the  lips  of  the  groove  are  separated. 

.Above  the  decussation  the  anterior  median  fissure  increases  in  depth  in  conse- 
(|uence  of  the  greater  projection  of  the  bounding  pyramidal  tracts.  Its  upper  end, 
just  below  the  inferior  border  of  the  pons,  is  marked  by  a  slightly  expanded  triangular 
depre^ion,  the  foramen  ftecum. 

The  posterior  median  fissure,  the  direct  continuation  of  the  corresponding 
groove  on  the  cord,  extends  along  only  the  lower  half  of  the  mediilla,  since  above 
that  limit  it  disiipiiears  in  consequence'of  {a)  the  separation  and  divergence  of  the 
dorsal  tracts  ol  the  bulb,  which  below  enclose  the  fissure,  to  form  the  lower  lateral 
iMundarics  of  the  loxenge-shapetl  fourth  ventricle  (fossa  rhomboidalis).  and  (*) 
the  gradual  luickward  tlisplactment  of  the  central  canal  within  the  closed  part  of  the 
medulla  until,  at  the  lower  angle  ol  the  ventricle,  it  opens  out  into  that  space. 

Kiich  half  of  the  me<lulla  is  superficially  subdivided  into  three  longitudinal  tracts 
or  areas  by  two  grooves  siuiatetl  at  s«>me  distance  to  the  side  of  the  ventral  and  dorsal 
median  fissures  rcs|)ectively.  One  of  these,  the  antero-lateral  furrow,  marks  the 
line  of  emergence  of  the  root-fibres  of  the  hypoglossal  nerve,  which,  being  entirely 


THE  MEDULLA  OBLONGATA. 


1065 


motor,  correspond  to  the  ventral  roots  of  the  spinal  nerves  with  which  they  are 
in  series.  The  other  groove,  the  postero-lateral  furrow,  continues  upward  in  a 
general  way  the  line  of  the  dorsal  spinal  root-fibres  and  marks  the  attachment  of  the 
hbres  of  the  ninth,  tenth  and  bulbar  part  of  the  eleventh  cranial  ner\'es.  Unlike  the 
posterior  root-fibres  of  the  cord,  which  are  exclusively  sensory,  those  attached  along 
this  groove  of  the  medulla  are  pardy  efferent  and  partly  afferent,  the  fibres  belong- 
ing to  the  spinal  accessory  being  entirely  motor,  while  those  of  the  glosso-pharyngeal 
and  the  pneumogastric  include  both  and,  therefore,  are  mixed. 

The  Antenor  Area. — This  subdivision  of  the  medulla,  also  known  as  the  pyra- 
mid, includes  the  r^on  lying  between  the  anterior  median  fis.sure  and  the  antero- 
lateral furrow.  Superficially  it  appears  as  a  slighUy  convex  longitudinal  tract,  from 
6-7  mm.  in  width,  that  continues  upward 


Fic.  916. 


Cerebral  cortex 


the  anterior  column  of  the  cord.  Each 
pyramid  constitutes  a  robust  strand,  which 
below  beginsat  thedecussationand,  increas- 
ing slighdy  as  it  ascends,  above  disappears 
within  the  substance  of  the  pons.  Just 
before  its  disappearance,  or,  strictly  speak- 
ing, after  its  emergence,  the  pyramid 
is  slighdy  contracted  on  account  of  the 
increased  width  d,.  tlie  bounding  furrows. 
Its  chief  components  being  the  descending 
motor  paths  formed  by  the  cortico-spinal 
fibres,  of  which  approximately  four-fifths 
[Kiss  to  the  opposite  side  by  way  of  fhe 
decussation  to  gain  the  lateral  pyramidal 
tract,  it  is  evident  thnt  only  to  the  extent 
uf  the  direct  pyramid<tl  fasciculus  and,  for  a 
short  distance,  the  anterior  ground-bundle, 
are  its  constituents  represented  in  the 
anterior  column  of  the  spinal  cord. 

The  fibres  destined  for  the  direct 
pyramidal  tract,  which  above  the  decussa- 
tion occupy  the  lateral  part  of  the  pyramid, 
gradually  converge  toward  the  mid-line 
as  the  decus.<iating  fibres  disappear,  until,  at 
the  lower  limit  of  the  crossing,  they  lie 
next  the  median  fif^ure,  which  position 
they  retain  in  their  further  descent  within 
the  cord.  The  space  thus  afforded  at  the 
lower  end  of  the  meilulla,  to  the  outer  side 
of  the  uncrossed  fibres,  is  occupied  by 
the  prolongation  of  the  anterior  ground- 
bundle,  wnich,  however,  soon  suffers 
displacement  as  it  encounters  the  pyramid. 
The  ground-bundle  lies  at  first  to  the  outer  side  of  the  strands  of  decussiiting  fibres 
and  then  behind  the  pyramid;  higher,  it  is  pushed  backward  towards  the  mid-line 
by  the  appearance  of  the  inferior  olive  and  the  mesial  fillet  until,  finally,  it  is 
continued  as  the  posterior  longitudinal  fasciculus  at  the  side  of  the  me<lian  raphe 
beneath  the  gray  matter  covering  the  flcxir  of  the  fourth  ventricle. 

The  proportion  of  the  pyramidal  fibres  taking  (art  in  the  motor  deciissiition  is 
not  always  the  same,  from  H0-90  per  cent,  being  the  usual  number.  Vary  rarely  all 
the  fibres  cn»ss,  with  suppression  of  the  direct  pyramidal  tracts— an  arrangement 
found  normally  in  many  lower  animals.  On  the  other  han«l,  the  direct  pyramidal 
tracts  may  appropriate  an  unusually  large  number  of  the  fibres,  even  to  90  \m.-x  cent, 
of  the  entire  pyramid,  the  crossed  tract,  however,  never  lieing  entirely  inirepresentwl 
Ordinarily  the  tracts  of  the  two  sides  are  approximately  of  ef|ual  extent,  but  occasion- 
ally fhey  may  be  asymmetrical,  in  which  case  th*?  excess  of  the  one  is  offset  by  a 
corresponding  diminution  in  the  faiicicului  of  the  opposite  side  (Flechsig). 


pyramidal 
dKUHalion 

l.alenl 

pjrtmoiidiit  Irart 
Direct 

pyramidal  irai't 


Spinal  nerve 


Diaaram  ahowing  course  and  dccuaaatioii  of  cortico. 
•pinal  (iiyramidal)  tract ;  M.  molulla:  P.  ponas  CP, 
cereliral  padanclei  T,  thalamuai  C,  t.  caiMlat*  and 
lenlicular  nuclei  \  CC,  corpui  ralloaum. 


I066 


HUMAN   ANATOMY. 


/ 


I 


The  Lateral  Area. — ^This  region  is  defined  on  the  surface  by  the  antero-lateral 
and  postero-laieral  furrows  in  front  and  behind  respectively,  and  includes  a  narrow 
strip  on  the  lateral  aspect  of  the  medulla.  Below,  the  tract  is  continuous  with  the 
lateral  column  of  the  cord,  a  resemblance  which  is,  however,  only  superficial  since 
within  the  medulla  the  large  crossed  pyramidal  tract  no  longer  lies  laterally  but 
within  the  anterior  art-a  of  the  opposite  side.  The  upper  part  of  the  lateral  area  is 
conspicuously  modified  by  the  presence  of  an  elongated  oval  prominence,  the  olivary 
eminence  (oliva),  produced  by  the  underlying  corrugated  lamina  of  gray  matter 
composing  the  inferior  olivary  nucleus.  The  olive  measures  about  13  mm.  in  length 
and  about  half  a.s  much  in  its  greatest  width.  Its  upper  end,  more  prominent  and 
slightly  broader  than  the  lower,  is  separated  from  the  inferior  border  of  the  pons  by 
a  deep  groove,  which  medially  joins  the  furrow  occupied  by  the  hypoglossal  root- 
fibres  and  laterally  is  continuous  with  a  broad  depressed  area,  \\\^  paraolivttry  fossa, 
that  separates  the  olive  from  the  restiform  body  and  lodges  the  fibres  of  the  glosso- 
pharyngeal and  pneumogastric  nerves.  The  demarcation  of  the  lower  tapering  end 
of  the  olive  is  somewhat  masked  by  the  anterior  superficial  arcuate  fibres,  which  cover 
for  a  variable  distance  the  inferior  part  of  the  olive  in  their  course  backward  to  gain 


Thalamn* 


Fiilvinar 


Fig.  917. 
Lateral  Kcnicnlatc  body 


Mcdiftti  ,;eilicul«t'?  body 
initerlor  brachium 

Supeflor  colliculut 
Cerehrtil  peduncle 
Inferior  colliculiu 


SLfirrior  cerefae'lar  |)edunclc 

Superior  medullary  velum 

Middle  cerebellar  peduncle 

l.iiie  nf  attachment  of 
roof  «►!  IV  ventricle 
Inlerior  cerebellar  netlunclc 
V  restiform  hotiyi 

Cliva 

Tubercui:<m  cuneatum 

Tuberculum  Kolandi 


Superior  brachium 

Meaial  root  of  oplic  tract 

Anterior  perforated  apace 

Optic  tract 

1  jileral  ollactory  root 


Upllc  nerve 
'Optic  commissure 
■Tuber  cinereum 
Mammillary  bod> 


-Olivary  eminence 
-Arcuate  librra 

Lateml  area  of  medulla 


Brniiistem  viewed  from  the  side.  ahowlnR  lateral  aspect  of  medulla,  pona,  and  mid-brain 


the  restiform  body.  The  components  of  the  lateral  column  of  the  cord  traceable  into 
the  inetliilla — thi-  direct  cerebellar  and  Gowurs'  tract  and  the  long  paths  of  the  lateral 
groiind-buiKllf— for  the  most  jjart,  with  the  exceptiim  of  the  direct  cerebellar  tract, 
pass  iHMicath  or  to  the  outer  side  of  the  olive.  The  superficially  placed  direct  cere- 
bellar tract  gradually  !i-a\es  the  lateral  area  anil  pas-ses  outward  and  Ixjckward  to  join 
tht!  inferior  cerelx-Uar  pediinile  by  which  it  reaches  the  cerebellum. 

The  Posterior  Area. — The  iM>steri()r  region  oi  the  medulla  is  bounded  laterally 
by  the  fibres  of  the  ninth  and  tenth  nerves  ;  and  niesially,  in  the  lower  half  of  the 
bull),  by  the  posterior  median  fissure  and,  in  the  upi^r  half,  by  the  diverging  sidi-s 
of  the  fmirili  ventricle.  Below,  the  posterior  area  receives  the  prolongations  of  the 
tracts  of  Col!  and  of  Hurdath,  which  within  the  metliilla  are  known  as  the  funic- 
ulus gracilis  and  funiculus  cuneatus  respectively,  ant!  are  separated  from  each 
other  by  the  ]>ariiinedian  sulcus.  Beginning  with  a  witlth  of  al)»iit  2  nun.,  the  gra- 
cile  funiculus  increases  in  breadth  .~s  it  ascends  until,  just  Infore  reaching  the  lower 
end  of  the  fourth  ventricle,  it  e.xpaiuls  into  a  well-marked  swelling,  the  clava.  alxiut 
4  mm.  wide,  which  is  caused  by  a  subj.icent  a'cumiilation  of  grav  matter.  Then, 
diverging  from  its  fellow  ol  the  opposite  side  to  Ixnind  the  ventricle,  after  a  short 
course  it  loses  its  identity  us  a  distinct  strand  and  Ix-coines  continuous  with  the 


i 


THE  MEDULLA  OBLONGATA. 


1067 


inferior  cerebellar  peduncle  or  restiform  body.  The  expansion  within  the 
upper  part  of  the  funiculus  gracilis,  the  clava,  contains  the  nucleus  gracilis  ( nucleus 
funiculi  gracilis),  the  reception  sution  in  which  the  long  sensory  fibres  of  GoU's  tract 
are  interrupted.  The  triangular  interval  included  between  the  gracilc  funiculi,  where 
these  begin  to  diverge,  corresponds  to  fhe  level  at  which  the  central  canal  of  the  cord 
ends  by  opening  out  into  the  fourth  ventricle.  A  thin  lamina,  the  obex,  closes  this 
interval  and  is  continuous  with  the  ventricular  roof. 

Along  the  outer  side  of  the  gracile  fasciculus  and  separated  from  it  by  the  para- 
median furrow,  extends  a  second  longitudinal  tract,  the  funiculus  cuneatus,  which 
at  the  lower  end  of  the  medulla  receives  the  column  of  Burdach.  Slightly  above  the 
lower  level  of  the  clava,  the  cuneate  strand  also  exhibits  an  expansion,  the  cuneate 
tubercle  (tuberculum  dnereum),  that  is  less  circumscribed,  but  extends  farther  upward 
than  the  median  elevation.  Beneath  this  prominence  lies  an  elongated  mass  of  gray 
matter,  the  nucleus  cuneatU8( nucleus  funiculi  cuneati),  around  whose  cells  the  long 
sensory  fibres  of  Burdach' s  tract  end. 

Still  more  laterally,  between  the  roots  of  the  ninth  and  tenth  ner\'es  and  the 
cuneate  strand,  the  posterior  area  of  the  medulla  presents  a  third  longitudinal  eleva- 
tion, the  funiculus  of  Rolando.     The  latter  is  caused  by  the  increased  bulk  of  the 


Fig.  918. 


Inferior  coHlculiu 


Cerebral  peduncle 


Median  fo 


Median  tulriu 

Middle  cerebellar  peduncle 

Acoustic  atrbe 

Acoustic  trivone 

Restiform  body 

AtUchmeiit  o(  ventricular  rool 
Obex 

Funiculus  cuneatus 


rmralnin 

Superior  trochlear  nerve 

Orebellar  peduncle 
.  Floor  ol  fourth  ventricle 
Fovea  superior 

Eminmtia  teres 

Trigonum  hypogloai*! 

Trlssnum  vaci  (fovea  inferioi ) 

FttniculUB  sepatans 
—     ~-       Area  pnslrema 

Funiculus  gracilis 

- —    Laleial  area 


Me<lulla  and  lloor  of  fourth  ventricle  seen  from  behind,  alter  remonl  of  c'rcbeltam  and  ventricular  roof    x  \%. 

underlying  substantia  gelatinosa  that  caps  the  remaiiis  of  the  posterior  horn  ijf  gray 
matter,  and  is  overlaid  by  a  su|Mfrficial  sheet  of  whiti-  matter  ctimiKKM-d  of  thf  longi- 
tudinal fibres  of  the  descending  root  of  the  trigeminal  nerve.  VVhilc,  thcrtiore,  the 
tubercle  of  Rolando  is  producwl  by  the  ex.tggi'ration  ()f  gray  matter  repPMntid 
within  the  spinal  cord,  tht  gracile  and  cuneate  nuclei  are  new  stations  in  w  iiicli  the 
posterior  root-fibres  not  interrupte<l  at  lower  levi^ls  end,  and  from  v/bich  the  seiisi.rv 
impulses  collecte<1  by  the  cord  are  distribiitetl  to  the  ccnlM-lliim  an  '  he  hi),'!'  r 
centres  by  neurones  of  the  second  ortler. 

The  upper  half  oi  the  iMwterior  area  of  the  medulla  is  miMlified  l>y  thi  |  umii.  c 
of  the  fourth  ventricle,  the  lower  lateral  boundary  of  which  it  largely  forms,  into  a 
robust  rope-like  strand  that  diverges  as  it  ascends,  Above,  it  abuts  against  ami  fuses 
with  the  literal  continu.ition  of  the  pons  and  then,  l)ending  hackw-nrd,  enters  the 
overhanging  cerebellum  as  the  inferior  cerebellar  peduncle.  This  straml,  also 
known  as  the  restiform  body  ( conius  restiforme),  is  seemingly  the  direct  prolongation 
of  the  gracile  .md  cuneate  funiculi.  Such,  however,  is  not  the  rase,  since  the  fibres 
passing  from  these  tracts  to  the  cerebellum  bv "ay  of  the  restiform  ImmIv  are  the  axonen 
of  the  gracile  and  cuneate  nuclei  and,  therefi)rc,  new  links  in  the  chain  of  condmtiun. 


k/ 


.    ! 


1068 


HUMAN  ANATOMY. 


The  inferior  cerebellar  peduncle  is  the  most  direct  path  by  which  the  cerebellutn 
is  connected  with  the  medulla  and  the  spinal  cord.  In  addition  to  the  tracts 
originating  in  the  cord  and  desdned  'or  the  cerebellum  (the  direct  cerebellar  and 
possibly  part  of  Cowers'  tract),  it  coniprises  probably  fibres  passing  in  both  direc- 
tions; that  Ls,  from  the  cells  within  the  medulla  to  the  cerebellum,  and  from  the 
cerebellar  cells  to  the  medulla.  A  more  detailed  account  of  theK  components  will 
be  given  in  connection  with  the  structure  of  the  medulla  (page  1072).  l'p>m  c\n>x 
inspection  of  the  surface  of  the  medulla,  the  direct  cerebellar  tract  is  seen  as  an 
obliquely  cuursing  band  that  at  the  lower  level  of  the  olive  leaves  the  lateral  area  and 
gradually  passes  backward,  over  the  upper  and  outer  end  of  the  Rolandic  tubercle, 
to  join  the  restiform  body,  within  which  it  continues  its  journey  to  the  cerebellum. 
The  anterior  superficial  arcuate  j^bres  also  enter  the  restiform  body,  after  sweeping 
around  the  inferior  pole  of  the  oUve,  or  crossing  its  surface,  and  the  upper  part  of  the 
funiculus  of  Rolando.  Additional  contributions,  the  posterior  superficial  arcuate 
fibres,  proceed  to  the  restiform  body  from  the  gracile  and  cuneate  nuclei  of  the 
same  side.  Just  before  bending  backward  to  enter  the  cerebellum,  the  restiform 
body  '»  crossed  by  a  variable  number  of  superficial  strands,  the  stric  acuaticc, 
that  may  be  traced  from  the  floor  of  the  fourth  ventricle  and  around  the  inferior 
(leduncle  to  the  cochlear  nucleus. 

INTERNAL   STRICTURE   OF   THE    MEUt'M.A   OBLONGATA. 

As  already  pointed  out,  the  correspondence  between  the  spinal  cord  and  the 
metlulla  is  only  superficial,  sections  across  the  medulla  rev^raling  the  presence  of  con- 
siderable mass<-s  of  gray  matter  and  important  tracts  of  nerve-fibret  not  representetl 


Fiii.  919. 


Flf.  tjji 
FIk.  wr 


Wnlral  i  A )  (till  ilorMi  <  H\  ■■poin  of  hrain  Mem,  thowinc  livch  -f  Mctionii  whiih  follow. 


in  the  curd,  as  well  as  the  rearrangement,  modification  or  (lisap|>earance  of  spinal 
tracts  which  are  prolongeil  into  the  bulb.  In  consequence,  the  medulla,  even  at 
its  lower  end,  ori-sents  new  features,  and  towards  its  upper  limit  \aries  so  greatly 
from  the  cmd  titat  but  slight  resemblance  to  the  latter  is  retained.  The  character- 
istic features  displaved  by  transverse  sections  of  the  metlulla  at  different  levels 
de|)en<l  upon  the  changes  induced  by  four  chief  factors  : — ( 1 )  the  decussation  of 
the  pyramids,  (2)  the  appearance  of  the  dorsal  nuclei,  (3)  tlie  pnxluction  of  the 
formatio  reticularis,  and  (4  )  the  ofiening  out  of  the  fourth  ventricle. 


THE  MEDULLA  OBLONGATA. 


1069 


The  efiects  of  the  decussation  of  tiie  pyramidal  tracts,  assuming'  for  convenience 
that  the  latter  piss  from  below  upward,  are  conspicuous  when  followed  in  consecutive 
transverse    sections    from 

the  spino-bulbar   junction  ^'^'  9*o. 

cerebralward.  The  Itrst 
suggestion  of  the  decussa- 
tion appears  ( Fig.  920 )  as 
strands  of  nerve- fibres,  that 
pass  from  the  field  of  the 
lateral  pyramidal  tract  in 
the  lateral  column  obliquely 
through  the  adjarunt  ante- 
rior horn  of  gray  matter  and 
across  the  bottom  of  the  an- 
terior median  fissure  to  gain 
the  opposite  anterior  col- 
umn. At  a  slightly  higher 
level,  where  the  decussation 
fully  established    (Fig. 


Subiktxntia 
gvbtiiti 

01  IM 


Anlrrior 
conm 


Tiamvcrac  Kcttov  of  medulla  «l  Imd  A.  Fto.  919;  beginning  oi  m  ramidai 
■'—     Wcifctt-Pal  •uinint.    v  jv<     Preparalioii  nude  hy Vrofnsut 


dKiuMilon, 
Spillcr. 


931 ),  the  large  strands  of 
obli(|uely  sectional  fibres 
are  seen  cutting  through  the  gray  matter,  partly  filling  the  median  fissui  e,  and  collecting 
on  either  side  of  the  latter  as  the  large  ventral  bundles  which  thence  upward  constitute 
the  prominent  pyramidal  fields.  In  consequence  of  the  greater  space  required  by 
the  pyramids,  the  isolated  anterior  horns  of  the  gray  matter,  cut  off  by  the  crossing 
strandA,  and  the  adjacent  anterior  ground-'ufidle  are  displaced  laterally  and  at  first 
lie  to  the  outer  side  of  the  decussated  fibres.  I^ter,  the  ground-bundle  assumes  a 
|)osition  behind  the  pyramid  and  eventually  becomes  continuous  with  the  posterior 
longitudinal  fasciculus  (page  iii6)  The  detached  anterior  cornu  of  the  gray 
matter  is  pushed  outward  and  backward  and  gradually  becomes  broken  up  l>v  and 
interspersetl  among  the  fibres  of  llie  formatio  reticularis. 

The  Poatenor  Nuclei  and  the  Arcuate  Fibres.— The  robust  tracts  <>f 
white  matter  { nerve-fibres/  prolonged  into  the  gracile  and  cuncatc  funiculi  from  the 
tracts  of  Goll  and  of  Burdach  become  invaded  by  new  masses  of  gray  matter,  the 
nucleus  gracilis  an<i  cuneatus.     The  gracile  nucleus,  the  tirst  encounter ..1I,  'u-^ins 

as  a   narrow   area   ol   gray 
Fh;.  911.  matter  within  the  corresponfl- 

ing  strand,  on  a  level  with 
the  pyramidal  decussatii  'ii 
(Fig.  921).  It  rapidly  in- 
creitses  in  bulk,  until  it 
not  only  invadi-s  Tjie  t-ntire 
funiculus  gracilis,  but  also 
joins  the  gray  matter  sur- 
rounding the  central  canal. 
The  superficial  stratum  of 
spinal  fibres  gradually  dimin- 
ishes as  more  and  more  of  its 
com|>onents  en<l  around  the 
cells  of  the  gracile  nucleus, 
until,  finally,  all  are  intcr- 
nipte<l.  Meanwhile  the 
cuneate  nucleus  a|>p«'ars 
within  the  funiculus  ciuicatus 
as  a  dorsiilly  <lirpcte<l  club- 
shaped  mass  of  gray  mat- 
ter (Fig.  q22)  which  soon 
by  the  oxerlying  stratiuii  of 
higher  li  vel  than  the  nucleus 


Nuclrin  unicMit, 


Central 


laolalrd 
■nlrrior 
cori.a 


Pvramiiliil  'IrtunHtiun 


1  rainvetiw  •rctiim  nf  nwdnlla  at  Icvrl  H,  Fii.  oii:  prramMal  dfrtm- 
^Uirii  MctI  mtahliiUmI;  poatrrinr  rfirniia  are  dinplarrd  Interatly  by 
in.trrlnr  I'olumiia.         514.     Prrtiaralinn  h>  Prnfcwor  Spillar 

liecomes  a  prominent  mottletl  area,   sharply  ilefined 
Hurrlach  tibrcs.     The  cuneate  nucleus  extends  to  a 


I070 


hUMAN   ANATOMY. 


!     I 


t^racilis  and,  even  after  the  disappearance  of  the  latter,  continues  as  a  striking  coll'c- 
tion  of  gray  matter  beneath  the  dorsal  surface  of  the  medulla,  from  which  it  is 
separateid  by  the  posterior  superficial  arcuate  fibres.  Within  the  upper  part  of  the 
fasciculus  cuneatus  the  gray  matter  becomes  subdivided  into  two  mas.M-s  (Fig.  924), 
the  more  superficial  and  continuous  of  which  is  called  the  nucleus  cuneatus  extemus, 
and  the  deeper  and  more  broken  one,  the  nucleus  cuneatus  inlemus. 

Owing  to  the  increased  bulk  of  the  fasciculi  of  the  posterior  area  occasioned  by  the 
appearance  and  expansion  of  the  contained  nuclei,  the  dorsal  horns  uf  the  gray  matter 
are  displac(>d  laterally  and  forward,  su  that  they  come  to  tie  on  a  level  with  the  central 
canal.  Meanwhile  the  posterior  cornua  themselves,  especially  the  capping  substantia 
gelatinosa,  materially  gain  in  bulk  and  now  appear  as  two  club-shaped  masses  uf  gray 
matter  that  cause  the  dorso-lateral  projections  of  the  Rolandic  tubercles  seen  on  the 


Fig.  933. 


Nudcin  Kracili* 


Fanicalai  (cncilli 
FMiicnliift  cuneatus 


Spinal  root  o<  V  nerve 
Substantia  (elatintiaa 


Accessoo'  oHvan'  nucleui 
Anti*rf>latcnil  jcrouiid-huiidle 

.'\nitrrior  supeificial  arcuate  fibres' 


Nuclcua  cuncatua 


Centi»t  gray  matter 
Uccp  arcuate  fibres 

Fibres  o(  XII  nerve 

Sensory  dccuMatkiii 


Pyramidal  tracts 


Traosveme    Ktion  of  medulla  nl  level  C.  Fll.  9iq,  <,li..«in  sensory  decuMution,  postrlior  nuclei  and 
pyramidal  traits       •  5H-     Preparation  by  Pro(e»sor  Spillcr 

surface,  fkniath  the  latter  and  v  losely  overlying  the  outer  bi)rd(  r  of  the  extensive  area 
of  thi  siiljstantiu  gelatinosa,  a  crescentic  tract  of  the  longitudinally  coursing  nerve- 
fibre.-i  marks  the  position  of  the  descending  root  of  the  trigeminal  ner\-e  (Fig.  922). 
The  cliief  purpose  of  the  gracile  and  cuneatc  nuclei  being  the  reception  of  the 
long  sensorv  tnicts  continued  from  the  cord  and  the  distribution  of  impulses  so 
rcoeivetl  t'>  :hc  ccnbellum  :ind  to  the  higher  centres,  it  is  evident  that  new  paths  of 
the  seconil  order  must  arise  within  these  nuclei.  About  on  a  level  with  the  upper  limit 
of  the  pynimidal  or  mot<.i  decussation,  fibres  emerge  from  the  gracile  and  cuneate 
nuclei,  sweep  forward  ami  inward  in  bold  i-ur\'es  and  cross  the  median  raphe  to  the 
op|K>site  side  of  the  medulla,  immediately  behind  the  pyramids  (Fig.  922).  They 
then  turn  sharply  upward  and  form  the  beginning  t)f  the  imjjortant  sensory  pathway 
known  as  the  median  fillet  (lemniscus  medialis)  thn?  connects  the  medullary  nuclei 
with  the  higher  centres,  as  the  superior  corpora  qiiatli  i^emina  and  the  optic  thalannis. 
The  first  fibres  that  emerge  ii,  this  manner  from  the  gracile  and  cuneate  nuclei 
constitute  a  fairly  well  defined  strand  to  which  the  name  sensory  decussation  or 
decussation  of  the  fillet  is  given.  It  must  not  Ix-  supjiosed,  however,  that  with 
this  decus,satioii  'he  cros.sing  ceases,  for,  quite  the  contrary,  it  is  only  the  iK-ginning 
in  extenileil  series  of  sensory  fibres  that  pass  across  the  raphe  at  various  levels 
tliKiughout  the  hrain-stem.  .As  many  longitudinally  coursing  fibres  are  encountered 
by  those  sweeping  from  side  to  side,  an  interweaving  of  vertical  and  horizontal  fibres 
occurs,  which  results  in  the  |>riKluction  of  the  characteristic  formatio  reticularis  that 
constittit*-*  a  large  jxirt  of  t!v  inediilla,  as  well  as  of  the  dnrs;il  or  tegmental  portion^ 


-1 


THE  MEDULLA  OBLONGATA. 


107 1 


J 


of  the  pons  and  cerebral  crura.     A  feeble  expression  of  a  somewhat  similar  structure 
is  seen  in  the  reticular  formation  within  the  lateral  column  of  the  spinal  cord. 

The  Arcuate  Fibres. — These  originate  as  the  axones  uf  the  ci  lis  of  the  gracile 
and  cuneate  nuclei  and  include  three  sets.  The  first,  the  deep  arcuate  fibres,  f  <im 
sharply  brainward  after 


Fig. 


NiKl«m  cuncUa* 


Nuilens 
KTacilii 


Fibres  from 

Ooll't  trad    Fibre*  from  Burdarh'a  tract 
Poal.  lupcrficial  arcaalc 


croasii^  the  raphe  and 
constitute  the  chief  con- 
stituents of  the  mesial 
fillet  The  second  .set,  the 
anterior  superficial 
arcuate  fibres,  also 
cross  the  mid-line,  but 
these,  instead  of  turning 
upward,  pass  forward, 
enter  through  the  pyra- 
mid or  along  its  median 
aspect,  and,  gaining  the 
surface,  sweep  over  the 
pyramid  and  olivary  emi- 
nenceand  thenceproceed 
backward  to  the  restiform 
body  and  on  to  the  cere- 
bellum. An  oval  collection  of  small  fusiform  nerve-cells,  the  arcuate  nucleus 
( nnclcus  arautas )  lies  in  the  path  of  these  fibres,  at  first  on  the  ventral  surface  of  the 
pyramid  and  then  along  the  median  fissure.  Whilst  some  additional  arcuate  fibres 
arise  from  the  cells  of  the  nucleus,  the  majority  sweep  by  without  interruption. 
The  third  set,  the  posterior  superficial  arcuate  fibres,  proceed  from  the  cells  of 
the  gracile  and  cuneate  nuclei  of  the  same  side  and  pass  beneath  the  ventricular 
floor  to  the  adjacent  restiform  body  and  thence  to  the  cerebellum. 


Deep  arcuate 


Anterior  aapcrCclal  arcuate 


Arcuate  aocleua 


Diacram  illuatrBtins  aourcc  and  patii  of  arcuate  filim:  RB,  restiform  body; 
P,  pyramidal  Inct ;  O,  inferior  olivary  nucleus. 


Fig.  934. 


Nucleus  jcracilia 


NtKlctts  cuncatus  intemua 
Nttc.  cttncatus 
cxtcmus 


Funiculus  cuncatua 


Fasciculus  soUurloa 


Nucleus  lateratb 


Nucleus  amhigaus 


Declination  of 
fillet  fibre* 


Median  filM 


Soinal  root  of 
V  nerve 

Deep  arcuate  fibres 
and  lormatio 
reticularis 


Pyrtmldal  tract 


Dorsal  access, 
olivary  nurteus 

Inferior  oli\-ary 
iiucleus 


Mesial  access, 
otivarv  nuileus 


Ront-fihrw  of 
h>'puKlos<ial 


Anterior  superficial  arcut»  Kbrea 

Transverje  section  of  medulla  at  level  P,  Fie.  oiq.  ^howlna  pc.icrior  nudei.  inferior  olivary  nuclei,  formatio 
reitcutarls  and  dorsal  displacement  of  central  lanaC         ■       -  .     _    .  _  ... 


Arcuate  nucleus 

i.  inferior  olivary  ... 

■'  5'i.     Prcimration  by  Profesfwif  Rpiller. 

in  each  half  ot  the  medulla,  three  nia-sses 


The  Olivary  Nuclei.— These  inciutl 
of  gray  matter — the  inferior  olivary  nucleus  and  the  two  accis-sory  olivary  nuclei. 
Beneath  the  prominent  olivary  eminence  lies  a  cc.migat.-t!  -atrk-Iike  lamina  of  gray 


I072 


HUMAN  ANATOMY. 


Fig. 


Ventral 

Dorso-latenil  aspect  of  inferior  olivary 
nucleus  as  reconstructed  by  X>r.  Florence 
R.  Sabin.    X  5- 


matter,  the  inferior  olivary  nucleus  (nnckms  olivaris  inferior),  which  in  bvorable 
transverse  sections  appears  as  a  conspicuous  sinuous  C-like  figure.  The  nucleus 
resembles  a  greatly  crumpled  bag,  of  which  the  closed  end  lies  beneath  the 
corresponding  superficial  protuberance  and  the  mouth,  or  hHum,  looks  mesidly 

and  somewhat  dorsally.  When  reconstructed  and 
viewed  from  the  side  (Fig.  925),  the  plications  of 
the  lateral  and  dorso-lateral  surfaces  display  a 
general  antero-lateral  disposition.  On  the  ventral 
surface  the  grooves  radiate  from  the  ventral  border 
of  the  hilum  (Sabin).  The  greatest  length  of  the 
inferior  olivary  nucleus  is  from  12-15  mm.,  its 
transverse  diameter  is  about  6  mm.,  and  its  vertical 
one  about  one  millimeter  less.  The  somewhat 
compressed  hilum  measures  sagittally  from  8-9  mm. 
The  plicated  lamina  of  gray  matter  composing  the 
wall  of  the  sac  is  from  .2-.  3  mm.  in  thickness 
and  contains  numerous  small  irregularly  spherical 
nerve-cells,  each  provided  with  a  variable  number 
of  dendrites  and  an  axone,  embedded  within  a 
compact  feltwork  of  neuroglia  fibres.  The  interior  of  the  gray  sac  is  filled  with 
white  matter  consisting  of  nerve-fibres  that,  for  the  most  part,  stream  through  the 
hilum  and  thus  constitute  the  olivary  peduncle.  These  strands,  known  as  the 
cerebello-olivary  fibres,  connect  the  cerebellar  cortex  with  the  inferior  olivary 
nucleus  and  probably  pass  in  both  directions.  Many  fibres,  the  axones  of  the  olivary 
neurones,  issue  from  the  hilum  on  the  one  side,  cross  the  mid-line  and,  sweeping 
through  the  opposite  olivary  nucleus  either  by  way  of  the  hilum  or  directly  traversing 
the  gray  lamina,  continue  their  course  to  the  restiform  body  and  thence  to  the 
cerebellum.  Other  fibres  originate  in  the  cells  of  the  cerebellar  cortex  and  proceed 
in  the  opposite  direction  along  the  same  pathway  to  end  in  relation  with  the  cells 
of  the  inferior  olivary  nucleus.  The  further  links  in  the  chain  of  conduction  are 
uncertain  ;  according 
to  KoUiker  it  is  prob-  Fig.  916. 

able  that  from  some  erf  _^arr!^::=j!r7r;S^:5Z3?!tes.   Cerehelloollvary  •traiids 

the  olivary  cells,  fibres 
pass  downward  into  the 
antero-lateral  ground- 
bundle  of  the  cord. 

The  accessory 
olivary  nuclei  are 
two  irregular  plate-like 
masses  of  gray  matter 
that  lie  respectively 
mesially  and  dorsally 
to  the  chief  olive.  The 
first  of  these,  the  mesial 
accessory  olivary  nu- 
cleus (nucleus  nlivarU 
accesHorius  mesialis) 
is  a  sagittally  placed 
lamina, from  lo-i  i  mm. 
in  length,  which  lies 
between  the  tract  of  the 
fillet  and  the  root-fibres 
of  the  hypoglossal 
ner\'e.  It  extends  be- 
low the  inferior  olive 
and,  therefore,  is  encountered  in  transverse  sections  at  a  lower  level— immediately 
above  the  pyramidal  decussation— than  the  main  nucleus.  According  to  the  recon- 
structions of  Sabin,  the  nucleus  comprises  three  dorso-ventral  columns  of  cells,  of 


Section  of  inferior  olivary  nucleus,  shnwinn  pllratrri  sheet  of  gray  substance 
traversed  by  strands  of  i-erehello-olivary  fibres.    X  i« 


THE   MEDULLA  OBLONGATA. 


1073 


which  the  lower  and  middle  are  <»ntinucn«  -d.'J-PPjJ^^^Tr^.luT'  tZ 
snudl  isolated  -^  «' g^n^^S  .Sen^tiTU^^^^^  ^  that  its  plane 

Wenor  or  spinal  end  of  the  ""/^^^J*^*™^  the  chid  olive.     Higher,  when  the 
bobh^ueandpara^elwiththevenuaisu^e  represented  by  a  narrow 

latter  a  well  <stebUshed,  the  m«i^  d^^^Uh  the  sagitt/plane.     In  this  situa- 
r  rheSei^ir^fwrnte-'fiTet^e*^^^^^^^^       'of  the'^chiel  olive  and  across 


Fig.  927. 


DoiMl  nucleus  of  vagus 


Ventriculsr  rool 


Nucleus  cuncstus 


Funiculus  cuna- 

tus,  overlsia  ojr 

restUorm  body 

Fasciculus 
soliurius   ' 


Subsuntia  (elsj 
tinosaoverlalj 
by  rook  of 
Nucleus  smbignui 

Nucleus  lateralii 


Post.  kmKitttdinsI 
fasciculus 


Root-fibres  of  XII 


Inferior  olivaty 
'nucleus 


Tract  of  mesial  «llet 


Pvramidal  tract 


rvramia.. ...«  Anterior  superficial  arcuate  fibres  

Transverse  section  of  .^u.U«Jjv^^E,F...,.^=«nJ^^ 


its  hilum  The  dorsal  accessory  olivary  nucleus  ( nucleus  olivaris  accessorlus  dorsalis) 
i?l^  extensive  fhan  the  median.  m«2uring  about  9  mm  in  length,  and  lies  close  to 
and  behind  the  posterior  lip  of  the  hilum  of  the  inferior  olive. 

The  CentVal  Gray  ^«tter.-As  pointed  out.  within  the  dosed  part  of  the 
meduUa  the  '  eJtral  caJ  and  the  surr  Jing  gray  ^^^l^.f^^^^^  ^^f£ 
dorsally  in  consequence  of  the  increasing  space  required  bvthepyramid  the  hUet 

Sand  the^erior  longitudinal  J^«=">"».  ^""^  .P^^^f^.^' J^rTTotwe^ 
coursing  fibres  that  lie  close  to  the  median  raphe  »"<*  «"lf8«^f«  *5,irfe  the  ^ur 
upward  When  the  central  canal  opens  out  into  the  fourth  ventricle  the  sur 
rounding  gray  matter  is  correspondingly  spread  out  and  forms  the  lining  of  the 
[^ntricuTar  floor.  Within  this  gray  sheet  and  near  the  mid-line.  on  each  side,  is  seen 
thr^UD  of  eels  constituting  the  hypoglossal  nucleus  from  which  the  fibres  of  the 
twelKntl  ne^rS.  T^ese  sti4ndS  take  a  direct  ventro-lateral  course  through 
the  meduUa  and^erge  on  the  surface  in  the  groove  between  the  pyramid  and 
oUva^  emSence  Sightly  more  lateral,  and  to  the  outer  side  of  the  hypoglos.sal 
nSs  Tnothe^r  group  0I  cells  marks  the  position  of  the  « Ungated  tae^'-W''"''- 
Sw«;«/«««'««  partly  sensory  and  partly  motor,  belonging  to  the  -.  h  and 
fth  cranial  nei^«  The  fibres  of  the  vagus  traverse  the  medulla  laterally  and 
St  thT^rfa^rt  the  junction  of  the  latlral  and  posterior  areas      I"  this  way 

rdiXTfi"-  °'  '^^  ^-*  ""I^.  ^*f '"^  "r !?  '"^^SorTpiS  ig) 
into  three  tnaneular  area«— a  mesial,  a  lateral  and  a  posterior  (Flechsig). 

Vi^fS^inTmsverse  sections  through  the  upper  thW  o' /h-^?"  '^j^^^K- 
rior  area— the  soace  between  the  vagus  fibres  and  the  dorsal  surface  of  the  medulla— 
SSeH  to  conta'nTnumS^  of  importilrt  fibre-tracts.     ( i )  The  resfi/^  body  appears 

68 


I074 


HUMAN  ANATOMY. 


as  a  large  irregularly  crescentic  tract  of  transversely  cut  fibres  that  occupies  ttie 
greater  part  of  the  periptiery.  (2)  Ihs  descending  root  0/ the  vestibuiar  nerve  \s  a/e^a 
to  the  inner  side  of  the  dorso-mesial  border  of  the  restiform  body  as  a  field  of  loosely 
grouped  bundles  of  cross-sectioned  nerve-fibres.     (3)  The  fasciculus  solitarius,  or 


Faiciculiu  loliuriiu 


Fig.  938. 

Ootial  nuclcns  oi  X 

NuckotolXII 


Ventricular  roof 


Nucleus  ambiguns- 
Root-fibre*  of  XII 


Restilorm  body 


Descending 
vestibular  root 


Gray  column 
'o{  vestibular  root 
Form.reticKrisea 
Form.  letic.  alba 
Interotfvary  stratum 
(median  fillet) 


Inferior  olivary  nucleus 


Pyramidal  tracts 

Transverse  section  of  medulla  at  level  F,  Fi(.  919;  ventricular  floor  Is  wide;  restiform  bodv  well  establislied  ; 
descending  root  of  vestibular  nerve  is  seen.    X  s-    Preparation  by  Professor  Spillcr. 

descending  root  of  the  vagus  and  glosso-pharyngeal  nerves,  shows  as  a  conspicuous 
transversely  cut  bundle  which  lies  ventro-mesially  to  the  vestibular  root.  (4)  The 
descending  root  of  the  trigeminal  nerve  is  easily  identified  as  a  superficial  crescentic 
field  that  on  its  mesial  aspect  encloses  the  remains  of  the  substantia  gelatinosa  Kolandi. 
The  lateral  area,  between  the  diverging  vagus  and  hypoglossal  root-fibres,  is 
chiefly  occupied,  in  addition  to  (i)  the  inferior  olivary  and  (2)  dorsal  accessory 
olivary  nucleus,  by  the  feltwork  of  fibres  producing  the  reticular  formation.  In  con- 
trast to  that  within  the 
anterior  art  the  retic- 
ulum within  the  lateral 
area  contains  a  con- 
siderable amount  of 
diffuse  gray  matter  be- 
tween its  fibres,  and, 
hence,  is  known  as  (3) 
tYi^formatio  reticularis 
grisea.  Accessions  to 
the  irregularly  distrib- 
uted nerve-cells  occur 
as  two  moredefinitecol- 
lections  ;  one  of  these, 
(4)  the  nucleus  am- 
biguus,  consists  of  an 
inconspicuous  group  of 
large  cells  lying  about 
the  middle  of  the  gray 
reticular  substance  and  is  of  importance  as  the  nucleus  of  origin  of  at  least  part  of 
the  motor  fihres  A  the  v.igus  ner\'e.  The  other  (5^  the  nufleus  lateralis,  includes 
an  uncertain  aggregation  of  medium  sized  cells,  situated  near  the  periphery  and  ventral 


Portion   of  formatio  reticularis    RriNea,   showing 

transverse  iin'I  longitudinal  fibres. 


nerve-cells  and 
X  ijo. 


interlacing 


THE   MEDULLA  OBLONGATA. 


1075 


and  by  KoUiker  regarded  as  belonging  to  the  ong.n  ol  the  spinal  accessory  ncrxe. 


Fig.  930. 


1  bodr 


RntiAHm  body 


E>ctccadliiKraolaf 
vMttbuUi  Mm 


Medlaji 
Nucloa    nulbulu 


.    Vlbno)  IX  MTYC 
,    Spinal  root  of  V  B«iv« 
SubMsMU  gcUliwMO 
Facnatio  i«ilcula<lc  KriMa 


lafcrior  oUnry  body 


l^HI^MH^^^'     ^^HHhhH^^^^*^  PyfOmMol  men 


In  a  eeneral  way  the  cells  of  these  nuclei  (ambiguus  and  lateralis)  of  the  substantia 
X  m^l^CdS  L  the  analogues  o\theTateral  horn-cells  of  the  co^jus^^s 
those  of  the  hvpoclossal  nucleus  resemble  the  anterior  root-cells  of  the  spinal  nerves. 
The  anJS  area,  between  the  mid-line  and  the  hypoglossal  root-fibres  is 
occupied  vent'rluy  by  (.  the  />yra.i.iai  tract,  which  ^^PP^^J-^^h^^trer'nS 
of  the  field  with  the  exception  of  a  very  narrow  peripheral  zone  that  intervenes 

Fig.  931. 


cell 


Nerve-  Lon«itndliml   TrjnsvetM 
nbret 


fibres 


Median  raphe 
Portion  ol  ln.n,v.r«  «ctlon  of  medull..  .howing  median  raphe  and  adjacent  (orm.tio  rellculari.  alba.     X  .y. 

between  the  pyramidal  fibres  a..d  the  suriace  along  the  median  1       -e  and  the  ventral 
Sp^ct  of  the'^^edulh.     This  .ne  i.  tr..yersed  by  (2)  the  .nten.  ^"P-jJ^-^^^^^^^ 
fibres,  among  which  is  lodged  an  irregular  column  of  nerve-cells  that  constitute  (?,) 


1076 


HUMAN  ANATOMY. 


the  arcuate  nucleus.  The  latter  lies  at  first  chiefly  on  the  ventral  and,  higher,  on  the 
mesial  aspect  of  the  pyramidal  tract.  The  cells  of  this  nucleus,  small  and  fusiform, 
are  the  origin  of  not  a  few  of  the  superficial  arcuate  fibres,  although  those  from  the 
dorsal  nuclei  continue  their  course  over  the  nucleus  without  interruption.  At  the 
upper  end  of  the  medulla,  the  cells  of  the  arcuate  nucleus  increase  in  number  and 
mingle  with  those  of  the  nucleus  of  the  raphe  and  the  pontine  nucleus. 

Dorsal  to  the  pyramid  and  immediately  next  the  mid-line  lies  (4)  the  compact 
tract  of  the  median  fillet,  composed  of  longitudinal  fibres  that  are  the  upward  continu- 
ation of  the  deep  arcuate  fibres,  which,  from  the  sensory  decussation  to  the  upper 
limit  of  the  cuneate  nucleus,  bend  sharply  brainward  after  crossing  the  mid-line.  The 
fillet-tracts  are  also  known  as  the  interolivary  stratum,  as  they  constitute  a  compact 
and  laterally  compressed  field  l)etween  the  inferior  olivary  nuclei.  Lateral  to  the 
fillet,  between  the  latter  and  tl.  •  hypoglossal  fibres,  lies  (5)  the  mesial  accessory- 
olivary  nucleus.  (6)  The  posterior  longitudinal  fasciculus  appears  in  cross-section 
as  a  compact  oval  or  laterally  flattened  strand,  which  lies  next  the  raphe  and 
immediately  beneath  the  gray  matter  covering  the  floor  of  the  fourth  ventricle. 
This  important  path  will  be  later  described  (page  11 16).  The  remaining  space 
of  the  anterior  compartment,  between  the  pyramid  and  the  ventricular  gray  matter, 
is  occupied  by  the  formatio  reticularis  alba,  so  designated  in  distinction  to  the 
formatio  grisea  on  account  of  its  meagre  number  of  nerve-cells,  since,  with  the  excep- 
tion of  those  scattered  in  the  immediate  vicinity  of  the  mid-line  (nucleus  raphe),  few 
cells  are  present. 

The  Formatio  Reticularis. — Repeated  mention  has  been  made  of  the  reticu- 
lar formation  produced  by  the  interweaving  of  the  horizontal  and  vertical  fibres. 
Whilst  particularly  conspicuous  within  the  medulla  at  the  levels  occupied  by  the 
gracile,  cuneate  and  inferior  olivary  nuclei,  on  account  of  the  prominence  oi  the 
arcuate  and  cerebello-olivary  fibres,  the  formatio  reticularis  does  not  end  with  the 
disappearance  of  these  nuclei  and  fibres,  but  is  prolonged  upwaro,  although  less 
marked,  by  transversely  coursing  fibres  derived  from  the  reception-nuclei  of  various 
cranial  nerves— the  vagus,  glosso-pharyngeal,  auditorv,  feicial,  and  trigeminal— from 
whose  neurones  axones  of  the  second  order  arise  that  sweep  across  the  mid-line 
to  join  chiefly  the  fillet  tract  or  to  end,  perhaps,  about  nerve-cells  of  other  nuclei. 
In  this  manner  the  formatio  reticularis  finds  representation  within  the  dorsal  or 
tegmental  areas  of  the  pons  and  the  cerebral  crura.  The  longitudinal  fibres  within 
the  formatio  reticularis  grisea  are  derived  from  many  sources.  Some  are  the 
continuation  of  Gowers'  tract ;  some  belong  to  the  long  strands  concerned  in 
establishing  reflex  paths  connecting  the  corpora  quadrigemina,  nucleus  rubrum, 
vestibular  and  olivary  nuclei  with  the  spinal  cord  ;  some  are  the  axones  of  tegmental 
neurones  and  pursue  shorter  courses,  both  descending  and  ascending,  as  association 
fibres  linking  together  different  levels  of  the  brain-stem  ;  while  still  others  are  the 
pro'  ongations  of  the  spino-thalamic  and  other  long  tracts  of  the  antero-lateral  ground- 
bundle  of  the  cord.  The  longitudinal  fibres  of  the  formatio  alba  are  chiefly  the 
components  of  the  mesial  fillet  and  of  the  posterior  longitudinal  fasciculus  with, 
possibly,  the  addition  of  short  association  fibres  proceeding  from  the  nerve-cells  that 
arc  found  within  the  anterior  area. 


\  \\\ 


The  details  of  a  transverse  section  passing  just  beneath  the  lower  border  of  the  i>ons  (Fig. 
931)  vary  considerably  from  those  of  the  level  shown  in  Fig.  930.  The  ventral  half  of  the 
medulla  has  lost  in  width  in  consequence  of  the  disappearance  of  the  superficial  olivary  emi- 
nence, the  inferior  olive  being  at  this  level  represented  by  only  a  few  irregular  plications.  The 
pyramids,  likewise,  are  narrower,  and  separated  by  the  broadened  anterior  median  fissure.  The 
mesial  fillet  and  the  posterior  longitudinal  fasciculus  are  now  widely  separated  by  the  inter- 
vening nucleus  centralis  inferior  that  appears  between  them  along  the  raphe.  The  nuclei  of  the 
hypoglossal  and  glosso-pharyngeal  nerves  are  no  longer  seen,  but  instead,  along  the  floor  of  the 
ventricle  underlying  the  area  acustica,  appears  a  large  triangular  mass  of  gray  matter,  the 
mesial  vestibular  nucleus.  F.xtemal  to  the  latter  the  lateral  or  Deiters'  tmcleus  and  the 
descending  or  spinal  acoustic  root  lie  close  to  the  restiform  body,  which  in  transverse  section 
presents  a  bean-shaped  outline.  Between  the  restiform  body  and  the  descending  trigpminal  mot, 
the  fibres  of  the  mesial  or  vestibular  part  of  the  auditory  nerve  pass  backward  to  gain  the  vestib- 
ular nuclei.    The  outer  surface  of  the  restiform  body  is  closely  related  to  a  considerable 


THE   PONS  VAROLII. 


1077 

Se  the  fibres  o|  the  coch.«^  f^^'^^t^rrLl^^f  th^^^rizontally  inward,  many 
nucleus  is  the  starting  pomt  of  a  ^^"[^"^^  intem^ingle  wWi  those  from  the  opposite 
traversing  the  fillet  and  "^'"^  ♦'^ 'S^^";^  TJ^pMes,  that  within  the  pons  .xcupies 
tS^-low^ffof^r  tegrinSon^hirtt  separates  from  the  ventral,    .n  F.g.  ,3« 


Fici.  93i. 


SubttBBda 
(ClaUi 


MnUl  >eHI>iutei 
nucl«u> 


Vcnml  cochlear  nuclcu* 


Corhlcu  nCTTC 

and  wnttJ  cocMmrnocWiM 

Tnpuoidal  «brt«'        / 

Pyninktel  tnct ' 

T™™v.«e  «ct.on  o,  .«.«,.  ..  .eve,  H,  Fi,  ,.  =  .^-^-SXl'  -^i"'^^.^^.''^^'^^^""''' 
root!  of  auditory  nerve  »re  enterinj  in  retotlod  10  re«lltorm  Doaiei.    a  4  h- 

only  the  beginning  of  this  .r^t  is  visible,  ^ut  =>  W  ^^he  cllcW^^^^^^^ 

trapeaiidal  fibres  are  shown  in  force.    Strands  °' fi''^™"' 'Cmld  w^vu  ■   these  mark  the 

restiform  body  and  proceed  beneath  'he  ventrjcular  fl~r  to  *^^^^^  ^^^ 

course  of  the  stria  acusHca  ««*"^"T  I-    o!wr„«  the  «»^/W  Mr /a«a/»<rri<"  appears 

1:11  '^^,':^:^LT^::^^T^^^^^^^         <^>^. '-  -^^- «- 

strands  of  root-fibres  pass  dorso-medmlly. 

THE  PONS  VAROLII. 

"•^"Vhe  ventral  surface  of  the  pons,  strongly  convex  transversely  ^fd  less  so  ^n 


1078 


HUMAN  ANATOMY. 


ridges  are  produced  by  the  underlying  pyramidal  tracts  in  their  journey  through 
the  pons  from  the  cerebral  peduncles  to  the  medulla.  The  transverse  striation 
indicates  the  general  course  of  the  superficial  fibres  towards  thf  cerebellum. 

The  lateral  surface,  continued  from  the  ventral  without  interruption,  above 
is  rounded  and  sloping  and  separated  from  the  cerebral  peduncles  by  a  distinct 
furrow.  Below,  it  passes  insensibly  into  the  middle  cerebellar  peduncle,  into  which 
the  lower  and  lateral  part  of  the  pons  is  prolonged.  Whilst  the  superficial  striation 
in  a  general  way  follows  the  contour  of  the  |x>ns,  a  broad  band  ( fasciculus  obliquuH 
pontis)  from  the  upper  part  of  the  ventral  surface  sweeps-obliquely  backward  and 
downward  and  overlies  the  more  horizontally  directed  middle  and  lower  fibres. 

The  free  portion  of  the  dorsal  surface  of  the  pons  contributes  the  upper  half 
of  the  floor  of  the  fourth  ventricle  and  is,  therefore,  not  visible  until  the  roof  of  that 
cavity  is  removed.  Above  the  middle  peduncle,  the  sides  of  th^?  pons  are  blended 
with  the  overlying  superior  cerebellar  peduncles,  which,  in  conjunction  with  the 
intervening  superior  medullary  velum,  complete  "dorsally  the  ring  of  tissue  sur- 
rounding the  narrowed  superior  end  of  the  fourth  ventricle. 

INTERNAL   STRUCTURE   OF   THE    PONS   VAROLII. 

Viewed  in  transverse  sections  the  pons  is  seen  to  include  two  clearly  defined 
areas,  the  ventral  and  the  dorsal  (Fig.  933).  The  ventral  part  (pars  basilaris) 
presents  a  characteristic  picture  in  which  the  lai^e  pyramidal  tracts  are  covered  in 


Fig.  933. 


AhliKcat  ftarm 


f^mersliic  ficUl  (ifam 
VaHbolu  Bbia 


SplDtl  root  of  V 
.01ivar>'  peduocle 


'onnatio  reticularis 
irte,£nicat'.iin 


P>Tami(tal 


ransverse  Abrcs 


Transverse  section  of  jhjiis  at  level  I.  Fijf.  919:  showing  Keneral  subdivision  into  veniral  and  dorsal  (tegmental) 
:iu-n»  and  nuclei  ol  sixth  and  seventh  nerves,     x  3. 


i  \ 
\  1 


and  excluded  from  the  surface  by  a  conspicuous  layer  of  superficial  transverse  fibres 
(stratum  supcrficlalc  pitntis),  that  laterally  sweep  backward  into  the  cerebellar  peduncle 
and  are  traversed  by  the  root-fibres  of  the  seventh  and  eighth  nerves.  The  pyra- 
mids no  longer  appear  as  compact  fields,  but  are  broken  up  into  smaller  bundles  by 
the  transverse  strands  of  ponto-cerebellar  fibres.  This  subdivision  becomes  more 
marked  at  higher  levels  of  the  |X)ns  (Fig.  936),  in  which  the  int<:  weaving  of  the 
longitudinal  and  transverse  bundles  produces  a  coarse  feltwork  (stratum  complexum  ). 
At  the  upper  border  of  the  |X)ns,  the  scattered  pyramidal  bundles  become  once  more 
collected  into  two  compact  strands,  which  are  continued  into  the  central  part  of  the 
cmsta  of  the  cerebral  pedimclc.  The  dnrs.1l  limit  of  the  ventral  field  is  occtipied 
by  a  well  marked  deeper  layer  of  transverse  fibres  (stratum  profundum  pontis).  A 
considerable  amount  of  gray  matter,  collectively  known  as  the  pontine  nucleus 


^■mPPPBIWP!" 


THE   PONS  VAROLII. 


1079 


Portion  ol  cioM-MCtion  oT  pon.,  .bowing  cells  ot  pontine 
nucleus.     .'  300- 


t^£^':^'^n^^'^'  »  -1-  Sid.  o,  ,h.  .,^u.  »ph..    Th.  ,pp«r- 
ance  of  certain  new  masses  p,G.  534, 

oJ  eray  matter  and  of  nerve- 
fibres,  together  with  change 
in  the  position  of  the  hiiei, 
produce  details  that  vary 
with  the  level  of  the  section. 
When  this  passes  above  the 
lower   margin  of   the    pons 

(Fig.    933).   two  diverging 

and  obliquely  cut  strands  of 

fibres,     coursing    from    the 

ventricular  floor  towards  the 

ventral  a.spect,  mark  the  root- 
fibres  of  the  sixth  and  seventh 

cranial  nerves  and  divide  the 

dorsal  region,  on  each  side, 

into  three  areas.  The  middle 

area,  between  the  abducent 

fibres  mesially  and  the  facial 

fibres  laterally,  contains  three 

important  coUectionsof  nerve- 
cells.    One  of  th«f- tj;^  ""-  ..       .^  ^^  the  floor  of  the  ventricle  and  beneath  the 
deus  of  the  sixth  nerve,  lies  close  to  inc  produce,  and     ives 

rounded  prominen.^  of  the  ^^^^1^^^^^^^^''' jh^lbrJ V.^..  an  oblUiuely 
origin  to  the  root-fibres  of  the  ^^"^^"V^X  and  cut  through  not  only  the  dorsal 
ventral  path,  slightly  ^^^f,  ^'oons  to  g^n  hs  lower  bord^er,  along  which  they 
but  also  the  ventral  part  of  ''^^/"^^  ."/'"in  favorable  sections  the  nucleus  of  the 

3:  i:::^::^''^r^:^^"^^^^^  ^-^  ventriCe  by  the  arching  fibres  of 
^'^^  SthTc^onspicuous  nucleus  0/ ,  the  middle  ar^.^e-^^^^^^^^^ 
oHvarlsVior).  «- --£  TuS  oT^h  foVs^u^  tra^' o'f  tlsve'rse  fibres, 
an  indentation  on  the  dorsal  ^"r'\«  "^ ^^.^ from  the  ventral  cochlear  nucleus 
known  as  the  corpus  trapezoidcs.  that  ^^f  "4;;™,"'bo"„dary  of  the  dors;il  area, 
n^edially  and  ^t^-^dly  aids  in  defining^^^^^^^  ^^^^.^^     j  „^,.^,„ 

The  superior  olive  (Hg.  933)  's  *"  '^;,  .H"'  ^-  ^.V;  ..ith  the  cerebral  cortex,  and 
interposed  in  the  path  connecting  the  auditory  nuclei  x^n  .^^  ^^  ^^^^^^.^ 

closed  related  with  the  ^^;-';^,^\^^^^^^^  others  to  the  abducent 

uting  numerous  fibres  to  the  '■'ttf;'  j^^  f^l^.  ^.  ^^rf„„^/^  of  the  superior  obve.  that 
nucleus  which  are  seen  *^,'lt'=^  ^.^"^^^t' and  bring  tbis  centre  into  relation  with 
pass  towards  the  nucleus  «V     11    til  of  ne^e-ceUs  between  the  fibres  of  the  trape- 

^S;  r''i*X-S'.tSrir»^«in;rji  These  «b,os  «e  prob^Uy 
derived  from  the  olivar>-  nucleus  (Obersteiner).  j  ^^^^^^ 

The  facial  nucleus,  a  conspicuous  but  boken  ma    .    ^.^  ^^^.  >^^^^, 

(Fig.  933).  includes  several  groups  of  J^^f  ^^  emergTng  facial  fibres.  From  the 
t\e  superior  olive  and  to  the  inner  sule  o^he  emerging^  ^^^^^  ^^^^^  ^^^ 


io8o 


HUMAN  ANATOMY. 


a  compact  strand  that,  as  the  ascending  portion  of  the  nerve,  courses  beneath  the 
eminentia  teres  seen  on  the  ventricular  floor,  close  to  the  mid-line,  until  it  bends 
outward  and,  arching  around  the  abducent  nucleus,  (..ntinues  ventrally  as  the 
emeiving  root-fibres. 

The  ventral  part  of  the  inner  area  and  the  adjoining  part  of  the  middle  one  are 
occupied  by  the  field  of  the  mesial  fillet  which,  at  the  level  under  consideration,  no 
longer  has  its  longest  axis  directed  dorso-ventrally,  but  approximately  horizontij. 
The  tract  now  appears  as  a  modified  oval,  somewhat  compressed  from  before  hack- 
ward,  the  thicker  inner  end  of  which  reaches  the  raphe  while  the  tapering  outer  end 
lies  near  the  superior  olive.  The  posterior  IcgitueHnal  fasciculus  is  seen  as  a  com- 
I>act  strand,  immediately  beneath  the  gray  matter  of  the  ventricular  floor  and  at  the 
side  of  the  raphe.     To  the  outer  side  of  the  emerging  facial  fibres,  and  therefore  in 


Fig.  935. 


McrniccpbaHc  root  el  V- 
Posterior  longitudinal  iatclculin 


Saperlcr  cerebellar  pedanclc 
Inferior  cerebellar  peduncle 

Scmory  lri(eminal  nucleni 

Middle  cerebellar  pedum 


Motor  trigeminal 
'nucleus 


^^j^;^^  Motor  fibres  of  V 

J 

'Trigeminal  nerve 

Superior  olive 

Median  fillet 

Deep  transverse  pontine  fibres 

Pyramidal  tracts 
Middle  transverse  pontine  fibres 


Transverse  section  ol  pons  at  level  J,  Fig.  919,  showing  root  of  trigeminal  nerve  with  its  nuclei. 
Preparation  by  Profctior  Spiller. 


X3- 


the  lateral  pontine  area,  appear  the  substantia  gelatinosa  and  the  associated  spinal 
root  of  the  trigeminal  ner\'e.  Just  behind  the  latter  the  descending  vestibtdar  root 
lies  close  to  the  inner  side  of  the  lestiform  body.  The  collection  of  nerve-cells 
marking  Deitirs'  nucleus  is  seen  beneath  the  ventricular  floor  in  close  relation  with 
the  descending  vestibular  root. 

Sections  passing  at  the  level  of  Fig.  935,  and,  therefore,  about  three  millimeters  above 
that  of  Fig.  933,  show  interesting  details  connected  with  the  nuclei  and  roots  of  the  trigeminal 
nerve.  At  this  level  the  nuclei  and  roots  of  the  sixth  and  seventh  nerves  are  no  longer  seen. 
The  median  filet  appears  on  each  side  as  a  compressed  oval,  the  long  axis  of  which  is  hori- 
zontal and  whose  inner  end  almost  touches  the  raphe.  Just  above  the  outer  end  of  the  fillet, 
the  cerebral  extremity  of  the  superior  olive  is  still  visible,  to  whirh  a  few  strands  of  trans\erse 
fibres— the  last  of  the  trapezoid  body— pass.  The  lateral  boundary  of  the  ventral  part  of  tlie 
pons  is  defined  by  a  hugh  tract  of  obliquely  cut  fibres  that  marks  the  entering  sensory  root  of  the 
trigeminal  nerve.  On  following  this  tract  dorsally  it  is  seen  to  enter  a  large  mass  of  gray 
matter,  the  sensory  nucleus  of  tht;  (rigeniiiial  nerve.  This  ganglion,  composed  of  closely 
packed  small  multipolar  cells,  corresponds  to  an  accumulation  of  the  substantia  gelatinosa, 
which,  it  will  be  remembered,  is  to  be  seen  in  all  the  preceding  lower  levels  intimately  related 


THE   PONS  VAROLII. 


1081 


.^•_-/  ««./  o«  the  fifth  nerve.  A  second  and  more  compact  ganglion,  the 
to  Ae  tUueuAngo,  ^P"^ ."^  Z^^^Ja^ldit  and  slightly  farther  back.  It  contains  large 
,„ctar  MUcU^ol  the  ^'^"'^J^^^J^i  ^  the  sensory  nucleus,  and  is  separated 
m„ltipotarcete.ext«djtoa«««wta^^^^^  jj^  ^  ^^  passjrHrsially 

from  the  tatter  by  a  strando^  fibr«  whKh  ^  °^  ,„  ^^e  motor  nucleus  of  the  oppo- 

^"^  'IS.^'^SI^.^^of  dTeSSs^  Stueitsof  the  motor  trigeminal  root.  A«W.tK>nal 
site  side.  These  fibres  are  part  of »«  "°™~  m^sfncet>luilu  root,  are  seen  in  the  interval  between 
components  ol  the  tatterthe  drsce»dtv  ^j,"^f3^  thTvwtricle.  The  .notor  root  itself  is 
U^^SSr-^  ^n-Sr^rous^rnd^b^ie^sLds  of  fibres  that  emerge  from  the  motor 

'^^^Z  close  to  the  inner  ^^'^.'^.^S'^Tii^r^or.  beyond  the  conventional 
Uiteral  to  the  sem»ry  nucleus  andnx^nof  the  fifUija^  >        ^^^^  cefbeltar 

limit,  of  the  pons,  the  'f^  ''^y^^^^'^^^^.^einio  which  the  corresponding 
^Sf^  J.L'^lsrdn^'^.e  ^tr'mii^.e  tract,  joinir*  the  tegmentum  to  the 


F<H*  TCMricte 


Fig.  936. 


uwih  o>ifiyix  wpote  ■•*ill"ni  ' 


Fkioc  of  f>uitk  inmkic 

Hcicaccplulk  root  uf  trifcmlaut 


rynmidal  tiftctk 


Tr.„.v««  ^.on  o.„po^^« -- r&%.-.-X^^^^^^^  ''"""'' 


border  onto  the  free  poste  ior  surface  of  the  projertrng  part  of  '•'f.  P°"*-     "T'T' „^  ^.,,1,  „, 
SL'nded  with  the  rob^  arms,  the  -{'I- ^HT*' Th^ttrt^ S^^  S  in  bf the  .-^l^."' 


io83 


HLMAN  ANATOMY. 


^lurarfD^nu  to  this  part  <)<  the  ventricle  (poKv  1097).  Mesial  to  these celb  the /oji^norAm^- 
Itulinal  fascituhu  shows,  in  transvenie  section,  as  a  triangular  field  close  to  and  on  each  side 
of  the  ra(>he. 

The  most  conspicuous  feature  01  the  dorsal  part  of  the  section  is  the  comma-shaped  fibre- 
tract  of  the  superior  cerebellar  peduncle  (brKhlnai  CMjuacUviM ).  The  thicker  part  of  the  tract 
lies  dorsally  and  its  thinner  edge  cuts  into  the  lateral  part  of  the  posterior  area  of  the  pons 
about  half  way  between  >ts  dorsal  and  ventral  boundaries.  Between  the  cerebellar  tract  and  the 
lateral  angle  of  the  ventricle,  a  slender  crescentic  strand  of  transversely  cut  fibres  marks  the 
tUicmding  motor  or  mesencepkalic  root  of  the  trigeminal  nerve.  The  tract  of  the  median  foUet 
no  longer  touches  the  raphe,  but  lies  as  a  compressed  and  horizontally  elongated  oval  along  he 
ventral  border  of  the  dorsal  field.  The  three-cornered  area  included  between  the  outer  end  of 
the  mesial  fillet,  the  cerebellar  arm  and  the  surface,  contains  a  curved  triangular  tract  that 
sweeps  backward  and  insinuates  its  pointed  dorsal  extremity  along  the  outer  side  of  the  cere- 
bellar strand.  This  tract  is  the  lateral  fillet  (Icmniacus  lauralls),  an  important  part  of  the 
pathway  by  which  auditory  impulses  are  carried  from  the  reception-nuclei  of  the  eighth  nerve 
to  the  inferior  corpora  qiadrigemina,  the  internal  geniculate  body  and  the  cerebral  cortex.  A 
collection  of  small  nerve-cells,  embedded  within  the  outer  angle  of  this  tract,  gives  rise  to  a 
number  of  its  component  fibres  and  is,  therefore,  known  as  the  nucleus  of  the  lateral  fillet 
(dikUu*  IcnniKus  lauralis).  An  additional  group,  between  the  lateral  fillet  and  the  cerebellar 
tract,  constitutes  the  nucleus  tegmenti  lateralis  (Kolliker).  The  remainder  of  the  tegmenul 
area  is  occupied  by  the  formatio  reticularis. 


THE  CEREBELLUM. 

The  cerebellum — the  "little  brain,"  in  contrast  to  the  cerebnjm  or  "^jreat 
brain" — is  placed  in  the  posterior  fossa  of  the  skull  and  beneath  the  tent-like  shelf 
of  dura,  the  tentorium,  which  separates  it  from  the  overlying  posterior  part  of  the 


Fig.  937. 


Pons 


Anteriot  ckcfscentk  lobule 


Grmt  horiiontal, 
fissure' 


Postenxaperior 
lobr 


Poslero-inferior 
lobule 


Middle  cerebellar 
peduncle 

Medulla 

Accessory  flocculu 

Flocculus 
Biventral  lobule 


P>-raRiid  Posterior  cerebellar  notch  Tuber 

Cerebellum  viewed  from  in  front  and  below;  pons  and  medulla  occupy  greater  j>art  of  vallecula  and  mask  worm. 

cerebral  hemispheres.  It  lies  behind  the  pions  and  medulla  and  the  fourth  ventricle, 
with  the  roof  of  which  space  it  is  intimately  related.  By  means  of  its  three  peduncles 
— inferior,  middle  and  superior — the  cerebellum  is  connected  with  the  medulla,  the 
pons  and  the  mid-brain  respectively. 

The  general  form  of  the  cerebellum  is  that  of  an  ellipsoid,  compressed  from 
above  downward  and  constricted,  save  on  the  dorsal  aspect,  by  a  median  groove  of 
varying  proportions.  Its  greatest  dimension  is  the  transverse  diameter,  about  10  cm. 
(4  in.  ) ;  Its  least  is  the  vertical  {j,  cm.  ),  while  in  the  sagittal  direction  the  cerebellum 
measures  about  A  cm.  in  the  mid-line  and  about  6  cm.  at  the  side.  The  cerebellum 
weighs  about  n\\.  (5  oz. )  and  constitutes  approximately  one-tenth  of  the  entire 

brain-weight 

The  conventional  division  into  a  narrow  median  part,  the  worm,  and  the  two 
lateral  expansions,  the  hemispheres,  while  convenient  for  the  description  of  the 
cerebellum  of  man,  is  not  warranted  by  recent  coiapaiative  aiul  developmental 


THE   CEV   .BELLUM. 


1083 


Ul  inese  uic  •••»«•  .w  ------  r 

rindsura  cerebelH  anterior),  which  is 
lUy  by  the  cerebellar  hemispheres 
i  occupied  by  :he  inferior  corpora 

Fig.  938. 

f  SylvUn  •quedwt 
y        SufjcnormeduUvy  v«hia 


J    cii-  ,.  Cmith   Rradle'      A)lk  and  other9\  since  some  d«^  ='•  s-^^ii 
'"SeSr'huSrinftry  '^^^^  -^  -"^^  -^- 

^M^<^  significance  -  ^M;,^^^^^  fi.sure,  in   •   .    •    or  less 

'The  surface  of  th  •  cerebellum  »  7*^ ^^''J,  ^^J^d^^^ed  by  shallow  ..efts  into 
well  defined  ar«9,  th  ^"'''•J^^?^  ^"^^^^  tSTusually  pursue  a  curved  course 
narrow  trac.-.  He>  1.  from  f  ^  ^«^'™l%i,el  to  one  a-other  and  to  the 
within  a  giver  lobu'  and.  «"  » J^^^  *^^;  ™ute4ike  folia,  or  on  makinR  a  section 
sulci  bounding  t ..  .fact.  O"  *^P^  "^  '^n^hat  the  i«ttem  of  the  folia  is  gr«uly 
across  the  plications  (Fig.  943)- "  ^'»  »f^^  ^.J^^^i.,  „„  ,he  deeper  and  hidden 
extended  by  the  presence  of  numerous^dmon^^^^^      ^  ^.^^  ^^^K^  ^^^  ^^^^^^ 

aspects  of  the  >«'^tt„*^''J  "*  ri^^nhe  cerete^^        is  everywhere  formed  by  a 
\Vhether  free  or  sunken   the  "tenor  ot    "«  cere  j^  ^  „udullary  layer 

coriicallayrroi  f'^'^f  j,-^""  ' ' '  (^^"^g  \o  this  a^^^  sagittal  sections 

"J  Th^fceSC*  e\^^'^*l'=e  jy:;e^^^   branching  tracts  of  white  and  gray 
matter,  designated  as  the  ^r^w/^  (^«•  9^^^^  comprising  the  narrow  central 

j^a^T'irp"."^  «?^  "     ■  -  - 

much  larger  than  the  postenor  » 'd  »x>unded 
and  behind  by  the  antenor  part  of  the  worm, 
quadrigemina  and  the  superior 
cerebellar  peduncles  and 
intervening  superior  medul- 
lary velum.  The  pos'c  or 
border  is  interrupted  .■  a 
Jler  median  indentui..->.i. 
the  posterior  i»otch  (inclsura 
ccrebelll  posterior),  which  is 
bounded  on  each  side  by  the 
hemispheres  and  at  the  bottom 
by  the  hind  part  of  the  worm, 
and  contains  the  crescenttc 
fold  of  dura  known  as  the  falx 

cerebelli. 

The  upper  surface  ot 

the  cerebellum  is  modelled  by 
the  overlying  tentorium  and 
presents  a  slight  median  trans- 
versely furrowed  ridge  that  cor- 
responds to  tho  upper  surface 
of  the  middle  divi>«on.  o™";^         j^,  ^^^^  ^j^^.^^^j      ^  of  this  surface  lies 

r  h^rt'srncrii^rirh-a^^^^^^^  not^..  ^^rs;^^^'^:^ 

1^-;::^;^^^^^^^^  orm":rfra^.y  towards  the  posterior 
"^he  lower  surface  of  the  ce^bdl^m  is  m^^^^^^^^ 

^s^middiir^hTwrht^^^         ^^^-  ^^^  -"^ 

of  the  valley  receives  the  dorsal  surfa,    ."l^^ie  m^uUa.  ^ 

The  cerebellum  i^i"-X^fiL'sure  S«Ss  Tor&is  «rebelli).'^ThJ  sulcus 
cleft,  the  great  honzontal    fissure   (suUm^  junction  of  two 

begins  in  ^JP^J- ^^VSVi'^^i  Jhe^^^^^^^^^^         ^^^^^^-    '^'  ^"^  "•'"""''  '?::; 
SSjio^md'the  a>c'uXen«  ofihe  cerebellu^  but  sometimes  is  intern^pted 


Telm  chorloldea- 


'Pyrminift 


«-     .  «i,llt.l  MCllon  ol  br.iiiH.teni  .nd  cerebjllum.  showiiiK  fourth 
M'   -'  '••i'^'Sltt^J.  Sylvian  aqu«luct,.n.l  cerebellar  worn.. 


io84 


HUMAN  ANi»TOMY. 


on  the  worm,  and  cuts  deeply  into  the  lateral  and  posterior  portions  of  the  hemispheres 
and  the  worm  behind.  It  is,  however,  visible  on  the  upper  aspect  <  the  cerebellum 
only  for  a  short  distance  as  it  approaches  the  posterior  notch,  the  remainder  of  its 
course  being  masked  by  the  overhanging  border  of  the  hemisphere.  Although 
of  cardinal  importance  in  the  usual  description  of  the  human  cerebellum,  the  great 
horizontal  sulcus  is  of  secondary  morphological  significance,  being  a  secondary 
fissure  that  is  developed  relatively  late  in  man  and  feebly  or  not  at  all  m  many 

other  animals.  .......  ,  w  .       u 

Both  the  vermis  and  the  hemispheres  are  subdivided  mto  tracts,  or  lobules,  by 
the  deeper  fissures  ;  these  are  grouped  into  lobes,  in  the  conventional  division  d 
the  human  cerebellum,  by  regarding  each  median  division  of  the  worm  as  associated 
with  a  pair  of  lateral  lobules,  one  for  each  hemisphere. 

Lobes  and  Fissures  of  the  Upper  Surface.— The  subdivisions  of  the 
superior  worm  are,  from  before  backward  :— (i)  the  lingula,  (2)  the  lobulus  cent  raits, 
(3)  the  culmen,  (4)  the  clivus,  and  (5)  the  folium  cacuminis.  With  the  exception 
of  the  lingula,  which  usually  is  unprovided  with  lateral  expansions,  these  median 
tracts  are  connected  respectively  with  (i)  the  alte  lobuli  centralis,  (2)  the  anterior 
crescentic  lobule,  (3)  the  posterior  crescentic  lobule,  (4)  the  posterosuperior  lobule. 

Lobus  Lingnta.— The  Ungula,  the  extreme  anterior  end  of  the  superior  worm,  is  not  free, 
but  lies  attached  to  the  upper  surface  of  the  superior  medullary  velum,  covered  by  the  over- 
hanging adjacent  part,  lobulus  centralis,  of  the  worm,  which  must  be  displaced  to  expose  the 

Fig.  939. 


Cllvui 


Great  horiionltl  Ahuk 

Ptntero-inlerior  lobule 


Tuber 


Cerebellum  viewed  from  above. 

structure  in  question.  The  lingula  consists  of  a  tongue  of  gray  matter  composed  of  five  or  six 
rudimentary  transverse  folia,  that  overlies  the  median  and  lower  part  of  the  superior  medullary 
velum  and,  therefore,  is  behind  the  upper  part  of  the  fourth  ventncle  (Fig.  938  •  Occasionally 
the  lingula  is  prolonged  laterally  by  rudimentary  folia  onto  the  superior  cerebellar  petluncles  in 
which  case  these  extensions,  known  as  the  .!>  llngul.  (vlncula  llngulae)  are  reckoned  as  the 
lateral  divisions  of  the  lobus  lingulse.  ...  j  .    *  .u 

Lobu.  Centr.liB.-The  median  part  of  the  subdivision  includes  the  second  segment  of  the 
upper  worm,  the  central  lobule  (lobalu.  centr.ll.),  that  lies  chiefly  at  the  bottom  of  the  anterior 
no  ch  and  is  visible  to  only  a  very  limited  extent  on  the  upper  surface  "f  the  cerebellum  The 
cemral  lobule  consists  of  from  15-18  folia,  but  not  infrequent  y  is  divided  into  two  sets  of  leaflets 
which  then  are  collectively  somewhat  more  numerous.  It  is  se|«rated  from  the  ingul.i  by  the 
precentral  fl.aure  and  from  the  culmen  by  the  poatcentral  fl.aure.  On  each  side  the  central 
^.lia  are  prolonged  into  a  triangular  tract  that  curves  along  the  side  of  the  anterior  notch,  form- 
ing a  lateral  wing-like  lobule,  the  ala  (ala  lobaH  centralla).  The  two  al*.  in  conjunction  with 
the  median  wom^,  seRment,  constitute  the  lobus  centralis.  .     ,    ,       ,  .  .     ,„  „^,- 

Lobut  Culminia.-The  third  division  of  the  upper  worm  includes  the  most  proimiieiu  part 
of  the  upper  surface  of  the  hemisphere  and.  being  the  crest  or  summit  of  the  general  elevaUon. 


mam 


THE  CEREBELLUM. 


1085 


.  .  11^  .1-  ^imM  (nlBca  ■oBlkuH).  It  is  formed  by  a  half  dozen  or  more 
the  monticnius.  is  ««»*»«,  "^"i"^'"*!:"'^^^  a  lunate  area  of  the  hemisphere  known 
longer «ulshorterfol«t^t.ateraUya«^n^^^^^  ^  ,^„  ;,  ^he  most 

as  the  .nteriof  cre.centic  »»»»^«J»'"  .'"C.Tem^        and  te  a  broad  crescentic  tract  hmited 

culmen  and  «ceives  *«  "7^?,f^^ifSrt  o?X  pr^liv^^  sulcus,  which  on  account  of  its  mor- 
of  the  worm  by  a  d**? ^^'^'/il'^  !*,'^^l,^^^^a  L„a  (Elliot  Smith).  Laterally  the  cl.vus  .s 
pholoRical  importance  has  been  ^J^  ^cent^Tlobule  (par.  pcWrior  loball  quadraagulari.) 
connected  ""  e»<=h  "^f  ^ f  ^^S^t ^  is^^tedXmThe  ^  behind  by  the  pctcUval 
;.*::t  "^.r-P^Ht/^^tn:").'"^^^  two  posterior  crescentic  lobules  constitute 

the  lobus  clivi.  ,        ^    .  .  .„  j  _~,t..rinr  are  retarded  by  German  anatomists 

as  J^Z.-^^,  "t'^  ^^T^^^^'^^  'o-  then  become 

(mum  v.r-UV  varies  ^J '"  ;^.  ^»!^^  iidudS^ly  only  one^r  two.  e.xceptionally 
ihe  clivus  abo...  and  the  ^^'^Z,^^ir^^L  level  of  the  adjoining  parts  of 
as  many  as  five  or  V*\^^\l°^'t.*S^^ It  oAer  times  it  is  so  sunken  and  buried  that 
the  worm,  of  which  it  fo"™  *f  P°^^"°!^„  ^S  the  div-us  and  tuber,  with  either  of 
ta  p,esen«  can  be  demo|»trated  °^'y^«  ^ "^S^ifieant  in  comparison  with  the  large 
which  it  is  occasionally  jomed.    At  best  11  o  •     »  ^he  postero-supenor  lobule 

crescentic  tracts,  the  P~t«";»»PrTL  fh^ «,;ilin^^^^^  S^ "he  upper  cerebellar  hemisphere  of 
(lobulu.  ««U»n.rl.  P~"ri»'Li!S"nd  li^^rd^  In  front  it  Separated  from  the  p<»terior 
Uichitformsthemostexpandedand  lateral  ^r«:t     in  ^        limited  by  the  great  horizontal 

S"  whlctl^v^^iCrirThe^^^^^^  cacuminis  and  the  two  postero-supenor 

lobules  constitute  the  lobus  cacummis. 

I      .=    »vn  Fissures  of  the  Lower  Surface. -The  inferior  surface  of 

received.     The  bottom  01  »"«=  *~'^y   hrain-stem  is  in   place,    s  covered  and  not 

the  inf*"^';^"™' *J;:L  JhTrd  (F^^^^^^  Aft-  «"'<'-l  °'  '"^^  ^^  ^"' 
seen,  except  at  its  po«*«"°  V„ '!r,Xl&r  oeduncles  and  the  medullary  vela,  not 
medulla  by  cutting  tht-^-J^  the  *:*J,"^  UtaSTthe  lobulus  centralis  and  its 
only  the  entire  mfenor  worm   is  "E?^-  °";^  j    separated  on  each  side 

related  parts  o  the  hemisphere  are  i«sevi  ^^.^^    ^^^^  ^^^^^ 

tZ^T^^)  th?>wX  (")  tHe  W'(3)  the  ..W.-/  Mu^e  and  (4)  the 
postero-in/erior  lobule. 

,    K...  NoduU-The  nodul.  (aodalii.).  the  most  anterior  segment  of  the  inferior  worm^ 
varies^rhi^raJ!:.^^^^^ 

'•'"^^fSlva^f  Ihe  hemisphere  a.,ocia^«i  w'^the  nod^^^he  «occu^^^^ 
distance  from  the  worm  and  "PPeat*  on  either  ''"l^.  "• ''^^  .^'^^'^"^.^'p^^^^nd  the 
group  of  short  'T"!^'- J,"»  ^^)^  w^^r^^  o^  \tta    t^u^  tU^^^   manrin 
;rr^n'^ri':;?r^nUc"Kirof'Jh'e  upper  suHace':"ln  addition  to  the  chief  Boccules. 


I086 


HUMAN  ANATOMY. 


composed  of  from  ten  to  twelve  leaflets,  a  second  and  smaller  set,  known  as  tiiepara/hccuius 
or  acceaory  fiocctUus,  lies  behind  and  lateral  to  the  main  group,  often  completely  buned  beneath 
the  overhanging  margin  of  the  biventral  lobule.  In  the  embryo  and  in  many  mammals,  the 
paraflocculus  Ls  of  considerable  size  and  then  shares  the  relatively  much  greater  development 
U  the  flocculus  than  seen  in  the  adult  human  brain.  The  connection  between  the  flocculiB 
and  the  nodule  is  established  by  the  lateral  part  of  the  mferior  medullary  velum,  which 
constitutes  the  peduncle  of  white  matter  for  the  floccular  folia.  In  this  manner  the  nodule 
and   the  two   flocculi,  with  the  intermediate  part  cA  the  medullary  velum,  coastitute  the 

lobus  noduli.  .    •         »  j 

Lobus  Uvul«.— The  uvula,  the  next  part  of  the  inferior  worm,  is  laterally  compressed 
between  the  deeper  parts  of  the  two  tonsils.  It  varies  in  form  and  often  appears  as  a  narrow 
ridge-like  structure,  triangular  on  section,  of  which  the  median  crest  alone  is  seen  when  the 
tonsils  are  in  place.  The  uvula  is  limited  in  front  by  the  poatnodular  flaaure,  and  behind  by 
the  prepyramidal.  which  late..  Uy,  as  the  post-ton.illar  fiaaure.  curves  .mtward  along  the  postero- 
lateral border  of  the  tonsil.  The  free  median  surface  of  the  uvula  i  usually  cleft  into  two  or 
three  major  subdivisions,  which  in  turn  are  scored  by  shallower  incisions,  so  that  from  six  to  ten 
leaflets  are  present.  Some  two  dozen  additional  folia  mark  the  hidden  lateral  surfaces,  the 
entire  number  being  thus  usually  raised  to  thirty  or  more.  :,....  . 

The^OT.a  or  iny^dala  (u>B.ill.),  the  segnient  of  the  hemisphere  associated  with  the  uvula 
is  a  pyramidal  mass  lying  between  the  worm  and  the  biventral  lobule  and  forming  the  central 
lone  of  the  general  quadrant  embracing  the  lower  surface  of  the  entire  hemisphere  The  free 
convex  inferior  surface  of  the  tonsil  is  irregulariy  triangular  in  outline  and  bounded  by  a  rela- 
tively straight  median  margin  (along  the  sulcus  valleculae),  an  outwardly  arched  postero-lateral 


Fio.  940. 


Lobulus  ccnttmlis 
Soprrior  cerebellar  peduncle 

Middle  cerebeltar  peduncle 

Inferior 
me<lullary  velum 

Great 
horiionul  fiuure 


PoMero-inferior. 
lobule 


Biventral  lobule' 


Ala  lobuli  cenlralil 

Superior  medullary  velum 
Fourth  ventricle 

Nodule 

Accessory  flocculus 
Flocculus 

llvula 
Pyramid 


Posterior  notch 


Tonsil 


inferior  aspect  of  cerebellum,  after  removal  of  pons  and  medulla. 

border  (along  the  curved  |)osttonsillar  fissure)  and  a  notched  anterior  edge.  This,  the  chief 
Miriace  is  marked  bv  a  straight  furrow  that  extends  from  the  indentation  on  the  anterior  border 
^ck^^ird  and  intanl  and  m'arks  a  line  along  which  the  curved  'f  »J;;"-J°J°"rS  t 
number,  abut.  Oi  the  other  surfaces  bearing  folia-the  median,  posterior  and  "af^^  »™ 
IS  towards  the  uvnila  (median)  alone  Is  entirely  unattached,  the  ?»he.%w.th  the  superior 
receiving  the  stalk  of  white  matter.  The  deeper  part  of  the  tonsi  is  ""^mded  so  t^t  on 
removing  the  larger  and  more  superficial  portion  of  the  amygdala  a  buried  and  accessory 
^gment'onts  ^s  often  remain^:.  BeneMh  (really  above>  the  J-f^vula^'^oT,  the"?:::^ 
marked  with  short  transverse  folia,  stretches  from  the  posterior  part  "' '•'^^  "^"i-*  .«"%'^^™ 
of  the  space  occupied  by  the  tonsil  to  the  upper  and  lateral  part  of  the  ""^^^^X  J ^'d  thus 
known  as  the  funowd  band  (.!«.  uvula.)  connects  the  worm  w«h  »'r'^n"^P^7^e,  of  the 
joins  the   uvula   and   the  two  tonsils   into  the  lobus   uvul;.       The   p<»terior  ho™"  °V|!l 

urowed  band  is  free,  whilst  its  anterior  one  is  continuous  wi.h  the  'f  ri°^.  J"^''^';'^^^  "^'^^ 
After  removal  of  the  tonsil  by  cutting  through    ts  ""If^-'^'f/"', ^'^'^,V »  '^^uf,,eTnd  4ofed 

which  is  bounded  medially  by  the  tn-ula  and  laterally  by  ♦he  hwentral  lobu^  and  r^^^^ 
in  bv  the  furrowed  band  and  the  inferior  velum.    To  this  space  the  older  anatomists  gave  the 

"'"\2i'i^.m\di.* -The'^mld  (pyraml.)  the  segment  of  the  inferior  worm  lying  behind 
the  uvula  and^:tont  IVZ.r,  is  '.Lrtly  covered  by  the  tonsils.     Posterior  .0  the  latter 


THE   CEREBELLUM. 


1087 


H  is  seen  .t  the  botto.  o.  the  .va..-|a  ^^w^-^e  n^'^  f  ^^^^^^^ 
where  it  forms  the  most  P'"™"™*  ^'!^J?  ^m  uTadiaLnt  parts  of  the  worm  by  the 
mass,  attached  by  a  narrow  stalk  and  «=P":"f*^"Jfl,^S,er«rby  the  sulci  vallecula:, 
pc-j^unidal  and  po.tpyr.mid.1  ft..ur..  ami  horn  the  »^P"^™  jj^  ^^ose  towards  the 
?te^vex  inferior  surface  usually  P«T  „rf^The' toter  S  .emoval  of  the  tonsil,  a 
uvula  being  longer  *an. 'ho«e  d'r^»^„^ov^^„*;,/:L^h  sid^^^^^ 
^rm^drAr^nt-riafflo? rbi^::!'.obe.  which,  in  this  manner,  is  b«,ught  into 

divisions  which  to«^herappea^  the  -^^f^f  ^^J-;:^ ^readU,  of  .5  mm.  and  more.    The 
more  contracted  than  *«  .'"J'="2~X  variable   the  lobule  being  not  only  sometimes  much 

arched  po.tpyn^.d^fl«.ur.^  j„^  ^  „^t         terior  division  of   the 

•  .    -^   „J^d  lies  tenSSTthe  greP.t  horizontal  fissure  when  that  sulcus  is  continuous 
^r t:e^id^;le'3n  tj^^^^^^^^ 
Tnt^^S  Sllprin^n*  S^m'T^Lmlltll;:  ol' white  matter.    The  tuber  is  of  a  genera. 


Fig.  941. 


Root  irf  fourth  ventricle 
Superior  cerebellar  peduncle 
Middle  cerebeltar  peduncle. 
Floccului 


Great 
taoriiontal  fissuie' 


Superior  worm 
(lobulus  centralli) 


PoBtero-inferlor 
lobule' 


Biventral  lobule' 
Position  of  removed  tonsil 


Inferior  metlulUiry  velum 
I'vula 
Furrowed  band 

Pyramid 


Tuber 


Cerebellum,  aeen  from  below  after  removal  of  tontlli. 

conical  form,  with  the  base  di,*cted  towards  the  PV™-'^' ';?'"  ^J^^^^J^iil/^J^^t'^lfpr^^^^^^^^ 
postpyramidal  fissure,  and  its  apex  projec.inif  into  the  Pp^t^""' "X'^^,  viewed  from" 
kfew.  from  1-4,  superficial  folia,  which  model  the  posterior  pole  of  the  worm,  as  viewea 

'"""^TlutrTs  directly  connected  on  each  side  with  r.  .considerable  c-^^^-^^^-f  •J,''^ 
po.t.ro.inf.rior  lobule  (lobalu.  «m«anari.  Inferior),  that  is  «'"'t^  '"'"'"*  ^^  *J^,hori- 
nJension  of  the  postpyramidal  fissure  '  "'«V'"'*''»^"";*»'>  »"^^^;"^5,;*'*ex^nd 
zontel  fissure.  After  emerging  from  the  sulcus  vallecula,  the  '""» .."P'°r,,!r'  hnrder 
a  "unate  tract,  from  ,5-.5  n^- in  it''  widest  part,  that  forms  the  '•:rf'"'^P^'^Tnt^tv^o 
of  the  hemisphere.  The  postero-inferior  lobule  is  usually  described  /«  f'^'*^'!  "J"  '^..'J 
parts,  an  anterior  and  a  posterior,  by  the  po.tgraci  1.  ft..ur.  '•"'«« '"'''"'PXr'^;^,^ 
quite  frequently  further  subdivision  of  the  superficial  folm.  [O"/^-^.'"  ™'"^*^'„'^^ " 
I  defining  three  sublobules.  The  anterior  of  the  two  conventional  ""W^^^*  '^e  E 
tract  of  fairiy  uniform  width  to  which  the  name  /oht/u'  zrart/is  is  applied.  The  'unaw 
*;:^teri;r  aS  much  less  regular  in  contour  and  foliation.  ,"<""- »*"„/tXisbnin'^ 
Mule  (lobulu.  «mllun.ri.  Inferior)  and  sometimes  pres,...s  evidence  "«  ^^'^te  the 
two  secondary  crescentic  areas.  The  postero-mft-nor  lobules  and  the  tuber  constitute 
lobus  tuberis. 


io88 


HUMAN   ANATOMY. 


In  recapitulation,  the  foregoing  cerebellar  lobes,  with  their  component  worm-segments  and 
associated  hemisphere-tracts,  and  the  intervening  fissures  may  be  followed  in  order,  fro>"  the 
anterior  and  superior  end  of  the  worm  to  its  front  and  lower  pole.  Although  not  agreeing 
with  a  morphological  division,  such  grouping'  is  convenient  as  applied  to  the  adult  human 
cerebellum. 


The  Lobes  of  the  Cerebellum. 

WORM  hemisphere 

Lingula  (Vinculum  lingulx) 
SiJcMs  precentralis 


Lobulus  centralis  Ala  lobuli  centralis 

-  Sulcus  postcentraKs 

Culmen  monticuli  Lobulus  lunatus  anterior 

— Sulcus  preclivalis 

Clivus  monticuli  Lobulus  lunatus  posterior 

Sulcus  poslcKvalis 

Folium  cacuminLs  Lobulus  postero-superior 

Sulcus  horizoutalis 

Tuber  vermis  Lobulus  postero-inferior 

Sulcus  postpyramideUis 

Pyramidis  Lobulus  biventer 

Sulcus  prepyratnidiUis- 


Uvula 


Tonsilla 


Sulcus  postnodularis 


Nodulus 


Flocculus 


LOME 
Lobua  lingulje 

Lobua  centrali* 

Lobua  culminia 

Lobua  cUvi 

Lobua  eacuminla 

Lobua  tubcris 

Lobua  pjpramidis 

Lobua  uvuls 

Lobua  noduli 


Architecture  of  the  Cerebellum.— With  the  exception  of  where  the  robust 
peduncular  collections  of  nerve-fibres  enter  the  hemispheres  and  immediately  above 
the  dorsal  recess  of  the  fourth  ventricle,  the  cerebellum  is  everywhere  covered  by  a 
continuous  superficial  sheet  of  cortical  gray  matter  which  foUows  and  encloses  the  sub- 
divisions of  the  white  core.  The  latter,  as  exposed  in  sagittal  sections  of  the  hemi- 
sphere is  seen  to  be  a  compact  central  mass  of  white  matter,  from  which  stout  stems 
radiate  into  the  various  lobules.  From  these,  the  primary  stems,  secondary  branches 
penetrate  the  subdivisions  of  the  lobules,  and  from  the  sides  of  these,  in  turn,  smaller 
tracts  of  white  matter,  the  tertiary  branches,  enter  the  individual  folia.  Over  these 
ramifications  of  the  white  core,  the  cortical  gray  matter  stretches  as  a  fairlv  uniform 
layer  about  1.5  mm.  thick,  that  follows  the  complexity  of  the  folia  and  fissures. 
The  resulting  arborization  and  the  contrast  between  the  white  and  gray  matter  are 
particularly  well  shown  in  sections  passing  at  right  angles  to  the  general  direction  of 
thfe  folia  This  disposition  is  especially  evident  in  median  s^ttal  sections  (Hg.  938). 
where  the  less  bulky  medullary  substance  of  the  worm,  also  known  as  the  fjwjftwj 
trapezoideum,  and  ite  radiating  branches  produce  a  striking  picture,  to  which  the 

name,  arbor  vita  cerebelli,  is  applied.  .  j      vu  tk«  ^„,*;.,oi 

The  Internal  Nuclei.-In  addition  to  and  unconnected  with  the  cortical 
layer  four  paired  masses  of  gray  matter,  the  intemal  nuclei-one  of  considerable 
size  and  three  small— lie  embedded  within  the  white  matter. 

The  d^tate  nucleus  (nucleus  dentatns).  or  corpus  denialum,  the  largest  and 
most  important  of  the  internal  nuclei,  consists  of  a  plicated  sac  of  gn.y  m^XXtr 
7^1  9S0  and  resembles  in  many  respects  the  inferior  ohvarv  ""^l""'-.  Jj*5j'^ 
lattfr,  it  is  a  crumpled  thin  lamina  of  gray  matter  which  is  folded  on  '^«  «nto  a 
^uch,  enclosing  w&te  matter,  through  whose  media  ly  d'"^^.  """^uncr  The 
Tilum  emerge  many  fibre-constituents  of  the  superior  cerebellar  ?«!""<:'«•  The 
deSenuckus  never  encroaches  upon  the  core  of  the  worm,  but  lies  embedded 
Shin  the  anterior  part  ol  the  median  half  of  the  hemisphere,  with  its  long  axis 

'  Modified  from  SchSfer  and  Thane  in  Quain's  Anatomy,  Tenth  Edition. 


THE  CEREBELLUM. 


1089 

^ed  forward  and  somewhat  inw^  ajjd  .herdore  'Jj^f^V^Sie^"^";^^^^^^^^^ 
plane.     Anteriorly  the  nucleus  r«ch«  the   evel^«  a  'J^-^yke  of\he  hemuphere 

measures  from  15-2?  "J"!" ',  "^l/^^w^     oTSaymatter-the  nucleus  fastigii.  the 

Of  the  other  paired  internal  coUecUo   >  °*  8"^  """^.y.  fa,ti«i,  or  the  roof 

nucleus  emboUformis  and  the  "-^^thb^l^o':  ^h^woS:.'^n^^^^^  part 

nucleui.  IS  the  best  defined.     " 'r^^'^'u^^^id.iine  and  to  its  fellow  of  the  oppo- 


Fio.  943- 


Superior  worm 


Nncteos  futisii 
Nnclciii  floboiu* 


Nnclcui 
anbolUormi* 


Rotiform  body 
(cxtemat  diviiion) 

Noclcui  denUti 


Keitllormbody^ 
<intenwl  diviilon)  . 


Ventral 
cochlMr  nuclcttx 


DecuMatloB  ct 
roof-OBClei 


Fouhh  ventricle 


Vestibular  nerve 

Inferior  olivary  nucleus 


^  Poaterfc»rlontlludiii..l  tasciculna 
Pyismidal  tracts 


*'  °-?rnucieus  emboliformis.  or  embolus,  is  an  irregular  wedge-slmped  plate 
connS;Jd'Shl"^»«X'  Si.he  .™bc.-,  «d  ^»  join,  .he  po«r„.n*-« 


logo 


HUMAN  ANATOMY. 


Molccnkr  Imyer 
Gnuiule  layer 

White  maucr 
elliol  Purkinlc 


part  of  the  dentate  nucleus.  Since  the  latter  and  the  embolus  are  likewise  slightly 
connected,  it  is  evident  that  all  four  internal  nuclei  are  more  or  less  continuotu 
masses  of  gray  matter. 

In  structure  the  internal  nuclei  differ  markedly  from  the  cerebellar  cortex, 
since  in  the  main  they  are  composed  of  irregularly  disposed  nerve-cells  of  one  kind 
intersjiersed  with  numerous  nerve-fibres.  The  dentate  nucleus  contains  cells  from 
.020-.030  mm.  in  diameter  whose  bodies  are  angular  or  stellate  in  outline  and  pig- 
mented in  varying  degrees.  Their  processes  are  usually  so  disposed  that  the  axones 
bass  into  the  medullary  substance  enclosed  by  the  plicated  lamina  and  the  dendrites 
mto  the  surrounding  white  matter  of  the  hemisphere.  Numerous  fibres  enter  the 
dentate  body  from  without,  many  being  the  axones  of  the  Purkinje  cells,  and  break 
up  into  a  rich  plexus  within  the  folded  sheet  of  gray  substance.  Since  the  nucleus 
embolifonnis  and  the  nucleus  globosus  are  only  incompletely  isolated  parts  of 
the  dentate  nucleus,  their  structure  corresponds  closely  with  that  of  the  chief  mass. 

The  roof-nuclei,  on  the 
Fig.  943.  contrary,  possess  cells  of 

much  larger  size  (.040  to 
.080  mm.),  more  rounded 
form  and  greater  uniform- 
ity in  tint,  although  their 
general  yellowish  brown 
color  implies  less  intense 
pigmentation.  Numerous 
strands  of  nerve-fibres  sub- 
divide the  nucleus  into 
secondary  areas,  while 
some  large  transversely 
coursing  bundles  establish 
a  decussation  with  the  roof- 
nucleus  of  the  opposite 
side. 

The  Cerebellar 
Cortex.— When  the  folia 
are  sectioned  at  right 
angles  to  their  course,  each 
leaflet  composing  the 
characteristic  arborization 
is  seen  to  consist  of  a  cen- 
tral tract  of  white  medul- 
lary substance,  covered  in 
by  the  continuous  super- 
ficial sheet  of  cortical  gray 
matter.  The  latter,  usually  somewhat  less  than  one  millimeter  in  thickness,  includes 
two  very  evident  strata — the  outer  and  lighter  molecular  layer  and  the  inner  and 
darker  granule  layer. 

The  molecular  layer  is  of  uniform  thickness,  about  4  mm. ,  and  contains  thrt^ 
varieties  of  nerve-cells — the  Purkinje  cells,  the  basket  cells  and  the  small  cortical 
cells.  The  Purkinje  cells,  the  most  distinctive  nervous  elements  of  the  cerebellum, 
occupy  the  deepest  part  of  the  molecular  layer,  where  they  are  disposed  in  a  single 
row  along  the  outer  boundary  of  the  subjacent  granular  layer.  The  cells  are  most 
num  ')us  and  more  closely  placed  upon  the  summit  of  the  folium  and  fewer  and 
m<  >  attered  along  the  fissures,  in  which  situation  they  are  also  often  of  less  typical 
pyi  iorm  shape.  They  possess  a  large  flask -like  body,  about  .060  mm.  in  diameter, 
from  the  pointed  and  outwardly  directed  end  of  which  usually  one,  sometimes  more, 
robust  dendritic  process  arises.  The  chief  process,  relatively  thick  and  very  short, 
soon  divides  into  two  branches,  which  at  first  diverge  and  run  more  or  less  horizontally 
and  then  turn  sharply  outward  to  assume  a  course  vertical  to  the  suriac^  and  undergo 
repeated  subdivision.  The  arrangement  of  the  larger  dendrite'  is  very  striking  and 
recalls  the  branching  of  the  antlers  of  a  deer.     The  smaller  prot    .ses  arise  at  varying 


Central  limb 
of  white  matter 

Transverse  section  of  cerebellar  folium,  showing  relations  of  cortex  to 
underlying  white  matter.    X  lo. 


THE   CEREBELLUM. 


1091 


""  Ota,  -» »^». .!» rrsi;£~T„,'s£i^h„'s':Jdnx';Lls 

mpregnations  (Fig.  944).  "»  ^  Ivlfu^"  f  .k^  molecular  layer.  The  dendritic 
olt^nTeaches  almost  '«  the  ouj^r^ boundan^  t  a  nr^zSieTxYending  acrc«s  the 
ramification  of  each  cell  is  ^  '^"f°'.^^^^„'  „,.  _._,..i  ^th  the  plane  of  the  folium, 
folium  and,  hence,  when  ^''f -"^f '"  ^°"' ^  ^^^^^  of  the  molecular 

these  expansions  are  found  to  »^.  "'"^"^J-  ° ''^f^h^PSdnje^ells.  The  axones  of 
layer  that  are  unmvaded  by  'j^**^"^  "f -1^^^^^^  bo<lv  and  at 

feature  of  interest  is  the 

remarkable      relation     of  »''0-  944-  ^ 

the  axone,  which  extends 

across  the   folium  in  an 

approximately   horizontal 

plane  along  and   to  the 

outer  side  of  the  row  of 

the  Purkinje  cells.   During 

this  course  the  axone  gives 

off    from    three    to    six 

collaterals    that    descend 

to  the  cells  of   Purkinje, 

whose   bodies    they   sur- 
round and  enclose  with  a 

basket -like   arborization, 

the  terminal   ramification 

of  the  main  process  itself 

ending    in   like   manner. 

By  means  of  this  arrange- 
ment each  basket  cell  is 

brought  into  close  relation 

with  several  of  the  larger 

elements. 

in  which  they  appear  as  diminutive  multipolar  elements  wim  rauw     » 

axones  of  uncertain  destination.  ,  ^      jy  colored  in 

U^t  clearly  distinguished  from  the  medullary  substance.     The  8Tanu«r  '^X" 
SL'^^o'v'a^'of  nerve-cells-the  g^^^^^^^ 

The  eranule  cells  are  very  small  (.007-.010  mm.)  ana  numciu  nrovided 

packed  that  they  confer  upon  the  stratum  its  dist.nct.ye  d^^^'^^^/^^^  ^'^jPrcSw- 
S^th  fmm  three  to  six  sho^  radiating  dendnt.c  Processes  that  end  '«  P^^^^^^^I^^^Ji, 
like  arborizations  in  relation  w.th  other  g™n«>e  cdls.  J;ei^^°",^^,S'c^„esponding 
the  surface,  enter  the  molecular  layer,  *'»»?'"  ^^ich,  at  ™^  ^^^^ni      branch^ 

""  T^  iS!L°M.ll.t.  cell,  are  pr=...  in  v;»vinn  number,  b«t  are  "ever  numer- 


*.'-f.5ffWRK^x'="«:^>SS»'^"''°-* 


I093 


HUMAN  ANATOMY. 


several  richly  branched  dendrites  pass  in  various  directions,  but  Uu^dy  uito  the 
molecular  layer.     The  axone  is  most  distinctive,  as  very  soon  after  leavmg  the  ceU  it 
splits  up  into  an  arborization  of  unusual  extent  and  complexity,  which,  however,  is 
wnfined  to  the  granular  layer.     These  cells,  therefore,  belong  to  those  of  type  II 
(page  998).     Since  by  their  processes  they  are  brought  into  mOmate  relation  with 
ai^mber  of  other  neurones,  the  elements  under  consideration  are  probably  of  the 
nature  of  association  cells.  .....  ,   „  ,t-  ^ 

The  nerve-fibres  encountered  within  the  cerebellar  cortex  (Fig.  945)  comprise 
three  chief  varieties.  ( i )  The  first  of  these  includes  the  axones  of  the  cells  of  Purkinje 
which  contribute  no  inconsiderable  portion  of  the  fibres  passing  from  the  cerebellar 
cortex  to  other  parts,  either  of  the  cerebellum  itself  or  of  the  cerebrum  and  brain-stem. 
(2)  The  moss-fibres  destined  especially  for  the  granular  layer,  which  upon  enter- 

Fio.  945- 


Molecular  layer 


Giaanlc  layer 


White  matter 


Moaa-Abrc* 


Asonea  of  Purkinje  celb 


.Oimbing  fibrea 


Diaatammatlc  r«on.tniclion  of  p„.t  J  fol.um.  illustnwinit  relatiom  of  nerve^ells  and  «btCT  of  cer^lmr  cor^ 
ttx ;  fS?^  iTKhowTcut  transversely  and  longitudinally  j  a,  Purkinie  cella ;  ».  gnnule  .ell. ;  <r,  .nu.ll  cortical  cell. ; 
d,  basket  cells ;  r,  large  Mellate  cells. 

ing  the  latter  break  up  into  a  number  of  branches  that  bear,  either  at  the  points  of 
division  or  at  their  ends,  thickenings  from  which  bundles  of  short  diverging  twigs  are 
given  of!  By  this  arrangement  each  moss-fibre  ends  in  relation  with  a  large  number 
Zl  granule  cells.  (3)  The  climbing-fibres,  so  named  (Cajal)  on  ace  nt  of  their 
tortuous  and  vine-like  course,  ascend  through  the  granular  to  the  mokcular  layer, 
to  which  they  are  chiefly  if  not  exclusively  distributed,  where  they  entwine  and 
cling  to  the  primary  and  secondary  dendritic  processes  of  the  Purkinje  cells. 
Additional  fibres  encountered  within  the  granule  layer  are,  evidently,  the  axones  ol 
the  granule  cells  and  the  collaterals  of  the  cells  of  Purkinje,  whilst  a  large  propor- 
tion of  the  fibres  within  the  molecular  layer  are  formed  by  the  ramifications  of  the 
axones  of  the  granule  cells  and  of  the  basket  cells.  ,      . ,      .      •      u    u 

The  neuroglia  forms  a  supporting  framework  of  considerable  density  both 
within  the  white  matter  and  the  cortex.  As  seen  in  preparations  colored  with  the 
usual  nuclear  stains,  the  neurogliar  elements  are  conspicuous  within  the  granule 
layer,  to  whose  numerous  small  nuclei  they  contribute  no  small  part.  The  cells 
occupying  the  outer  zone  of  the  granule  layer  exhibit  a  peculiar  arrangement  of  their 
processes  that  in  a  measure  recalls  the  disposition  of  those  of  the  Purkinje  cells.     In 


THE  CEREBELLUM. 


1093 


vertical  striation  that  is  often  marked. 

same  hemisphere.  ,  ,.     j^  j^j  „!  ti,e  dentate  nucelus  and  the 

a.  The  commissural  tracts,  of  which  *e>«^  ^d^taeand  into  the  opposite  hemisphere 
Mialler  behind  this  nucleus,  are  conunued  ac««the  ™^^^S«issation» 

cro;"r^i-"'«^crehyX?e^^c= 

*^  T^  1:/JZ'7::^^^^^mTJ^^P^  beWnd  the  roof-nucleus  and  consists  of  a 
from  that  of  the  cerebellar  ~™™''*"^"„'"?^,f^'^„„dfetaHy  Girting  its  dorsal  margin 

„ucle;^s;i:?::3^re^tr^^c^^wo::;;rat!;e^^t^^  fres  are  continued  upward  through  the 
velar  frenum  and  into  the  infenor  ^-f  ge",^  col^-^        ^^^^  ^  ^  medullary  tree^ 

In  addition  to  the  foregomg  tracts  tne  "J"™J"  ,.  ^v  longitudinally  coursing  fibres 

not  only  of  the  hemispheres  but  dso  o^«^  *^™;^"',SS  imo  thf  «rebelL  peduncles  as 
r  a&1'SK^nna^l:i  wThicirfhl^'S^^^^^^  is  brought  into  relation  with  o-her 

parts  of  the  brain  and  spinal  cord. 

Fibre-Tracts  of  the  Cerebellar  Peduncles. 

Repeat^i  mention  has  been  made  of  the^rtjre.  robust  a-^J^^Jtite^---. 

wl  te'clSurto  coSer  more  in  detail  the  constituents  of  these  important 

•^^^he  Inferior  Cerebellar  Pedunde.-This  robust  stalk  (corpus  restiforme), 
,     7      n«  the  restiform  body,  includes  not  only  the  tracts  connecting  the  cere- 
Suum'wTh  th?i  n^  Srbm  ^^^  that  link  (he  cerebellum  and  the  medulla. 

Two  diSns  the  spinal  and  the  M6ar,  are  therefore  often  recognized. 

The  chirf  constituents  of  the  inferior  Muncte^«  :  ^^  ^^^^  ^^  ^,^^^^,^  ^^,^„„ 


1094 


HUMAN  ANATOMY. 


3.  The  olhro-c«rab«llar  Abraa,  chiefly  from  the  opposite  inferior  olivary  nucleus  but  to  a 
limited  extent  also  from  the  nucleus  of  the  same  side.  They  contribute  in  large  measure  to  the 
iormation  of  the  lateral  part  of  the  restiform  body  and,  on  reaching  the  cerebellum,  end  within 
the  cortex  of  the  hemisphere  and  worm,  as  well  as  within  the  fibre-complex  enveloping  the 
nucleus  dentatus.  Whilst  for  the  most  part  afferent,  it  is  probable  that  some  of  the  fibres  within 
the  tract  are  efferent  and  hence  conduct  impulses  m  the  contrary  direction. 

4.  Fibm  Itom  the  nucleus  latcnlis  of  the  medulla,  which  pass  to  the  cortex  of  the  cere- 
bellar hemisphere. 

5.  Pibraa  ftom  the  atenata  nudaus,  which  pass  to  the  cerebellar  cortex. 

6.  The  noclso-cerabaUar  tract,  comprising  fibres  from  the  cells  within  the  reception-nuclei 
of  the  trigeminal,  facial,  vestibular,  gtosso-pharyngeal  and  vagus  nerves.  The  tract  occupies 
the  median  part  of  the  peduncle  and  ends  chiefly  in  the  roof-nucletis  of  the  same  and  of  the 
opposite  side. 

7.  Other  fibres  pass  in  reversed  direction  from  the  roof-nucleus  to  the  dorso-laterai 
(Deiters' )  vestibular  nucleus  of  the  auditory  nerve  and  thence,  as  the  veslibalo-apiaal  tract, 
descend  through  the  medulla  into  the  antero-lateral  column  of  the  cord. 

8.  Additional  vestibular  (and,  possibly,  other  sensory)  fibres  pass  without  interruption  by 
way  of  the  restiform  body  to  the  roof-nuclei  and  constitute  the  direct  scasotjr  caieballar  tract 
of  Edinger. 

The  Middle  Cerebellar  Peduncle.— The  middle  peduncle  (brachinm  pontia), 
which  continues  the  pons  laterally  into  the  medulla  of  the  cerebellum,  transmits  the 
fibres  whereby  the  impulses  arising  within  the  cerebral  cortex  are  conveyed  to  the 
cerebellum.  It  does  not  esUblish  direct  connections  between  the  cerebellar  hemi- 
spheres, as  it  might  be  supposed  to  do  from  its  transverse  position  and  intimate 
relation  with  the  cerebellar  hemisphere,  such  bonds  from  side  to  side  passing 
exclusively  by  way  of  the  commissures  within  the  worm. 

The  chief  constituents  of  the  middle  peduncle  are  : 

I.  The  continuations  of  the  fronto-cerebeUar  and  tcmpoto-occipito-eerebeUar  tracu,  the 
fibres  of  which  arise  from  the  cortical  cells  within  the  frontal,  temporal  and  occipital  lobes 
respectively,  descend  through  the  internal  capsule  and  the  cerebral  crus,  and  end  around  the 
cells  of  the  pontine  nucleus.  From  the  latter  cells  arise  the  ponto-ccrcbeUar  fibres,  the  imme- 
diate constituents  of  the  middle  peduncle,  that  for  the  most  part  cross  the  mid  line  and  traverse 
the  peduncle  to  be  distributed  to  all  parte  of  the  cortex  of  the  hemispheres  and  of  the  worm  and, 
possibly,  also  to  the  nucleus  dentetus.  A  small  number  of  these  fibres  do  not  decussate,  but 
pass  from  the  pontine  cells  to  the  cerebellar  cortex  of  the  same  side.  It  should  be  remembered 
that  the  pontine  nuclei  are  also  influenced  by  cortical  impulses  that  descend  by  way  of  the  pyra- 
midal tracts,  since  numerous  collaterals  from  the  component  fibres  of  these  motor  paths  end 

around  the  pontine  cells.  _     .       „  ,.        l      ,.  •    , 

2  Efferent  cetebcllo-pontine  fibrea,  distinguished  frdfh  the  afferent  fibres  by  their  larger 
diameter,  originate  as  axones  of  the  Purkinje  cells  and  pass  from  the  cerebellar  cortex 
through  the  middle  peduncle  into  the  dorsal  part  of  the  pons,  where,  after  crossmg  the  mid-lme, 
they  are  believed  (Bechterew)  to  end  within  the  tegmentum  in  relation  with  the  cells  of  the 
nucleus  tegmenti  situated  close  to  the  raphe.  The  assumption,  often  made,  that  many  of  the 
efferent  cerebello-pontine  fibres  end  around  the  cells  of  the  nucleus  pontis,  lacks  the  support  of 

the  more  recent  observations. 

• 

The  Superior  Cerebellar  Peduncle.— The  superior  peduncle  (brachinm  con- 
jonctlvum)  forms,  with  its  fellow  of  the  opposite  side,  the  important  pathway  by  which 
the  cerebellar  impulses  are  transmitted  to  the  higher  centres  and,  eventually,  to 
the  cerebral  cortex,  as  well  as  indirectly  to  the  spinal  cord. 

Its  chief  constituents  are  (i)  the  cerebello-rubral  and  (2)  the  cetebello-thalamfc  fibres 
collectively  known  as  the  cerebello-tegmental  tract.  The  principal  components  of  the  latter  are 
the  fibres  arising  from  the  cells  of  the  dentate  nucleus,  which,  emendnK  *">"»  the  hilum  of  the 
corpus  dentatum  and  receiving  augmentations  from  the  roof-nucleus  and,  probably,  to  a  limited 
extent  from  the  cortex  of  the  worm,  become  consolidated  into  the  rounded  arm  that  skirts  the 
supero-lateral  boundary  of  the  fourth  ventricle.  Converging  with  the  tract  of  the  opposite  side 
towards  the  mid-line,  the  peduncle  sinks  ventr.illy  and  disappears  beneath  the  corpora  quadn- 
gemina  many  of  ite  fibres  continuing  their  course  through  the  t««mentum  of  the  cerebral  peduncle 
into  the  subthalamic  region  and  the  thalamus.  On  reaching  a  level  corresponding  to  that  of 
the  upper  third  of  the  inferior  colliculi  of  the  quadrigemina  bodies,  the  tracte  of  the  two  side! 
meet  and  begin  to  intermingle,  the  decussation  of  die  superior  peduncle  (Fig.  1 112)  thus  estab- 


THE  CEREBELLUM. 


t095 


IS^Ution  to  the  ««>»  o'.r.'''*  *^'n^teTthe  m.Jority  tnmsfcr  their  impulses  to  fibjr»  that 

temipted   fibre*.    From   the 

thatamus   the    impukes   are  H°-  94° 

carried  by  the  thalamo<or«cal 

natte  (page  n»a)  to  the  cere- 

Sr«lco{tex.thecelbo.whidi 

m  thus   influencea  by  the 
coordinating  reflexes  ol  the 

cerebeUum.  ^ 

A  considerBWe  part  tH 
the  impubes  conveyed  to  the 
fed  nucleus  is  diverted  by  the 
axones  o<  some  of  its  neuroijM 
into  an  entirely  different  path. 
Mmely.the  ™bro..pto«l»iCt. 
by  which  the  impulses  from 
the  cerebeUum  are  earned 
through  the  brain-steni  ana 
antero-lateral  column  ol  the 
cord  to  the  anterior  root-cells 
of  the  spinal  nerves. 

From  the  foregoing 
descriptions  it  is  evident  tlwt 
by  means  of  its  peduncles  the 
cerebellum  receives  no  small 
part  of  the  sensory  impulses 
collected  by  the  spinal   and 
cranial  nerves  and,  in  turn, 
issues  the  impulses  necessary 
to  maintain  coordination  and 
equilibrium.    Such    impulses 
may  be  entirely  reflex,  as  in 
the  case  of  movements  per- 
formed automatically,  in  which 
instance    the    circuit   is    (a) 
from  the  spinal  cord  and  the 
medulla,  cUrectiy  or  indirectly, 
to  the  cerebellum  chiefly  by 
way  of  the  tracts  within  the 
inferior  cerebellar  peduncles ; 
(«)  from  the  cerebellum  to  the 
motor   root-cells   within   the 
brain-stem  and  the  cord  by 
way  of  the  cerebello-vestibulo- 
spinal  tract  and  the  cerebello- 
rubro-spinal  tract. 

When  the  necessity 
arises  for  volunttry  efforts 
in  maintaining  equilibrium, 
the  circuit  includes  impulses 
from  the  cerebral  cortex,  in 
which  case  the  cerebello- 
rubro-thalamo-cortical  tract 

and  the  cortico-spinal  tract  form  the  most  direct  path 
;-,™,i««  hv  wav  of  the  cortico-ponto<erebellar  and  i 


NuclwxCTebellar    / 

OUv€>-cer«bell»r 

Posterior  nuclei 

"^     ro-»pin«l  tract 


,  VestibuUir 
From  n.  lateralis 
Ant.  superf.  arcuate 
Post,  auperf.  arcuate 
Direct  cerebellar 


Diagram  lllut^tlna  ^h.d  «mp«,^-.  °' «'S!rXr^^'u"c«e?sn 
paMmgl>y  inferior  Peduncle  ( IP^  f«,  ■  ;,.  i,*?!  bUcV ;  C,  cerebrum :  T. 
SlTblSe:   thoae  by  f^dle   pedunci    ■  _^^are  »ia« .        _^   ^   ^^^^^^^ 

thalamaa;  IC.  internal  capaue:  «•  "^  "Xtar!  laliral.  and  inferior  olivanr 
nucleua:  P.  pontine  nucleus;  v,  I. o.  vesuou""  ■»  ,_j,u,i  nne  on;  i,  a. 
Sllclerf'.,'^«eStlon  nuclei  of  «;\fj^,  "«ir^onthfued'^d?wnwar.l  a.  rubro- 
cerebe  lo-rubral  (ibr»,  one  erf  "^ich  (4)  »  "Jl^i^j  ^  thalamocortical; 
;!l^r,2.i.i'ner8"^-^i!SlSl^puip^^^^^^^^^  pin..M:.«be.l.r  fibre.. 


rubro-thalamo-comcai  waci  ..»  j-„^  „„,h      a«  arre«orv  to  this  an  indirect  path, 

Zd  the  cortico-spinal  tract  form  the  """^  *rect  p^h      A^««^ry  to^  ^^^  ^^^  ^ 

impulses  by  way  of  the^cortico-ponto^erebellar  ^^«  «^^;'^,,„^. 
assumed  as  probably  taking  part  in  securmg  the  neces8ar>  muiui 


1096 


■       'i 

i 

' 

'■ 

\       i 

1 

1 

LV 

t 


HUMAN  ANATOMY. 


THE  FOURTH  VENTRICLE. 


The  fourth  ventricle  (vcntricvlM  q«arta«),  the  persistent  and  modified  hind-brain 
segment  of  the  primary  neural  canal,  is  an  irregular  triangular  space  between  the 
pons  and  the  medulla  in  front,  and  the  inferior  cerebellar  worm  and  the  superior  and 
Werior  medullary  vela  behind.  The  lateral  boundaries  are  contributed  by  the  supe- 
rior and  inferior  cerebellar  peduncles.  Its  long  a-xln  is  approximately  vertical  and 
about  3  cm.  in  length,  measured  from  the  lower  extremity,  where  the  ventricle  »» 
direcdy  continuous  with  the  central  canal  enclosed  within  the  medulla  and  spinal 
cord,  to  the  upper  end,  where  it  passes  into  the  aqueduct  of  Sylvius.  lis  wi  1th  is 
greatest  (about  2.75  cm.)  somewhat  below  the  middle,  where  this  dimension  is 
increased  by  two  lateral  recesses,  one  on  each  side,  that  continue  the  cavity  of  the 
ventricle  over  the  restiform  body. 

The  Floor  of  the  Fourth  Ventricle.— The  floor  of  the  ventricle,  really  its 
anterior  wall,  when  viewed  from  behind  after  removal  of  the  cerebdlum  and  the 
medullary  vela,  appears  as  a  lozenge-shaped  area  (fossa  rhomboidea).  The  upper  half 
of  the  floor  is  formed  by  the  dorsal  or  ventricular  surface  of  the  pons  and  is  bounded 

Fio.  947. 


iyhrtan  wiMilact 


Saperior 

poMertor  raccn 


iVventrick 


Latcrml  recess 


Posterior  cominiBsiiri 

Sylvian  aqacdnct 
Isthmus 

'Superior  median  sulcus 


Superior  lateral  sukus 

Foramen 
uf  Luscbluk 


Superior  posterior 
Lower  end  of  ventricle  containin(  foramen  of  Macendie 

Castof  cavity  of  fourth  ventricle i  ^,  from  the  side;  *,  from  above.    XI.     (Kettius.) 

laterally  by  the  upwardly  converging  superior  cerebellar  peduncles.  The  lower  half 
is  formed  by  the  ventricular  surface  of  the  open  part  of  the  medulla  and  is  bounded 
by  the  downwardly  converging  inferior  cerebellar  peduncles  and  the  clava.  The 
narrow  lower  angle  of  the  rhombic  area,  long  known  as  the  calamus  scriptorius, 
corresponds  to  the  interval  between  the  davae,  where  the  central  canal  of  the  cord 
communicates  wii..  the  fourth  ventricle.  The  upper  angle,  situated  beneath  the 
superior  medullary  velum  and,  therefore,  described  by  some  anatomists  as  belonging 
to  the  isthmus  of  the  hind-brain  (rhombencephalon),  marks  the  lower  end  of  the 
Sylvian  aqueduct.  The  length  of  the  rhombic  fossa  is  about  3  cm. ,  and  its  breadth, 
greatest  at  the  level  of  the  auditory  nerve,  is  about  2  cm. 

In  consequence  of  the  elevation  of  its  lateral  boundaries,  the  floor  appears  sunken 
and  corresponds  approximately  with  the  frontal  plane,  being  almost  vertical.  It  i& 
divided  into  symmetrical  lateral  portions  by  a  median  groove  (sulcus  medianus  longi- 
tudinalis  sinus  rtaomboidalis),  and  into  an  upper  and  a  lower  half  by  transverse  mark- 
ings, the  acoustic  striae  (striae  acusticae),  which  on  each  side  arise  from  the  nuclei  of 
the  cochlear  nerve,  wind  over  the  restiform  body  and  cross  the  floor  of  the  ventricle 
to  disappear  within  the  median  furrow.  At  its  lower  end,  where  it  sinks  into  the 
central  canal  of  the  cord,  the  median  groove  becomes  somewhat  wider,  the  resulting 
depression  being  sometimes  designated  the  ventriculus  Aurantii.  Roofing  in  the 
ventricle  at  this  point  and  bridging  the  cleft  separating  the  posterior  columns,  lies  a 
thin  triangular  sheet  of  loose  vascular  tissue,  the  obex,  which  laterally  is  continuous 


THE  FOURTH  VENTRICLE. 


1097 


i 


•«=r*^  iSr*:::^  S^  t  "S^^u^  A^S"  «««  divergence,  or  they  .nay 
weU-iiMtfked  bands  that  crosa  ««  ^"yj*=T"  j^  ^y  be  irregularly  disposed  or 

constitute  a  fan-shaped  group  m  ^^'^^the  jnu^  may  c^^  ^.^y  ^^  ^  ^^^^^ 

*"«wT'''L;.h  ^^'JrbT^rSSnS^  yStiTe^uenUy  one  band  diverges  from 
marked  on  both  as  »«  *^  ""r~8"Ee  y  upward  and  outward.  This  strand,  spe- 
'X^^^^:^oXJiZ^^.  is  seido.  equally  distinct  on  the  two 

"'^^vS^^fSr 'dSr^?  ^"e'iUtricuUr  Boor,  that  lying  below  the  acoustic 
•  ^^iJ^^thr^e^lneral  fields  of  triangular  oudine.     The  one  next  the  medun 

Est;  j-^j  ts^ui^oTsn^ -=■  c^ .-  *.  ^ 


Fig.  948. 


Fovn  •op*'**' 


"  Corpora  qwi<lr<|[«nliM 
Sylvian  aqu^uct 

cerebellar  pcdunclei 

Eminentia  Km 


Trlgonum 
hypoclogai 


White  core  ol 
ccrcbeUum 


Trigonum  acumtici 


Trigonom  v«fl^^  IQ0I         ^■"■*«  Funiculua  gracilia 

Floor  of  fourth  ventricle  .«p«.«l  alter  removal  of  It.  roof  by  Irontal  ««rtion. 

named  area  is  a  somewhat  depress«l  trian^lar  fieM  ^^^  ^^^^ 

is  placed  above,  near  the  acoustic  stn*  and  the  ^  '^•°*^;„';^  ,,„,  j  j^g  beneath. 


1098 


HUMAN  ANATOMY. 


superior  fovea,  the  ventricular  floor  presents  a  slightly  sunken  field,  the  locus 
coeruleus,  which  extends  upward  to  the  Sylvian  aqueduct  and  in  fresh  preparations 
possesses  a  bluish  gray  tint  in  consequence  of  the  deeply  pigmented  cells  of  the 
underlying  substantia  ferruginea  (page  1081)  showing  through  the  ependymal  layer. 

The  accurate  description  of  the  surface  markings  of  the  ventricular  floor  given  by  Retiius,' 
has  been  supplemented  by  Streeter's '  careful  study  of  the  relation  of  these  details  to  the  under- 
lying structures.  The  most  important  results  of  these^  obstrvation-s,  which  have  materially 
advanced  our  understanding  of  this  important  part  of  the  brain-stem,  may  here  find  mention. 

The  tiifonum  hypogloui  is  seen,  especially  when  examined  under  fluid  with  a  hand-lens, 
to  include  two  subdivisions,  a  narrow  median  and  a  broader  lateral.  The  first  of  these  is  con- 
vex, about  s  mm.  long  by  i  mm.  wide,  and  corresponds  to  the  rounded  upper  end  of  the  nucleus 
of  the  twelfth  nerve ;  it  is,  therefore,  appropriately  called  the  eminentia  hjrpogloMi  (Streeter). 
The  entire  hypoglossal  nucleus,  however,  is  of  much  larger  size  (about  12  mm.  long  by  2  mm. 
wide)  and  extends  some  5  mm.  below  the  tip  of  the  calamus  scriptorius,  ventral  (anterior)  to  the 


Fig.  949. 


Colliculus  inferior 


IV.    nerve 


Superior  cerebellar  peduncle 

Stria  ponti* 
Median  fovea -^.^ 
v.  nerve 

Superior  fovea 
Eminenlia  tereS' 

Acoustic  striae 

VIII.  nerve 

IX.  and  X.  nerves 

TriRonum  acuslici  • — 

TriRonuiH  hypoglossi 

Trigunum  or  (ovca  vnKi 

Funiculus  scparanS' 

Area  postrema 

Nucleus  cuneatuH. 

Nucleus  gracilis 

Fluor  of  the  fourth  ventricle ;  areas  corresponding  to  nuclei  of  nervei  are  shown  on  right  half  of 
figure.     ■  I-  JSirffter.) 


Area  n.  trigemini 

N.  facialis 

Area  n.  abducentis 

Area  n.  vestibularis 
Area  n.  cochlearis 


Area  nuc.  funic,  teretis 
Funiculus  solitarius 
.Area  n.  vagi 


Area  n.  hypoglossi 


vagus  nucleus  and  nucleus  gracilis.  Lying  immediately  above  the  hypoglossal  eminence  is  a 
second  and  somewhat  less  pronounced  elevation,  formed  by  the  nucleus  funiculi  teres  and  meas- 
uring nearly  6  mm.  in  length  by  1  mm.  in  breadth.  lateral  to  these  two  median  elevations  and 
limited  externally  by  the  ala  cinerea,  lies  a  wedge-shaped  field  that  is  insinuated  between  the 
hypoglossal  eminence  and  the  vagal  trigone.  It  stretches  from  the  acoustic  strite  above  to  the 
nib  of  the  calamus  scriptorius  below.  This  field,  named  the  ana  plumiformis  by  Retzius  on 
account  of  its  feather  like  markings,  is  regarded  by  Streeter  as  corresponding  to  a  group  of  cells, 
the  •■  >ui  intercalatus,  that  occupies  a  superficial  position  in  the  ventricular  floor  and  partly 
ovei        the  hypoglossal  nucleus. 

ihe  fovea  vagi  (ala  cinerea),  which  lies  lateral  to  the  nucleus  intercalatus,  corresponds  to 
the  middle  and  superficial  third  of  the  vago-glosso-pharyngeal  nucleus,  the  entire  extent  of  the 
latter  including  a  tract  measuring  about  13  mm.  in  length  by  2  mm.  in  breadth,  that  stretches 
irom  beneath  the  vestibular  nucleus  above  to  over  2  mm.  beyond  the  inferior  angle  of  the 
ventricle.  The  lower  third  of  the  area  of  the  vagus  nucleus  is  partly  within  the  ventricle; 
immediatelv  above  the  obex  this  intraventricular  portion  is  covered  by  «  layer  of  loose  vascular 
tissue  and  appears  as  an  upwardly  diverging  pointed  fieltl,  area  postrema  of  ReUius.  This  is 
separated  from  the  ala  cinerea  by  a  translucent  ridge,  the  funiculus  leparant,  composed  of 
thickened  ependymal  neuroglia  (Streeter). 


'  nas  Menchenhim,  i8q6. 
•Amer.  Journal  of  Anal.  Vol  II, 


1903. 


THE  FOURTH  VENTRICLE. 


1099 


Trtachorioidet 
iihI  choroid  plain 


The  prominence  of  the  eminentia  teres  is  due  to  the  underlying  nucleus  of  the  sixth  nerve, 
enclosed  by  the  knee  of  the  facial ;  for  it,  therefore,  Streeter  proposes  the  naine  emmenti.  abdu- 
^I^  The  longitudinal  ridge  that  continues  upward  and  boon^sthe  median  fovea,  the  las 
^kuthor  interprets  as  due  to  a  field  of  gray  matter,  th.n  in  the  vicinity  °<  ']•«  »f<^"«"' 
eminence  and  thicker  above,  to  which  the  name  nudeui  uicertu.  is  applied  Lateral  to  the 
nSTn^rtus  and  the  facicvabducent  eminence,  lies  the  fovea  antenor  which  elongated  and 
deor^d  area  (nearly  6  mm.  k>ng  by  i  mm.  wide)  is  due  to  the  exit  of  the  root  of  the  fifth 
ne^rtt  ml^  Aerefore,  be  called  the  fove.  trigemini.  The  medi«,  portion  of  the  elevated 
™tic  area  includes  the  elongated  and  irregularly  lozenge-shaped  ve.ubuUr  area,  that 
Ti^u^^u  .6  mm.  in  length  by  4  nun.  in  breadth  and  extends  from  the  fovea  antenor 
rS^i)  to  the  nucleus  gracilis.  The  lateral  part  of  the  area  acu«t.ca  ^  occup^edby  the 
cortle«  area,  which  stretches  into  the  recessus  lateralis  and  overlies  the  nudeua  cochlewii. 

The  Roof  of  the  Fourth  Ventricle.— Viewrd  in  median  sagittol  section  (Fig. 
018-)  the  roof  of  the  fourth  ventricle  appears  as  a  tent-like  structure,  whose  wings, 
where  they  come  together,  bound  a  space,  the  recessus  tecti,  that  penetrates  the 
cerebellar     medulla 

between  thesupenor  '^'"-  "S" 

and  inferior  worm. 
The  upper  wing  of 
the  tent  is  formed  by 
the  superior  med- 
ullary velum,  the 
triangular  sheet  of 
white  matterstretch- 
ing  from  beneath 
the  quadrigeminal 
bodies  above  to  the 
medullary  substance 
of  the  cerebellum 
below,  and  is  over- 
laid by  the  rudimen- 
tary cerebellar  folia 
of  the  lingula.  It 
must  be  understood 
that  the  ventricular 
surface  of  the  velum 

eoendima-S  are'all  other  parts  not  only  of  the  fourth  ventricle  but  of  all  the 
venSS  c?vid«.  LaterallVthe  superior  medullary  velum  is  attached  to  the 
superior  cerebellar  peduncles,  which  to  a  limited   extei.t  share  in  closing  in  this 

P'"  Th?Lw?£f'o7the  ^comprises  two  parts,  an  upper  and  thicker  crescentic 
nlate  of  white  matter,  the  inferior  medtdlary  velum,  and  a  lower  and  extremely  thin 
membrane  he  tela  chorioidea.  Medially  the  inferior  medullary  velum  is  attached 
SrTomed  stance  to  the  front  and  lower  surface  of  the  nodules,  which  it  excludes, 
iSyregaSfrom  the  ventricle,  whilst  laterally  the  velum  is  prolonged  to  the 
floccuhis  its  fib;es  becoming  continuous  with  the  white  core  of  th.s  subdivision  of 
the  cerebellum.  The  nervous  constituents  of  thevclum  extend  only  as  far  as  its 
crLcentic  lower  border,  beyond  which  the  roof  of  the  ventricle,  in  a  morphological 
^"e  is  formed  by  the  ependymal  layer  alone.  This,  however,  is  supported  by  a 
Tacking  of  Dial  ti^ue.  which,  in  conjunction  with  the  ependyma  forms  the  tela 
Chorioidea^  On  nearing  the  lower  angle  of  the  ventricle,  the  roof  presents  a  trian- 
gular  thickening,  the  obex,  that  closes  the  cleft  between  the  clav«  and  lies  behind 
f  above)  the  nib  of  the  calamus  scriptorius.  ,       1     -.u  »i. 

On  each  side  the  obex,  which  consists  of  a  layer  of  white  matter  fused  with  the 
undeZng  ependyma,  is  continuous  with  the  slightly  thickened  margin  of  the  roof 
The  tSa  ventri^:ul  .  whose  line  of  attachment  passes  from  the  rhva  ..pward  and 
outwa*d  over  the  cunelle  tubercle  of  the  ineduHa  and  the  rctiform  hn<lv  l^d.  farther 
up  Jai^  niM  obliquely  across  the  dorsal  surface  of  this  peduncle  to  close  m  the  lateral 


I  nferfor  worm 


Donul  portion  ol  preparation  shown  i«  FlfC-  <¥** 
from  below. 


roof  of  fourth  ventricle  is  seen 


IIOO 


HUMAN  ANATOMY. 


recess — one  of  the  pair  of  diverticula  that  overlie  the  inferior  cerebellar  peduncles 
and  add  materially  to  the  transverse  dimension  of  the  ventricle.  After  enclosing  the 
lateral  recess  the  txnia  leads  to  the  stalk  ol  the  flocculus  and  the  inferior  \  clum. 

Within  the  triangular  field  of  the  tela  chorioidea,  the  pia  mater  takes  advantage 
of  the  attenuation  of  the  ventricular  wall  to  effect  invaginations  by  which  its  blood- 
vessels apparently  gain  entrance  into  the  ventricle.  Such  invaginations,  known  as 
the  choroid  plexus  of  the  form.h  ventricle,  occur  in  the  ventricular  roof 
on  each  side  and  in  the  immediate  vicinity  of  the  mid-line,  where  they  appear  as 
parallel  villous  or  fringe-like  stripes,  the  median  plexus,  which  extends  upward 
from  near  the  obex  to  the  inferior  medullary  velum.     Opposite  the  nodules  they 

Fig.  951. 

Roof-nuclei 


Nucleui  (kibotus- 


Nucleut  dentttus' 


Cllonld  pJeius—^T 


Foufth  -  entrldt 


RnHforni  body- 
Fibres  of!  X.  nerve. 
Spinal 
of  V,  nerve 


Ijtteral  ivccH  at  ventrkl 


Inferior  olivary  nucleus' 


Choroid  plexu* 
PosOTlor  lonffitudinal  fiudculua 


Pjnmmldal  liBcIs 


Section  across  lower  third  of  fourth  venlrlrle.  showinfc  intemml  cerebellar  nuclei,  choroid  plexui,  lateral  recencs  and 
medulla  ;  new-born  child.     X  3^*    Preparation  by  Professor  Spiller. 

diverge  and,  as  the  lateral  plexuses,  invaginate  the  wall  of  the  lateral  recesses. 
The  vascular  complex  lies  within  the  fold  of  pial  tisssue,  the  space  between  the  pial 
layers  being  occujiied  by  prolongations  of  the  arachnoid. 

Notwithstanding  its  conspicuous  thinness  during  the  first  half  of  foptal  life,  the  tela 
chorioidea  suffices  to  completely  close  the  ventricle.  From  about  the  fifth  month, 
however,  the  delicate  membrane  is  perforated  by  an  aperture  that  remains  throughout 
life.  This  opening,  the  foramen  of  Magendie  (apertnra  mcdialis  ventriculi  quart!) 
lies  immediately  above  the  obex  and  between  the  strands  of  the  choroid  plexus. 
Two  additional  clefts,  the  foramina  of  Luschka  (aperturae  laterales),  usually  exist, 
one  on  each  side,  in  the  wall  of  the  lateral  recesses  in  the  neighborhood  of  the  vago- 
glosso-pharyngeal  nerves.  By  means  of  these  three  openings,  and  probably  by  these 
alone,  the  system  of  ventricular  cavities  and  the  central  canal  of  the  spinal  cord  are 
brought  into  communication  with  the  subarachnoid  lymph-space.  A  path  is  thus 
provideil  by  which  the  cerebro-spinal  fluid,  secreted  within  the  lateral,  third  and  fourth 
Ventricles  by  the  various  choroid  plexuses,  constantly  escapes  and  thereby  prevents 
undue  accumulation  and  distension  within  the  cavities  of  the  brain  and  spinal  cord. 


THE  DEVELOPMENT  OF  THE  HIND-BRAIN  DERIVATIVES. 

In  the  Rener.il  sketch  of  the  development  fif  the  Ijmin  previously  given  (oage  1061),  it  was 
pfiinted  out  that  the  hind-brain,  or  rhomheiicfphalon,  includes  two  suhdivisionR,  the  myetenceph- 
n/nn  and  thp  tnrtrnrrphalnn .  the  extreme  iipixr  part  nf  tho  latter  VwinB  Hrsignatrd  the  ixikmux. 
It  has  been  further  noticed  that  the  junction  of  the  cord  and  hrain-»e(tments  of  the  neural  tube 
corresponds  with  the  conspicuous  cer\ical  flexure,  whose  early  appearance  i«  followed  by  an 


DEVELOPMENT  OF   HIND-BRAIN   DERIVATIVES. 


IIOI 


outward  bending  of  the  lateral  walls  of  th.  brain-vesicle  and  the  stretching  and  flattening  of  the 
Slate  In  consequence  of  these  changes  the  roof  of  the  rhombencephalon  becomes  reduced 
loan  attenuated  sheet  which,  when  viewed  from 


Fig.  952. 


Mid-brain 

Riglit  ticmisphere 
Inferior  colliculus 


Roof-plate 

Cerebellum 
Cavity  III 
hind-nraiii 
Lateral  rccelt 
Rhombic  lip 
Attachment  oi 
rouf 


Medulla 


Reconstruction  of  brain  of  human  .Mnbrjro  of  aa^ 
mm.,  showing  hind-brain  and  part  of  mld-hrain  viewed 
in:  ill  hind.  X  11.  Drawn  from  model  made  by 
Dt   1  .•  iig  Taylor. 


above,  appears  as  a  lozenge-shaped  membrane 
that  closes  in  the  subjacent  cavity,  the  subse- 
quent fourth  ventricle.  It  has  also  been  pointed 
out  (page  1049)  that  the  relatively  thick  lateral 
walls  of  the  neural  tube  exhibit,  even  withm  the 
cord-segment,  a  differentiation  into  a  dorsai 
and  a  venira/  zone  (the  alar  and  basal  lammae 
of  His),  which  subdivisions  are  associated  with 
the  sensory  and  motor  root-fibres  of  the  nerves 
respectively.  Similar  relations,  in  a  more  pro- 
nounced degree,  are  evident  within  the  brain- 
stem and  are  of  much  interest  as  indicating  the 
morphological  correspondence  of  the  purely 
motor  nerves  (the  third,  fourth,  sixth  and 
twelfth)  on  the  one  hand,  and  of  the  mixed 
nerves  (the  fifth,  seventh,  ninth  and  tenth)  on 
the  other. 

The  Medulla.— The  great  preponderance 
of  the  nervous  matter  along  the  floor  of  the 
fourth  ventricle,  as  represented  by  the  medulla, 
is  due  primarily  to  the  outward  bending  of  the 
lateral  walls  of  the  myelencephalon,  supple- 
mented by  the  accession  of  large  tracts  of 
nerve-fibres  that  later  grow  in  from  other  parts 

of  the  cerebro-spinal  axis.    In  consequence  of  .     „     j-    1      j  1  .„„ii,. .  -» 

d^e  former  change,  the  dorsal  zones  of  the  side-walls  are  gradually  displaced  laterally,  at 
Ae  «re  time  tfey  become  partly  folded  on  themselves  to  produce  along  their  outer  margm 
the  fhZbU  lip  (His),  which  is  directly  cominuous  with  the  expanded  and  thin  roof-plate 
Uter  the  dorsal  zones  come  to  lie  almost  horizontally,  their  -"'^'^"  »""f  =^  ^^t^f'fou^^^ 
with  d>at  of  the  ventral  laminae,  in  conjuncUon  with  which  the^^^^J.^^I'^J^^^^^^^^  ^ 

^^'^   '^iucuiu.  cidently  with  the  outward  mi- 

supmtoi     j^","J^^j.,^,  gration  of  the  dorsal  laminae, 

the  ventral  zones  also  thicken 
and  assume  a  much  more  hori- 
zontal position,  with  their  inner 
ends  sei>arated  superficially  by 
a  median  furrow  and,  deeper, 
by  the  compressed  remains  of 
the  floor-plate.   Very  early  and 
before  the  flattening  out  of  the 
myelencephalon  has  advanced 
to  any  marked  extent,  the  de- 
marcation between  the  dorsal 
and  ventral  zones  is  evident  as 
a   lateral  longitudinal   groove 
on   the  ventricular  surface  of 
the   iiiyelcniephalon.      Indica- 
tions of  this   division  persist 
and  in  the  adult  medulla  are 
represented  by  the  fovea  pos- 
terior and  the  sulcus  lateralis 
seen  of  the  flt>or  of  the  fourth 
venti'-'C.     As  in  the  cord-seg- 
ment, 30  in  the  myelencepha- 
lon the   lateral   walls  are   the 
only  regions  of  the  neural  tube 
in  which  neuroblasts  are  devel- 
oped, the  roof-plate  and  the  floor-plate  containing  spongioblasts  alone. 

Very  iiirly  and  l<efore  the  flattening  out  of  the  myelencephalon  has  advanced  to  any  marked 
extent  within  the  ventral  zones  and  close  to  the  mid-line,  appear  groups  of  iieurobUst,  Irom 
which  axoiies  grow  ventrally  to  form  the  root-fibres  of  the  motor  (hypoglossal )  nerves.    .Sensory 


'iBftrloriollkului 


Su|<eriof 
medulUry  velum 


Corpul  «rtatum 

Cut  wall  of  cerfbrM 
hcmUphtn 

Pontine  flexure 


Lateral  recess 
CavUy  rif  hiMi|.hr«ln 
(IV  ventricle) 

Rouf  of  hind-lifaln.  lower  part 


Recnnntruction  of  hind-brain  of  human  embn,o  <.l  about  Ihreenionihs 
ISO  mm.),viewedirom»ideandbehiiid.     Drawn  from  His  model. 


II02 


HUMAN   ANATOMY. 


ill! 


Fig. 


1    I 


n 


\ 


fibres  are  also  early  represented  by  bundles  which  grow  centrally  from  the  ganglion  of  the  vagus 
towards  the  developing  medulla,  upon  whose  surface,  opposite  the  junction  of  the  dorsal  and 
ventral  zones,  they  appear  as  a  flattened  oval  bundle  (fasciculus  solitarius).  For  a  time  super- 
ficial and  loosely  applied,  this  bundle  gradually  becomes  more  deeply  placed  in  consequence  of 
the  extension,  ventral  folding,  and  final  fusion  of  the  rhombic  lip  with  the  remainder  of  the  dorsal 
zone.  Subsequently  the  fasciculus  soliUrius  becomes  still  farther  removed  from  the  surface  by 
the  ingrowth  of  tracts  of  nerve-fibres  from  the  neuroblasts  of  the  rhombic  lip  and  from  other 

sources  until,  finally,  the  bundle  comes  to  lie 
beneath  the  ventricular  floor  where  its  position 
permanently  indicates  the  junction  between  thr 
original  dorsal  and  ventral  zones  of  the  medui 
lary  wall.  In  a  similar  manner  the  sensory  fibres 
of  the  •''jeminal  nerve  are  applied  to  the  sur- 
face rti  e  developing  pons;  since,  however, 
the  buiuilc  is  attached  after  consolidation  of  the 
dorsal  zone  of  the  medulla  has  begun,  the 
descending  trifacial  fibres  retain  the  relatively 
superficial  position  characterizing  the  spinal  root, 
while  the  descending  root  (fasciculus  solitarius) 
of  the  glosso-pharyngeo-vagus  lies  more  deeply 
placed.  Subsequent  to  the  invasion  of  the  medulla 
by  the  sensory  parts  of  this  nerve,  the  outgrowth 
of  the  a.xones  from  the  neuroblasts  constitut- 
ing the  nucleus  of  origin  provide  its  motor  root- 
fibres. 

The  rhombic  lip  is  a  region  of  much  impor- 
tance, since  from  the  neuroblasts  which  appear 
within  it  are  derived  the  cells  of  the  reception 
nuclei  (substantia  gelatinosa)  of  the  sensory 
cranial  nerves,  of  the  nuclei  of  the  posterior  col- 
umns, of  the  inferior  and  accessory  olivary  nuclei 
and  of  the  arcuate  nucleus.  From  the  neuro- 
blasts many  axones  grow  medio-ventrally,  pierce 
the  median  spongioblastic  septum  derived  from 
the  primary  floor-plate,  which  later  becomes  the 
median  raphe,  and  gain  the  opposite  side  and 
thus  establish  the  systems  of  arcuate  fibres.  Other 
axones  grow  dorsally  and  take  part  in  even- 
tually producing  the  fibre-tracts  connecting  the 
olivary,  dorsal  and  arcuate  nuclei  with  the  cere- 
bellum. It  :s  evident  that  the  development  of  the 
myelencephalon  primarily  contributes  the  nerv- 
ous Hubstance  that  becomes  the  dorsal  part  of  the 
medulla  and  underlies  the  fourth  ventricle.  Later 
the  closed  part  of  the  medulla,  which  at  first 
i"  "vanting,  as  well  as  the  conspicuous  pyramidal 
tracts,  are  added  as  the  strands  of  ascending 
and  descending  fibres  grow  into  the  medulla 
from  the  spinal  cord  and  from  other  parts  of  the 
brain.  In  this  manner  the  important  tracts  of 
the  posterior  columns  and  the  spinal  constitu- 
ents of  the  restiform  body  and  of  the  brain-stem 
are  added  and,  still  later,  the  bulky  pyramids 
take  form  when  the  cerebro-spinal  paths  are 
established. 

In  accord  with  the  falling  apart  and  thick- 
ening that  affect  the  lateral  walls  of  the  mye- 
lencephalon and  lead  to  the  production  of  the 
medulla,  the  roof-plate  of  the  brain-vesicle 
becomes  flattened  and  laterally  expanded  to  keep  pace  with  the  increasing  width  of  the  ventricular 
floor.  In  consequence,  the  roof-plate  is  converted  into  a  rhomlwidal  sheet  of  great  delicacy,  the 
pHiiiary-  'Clum,  whiL-h  hiNtt.U»gic:t!ly  consists  of  little  morp  tlwn  the  Liver  of  ependymal  cells 
These,  however,  soon  come  into  close  relation  with  the  overiying  me»obla.stic  tissue  from  which 
the  pia  is  differentiated.  During  the  third  month  a  transverse  fold,  the  plica  chon<ndea,AV\)CArs 
in  the  roof-sheet  near  the  posterior  limit  of  the  developing  cerebellum  (Fig.  955,  B).    Into  this 


Trat)svenw  Rections  of  hind-hratn  of  human  emhr>"o«. 
showiiiK  three  stajres  in  dwetoitment  of  medulla;  A, 
about  four  and  a  half  weeks;  fl,  about  six  weeks;  C 
about  etjrht  weeka ;  rp.  roof-plate :  r,  raphe :  rf,  v, 
dorsal  (alar)  and  ventral  (ha»1>  laminir  ;  r/,  rhombic 
lip;  Ir,  lateral  recess;  /j,  fasciculus  solitarius;  ci . 
restiform  \kv\v  ;  xii,  hvpo|rlostial  ner\*e  ;  Jf',  spinal 
root  of  trifteminus ;  lo,  iiiferior  olivary  nucleus.    ( His. ) 


DFAELOPMENT   OF   HIND-BRAIN    DERIVATIVES.  1103 

duplicature,  directed  towards  the  brain  cavity,  the  mesoblast  grows  and  later  'l.^ve'ops  blood- 
veLls,  and  is  converted  into  a  vascular  complex  that  eventually  forms  the  choroid  plexus  of  he 
S  ventricle.  From  the  manner  of  iU  development,  it  s  evident  that  the  plexus  is  excluded 
S^yie  ependymal  layer  from  the  ventricular  space,  outeide  of  wh.ch  the  P'"'  b'"Vf ;7^^'!; 
therefore  really  lie.  The  conversion  of  the  upper  part  of  the  pnmary  velum  mto  the  thicker 
definite  nferior  medullary  velum  follows  the  addition  of  nervous  substance  during  the  develop- 
ment of  tb^"^eWlum.  ^Similar  thickening  of  the  roof-sheet  at  the  lower  angle  o.  the  ventricle 

results  in  the  production  of  the  obex  and  the  tuiniie.  ,  ■  u  t  

The  Pon.  -The  pons  arises  as  a  thickening  of  that  part  of  the  metencephalon  which  forms 
the  anterior  wall  of  the  pontine  flexure.  In  its  essential  phases  the  development  of  the  (wns 
probably  closely  resembles  that  of  the  medulla,  since  the  early  metencephalon  presents  the  same 
^^1  feature  as  does  the  myelencephalon.  Thus,  the  ventral  «.nes  of  its  lateral  walls  pla, 
^  active  rAle  in  the  production  of  the  tegmental  portion  of  the  pons  and  the  ""f'^'"*  ""«•""* 
the  motor  root-fibres  of  the  fifth,  sixth  and  seventh  nerves,  whilst  the  fioor-plate  becomes  the 
.•aphe.  In  addition  to  providing  the  rec-eption-nuclei  of  the  sensory  cranial  nerves,  ana.  per- 
haps, the  pontine  nuclei,   the  dorsal 

zones  contribute  the  neuroblants  which  Fic.  955.  ^ 

become  the  nervous  elements  of  the  ^ 

cerebellum.    As  in  the  medulla,  so  in 
the  pons  the  great  ventral  tracts  are 
secondar>'  and  relatively  late  additions 
to  the  tegmentum,  which  must  be  re- 
garded as  the  primary  and  oldest  part 
of  this  segment  of  the  brain-stem,  the 
bulky  ventral  nervous  ma.sses  taking 
form  only  after  the  appearance  of  the 
cerebro-spinal  and  cerebro-cerebellar 
paths.    In  a  manner  analagous  to  that 
by  which  the  sensory  part  of  the  vagus 
is  at  first  loosely  applied  and  later  in- 
corporated with  the  medulla,  the  sen- 
sory fibres  of  the  trigeminus  are  for  a 
time  attached  to  the  surface  of  the 
dorsal  zone  of  the  pons,  subsequently 
becoming  covered  in  and  more  deeply 
placed  by  the  addition  of  peripheral 
tracts.  Likewise  the  fibres  of  the  audi- 
tory nerve  come  into  relation  with  the 
superficially  situated  reception-nuclei 
of  the  cochlear  and  vestibular  nerves. 
The  Cerebellum.— The  develop- 
ment of  the  human  cerebellum  pro- 
ceeds from  the  roof-plate  and  adjacent 
parts  of  the  dorsal  zone .  of  the  lateral 
walls  of  the  metencephalon.     In  an 
embr>o  22.8  mm.  long,  the  cerebellar 
■niage  consists  of  two  lateral  plates  ,    ,  .    ,c.-        „x      4,,„, 

inected  by  anarro-v  thin  intervening  lamina  representing  the  roof-plate  (Fig.  95a).    Alter 
apposition  of  the  lateral  plates,  which  soon  occurs,  this  bridge  disappears,  the  developing 
rebellum  for  a     ■■      appearing  as  an  arched  lamina  enclosing  the  upper  part  of  the  cavity  of 

„,e  hind-brain  (Kuiiii.m')-  .  ,  j  „     .  j-    1 

The  subsequent  development  of  the  human  cerebellum  has  been  recently  carefully  studit  <1 
by  Bolk » in  a  series  of  about  forty  foetuses,  hardened  in  formalin  and  ranging  from  5  to  30  cm.  in 
their  entire  (crown-sole)  length.  The  following  account  is  based  largely  on  these  investigations. 
In  a  f.Etus  of  5  cm.,  about  nine  weeks  old,  the  cerebellar  anlage  is  represented  by  a  horseshoe- 
shaped  thickening  of  the  metencephalic  roof,  the  cerebellar  lamina,  whose  upper  margin  is  con- 
nected by  the  encephalic  fold  with  the  mid-brain  and  whose  lower  border  has  attached  to  it  the 
primary  velum— the  thin  rhomboida!  roof-plate  of  the  myelencephalon.  Median  sagittal  section 
of  the  cerebellar  lamina  at  this  stage  ( Fig.  955.  ^)  sh"*'  its  form  to  be  asymmetrically  biconvex, 
the  more  convex  surface  encroaching  upon  the  brain-cavity.  In  a  slightly  t)lder  f»etus  (Hg. 
955,  B)  the  cerebellar  lamina  has  become  triangular,  in  section  presenting  a  supenor,  an 
anterior  and  an  inferior  suriace.  From  its  attachment  along  the  superior  margin  of  the  lamina 
the  inferior  velum  dips  forward  toward  the  pontine  flexure  and,  forming  a  transversely  cresentic 

'  Miinchner  med.  Abhand.,  1895. 
•Petrus  Camper,  30  Deel.  1905- 


Median  Uf{iUa1  sectionn  showiHR  four  early  stages  of  develop- 
ment of  human  cerebellum,  from  fictuses  from  5  to  q  cm.  long; 
ml>.  mid-brain  ;  c.  cerebellum  ;  in,  iv,  superior  and  mferior  medul- 
lary velum  :  vc,  ventricular  cavity  ;  rf,  cavity  of  diencephalon  ;  A. 
pons ;  m.  medulla ;  J.  spinal  cord  ;  r/.  incisura  fastiml ;  /,  sulcul 
primariut ;  j,  sulcus  postnodularis.  {Drawn/rom  figures  of  Bolt.) 


„o4  HUMAN  ANATOMY. 

fold  the  PlUa  chorioidea,  bounds  a  narrow  recess  that  extends  along  the  inferior  surface  of  the 
cerebellaflamina.  This  recess  is  only  temporary  and  is  soon  obliterated  by  the  subsequent  at- 
tachment of  the  roof-membrane  to  the  inferior  surface  of  the  cerebellarlamma  The  succeedmg 
staee  ( Fie  QSS  C\  emphasizes  the  alteration  in  the  planes  of  the  cerebellar  surfaces,  the  former 
suiirior  now  becoming  the  anterior,  the  anterior  the  inferior  and  the  inferior  the  posterior. 
From  the  posterior  margin  of  the  dorsal  surface  the  choroid  fold  dips  into  the  bnun-Kravity. 
Between  themid-brain  and  the  cerebellum  now  stretches  the  first  definite  indication  of  the  later 
superior  medullary  velum,  in  agreement  with  His,  Bolk  recogniz^  Oiat  the  former  intraven- 
tricular (inferior)  surface  has  now  become  an  extraventricular  one  and  that  the  permanent  attach- 
ment of  the  plica  chorioidea  corresponds  to  a  secondary  and  not  to  the  primary  line  of  union. 
The  stage  represented  in  Fig.  955.  D  is  important,  since  it  marks  the  beginning  of  the  first 
fissures  One  of  these,  the  sulcus pritnarius  (the  ^ssura  prima  of  Elliot  Smith )  appears  as  a 
transverse  groove  on  the  upper  part  of  the  anterior  surface  and  thus  early  establ.>hes  the  hinda- 
mental  division  of  the  cerebellum  into  an  anterior  and  a  posterior  lobe.  The  other  fissure 
appears  in  the  median  area  near  the  posterior  margin  of  the  cerebellum  '«'»'''*«  ^"''""f^J*^ 
nodularis.  On  each  side  (Fig.  956.  -« )  an  additional  fissure  cuts  off  a  narrow  tract  that  embraces 
the  postero-lateral  area  of  the  cerebellum.  This  fissure,  Hf^^  sulcus  floccuUns,  for  a  time  reinair« 
unused  with  the  postnodular  sulcus;  but  later,  with  its  fellow,  't  becomes  continuous  wuh 
the  postnodular  sulcus  and  thus  defines  a  narrow  band-like  tract,  the  median  part  of  which 


Fig.  956. 


Six  ,.a,^.  in  devrfopm™.  of  human  «„b.num  'rom^'«'Mr  °'  "s'lilsPn^^ulA*:'"/, "  fn%py™m'daTu ;'"".: 
(^     ength;  /.  sulcus  P"m«riu»  (preclival)-,^,  s.  Hwcuians .  j,  s.  ix.»^^^       roof-mimbnme ;  >,  ateral  recew; 

:rKfusTS.Tu^i??,'i:;r:!i;s^.SS'n'>?7cTur' ^ 

eventually  l^ecomes  the  nodule,  the  lateral  portions  the  flocculi,  whilst  the  i"'«™K  strips 
become  the  fioccular  peduncles  and  part  of  the  inferior  ."^«<lf  ^.^^j'""^"  ^,^^,"^  \^^'J^"rth 
bounded  on  each  side  by  the  floccular  area  is  the  beginning  of  the  «teral  recess  of  the  fourth 
ventricle  and  is  eariy  filled  by  the  rapidly  growing  choroid  plexus  A  shallow  transverse 
groove,  the  innsuraja.ti.ii,  just  suggested  in  Fig.  955,  C  but  rf''*"'^' '" J^^^^^/^^f  ^f^f  th^^ 
mirks  the  beeinninK  of  the  tent-like  recess  that  later  conspicuously  models  the  root  ot  the 
f"  r,h  ventr^le  Coincidently  with  and  al..ut  midway  l.tween  the  «<**>;- J"^  J^^^;"';^^^," 
third  furrow  appears  on  the  posterior  cerebellar  lobe.  This  is  'heyi-v«..  ..,»«rf«  (E^^^^ 
or  the  infrapvramidal  sulcus.  Very  shortly  a  fourth  groove  appears  ^»""^  the  su'cus  prim^^ 
and  marks  the  beginning  of  the  prepyramidal  fissure.  In  this  -"/Xh  from  ^hind  toward 
posterior  lobe  is  eariy  subdivided  by  three  fissures  into  four  areas,  which  '™'"  °^^^^^^^^^ 
«{e  sulcus  primarius,  give  rise  to  the  nodule,  the  uvula,  the  pyramid  and  a  still  ""differentiated 
one  Hv  .'he  subsequ^ent  appearance  of  additional  furrows,  this  "»"°-/,X^o7the  ce  ebLuur^ 
tulK.r,  the  folium  cacuminis  and  the  ...vus.  Meanwhile  on  the  »"*7°J°*^  °' '^",j*^ts'^"ke^ 
three  short  transverse  fissures  appear,  by  which  the  antenor  end  of  '^^/.^T^.  \"^*  '^^?:;'^„^^^^ 
up  into  areas  that,  while  establishing  subdivisions  of  mon^hological  value  (BolVc  •  are  later  lost 
in  the  uncertain  foliation  of  the  tlnKuta  and  lobulus  ccntnihs  of  'he  njatuirrerehellum^ 

.\fter  the  fundamental  subdivision  of  the  median  area  (worm)  has  ^".^f^°"lP''^rf,^,;,^^,^ 
lateral  masses  (hemispheres)  of  the  cerebellum  become  subdivided  into  •!! fi"'  ^^^j^^^'j";^^^^^^^^ 
by  fissures  that  appear  during  the  fourth  and  fifth  months  of  foetal  We.    The  lateral  extensions 


THE  MESENCEPHALON. 


1105 


on^he  upper  suHace  of  ^e  P<«te"<^  >"^-   Bv'he^f^^^^^^  7\Wu^posMivai  fissur,)  and  the 
about  the  end  of  the  fifth  month,  and  is  at  first  represented  "V  »  ™,^,         ^.^  ;„  ^^  ..^Hance 

lateral  tracts  (postero-supenor  lobules) .    Th.s  Part  of  the  «orm,  ^         •    ^^  .„  ^    these 

with  the  cortical  expansion  of  ^^e  surrounding  j^m  and  he„ce^or^^^^^  .^  ^^y^ 

and  «nks  into  the  relative  •n-'*'g"'fi«^»"'=%''^»' ^^d^owth  aXxpans^^  of  the  peripheral 
matured  cerebellum.  In  ^rr'"^"^  °'fi«uri,'^f  Sdar>  lr^&^^  im,x,mnce,  as 
portions  of  the  human  cerebellum  some  figures  of  ^^"^''^^  "^^„„,'^  „.,„  ,{,„„  ,h„«,  of 
the  horizonul.  become  excessive  y  ^e^f«"^ J»nd^^^  This 

are  derived  the  earliest  constituente  of  the  granule  layer.   "e»"*l?"'^*'™"„  ?  ,„,_^^^^       con. 

natal  life. 

THE   MESENCEPHALON. 

Notwithstanding  its  considerable  size  and  prominent  position  in  the  embryo,  in 
its  mature  nondiSn  d.e  mesencephalon,  or  mid-brain,  forms  the  smallest  -"^  least  con- 
picuous  division  not  only  of  the  brain-stem  but  also  of  the  -'"'^e  bra.n^     Neverthe- 
less   the  manv  fundamental  tracts  which  it  contains,  as  well  as  the  new  paths  ana 
comblnationTUSari^^  it.  substance,  confer  on  the  mid-brain  an  importance 

7" 


iio6 


HUMAN  ANATOMY. 


not  suggested  by  its  size.  Its  upper  limit  corresponds  with  an  oblique  plane  passing 
through  the  base  of  the  pineal  body  and  the  posterior  border  of  the  corpora  mam- 
millaria  ;  its  lower  one  is  indicated  on  the  ventral  surface  by  the  upper  border  of  the 
pons  and  on  the  dorsal  aspect  by  the  upper  margin  of  the  superior  medullar}-  velum. 
As  seen  in  sagittal  sections  (Fig.  938,)  the  mid-brain  is  about  11  mm.  in  length, 
although  when  measured  on  the  ventral  surface  it  is  slighriy  shorter  (9  mm. )  and 
on  the  dorsal  aspect  a  little  longer  ( 1 3  mm. ).  Its  greatest  breadth  is  approximately 
23  mm.  The  mid-brain  is  traversed  longitudinally  by  a  canal,  the  Sylvian  aqueduct, 
which,  however,  lies  much  nearer  the  dorsal  than  the  ventral  surface  of  the  brain-stem. 
When  the  several  parts  of  the  brain  are  undisturbed,  only  a  portion  of  the  ventral 
aspect  of  the  mid-brain  can  be  seen.  Its  dorsal  and  lateral  surfaces  are  hidden  by 
the  overhanging  cerebral  hemispheres,  the  splenium  of  the  corpus  callosum  and  the 
puKinar  of  the  thalamus  being  in  close  relation  with  these  surfaces  respectively. 
Notwithstanding  its  ventral  position  and  apparent  removal  from  the  exterior  of  the 
brain  behind,  the  dorsal  surface  of  the  mid-brain  is,  in  fact,  directly  continuous  with 

Kio.  957. 


TriKonum  habenulae 

Pulvinar 
CoUiculus  superior 

Cerebral  peduncle 

Fouith  nerve 

Pons 

Superior  terebellar  |>eduncie 


Tsrnia  thalami 


Commissura  habenulae 
Pineal  btxiy 


Median  geniculate  body 
Brachiuin  inferior 
CoUiculus  inferior 

Frenulum  \v\\ 


Lingula 

Cerebellum,  cut  surface 


Ml  J-hrain  viewed  from  behind  ;  upper  part  of  cerebellum  has  been  removed  to  expose  superior  medullary 

velum  with  lingula. 

and  a  part  of  the  free  posterior  surface  of  the  brain.  It  is,  therefore,  covered  with 
the  pia  mater,  as  may  l)e  demonstrated  by  drawing  aside  the  overhanging  cerebral 
hemispheres.  In  silit  the  mid-ljrain  occupies  the  opening  bounded  by  the  tento- 
rium and  thus  connects  the  divisions  of  the  brain  which  lie  within  the  posterior  cra- 
nial fossa  (ccrebiUum,  pons  and  medulla)  with  those  (cerebral  hemispheres)  that  lie 
above.  Its  cavity,  the  Sylvian  aqueduct,  establishes  direct  communication  between 
the  third  and  fourth  ventricles.  The  mid-brain  includes  two  main  subdivisions,  a 
smaller  dorsal  part,  the  qitadrif;eminal plalc,  which  roofs  in  the  .Sylvian  aqueduct  and 
bears  the  corpora  quadrigemina,  and  a  much  larger  ventral  part,  made  up  by  the 
cerebral  peduncles. 

Tlie  quadrigeminal  plate  lies  Ix^hind  the  plane  of  the  roof  of  the  Sylvian 
aqueduct  and  extends  from  the  base  of  the  pineal  body  alx)ve  to  the  upper  margin 
of  the  anterior  niedullary  xeliim  below.  Its  dorsal  surface  is  subdivided  into  four  white 
rounded  elevations,  the  corpora  quadrigemina,  by  two  grooves,  one  of  which  is 
a  median  longitudinal  furrow  and  the  other  a  transverse  furrow  that  crosses  the  first 
one  at  right  angles  and  slightlv  below  its  middle  point.  The  upper  part  of  the  longi- 
tuilinal  groove,  l>etween  the  iij)per  pair  of  elevations,  broadens  into  a  shallow  trian- 
gular depression,  the  pineal  fossa  ( triKonum  stihpinealc)  in  which  ri*sts  the  pineal 
body.  Below,  the  mid-furrow  ends  at  the  base  of  the  frenum  of  the  superior  medul- 
lary velum. 


THE   MESENCEPHALON. 


1 107 


Pnlrinar 


Superior  collicul 
Inferior  collicul 


Superior  medullary 

h-elum' 

Superior  cerehellar 

peduncle' 

Lin{{u! 


Middle  cerebellar 
peduncle,  cut 


Fig.  958. 

Superior  hrachinm 

Median  geniculate  body 

Lateral  geniculate  hcxly 
Tractus  tranRvcrsus 
Cerebral  pwluncle 
Uptic  tract 


The  elevations  forming  the  upper  pair  of  quadrigeminal  bodies,  the  coUicuh 
auoeripres.  are  the  la^er  and  more  conspicuous,  and  measure  from  7-8  mm.  in 
?en??h   about  10  mm.  in  breadth,  and  6  mm.  in  height.     Laterally  e.ch  superior  col- 
IkuC is  continued  into  an  arm.  the  superior  brachium  (braehium  quadriReminum 
Srius)  which  is  defined  by  a  groove  above  and  below,  and  pa^  upward  and 
^utwlrd    between  the  optic    thalamus  and  the  median  geniculate  body,  to  be  lost 
Shin  aritdStly  cir'!:umscribed  oval  eminence,  the  later,    geniculate  body 
7«™is  «nicttlatum  Uttsrale).  which  lies  beneath  the  pulv.nar.     In  like  manner  «,ch 
ortrsmaUw  lower  pair  of  quadrigeminal  bodies,  the  coll.culi  infenore.  (about 
6  mm   rength  by  8  mm.  in  breadth  and  5  mm.  in   height)  «  prolonged  laterally 
into  the  inferior  brachium  (brachium  qaadrigemioum  Inferius).  which  in  turn  ends 
in  the  sharply  defined  median  geniculate  body  (corpus  Reoiculatummedialc).  an 
oval  elevatbn  about  10  mm.  in  length.      Ventrally  the  quadrigeminal  plate  becomes 
direcdy  continuous  with  the  adjacent  part  of  the  cerebral  pedunclw. 

The  cerebral  peduncles  (peduncuH  cerebri),  also   called  the  cerebral  crura, 
constitute  the  bulky  ventral  part  of  the  mid-brain.      Dorsally  the  two  peduncles  are 
fused  into  a  continuous  tract,  the  tegmentum,  which  contributes  the  side-walls  and 
floor  of  the  Sylvian  aqueduct  and  blends   on  each  side  with  the  overiying  quadn- 
aeminal  plate.     Ventrally  the  peduncles  are  unfused  and  appear  on  the  inferior  sur- 
face of  the  brain  as  two  robust  stalks   (Fig.  993)-     These  emerge  from  the  upper 
border  of  the  pons  and  pass,  diverging  at  an  angle  of  from  70-85°.  upward  and  out- 
ward to  enter,  one  on  each 
siJ.e.  the   cerebral   hemi- 
sphen  -    just   where    the 
peduncles  are  crossed  by 
the   outwardly  winding 
optic  tracts.     At  the  pons 
each   peduncle   possesses 
a  breadth  of  from  12-15 
mm.,   which  increases  to 
from   18-20  mm.    at  the 
upper  end  of  the  stalk  ;  the 
borders  of  each  peduncle 
are.  therefore,    not   quite 
parallel,  but  slightly  di- 
verging.    Neither  are  the 
mesial  margins  of  the  pe- 
duncles in  contact  as  they 
issue  from  the  pons,  but 
separated  by  an  interval 

disUnceSn^cr«i™;  unTJ  at  their  upper  ends  the  peduncles  are  about  n  «"«"•  apart. 
SSrciaUy  each  peduncle  is  formed  by  strands  of  fibres  which  do  not  pursue  a 
stricriy^on^tudinal  course,  but  wind  spirally  from  withm  outward  ;  in  consequence 
of  this  arrangement  the  surface  of  the  peduncle  presents  a  characteris  ic  twisted  or 
roi-Hke  strfation.  The  regularity  of  this  marking  is  sometimes  disturb  by  a 
Smlv  defined  strand  of  ribr«  (tractus  peduncularis  transversus)  that  winds  over  the 
m«  an  border  and  ventral  surface  of  the  peduncle,  passes  upward  and  outward  ac  oss 

hf  hteral  swfacc  of  the  mid-brain,  to  te  lost  in  the  vicinity  of  the  medial  geniculate 
todv  The  depressed  triangular  area  included  between  the  diverging  V^duncles  is  the 
Soeduncular  fossa,  the  floor  of  which  is  pierced  by  numerous  minute  openings 

h-tftSm"  small  bloo<Uessels,  and  hence  is  known  as  the  posterior  perforated 
substance  The  blunted  inferior  angle  of  the  fossa,  ""'""^'f -■'>' .'''^Y  .'.S 
corresponds  with  a  depression,  the  recessus  posterior;  another,  but  less  market 
Ss  "     the  recessus  anterior,  is  Ix.unded  by  the  postero-med.an  surfaces  o 

'r  ma  nn  illary   bodies.      A  shallow   lateral   groove  (sulcus   mcscncepha.    lateralis 
extends  along  the  outer  surface  of  the  peduncle,  whilst  al.Mig  its  inner  aspect,  .md 
Sore  looking  into  the  interpeduncular  fossa,  runs  the  median  or  oculomotor 
groove  (sulcus  ner>i  oculomotorius ^  that  is  more  distinct  than  the  lateral  furrow  and 


Dono-lateral  aspect  of  mid-brain. 


i 


i 


1108 


HUMAN  ANATOMY. 


marks  ihe  line  along  which  the  root-fibres  of  the  third  cranial  nerve  emerRe.  On 
transverse  section  ( Fig.  963)  these  furrows  are  seen  to  correspond  with  the  edges  of  a 
crescentic  field  of  deeply  pigmented  gray  matter,  the  Bubatantia  nigra,  by  which 
each  peduncle  is  subdivided  into  a  dorsal  portion,  the  tegmentum,  and  a  ventral 
part,  the  crusta  (basis  pedunctili).  The  latter  lies  ventral  to  the  superficial  lateral 
and  median  furrows,  and  contributes  largely  to  the  bulk  of  the  free  part  of  the 
peduncle.  When  traced  upward  it  is  found  to  enter  the  cerebral  hemisphere  and 
become  continuous  with  the  internal  capsule.  It  contains  the  great  motor  tracts  and 
is  the  chief  pathway  by  which  efferent  conical  impulses  are  transmitted  to  the  lower 
lying  centres.  The  tegmentum,  on  the  contrary,  in  a  general  way  is  associated 
with  the  sensory  tracts,  and,  above,  enters  the  subthalamic  region  (page  1 127). 

The  dorao-lateral  surface  of  the  mid-brain,  just  where  it  passes  into  that  of 
the  superior  cerebellar  peduncle,  shares  with  the  latter  a  triangular  area,  the  trigo- 


FiG.  959. 


Emerging  6bra  of  fourth  nerve 
Fourth  nerve,  cut 

Lateral  fiUet 

Posterior  longitudinal 
laiwiculus 

Tegmental  field 
Mesial  fillet 


. ition  of  fourth  nerve 

.Sylvian  aqueduct 

Central  Kray  mbstancc 

Mesencephalic  root  of  trigen.  jus 

Subatantia  ferruglnea 

Superior  cerebellar 

peduncle 

Decussation  of  cerebellar 

peduncle 


P\'ramidal 


Transverse  fibres 


Transverse  section  of  hrain-stem  at  level  L  (Fig.  919).  lunctlon  of  pons  and  mid-brain  :  superior  cerebellar  pedun- 
cles are  heKinning  to  <lecussale ;  trochlear  decussation  seen  above  Sylvian  aqueduct.  Weigert-Pal  slaiuing.  a  3. 
Preparation  by  Profensor  Spiller. 

num  lemnisci,  which,  as  implied  by  its  name,  is  related  to  the  underlying  and 
here  siperficially  placed  tract  of  the  fillet  (lemniscus).  Above,  this  area  extends 
as  far  as  the  inferior  brachium  and  is  limited  in  front  by  the  sulcus  mesencephali 
lateralis,  whilst  behind  it  is  defined  from  the  superior  cerebellar  peduncle  by  a  slight 
furrow  (sulcus  limitans  posterior).  When  closely  examined  the  triangular  field  is  seen 
to  be  subdivided  by  a  faint  groove  into  an  upper  and  a  lower  area,  which  correspond 
with  the  underlying  fibres  of  the  lateral  and  of  the  mesial  fillet  respectively.  A 
superficial  strafid  of  fibres,  the  tractus  peduncularis  transversus,  is  sometimes  seen 
crossing  the  lateral  surface  of  the  mid-brain.  It  appears  on  the  dorsal  aspect  of  the 
latter,  between  the  inferior  brachium  and  the  median  geniculate  body,  winds  around 
the  latero-ventral  surface  of  the  peduncle  and  disappears  in  the  vicinity  of  the 
mammillary  body.  According  to  Marburg,  the  strand  establishes  a  connection 
between  the  optic  tract  and  a  nucleus  in  the  floor  of  the  third  ventricle  and  represents, 
in  a  rudimentary  condition,  the  ba.sal  optic  root  found  in  many  animals. 

The  Sylvian  aqueduct  (aquaeductus  cerebri)  represents  the  cavity  of  the  middle 
brain-vesicle  and,  therefore,  is  lined  with  an  ependymal  layer  continuous  above  and 
below  with  that  clothing  the  interior  of  the  third  and  fourth  ventricles.     As  seen  in 


THE  MESENCEPHALON. 


1109 


croM-sections.  (Fig.  960)  its  outline  in  a  general  way  b  tnangiilar.  with  the  baa* 
^eTnd  t^;  apex  dii^Uy  below  ;  but  the  contour  oJ  the  canal  vane,  a  rf^^?^ 
feVeb.  being  tiianguUr  near  its  extremities  and  irregularly  cordilorm  or  elliptical  m 
the  intervening  part  of  its  course. 

INTERNAL  STRUCTURE  OF  THE  MESENCEPHALON. 

Disregarding  the  several  small  nuclei,  the  nuclei  of  the  corpora  quadrigemnw 
.nA  the  r^nudei  the  gray  matter  within  the  mesenc^halon  is  disposed  as  three 
^rts  thafextend  the  emfre  length  of  the  mid-brain,  these  are  the  tubuhr  mass 
7^cc^rSgray  matter,  which  surrounds  the  aqueduct,  and  the  two  crescen Uc 
foxZnTollh/sJstantia  nigra,  which  subdivide  the  peduncles  mto  the  tegmental 

*"'*S'Slll\r.y  matter  (stratum  gris«m  centrale)  completely  encloses 
the  cavity  of  the  mid-brain  and  hence  is  often  called  the  Syh.an  gray  '"^f^-  J^ 
conS  numerous  irregularly  scattered  nerve-cells  of  uncertam  form  and  s  ze 
^r^^ng  its  ventral  Wderf  the  nuclei  of  origin  of  the  «<;:;^°  "l^^^^il'^f'^^^^ 
nerCes ;  within  '-  lateral  parts  lie  the  nuclei  from  which  proceed  the  fibres  of  the 
mesencephalic  roots  of  the  trigeminal  nerves. 

Fig.  96a 


Interior  collicalot 


Mcseticcphmlic 
root  of  trigeminus 

Lateral  fillet 


Fibre*  of  fourth  nerve 


Sylvian  aqueduct 


I ^  Centra!  «™y»uh»tanie 


Posterior  longitudinal 
fasciculus 


Fountain  decussation 


Mesial  fillel 


'^r^'.y- 


■  Cerebellar  peduncle 
nerwnation  of  cerebeltor  peduncle 


Transverse  section  of  dorsal  par.  of  ""»«'"  'hj^Kh'^^j.^d^j^'J^'^^il^^P^^  "seating"' X  ''5' 
showing  nucleus  of  trochlear  nerve,  and  decussation  of   cerebellar  peauncie.      vieigti.r.. 
Preparation  by  Professor  Spiller. 

The  substantia  nigra  is  disposed  as  two  irregular  crescentic  columns  of  dark 
.y  matter  that  separate  the  tegmentum  from  the  crusta-  of  the  peduncles.  Ihe 
substance  begins  below  at  the  upper  border  of  the  pons  and  continues  uninterruptedly 
through  thVlength  of  the  mid-brain  into  the  subthalamic  region  of  the  diencephalon, 
where  it  gradually  disappears.  The  deep  color  of  this  tract  is  due  to  the  conspicuous 
pigmentation  of  its  numerous  nerve-cells.  These  cells  are  of  medium  size  and  of 
various  form,  spindle-shaped  elements,  interspersed  with  some  of  stellate  and  a  few 
of  pvramidal  form,  predominating.  They  enclose  consulerable  accumulations  of  dark 
brown  pigment  that  render  the  cells  unusually  conspicuous.  During  t^^e  eariest 
vear-  of  childhood  the  pigmentation  is  absent  or  very  slight  but  after  the  sixth 
year  it  is  marked,  and  by  the  seventeenth  has  acquired  its  full  intensity,  been  in 
cross-sections  (Fig.  961),  the  convexity  of  each  column  directed  forward  and  out- 
ward, is  not  uniform,  but  brt)ken  into  irregular  scallops  by  processes  of  gr^y  m.-itter 
that  penetrate  the  subjacent  crusta.  The  concave  dorsal  margin  on  the  contrary,  is 
unbrSen  and  even.  The  horiis  of  the  crescentic  area-s.  of  «h.ch  the  "ledmn  is 
somewhat  the  thicker,  approach  the  free  surface  along  the  Ixrttom  of  the  superficial 


I  no 


HUMAN   ANATOMY. 


I 


lateral  and  median  grooves  of  the  mid-brain.  Concerning  the  functions  and  connec- 
tions of  the  neurones  within  the  substantia  nigra  very  litde  is  known. 

The  Quadrigeminal  and  Geniculate  Bodies. — The  infer.or  colliculua 

consists  chiefly  of  a  biconvex  (in  section  oval)  mass  of  gray  matter,  the  nucleus 
coUiculi  inferioris,  in  which  many  nerve-cells  of  varying  form  and  mostly  of  small 
size  lie  embedded  within  a  complex  of  nerve-fibres.  The  lower  end  of  the  nucleus 
stands  in  intimate  relation  with  the  acoustic  fibres  composing  the  lateral  fillet,  many 
of  which  enter  the  ventral  aspect  of  the  nucleus  colliculi  to  end  around  its  cells,  whilst 
a  considerable  number  pass  superficial  to  the  nucleus  and  thus  form  an  external  fibre- 
layer  that  intervenes  between  the  gray  nucleus  and  the  surface.  Although  many  of 
these  external  fillet- fibres  enter  the  coUiculus  at  higher  levels,  not  a  few  continue, 
by  way  of  the  inferior  brachium,  to  the  median  geniculate  body,  around  whose  neu- 
rones they  end.  A  much  smaller  and  less  well  defined  tract  of  fillet-fibres  passes  to 
the  mesial  side  of  the  nucleus,  the  ventral  margin  of  which  is  thus  embraced  (  Fig.  960) 
by  the  diverging  but  unequally  robust  fillet-strands  that  in  this  manner  partially 
encapsulate  the  collicular  nucleus.  From  the  supero-lateral  parts  of  the  nucleus 
fibres  proceed  which,  in  conjunction  with  those  continued  from  the  lateral  fillet, 
form  the  chief  constituents  of  the  inferior  brachium.  A  part  of  this  anr.  how- 
ever, is  composed  of  strands  of  fibres  that  pass  from  the  cerebral  lortex  (especially 
the  temporal)  to  the  inferior  coUiculus.  Towards  the  upper  pole  of  the  nucleus 
some  loose  strands  of  fillet-fibres,  probably  along  with  commissural  fibres  uniting 
the  inferior  colliculi,  cross  the  mid-line  and  establish  a  decussation. 

The  internal  or  median  geniculate  body  (corpus  Kcniculatum  mediate), 
although  genetically  belonging  to  the  diencephalon,  is  so  closely  related  to  the 
inferior  coUiculus  as  to  require  description  in  this  place.  It  consists  of  a  superficial 
layer  of  white  matter  composed  of  fibres  from  the  inferior  brachium,  which  pass 
outward  as  >  ntinuations  of  the  lateral  fillet,  as  axones  of  the  cells  of  the  inferior 
coUiculus,  or  /..  nbres  forming  the  lateral  root  of  the  optic  tract,  also  known  as  the 
inferior  commissure  of  Gudden.  Within  this  fibre-capsule  lies  an  oval  mass  of 
gray  matter,  the  nucleus  corporis  geniculati  medialis,  from  whose  cells  axones 
proceed  chiefly  towards  the  cerebral  cortex  in  continuation  of  the  auditory  paths 
of  which  the   inferior  coUiculus   and   the   median   geniculate  body  are   important 


stations. 


1 


Connections  of  the  Inferior  CoUiculus  and  Median  Geniculate  Body.— Mention  has  been 
made,  when  describing  the  reception-nuclei  of  the  cochlear  portion  of  the  auditorj-  nerve  ( (xige 
1076) ,  that  the  tract  of  the  lateral  fillet  takes  oripn  to  an  important  extent  from  the  cells  of  these 
nuclei,  and,  further,  (page  1082),  that  the  fillet-fibres  end  around  either  the  cells  of  the  inferior 
coUiculus,  or  thosi  of  the  median  geniculate  body.  It  is  evident,  therefore,  that  these  parts  of 
the  mid-brain  stand  in  intimate  relation  with  the  parts  concerned  in  conveying  auditoo'  impulses. 
The  more  detailed  account  of  the  chaining  together  of  the  neurones  forming  sucli  paths  is 
deferred  until  the  auditory  nerve  is  considered  (page  1257)  The  connection  of  the  fibres  com- 
posing the  median  root  of  the  optic  tract  with  the  median  geniculate  body  and  the  inferior  coUic- 
ulus has  been  established  beyond  doubt ;  further,  that  this  pan  of  the  optic  tract  is  not  concerned 
in  conducting  visual  impulses,  is  shown  by  the  fact  that  these  fibres  remain  unaffected  under 
condi-ions  1  after  removal  of  the  eyes)  that  lead  to  degeneration  of  the  fibres  of  retinal  origin. 
The  destination  and  significance  of  the  fibre-systems  included  within  the  median  root  of  the 
optic  tract  are  only  imperfectly  understood,  but  it  may  be  accepted  as  certain  that  they  can  no 
longer  be  regarded  as  merely  establishing  a  bond  between  the  median  geniculate  and  indirectly 
the  inferior  quadrigeminal  bodies  of  the  two  sides,  as  implied  by  the  name  commissure,  since 
many  of  these  fibres  are  probably  directed  after  decussation  to  the  lenticul.ir  nucleus  (globus 
pallidus),  while  others  possibly  may  end  on  the  same  side  in  the  subthalamic  nucleus  ( p.iKe  1128). 
The  gray  matter  of  the  inferior  coUiculus,  like  that  of  the  superior,  gives  rise  to  fibres  of  the 
tecto-buibar  and  tecto-spinal  tracts,  presently  to  be  described  (page  iiii). 

The  superior  coUiculus  is  composed  of  a  number  of  alternating  layers  of  white 
and  ^rav  matter.  The  latter,  however,  is  not  aggregated  into  a  definite  nucleus,  as 
in  the  case  of  the  inferior  coUiculus,  but  is  broken  up  into  uncertain  zones  by  the 
tracts  of  nerve-fibres.  Although  as  many  as  seven  layers  have  been  described, 
some  of  these  are  so  blended  that  only  four  weU-defined  strata  can  be  readily 
distinguished.     From  the  surface  inward  these  are : 


THE   MESENCEPHALON. 


lilt 


"""•  r'^r.C'^c^^u2::^l^hT,l;>ruffi::  but  .^^^  a„U  n-t  .nar..c.  over  U« 

celU  contained  '" '*>  *  j^P  "r/[,7^„    whilst  their  dendrite*  are  directed  ,*npherally.     I  he 
:^j:l  r-  --  cX^'el^irS  of  «ray  matter,  but  is  invaded  by  nu.ny  meduUated 

nerve-fibres. ,„^^-   «.hich  consists  of  a  complex  of  gray  matter  and  ner^e-fibres, 

u    .  ^   ^^^iS^tr^nrTe'rived  frL  the  optic  tract  which  gain  the  side  of  the  colliculu. 
the  latter  mdudmKsn^n<lsde^^^^^^  P^  continuations  of   the  optic  fibres,  or  aft.r 

by  way  of  ♦^«.^"'^"°',  "^i'T,e  body     That  this  stratum  includes  other  fibres,  is  shown 
lrtrro:;l^e'trowlmen  t'::!  ^^aylr  in  conditions  producing  degeneration  of  the 


Fig.  961. 
Sylvian  iqiKduct 


Inferior  colUcalui 


Ccntnl  (ray  suhMancc 


Inferior  brmchium 


Posterior 

lonRiludinal 

fasciculiM 

Tegmental  field 

Lateral  aulcu* 


Foantain  dccuwtation 


Mesial  fillet 
Det-UHsation 
of  cerebellar 
peduncles 


Substantia' 

niRra,  separat- 

inK  crusta  from 

tegmentum 


Motor  tracts 


Stratum 
Intemicdium 


rcrebellar 
peduncle 


Pontine    Interpeduncular     SubsUntia 
fibres  spaie  nigra 


Crusta  of 
peduncle 


^ ,  „ij  hrain  at  level  N  (Fig.  919) :   decussation  of  cerebellar  peduncles  is  )u»t  ending. 

Transverse  «=ct.on  '^^^^}p,{'l^^Slg      <y    1>^ration  by  Professor  Spiller. 

ontir  oaths  as  well  as  by  the  prominence  of  parts  of  the  stratum  in  animals  Pofessing  only 
ri^rmenS  4ua  \^ths^Edinger).  The  stratum  opticum.  however,  consists  by  "o  "  eans 
exclusSof  fibres,  but  contains,  especially  in  its  dee,,er  p..rt.  numerous  nerve-cells  of  large 
size,  around  which  the  end-arborizations  of  the  optic  fibres  terminate  intersnerse<l 

A  The  stratum  lemnisci,  which  likewise  includes  masses  of  gray  matter  '"'er'P^r^" 
betw^n  the  sS^of  n"rve-fibres.  The  latter  are  chiefly  from  that  part  of  the  median  fillet 
whicrtermtn^te  "with  n  the  superior  colliculus ;  a  certain  numl^r  of  the  fibres,  hp^p^  -  f^^ 
;^^lb  derived  f"m  the  late^fillet.  which,  while  having  its  principal  ^'-d-'. -^^  "  "^'"^ 
with  the  inferior  colliculus,  also  sends  a  small  contingent  to  the  upper  Ixxly.  I  r .  ^'f  P^^  ^^^ 
of  the  fiUet^ayer  contains  k  considerable  amount  of  gray  matter,  m  which  numero..  nerve-cells, 

''^"''':^':li:m;:ll1r;^vS'5^'^^^^  the  gray  matter  of  the  colliculus  gives  origin 

tc  ^nm^rlant  system  of  dScending  fibres  which  establishes  connections  (between  he  "'  <1-''^-'  " 
and "rCer  S  of  ?he  brain-stem  and  the  spinal  cord.  These  fibres  emerge  from  the  v^n- 
?ral  b^rderof  the  colliculus  as  radiallv  disposetl  strands  which,  on  nearing  the  K^ay  matter 
suio^ndrng  theaqueduct.  turn  ventrally.     The  more  laterally  situated  fi^-;.  -'  ,2"t  th 

h.V^  from  the  onIx>^it^-  -ide  desrpml  within  the  tearmenta!  field  to  end  partly  in  r.  lation  witl 
l^em  cTei  withinX  b;ain-st;^  (tractu.  t«tn-bulbaris  Utetj.!..^  and  partly  with-n  t .    ;^mal  cord 

tra««s  ..cto.,pina..s  later.!..),    ^he  mediaUy  situated  fibres  sw;eep  arotmd  the  S^ 
matter  and,  for  the  most  part,  cross  the  raphe  imrned.ately  ^^"♦"'"^^.'^XTnrther  course 
fasciculus,  thus  establishing  the  fountain  decussation  of  Meynert  ( Fig.  96"'    T  he  further  course 


1 1 12  HUMAN   ANATOMY. 

of  these  fibres  is  downward  tlirougli  the  brain-stem  and  into  tlie  anterior  column  of  the  cord 
(tractus  lecto-spinalis  medialis).  \Vhether  these  fibres  are  interrupted  in  small  secondary  nuclei 
within  the  tegmentum,  or  pass  unbrokenly  from  the  collicular  cells  to  the  cord  is  undetermined. 
It  is  probable  that,  as  constituents  of  a  spino-tectal  path,  fibres  also  ascend  from  the  spinal  cord 
to  the  quadrigeminal  bodies.  According  to  Kolliker,  some  of  the  radial  fibres  are  traceable 
through  the  tegmentum,  passing  to  the  outer  side  of  the  red  nucleus  and  piercing  the  tract  of 
the  median  fillet,  and  into  the  substantia  nigra,  whose  cells  they  probably  Join  as  axones.  The 
commiuure  of  the  superior  colliculi  is  formed  by  fibres  that  cross  the  mid-line  to  the  opposite 
quadrigeminal  body  and  probably  includes,  in  addition  to  the  axones  of  cells  within  the  colliculi 
themselves,  fibres  from  the  fillet  and  optic  tracts. 

The  most  important  connections  of  the  superior  colliculus,  as  may  be  anticipated  from  the 
foregoing  description  of  its  structure,  are  : 

I.  With  the  optic  tract,  directly  or  indirectly  from  the  lateral  geniculate  body,  by  way  of 
the  superior  brachium.  2.  With  the  cerebral  cortex  of  the  occipital  lobe  by  way  of  the  superior 
brachium  and  the  optic  radiation  (page  1175).  3.  With  the  posterior  sensory  colunms  of  the 
spinal  cord,  indirectly  by  way  of  the  median  fillet.  4.  With  the  cochlear  nuclei  by  way  of  the 
lateral  fillet,  thus  establishing  a  path  for  audito-visual  reflexes.  5.  With  nuclei  of  the  third, 
fourth  and  sixth  cranial  ner\'es,  controlling  the  eye-muscles,  especially  the  oculomotor,  by  way 
of  the  posterior  longitudinal  fasciculus.  6.  With  the  lower  levels  of  the  brain-stem  and  the 
spinal  cord  by  way  of  the  tecto-bulbar  and  tecto-spinal  tracts. 

The  lateral  geniculate  body  belongs  to  the  diencephalon  and  may  be  regarded  as  a  special- 
ized part  of  the  tfptic  thalamus  ;  the  consideration  of  its  structure  therefore,  properly  falls  with 
that  of  the  metathalamus  (page  11 26). 

The  Tegmentum. — The  tegmental  regrion  of  the  mid-brain  includes,  as  seen  in 
transverse  sections  (Fig,  961),  the  U-shaped  area  extending  from  the  quadri- 
geminal bodies  behind  to  the  crescents  of  the  substantia  nigra  in  front.  In  the  vicin- 
ity of  the  central  gray  matter  that  surrounds  the  Sylvian  aqueduct,  the  tegmentum 
consists  chiefly  of  a  foundation  resembling  the  formatio  reticularis  seen  at  lower 
levels.  This  substance  is  produced  by  the  intermingling  of  transverse  or  arcuate  and 
longitudinal  fibres  and  a  meagre  amount  of  gray  matter  with  irregularly  distributed 
ner\'e-cells,  that  fills  the  interstices  between  the  strands  of  nerve-fibres.  The  more 
lateral  and  ventral  parts  of  the  tegmentum  are  to  a  large  extent  occupied  by  the 
prominent  fibre-tracts  belonging  to  the  fillets  and  to  the  superior  cerebellar  peduncles, 
or  by  collections  of  gray  matter,  as  the  red  nuclei.  Special  groups  of  nerve-cells 
and  of  nerve-fibres  mark  the  origin  and  course  of  the  oculomotor  and  trochlear 
nerves. 


■11 
111 

"1 


« 


The  details  of  the  tegmentum  vary  with  the  level  of  the  plane  of  section.  Thus,  at  the  lower 
end  of  the  mid-brain  the  tracts  of  the  cerebellar  peduncles  approach  the  mid-line  as  they  ascend 
and  those  of  the  fillets  assume  a  more  lateral  position  ;  whilst  at  higher  levels  these  tracts,  which 
lower  in  the  mid-brain  are  so  conspicuous,  either  terminate  to  a  large  extent,  or  become  so 
broken  up  as  to  no  longer  form  impressive  bundles. 

In  sections  passing  through  the  lower  pole  of  the  inferior  quadrigeminal  bodies  (Fig.  960), 
the  zone  overlying  the  substantia  nigra  is  occupied  to  a  great  extent  by  the  median  fillet,  which 
here  appears  as  a  broad  but  thin  crescentic  or  comma-shaped  field,  whose  outer  and  thicker 
end  lies  at  the  peripher>'  and  abuts  against  the  base  of  the  dorsally  arching  tract  of  the  lateral 
fillet.  At  the  inner  end  of  the  median  fillet,  near  the  mid-line,  an  isolated  group  of  obliquely 
cut  fibres  sometimes  indicates  the  position  of  the  lemnisco-crustal  bundle  that  appears  ventrally 
among  the  robust  strands  of  the  crusta.  Taken  together,  the  two  fillets  form  a  compact  tract, 
the  outer  contour  of  which,  at  the  level  now  considered,  resembles  a  horizontally  pl.iced  Oothic 
arch,  the  summit  of  the  curve  lying  at  the  surface  and  the  lower  and  upper  limits  of  tht  arch 
tieing  the  median  and  lateral  fillets  respectively.  The  lateral  fillet  continues  the  sweep  of  the 
fillet-stratum  along  the  peripher)-  of  the  tegmentum  until  it  embraces  the  lower  pole  of  the 
inferior  colliculus  in  the  manner  previously  described  (page  1110). 

Dorsal  to  the  tract  of  the  median  fillet,  and  separated  from  the  latter  by  a  thin  layer  of  com- 
pact foundation-suttstance,  the  ventral  tegmental  field,  lies  the  broad  curved  band  formed  by 
the  blending  of  the  two  superior  cerebellar  peduncles.  At  lower  levels  (  Fig.  936)  these  stalks 
are  separate  and  appear  as  laterally  placed  and  conspicuous  crescentic  areas  of  transversely  cut 
fibres  ;  hut  opposite  the  lower  limit  of  the  inferior  quadrigeminal  bo<lies  the  ventral  ends  of  these 
crescents  meet  at  the  mid-line  and  interlace  to  form  the  decussation  of  the  cerebellar  peduncles. 
At  a  slightly  higher  level,  after  their  decussation  has  been  almost  completed  (Fig.  961),  the 
cereliellar  peduncles  appear  as  prominent  rectangular  fields,  with  rounded  comers,  on  each 
side  of  and  close  to  the  mid-line.    These  fields  of  transversely  cut  fibres  represent  the  peduncles 


THE  MESENCEPHALON. 


1113 


-rf  .„  ,      ,-.(   .iirlei   in  which  a  larce  number  of  their  component  fibres  end. 
asthey  pas.s  upward  to  ....r  ■     .ucle^    he  teRmental  field  and  above  (behind)  the  peduncular 

P^ct'Ts  s^^thi  X^rbngTudinal  faLlcX.  which  here,  broader  than  in  the  pons  passes 
tract,  IS  seen  tne  P""^^""",""  „„.,„„  _f  .u^  trochlear  nerve.  The  'tnuated  crescentic  tract 
close  to  the  ventral  s.de  °'j,.^-,,P;/^^  °  ^e  fate^l  mar^^  of  the  cent.  .,1  gray  substance,  n,edial 
of  transverely  "^f  ^J^^Xoi^co  icuC^re^^^  the  mesencephalic  root  of  the  trigemin.il  ,Hr%e. 

,0  *e  nucteus  of  the  .nfe nor  ^^^,P^^  .  ,,„„^,^^  of  obh^uely 

^tTbr  marlTe't'llM^^^^^  course  of  the  fourth-nerve  to  gain  its  decussation  m  ther... 
of  the  aqueduct  at  the  lowest  limit  of  the  mesencephalon  (Fig.  959)- 

Fig.  962. 


Caudate  nucletti 


Anterior  nucleus 


Thalamus' 
Ventral  nucleoi. 


Pulvinar 
Posterior  commissure 

Pineal  body 
Sylvian  gray  matter 
Corpora  quadrigemina 


Posterior  longit-dinal 
fasciculus 

Superior 
medullary  velum 


Cerebellum 


Fourth  ventricle 

Fibres  of 
abducent  nerve 


Floor  of  IV  ventricle 
(medulla) 
Kormatio  reticularis 

Internal  arcuate  fibre* 
Nucleus  cuneatua 

Nucleus  Kracilis 
Posterior  fasciculi 


Internal  capsule 

External 
medullary  lamina 

lenticular  nucleus 

Stratum  medulLire 
hypothalamicuni 
Tuber  cinereuni 

Optic  commissure 


Crusta and  substantia  nigra 
(latter  to  left ) 

Red  nucleus 

Fibres  of  oculomotor  nerve 
Superior  cerebellar  peduncle 
.Ponto-cerebellar  tracts 


Pyramidal  tracts 
Mesial  fillet 


Inferior  olivar>'  nucleus 


Sagittal  section  of  brain-stem  ;  plane  of  section  i,  '-mewhat  lateral  to  mid-line. 
■  by  PrnlesMtr  Spilier. 


j.    Pretmrnlion 


As  seen  in  cross-sections  passing  through  the  superior  ^l^^^^t^T'"'""' ^''^1^;;;;';^%''^,^^^ 
the  tegmentum  differ  considerably  from  those  at  the  levels  P'.^^''°";'>- *'*'tf  •..^''^^.^1    *e  con 


1 1 14 


HUMAN   ANATOMY. 


i 


i.ua 


9 


The  most  conspicuous  object  within  the  tegmentum  in  the  superior  half  of 
the  mid-brain  is  a  large  round  reticulated  field  on  each  side  of  the  median  raphe, 
which  marks  the  position  of  the  red  nucleus  (nucleus  ruber).  This  body,  also 
called  the  nucleus  tcgmenti,  is  of  an  irregular  ovoid  form  (Fig.  963)  and  of  a  reddish 
tint  when  seen  in  sections  of  the  fresh  brain.  Its  lower  limit  corresponds  with  the  level 
of  the  lower  margin  of  the  superior  colliculus,  whilst  its  upper  pole  extends  into  the 
subthalamic  region.  Its  diameter  increases  towards  the  upper  end  and  its  long  axis 
converges  as  it  ascends,  so  that  the  upper  enlarged  portions  of  the  two  nuclei  lie 
close  to  the  mid-line  and  nearer  each  t>ther  than  do  the  lower  poles.  Each  nucleus 
consists  of  a  complex  of  gray  matter  and  nerve-fibres.  The  latter  preponderate 
below,  where  the  red  nucleus  receives  the  fibres  of  the  superior  cerebellar  peduncle, 
and  are  much  less  numerous  above,  since  many  fibres  come  to  an  end  around  the 
rubral  cells.  These  elements  are  very  variable  in  shape  and  size  (.020.-060  mm.), 
but  are  most  often  irregularly  triangular  or  stellate.     The  red  nuclei  constitute  not 

Fig.  963. 


turtle  fibivs  joining 
su[)CTior  coUii  ulus 


thaluutf 


Part  of  iiiettiAn 
IfrnicuUte  nucleus 

MnlUn 

t:riii(ulate  Iwdy 


VMitro-lat«T«l 
tiiicl«i«  of' 
thiril  n< 


Knot  (iht«s  of 
third 


Lateral  ifcnkulatr  hodjt 
^ratuni  intcrinediiiin 


■Crmtoofcetebml  |*,iiincle 
Suhslailtla  nllira 


Fnierirdlir  flhwt  of 
otultmuitf-r  nerve 

Transversa  section  of  midbrain  at  level  O  (FIr.  9l9).|nMinK  through  superior  colliculus  »nd  Reiiiciilatc  bodies; 
red  nucleus,  itnl  nuclei  and  root-fibres  of  oculomotor  nerve.  Welgert-P»l  staininf.  X  3-  Preparation  by  Professor 
Spiller. 

only  important  stations  in  the  path  connecting  the  cerebellum  and  spinal  cord,  but 
also  probably  contribute  links  in  chains  uniting  the  cerebral  cortex  and  the  internal 
nuclei  with  the  cord.  Whilst  some  fif  the  constituents  of  the  superior  cerebellar 
peduncle  |>a.ss  around  the  red  nucleus  and  continue  as  ccrcbello-thalamie  fibres  uninter- 
ruptedly to  the  optic  thalamus,  the  majority  of  the  fibres  of  this  arm  end  around  the 
ceils  of  the  nucleus.  Of  these  many  give  off  axones  that  i)roceed  brainward  as  rubro- 
thalamic fibres  ;  others  emerge  from  the  ventro-medial  surface  of  the  nucleus,  cross 
the  mid-line  (decussation  of  Korel )  and  bend  downward  as  the  rubro-spinal  tract. 
The  latter  descends  within  the  tegmentum  of  the  mid-brain  and  pons,  traverses  the 
niithilla  and  finally  enters  the  lateral  column  of  the  cord  as  one  of  the  important  but 
un<  <  riainly  defined  descending  tracts.  Other  fibres  enter  the  red  nucleus  on  its 
lateral  aspect  and  establish v^onnections  between  the  cerebral  cortex  (Dejerine),  and 
proiwbly  also  the  corpus  striatum  (Edinger),  and  the  nucleus.  P'rom  the  cells  of 
the  latter  the  path  is  continued  hv  fibres  which  join  the  rubro-spinal  tract,  and  in 
this  manner  establish  an  indirect  motor  path  that  supplements  the  cortico-spinal 
tracts  identified  with  the  pyramidal. 


THE   MESENCEPHALON. 


1115 


The  Crusta.— The  crusta,  or  pes  pfdunculi.  appears  in  transverse  sections 
,  v\.r  ohx  \  as  a  bold  sickle-shaped  field  that  occupies  the  most  ventral  portion  of  the 
Sbr^n'Ttco^fstscSieflyononKitudinallyco^^^ 

fhe  internal  capsule,  are  pacing  from  various  parts  of  the  cerebral  cortex  to  louer 
evels  in  The  brain  stem  andthe  spinal  cord.  The  lonRitudmal  hbres  are  separated 
•  y  LinHl^  bv  the  invasion  of  numerous  strands  frum  the  tibre-comple.x.  known  as 
Tstratm^'Uer^^^^^  which  lies  along  the  ventral  border  oj  the  substantia 
nigra      Thrfibres  of  the  crusta  comprise  three  general  sets:  the  rortuo-fion/n.e,  the 

^''''thetorticoVonUn^^^^^^^^^  those  passing  from  the  cells  of  the  cerel.al 

rt.v  to  the  cells  of  the  m.ntine  nucleus  as  links  in  the  cortico-cereliellar  paths, 
Thev  are  repr2nt«l  by  the  fronto-pontine  and  the  temp,ro.o<dpito-ponUne  tracts, 
trrULova^ro^mately  the  median  and  lateral  fifths  of  the  crusta  respectively. 
Se  coS'^bSrbar-fibres  include  the  efferent  strands  ^hich  p=u.s  from  the  motor 
IreL  ofVhe  fronul  lobe  to  the  nuclei  of  the  motor  fibres  originating  in  the  bulbar  portion 
f.f  the  brain'stem  (trigeminal,  abducent,  facial,  glosso-pharyngeal,  vagus  and  hypo- 
^ols^l  ne^es)  ThL  tracis  occupy  something  less  than  the  hfth  of  the  crusta 
SfnextThe  ronto-pontine  tract.  The  cortico-spinal  fibres  include  the  great 
motor  sfrirds  which  as  the  pyramidal  tracts,  are  so  conspicuous  at  lower  levels. 
ThSe  Vhare  with  the  fronto-bulbar  paths  the  middle  three-hfths  of  the  crusta. 

iDDTO'  pproximately  the  lateral  three-quarters  of  this  area  (  Hg.  loi  2 ) . 

appro  ^     ^.^^  Fillet.— Repeated  reference  has  been  made  to  the  median  fillet 

n-mni^      medialis )  in  the  preceding  descriptions  of  the  brain-stem  ;  a  general  con- 
id"a"on"o7S Tmi^^rmtLnsory  tract  ma^  here  be  given      It  begins  at  the  lower 
part  o    "he  meduul,  about  on  a  level  corresponding  with  the  upper   imit  of  the 
otramWal  decussation,  as  axones  of  the  cells  within  the  nucleus  gracilis      These 
^wetpventro  medially  as  the  deep  arcuate  fibres,  for  the  most  part  cross  the  ra,,he 
and  bend  sLply  brainward.     Succeeding  the  condensation  of  the  ^  et-tibres  into 
the  Sisorv  d^ussation  (Fig.  922)  which  marks  the  lowest  hmit  o    the    ract.  the 
Set  receLconlTnuous  additions  ««  ^^'^^'^t^  ^^'"^  ^'"""^  .^^  RJ'*'^' ^ '"?'•  ^T 
nuc  ei^    o^g  as  these  collections  are  present.     On  reaching  the  inferior  o  ivary 
Tele    Z  its  journey  brainward,  the  fillet  forms  a  laterally  compressed  tract    the 
U^^olivarv   stratum     lying    immediately    dorsal    to    the    pyramids    (Pg.    928). 
TowaSs  S^e  uVper  end  of  fhe  pons,  the  fillet  gradually  exchanges  its  s^igittal  plane 
and  m«lian  position  for  an  obliquely  horizontal  disposition,   with  an    'ncreasng 
tendenS  to  migrate  laterally.     The  fibres  arising  from  the  nucleus  cuneatus   wh  ch 
Sow  c^cupied  the  ventral  part  of  the  fillet,  now  constitute  the  lateral  part  of    he 
St    St  those  from  the  nucleus  gracilis  form  its  medial  portion.     Within  the 
r^d  br^in  the'median  and  the  lateral  fillets  form  a  continuous  crescent.c  tract  which, 
wUhin  the  up^rpart  of  the  tegmentum  and  after  the  disappearance  of  the  acous  c 
Shs  is  reprinted  chiefly  by  the  superficial  and  lateral  y  placed  tract  «1  'ch  the 
San  fil  et  has  now  become.     A  considerable  part  of  its  hbres  end  around  the  cells 
of  the  deeper  gray  stratum  of  the  superior  coUiculus,  some  passing  over  the  aque- 
duct to  thTcoLulus  of  the  opposite  side.     The  remaining  fibres  continue  upward 
through  the  tegmentum,  late  J  and  dorsal  to  the  red  nuc  eus  and  the  subthalamic 
rSn   to  te  minate  chiefly  in  relation  with  the  cells  within  the  ventral  part  of  the 
ODtictimu        After  such  interruption  the  impulses  are  earned  bv  hbres  arising 
Sn  the  thalamus  to  various  parts  of  the  cerebral  cortex.     Whether  hllet-fibres 
Sn The  coriJ^l  grav  matter  without  interruption  within  the  thalamus  is  uncertain. 
Other  fibr^  said  to  W  derived  from  the  cuneate  nucleus,  end  m  the  corpus   subtha- 
lanicum  a^dd^elenticular  nucleus  ( globus  pallidus)  from  whose  cells  a  -r  am  num- 
bT  oHbres  proceed  by  way  of  a  strand  placed  alxive  the  optic  ch.asin,  the  com- 
missure of  fileynert.to  the  globus  ,«llidus of  the  opposite  side.    Still  <.thor  hbres 
^e"raceable  into  the  posterior  commissure  of  the  brain  and  into  the  mamm.Uary 

'^'^The  constituents  of  the  median  fillet,  however,  are  by  no  means  restricted  to 
the  fibres  arising  from  the  gracile  and  cuneate  nuclei  of  the  PJ-ter-r  -luninO^^^ 
intude  numerous  important  accession,  In.in  the  rec*:ptinn-nuclci  of  ;.ll  the  scns"r> 
cranial   nerves  connected  with  the  brain-stem.     From  the  cells  within  the  more 


iii6 


HUMAN   ANATOMY. 


extensive  of  such  nuclei,  as  those  within  the  column  of  substantia  gelatinosa  accom- 
panying the  spinal  root  of  the  trigeminus,  numerous  arcuate  fibres  sweep  towards  the 
raphe  and,  with  few  exceptions,  cross  to  join  the  median  fillet  of  the  opposite  side. 
In  this  manner  provision  is  made  for  the  transmission  to  the  higher  receptive  centres 
of  sensory  impulses  collected  not  only  by  the  strands  of  the  posterior  column  of  the 
cord,  but  also  by  the  sensory  fibres  of  the  cranial  nerves  attached  to  the  brain-stem. 
Although  the  principal  components  of  the  fillet-tract  are  the  bulbo-tecto- 
thalamic  strands,  some  fibres  running  in  the  opposite  direction  are  also  present. 
Some  of  these  probably  arise  from  cells  within  the  optic  thalamus  and  the  corpora 
quadrigemina.     Others  are  efferent  strands  which   establish  connections  between 

the  cortical  gray  matter  and 
the  nuclei  of  the  motor  cranial 
nerves,  especially  the  facial  and 
hypoglossal.  These  cortico- 
bulbar  tracts  descend  within 
the  crusta  to  the  lower  end  of 
the  cerebral  peduncle ;  then, 
leaving  the  latter,  they  traverse 
the  stratum  intermedium  and  in 
the  upper  part  of  the  pons  join 
the  median  fillet  and  descend 
within  its  ventro  -  median 
part  as  far  as  the  superior  end 
of  the  hypoglossal  nucleus. 
During  their  course,  the  fibres 
of  this  cnistal  fillet,  as  it  is 
called,  for  the  most  part  undergo 
decussation  on  reaching  the 
levels  of  the  motor  nucleus  for 
which  they  are  destined  ;  some 
fibres,  however,  possibly  end 
around  the  cells  of  the  nucleus  of 
the  same  side. 

The  Posterior  Longi- 
tudinal Fasciculus.  —  This 
bundle  (fasciculus  longitudinulis 
dorsalis)  is  an  association  path 
of  fundamental  importance,  be- 
ing present  in  all  vertebrates.  As 
a  distinct  strand  it  begins  in  the 
superior  part  of  the  mid-brain 
and  thence  is  traceable  as  a  con- 
tinuous tract  through  the  teg- 
mental region  of  the  pons,  the  dorsal  and  lateral  "ventral  field  of  the  medulla  into  the 
anterior  ground-bundle  of  the  spinal  cord.  Throughout  the  greater  part  of  its  course 
through  the  brain-stem,  its  position  is  constant,  the  fasciculi  of  the  two  sides  lying 
close  to  the  median  raphe  and  immediately  beneath  the  gray  matter  flooring  the  Sylvian 
aqueduct  and  the  fourth  ventricle  (Figs.  959,  961).  In  the  lower  part  of  the  medulla, 
the  bundle  gra  .aally  leaves  the  ventricular  floor  and  rests  upon  the  dorsal  border  of 
the  median  fillet,  and,  at  the  level  of  the  pyramidal  decussation,  where  the  fillet  no 
longer  intervenes,  lies  behind  the  pyramid  and  at  some  distance  from  the  mid-line. 
Lower,  it  assumes  a  more  ventral  position,  to  the  medial  side  of  the  isolated  anterior 
cornu,  and,  finally,  enters  the  anterior  column  of  the  cord  to  be  lost  within  the  upper 
part  of  the  ground  bundle. 

The  f.xsciculus  includes  association  fibres  of  varying  lengths,  some  of  which  are 
ascending  and  others  descending  paths.  The  constitution  of  the  bundle  is,  there- 
fure,  continually  chanxiaj;,  tlic  loss  of  certain  fibres  being  replaced  by  the  addition 
of  others.  Its  fibri'S  are  among  the  very  first  in  the  brain  to  become  medullated,  and 
liegin  to  acquire  this  coat  during  the  fourth  fcEtal  month  (  Hiisel). 


Superior  coltlculus 


SenNory  decussatioii 

Posterior  nuclei 
Posterior  tracts 

Spino-thalamic 
Spinal  ganglion 


Diagram  showing  chief  afferent  constituents  of  median  fillet. 


(senHory  part) 


I.\.  X  nerves 

(sensory  part) 


THE  MESENCEPHALON. 


III? 


Fig.  965. 


Notwithstamlin.  the  admitted  i-porta„«  oMhe  -f^^^-f^^V^^.l^'^'ir^^^^         iS 

rir:sir.e%^T;:ix^^^^^^^^^^^^ 

^"TKe'u7;"^nd^ortHTrrc.ts  .  -Id«.«e^-^r^o^^^^^^^^^^  the  ceHs 

of  the  nudeu.  of  .h.  I^*"""  "Ti'^^C t^r  ^t-^^dfng    he  ^^^"r'rend  of  the  Sylvian 
t:^T:'''TZ^^k^:^  '^^SrSngent  tales  origin  fron,  a  nuc.eus  (n.  fa. 
d™inon«it«din.lU  dorMll.)  whhin  the  gray  matter  of  the 
fl^r  of  the  third  ventricle  in  the  vicinity  of  the  corpus  mam- 
mUlare.    The  contributions  from  both  these  sources  ,om 
Se  f^iculus  as  crossed  fibres  from   the  nude,  of  the 

°PP°fVte  fibres  arising  from  the  vestibular  (Deiters) 
nucleus  constitute  an  important  element  of  the  ^sterior 
longitudinal  bundle,  since  they  estebhsh  reflex  paths  for 

^uilibration  impulses.  T''^  fi''"=^>  .'t^  "^,^,io„, 
uncrossed,  join  the  fasciculus  and  pass  m  both  directions^ 
S  pling  brainward  have  as  their  chief  objective  point 
L  ocilomoTor  nucleus,  although  the  nuclei  of  the  sixth 
and  fourth  nerves  receive  fibres  or  collatera  s.  In  this 
manner  the  filaments  supplying  the  various  ocular  musdes 
Tre  brought  under  the  influence  of  the  vestibular  impulses. 
I,  is  pmbable  that  the  facial  nucleus  likewise  receives 
collaterals,  if  not  main  stems,  of  the  vesjibulo-nuclear  fibr^ 
V  Upon  dinical  and  experimental  evidence,  it  may  be 
as.sumed  that  fibres  pass  by  way  of  the  longitudinal  bundle 
^Tthe  abducent  nucleus  to  that  part  of  the  oculomotor 
nucleus  sending  fibres  to  the  internal  rectus  tn-f  ^  °  *e 
opposite  side  (perhaps  also  from  the  nucleus  of  the  third 
^er^to  that  of  the  abducens  of  the  same  side),  by  which 
arrangement  the  harmonious  action  of  the  internal  and 

eSal  recti  musdes  is  insured.     Basing  their  '^J^f^^^-^ 

upon    similar    evidence,    many    anatomists    accept    the 

e^tencLof  fibres  which  pass  by   way  of  the  p*»tenor 

longitudinal  bundle  from  the  oculomotor  nucleus  tothe  cells 

of  the  facial  nucleus  (page  125 «)  f™"'^**"^''  P'^  cwnieator  superdlii.    In  this  manner 

fibres  supplying  the  orbiculans  P»'Pf''"™",.""VJLto~SSrL  su^^^^^^  -xp'^ined.    A 

the  coordinated  action  of  th«je  «"J^^'^^''  '  ,  J  "^^^^^^^^  bundle  between  the 

.  similar  connection  is  P'°t'^'''y  f  ^"'*^~  ^e  faciaT^iierve    whereby  the   closely  a.ssociated 

nucleus  of  the    hypoglossal  and  that  of  the  '*S1?^'  "f^^:   *J^,„  Jf  the  posterior  fasciculus 

areas  lietween  the  afferent  and  efferent  paths.  ««ociation  fibres  the  various  levels  of 

cerebellum. 

DEVELOPMENT  OF  THE  MESENCEPHALON. 

of  the  cerebral   hemispheres  in  man,  the  mid-brain  becomes  co^e  j,  ,^.,g 

s^:r!S^r  iisrjti^ntn.  ii°"-r.ES5n  i  ,»,«.„  ,«o,„« 

eventually  reduced  to  the  narrow  Sylvian  aqueduct. 


OiaKTam  sh.)»i>i|!  ihief  consliluents 
of  pcteriorlongiludinal  fasciculus.  111. 
IV^I  VII,  XI!.  iiuclri  of  respective 
nerves •'  DN,  vestibular  (Deilersl  im 
cleus-  CN,  common  nucleus  of  posterior 
commissure  and  posterior  longitudinal 
bsciculus. 


III8 


HUMAN   ANATOMY. 


The  dorsal  zones  of  the  lateral  wall  of  the  mid-brain  give  rise  to  the  quadrigeminal  plate, 
whose  external  surface  is  at  first  smooth  but  later  marked  by  a  temporary  median  longitudinal 
ridge.  AUtut  the  third  ftetal  month,  with  the  exception  of  its  lower  end,  which  persists  as  the 
frenulum  veli,  this  ridge  is  succeeded  by  a  longitudinal  groove  bounded  on  either  side  by  an 
elevation.  The  elevations  of  the  two  sides  mark  the  appearance  of  the  corpora  bigemina,  cor- 
responding to  the  optic  lobes  of  the  lower  vertebrates.  During  the  fifth  month,  an  obliquely 
transverse  furrow  forms  on  each  side,  by  which  the  paired  elevations  are  subdivided  into  four 
eminences,  the  corpora  quadrigemina.  About  this  time  the  corpora  geniculata,  which  however 
belong  developmentally  to  the  diencephalon,  are  also  differentiated  and  for  awhile  are  rela- 
tively very  large  and  prominent. 

The  ventral  zones  greatly  thicken  and  give  origin  to  the  tegmentum,  including  the  nuclei 
of  the  oculomotor  and  of  the  trochlear  nerves  and,  perhaps,  the  red  nuclei,  and  the  mantle  layer 
of  the  cerebral  peduncles  with  the  interpeduncular  substance.  The  floor-plate  becomes  com- 
pressed between  the  expanding  ventral  zones  of  the  l.-iteral  walls  and  probably  is  represented 
by  the  raphe.  Since  the  fibre-systems  of  the  crustae  are,  for  the  most  part,  derived  from  sources 
nutside  the  brain-stem,  their  appearance  within  the  peduncles  follows  a  secondary  ing^rowth, 
and  only  after  such  invasion  do  the  cerebral  crura  present  their  characteristic  ventral  prom- 
inence. The  cortico-pontine  tracts  share  with  the  pyramidial  fibres  the  characteristic  of  tardy 
niyelination,  since  they  do  not  acquire  their  medullary  coat  until  some  time  after  birth.  Among 
the  eariiest  of  the  cortico-bulbar  fibres  to  become  medullated  ( a  few  weeks  after  birth )  are  those 
destined  for  the  motor  cranial  nerves  by  way  of  the  crustal  or  pyramidal  fillet  of  Flechsig. 
.According  to  Kolliker,  the  stratum  intermedium,  which  is  closely  related  to  the  substantia 
nigra,  not  only  in  position  but  also  by  the  destination  of  many  of  its  fibres,  contains  a  consider- 
able number  of  medullated  fibres  by  the  ninth  foetal  month. 

THE   FORE-BRAIN. 

It  will  be  recalled  that  the  fore-brain,  the  anterior  primary  cerebral  vesicle,  gives 
rise  to  two  subdivisions,  the  telencephalon  and  the  diencephalon  (page  1060).  Since 
the  latter  lies  immediately  in  front  of  the  mid-brain,  in  following  the  order  in  which 
the  brain-segments  have  been  described,  the  diencephalon  next  claims  attention. 

THE   DIENCEPHALON. 

Strictly  considered  upon  the  basis  of  the  classic  subdivision  suggested  by  His,  the 
diencephalon,  or  inler-drain,  includes  (i)  a  large  dorsal  portion,  the  thalamen- 
cephalon  and  (2)  a  small  ventral  portion,  the  pars  mammillaris  hypothatni, 
together  with  ( 3 )  the  enclosed  remains  of  the  posterior  part  of  the  cavity  of  the 
fore-brain,  as  represented  by  the  greater  part  of  the  third  ventricle.  The  thalamen- 
cephalon,  in  turn,  includes  :  (a)  the  thalamus,  (^)  the  epithalamus,  comprising  the  . 
pineal  Ixxiy,  the  habenular  region  and  the  posterior  commissure,  and  (r )  the  meta- 
thalamus,  including  the  corpora  geniculata.  Since,  however,  the  description  of  the 
third  ventricle  and  its  surrounding  structures — the  essential  features  of  this  segment 
of  the  adult  brain — requires  the  inclusion  of  parts  belonging  to  the  telencephalon 
( pars  optica  hypothalami),  it  will  be  more  convenient  to  disregard  their  strict 
ilevclopmcntal  relations  and  include  the  representatives  of  the  pars  optica  in  the 
consideration  of  the  diencephalon. 

The  Thalamus. — After  removal  of  the  overlying  structures — the  corpus  callo- 
suin,  the  fornix  and  the  velum  interpositum — the  thalami  (thalami),  also  called 
the  optic  thalami,  are  seen  as  two  conspicuous  masses  of  gray  matter  separated  by  a 
narrow  cleft,  the  third  \entricte.  Each  th.tlamus  is  an  ovoid  ganglionic  mass,  blunt 
wedge-shaped,  .is  seen  in  crr>ss-sections  (Fig.  967),  whose  long  axis  extends  from 
the  narrow  anterior  pole  backward  and  outward.  Of  its  four  surfaces,  the  lateral  and 
ventral  are  blended  with  the  surrounding  nervous  tissue,  and  the  mesial  and  dorsal 
are  to  a  large  extent  free.  The  large  superior  surface  is  irregularly  triangular 
in  (iiidine,  slightly  convex  in  the  frontal  plane  and  markwily  so  in  the  s.-igittal,  and 
covered  with  a  thin  layer  of  nerve-fibres,  the  Stratum  zonale,  which  imparts  a 
whitish  color.  This  stratum  is  compose<l  of  fibres  which  are  traceable  on  the  one 
hand  to  the  optic  tract,  and  on  the  other  to  the  optic  radiation  in  the  hind  |)art  of 
the  internal  r;ip>sii!<-.  T.;itrra!ly,  thr- suporinr  surface  ih  separated  from  the  caudate 
luicleus  by  a  gro<)\e  which  f)bliquely  crosses  the  floor  of  the  lateral  \entriclc  and 
lodges  a  narrow  band  of  fibres,  the  taenia  semicircularis  (stria  terminalis)  and,  in 
its  anterior  part,  the  vein  of  the  corpus  striatum.     In  its  front  half,  where  it  bounds  the 


THE  DIENCEPHALON. 


1 1 19 


ventricle  the  inner  border  is  sharply  defined  from  the  m^sia  surface  by  a  delicate  hut 
weU  defined  r^dge,  t«nia  th-iami.  produced  by  ine  thickening  of  the  ependyina 
nf  heS  ventricle,  alo-.g  its  line  of  reflection  onto  the  membranous  roof  and 
1  Underlying  strand  of  nerve-fibres,  the  stria  medullaris.  Traced  backward,  the 
tenia  Sami  becomes  continuous  with  the  stalk  of  the  P'"«»l  b'^y.  B'^^^'-'^" 
^i^  ridge  and  the  diverging  mesial  border  of  the  upper  surface  of  the  thiJamus.  is 
nduded  a  narrow  depr^Jd  triangular  area,  known  as  the  tngonum  habenul« 
It  li«  on  a  distinctly  lower  level  than  the  adjoining  convex  upper  surface  of  the 
ha lamus  Since  it  contains  a  special  nucleus  and  belongs  to  the  epithalamus,  its 
dc'Sion  will  be  deferred  until  that  region  is  considered  page  .  .23).  The  upper 
surface  s  not  quite  even,  but  subdivided  by  a  shallow  oblK,ue  furrow,  which  runs 
from  before  backward  and  outward  and  marks  the  position  of  the  over  ving  latera 
border  of  the  fornix.  External  to  this  hirrow  lies  a  free  marginal  zone  that  forms  a 
mrt  of  the  floor  of  the  lateral  ventricle  ;  internal  to  it  is  an  attached  inner  zone  ov^t 
ffich  the  velum  interpositum  is  united  to  the  thalamus.     By  the  attachment  of  this 


lie.  966. 


.Corpus  canoKtim 


Septum  ludduia 

Taenia   semicircularis  and 
vena  terminaliii 

Ttenia  chorloidea 
Furrow  for  fornix 

Tsnia  Ihalami 

Trigonum  habenulK 

Pulvinar 


Corpora  quadrigeniina 


Caudate  in    leus 

Anterior  pillars  of  fornix 
Foramen  of  Monro 

Anterior  commissure 

Middle commiHHurc  in  HI 
ventricle 

Thalamus 

Posterior  commissure 
Pineal  Iwily 


l.iMfi^ila 


sheet  to  the  fornix  above  and  to  th-  thalamus  below,  direct  communication  between 
the  tWrd  and  kteral  ventricles  is  shut  off  save  through  the  foramen  of  Monro.  In 
fron  he  su^rior  surS ends  on  the  rounded  elevation  (tuberculum  antenus  thalam. ) 
wSh  maXr  anterior  pole  of    the  ganglion.  -^^^^^^Z^ 

fmmediate  lining  of  the  ventricle,  the  ependyma.     The  upper  boundary  of  the  r.Rs  al 
3  Sts  sharply  define.l  hv  the  ta-nia  thalami,  which  behind  is  continuous  w.  h  tlu- 
mlk  of  the  ^i^eal  body  (Fig    966).     Us  lower  limit  is  i"^-;^;;',,^'^^:;^  "lie 
furrow,    the  sulcus    hypothalamicus.   which   separates   the    Jf^si-i   surf-ices 
hvnothalamic  re^nons.      Somewhat  in  advance  of  their  middle,  the  mesial  surlaits 
dihe  two  thalami   are    r  .nnected  bv  a   bridge  of   gray   matter,    known   as   the 
middle  comSure  (massa  intermedia),  usually  about  7-S  mm.  ,n  diameter juu 
Tvai  in  section,  but  very  variable  in  thickness  and  form.     F--"»he  -eagre  numlx 
of  medullatcH  nrrve  fibres  that  it  contains,  its  importance,  at    cas    m  "i- "•  ,^  '  "^ 
to  brsm'in      The  lateral  surface  of  the  thalamus  is  inseparab  y  blended  w.tl.   lu- 
adiacenT  hick  and  conspicuous  stratum  of  white  matter,  the  internal  capsule 
which    nten.eni  between  the  thalamus  and  the  more  laterally   placed  lenticular 


m.  k:1 


HUMAN   ANATOMY. 


nucleus,  and  establishes  the  important  pathway  transmitting  the  fibre-tracts  con- 
necting the  cerebral  cortex  with  the  thalamus  and  with  the  lo^^L•r  levels  by  way 
of  the  crusta  of  the  cerebral  peduncle.  Since  the  innumerable  fibres  which  pass 
to  and  from  the  thalamus  along  its  ventro-lateral  surface  interlace,  this  surface  is 
covered  by  a  distinct  reticulated  stratum,  to  which  the  name  external  medullary 
lamina  is  applied.  The  ventral  surface  is  also  attached,  but  instead  of  being 
imited  with  the  internal  capsule,  as  is  the  lateral,  it  rests  uf>on  and  is  intimately 
blended  with  the  upward  prolongation  of  the  tegmental  portion  of  the  cerebral 
peduncle,  here  known  as  the  subthalamic  tegmental  region,  presently  to  be 
described  (page  1127). 

Fig.  967. 


Mifhlle  c<iiiimis.sure 

Third  ventricle 

Mammillo-thalaniic 

tract 

Mammillary  body 


Caudate  nuclcUH 


Thalamus, 
mesial  nucleuA 


Thalamus, 
lateral  nucleus 

Lenticular  nucleufl 

Subthalamic 
nucleus 

Optic  tract 


Tail  of 

caudate  nuclwa 
Inferior  horn  of 
lateral  ventricle 


Hippocampus,  cut  obliquely 
Crusta  of  cerebral  peduncle 

FronUl  section  of  brain  passing  through  thalami.  middle  commissure  and  mammillar}'  bodies. 

Structure  of  the  Thalamus. — Although  composed  chiefly  of  gray  matter, 
the  thalamus  is  partially  surrounded  and  penetrated  by  tracts  of  white  matter.  In 
addition  to  being  invested  on  its  superior  and  ventro-lateral  surfaces  by  the  stratum 
zonale  and  the  external  medullary  lamina  respectively,  the  general  ganglionic  mass 
is  subdivided  by  a  vertical  internal  sheet  of  fibres,  continuous  with  the  stratum  zonale 
and  known  as  the  internal  medullary  lamina,  into  three  fairly  marked  nuclei, 
the  anterior,  the  mesial  and  the  lateral  (Fig.  967).  Of  these  the  lateral  nucleus  is 
much  the  largest  and  is  included  between  the  external  and  internal  medullary  lamina. 
Whilst  the  later.il  nucleus  does  not  reach  as  far  for^vard  as  the  anterior  pole  of  the 
thalamus,  its  caudal  extremity  includes  the  entire  pulvinar.  The  lateral  nucleus 
consists  histologically  of  an  intricate  complex  of  nerve-fibres  and  cells.  The  latter 
are  in  general  of  the  multipolar  type,  although  \ery  \ariable  as  to  details  of  form 
and  size.  Two  principal  types  are  recognized  by  Kiilliker,  the  one  being  elongated 
or  fusiform  and  possessed  of  relatively  few  branches,  and  the  other  being  stellate  and 
provided  with  richly  branched  dendrites.  Many  of  the  fibres  represent  paths  ending 
within  the  thalamus  ami  therefore  terminate  in  arborizations  around  the  thalamic 
cells  ;  others  are  the  axones  of  such  cells  and  pass  to  various  parts  of  the  cortex  or 
other  parts  of  the  brain.     The  histological  characteristics  of  the  lateral  nucleus,  in  the 


THE  DIENCEPHALON. 


lilt 


■    i,«IH   m«'  for  the  other  nucld.  although  the  lateral  nucleus  is  paniculariy 

'■•••rher^iI^1;cl.^s:•^t:^^^r  C~V  o.  .he  v„t,icuu, 

r.s.^Ti^^^-^^^vrth^tis'nS'n;^^^^^^^^^^ 
'ss^t^.?^'n:£co^9^^^-i^^^^^^ 

S.";?h2.S  ".«^S^'<1^  X  >  2;r  "*c£  a  large  par.  o.  the  hht» 


Fig.  968- 


Corpus  caUodum 
Choroid  plexus 
Latenl  ventricle 
Stratum  zonsle 
Caudate  nucleus 
Genu  of  internal  capsule 
Thalamus,  mesial  nucleus 

Thalamus,  latiil 
nucleuA 

Internal  capsule 


PttUmi 


Gyrus  callosus 

Cingulum 

Corinu  calloaum 

iriate  vein 


Caudate  nucleus 

Taenia  semidrcularls 


Internal  medullary 
lamina 


Globua  pallidus 


Anterior  pillars  of  fornix 

l.amina  dnerea 


External  medul- 
lary lamina 

Mammillo- 
tbalamic  tract 


Futamen 
Globus  pallidus 


Thalamo-tegmental 
'    tract 


Olfactory  6br«s 


Anterior  cnrnmiasarc 


Oblique  frontal  section  through  thalamus  and  snterior  commissure ;  Weigert-Pal  MainiuR.    X  |. 
^  Preparation  by  Professor  Spiller. 

coursing  within  the  anterior  pillar  of  the  fornix  are  carried  to  the  thalarnus(  page 
„sq  The  entire  ventral  part  of  the  thalamus  is  occupied  by  an  illy-defined  ma^ 
o  gray  matter,  known  as  the  ventral  nucleus  which  lacks  «harp  definition  from 
the  overlying  nuclei  and  in  fact  is  continuous  with  the  lateral  nucleus.  The  ventraJ 
nucleus  Snts  a  differentiation  into  the  nucleus  centralis  of  Luys,  which  occupies 
a  mSal'^^sition  and  appears  round  in  section  (Fj^/o).  a"d  re^^^^^^^ 
the  red  nucleus  and  the  posterior  commissure  and  the  nucleus  «r'=*^°';!?»"; .^"'"^ 
ies  ventro-lateral  to  the  preceding  nucleus  and  is  crescentic  in  ouriine.  The  ^f  nt-^ 
nucleus  is  of  importance,  not  only  because  it  receives  the  great  sensory  paths,  but  a  so 
"^account  of  ite  phylogenetic  rank,  since,  according  to  Edinger.  it,  .together  with  the 
gangUonhabenute,  represents  the  oldest  of  the  thalamic  nuclei  and  is  found  through- 

*'"'*ConnTcSs1)'f^he  Thalamus.-Broadly  considered,  the  thalamus  may  be 
regarded  as  a  great  ganglionic  internode  interposed  ui  the  corticipctal  paths  around 
vwTelU  mSt  of'^the^  constituents  of  the  important  secondary  P^ths  conveying 
aSt   impulses  from  the  spinal  cord,  the  brain-stem  and  the  cerebellum  end, 

7' 


II33 


HLMAxN   ANATOMY. 


: 


and  from  whose  cells  corticipetal  fibres  pass  to  all  parts  of  the  cerebral  cortex 
and  to  the  corpus  striatum.  P'urther,  it  must  be  understood  that  the  thalamus 
receives  fibres  from  all  parts  of  the  cerebral  cortex,  and,  lastly,  that  from  it 
proceed  efferent  fibres  to  the  lower  centres  within  tht  brain-stem  and  the  cord. 
It  is  evident,  therefore,  that  the  connections  of  the  thalamus  are  very  intricate 
and  far  reaching. 

I.  The  lower  thalainocipetal  trmcts  include :  (a)  those  passsing  directly  from  the  spinal  cord, 
as  the  spino-thalatnic  and  probably  a  part  of  Gowers'  tract ;  (b)  those  passing  from  the 
various  nuclei  by  way  of  the  median  fillet;  (f)  those  pa.ssing  from  the  cerebellum,  either 

directly,  as  the  cerebello-thalamic 
Fig.  969.  tract,  or,  after  interruption  in  the 

red  nucleus,  as  the  rubro-thala- 
mic;  (d)  probably  other  tracts 
which  arise  within  the  tegmen 
tal  area  of  the  brain-stem.  The 
fibres  from  the  various  sources 
enter  the  under  surface  of  the 
thalamus  to  end  within  the  ven- 
tral nucleus,  or  by  means  of  the 
internal  medullary  lamina  to  be 
distributed  to  the  other  nuclei. 

2.  The  thalamic  radiation 
comprises  the  fibres  which  stream 
from  the  latero-ventral  surface  of 
the  thalamus  to  all  parts  of  the 
hemisphere  { thalamo-cortical) , 
some  cros.sing  by  way  of  the 
corpus  callosum  to  the  oppo- 
site side,  as  well  as  those  which 
pa.ss  in  the  opposite  direction 
(  corlico-thalamic  )  towards  the 
ganglion.  Although  as  they 
traverse  the  external  medullary 
lamina  the  fibres  are  not  particu- 
larly grouped,  their  various  rela- 
tions to  the  cortex  or  other  parts 
are  established  by  different  and 
more  or  less  definite  paths. 
These  are  designated  as  the 
stalks  of  the  thalamus,  of  which 
a  frontal,  a  parietal,  an  occipital 
and  a  ventral  are  conventionally 
distinguished.  The  anterior  or 
frontal  stalk  emerges  from  the 
fore-part  of  the  lateral  surface  of 
the  thalamus,  traverses  the  an- 
terior part  of  the  internal  capsule 
between  the  caudate  and  lentic- 
ular nuclei,  to  which  it  distributes 
fibres,  and  finally  gains  the  cortex  of  the  frontal  lobe.  From  the  cells  of  this  region,  cortUo- 
Ihalamic  fibres  follow  in  reversed  order  the  paths  just  mentioned,  thus  establishing  a 
double  relation  between  the  cortex  and  the  basal  ganglion.  In  addition  to  the  preceding 
cortico-thalamic  fibres,  the  antero-ventral  part  of  the  thalamus  receives  a  strand  from  the 
cortex  of  the  olfactory  bulb.  The  parietal  stalk  leaves  the  lateral  surface  of  the  thalamus  and 
enters  the  internal  capsule  and  often  the  lenticular  nucleus,  in  'ts  course  to  the  parietal 
cortex.  Other  corticipetal  fibres,  destined  for  the  parietal  and  adjacent  parts  of  the 
frontal  lobe,  are  the  continuations  of  the  path  of  the  mesial  fillet.  To  a  large  extent 
these  fibres  pass  from  the  ventral  thalamic  nucleus  outward  to  the  under  surface  of 
the  lenticular  nucleus,  then  bend  upw.ird  and  traverse  the  lenticular  nucleus  by  way  of 
the  medullary-  strire  or  the  globus  pallidus  to  gain  the  cortex.  Other  fibres  continue  the  fillet- 
path  by  entering  the  internal  capsule  and  thus,  perhaps,  directly  proceed  to  the  cortex.  Tlie 
occipital  stalk  includes  the  fibres  that  connect  the  thalamus  with  the  visual  cortical  areas  of  the 
occipital  and  parietal  lobes.    They  is.sue  from  the  lateral  surfat-e  of  the  pulvinar,  and  as  the 


Median  fillet 
Spino-thalamic 


DiaKram  showtnfc  chief  connections  of  thalamus ;  lilack  fibres  rep- 
resent afferent  tracts  endinK  in  thalamus  and  thalanio-i-ortical  paths; 
red  fibres  are  the  cortico-thalamic  and  strio-thalamic  paths;   /.thal- 


amus; C.  /,,  caudate  and  lenticular  nuclei;  C  ^'.corpus  callosum; 
/■.  /',  7;  O,  frontal,  patietal,  temporal  and  occi[>ital  lolws ;  Fx^  fornix; 
J/.  mammillar>'  body;  Pd,  cerebral  peduncle;  SC,  IC,  superior  and  in- 
ferior collicuti ;  A*,  red  nucleus ;  Ps,  pons  ;  /.  frontal  stalk ;  2,  parietal 
stalk  ;  J,  /,  lenticular  and  temporal  parts  of  ventral  stalk  ;  5,  occipital 
•talk. 


THE    OlENCKFHALON. 


«>-,^ 


ventricle  to  end  in  the  cortex.     Ihe  '«"""•""         .   K  ,  ^u^..^.^  „f  ,he  thalamus, 

include  two  systems^  ^;"-'«:«  j'","^; t. rp^«s  d.  u^w^S  and  ou.v.ard  Umath  the 
from  the  lateral  »'«',.~'^  ""^^'^'k*.,;,  ^^tir-.^w  pedunculari.,  c.mtinues  laterally  into 
lenticular  nucleus.  U.  '"*"i',^'^;,X'';^;,„l  IoIk-  ;  itV  u,n*r  ,«.rt.  the  ansa  UntkHtarn. 
r  ?"I^:\he  adi3.lr1i'r  o  0^  iSal  nucleus  wh^i.  Inters  to  Rain  the  ,.utan...,. 
closely  skirts  the  ''"'■'^*^"*  "V™, ;' ,,'     _„.,„„,  ,,..  way  of  the  medullary  laminif.  to  reach  the 

direct  route  of  the  '"'«=™»',f' ."T'''^;  .,  ,^^„  „,  ^hite  matter  which  covers  the  superior  aspect 

3.  The  .tratum  »«>".•»«•  »h«  thin  '-^V"  «  7^^^^,  fibresderiveil  from  the  optic  tract  or  the 

"'  '"'^  '"iTon"'  Th.^'f'rom  tlTc Cra    rtf""  .Kct  su,.rficially  cro.s  the  external  genic- 

optic  radiation     Th<«*  ''"■"/.";;.  "TL       „hile  those  from  the  .x:cipital  cortex  by  way  of  the 

t^.'^:^^^^z'X^:''^^^^rr'''-  -  ^^  —  --"=  '-'-"^  '''-- 

f^m  the  temporal  cortex  by  way  of  the  ventral  stalk. 

TheEoithalamus.-rnder  this  suMivision  of  the  thalamencc-phctlon  are 
•  I  J  1  (^^i^^triironum  habenulw,  (2)  the  pineal  body,  and  (3)  ^S^^  posterior 
riSn-i  Srum^^^  as^K^iated  with^he  su,x.rior  and  posterior  Ix^un- 

daries  of  the  third  ventricle. 


Fic.  97" 


Veins  of  r.alen  in 
velum  inlerpositum 


nannlion  hahenula: 


External 
medtillary  lamina 


Internal  capsule 


Optic 
tract 


Subthalamic  nucleus 


Oblique  fronUl  «Cion  thmuKh^thaJlamu- and  ,uWb^aU,m 


Weigert-Pal  staining.    X  |. 


Th-  trigonum  habenulae  is  the  narrow  trianRular  area  Iv-nR Jf  «^;;n  ;J^ 
sharpy  dSed  edge  (t*.iia    thalami)   of  the  ventnctilar  -^-^^'^^f^.^i^^ 
dive^ginK  mesial  border  of  the  upper  surface  of  the  \ha  -ni"^,,';;™  '>,„'a^'£hS  i; 
Its  surface  is  depressed  and  at  a  lower  leve   than  that  of   ho  thalamus  ^^^^^^\ 
continuous  with  a  mesially  curvinR  strand    the  pmeaj^dt^nclc-e^^^^^^^^ 
ridge  of  thickened  ependyma  marking  the  taenia  thalan";   ^..1  .nd  c"  ire"by 
of  ner^.e-tibres,  the  stria  mcduUaris.  while  at  a  still  '^'i^^^l^^'''^,.^'''^^^ 
the  superficial   fibres  is  situated  an  aggregation  of  ^'^'''!  "*l\^;'^.^1^,,3l"rU 


1 1 24 


HUMAN   ANATOMY. 


m  > 


til 


-:h 


:,  ;5: 


lucidum  and  the  olfactory  area,  and  (  2 )  cartiro-habeHiilar  fibres,  which  spring  from 
the  cortical  cells  within  the  hippocampus  or  the  adjacent  region,  and  by  way  of 
the  fornix  and  its  anterior  pillar  are  carried  to  the  fore-end  of  the  thalamus,  whence 
they  pass  backward  within  the  medullary  striii.  (3)  ^M^tx  tkalamo-habenular fibres 
als«>  probably  join  the  stria  medullaris  from  the  interior  of  the  thalamus.  Whilst  many 
of  the  fibres  compf>sing  the  stria  end  around  the  cells  of  the  ganglion  habenular, 
some  continue  backward,  without  interruption,  within  the  strand  known  as  the 
jxtluncle  of  the  pineal  Ixxly,  cross  to  the  other  side  in  the  bundle  bearing  the 
name,  commissura  habenulce,  and  end  in  relation  with  the  cells  of  the  opposite 
habenular  nucleus.  The  g-anglion  habenulo-  (Fig.  970),  in  turn,  gives  origin  to 
an  im|}ortant  bundle,  the  fasciculus  retroflexus  of  Meynert,  which  arches  down- 
ward and  backward,  pa.ssing  at  first  between  the  central  gray  matter  of  the  third 
ventricle  and  the  thalamus  proper,  and  later  to  the  medial  side  of  the  red  nucleus, 
to  reach  the  base  of  the  brain,  and  for  the  most  pwrt  to  end  around  the  cells  of  the 
interpeduncular  ganglion.  This  nucleus,  which  in  many  animals  is  a  well-defined 
collection  of  cells,  in  man  is  represented  by  a  more  scattered  median  cell-group 
within  the  posterior  perforated  substance  close  to  the  anterior  border  of  the  pons. 
The  fasciculus,  also  termed  the  habenulo- peduncular  tract,  receives  contribu- 
tions from  the  ganglion  habenula;  of  both  sides,  some  fibres  having  cro.~-sed  in  the 
habenular  commissure ;  although  the  majority  of  its  fibres  end,  mostly  crossed,  in 
the  interpeduncular  ganglion,  not  a  few  may  be  traced  farther  caudally  within  the 
tegmentum  of  the  brain-stem  (Obersteiner),  as  may  also  the  fibres  from  the  cells 
of  the  ganglion  interpedunculare. 

The  Pineal  Body. — The  pineal  body  (corpus  pineale),  also  often  called  the 
epiphysis,  is  a  cone-shaped  organ,  from  8-10  mm.  in  length,  attached  to  the 
posterior  extremity  of  the  roof  of  the  third  ventricle.     It  is  slightly  compresseil  from 

above  downward   and 
Kio.  971.  rests,    with    its    apex 

pointing  backward,  on 
the  dorsal  as|}ect  of  the 
mid-brain  in  the  trian- 
gular pineal  depression 
between  the  superior 
corpora  quadrigemina 
(Fig.  966).  Its  base, 
as  its  anterior  end  is 
called,  is  attached 
abcve  to  the  comml  - 
sura  habenulze,  from 
which  on  each  sidf  a 
narrow  but  distinct 
ridge,  the  pineal  stalk, 
curves  forward  to  be- 
come continuous  with 
the  stria  medullaris. 
Below,  its  base  is  united 
with  the  posterior  com- 
missure of  the  brain 
overlyine  the  entrance 
into  the  ylvian  aqi;e- 
duct.  Between  the 
habenular  and  posterior  commissures  a  small  pointed  diverticulum,  xhc  pineal  recess, 
e.xtends  from  the  third  ventricle  for  a  \  ery  short  distance  into  the  pineal  body, 
and  thus  recalls  the  early  condition  in  -vhich  .he  organ  is  de\eloped  as  a  tubular 
outgrowth  in  the  roof-plate  of  the  diencephalon.  This  relation  to  the  thin  ventricular 
roof  the  body  retains,  its  apex  later  becoming  closely  surrounded  by  and  embedded 
within  the  loose  vascular  tissue  of  the  pia  '.sater. 

The  structure  of  the  pineal  body,  as  seen  in  cross-section  (Fig.  971 ),  includes 
a  reticular  framework  of  connective  tissue  trabecuke,  whose  meshes  are  tilled  with 


Calcare  m-, 
ci)iicrt;i<»ii 


Connect 
tisHut  .^1 


St'ction  of  pineal  body  showinfr  calcareous  conrreliohti  ur  braiii  sand.     X  l,v>. 


i   t' 


THE    DIENCKPHAI.ON 


>>25 


l.riitKular  urta  \ 
Retinal  area 


Blood 


Uiverticulom 

dividinK  into 

tubnla 


lal  ••ctlon  of  pinnil  orgmn 
nnbr\o. 


Lacerla  agilii) 


1         .  A    .,;t»,«i;il  r.-lU   which  ofu-n  contain  bmwnish  pin- 
n.unaecl  or  so^etu^e,  e..n«.U^q.t^^^^^  ,H.-  anu-rior  ,«rt.  ,,roba.,1v 

:;::::;ath!i^'in':;r:K;,:!;:;d\.itLa ..  the  h...u.^k  .-..  a  ae„.c  nct-woru  o. 

neuroKlia  fibres  in  the  L.iider  piirt,  ,,-,^j   ,., 

the  pineal  b<Kly  contains  no   ele- 
ments of  a  nervous  character,  ncr\c- 
cells  beinK   alisent.      (Juite   com- 
monly th-    ?'lult  or^an  encloses  a 
variable    ,..  i  iber    of   concretions, 
often  csiWeddrai'i-sandi  acenu/us ), 
which  consist  of  laminated  particles 
composed    of    calcium    carbonate 
and  phosphate  mingled   with    or- 
ganic material.     They  may  be  ij^ 
microscopic  dimensions,  or  reach 
the  size  of  a  millet  seed,   and  by 
aggregation  assume  a  mammillated 
form. 

The  significance  of  the  pineal 
iKxly  loHB  remained  an  unsolved 
riddle  and  served  as  the  theme  for 
unrestrained  speculation.  » "^  em- 
bryological  and  comparative  studies  rt  animals,  especially  in  the  reptiles 

(l^aaf,  Spencer  and  others  have  shown  tlj^^^^^  .•   J^^^^^^^^  cup-sha,^ 

(lizards),  the  pin'='^>»^>  '^'"=''5^. '  «!lk  cSntngne^e  fibres  The  structural  resemblances 
orKan  connected  with  the  brain  b>  >«»^""^'"'^  "^j^^^  of  purpose  in  the  hipher  types, 
to  the  invertebrate  visual  organ  su^ed  a  pc^^^^^^^  ,^    „„,  „„,y 

an  assumption  tha  was  '*'"="f ''*"^.  ^^ J^Hetel  ^^^^^^  POsi'i«n  °"  '»^  ''««'  ^^'  ^'""^, 

is  borne  by  a  sUlk  but  reaches  an  '"t«^™^' '"P^,,  "^^  orean  was.  therefore,  designated 
through  or  lying  within  a  n-oaloramen^m^^^^^^^  Whilesucha 

thepin.rieye.athouRh  protably  mnoexist^^^^^^^  embryonic  relations  in  many  reptile^ 

superficial  position  in  the  adult  is  very  "«^fP"°r'  ,"  „„  .,  l^e  pineal  body,  at  least  in  such 
(Fig.  97»)  are  very  suggestive  of  the  P;:°b«ble  «gn^ca^  °»  an  eyTThes^  conclusions  are 
for^^a  rudimentary  sense  °'K^";  »^^8^„"f  ,o^'^„7t^^^^  in  man,  which  is 

likewise  suggestive  m  formmg  ou^  co^^'^"s  'r^^Zls  representing  a  very  imperfectly 

develop  and  ^eatly  modified  sensory  structure 

AUhough  strictly  belonging  to  the  telencephalon,  men- 
tion may  here  be  made  of  a  second  evagination,  know  as  the 
^.p^y.i.!which  arises  from  the  roof-plate  of  the  fore-brain 
ThXuch  appears  in  advance  of  the  pineal  outgrowth  and  s 
atenvporary  s^cture.  seemingly  being  in  nature  comparable 
to  a^^mwardly  directed  choroid  plexus.  The  paraphysis 
has  be^n  described  in  the  lower  vertebrates,  including  reptiles 
and  Wrds,  in  some  mammals  «"<>  'ndeed  according  to 
the  observations  of  Francotte  and  of  Ewing  Taylor,  it  is  not 
improbable  that  a  corresponding  evagination  is  recognizable 
in  the  early  human  embryo. 


Fig.  973- 


Small  portion  of  pine»l  b<Klv, 
showing  conrtitBCTt  cells  more  higlily 
maxnilKd. 


X  6oo. 


The  posterior  commissure  (commissura  t»«*te- 
rior cerebri)  is  a  narrow  but  distinct  cord-like  hand  o 
white  matter  which  overlies  the  superior  entrance  into 


1 1 26 


HUMAN   ANATOMY. 


h 


i  i 


'I 


opposite  side  which  descend  within  the  tegmentum,  lateral  and  ventral  to  the 
posterior  longitudinal  fasciculus  ;  (3)  fiores  which  cross  to  join  the  fasciculus  retro- 
flexus ;  (4)  fibres  from  the  median  fillet  and  (5)  from  the  superior  cerebellar 
peduncle  which  traverse  the  commissure  to  reach  the  opposite  thalamus  ;  (6;  per- 
haps fibres  from  the  deeper  gray  stratum  of  the  corpora  quadrigemina  to  the  cerebral 
cortex  of  the  other  side.  Its  presence  in  all  vertebrates  and  the  very  eaily 
acquisit  n  of  a  medullary  coat  by  its  fibres  indicate,  as  pointed  out  by  Edinger, 
the  fundamental  character  of  the  commissure. 

The  Metathalamus. — This  subdivision  of  the  thalamencephalon  includes  em- 
bryologically  both  the  median  and  lateral  geniculate  bodies.     Since  in  the  fully  formed 

Fig.  974. 


Corpus  cnllosoin 

Fornix 
Choroid  plexus- 
Velum  iuter-. 
pimitum 

Nucleus  habeitulae' 

Subthalamic 

nucleus 

Red  nucleus 

Substantia  niKiu 


Oculomotor  nerre 


Cnista  of  ccrfbrnl  peduncle 


Caudate  nucleus 


Vhalamus 


'Subthalamic  region 

choroid  plexus  in  ioferinr 
horn  of  la  ten)  vmtrkle 

Caudate  nucleus,  tail 

Hippocampus, 
obliquely  cut 

Gyrus  dentatus 

Cyrus  hipiMcampi, 
bouudiuK  inferior 
6ssure  leading  into 
choroidal  plexus 


Frontal  section  of  brain  passinR  Ihrotigh  thalami.  Mibthalamic  reition  and  cerebral  peduncles ;  inferior 
horn  of  lateral  ventricle  wi;h  hippocampus  in  section  also  seen. 


\(< 


brain  the  former  are  closely  associated  with  the  inferior  colliculi  and  their  arms,  the 
inferior  brachia,  they  may  be  conveniently  described  in  connection  with  the  mid- 
brain, as  has  been  done  (page  11  to). 

The  lateral  geniculate  bodies,  (corpora  Kcniculata  lateraks),  one  on  tach  side, 
are  two  fusiform  elevations,  about  10  mm.  in  length  and  half  as  much  in  width,  which 
project  from  the  outer  and  under  surface  of  the  posterior  part  of  the  thalamus  ( Fig. 
958).  They  are  so  buried  within  the  thalamus  that  they  are  much  less  distinct  than  the 
median  geniculate  bodies.  In  front  they  recei\  e  the  outer  division  of  the  optic  tracts, 
while  behind  they  are  connected  by  the  superior  brachia  with  the  superior  corpora 
quadrigemina.  In  structure  the  lateral  geniculate  Iwdy  consists  of  alternating  layers 
of  white  and  gray  matter.  The  former,  somewhat  thinner  than  the  gray  suljstance, 
are,  to  a  large  measure  the  optic  fibres,  many  of  which  end  around  the  cells  within 
the  gray  laminw.  Other  fibres  of  the  optic  tract  continue  without  interruption  into 
the  superior  brachium  and  so  to  the  upper  colliculus,  while  a  certain  number  end 
within  the  thalamus,  and  in  their  course  over  the  surface  of  the  latter  take  part  in  the 
production  of  the  stratum  zonale  (page  11 18).  From  many  of  the  cells  within  the 
geniculate  body,  fibres  proceed  by  way  of  the  optic  radiations  to  the  cerebral  cortex. 


THE   DIENCEPHALON. 


1 127 


Then  too  many  cortidfugal  fibres  course  in  the  opposite  direction  as  the  axones  ol 
the  corti^  cells,  and  end  in  relation  to  the  geniculate  neurones,  thus  establishing  a 
double  relation  between  the  lateral  geniculate  body  and  the  occipital  cortex. 

The  Hypothalamus.-Although.  stricUy  regarded  according  to  its  develop- 
mental relations,  the  diencephalon  claims  only  the  posterior  or  mammillary  part  of 
Se  Spothalam.^.  it  is  desirable  to  consider  at  th«  tune  the  derivations  of  the  entire 
K  ^^Sllomir  subdivision  of  t^-c  iore-brain.  Under  the  above  heading  will  be  de- 
scSf  thTefoJ^^rstructures  lying  within  or  forming  the  floor  and  the  anterior 
wall  of  the  third  ventricle,  including  the  subthalamic  region.  ,         . 

The  subthalamic  region  in  its  developmental  rektions  stands,  as  it  were,  as  a 
link  connecting  the  diencejhalon  and  the  mid-brain.  The  subthalamic  region  is  the 
uJwaTd  prolonlation  of  the  tegmentum  of  the  cerebral  peduncles  ajid  occup.«  on  each 
sSe  of  the  mid-line,  the  triangular  area  between  the  thalamus  above  and  the  internal 
^psuk  i^d™  continuation,  the  crusta  of  the  peduncle,  below  (Fig.  974)-  It  «  msepa- 

Fig.  975- 


Red  lutcteus 


Subfttantla 


Choroid  plexua 


FomU 

Pulviiiar 

Lateral  geniculate 

l>od>(leartcrcro»»e» 

cut  tail  of  caudate 

nacleua) 

Median  geulcuiale 

body 


Hippocampus 


Superior  cerebellar 
peduncle 


rront.1  .ection  oi  brain  pu.l>«  through  poaterior  pole.  oC  Ihalaml.  pii»*l  body  and  brainilem. 

rablv  blended  with  the  ventral  surface  of  the  thalamus,  which  thus  obliquely  overlies 
Se  teStiorof  the  tegmental  or  senst,ry  portion  of  the  cerebral  stalk.  Through 
tWs  ar^the  im^rtant  tSamocipetal  paths^the  fillet  and  of  the  superior  cerebellar 
D^uncles  reach  the  thalamus,  and  witliin  it  are  seen  the  upper  extremities  of  the 
St^^gHao?  the  mid-brain  the  su6siaHfia  nigra  and  the  red  nucleus,  and  a  new 
S  dXv  matter,  the  corpus  subihalamicum.  The  substantia  nigra  presents  the 
^me  chfrTcteristra  here  as  in  the  peduncle,  being  conspicuously  dark  and  overlying 
?h^crusSbr^  As  it  ascends,  ^decreases  in  bulk  from  within  outward  until  at 
the'evS  of  the  mammillary  body,  the  substantia  nigra  is  m.  longer  recognizable. 
The  conn^tions  of  the  cells  within  the  substantia  nigra  are  imperfectly  understood 
Jut  iHs^obable  that  they  receive  many  fibres  from  the  caudate  nucleus  and  the 
puumen  and.  perhaps,  als^  from  the  frontal  cortical  areas.  From  the  cells  on  the 
other  hand,  fibres  pass  into  the  tegmentum  and  into  the  crusta  and  thence  to 
lower  levels.  According  to  Bechlerew,  some  fibres  join  the  fillet-tract  and  thus 
relch  the  superior  quadrigeminal  bodies.  At  first  the  red  nucleus  is  a  v.r> 
prominent  feaCe  in  frontal  sections  of  the  subthalamic  region  (Fig.  970).  api,eanng 


II38 


HUMAN  ANATOMY. 


I   jl 


as  a  circular  area  of  gray  matter  enclosed  by  a  zone  of  cerebello-thalamic  fibres  ; 
farther  forward  it,  too,  gradually  diminishes  and  disappears  at  a  level  somewhat 
behind  that  of  the  corpora  mammillaria.  The  connections  of  the  red  nucleus  have 
been  considered  in  connection  with  the  superior  cerebellar  peduncle  (page  1095)  ; 
suffice  it  here  to  recall  its  twofold  significance  as  an  interruption  station  for  many 
of  the  cerebello-rubro-spinal  and  for  the  cerebro-rubro-spinal  tracts. 

The  corpus  subthalamic um  (nucleus  hypothalamicus),  or  nucleus  0/ Luys,  is  a 
mass  of  deeply  tinted  gray  matter  peculiar  to  the  subthalamic  region  and  unrepresented 
in  the  mid-brain.  It  appears  in  cross-section  (Fig.  970)  as  a  small  biconvex  area, 
immediately  dorsal  to  the  tract  of  crustal  fibres  and  lateral  to  the  red  nucleus  and  the 
substantia  nigra.  As  the  latter  diminishes,  the  subthalamic  nucleus  expands  to  take 
its  place  and,  where  fully  represented,  measures  from  3-4  mm.  in  thickness  and  from 
10-12  mm.  in  its  longest  diameter,  and  extends  superiorly  considerably  beyond  the 
level  of  the  red  nucleus.  Histologically  the  subthalamic  body  is  distinguished  by  a 
dense  net-work  of  fine  meduU,'  id  nerve-fibres,  enclosing  pigmented  multipolar  nerve- 
cells  of  medium  size,  and  by  an  unusually  close  mesh-work  of  capillary  blood-vessels. 
The  dorsal  surface  of  the  nucleus  is  defined  by  the  overlying  lateral  part  of  the  field 


Fig.  976. 


Septum  luddum 
Choroid  plexuii 

Fonmen  o(  Monro 
n«nu  of  corpus  calloaum 


Roatnim  of 
corpua  calloaum 

Anterior  commiaaun 

l.amia«  dnem 

Optic  recna 

Optic  commiaaute 

Anterior  lobe  of  pituitary  tiody 
Poaterior  lobe  of  pftt  '• 


Body  of  fornix 
Velum  interpoaitum  coveriti<^ 
Thalamua.       [thalamus 
mesial  autfacc 


Tenia  thalami 
plenium 


lommiaaura  habenulie 
Pineal  recess 


ituilary  body 
lafundibulum' 


Pineal  body 


Posterior  commissure 


^^Quadriiceminal  plate 
Sylvian  aqueduct 
Cerebral  peduncle 
Middle  commlaaure 
Sulcua  hypothalamictu 
Mammillary  body 
,  Amerior  pillar  of  tbmix 
Tuber  cinereum 


Right  lateral  wall  of  third  ventricle :  velum  interpoaitum  coven  auperlor  aurface  of  thalamus. 


of  Porel,  as  the  stream  of  fibres  passing  between  the  red  nucleus  and  the  thalamus 
and  the  internal  capsule  is  called.  From  the  ventral  surface  of  the  nucleus,  fibres 
pierce  the  adjacent  crusta  and  join  the  ansa  lenticularis  to  gain,  probably,  the  globus 
pallidus;  other  perforating  fibres  perhaps  connect  the  subthalamic  body  with 
Meynert's  and  Gudden's  commissures  (Obersteiner).  The  ventro-medial  ends 
of  the  bodies  of  the  two  sides  are  connected  by  a  bridge,  the  cominissura 
hypothalamica,  which  traverses  the  floor  of  the  third  ventricle  above  the 
mammillary  bodies.  In  addition  to  connecting  the  two  subthalamic  nuclei,  the 
commissure  contains  decussating  fibres  from  the  anterior  pillars  of  the  fornix  and, 
according  to  Edinger,  probably  fibres  from  the  fore-end  of  the  posterior  longitudinal 
fasciculus. 

The  corpora  mammillaria  (corpora  mamlllaria),  also  railed  the  corpora  albi- 
caniia,  are  two  hemispherical  elevations,  about  5  mm.  in  diameter,  which  lie  close  to  the 
mid-line  within  the  interpeduncular  space  on  the  basal  suriace  of  the  brain  (Fig.  993). 
They  are  almost  but  not  (juite  in  contact,  being  separated  by  a  narrow  interval  which 
immediately  behind  the  little  bodies  deepens  into  the  anterior  recess  mn'"  ing  the 
front  end  of  the  shallow  median  furrow  that  grooves  the  posterior  perforated  sub- 
stance. The  posterior  surfaces  of  the  mammillary  bodies  indicate  the  anterior  limit 
of  the  ventral  surface  of  the  mid-brain.     When  examined  in  section  (Fig.  970"), 


THE    DIENCEPHALON. 


1 139 


each  body  is  seen  to  be  composed  of  an  outer  layer      white  matter  encl(«ing  a  core 
^eraVsubstance,  known  collectively  as  the  nucleus  mammiUans      The  latter.. 
suMiv^ded  into  a  medial  and  lateral  part  by  fibres  from  the  downward  archmg  ante, 
rior  pillar  of  the  fornix,  which  penetrate  the  gray  matter  as  well  as  mvest  to  a  larj,e 
extent  ^  exterior.     Only  a  part  of  ( i )  the  fornix  fibres  however,  end  directly  in 
the  Sa^mUkry  nuclei,  since^ome  pass  above  and  behind  the  ganglion  to  gain  the 
hv  J^c  ^mmissure  (page  .128)  and.  after  decussation    to  end  in  the  mam- 
SuSTtody  of  the  opposite  side.     From  the  dorsal  part  of  the  medal  nucleus 
SSSisH^from  thedl  one  by  its  larger  nerve-cells,  emerges  a  disUnct  and 
com^  bundle  of  fibers  (Fig.  967 ).  which  on  clearing  the  nucleus,  separat^  into  two 
Sr    One  of  these,  known  as  (2)  the  fnammiUcthalamic  tract,  or  the  bundle 
oTvkqiAzyr,  course,  upward  and  forward,  a    '.  ends  within  the  anterior  nucleus  of 
the  tlmlamus  :    n  this  manner  it  completes  the  paths  by  which  the  cortical  olfactory 
centr«  withiA  the  hippocampus  major  are  connected  (by  way  of  the  fimbria,  body 
and  ^terior  pUlar  of  tKmix  and  the  mammiUo-thalamic  strand)  with  the  thalamus 
TFie   1S9)      That  fibres  pass  between  the  latter  and  the  mammiUary  nucleus  in 
bothdir^iions,  is  shown  by  the  fact  that  destaiction  of  either  of  these  centra  is  fol- 
lowed in  turn  by  ascending  or  descending  degeneration  of  the  fibres.     (3)   The 
Sh^part  of  the  bundle  issuing  from  the  mammUlary  nucleus  arches  backward  and 
do^,^  and,  as  the  mammiUo  ^gmental  tract,  is  trac^ble  into  the  tegmentum  of 
SHTd  brain  to  the  vicinity  of  the  inferior  colliculus.   (4    Under  the  name^  pedm^ 
c^^  corporis  mammUlarU,  another  mammillo-tegmental  tract  «  described.     This 
sb-and  ^ngs  from  the  lateral  mammiUary  nucleus,  and    coursing  backward  and 
downw^  along  the  medial  mar^n  of  the  cruste.  enters  the  tegmentum      Its  d^- 
S^tion  is  uncertain,  but  according  to  KoUiker  the  tract  probably  ends  '"  the  ce""^ 
gray   matter  surrounding  the   Sylvian  aqueduct  m  proximity  wrth  the  trochlear 
Sur  Other,  but  much  less  well  established,  strands  have  been  descnbedby 
LenWk  as  proceeding  forward  from  the  peripheral  layer  of  the  mammillar>-  body 
ovTr^  tuber  cinereum.     Concerning  their  further  course  httie  is  known  with 

*'^'^The"  tuber  cinereum  is  the  first  of  a  series  of  median  outpouchings  which 
model  the  thin  sheet  of  gray  matter  constituting  the  floor  and  the  anterior  wall  of 
^ifthii  ventricle  and  bdong  to  the  pars  optica  of  the  hyjK,thalamus.  As  seen  from 
he  exterior  (Fig.  993).  the  tuber  cin«eum  is  a  median  elevation  placed  between  the 
mammilUr^  boSes  behind  and  the  optic  chiasm  in  front,  and  the  cerebral  peduncles 
Td  t^  Sic  tracts  at  the  sides.  T^ether  with  the  infundibulum  it  forms  the  most 
dependent  part  of  the  third  ventricle  and  consists  of  a  thin  layer  of  gray  matter,  less 
than  1.5  min.  thick,  that  is  continued  forward  as  the  attenuated  extension  o  the  im- 
portant sheet  found  within  the  mid-brain  and  fourth  ventricle.  In  addition  to  the  fibre- 
Sds  coming  from  the  mammiUary  bodies  noted  by  Lenhoss^k^  this  investigator 
and  KoUiker  credit  the  tuber  cinereum  with  possessing  small  paired  composite  gang- 
lia, the  nuclei  tuberis  and  the  nuclei  supraoptici  of  KoUiker  Concerning  their  con- 
nections nothing  is  definitely  known.  The  anterior  part  of  the  tuber  immed.atel. 
Sd  the  optic  chiasm,  descends  abruptly  and  somewhat  forward  to  form  *  funnel- 
shaped  stalki  the  infundibulum,  to  whose  lower  end  or  apex  is  attached  the  pos- 
teri^obe  of  the  pituitary  body  (Fig.  976),  Although  in  tlie  very  young  child  the 
infundibulum  retains  to  some  extent  its  orig  nal  character  as  »,hollow  outgrow^ 
from  the  ventricle,  in  the  mature  subject  this  cavity,  the  rece.tu.  nfundibuli. 
has  mostlv  disappeared  and  the  stalk  is  solid,  save  for  a  slight  diverticulum  within  its 

"'''"The  pitlrior'^'pi  of  the  tuber  cinereum.  between  the  root  of  the  infundibulum 
and  the  mamillary  bodies,  exhibits  occasionally  in  the  adult  brain  and  almost  con- 
stantly in  that  of  the  foetus,  a  smaU  rounded  median  projection  flanked  on  each  side 
by  a  slight  elevation.  To  this  modelling  Retzius  has  applied  the  name,  ''«";'•«"« 
saccularis  in  recognition  of  its  similarity  to  the  evagination  (saccus  vasculosus)  f.uind 
in  fishes.     The  eminence  encloses  a  shallow  iwuch,  recessus  saccularis,  which  opens 

into  '"J^  *J\'jJ,i\^"/"bo<iy  (hypophysis  cerebri)  is  attached  to  the  dependent  li-  of  the 
infundibulum.  and.  closely  invested  by  a  loose  sheath  of  connective  tLssut    hangs 


II30 


HUMAN   ANATOMY. 


within  the  pituitary  fossa  on  the  base  of  the  skull,  just  in  advance  of  the  dorsum  sellse 
( Fig.  996) .  Above,  the  fossa  is  dosed  by  a  special  partition  of  dura,  the  diaphragma 
sella,  through  an  opening  in  which  the  jnfundibulum  passes  to  the  mushroom -shaped 
organ.  The  pituitary  body  consists  of  two  distinct  parts,  of  which  the  so-called 
anterior  lobi  is  much  the  larger  and  of  a  darker  grayish  red  color.  Ite  posterior 
surface  is  concave  and  receives  the  small  posterior  lobe,  which  is  partially  embraced 
at  the  sides  by  the  expanded  lateral  margins  of  the  anterior  division.  Although  the 
two  lobes  are  closely  bound  together  by  connective  tissue,  they  are  not  only  distinct 
as  to  structure  and  probably  function,  but  are  developed  from  entirely  different 
regions.  The  anterior  lobe  is  formed  as  an  outgrowth  from  the  oral  diverticulum, 
while  the  posterior  lobe  first  appears  as  a  ventral  evagination  from  the  diencephalon 
(FJK-  1530)-  The  anterior  lobe,  glandular  in  character,  has  been  described  in  con- 
r  xnon  with  the  Accessory  Organs  of  Nutrition  (page  1806)  and,  therefore,  calls 
fu'/  ao  further  consideration  in  this  place. 

Fio.  977. 


Im-'loharscptmn 


Posterior  or  c«rebr»l  lobe 


Blood-vetKl 


Connective.tinue. 
trabecula 


.Capsule 


TtmnaverM  section  o(  piloltaiy  body,  showing  relation  ot  anterior  (oral)  and  poMerior  (cerebral)  lobei.    X  7' 


The  posterior  lobe  of  the  pituitary  body  is  lighter  in  color  and  softer  in  con- 
sistence and  directly  attached  to  the  floor  of  the  third  ventricle  by  means  of  its  stalk, 
the  infundibulum.  During  the  eariy  stages  of  its  development,  this  lobe  is  repre- 
sented by  a  tubular  outgrowth  whose  walls  partake  of  the  general  character  of  the 
adjacent  brain -visicle.  Lattsr  the  lumen  within  the  lower  end  of  the  diverticulum  dis- 
appears in  consequence  of  thickening  and  approximation  of  its  walls,  a  funnel-shaped 
recess  of  variable  depth  within  the  infundibulum  alone  remaining.  In  the  adult  con- 
ditit>n  the  posterior  or  cerebral  lobe  retains  few  histological  features  suggesting  its 
nervous  origin.  Of  the  demonstrable  interfacing  fibres,  with  fusiform  enlargements 
and  elong-atetl  nuclei,  none  can  be  identified  as  ner\e-fibres,  while  of  the  numerous 
celts  which  the  lobule  contains,  only  a  few  of  large  size  and  pigmented  cytoplasm 
uncertainly  resemble  ner\«us  elements.  With  the  exception  of  possibly  neurogliar 
cells,  the  existence  of  definite  nervous  tissue  within  the  cerebral  lobe  of  the  mature 
human  hy|)ophysis  is  doubtful.  .... 

The  optic  tracts  and  commissure  are  elsewhere  described  (page  1223), 
suffice  it  at  this  place  to  mention  their  relation  to  the  interpeduncular  structures. 
The  t)ptic  tracts  diverge  biickward  and  wind  around  the  ventral  surface  of  the  cere- 
bral peduncles  (Fig.  993).  Their  medial  ends  are  fused  into  a  transversely  flattened 
white  band,  the  optic  commissure  or  chiasm.  The  latter  is  connected  with  the  front 
nur{.ice  of  the  tiibtr  rinoretim,  whilst  above  the  chiasm  the  anterior  wall  of  the  ventricle 
consists  of  a  ilelicate  sheet  of  gray  matter,  the  lamina  cinerea  ( lamiaa  termlnalis). 
This  structure  lies  in  the  mid-line,  passes  almost  vertically  upward,  with  a  slight 
forwardly  directed  curve,  and  becomes  continuous  with  the  rostrum  of  the  corpus 


THE    DlENCEl'HALON. 


ii3> 


caUosum.     Just  before  meeting  the  latter,  the  lamina  passes  in  front  of  the  anterior 

'^"^  The  Thtd'vi'nTricieiThe  ^  ventricle  (veotriculus  tertius  cerebri)  is  the 

narrow  cleft-like  si«ce  that  separates  the  medial  surfaces  of  the  thalami  (big.  966)- 
r^Imewhat  broader  behiJId  and  much  deeper  in  front,  where  it  comes  mto  close 
relation  with  the  exterior  of  the  brain,  the  interpeduncular  lamina  alone  .ntervenmR. 
S Tom  the  side,  as  in  mesial  sagittal  sections  (Fig  996).  the  ou'l'nf  ««,  ^e 
ventricle  b  irregular  y  comet-shaped,  with  the  broader  end  above  and  behmdand  the 
UunS  (^inV^ccti  downward  and  forward  ( Fig.  978).  Behmd.  it  commun.ca  es 
wi"Ke Cvian  aqueduct,  and  through  this  canal  indirectly  w.th  the  fourth  ventricle; 
Ser brly  U  connects  with  the  two  lateral  ventricles  by  means  of  the  Gramma  of 
Monro  Its  sagittal  diameter,  measured  between  the  anterior  commissure  and  the 
We  of  the  pirell  body,  is  approximately  2. 5  cm.  The  lateral  wall  of  the  ventricle 
J^fg  9r6)  ^formed  chiefly  by  that  part  of  the  thalamus  which  lies  below  the  level 
of  h;  ?L  a  thalami.  On  this  surface,  slightly  in  advance  of  the  middle,  '«  «een  he 
small  oVal  field  of  the  middle  commissure,  and  in  front  of  this  the  downward  curv  ng 
ekvatbn  produced  by  the  anterior  pillar  of  the  fornix.  Between  the  latter  and  the 
Snent'^amerior  tubercle  of  the  thalamus  lies  the  foramen  of  Monro  (foramen 
Kent"  c«  are),  which  establishes  communication  between  the  third  and  the  cor- 


Fig.  978. 


Pineal  ncf* 


Suprapineal  recfsa' 

Posterior  commissure 
Sylvian  aqueduct 


Middle  commiHure 

Foramen  of  Monro 


Anterior  commissure 


Mammillary  body 

Infundibulum  ' 


Optic  recesa 


optic  chiasm 
Cast  of  third  ventricle,  viewed  from  the  side.     >,  J.     {Krlxms.) 

responding  lateral  ventricle,   and  transmits  the  trunk  formed  by  '^e  union  of  the 
vein  of  the  corpus  striatum  and  the  choroid  vein.     A  shallow  furrow  on  the  ventric- 
ular wall  the  sulcus  hypothalamicus  leads  from  the  foramen  backward  and  some- 
what downward  (Fig.   976).      It  is  of  importance  as  indicating,  even  in  the  adult 
brSi,  the  demarcation  towec.  the  thalamencephalon  and  the  hypothalamus_pa  ts 
derived  respectively  from  the  dorsal  and  ventral  zones  of  the  embryonic  brain-%  esice^ 
The  roof  of  the  ventricle  extends  from  the  foramina  «^M«nrc^  bo imded  alx  ve 
and  in  front  by  the  arching  piliars  of  tlic  fornix,  to  the  pin^l  body  liehind,  o%er 
which  it  pouches  out  into  the  %ra/,ineal  recess,  as  the  little  dwertK"'"^  ^^^^^^^^^ 
The  body  is  termed.     The  immediate  and  morphological   roof  consists  "'  the  delicate 
epenTmal  layer,  which  is  attached  to  the  t^nfa  thalami  on  each  side  and    stretch  ng 
aS^he  interthalamic  cleft,  closes  in  the  ventricle.      The  ependymalayehtw 
ever    is  backed  by  a  vascular  folu  of  pia  mater,   which,    in  conjunction   «'th  t^^ 
epUhelTal  layer,  constitutes  the  ve/um  iHterposilum.     This  structure  is  more  Jul  y 
Scril^  in'connection  with  the  lateral  vemricles  (page  ..62):  ^-tits  relation  .0 
the  third  ventricle  finds  appropriate  mention  at  this  place.     As  '"  ^J^  "  "*  f.  JJ^. 
fourth  ventricle  and  in  the  lateral  ventricles,  so  in  the  third  does  the  %  ascula.  Mssut 
of  the  pia   mater  invaginate  the  ependymal  layer  to  form  vascular  fnnges  which 
pro  ect  ^l™he  ventriL  (Fig.  97/).     A  doubfe  line  of  -ch  invaginations  han^i 
{rom  the  roof  of  the  third  ventricle  and  constitutes  the  chorotd  plexus  of   that  ^jace^ 
Since  the  ependyina  everywhere  covers  th.::>c  pial  procPS-^-s,  it  is  evident  th-it  tne 
fringes  are. Trktiy  regarded,  outside  the  ventricle  and  excluded  by  the  continuous 
layer  of  the  epithelium. 


1133 


HUMAN  ANATOMY. 


The  posterior  wall  of  the  third  ventricle  is  very  short  and  includes  the  base  of 
the  pineal  body,  with  the  opening  into  the  minute  pineal  recess,  the  posterior  com- 
missure and  the  orifice  leading  into  the  Sylvian  aqueduct.  The  floor  slopes  rapidly 
downward  and  forward  (Fig.  976)  and  comprises  a  small  part  of  the  tegmentum 
of  the  cerebral  peduncles,  the  posterior  perforated  substance,  the  mammillary  bodies, 
and  the  tuber  cinereum  with  the  infundibulum — structures  already  described  and 
included  within  the  interpeduncular  area  on  the  base  of  the  brain.  Corresponding 
with  the  position  of  the  superficial  elevation,  the  ventricle  exhibits  the  diverticulum 
of  the  inhindibulum.  The  optic  chiasm  marks  the  anterior  limit  of  the  floor  and  the 
beginning  of  the  anterior  wall.  Immediately  above  the  chiasm  the  anterior  wall 
exhibits  a  diverticulum,  the  optic  recess,  from  which  the  lamina  cinerea  ascends  to 
join  the  rostrum  of  the  corpus  callosum,  in  its  course  passing  close  to  and  in  front 
of  the  anterior  commissure.    The  latter  structure  shows  on  the  front  wall  of  the 


Fig.  979. 


Cavity  tn  wptum  lucidiim 


Corpun  cmlkwum.  cut 


Caudate  nucleus 


Internal  capsule 

Putamen  of 
lenticular  nucleus 


cm  anterior  end 
of  fornix 


Anterior  pillars 
of  fornix 

Anterior  commissure 


Lamina  cinerea,  above, 
optic  recess 


Lateral  ventricle 


Epeudyma  covering 

^  tKnia  xemicirculans 

and  vena  terminaliH 

Thalamus,  anterior  tubercle 

Foramen  of  Monro 


lamina  cinerea 


Optic  chiasm 

Portion  of  frontal  section  of  brain  (mssinjc  through  foramina  of  Monro,  showing  anterior  wall  of  third  ventricle 
modelled  by  anterior  commissure  and  pillars  of  fornix. 

ventricle  as  a  transverse  ridge  between  the  descending  and  slightly  diverging  anterior 
pillars  of  the  fornix  (Fig.  979).  Although  distinctly  modelling  the  ventricular 
walls,  all  of  these  bands  are  excluded  from  the  ventricle  by  its  ependymal  lining. 

THE  TELENCEPHALON. 

The  telencephalon,  or  end-brain,  consists  of  two  fundamental  parts,  the  hemi- 
■phaerium  and  the  pars  optica  hypothalami.  The  latter  includes  :  ( i )  the 
lamina  cinerea  {lerminalis),  (2)  the  optic  commissure,  (3)  the  tuber  cinereum  and 
(4)  the  pituitary  body,  all  of  which  have  been  already  considered,  as  a  matter  of  con- 
venience, in  connection  with  the  diencephalon  and  the  third  ventricle.  The  hemi- 
sphere comprises:  d)  the  pallium,  (2)  the  rhinencephalon,  and  (3)  ^e  corpus 
striatum.  The  first  of  these  subdix^sions  undergoes  such  enormous  development  in 
the  anthropoid  apes  and  in  man,  that  the  pallium  becomes  the  dominating  factor  and, 
expanding  upward,  laterally  and  backward  as  the  great  cerebral  mantle,  not  only 
forms  the  chief  bulk  of  the  cerebrum,  but  overlies  the  derivatives  of  the  other  brain- 
segments  to  such  an  extent  that  these  parts  are  to  a  large  measure  covered  and 
deposed  from  their  primary  position  on  the  free  dorsal  suriace  of  the  brain.  In  conse- 
quence in  man,  in  whom  the  pallium  reaches  its  highest  development,  the  thalami, 
corpora  qiiadrigemina  and  the  cerebellum  are  maskeid  by  the  hemispheres  and  occupy 
topographiaillv  a  dependent  position.  The  rhinencephalon,  on  the  coiitrary,  is  in 
man  only  feebfy  developed  and  rudimentary  in  comparison  with  the  conspicuous  and 
bulky  ciirresponding  structures  possessed  by  animals  in  which  the  sense  of  smell  is 
highly  developed.      The  corpus  striatum,  consisting  of  two  large  masses  of  gray 


THE  TELENCEPHALON. 


U33 


matter  the  caudate  and  the  lenticular  nucleus,  represents  the  internal  nucleus  of  the 
Sbmin     Certain  commissural  structures,  as  the  corpus  callosum,  the  -ntcnorcon,. 
S™  and  ih^/onnx  are  to  be  regarded  as  secondar>-  and  ^  ser^'mg  to  connect 
d^L  hX«  of  the  great  brain.     The  immediate  free  or  outer  surface  of  the  Pall.um  .s 
Sen^hTre  formed  by  a  thin  peripheral  layer  of  cortical  gray  matter  which  as  an 
unb?Ien  sh«;t   clothL  the  various  ridges  and  intervening  iy^rxo^-^Xh^  convolutions 
and?.«r«-which  model  the  exterior  of  the  cerebrum  and  prov.de  the  nec^ry 
extent  ^surface.      Beneath  the  cortical  gray  substance  hes  the  M  matter  which 
coSutes  the  bulk  of  the  hemisphere  and  consists  of  the  tracts  of  nerve-hbres  pa*. 
W  to  and  from  the  cortex,  as  weU  as  of  those  connecting  the  various  regions_o    the 
cortS^thTe  another.     Embedded   within   the  core  of  white  matter  and  lying 
much  nearer  the  basal  than  the  superior  surface  of  the  hem^phere  (F'g-  >«^).;»;^ 
rrous  Sum  is  closely  related  tVthe  ventricular  cavity  by  means  o    the  caudate 
nucC  oT  he  one  hand,  and  to  the  cortical  gray  matter  by  the  lenticubr  nucleus 
on  the  other      In   -iew  oi  the  rudimenury   condition  of  the  rhinencephalon    and 
the  over^shadowin,    development  of  the  pallium  inman,  it  is  usual  and  convenient 

o   Sd  most  of  the  pam  derived  from  the  telencephalon  as   belonging  to    he 
hemSes%e  latter  term  being  used  in  a  less  restricted  sense  than  warranted 

by  a  precise  interpretation  of  its  developmental  significance. 

The  Cerebral  Hemispheres. 

Viewed  from  above,  the  human  brain  presents  an  ovoid  form   the  narrower  end 
being  dSed  forward  ;nd  the  broader  backward,  the  greatest  width  corrjpond.ng 
Sh^he  parietal  eminences   (Fig.    984)-      T^e  convex  sujfacefo^^^^ 
hemisDhereTis  divided  by  a  deep  median  sagittal  cleft,  the  lonptudinal  nwure 
iSSud^alls  cerebri),  that,  for  a  distance  less  than  one-third  of  ,te  length 
iSSly  Sd    more  than   one-third  posteriorly.  '?o«"P»«t«ly, 'T*^*^  ^'^^  S.'/t 
sDhwr    In  its  middle  third  or  more,  the  fissure  is  interrupted  at  a  depth  of  about 
T,  m'  by  thi  arched  upper  surface  of  the  corpus  callosum   the  chief  connect,.on 
between  the  hemispheres,  ^he  upper  and  back  part  of   the  longitudinal  fissure, 
throughout  its  length,  is  occupied  by  the  sickle-shaped  mesial  fold  of  dura  rnater 
the    /X  «rr*n,    which    incompletely    subdivides    the    space    occupied  by   the 
Srebmm  into  two  compartments.     Under  the  name,  transverse  fissure  (lissura 
Sv7«a  cerebri),   is  kometim^  described  the   deep   deft  which   separates   the 
Ser^ferior  surface  of  the  hemisphere  from  the  cerebellum   the  corpora  quad- 
Smina  and  the  pineal  body.     This  cleft,  so  .f'^ent  after  the  bramh^b^^^ 
removed  from  the  skull,  when  the  parts  are  m  situ  is  filled  behind  by  the  tentortum 
cerehelli  and  in  front  by  a  fold  of  pia.  .    .  ,  ,  , 

The  hemispheres  are  advantligeously  studied  after  being  separated  from  each 
other  by  Sta^  section,  and  from%he  brain-stem  by  cutting  across  the  mid-brair. 
When  exai^ned  after  such  isolation,  especially  when  hardened  before  removal  from 
the  skulleach  hemisphere  presents  a  dorso-lateral.  a  mesial  and  an  '"fenor  surface 
The  dorio-lateral  surface  (1  ig.  980)  is  convex  both  from  before  backward  and 
from  above  downward  and  closely  conforms  to  the  opposed  inner  surface  of   the 
Sal  vault.     The  mesial  surfa'ce  (Fig.  987)  «  flat  and  vertical  and  bounds  the 
loniritudinal  fissure.     It  is  in  contact  with  the  sagittal  fold  of  dura,  the  falx  cerebri. 
exc?p"  in  front  and  below  where  the  partition  is  narrow;  here  the  mesial  surfaces 
of  the  hemispheres,  covered  of  course  by  the  pia  and  «™<=hnoid,  lie  in  apposition 
The  inferior  surface   (Fig.   989)   «  irregular,   its  »PP^^'''"'«t^.,f  *3^  *X 
resting  in  the  anterior  cerebral  fossa  of  the  cran«l  floor   the  middle  third  in    he 
lateral  part  of   the  middle   fossa,  whilst  the  posterior  th-      is  supported  by  the 
upp'r  aTr^t  of  the  tentorium,  which  separates  it  from  f         bjacent  cerebe lum^ 
At^he  jVmcture  of  its  anterior  and   middle  thirds    the   uitenor   su-face  o     he 
fm  sphere  is  crossed  transversely,  from  within  outward,  by  the  stem  of  jjie  Sylvian 
fissure  and   thus  subdividctl  into   an   antenor  an.l  a  If't^^^/'^f:*; /.'T    X„ 
and  smaller,  known  as  the  orbital  area,  rests  upon  the  orbital  plate  of    he  fmntal 
bone  and  is  modelled  by  this  convex  bony  shelf  '"»«»,  <=.°"^,P?";J'"ffitf'„""r^ 
cavity  from  side  to  side.     The  tract  behind  the  deep  Sylvian  cleft  is  at  first  convex 


H34 


HUMAN   ANATOMY. 


I 


and  rounded,  as  it  lies  within  the  middle  fossa,  but  traced  backward  it  passes 
insensibly  into  the  tentorial  area,  supported  by  the  tentoriu.:i  cerebelli.  This  area 
is  concave  from  before  backward  and  directed  inward  as  well  as  downward,  in 
correspondence  with  the  characteristic  curvature  of  the  tent-like  dural  septum. 

The  borders  separating  the  surfaces  of  the  hemisphere  are  the  dorsu-mesial, 
the  infero-lateral  and  the  infero-mesial.  The  dorso-mesial  border  inter\'ene8 
between  the  mesial  and  lateral  surfaces  and,  therefore,  follows  the  arched  contour  of 
the  hemisphere  beneath  the  vaulted  calvaria.  The  infero-lateral  border,  between 
the  lateral  and  inferior  surfaces,  is  better  defined  in  front,  where  it  separates  the  orbi- 
tal area  from  the  external  surface  as  the  archefl  superciliary  border  (Cunningham), 
than  behind,  where  it  is  so  rounded  off  as  to  scarcely  be  recognizable  as  a  distinct 
margin.  The  infero-mesial  border  intervenes  between  the  mesial  and  the  inferior 
surface  of  the  hemisphere.  It  is  well  marked  in  front,  where  it  limits  the  orbital  area 
mesially,  and  again  liehind.  where  it  corresponds  to  the  line  of  juncture  between 

Fig.  980. 


Ijiteral  aspect  of  left  cerebral  hemisphere;  dono.median  iurface  Is  somewhat  foreshortened  ;  red  lines  indicate 
bound.irie!«  separatinK  parietal,  temporal  and  occipital  lobes ;  r.  Rolandic  fissure ;  i.  g.,  i.  g.,  its  superior  and  inferior 
(fenu;  .V,  .V.  S-^,  .V*  ajc.  vertical,  horizontal,  posterior  and  ascendine  limbs  01  Sylvian  fissure:  i.p.  c,  s.  p.  c, 
inferior  and  superior  preienlral ;  sf.,  if.,  superior  and  inferior  frontal ;  p.m..  paramedian  ;  m./.,  mid-frontal ;  d., 
dla)(unal,  here  continuous  with  inferior  nrecentral ;  ^>.  ^,  ^./i.  inferior,  superior,  horizonlal  and  occipital  limbs 
of  niter-parietal;  p.  t;..  parieto-occipital;  /',  /*  asc,  superior  temporal  and  its  upturned  limb;  /», /•  ajc,  middle 
temporal  and  its  upturned  limb;  /.  o.,  l.-ansverse  wcipllal ;  /.  o  ,  lateral  occipitaf;  A.,  arm  centre;  i>.  T.  O..  pars 
basalts.  trianKularis  and  urbilalis  ;  Arc.  p-a.,  arcus  parieto-occipitalis. 

the  fal.x  cerebri  and  the  tentorium  and  marks  the  division  between  the  mesial  surface 
and  the  tentorial  area.  This  margin  has  been  designated  the  internal  occipital  border 
by  Cunningham. 

The  extreme  anterior  end  of  the  cerebral  hemisphere  is  known  as  the  frontal 
pole  (polus  frontalis),  and  the  most  projecting  part  of  the  posterior  end  as  the 
occipital  pole  (polus  occipitalis),  while  the  tip  of  the  subdivision  of  the  hemisphere 
which  projects  below  the  Sylvian  fissure  constitutes  the  temporal  pole  (polus  tem- 
poralis). A  short  distance  l)ehind  the  latter,  the  inferior  surface  exhibits  a  well 
defined  petrosal  depression  (imprcssio  petrosa):  this  is  caused  by  the  elevation  cross- 
ing the  petrous  portion  of  the  temporal  bone  which  corresponds  to  the  position  of 
the  superior  semicircular  canal.  Under  favorable  conditions  of  hardening,  the  infero- 
mesial  asj)ect  of  the  occipital  pole  sometimes  displays  a  broad  shallow  groove  which 
marks  the  commencement  of  the  lateral  sinus.  The  groove  is  usually  better  marked 
on  the  right  side  than  on  trie  left,  in  accordance  with  the  larger  size  of  the  right 
sinus  .IS  commonly  found  ;  occasionally  these  relations  are  reversed,  and  frequently 
no  groove  is  recognizable  on  the  side  of  the  smaller  sinus.  In  brains  hardened  in 
situ,  tile  gently  arching  cune  of  the  hind-half  ot  the  infero-lateral  Ixirtlcr  of  the  hemi- 
sphere is  interrupted  by  a  more  or  less  evident  indentation,  the  preoccipital 
notch  (inclsura  prai-occipitalis ),  at  a  (joint  about  3.75  cm.  (1  [■-.  in.)  in  front  of  the 
o< cipitai  pole  (  Fig.  9«o).     This  notch,  prominent  in  the  child  but  later  variabl'  in 


THE  TELE^CEPHALON. 


"35 


its  distinctness,  is  produced  by  a  fold  of  dura  over  the  paneto-mastoid  l-utu-^^  •'nj 
Jtove  the  highest Vrt  of  the  lateral  sinus  (Cunmngham)  It  .s  of  .mpo^nce 
fn  the  toDoeraphy  of  the  brain,  since  it  is  often  taken  as  the  lower  1  mit  of  the 
IrUto^ZpllTL,  establishing  the  conventional  div^.  on  on  the  lateral  surface  of 
{he  hemisphere  between  the  parietal  and  occipital  lobes  (page  ii43)- 

The  complex  modelling^  the  surface  of  the  cerebral  hemispheres,  the  charac- 
teristic feature  o1  the  human  brain,  is  produced  by  the  presence  of  'rregular  eleva^ 
ttons  the  convolutions  or  gyri,  separated  by  the  intervening  furrows,  the  fissures 
or  sulci!    Although  presenting  many  variations  in  the  details  of  their  arrangement 
nLtonly  in  different  individuals  but  even  in  the  hemispheres  of  the  same  bnun.  the 
convdutions  and  fissures  of  every  normal  human  brain  are  grouped  according  to  a 
aenS  and  definite  plan  to  which  the  brain-patterns,  whether  elaborate  or  s'njple.m 
fhe  mi  Snfor^      The  fissures  differ  gready  not  only  as  to  their  depth  as  observed 
nthTfuS  fomed  brain,  but  also  as  to  their  relation  with  the  developing  hemi- 
sphere a  ve^Tew.  known  as  the  complete  fissures,  involving  the  entire  thickness 
of  the  wall  of  the  cerebral  vesicle  and  in  consequence  Producing  corresponding  eleva- 
tions on  the  internal  suHace  of  the  ventricular  cavities.     Of  such  total  sulci  the  most 
m^i^nt^rmanent  ones  are  :  (i)  the  hippocampal fissure  which  Fod"C«  the  p^- 
Xn  known  as  the  hippocampus  major  within  the  lateral  ventricle  ;  (2)  the  ante- 
rior part  of  the  calcarine  fissure,  which  gives  "se  to  the  calcar  avis  ;  and  ( 3 )  the 
fore-Srt  of  the  collateral  fissure,  which  is  responsible  for  ^^e  variable  conaterale^^^ 
nencr    The  choroidal  and  the  parieto-occipital  fissure  are  also  complete  fissures  of 
tefal  ife  but  give  rise  to  invaginations  which  do  not  permanently  model  the  ventric- 
uto  wSs      The  remaining  fSrrows  merely  impress  the  surface  of  the  hemispheres 
and  are  termed  incomplete  fissures.   Their  depth  varies,  «"  ^''"^  ^''^  ^"«  """y  "^ 
few  millimetres  and  in  others  as  much  as  2.5  cm.,  with  an  average  o    about     cm. 
fhe  height  of  the  convolutions  usuaUy  exceeds  their  width,  the  latter,  in  turn   bcMUg 
commonly  somewhat  greater  at  the  surface  than  at  the  bases  of  the  gy;ri.     It  is  evi- 
dent  before,  that  th"^  convoluted  condition  of  the  hemispheres  proudes  a  ^^ead^^ 
increased  area  of  cortical  gray  matter  without  unduely  adding  to  the  bulk  of  the 
brain   Se  extent  of  the  sunken  surface  being  estimated  as  twice  that  of  the  exp^ed 
The  larger  and   longer  adjacent  convolutions   are    frequently  connected  b>    short 
ridees  the  annectant  gyri,  which  have  no  place  in  the  typical  arrangement.    They 
may^ris  the  bottom  of^  the  intervening  fissure  and  ordinarily  be  entirely  liidden 
H^om  vkw  (»ri  profundi):  or  they  may  be  superficially  placed  (gjri  transit.vi)  and 
materially  add  to  the  complexity  of  the  surface  configuration. 

The  cause  and  origin  of  the  cerebral  convolutions  are  still  subjects  for  discussion  The 
fact  that  at  the  time  the  fissures  begin  to  appear,  towards  the  end  of  the  fifth  fecial  month,  tne 
suria*  of  Ae  young  brain  is  not  in  close  conuct  with  the  cranial  wall,  disproves  the  assumption 
that  the  latter  is  directly  responsible  for  the  production  of  the  fissures  and  convolutions,  it  is 
probable  that  the  immediate  cause  of  the  surface  modelling  must  be  sought  m  the  ""fl"/"' 
CTowth  and  consequent  localized  tension  which  affect  the  hemispheres,  excessive  growth  m  the 
longitudinal  axis  resulting  in  transverse  furrows,  and  that  In  the  opposite  axis  producing  fissures 
extending  lengthwise.  Whether  the  excessive  expansion  is  cjiused  by  increase  in  the  gray  or 
■  white  matter  is  uncertain,  although  local  augmentation  of  the  cortical  gray  substance  is  prol> 
ably  the  more  important  factor.  After  the  beginning  of  the  eighth  month  when  the  p-owmg 
brain  comes  Into  contact  with  the  cranial  wall,  the  convolutions,  which  before  were  to  a  large 
extent  unrestrained  f  id  therefore  relatively  brojid  and  roundwi.  sulTer  compression,  the  results 
of  which  are  seen  in  the  flattening  ami  closer  packing  of  the  gyri  and  the  narrowing  and  deepen- 
ing of  the  intervening  fissures.  By  the  end  of  f.ctal  life  the  salient  features  of  the  plan  ot 
arrangement  have  been  establish^,  although  the  final  deUils  of  the  brain-pattern  are  not 
acquired  until  sometime  after  birth. 

The  Cerebral  Lobes  and  Interlobar  Fissures.— For  the  purposes  of 
description  and  topography,  the  cerebral  hemispheres  are  subdivided  into  more  or 
less  definite  tracts,  the  lobes,  by  certain  sulci,  uppropn.itely  know-n  as  the  inter- 
lobar fissures.  With  few  exceptions,  however,  the  lobes  so  defined  have  little 
fundamental  importance,  since  their  recognition  is  warranted  by  convenience  and  not 
by  morphological  significance,  in  most  cases  the  conspicuous  limiting  sulci  being  01 


1136 


HUMAN  ANATOMY. 


secondary  importance,  while  those  of  primary  value  are  comparatively  obscure  in  the 
hilly  formed  human  brain.  The  interlobar  fissures,  six  in  number,  are :  ( i )  the 
fissure  of  Sylvius,  (2)  the  central  fissure,  (3)  the  parielihotcipital  fissure,  (4)  the 
collateral  fissure,  (5)  the  calloso-marginal  fissure  and  (b)  the  limiting  sulcus  of 
Reil. 

The  lobes  marked  ofi  by  these  fissures  with  varying  degrees  of  certainty  are :  ( i ) 
y^'i  fronted,  (2)  the  parietal,  (3)  the  temporal,  {4)  the  occipital,  (5)  the  limiic,  and 
(6)  the  insula.  An  additional  division,  (7)  the  olfactory  lobe,  although  of  impor- 
tance as  representing  the  peripheral  part  of  the  rhinencephalon  of  osmatic  animals  (as 
those  possessing  the  sense  of  smell  in  a  high  degree  are  called),  is  not  related  to  the 
foregomg  sulci  and  comprises  the  rudimentary  olfactory  bulb  and  tract  and  associated 
parts  (page  1151).  It  will  be  of  advantage  to  describe  the  interlobar  fissures  as  pre- 
paratory to  a  detailed  consideration  of  the  lobes. 

The  fissure  of  Sylvius  (fissura  cerebri  lateralis)  is  the  most  conspicuous  fissure 
of  the  hemisphere.  It  begins  on  the  inferior  surface  of  the  brain  in  a  depression,  the 
vallecula  Sylvii,  which  opens  out  on  the  anterior  perforated  space.  The  first  part  of 
the  fissure,  its  stem,  passes  horizontally  outward  to  the  lateral  surface  of  the  hemi- 
sphere, forming  a  deep  cleft  which  separates  the  orbital  area  from  the  underlying  tem- 


FiG.  981. 


Rolandic  tmarc 


Inferior  ptcccntnl  mlciM 

Inferior  fr 


AfW'Ttiflinir  limti 


Pc«terior  limh- 


taleiM 


OrbiUI  surface 
HoriionUI  limb 


Portion  of  laterxl  surface  of  riclit  hemisphere,  showing  ascending,  horiiontal  and  posterior  limbs  of  Syh-ian 
■int.     -  ~  "  •       ••     -  • • — ' J  — Li.-..-    »  .  .    ,      ... 


688ure  radiating  from  Sylvian  poi 
ST,  superior  temporal  gyrus. 


B,  T,  O,  pars  baaalis,  triangularis  and  orbitalis  of  inferior  frontal  gyrus ; 


poral  pole.  On  reaching  the  surface  at  the  Sylvian  point,  the  fissure  divides  (Fig. 
981 )  into  («)  a  short  anterior  horizontal  branch,  {b)  a  somewhat  longer  anterior 
ascending  branch,  and  (c)  a  long  posterior  branch. 

The  anterior  horizontal  branch,  (ramus  anterior  horizoatalis),  about  2  cm.  in 
length,  extends  forward  into  the  inferior  frontal  gyrus  parallel  to  and  just  above  the 
infero-lateral  border,  and  forms  the  lower  limit  of  the  pars  triangularis  (page  1141). 

The  anterior  ascending  branch  (ramus  anterior  ascendens)  passes  upward  and 
slightly  forward  into  the  hind-part  of  the  inferior  frontal  convolution  for  a  distance  of 
about  3  cm.  The  frequendy  observed  variations  in  the  relation  and  arrangement  of 
the  anterior  branches  of  the  Sylvian  fissure — the  ascending  and  horizontal  limbs  in 
many  cases  arising  from  a  common  arm,  sometimes  being  fused  into  a  single  sulcus, 
or  again  being  absent — are  due  to  atypical  growth  of  the  opercula,  particularly  of 
the  frontal. 

The  posterior  branch  (ramus  posterior),  the  main  continuation  of  the  fissure  and 
about  8  cm.  in  length,  is  directed  horizontally  backward,  with  a  slight  inclination 
upward.  It  forms  a  very  evident  boundary  between  the  anterior  parts  of  the  parietal 
and  temporal  lobes  which  it  separates  by  a  deep  cleft  that  usually  ends  behind  in  an 
ascending  limb  surrounded  by  the  angular  gyrus  (Fig.  980).  Not  infrequently  the 
fissure  ends  by  dividing  into  two  short  arms,  one  of  which  penetrates  the  pwrietal 
lobe  while  the  other  arches  downward  into  the  temporal  lobe. 


THE  TELENCEPHALON. 


"37 


Fig.  98a. 


The  forai  and  retetions  ot  the  fissure  of  Sylvius  are  ao  dependent  upon  the  growth  ol  the 
«,rroJndinTSm  ttatV^tch  of  the  <Jevelopment  of  this  region  of  the  hem«phere  «  "•^'^ry 
K^ilS^SinTof  the  ,.Knifica„ce  of  this  conspicuous  sulcus.  Dnrmg  the  th.rd  f..tal 
month  the  lateral  suriace  of  the  cerebral  hemisphere 
presents  a  crescentic  depressed  area,  the  fosM  Sylvil. 
whose  floor  corresponds  to  the  insii/a  or  is/and  0/  Keil. 
The  latter  is  seen  in  the  adult  brain,  on  separating  me 
margins  of  the  Sylvian  fi.ssure,  as  a  sunken  area  which  is 
completely  hidden  by  the  overhanging  parts,  theopercuta 
3i.  of  the  surrounding  lobes  (Fig.  990).  During  the 
fifth  month  the  former  shallow  crescentu:  Sylvian  fossa 
gives  place  to  a  more  definitely  walled  triangular  depres- 
^on,  which,  during  the  succeeding  month,  begms  to  be 
«Ki;»ed  by  the  formation  of  the  opercula.  The  details  o^ 
this  process  have  been  carefully  studied  by  Cunningham' 
and  more  recently  by  Retzius.'  J^e  opercula  which 
bound  the  triai«ular  fossa,  named  from  the  regions 
which  contribute  them  and  at  first  three  in  number,  are 
the  upper  or  paririo-frontal,  the  lower  or  lemporal,  and 
the  anterior  or  orbital.  The  upper  and  >°*«^"'^«'*l  ..  g^,^;^  fissure.  Later  the  angle 
cme  in  contact  and  thereby  form  the  P°»'«n°L^^  1^^^^^  by  the 

between  the  ^r^^ -^t^'^^^f^^^'t^^f^^  '^^^^'^  '»-« 

appearance  of  a  wedge^aped  projection,  later  ine  jroma.  »r"      betVeen  the  adjacent  end 

Fig.  983- 
InfeHorprwwitnil  Rotandlc  a»ore 


L«fl  hemisphere  o«  brain  of  «ve  months 
loetiu;  thrce-lonnhs  natural  liie. 


Inferior  (ronUt 


Psticto- 

frontal 

operculum 

Frontal 
operculum 

OrMul 
operculum 

Olfactory  bulb 

IIMU 


-Intciiianclal 


Srl*lan 


or  temporal  ralcn* 


Lateral  .uriace  of  left  hemiaphere  ol  etaht  months  tons :  Iwula  i»  partly  covered 
Lateral  •"™«^™^'j^„|;ri;j;je-lourths  natural  site.    (Rttnmt.) 


of  the  parieto-frontal  and 
the  orbital  opercula.    The 
orbital  and  particularly  the 
frontal  operculum  are  late 
in  their  differentiation  and 
gro'-th,    and    not     until 
towards  the  second  year 
after  birth  do  they  come 
into  apposition  with  each 
other  and  the  remaining 
opercula  to  complete  the 
curtain  that  overhangs  the 
insula.     Along  with   the 
closure  of  the  front  part  of 
the  Sylvian  fossa,  the  dif- 
ferentiation of  the  anterior 
limbs  of  the  fissure  pro- 
gresses,  since   upon   the 

The  central  fissure    (sulcus  centralis),   or  fissure  of   Rolando,   extends 
transve«elv  across  the  upper  half  of  the  convex  dorsal  surface  of  the  hemisphere  and 
KeforTwith  d^  borden^ng  precentral  and  postcentral  convoutions   uiterrupte  the 
LenSloStudinal  course  of  the  gyri  and  sulci.     Bearing  this  peculiarity  in  mind 
fhe  fissure  b  readily  identified  even  in  brains  exhibiting  an  elaborate  and  complex 
m^ellin?     It  begins  above  on  the  supero-mesial  margin  of  the  hemisphere  a  short 
SSSce  behind  th^  middle  of  the  bord!er.  and  descends  with  a  slight  general  forward 
owStvTo  the  vicinity  of  the  posterior  limit  of  the  fissure  of  Sylvius,  above  whose 
mW  S  k  u^u^lv  ends      Its  upper  extremity  usually  extends  over  the  supero- 
SSSr^ylSl  hemisphere  Td.  passing  ^bliauelybackwar^  ^Jlow^er^^x^ 
distance  into  the  marginal  gyrus  of  the  mesial  surface  (Fig.  987)-     '»    ower  ex 
iSuTually  ends  short  of  the  Sylvian  fissure    but  <'<=P«'°';'^'y  f  "'^^y^  Ke 
into  tWs  cleft      It  constitutes  a  very  definite  boundary  on  the  external  surface  of  the 
hemiphere  Uween   the  frontal  and  parietal  lobp^     Although  passing   obliquely  . 
downwarf  and  forward,  the  course  of  the  central  fissure  «  by  no  means  straight 

>  Contribution  to  the  Surface  Anatomy  of  the  Cerebral  H.,v spheres,  Irish  Academy,  189:*. 

'  Das  Menschenhim.  1896. 

7* 


I 


i 


tias 


HUMXN  ANATOMY. 


owing  to  a  marked  angi  '  r  ixickward  projection  of  the  substance  of  thi-  precentral 
convolution,  situated  at  tlie  junc.ion  of  the  upper  and  middle  thirds  '  '  the  fissure. 
In  consequence,  the  R*  rr  presents  in  t'^.s  part  of  its  course  a  distin.  <ur\  c,  with 
the  concavity  directed  :or.vai  !  th  •  iipv»er  ai  ;  lower  limits  of  this  iiend  consti- 
tuting the  superior  ami  ih  •  inffi"  fr'Hu  rttspectively  (Fig.  980).  The  cortical 
tissue  filling  this  recess  is  i  '  '.mpon.u.'  ,  since  it  reprosi-nts  the  part  of  the  precentral 
gyrus  devoted  to  the  motor  centre  U"  i!i<  .>rm.  Below  the  inferior  genu  the  fissure 
descends  almost  vertically,  its  lower  ind  often  bending  slighdy  backward.  The 
angle  which  the  general  direction  of  the  >  ntral  tissure  makes  with  the  mesial  plane 
in  the  adult  brain  is  on  an  average  71.7°  (Cunningham),  the  Kolandic  angle,  as  it 
is  called,  of  the  two  sides  subtending  th'-r-fore  about  143°  TFig.  984)- 


Fig.  9h4. 


t 


Superior  upcct  ol  cerebral  hemijpnr  <s:  LF.  longitudinal  Sasu       • 
and  imerior  ^enu;  i.pc,  superior  prevenlial;  i.f.  i./,  superior  and  insr; 
inferior,  superior,  honzonul  and  occtpital  limbs  of  interparietal ;    f>-o 
lateral  occipital;  .Siijc,  aacending  limb  of  Sylvian ;  t^asc.^f^asc.   ^^^  endi 


,  Kuiaitdic  iissuie ;  V,         its  fc  JT 

fTimUl  ;>«.  paramediai     A',^  ^. 

rtf   'iccipiul ,         .  I.O.,  U'^~\^-  all 

imbs  of  superi-     and  mldtf  ^1 


nci 


Since  the  central  fissure  i    usually  developed  tror.  two  sepsrdK 
lower  and  a  short  upper  (Cunningham,  Retzius)  uhii  h  later  he.  <«» 
deep  annectant  gyrus  is  generally   found  crossing   ^ 
junction  of  its  iipjier  and  middle  thirtis.      In  exceptii 
is  continued  by  the  deep  annectant   ifyr^s  maintair 
adult  fissure  then  being  interrupted  by  the  bridge  u' 
bottom  of  the  cleft.     As  a  variation  of  very  great  r 
central  hssure  has  been  observed. 

The  parieto-occipital  fissure    iissura  parieto-occipital 
mesial  surface  of  the  hemisphere  CFig.  987),  where  it  appc;i 
extends  from  a  point  on  the  supero-mesia'  border  of  the  hem 
front  of  the  occipital  pole,  downward  an     forward.     This  inn< 


-  bottf 
i  cas< 

r  its    SUJ- 

1  ordin;* 
>mpk 


parts,  a 
continut 
oi  tar  sulcus  at 
orij-    >:il  rieparatii 


■iHtions,  th' 
■d  to  tht 
lig  of  the 

tly  on  the 

cleft  which 

out  4  cm.  in 

*f  the  fissure, 


THt  TELENCEPHALON. 


the 


sM-calkd  internal  paruto-o(,  Mtal  fiaurt.  -ieparates 

•    •.111  .1       ...1^    V^^lnur    liv    iikintnii 


panetal  and  <  xipital   1' 
two   sulci    tt^ether   toi 
cludt   a  wedgici  shape<! 
I«ri'  'o-occipit;i!  lissun 
the  1    misphere  and  ont 
sion.    isually  only  Jrom  i 
issu-     and  terminates  .r 
■jrcHi   -arieto-iKci'italis,  » 
. .'  thf     terparii '      fissure 


,l)es  and  iiids  l>elow  by  joining 


linv    »  > 
,« trill  11  ot 

ontiniH'  '■■ 
th<-  e.ttf! 
-,  mm 

Itsli 

\   iuch  sii 

AlthOi: 


...L-  mesial  surfaces  of  the 

„M.,  .^.v,-    -.    , r,   the  calcarine  iissure,   the 

whoM.-  posteriorly  directed   diver^inj;    Mmlw   iu- 

th<     occipital  lobe  known  as  the  cuiuus.     'He 

i     ithout  interruption  acr(»ss  tin     i.per  margin  ti 

a  surface  for  a  short  disfcmce^     This  outer  exten- 

length,      iistitutr^  thefi     ri.    I  fiarieto-otiipital 

■\  trans-     rse  course  in  a  b-   'e,i  convolution    the 

eparates  its  en<l  th<  mcipital  part 

IS  ending  in  t»>    ^hort  ,ind  somewhat 

■occipital  tissure  is  usially  rtlatively 

itf  much  import- ;»ce  iis  atlonl    <a 

"'  iP' 


mds  ail 
;h  somt 
.«)«»  i    anches    u,     extern     limit  of  the  par 

irwoniiiticuous'   noiwithstai,   inc.  the  sulcus        — ',.    '  , 

St'^^n..^  upper  hr.it  of  the  co„ve„f.....l  boundary  hne  ^twe.  n  1 1, 

'laiW    hep-   tal  and  tern  -oral  lobes.      1„  the  >a|tal  bnun  the  ^..rR-to-...ui 
cu^p^oduce^   .    iistinct  invagination  of  the  wall  of  the  cerebn.m  ami    om 
therrfX   ^   ..  c    mplete  fissure.    In  the  adult  bra.n.  howx-ver.   dl  trac  o^  th> 
L  L  disappeared  in  consequence  of  the  growth  and  th,cken>nu  ..(  ,h. 
waU  which  ^  ibsequently  takes  place  (Cunnmghan,  '. 

The  .;o»ateral  fiasure  (fiiwara  collatcralls )    -  a    v. 
inferior  surfa.  e  of  the  hemisphere^     It  begn  s  behi.ul  a  1, 
ocripifc.   IK>1*-  and  extends  forward,  crossin,    the  teuton 
and  Wial  t. .,  the  calcarine  fissure,  until  opposite  th.     .>8t. 
sum    vhere  it  mc  ts  the  hippocampal  gyrus.     It 
form  .«  the  laterai    K)undary  of  the  last-named  coi 

well  toward  tue  t        wral  pole,  near  which  it  eith> 

riirveci  iuirow,   tl        nrisura  temporalis,  which    m 

tts-«re.  separates  tli     jwer  or  hippocampal  part 

iotK;^     According  to  Cunningham,  the  collater 

three  ■  sstin  '  parts— a  posterior  or  occipital,  an 

later  becon  c  one  continuous  furrow^     Of  these 

(liate,  and  usually  also  the  tempf>ral,  ar        mi 

t  At  coV.  teral  protuberance  and  the  coll.       i! 
age  1 164).     The  occipital  portion  of  ti 

,    es  no      ive  rise  to  any  elevation. 

Thr  calloso-marginal  fissure  (sulcu 


thei 


in,  o\ 


f  tl 


A  sul- 

inds, 

afold- 

,tri<  "'ar 

.iikiii  sulcus         the 

the  outer  sidt        the 

.irallel  with,     How 

*  the  corpus  callo- 

lightiy  outward. 

e  temporal  area 

'ts  with  a  short 

the  collateral 

i  the  temporal 

^   ,  cpresented  by 

edia;     sm;     ,,  inporal — which 

primal  \  divisions,  the  interme- 

tissiires,"  producing  respectively 

...i,         seen  in  the  lateral  ventricle 

re  is  !    ver  complete  and,  therefore, 

calloso-marginai  nssurc  tsu.u.  ..  «iili)  «  the  most  conspicuous  sul- 
c>  ,  the  medial  surface  of  the  hemusphetc.  where  it  appears  .is  a  curN«l  urrow 
miunue  atov^^nd  concentric  with  the  arch,  d  upper  surface  of  the  corpus  call.^um 
k  teufns  Sont  below  the  fore-en.l  of  this  ndge,  iust  aU.ve  the  anterior  ..eriorated 
soacesw^P^  around  the  genu  of  the  cor  call «um  and  .rches  backward  al.n.- 
the  latter Tt^cture  almost  L  far  as  th.   .pi  ■ .  where  it  turns  upward  (ramus  «ar- 

Xu"  LI  reaches  the  supero-mesial  the  hemisphere  ;-h.-t  d^ta^^^^^ 

hind  the  overturned  end  of  the  Roland  ^^ure.  By  its  course  the  cidliKjO-marginal 
S  marks  of!  on  the  anterior  two-t..rds  of  the  mesial  surface  of  the  hemisphere 
helar^S Convolution  of  the  fronUl  lobe  from  the  callosal  gyrus  of  the  l.|nbic  lo be^ 
the  ^mewhat  uncertain  posterior  boundary  of  th<- latter  beyond  the  sulcus  being 
SiS  b7the  inconspi^ous  postlimtic /issuer .  ^''''"NrlutTthc  c"C- 
tricallv  with  the  splenium.  The  frequent  ^■arlatu.ns  n  xW  ^'^'^'^^J^^^^'J^^ 
marginal  fissure  depend  upon  irregularities  in  the  ar^.^.-ment  and  hism.  of  the 

three  separate  furrows  by  the  union  of  which  a  roniinuoa-   ^«icus  is  lormed. 
three  scpantteUi  y^^    ^  ^^.^  ^^^  ^.^^^.^  ^.^   ^  , 

that  incompletely  surrounds  tiu-  msub  an,,  u„«^e.tlv  ^-^-^ZS^^'^'^'Z^ 
of  the  central  cortex  from  H.  d.-^-  '^«  ot  th^  enclosmg  'TT"^*^  ''^, ^^  J*!  I'"  ^;„: 
consists  of  Uiree  parts-n  -^«^  -^m;  th^  island  ^,^°'"  f'^^J  ^-^^^.f ,  i'Tn"  1 
tal  lobes  an  anterior  inr  ny  m  »««  .etween  tiw  insula  and  the  fron  al  lobe,  ana 
tal  loDes,  an  anierwr.  ,  *•._  .^  j^^  ..^  ^  »i.„  jjand  from  the  limbic  lobe, 
a  posterior,  imperfr-      ^-s—- ■'=■  ' —  «^^  '■"  —  i-^ju^j 

The  Frontal  ;^obe--The  fronw?  M*e  (totas  Ir^Malis)  is  the  largest  of  the 
subdivisions  of  the  liem,s,«..re  ami  inriad^  approxin.      ly  one-th.rd  of  th.-  hem.- 


1140 


HUMAN   ANATOMY. 


cerebrum.  It  appears  on  each  of  the  three  aspects  of  the  hemisphere  and  has, 
therefore,  a  dorso-lateral,  a  mesial  and  an  inferior  surface.  On  the  external  surface 
of  the  hemisphere  it  is  bounded  behind  by  the  central  fissure,  which  separates  it  from 
the  parietal  lobe,  and  below  by  the  fore-part  of  the  Sylvian  fissure,  which  intervenes 
between  it  and  the  temporal  lobe.  On  the  mesial  surface  the  frontal  lobe  includes 
an  irregular  -1 ,  marked  off  by  the  calloso-marginal  sulcus,  the  longer  upper  limb 
ending  behind  the  central  fissure.  On  the  inferior  surface  of  the  hemisphere,  the 
frontal  lobe  includes  the  concave  orbital  area,  bounded  behind  by  the  transversely 
directed  stem  of  the  Sylvian  fissure,  which  sulcus  thus  separates  it  from  the  temporal 
lobe. 

The  principal  fissures  on  the  dorso-lateral  surface  of  the  frontal  lobe  are:  ( i )  the 
inferior  precentral,  (2)  the  superior  precentral,  (3)  the  superior  frontal  and  (4)  the 
inferior  frontal.  The  inferior  precental  sulcus  which  consists  of  a  longer  vertical 
and  a  short  transverse  limb  and  has  a  general  T  or  T  fc>rm.  The  vertical  limb 
begins  above  the  fissure  of  Sylvius  and  in  front  of  the  central  fissure  and  extends 
upward  parallel  to  the  latter  and  separated  from  the  lower  part  of  the  precentral 

convolution.  The  horizontal  limb 
passes  obliquely  forward  and  upward 
and  cuts  for  a  variable  distance  into 
the  middle  frontal  convolution.  Fre- 
quently the  inferior  precentral  sulcus 
is  directly  continuous  with  the  inferior 
frontal  hirrow;  sometimes  it  opens 
below  into  the  Sylvian  fissure  and 
above  may  join  the  superior. 

The  superior  precental  sulcus 
prolongs  upward  the  anterior  boun- 
dary oithe precentral  convolution.  It 
lies  parallel  with  the  up{)er  half  of  the 
Rolandic  fissure,  but  does  not  usually, 
although  sometimes  reach  the  upper 
margin  of  the  hemisphere.  Almost 
constantly  it  receives  the  posterior 
end  of  the  superior  frontal  sulcus  with 
which  it  forms  a  H  shaped  furrow. 

The  superior  frontal  sulcus 
extends  forward  from  the  preceding 
fis-surc  with  a  course  which  corresponds  in  general  with  the  supero-mesial  border 
of  the  hemisphere  and  thus  marks  off  a  longitudinal  marginal  tract,  the  superior 
frontal  convolution.  Anteriorly  the  superior  frontal  may  join  the  median  frontal 
sulcus,  while  its  posterior  end  may  incise  the  precentral  convolution.  Often  the 
course  of  the  fissure  is  interrupted  by  superficial  annectant  gyri  which  connect  the 
adjacent  borders  of  the  upfier  and  middle  frontal  convolutions. 

The  inferior  frontal  sulcus  begins  behind  in  the  interval  between  the  hori- 
zontal and  vertical  limbs  of  the  inferior  precentral  furrow,  or  in  confluence  with  one 
of  these.  In  its  general  course  it  arches  forward  and  downward  towards  the  anterior 
or  superciliary  margin  of  the  hemisphere  and  terminates  a  short  distance  behind 
this  border  by  bifurcating  into  a  transverse  limb.  The  line  of  the  fissure  is  often 
obscureti  by  superficial  annectant  gyri  and  complicated  by  small  secondary  furrows 
which  pass  from  it  into  the  bordering  middle  and  inferior  frontal  convolutions. 

The  convolutions  .-m  the  dorso-lattral  surface  of  the  frontal  lobe  are  the  pre- 
central, the  superior  frontal,  the  middle  frontal  and  the  inferior  frontal. 

The  precentral  gyrus  (gynis  ceotralis  anterior),  also  known  as  the  ascending 
frontal,  is  bounded  behind  by  the  central  fissure  and  in  front  by  the  superior  and 
inferior  precentral  sulci.  Below  it  is  limited  by  the  Sylvian  fissure,  whilst  its  upper 
end  is  continuous  with  the  paracentral  lobule  of  the  mesial  surface.  Anteriorly  it  is 
connected  with  all  three  frontal  convolutions.  A  short  distance  above  its  middle,  it 
sends  backward  a  conspicuous  projection,  triangular  or  rounded  in  outline,  which 
encroaches  upon  the  postcentral  gyrus  and  correspondingly  modifies  the  line  of  the 


Anterior  Mpcct  of  ccrabral  hcmlapherai,  hardened  in 
t'iM;  tf,if,  »uperior  and    inferior  fronul   fiuurn 
ncuian;        '     '''      '  *     '       '  ^     ' 


parame 


;  M./,  mid-fronul;  f-m.,  fronUMnarcinal. 


THE  TELENCEPHALON. 


1141 


the  external  surface  and  reaches  the  trontaJ  P^j^    "  '     .  .     ^    precentral  convolu- 


Inferior  frontal  nilcu* 


Fig.  986. 
Inferior  precentr»t  aulciu 


.Rotandle  fissure 


AicendinK  limb 


Orbiul  anrfacc. 

HoriionUl  limb' 


Ponltrior  limb 


i_  .11.  i«l    iriinluUris  ( D  md  orblUlis  fO)  of 

above  and  below  by  the  superior  and  the  «-/;|j;» -',7„;irJ;;'r^mf  al^^^^ 
Anthropoid  apei.  is  almost  constantly  subdi.ded  into  an^PP^"^^     j      ,       ^^^^en 

dWisTon  byV-  -^?/-''^"f-  !"S^^^^^^  to  forrn  the 

{;£:  a  sh^ort  disunce  above  th;;  Hupe-ihary  TO^^  ,^^,^^  ^^^.  .^^^, 

^  The  inferior  fronta  gyrus,  the  J""^^",  J  J,7„„"i  t,,.  anterior  limbs  of  the 
frontal  sulcus  a.ul  arches  f'™  ""^  f  ^^^^'l^h  the  lower  end  ..f  the  pre- 
Sylvian  fissure.      Below  and  behind  it  is  conm^^^^^  ^^^  ^  ^  ^  ^^^^  .^,^.^j^^ 

central  convolution  by  a  narrow  bridge  ^"™^;,^  „f  the  Svlvian  fissure  the 
central  sulcus.  By  the  .''''«^^'«»\"K,^"  •  •^rj' •  io  h  S^  portions--tlu.  /,an  f^salh. 
inferior  frontal  gyrus  is  \"^; "'M^^telyJ  udcd  ..m.  mr      p^^^^  ^^^^j.^  , 

the  /><!«  triangulam  and  the  /Mr^  <>/0//<i/»  *  ?^'^••  ^  ,  ,;„„  .^na  Ues  iKtwcen  the 
operfulariH)  occupies  the  P^lf"";"  jSntUvlviriimb  it  forms  the  fore-part  of 
i,\ferior  prece.Ural  sulcus  and  the  f '''^  « .^,>  .' ! '„^  although  constant 

the  fronto-parietal  operculum  and  "«  ^^"^^^  J^  ; i*^,  !^^\,„„';,,..rd  and  forward  across 
furrow,  the  shIchs  dmgonaln,  «h.ch  «™  "''Xliv  distinct,  the  diagonal  sulcus 


1143 


HUMAN  ANATOMY. 


apex  towards  the  Sylvian  point.  The  pars  orbitalis  lies  below  the  horizontal  limb 
and  is  continued  around  the  margin  of  the  hemisphere  onto  the  orbital  surface  of 
the  frontal  lobe.  It  b  evident,  from  the  description  of  the  boundaries  of  the  Syl  ian 
fissure  already  given  (page  1137),  that  the  preceding  subdivisions  of  the  inferior 
frontal  gyrus  correspond  with  certain  of  the  opercula — the  pars  basalis  with  the 
anterior  part  of  the  fronto -parietal,  the  pars  triangrularis  with  the  frontal  and  the 
pars  orbitalis  with  the  orbiul  operculum.  The  posterior  extremity  of  the  inferior 
frontal  gyrus  on  the  left  side  is  known  as  Broca's  convolution  and  has  long  been 
regarded  as  the  centre  for  the  movements  for  articulate  speech,  although  the  accuracy 
of  this  view  has  been  questioned.  According  to  Marie,  Broca's  convolution  has 
no  relation  with  speech,  a  conclusion,  however,  so  far  not  convincingly  supported. 
The  convolution  is  sometimes  better  developed  on  the  left  than  the  right  side  of 
the  brain,  the  pars  triangularis  particularly  being  increased.  As  previously  noted, 
the  development  of  this  wedge — the  frontal  operculum — bears  a  direct  relation  to 
the  degree  of  independence  of  the  two  anterior  limbs  of  the  Sylvian  fissure. 

The  mesial  surface  of  the  frontal  lobe  {Y\%.  987),  includes  only  one  convolution, 
the  marginal  gyrus,  which  lies  between  the  dorso-mesial  margin  of  the  hemisphere 
and  the  calloso-marginal  sulcus  (page  11 39),  and  by  the  latter  is  separated  from  the 
limbic  lobe.  It  is  -^-shaped  and  directly  continuous  with  the  superior  frontal  gyrus 
above  and  with  the  gyrus  rectus  on  the  orbital  surface  below.  Its  posterior  end  is 
almost  completely  cut  off  from  the  rest  of  the  gyrus  by  an  ascending  limb  (sulcus  para- 
ceatralis)  from  the  calloso-marginal  sulcus,  the  portion  so  isolated  forming  the  front 
part  of  the  paracentral  lobule,  which  is  bounded  behind  by  the  upturned  end 
(ramus  marKinaiis)  of  the  calloso-marginal  sulcus  and  contains,  near  its  hind  border, 
the  termination  of  the  fissure  of  Rolando.  By  means  of  an  annectant  convolution 
passing  below  the  last-named  furrow,  the  frontal  part  of  the  paracentral  lobule  is  con- 
tinuous with  the  part  contributed  by  the  parietal  lobe.  The  middle  of  the  mar- 
ginal gyrus  is  often  incompletely  subdivided  by  a  shallow  longitudinal  groove,  the 
mesial  frontal  sulcus,  into  an  upper  and  a  lower  tract,  whilst  its  anterior  and  lower 
end  is  uncertainly  cleft  by  two  or  three  short  downward  curving  furrows,  the  sulci 
rostrales. 

The  orbital  surface  of  the  frontal  lo6e  is  marked  by  two  fissures,  the  olfactory 
and  the  orbital  and  by  three  chief  convolutions,  the  inner,  the  middle  and  the  outer 
orbital.  Although  such  division  is  convenient  for  the  purposes  of  description,  it 
must  be  remembered  that  these  orbital  gyri  are  not  separate  convolutions,  but  largely 
the  inferior  p)ortions  of  tb<!  upper,  middle  and  lower  frontal  convolutions  of  the  outer 
surface  of  the  lobe. 

The  olfactory  sulcus  lodges  the  olfactory  bulb,  tract  and  tubercle,  and  ex- 
tends parallel  with,  or  inclined  somewhat  towards  the  great  longitudinal  fissure.  Its 
course  being  straight,  the  sulcus  marks  of!  a  narrow  strip,  about  i  cm.  in  width, 
along  the  mesial  border  of  the  lobe.  This  area,  although  specially  designated  as  the 
gyrus  rectus,  is  only  a  iKirt  of  the  broader  longitudinal  tract  which  corresponds  to 
the  orbital  surface  of  the  superior  frontal  con\olution. 

The  orbital  sulcus  includes  a  nunilx.-r  of  furrows  whose  arrangement  is  very 
variable,  not  only  in  different  brains  but  often  on  the  two  sides  of  the  same  brain. 
In  the  disposition  assumed  as  the  typical  one,  which,  however,  is  far  from  constant, 
the  orbital  sulcus  consists  of  two  longitudinal  limbs,  connected  by  a  shorter  trans- 
verse arm,  the  three  furrows  forming  a  common  fissure  which  corresponds  more  or 
less  closely  with  the  letter  H.  In  many  cases,  however,  the  sulcus  more  nearly  re- 
sembles an  X  or  K,  or  it  muv  be  still  further  modified  by  the  presence  of  additional 
secondary  grooves  of  variable  number  and  length.  Assuming  the  conventional  H- 
forni  to  exist,  the  orbital  surface  is  divideil  into  three  longitutlinal  tracts,  *he  inner, 
middle  and  outer  orbital  gyri,  by  the  long  limbs  ( sulcus  orbitalis  internus  et  exter- 
nus).  The  inner  tract  is  sulxlivided  by  the  olfactory  sulcus  into  the  gyrus  rectus, 
above  mentioned,  and  an  outer  part,  the  gyrus  orbitalis  intemus  in  the  more 
restrictetl  sense.  The  middle  orbital  gyrus  is  subdivided  by  the  curved  transverse 
limb  ( salens  orbitalis  transvcrsus)  into  the  anterior  and  the  fiostcriot  orbital  gyrus, 
which  lie  respectively  in  front  and  behind  the  transverse  furrow.  In  many  cases  the 
latter  curves  outward  and  backward  until  it  almost  reaches  the  Sylvian  fissure. 


THE  TELENCEPHALON. 


"43 


Th..  Parietal  Lobe.— This  division  includes  a  considerable  part  of  the  hemi- 
much  the  more  extensive  *"*>,  »"^"'*"'^,r'.  <;«„,«   but  behind  and  postero-mfe- 

A=  Ritandic  fissure.  It,  P""^"' 'r'""^J,"SKuS?d™riron,  >he  potal 
Kcipiul  lobe.  »  b»g.  Iv  ";'"»"<r'„"^  ZS^SS.  ol  tte  hemisphere  to  »  in- 
.here  the  Pf^"''-''^^"  ^  '.^  JfChiXl^ve,  the  WerS-teeral  border 

'St'^^rtn  £  s7vis;  £S'  'sjs;  ^^.^  ^^  o,  th.  u.t». 

Fig.  987. 


Infero-mcsial  «P«t  of  lelt  ,c«r«br.l  h«".tapli.rej,  r- 
tnd  ot  Rotandic ;  /.  V.,  port^limWc 


""'  Ce  °"5w'"^'  .J/-  ^^  P-rielal  lohc  is  subdivided  by  a  composite  fissure, 
the  iJterpIriStulcus.  intoVeVeneral  tracts,  the  postcentral,  the  superior  ^n- 

inferW  anj e'S^the  lobe  a  short  dis';;nce  above  the  Sylvian  h^u^^^^^^^^^^  - 

rarelv  continuous,  ascends  for  about  an  inch  parallel  with  »■}*/«"';*'  ".„.",r^ 
S'l^ps  backward  and  slightly  upward  across  the  .P^^^,!'"*"  »'\\*^S  il  th^ 
The  interparietal  sulcus  is  developed  as  four  onKinally  distinct  Part"' *X  -nferior 
7unv  foSbrain.  notwith.,tandinVVheir  usual  fusion,  are  ;:^.«=*^"i;^/,iif^'fSn- 
and  the  superior  postcentral  sulcus  and  the  horizontal  and  occipital  limbs  ^V-un 

""^^TTeUerior  po-tc.ntr.l  .ulcu.  lies  behind  and  P^-"^' ^JlJ^r^'thl^rpeS 
of  the  central  fissuJ^    AlthouKh  in  most  «=»f«J^«""""7„  ^^^^^^^^^^^ 
postcentral  Hulcus  (in  73  per  <-ent.  according  to  Retzius  ).  or«ith  the  noriio 

'  BioloRische  lintersuchunicen.  VIII.,  189*. 


->f^ 


1 144 


HUMAN  ANATOMY. 


(66  per  cent.),  <"■*'*  both  (55  per  cent.),  the  inferior  limb  may  remain  ununited 
( 17  per  cent ).  When  jomed,  the  two  limbs  together  form  a  continuous  postcentral 
sulcus  which  parallels  the  fissure  of  Rolando  and  bounds  the  postcentral  convolution 
behind.  In  rare  instances  the  inferior  postcentral  sulcus  opens  below  into  the 
Sylvian  fissure. 

The  ■uperior  postcentral  sulcus  lies  behind  and  parallel  with  the  upper  part 
of  tfie  fissure  of  Rolando,  gaining  the  superior  margin  of  the  hemisphere  between  the 
incisions  of  the  Rolandic  Sssure  and  the  upturned  end  of  the  calloso-marginal  sulcus. 
Although  in  59  per  cent,  of  the  brains  studieil  by  Retzius  the  fissure  was  confluent 
with  the  horizontal  limb,  in  24  r^er  cent,  it  remained  isolated. 

The  horizontal  limb  passe  backward  and  slighriy  upward  and  separates  the 
superior  and  inferior  parietal  convolutions  from  each  other.  It  is  usually  continuous 
in  front  with  one  or  the  other  or  with  both  postcentral  sulci  and  behind  with  the 


Lateral  upcct  ol  left  ildc  of  bnin.    /-A,  lon(itudimlliM«n:  r.,*-..  r.  Rolandic  fiHiii»' i  <.-    .  »,    i..<..i..  .  j 

i..diu  r^ESf^'"!^'""  °""""'  •  "■ '""'  ••"«'""  '«"•»"' "« »» «pJ^^m».f^.?f«?rSdaii'?LUf 

IJosteri(»r  or  occipital  limb.  As  a  rule  it  joins  a  continuous  postcentral  sulcus  in 
which  case  the  three  furrows  form  a  h- shaped  fissure,  which  subdivides  the  parietal 
l<ibe  into  Its  three  mam  convolutions. 

The  occipital  limb  is  u.sually  attached  to  the  horizontal  one  and  then  directly 
prolongs  the  interparietal  sulcus  into  the  occipital  lobe.  Sometimes,  however  it 
retains  its  original  independence  and  is  separated  from  the  ramus  horizontalis  by  a 
deep  annectant  gyrus.  It  is  irrcgulariy  curved  and  marks  the  lower  boundary  of  the 
gyriis.  the  arcus  parieto-occipitalis,  which  receives  the  outer  end  of  the  parieto- 
"^j  t"i  •  J  !!''''■  ^^>""''  '•«-'  ""«  of  this  furrow,  the  sulcus  lies  in  the  occipital  lobe 
and  behind  the  arcus  paneto-occipitalis  ends  by  bifurcating  into  two  widely  diverifent 
arms,  which  constitute  the  transverse  occipital  sulcus. 

The  chief  corn'o/utions  on  the  exUrnai  surface  of  the  parietul  lobe  are  three— the 
postcentral,  the  superior  parietal  and  the  inferior  parietal. 

II  ''",*i<|  PO'tcent"!  gyrus,  also  calletl  the  ascending  parietal,  forms  the  posterior 
wall  of  the  fissure  of  Rolando,  and  itself  is  bounded  behind  by  the  |Kwtcentral  sulcus 
either  by  the  continuous  fi.ssure  or  by  its  iwo  divisions.     The  lower  end  of  the  gyrus 
IS  connected  with  the  precentral  convolution  in  front  and  with  the  inferior  parietal 
one  behind  by  the  annectant  gyri  closing  the  lower  ends  of  the  central  and  postcen- 


THE  TELENCEPHALON. 


"45 


^1  ..,!«  r«n«tivelv      Above,  the  convolution  is  continuous  with  the  precentral 

^S»™1».  S,.TS  modelling  o1.L«,™J  .urface  ol  ,he  hem.ph.re  and 

*ti  »iCr;.rilS''S^'  ^"KlSr  ««  ,«  hetweej  .upeH„ 

.Z5f„TC™    £  iKirijoiBl  limb  of  the  inlerfmietiil  .ulcus  and  the  »u|kto- 

■^S  h^«  rfJh^  hembphere.     Behind,  it  U  limit«i  by  the  oven-raed  o.,  er  end 

""'1,fiS.'£'SiS»';°^™i^rSiXS?- between  the  corded  i„te,pan«al 
b  condnuou.  «.th  the  «Jp«M  <^^^^^  ^^^e^inuio^  ol  the  fi«  and 

fissure.     It  lies  behind  and  below  ^^e  front  pirtoJthe^mer^^^  ^.^^  ^^^ 

whose  lower  end  it  b'jlV.*'^^  P^^l JS^r^n^r  S  ang^  surmounts 

superior  temporal  and  ^ehmd  w.th  th.  angubj^^^  .^^^ 

the  upwardly  ^'^"^J  f  "'^  °' '^^^f^TvolS^     It  is  commonly  imperfectly  sepa- 
the  superior  and  middle  temporal  /^"J'"'"""      ,  jhe  postparietal  gyrua 

rated  Irom  the  postparietal  gyrus  by  a  P'j""?*:  *""^?,*^L  temooVal  sulcus  and  below 

Rolandic  fissure  in  front;  below  '' «  •^l^!^"y^„d  itTcontinuation,  the  post-limbic 
c.lloso.marg.,« Uucus  to^^  by  the  q-dra^lobule 

upturned  terminal  limb  of  th^<=''"'»*;-7;.«'"^'^"f„r  m^f^^^^^^  is  usually 

'he,  b?:nlt  mor'e%urwsX'/.™^^^^^       whSlncise  the  up,.r  margin 

the  Sita?"=^r;ni  the  adjacent  parts^o,  .He  hemisph^^^^^^  ,  f.^rS  fand  t 
of  the  alpectH  of  the  hemisphere  and  pos*«^^ee  or     a  h^al.^a  m._^  ^^^  ^^  .^^ 

inferior  or  tentorial  suriT.e.    A  «'^"-™f^.'^SS  ^Ts  a  backward  prolongation  of 
„f  man  and  of  the  anthropml  apes  and  is  dcve lop^^^^^^ 

'K  rS\reV:hui  '^"extZ  rsSnl^rhmited  by  the  internal  parieto. 

S^t^  ^tf^.  boundary^ ^^T  ^l^lSif  1  ^it 
,>arieto-occipitat  Ime  ^l--^^ "  ^^'V  t„"'^''":L  jS^  as.KC   its  demar- 

S*^  tr-^r^SeSl;  r^cci^llLfu^r.  Ind  temporal  .L  being  here 


1 146 


HUMAN  ANATOMY. 


directly  continuous,  and  depends  upon  the  recognition  of  an  arbitrary  line  which 
may  be  drawn,  as  suggested  by  Cunningham,  from  the  preoccipital  notch  on  the 
infero-lateral  border  to  the  isthmus  of  the  limbic  lobe,  just  below  the  splenium  of 
the  corpus  callosum. 

The  external  sm/ace  of  the  occipital  lobe  is  modelled  by  two  well-defined  fissures, 
the  transverse  occipital  and  the  lateral  occipital,  and  by  two  somewhat  uncertain 
convolutions,  the  superior  and  the  inferior  occipital  (Fig.  988). 

The  transverse  occipital  sulcus  is,  as  above  pointed  out,  the  widely  diver- 
gent terminal  bifurcation  of  the  interparietal  fissure,  whose  last  segment  beyond  the 
outer  end  of  the  parieto-occipital  sulcus  enters  the  occipital  lobe  to  end  in  the  manner 
just  indicated. 

Fig.  989. 


Inferior  .ipKi  of  «rehr.l  hemi»ph»rM.     io     /.»..  ,.„.,   internal,  transvcrx  and  external   orbital   fSiaurea' 
I./.,  incisura  temporalii;  «/..  calcarine.  «/..  .ullaieral :«-/..  occi|.iio.tenuK.ralfi™ur«  """««• 

The  lateral  occipital  sulcus  arches  horizontally  forward  below  the  lower  end 
ot  the  precedmg  furrow,  not  mfreiiuently  dividing  into  an  ascending  and  a  descending 

The  superior  and  inferior  occipital  gyri  are  the  upper  and  lower  areas  into 
which  the  outer  aspect  of  the  (Mrcipital  lobe  is  somewhat  uncertainly  subdivided  by 
the  lateral  occipital  sulcus.  Secondary  furrows  and  ridges  often  obscure  the  charac- 
tenstic  modelling  of  this  surface,  whilst  annectant  convolutions  connect  itsuyri  with 
the  parietal  and  temporal  lobes. 

The  mesial  surface  of  the  occipital  lobe  presents  one  sulcus,  the  calcarine  fissure 
a  triangular  tract,  the  cuncus,  and  jwrt  of  the  gyms  lingualis. 

The  calcarine  fissure  Ijesfins  by  a  forked  cxtrrmitj,  the  longer  lower  limb  of 
which  incises  the  occipital  jjole  in  the  impression  made  on  the  hemisphere  by  the 
lateral  sinus.  It  then  continues  forward,  slightly  arched,  a  short  distance  above  the 
border  of  the  lobe  formed  by  the  junction  of  the  falx  cerebri  and  the  tentorium,  and 


THE   TELENCEPHALON. 


"47 


ends,  after  a  short  bend  outward.  Iw  citing  '■^j'-£f  ^"^.,  ^£ 
spl.nium  of  the  corpus  ^^^^^^^f  J«J  ^^  J^"  ^^  ct.  the  isiAm^^hich 
extremity  of  the  hippocampal  gyrus  '"to  f  "^^°*  .  ^'^roader  lower  arm.  which 
links  the  gyrus  with  the  «11<^1  ^^S^d  f^fonn  gyri     A  short  distance 

establishes  contmuUy  ^l*^"  J*  •VPP"?^S„^''  the  lower  end  of  the  parieto- 
infrontof  its  middle,  the  calcanne  fissure  IS  pineaov  ^^^ 

T'^^.'iX  U«  rtS^ar'rnei^hh^u^usuaUy 'appearing  as  one 
diverging  limbs  li«  ^"^ .  "^"^;„;,m  and  calcarine  sulci  are  ncompletely  iseparated 
continuous  fissure,  the  P*"«'«-^"P'^„^t fh?  cuneus  with  the  limbic  lobe.  The 
by  a  deep  annectant  ?yn>f.  ^^'^j^  k„  a^nd  sunken  gyrus  into  an  anterior  and  a 
Jloirine  ^ure  .^H  ^^^^;^t%s'^^,rar^l^tH::jss!^^,  is  shorter  and  shallower 

gilt r^rthTeaSr  iX  L'thTS  U  ^n  on  the  inner  boundary  of 
the  posterior  horn  of  the  >fte«^ J'^ntride.  ^^^  ^^^      ,t 

The  cuneu.  forms  »h;  ch.d^'l°^t%^eto-Stal  sulcus  in  front  and  the 
is  triangular  m  outlme  f^  Uf  ,^^f ^£^  S^above  and  behind  it  reaches  the 
^^^'^6^':'^fSi'^'iFT^7^  I-  -rf-  is  frequently  impressed 
by  one  or  more  shallow  vertical  Junows.  .       j     j^    irregular  elongated 

Uition.    The  By™  »»  '.»'»  ""f  *^ -..TS;,  J  the  h-nUphere  .nd  appsais  on 
a,rf  therefor,  bear,  the  i""™^"^^^  ^^IL^ymoSS  bj  ineg-l.r  sh.no. 

..te„T!iv^s%"rsi4"S^43£Ss:3jh^^^^^ 

tl™  to  the  «»•»*', P"»''te''"S~S'i5?»^he  la^»lnclades  .S  irreg' 
™'"Tte  iSporrf  Lote-The  temporal  lobe  include,  *ti"r.l"'ly  Py"™"" 

£Ul^,e<'.T;^?tStSlrd  tht=.:;.™rS2!»';Ut!:S«  .he  ,«ip„al 
•"'  '•fjnl^'S-  lobe  pr.«nt.  three  ™H„ce,.  tt»  eoovex  '^^^^SSIZ 
Si'aS-^^-^yrb^ert'&Sf^l^M^S^^^^^^ 


1 148 


HUMAN  ANATOMY. 


inferior  temporal  (Fig.  988),  all  of  which  correspond  in  the  general  direction  of 
their  course  with  the  posterior  limb  of  the  Sylvian  fissure  and  extend  backward 
and  slighdy  upward. 

The  superior  temporal  sulcus,  also  called  the  parallel  sulcus  in  recognition 
of  the  similarity  of  its  course  with  that  of  the  posterior  limb  of  the  Sylvian  fissure,  is 
the  first  in  the  series  of  longitudinal  furrows,  the  third  of  which  appears  not  on  the 
outer,  but  on  the  inferior  aspect  of  the  lobe.  It  begins  near  the  temporal  pole,  run? 
parallel  with  the  posterior  limb  of  the  Sylvian  fissure  and  ends  by  cutting  upwar 
mto  the  inferior  parietal  convolution,  whose  angular  gyrus  surrounds  the  upturned 
extremity  of  the  sulcus. 

The  middle  temporal  sulcus,  the  second  in  the  series,  lies  below  the  pre- 
ceding fissure,  whose  direction  in  a  general  way  it  follows.  It  is,  however,  much 
less  certainly  marked  and  in  most  cases  is  not  a  continuous  furrow,  as  is  the  superior 
sulcus,  but  broken  by  superficial  annectant  convolutions  into  a  number  of  separate 
pieces,  the  exact  sequence  of  which  is  often  difficult  to  follow.  The  upturned  end  of 
the  middle  temporal  sulcus  cute  into  the  lower  parietal  convolution  towards  the  pos- 
terior limb  of  the  interparietal  sulcus  (Fig.  988)  from  which,  however,  it  is  separated 
by  the  arching  postparietal  gyrus. 

Fig.  990. 


RoUndic  fiMura 


Rijcht  cerebim.  iieinlipliere.  with  opercula  displaced  to  expoK  island  of  Reil. 

The  superior  temporal  gyrus  intervenes  between  the  posterior  limb  ot  the 
Sylvian  fissure  and  the  superior  temporal  sulcus.  Ite  lower  end  lies  at  the  tempural 
pole,  whilst  above  the  tract  is  continuous  with  the  supramarginal  and  angular  gyri 
of  the  parietal  lobe. 

The  middle  temporal  gyrus,  between  the  upper  and  middle  temporal  sulci, 
is  connected  with  the  subjacent  convolution  by  the  bridges  which  interrupt  the  sec- 
ond temporal  furrow.  Above  and  behind  it  is  continuous  with  the  angular  and 
jjostparietal  convolutions. 

The  inferior  temporal  gyrus  occupies  the  rounded  infero-lateral  margin  of 
the  hemisphere,  and  appears  on  both  the  lateral  and  the  inferior  surface  of  the  lol)e, 
Iwing  continuous  with  the  fKrcipital  lobe  behind  (Fig.  988).  Its  upper  boundary, 
formed  by  the  middle  temporal  sulcus,  is  indistinct  ;  its  lower  and  mesial  limit  Ls 
(k'fiic'd  l)y  the  inferior  temporal  sulcus,  which  separates  it  from  the  occijjito- 
temporal  gyms. 

The  inferior  surface  of  the  temporal  lobe  is  rounded  in  front,  where  it  rests  in 
the  anterior  cerebml  fossa,  but  behind  is  modelled  by  the  upper  surface  of  the  ten- 
torium cerebelli  and  is,  therefore,  concave  from  Ijefore  backward  and  slightly  convex 
from  side  to  side.  It  j)resents  one  fissure,  the  inferior  temporal,  ami  one  convolu- 
tion, the  anterior  jKirt  of  the  nccipito-temporal. 

The  inferior  temporal  sulcus,  also  called  the  occipitotemporal,  courses  longi- 
tudinally a  short  distance  internal  to  the  infero-lateral  border  of  the  hemisphere  and 


THE  TELENCEPHALON. 


1149 


partes  the  infenor  .^r.Uro^  £^-^1X:^'L'lZ.JT£^ 
'^l^nT^uS^dZXc^^P^  lobi^hich.  therefore,  claims  it  as  one  of  .ts 
Cws      The  suJcas  Is  «rely  co'l.tinuous,  usually  being  broken  by  annectant  gyn 

'""-TroiVtol'mprrr^^^^^^^^^  is.  as  its  names  imply,  a 

,  Honn  trartSnSng  partly  to  the  Scdpital  and  partly  to  the  temporal  lobe 
Ff.^^8oT  Ite  twoTnd?  i/ front  and  behind,  are  pointed  and  connect«l  by  a 
L  Vr^nierveninetrart  which  is  commonly  broken  up  by  secondary  furrows. 
TheiLSSoi^f  the  gyrus,  including  approximately  its  anterior  two-th.rds 
•  !mKd  ^t^^n  the  converging  collateral  fissure  mesially  and  the  mfenor 
,s  embraced   l«tweentne  co        «    «    ^  posterior  limit  is  the  line  drawn  from 

r'^rl^lS  no^cft'o'thJ  i^thTuTof  the^mbic  lobe,  immediately  beneath  the 

*""'*^e  iiSLT«"/«.f.7X  ^e^poral  late  is  direct«l  towards  the  insula  and 
The  ^''P*^^^"'J":''„J^  On  separating  the  wa  Is  of  the  Sylvian  fissure  to 
e^x^lrXSturia^of  ?h"eTe';^poraflobe  often  exhibits^eral  shaUow 
tra^er!^  fui^ows  and  indistinct  gyri  ;  the  deep  aspect  of  the  temporal  pole  being 
similarly  indented. 

Fiu.  991. 

Sulcus  aubdividins  prccrntral  lobule 

Cut  surface  of  frontal  lobe 


Rolaudic  fiasuic 


S<ilcua  centralLi 


Sulcus  centralis  insulee 


Sulcus  circularis 


Gyri  breves 


Gyrus  longus    Temporal       Apex 
'  lobe,  cut 


Limen 


island  of  Rell  exposed  alter  cutting  away  surrounding  part,  of  right  cerebral  heml.pl«re. 

The  In.ula.-Thc  insula,  or  island  of  f^'' -;:|f  [",f  s^Waf  SiuS  b^tt 
lobe.  is.  in  the  human  brain,  entirely  ^°"«^'^  J"*^'"  ^^r  in  whfch  the  latter  are 
approximation  of  the  overhanging  opercula.  J'^^^P^f ""^j"^ '^^''"been  described 
d^eveloped  from  the  wall  surrounding  the  ^y  f^^^^^^^^T^l,  the  adult 
(page  1137)  :  it  rern^ms  here  '"  "f^.^^^ts^a  ^«Sn  in  fronul  sections  of  the 
brain.  On  examining  .,^5'*  "°.  ,  \  that  the  shell  d^cortical  gray  matter  cover- 
brain  (Fig.  967).  it  will  be  noted  («)  that  ^^^,f^"  °\^° 'L^^^^^ 
ing  the  sunken  convolutions  is  directly  continuous  ^ong  the  byJ^ia^nM 

cohering  the  convolutions  -/»^2-'y  Xnf  m'^fof  «^y  ^^^^^^^^        lenticular 

marrrelation  to  the  surface  of  the  hemisphere  is  largely  responsible  'fjje  failure  01 

t^O    tt    insuC^ai;Ta"riangular  c-ex  field  com^  of  a  RK,up  of  radi- 
oing convolutions,  whose  broader  ends  lie  above  and  pointed  ones  beJo*. 


II50 


HUMAN  ANATOMY. 


dependent  apex  of  the  insula  lies  close  to  the  anterior  perforated  space,  with  the 
gray  matter  of  which  the  cortical  sheet  of  the  island  is  continuous  by  way  of 
a  transitional  area,  known  as  the  limen  insula,  where  the  limiting  sulcus  of  the 
island  is  incomplete.  In  addition  to  being  imperfectly  separated  from  the  surround- 
ing opercula  by  the  curved  limiting  sulcus  (sulcus  circularis  insula),  the  island 
is  divided  into  an  anterior  and  a  posterior  part  by  the  sulcus  centralis  insula. 
This  furrow  continues  in  a  general  way  the  downward  and  forward  direction  of  the 
fissure  of  Rolando,  the  deeper  part  of  which  is  seen  above  the  island  (Fig.  991). 
The  anterior  part,  or  precentral  loMe,  is  subdivided  by  two,  sometimes  by  three, 
shallow  grooves  into  three  or  four  short  downwardly  converging  ridges,  the  gyri 
breves,  of  which  the  front  one  is  connected  with  the  deeper  part  of  the  inferior 
frontal  convolution  by  a  small  arched  annectant  gyrus  transversus.  The  hind-part 
of  the  island,  the  postcentral  lobule,  includes  a  longer  wedge-shajjed  tract,  the  gyrus 
longus,  which  below  is  continuous  with  the  limbic  lobe.  The  gyrus  longus  Ls 
frequently  subdivided  by  one  or  more  shallow  furrows  into  secondary  ridges. 

The  Limbic  Lobe. — The  limbic  lobe  (gj'ms  fomicatus;  appears  on  the  mesial 
and  inferior  surfaces  of  the  hembphere  (Fig.  987)  as  an  elongated  n-shaped  tract, 


Splcnium  of  corpus  callomim 
Coltoiial  fiMure 


Fig.  992. 
Fornix,  body 

ThalmuK.  partly  citt  away 
/  Septum  Incidnm 


Fa.sdota  cinerea 


Calcarlne  fiafture 


Nthmiw 


Rhinal  6uure 


Collateral  fiasure 

(fyrua  dentatus 


Gvrua 
hippocampi 


^Uncu* 

Fimbria 
impi 

Portion  of  inkro-mesial  surface  of  left  benisphere,  showinfc  lower  part  of  limbic  lobe  and  adjacent  structures. 

whose  ends  lie  closely  approximatetl  with  each  other  and  with  the  anterior  per- 
forati  '1  space.  These  extremities  are  further  intimately  associated  with  the  two  limbs 
of  tht  olfactory  tract,  in  this  manner  the  limbic  and  olfactory  lobes  becoming,  at 
least  topographically,  continuous.  The  limbic  lobe  comprises  two  parts,  an  antero- 
superior  and  an  inferior,  of  which  the  former,  the  callosal  gyrus,  lies  concentric 
with  the  upper  surface  of  the  corpus  callosum,  .ind  the  inferior  part,  the  hippo- 
campal  gyrus,  forms  the  mesial  tract  of  the  tentorial  surface  of  the  hemisphere. 
The  limbic  lobe  is  separated  from  the  adjacent  convolutions  1  >y  the  calloso-marginal 
sulcus  in  front  and  aboxc,  by  the  postlimbic  sulcus  behind,  and  by  the  anterior 
part  of  the  collateral  fissure  below.  Its  demarcation  from  the  anterior  part  of  the 
temporal  lobe  is  effected  by  the  inconspicuous  rhinal  sulcus  ( fissura  rhinica),  or 
incisura  temporalis,  which  feeble  furrow  in  man  represents  the  important  and 
fundamental  ectorhinal  fissure  of  the  lower  animals. 

The  callosal  gyrus  ((orus  ciiiKuli),  also  called  the  gyrus /oniicatus  (not  to  be 
mistaken,  however,  with  the  same  iiaiiie  as  applied  li>  the  entire  limbic  lobe),  begins 
at  the  anterior  perforated  space,  l>clow  the  recurved  rostrum  of  the  corpus  callosum. 
Thence  it  winds  around  the  genu  of  the  latter  and  follows  the  convex  dorsal  surface 
of  the  corpus  callosum,  separateii  however  from  it  by  the  narrow  callosal  sulcus 
(sulcus  corporis  callosi).    On  reaching  a  point  just  below  the  splenium,  around  which 


THE  TELENCEPHALON. 


US' 


it  hM(h  the  caUosal  zyna  is  markedly  reduced  in  width  by  the  encroachment  o  the 
L^e  figure  X  rwrrowed  tapering  tract  thus  formed  being  the  upper  ,«rt  of  the 
SAmu.  ( Whim  «ri  fomlortDrwhich  below  joins  the  similarly  reduced  upper  end 
S?hrWpt!jSm^"<^nv"ution'and  so  establishes  the  continuity  between  the  two 

•"^The  hiJjSc.mp.1  gyru.  (on.s  hlppocmpi)  curves  forward  from  the  isthmus 
akMK  the  S  border  of  the  tentorial  surface  of  the  hemisphere  towards  the  apex 
Tdfe  ten^S  lobe  which,  however,  it  fails  to  reach  (Fig.  9").  ts  anterior 
i^mityTdisSSly  thickened  and  forms  a  rounded  hook-like  projection,  the 
S.  wWch  is  recirvcd  and  directed  backward  and  mward.  The  uncus  is 
.Li   fc^rim  fh^   loex  of  the  temporal  lobe  by  the  mcisura  temporalis  (fissnra 

ffif  wS  the  hi'pp-mpl"  co3""- » -W''  f  '"'^-"yK-'y  *'^  ""^""a 

S'^f^'the  CO  lateral  fiS.  Although  blended  with  the  ?y"-,hjppocamp.  and 
pan  ui  lilt  limbic  lobe    the  uncus,  strictly  considered,  belongs  to  the 

SntjhaVKd  no  tote  Jrm'Cic  lobe  (Turner.  Elliot  Smith).  The  posterior 
end  of  the  hipp.Kampal  convolution  is  incised  by  the  antenor  extremity  of  the 
Scarinl  Lur^  and  ^divided  into  two  parts  ;  of  these  the  upper  aids  in  formmg 
^eTthmus  and  is  continuous  with  the  callosal  gyrus.  whOst  the  lower  one  blends 
with  the  front  part  of  the  gyrus  lingualis  of  the  occipital  lobe.  ,  .        _^  „  . 

The  iSinencephalon.-Aldiough  a  division  of  hmdamental  importance  and 
diflerentfatS^at  a  very  early  period  in  the  development  of  the  human  telencephalon. 
fnTh^bSn  of  manltl  re^r^nted  by  structures,  which  to  a  great  5«f"* '^V-^' 
menurvand  feeble  expre^ions  of  the  bulky  corresponding  parts  m  the  brains  of 
manv  d  the  lower  anin^ls.  Its  small  size  in  man.  as  compared  with  the  voluminous 
Sure^  ^T!n  some  mammals  in  which  the  rhinencephalon  constitutes  a  large 
«[Ji  of  the^tire  hemisphere,  is  no  doubt  associated  with  the  relatively  feeble  olfac- 
^  Je^  t^Lsed  by  man.  It  is  probable,  however,  that  other  and  unknown 
f^c^o^^  r^'^e  forThe  development  of  this  part  of  the  hemisphere  to  a  degree 
SrSonate  to  the  olfactory  capacity  of  the  animal,  as  striking  y  observed  among 
fhe'^lX  vertebrates.  Th.  conclusions  deduced  from  commuative  studies  empha- 
size the  fundamental  character  of  the  rhinencephalon  as  P»'y'°8«"«t?«=f  y.^'"^  J^ 
oldest  Lrt  of  the  hemisphere.  Indeed  of  such  primary  "no-Ph^l^g'?^  JJK^'*^''"^^ 
Tt^e  Ainencephalon  that  it  is  termed  the  archipaUum,  ^s  distinguished  from  he 
LS^S   wh?ch  comprises  almost  the  entire  remainder  of  the  hemisphere  with  the 

excpotion  of  its  nudeus.  the  corpus  striatum.  ...  ..        ^       ^ir-- 

excepUon^Mts  ^^^  ^^,  ^^^  rhinencephalon  includes  the  rudimentary  olfac- 

tory llbT-represented  by  the  olfactory  bulb,  the  olfactory  tract  «"th  •«  ^?«'!' ^^^ 
olfactory  trigone,  and  the  parolfactory  area-and  the  uncus  and  a  number  of  acces- 
wry  ^rtifincluding  the  anterior  perforated  space,  the  g>rus  subcalbsus.  the  sep- 
tum luddum.  the  fornix,  the  hippocampus  and  the  gyrus  dentatus.  Some  of  these 
acceMory  st^ctures  can  be  understood  only  after  their  relations  to  outer  parts  of 
?he^^  W  been  considered.  Deferring  the  details  of  certain  of  these  struc- 
tures, as  the  septum  lucidum.  the  fornix,  and  the  hippocampus  '"'»)«•■.  until  the 
lateral  ventricles  are  described  (page  .160,.  it  will  suffice  for  the  present  to  point 
out  their  general  features  as  related  to  the  rhinencephalon  ^    .     .  „  ,„j 

The  Olfactory  Lobe.— This  division  of  the  adult  human  brain  is  small  and 
rudimentary  and  comprises  the  olfactory  bulb,  the  olfactory  tract  the  olfactory 
CiXe  anJ  the  parolfactory  area  (Fig.  993).  Of  these  all  but  the  last  he  on  the 
inferior  surface  of  the  brain,  whilst  the  parolfactory  area  occupies  a  small  space  on 
the  mesial  aspect  of  the  hemisphere. 

The  olfactory  bulb  (bulbus  olfactorius)  is  an  elongated  irrcgulariy  oval  swell- 
ing, about  10  mm.  long,  from  3-4  mm.  wide  and  about  2.5  mm.  thick  which  bchinrt 
is  continuous  with  the  olfactory  tract  and  below  receives  the  olfactory  filaments.  Ite 
upper  surface  underiies  the  olfactory  sulcus  of  the  orbital  aspect  of  the  frontal  lobe, 
and  its  under  one  rests  upon  thr  .-rihriform  plate  of  the  ethmoid  hone,  through  the 
apertures  of  which  the  bundles  of  the  olfactory  nerve-fibres  ascend  from  the  nasai 
mucous  membrane  to  the  bulb.  , 

The  ttrueture  of  the  olfactory  bulb  shares  the  Reneral  mdimentary  condition  which  cnarac- 
terizes  the  lobe  in  man,  the  bulb  having  lost  the  central  cavity  ( w)./r.f«/i<i  fmlbi  o//aclont). 


1152 


HUMAN  ANATOMY. 


which  in  many  aninub  is  continuous  with  the  fore-part  o(  the  lateral  ventricle,  as  well  as  some 
of  the  six  layers  that  may  be  typically  represented,  as  in  th«-  ■i-.-^a  bulb.  The  ventral  aspect  of 
the  bulb,  receivinK  th<f  olfactory  nerves,  retains  most  complei^iy  its  nervous  character  and  pre- 
sents three  chief  strata  ( Fig.  995).  ( 1 )  The  stratum  of  olftutory  fibres  appears  as  a  narrow 
zone  made  up  of  the  irregularly  intemiingled  bundles  of  axones  of  the  olfactory  cells  situated 
within  the  olfactory  area  of  the  nasal  mucous  membrane.  This  layer  is  succeeded  by  a  broader 
tract,  ( 2 )  the  strahint  of  the  mitrai  celU,  so  named  on  account  of  the  numerous  ner\'e-cells  of 
peculiar  bishop's-hat  form  which  occupy  its  upper  border.  Along  its  lower  margin  extendi  a 
narrow  zone  of  large  spherical  masses,  the  olfactory  flomeruii.  These  bodies,  from  .06S-.090 
mm.  in  diameter,  consist  of  an  intricate  complex  formed  by  the  intertwining  of  the  richly 
branching  axones  ascending  from  the  olfactory  cells  and  of  the  dendrites  descending  from 
the  mitral  cells.  The  interval  between  the  upper  and  lower  margins  of  the  second  stratum  is 
occupied  by  the  molecular  layer,  composed  ■>{  small  nerve-cells  \.'i-'ose  dendrites  also  enter  the 
glomeruli.  (3)  The  stratum  of  central  fibres  includes  the  centrally  directed  axones  of  the 
mitral  and  other  nen-e-cells  which  constitute  the  second  link  in  the  complicated  paths  by  which 
the  olfactory  stimuli  are  carried  to  the  cortical  areas.    The  outer  zone  of  this  stratum  is  known 


^■»^•  993- 


olfactory  bulb' 


OUactoiy  ti 

Meatal 

otfmctory  Mria 

Lateral 

olfactory  atna 

Island  of  Rcil 

Anterior 
perforated  space 

Cut  surface  of 
temporal  lobe 

Cerebral  peduncle 
oroased  by 
optic  tract 

lateral 
geniculate  tMxly 


Olfactory  snlcua 
Parolfactory  area 

Tnberculum 
olfactorium 


Trigonum 
olfactorium 


Optk  chiasm, 
partly  cut  away 
Mammillary  tiody 

in  interpeduucular 

space 
-~  Oculomotor  nerve 


Cerebral  peduncle 


Pulvinar 
Median  geniculate  body 


Sylvian  aqueduct 


Anterior  part  of  inferior  surface  of  brain,  showing  parts  of  olfactory  lobe  and  stracturea  within  interpednn- 
cular  space  ;  tip  of  right  temporal  lobe  has  been  ren^oved. 

as  the  granular  layer  and  consists  of  many  small  nerve-cells  intermingled  with  the  fibres.  The 
deeper  part  of  the  stratum  of  nerve-fibres  encloses  some  larger  nerve-cells  of  stellate  or 
enlongated  form.  The  central  part  of  the  bulb,  which  represents  the  obliterated  ventricular 
space,  is  filled  by  a  gelatinous  substance  resembling  modifieid  neuroglia. 

The  olfactory  tract  (tractus  olfactorius)  is  a  narrow  band  of  light  color,  which 
extends  from  the  olfactory  bulb  in  front  to  the  olfactory  trigone  behind  (Fig.  993). 
It  measures  about  2  cm.  in  length  and  2.5  mm.  in  width,  but  is  broader  at  its  pos- 
terior extremity,  from  which  the  olfactory  stria,  as  its  roots  are  called,  diverge.  Its 
ventral  surface  is  flat  and  its  narrow  dorsal  one  ridged,  the  tract  appearing  in 
transverse  section  more  or  less  triangular  in  outline. 

The  structure  of  the  olfactory  tract  further  emphasizes  the  rudimentary  condition  of  the 
part  in  man.  The  ventral  aspect  and  the  rounded  adjoining  borders  consist  of :  ( 1 )  a  stratum 
of  nen'e-fihrrs,  longitudinally  coursing  and  therefore  tran^Jversely  «it  in  cross-sections,  which 
covers  the  sides  and  dorsal  surface  of  the  tract  and  is  reduced  to  an  extremely  thin  and  rudimen- 
tary sheet.  Next  follows  (a)  a  gelatinous  stratum,  which  represents  the  obliterated  ventricular 
cavity  seen  in  many  lower  animals.  Succeeding  this  and  forming  the  thickest  layer  of  the  tract 
lies  (3)  the  dorsal  stratum  of  gray  matter,  which  still  retains  its  importance  as  a  tract  of  cortical 
gray  substance  from  which  fibres  pass  to  other  parts  of  the  hemisphere  (page  1313). 


TME    EEi-tKCEPHALaN 


««53 


usually  two.  the  ."'f^'^'f'^^ir^Th,  •<.«,/  ^/na  l-m«K  sharply  inward,  passes 
along  the  inner  manfin  o'."*  "^^J  .-ST  th*-  caHosal^t".  partly  the  .«ilK^lli«al 

It  can  be  traced  to^^T*  -^\<--,nd«  an  .mter  .-rf  an  inner  the  last  onr  fading 
lateral  root  is  "lepre^^twl  by  "^Zr^^^^^t^^.  An  a.Witional  intrrmedimtr 
away  in  the  sub*ta«ce  ot  the  ^T^ y^^^^,^  i,  ,^,  smks  into  the  unteri«r 
itria  is  sometimes  recogiBJMhfe  mt  a  short  iiwh?  \MmmK 

perforated  space^^  ^„„_    .    ,„  ollacl.ri.*)  is  'he  thr^-si<l«l  slightly  «>nvcx 

arealml^ct^hrtli:"'.^^  olSTry  ' ««  ;i:^  tS^I.^^'rr 
p\om  the  --n<^'^-  K.^^.;:,^^^  htZlS^cTig^^  is 
The  triangular  areajern  «" J"^ '"^  ""^  jj^  devauon.  the  tubercmium 
really  the  under  aspect  of  a  «"'«^'«^^  J^^T^ithin  the  afoctor>-  «.lcus  a.^  is 

jccept  at  its  bw;,  the  trigone.      Reuius  regards 


!• 


ihi- 


Fig.  994- 


ForanMti  of 
Monm 

Anterior  ptlltr 
'of  fombc 
.Anterior 
'commiMofe 


Rottnim  of   . 
cunxM    callumB 

Septuio  luct"!""      y 


-Uiniii" 
Snkas  piirolf««orlM  poiaenor 


(nnerc* 


Portion  oi  me.al  .»rf«»  d  ri^t  l.en.iH*««,  lowing  nm»  .ubcallo.u» 
and  p«roll»ctory  area. 


olfactorium,  which,  ho'> 
therefore  superhciaUy  -  -^i 
this  part  of  the  hemispht 
as  a  constant  deep  convc 
lution,  gvm^  tuberis  olfme- 
tortus,  from  which  proceed 
two  riches,  ifrrus  c'fatio 
ritts  medialis  and  ItUeraii  . 
These   bend    respectively 
inward   and    outward    and 
support  the  white  strands  of 
ner\  e-fibres.  the  stria  olfac- 
torii,  which  are  usually  de- 
scribed as  the  roots  ck  the 
olfactory  tract.    The  tuber- 
tulum  olfactorium  contains 
;,    considerable   amount  ot 
grav  matter,  which  is  a  part 
ot  the  peripheral  olfactory 
cortex  ami,  with  other  por- 
tions of   this   sheet,  shares 
in  the  n     ption  of  axones 
from  the  mitral  cells  and  in  the  ongin 
rhineno^halon.  ^^^^    ^.^  ^^  ^        „  ^^^,  he 

mesiMTuS::  of%heTmisphere-;*iust-'in  front  of  -d  bdow  t^e  ,yrus  .«^^W 
-list  1™:- =rW^:«qS^|f^ 

"^^Sl^^^^  ^y  i^e  large  -^^  ^  ^^^^td  ^^ 

irLfgrrp^rx  i^^rrii^Tht-dsri^  ^^~;::^  ^^ 

Iron?  mS  of  the  space,  are  disposed  with  some  regularity  in  parallel  ro^s  an.l 

7.1 


of 


fibres   passing   to  other   parts   of   the 


HUMAN  ANATOMY. 


decrease  in  «ze  as  the^  approach  the  inner  border  (Foville).  The  substance  of 
the  space  proper  consists  of  a  thin  sheet  of  ^;ray  matter  containing  groups  of 
nerve-ceUs,  some  of  which  constitute  the  nuclei  of  primary  centres  interposed  in 
the  paths  connecting  the  olfactory  lobe  with  the  secondary  (cortical)  olfactory 
centres  (page  1233).  In  addition  to  the  white  strands  of  nerve-fibres  composing 
the  olfactory  striae  which  after  a  longer  or  shorter  superficial  course  sink  into  the 
substance  of  the  perforated  space,  an  obliquely  directed  narrow  ribbon-like  tract, 
the  diagonal  band  0/  Broca,  may  be  sometimes  made  out  along  the  Inner  margin 
of  tiie  area  perforata.  In  front  it  is  continuous  with  the  subodlosal  gyrus  and 
behind  passes  along  the  optic  tract  towards  the  anterior  end  of  the  hippocami»l 
convdution.     The  band  is  of  interest  as  being  probably  the  beginning,  on   the 

basal  sur&ice  of  the  brain,  of  at  least 
Fig.  995.  a  part  of  the  fibre-trarts  contained 

within  the  rudimentary  supracallosal 
gyrus  (page  1157)  that,  in  turn,  is 
prolonged  into  the  gyrus  dentatus. 
The  uncut  is  the  thickened 
anterior  extremity  of  the  gyrus 
hippocampi,  recurved  around  the 
front  end  of  the  hippocampal  fissure 
(I^'R-  993)-  Antero-infenorly  it  is 
sefiarated  from  the  adjacent  part  of 
the  temporal  lobe  by  the  inconspicu- 
ous incisura  temporalis  or  rhinal 
sulcus,  which  in  animals  possessing 
a  well  developed  rhinencephalon 
constitutes  a  definite  boundary  be- 
tween this  part  of  the  hemisphere 
and  the  pallium.  With  its  deeper 
surface  the  uncur  is  in  close  relation 
with  the  anterior  perforated  space, 
whilst  uostero-mesially  it  is  connected 
with  the  fimbria  (|)age  1165)  and 
the  gyrus  dentatus  (page  11 66). 
Although  seemingly  a  part  of  the 
limbic  lobe,  the  comparative  studies 
<jf  Turner  and  of  Elliot  Smith  have 
establish^  its  morphological  inde- 
|K-ndence  from  the  last-named  lobe 
and  emphasized  it.s  relation  with  the 
rhinencephalon.  With  the  lateral 
olfactory  stria,  the  uncus  constitutes 
in  man  the  feeble  representation  of 
the  large  and  conspicuous  pyramidal 
lobe,  which  in  many  animals  forms  the  most  massive  j>art  of  the  olfactory  brain. 
The  accettory  parts  of  the  rhinencephalon  include  structures  which,  for  the 
most  |>art,  constitute  collective'y  an  elaborate  path  by  which  the  olfactory  a)rtical 
centres  are  connectwl  with  each  other,  on  the  one  hand,  and  with  the  optic  thalamus 
and  lower  levels  on  the  other.  Since  these  structures  are  by  |M>sition  closely  asso- 
ciated with  parts  of  the  brain  still  to  l)e  described,  with  the  exception  of  the  anterior 
perforate<l  s|)acc  already  notetl  (page  115,1).  they  will  be  merely  mentioned  here,  as 
com|K)nents  of  the  rhinencephalon,  their  details  t^ing  deferretl  until  the  related  parts 
are  considered. 

The  fornix  (page  ii.sH),  the  fimbria  (page  1165)  and  the  hippocampus 
(page  1165),  all  seen  within  the  lateral  ventricle  (page  11 64),  constitute  important 
fiaths  by  which  fibres  jkiss  to  ami  from  the  ollactorj'  cortical  centre.  The  gyrus 
subcaliosus  (page  115.'^).  the  gyrus  supracaltosus  (page  1157)  and  the  gyrus 
dentatus  (page  1 166)  together  form  an  additional  arched  tract,  which,  beginning  ut 
the  base  of  the  brain,  follows  closely  the  convex  surface  of  the  corpus  callosum  as  far 


Aliophic  ▼ratricu- 
(■ram 


Nerrofibre  layer 


GraanlU'  tajm- 


layer  of  odlnl 
ocUa 


Molccniar  layrr 


Olfacton- 

glomcrtUi 

Bkiad-vciarl 


olfactory  flbrr 
layer 


TiaMvmc  Mction  n(  olfactory  bu>b ;  drawinx  iiKlwin  |iut 
o(  balb  lying  vaiitral  to  atrophic  ventricular  area.    X  90b 


THE  TELENCEPHALON. 


"55 

•  u-  A^A  =.nH  thM  as  the  denute  gyrus,  extends  forward  along  the  inner  sur- 
as Its  hind-end  and  then,  as  ine  ucnutic  kj  •  lucidum  ( pane  1 159).  a  sickle- 
face  of  the  hjppocampus  to  the  uncus,    ^he  '"P^^^^.S.  ™e  ^^us  ^losum  and 

RHINENCEPHALON. 

I.    Ptriph*r*l  Portion 

Amittior  ftrl.- 

I.    Bulbin  oltactoritn 
1.    Trmclm  olfactonu* 
J.    Tubcrculum  oltaciorium 
oirACTOKV  UME     \  4!    Are«  poioltortori* 

PMleriar  part : 

«.    Subounlla  periormU  »nl«nof 
6.    Gyino  rabollaoitt 


II.    Control  Portion 


I.  Gym  calkan* 

J.  Gyittt  hippocampi 

1.  Gyroi  uoctnotiu 

4.  Hippocmmpw 

5.  GyrM  dcnUltn 
i.  Cymi  npn'^lh 


MUltn 
npnrallaaiM 


Architecture  of  the  Cerebral  Hemispheres. 

are  connected  in  the  intervening  ^rt  of  t^«'^'^"f "  .^^.  ^^  ^  ■^^^  course.  On 
corpus  callosum.  which  floor,  the  figure  Jo  «  ^f «  ThS  bridge  eUher  in  the  frontal 
making  sections  of  the  h«'"«P»'^^^^'^y= ''l^ J^Tt^JCi^^^^  thin  red<lish  brown 
or  transverse  plane,  the  hen^'hram  « found  to  be  com^^  constitut.-s  an 

sheet  of  cortical  gray  miM<r  ^^^^^^^^^^^vi  mJx&,  the  ccnirum  male. 

'*  "tSc.™.  C.ll«iuin.-Th»  .miclurc-  o  the  l!t.-..t  c<,mm««.r.-  «hich  ™- 

mmmBmm 

l^Z.Jl^::^'^^^:^^  th.  .enu.  b,-nds  l^ckward  and  i. 


1.!) 


1156 


HUMAN  ANATOMY. 


prolonged  into  the  sharply  recurved  and  tapering  roatrum,  whose  thin  edge  is 
continued  baclcM  ird  and  downward  into  the  lamina  cinerea,  the  attenuated  anterior 
wall  of  the  third  ventricle  (page  11 32).  The  rounded  and  massive  posterior  end  of 
the  corpus  callosum,  known  as  the  splenium,  overlies  the  pineal  body  and  the 
superior  coUiculi,  and  above  bounds  the  cleft  through  which  the  pia  mater  gains 
the  velum  interpositum  (page  1162). 

The  convex  upper  surface  of  the  corpus  callosum,  where  it  forms  the  bottom  of 
the  longitudinal  fissure,  is  free,  except  behind  where  in  contact  with  the  posterior 
p:irt  of  the  falx  cerebri  ;  laterally  it  is  partially  overlaid  by  the  callosal  gyrus,  which, 


(pnUff  of  c«m> 


UoUtliM  ctalralis 

I  ulmrtt 


Fall  tcMUl,  i:al 
Siraicht  siain 


FoUuni  cacuntiall 


Tul«t  rti , 

■  ■MfffWduacHtor 

MammUhrr  ^Hf 

»fllMH4d«l  llM, 

■aallar  aitiry 

Carimrj  MaadHgaailav 

At|ti».  luct  of  Sylvf L    . 
SupaHor  mrivXm^  talaai 
HouHk  vaabMla 
Ckovoltlal  ptaaut' 


Meiial  Hcrtlon  of  hrnln  \m  .ti/m.  Hhowinie  relaUonn  tn  akull  and  dura;  rerrhmt  faU  hati  been  partly  removed,  l*ul 

ai««  hnoid  and  pin  niv  <«lill  in  iil.trt- 

how(.'\'i-r,  is  separated  from  it  by  the  intervening  callosal  sulcus  (huIcun  corporis  callttNl ). 
Altliiiugh  ci>n»istiiig  pnu-tically  exclusively  of  transversely  coursing  nervt-fihri-s, 
whiili  prexlucf  a  corri'S|M)nding  cross  striatum,  thi'  ii[)|ier  surface  of  the  corpus 
I'dlliisuiii  •:  Fig.  997  I  is  covcn-d  by  a  thin  atrophic  layer  of  gray  matter  ( induHvum 
uriNCum  I  which  laterally  is  coiitiiuioiis  with  the  cortical  sulistance  .of  the  callosiil 
gyrus  :,n<l  contains  nuli'iientary  strands  of  longitudinal  nerve-rthri's.  Thi-se  are 
arrangetj  on  each  siile  of  the  slight  grrwive  ni.irking  the  mid-line  in  two  strands  ;  the 
<>ne,  the  atria  medialia,  is  placed  .  ..ise  to  the  strand  of  the  opposite  side  and  with 
it  constitutes  the  so-i'ailcd  iicnrs  of  Lancisi.  The  other  strand,  the  atria  iateralia, 
ur  htnia  Inla,  lies  farther  oiituanl  an<l  is  covered  by  the  oycihanging  callosal  gyrus. 
These  rudimentary  structures,  including  the  thin  sheet  of  gray  matter  and  thv  '■■■■ 


t\V<l 


THE  TELENCEPHALON. 


1157 


.tri«.  represent  an  atrophic  convolution  the  ^--^^^f  f^  J^^:?  fS 
and  ;rou%  the  -"-^Xcre^nti^  ^rt'^^^^^^^  «-->  -'ace  o.   the 

gy,rus  SHbca/Zosus  .i  *«"*"  ""^'l"!Jz;r^(  pie  gg.,;  while  the  lateral  stria  is 
Kmisphere  '■"^^''^^^'y^S^  '''^'^e  .  53^^'^^  the  anterior  ,M.rforHt«l 
continued  into  the  ar^^««^J^^^^^^^  ,p,e„iun,.   the  stri*  and  ^ray 

Sr  o?^tt%oSll!=^"-  -"""--  -'"^  '"^  ^™^  '^""'"'^  "^'*'  '^ 
way  of  the  latter  with  the  uncus  ^^^   exhibits   a    very 

The  under  surface   ™  ^ne  c  )n  ^^^  ^^^^,  ^„j  body  of 

evident  transverse  smationj^^^^^^^^  ^,  ^^^^^  ^ij  ,  ,,         ,he 

SJrpl^nel'Se  atuSto  t^^  sejtum  lucidum  in  front  and  to  the  tnan«ular 


Kio.  997- 


FronUl  piile 


MnUI  longiluilinal 


rpprr  «iirf«c« 
of  conjun  calkrtwnt 


l^alrrHl  longJtudiiial 
•trill 


Forcf  |>s  aiiti'rior 


Trnnnvcriir  fibres 


Tnprliini 


Hun-clw  )»>«lrrlur 


.Ocdpital  pule 


Slilrnilllli 
Ctrebral  heniinulwrcn  from  which  un 


•Ide  loiiKitwHnal  »»rl«  »n.l  Ihiii  !•>•«  ol  «rmy  m«u»r  '-o^'r  !'PP«.'_5''™'.^,S'.,  i^',,.n.. 


txHly  of  the  fornix  behind,  the  .onn.s  rallnsum  i.  fn-e  an.l  .^.^'f "I  *'**; J,','^ 
Z^dvma  which  lines  the  ventricular  spac-s.  In  -"-«  qnence  of  th^  J"  ^^ j^;  "« 
shorter  than  the  lenifth  of  the  hemisphero.,  from  ni<.st  parts  of  «hicn  it  rece 
SS  the  latter  are  S.ns<.lidaU.d  at. he  ends  .,1  the  ^^:f:^J^,r^^^, 
the  K.MU1  and  the  spleniuin.  On  frainm^r  the  lateral  margins  "^^ J^'J  '  ,  ,^  ,,,,. 
its  fibres  are  no  longer  restrained  ''"' ra.lu.te  in  a  d.recUrnw  ^ra4U^^ 
U«l)  towards  the  cortex  an.l  interscrt  the  ^^''-^/''j' "=  V'^'^J  •.  m  the  oo.n- 
Those  traversing  the  thinner  lx.dy  a"*'  upper  iwrt  "*t''^,''P''^""''i,p '.,,., ..^u^^, 
,„L.re  pass  laterally  and  in  each  hemisphere  from  a  thin  '«'    '   .fi"'*^'^^^!?.,^;^!;; 

szd:;rrstiS:^\^ear^"'"  i^'^^^^^z^i  t 


ti58 


HUMAN  ANATOMY. 


■At 


pole  of  the  hemisphere,  whibt  those  constituting  the  greater  part  of  the  splenium 
are  consolidated  into  a  robust  strand,  the  forceps  posterior,  which  sweeps 
abruptly  backward  into  the  occipital  lobe  and  in  its  course  produces  a  curved  ridge 
on  the  fore-part  of  the  inner  wall  of  the  posterior  horn  of  the  lateral  ventricle. 

The  Fornix. — The  forn-x  is  an  arched  structure,  white  in  color,  and  composed, 
for  the  most  part,  of  two  crescentic  tracts  of  longitudinally  coursing  ner\'e-fibi«s. 
The  two  ends  of  these  narrow  crescents  are  free  for  some  distance,  but  along  their 
'.nedial  borders  the  intervening  parts  are  connected  with  the  under  surface  of  the  cor- 
pus callosum  and  with  each  other  (Fig.  998),  thus  producing  a  triangular  field,  the 
body  (corpus  fomlcis),  whose  apex  is  directed  forward  and  is  prolonged  into  two 
slender  diverging  stalks,  the  anterior  pillars,  and  whose  lateral  angles  are  con- 
tinued into  the  (lovnwardiy  arching  posterior  pillars.  The  upper  surbce  of  the 
body  is  subdivided  into  an  attached  and  an  unattached  area.      The  former  is  a  small 

Fio.  998. 


Bcdy  of  fornix 


Mntiitnillary  hndii 


Splenium  of 
oorpu*  calloiHtin 


Lyri 


FmmirKinof 
fornix 

I'ndrr  surface  of 
corpuiicalloHum 

Cut  KurfacTH  of 
hrmiftplicrv 


:)Cptuiu  lucidum 


Anurior  pillar  of  foniix 
rndvT  aurface  of  fccnii  of  curpimcalkmum 

f>iKKe(itnti  111  hrniii,  tthowini^  under  surlact*  of  foniiit  and  corpus  cattoauni 

narrow  trian^ile.  the  posterior  and  broader  p;irt  of  which  corrcKponds  with  the  attach- 
ini'nt  of  the  fornix  to  the  under  surface  of  the  corpus  callosum  ;  whilst  the  anterior 
part  is  a  mere  mesial  strip  denoting  the  line  along  which  the  arching  fornix  is  bli-iuU>d 
with  the  Sf|>tiim  lucidum,  the  sickle-shaped  {Kirtition  that  tills  the  interval  l»etween 
the  corpus  callosum  and  the  fornix  and  se|)aratis  the  anterior  horns  of  the  lateral  ven- 
tricles. On  either  side  of  the  attachtxl  field,  the  fornix  presents  a  smooth  and  some- 
what thicker  marginal  zone,  which  forms  part  tif  the  floor  i>f  the  lateral  ventricle  and, 
<U'|M'n(ling  upon  the  size  and  distention  of  the  ventricular  s|>ace,  either  extends  later- 
ally as  a  horizontally  directe<l  wing  that  overlies  a  jxirt  of  the  thalamus,  or  descends 
ol>Ji(|iiely  towanls  the  thalamus  up<m  whose  iii)per  surface  the  margin  of  the  fornix 
indirectly  rests.  The  triangular  central  sheet  of  the  fornix,  iKiiinded  by  its  unattached 
marijins  latenitly  and  the  splen'um  Ix'himl,  exhibits  transverse  striation  due  to  the 
presence  of  Inmdles  of  commissural  fibres  connecting  the  hipp(K'ampi  of  the  two  sides. 
This  part  of  the  fornix  constitutes  the  commisBurs  hippocampi,  also  known  as  the 
psaltniiini  or  lyra.     A  narrow  horizontal  cleft,  the  so-called  wnlritle  of  I  'crga  ( cavun 


THE  TELENCEPHALON. 


"59 


•rf^ould  be  unde«t^.  however  that  th«  cWt  «  not  a  PJJ^^  .'J^Xm^^f^^^^Tm^ 
rdTtK-pa  Jt'e:  ^t" t ri^ni^ld^Vrde  S  t^per  surfaces  We  two 

^Ltnteriorpm«.  of  the  fornix  (col-nae  foroWs)  are  two  slend«  cyUn- 
dri  JstrarS  wK  .UghUy  diverging  as  they  leave  the  antenor^-«J  d  the  l^ 
arch  downward  and  forward,  then  somewhat  backward,  ?"° . ™='*^^"'^ ,["■ '  j.^ 
^L.  of  the  brain,  where  theyend  i;;^  »»>«  -jnmjjan.  ^^  ^^^e'S 

?h%'l:  t^SrcFrXa^dtn^'on'e^^de.  the  upper  and  anterior 
they  show  as  ndges  I  rig.  97^^^  ^^^  ^^^  ^  ^^^^  opening. 

a  large  extent  in  the  mammdlary  nuclei  (Fig.    96?).     The   connm^ons^oi 
staUo^s  are  d^ri^d  dsewhere  (P^^^^.J-^  j  -ffir^'U^^de'^Ur^^^^^  Tntn 
^"ly^'tnS/^Tl^^^ZrtrSi^^^^^^^^  the  connection  between 

connection  with  the  olfactory  nerve  (page  1222).  .     .  .^    divereing 

TJi..  noaterior  oilUn  of  the  fornix  (crura  fomkU).  the  wiaeiy  «»«n{»'B 
backward ?roon^tions  from  the  lateral  anglesof  its  body,  are  at  ^r.t ^XUch^^ 
Se  under  s'iriace'^f  th-  corpus  callosum.      They  then  turn  ,«>»»*„»  .^•;"/*'»^Xhl 
around  the  posterior  ends  0I  the  optic  thalami   enter  the  descendmg  horn,  ol  the 
lateral  v.-ntrWes  and  arch  downward  along  the  dorso-mesial  border  .il  the  conspicu 
ot  4m-S.  the  elevations  which  mark  the  inferior  h"r-  "Hhe  k^end -^^^^^^^^ 
On  reaching  this  situation,  however,  th.^  P<?tenor  pUlar  no  longer  reigns  its  previous 
f^rm   h.it  now  auoears  much  reduced  in  size,  as  a  white  flattened  band,  known  as 
rfimbrirwhTcKoXt  in  the  middle  of  its  cou«e,  nan^ws  -  |t^esc-d«^»^^^^ 
ends  bv  ioininir  the  uncus  at  the  lower  extremity  of  the  ventnde.     Tht  progrewive 
SnuL^:.  of  fhe  fimbria  during  its  descent  is  due  to  the  -"tr.butu.n  of^^^^^^  o    .ts 
fibres  to  the  sheet  of  white  matter,  the  u/vfus,  which  covers  the  hippocampus^     a  « 
evident  that  the  fornix  constitutes,  by  means  of  its  several  parts,  •";"™"*  t-^c 
of  loniritudinally  coursing  fibres.  whicK  convey  impulses  from  the  ^h'c^  cort  cal  olfac 
tory  centre,  the  uncus  and  the  hipp<Krampus,  t..  the  mamm.llary  nude,  and  thence,  m 
groit  part,  by  the  bundle  of  Vicq  d' A«yr  to  the  thalamus. 

TU.  *«™i.  n»v  he  considered  in  a  sense,  as  a  tract  of  white  matter  representinR  the  lower 

°h^'».«Kiated  structures  have  been  descri»«d  in  cnnectlon  with  the  lateral  ventricle. 

The  8eptum  Lucldum.-The  septum  luoidum  ( sephim  P*""'"""!','; '"^^jj;" 
median  vertical  partition  which  fills  the  interval  lK.tween  the  corpus  .allosum  above 
" d  n  froSTmfflornix  behind  (Fig. .996).  -th  which  structure  Us  m.jx.ns«^e 
Hrmlv  attached.  It  se,»rates  the  anterior  horns  an.l  a.l)...n.ng  P^^h  of  the  lateral 
SeScles  and  is.  in  a  m'odifie<l  form,  triangular  n  shape  -l^e"  v|ew«  >«t^^^^^^ 
sidi-sof  the  triangle  are  all  curv«l  and  its  anterior  angle,  receivetl  within  t>ie  nenci 


ii6o 


HUMAN  ANATOMY. 


Corpus  calliMum. 
wirfftcc 


Anterior 
nillnr  of 
fornix 


y 


of  the  fornix.  The  septum  consists  of  two  thin  layers  (laminae  septi  pelluddi), 
between  which  lies  a  narrow  cleft  (cavnm  septi  pellucidi)  to  which  the  misleading 
name,  fifth  ventricle,  has  long  been  applied.  This  space,  very  variable  in  extent 
and  width,  is  usually  so  narrow  and  contains  such  a  small  quantity  of  modified 
lymph,  that  the  lamime  forming  its  walb  are  in  apposition.  It  is  entirely  closed  and, 
therefore,  cut  of!  from  the  true  ventricular  system  ;  neither  is  it  lined  with  ependyma! 
The  septum  lucidum  in  man  is  the  rudimentary  representation  of  what  in  many 
of  the  lower  (macrosmatic)  animals  is  a  much  more  important  tract  of  cortical 
substance.  In  some  animals,  as  for  e.\ample,  the  rabbit,  cat  and  dog,  the  septum 
is  solid,  a  cleft  never  appearing  within  it  Notwithstanding  the  reduction  which 
it  has  suffered  in  man,  the  septum  exhibits  in  its  structure  its  relation  to  the 
cortex,  comprising,  from  its  clefi  outward  :  (  i )  a  thin  layer  of  nerve-fibres,  (2)  an 
uncertain  layer  of  gray  matter  containing  numerous  nerve-cells  of  pyramickl  form, 
and,  next  to  the  lateral  ventricle,  (3)  a  layer  of  nerve-fibres,  the  ventricular  surface 

of  which  is  clothed  with 
y°-  99»  the  usual  ependyma.     It 

Boity  of  fornix  .  i_   li  ^t.   ^ 

'  -  IS   probable   that  axones 

proceeding  from  the  cells 
within  the  septum  lucidum 
are  constituents  of  the 
olfactory  strands  within 
the  fornix,  which  pass  to 
the  hippocampus  and  the 
uncus,  and  of  the  tirnia 
semicircularis  (page 
1 162),  terminating  in 
the  amygdaloid  nucleus 
(page  1172). 

The  Lateral  Ven- 
tricles.—The  lateral 
ventricles  (ventricula  late- 
rales)  are  a  pair  of  irreg- 
ular cavities  contained 
within  the  cerebral  hemi- 
spheres. They  are  devel- 
oped as  outpouchings 
from  the  original  cavity 
of  the  end-brain  and  for 
;i  time  coininunicate  with  this  space  by  wide  openings.  The  latter,  however,  fail  to 
keep  iwce  in  their  growth  with  the  expansion  of  the  hemispheres,  and  in  the  fully 
(leyelopetl  brain  are  represented  by  the  small  apertures,  the  foramina  of  Afonro, 
which  maintain  communication  between  the  lateral  and  third  ventricles^  the  last- 
named  s|)ace  representing  the  primary  cavity  of  the  fore-brain. 

When  \  iewed  from  above,  after  removal  of  its  roof,  the  corpus  callosum  and  its 
lateral  extensions,  each  lateral  \entricle  appears  as  an  elongated,  irregularly  curved 
cavity  (Fig.  icxio),  which  extends  for  aljout  two-thirds  of  the  entire  length  of  the 
hemisphere  and,  in  addition,  penetrates  the  temporal  lobe  almost  to  its  pole.  It 
is  lined,  as  are  all  the  other  true  ventricles,  with  i  «lelicate  epithelial  layer,  the 
tpfndyma.  which  likewise  clothes  the  structures  which  encroach  ujMin  its  lumen,  as 
the  caudate  nucleus  and  the  thalamus,  as  well  as  those  which  seemingly  hang  free 
uithin  it,  as  the  choroid  |)lexus  an<l  the  fornix.  It  is  usual  to  descril«'  the  ventricle 
as  consisting  of  four  parts,  the  Wr,  and  the  autirior,  fHisUriot-AwX  inferior  horns. 
1  he  anterior  horn  and  the  Ixnly  are  practically  one  and  separated  by  only  an  arbi- 
trary ilivision  ;  the  posterior  and  tht-  inferior  horn  extend  into  the  occipital  anil  the 
temporal  IoIr-  ri|spectiveiy,  whilst  the  anterior  horn  enters  the  frontal  loU-, 

The  anterior  horri  (cornu  anti-rius )  includes  from  the  lip  ol  the  ventricle  to 
the  foramen  nl  .Monro,  the  latter  correspo:i<ling  with  the  anterior  limit  of  the  con- 
spicuous choroid  plexus,  curxes  forward  and  outward  around  the  head  of  the  caudate 
nucleus  into  the  white  substance  of  the  frontal  lolje  and  in  fronuil  sections  (Fig. 


Fimhrta 

Hippocampiu 


Oyni» 
dentatiut 


rncua.  pCTlially 
cut  away 

Oimeclioii  ihowmii  lonii«  in  (rout  and  atwve ;  drawn  from  prcparMion  and 
Stei^r  inu<lcl. 


THE  TELENCEPHALON. 


1161 


,007^  aopeani  trianeular  in  outline.  The  upper  side  or  ba.se  of  the  trianKle.  slinhtly 
c^idToSthe^entride.  i*  the  lower  surface  of  the  arched  '--n-u^^  caUosu.n  and 
ff^^ero-lateral  radiations  ;  the  mesial  side  is  approximately  vertical  and  lormwl 
KS  septum  ucidum;  the  lateral  side  bulges  strong  y  towards  the  ventnclcm 
^rrefoondence  with  the  convexity  of  the  massive  head  of  the  caudate  nuc  eus.  I  he 
CrrthSrt  o  the  ventricle  is  narrow,  often  a  mere  groove  along  the  n.nct.on  .rf 
fhTslooine^teral  and  vertical  mesial  wall,  and  in  front  p;.sses  msens.bly  mto  the 
co„<Sve  anterirwall.  formed  by  the  lateral  part  of  the  hind  surface  of  the  genu  of 

'**"  'Trb^yTpir«  centrallH)  of  the  lateral  ventricle  includes  that  ,«rt  of  the  si«ce 
ch  extends  frcmi  the  foramen  of  Monro  to  the  bifurcation  of  the  ventricle  into  its 


which 


Fig.   1 000. 


Anterior  hota  ^ 
Utnui  ventriLlt 


Cftixtelf  nu>  Inn,  Im«<1< 
|-uraiii«n  iif  Monro 


LcnlkuU    niirlcu«. 


T»bU  teniUirL-ubiri* 


llf|n>wain|H>o 

Collateral  rmiiiM" 

Fim'.H.t 

Posterior  i-illar  .if 

timhria 

CoIUlrtiil  i»'i*riitfr 

UKC  in  thiioniiiM 

niitrittili 

Bull)  of  fxifp* 

[lorteri"* 

Cakv  •«)> 


p.nwrtorttoni'il 
Utor.*l  .rnlffLle 


'Sri4u'<i  liHiiliim 


ia»ily  ««l>iii  M-(4iim 


>.inii».»ntrri'*i>il 

[  IhffMi*!  I>lr«< 

k 

-|*i.|>  off.«.. 

(-h<m<lil|>lrM 

-.lr<»rn(ltnt(ii 

infrrier  h<<rti 

l'" 

lllll 

V*  l.»t«-T..I  -mirt.  te 


I.«lrr,..  vrntriclr.  « r,>  from  «l..vr  .ftrr  v>nM  r..,«ov,1  of  Corp,.,  mil.,-.,,..   , n.l  <r  ,..r,1  hrml.ph»r»« 


,K,sterior  and  inferior  horns,  oppos.te  th.  spUnnrn  ..t  .'..■  '"H- ;;    -"";,, ^j^,. 

iew«l  in  frontal  sections  i  Fig.    .o.o,.  |f  ....p-ars  as  a  narr..w    .  b.   uelx   ^  "^^^  ■ 
cleft     directe<l    so.ncwhat    upward,    roofed  ...     -   iht-  ...nMis      >1 -unv      U>  ...m. 
wal  'is  for„u-d  in  front    l.y  the  hind  part  of  th.  .q.t.n  ,  U-cu,.-n  an.l  'Hh.n.i    he 
h  Iter   .V  the  fornix  wlu-r.  it  i.  .U.ached  f.  th.;  .uu  or  ,u.   .. .-  of  ,iu   .  -!'----"; 
-\  .listinrt  lateral  wall  is  wanting,  tho  veniri.K'  lx-ing  here  .l.-s.-il  bv   On   mk   ti    .. 
of  the     o«    an     r.K.f.      Its  floor  is  constitute.!  by  several  ,ln..t.ns  of  ,m,«.r tame 

hich        Ll  tm  without  inward,  are:  fn  the  ra.o^af<-  ,„uln,s  :     2.  .an  o  .!..,ue 
Irr     "ulws    intcrmedlus).    which    .xtemis   from  bc-iorc  t.ackwan    a.fl  outward. 

riwXn  tTc^ite  nucleus  and  the  thahunus,  an.l  lodg.-«.  in  a.ld.t.on  t.,  th.^  v.-.n 

^th      <    rpus    St  iatUP,,     a    white    iK.n.l    of    n.rv  fibres    known    as    the  /,/•«'" 
L  aW,  «r  Z  :■-  narrow  portion  ..f  the  upp.r  surface  of  the  thalamus,  whi.h  .. 


Il62 


HUMAN  ANATOMY. 


• 


ilerior  horn 


almost  completely  masked  by  the  overlying  choroid  plexus;  (4)  the  choroid  plexus 
of  the  lateral  ventricle  ;  and  (5)  the  lateral  edge  of  the/bnwjr.  The  caudate  nucleus 
will  be  subset .'^ntly  described  (page  1169),  suffice  it  to  note  its  rapid  diminution 
in  size,  as  it  cur\cs  backward  and  downward  on  the  roof  of  the  inferior  horn. 

The  taenia  semicircularis  is  more  or  less  hidden  by  the  superficially  placed  vein 
of  the  corpus  striatum  (vena  termlnalis),  which  lies  immediately  beneath  the  epen- 
dyma  and  shaws  as  a  distinct  sinuous  ridge.  Receiving  tributaries  from  the  adjacent 
parts  of  the  thalamus,  the  caudate  nucleus  and  the  walls  of  the  anterior  horn,  includ- 
ing the  septum  lucidum,  the  vein  passes  to  the  foramen  of  Monro,  where,  meeting 
with  the  choroid  vein  at  the  apex  of  the  velum  interpositum,  it  fprms  with  the  last- 
named  vessel  the  vein  of  Galen. 

The  tenia  semicircularis,  the  band-like  tract  of  nerve-fibres  which  occupies 
the  sulcus  intermedius,  is  probably  a  part  of  the  complex  pathway  by  which  the  pri- 
mary and  secondary  olfactory  centres  are  united.  Its  component  fibres  arise  partly 
"n  the  anterior  perioral  ttl  space  and  partly  in  the  septum  lucidum  from  which  centres, 
reinforced  by  hbres  from  the  anterior  commissure,  they  converge  towards  the  sulcus 

intermedius     which     they 
Fig.  iooi.  then  follow.     After  leaving 

the  iKKly  of  the  lateral 
ventricle  they  descend  with- 
in the  roof  of  the  inferior 
horn,  in  close  relation  to 
the  recurved  tail  of  the 
caudate  nucleus,  to  end 
within  the  amygdaloid 
nucleus  (page  11 72). 

■  The  choroid  plexus 
(  plexus  choriuidetis  ventdt  ili 
lateralis)  is  a  cuiiv uluted 
vascular  comi)lex  which 
occupies  the  lateral  margin 
of  the  pi;.'  .sheet,  the  velum 
interpt»itum.  within  the 
body  of  the  laterp'  ventricle, 
and,  in  addition,  (k-scends 
along  the  inferior  horn  of 
the  lateral  ventricle  to  its 
tip.  I  n  order  to  understand 
the  relations  of  the  choroid 
pkxus,  those  ot  the  larger 
i-heet,  of  which  it  is  part,  must  be  dcscrilxxl.  The  velum  interpositum  ^tela 
chorloitlca  ventnculi  tcrtii)  is  a  delicate  sheet  of  pia  mater  whc^se  upper  suiiace  i.s 
exposed  alter  removal  of  the  corpus  callosum  and  the  body  of  the  fornix.  VVhen 
viewetl  from  above  (Fig.  rioa)  it  is  trian.^^^ular  in  outline,  its  apex  iyinj,;  at  the 
fiirainina  of  Monro  aiul  iis  lateral  basal  angles  extending  into  the  descending  horns 
of  the  lateral  ventricles.  Its  inferior  surface  forms  tht-  roof  of  the  third  ventricle, 
beyond  which  on  each  side  it  coven;  the  greater  part  of  the  upper  surface  of  the 
thalamus  .ind,  in  turn,  is  overlaid  by  the  fornix.  Behind,  the  velum  interpositum  is 
continuour.  l)oneath  the  splenium  of  the  cor|)us  callosum  with  the  pia  mater  investinr 
the  <>xternal  surface  of  the  hemv^pheie.  This  relation  rejulily  gives  rise  to  the 
impression  that  the  pial  tissue  has  gjiiiied  entrance  to  the  ventricles  by  growing 
forward  through  the  cleft  beneath  the  splenium  and  the  fornix.  That  such,  however, 
is  not  the  case  will  Ik'  [K>inted  out  later,  when  the  development  of  this  sheet  is 
considered  (page  1194).  TKe  relation  of  the  velum  interpositum  to  the  ventricular 
cavities  should  he  carehiliy  noted  by  tracing  the  ependyma  from  the  caudate  nucleus 
inward.  Leaving  the  convex  surface  of  this  structure,  the  ventricular  lining  covers 
the  sulcus  terminalis  with  its  vein,  and  passes  for  a  short  distance  over  the  adjoining 
outer  part  of  the  upwr  surface  of  the  th.ilamus.  This  zone  ( lamine  afGxa )  narrows 
in   front   and  behind,  and  where  broa<lest   me;»sures   from    5-7    mm.     Along    the 


I-.Tlcral 

rprtM 


Cast  ttf  vrntriclM,  virwed  frirni  «ho\i' 


Posterior 
huru 


S.    (KftriKs.) 


THE  TELENCKPHALON. 


Il6.^ 


•  I  this  Tnne  the  eoendvma  leaves  the  sjriace  of  the  thalamus  and 
inner  '^''^g'"  j'' .J"^/f;"„-e;tions%"i^cx>3 )  of  piu  mater  contai.iins  the  convolu- 
'^*^?t™ive^STonS"hV  choroid  JlexJ  is  com,M«ed.  Each  projec.u.n 
tions  of  WofKl-vesM-soiwrncn  u.e  ^oiUarv  romplex  fonned  by  the  teruun.il 

(^o««s  choriold«.«  --;;^,,^i;/i^„i^'J'!;S..  which  Kain  tJinterior  of  the 
twigs  of  the  ^"*^"°^,*""  .•^'i^-i  rts^„re  in  the  inferior  horn  of  the  lateral  ventricle  : 
hemisphere  throuRh  the  '^J";"^^  J'"""'^ '"  ,  jh,.  ..,,endvmal  laver  (lamina  chorioidea 

'^t  'l^.'it^lKr-o.r'rhlEr:,..;  i„v„U„.  U,.  va^-uU,  pro. 


Fk;.  I002. 


Anterior  end  of  fornix,  cut 


Hippocampus 

Velum  iuterpositum. 

Ciioroid  ul.xun  in  inferior 
horn  of  luurKl  ventricle 


epicnium,  under  MrfBce — 


PuMerior  liorn  of  lateral 
ventricle 


Lateral  pnn^of  fornix 
under  •urfa'^ 


.Corpti*  caliosum 


.('Riidnte  nucleus 


rhoroid  plexii«  nverlyiug 
I'aranien  of  Monro 


Vein  of  corpu«  slnaium 
Choroid  vi'  1  inplt^u* 

.Veins  of  (".alcu 


Crud  of  fornix  and  (Kxlcriot 
_fi>rcep!i  of  corpus  calUi-um, 
cut 


I'ndcr  surface  of  fornix, 
"l.vrn 


Cot  -lUrrioT  end  <tf  fori.tx 


e«i>otiiix  it»  under  nutlace. 

ictions  constitnting  the  choroidal  plexus,  .th^  epcmlyma  ^^^S^j^  ^jlll^ 
the  taenia  fornicis  to  the  thin  lateral  margin  uf  the  f.irni.x,  '"^V\'^"  J?  ",'',.  ,.,  ,u,. 
Smer*sit!im  protrudes  to  expand  into  the  choroid  plexus  u.thm  the  IhkIv  of  ,hc 

''"'It  plexus  ,s  not  confin^  to  this  part  of  the  space.  »";'«"""-«»«' "^j;'';^:::!';::; 
to  the  lower  end  of  the  inferior  horn.     The  relation  of  the  vascular  pial  ju*^^^  to 
hi:«te;:Jon  of  the  ventricle  is.   however.,  th.-  ..me  as  w.thm^^^^^^^^ 


!^ji*;^j«a 


I- 


m 


iilf 


1 164 


HUMAN  ANATOMY. 


the  entire  choroid  plexus  of  the  lateral  ventricle,  the  (-|><'iidyma  is  torn  away  and  an 
artificial  opening  is  produced,  which  may  be  followed,  as  a  curved  narrow  cleft,  from 
the  lower  end  of  the  inferior  horn  upward  above  the  hip|x>canipus  and  omt  the 
dorsal  surface  of  the  thalamus,  beneiith  the  fornix  and  the  splenium,  to  the  exterior  of 
the  hemisphere.  When  tiared  forward  from  its  attachment  along  the  upper  surface 
of  the  thalamus,  the  line  of  the  reflection  of  the  ependyma,  tenia  chorioidea,  leads 
to  just  above  the  foramen  of  Monro  CFig.  103 1),  where  it  is  joined  by  the  similar 
line  of  the  opposite  ventricle.  From  thi.s  point  the  choroidal  line  of  ependymal 
reflection  is  continuous  with  the  taenia  thalami,  the  sharp  ridge  which  marks  the 
junction  of  the  superior  and  mesial  suriace  of  the  thalamus  ( pstge  11 19).  Leaving 
the  surface  of  the  latter  along  this  ridge,  the  ependymal  layer  covers  the  under  side 
of  the  velum  interpoaitum,  as  well  as  the  double  row  of  vascular  villous  projections, 
which,  one  on  each  side  of  the  mid-line  of  the  roof,  constitute  the  choroid  plexus 
of  the  third  ventricle  (Fig.  974).  Although  similar  in  its  general  structure,  thi-- 
vascular  fringe  is  much  smaller  and  less  conspicuous  than  that  within  the  lateral 
ventricle. 

It  is  evident  from  the  foregoing  description,  that  communicntion  between  tlie  third  and 
lateral  ventricles  is  completely  interrupted  by  the  attachment  of  the  ependymal  layer  and  that 
at  only  one  place,  the  foramen  of  Monro  (page  1161 ),  does  such  communication  exist.  It  Ls 
of  interest  to  note  that  these  several  lines  of  ependymal  reflection — the  ta-nia  chorioidea,  the 
ta-nia  thalami  and  the  t£eni.i  fomicis  and  its  prulunKation,  the  txnia  fimbria: — form  a  contin- 
iiuiis  line  which  mor|)holn)(ically  marks  the  transition  of  the  thicker  nerxuus  pan  of  the  wall  of 
the  hemisphere  into  the  thin  and  atrophic  area,  vvhirh  early  undergoes  an  invaionation  leading 
to  tlie  prtKluction  of  voluminous  va.scular  structures  iaier  seen  in  the  delinite  choroid  plexuses 
i>f  the  lateral  and  third  ventricles.  Along  the  m.-uTfin  of  the  choroidal  fissure,  at  Hhich  such 
iiivaKination  primarily  occurs,  the  white  matter  of  the  hemisphere  iM-ronies  condensed  intn  the 
tract  of  the  fornix  and  its  downward  prolongation,  the  fimbria.  These  structures,  together 
with  the  reflected  ( |>endyma  and  the  septum  lucidum,  are  regarded,  therefore,  as  modified 
imrts  of  the  mesial  surface  of  the  hemisphere. 

The  inferior  horn  (cornu  inferius),  iUso  called  \.\\e deicfm/hig  horn,  begins  alx»\e 
at  the  hind-end  of  the  body  of  the  \'entricle,  thence  curves  biickward  and  outward 
around  the  thalamus,  and  sweejis  downward  and  forward  and  a  little  inward  (  Fig. 
1000)  into  the  temporal  lobe  well  t(i«ard>  its  tip,  which,  however,  it  fails  to  reach  by 

about  2  cm.  Its  descent  is  not 
only  very  abrupt,  but  limited 
for  the  most  part  to  almost  a 
vertical  plane  ;  hence  this  part 
of  the  \  (Utricle  does  not  diverge 
to  any  consideraH1»  extent  be- 
yond the  planpri  fbeK>rus  hip- 
|x>catnpi,  ju.-t  to  liie  outer  side 
of  which  the  I'j>»er  end  of  the 
inferior  horn  lies.  The  roof  oi 
this  cornu  is  formed  chiefly  hy 
the  tapetum  of  the  <i(rpiis  cal- 
losum,  and  within  it  descend  the 
recurved  attenuated  tiiil  of  the 
caudate  nucleus  ami  the  fu-nia 
semicirctilaris  to  join  a  roundetl 
mass  of  gray  matter,  the  amyg- 
daloid nucleus  (page  1172), 
which  lies  embedded  within  the 
temporal  IoIk-,  sli^jhtly  alM)ve 
ami  in  front  of  the  lower  end  ni  the  inferi<tr  horn  (Fig.  967).  Tlit  floor  of 
the  inferior  horn  l)egiiis  at)«)ve  in  the  triangular  area,  the  trigonum  ventriculi, 
iK'lween  the  diverging  inferior  :ind  j)Osterior  horns.  The  greater  part  of  this  field  is 
occupied  by  a  low  c(mvexity.  the  collateral  protuberance  (trigonum  collatcrale), 
which  is  continuefl  into  a  roiindee!  ridge,   the  collateral  eminence  (eminentia 


.o.  1003. 


C     C 


T;rnin  chorinulrfl 


^T«nin  fontids 


Ticnin  thnlanii 


^,.  Choroii,  pIrxuM 
of  III  ventricle 


IHaK^.'in  showiiiK  rclalion  of  pial  iKsiie  in  vrriim  interpoitiliim  ti> 
I'tMfiitlyni.t  III  liiUTai  and  third  venuicic  ;  v|ifnd\ma  in  represetitrtl  hv 
red  line;  c,  i\  riirpun  talloMiim;  /■',  fornix,  ft'.  soH.-allefl  ventricle  t(( 
Verica:    (\  7'.  caudnte  nurleus  and  thalamui*. 


THE  TELENCEPHALON. 


1165 


collatenlta)  that  extends  for  a  variable  disUnce  along  the  outer  |wrt  of  «he  flo.  r 
^  .hTSlerior  horn  This  elevation  is  uncertain  as  to  prominence  and  len^t!  . Imt 
of  the  '"'"'"'  ?T;.ncd  does  not  reach  the  lower  extremity  of  the  ^ .  .uric  e. 
r:Li:i!^r;om  tht  Int&LTof  the  .an  ol  .he  early  hemisphere  by  the  .n,er.or 

»""  A  l^'o^d  SuSfelevation.  constant  and  much  more  co.«picuous  than  the 
«.UaterremSence  and  separated  from  the  latter  by  a  groove,  forms  the  mner  ,Mrt  ..f 
iXrlnd  the  adjoining  mesial  wall  ot  the  inferior  horn  of  the  latera  ventricle^ 
Vhisdevat"on  known  as  the  hippocampus,  is  the  most  promment  feature  o  he 
hi  and  curv«  downward  and  inward  to  the  extreme  lower  hm.t  of  this  part  of  the 
horn  ana  c*";v«  ""*"  ,    i„,.^gi^tion  of  the  hemisphere  by  the  hippocampal 

CTe  ThVlower  enS^Tthe  hiJ?K.n,pus  is  dLstinctiy  broader  and  s.>mewhat 
Sened  and  nSric^  by  a  number  of  oblique  shallow  furrows  and  mterxenmg  low 
SaSS  ridgTStaOones  hippocampi ).  These  confer  on  the  upper  surface  and 
^rSfy  on^e  outer  rounded  border  of  the  elevation,  a  corrugated  ^^'d  "Otch^ 
Tp^rance  (  Fig.  .004). which  suggests  a  fancied  rescmbUnce  to  a  paw,  the  lower 
end  of  the  projection  being 
known  as  the  pes  hippo- 
campi. The  upper  surface 
and  the  anterior  and  lateral 
border  of  the  pes  are  free 
and  well  defined,  but  its 
deeper  suriace  and  inner 
border,  to  a  large  extent,  are 
blended  with  the  surround- 
ing piirts  of  the  hemisphere. 
The  intimate  structure  of  the 
hippocampus     is    described 

with   that    of    the    cerebral 

cortex  (page   1181). 

The  dorso-mesial  aspect 

of  the  hippocampus  is  over- 
laid   by    a   white    flattened 

Iwnd,  the  fimbria  (fimbria 

hippocampi),  which,  although 

bearing  a   special   name,  is 

the  direct  prolongation  of  the 

j>isterior  cms  of  the  fimbria, 

continued  from   the  lateral 

angle  of  the  corpus  fornicis 

into  the  inferior  horn.     Us 

concave    mesial    margin    is 

smooth,  rounded  and   free 


Hn  hit>(wc4lit|4 


Inferior  honi  o(  lift  l«ler«l  venlrklc,  viewed  from  abovi-. 


rhS^uTuoustaTerif'^.rder  is  thin  and  shan^  and  give,  attachment  throt^^h- 
out  its  SitiJe  length  to  the  delicate  ependymal  layer  which  completes  the  mes.a 
wa  1  md  hus  clmes  in  the  descending  horn  (  Fig.  1005  )•  Above  narrow  and  then 
brLer  on  rSg  the  pes  .!u  fimbria  becomes  abruptly  reduced  to  a  i,arrow 
MrTnd  which  may  be  foUowe.!  ,i..ng  the  inner  margin  of  the  pes  to  the  uncus 
whtre  it  eS  graced  upward  the  fimbria  passes  without  mterruptum  into  the 
posterior  hmb  of  the  fornix,  of  which,  as  already  noted,  it  is  the  d.rc. .  downwa  d 
Songation  Beginning  in  the  uncus,  the  fimbria  continually  r.^e.xes  acc«>ss'.r^ 
Ses  n"n  th.-  .mderlving  hipp<K:ampus,  with  which  .t  is  closely  un.t«l  along 
its  dS  «V^ace,   and  the■refo^e  increa.ses  in  bulk  as  it  ascends  towards  the  l..dy 

"'  '""When^the  structures  within  the  inferior  horn  of  the  lateral  ventricle  are  viewed 


1166 


HUMAN  ANATOMY. 


horn  to  its  lower  end.  On  turning  aside  the  vascular  fringe,  its  relations  to  this 
pan  of  the  ventricle  will  be  found  to  be  identical  with  those  exhibited  in  the  body 
of  the  ventricle,  since  here,  as  there,  the  vascular  complex  is  everywhere  covered 
by  the  thin  layer  of  reflected  ependyma  and,  therefore,  excluded  from  actual 
entrance  into  the  ventricular  space.  Tracing  the  line  of  attachment  of  the  reflected 
ependyma,  which  alone  represents  the  true  ventricular  wall  closing  the  crescentic 
choroidal  fissure  along  the  dorso-mesial  aspect  of  the  inferior  horn,  it  will  be 
found  to  be  continuous  with  the  thin  lateral  edge  of  the  fimbria  throughout  the 
entire  length  of  this  attenuated  margin,  just  as  it  is  connected  with  the  fimbria 
within  the  body  of  the  ventricle.  Passing  from  this  line  of  attachment  (taenia 
fimbriae)  over  all  the  villous  projections  of  the  choroid  plexus,  the  reflected 
ependyma  returns  to  the  thicker  vcuUicular  wall,  which  it  joins  along  the  mesial 
border  of  the  roof.  Thence  the  ependyma  remains  in  close  contact  with  the 
remaining  parts  of  the  walls  of  the  inferior  horn,  all  the  surfaces  of  which,  including 
those  formed  by  the  hippocampus  and  the  collateral  eminence,  it  covers.  From 
these  relations  (Fig.  1005)  it  follows  that  the  fimbria  in  large  part  is  excluded, 
as  are  some  other  parts  of  tne  fornix,  from  the  ventricle,  only  that  portion  of  its 
surface  which  extends  from  its  sharp  lateral  border  to  the  underlying  hippocampus 
forming,  stricdy  regarded,  a  part  of  the  ventricular  wall.  The  rounded  mesial 
border  and  the  doreal  suriface  of  the  fimbria  belong  to  the  free  mesial  surface  of 
the  hemisphere. 

The  dentate  gyrus  (fascia  dentata)  is  part  of  an  atrophic  convolution  belong- 
ing to  the  rhinencephalon  (page  1151),  and  as  such  belongs  systematically  to  that 

division  of  the  hemisphere, 
Fig.  1005. 

ClioroM  plexu* 
Epcndymm    \  Caudate  niiclma.  tail 

'     Tenia  btmidrcularit 


Cavity  of  iofcrioi 
horn  of  lateral  ^ 


Entrance  to 
choroidal  fissure 

Fimbria 
imbricMlenlate 
fissure 
yrus  dentatus 


Hippocampal  fissure 
Aiveus 


Since,  however,  it  is  closely 
associated  with  the  struc- 
tures found  within  the  inferior 
horn  of  the  lateral  ventricle, 
its  description  has  been  de- 
ferred until  this  place.  The 
dentate  gyrus  lies  on  the 
mesial  suriface  of  the  hemi- 
sphere, but  is  so  hidden  be- 
hind the  hippocampal  gyrus 
that  it  is  satisfactorily  dis- 
played only  after  the  over- 
hanging parts  of  the  thala- 
mus and  cerebral  crura  are 
removed.  On  cutting  away 
these  structures  and  drawing 
downward  the  hippKxampal 
gyrus,  a  narrow  band  of  gray 
matter,  notched  and  corru- 
gated by  numerous  minute  transverse  furrows,  is  seen  protruding  between  the  free 
rounded  mesial  border  of  the  fimbria  above  and  the  hippocampal  fissure  below  (  Fig. 
993).  This  band  is  the  gyrus  dentatus.  On  examining  frontal  sections  passing 
through  the  interior  horn  of  the  lateral  ventricle  (Fig.  1005),  the  rel.itions  o(  the 
dentate  gyrus  will  be  appreciated.  In  such  preparations  the  gyrus  appears  as  the 
free,  somewhat  thinned  off  edge  of  cortical  gray  matter,  which  is  pushed  to  the 
surface  just  below  the  choroidal  fissure  through  which  the  pial  tissue  invaginates  the 
ventricular  wall  to  gain  a  seeming  entrance  to  the  inferior  horn.  Between  the  fimbria, 
which  lies  immediately  above  and  parallel  with  it,  and  the  gyrus  a  shallow  groove, 
the  sulcus  /imbrio-dentalus,  intervenes,  whilst  below  it  is  bounded  by  the  remains  of 
the  hippocampal  or  dentate  fissure.  The  latter  is  no  longer  an  evident  furrow,  as  it 
was  when  producing  the  hippocampus,  since  it  has  become  closed  and  almost  com- 
pletely obliterated  by  the  apposition  of  the  bordering  cortex. 

Traced  forward,  the  gyrus  dentatus  gradually  leaves  the  fimbria  and  passes  deeply 
along  the  inner  side  of  the  uncus  in  connection  with  which  it  ends.  The  terminal 
[lart  nf  the  gyms,  somewhat  rethiced  in  size,  at  first  bends  sharply  medially  along 


.  Hippocampus 
Gyrus  hippocampi 
Collateral  fissure 

Frontal  section  of  part  of  left  hemisphere  pauing  through  lower  end  of 
iiiierior  horn  of  lateral  ventricle.    X  >. 


THE  TELENCEPHALON. 


1167 


.pfcni«m.  «  *' 'j'J'iSS'i^^*  SuSn  whib.  fcgy,™  dSu.u..  losing  i" 
passing  to  the  under  siae  01  uie  wi^  t_„™n  as  the  fasc'ola  cinerea,  bends 

Sru^tions  and  ^-"^'^^^ Tfl^^^^lF^^^ lospr^d  out  over  the  upper 
backward  and  curves  around  the  splemum  <  »*«•  992;        h  ^^^^     ^^^^ 

surface  of  the.  corpus  callosum  -  U^c^ thm  aj-?!^;  ^^J^*^^  ^«^^  longitudinal 
l^T^S  fr")"%he:t!^c'?rof'^h':'^t.^d^  ■.  described  with  that  of 

Sr  S^  of  the  cerebral  cortex  (page  118.). 

Fig.  1006. 
,  Splcnium  of  corv>n»  c»Uo«uin 


.Uncus 
Frenulum  of  Giacomini 


F»«dol«  cfnetM       Rynw  hippocampi 


CollBlenil  RMure 
Gynu  dcnUtus 


P..on.n.n„H.ppoc.n.p....^n^c..«£to^»^J^^^^ 

The  fornix  is  to  be  re^rded  as  the  chjeT  fib^-^  - -."g  ^^^^^^^^ 
within  the  uncus  and  the  WP»^'^"'C,;d*^thtch*nS  which  affert  the  position  of  ihe  hippo- 
couise  as  seen  in  the  adult  ^'"^X^^^l^f^'Z^^oi.,  will  recall  the  origin  of  the  hem.- 
campus  during  development     R«f '*"**J°  „'?l- 'j"^  l,„d  farther,  that  the  hemisphere  in  man 
sphJre  (pallium)  as  an  o"»8™^'^''°"  V'^^Aer^^^^^^^  and  the  mid-brain     For  a  time 

early  covers  in  the  thalamus  and  other  P^'*'' °' "^„  ™t_;  .,  only  the  thin  recurved  under  and 
the 'thalamus  « '^o^'^^-'.-'t't'rrof  white  ^att^^^  it  -  later  embedded  being 

inner  wall  of  the  pallium  the  ^^'ky  «««^  «*  *''™  ™i„^  by  ,he  thalamus,  even  m  the  adu 
for  a  time  wanting.    This  same  '  '^^P^-^f  *  " ''^e  „ceisively  thinned  out  ventricular  wall 
condition,  on  its  upper  «"d  postenor  a^M^s  w^^^^^^^  J^^^^  ^,^  ,,„,  i,     „■ 

alone  forms  the  partition  between  the  venr^te  and  w^  ^^  ^^^  partition,  as  after 

laid  by.  but  not  in  contac^  wrth.  the  ';?""*P^f^^„,  ^a    ^  jir^tly  reached  by  passing  beneath 
removal  of  the  velum  '"ten»situm  the  thalwnus  may  /  becomes  developed.  :m  area 

the  splenium.    When  a.defi"'te  mesml  ^^^  f  J^^J^f^^  Sy  two  primary  grcx,ves.  wh.ch  are 
along  the  inferior  margin  of  this  aspect  becomes  rna^^^  '     .  ^^e  area  so  defined  is 

Sriy  choroidal  fissure  »«'- «"^  theJi^P-^Z  fs'Zne^d  with  the  thalamus  by  the 
the  primary  gyrus  dentatus  J^J^^^^'^^^^/^^^^T^nA  of  the  choroidal  fissure.  In  many 
fornix.  wWch  reaches  the  thalamus  around  *« '^^  ,  ^^^a,  the  dentate  gyrus,  or  its 
animals,  as  in  the  rabbit,  a  ''"]^''»V„^  !^°"i,^\^Sn"us  by  a  fornix-tract  which  sw«^ 
equivalent,  the  hippocampus,  being  """^  *"*?  „!^ampus>  over  the  nK,f  of  the  third  vemricle 
^he  lower  and  posterior  part  of  ^^e J^'^e  JX  S\„,ammillary  b«^^  and  thence  by 
forward  and  downward  to  the  ^^"'^"J^^'^Vhe*.  primary  are  changed  by  the  future 

the  bundle  of  Vicq  d'Azyr  to  «he  thalamus.    These  prim  backward,  but  also  downward 

expansion  of  the  hem  sphere.  «'h'=h  pows  n<^  on^y  upw  ^^^  ^^^  fornix  and  likewise 

to  form  the  temporal  lobe,  'nc°"»"^""="«!°i^'' wkwanl  dow^^^^        and  forward  around  the 
the  choroid  plexus  and  '''!  ,»'»"':;ri  J^^J^f,  ^"^.trm^^^^^^ 
thalamus  into  the  temporal  '?»^^«'*''''"l!7^;^ed     Whilst  in  this  manner  the  chief  mass  of  the 


ii68 


HUMAN   ANATOMY. 


'<ie  definite  dentate  gyrus,  a  part  of  it,  greatly  attenuated  and  reduced,  retains  its  connection  with 
lilt-  anterior  l>asal  surface  of  the  brain  (later  the  anterior  perforated  substance)  and  follows  the 
upper  surface  of  the  corpus  callosum,  which  likewise  has  extended  backward,  into  the  descend- 
ing horn  of  the  lateral  ventricle.  These  parts — the  gyrus  sut>callosus,  the  longitudinal  stria, 
the  fasciola  cinerea  and  the  g>rus  dentatus  of  the  adult  brain — constitute  the  supracallosal  gyrus, 
whose  gray  matter  is  an  atrophic  outlying  part  of  the  primary  gyrus  dentatus  and  whose  con- 
nections with  the  basal  olfactory  centres  are  retained  by  the  fibres  of  the  longitudinal  stria:. 
The  fornix  shares  the  displacement  of  its  cortical  area,  the  hippocampus,  and  is  consequently 
carried  with  the  latter  into  the  descending  horn  of  the  lateral  ventricle.  In  this  manner  parts 
which  at  first  lay  in  proximity  and  were  connected  by  short  paths,  become  widely  separated, 
with  corresponding  lengthening  of  the  fibre-tracts  uniting  them,  as  illustrated  in  the  long 
course  of  the  fornix  in  the  adult  brain.  Further,  since  the  path  of  migration  of  the  fornix 
and  associated  structures  of  the  inferior  horn  of  the  la'eral  ventricle  describes  a  curve, 
it  follows  that  the  relations  of  these  parts  becomi  reversed,  those  originally  lying 
above,  in  regard  to  adjacent  structures,  within  the  iescending  horn  being  below  and 
vice  versa. 

The  posterior  horn  of  the  lateral  ventricle  (cornu  posterius),  much  smaller 
than  either  of  the  others,  is  an  elongated  diverticulum  which  curves  backward  from 


Fig.  1007. 


Superior  frontal  g>'niM 

Middle  froDtal  gyrus 


Longitndiiial  linure- 


(iemi  of  corpus 

callosuni' 


IjitrmI  \-entricIe. 

Ruterior  horn- 


Inferior  frontal  g>-rui( 


Caudate  nucleus,  head 


^^Orhital  gyri 
Frontal  section  of  brain  paasing  tlirough  genu  of  corpus  callosum. 


the  Ixidy  of  the  ventricle  into  the  occipital  lobe.  In  frontal  sections  ( Fig.  1034)  its 
form  is  irregularly  crescentic,  the  convexity  of  its  outline  including  the  roof  and  the 
lateral  wall  and  the  concavity  corresponding  with  the  mesial  wall  and  narrow  floor. 
Above  and  to  the  outer  side,  the  horn  is  bounded  by  the  arching  fibres  of  the  tape- 
turn  of  the  corpus  callosum,  lateral  to  which  lies  the  important  thalamo-occipital  or 
optic  radiation  (page  1 123).  The  lower  part  of  the  mesial  wall  is  modelled  (Fig. 
1000)  by  a  narrow  but  well  marked  crescentic  elevation,  the  calcar  avis,  also 
called  the  hippocampus  minor,  which  is  produced  hv  the  early  invagination  of  the 
wall  '  f  the  hemisphere  by  the  anterior  part  of  the  calcarine  fissure.  On  the  same 
w- ■  and  just  above  the  calcar  avis,  a  second  and  broader,  but  less  sharply 
d<_  ned,  elevation  (bulbtis  cornu  posterioris),  .narks  the  course  of  the  fibres  of  the 
forceps  poster  .  as  thf  y  encircle  the  parieto-occipital  fissure  in  their  journey  to  the 
occipital  lo!)e. 


iMIII 


THE  TELENCEPHALON. 
The  Internal  Nuclei  of  the  Hemisphere. 


1169 


Embedd«l  within  the  white  matter  «<  each  ^emb^here  a^f-  ^e  most^P-J. 

completely  separated  from  the  cerebral  cortex  he  £.6^^"^^.  ^f^  (he  ca,4date 
whic^h  the^na^he  basalgangha. soften  ap^^^^ 

ntuieus,  (2)  the lenlicu/arntu/fus,  (.3)  *''e"*?*n^*""  ^T;,  .he  corpus  striatum. 
The  fir^t'two.  the  caudate  and  lent.^lar  "ucl^.^M^^  telencephalon.  Although 
one  of  the  three  hmdamenta^  ll'^iTinte^enkS  S  of  white  matter,  the  interna! 

almost  -™P»e^tte"aK^ic«CLSS^^^^  »  «'"'^«*i^"'l^- V"*; 

caPsuU,  the  caudate  and  lenticular  """;' f'^  .  ,    „e  n,ass  composed  chiefly  of 

Ji  in  front  (Fig.  '°f  ^'.^^o ^^S^TTv^tn^le^^^^       to  thi^ex  of  the 

rSrttrtn^^n*  tt'' i^^^rh^rTCMteral  ventHde.  is  situated  the 
--«^CruS  Nucleus.-This^ma.^^^^^^^^^^^^ 

ho^,  and  the  outer  part  o   the  floor  of  the  body  ^  Jg^^^atter.  whose  bulky 
nucleus  is  an  elongated  pynform  or  <^mrt-B^^^^^  diminishes  into  the 

rounded  anterior  end  or  head  (<»P"^  ""'='*^ '^7' hich  s^^^ 
attenuated  and  recurved  tai  (cauda  ""'•"  "»W  j'^ho^^^^^        rfp  of  the  temporal 

and  laterally  is  embedded  within  'JefUe  matter  of  the  henu«P  ^^^  „„^,,„,  has 
passing  a  few  millimeters  farther  ^^^^'f'^'^l'rnore  extensive  and  its 
beTome  somewhat  changed,  its  >««»?•  ."'"^^'L'T^  the  invasion  of  obliquely  hori- 
outer  one.  now  somewhat  concave.  ^^'"8  sernit^by  the   ™n        ^  J„^/^j  ^he 

ateTt^i;iaKi^^=  a^S^^^^^^  coarse  striation  from 
whTch  the  entire'mass.  the  -n>ussmamm   derives  lUn^^^^^  ,^^^ 

In  sections  oassing  through  the  body  d  the  ventn^^R^^^  .^  ^^^^  ^^^^^^ 
the  plane  of  the  loramina  of  ^onjo  backward  me  ca  thalamus,  become 

in  sue.  whilst,  on  the  contrary,  the  'enticular  nucleus  as  wei  ^  ^  ^ 

more  conspicuous.  The  internal  <^lf  }»1^' ^"^  X  sTmra^  the  two  ^rts  of  the 
large  oblique  tract  of  white  matter,  which  <^«'"P>f  £,!i^'7^^^^  '  By  reason 

co^us  striatum  and  lies  to  the  outer  side  f  ^J^  ^^'i^^S,  ^Jil  as  in  frontal 
of  the  recurved  course  of  its  attenuated  »="'•'" '«^"Jf„'^'^^^^^^  cut.  one  cross- 

S*eiLrs\;'pSkt=in^^^^^^^^ 

d  tSula  by  a  narrow  tract  of  white  --^^^'^^^^i:±;^TTo^^Tlnr  as 
stance,  the  claustrum.     The  lenticular  nucleus  readies  ^^^^^^^  ^^  ^^  thalamus. 

high  as  the  caudate  nucleus.  ""'I  >'"  ^f  «^' .'^,  J^^^  the  internal 

serrated  from  them  respecUvcly  by  Je  =»ntenor  and  pjtenor^^^  ^^^^ 

capsule.     Its  dorso-mesial  surface    >*hen  ^  l:tions     fS    1°  O  this  suriace  is 
alive  downward  and  inward  ;   m  t^"f:;"*  ^^X'    „  c,r''=*Po"d^^^^^ 
L«  SettS^l^i^^Vs  SSTnt'Lteral  .uHa^  is  approximaUy 

74 


1170 


HUMAN  ANATOMY. 


Fig.  1008. 


Thalamus 


Caudate  nucleus 


vertical  and  in  immediate  contact  with  a  thin  sheet  of  white  matter,  the  external 
capsule,  which  separates  the  nucleus  from  the  daustrum.  Its  ventral  surface  is  hori- 
zontal and  only  feebly  curved  and  is  continuous  in  front  with  the  caudate  nucleus 

and  farther  backward,  about  its  middle,  with 
the  anterior  perforated  substance  on  the 
basal  surface  of  the  brain.  The  lenticular 
nucleus  is  unequally  subdivided  by  two  thin 
concentric  sheets  of  white  matter,  the  ex- 
ternal and  internal  medullary  laminK, 
into  three  segments.  The  outer  of  these,  the 
putamen,  is  much  the  largest  and  occupies 
the  base  of  the  nucleus,  being  bounded  by 
the  external  capsule  ..iterally  and  by  the 
external  medullary  laminae  mesially.  Of  its 
two  somewhat  rounded  ends,  the  anterior 
is  the  broader  and  extends  farther  forward 
and  alone  joins  the  caudate  nucleus  of  which 
it  morphologically  is  a  part  (page  ii6>)). 
The  putamen  is  the  most  conspicuous  part  of 
the  lenticular  nucleus,  not  only  on  account  of 
its  size  but  also  by  reason  of  its  darker  color, 
in  which  respect  it  corresponds  with  the  caudate  nucleus.  This  contrast  depends 
less  upon  the  actual  pigmentation  of  the  cells  of  the  putamen  than  upon  the 
lighter  color  of  the  other  zones  of  the  nucleus.  In  consequence  of  the  small 
number  of  fibres  entering  the  external  capsule  from  the  putamen,  the  attachment 
between  the  latter  and  the  capsule  is  relatively  loose  and  the  two  structures  may  be 


Lenticular 
nucleus 
Reconstruction  of  corpus  striatum  and  thala- 
is;  lateral  aspec 
by  internal  capsule. 


Tail  of  caudate  nucleus 


mus;  lateral  aspect;  probe  lies  in  space  occupied 
Drawn  from  Slejfer  modeK 


Fig.  1009. 


Corpus  calkwum' 


Septum  luddum 


Right   lateral    ventricle, 
anterior  horn 


Internal  orbital  gyms 


.^Superior  frontal  gyrus 

Middle  frontal  K>'rus 

Inferior  frontal  gyrus 

.Caudate  nurleuw 

Internal  capsule 
Lenticular  nu.leu.^ 

Temporal  lobe 
Continuity  of  caudate  and  lenticular  nuclei 


Frontal  itectlnn  of  brain  passing  throug'.i  anterior  end  of  corpus  striatum  where  caudate  and  lenticular  nuclei  are 

continuous  below. 


readily  separated.  his  condition  influences  the  course  taken  by  extravasations  of 
blood,  which  are  frci  aent  in  this  locality  and  may  occupy  a  large  part  of  the  lateral 
surface  of  the  putamen.  The  remaining  divisions  of  the  lenticular  nucleus  are  much 
lighter  in  tint  and  together  constitute  the  globus  pallidua.     They  are  subdivided 


HP 


B«pwflB^l|F 


THE  TELENCEPHALON. 


1171 


with  the  internal   "^^P"'*.  ,,  "  ..icularv  the  inner  two.  are  traversed  by  numerous 
SS  of  ttfibrtX^brSrhe^^^^^^^       of  the  gray  substance  and  produce 

an  appearance  of  radial  s"™-        -triatum  varies  in  its  several  parts,  that  of  the 
•fhe  structure  of  the  fOJJ" 'J^'^T^^idVntical.  whilst  that  of  the  globus 

caudate  nucleus  and  ^.^^  P"^"^^",„*^^"^diff?«  from  "he  histological  make  up  of  the 
paUidus.  although  smnlambo^^^^^^^^  ^^^,^^^       «^,^ 

other  parts.     The  close  r'-**mwan^^  constitute  a  smgle  mass  and 

the  internal  capsule.  .  tUmno-hout  the  greater  part  of  its  periphery 

Fig.  loia 


Corpus  c»lU»ur.-. 
Choroid  plMM 

Fornix 

Thalamus, 
mesial  nucleus 

Thalamu«. 
lateral  nucleus     ~— 

MammiUo- 
thalamic  tract 

Third  ventricle 

Anterior  pillar  ^ 

of  fornix 

Optic  tract— 


Caudate  nucleus 


Internal  cap»«le 

Lenticular 
nucleus,  pulaineu 

Insula 

Globus  pallidua 

Claustrum 


Amygdaloid  nucleus 


.ron..ls.c..ono.hr.in.^i.t=c- r  and  l^S-  —  ^  "^^  ^  " 

and  from  the  nucleus.     The  "erve-cells  ar.  for  the  --t  Pa>..  rathe^niaU^^ 
and  stellate  or  fusiform  m  shape  ^^^d  Pro^^ded  w  ith  ""J  „f  ^^e  second 

minute  irregularities.     They  are  chiefly  '^^ells  o^  g  P*^^'  -^^^      ^     ^J^,  and  are  not 
type   are   encountered,  whose  axones  are  limited  to  tne  gr  y 
prolonged  as  nerve-fibres  ( KoUiker)  mrticulailv  on  the  mesial  one.  with  a 

^       The  putamen  is  invested  on  '^^  'wo  sides   partKuW^""^  ,  ^^      ,     j^e 

fibre-layer  derived  from  the  external  •"'^""'''^'^"Xr  centres  by  wav  of  the  med- 
fibres  being  -hiefly  such  as  enter  the  ""'•'j";;,/;^^^^^ , ate  form.  KolUker  describes 
ullary  layer.  In  addition  to  ner^'e-cells  "^"r^.^/jSorm  bod^  and  dendrites  few 
those  of  distinctive  appearance  possessing  a  slender  iusitorm  do  y 

in  number  but  of  unusual  length.  ^„  •„,:_  _„inr  to  the  light  yellowish  tint  of 

The  g/oius  pallidm  owes  its  «-:h»[»«^t«^"«\'^^7;,  medt.Uat«l  nerve- fibres  which 
the  pigment  within  its  cells  »ndto.the  large  number  of  m«  ^^^^^ 

travei^e  its  substance,  especially  its  «  ^one     Jl^c  ner^e   ^^^^^ 
and  stellate,  possessing  numerous  short  but  nchl>  Dnncn 


II72 


HUMAN  ANATOMY. 


i| 


The  ConnectioiM  of  the  Cofput  Striatum — Much  uncertainty  prevails  as  to  the  details  erf 
the  connections  oi  the  several  parts  of  the  corpus  striatum  and  little  is  known  regarding  the 
function  of  these  nuclei,  notwithstanding  their  size  ;  certain  general  principles,  however,  may  be 
accepted  as  established.  The  comparative  studies  of  Gehuchten,  Sala  and  others,  and  especially 
of  Edinger,  emphasize  that  the  corpus  striatum  is  to  be  considered  as  supplemental  to  the 
cortical  substance,  in  the  lower  vertebrates  in  which  the  cortex  of  the  cerebral  mantle  is  feebly 
developed  constituting  the  chief  mass  of  cortical  gray  matter,  and  in  the  mammals  and  man 
being  subservient  to  the  overshadowing  cortex  of  the  hemisphere.  Such  being  the  warranted 
presumption,  it  is  to  be  anticipated  that  the  striate  body  both  receives  fibres  conveying  sensory 
impulses  and  gives  off  fibres  (perhaps  motor  in  function)  originating  from  its  cells,  these  latter 
tracts  constituting  the  strio-ihaiamu:  radiatioH. 

The  centripetal  or  afferent  paths  probably  include  :  ( t )  the  tegmento-striate  fibres,  which 
are  continued  chiefly  from  the  mesial  fille .,  and  perhaps  also  from  the  red  nucleus  and  subthal- 
amic region,  by  way  of  the  internal  capsule,  to  end  around  the  cells  of  the  putamen  and  head  of 
the  caudate  nucleus ;  (a)  the  thalamostriate  fibres,  already  mentioned  in  connection  with  the 
thalamus  (page  iias),  which  pass  from  the  thalamus  either  by  way  of  the  internal  capsule  directly 
to  the  caudate  nucleus,  or  by  way  of  the  ansa  lenticularis  to  the  putamen  or,  traversing 
the  medullary  laminae,  to  the  caudate  nuc!  ,us.  No  doubt  many  of  the  fibres  which  enter  the 
lenticular  nucleus  do  not  end  within  the  tatter,  but  traverse  its  substance  as  part  of  their  path  to 
the  cerebral  cortex. 

The  centrifugal,  or  efferent  fibres,  which  arise  from  the  cells  of  the  corpus  striatum  include : 
(i)  the  strio-thaUuMic  fibres,  passing  from  the  major  div'«ions  of  the  striate  body,  which 
comprise  (a)  those  from  the  caudate  nucleus  to  the  thalamus  direct ;  (4)  those  which  traverse 
the  internal  capsule  and  the  medullary  laminae  and,  joining  fibres  from  the  putamen,  pass  by 
way  of  the  ansa  lenticularis  to  the  thalamus ;  (<:)  those  from  the  putamen  which  reach  the 
thalamus  by  pa.ssing  partly  by  way  of  the  globus  pallidus  and  partly,  in  greater  numbers,  by 
means  of  the  ansa  lenticularis.  (2)  Strio-peduiuular  fibres,  well  represented  in  the  brains 
of  the  lower  animals  as  the  continuation  of  the  basal  tract  of  the  fore-brain  ( Edinger),  which 
pass  from  the  caudate  nucleus,  and  probably  from  the  lenticular  nucleus  also,  into  the 
sub-thalamic  region  and  the  cerebral  peduncle,  within  the  latter  forming  the  stratum  inter- 
medium closely  related  to  the  substantia  nigra.  Whether  cortico-striate  fibres,  extending 
from  the  cerebral  cortex  to  the  corpus  striatum,  exist  in  man  is  uncertain,  Dejerine  denying 
their  presence,  whilst  Edinger  regards  the  presence  of  a  meagre  number  of  such  bundles 
as  established. 

The  Claustrum. — The  claustnim  is  a  thin  lamina  of  gray  substance  embedded 
within  the  white  matter  intervening  between  the  lateral  surface  of  the  putamen  and 
the  cortex  of  the  island  of  Reil.  Its  mesial  surface  is  smooth  and  parallel  with  the 
outer  aspect  of  the  putamen,  from  which  it  is  separated  by  the  thin  tract  of  white 
matter  constituting  the  external  capsule.  Its  lateral  surface  presents  a  series  of 
elevations  and  depressions  which  in  a  general  way  repeat  the  contour  of  the  ^y 
cortical  lamina  of  the  insula,  the  intervening  layer  of  white  matter  being  sometimes 
called  the  capsula  extrema.  Seen  in  horizontal  sections  (Fig.  loii),  the  claustrum 
fades  away  both  in  front  and  behind  ;  in  frontal  sections  (Fig.  loio),  however,  whilst 
it  gradually  disappears  above,  below  the  claustrum  materially  thickens  and  mesially 
becomes  :ontinuous  with  the  anterior  perforated  substance.  Upon  comparative  and 
developmental  grounds,  the  claustrum  must  be  regarded  as  a  separated  portion  of 
the  corpus  striatum.  Its  nerve-cells  are,  for  the  most  part,  small  and  either  stellate 
or  fusiform  in  outline.  Nothing  is  known  with  certainty  as  to  the  course  or  connection 
of  its  fibres. 

The  Amygdaloid  Nucleus.  — This  structure  (nucleus  amygdalae)  comprises 
a  considerable  rounded  mass  of  gray  suljstance  (Fig.  lOio)  which  occupies  the 
fore-part  of  the  temporal  lobe  and  lies  in  close  pro.ximity  with  the  uncus,  overlying 
the  extremity  of  the  inferior  horn  of  the  lateral  ventricle.  Anteriorly  it  is  continuous 
with  the  cortical  gray  matter  of  the  temporal  lobe  as  a  thickened  portion  of  which 
it  may  be  regarded.  Its  lower  part  receives  the  tail  of  the  caudate  nucleus  and 
close  to  this,  the  tania  semicircularis  (page  1162),  which  accompanies  the  recurved 
nuclear  tail  in  its  descent  within  the  roof  of  the  inferior  horn.  The  nucleus 
approaches,  if  indeed  it  does  not  touch,  the  anterior  perforated  substance,  and  above 
comes  into  intimate  relations  with  the  lenticular  nucleus.  It  is  highly  probable  that 
the  nucleus  amygdala:  forms,  along  with  the  uncus  and  the  hippocampus,  a  part 
of  the  olfactory  cortex  (Dejerine). 


wc 

i 


THE  TELENCEPHALON. 


H73 

1  n.^»\^      Reneated  mention  has  lieen  made  of  the  important 
The  Internal  Capsule.— Repeateamenuo  (capsula  interna):  its 

tract  of  white  matter  beannR  the  "^f  °« J^'^^^^en  aMhb  pTace.     It  is  a  broad. 

description,  therefore,  may  be  WP™^^  "t^tJe"  the  three  large  basal  ganglia. 

compact  tend  of  "^'^^r'jSl"  ^J.'^t'Si  a^d  tte  thalamus.     Although  the  details 

rhti-^^nS^Sl^ul-al;  wi;KSer"ent  both  of  direction  and  of  pos.t.on  of  the 

Fig.  loii. 


Uienl 

iitrkls 


Csuftaftt 
nuclcuft 


Splcnium 
of  corpus' 
callatum 


CalcartMC  (Iciure 


planes  of  section,  its  general  r^'ation  to  the^^^^^^ 

stant,  the  caudate  nucleus  and   n^^^^^^^^  ^^.^^^^  p^^^.^^ 

lenticular  nucleus  to  "«  o"'"P^"„i  ventricles  (Fig.  ibio),  the  internal  capsu.e 
through  the  anterior  part  of    Jelatera    ventricles ^h.g.        ^^^,^^__^^^  ^^^  j^^.^^j 

rTa1>v%hril?cTuda?^^^^^^^^  the  lenticular  nucleus  lateral  v. 

SrtL\f  ^i  S^y  suS^^^^  establishing  continuity  between  the  two  nuclei. 


1 174 


HUMAN  ANATOMY. 


Seen  in  frontal  sections  passing  some  distance  behind  the  preceding  section, 
whilst  the  capsule  is  limited  laterally  by  the  lenticular  nucleus,  its  mesial  boundary 
now  includes  the  caudate  nucleus,  the  taenia  semicircularis  and  the  thalamus.  Still 
further  back  (Fig.  968),  the  internal  capsule  is  bounded  internally  in  addition  by 
the  subthalamic  structures  and  becomes  continuous  below  with  the  crusta  of  the  cere- 
bral peduncle.  An  upper  and  a  lower  part  of  the  capsule  are  therefore  recognized, 
the  for'-'cr — between  the  lenticular  nucleus  on  the  one  side,  and  the  caudate  nucleus 
on  the  other — is  known  as  the  thalamic  region  (recio  thalamica  capsulae  inttrnae), 
whilst  that  between  the  lenticular  nucleus  and  the  subthalamic  structi  ress  s  termed 
the  subthalamic  region  (rcgio  mibtbalamica ). 

Viewed  in  horizontal  sections  (Fig.  loii.  A),  the  capsule  appears  not  only 
.nuch  more  extensive,  but  is  seen  to  consist  of  two  mesially  converging  parts,  a 
shorter  anterior  limb  (pars  frontalis)  and  a  longer  posterior  limb  (pars  occipitalis). 
The  two  limbs  form  an  angle  which  opens  outward  and  encloses  on  two  sides  the 
gray  triangle  of  the  lenticular  nucleus.  The  juhction  of  the  two  mesially  converging 
limbs  forms  the  knee,  or  genu,  of  the  internal  capsule  which  points  inward  and  lies 
opposite  the  taenia  semicircularis,  between  the  caudate  nucleus  and  the  thalamus. 
At  deeper  planes  (Fig.  loii,  B^,  passing  through  the  level  of  the  continuity 
between  the  two  parts  of  the  corpus  striatum,  the  anterior  limb  is  greatly  reduced 
in  length  or  entirely  disappears,  the  posterior  one  being  prolonged  into  the  cerebral 
peduncle. 

'  The  importance  of  the  internal  capsule  will  be  appreciated  when  its  function  as 
the  great  pathway  connecting  the  cerebral  cortex  with  the  lower  lying  centres  is 
recalled.     Its  fibres,  both  corticipetal  and  corticifugal,  after  passing  beyond,  or  before 

coming  under  the  restraint  of   the  boundaries  of  the 
Fig.  loia.  capsule,  as  the  case  may  be,   radiate  to  and  from  all 

parts  of  the  hemisphere,  and  in  this  manner  form  the 
striking  fan-shaped  fibre-mass  known  as  the  corona 
radiata,  which  continues  the  internal  capsule  upward 
to  the  cerebral  cortex.  The  radiating  strands  of  this 
great  tract  interlace  with  the  radiation  of  the  corpus 
callosum  and  thereby  contribute  a  large  part  of  the 
fibres  composing  the  oval  centre  of  white  matter  within 
the  hemisphere. 

The  anterior  limb  of  the  internal  capsule  { pars  Icnticulocau- 
data )  includes  the  front  third  of  the  tract  and  extends  from  the 
genu  forward  and  outward.  It  contains  fibres  passing  both 
toward  and  away  from  the  cortex,     it^  corticipetal  fibres  are  : 

( 1 )  the  thalanto-f rental,  wliich  padMbm  the  thalamus  by  way 
of  its  frontal  stalk  through  the  anterior  limb  of  the  internal  cap- 
sule and  the  corona  radiata  to  the  cortex  of  the  frontal  lobe  ; 

( 2 )  the  thalamo-striale,  which  also  pass  from  the  thalamus  into 
the  internal  capsule  a:'d  proceed  to  the  caudate  and  lenticular 
nuclei.  The  corticifugal  fibres  include  :  '  i )  \\v&  fronto-pontine, 
which  arise  in  the  cortex  of  the  frontal  lobe  and  descend  by 
way  of  the  corona  radiata,  the  anterior  limb  of  the  internal 
capsule,  the  crusta  of  the  cerebral  jieduncle  and  the  ventral 
tracts  of  the  pons  to  end  around  the  cells  of  the  pontine  nucleus 
iis  links  in  the  connection  between  the  cerebral  and  the  cere- 
bellar cortex  (page  1094);  (2)  Xhc  fronto-tltalamif,  which 
extend  from  the  cortex  of  the  frontal  lobe  to  the  thalamus ; 
and  (3)  the  strio-lhalamic ,  which  proceed  from  the  caudate  and 
lenticular  nuclei  to  the  thalamus. 

The  posterior  limb  of  the  internal  capsule  (pars  lenticulo- 
thalamica)  extends  backward,  outward  and  downward  from 
the  genu,  and  includes  the  remaining  two-thirds  of  the  trart.  Its  hind  part  extends  lieyond 
the  posterior  limit  of  the  lenticular  nucleus,  hence  the  posterior  limb  is  subdivided  into  a 
lenticular  and  a  retrolenticular  portion.  As  does  the  anterior  limb,  so  also  does  the  (XKiterior 
limb  of  the  capsule  contain  both  corticipetal  and  corticifugal  fibres. 

The  lenticular  portion  includes  corticipetal  fibres:  ( 1 )  the  ttialamo-cortical.  which  issue  from 
the  lateral  and  lower  aspect  of  the  thalamus,  traverse  the  internal  capsule  and  to  a  considerable 


Diagram  ahowinj;  relative  posi- 
tions of  chief  trai.ts  in  internal  cap- 
sule (As  ;.nd  in  crusla  of  cerebral 
peduncle  (/?);  F-T,  {ronto-thala- 
mic  :  /■-/*,  fronto-pontine ;  T-O-P, 
teiniiorti-occipito-itontine;  C-Iixor- 
ticti-buUmr ;  05,  cortico-spinal ;  S. 
tegmental  sensory;  OR,  optic  rad- 
iation. 


THE  TELENCEPHALON. 


1175 


u.  .  ,„H  th*  external  capsule  and  proceed  to  the  cortex  ol  the  hind 
number.  *«.»««™''^""*=^h;.^e^  lobL T^dT)  protably  s..me  Ikata^Untic^ar  fibres 
part  of  the  Irontal  and  ol  the  panetal  looe  .       ^^J    ^   '    rha,«,  the    caudate    nucleus 
&    pass    from    the    t'«'-J^"»     °  thT  im J^^t^  moto^  rortulbulbar  >nA  cCuo- spinal 
The  coitictfuf .1  «bre.  '"«^'"™  •  ^1'  "^^^^  tracts,   which  descend  from  the   precentral 

„a,  ts.  conective.y  often  '^^^^J^J^'^^^tLJ.Z  a^d  the  fore-part  of  the  posterior  limb  ..t 
(Rolandic)  cortical  regi<^  through  the  corona  ^^^^^  ^^  ^^^^  ^^  ^^ 

ihe  internal  <^p.ule  mto  the  ^™»»  "'  »^,  "^Ix.  A  tract  supplennrntao'  to  the  pyramidal 
priate  levels  of  the  *''»"'-^"^°^"X/  St  be  mentioned.  These  arise  from  the  cortex 
^tor  paths,  the  '^^°'^,'^?^.'™„^'Ji^^d  through  the  lenticular  portion  of  the  posterior 
(perhaps  of  the  piinetal  ]^\r^ ^^^l"^  with  the  red  nucleus.  (2)  The  iortuo- 
\Q^  to  the  ^^'^■^t\'"  \^^ b^  the  Sral  cortex  to  the  thalamus.  The  »tro- 
thabimic  fibres,  which  converge  *™^^ '"'^ "™  ^j  by  important  corUcipetal  Bbf«.  con- 
l«.tlcuUr  ponk«  of  the    posterwr   ^^^^  «   ttaver^ed  by        po^^  ^^  ^^  ^^^..   ^^^ 

cemed  in  conveying  ™P'f  t'""!,.  °*  '^t  thT^Mamus  and  the  lateral  geniculate  and 
which.  is.suing  as  the  '^"P"?i '^'^hX^dpita  cortex;  and  I2)  those  of  X).^  auditory 
the  superior  quadngemina^  b.K|>  withthe  ««'P"^  ^  \^  j^^^or  quadrigeminal  body 
radiation,  x.hich  link  together  .*^.  "^•»'  ^7^'^  ^^  corticifugal  fibre,  are  represented 
withthe  auditory  cortical  area  in  '»^  **'"P°"^'  ?*^.«  {„mi  the  ceTebral  cortex  through  the 

I;      •»!   geniculate  body.  . ,     ■  ,  _.i  raosule  as  seen  in  hori- 

he  reUtlv.  position,  of  the  longer  tracts  composing  the  ^»«'^',^„»P*"'^anterior  limb 
„„.ta.  secUons,  are.  in  t«t"'="^*^>\l"i'T.^'llarr^rany  he  f^^^^  tracts  in  the 

is  shared,  from  before  backward.  >>>  .t'^^'^  .'^"^'T*''^'^^^  tracts,  the  facial  fibres  lying 

order  named.     The  genu  is  appropriated  by  '^e  corticc^^r  tra     .      ^^        ^^^^  ^.^^^ 
immediately  in  advance  of  the  hypoglossal.     The  succeed  Next  follows 

approximately  ""^i^ird,  affords  pas^e  to  th^^^^^  ^^^^  ^  occipito-tempor.. 

"poX*t.Srl,^r^"a':aTeTast^^^^^^^^^^  -trolenticular  field  being  uken  up  by 
the  optic  radiation. 

STRUCTURE  OF  THE  CEREBRAL  CORTEX. 

ness  not  only  in  the  same  area,  beinfc  p,^    ,0,3. 

thicker  over  the  summit  than  at  the  sides 
of  the  convolutions  or  at  the  bottom  of 
the  bounding  fissures,  but  in  different 
regions  of  the  hemisphere.     Its  average 
thickness  is  about  3  mm--  but  where  it 
borders  the  upper  end  of  the  Rolandic 
fissure,    particularly  in  the   paracentral 
lobule,   this   increa.ses  to  over  5  mm., 
whilst  over  the  frontal  and  occipital  poles 
the  thickness  of  the  cortex  is  reducwl  to 
almost  2    mm.     The    entire   superficial 
extent  of  the  cortex  of  the  two  hemi- 
spheres has  been  estimated  to  be  about 
2000  sq.  cm.,  of   which  scarcely   one- 
third  is  e.xi-osed  surface,  the  remainder 

being  sunken.  i    u    t      u 

On  examining  sections  of  the  Iresn 
brain,     the    cortex    does     not     appear  indistinct   division 

p.riphen,l   layer    of   wh.mh   "^;.    'k^  f  f 'f  ,£T;,.  j U^dAh.  ,.*r W 


StrBtum  lonale 

External  uray  iltalum 

Outer  itripe  of 

Baillarger, 

(Stripe  o(  (^ennari) 

Internal  irny  itrmtu 

Medullary  nbrc* 


Calcarine  fisaure 
Frortal  section  ol  hemUphere  inclBdlnp  coit«  «u^ 
round"g  calcarine  figure;  »'"PJi " 'S^T,'"""'  '*'"" 
of  Baillariter)  is  here  unusually  distinct.     X  3- 


11-6 


HUMAN  ANATOMY. 


stratum — four  lavera  being  more  or  less  clearly  recognizable.  In  certain  localities, 
as  in  the  prcct  ntral  convolution,  the  inner  gray  lamina  is  subdivided  by  an 
additional  white  line,  the  inner  stripe  of  Baillarger.  In  tlie  vicinity  of  the 
calcarine  fissure,  particularly  in  the  adjacent  part  of  the  cuneus,  the  outer  stripe  of 
Baillarger,  whilst  narrow,  is  unusually  distinct  and  confers,  therefore,  a  character- 
istic appearance  upon  the  cortex  of  this  region  (Fig.  1015).  The  band  in  this 
location  receives  the  name  of  the  stripe  of  Gennari,  or  the  stripe  of  V'icq  ct  Azyr. 
In  recognition  of  the  priority  of  description,  Gennari's  name  is  sometimes  applied 
to  the  external  stripe  of  Baillarger  wherever  found.  The  significance  of  these 
light  colored  strata  will  be  pointed  out  in  connection  with  the  intimate  structure 
of  the  cortex,  suffice  it  here  to  note  that  the  stripes  of  Baillarger  correspond  to 
zones  in  which  the  felt-work  of  horizontal  cell-procesaes  is  unusually  dense,  the 
stratum  zonale  corresponding  to  a  compact  layer  of  fibres  running  parallel  with 
the  surface.  Occasionally  a  condensation  of  tangent-al  fibres  immediately  beneath 
the  stratum  zonale  produces  the  appearance  of  an  additional  light  line,  which  in 
honor  of  its  discoverer,  is  known  as  the  stripe  of  Bechterew. 

The  essential  histological  elements  of  the  cerebral  cortex  are  the  nerve-cells  and 
the  nerve-fibres.      The  importance  of  the  fonner  is  evident  when  their  three-fold 

activity  is  recalled — ( i )  as  receptors  of 
Fig.  1014.  corticipetal  impulses,  (2)  as  distributors 

of  the  impressions  so  received  to  other 
parts  of  '.he  brain,  and  (3)  as  originators 
of  corticifugal  impulses  which  control 
the  nuclei  from  which  immediately  arise 
the  motor  nerves.  No  single  method 
of  preparation  suffices  to  display  satis- 
factorily both  group  of  structural 
elements,  for  when  stains  are  employed 
which  best  bring  out  the  cells,  the 
fibres  are  ir-ade  -lately  shown ;  and, 
conversely,  » lien  i.iethods  adapted  for 
the  den.onstraaon  of  the  fibres  are 
followed,  the  cells  are  but  imperfectly 
displayed.  It  is  advantageous,  there- 
fore, to  study  the  histological  details 
of  the  brain  by  more  than  a  single 
method,  combining  the  results  ob- 
tained by  the  use  of  cellular  stains 
with  those  yielded  by  procedures  ex- 
hibiting the  fibres.  Among  the  latter, 
the  well  known  method  of  Weigert,  or 
its  modifications,  has  been  of  great 
service  in  extending  our  knowledge 
concerning  the  various  fibre-tracts. 
The  methods  of  silver  impregnation 
introduced  by  Golgi,  although  not 
producing  true  staining  but  only  in- 
crustations on  the  cell  and  its  pro- 
cesses, have  materially  advanced  our 
knowledge  concerning  the  form  of  the 
cell-bodies  and  the  number  and  extent 
of  the  processes  of  the  neurones. 

Whilst  varying  as  to  details  in 
(^■"•rent  regions,  the  cerebral  cortex 
presents  a  general  plan  of  structure  whic!  .y  be  considered  :  (a)  in  relation  to 
the  ner\'e-cells  and  (^")  in  relation  to  the  neive-fibres. 

The  Nerve-Cells  of  the  Cortex.— When  .sections  tut  perpendicular  to  the 
surface  of  the  convolution  are  stained  with  basic  stains  (Fig.  1015)  or  prepared 
after  silver  impregnation   (Fig.   1016),   the  cerebral  cortex   exhibits  four  layers. 


Snbptal  layer 
Tangtf^tisl  fibre* 

Slralnm  looale 


Layer  ol  amall 
pyrmmidal  cellv 


Outer  stripe  of 
BaiHarger 

Layer  of  taree 
pyfamklal  ceVb 


Layer  of  poly- 
morphic cellB 


Med-jllary  fibre* 


DlaKTBin  showing  constituents  of  cerebral  cortex; 
cells  in  the  right  hair,  fibres  in  left  half  of  figure;  A,  B, 
large  and  small  p\i  \midal  cells;  C.  polymorphic  cells; 
/).  cell  of  Martinotti :  E.  cell  of  t\-pe  II ;  F.  association 
cell;  /,  /,  corticipetal  ^bres;  J,  ^,  corticifugal  fibres 
(axones  of  pvnimiclal  cells) ;  ^,  N^  neuroglia  cells. 


mmm. 


THE  TELENCEPHALON. 


"77 


Fio.  1015. 


which,  from  without  inward.  -  =  <•>  \^^,Sr"  innd?4\'Se'Ker  o^  S" 
pyramidal  celU.  (3)  the  layer  ot  ^«  P>;^"J' ^£  which  are  distinctive,  uith 
K'hic  cells.  Although  .««=»}  Pr^^^H^^'^^i^ondUyen,  where  the  change 
the  exception  of  the    unction  between  th«^«J  "»  f^^'^^'"*    ,,         i„g  insensibly 

The  .tratum  «<>n*»«'f*?„7uX^      The  layer  contains  few  nerve-cells  .t  ' 

:;Je^^SSni^%Tan:^» 
SoLd  of  a  subpial  condensation  of  neuroglia 
S^a  deeper  zone  charactenzed  by  numer- 
oS  fibres  or7r«:e3ses.  which  course  parallel  to 
T  surface,  and  a  meagre  number  of  nerve-cells 
wh<^  mos  distinctive  representatives  are  sn«ll 
TusH^nn  elements  {Cajai's  cells,  P™\L^j«*,!',  J^, 
lone  tangentially  directed  processes.     The  latter 
Sve  off  ihort  collaterals,  which  ascend  towards 
fhe  surface,  and  intermingle  with  the  number- 
ed twrnin^  filanients  derived  from  the  Penph- 
Slv  Sng  processes  of  the  pyramidal  and 
^2  c^lb  lying  at  deeper  leve  s  and  from  the 
^rticioetal    fibres    which    continue    from    the 
wSe  Ce  rSe  gyms  into  the   outermost 

'''^'^tty^r'of  .mil  pyramid^  cell,  is 
marked  off  from  the  stratum  zo  J.  which  it 
Ttoutlquals  in  thickness,  with  some  distinctness 
sSr<^^  contrast  to  the  last-mentioned  zone^ 
Stains  very  many  cells.  These.  ««  '  "dicat^ 
by  the  name  of  the  stratum,  »'«. «'  «7«"  ^'!^^ 
O007-.010  mm.)  and  P/"'";'^  *«7„'  .** 
least  in  the  deepest  part  of  the  layer.  In  the 
sSrficial  part  tvT  cells  are  rounded  or  irre^u- 
K  trian^lar,  but  they  assume  the  d«tinctive 
nvramidal  outline  as  they  approach  the  sub- 
ET  layer,  whose  element  they  resemble  m 
Possessing  apical  and  lateral  proce^. 

•^  The  layer  of  large  pyramidal  cell,  con- 
tains the  most  distinctive  neurones  of  the  cere- 
bral  cortex.     It  measures  usually  about  1.25 

mm   in  thickness,  but  in  some  localities  much 

more    and   blends   with   the    adjoming    ayers 

wkhout    sharp     boundaries.      The     cells    in- 

CTeLe    in    size    but    diminish   in   numbers  as 

^^are  traced  from  the  second   ayer  inward 

the  largest  (from  .020-.040  mm.  in  width)  and 

most  Characteristic  lying  in   the  deepes    part 

"the  stratum.     The  typical  PXr-^'d^ "" 

oossesses  a  conical  body,  triangular  in  section, 

i;^x  of  which  is  continued  into  a  long 
tapering  dendrite  the  ap,cal  Z'^;"'  J^^J  ^ut  usually  conside.  Me  distance, 
extends  toward  the  P^.^^'^^y  *f  ^^^.  "^^Z.  iLbing  the  stratum  zonale,  towards 
depending  upon  the  position  of  the  cell.  ,V  P°"  |*'"/ /  ess  breaks  up  into  a 
which  the  apical  dendnte  is  »l*^y«,, ^''^^'^'''ue  suril^  and  contribute  to  the 
number  of  end-branches  th«t  nm  pa^lel  -ith   the J^^^^^j,^  ^„^^,,,   ,he  apical 

SSndr &  offt  urertJrumlSr-rbraUes  thJt  continue  horizontally  and. 


mUGil  cells 


■■  Polymorphic 
•  cell's 


Section  of  cerebiml  corte«.    X  90- 


II78 


HUMAN   ANATOMY. 


Small  pyTB- 
midal  celU 


with  the  collaterals  and  similarly  directed  processes  from  other  cells,  ta.  e  part 
in  producing  the  felt-work  giving  rise  to  the  outer  stripe  of  Baillarger.  From 
tiie  deeper  or  basal  surface  of  the  cell  arises  the  delicate  centrally  directed  axone, 
which,  penetrating  the  intervening  fourth  layer,  acquires  a  medullarj-  coat  and 
enters  the  white  core  of  the  convolution  as  one  of  the  component  nerve-fibres. 
The  axone  gives  off  one  or  more  collaterals  which,  after  a  shorter  or  longer 
course,  establish  relations  with  other  and  often  remote  cells.  In  addition  to  the 
two  chief  processes,  the  peripherally  directed  apical  dendrite  and  the  centrally 
coursing  a.xones,    a   variable   number — from  four  to  twelve — of  secondary  lateral 

dendrites  spring  from  the  basal 
angles  of  the  cell.  These  processes 
usually  divided  ichotomously,  each 
succeeding  pair  of  branches  in  turn 
splitting  into  twigs,  until  the  den- 
drite is  resolved  into  an  end-brush 
of  librillse  which  aid  in  producing 
an  intricate  felt-work  of  finest 
threads.  Elach  pyramidal  cell  con- 
tains a  conspicuous  spherical  or 
ellipsoidal  nucleus,  within  which  a 
distinct  nucleus  is  usually  distin- 
guishable. The  cytoplasm  exhibits 
a  striation  and,  in  addition  to  the 
masses  of  tigroid  substance,  the 
Nissl  bodies,  a  mass  of  brownish 
pigment  granules.  The  larger 
pyramidal  cells  are  surrounded 
by  an  evident  pericellular  lymph- 
space. 

The  layer  of  polymorphic 
cells  includes  a  large  number  of 
small  nerve-cells,  from  .008 — .010 
mm.  in  diameter,  whose  forms 
vary  greatly,  irregular,  spherical, 
triangular,  stellate  and  fusiform 
elements  being  present.  Small 
pyramidal  cells  are  also  often  seen 
within  this  layer.  In  contrast  to 
dendrites  of  the  typical  pyramidal 
cells,  those  of  the  polymorphic 
elements,  although  peripherally 
directed,  do  not  reach  the  stratum 
zonale  but  end  before  gaining  the 
outermost  layer.  Their  a.xones 
pass  into  the  subjacent  fibre- 
layer.  The  radial  disposition 
of  the  groups  of  fibres  within 
the  deepest  stratum  of  the 
cortical  substance,  limit  the 
polymorphic  cells  chiefly  to  the 
interfascicular  areas,  within  which  the  cells  consequently  appear  arranged  in  a 
sonu'vvh:it  columnar  order. 

Within  the  deeper  layers  f)f  the  cortex,  therefore  among  the  |K>lymorphic 
and  the  pyramidal  elements,  two  additional  varieties  of  nerve-cells  are  encountered. 
These  are  the  cells  of  Martinotti  and  the  cells  of  Golp^i. 

The  cells  of  Martinotti  are  of  small  size  and  triangular  or  spindle-form  in 
out-line  and  particularly  distinguished  by  the  unusual  direction  of  their  axones. 
These  processes  pass  towards  the  surface  and  within  the  stratum  zonale  divide 
intii  branches,  which  are  i-ontinued  horizontally  in  the  (ctt-work  of  tangential  fibres.   As 


Large  pyra- 
midal celN 


Pol  yiliui  pliic 
ctlls 


'•■*T\e  celK  fif  cerebral  cortex  as  seen  after  silver  im- 
tircKtialion.  >  qo.  Drawn  from  preparation  made  by  Fro- 
leuor  T.  f>.  Lee. 


THE  TELENCEPHALON. 


1 179 


in  other  parts  of  the  central,  nervous  sy.,e^so  too  m^^^^^^^^ 

ound  a  sprinkling  of   Qolgi' «  cells  of   *>P^  .J^ji„„ '\he  axone  is  confined  to  u 

uS   tlrS^y   ifr'^StfSTe^raXtherefo.    never    reach,  the 

-"TuroSaccUsare  pr^entin  all  ^^^I^^^TI^^^:^:^' ::^ 
a  general  way  they  send  hbnls  in  =*"  ;|'"^^|''L" ^bri^^^^^  ;,  foirly  definite  in  certain 
thkh  they  then  support,  the  ^^^ngXlron  of  5he  n^u  oglia.\he  glia  cells  send 
Ttrata.     Thus  within  the  -"^pml  ^°"'^,^  ^^^^  The  cells  within  the  deq>cr 

„,ost  f  ^f'^'rJ^^'^Ve  of^Th"'  \>rocSSin  two  chief  groups,  one  extending 
part  of  the  cortex   give   »"   "'"  .        .„^.,ras  the  wh  te  core.  .      , 


thev  traverse  tne  cinicA  »..v —  J         .  • 

atJbout  the  level  of  the  outer  border  of  the     ^^«^^, 


-•••' -^i»v^  T.innrnlial 
-  V;  '  -  ;  0/ ,'  "TV  fibre-layer 


Siipra  radial 
telt-work 


outer  Hi  ri  lie 
)f  Baillarger 


favenarVepyra'nWal  cells.     The  radial        ,_ 
£^a«  ^t^afferent  and  partly  efferent.      [.  ■ 
T\^^c<^ki^gal  components,  which  predomi- 
late  ?eT/rgdy  the  centrally  directed  a.xones 
ofthe  pyramidal  and  the  polymorphic  cells 
wh  ch  a^e  continued  as  the  axis-cylmde.^  of 
Z  fibres  composing  the  subcortical  white 
*:tter     The  p^pherally  -u-mg  axones  of 
the  cells  of  Martinotti  also  contribute  to  tne 
pr^uctionof  the  fibre-radii,     The..W.«/J^a 
constUue,tts  of  these  tracts  include  the  nerve^ 
fibres  which  are  derived  f-om  cells  situatea 
t'or'less  remote  from  the  con-lutKin  jn 
which  the  fibres  (their  axones)  end      ^uen 
S  example,  are  the  thalamo-cort.cal  and  the 
te^mento-cortical  fibres,  as  well  a^  the  many 
cXnissural  fibres  that  arise  '" jhe  opp«  te 
hemisphere  and  cross  by  «;ay  of  the  corj  u. 
callosum.     Although  for  the  l"ost  par    the 
corticipetal  fibres  end  at  various  levels  in 
Sri^tions  around  the  pyramidal  cells,  some 
"rcontinued  into  the  stratum  zonale  where 
brtaldng  up  into  horizontal  fibrill*.  they  assist 
in  producing  the  tangential  zone. 

The  sr»ces  between  these  radial  bundles 
are  occupied  by  a  delicate  interiacement,  the 
inteVradial  felt-work,  which  is  composed 
n  large  part  of  the  lateral  and  collateral 
proSes  of  the  cells.  Within  the  third 
fa^the  horizontally  coursing  collatera  s 
and  processes  of  the  large  pyramidal  cells 
form  a  complex  of  unusual  intricacy,  which 

condensation   gives  rise  to  the  outer  stnpe  fibre-bundles,    the  intercel- 

of  Baillarger.  Beyond  the  .«"'^:/"''*  "^^  f  "dSe  interlacement  of  processes 
lular  ground-work  IS  occupied  bv  J  ^f^^J^™^,;  ..^ ;  whilst  immediately 
and  collaterals,  the  .upraradial  ,.«"-^°'^;„™,  J„V,fe  del  cate  terminal  fibrilUe 
beneath  the  narrow  ^^^P"'  ^iT'^Sr  the  sure"  and  constitute  the  tangential 
course  horizontally  and  P»"",^' ^' this  laver  are  the  terminal  branches  of  the 
fibre-layer.  The  components  "  J^^^  >'j>if  ^  ad  the  axones  of  the  cells  of 
^^S^^^T^:^  ^^trSrocesses  of  the  fusiform  element, 
of  the  stratum  zonale. 


Katlial  fil'ri" 


Section  o(  cerebral  cortex  stained  to  »how  fibi«». 


ii8o 


HUMAN  ANATOMY. 


Choroid  plexus 


The  evident  parpose  of  the  horizontally  directed  processes  and  collaterals  being  to  bring 
into  relation  different  cortical  cells,  such  association  tracts  become  evident  only  after  the  neces- 
sity for  the  exercise  of  the  corresponding  psychic  functions  has  arisen.  Hence  in  the  cortex  of 
young  children  the  strata  of  horizontal  fibres  are  very  feebly  developed.  With  the  progressive 
advance  of  intellectual  capacity,  the  association  paths  become  correspondingly  more  marked, 
according  to  the  suggestive  observations  of  Kaes,  the  increase  continuing  beyond  even  middle 
life.  Whether  this  augmentation  is  due  to  actual  increase  in  the  number  of  a.ssociation  fibres, 
or,  as  suggested  by  Edinger,  is  dependent  upon  the  further  growth  and  myelination  of  collaterals 
already  present  in  an  immature  condition,  is  uncertain. 

Local  Variations  in  the  Cerebral  Cortex. — It  has  been  pointed  out,  in 
prefacing  the  foregoing  description  of  the  structore  of  the  cerebral  corte.x,  that, 
whilst  in  the  main  certain  features  are  common  to  the  cortex  wherever  well  devel- 
ojjed,  more  or  less  evident  variations  occur  in  different  'ocalities.  Such  variations 
are,  for  the  most  part,  slight  and  depend  upon  the  size  and  number  of  the  nerve-cells 
and  the  richness  and  direction  of  the  nerve-fibres — changes  which  produce  alterations 
in  the  relative  proportions  of  the  strata.  The  width  of  the  stratum  zonale  is  almost 
constant  and  subject  to  little  modification,  being  usually  well  defined  from  the  layer 
of  small  pyramidal  cells.  The  layer  of  the  large  pyramidal  cells,  on  the  contrary, 
exhibits  considerable  variation,  either  in  increased  thickness,  as  in  the  precentral 
c-,„   ,„,o  gyrtJS,   or  in  diminished 

breadth,  as  m  the  occipital 
lobe.  The  layer  of  poly- 
morphic cells  is  fairly 
uniform,  but  within  the 
precentral  convolutions 
IS  reduced  almost  to 
disappearance,  although 
Gynndenutua  the  pyramidal  cells  of 
the  superimposed  (third) 
layer  are  here  of  unusual 
size.  Such  variations  in 
the  histological  features 
of  the  cortex  are  prob- 
ably correlated  with  dif- 

FronUl  acctlon  acroH  left  hippocampua  and  g>-nia  dentatua.    X  »«.         ferences    in    the    function 

of  its  various  regions, 
although  the  exact  relations  between  such  differences  are  in  many  cases  still  obscure. 
Disregarding  the  cortical  regions  which  are  profoundly  modified  by  their  rudi- 
mentary character,  such  as  the  olfactory  lobe  (page  1 152),  apart  from  minor  varia- 
tions in  details,  the  cortex  of  the  greater  part  of  the  frontal,  panetal,  occipital,  temporal 
and  limbic  lobes  aiid  of  the  insula  closely  corresponds  in  its  structure.  That  of  the 
motor  (Rolandic)  region,  of  the  calcanne  (visual)  area  of  the  occipital  lobe,  and 
of  the  hippocampus,  dentate  gyrus  and  adjacent  part  of  the  hippocampal  gyrus, 
however,  presents  modifications  which  call  for  brief  description. 

The  RoUndic  cortex  of  the  precentral  gyrus,  particulariy  towards  the  upper  margin  of  the 
hemisphere,  of  the  paracentral  lobule  and  of  the  adjoining  part  of  the  postcentral  gyrus— the 
great  cortical  motor  area  of  the  hemisphere— is  distinguished  by  the  great  breadth  of  the  layer 
of  large  pyramidal  cells,  the  unusual  sire  of  the  last-named  elements  and  the  feeble  development 
of  the  layer  of  polymorphic  cells.  The  pyramidal  cells  collectively  tend  to  larger  size  as  the 
upjxT  end  of  the  precentral  convolution  is  approached  and,  in  addition,  cells  of  extraordinary 
dimensions  appear.  These  elements,  known  as  the  fiant  pyramidal  calli  of  Betz,  teach  their 
maximum  size  within  the  paracentral  lobule,  where  some  attain  a  breadth  of  .065  mm.  or  almost 
double  that  of  the  pyramidal  elements  in  other  regions.  The  giant  cells  are  further  distinguished 
by  their  robust  and  rounded  form,  their  distribution  in  small  groups  of  from  three  to  five  in  the 
deeper  layers  of  the  cortex,  and  the  exceptional  thickness  of  their  axones. 

The  occipital  cortex  in  the  vicinity  of  the  calcanne  fissure  (Fig.  1013)  is  distinguished  even 
macroscoplcally  by  the  clearness  of  the  outer  stripe  of  Baillarger,  here  called  the  sM/>e  of 
Cennari  or  of  Vkq  d'  Azyr.  The  stratum  zonale  is  somewhat  smaller  than  usual,  but  is 
exfepli.iiiatty  ricii  in  tangential  filires  and  fusiform  cells.  The  more  superficially  placed 
elements  of  the  .second    stratum  are  spindle  form  rather  than  pyramidal  and  give  off  two 


Atveus  covering 
hippocampus 


Fimbria 


Subiculum 

(Gyrus 

hippocampi) 


THE  TELENCEPHALON. 


Il8l 


represented.  ,    ,  .     ^^   d«nutu»  is  a  prolongation  of  that  of  the 

^    The  cortex  of  th.  WPP»«^P»»  "L*^  °Vf„Id^whrc^^^^^   occurs.    Reference  to  Fig.  99» 
gyrus  hippo-mpi  modified  by  the  pe^h^foWmg  ;|-h  here^^     ^^^^^  ^^^  ^^^^ 

wUl  recall  the  relaUons  o  these  gyn  as  seen  o"  "»  hippocampal  convolution  lies  the  corru- 
of  the  deep  groove  (the  h>PP<^^P^'^'^S^>^rth*thiSed  mesial  border  of  the  hippo- 
gated  free  surface  of  the  dentate  g>n«  ""•'^X  to^^^^  ^  ^he  hippocampal  convolution  is  seen 
rCd  £:g  r/^tirtK^tltt^  htp^rpus.  .hich^^hes  upward,  mesially  and 

Fig.   1019. 


Fimliria 


P.n  of  frontal  .«..on  acro«  1...  hlppocmpu.  .nd  gyru.  d«u,u..  .hawing  .r»n««««rt  o.  c..M.y.r..    /  .,. 

h^ll  somewhat  like  the^e  of  an  interrogation  mark.  On  approachm^  its  "Pt*' ™^"'  ' 
htcoX  of  he  hippocampal  convolution,  here  called  the  .uMcuum.  h^f  ""^^  "'^f "' ''y 
the  excessive  but  une^^l  thickening  of  the  tangential  fbre-layer  o  |ts  stratum  «male  and  th^ 
irre^laritv  of  its  layer  of  small  pvramidal  cells,  the  large  pyramidal  cells  at  «he  same  mie 
W^Z  the  sole  representatives  of  the  third  stratum.  The  layer  of  (anfreritia/  fibres-  s.  me- 
wh"uhinn  S  ."Lr^to  the  hip,>ocampus  which  it  follows  throughout  and  comes,  therefo  e 
r„toap^sition'with  the  corres,x,ndinK  tangential  zone  of  the  denote  KV.nm.  ^^J;\^2. 
avers  are  so  blended  that  a  differentiation  between  the  two  is  impracticable  IJeneatli  (  n  ine 
In^J^nflZen^hl  fibres  lies  a  second  stratum  of  medullated  fibres.  (2)  the  hmtxa  tnedullars 
Z7umviZaM\s\«My  an  intrarortical  ass.x-iation  tract  limited  to  the  h.,„HH;ampus. 
XreTcme  "ccecding  the  m«lullar>  lamina  i*  pe„e.rat«l  by  innumerable  long  dendnt.c,^.j- 
cmLs  of  the  large  pyramidal  cells  and  in  consequence  presents  a  radial  striatum,  the  l.mr 


1I»2 


HUMAN  ANATOMY. 


being  appropriately  termed  (3)  the  stratum  radiatum.  Following  this  comes  (4)  the  layer 
of  pyramidal  cells.  These  are  uniformly  of  large  size  and  closely  packed  within  a  clear 
ground-work  which  confers  a  light  appearance  upon  the  winding  lamella,  which  is  therefore 
sometimes  known  as  the  stratum  lucidum.     Beneath  the  pyramidal  cells  lies  a  layer  of  fibres, 

(5)  the  stratum  oriens,  which  pass  to  and  from  the  hippocampus  ;  among  these  fibres  are 
embedded  spindle  cells,  as  well  as  peculiar  association  cells  (Cajal)  possessing  richly  branched 
axones  which  ramify  among  the  pyramidal  cells  which  they  probably  serve  to  link  together. 
The  axones  of  the  pyramidal  cells  are  directed  chiefly  towards  the  centre  of  the  gyrus  where, 
next  the  descending  hom  of  tlie  lateral  ventricle,  they  form  a  coaspicuous  layer  of  fibres  called 

(6)  the  alveus.  It  is  this  sheet,  covered  by  (7 )  the  ventricular  ependyma,  in  connection  with  the 
stratum  oriens,  which  confers  the  white  color  to  the  hippocampus,  as  seen  within  the  ventricle. 
On  reaching  the  recurved  end  of  the  hippocampus,  the  layer  of  pyramidal  cells  of  the  latter 
is  not  continuous  with  that  of  the  dentate  gyrus,  but  ends  irregularly  and  is  enclosed  by  the 
arched  dentate  cell-layer. 

The  cortex  of  the  gyrus  denutu*  is  highly  modified  and  less  in  accord  with  the  typical 
structure  of  the  cortical  substance  than  that  of  the  hippocampus.  The  outer  surface  where 
buried  in  the  concavity  of  the  hippocampal  arch  lies  in  contact  with  the  similar  surface  of  the  hip- 
pocampus, hence  the  peripheral  layers  of  the  two  gyri  are  opposed.  Within  the  g)-rus  dentatus 
may  be  recognized  { i )  the  stratum  zonate,  relatively  narrow  and  meagre  in  fibres.  The  surface 
of  the  gyrus  is  paralleled  by  a  narrow  layer  of  small  and  densely  packed  cells,  (2)  the  stratum 
granulosum.  These  almost,  but  not  quite  completely,  surround  the  gyrus  and,  therefore,  leave 
an  interval,  the  hilum,  through  which  the  fibres  gain  and  leave  the  deeper  parts  of  the  convolu- 
tion. Within  the  area  so  circumscribed,  known  as  (3)  the  nucleus  of  the  gyrus,  are  found, 
irregularly  disposed  elements,  the  represenutives  of  the  layer  of  large  pyramidal  cells.  They 
are  for  the  most  part  small  in  size  and  atypical  in  form.  Their  axones,  together  with  the 
continuation  of  the  stratum  oriens,  pa.ss  through  the  hilum,  the  dentate  gyrus  thereby  forming 
connections  with  other  parts,  either  of  the  hippocampus  or  of  the  fimbria. 


The  White  Centre  of  the  Hemisphere. 

The  extensive  medullary  substance  enclosed  by  the  cerebral  cortex  appears, 
above  the  level  of  the  corpus  callosum,  as  a  grayish  white  tract  {centrum  semiovale)  of 

seemingly   homogeneous  structure. 
Fig.  loao.  its  uniform  character  being  broken 

at  most  by  minute  blood-vessels. 
At  lower  levels,  where  the  intercor- 
tical  area  is  encroached  upon  by 
the  large  collections  of  gray  sub- 
stance composing  the  corpus  stria- 
tum and  the  thalamus,  the  white 
matter  is  most  conspicuous  immedi- 
ately subjacent  to  the  cortex.  When 
examined  with  the  microscope  after 
suitable  preparation,  the  apparently 
homogeneous  subcortical  tissue  is 
resolved  into  an  intricate  maze  of 
medullated  nerve-fibrey.,  supported 
by  neuroglia,  which  run  in  various 
directions  and  are,  therefore,  cut  in 
different  planes.  When  analyzed 
as  to  their  relations  with  the  cortex, 
the  components  of  the  medullary  sub- 
stance of  the  hemisphere  fall  into 
three  general  groups:  ( i )  the  assoa- 
ation  fibres,  (2)  the  commissural 
fibres,  and  (3)  x\\c  projection  fibres. 
The  Association  Fibres. — The  association  fibres  link  together  different  por- 
tions of  the  same  hemisphere,  many  uniting  adjacent  areas  whilst  others  connect  parts 
widely  separated.  They  are  grouped,  therefore,  as  fong  xnA  short  association  bundles. 
With  the  exception  of  .-i  narrow  zone  in  the  immediate  vicinity  of  the  upper  end  of  the 
Rolandic  fissure,  the  cerebral  corte.x  at  birth  is  unprovided  with  association  fibres 
which  have  acquired  their  medullary  coat  and,  therefore,  are  capable  of  functioning. 


Frontal  iwrtion  of  brain  paMintt 

'  wh 


Ihrouxh  hemispherm  In 


front  of  rorinis  caiioRum ;  coi^  of  white  matter  is  e\'erywhere 
enclosed  by  rortical  Kray  matter 


THE  TELENCEPHALON. 


1183 


Fig.  I02I- 


Within  .he  .ariy  n,o„,hs  »«"  ««^J 'l-STiil'^.^"^""- ^i^elT^^^^ 

believe  that  myelination  of  addittona^ 
fibres  continues  so  long  as  intellectual 
effort  is  progressive,  the  demands  made 
bv  education  and  special  mental 
exercise  being  met  by  a  corresponding 
completion    of     addiUonal    association 

fibres.  .     .   _   fit,-.. 

The  short  association  fibres 

pass  in  great  numbers  from  one  convo- 
lution to  the  ne.xt,  bending  in  L -like 
strands  around  the  intervening  fissure. 
Some  of  these  loops  are  confined  to  the 

deeper  layers  of  the  gray  matter  and  ^ 

constitute   the   MracorHcal  assoaalton         D»g«m  .howmK  .s^Ki.t;™.  fibr«^t.™i  ."r|.;« 

fibres,  whilst  others  occupy  the  adjacent  „,  ^  h-i.ph«^";ov^j;'  JJ^^h'^Lp"-"? 

white  matter.     These  latter  are  known    la.«S^e;''.?J^P.';:jS^or  ,ongUudi«.i  .Isc.cu.us;  if, 

as  the  subcortical  association  fibres.     In    u„cin.w  fasciculus. 

addition  to  the  innumerable  fibres  which  j  ^^e  white  matter 

unite  the  .'adjoining  convolutions   (y.*^^^^  Somewhat  more  widely  separated, 

immediately  below  the  cortex,  ""^"y  .^^""^' ^^  constituting  the  intralobar  fibres 

those  limited  to  the  convolutions  o   the  ^melo^^^^^       subSance. 

and  lying  at  somewhat  deeper  levdsw.th.n^he^^^^^^     y       ^^^^^         j^^    f  .^e 

the  long  association  fibres  f  o""«=^  '".°\„'  ^  but  are  sometimes  of  con- 
cortex  of  the  hemisphere,  -"d.  therefore^^O^  m^l^^^^^^^  ^^^  ,„1  ,  ,e, 
siderable  extent.  Numerous  as  such  ';^^;''^*''[he  most  definite  of  these  are :  (.)  the 
r.S/f;.^Si^(^; th?S^^^^^^                           /.«..«W>W«.  and 

the  frontal  lobe,  arches  over  .'^e  f "»  °«^  ^^^^j^^S^ri  the  temporal  lobe. 

border  of  the  insula,  and  ends  m  the  '^^^T';,  ^t^  with  n "he  limbic  lobe.     It  begins  in 
The  cingulum  is  a  long  arched  tract  ly\"« J*^'"''" 'V^^^  ^^ound  the  anterior  end 

front  in  the  vicinity  of  the  anterior  Perfo-ted^^-^'^^^J^f  Xum,  j^„^^^  ,^ 

per   surface   of  this  structure,    lodged 
'''°-  ""•  S'[hin  the  callosal  xy-^^.  and   curving 

around  the  ^pleni-im,  descends  within 
the  hippocampal  gyrus  to  end  in  the 
fore-part  of  the  temporallobe  and  per- 
haps also  in  the  uncus.  The  cmgulum 
is  not  composed  of  fibres  which  extend 
its  entire  length,  but  is  made  up  ol  a 
number  of  shorter  tracts,  as  shown  by 
its  incomplete  degeneration  after  section 

of  the  fa-sciculus.  ...      1  f„. 

The  superior  longitudinal  tas- 
ciculus.    also    called    the   fasciculus 
araatus,  pas.ses  from  the  frontal  and 
parietal  opercula,   over  the  region   of 
ihe  insula,  to  the  inferior  parietal  con- 
volution, the  occipital  lobe  and  the  «X""VT'.:::!Sd  In'^ll'the  fl^on^SrpartJ; 
is  composed  of  a  number  of  sho     ^""d''^^«^';^^  Pr^^^^L  "'"^t  v  in  curves  into  the 
in  the  sagitUl  direction  towards  che  occipital  lobe,  and  parti> 

"'"^  IS^or  longitudinal  fasciculus  is  a  -"-"^^H-'^'S'li;:  optic 
from  the  tip  of  the  occipiul  lobe  and  the  cuneus,  along  tht  outer  side  01  , 


niarram  ahowitiK  aMocialiou  fihrM.  mesial  jurface;  fibres 
a??suppi^l  w  .how  IhrouKh  Iransparei.l  hemisphere. 


II84 


HUMAN  ANATOMY. 


Fig.  1023. 


radiation  and  the  poF  tenor  and  inferior  horns  of  the  lateral  ventricle  to  the  fore-part 
of  the  temporal  lobe.  It  is  probably  an  important  path  by  which  visual  impressions 
are  transmitted  to  other  parts  of  the  cortex  (Dejerine). 

Among  the  additional  association  tracts  which  have  been  described  may  be  mentioned  : 

The  faiciculus  oecqritalis  pcrpcndieulam,  which  extends  from  the  upper  part  of  the 
occipital  lobe  and  the  upper  part  (k  the  inferior  parietal  convolution  to  the  occipito-temporat 
convolution. 

The  faiciculus  ironto-acetpitalis,  which  courses  sagittally  and  lies  in  intimate  relation  with 
the  lateral  ventricle  and  the  caudate  nucleus,  and  to  the  mesial  side  of  the  corona  radiata. 

The  faiciculua  temporo-parietalis,  wh'ch  unites  the  temporal  convolutions  with  the  cortex 
of  the  parietal  region. 

Tlie  fascicului  fronto-parietalit,  which  runs  between  the  base  of  the  lenticular  nucleus  and 
the  claustrum  and  connects  the  frontal  and  parietal  cortex. 

The  fasciculus  lobi  Unfuslis,  which  is  a  bundle  passing  from  the  ventral  boundary  of  the 
calcarine  fissure  to  the  occipibd  cortex  of  the  lateral  surface  of  the  hemisphere. 

The  Commissural  Fibres.— Under  this  heading  are  included  the  fibres 
which  cross  the  mid-line  and  connect  the  cortex  of  one  hemisphere  with  that  of  the 
other,  the  regions  so  united  being  by  no  means  necessarily  identical  on  the  two  sides. 

Such  discrepancy  is  accounted  for,  at 
least  in  part,  by  the  frequent  introduction 
of  an  association  neurone  in  the  com- 
missural circuit,  the  impulse  carried  from 
one  hemisphere  to  the  other  being  thus 
transferred  to  another  region  of  the  cor- 
tex, from  which  there  arises  the  return 
commissural  fibre.  Preparatory  to  cross- 
ing '.le  median  plane,  the  fibres  are  col- 
lected i.,M  compact  masses  which  form 
three  definite  bridges  or  commissures  : 
( I )  the  corpus  callosum,  (  2  )  the  anterior 
commissure  and  (3)  the  hippocampal 
commissure. 

The  fibre-system  of  the  corpus 
callosum,  the  chief  commissure  of  the 
pallium,  is  so  extensive  that  it  includes 
connecting  strands  from  all  parts  of  the 
cortex  of  the  hemispheres  with  the  ex- 
ception of  the  front  and  under  part  of  the  temporal  lobes  and  the  two  rhinencephala, 
which,  on  account  of  their  isolated  position,  are  provided  with  special  bonds  of  union. 
The  callosal  fibres  stream  out  in  all  directions,  constituting  the  radiation  of  ike 
corpus  callosum  (radiatio  corporis  callosi),  of  which  an  anterior,  a  middle  and  a  pos- 
terior portion  are  recognized.  The  anterior  division,  the  pars  frontalis,  comprises 
the  fibres  which  cross  in  the  genu  and,  as  the  forceps  minor,  pass  to  the  frontal  pole. 
The  fibres  constituting  the  middle  portion,  the  pars  parietalis,  traverse  the  body 
of  the  corpus  callosum  and  continue  outward  to  the  hind-part  of  the  frontal  and  the 
parietal  and  temporal  lobes.  The  posterior  portion  includes  the  fibres  which  form 
the  splenium  and  the  adjoining  segment  of  the  body  of  the  corpus  callosum. 
These  course  outward,  downward  and  backward  and  as  the  pars  temporalis  and  the 
pars  occipitalis  reach  respectivelv  the  hind-part  of  the  temporal  and  the  occipital 
lobes.  The  fibres  destined  fo'  e  latter  region  lie  within  the  splenium,  from 
which,  as  a  condensed  bundle,  forceps  major,  they  arch  backward  alon^  the 

innirwall  of  the  posterior  horn  ol  the  lateral  ventricle  (page  1158)  into  the  occipital 
cortex. 

The  fibres  composiiiR  the  corpus  callosum  probably  all  terminate  in  arborizations  within  the 
rnrtcx  i>f  one  or  the  other  nf  the  hemispheres.  Their  source  in  the  opposite  hemisphere,  how- 
ever, is  by  no  means  always  the  same,  since  they  may  arise:  { i)  as  the  axones  of  the  pyramidal  or 
of  the  polymorphic  cells;  (1)  as  the  collaterals  of  association  fibres;  or  (3)  as  collaterals  of  projec- 
tion fibres,  in  the  last  two  cases  being,  therefore,  of  the  nature  of  association-fibres  rather  than  of 


Diagram  showlnj^  commissural  fibres  passing  tKtwe«n 
ccrebrarhemisplieres  by  way  of  corpus  callosum  ( CC)  an- 
terior commissure  (AC),  and  hippocampil  commissure 
(«C). 


THE  TELENCEPHALON. 


1185 


have  conferred  additional  Fig.  10J4. 

interest  upon  this  struc- 
ture as  a  possible  index 

as  to  intellectual  develop- 
ment    The  examination 

of    a     series     of    brains 

which  included  some  from 

men   of   acknowledged 

intellectual    superiority, 

demonstrated   a  corpus 

callosum  of  unusual  area 

as  a  constant  feature  in  the 

brains  of  the  more  highly 
endowed  individuals. 
And,     further,    that    the 
size  of  the  corpus  callo- 
sum  bore  a  direct  rela- 
tion to  the  character  of 
intellectual  superiority 
which     the     individual 
was   known   to    possess, 
the    largest    commissure 
being  found  in  the  brain 
of    a    man    whose    intel- 
lectual greatness  implied 
the  exercise    of    associa- 
tion paths  to  an  unusual 
degree.     The  later  con- 
clusions of  Bean,  however, 


Median  km] 


Lateral  long.. 
■tiu 


Choroid 


"ISTSS*^ 


■Tapetum 


Occipit*>- 
thalaniic 
radiation 


-Fuc.  long,  inferior 


Kron«,.e.>«.^.^.^J.^^i.^-«^SS^tt^^^^^^^^^  ""'  ^ 


•  cut  obliquely. 


S;s^°'cSrsS;,MSlt  page  „97)  the  constancy  of  the  relations  above  suggested. 

The  anterior  commissure  consists  of  a  compact  cord-like  strand  slightly 
comprie^  from  beCore .  backward  -^ jherebre  oval  m  section  (F'gjg^ 
which  connects  the  anterior  ends  f'''^^  »3^f, '^^^^c^  Immediately  in  front 
bulbs.  As  it  crosses  the  mid-line,  the  «^«"»7'*?"/^ 'l.P'**'^  the  interval  between 
of  the  downward  arching  anterior  P'»la«  «]  *^  thTniriow  anterior  wall  of  the 
which  it  appears  as  a  white  t-"--;^;; ^^rf^^,  t%ov«ed  S  the  ventricular 
third  ventricle  ^Fig.  979).       ?'^ff„*^7ntimate  relation  with   the   lamina  cinerea 

broaden    as    they   sweep    oacKwaru    mtw  J^  i^bes    the  anterior  commis- 

convolution;  (3)  lhos.wh.ch  '«'™' ''°™  '|«iSS  tht  it3ion|,  .h.  rod 
SVetS^rr.tn=™^eK,."rl^1n'^^^^^^^^^^ 

mg  almost  honzonUUy  outwara  uent»ui  i         .     .        j       j  continues  its  course 

;^rslcS£iirnli'»r="i.v;-St,r;3  :^ion.  .,.^^^^, 

75 


ii86 


HUMAN  ANATOMY. 


ili 


cut  oval  bundle  until,  farther  backward,  it  bends  abruptly  downward  to  disappear 
in  the  white  matter  of  the  temporal  lobe,  to  the  outer  side  oi  the  inferior  horn  of 
the  lateral  ventricle,  preparatory  to  ending  in  the  cortex. 

The  fundamental  and  archaic  character  of  the  rhinencephalon,  this  division  of  the  hemi- 
sphere appearing  in  animals  in  which  the  pallium  is  only  feebly  developed,  early  led  to  the 
establishment  of  a  special  connection  between  the  olfactory  lobes  of  tlie  two  sides.  Wtien  to 
this  necessity  was  added  that  of  linking  together  the  fore-parts  of  the  temporal  lobes,  which  are 
to  a  considerable  degree  isolated,  the  establishment  of  a  commissure  supplementary  to  the 
corpus  callosum  was  effected. 

Fig.  imj. 


Corpus  calkMuni' 

Latent  TMitricIe 
Septum  luddum 

Anterior  end  of 

fornix,  cut 

Foimmen  o(  Monro 

Anterior  pillars  of 

fornix 


Caudate  nuclcua 

riate  or  terminal 
vein 

Internal  capanle 

.Ttialamus,  anterior 
nucleus 

Lenticular  nucleus, 
putaman 

Clanatrum 
Globus  palUdua 


Anterior  commissure  Olfactory  strands 

Frontal  section  of  brain  paaaing  thtouich  anterior  commissure. 

The  hippocampal  commissure  connects  the  two  hippocampi  by  means  of 
fibres  which  cross  in  the  psalterium  (page  1 158),  in  addition,  some  fibres  thus  under- 
go! ;  decussation  join  the  longitudinal  stranc^  of  the  fornix  and  proceed  towards  the 
thalamus. 

The  Projection  Fibres.  —  These  fibres  connect  the  cortex  of  the  cerebral 
hemisphere  with  the  lower  lying  parts  of  the  brain  —  the  thalamus,  the  corpus 
striatum,  the  tegmental  region,  the  pons  and  the  medulla  —  and  the  spinal  cord. 
Proceeding,  as  they  do,  from  all  parts  of  the  extended  cortical  area  towards  nuclei 
grouped  within  the  comjjass  of  a  relatively  small  space,  the  fibres,  for  the  most  part, 
at  first  curve  toward  their  objective  points  and  collectively  form  the  extensive  con- 
verging tract  known  as  the  corona  radiata.  The  greater  number  of  the  components 
of  the  latter  pursue  a  direct  path  to  the  lower  levels  and  take  part,  therefore,  in  the 
formation  of  the  compact  internal  ca{}sule.  The  projection  fibres  are  by  no  means 
uniformly  numerous  in  all  parts  of  the  cortex,  relatively  few  issuing  from  the  frontal, 
parietal  and  latero-inferior  part  of  the  temporal  regions — areas  which,  according  to 
Flechsig,  are  particularly  significant  as  association  centres.  Furthermore,  the  olfac- 
tory cortex  does  not  contribute  to  the  corona  radiata,  its  own  special  projection  fibres 
being  represented  by  the  cortico-mammillary  tract  within  the  fornix  (jjageiisS). 
The  projection  fibres  are  not  exclusively  corticifugal  tracts,  since  the  connections  of 
the  thalamus  are  of  a  double  nature,  numerous  corticipetal  paths  passing  from  this 
great  sensory  nucleus  to  the  cortex  of  the  hemisphere.     The  projection  fibres  may 


THE  TELENCEPHALON. 


1 187 


,.co„ve„.e„Uv  considered  -derr  g-P«.*-^Slef ''^^ ''"''"  '"^"'''" 
Si  to  the  position  of  the  nude,  with  wh  ch  they  "^  =^1^'"=^  jhe  cartico-thalamic 
"^  The  .Wt  projection  tract.  '««^J^S'=J^"^*rtel  of  the  hemisphere  to  the 
trads,  the  fibres  of  which  pass  from  all  parts  of  the  corwx^  ^v^  ^^  ^^^^ 

SSus.  The  components  of  these  tracts  are  ^^^^  ^^  g,^  parsing  from 
ol  the  frontal  »obe  ^  the  antenor  extremity  d^^^^^^  .^j^^  ^^^,  ,„be  to  the 

Associated  with  the  foregomg  p,j,    „^ 

corticihigal  paths  are  the  tkalamcH 
eartical  tracts  which,  couremg  in  the 
opposite  direction   (cortiapetelly), 
proceed   by  way  of  the  stalks  or 
beduncles   of   the  thalamus   (page 
n22)  to  all  parts  of  the  cortiral 
sheet  of  gray  matter  investtng  the 
cerebral  hemisphere.    The  thalamo- 
cortical  tracu  (Fig.  966).  are  the 
continuations  (by  means  of  the  thala- 
mic neurones)  of  the  afferent  paths 
conveying  impulses  from  the  spmal 
cord  and  the  brain-stem  and  from 
the  cerebellum  to  the  great  sersory 
intemode,    the    thalamus       Th«e 
include,  on  the  one  hand,  chiefly 
the   median   Jillet,^}>^    sptno-tha. 
iamu  tract  and,  probably,  a  part  of 
Gaweri  tract,  by  which  paths  the 
sensory  impulses  collected  by  the 
spinal  and  the  cranial   nerves  are 
transmitted  to  the  thalamus ;  and, 
on  the  other  hand,  the  cereM^ 
rubrothalamic  tracts,  by  which  the 
cerebellum  b  linked  with  the  th^- 
amus  by  way  of  the  superior  cerebel- 
lar peduncle.     The  visual  impulses 
earned  by  the  fibres  of  the  optic 
tract  to  the  pulvinar  are,  m  a  similar 
manner,  conveyed  to  the  ocapit^ 
cortex,  along  with  those  interrupted 
in  the  lateral    geniculate  and   the 
superior  quadrigeminal  body,  by  the 
oMic  radiation  of  which  the  occipital 
stalk  of  the  thalmus  is  a  part. 

2.  The    cortico-gentculate    and 

i_-~._V«/>/  traHt  an 


FrontO'pontine 

Tempore^, 
ocdpito-ponUac 


C«i«bello- !»"«*" 
.R»br<«l>>n«l 


Latent 
pyrunidu 


-DJrtct  pjmmktol 


_ .  ^--.^i.^'^^^i^^^'^"^-^-"^  '" 

'"""2"  The    cortico-gentculate    and        mnstituents  of  the  optic  radiation. 

V'^^^A  ^^-'P-^-  fom^tTuadriernal^nd  geniculate  bodies  and 

which',  in  proceeding  outward   pa^Jrom^^^^^^^  ,„;,  „, 

geniculate    body    through    the    'l^'XJ^V'^"^^^^  to   the  auditory  centre 

fhe  internal  corpuscle  and  '^".f  ^^^^Jt^^Jrf  inSes  the  middle  portion  of 
t^t;'rior"r^rir'lonvI£oran<l,  probably,  the  adjoining  part  of  the 
temporal  operculum. 


Ii88 


HUMAN  ANATOMY. 


4.  The  corHco-rubral  tract  constitutes  a  supplemental  motor  path.  The  exact 
location  of  its  cortical  origin  is  uncertain,  but  may  be  assumed,  at  least  provisionally, 
to  lie  within  the  parietal  lobe. 

The  loig  projection  tracts  embrace  two  important  eroups,  the  cortico-pontine 
and  the  motor  tracts,  the  former  contributing  the  first  link  in  the  chain  connecting 
the  cerebral  and  the  cerebellar  cortex,  and  the  latter  constituting  the  bond  between 
the  cortical  gray  matter  of  the  hemisphere  and  the  motor  nuclei  of  the  cranial  and 
of  the  spinal  nerves.  The  long  projection  fibres  are  important  constituents  of  the 
internal  caosule  which  they  all  traverse. 

1.  The  cortico-pontine  tracts  include  two  chief  subgroups,  the  fronto- 
pontine and  the  temporo-occipito-pontine,  which  below  end  around  the  cells  of  the 
pontine  nucleus,  whence  the  impulses  are  transmitted  to  the  cerebellum  by  the 
ponto-cerebellar  strands  of  the  same  and  opposite  sides. 

a.  The  fronto-pontine  tract  arises  from  the  cortex  of  the  frontal  lobe  and, 
passing  by  way  of  the  corona  radiata,  enters  the  hind-part  of  the  anterior  limb 
of  the  internal  capsule.  Descending  into  the  crusta  of  the  cerebral  peduncle,  in 
which  it  occupies  the  mesial  fifth,  the  tract  ends  within  the  ventral  part  of  the 
pons  around  the  nerve-cells  constituting  the  pontine  nucleus. 

b.  The  temporo-occipito-pontine  tract  proceeds  from  the  cortex  of  the  temporal 
and  the  occipital  lobes  through  the  hindermost  segment  of  the  posterior  limb  of 
the  internal  capsule.  On  reaching  the  cerebral  peduncle,  its  position  corre- 
sponds approximately  with  the  lateral  fifth  of  the  crusta.  It  ends  within  the  pons 
around  the  cells  of  the  pontine  nucleus  in  the  same  manner  as  does  the  last- 
described  tract. 

2.  The  motor  tracts  are  composed  of  fibres  which  connect  the  cells  wtthm  the 
cortical  areas  of  the  Rolandic  region  with  the  nuclei  from  which  arise  the  root-fibres 
of  the  motor  nerves.  Since  the  latter  take  origin  within  the  brain-stem  as  well  as 
within  the  spinal  cord,  the  motor  tracts  comprise  two  groups — the  cortico-bulbar  and 
the  cortico-spitial  tracts.  The  exact  locations  of  the  cortical  areas  controlling  the  vari- 
ous cell-groups  giving  origin  to  motor  nerves  are  still  Sax  from  being  accurately 
known.  Clinical  and  experimental  studies  have  indicated  with  considerable  certainty, 
however,  that  the  cerebral  cortex  in  the  immediate  vicinity  of  the  Rolandic  fissure, 
chiefly  in  the  precentral  convolution  and  paracentral  lobule,  and  probably  also  in  the 
adjacent  parts  of  the  superior  and  middle  frontal  gyri,  is  the  most  important  seat  of 
such  motor  centres.  In  a  general  way,  the  areas  controlling  the  muscles  of  the  lower 
limb  lie  highest  and  are  situated  in  advance  of  and  around  the  upper  part  of  the 
Rolandic  fissure.  The  conspicuous  backward  projection  of  the  precentral  gyrus 
(Fig.  984)  corresponds  to  the  arm-area,  whilst  the  lower  part  of  the  same 
convolution  contains  the  centres  for  the  neck  and  face.     (Conssult  also  page  121 2. ) 

a.  The  cortico-bulbar  tract  includes  the  fibres  ending  around  the  nuclei  from 
which  proceed  the  motor  fibres  of  the  cranial  nerves.  The  fibres,  therefore,  arise 
from  the  pyramidal  cells  of  the  cortex  of  the  lower  part  of  the  precentral  gyrus  and, 
foi  the  eye  muscles,  of  the  posterior  portion  of  the  inferior  frontal  convolution  (Mills). 
Proceeding  by  way  of  the  corona  radiata,  the  cortico-bulbar  path  occupies  the 
segment  of  the  internal  capsule  which  forms  the  genu,  being  bounded  in  front  by  the 
fibres  of  the  fronto-pontine  tract  and  behind  by  those  of  the  cortico-spinal  tract  The 
exact  location  of  the  strands  destined  for  the  several  nerves  is  known  only  for  the  facial 
and  the  hypoglossal,  those  for  the  last-named  nerve  occupying  the  most  posterior 
part  of  the  genu,  whilst  those  for  the  facial  lie  just  in  advance  of  the  fibres  for  the 
twelfth.  Within  the  cerebral  peduncle  (Fig.  1012),  the  cortico-bulbar  strand 
occupies  the  lateral  part  of  the  mner  third  of  the  crusta,  the  fibres  destined  for  the 
third  and  fourth  nerves  soon  turning  dorsally  and  crossing  the  raphe  to  end,  for  the 
most  part,  in  relation  with  the  nuclei  of  the  opposite  side.  The  fibres  for  the  lower 
lying  nuclei  continue  through  the  crusta  and  enter  the  ventral  part  of  the  pons  ;  they 
then  assume  a  medium  position  and  at  appropriate  levels  bend  dorsally  and  cross  the 
mid-line  to  end  in  relation  with  the  cells  of  their  objtxtive  motor  nuclei,  some  few 
fibres  probably  ending  in  the  nuclei  of  the  same  side. 

b.  The  cortico-spinal  or  the  pyramidal  tracts  include  the  longest  of  all  the 
projection  fibres,  which,  as  in  the  case  of  those  passing  to  the  nuclei  of  the  sacral 


THE  TELENCEPHALON. 


1189 


nerves,  may  traverse  the  entire  t^cWn^  ^'J^^nd'S  i'nextSow  tt  ^1 
of  the  bram-stem    the  greater  Dart  01  tn    py  ^^^  .^^  to  their  appropriate 


„  <■.„«.    th..  areater  Dart  o   the  pyramidal  stranas  xaKc  pan.  •..  v..,.  ...^>". 


i..rp  thi'v  end  in  relation  with  the  raaicuiar  ecus  ui  >"v  »■"- -•        "^  " 

end  around  the  root-cells  oJ  the  opposite  side. 

Devklopment  or  the  Parts  Derived  from  the  Fore-Brain. 
U  has  been  pointed  out  in  the  general  tttilttoT^lrSdi'c:^  S^^^h; 

r*:rsrs?;^^sr::^^ra.:rhr^i:H^^  -ch 

oJ  these  secondary- vesicles  ^^^    ^^^ 


IMcncephalon 
Tlmlainencephaloo, 

Hypothalam 
Future  Uteral 
ventricle 

Pallium 

Foaterior  limit 
of  telenceph- 
alon 

Rhinenceph- 

alon 

Corpu*  atriatu 

Optic . 

Infundibular 

Tuber  cinereui- 

Geniculate  ganglion  of  facuil 

Vestibular  gan((l>on 

Membntnoua  labyrinth 


RecoiistrucUon  of  brain  of  human  embryo  of  fc" 
mm.,^nner  .Sri.ce  ol  '"e  (orc-braln  and  m.d-b™. 
(Exterior  of  same  brami*  shown  in  Fi».  ii«i  )     >-  ' 


Tegmentum 

Mid-brain 

III  nerve 

[ammillary 
body 


gives  rise  on  each  side  to 

two   general    regions,  an 

tipper  and  a  lower,  which 

in  the  telencephalon  are 

the  hemispharium  and  the 

pars  opticx    hypothai'imi 

and  in  the  diencephalon 

are  respectively  the  (halo- 

mencephaloH  and  the  pars 

mamillaris    Mypo/kalami. 

These  two  parts  of  the 

hypothalamic  region  to- 
gether constitute  the  Mypo- 
IMalatHHS,  which  includes 
the  portion  of  the  lateral 
wall  of  the  fore-brain  lying 
below  the  level  of  the  fo- 
ramen of  Monro  and  cor- 
responds to  the  ventral  or 
basal  lamina  of  the  neural- 
tube  (Fig.  914)-  Thistract 
gives  rise  to  the  structures 
situated  along  the  floor  of 
the  third  ventricle  — the 
mammillary    bodies,    the 

S^IbtZ3th?;oirior.ol.of«^^^ 

The  anterior  wall  and  the  roof  of  the  «"r«r^™"  "'^ "  '^rt  ^^^^^^         posterior  ^mmLssure 

of  the  roof,  which,  with  the  excepUon  "' '^\^mdm<^^  p«rt  wl«re  tn    p^      ^^ 

is  formed,   'l*-,  ^  tira.tlnu't:d  e^S^^       Thkh  ^otlstitmes  the  morphological  roof 

'r;e^;^"i?nt^'  ^E^rL\K?h"H."r^  ;u^irta;^t-.-rs 

=  f-rSSrc^etfaka  f  sf^u^  l^Sdum.  is  to  a  large  extent  concerned 
in  the  production  of  the  great  commissure,  the  co'?"*,^?'"?;"'^;.  irreaternortion  of  the  end-brain 

The  HemispH^u,n,  one  -J-^  side^^i;:^^^^  Very  eariy  it 

and  represents  an  enomiousexpansionofthedo^^^^ 

exhibiteadifferentiauonrnto^^^^ 

most^n^^"u^"u^;^e''f iThfw^^^  of  ^His  ^pif^-X^xPandin^^^^^^^^^^^^^ 

^sr  atirs  ^u^  thrwX  trp;::uur         -soudat^i  by  the 


Salf  weeks  (ii>.a 
mesial  section. 
•>m  His  model. 


II90 


HUMAN  ANATOMY. 


I  ; 


^ 


intergrowth  of  the  iibre-tfacto  (later  the  white  matter),  which  ariiie  partly  from  the  young 
nerve-ceilH  within  itH  walb  and  partly  from  neuroblasts  situated  in  other  segments.  An  ad- 
ditional factor  of  moment  in  the  production  of  the  balky  cerebral  hemisphere  is  the  special 
mass  of  gray  matter,  the  corpus  striatum,  which,  with  the  increasing  fibre-tracts,  leads  to 
the  reduction  and  conversion  of  the  cavity  of  the  pallium  to  the  irregular  lateral  ventricle.  Its 
once  wide  communication  (Fig.  1030)  with  the  cavity  of  the  fore-brain  is  retained  as  the 
proportionately  narrow  foramen  of  Monro.  The  pallium  expands  in  all  directions  save 
directly  downward,  where  increase  concerns  chiefly  the  rhincncephalon,  but  the  lines  of  its 
growth  are  particularly  backward  and  downward,  in  coasequence  of  uhich,  in  addition  to 
the  production  of  a  temporal  and  the  distinctive  occipital  lobe,  the  other  brain-segments 
become  gradually  covered  over  and  deposed  from  their  original  superior  position  toward  the 
basal  surface  of  the  brain.  This  process  is  already  marked  during  the  third  month  (Fig.  1031), 
by  the  end  of  which  period  the  pallium  covers  the  diencephalon.  By  the  beginning  of  the  fifth 
month  the  mid-brain  is  completely  overlaid,  and  by  the  eighth  month  the  entire  upper  surface 
of  the  cerebellum  is  covere<l. 

Development  of  the  Sulci  and  Oyn.— The  modelling  of  the  surface  of  the  cerebral  hemi- 
sphere begins  towards  the  end  of  the  fifth  month  of  fcetal  life,  by  which  time  the  occipital  k>be 
is  well  formed  and  the  brain-case  is  separated  from  the  cerebral  surface  by  an  intervening  layer 


Fig.  1038. 


Pattium 


Lateral  vtnlricl* 


Roof-platr  of  in 
ventricle,  with- 
choroid  plexus 


Corpus  iitni>tuill 


Thalamui 


Longitudinal 
fiuure 

Choroid  plexus 


Choroidal  llimre* 


Frontal  section  ol  brain  at  rabbit  embryo  showing  invasination  of  mesial  wall  of  hemisphere  alonit  hippocampal  and 
choroidal  fissure*  -  thin  roof-plate  of  third  ventricle  stretches  between  thalami.     >,  13. 

of  yielding  arachnoid  tissue,  which  offers  little  opposi*'  .1  to  the  production  of  the  convolutions 
which  now  follows.  Preceding  this  period,  the  outer  surface  of  the  young  hemisphere  is  quite 
smooth,  with  the  exception  of  the  crescentic  Sylvian  fossa  (Fig.  98 j)  which  marks  the  position 
of  the  later  insula.  This  depression  has  been  describerl  (page  1 137)  in  connection  with  the  pro- 
daction  of  the  Sylvian  fissure.  The  uncertain  crea.ses,  the  so-called  "  transitory  fissures,"  some- 
times seen  on  brains  of  a  much  earlier  period  are  without  morphological  significance  and  are 
now  usually  regarded  as  artefacts  (Ziehen,  Hochstetter) . 

Loi.„  antedating  the  appearance  of  the  fissures  on  the  outer  a.spect  of  the  pallium,  the 
mesial  surface  of  the  latter  is  early  marked  by  two  gro<ives,  the  choroidal  and  the  hippocampal 
fissures.  The  first  of  these  (Fig.  1031 )  appears  by  the  end  of  the  fifth  week  as  an  invagination 
of  the  mesial  wall  of  the  pallium  just  above  the  position  of  the  foramen  of  Monro.  At  firet 
small,  the  groove  is  carried  backward  and  downward  by  the  expansion  of  the  iiallium  until, 
finally,  it  is  traceable  along  the  inner  wall  of  the  inferior  horn  of  ihe  lateral  ventricle  as  far  as 
its  lower  limit.  Entering  by  means  of  this  invagination,  the  mesoblastic  tissue  forces  before 
it  th«?  attenu-ited  cerebral  wall  and  expands  into  a  voluminous  mass,  the  choroid  body,  which 
on  becoming  supplied  with  blood-vessels,  forms  a  vascular  complex  that  for  a  time  almost 
completely  fills  the  early  lateral  ventricle.  With  the  subsequent  growth  of  the  pallium 
backward  and  downward,  the  choroidal  fissure  and  the  contained  vascular  fringe  are  carried 
from  the  foramen  of  Monro  over  and  around  the  thalamus  into  the  inferior  horn  of  the  lateral 


THE  TELENCEPHALON. 


ii9t 

.k.  .{..Aiiit*  rhotnid  olcxut.    The  •ecood  furrow,  the 
stride,  where  it.  .e««in.  «es«en  "  V«^«5™"  S^XSdi  «  »urf»«<^  ^ 

^^^^i^fissur*,  appean.  shortly  -^"V^  "^^^^.^^^^Secting  the  entire  thiclcnes,  o( 
gSvSTlli  primary  porioon  a  '?*^^'"J2!^S^  o<  the  wall  oi  the 

Se  cerebral  waU  (Fig.  «<»?)•  *'''f*.!^'f,^;,'S^IlS„^^  on  the  mesial 

fe  S.^:StSan^^'ll^rea^^Srhy  the  <Wnu.e  gyr..  -„-  m  the 

to  appear  on  the  outer  surface  <rf  '^^^«^^"^„  ^  dSa^ed  untiU  month  later  (Cunning- 
J^dh^  fihh  n»nth.  »1»^K'' J^^K^J^  it^Sequently  is.  the  lateral  one  is  the 
ham).    When  laid  down  as  two  separate  •""?*?•  """^^^  into  a  continuous 

to«er  and  usually  the  deeper.  Subsequently  the  ^"^^^"^t^^  the  Rolandic  fissure  be 
K.  Xough  Cery  rarely  the  primary  condition  "^  P^'  ,^^,  ^S  o«  -he  heml- 
^temlpted  by  a  superfda^  ^^^^^J^S^^'j^  The  first  oJ  these  is  often 
sphere,  also  appear  the  calcan^*  !^*i^S^wWch  Ae  front  one  is  complete  and,  as  the 
h^  Z^'J^^^'^^^'^^^^^^^^^  Wnown  as  the  calcar  avt.    The 


Soperior  calUcnt< 


Fig.   1039. 

(•inM\  body     H«t 


Median  gttiiculat*  body 


IpiUI  lobe 

tricUllobc 


PalUnm 


.  ronUI  lotie 
■i'cDiporal  lobe 


SylvUn  fo 


Rhinencephalon 


Rhombic  lip 


VIII  nerw 


_  Spinal  cord 

K.con.n.c.io„  o,  b«in  o,  b-n-n  e»b^^.  fi«w«W.J^.  »".•);  .x..n»I  U««.  MpeC. 


Xtt. 


other  p..rts  subsequently  unite  to  form  the  p.«t^o^  l|,'C^1hL''^rS?  wUrwhich^'ho;^^^^^ 
formed  the  p^irieto^cipital  fissure  B  "^"^'Mistinrt  ^o^^^^'^^^  collateral  fiuure  appear, 
it  soon  becomes  confluent  To^-^^'^the  «"d  of  ^"^X  ^pMor  precenlral  sulcus  vc^y 
on  the  imerior  surface  of  th*  hemisphere.  The  ^Vf^J^f^"  J^  ^^  j^e  early  weeks  of 
usually  be  distinguished^  the  lower  shghUy  m  aj^nce  of  ^^"P^^.  *^  ^^^,^  ^"'^^J^ 
the  sixth  mouth,  and  about  the  same  Ume  ^l^^'T.'^'Z^enXT^i  and  occipital  limbs  of  the 
middle  of  the  sixth  month  marks  the  «PP^^^„^f  °*^ '^K^^«'^  and  the  «/A>«^«ar^-f 
interparUial  sulcus  and  the  first  suggestion  °^ }^JT'fl{"^„  nrecentral  sulcus.  Towards 
;S  as  well  as  the  junction  of  the  Wenor  f  ronUlv^th  the^^^^  ^  ^^  ^^ 

the  close  of  the  same  month  are  added  the  f'A^'^ /'^V^'       „i_„  of  the  fissures  already 
"Zci^sulci.    Theseventhmonthwitne^theex.e,«.ona„ddeep^^^^^^  During  the 

Jor^Tand  the  union  into  ~"t™*  *"^"  ^r'^nTthe  b^^^^^^  "^  '""^  '"'^' 

succeeding  month,  the  s'-irface  <>   ^^e  hem  sphere  Mid  the  Dram  ^^  convolutions  can 

mate  relation,  from  which  it  fol  ows  that  the  round««^  ^^^Te  themselves  in  their  growth 

no  longer  unrestrictedly  expand,  l>ut  from  now  O"*  "™^t  ^^^j^tion  the  convolutions  become 

to  tSier  «irface  of  the  cranium      YnS^T^surfl^  ciSemisphere  conforms  with  the 

ES-Se^A-  ';;r'*^^^' ~i*^Kd:uils  of  the  convVions  aris«  from  the 


1 193 


HUMAN  ANATOMY. 


J- 


if 


development  of  secondary  gyri  and  sulci,  although  the  definite  brain-pattem  is  not  completed 
until  long  after  birth. 

Histogeneiii  of  the  Cerebral  Cortes. — The  changes  in  the  walls  of  the  brain-vesicles 
incident  to  the  development  of  the  nervous  elements  of  the  cerebral  cortex  correspond 
essentially  with  those  occurring  in  the  cord-segment  of  the  neural  tube  (page  1049).  The  wall 
of  the  pallium  early  differentiates  into  three  zones :  an  inner  layer,  at  first  crowded  with 
closely  packed  and  radially  disposed  proliferating  cells ;  an  intermediate  or  tnant/e  layer, 
composed  of  more  loosely  and  less  regularly  arranged  cells ;  and  a  narrow  marginal  layer,  in 
which  nuclei  are  absent  The  cells  of  the  intermediate  layer  very  soon  are  differentiated  into 
two  kinds,  which,  in  recognition  of  their  fate,  are  known  as  the  neuroblasts  and  the  spongio- 
blasts. Although  both  varieties  are  derived  from  the  indifferent  primary  elements  composing 
the  walls  of  the  brain-tube,  the  spongioblasts  are  concerned  in  producing  the  sustentacular 
tissue,  the  neuroglia,  whilst  the  neuroblasts  give  rise  to  the  neurones.  The  derivatives  of  the 
spongioblasts  become  elongated  into  nucleated  radial  fibres,  which  by  their  numerous  pro- 
cesses form  a  supporting  syncytium  that  at  the  inner  and  outer  borders  of  the  brain-wall 
is  condensed  into  the  internal  and  the  external  limiting  metnbrane  respectively.  The  neuro- 
blasts are  soon  distinguished  by  the  outgrowth  of  a  single  and  centrally  directed  process, 


KiG.  1030. 
Subthalamic  region  Pineal  body 


Tegmentum 


Foramen  of  Monro 
Choroid  plexus 


rallittm 

Lamina  terminalin' 
Rhint^ncephalou 


Mid-brain 


MammiUary  body 


Isthmus 


Cerebellum 


CorpuA  striatum' 
Optic  rece« 
Optic  chiasm.        y    .    .■ 
Pituitary  body      /  / 
Infundibular  recess    / 
Tuber  cinereum     ^ 
Pons 


Cervical  flexure 


Spinal  cord 
Mesi.il  surface  nf  precedmg  reconstruction.    Drawn  from  His  model. 

which  later  is  continued  as  the  axis-cylinder  of  a  nerve-fibre.  They  are  further  distinguished 
by  their  peculiar  affinity  for  stains,  which  deeply  tinge  the  pointed  ends  of  the  cells  from 
which  the  axones  are  prolonged.  A  second  process  later  grows  from  the  young  neurone  in 
the  opposite  direction,  that  is,  towards  the  exterior  of  the  brain,  and  becomes  the  peripherally 
directed  apical  dendrite.  The  latter  ^*-\\ra  slightly  and  gradually  invades  the  marginal  layer. 
After  the  appearance  of  the  apical  cesses,  the  conversion  of  the  neuroblasts  into  the 
characteristic  pyramidal  cortical  n-ll-,  ollows,  so  that  by  the  end  of  the  eighth  week  these 
distinctive  elements  are  recognized.  The  production  of  additional  pyramidal  cells  is  con- 
tinued by  the  migration  of  neuroblasts  from  the  nuclear  layer.  The  subsequent  formation 
of  the  subcortical  white  matter  follows  the  invasion  of  the  inner  part  of  the  intermediate  layer 
by  not  only  the  axones  of  the  pyramidal  cells  but  by  those  of  cells  lying  in  more  remote 
parts  of  the  brain,  ingrowth  of  fibres  takintr  place  particularly  from  the  thalamus.  The  young 
ner\'e-fibres  for  a  time  are  unprovide<l  with  medullary  coats,  the  period  at  which  myelination 
occurs  marking  the  completion  of  the  fibre  as  a  path  of  conduction.  The  time  at  which 
the  fibres  composing  the  various  tracts  within  the  brain  acquire  a  medullary  coat  varies  greatly. 
In  a  general  way,  according  to  Flechsig,  those  constituting  the  corticiiietal  sensory  paths  first 
myclinatp  ;  thrn  thp  pm}«Ttir>n-fihrp=  from  the  wnw-arcai;,  and  la«t  of  all  the  association  strands, 
which  link  together  the  sense-areas  and  the  association  fields. 


THE  TELENCEPHALON. 


U93 


o.  the^«phere  coru:^^v.'^J^'''T',u^J^S^TXi7dMsion.  The  oliactory  lobe 
anterior  divSion.  the  o//ac^  ''^^Ju'^il  IrT  ^^i  by  an  elongated  oval  area,  "nperfecUy 
fa  WBtested  in  embryos  oi  the  "f*  *«"'^,.  .^"^L'TJ  rhinal  furrow,  and  partially  subdivided 
Ita^from  the  under  suriaceof  the  pallium  by  he  rhmal  «        .        ^^^^.^^  ^.^.^j^„ 

STfaint  transverse  groove  into  a  '"^"J^  f^^ri^nd  Sie  parolfactory  area;  from  the 
^^veloped  the  olfactory  bulb,  tract,  tuterelej^d^^"^^^^  always  relatively 

D^^the  anterior  perforated  ^If "^ »"V«f  coSVa  ravity  prolonged  from  the  latera 
SSntkry  in  man.  the  olfactory  lobe  ^  6^'^^"^^^  ^^,  ^Zh  larger  olfactory  Jobe  of 
ventricle,  and  in  this  respect  "-esembles  the  correspon      b  however,  this  cavit>%  the 

*e  osmetic  animals  which  remains  h°']°*^^/^2ely  disappears,  its  former  position  being 
oi/actory  ventricle,  is  only  t™"^''="»  "^il''^^^^^  ^P^'^^^^,  us 

i„4ica^  in  the  adult  '''^e^.^.  ^X  *^  SdL^^^^^  *e  hippocampus,  the  gyrus  denums 

The  posterior  or  coriual  diitsum  '"^^'^°^\.  „erve-strands.  The  original  position  of  the 
with  the  ^ociated  supracallosa  gray  """"f^!,^!  "5^„esponds  with  the  permanent  locaUoi. 
olfactory  cortical  area  in  the  early  hunr.anhem.sph«ecorr«^^^  ^^.^^  ^^^^^  ,^^^^  ^,,^ 
of  tSeSmilar  region  in  animals  in  «^>ch  the  ex^nsion  o,  ^  ^^^^  ^^  ^^^ 
?orm^tion  of  a  well-marked  ^occipito-tem^rd  '°^  ^ J^^^^  ^po!;*;^e  mesial  surface  of  the 
W^ampal  and  choroidal  fi«"«=%«l^fi"^,^"^^nXhe  hipp<Icamp.l  invagination  repre- 
palHum.  This  is  th^ prtfnaty  ^yn"^,'^^'"f"^t,^^\  area.  Connection  between  the  latter 
^L  the  eariiest  diR^entiation  rf  theolfartory^ural^^  established  by  the  advent  of  the 
and  the  region  of  the  mammiUary  body  »  sureeque     ,  column  of  the  fornix.     In 

Si  cmammillary    strand.   >-'«  .^rhiJ-^J^san*  th'lntate  gyrus  incidem 
consequence  of  the  ««iK™"°",°L*^''^P^m" sphere,  the  chief  parts  of  the  olfactory  cortex 
mation  of  the  occipit<^temporal  reP"'^  «  *e  hemi^Pn«^  ,^^^^^1  ^^ntricle.    Along  with 

"e  carried  downward  and  ^»!,d  .^o  ^^s  Ae  s^^™  connecting  it  with  the  mamm.llary 
the  displaced  cortical  area  necessarily  follows  tne  smm  ;„,    ^^^  ^nd  the  fimbria, 

^on.  hence  the  prolongation  t»^Al3cte  ^oughtte  major  part  of  the  olfactory 
tato  tiU  descending  hom  of  the  lateral  'en'Hf ,«•  ^J^  rerfon,  a  small  portion  retains  its 
Sirtefthus  comes,  to  cKxnipy  ^^^^^Xetl^^^^-^'  b«=°-f  *«  ^'"'^ 
superior  connection  and  ^^^  '  *^trch    ^th Ttt  %^uced  fibr^nds.   overiies  the   upper 

rarS  t--^^rgoS^-Xrstriatum.  the  fundamental  gan£n  of 

.een^d^brarirre^^pjrS^^^^^^^ 

lar  elevation  between  the  cavity  <>' *«  P^"'""' ^.ial  thickening  of  tiie  brain-wall,  is  seen  pro- 
pter (Fig.  1030),  tills  elevation,  produced  .^V  * '^\  "Ij^^nce  of  the  large  foramen  of  Monro. 
Sfr^omtfe'infero-lateral  ^'^^^^  ^'j^  ^eS  c^^^^^^^  *e  fl.x,r  of  the  Sylvian 

On  the  external  surface  o  the  paU.um  *^^^,!^^"'^t^"een  Se  corpus  striatum  and  this  area, 
fossa  (Fig.  98^).  «nd  it  is  t^««  do«  assoc  at^on  parts  of  the  hemisphere,  that  leads 

which  fails  to  keep  pace  in  its  P«*'^n  w  '^'l  nlmaiwnt  coven'ng  of  the  insula.  The  subsequent 
,0  its  envelopment  by  *«  opercula  and  tte  ^jman^^^^^  ^^^  ^^^^^  ^„d  the  lenticular 

partial  separation  of  the  corpus  smatummto  us  two^^^^^^  ^^^  daustrum,  is  effected 

Imcleus.  as  well  as  the  'eolation  of  a  J^^y'g'^^  which  later  become  the  internal  and 
by  the  subsequent  ingrowth  of  the  stranas  oi  nu.<^ 

external  capsule.  HivUion  of  tiie  fore-brain,  tiie  diencephalon.  very  early 

The  Dienceph.lon.-The  posterior  d  V  s,^^^^^^  .  j^^^^  j^  ^^  thalamen- 

(Fig.  loar)  exhibits  differentiation  »'^''"f?l^^^,„ZM  correspond  to  expansions  from 
Ua«/<'«  and  the  latter  the /a««.«J«m«/WA^^^  thalamencephalon  is  much 

Z  dorsal  and  ventra  '''""^llv  maS  of^hrM«/«l«?  from  its  anterior  two-thirds  and  to 
the  larger  and  gives  rise  to  the  bulky  mass  o   ^"^  '     ,       ...     ^^    epithalamus  is  prolongeil 
he  epk^alamus  and  the  "^eUthalamus  from  ta  poste^or^jj-  d^    T     J^,^.^^  ,^^^^  ^,i^.^,„  ,^ 
backward  and  from  its  upper  surface  an  ^a^^^^^^^  ^^^  ,,^  j^„„„    ,      ^ansverse 

become  the  pineal  body.     Subsequent  inKrowtn  o  establishment  of  the  posterior 

groove  behind  and  below  the  P;^;«' ''^''^ '^,'^"  ^  in  front  of  the  pineal  recess 

commissure,  whilst  thickening  of  the  part^f  the  epuh^^  ^^^  ^  ^  ^^^  ,j.,„g 

gives  rise  to  the  habenular  region_     Jll^  '^Jf  *;^7^hich  it  is  cl.^sely  connected,      t  early  pre- 
behindand  to  the  outer  side  of   he  thalamus  w«n  ^^^  ^^^^^  geniculate  bodies. 

sents  two  slight  external  ^'«~!^.^X««^^47yshows  adifTere^^^ 
Sn^tTfJlSs-Jrircketd^^^^^^  the  mammillary  body  and  tiie  subtiialainic 

Sn^o- tt=r>£S  irrialilina  termina.is  that  closes  the  cavity  o,  the 


"94 


HUMAN  ANATOMY. 


fore-brain,  the  later  third  ventricle,  and  contributes  the  anterior  wall  <A  this  space.  Attention 
has  been  called  to  the  invagination  of  the  mesial  pallial  wall  along  the  primary  choroidal  fissure 
immediately  above  the  line  of  attachment  of  the  roof-plate  to  the  hemisphere  i  Fig.  1031 ).  The 
latter  is  connected  with  its  fellow  of  the  opposite  side  by  means  of  this  thin  lamina,  upon 
whose  upper  surface  the  mesoblastic  sheet  of  the  young  pia  is  spread.  On  each  side  the 
same  sheet  is  prolonged  through  the  choroidal  fissure  into  the  cavity  within  the  pallium, 
where  it  forms  an  extensive  vascular  mass,  the  choroid  body,  which,  for  a  time,  fills  the 
greater  part  of  the  hemispherical  space,  Imt  from  actual  entrance  into  wlN,jh  it  is  now,  as  well  as 
subsequently,  separated  by  the  attenuated  invaginated  wall  of  the  pallium.  This  displaced 
wall,  with  the  enclosed  pial  tissue,  afterward  becomes  the  choroid  plexus  of  the  lateral 
ventricle  and  is  carried  downward  along  the  mesial  surface  of  the  inferior  horn  with  the  for- 
mation of  the  temporal  lobe.  Where  the  mesoblastic  sheet  overlies  the  roof  of  the  fore-brain 
it  becomes  the  velum  interpositum,  which,  it  is  evident,  is  continuous  on  each  side  with  the 
choroid  plexus.  Since  the  choroidal  fissure  begins  in  front  at  a  point  which  later  overlies  the 
foramen  of  Monro  and,  further,  since  the  choroid  plexuses  of  the  two  sides  are  connected  by 


Choroidal  fisxui 


Fig.  1031. 


Choroidal  artery 


rallium 


Roof  of  third  rentrteic 
Habeiiula 


Mld-braln 


Lamlnn  terminaliv 

Corpus  striatum' 
Hypothalamic  region 


Cavity  of  mld-braln 
Ifthmus 


erebellum 


Khlnencephalon' 
Optic 

Uptic  chiasm' 
Infundibular 

Mamminar>'  hod; 

Pontine  flesnre 


Spinal  cord 


Pons 
Floor  of  IV  venlrlde 
Medulla 


Cervical  (lexnr« 


Reconstruction  of  brain  of  human  foetus  of  3  months  (50  mm. ) ;  mesial  nurface.    X  4M.    Drawn  from  Rla  model. 


the  intervening  velum  interpositum,  it  follows  that  the  plexuses  converge  towards  and  meet 
over  the  foramina — a  relation  which  they  retain  in  the  adult  brain.  The  backward  expansion 
of  the  hemispheres  is  accompanied  by  a  corresponding  backward  prolongation  of  the  young 
pia  mater  covering  the  roof  of  the  diencephalon,  later  the  third  ventricle.  After  the  corpus 
callosum  and  the  fornix  have  been  superimposed,  the  impression  is  given  from  the  relation  of 
the  stnicturcK,  as  seen  in  t)ie  completed  brain,  that  the  pia  has  gained  its  position  over  the 
r<H)f  of  the  third  ventricle  by  growing  forward  beneath  the  splenium  and  fornix.  That  such, 
however,  is  not  the  case  Is  evident  from  the  developmental  history  of  the  velum  interposi- 
tum. The  secondary  invagination  of  the  brain-roof  on  each  side  along  the  median  line  by 
the  va.scular  tissue  of  the  pia  accounts  for  the  production  of  the  choroid  plexus  of  the  third 
ventricle. 

The  Cerebral  Commissures. — The  primary  simplicity  of  the  connections  between  the 
hemispheres  is  disturbed  by  the  formation  of  the  commissu-es,  which  become  necessary  in 
order  to  link  together  the  increasing  sheets  of  cortical  gray  matter.  The  development  of 
thesf  ctmimissures,  the  corpus  callosum  and  the  anterior  commissure,  as  well  as  of  the 
septum  lucidum,  are  intimately  associated  with  changes  which  affect  the  lamina  terminalis. 


MEASUREMENTS  OF  THE  BRAIN. 


1 195 


About  the  fourth  n,o„th.  the  ^-^r^^ ^''Z' '^^'^^^'^^'^^oZ.n  ^1  MonrT rnut 
exhibits  ajocal  tWck««ng  -n  Us  u^e  Pgrt  ^t  '"  ^"^j^^^j  „j  ^^e Junina  terminal^ 
advance  of  the  front-end  of  "^«^™™'"J^J:L^  ^jth  the  point  directed  downward  (Fig. 
at  fi«t  oval  ".section.  soonj^m«  P«^^|»^rf^  ^  „^^e«e  fibres. 

,032).  The  point  enlarges  and.  aftff '»*  '^^  ™^  ^^e  thickened  area  expands  m  the 
fo^  the  anterior  comm.ss.|re^  S^fib^^whwTpwsl^m  one  hemisphere  to  the  other 
sagittal  direction  and  is  t"*^' f^.^^^  "^J^  ^^re  soon  assumes  an  elongated  and 
It  thus  becomes  the  corp  »  caUosum.  This  «™«"T1  Zaut):^  upper  part  of  the  ongi- 
s  irf^^  arched  form,  but  aoes  not  «PP«>P"^'«.^^«  ^^  IS  by  the  corpus  callosum. 
S  pyriform  area.  The  '»\'Vr't:^ZS^^Zk^m  ^^T^^'^^^^  P°^  <^  "^  «=?'- 
™„4iS;  thin  and  •»  converted  '"^/^^ '^P^'^'^,K^f  the  anterior  pill^  of  the  fornix  by 
losum  forward  and  downward,  f"^  *;^  .^^7„'^  ^h^^^^^  to  the  basal  surface  of    he 

fibres  which  pass  from  the  gyrus  d^nt-^  "^ana  tne  nip^     v  ^^.^  although  thm  ; 

brain,  the  septum  »«cid«™^";!^  '^^  l^eL  by  a  na^ow  cleft,  the  socalled  fifth  ven- 
::ir wSu  S.SS  St  ni^^Te^y-'  Uning.  and.  therefore,  is  no  part  of 


Fig.  1032. 


Choroidal  fiamirc 
Priman-  gyrus  dentatu* 

Roof-plate  of  111  ventricle 
(tunia  thalaml) 

Thatamiw 
Posterior  commiasure 

Uuadrigeminal  plate 

Mid-brain  cavity 

Cerebral  peduncU 

Cereliellum 

IV  ventricle 


Corpus  calloaum 
Roatruni 
iieptum  lucidum 

Anterior  commi»»ur« 

III  ventricle 
Olfactory  lohe 


Lamina  lerminalia 
Optic  chia»m 
Pit\iitary  body 


.  Medulla 
Me.ial.uriac.o.le.thalfolhumanf«tu.offo»rih«onth.    X..  (^.«W.) 

the  system  of  true  ventricular  '^^r;..'i^'^^^^n.TZ:i:^ ^^^^^  S^eSd" 
opinions  differ.    The  older  view.  »h»t  the  space  represen«^  fa^stained  neither  by  its 

nkl  fissure  cut  off  during  the  d^^e  oF«nent  of  tl^e  c^^  _^,^  .^  ^^j^^  ^^      rtiUon 

history  nor  by  the  adult  ""^.tion  o  th«  sepUim  1^^^^^^^  Y       ^^^^  Marchand.'  His  and 

is  solid  and  no  space  exits.  ^"J^*'"'  ''"V^^oiiKque^^^  of  the  growth,  increasing  bulk  and 
others,  regard  the  spl  tting  ««  «;^^^^,„  ind  ?Sion  of  the  fo^ix  along  its  under  suriace^ 
backward  extension  of  the  con>uscallosum  »"<^ \^^^"*^ ^^,,  forward  along  the  mesial  suriace 
the  primary  upper  part  of  the  h.ppocamps«extenfl^^  fissure,  being  later  repre^ 

of  the  hemisphere,  entirely  d^^PV^^'  '™  °*d  ng  po^dTof  the  gyrus  dentatus  is  reduced 
::r  XttS'c^^S  rilfrr  thT^gitud^nS'stria.  found  upon  the  uPper  surfa.  of 

the  corpus  call'--  m.  „„  .  ,xt 

MEASUREMENTS   OF   THE    BRAIN. 

The  brain  f^ts  within  the  cranial  c- so  accurately  tha^^^^^^^^      ^0^"^' 
the  general  shape  of  the  skull.  b«='"K  .^'^ '^  '^^L  °"v «^^^^^^^  The  usual  length 

subjects  and  shorter  and  ""^^  ^Ph"'-*^  the  SEl  ^le?  is  from  ,60-170  mm. 
of  tie  brain,  measured  from  the   ronta   to  the  ocapitai  po  ^^^ 

tSrL'rmt^trut^t  (S'")^o^'^th  seL  and  its  greatest  verti- 

'  •\rchivf   Anatom.  «.  Entwicktlung.  1903. 
>  Archiv  f.  mikros.  Anatom  .  Bd.  xxxvu.,  1891. 


II96 


HUMAN  ANATOMY. 


cal  dimension  through  the  hemisphere  is  about  125  mm.  (5  in.).  The  female  brain 
is  commonly  somewhat  shorter  than  that  of  the  male,  and,  therefore,  relatively 
broader  and  deeper. 

The  weight  of  the  brain  has  been  the  subject  of  repyeated  investigation  with 
results  that  fairly  agree.  The  conclusions  of  Handmann",  based  on  recent  examina- 
tions of  1014  brains  (546  male  and  468  female)  from  persons  ranging  in  age  from 
fifteen  to  eighty-nine  years,  are  of  interest  since  they  confirm  in  the  main  the  results 
obtained  from  previous  observations;  The  average  weight  of  the  adult  brain  (from 
15-49  years),  without  the  dura  but  surrounded  by  the  arachnoid  and  pia,  is  1370 
grams  (48.6  oz. )  for  men  and  1250  grams  (44.4  oz. )  for  women.  The  weight  of 
these  membranes,  including  the  enclosed  arachnoid  fluid,  has  been  estimate*!  at  56 
gm.  and  49  gm.  in  male  and  female  brains  respectively  (Broca).  The  brain  iially 
attains  its  maximum  weight  about  the  eighteenth  year,  perhaps  somewha  arlier 
in  women,  no  increase  taking  place  after  the  twentieth  year.  Subsequent  to  the 
sixtieth  year  in  both  sexes  a  progressive  diminution  occurs,  by  the  age  of  eighty  the 
brain  having  lost  approximately  one-fifteenth  of  its  entire  weight  ( Boyd ).  Including 
the  brains  of  individuals  between  fifty  and  eighty-nine  years  in  his  series,  Handmann 
found  the  average  weight  to  be  1 355  gm.  (47. 8  oz. )  for  men  and  1 223  gm.  (40. 3  cz.  ) 
for  women.  Approximately  81.5  per  cent,  of  adult  male  brains  have  a  weight  be- 
tween 1200  and  1500  gm. ;  8.8  per  cent,  one  cf  from  950-1200  gm. ;  whilst  20.3 
per  cent,  possess  a  weight  over  1450  gm.  Correspondingly,  about  84  per  cent,  of 
female  brains  weigh  between  1 100-1400  gm. ;  44  per  cent  between  1 200-1 350  gm. ; 
and  46  per  cent,  below  1 200  gm.  The  average  weight  of  the  brain  of  the  new-born 
male  child  is  400  gm.  (140Z. )  and  that  of  the  female  one  is  380  gm.  (13.40Z. ). 
During  the  early  years  of  childhood  the  brain  rapidly  becomes  heavier,  its  weight 
being  doubled  by  the  end  of  the  first  year  and  trebled  by  the  completion  of  the  sixth 
year.  At  first  the  increase  affects  the  brain  equally  in  both  sexes ;  later  the  young 
female  brain  fails  to  keep  pace  in  its  growth  with  the  male  one,  the  differences 
becoming  progressively  more  marked. 

Whilst  the  brain-weight  and  stature  stand  in  direct  ratio  in  the  new-born  and  in 
children  up  to  75  cm.  in  length,  irrespective  of  age  and  sex,  after  attaining  such  .stat- 
ure the  relation  is  irregular  and  uncertain.  Likewise  in  the  adult,  Handmann  found 
no  constant  ratio  between  the  stature  and  the  brain-weight,  although  in  general  a 
lower  average  weight  of  the  brain  is  found  in  short  individuals  than  in  those  of  mod- 
erate and  of  large  height.  The  relative  brain-weight,  as  expressed  in  the  ratio 
between  each  centimeter  of  height  and  the  brain-mass,  Handmann  found  to  be  8. 3 
gm.  for  each  centimeter  of  height  in  men  and  7.9  gm.  in  women,  a  slightly  higher 
proportion  in  favor  of  the  male  subject  being  thus  observed.  The  average  ratio  of 
the  weight  of  the  adult  brain  to  that  of  the  entire  body  is  approximately  1 150  (Ober- 
steiner).  In  the  new-born  child  this  ratio  is  much  greater,  being,  as  determined  by 
Mies,  I  :5.9.  Of  the  entire  weight  of  the  brain,  the  hemispheres  contribute  78.5  per 
cent.,  the  brain-stem  11  per  cent.,  and  the  cerebellum  10.5  percent,  ;iO  material 
difference  being  observed  in  the  two  sexes  (Meynerl). 

The  extent  of  the  superficial  surface  of  the  cortex  has  been  determined,  at  least 
approximately,  by  Wagner,  who  by  completely  covering  the  convolutions  with  gold 
leaf  concluded  that  the  large  brain  of  the  mathematician  Gauss  ( 1492  gni.  )  presented 
an  aggregate  area  of  221,000  sq.  mm.,  or  not  quite  one-iialf  square  meter.  Of  this 
entire  area  alxnit  twice  as  much  lay  along  the  sides  and  bottoms  of  the  fissures, 
tlierefore  sunken,  as  upon  the  exjxised  surface.  The  estimate  of  the  same  observer 
concerning  the  brain  of  a  workman  placed  the  area  at  187,672  sq.  mm. 

The  significance  of  brain-weight  as  an  index  of  intellectual  capacity  has  long  excited  inter- 
est. Accumulating  data  prove  beyond  question  that,  as  applied  to  individuals,  the  weight  of 
the  brain  is  an  untnistworthy  index  of  relative  intelligence.  For  whilst  in  a  number  of  conspic- 
uous examples  the  weight  of  the  brains  of  men  of  acknowledged  intellectual  superiority  has  been 
markedly  above  the  average,  it  is  equally  tnie  that  some  of  the  heaviest  brains  recorded  have 
been  those  of  persons  of  ordinary,  and  indeed  in  some  cases  of  even  decidedly  inferior,  intelli- 
gence.    I'"urllicr,  the  brains  of  not  a  few  men  of  remarkable  achievement  in  the  fields  of  Science, 

'  Archiv  f.  Anat.  u.  Entwickelung.,  1906. 


11 


THE  MEMBRANES  OF  THE  BRAIN. 


"97 


„.  Letters  =u,d  of  Art  have  po^se^  -^t'lJ  tarSoT  ^';^:r;Z  ^^Z^^^  "^^ 
"        In  this  connection  it  must  be  ^'r"'*,""'^^^  **' ^^^  ^wer  o!  retaining  impressipns; 

^diflerent  brains  vary  in  the.r  c=^.t^«or  ^^^'r  tt^notwit^tanding  the  possible  lu.  ^n- 
that.  in  short,  differences  of  'f^'^^'^J^^^-jL^^i''  matter,  especially  of  certain  regions  con- 
eral  weight  of  a  brain,  the  amount  of  '•'f  .<=""^.^?' «"^  ™ist  •„  u^ual  abundance.  Moreover, 
^med  i^  some  particular  P^^- »' "f  ^?^^^^r\>  JS  „crease  of  the  functioning  as.socia- 
it  is  probable,  from  the  investigations  of  l^?**  •  "*"  °"^  ^v  excessive  exercL-*  of  certain  parts 
tion  fibres  takes  place  in  response  to  the  ^^^^^^^J^^^^X  "dividual,  brain-weight  alone 
li  the  cortex.  It  is  evident.  ^^JP'^'^'  **\J^„S  I»wer,  and  that  brains  which,  judged 
afford-  tittle  dependable  •"°™^rw^„*^i^"S!Tay  h^ve  b;^n  exceptional  in  the  amount  of 
from  .L.  f  weight.  «PP»r«nt'y'^^^heunS  canity  of  their  neurones.  _ 

cortical  gray  matter  and.  perhaps,  n  the  """f  ^*^"\"  ^^^  or  to  races,  brain-weight  has 
"*  Co^idered.  however,  in  ^-'»f°"J^,  ^[^/^'^S^i^^rind  culture.  In  this  connection 
been  found  to  correspond  to  the  genial  P^«  °«„~f^^g,  brain-weight  of  the  male  negro 
the  observations  of  Bean'  are  s''pestive^  "  d  ,c6o  em  ■  that  of  the  male  Caucasian  i34«  P"  • 
to  be  ,292  gm.,  with  extremes  of  .010  gn^and^^5feK^^.t^«  ^^,.,^i^^,     j^^  rfa-ss  o   the 

with  extremes  of  1040  gm.  and  i555  K""  .{:°Vj'\heir  brains  was  greater  than  that  of  the 
white  subjects  examined.  *e  average  w«ght«^the^braiM 

high-class  negroes.  Bean  concludes  hat  ♦^«^^"^'''"^t^j;  relatively  and  absolutely  smaller, 
frontal  lobe.  and.  therefore,  that  the  .mteriorassoc^a^^^^^^  ^^5^^^  ^  ,^  ^i 

The  observations  of  E.  A.  Spitzka  concerning  i  j  ■    ,he  brains  of  men  of  con- 

sagittal  section,  call  attention  to  the  """''"»\f,'f  °*£,~pou7o^^^  thus  examined  var^a- 
^cuous  intellectual  power.    Moreover  in   he  part^cu^^^^^  .^  ^^^  ^^„^,  ^^^.^^ 

tions  in  the  details  of  the  callosa  strikingly  ^««K^t*^*^»  cMosxxm  as  a  trustworthy  index  as  to 
of  the  persons  during  life     The  Y'^hdity  ofAe  area  oHhe^^^^^^  ^^^^^  ^^  ^^  Bean, 

intelle^ual  capacity  has  been  ^"°^^y^^^^^^^^i,^l^ight,  aiid  that  not  infrequently 
that  callosa  of  uncommon  size  «f««"y  h«l°"K  *°  e^JTof  low  intelligence,  as  exemplified  by  the 

*^''jrtarirngti;;?:fnl°^^^^^^^^^^^         - — «-■"  'o— ^'^'- 

and  even  from  negroes. 

THE  MEMBRANES  OF  THE  BRAIN. 

Like  the  spina,  cord,  the  brain  i-;a^^>i:^.  T^rS^^--^  5") 
which,  from  without  tnward,  are^  .^JJ^^^P^^^o  ihe  inner  surface  of  the  cra- 
the  pia  mater.  The  first  o[  »''^.'^"'^'y  l']_  addition,  by  means  of  its  processes 
nium.  of  which  it  constitutes  he  P^'^^«,^""^;i"„^,;\"hf  e^^^^^^  of  nervous  tissue, 

serves  to  support  and  guard  from  .""^^^  P^^^^iJ/^^^s  for  the  nutrition  of  the 
The  pia  mater  is  the  vascular  tunic  «^^^5y'"g 'J\\;\X  el^emal  surface  of  the  organ  ; 
irain'^and.  therefore  li^  in  contact  with  f  P^J^^jP*^  ^^f  f  ™ tie  coats,  is  free  from 
whilst  the  arachnoid,  the    l^/""^\!^"tir^he  intracranial  lymph-paths.     Although 

blood-vessels  but  is  •"'''"^'^•y/^if,*!^^:*^  '^VskuU  an^^^^^  "^^J 

the  dura  and  the  pia  are  closely  f"f '='^^1,*°. '^v  dSto  two  compartments  by  the 
are  separated  by  an  '"f^^^lf  if '; '"^t^  ^tw^n  the  dura  and  the  arachnoid  and  is 
arachnoid.  The  outer  of  t'  ^clefte  »u^  ^l^^n\ht  arachnoid  and  the  pia  s  the 
called  the  subdural  sp  >e  othe^'f  ^^^  j^  y,^^,,    ^  mere  capillary  cleft,  the 

subarachnoid  space.  /'aX^taT       mall  amount  of  a  clear  light  straw- 

arachnoid  lying  against  tl,  a.  and  conwi  although  much  more  cana- 

colored  fluid  of  the  nature  of  IJ'^P'^:  J*'^ '^^"rab^^ulx  of  arachnoid  tissue  tiiat 
cious  than  the  subdural,  is  ^i^^^^-^^J^y  ^^^^^^^  rather  than  of  an 

in  many  places  it  acciuires  the  character  «»  »  «P^"KS  j  ^  suburachnoitl  spaces 
unbroken  channel.  \Vhilst  -"'''t°'"'";«"y  J'^;„",Si\";^are{ul  artificial  injections 
are  distinct  and  nowhere  S"'"™""!^,*'^;!^  £°"  Se  cerebro-spinal  fluid  finds  its 
into  the  subdural  cle  t.  it  '^P.■•«^^le  that^rin^  hfe  th^  <:ere         ^    ^^^^^^ 

way  through  the  thm  P»"'^'«"  °'  'f ''£irth^^  fluid,  a  modified 

The  interstices  of  the  arachnoid  ^«^^^H^  „r*^^J^\'^hin  the  ventricles.  After  dis- 
lymph,  which  is  produced  by  he  ^^Jf^'f  £XoS  space  by  way  of  the  foramen 
SferanTtSn^rtiSao^f  &t^ s£Sn"the aVnu Jtc^  rU  o,  the  fourth 

!  Hie  r,m«shimrinde  <|ps  Menschen,  iqo? 
'  Amcr.  Journal  of  Anat.,  vol.  v.,  1906. 
»  Amer.  Journal  of  Anat.,  vol.  iv.,  1905- 


1 198 


HUMAN  ANATOMY. 


ventricle  (page  iioo).  The  paths  by  which  the  fluids  collected  within  the  brain- 
membrane  are  carried  oil,  thereby  insuring  under  normal  conditions  the  prevention 
of  excessive  intracranial  tension,  will  be  considered  with  the  description  of  the  dura 
and  arachnoid,  suffice  it  here  to  mention  the  sheaths  contributed  by  these  envelopes 
along  the  nerve-trunks  as  they  leave  the  cranium  and  the  Pacchionian  bodies  as  the 
most  im[>ortant. 

The  Dura  Mater. — This  structure  (dura  mater  encephali)  is  a  dense  and  inelas- 
tic fibrous  membrane,  which  lines  the  inner  surface  of  the  cranial  cavity  and  sends 
partitions  between  the  divisions  of  the  brain.  In  contrast  to  its  relation  within  the 
vertebral  canal,  where  it  is  separated  from  the  bony  wall  by  a  considerable  space 
(page  1022),  within  the  brain-case  the  dura  everywhere  lies  closely  applied  to  the 
bone — a  relation  essential  in  hilfilling  its  function  as  a  blood-carrying  organ  for  the 
nutrition  of  the  cranium.  Around  the  margins  of  the  larger  foramina,  over  the  pro- 
jecting inequalities  of  the  fossae  and  along  the  lines  of  the  more  imjxjrtant  sutures,  the 
attachment  of  the  dura  to  the  skull  is  particularly  close,  and  at  some  of  these  points 

Fig.  1033. 


:  i] 


'Falx  cerebri 


Junction  of  falx 
and  tentorium 


Tentorium  cerehel!i 

Opening  Tor  hrain-nteni' 


ntphngma  Mllee 
:  margins  of  tentorium 


Portion  of  skull  removed,  showing  partitions  of  dura  in  place. 

— the  foramina  and  the  ununited  sutures — the  dura  is  continuous  with  the  periosteum 
covering  the  exterior  of  the  skull.  On  separating  the  dura  from  the  bone,  as  may  be 
readily  done  beneath  the  calvaria,  except  along  the  line  of  the  sagittal  suture,  its 
outer  surface  is  marked  with  the  conspicuous  ridges  produced  by  ihe  meningeal 
blood-vessels,  which  lie  much  nearer  the  outer  than  the  inner  surface  of  the  mem- 
brane and  hence  give  rise  to  the  corresponding  furrows  seen  on  the  inner  aspect 
of  the  skull.  In  addition,  the  roughened  surface  of  separation  is  beset  with  fine 
fibrous  processes,  the  larger  of  which  contain  minute  blood-vessels,  that  have 
been  drawn  out  of  the  canals  affording  passage  for  the  nutrient  twigs.  The  inner 
aspect  of  the  dura,  on  the  contrary,  is  smooth  and  shinny  and  clothed  with  a  layer 
of  endothelium  which  lines  the  outer  wall  of  the  subdural  spwce.  As  the  nerves  enter 
the  foramina  in  their  exit  from  the  cranium,  they  receive  a  tubular  prolongation  of 
the  dura  which  accompanies  the  nerve-tnmk  for  a  short  distance  as  the  dural  sheath^ 
separated  from  the  nerve  by  the  underlying  subdural  cleft,  and  finally  becomes  con- 
tinuous with  the  epineurium,  whilst  the  subdural  space  communicates  with  the 
lymph-clefts  \yithin  the  connective  tissue  envelopes  of  the  nerves.     The  dural  sheath 


THE  MEMBRANES  OF  THE  BRAIN. 


1199 


«.rround,ng  the  optic  nerve  through  its  entire  length  is  noteworthy  on  account 
of  its  unusual  thickness  and  completeness  (l««V\"3^  ,      , 

partSn.,  which  protet  ln.«rd  a»d  '"Ifi™  !^f^h.  brata  SS  "ll  "  enclcie  the 
5mpanm»ts  occpM  by  the  1«^^;~>™  ?<  ™c»  Evf  b^r  desnibrf  with 

fcr^— eivii^^^TrtJAss^^-s 

localiti^in  which  the  Pacchionian  bodies  may  a,me  into  rj;^^^^^  ^^^ 

stream.    The  septa  thus  formed  by  dupUcatur«  of  the  mn«^^^^^  V^^^^ 

falx  cerebri,  (2)  the  tentorium  cerebelh,  (3)  the/a/*  fw-^^w*.  anu  ^4; 

^'^"f  hTflSic'^cerebn  is  a  sickle-shaped  V^^S'^:S^:^:'^TXv^^S.  ffg^r 
the  longitudinal  fissure  separating  the  cerebri  hem.spher«^It^^^^^^  ^^^^^S.^ 

border  is  attached  in  the  mid-hne  and  extends  fr«"\  ^^e  cnsti  gam 
bone  in  front  to  the  internal  occipital  P^^^^^^^^^^^'^i^Hn  „^^^^^^ 
longitudinal  sinus.     The  latter  channel  appear  J'^^g^  ^ay  "r  of  the  dura  and  the 
.OM).  the  "P-rd  placed  base  ^mg  the  out^^^^^^^  ,f  ,he  falx  is 

sides  the  separated  lamella  of  the  talx.      ine  •°''^y^J'"        .    ,         (^e  hind  part  of 
free  and  more  sharply  arched  than  is  the"PP«r,  and  extends  Jro^^  .^ 

the  cristi  galli  to  the  highest  poino    the  tent^um      W'f^/"      J^.  ^^.j. 

encloses  the  inferwr  lanpludinal  sinus.     The  b^^  tne  m  ^^  ^^^ 

mately  at  45°  with  the  horizontal  plane,  and  attached    «  the  uppe  ^^^ 

tento^um  in  the  sagitta    plane.     A»«"?this  junction  li«    he  .^^^^^^  ^^^^ 

narrow  forepart  of  the  alx  is  the  thmnest  portion  «'  the  F^rtmon  an  ^  ^ 

especially  cWing  the  latter  half  of  life,  the  ^^*t  of  perforations^  w  -^^j^^^ 

numerous  as  to  reduce  this  part  of  the  ^Pt«"»  t^^ '^"^^^^^^^^  pathological 

slSSncI  Tnd  '7^^:J'^^Z'^.r:^^o:..  ..l  partition  seen  in  some 

''niieunt^rlutn  cerebelU  is  the  large  tent^Je  Pa-Uion^^^^^^^^^^^^^^ 
tenor  fossa  of  the  skull  and  separates  the  <=^;^^^^"'^^  *'7 J^^^enUc.  the  longer 
parts  of  the  cerebral  hemispheres.     In  its  gfn^";j°n^  '^ '^  S  margins  of  the 
?^nvex  border  lying  behind  and  attached  to  t J^^P"^*^;  "^X  e^^^^^ 
posterior  cranial  fossa,  and  the  shorter  con^ve  ^"tenor  Iwrder  c"rv    j^^^  ^ 

^  upward  from  the  anterior  chno.d  P/f  «!^:.  ^f„^"X^^eISl  plane,  and  in  this 
is  attached  by  its  entire  width  to  the  fax  ^^.^li"  ^PK  ^'^^'^^'^^J^  „f  he  tent-like 
manner  the  partition  is  mamumed  m  « J^^f  ^t  X*  J^^d  y  ^^^^^  convexity 
fold  are.  however,  not  simply  fla  .  but  P'-^T'^^^^  f^'^',„,e  of  the  under  surface  of 

ihe'^StiSs  tTciS^^^^^^^^  "PP^^  -•'-  "'  ^'^  --'-"""' 


I200 


HUMAN  ANATOMY, 


'  1  1 


of  the  petrous  portion  of  the  temporal  bone,  and  thence  to  the  posterior  dinoid  pro- 
cess. From  the  internal  occipital  protuberance  as  far  as  the  parietal  bone,  this  line  of 
attachment  corresponds  with  the  course  of  the  enclosed  lateral  sinus  (page  867; ;  but 
beyond,  the  venous  channel  leaves  the  tentorium  in  its  descent  to  the  jugular  fora- 
men, the  farther  attachment  of  the  tentorium  enclosing  the  superior  petrosal  sinus. 
Since  the  anterior  border  of  the  tentorium  springs,  on  each  side,  from  the  anterior 
dinoid  process,  it  follows  that  the  two  margins  of  the  crescentic  septum  intersect  in 
advance  of  the  apex  of  the  petrous  bone,  the  posterior  border  turning  inward  to  the 
posterior  dinoid  process,  whilst  the  anterior  margin  is  connected  with  the  anterior 
process.  The  free  tentorial  border,  in  conjunction  with  the  dorsum  sellae,  defines  an 
arched  opening,  the  incisura  tentorii,  through  which  the  mesencephalic  portion  of 
the  brain-stem  is  continued  into  the  cerebral  hemispheres,  the  highest  point  of  this 
aperture  lying  just  behind  the  splenium  of  the  corpus  callosum. 


Fig.  1034. 


^Skin 


Superior  longitudinal  sinus- 


F«Ix  cerehri 


Fibro.ipan«nrMic  layers  o(  icmlp 


ParieUI  layer  of  dun 


Posterior  horn  of 
lateral  ventricle 


Tentorium 
Left  lateral  sinus. 


Superior  wonS' 


Inferior  kMicitndi- 

nal  sinus,  cut 

obliquely 


'osteriorhom  of 
lateral  veuirici* 


'entoriom 
Richt  lateral  slnii* 

'erebellum 
Inferior  worm 


(Vcipltal  sinus 


Frontil  section  of  liead,  viewed    from   behind,  showing  relations  of  dura  mater  to  cerebral    hemispheres  and 

cerebellum  and  position  of  sinuses. 

The  falx  cerebelli  is  a  small  sickel-shaped  dural  fold  which  descends  in  the 
mid-line  from  the  under  surface  of  the  tentorium,  with  which  its  broader  upper  end 
is  attached,  towards  the  foramen  magnum.  In  the  vicinity  of  this  opening  its  apex 
bifurcates  into  smaller  folds  that  fade  away  on  either  side  of  the  foramen.  Its  poste- 
rior border,  attached  to  the  vertical  internal  occipital  crest,  contains  the  small  occipital 
sinuses,  or  sinus  when  these  channels  are  fused.  The  narrow  crescent  projects  into 
the  posterior  cerebellar  notch  and  thus  intervenes  between  the  hemispheres  of  the 
cerebellum. 

The  diaphragma  sellze  is  an  oval  septum  of  dura,  which  roofs  in  the  pituitary 
fossa  and  is  continuous  on  either  side  with  the  visceral  or  Inner  layer  of  the  wall  of 
the  cavernous  sinus.  The  diaphragm  contains  a  small  aperture,  the  foramen  dia- 
phragmatis,  through  which  the  infundibulum  connects  the  enclosed  pituitary  body 
with  the  brain. 

The  structure  of  the  dura  presents  the  histological  features  of  dense  fibro- 
elastic  tissue,  in  which  the  elastic  constituents,  however,  are  greatly  overshadowed 
by  the  white  fibrous  bundles.     The  inner  surface  of  the  dura  is  covered  with  endo- 


THE  MEMBRANES  OF  THE  BRAIN. 


I301 


thdial  plates  which  constitute  the  -™edbte  ^^  w^^];^^-^^^ 

^Sch^cA  endothelium  ^"«*'"«  ^.^.i/ 1«*1^«      Tte  o^ter  or  periosteal 

Sped  as  ■^-^<-^-'^?^,^^^^t£:^''Z£rly:^         contain^a  wide- 
laS^Ua  is  less  comi»ct  ^^5^  ncherin  c^  tnan^  «  j;^^  ^  ^^^^^^  tissue  are 

meshed  net-work  of  capillary  ^ «od-v«aeJ-   ^"^^^j         j^e  two  ends  of  the  falx 

STLTo^^^X^^^^^^ 

s:5o^vStacta^nSs:i;^^  ^-^^^-^ 

JLint.the  fibres  within  the  tentonum  P^l^f  "^^y-  ^  irain-saml  or  acrrvulus,  are 
P°    Minute  c^-^^"'  Sr/he  iw^  no^^^^^  especially  in  subjects  of 

not  infrequenuy  «°""J  '"^^.V^ '^Uons  of  particles  o&ium  carbonate  and 
advanced  years.  They  consist  oi  ^K^***"  ,  .,,  J^ounded  by  a  capsule  of  fibrous 
phosphate  arranged  in  concentnc  ^^V^"^  ^'^J^^'^^  "Lt  may  be  so  numer- 

Fig.  1035. 

Medullary  bimncli 


Larger  plal  arlery- 


Ite  matter 


"'ptrnlr:';!.  cer..»l  con..,  -.o,.„.  capnur,  .uppiv  «.  ^r  •"<•  «-  —    ><  '«• 

internal  maxillary,  vertehnd  --^inf  ghaiy^geal  a^^^^  JheJ^-^ 

destined,  for  the  most  part,  for  the  ""t^of^J^      Some  Lper/oratinfr  arUrUs 
;t^^^Th?UraT;trmSfe  w-itfthrSHcr^  vessefs.  ihilst  others  are 

i;SrpalK::;:^un^in^^^^^^^^^  -^  ^'-^^^^^  "" 

tL  venous  «i""««,^rlL  indudtSp^ly^yn^Pathetic  filaments,  distributed 
The  nerves  of  the  dura  include  P""*^'P="2,Jf  Xes      The  immediate  sources 
to  the  blood-vessels  and  to  t^bone   and  sen^ry^fibres.^   T^^^^    ^^^  ^^^ 
are  the  meningeal  twigs  contnbued  by  he  t"gemmu..  f^^^^j,  ^^^  ,,^iy 

£:o™Xryt^^^^^^^^^  ^"S  s^u^;ltL  comVnionship  by  ^means  of 


I303 


HUMAN  ANATOMY. 


Gray-  mmttcr 


White  matter 


the  commui  sitions  which  these  cranial  nerves  have  with  the  plexuses  surroundings 
the  arteriesi  or  with  the  superior  cervical  ganglion.  The  sensory  nerves  of  tho  dura 
form  a  rich  net-work  of  delicate  twigs  from  which  filaments  lu..ve  been  traced  to  the 
inner  surface  in  relation  to  which  some  end  in  bulbous  expansions. 

The  Pia  Mater. — ^This  membrane  (pia  mater  encephali)  lies  next  the  nervous 
substance  and,  being  the  vascular  tunic  supporting  the  blood-vessels  for  the  nutrition 
of  the  brain,  follows  accurately  all  the  inequalities  of  its  exterior.  It  not  only  closely 
invests  the  exposed  surface  d  the  cerebrum  and  cerebellum,  but  penetrates  along  the 
sides  and  to  the  bottom  of  all  the  fissures  as  well,  although  within  the  small  shallow 
fissures  of  the  cerebellum  a  distinct  process  of  pia  mater  can  not  be  demonstrated. 
Additionally,  in  certain  places  where  the  wall  of  the  brain-tube  is  very  thin,  the  pia 
pushes  before  it  the  attenuated  layer  and  seemingly  gains  entrance  into  the  ventricles. 
Examples  of  such  invs^nation  are  afforded  in  the  relations  of  the  velum  interpositum 
and  the  choroid  plexuses  to  the  lateral  and  third  ventricles  (pa^e  1162)  and  of  the 

similar  plexuses  m   the  roof  of  the 
Fig.  1036.  fourth  ventricle  (ps^e  1 100).    The  pia 

also  contributes  a  sheath  to  each  nerve, 
or  to  its  larger  component  bundles,  as 
the  nerve  leaves  the  brain  at  its  super- 
ficial origin,  which  sheath  surrounds 
the  nerve  during  its  intracranial  course 
and  for  a  variable  distance  beyond  its 
emergence  from  the  dural  sac 

The  pia  is  so  thin  that  the  larger 
vessels,  especially  at  the  base  of  the 
brain,  lie  within  the  subarachnoid 
space,  although  in  most  cases  they  are 
enclosed  within  a  delicate  investment 
of  piai  tissue.  The  smaller  vessels, 
however,  ramify  within  the  pia  and  in 
this  situation  divide  into  the  twigs 
which  directly  enter  the  subjacent 
nervous  tissue.  As  they  penetrate  the 
latter  they  are  accompanied  by  a 
sheath  of  pia,  which  thus  gains  the 
ner\'ous  substance  within  which  it  fol- 
lows the  subdivisions  of  the  arteriole, 
even  their  smallest  ramifications. 

Whilst  within  the  pia  the  larger 
arteries  form  frequent  anastomoses, 
the  smaller  twigs  remain  isolated  and, 
being  "end-arteries,"  on  entering  the 
subjacent  gray  matter  break  up  into 
terminal  ramifications  which  furnish  tiie  only  supply  for  a  pardcular  district.  The 
capillary  net-work  within  the  cortical  gray  matter  is  much  closer  than  that  within  the 
subjacent  white  matter  (Fig.  1035),  in  which  the  vessels  are  comparatively  meagre. 
Here  and  there  larger  medullary  branches  are  seen  traversing  the  cortex,  to  which 
they  contribute  but  few  twigs,  to  gain  the  white  matter  within  which  they  find  their 
distribution.  The  contrast  in  richness  between  the  supply  of  the  gray  substance  and 
that  of  the  adjoining  white  matter  is  not  limited  to  the  cerebral  cortex,  but  is  also 
well  shown  when  the  internal  nuclei  are  examined  (Fig.  1036).  The  veins  emerge 
from  the  surface  of  the  brain,  but  do  not  retain  a  definite  relation  to  the  arteries,  since, 
instead  of  following  the  latter  to  their  points  of  entrance,  they  for  the  most  part  seek 
the  dural  sinuses  into  which  they  empty. 

The  special  invaginating  layers  of  pia  mater,  the  velum  interpositum  (page  1 162) 
and  the  choroid  plexuses  of  the  lateral  and  third  ventricles,  and  the  choroid  plexus  of 
the  fourth  ventricle  (page  iioo)  have  been  described  in  connection  with  the  appro- 
priate parts  of  the  brain.  Attention  may  be  again  called  to  the  manner  in  which  the 
velum  interpositum  and  the  associated  plexuses  are  formed  (page  11 94),  and  to  the 


Portion  of  injected  dentate  nucleus  of  cerebellum,  show- 
ing capillary  supply  of  internal  nucleus,    x  ao. 


THE  MEMBRANES   OF  THE  BRAIN. 


IJ03 


Fig.  1037. 


Vucular  tuft 


backward  (page  U94)-  oresents  little  for  special  mention      The 

The  mtructure  of  .he  pa  J»  !!_  P'^^J^ti^e  tissue  enveU.pe  in  which  inter- 
membrane  consists  essentally  of  a  d«"l'^t^  "'""g'^^i^^^^i^^ji^  fibrw  and  conuining 
Sdng  bundles  of  white  fibrous  t.s«ue-te™^^^^^^  ^^^ 

numerous  nucei.  are  the  '^^'^'  'f^'^'^-^u^^jthin  which  are  prolonged  the  lymph- 
the  brain,  they  receive  *'?^»'*'''^,P'fJT^^  Along  the  basal  surface 

spaces  enclosed  between  th-  »-bec^f  ^f  th^  P^'^^'^^,^  ^^e  pia  frequently  conuins 
of  the  brain,  especially  on  the  v  ^""^f^ .^P^^j  ™  "^^Hs  These  may  be  so  numerous, 
deeply  pigmented  branch^  Tt  £  memb^ne  appeari  of  a  disJnct  brownish  hue. 

roSirt^iSeJS  ^cattid'  iTd^t^-^e^li^^leHes.       AdditioJ   nerve- 

fibres,  probably  sensory  in  Jun^'on- XJr 
in  s^ai  numbers,  the  mode  of  their 
ending  is  uncertain,  although  terminal  bul- 
bus  expansions  and  tactile  corpuscles  have 

'^"TK^Arachnoid.-This  covering 
(arachnoidea  encephaU)..the  intermediate 
membrane  of  the  brain,  is  a  delicate  con- 
Se  tissue  envelope  that  intervenes 
between  the  dura  «t"'«"y  ^'^'^ /^^  Pj^ 

internally.     In  contrast  to  the  If  t-nf^fj 

membrane,  which  follows  closely  aU    Je 

irregularities  of  the  sunken  as  well  as  of  the 

fre^surface  of  the  cerebrum,  the  arachno^ 

is  intimately  related  to  the  convolutions 

only  along  their  convexities,  and  on  ^vmg 

at  the  m^ns  of  the  inter%ening  fissures 

stretches  across  these  furrows  to  the  con- 
volutions beyond.     From  this  arrangement 

it  follows  that  intervals,  more  or  less  m- 

angular  on  section,  are  left  over  the  lin« 

of  the  fissures  between  the  arachnoid  and 

the  fold  of  pia  whirH  dips  into  the  sulcus. 

These  clefts  form   .  system  of  mtercom- 

municating  channels  which  are  ^J^Ae  summits  of  the  convolutions,  the  arachnoid 

general  subarachnoid  «P^<=^-.    °^!' *?u,t"^nstitute  practically  a  single  membrane. 

and  piaaresointimatelyunited  that  they  con^^^^^^  connected  only  by  the 

whilst,  where  parteu  by  th^  ^^Z^lcShol^^r.  where  the  intervening  cleft 
trabecule  of  arachnoid  ti^ue  In  ^^^ous That  the  space  is  occupied  by  a  delicate 
is  not  wide,  these  trabecule  »^f  J°.  7'"/  °"' ^^^^^^  Where, 

reticulum  and  becomes  converted  •"^°  ^^^y^^^J^'^considerable  size,  as  it  does  on 
on  the  other  hand,  the  ^f^'^l'^^'^/^f^P^f^i^P^re  reduced  in  number  to  relatively  few 
the  basal  suriace  of  the  brain,  the  *^*^"r  .f ^ '^^Xoid  to  the  pia  mater.  Over 
long,  cobweb-like  threads  that  expend  fr^^^^^^  ^,^  J^^^,     id  foUows. 

the  upper  and  outer  aspects  of  »"«  ^f  ^'/V"'  ^  Qn  the  ventral  surface,  however,  it 
in  a  general  way,  Uie  contour  dt^br^".      On  the  v. ^^  ^^  ^^^  ^^.^^^_^^  ^^^^._ 

SS^K'^^:^:lsSm^K  1^. 

t'^rc^rnT^^^^^^^^^TTl^^^i  ^er^l  suUvisions  are  recognized 
according  to  locality.  ..„K.ii„™Mi„ilaris^   the  largest  of  these  spaces. 


Velum  inter- 

poftittim 


Small  portion  oJ  in)«trf  choroid  pkxut  ot  lateral 
small  pu.       ventricte-.iurfaceview. 


I204 


HUMAN  ANATOMY. 


magnum  with  the  posterior  part  of  the  subarachnoid  space  d  the  cord.  The  arach- 
noid  passes  from  the  back  |»rt  of  the  under  aspect  of  the  cerebellum  to  the  posterior 
surface  of  the  medulla  and  thus  encloses  a  considerable  space  which  at  the  sides  of 
the  medulla  is  continuous  with  the  upward  prolongation  oi  the  anterior  subdural 
space  of  the  cord.  The  lower  part  of  the  brain-stem  is  thus  completely  surrounded 
by  the  subarachnoid  cavity.  The  ventral  surface  of  the  pons  is  enveloped  by  the 
upward  extension  of  the  anterior  part  of  the  spinal  arachnoid,  the  cleft  so  enclosed 
constituting  the  cisterna  pontis,  of  which  a  median  and  two  lateral  subdivisions 
may  be  recognized.  From  the  upper  ventral  border  of  the  pons  the  arachnoid 
passes  forward  to  the  orbital  surface  of  the  hronUl  lobes,  covering  the  corpora  mam- 
millaria,  the  infundibulum  and  the  optic  chiasm,  and  laterally  to  the  adjacent  project- 
ing temporal  lobes  and  thence,  covering  in  the  transverse  stem  of  the  Sylvian  fissures. 

Fig.  1038. 


Olfactory  tract. 


Optic  chiaun 

Intemftl  cmrotid 
artery 


Kasilar  artery 


Vertebral  arteriei 


Eztctuioa  along 
laigittKlilial  fiiaure 


Extenaion  akMiK 
Sylvian  fiaanrc 


Cisterna  liaialis 


ClMaiia  pootia 


Cistenia  maittta 


Inleriur  aspect  o(  braiti  covered  with  i^-i  and  arachnoid,  showing  large  aubarachuoid  spacca. 

to  the  frontal  lobes.  This  large  space,  which  includes  the  deep  depression  on  the 
basal  surface  of  the  brain,  is  the  cisterna  basalis.  It  is  imperfectly  subdivided  by 
incomplete  septa  of  arachnoid  tissue  into  secondary  compartments,  one  of  which  lies 
between  the  peduncles  (cisterna  interp«<luna>laris),  another  behind  the  optic  commis- 
sure (cisterna  chiasmatis)  and  a  third  above  and  in  front  of  the  chiasm  (cisterna 
laminae  terminalis).  Anteriorly  the  cisterna  basalis  is  continued  over  the  convex 
dorsal  surface  of  the  corpus  callosum  (cisterna  corporis  callosi),  and  on  either  side 
along  the  stem  of  the  Sylvian  fissure  (cisterna  fissurae  lateralis).  Within  the  median 
region  of  the  cisterna  tesalis  lie  the  large  arterial  trunks  forming  the  circle  of  Willis. 
These  vessels  are  invested  with  delicate  sheaths  of  arachnoid,  which  accompany  the 
smaller  branches  until  they  enter  the  vascular  membrane  to  become  pial  vessels. 

The  arachnoid  also  contributes  sheaths  to  the  cranial  ner\'es  as  they  pass  from 
their  superficial  origins  to  the  points  where  they  pierce  the  dura,  these  sheaths  over- 
lie those  derived  from  the  pia  and,  as  do  the  latter,  accompany  the  nerve-trunks  for  a 


THE  MEMBRANES  OF  THE  BRAIN. 


iios 


;  ^ccWonton  body 
mn.  n(l«t«i  mwltallv                        \^ 

CrrtlTal  vtin                             N^^^MBii 

Fig.  1039. 

Ccrcbnl  vrin 

Aitery  in                '■', 

f '■^•'^aiaHi^^.  .|iK'^ 

?%*^^n 

kmsUndlaal  >inu*. 

Sheaths  into  a  subdural  and  a  subarachnoid  perineural  con^partment.  directly  contin- 
uous with  the  corresponding  intracranial  spaces,  ventricles 

As  previously  noted,   the  "f^'^^^?'",^  £^h  tS[Scl^ 
escapes  tLough  the  openings  m  ^^'^'^''^^^^^^  space.     After 

and  the  foramina  of  ^uschka  (page  i  00)     m^^^^^ 

fiUing  the  cistema  magna  and  the  o»%'^8^X  ite  way  into  the  smaller  spaces  on 
and  surrounding  the  spmal  «=«'?•  ^Jf^'^^J^.'^'th? e*^^^^  mass  of  nervous  tissue  is 
the  exterior  of  ^^e  c-^^j^  ..i-^jJ^^S^^^^  particularly  at  the  base 

^rt£  somtSi^trmiT^^^^^  - '--  -^-  — ^ 

conditions,  the  maintenance  of  mtra- 

cranial    and    intracerebral    pressure  Fig.  .04 

within  due  limits.    The  paths  by  wl»  ch 

this  is  accomplished  include  :  (i )  tne 

extension  of   »''e  subarachnoid  space 

along  the  nerve-trunks,  and  (2)  the 

villous  projections  of  arachnoid  tissue. 

the    Pacchionian    bodies,    along    the 

course  of  the  dural  blood-sinuses. 

The  Pacchionian  bodies  (gran- 

ulaUones  arachnoidales)  are  numerous 

cauliflower-like    excrescences    of    the 

arachnoid,  for  the  most  part  small  but 

occasionally   reaching   a   diameter   ot 

S  mm.  or  over,  which  lie  on  the  outer 

surface   of    the   membrane  along  the 

course  of  the  dural  venous  sinuses 

Their  favorite  site  is  on  either  side  ot 

the  superior  longitudinal  sinus    where  ^^^^^^  ^^^  ^.^^  -^  ^  . 

they  occur  in  groups,  ^'h.  ugh  th>   occur   ns  ^^^  ^ 

iX*  Sets  'riStS\Crr /W,.  ..r'*W-««.  in  «  „«»» 


Diagram  »ho«.n.  r..a|i.r«  o.  ^cchjojj.^.L^JJ^Ju;" 


12o6 


HUMAN   ANATOMY. 


they  encroach  upon  the  lumen  of  the  main  channel  itself,  within  which  they  appear 
as  irregularly  rounded  projections  on  its  lateral  walls.  Whatever  their  relation, 
whether  with  the  sinus  or  the  lateral  diverticula,  the  Pacchionian  bodies  never  lie 
free  within  the  blood-space,  but  are  always  separated  from  the  latter  by  the  dural 
wall.  0\er  the  summit  of  the  elevation  the  dura  becomes  jjreatly  attenuated,  but 
never  entirely  disappears,  so  that  only  a  thin  membrane  and  the  subdural  cleft, 
theoretically  present  but  practically  more  or  less  obliterated,  intervene  between  the 
subarachnoid  spaces  and  the  blood-stream.  This  partition  offers  little  obstruction 
to  the  passage  of  the  cerebro-spinal  fluid,  which,  unless  the  pressure  within  the 
venous  channel  is  higher  than  that  within  the  subarachnoid  space,  passes  from  the 
latter  into  the  sinus  and  thus  relieves  the  intracranial  tension.  When  well  developed, 
as  they  often  are  after  adolescence  but  never  during  childhood  when  they  are 
small  and  rudimentary,  the  Pacchionian  bodies  are  frequently  lodged  in  depressions 
within  the  calvaria,  whose  inner  surface  is  sometimes  so  deeply  pitted  that  the  bone 
in  places  is  translucent. 

THE    BLOOD-VESSELS    OF    THE    BRAIN. 

The  course  and  distribution  of  the  individual  blood-vessels  supplying  and  drain- 
ing the  nervous  tissue  of  the  brain  have  been  described  in  the  sections  on  the  Arteries 
(page  746)  and  the  Veins  (page  861).  It  remains,  therefore,  only  to  consider  at 
this  place  the  more  general  relations  concerning  these  vessels. 

The  arteries  supplying  the  brain  are  derived  from  two  chief  sources — the  inter- 
nal carotid  and  the  vertebrEd  arteries.  After  entering  the  cranium  these  vessels  and 
their  branches  form  the  remarkable  anastomotic  circuit  known  as  the  circle  of  Willis 
(page  760).  The  latter  gives  off,  in  a  general  way,  two  sets  of  branches,  the  gang- 
lionic— for  the  most  part  short  vessels  which  soon  plunge  into  the  nervous  mass  to 
supply  eventually  the  overlying  intetial  nuclei,  the  corpora  striata  and  the  optic 
thalami — and  the  cortical,  which  pursue  a  superficial  course  and  are  carried  by  the 
pia  mater  to  all  parts  of  the  extensive  sheet  of  cortical  gray  substance,  as  well  as  to 
the  .vjbjaccnt  tracts  of  medullary  white  matter. 

The  medulla  oblongata  and  the  pons  are  supplied  by  branches  from  the  anterior  spinal,  the 
vertebral,  the  basilar  and  the  posterior  cerebral  arteries.  These  branches  gain  the  nervous 
substance  as  two  sets,  the  radicular  and  the  median.  The  radicular  branches  follow  the  nerve- 
roots  and,  just  before  reaching  the  superficial  origins  of  the  nerves,  divide  into  peripheral  and 
central  twigs,  the  former  being  distributed  superficially  and  the  latter  following  the  root-fibres 
to  their  nuclei.  The  median  branches  are  numerous  minute  vessels  which  ascend  within  the 
median  raphe  towards  the  floor  of  the  fourth  ventricle  and  assist  the  centrally  directed  twigs  of 
the  radicular  branches  in  supplying  the  nuclei  of  the  nerves  situated  within  that  region.  Those 
supplying  the  nuclei  of  the  hypoglossal  and  the  bulbar  portion  of  the  spinal  accessory  nerves 
are  derivations  from  the  anterior  spinal  arteries ;  those  to  the  nuclei  of  the  vagus,  the  glosso- 
pharyngeal and  the  auditory  are  from  the  vertebral  as  they  join  to  form  the  basilar ;  whilst 
those  to  the  nuclei  of  the  facial,  the  abducent  and  the  trigeminal  are  from  the  basilar.  The 
choroid  plexus  of  the  fourth  ventricle  is  provided  with  branches  from  the  posterior  cerebellar 
arteries. 

The  cerebellum  receives  its  supply  from  three  arteries,  the  anterior  and  posterior  in- 
ferior and  the  superior,  cerebellar.  The  general  course  of  these  vessels  is  approximately  at 
right  angles  to  the  direction  of  the  fissures  and  folia  of  the  hemispheres.  In  the  mid-brain  the 
interpeduncular  space  is  provided  with  branches  from  the  basilar  and  the  posterior  cerebral  arter- 
ies ;  the  cerebral  peduncles  with  those  from  the  posterior  communicating  and  the  terminal  part 
of  the  basilar ;  and  the  corpora  quadrigcmina  with  those  from  the  posterior  cerebral,  additional 
twigs  passing  from  the  superior  cerebellar  to  the  inferior  colliculi. 

The  thalamus  is  supplied  by  branches,  all  end-arteries,  from  different  sources,  those  for  its 
antero-median  portion  being  from  the  posterior  communicating,  those  for  its  antero-lateral  por- 
tion from  the  middle  cerebral,  whilst  those  for  its  remaining  parts,  as  well  as  for  the  pineal  and 
the  geniculate  bodies,  iire  from  the  posterior  cerebral.  The  last  vessel  also  supplies  the  velum 
interpositum  and  the  choroid  plexus  of  the  third  ventricle. 

The  structures  ou  tlie  base  of  the  brain,  such  as  the  corpora  mammillaria,  the  tuber  cine- 
reum,  the  infut.r'ibulum  and  the  pituitary  body,  receive  twigs  from  the  posterior  communicating 
arteries.  The  optic  i-hiasm  and  tract  are  supplied  with  branches  from  the  anterior  cerebral,  the 
anterior  eomn.utii'.tliiig.  the  internal  carotid,  the  pwjterior  communicating  .ind  the  anterior 
choroidal  arteries. 


PRACTICAL  CONSIDERAnC>NS:  THK  HRAIN. 


1207 


The  corpu..tri.tum.  both  the  caudate  and  Wnucuiarnuc..^^ 
ftomS^m^lecerebral  artery'  which  Pi-'--}^^':^'^^:^:'^:^Z'tuXn6c^l.r  nucleus 
^ticulo^triate  and  lenticulo-thalam.c  ^f^^'^'i'^^^^Ss  and  the  thalamus.     One  of  the 
and  the  internal  capsule  and  •-— ^   L^uter  ^ "  of  the  putamen.  w.«  named  by  Charcot 

S:anterior  and  lower  part  of  *e  ctoroda^^^^^^     the  hj^ampus.    The  posterior  chorouia 
ent  portion  of  the  vascular  ~'nP>^;  "'''^y,'^^^^^^^^^  i^Trived  from  the  posterior  cerebral 

artery,  usually  represented  by_  a  numb  r  "^  ^^^^^^^^'^j^'    ,^^  ,,,„„,  mterpositum.  it  completes 
and  enters  the  upper  part  of  the  n^^"'^^-    ^"'^'.    ^ie  b,5y  of  tl'c-  lateral  ventricle, 
the  choroid  plexus  in  the  ^e^^^ndrng  hom  and  m  the  ^^^^^^  ^^  ^^^  ^„,^rior.  middle  and 

The  cerebral  hemLpheres  are  supplied  by  ff  ^"™>^   .     ,         j  ^^^  jg  distributed  to  the 

posterior  cerebral  arteries     Of  ^l^^- *«J"^,t  "^^'^^  Jot  K  the  external  surface  of  the 
^st  extensive  area,  which  f^^races  the  greater  i^rt  but  no  ^^^.^^^  ^^^^^^  ^^^ 

hemisphere.  This  vessel  also  ^PP'i;*^^  "^^™bra,  iT^ntially  the  artery  of  the  mesia 
anterior  part  of  the  temporal  lobe.  The  ?n™^^^™  j^^  an  adjoining  zone  on  the  external 
surface,  the  anterior  two-th.rds  of  wh.ch. '"  ^^  ^^^^'^j  ^^e  posterior  cerebral  is  chiefly  on 
•  and  on  the  orbital  surface,  it  suppl  es.  J}^.^'^°"^^^  region,  and  in  addition  an  adjommg 
the  mesial  and  tentorial  surface  of  the  °^^^P"^°;  ^^P^™ /'^ follows,  therefore,  that,  with  the 
strip  along  the  postero-in  erwr  "'.^^K'"  °*  *^^^;™S  by  the  posterior  cerebral  artery,  all  of 

rrv^nt'^r.rifis'^f'Thet^isp^^^^^^^^^ 

-"'-The  .^n..l  lob.  is  supplied  by  the  anterior  -ebral  anery^^^^^^^^ 

over  the  superior  and  the  anterior  »*"-'»'';^^^  "'^'^^^^.'S^!^,  ^^^^^     internal  to  the  orbital  sulcus 

st-Lii^'^r^^^^iT^^^^^^^  ^'^ '--'- "'  ^"  """'''  '''''''' 

''"' V  p-rieul  lob.  is  supplied  by  the  ^^^  rrtTg^h^r^XKeK!!^^: 
exception^  a  narrow  strip  along  the  "PP^^,^"'^!!  '  *^hr^^;ip°S  lobe  is  supplied  exclusively 

districT*!:.";i;rirert=;*'rhf^r7^^^  vicim^  of  the  isthmus.  Whilst  that 

ollhe  p^terior  cerebral  includes  the  remamder  of  the  lobe. 

The  veins  returning  the  blood  .^--^V'^trwltuSd  1'^^^^^^^^^^ 
sinuses,  and  they  therefore  on  y  to  ^''/"'*^J*X""^£;^^^  of  vXes.     The  superior 
arteries.     They  are  further  d«t«ngu.shed  by  the  ateenc^^^^^  ^.^^^  ^^^ 

cerebral  veins,  after  emerging  from  ^'^^^/^^^^'j'o;"^  "for  the  most  part,  towards 
over  the  convex  aspect  f  jhe  hem^ph^re  and  PJ^-„«^^;£^  directly  or'lhrough  the 
the  superior  longttudmal  ^^"^  ^„^f  V'tfvei^  draining  the  structures  situated 
lacunae  laterales,  by  from  12-15  f"'""";    ,  ^  ..^^v  to  the  paired  lesser  veins  of  C.alen, 

falx  cerebri  and  the  tentorium  cerebelli. 

PRACTICAL  CONSIDERATIONS.  THE   BRAIN   AND   ITS 
MEMBRANES. 

Con,.niial  Errors  of  /^-/''/^--'•-^'^"t^^^^^^^^  t^l 

brain  an^d  its  membranes  f-  -^^  ^^^Tr"^^^^ 
cet>halus),  it  may  escape  from  the  skull  K^-^^f^P"r'\  ''      .here  may  be  arrest  of 


I208 


HUMAN  ANATOMY. 


The  most  common  enlargement  of  the  head,  hydrocephalus,  is  due  to  a  retention 
of  cerebro-spinal  fluid  within  the  cranium,  ordinarily  within  the  ventricles,  but  some- 
times in  the  subarachnoid  space.  It  is  usually  a  congenital  condition ;  its  cause 
is  not  clearly  known.  It  is  believed  by  many  that  it  is  due  to  a  prenatal  inflam- 
mation of  the  ventricular  ependyma,  and  by  others  to  a  disarrangement  of  the  orifices 
of  communication  between  the  ventricles  (Luschka,  Monro,  and  Neurath).  The 
aqueduct  of  Sylvius  has  been  found  obliterated,  and  inflammatory  processes  have 
been  seen  about  the  foramen  of  Monro. 

Congenital  defective  ossification  of  the  skull  may  result  in  a  gap  through  which 
may  protrude  a  portion  of  the  meninges  with  or  without  brain  substance.  If  such  a 
protrusion  consists  of  a  meningeal  sac  containing  only  fluid,  it  is  called  a  meningocele. 
If  it  contains  a  portion  of  the  brain  also,  it  is  an  encephalocele,  and  if  the  protruded 
portion  of  the  brain  encloses  a  portion  of  a  ventricle,  a  hydrencephalocele.  Such 
tumors  may  be  concealed  from  view  at  the  base  of  the  skull,  or  in  the  pharynx,  or 
may  protrude  into  the  nose  or  orbit.  They  are  usually  in  the  median  line  and  most 
frequently  in  the  occipital  region.  Next  in  frequency  they  occur  at  the  fronto-nasal 
suture,  and  more  rarely  in  other  parts  of  the  skull.  Pressure  on  the  tumor  will  often 
reduce  it  partly  or  completely  within  the  cranium,  but  in  the  latter  case  symptoms  of 
pressure  on  the  brain  will  arise.  Violent  expiratory  efforts,  as  in  crying  or  coughing, 
which  increase  the  cerebral  congestion,  render  the  tumor  more  tense. 

The  Meninges. — Diseases  of  the  meninges  are  relatively  more  common  than 
those  of  the  brain  proper,  and  many  conditions  often  spoken  of  as  brain  diseases  are 
affections  of  the  meninges,  the  pia  being  closely  adherent  to  the  brain  and  extending 
into  the  fissures.  Inflammation  of  the  dura  is  called  pachymeningitis,  of  the  pia  and 
arachnoid  together  lepto-meningUis. 

External  pachymeningitis  is  usually  secondary  to  disease  of  the  cranial  bones, 
traumatism,  infection,  or  tumors.  It  is  most  frequently  the  result  of  ear  disease,  and 
is  therefore  generally  of  surgical  interest. 

Internal  pachymeningitis  is  apt  to  be  associated  with  effusions  of  blood  in  o  the 
subdural  spiace  ;  they  may  cover  a  considerable  area  without  producing  marked  symp- 
toms, or  they  may  be  encapsulated  (haematomata  of  the  dura  mater),  and  may  reach 
the  size  of  a  man's  fist,  causing  compression  of  the  brain.  Occasionally  they  become 
purulent.  The  blood  or  pus  may  gravitate  to  the  base  of  the  brain  in  the  region  of 
the  cerebellum,  pons,  and  medulla,  when  the  pressure  symptoms  will  be  more  serious ; 
or  it  may  find  its  way  into  the  spinal  canal. 

The  dura  is  ecpecially  adherent  at  the  base  of  the  skull  and,  to  some  degree,  at 
the  sutures  of  the  vault.  In  the  rest  of  the  vault  it  is  loosely  attached,  and  accord- 
ing to  Tillaux,  particularly  so  in  the  temporal  region.  Collections  of  blood  may 
accumulate  between  the  dura  and  the  bone  {extradural  hemorrhage).  This  variety 
of  intracranial  hemorrhage  is  commonly  the  result  of  rupture  of  one  of  the  branches 
of  the  middle  meningeal  artery  in  the  temporal  region,  the  effused  blood  separating 
the  loosely  attached  dura.  If  the  blood  is  poured  out  rapidly,  compression 
symptoms  will  soon  appear,  but  if  the  hemorrhage  is  slow,  the  escape  of  cerebro-spinal 
fluid  into  the  spinal  canal  permits  of  more  delay  in  the  appearance  of  these  symptoms. 
The  patient  has  often  time  to  recover,  at  least  partially,  from  the  unconsciousness 
of  concussion  before  that  of  compression  appears  ;  and  it  is  this  recovery  of  mtelligence 
which  is  most  characteristic  of  the  condition.  There  will  often  be  localizing  symptoms 
indicating  the  part  of  the  brain  cortex  which  is  irritated  or  compressed. 

Subdural  hemorrhage  may  follow  the  rupture  of  a  number  of  small  vessels,  either 
of  the  pia  or  dura  under  a  depressed  fracture  ;  or  it  may  come  from  a  large  vessel, 
particularly  the  middle  cerebral.  The  symptoms  and  treatment  are  very  much  the 
same  as  in  the  extradural  variety. 

In  children  extradural  hemorrhage  is  very  rare,  because  of  the  relatively  firmer 
attachment  of  the  dura  during  the  period  of  growth.  The  blood  may  escape  under 
the  scalp  through  a  line  of  fracture  in  the  skull ;  or,  what  is  more  likely,  it  may  pass 
through  a  tear  in  the  <lura  into  the  subdural  space.  In  fractures  of  the  base  of  the 
skull,  at  any  age,  owing  to  the  adhesion  of  the  dura,  the  latter  is  likely  to  be  torn  ; 
cerebro-spinal  fluid  may  escape  into  the  adjacent  air  cavities,  as  into  the  nose,  pharynx 
or  middle  ear.     A  close  adhesion  of  the  dura  to  the  bone,  as  sometimes  found  at 


PRACTICAL  CONSIDERATIONS  :  THE  BRAIN. 


1209 


''''''ZtZZ^::J7uir^S^^t;i..  subdural  and  suba^chnoid  spaces   and 
;„  fhlvenTricS     O^er  the  vault  it  is  comparatively  scanty  in  both  spaces.     At  the 

mcio  to  vlulfmcMon,  rat  directly-  ■     ' '"  ^"'/J^^^Hhi  ...brachnoid 

*tT7.  ,Tcm  f  2  -^-Hn  )  vertically  above  the  external  auditory  meatus.  Under 
skull,  6.5-7.5  cm-  V2>^  3  '"-^J^,".  J._  ,_,  f.  ._  (a-2Vi  n.)  from  the  surface, 
normal  circumstances  the  ventricle  is  from  5-5.0  cm.  (,*  ^y9      -j 

subarachnoid  s|,ace.  3^^^i„„^„j  .^e  brain.  h.n,arr„aj,e  is  the  «""«»  frequent 

the  production  of  miliary  aneurisms^  A  sudden  s  r^  ^^^'^^^^..^  ,^p^,^,, 
tension  and  ruptures  one  of  these  diseased  vessels,  piMng  rise  i    | 
depending  on  the  seat  and  extent  of  the  hcmoirhaRC. 


I2IO 


HUMAN  ANATOMY. 


The  cortex  is  supplied  by  pial  vessels  distinct  from  those  supplying  the  basal 
ganglia  and  adjoining  regions.  The  latter  come  direcdy  from  the  branches  of  the 
circle  of  Willis  at  the  base.  The  cortical  vessels  anastomose  ;  those  in  the  region 
of  the  basal  ganglia  do  not.  The  latter  are  "end  arteries,"  so  that  when  one  is 
plugged  by  an  embolus  the  part  supplied  is  deprived  of  blood  and  undergoes 
necrosis  (softening  of  the  brain).  In  such  a  case  the  cordcal  supply  would  not  be 
permanendy  interfered  with.  VVhen  a  cortical  arteriole  is  blocked,  the  anastomosis 
may  furnish  a  sufficient  collateral  circulation  to  prevent  necrosis  in  the  affected 
part,  but  cortical  softening  is  e.\ceedingly  common.  When  one  of  the  arteries  forming 
the  circle  of  Willis  is  occluded,  as  an  internal  carotid  by  ligation  of  the  common 
carotid,  the  anastomosis  in  the  circle  is  so  free  that,  in  most  cases,  no  marked 
effect  is  apparent.  Cerebral  disturbances,  as  delirium  or  convulsions,  do  occur  in 
some  cases,  and  in  some  are  fatal.  Even  when  both  carotids  are  ligated,  with  an  in- 
ter\'al  of  some  days  or  weeks,  the  operation  is  not  more  frequendy  followed  by  cere- 
bral disturbances  than  when  only  one  is  tied  (Pilz).  A  case  in  which  the  patient 
lived  after  one  carotid  and  one  vertebral  had  been  obliterated  by  disease,  and  the 
other  carotid  ligatured,  has  been  reported  (Rossi).  In  another  case,  although  both 
carotids  and  both  vertebrals  had  been  occluded,  the  patient  lived  a  considerable  time 
afterward,  the  cerebral  circulation  being  maintained  through  the  medium  of  anas- 
tomosis of  the  inferior  with  the  superior  thyroids,  and  the  deep  cervical  with  the 
occipital  artery  (Davy).  Occasionally  ligation  of  the  carotid  has  been  followed  by 
hemiplegia. 

The  most  common  seat  of  intracerebral  hemorrh^e  is  near  the  basal  ganglia  in 
the  region  of  the  internal  capsule.  The  artery  most  frequendy  at  fault  is  a  branch  of 
the  middle  cerebri,  the  lenticulo- striate,  or  artery  of  Charcot  (page  1207).  Hemor- 
rhages occur  with  less  frequency  in  other  portions  of  the  cerebrum,  and  much  more 
rarely  in  the  pons,  medulla  oblongata,  and  cerebellum.  The  symptoms  produced  by 
the  hemorrhage  are  the  result  of  destruction  of  tissue  and  of  pressure  upon  adjacent 
parts,  and  will  vary  according  to  the  seat  of  the  lesion.  Tumors  or  inflammatory 
products  will  produce  essentially  the  same  symptoms. 

Cerebral  Localization. — In  order  to  understand  the  nature  of  the  symptoms 
pr-jduced  by  brain  lesions  it  will  be  necessary  to  study  at  least  some  of  the  functional 
areas  of  the  cortex  and  their  paths  of  conduction  through  the  brain  substance. 

Taylor  has  summarized  as  follows  the  researches  of  His  and  of  Flechsig,  which 
are  of  comparatively  recent  date  and  have  thrown  new  and  valuable  light  upon  the 
functions  possessed  by  the  cortical  regions  of  the  brain,  by  the  study  of  their  mode  of 
development.  Flechsig  succeeded  in  following  the  various  tracts  through  their 
myelination.  The  tracts  which  are  functional  earliest  receive  their  myelin  before  the 
others.  He  has  shown  that  the  fibres  in  the  spinal  cord,  medulla,  pons  and  corpora 
quadrigemina  are  almost  entirely  meduUated  when  the  higher  parts  show  littie  or  no 
myelin.  In  the  new-born  child  the  cerebrum  is  almost  entirely  immature,  and 
proportionately  few  of  its  fibres  are  meduUated. 

According  to  Flechsig,  the  sensory  paths  in  the  brain  first  become  meduUated, 
and  may  be  observed  devdoping  one  after  another,  beginning  with  that  of  smell  and 
ending  with  that  for  auditory  impulses  from  the  periphery  to  the  cortex.  In  this 
way  it  has  been  ascertained  that  the  individual  sensory  paths  terminate  in  tolerably 
sharply  circumscribed  cortical  regions,  for  the  most  part  widely  removed  from  one 
another,  being  separated  by  masses  of  c^jrtical  substance  which  remain  for  a  consid- 
erable period  immature  or  undeveloped.  The  cortical  sense  areas  thus  mapped  out 
correspond  entirely  to  those  regions  of  the  surface  of  the  brain  which  pathological 
observation  has  shown  to  stand  in  relation  to  the  different  qualities  of  sensation. 
Olfactory  fibres  are  found  to  end  mainly  in  the  uncinate  gyrus.  Visual  fibres  have 
been  traced  to  the  occipital  lobe  in  the  neighborhood  of  the  calcarine  fissure,  and 
auditory  fibres  to  the  temporal  lobe.  Flechsig  has  further  observed  that  new  paths 
begin  to  develop  from  the  points  where  certain  of  the  sense  fibres  terminate  and  pur- 
sue a  downward  course.  They  can  be  followed  from  the  cortex  to  the  medulla  and 
to  the  motor  nuclei  of  the  cord.  These  descending  paths  are  mainly  those  known  as 
the  pyramidal  or  rnotor  tracts,  and  the  area  from  which  they  proceed,  commonly 
called  the  Rolandic  region,  is,  according  to  Flechsig,  concerned  also  in  the  sensation 


PRACTICAL   CONSIDERATIONS  :  THE  BRAIN. 


I3II 


Of  touch  ;  he  calls  it  the  --£(,-- JUl"ffiLt^^^^^^^^^^ 
eonvolution,.^he  P--^^f  t'exS'  "0^^^ ^^^  temperature. 

^"^  ll?.^d  Tendon^nse  Suilibrium,  etc.  This  cortical  region  probably  repre- 
muscle-  and  5^"°°"  f  "f '  ^""^entres  rather  than  a  single  sensory  area,  and  in 
TdSoVrtrngTsenUTfie^rre  som^thetic  areal  tHe  ,r.ai  n,otor  r.,.on 

"-^^^t^JheiTthis  sensory-motor  area  and  the  various  sensory  areas  are  fully  taken  into 

,   thirpstm  Sin  atout  two-thirds  of  the  cortex  which  appear  to  have  noth- 

•'T"l  irkh  the  SLr7     nJThsig  calls  these  regions  of  the  cortex  - assoaa- 

;^  LtX'  ■  al  heSvLV  furnish  arrangements  for  uniting  the  various  central 

"^""Vhe  b^t  known  cortical  areas  are  the  motor,  speech,  visual,  and  auditory,  al- 
The  best  ''"?r^".'-""'~' „_  Unnwled^e  are  beine  made  from  Ume  to  time.     Re- 
though  new  contnbut^ons  to  o^^^^^^  .^  ^^^  ^^^^^  ^j  ^^^^^^ 

cently.  Gr"n^"™/"f  ^hern^^^^^  ^^  the  chimpanzee  and  gorilla,  that  the 

2r"^eat£  founTinMe  w^ole  len^h  of  the  precentral  convolution  and  the  en- 

Fig.  1041. 


Lcit 


crebr.1  hemi.phere  illu^nnlng  dtap.mm.tic.ny  molor  zone  .nd  lu  .ubdivl.ion..    (MUU.) 


tire  length  of  the  central  fissure.     It  did  not  at  any  point  extend  ^^f  ^  f  X"^^ 
f^«ure     They  demonstrated  other  important  facts  in  ^°^^^''ZZnth\Z\^x<TZ 
o^ol      Thpse  results  have  been  in  part  at  least  confirmed  by  recent  histological  re 
^hes  Sbv  fartdSoTof  the  human  brain  during  operation  for  the  purpose 
^^or^^ccurat^ly  M^       the  relations  of  the  opening  to  the  ar^  to  ^  expo^^ 

The  most  important,  because  the  best  known   area  of  the  cortex,  is  that  asso 
ciated  with  the  fissure  of  Rolando  and  l'...  fissure  of  Sylvius. 

Before  the  publication  of  the  experiments  and  observations  just  alluded    o  the 

ooinion  is  now  in  favor  of  the  view  that  the  motor  region  is  entirely  or  almost  en- 
STn  front  of  the  central  fissure  (Monakow,  Mills).  This  '  V'Tuo^^s^to  S 
of  considerable  importance  in  trephining  for  a  tumor  "^  .'?^X  Jride  Ke  fiSu^ 
situated  in  this  ar^.  as  instead  of  making  the  opemng  f'rectly  astnde  of  the  h^»;« 
of  Rolando  it  would  be  better,  if  these  views  are  correct,  to  operate  with  the  laea  01 
exS^ng  a  Je^on  two-thirds  or  three-fourths  i«  front  and  one-third  or  one  '  >.,rth 
behind  nie  centrm  fissure. 


i3ia 


HUMAN  ANATOMY. 


In  the  lower  one-third  or  fourth  of  the  motor  zone  are  found  the  motor  centres 
for  the /ace  and  tongue,  that  is,  for  the  fadal  and  hypoglossal  nerves.  In  the  middle 
third  or  half  are  the  arm  centres.  In  the  upper  part  of  the  region  and  paracentral 
lobe,  are  the  centres  for  the  lower  extremity.  Localized  lesions  of  the  motor  zone 
may  therefore  produce  a  paralysis  limited  to  one  part  controlled  by  the  affected  por- 
tion of  the  cortex,  as  of  the  face,  arm  or  leg  (monoplegia).  The  lesion  is  much 
more  likely  to  involve  two  adjacent  areas,  as  of  the  face  and  arm,  or  of  the  arm 
and  leg,  giving  rise  to  a  combined  paralysis ;  but  no  single  lesion,  unless  it  were 
crescentic  in  form,  could  involve  at  the  same  time  the  leg  and  face  areas  without 
including  the  intervening  arm  area. 

Within  each  of  the  larger  areas  a  more  s[>ecialized  differentiation  is  possible, 
although  none  of  them  can  be  sharply  defined,  not  even  the  larger.  That  the  facial 
centre  lies  in  the  lower  part  of  the  anterior  central  convolution  is  certain,  and  it  is 
believed  that  the  upper  and  lower  muscles  of  the  face  are  each  represented  by  a  sepa- 
rate centre.  In  the  upper  and  forward  part  of  the  bce-ar^a  are  represented  the 
movements  of  the  cheek  and  eye-lids ;  in  the  posterior  part  the  movements  of  the 
pharynx,  platysma  and  jaws. 

Fig.  I0I43. 


Diasntm  illiutrating  protwblc  reUtioni  oi  physiological  areu  and  centres  of  latenl  aspect  of  left  cerebral 

hemisptacre.    (MUU.) 

In  the  arm-area  it  is  considered  as  certain  that  the  centre  for  the  movements  of 
the  thumb  and  index  finger  is  below;  above  is  that  for  the  finger  and  hands;  and 
in  the  highest  part  is  that  for  the  shoulder.  In  the  posterior  parts  of  the  second 
frontal  convolution  and  in  a  portion  of  the  third  frontal  convolution  are  the  centres 
for  the  associated  lateral  movements  of  the  eyes  and  lateral  movement  of  the  head 
(Beevor  and  Horsley). 

Our  knowledge  of  the  more  special  localization  within  the  leg  centre  is  not  at  all 
exact,  and  the  many  views  held  are  very  contradictory.  It  is  believed  that  the 
centres  for  the  movements  of  the  thigh,  knee,  foot,  and  toes,  are  arranged  in  the 
order  named,  from  before  backward  on  the  lateral  border  of  the  hemisphere  and  in 
the  paracentral  lobe. 

A  narrow  zone  for  the  movements  of  the  trunk,  as  shown  by  Griinbaum  and 
Sherrington,  is  located  between  the  upper  border  of  the  arm-area  and  the  lower 
border  of  the  leg-area.  It  is  now  considered  probable,  however,  that  the  cutaneous 
sensory  centres  are  posterior  to  and  in  close  contact  with  the  motor  centres  in 
the  postcentral  convolution,  while  other  centres  for  stereognostic  perception  and  the 
muscular  sense  are  located  in  the  s'lperior  and  inferior  parietal  convolutions. 

The  speech  centres  are  in  the  posterior  part  of  the  third  left  frontal  convolution 
(Broca's  convolution),  in  right-handed  people  in  the  first  left  temporal  convolution, 
and  perhaps  in  the  left  angular  g^rus. 


PRACTICAL  CONSIDER. iTlONS  :  THE  BRAIN. 


I3I3 


In  Broca-s  convolution  is . probably  ^he  centre  for^^^^^^^ 

a„d  a  le«on  *"«  P"'t%'?TXl?l  IdtotS     The  exiMence  ol  .  motor 

although  it  is  probably  near  the  centre  for  smell. 

Fig.  1043. 


The  auditory  centre,  as  indicated,  is  in  the  upper  tempo|Blc.nvolutbn^   It « 

aUh»gh  the  tactions  of  •»7i"^  U!SeSve  S'ut  notable  .ymptoms  ol  any 
"p^yX^'taSS,"  tSSl  i.l'the'^JSronLihe,,  the  H.  .ide  bein„  perhaps 
and  of  the  temporal  to  nearmff     .'"^ !,„__„  .„_tre   while  the  lateral  a.spect  of  the 

'4K  -"£^eiI=iSr^»5s==r!ifn 

i'S,;SEpr.o|^!^p'™^^^^^^^ 


I3I4 


HUMAN  ANATOMY. 


i 


also  by  a  lesion  in  the  lateral  portion  of  the  occipital  lobe,  if  it  extends  inwards 
sufficiently  to  interrupt  the  optic  radiations. 

In  spite  of  extensive  researches  the  functions  of  the  central  ganglia  are  very 
little  known. 

Lesions  of  the  cerebellar  hemispheres  may  not  produce  distinct  phenomena 
until  the  median  lobe  or  vermiform  process  is  involved,  when  two  especially  charac- 
teristic symptoms  will  almost  certainly  develop.  These  are  a  peculiar  disturbance  of 
equilibrium  with  a  staggering  gait  (cerebellar  ataxia),  and  a  troublesome  vertigo. 
Although  the  patient  can  scarcely  stand  alone  he  may  possibly  be  able  to  perform 
the  most  delicate  movements  with  his  upper  extremities.  The  vertigo  occurs  only 
in  standing  or  walking,  and  is  then  almost  always  present.  Nystagmus  is  also  a 
frequent  symptom.  Vomiting  is  very  often  present,  but  is  not  characteristic,  since 
it  is  equally  frequent  in  other  brain  diseases. 

Extending  along  the  floor  of  the  aqueduct  of  Sylvius  and  of  the  fourth  ventricle, 
that  is,  along  the  cerebral  peduncles,  pons  and  medulla,  we  find  the  nuclei  of  origin 
of  the  motor  fibres  of  the  cranial  nen-es.  It  should  be  borne  in  mind  that  the  con- 
trolling centres  of  these  nerves  are  in  the  cerebral  cortex.  Many  automatic  centres, 
as  of  circulation,  respiration,  sweating,  and  regulation  of  heat,  as  well  as  the  motor 
and  sensory  tracts  are  found  in  the  medulla. 

Cranio-Cerebral  Topography. — In  order  that  the  surgeon  may  expose  and 
recognize  certain  areas  of  the  cortex,  it  becomes  very  important  that  the  relations 
between  these  areas  and  the  corresponding  external  surface  be  well  understood.  For 
this  purpose  advantage  is  taken  of  the  landmarks  of  the  skull  (page  241).  From 
these  bony  points,  ridges  and  depressions,  by  means  of  lines  and  measurements,  the 
known  cortical  areas  may  be  accurately  mappied  out. 

The  upper  limit  of  each  cerebral  hemisphere  is  indicated,  approximately,  by  the 
median  line  at  the  top  of  the  skull  from  the  glabella  to  the  external  occipital  protu- 
berance, due  allowance  being  made  for  the  superior  longitudinal  sinus,  which  lies 
under  the  skull,  in  the  longitudinal  fissure,  between  the  two  hemispheres. 

The  lower  limit  is  represented  by  a  transverse  line,  in  front,  just  above  the  upper 
margin  of  the  orbit.  At  the  side  of  the  skull  the  line  passes  from  about  a  half  inch 
abo\e  the  external  angular  process  of  the  frontal  bone  to  just  above  the  external 
auditory  meatus.  From  here  it  passes  to  the  external  occipital  protuberance  ;  this 
part  of  the  line  corresponding,  approximately,  to  the  lateral  sinus.  The  cerebellum 
lies  immediately  below  this  line. 

Of  the  brain  fissures,  those  of  greatest  importance  in  cerebral  localization  are 
the  Rolandic  and  Sylvian,  since  by  means  of  these  all  the  best  known  cortical  centres 
can  be  located.  Of  the  two,  the  fissure  of  Rolando  is  much  the  more  important, 
because  the  motor,  the  most  definitely  known  cortical  area,  is  associated  with  it.  Its 
upper  limit  is  at  a  point  about  12  mm.  (one-half  inch)  behind  the  mid-point  between 
the  glabella  and  the  inion,  and  about  one-half  inch  from  the  median  line.  It  passes 
outward,  downward,  and  forward,  approximately,  at  an  angle  of  71°  with  the  median 
sagittal  line  of  the  skull.  It  is  8.5  cm.  (3.)^  in. )  long  (Thane),  and  ends  below  just 
alx)ve  the  fissure  of  Sylvius.  Near  its  lower  end  it  turns  rather  suddenly  downward, 
so  that,  in  this  part,  it  is  not  in  the  line  of  the  angle  of  71°. 

Many  methods  have  been  devised  for  the  purpose  of  making  the  line  of  the 
fissure  on  the  scalp. 

Chiene' s  method  con^\^\s  o\  folding  an  ordinary  square  sheet  of  paper  on  the 
diagonal  line,  thus  dividing  an  angle  of  90°  in  half,  making  two  of  45°.  One  of  these 
angles  of  45°  is  again  halved  in  a  similar  manner,  making  two  new  angles  each  of 
221^°.  The  paper  is  then  so  unfolded  that  one  of  the  angles  of  22  J^  "  is  added  to  that 
of  45°,  making  a  new  angle  of  67)^°  ;  this  will  be  sufficiently  near  that  of  the  fissure 
of  Rolando  for  all  practical  purposes. 

Horslcy's  cyrtotneler  consists  of  two  strips,  either  of  thin,  flexible  metal  or  of 
parchment  paper,  each  graduated  in  inches.  The  lateral  arm  is  placed  at  an  angle 
>f  67°  with  the  long  arm,  the  apex  of  the  angle  being  at  a  point  12  mm.  or  one-half 
inch  behind  the  mid-point  of  the  long  arm. 

Le  Fort  simply  drew  a  line  from  the  beginning  of  the  fissure,  above,  to  the  mid- 
dle of  the  zygoma,  below,  and  marked  off  on  this  line  the  proper  length  of  the  fissure. 


PRACTICAL  CONSIDERATIONS:  THE  BRAIN. 


I3I5 


A^lerson  and  MacUins  sugg«t  :^  0 -^- j^j^^^^^^^^ 
the  inion  ;  (2)  a  frontal  me  fro^J^^*  "^^-"^'S^  ^^^  ,  ^^)  a  squamosal  Une  from 
of  the  ear  at  the  level,  of  '^\^P^.^''l,t£;^L:^iL  kvel  of  the  superior 
the  most  external  pomt  of  t^^  external  ang^arp       ^  ^^^^^  ^^^^^ 

Lder  of  the  orbit  to  ti«  J"««J-"  °    ^'^f^r^bfhind  ^^^^^  line.     The  upper  ex- 

and  prolonged  for  about  3-7  ^m-  t'>^  w^thVm  to  lie  between  the  mid-sagittal  pomt 
tremi'ty  of.  the  central  figure  w.s  found  ^X  f -^^^i^J^^^^^^Uy  of  thiXure  thev 
and  a  pomt  i8  mm.  (H  «n.)  '^'"IJ^,"'  g  _,_.  (ii  in  )  in  front  of  iw  unction  with 
located  near  the  squamosal  hne.  about  '»  ?""/ ^J^/^'rtion  of  the  Sylvian  fissure  « 


Fiamrc  of  Rolando 


Une  for  Rolandic  fissure 


Interparietal  fiiaurt. 


External  parieto- 
occipital fisanrt 


ParieUl  eminence 


Inlou 


Lateral  lini 


Posterior  limb 
of  Sylvian  fi^i»ure 


Une  for 
Sylvian  fissure 

Vertical  Iiml> 
of  Sylvian  fissure 

Horizontal  limli 
of  Sylvian  fissure 
Glabella 

Nasion 


Sen..dl.r."."-.i«  view  of  head,  showing  reUtion  o,  Rolandic  and  Sylvian  fissure,  and  Wnea. 

Th.  /issureo/S,i.,us  begins  an^-ioriy  «PP^x^^^^^^^^^^ 

in.)  behind  the  ^al  -«^i%h'J"J^eU  emin^?  ATtr'aight  line  <^tween  the^ 
a  point  1 8  mm.  (  H  "»• )  oeiow  ine  P*""f  ,  / .  ;„  )  long.     The  an- 

two  points  will  represent  the  fi^"'^;,*]"^^'*  *^"^^^  he  main  portion  of  the  fissure 
terior^S  mm...fi  in  )  ««  "onT^  «X^The ^^ertLl  limb  ascends  for  about 

^,t  ct  ^T"^^^^^^^^^  r^ariefrniit^n^^TiX 

convolution,  and  behind  with  the  ?n^>f'-£J»^  ^„  .^^  ^^sial  surface  of  the  brain. 

The  paHeto-ocdpUal  fissurtj^  "i^LTftri^htaJeleTt^  the  longitudinal  fissure 

The  external  limb  passes  otUwards  ^^"'^^^^/J  "^^^  in  front  of  the  l.tmbda. 

on  the  external  suHaceforaW2^5<^.andh«fr^^^^^^^^^^        ^^  ^^^  ^  . 

^erior^f'j^^ll/l^TL' lt«^^^^^  sulcus  passes  directly  backward 


I3l6 


HUMAN  ANATOMY. 


from  the  supraorbital  notch,  and  parallel  to  the  longitudinal  fissure  to  within  i8 
nun.  ( ^  in. ;  of  the  lisaure  of  Rolando.  The  inferior  frontal  sulcus  is  represented, 
approximately,  by  the  anterior  end  of  the  temporal  ridge. 

In  the  parietal  lobe  the  most  important  sulcus  is  the  intraparietal.  It  begins 
near  the  horizontal  limb  of  the  Assure  of  Sylvius,  and  passes  upward  and  backward 
about  midway  between  the  fissure  of  Rolando  and  the  parietal  eminence.  It  then 
turns  backward,  running  about  midway  to  the  longitudinal  fissure  and  the  centre 
of  the  parietal  eminence.  Above  the  sulcus,  in  front,  lies  the  ascending  parietal 
convolution,  just  posterior  to  the  fissure  of  Rolando  and  behind  the  sufterior  pari- 
etal lobule.  Below  the  sulcus,  anteriorly,  is  the  supramarginal  convolution,  and 
posteriorly,  the  angular  g>Tiis. 


Lateral  ventricle 


Pmterior  horn  of 
lateral  vrutride 


(Ii  Inion 


Lateral  sinuS' 


Middle  meninffeat  artery,  poaterior 
branch ;  inferior  horn  of  lateral 
ventricle  wen  beneath 


Middle  meningeal 
artery,  anterior 
branch 


SemiiliaKramnutic  \-iew  of  head,  showing  position  of  ventricles,  lateral  sinus  and  middle  meningeal  arteries 

as  projected  on  skull. 


The  temporal  lobe  lies  below  the  fissure  of  Sylvius  and  extends  forward  as  far  as 
the  edge  of  the  malar  bone.  The  first  temporal  sulcus  lies  about  one  inch  below  and 
parallel  with  the  fissure  of  Sylvius,  and  the  second  about  i8  mm.  (  Yi,  in. )  lower. 

The  occipital  lobe  lies  posterior  to  the  parieto-occipital  fissure  and  the  tem- 
poral lobe. 

The  motor  tracts  are  made  up  of  the  fibres  passing  from  the  motor  portion  of 
the  cortex  in  the  Rolandic  region  to  the  motor  nuclei  from  which  arise  the  nerves 
supplying  the  muscles  which  the  cortical  areas  control.  After  leaving  the  cortex  the 
fibres  pass  downward  in  the  corona  radiata,  and  converge  to  the  posterior  limb  of  the 
internal  capsule.  The  motor  fibres  of  the  cortico-bulbar  and  cortico-spinal  tracts, 
occupy  the  genu  and  adjacent  third  of  the  internal  capsule  (page  1x88),  although 
Dejerine  holds  that  the  whole  posterior  limb  is  motor.  They  continue  their  course 
downward  through  the  crura  cerebri,  pons,  and  medulla  ;  in  the  lower  part  of  the 
latter  the  greater  number  cross  to  the  opposite  side  and  pass  down  in  the  cord  as  the 
lateral  or  crossed  pyramidal  tract.     A  small  number,  sometimes  absent,  pass  down 


PRACTICAL  CONSIDERATIONS  :  THE  BRAIN. 


I3I7 


on  the  same  side  We  have  already  seen  that  lesions  of  the  cortex  produce  mono- 
Tje^  TnkL  laree  enough  to  involve  the  whole  motor  zone,  but  cort.ca  hemipleKia 
&ch  mS  common  than  cortical  monoplegia.  In  the  internal  capsule  the  motor 
fiC^are  SST^ether  so  compactly  that  a  small  lesion,  as  an  apoplectic  hcmor- 
S.  wiKequenSyrnterrupt  the  whofe  tract  and  give  a  hem.plegm  of  the  opposite 

''*^''  ^I't'lfe'^ilulla  and  cord  tne  tracts  of  both  sides  are  so  close  together  that  a 
lesio^may  e^Uv  par^"yze  toth  sides  (paraplegia)  ;  indeed,  diseases  of  the  cord  fre- 
SentirfnvXe'he  whole  transverse  section  para  yzing  sensation  f'^.^l'l  X2«he 
queniiy  mv  j^      fo^^  the  common  fonn  of  cerebral  jiaralysis  ;  /><ir«//^^w  the 

comi^n  f?.^^of  spinaTpLralysis  ;  while  monoplegia  occasionally  results  from  lesions 
^?hThrain^ortex   but  more  commonly  from  lesions  of  penpheral  nerv  es. 

The^"d«  and  convexity  of  the  brain  can  be  exposed  for  operation,  .o  tV.at  lesions 
of  thi  corter^n  rattacked  and  often  removal ;  but  the  region  ol  the  internal 

^^•'^tetf brifbeti^fdt^^^^  wans  when  the  head  is 

•  1  nJv^^WerthrsLVes  surrounding  the  brain  and  filled  with  fluid  permitting 
violently  ?_'}*'^*="-  '^^„^P^^'^J"S  The  injury  in  cerebral  contusion  occurs  more 
considerable  •"°^7«"^°*  ^^^.X^h  as  r^rds  the  cerebnim  and  cerebellum,  than 
frequently  on  the  under^i^c^,  bo  h  as  re^  ^^^^^^  ^^.^^  includes  the 

spinal  fluid,  and  is  least  frequendy  injured. 


r. 


THE  PERIPHERAL  NERVOUS  SYSTEM. 

In  a  broad  sense  and  as  contrasted  with  the  cerebro-spinal  axis,  the  peripheral 
nervous  system  includes  all  the  nerve-paths  by  which  the  various  parts  of  the  body 
are  brought  into  relation  with  the  brain  and  spinal  cord.  These  paths  embrace,  in 
a  general  way,  two  groups.     One  group,  the  somatic  nerve*,  includes  the  nerves 

Fig.  1046. 


OUmdorj  bnlo 


OrMUl  niifae*, 
of  rnmUl  lob* 


Trmporal  lobe. 

Anterior 

perforated  (pace' 

Mammillarr 

bodie*' 

Cerebiml 
pednnck' 

Poni 


Medulla 
pyramid' 

Hjrposloaial 
aerve 


Cenbellnin 


OUacloiy  tract 
OpUe  nerre,  cut 


Optic 
ODmuiissare 


Optic  tract 


Oculonotor 
nerve 

Tixichlear  nerve 
Trigeminal 
nerve 

Abducent  nerve 
Facial  neri'e 
Auditory  nerve 
Gloaao- pharyn- 
geal nerve 
Pneumogastric 
nerve 
Spiral 

acceaaory  nerve 
spinal  portion 

Pyramidal 
decussation 


Spinal  part  of 
311.  nerve 


Occipital  lobe 


Anterior  tooti  of  ipinal  ncrm 


Inferior  aspect  of  brain,  denuded  of  its  membranes,  showing  superficial  origins  of  cranial  nerves  ;   DTigh:  01  trochlear 
nerve  is  on  dorsal  surface  and  therefore  not  seen. 


supplying  the  voluntary  muscles,  integument  and  organs  of  special  sense  ;  the  sec- 
ond group,  the  viscera;  nerves,  includes  those  supplying  the  involuntary-  musdc 
throughout  the  body  ana  the  thoracic  and  abdominal  viscera.  The  h  matic  nerves 
are  subdivided  into  (n )  the  crania/  nerves,  which  are  attached  to  the  brain  and  pass 
through  foramina  in  the  skull,  and  (b)  the  spinal  nerves,  which  are  attached  to  the 
spinal  cord  and  traverse  the  intervertebral  foramina.  The  visceral,  or  splanchnic 
laiS 


THE  CRANIAL  NERVES. 


1219 


I  Er^  Zscr\u^h  tZ^  al^  contains  a  number  of  afferent  fibres  *h.ch  convey 
"ar^nsory  and  sympathetic  fibres  as  well  as  efferent  ones. 

THE  CRANIAL  NERVES. 

Ti.-  ^nJai  nprves  rnervl  ccrebrales)  include  twelve  pairs  of  symmetrically 
arranleS  nTrv^trunTs  w£  are  atuched  to  the  brain  and,  traced  r^-.-he^Uy^ 
S^omTe  skull  by  passing  through  various  foramma  at  .ts  bast  10  oc-    ..stnb- 

""nrtra^^hn'^rSrve^^wt'^^^^^^^  to  the  surface  of  the  brain  is 
,  •  f J^,r»«orrficial  oriKin  ;  the  group  of  more  or  less  deeply  situated  nerye- 
l7s'"S^SchTfibr«^re"&^^^  rdated'^is  often  spoken  of  as  L  <»«PO|:^«n; 

fhe  cent^r^eTvous^axis  and  somewhere  along  the  course  of  tje  "'^etrunks      It 

Jhich'he  Lnsory'^br-  c^^^^^^^  alter  entering  the  brain-subs.ance  are  m 

re^tv  nudei  Of  reception,  or  of  termination,  and  not  of  origin.     The  sensojy 

■"^'r^L^^'X^d  ,he brab  s.  to  ..prfci.1  origin,  »oh  c„na  .e,>e^ 
i,,veMrf  by™  hSfh  of  pia  mater.  Iraver«a  (or  a  longer  or  sbotter  dounn  (he  .nb- 
rtSd  .race  ofcral  the  arac^hnoid  and  Irom  the  Utler  acquires  an  additional. 
bS  il, Tot  eJSS^e. heath.     It  then  enter,  a  canal  in  the  dura  mate,  that 

-\-tissnSi"rcb'tq'A«^^ 


I320 


HUMAN  ANATOMY, 


Number. 

Name. 

I. 
II. 

IIL 

Olfactory  : 

Optic: 

Oculomotor 

IV. 
V. 

Trochlear  : 
Trigeminal  : 

VL 
Vlt 

Abducent  : 
Facial  : 

Certain  of  the  cranial  nerves  are  entirely  motor  ;  some  convey  the  impulses  of  special 
sense  ;  while  others  transmit  impulses  of  both  common  sensation  and  motion.  A 
general  comparison  of  these  relations,  as  now  usually  accepted,  is  afforded  by  the 
allowing  summary : 

THE  CRANIAL  NERVES. 

Function. 
Special  sense  of  smell. 
Special  sense  of  sight. 
Motor  to  eye-muscles  and  levator  pal- 

pebrae  superioris. 
Motor  to  superior  oblique  muscle. 
Common  sensation  to  structures  of  head. 
Motor  to  muscles  of  mastication. 
Motor  to  external  rectus  muscle. 
Motor  to  muscles  of  head  (scalp  and 

face)  and  neck  (platysma). 
Probably  si  cretory  to  submaxillary  and 

sublingual  glands. 
Sensory  (taste)  to  anterior  two-thirds  of 
tongue. 

Hearing. 

Equilibration. 

Special  sense  of  taste. 

Common  sensation  to  part  of  tongue 
and  to  pharynx  and  middle  ear. 

Motor  to  some  muscles  of  phaiynx. 

Common  sensation  to  part  of  tongue, 
pharynx,  oesophagus,  stomach  and 
respiratory  organs. 

Motor  (in  conjunction  with  bulbar  part 
of  spinal  accessory)  to  muscles  of 
pharynx,  oesophagus,  stomach  and 
intestine,  and  respiratory  organs ; 
inhibitory  impulses  to  heart. 
XI,  Spinal  Accrssorv  :  Spinal  Part :   Motor  to  stemo-mastoid 

and  trapezius  muscles. 
XIL  Hypoglossal  :  Motor  to  muscles  of  tongue. 


VIII. 
IX. 


Auditory, 

(a)  Cochlear  division : 
(it)  Vestibular  division : 

Glosso-Pharvngeal  : 


Pneumouastric OR  Vagus: 


Practical  Considerations. — Lesions  may  affect  a  cranial  nerve  within  the 
brain  or  in  its  peripheral  portion.  A  central  lesion  dinicalljr  is  one  above  the  nucleus 
of  the  nerve,  and  may  be  cortical  or  may  encroach  upon  its  intracerebral  connections. 
It  may  merely  irritate  the  nerve  or  may  paralyze  it.  By  a  peripheral  lesion  is  meant 
one  involving  the  nucleus  or  the  fibres  of  the  nerve  below  the  nucleus. 


THE  OLFACTORY  NERVE. 

The  olfactory  nerve  (n,  olfactorias),  the  first  in  the  series  of  cranial  nerves, 
presents  some  confusion  in  consequence  of  the  name,  as  formerly  employed,  being 
applied  to  the  olfactory  bulb  and  tract  as  well  as  to  the  olfactory  filaments — struc- 
tures of  widely  diverse  morphological  values.  As  already  pointed  out  (page  1151), 
the  olfactory  bulb  and  tract  (Fig.  993),  with  its  roots,  represent,  as  rudimentary 
structures,  the  olfactory  lobe  possessed  by  animals  in  which  the  sense  of  smell  is 
highly  developed.  It  is  evident  that  these  structures,  formerly  regarded  as  parts  of 
the  first  cranial  nerve,  are  not  morphological  equivalents  of  simple  paths  of  cpnduc- 
tion.  On  the  other  hand  such  paths  are  represented  by  a  scries  of  minute  filaments, 
the  true  olfactory  nerv'es,  that  connect  the  perceptive  elements  within  the  nasal 
mucous  membrane  with  the  rudimentary  olfactory  lobe. 

The  olfactory  nerves  proper,  some  twenty  in  number,  are  the  axones  of  the 
peripherally  situated  neurones,  the  oZ/ador)'  ce//s  (page  1414),  which  lie  within  the 
limited  olfactory  area.     The  latter  embraces  in  extent  on  the  outer  nasal  wall  less 


THE  OLFACTORY   NERVE. 


I23I 


t.  •  1  ...^^»  «f  tJiP  winerior  turbinate  bone  and  a  somewhat  larger  field 

Sfth^^dra'^t  up^rpa^rt  ofthrn^  ^7.-.     The  olfactory  nerves  (Fig.  .048). 

Fig.  1047. 


M*Hl  nerve,  cxt.  br. 


Exit  ext.  br.  mint  ncrre 


Olfactory  bulb 

tlfaetory  iierve-6brc» 

n  upper  Knt.  nawl  br. 
leckeV>  ganglion 

Jl'pper  post,  najil  br». 
J  Meckel's  ganglion 

Naao-palatine  nerve 


rSup.  ant.naialbr.  ol 
I  Meckel's  gangl.  and 

Iinf.  ant.  nanal  br.  of 
■nt.  descending 
palatine  nerve 
A  posterior  nasal  br. 
Meckel's  ganglion 


Ant  descending  palaUne  nerve,  the  middle  patoUne  appearing  poateriorlr 


Kigbtn....fo....bo,in,d.MHbut.o^o,o,^.o^«-^n«;^^^^^^ 

whose  fibres  are  nonmeduUated,  exhibit  a  plexifomi  arrangement  w|thin  the  deeper 
^Hf  the  n^S  muTous  membrane,  pass  upward  througli  the  cnbniorm  plate  of 


Fig.  1048. 


CriaU  gaitt 


Masai  ncnrt 


Tnt.  (seput)  br.  of  nasal  nerve 
olfactory  bulb 


Bat.  l>r.  aaial  nerve,  eat 


Maao-palatlne  ncrvt 


Olfactory  nerve-Bbrea 
.Sphenoidal  sinu< 

An  upper  ant.  nasal  br.  of 
Meckel's  ganglion 
■Naso-palatine  nerve 

An  upper  ant.  nasal  br. 
'of  Meckel's  ganglion 


usiachian  oriSce 


Vomer,  posterior  botdet 


>h  paUte,  cut  nmially 


Right  na-l  fo-a  .bowing  a.-r.but,on^of^UJjc.ory^^».-.^- ™^«P"'  ««;  »«co en.bra„e  Has 

the  ethmoid  bone  and  enter  the  under  suHace  of  the  olfactory  bulb.  Within  the 
alter  the  ner^efibrM  end  in  tenninal  arborizations  in  relation  with  the  dendnt.c 
^^X^^  ofTe  m!t^  cells  (Fig.  995).  sharing  in  the  production  of  the  peculiar 
olfactory  gloniemli. 


1333 


HUMAN   ANATOMY. 


Central  and  Conical  Connections. — The  impulses  conveyed  by  the  olfactory  nerves  and 
received  by  the  mitral  cells  of  the  olfactory  bulb,  which  cells  may  be  regarded  as  constituting 
the  end-station  or  receptioH-nucleus  of  the  peripheral  path,  are  carried  to  neurones  situated  either 
within  the  gray  matter  of  the  olfactory  tract,  the  anterior  perforated  space  or  the  adjacent  part 
of  the  septum  lucidum  (Fig.  1049).  Fibres  connecting  the  olfactory  centres  of  the  two  sides  pro- 
ceed from  the  cortex  of  the  tract  by  way  of  the  anterior  commissure,  forming  tticpars  olfactoria 
of  the  latter,  to  end  in  relation  with  the  cells  within  the  opposite  tract  or  bulb.  From  the.se 
primary  centres  the  impulses  are  transmitted  by  different  paths  to  the  secondary  or  cortical 
cntres  situated  in  the  anterior  part  of  the  hippocampal  convolution  in  the  vicinity  of  its  uncus, 
including  the  hippocampus  major  and  the  nucleus  amygdalx. 

I.  The  most  direct  path  Ls  by  way  of  the  lateral  root  of  the  olfactory  tract  (page  11 53),  by 
which  fibres  from  cells  within  the  trigonum  olfactorium  pass,  skirting  the  Sylvian  fissure,  to  the 
anterior  part  of  the  gyrus  hippocampi  to  terminate  in  relation  with  the  cortical  cells  of  that 
-onvolution. 

Fin.  1049. 


Diagram  showing  most  imporunt  connections  of  olfactory  tracts ;  LC  lamina  cribrosa  ;  H,  olfactory  bulbs :  TV, 
olfactory  tract :  Tg.  olfactory  trigone ;  Ls,  Ms,  lateral  and  mesial  striK ;  ^.anterior  commissure :  CC,  corpus  calk>- 
sum;  SL,  septum  lucidum:  F.r,  anterior  pillar  of  fornix;  M,  mammillary  body;  m-l.  maniminn.thalamic tract; 
^A  anterior  perforated  space;  ri^w.'taeniasemicircularis;  r,  thalamus;  A'w,  fimbria  descending  on  hippocampus; 
V,  uncus ;  AN,  amygdaloid  nucleus ;  TL,  temporal  lobe. 

2.  Fibres  from  the  ct\U  within  the  olfactory  trigone  (page  1153)  and  the  anterior  perfo- 
rated space  (page  1 153)  pass  into  the  septum  lucidum  and,  reinforced  by  others  from  cells  of  the 
septum,  enter  the  fornix  ;  thenc*  continuing  backward  and  downward  by  way  of  the  fimbria 
they  reach  the  hippocampus  major. 

3.  Fibres  from  "-ells  within  the  olfactory  trigone  turn  inward  and  by  way  of  the  medial  root 
of  the  olfactory  tract  gain  the  gyrus  subcallosus  ;  thence  they  pass  plong  the  upper  suriace  of  the 
corpus  callosum  within  Its  longitudinal  strix  and  descend  by  way  of  the  de'itate  gyrus  to  reach 
the  anterior  end  of  the  hippocampus  major. 

4.  Fibres  from  colls  within  the  anterior  perforated  space  and  septum  lucidum,  joined  by 
accessions  from  the  opposite  olfactory  tract  by  way  of  the  anterior  commissure,  converge  to  the 
txnia  semicircularis  (page  1 162)  and,  passing  along  the  floor  of  the  lateral  ventricle,  descend 
within  the  roof  of  the  descending  horn  to  end  in  the  amygdaloid  nucleus  (Dejerine).  During 
their  ascent  from  the  anterior  perforated  space,  some  fibres  diverge  almost  at  right  angles  and 
pass  backward  directly  to  the  optic  thalamus.  The  coimectioiis  between  the  cortical  centres  of 
olfaction  and  the  optic  thalamus,  as  well  as  those  lietween  the  olfactory  centres  of  the  two 
sides,  by  \— 'y  of  the  fornix,  are  described  on  page  1 167. 


Practical  Considerations. — Lesions  of  the  uncinate  ^rus  may  cause  loss 
of  the  sense  of  smtH  on  one  t"»r  both  sides.  Paralysis  of  the  olfactory  nert't  with  loss 
of  smell  may  also  occur  in  fractures  of  the  base  of  the  skull  in  the  anterior  fossa, 
involving  the  cribriform  plate. 


THE  OPTIC   NERVE. 


1323 


THE  OPTIC  NERVE. 

,„  addition  to  the  fibres  of  -«-' -^l^i^^.^'^es^KTe  'oTl^Sir^y^cC- 
nerve  contains  a  ~nsiderable  num^r  i-Pi;^-^''',:,^'?  J'^lt^^^  ^s  toward  the 
cemed  in  sight.  Some  of  these  P»'^vf  ?,""£^  f ^..^  primary  visual  centres  or  from  sympa- 
retina,  originating  w«hm  the  bmm  from  t^^^^^^  ^,^  retinal  blood- 

thetic  neurones,   and  Pf°»f  ^>  ^^*'^,JoX  way  of  a  centre  situated  within  the  medulla. 
^^^tm^rS'irrrfg^deT^^c^^^^^^^^  to  the  oculomotor  nucleus  the 

impulses  resulting  in  reflex  pupillary  movements. 

The  oDtic  nerve  (Fie.  1198)  extends  from  the  eyeball,  which  it  leaves  about 

muscles,  it  traverses  the  opt.c  foramen  m    he ^s^^^^^^^^  .^^^^^^ 

ophthalmic.artet       ■[^:^^^Z^:^r^':^:r:i.y..  opposite^i^e 'with  which  it 
or  part  of  the  optic  commissure  m  the  vic.nity  of  the  olivary 
.he  internal  carotid  artery.    The  entire  length  of  the  optic  nerve 
d  whkh  the  intraorbital  part  includes  from  2(^30  mm.    thus 

-^ (-«  -stt"  Tr  °s:\r^^;  rne:tu?::i^st£ 

central  artery  of  the  retina,  which,  ^""^  '^^  .^?^P''"^""  ^^^a  h  from  the  pia  mater 

lEXnSs  ^d  tz:;f&^^^^^^^^     - — -  -  -  ^- 

'^^^'h  *o'o"?c'clCSut^^^^^^  by  the  meeting  of  the  converging 

beneath  the  floor  of  the  third  ventricle  m  ^^  f "^^.jJ^'l'oSSrTy  into  the  two  optic 
tion  with  the  inferior  surface  of  the  brain  . «  ^^^ 'f f ;  H^'^Ses  called,  the  optic 
tracts.  On  reaching  the  ^'^'^l^JJ^f '^[nf^^'s'^iLV)  un^«go  partial  d;:ussation, 
fibres,  estimated  at  upwards  of  ha  fa  ^^/^j^f ^^;i,"ng  to  the  mesial  part  of  the 
those  from  the  nasal  o":  '""f.^  ^^^^^^^^  te™Ur  o^ter  half  continue  into  the 
opposite  optic  tract,  while  those  from  tli«  ^^""P"™  .     commissural  loop  con- 

lat^l  part  of  the  tract  of  the  same  side^    I.'^TJS  TlthoughToLerly  accented. 
nectingThe  two  optic  nerves  ^as  m>t  been  ^tabl^hed,  aUhmigh  .    ^^.^7^,  ^^^ 

Occasional  instance  have  ^^f^^f^^;^ J J„^^^^^^  that  normally  obtains 
optic  fibres  was  ^^PP'^'^' *^^^^^^^^  few  rodents  (mouse,  guinea-pig). 

Lfi;r o^^tmnSSrE  ^:l^n.,  the  optic  fibres  passing  directly  into 
the  tract  of  the  same  side. 


of  the  cranii"- 
joins  to  fon 
eminence,  n. 
is  from  30-4 
allowing  for 


1324 


HUMAN  ANATOMY. 


The  entire  commissure,  however,  is  not  composed  of  optic  fibres,  since  its  posterior  part 
is  formed  bya  bundle,  known  as  Qudden's  commiasurc  (commltMira  inferior)  (page  mo),  which 
passes  forward  along  the  mesial  side  of  the  optic  tract,  loops  around  the  posterior  angle  of  the 
commissure  and  enters  the  opposite  tract  These  fibres  have  no  connection  with  the  path  of 
sight-impulses,  but  are  probably  chiefly  related  with  the  median  or  internal  geniculate  bodies 
and  the  inferior  corpora  quadrigemina  ([>age  iiio). 

The  optic  commissure  also  contains  fibre-strands  that  arch  around  its  posterior  angle,  par- 
allel with,  but  separated  by  a  thin  layer  of  gray  matter  from  Gudden's  tract.  Concerning  the 
origin  and  destination  of  these  fibres,  termed  Meynert's  commiasurc  (comiiiiaaura  anperior),  little 
b  known.    By  some  they  are  regarded  as  continuations  of  the  mesial  fillet  that,  after  decussa- 

FiG.  lo.so. 


Diacram  thowinv  coune  of  nllnal  fibre*  fn  optic  palliwav  and  their  connection  with  basal  Kanglia  and  primary 
cortical  centres ;  •maUer  llRure  illuMralca  path  of  llcht-ray  and  multina  impulte  through  retina  :  K.  retina  :  ON.  OC. 
OT^  OR,  optic  ner\'e.  chiaitm,  tract  and  radiation,  f.pulvlnar;  Eg,  SQ,  lateral  geniculate  and  superior  quadrlgem- 
inal  bodies ;  Oc  Cx,  occlpiul  conea ;  ///,  ly,  yi,  nuclei  of  cye-muaci*  nerves. 

tion,  pass  to  the  globus  pallidus  of  the  lenticular  nucleus  of  the  opposite  side.  Others  deny 
such  relations,  while  Kolliker  describes  them  as  bending  upward,  traversing  the  ventral  part 
of  the  cerebral  peduncle,  to  end  within  the  corpus  subthalamicum  (page  1128). 

Additional  commissural  fibres  (commlaaura  aaaata)  descend  from  the  floor  of  the  third 
ventricle  and  from  the  [K-duncle  of  the  septum  lucidum,  by  way  of  the  lamina  terminalis,  to  the 
front  and  upper  part  of  the  optic  chiasm  ;  other  fibres  pass  from  the  ventricular  floor  to  the  back 
of  the  chiasm.  For  the  most  part  these  fibres  cross  to  the  opposite  side  to  be  lost  in  the  sub- 
stance of  the  optic  commissure.  Although  regarded  as  in  a  way  constituting  a  ventral  optic 
root,  their  connections  and  significance  are  not  understood. 


The  optic  tract  (Fig.  993)  is  the  continuation  of  the  optic  nerve,  its  chief 
constit.  Its  being  the  crossed  and  uncrossed  retinal  and  the  supplementar}'  fibres. 
On  leaving  the  commissure,  the  tract  diverges  in  front  of  the  interpeduncular  space, 
mesial  to  the  anterior  perforated  space  and  the  termination  of  the  internal  carotid 
artery,  and  sweeps  outward  and  backward  from  the  base  of  the  brain  around  and 
close  to  the  corebral  peduncle,  becoming  flatter  and  broader  as  it  proceeds.     Near 


THE  OCULOMOTOR  NERVE. 


1225 


™.»-^«r  ^nA  thf  tract  exhibits  a  furrow  that  indicates  a  subdivision  into  a  mesia/ 
.tspostenor  end  the  trart  exniDiBaiu  ^^  ^^^  ^^^  ,^ 

.      A'n^i^.i  Connt-ion*  — Arising  as  axones  of  the  retinal  neurones,  the  optic 

*^*^  :^'^^^^^^^xLuTrh^comn^i.sur^  and  tract  and  end  in  relation  with 

nerve-fibres  are  contmuedbackwaratnrougnine  ,  ;  ,^    ,^,^^81  geniculate  and  the 

the  neurones  of  the  pnmanr  ^^^^^^'^  ^mthX^r^  s^mcu\Me  b^y  ih^^ 
superior  quadngemnal  body  ^  I   >s.h^^        ™  ^.i^„,,  fi^r^  terminate,  relatively  few  pass- 
number   80  per  cent,  accordrng  to  "™^^?*' 7 ',  t^^  , cpiUer)    The  cortical  conntctioni  are 
ing  to  the  pulvinar  «"<>jh?  ^"P!"°r^"^tS  Jt^K^c^^^^^  »'*  the  optic  radia- 

rreTp;yd^>^r«e|r^9'£^ 

geniculate  and  quadngem.^^^^  ,  .p,^io„,  of  sight  are  vety 

St^r/ndT;  Jchlnr^uc^'mpr^^^^  being  capable  of  affecting  numerous  motor  and 
-■^^hfe^^pathbywhichpupina^impulsesreadU 

perhaps  »--'«{^  "  ^o^l^U^  fi^r^e't^uSy  ^^^^^^^^  o'f^?  '^^!.\-^^'' 

quadngeminal  body,  ^^P)^,,^^;^,"^^^^'"^^  Neurones  the  immediate  connecting  hnks  pro- 
but  end  withm  the  supenorcoUiculus,  from  wntw«neuro  existence  of  a  more 

ceed  to  the  oculomotor  «»^^^^^''^S^^^Zt^P'^Z,^M;.,\usuchc<^ih^ 
rir  l^^tTeri/rS^^^nflp^f  ^^^^^^  pass  .-  the  medullary  centre 

^ward  by  way  of  the  posterior  longitudinal  fasaculus  (Bach). 

Practical  Con.ideration..-The  cranial  nerves  of  the  o"  w"l  ^  discussed 
in  connection  with  that  organ. 

THE  OCULOMOTOR  NERVE. 

doS  surface  of  the  posterior  longitudinal  fasciculus  (F.g.  963). 

The  nucleus  is  from  ^  mm.  in  lengOj^nd  extends  'r°"^P»-^-rcorTaririm^ 
caudal  pole  of  the  supenor  ;i"»^nKem.na^tod.es.  ^"^^.^jP^^^  ^  ,  „,„„^  ,,.er^•al.  In 
contact  with  the  nucleus  of  the  '"""''."^.'^'J'"' 'f,^^"„f  „„„  or  less  distinct  cell-groups, 
its  entirety  the  oculomotor  "%'•="^ '"5.'"^f„i^J^S^,^' omirnce     « 

«  hich  vary  in  importance  as  well  as  in  the.r  '"f 'y.''"^' P~'"'"!"7hat  exten  one  on  each  side, 
tant  and  instant  are  two  long  ^JT "^f  ."L^^'i^i^nS^^^  Each  nucleus  tapers  slightly 
along  the  dorsal  surface  of  the  P<^'f"°' '??f '"°;^"'t  which,  from  their  relative 

towards  either  end  and  consists  of  two  '''j'y  ^'')y"^^^„*"'^^;e°„„ent  nerve-cells  include 
positions,  are  termed  the  ''ors^r.Mt  :MreU-^roup^^^^^^  .^  ^.,^^^_ 

UK.se  of  large,  medium  and  small  size,  »»'''.  ^/K^.-T^^X^";'  the  third  nerve  arise.  Dislo- 
:L^:^''™Xt'S«i:lrctus'r  rr^^^^^^  "--ceUs  .hat  lie  scattered 

rong -Te^  beneath  the  fibres  °' ^^^^^  P^lj'^l^-S "t^l^^^^^^^^  surface  is  .he  ta.^r- 

Dorsal  to  the  chief  nucleus  and  P'^t'^'y^^^^wS^  nucleus.    This  tract,  much 

i„g  column  of  sm..nnefve<ellskm^^^^^^^  ,,  ,„,^.Uieral  .md  a 

:Zr:SiT^2::.'^SS::T^^'i^  m  the  superior  pole  of  the  nucleus.    The 


1336 


HUMAN   ANATOMY. 


exact  relations  of  the  Edinger-Westphal  nucleus  to  the  fibres  of  the  third  ner\'e  are  still  unde- 
termined, and,  indeed,  even  its  close  association  with  these  has  been  questioned.  The  assumed 
importance  of  the  nucleus  as  a  centre  for  pupillary  reflexes  (Bemheimer)  has  been  seriously 
shaken  by  the  recent  observ-aUons  of  Tsuchida.'  This  investigator  also  denies  the  existence 
of  a  well  marked  and  consUnt  unpaired  median  nucleus  as  described  by  Periia,  but  admits  the 
presence  of  broken  groups  of  medially  placed  cells,  especially  in  the  upper  and  lower  thirds  o* 
the  nucleus.  The  lateral  group  of  cells,  beginning  in  the  floor  of  the  third  ventricle  and  extend- 
ing caudally  as  far  as  the  upper  third  of  the  chief  nucleus,  constitutes  the  nucUnt  of  Darksche- 
witsch.  Notwithstanding  its  proximity  to  the  origin  of  the  third  nerve,  this  nucleus  is  now 
regardc-d  as  having  no  direct  relation  with  that  of  the  oculomotor,  but  as  standing  in  intimate  asso- 
ciation with  the  posterior  longitudinal  bundle,  among  whose  fibres  the  celU  to  a  large  extent 
lie;  it  is,  therefore,  now  often  referred  to  as  the  nucleus  fasciculi  longitudinalis  posteriori*. 


Lachrymal 
■luid 

Lcrator  palpe- 
bne  ■uperiont 
Superior 
rectus  miucle 


_    :emal  rectus, 
fauertion 


Inferior  obliqar 
miucle 


CMMifkc*  of  malar 
bone 


Diaiectfoii  of  riftht  orbit,  showiiiK  oculomotor  and  abducent  nerves. 

Although  it  may  be  assumed  with  much  probability  that  the  fibres  destined  for  the  different 
eye-muscles  originate  from  definite  groups  of  nerve-cells,  all  attempts  to  locate  with  accuracy 
the  position  of  such  centres  within  the  oculomotor  nucleus  have  met  with  only  partial  success. 
Tsuchida's  conclusions,  based  upon  histological,  embryological,  comparative  and  clinical  data, 
point  to  an  unexpected  diffuseness  in  the  origin  of  the  oculomotor  fibres  with  only  a  limited 
relation  to  distinct  groups. 

Concerning  the  mooted  question  as  to  the  extent  of  decussation  of  the  oculomotor  fibres 
it  seems  probable  that  such  crossing  occurs  principally  within  the  caudal  portion  of  the 
chief  nuclei,  although,  according  to  Tsuchida  and  others,  some  decussating  fibres  are  found 
throughout  the  greater  part  of  the  nuclei. 

The  fibres  of  the  third  nerve  originate  principally  as  the  axones  of  the  cells  on 
the  same  side,  although  a  small  number  are  derived  from  the  neurones  lying  on  the 
opposite  side  of  the  mid-line.  Some  of  these  decussating  fibres  supply  the  internal 
rectus  and  are  related  with  the  nucleus  of  the  sixth  nerve,  which  sends  fibres  by  way 
of  the  posterior  longitudinal  bundle  into  the  oculomotor  nucleus.     Whether  these 

'  Arbeiten  a.  d.  I-Iirnanatom.  Institut  in  ZQrich,  Heft  ii.,  1906. 


'^^  ;.-: 


THE  OCULOMOTOR   NERVE. 


1327 


prac«d,  or  are  ac.rfy  ("''""SiitSISi^n  *«  intcr.»l  r5lu.  ol  one  ade  «.lh 

deviation. 

{l^VSJr^HsU"'ir:.n«-a:^^^^^^       the  neurones   within  the  postenor  part 


Fig.  1052. 


olfactory  bulb« 

Olfactory  tract 
Optic  nerve 


III.  ner\-e 
VII.  nem 
VIII.  neme 
IX 

X.  nerve 

XL  nerve 

XI.  nerve 

spinal  portion 

Part  of 

XII.  nerve 

Superior 

medullary 

velum 


nranch  of  supraorbiul  nerve 

Supratrochlear  branch  of  frontal 
SupraorbKal  branch  of  fronUl 
.Lachrymal  gland 


Ijichrymal  nerve 
Ophthalmicdivision  of 
.V  nerve— its  division 
into  frontal,  lachrymal 
III.  nerve  [and  nasal 
Maxillary  division 
of  V.  nerve  .  . 

IV  ner%e,  10  inner  side 
of  which  ia  VI.  nerve 

Mandibular  division  of 

V.  nerve 

Uasaerian  ganglion 

Sensory  root  of  VV 

VII.  nerve         Inetve 

VIII.  nerve 
Middle  cerebellar 
peduncle 

IX.  nerve 

X.  nerv« 

XII.  nerve 


IV.  ventricle 


Medulla,  cloi«*l»rt 


Base  of  skall,  viewed 


,^.l^,.o.n.^cr.nJ^n«;«.^^.ffi-^^^^ 


Of  the  inferior  frontal  convoUition  ^^^fyj^^^.f^^^^::^!^!^^^^^^^ 
by  way  of  the  corona  racHata,  the  '"'""«'/*P?7„j"^°ausW^y  on  the  opposite  side,  they 
niotornucleus.  around  whose  cells,  ^^'efly  b"t^J^'^^^^^^^^^  (,)  indirectly  with  the  cor- 
end.  Other  connections  of  the  nucleus  °' ''''=  J^^  'f^.  '"x  throu  the  optic  radiation  and 
tical  visual  area  by  fibres  that  pass  f^"" ^»';«,°$^^S„'°'7,^) ?„dh^^^  with  the  vi.sual  centres 
superior  brachium  to  the  *"P^""^5°;„^^?X  ^^r  comora  quadrigemina  ;  (3)  by  "-«"- 
bv  fibres  that  descend  from  the  cells  within  the  s"P"°;  f '"J*"  ocular  ner\es  (the  fourth  a..-. 
^  the  r^sterior  longitudinal  bundle  with  t^  nude'  °^;,^/„^°5^;,°*^SthTu)  with  the  facial 
the  sixrt.)  and  also  with  the  ^^/'bular  ( Deters  )n^^^^^^^         tne     g      ^  longitudinal 

„„clei.H  by  fibres  that  descend  from    he  oculomotor  n^^^^^^^^^ 

bundle  to  the  cells  from  v  hich  P"'?^„'*\t.,.  bmS  into  coordinated  action  with  the  levator 
corrugator  supercilii  mus  les.  which  are  thus  brought  imo  cooruin 

palpebrarum. 


1328 


HUMAN  ANATOMY. 


Intracranial  Course. — Leaving  their  deep  origin  as  the  axones  of  the  nuclear 
cells,  the  oculomotor  fibres  sweep  in  ventrally  directed  curves  (Fig.  963)  through 
the  posterior  longitudinal  bundle,  tegmentum,  red  nucleus  and  inner  margin  of  the 
substantia  nigra  and,  collected  into  about  a  dozen  root-bundles,  have  their  super- 
ficial origin  along  a  shallow  groove,  the  oculomotor  sulcus  (Fig.  974),  on  the 
medial  surface  of  the  cerebral  peduncle,  just  in  front  of  the  pons  and  at  the  side  of 
the  interpeduncular  space. 

Beyond  this  superficial  origin,  the  linear  group  of  root-fibres  soon  becomes 
consolidated  into  the  large  and  conspicuous  trunk  of  the  third  nerve,  although  not 
infrequently  one  root-bundle  emerges  more  laterally  from  the  ventral  surface  of  the 
cerebral  peduncle  and  for  a  short  distance  remains  separated  from  the  other  constit- 
uents. The  nerve  courses  forward  and  outward  from  the  posterior  perforated  space, 
between  the  posterior  cerebral  and  superior  cerebellar  arteries,  to  the  outer  side 
of  the  postenor  clinoid  process,  where,  in  the  triangular  interval  betn'een  the  free 
and  attached  borders  of  the  tentorium,  it  enters  the  dura  (Fig.  1033).  Embedded 
within  this  membrane,  the  nerve  follows  the  upper  {X>rtion  of  the  outer  wall  of  the 
cavernous  sinus  and  leaves  the  cranium  by  entering  the  orbit  through  the  sphenoidal 
fissure.  On  gaining  the  median  end  of  the  fissure  the  ner\'e  divides  into  a  superior 
and  an  inferior  branch,  which  enter  the  orbit  by  passing  between  the  two  heads  of 
the  external  rectus  muscle,  in  company  with,  but  separated  by,  the  nasal  branch  of 
tbo  trigeminal  nerve,  the  sixth  nerve  lying  below. 

Branches  and  Distribution. — ^The  superior  branch  (ramus  saperlor)  (Fig. 
1051),  the  smaller  of  the  two,  passes  upward,  over  the  optic  nerve,  to  the  superior 
rectus  muscle,  which,  together  with  the  levator  palpebrx  superioris,  it  supplies.  In 
both  cases  the  nerve  enters  the  ocular  surface  of  the  muscle. 

The  inferior  branch  (ramns  inferior)  (Fig.  1051)  is  directed  forward  and, 
after  giving  of!  twigs  to  the  ocular  surface  dt  the  internal  and  inferior  recti,  is 
continued  below  the  eyeball,  between  the  inferior  and  external  straight  muscles,  to 
supply  the  inferior  oblique,  whose  posterior  border  it  enters.  This,  the  longest 
branch  of  the  oculomotor  nerve,  in  addition  to  sending  one  or  two  fine  twigs  to  the 
inferior  rectus,  contributes  a  short  thick  ganglionic  branch  (Fig.  1051),  which  joins 
the  postero-inferior  part  of  the  ciliary  ganglion  (page  1336)  as  its  short  or  motor 
root  and  conveys  fibres  destined  for  the  sphincter  pupilke  and  ciliary  muscles. 
Sensory  fibres  from  the  ophthalmic  division  of  the  fifth  nerve  are  distributed  to  the 
muscles  along  with  the  fibres  of  the  third,  having  joined  the  latter  before  it  entered 
the  orbit.  Similarly  in  the  wall  of  the  cavernous  sinus,  the  nerve  is  joined  by 
sympathetic  fibres  from  the  cavernous  plexus  on  the  internal  carotid  artery. 

Vmriationa.— These  consiist,  for  the  most  part,  of  unusual  branches  which  at  times  seeminely 
replace  one  of  the  other  motor  orbital  nerves.  Thus,  the  third  nerve  may  give  a  branch  to  the 
external  rectusj  either  in  addition  to,  or  to  the  exclusion  of  the  sixth,  which  may  be  absent ;  or 
it  may  give  a  filament  to  the  superior  oblique.  Minor  deviations  in  the  course  of  its  branches, 
such  as  piercing  the  inferior  rectus  or  the  ciliary  ganglion,  have  also  been  recorded. 


THE  TROCHLEAR  NERVE. 

The  fourth  or  trochlear  nerve  (n.  trochlearis),  also  called  the  pathetic,  is  the 
smallest  of  the  cranial  series  and  supplies  the  supierior  oblique  muscle  of  the  eyeball. 
The  deep  origin  of  the  nerve  is  from  the  trochlear  nucleus,  a  small  oval  collection 
of  cells  situated  in  the  ventral  part  of  the  gray  matter  surrounding  the  Sylvian  aque- 
duct, that  extends  from  oppiosite  the  upper  part  of  the  inferior  quadrigeminal  body 
to  the  lower  pole  of  the  superior  collicuius.  This  nucleus,  about  2  mm.  in  length, 
lies  near  the  mid-line  and  immediately  below  (caudal  to)  that  of  the  third  nerve, 
from  which,  however,  it  is  distinct,  being  separated  by  a  narrow  interval  from  the 
ventral  part  of  the  oculomotor  nucleus.  It  lies  in  intimate  relation  with  the  pos- 
terior longitudinal  fasciculus  in  a  distinct  depression  on  the  dorsal  surface  of  that 
bundle  (Fig.  960).  In  structure  the  trochlear  nucleus  resembles  that  of  the  oculo- 
motor, its  nerve-cells  including  those  of  large,  medium  and  small  size. 

Arising  from  the  nucleus,  the  root-fibres  of  the  fourth  nerve  pursue  a  course 
uf  considerable  length  within  the  mid-brain  before  gaining  their  superficial  origin. 


THE  TROCHLEAR  NERVE. 


1329 


Leaving  the  upper  and  lateral  part  of  the  nucleus  as  axones  of  the  t;;«^hlear  "euron^ 
,>^,trands  of  ftbres  pass  outward  and  backward  within  the  gray  matter  of  the  floor 

cerebellar  peduncle. 

^_-    1  -M  e«.«.l  Connections—The  trochlear  nucleus  is  directly  connected  with  the 

Fio.  iQSJ. 


OrWWmlc  ill«.  V.  MX* 
MailUuy  dtr.  V.  acrr* 
Hwdlbutor  div.  V.  Mrr* 
C»iilcutat««M«llo«"'VII.  •€•»•(•[««  of  !«•• 

T<mpat«IU>M,cirt      C<M«rto«  gi>«ll<«> 

Side.    By  means  of  the  posterior  longitudinal  bundle  it  is  ^">l^''^'°^l'!^°^^^^^':  ?„"£" 

superior  olive  and  its  peduncle. 

Course  and  Distribution— Emerging  at  its  superficial  origin,  the  nerve  is 
directed  "mard  over  the  superior  cerebellar  peduncle,  then  winds  forward  around 
Jhe^^er  sSce  Tthe  cerebral  peduncle,  parallel  to  and  between  the  posteno, 
Sebral  and  superior  cerebellar  arteries,  and  appears  at  the  base  of  the  brain  (F.g^ 
cereDrai  »"«     P         ^        ^  ^^  ^^e  floor  of  the  cranium,  the  nerve  entere  the  dura 


123° 


HUMAN  ANATOMY. 


the  external  rectus  muscle  and,  directed  medially,  crosses  above  the  levator  palpebrse 
superioris  and  superior  rectus  and  reaches  the  superior  oblique,  which  it  enters  on 
the  upper  surface  close  to  the  external  border  (Fig.  1056). 

The  communications  of  the  trochlear  nerve,  as  it  courses  in  the  wall  of  the 
cavernous  sinus  are :  (i)  filaments  from  the  carotid  sympathetic  plexus;  (2)  fibres 
of  common  sensation  from  the  ophthalmic  division  of  the  fifth. 

Variations The  course  of  the  trochlear  nerve  Ls  sometimes  throug;h  instead  of  over  the 

levator  palpebrae  superioris.  Unusual  branches  to  sensory  nerves,  as  the  frontal,  supratroch- 
lear, the  iirfratrochlear  and  the  nasal,  are  probably  due  to  the  aberrant  course  of  sensory  fibres 
from  the  trifacial.  Tlie  fourth  nerve  occasionally  sends  a  branch  to  the  orbicularis  palpebrarum. 


THE  TRIGEMINAL  NERVE. 

The  fifth,  trigeminal  or  trifacial  nerve  (n.  trigeminus),  the  largest  of  the  cranial 
series,  is  a  mixed  nerve  and  consists  of  a  large  sensory  part  (portio  major)  and  a 
much  smaller  motor  portion  (portio  minor).  The  former  supplies  fibres  of  common 
sensation  to  the  front  part  of  the  head,  the  face,  a  portion  of  the  external  ear,  the 
eye,  the  nose,  the  palate,  the  naso-pharynx  in  part,  the  tonsil,  the  mouth  and  the 
tongue.  The  motor  portion  is  distributed  to  the  muscles  of  mastication,  the  mylo- 
hyoid and  the  anterior  belly  of  the  digastric.  The  relation  of  the  fibres  composing 
these  two  parts  to  the  cells  within  the  brain-stem  is,  therefore,  very  different,  in  the 
case  of  the  motor  fibres  the  ceUs  being  a  nucleus  of  origin  and  in  that  of  the  sensory 
fibres  one  of  reception. 

The  Sensory  Part. — ^The  fibres  comprising  the  sensory  part  of  the  trigeminal 
nerve,  which  convey  sensory  impulses  from  the  various  head-structures,  are  the  pro- 
cesses of  cells  lying  outside  the  central  axis  in  the  Gasserian  ganglion  on  the  sensory 
root  The  portions  of  the  fibres  between  the  periphery  and  the  ganglion  correspond 
to  elongatecf  dendrites,  while  the  much  shorter  centrally  directed  constituents  of  the 
sensory  root,  connecting  the  ganglion  with  the  brain-stem,  are  the  axones  of  the 
Gasserian  neurones.  The  general  resemblance  between  the  fifth  cranial  nerve  and  a 
typical  spinal  nerve  is  strikmg,  in  each  case  the  sensorv  root  bearing  a  ganglion  and 
the  motor  root  proceeding  from  cells  within  the  central  nervous  axis. 

Proceeding  brainward  as  axones  of  the  Gasserii  cells,  the  sensory  fibres  of  the 
trigeminal  nerve  become  consolidated  into  the  la-^c  sensory  root,  which  passes 
through  an  opening  in  the  dura  mater  (Fig.  1033)  situated  beneath  the  attachment 
of  the  tentorium  cerebelli  to  the  posterior  clinoid  process.  Coursing  backward 
through  the  posterior  fossa  of  the  cranium  it  enters  the  brain-stem  on  the  lateral  sur- 
face of  the  pons,  slightly  behind  the  superior  border,  as  the  conspicuous  group  of 
robust  bundles  that  mark  the  superficial  origin  of  the  nerve  (Fig.  1046).  Just  above 
it  is  the  superficial  origin  of  the  motor  root,  from  which  it  is  separated  by  a  small 
bundle  of  pontine  fibres  which  belong;  to  the  middle  cerebellar  peduncle.  Below  and 
in  line  with  it  are  the  superficial  origins  of  the  facial  and  auditory  nerves. 

Entering  the  tegmental  portion  of  the  pons,  close  to  the  overlying  superior  cerebellar 
peduncle,  the  sensory  fibres  soon  come  into  relation  with  the  extensive  triceminal  reception- 
nueleua,  a  columnar  mass  of  gray  matter  within  the  lateral  part  of  the  tegmentum  (Fig.  935). 
This  nucleus  extends  from  the  middle  of  the  pons  through  the  entire  length  of  the  medulla  and 
into  the  spinal  cord  as  far  down  as  the  level  of  the  second  cervical  segment,  where  it  becomes 
continuous  with  the  substantia  gelatinosa  of  the  cord.  The  rounded  and  enlarged  upper  end 
of  this  tapering  column  is  described  as  the  seneory  nucleus  of  the  fifth  nerve,  althougli  it  com- 
prises only  a  small  part  of  the  reception-nucleus.  The  latter,  in  turn,  is  the  upward  prolongation 
of  the  subttantia  geUtinosa  Rolandi,  conspicuous  in  all  cross-sections  of  the  lower  pons  and 
medulla  as  an  oval  field  of  gray  matter  (Fig.  930I. 

On  nearing  this  column  the  sensory  fibres  divide  into  ascending  and  descending  branches, 
much  in  the  same  way  as  the  posterior  root-fibres  bifurcate  within  the  posterior  columns  of  the 
cord.  The  ascending  fibres,  distinctly  finer  than  the  descending,  soon  penetrate  the  sensory 
nucleus  and  the  substantia  gelatinosa  and  end  in  arborizations  around  the  neurones  of  the 
reception  nucleus.  The  coarser  descending  fibres  become  collected  into  a  compact  bundle,  the 
descending  or  spinal  root  (tractas  spiaalii  a.  triiemlnl),  whose  medially  directed  concavity  closely 
embraces  the  lateral  surface  of  the  column  of  gray  substance.    Beginning  with  its  descent,  the 


THE  TRIGEMINAL  NERVE. 


laji 


_     „  , ^  .^  fih,-,  oi«t  bend  mediaJly.  enter  the  adjacent  substentU  gel- 

.pinal  root  jdves  oB  collmtermb  «»^.°^'*  ™1^^^^  that  nucleus.    Since  the  number  of 

Sa  and  etHl  in  '"^^f'^J^J^  J^«^?o<  AeVpinal  root,  the  tract  is  Upering. 

fibre,  is  thus  Pr<>S«»»'^«='y  ,'«i'«^,^^,SS»>  ^  »"«»  *>*'"  '^  "P**'  ^'{."^ '"! 
becoming  smaller  and  smaller  as  it  »fP™™ JJ*''^;  fii,,,v  disappears.  In  its  descent  through 
latter,  at  about  the  level  f  »^';^°^^X  ^"'^  e  ,^X^^'^«-«.  '"  *e  lower  part  o. 
the  brainstem  the  spinal  •'^^  ^,?T,*l^'So(H;ieparated  from  it  by  the  vestibular  divusion 
the  pons  lying  to  the  '"ner  srfe  of  ^f;^",^*^  ^7he  medalla.  occupying  a  position  close 
rf  the  auditory  nerve,  and  lower  «  *^«latK  substance  oJ  the  tuberculum  Rolandi. 

to  the  surface  as  it  resU  upon  *«  «^~~  ^"^he  trigeminus  ( Fig.  1054).  by  way  either  o 
Thec«tralcofm«ettoM«»fth«a«i«>nrP~tottneing^.n^  ^^^^  ^, 

thecollateraU  of  the  fibres  of  ttesinnjarootor^^^^^^  ^^,„^^  ^^  ,,i, 

the  reception  neutows,  »«  ^"^^"l^lL^'^'^^Snt  p^^^  for  sSch  distributions  are  : 
""•"rB^rnTth:? ?L*^ate S^":ir'tKls^  the  recepUon-nudeus  ..ross  the 
raphe  to  jom  the  opposite  mesial  fillet  p^^.    ,^j^ 

and  ascend  to  the  optic  thalamus  and 
thence,  after  interruption  in  the  cells  oi 
the  latter,  by  axones  of  thalamic  neu- 
rones to  the  c-i.bral  cortex.  It «  prob- 
able that  so:  f  of  the  arcuate  fibres  do 
not  cross  the  mid-line,  but  ascend  within 
the  mesial  fillet  of  the  same  side.  It  is 
also  probable  that  collaterals  of  the 
arcuate  fibres  pass  to  the  trigeminal, 
facial  and  glosso-pharyngeo-vagal  motor 

i.  By  axones  from  the  cells  of  the 
reception  nucleus  that  enter  the  infe- 
rior cerebellar  peduncle  of  the  same  side 
and  pass  to  the  cerebellar  cortex  as  con- 
stituents of  the  Muc/eo-tereMiar  tract. 

3.  By  collaterals  that  are  distrib- 
uted to  the  nuclei  of  origin  of  the  hypo- 
Klossal  and  of  the  motor  part  of  die  trv- 
geminus  and  facial  nerves,  whereby 
these  'mportant  motor  nen,es  are 
brought  directly  under  the  influence  of 
the  sensory  part  of  the  fifth. 

The  Motor  Part.— In  con- 
trast to  the  median  position  of  the 
nuclei  of  origin  of  the  oculomotor, 
trochlear,  abducent  and  hypc^lM- 
sal  nerves,  the  deep  origin  of  the         ""*-r"  """-.■••Rc-r-u.ertan  Rangiioii  wun  aiv..™..  >-. 

some  dMtance  from  the  raphe  and 
fall  into  series  with  the  laterally 
arlrmlxli'c^aTi^i^^^rfh^  facial,  the  g.osso-pharyngeal  and  the  vagus. 


within  6ram-«ein;  '''^'\'^;^''^%/i,  smsory  and  mcHor 
//,  ///)  of  seniory  p«rt  of  •"^« i,r,,n,t;  gelatinoU ;  Sp.K.  spi- 

5S.mi.11'nSSSJ. :  ca.  citico-bulbT  fibre.. 


,.  The  largest  contingent  of  the  motor  fi;'--l;|!:.Sf  (T^^t  ThTn^clercon! 
«,urones  within  the  chief  motor  nucleus  (m«.«  ~«;»„"^ll^fi„rwhich  lies  in  the  upper 
si-a.  of  a  short  columnar  collect|on  of  ^fV '"""f^^^^  °"„^eus.  It  is  composed  of  large  stel- 
part  of  the  pons,  close  to  the  medmn  »''»;^^^"^^"^'l^  outward  through  the  teginentum 

Erii'-sur^stSn^thT^s.^'^^^^ 

rt^irs-^trfrurv::^^  i^=f 

become  incorporated  in  the  "I^^^l'^^/;;^;  'ZZ  r^t,  the  descending  me.enc.ph.Uc  root 

2.  A  second  and  smaller  ^o^*"'"'"*  "'''I?  !?  "'^^    from  cells  lying  within  the  lateral  part 

(,«IU  d.K.nd.n.  -.  trig.n.ini    '"^'"'•'iK.^f  aauldu^    In  cr^sections  (Fig.  936)  this  root 

i  ^LTs^'-d^^rcr^nll^bu^^^^^^  the  mid-brain  to  join  the  larger  tract 


1 33a 


HUMAN   ANATO^'Y 


of  fibres  from  the  chid  motor  nucteus.  In  its  downwfl  I  ourse  th-  nK-«encephalic  root  b 
joined  by  numerous  fibres  which  h«ve  their  origin  in  the  •  j'liented  <.-el  s  of  th'j  subst-  ntia  ierru- 
ginea  (page  1081)  of  the  same  and,  possibly,  of  the  oppo-  itu  :iidc 

The  fibres  from  these  various  sources — the  mese  "ephalir  .1  cleus,  the  substan- 
tia ferruginea  and  the  motor  nucleus — become  consoi.dated  into  tht  motor  root  of 
the  trigeminal  nerve,  whose  superficial  origin  (Fi^  1046;  is  jint  iKne  that  of  the 
sensory  root,  from  which  it  is  separated  by  some  oi  the  superficial  uansversc-  fibres 
of  the  pons.  Leaving  the  side  of  the  pons,  the  motor  root  follows  the  sairsf  course 
to  and  through  the  dura  mater  as  does  the  sensory,  10  the  inner  side  of  which  it  lies. 
It  eventually  passes  beneath  the  Gasserian  ganglion  to  become  ex  tisivdy  an 
integral  portion  of  the  mandibular  division  of  the  trigeminal. 

The  cortical  connection!  of  the  motor  root  are  established  by  fibres  that  arise  from  cells 
within  the  cortical  i^ay  matter  of  the  lower  third  of  the  precentral  convolution.  Thence,  as 
constituents  <if  the  pyramidal  tracts,  they  descend  through  the  corona  radiata,  the  interoal  cap- 
sule and  the  cerebral  peduncle  into  the  pons,  where,  for  the  most  part  after  dttUSS.*tion,  they 
terminate  in  end-arborizations  around  the  radicular  cells  of  t.^e  motor  trigeminal  nnolei. 

The  Gasserian  Ganglion. — The  Gasserian  ganglion  (^KancHon  Mffliluaare 
[Gasaerl])  (Fig.  1055")  is  an  important  complex  of  nerve-fibres  and  cells,  which  lies 

in  a  slight  depression  on  the 
Fiu.  loss.  stp^x  ^^  t^^  petrous  piortion  of 

the  temporal  bone.  In  shape 
it  is  a  flattened  cresct  .it  with  its 
convexity  forward,  measurinjj; 
from  1.5-2  cm.  in  width  ami 
about  I  cm.  in  length.  The  sur- 
face of  the  ganglion  presents  an 
irregular  longitudinal  or  reticu- 
lar striation.  From  the  anterior 
exfianded  convex  border  of  the 
ganglion  arise  the  ophthalmic 
and  maxillary  nerves  and  the 
sensory  f>ortion  of  the  mandib- 
ular nerve,  while  its  narrow- 
concave  posterior  margin  is  con- 
tinued into  the  sensory  root  of 
the  fifth  nerve.  The  ganglion 
lies  in  Meckel' s  space  (cavern 
Meckelii),  a  cleft  produced  by  a 
delamination  nf  the  dura  mater 
anil  >mes  in  relation  internally 
witli  iie  cavernous  sinu-  and 
the  internal  carotid  artery.  Be- 
neath, but  unconnected  with  ii. 
are  the  motor  root  of  the  trifacial  and  the  great  superficial  fietrosal  nerve.  I  -triK- 
ture  it  resembles  a  spinal  ganglion,  being  composed  of  the  ■  laracteristically  mo»tifi«.rd 
neurones,  from  whose  single  processes  proceed  the  peripherally  directed  denontes 
and  the  centrally  coursing  axones. 

In  addition  to  the  three  large  trunks  given  off  from  the  anterior  margin,  tc 
branches  of  the  Gasserian  ganglion  include  some  fine  meningeal  filamer.'.x 
which  arise  from  the  posterior  end  of  the  ganglion  and  are  distributed  to  the  a>i.^ 
cent  dura  mater. 


GuKrian  ganglion  of   left  side  viewed  from   above;    seniory 
motor  roots  and  ttirec  divisions  of  trigeminal  ncr\-e  are  seen. 


Communications. — At  its  inner  side  the  t'lasserian  ganglion  receivo  iiiaments  from  the 
adjacent  carotid  plexus  of  the  sympathetic,  which  end  in  relation  with  the  cells  of  the  ganglion. 

Divisions  of  the  Trigeminal  Nerve. — These  arc  three  in  muiljer,  the  oph- 
ihaimic,  the  maxillary  and  the  mandibular  nerves.       They  arise  from  the  anterior 


THE  TRIGEMINAI    NFRVK 


"33 


^.  «l  the  (ia«erian  ffanfriion,  tl  o  tormatior  of  the  mandibular   ,erx-e  being  com- 
eyelid,  the  conjunctiva,  t»»e  eyenau   i  y        »  ^  anten.-r  por- 

Branches  ana  u»    nouasni  laehntii^l  (x)  i\\k  fronla    and 

r.^  the  recurrent,  (2)  &'-  communualmg,  (3)  thi   /of/ir)'"'  '•  ^'^>        J 
(J)  IS  I^*?^  whi4  t  e  last  thr,  e  a-     tenn.n  •!  branches 


Fig.  lojf 


SttpiBtochlcur  neni 


N«M>1  lltrrvt- 

lUctorj-  Imlti* 

nhliiai**  ^nwMCle 
r,     twrr^e 

CM'        V  <"  I""* 

ptJcc'  iaam 
■nal  rarotid         ry  — -, 
Oyyv-  ;  raci ' 

VI  uerve- 
III.  nenra 


>»pr«orWul  n»T\e 
.Lachrymal  gtaml 

Lmtor  palpebru      iperiori* 

luprrior  rectus 

Frontal  nerve 
External  recto* 


Lachrymal  nerve 

Ophthalmic  division  of  V.  ner 
Maxillary  division  of  \'  nerv 
Mandibular  divtaioii  i-«- 

Gaiaerian  ganglion 

Mcatu*  auditorius  interii- 

VH.  nerve,  motor  part 
Para  intermedia 

•VIII.  nerve 


-  ■--^.„'?rj^hii3.=,S!i:vlsl:M^^^^^^  ' 


Gataerian 


th. 
its  \ 


,e  recurrent  branch  (n.  tentorii)  arises  shortly  after  ^^e  nerve  leav^the 
U  p^  across  and  is  adherent  to  the  trochlear  nerve  and  is  distributed 

H:'c\Cmt;i?cVS;tr«ch:i^ire  three  slender  fi.a.en-hic^^^^^ 
e  the  nerve  breaks  up  into  its  terminal  branches  ;   ^-^yj"*" '^l^^'^'^r^rinK 
.riS  and  sixth  ner^-es':  to  whose  muscles  thcys"I|P>y  ^^.^'  ^  ^^^^, 
Its  1       «e  through  the  cavernous  sinus,  the  ophthalmic  n^rrve  r«: 
Warn.  .Its  from  the  cavernous  sympathetic  plexus.  «ji«t  of  tiie 

i.  The  lachrymal  nerve  (n.  lacrimalis)  (Fig   10     J"  J»^  ^  ^^^ 

terminal  branches.  It  lies  to  the  outer  side  ^^^l.^,;  :„^"^Xa  ^  It  passes 
outer  angle  of  the  sphenoidal  fissure  in  its  own  »h'^  °*^  ^SZl^  tlw  ..rhit. 
above  the  origin  of  the  orbital  muscles  and  courses  »7;^^1^  T  ^  ^  "ces  the 
above  the  external  rectus,  to  the  upper  outer  angle  <»  tbe  ^,  ^^^llT^'^if  ,,„„. 
S^bSl  fascia  near  the  external  canthus  to  tenmn^  ''^^^gTex^  canthl 
Eum  the  lachrymal  gland,  the  upper  eyelid  and  the  ston  .if«t»Kl  tne  extendi 


1*34 


HUMAN  ANATOMY. 


Within  the  orbit  the  lachrymal  nerve  communicate*  with  the  temporal  branch 
of  the  temporo-malar  nerve  and  on  the  face  with  the  temporal  branch  of  the  facial. 
The  latter  is  one  of  the  numerous  sensory-motor  communicaUons  between  the 
terminal  fibres  of  the  fifth  and  seventh  nerves. 

V«ri«tkm».— Occasionolly  the  lachrymal  nerve  seems  to  be  partly  derived  from  the  troch- 
lear :  the  true  source  of  such  fibres,  however,  is  probably  the  ophthalmic  nerve,  by  waX  °*  "* 
communicating  branch  to  the  fourth  Considerable  variation  is  found  in  <»™||«ct«on  with  the 
temporal  branch  of  the  temporo-malar  nerve.  The  techrymal  nerve  or  the  tempora^  branch  of 
the  temporo-malar  may  be  absent,  the  place  of  either  being  taken  by  the  other,  or  the  'achryma 
may  be  small  at  its  origin  and  later  increased  to  normal  sue  by  accessions  from  the  temporal 
branch  of  tlie  temporo-malar. 

4.  The  frontal  nerve  (n.  fronUlis)  (Fig.  1053)  is  the  largest  branch  of  the 
ophthalmic.  It  enters  the  orbit,  invested  by  its  own  dural  sheath,  through  the 
sphenoidal  fissure  and  above  the  orbital  muscles  and  passes  directly  forward  between 
the  periosteum  and  the  levator  palpebra  superioris.  At  a  variable  point,  usually 
about  the  middle  of  the  orbit,  it  divides  into  its  terminal  branches,  the  (a)  stipra- 
trochUar  and  (*)  the  supraorbita/. 

a.  The  ■upratTochlear  nerv*  (o.  MpratfKhlcarii)  is  the  smaller  of  the  two  terminal 
branches.  It  passes  inward  and  forward  over  the  pulley  of  the  superior  oblique  and  thence 
between  the  orbicularis  palpebrarum  and  the  frontal  bone,  leaving  the  orbit  at  its  upper  inner 
angle  Near  the  pulley  it  gives  off  a  branch  which  joins  the  infratrochlear  (Fig.  1057)  and  at 
the  edge  of  the  orbit  supplies  filamente  (nn.  palpcbralts  Miperiore*)  to  the  skin  and  conjunctiva  of 
the  upper  eyelid.  It  then  turns  upward  and  subdivides  into  a  number  of  small  branches  which 
pierce  the  substance  of  the  fronUlis  and  orbicularis  palpebrarum  muscles  to  supply  the  inner 
and  lower  part  of  the  forehead.  .         j.       ,    ..  , 

b.  The  auprwirbital  n«ve  (n.  Mprawbiulii)  (Fig.  1056)  continues  directly  the  course  of 
the  fronUl  nerve.  It  lies  close  to  the  periosteum  throughout  i»  entire  orbital  course  and  leaves 
the  orbit  through  the  supraorbital  notch  or  foramen.  In  this  situation  it  sends  a  small  filament 
to  the  frontal  sinus  to  supply  its  diploe  and  mucous  membrane.  As  it  leaves  the  orbit  it  sup- 
plies some  fine  twigs  to  the  upper  eyelid  and  then  divides  into  a  larger  outer  and  smaller  inner 
branch.  These  pass  upward  on  the  forehead  beneath  the  frontalis  muscle,  occasionally  occupy- 
ing quite  deep  grooves  in  the  frontal  bone,  and  terminate  by  being  distributed  to  the  scalp  and 
pericranium.  The  outer  branch  extends  back  neariy  to  the  occipital  bone,  while  the  inner 
passes  only  a  short  distance  posterior  to  the  coronal  suture. 

Both  branches  of  the  fronUl,  the  supratrochlear  and  the  supraorbital,  communicate  with 
branches  of  the  facial  nerve  and  thereby  supply  sensory  filaments  to  muscles  supplied  by  the 
seventh. 

Variations.— The  nerve  may  divide  before  leaving  the  orbit  and  in  that  event  only  the  outer 
branch  passes  through  the  normal  osseous  channel.  The  inner  sometimes  has  a  special  groove, 
named  by  Henle  ihefroHtal  nolek. 

5.  The  naaal  nerve  (n.  nasocillaris)  (Fig.  1057)  is  intermediate  in  size 
between  the  lachrymal  and  the  frontal.  It  enters  the  orbit,  clothed  in  dura  mater, 
through  the  sf)henoidal  fissure,  between  the  heads  of  the  external  rectus  and  between 
the  superior  and  inferior  divisions  of  the  oculomotor  nerve.  Turning  obliquely  in- 
ward, it  crosses  the  optic  nerve  and  passes  beneath  the  superior  oblique  and  superior 
rectus  muscles  and  above  the  internal  rectus.  Thence  it  traverses  the  anterior  eth- 
moidal foramen  to  enter  the  cranial  cavity,  where  it  passes  forward  in  a  groove  in 
the  lateral  part  of  the  cribriform  plate  of  the  ethmoid  bone.  Leaving  the  cranium 
through  the  nasal  fissure,  the  nerve  enters  the  nasal  fossa,  where  it  breaks  up  into 
its  three  terminal  branches. 

Branchee.— These  are  :  (a)  the  ganj^Honic,  (o)  the  /ongr  cilia/y,  (r)  the  tn/ra- 
trochlear,  (d)  the  internal  nasal.  (<•)  the  external  nasal  and  (/)  the  anterior  nasal,  of 
which  the  last  three  are  terminal  branches. 

a.  The  ganglionic  brunch  (radix  loaga)  (Fig.  1057)  usually  leaves  the  nerve  between  the 
heads  of  the  external  rectus  and  passes  forward  aUing  the  outer  side  of  the  optic  nerve  to  enter 
the  upper  posterior  portion  of  the  ciliary  ganglion,  of  which  it  forms  the  sensory  or  long  root. 

*.  The  /(W»e-  HOary  hranrhes  (bb.  dllares  loa«l)  {  Fir,  1058)  are  two  in  number.  They  pass 
forward  along  the  inner  Side  of  the  optic  nerve  and,  after  joining  one  or  more  of  the  short  ciliary 
nerves,  pierce  the  sclerotic  coat  of  the  eye  to  be  distributed  to  the  iris,  ciliary  muscle  and  cornea. 


THE  TRIGEMINAL  NERVE 


"35 


orbital  wall  and  beneath  tf.e  ?"P^™' °^''^^;L"i^£  U  re^ivw  a 'filament  (the  supratrochlear , 
rrt.aZ'^  J::e%"  'TZ^^  t^e1i;in  offilJeT?yeUd  and  root  o.  the  nose,  as  we.,  .s 
»"^T"T^?;wt;«fori-"^^^^^^^^^  ^^'^-  .048)  supplies  themucousmenw 

brane  »!«;« -^  S^fi" W.M^^^^^^^  (Fig.  ,047)  supplies  the  front  part  of  the  middle 

and  inferior  turbinate  bones  and  outer  waU  of  the  n^^*^^         downward  in  «  groove  in 
U.e  ^d^tiTKe  ri  ^•'^^hrt^ltwr  the  l^er  end  of  the  na..  bone  and  the 

Fig.  1057. 


gopnior  oblique  miiKl 
latemal  rectus  muncl 

itUfBtrochlear  l>r.  of  n«»al 
Nasal  nei 


Olfactory  bul 

Levator  palpebrse  «uper|-, 
oria,  inverted 

III.  nerve,  auperior 
divinon 

FronUl  nerv 
Optic  nerve 
Internal  carotid  artery- — 
III.  nerv' 

Pdoi.  dUplaced  backward- 

Cerebial  peduncle 


_^Le»ator  palpetwie  Mipefloito 
iperior  rectu* 


ichr>mal  gland 

erve  to  inferior  obllqat 

;xtemal  rectus  muacte 


-Ciliary  ganglion 


'Nasal  nerve 
Lacbrymal  nerve 

Maxillary  division  of  v. 

ihthalmic  division  of  V 
'Mandibular  division  of  V 
:rian  ganglion 

.VI.  nerve 
'IV.  nerve 

VII.  nerve 

VIII.  nerva 


>,^' 


Deep.,  dissection  ofHght  orbit.  vi.«d.romabove;b™.cb.so.na..l  nan-. -K«n. 

nenre  sent^bres  tothe  third  and  sixth  n^"^^^*,.    .'",*„  ,u!^,uoratrochlear.     Branches  to  the 
"nfmtr^h  ear  branch,  the  ^^ficiency  ^mg  su|jp  ed  I  y  thejupr^^^^^^^ 

rental  and  ethmoidal  sinuses  ?';f,d^r\'^„^*,^.^';^rS^^^^^        posterior  ethmodal  foramen  to 
men.  and  a  branch  has  ^t*" '"'"d  «h^h  jms^^^^^^      K       I_^k^ ^^^  ^„  ^^^^  by  Luschka 

The  0.ngli. ...eclated wlththeTri^^^^^^^^^^ 


t»3fi 


HUMAN  ANATOMY. 


with  the  ophthalmic  nerve,  the  spheno-palatine  with  the  maxillary  and  the  otic  and 
submaxillary  with  the  mandibular.  Each  is  the  recipient  of  three  rools — a  motor,  a 
sensory  and  a  sympathetic — and  from  each  ganglion  branches  are  given  of!  to  more  or 
less  contiguous  structures.  . 

The  significance  of  these  bodies — whether  of  the  nature  of  spinal  or  sympathetic 
ganglia— has  long  been  a  subject  of  discussion.  The  close  resemblance  of  their 
nerve-cells  to  the  stellate  neurones  of  undoubted  sympathetic  ganglia,  as  shown  by  the 
investigations  of  ReUius,  KoUiker  and  others,  as  well  as  the  results  of  experimental 
studies  (Apolant),  justifies  the  conclusion  that  these  ganglia  are  properly  regarded 
as  belonging  to  the  sympathetic  group.  They  are,  therefore,  probably  stations 
in  which  certain  motor  and  secretory  fibres  conbibuted  by  various  nerves  end  in 
arborizations  around  sympathetic  neurones,  from  which  axones  pass  for  the  immedi- 
ate supplv  of  involuntory  muscle  and  glandular  tissue.  The  fact  that  these  small 
ganglia  are  derivations  of  the  early  Gasserian  ganglion  is  in  accord  with  the  mode 
of  origin  of  the  sympathetic  ganglia  elsewhere  (page  1013). 


lamoal  carotid 

iV.  Her** 
Cvabcal  peduncl^ 


Levfttoff  (MlpchrsB  sujicTiorls 

Supetlnr  obllqiie  niincle 
LachrynMl  ^UmK 

SupcTtot  rectus  -nuicle 

.Long  cHUry  bnmdic*  irf  nasit  aerv« 

Eit.  rectus.  Intertluii 
iBfrrior  obllqtM  muacle 


MM<««  inshellar 
p«iluiKle 


Caaaerun  tfannnaa 

Eat.  rectuf  muicla 


VI.  I 

t^angltunic  Itianih  of  naul 


Short  ciliary  ■ 


-      .  .htolnf.  obtlqua 
Infcrfor  mrtut  niuKlc 


DIucctlon  of  rt|[ht  orbit  alter  removal  of  Its  lateral  wall;  external  aixl  anperior  cye-mutclea  have  been  cut  and 
diaplaced  to  txpoK  ciliary  ganglionand  nervca. 

The  Ciliary  Ganglion. — The  ciliary,  ophthalmic  or  lenticulat  ganglion 
(k.  citiare)  (Fig.  1058),  as  it  is  varyingly  called,  is  a  small  reddish  mass,  about 
3  mm.  long  in  the  antero-posterior  direction,  and  approximately  quadrilateral  in  out- 
line. It  is  compressed  laterally  and  to  each  angle  is  attached  one  or  more  bundles  of 
nerve-fibres.  It  lies  near  the  apex  of  the  orbit  on  the  outer  side  of  the  optic  nerve, 
between  the  latter  and  the  external  rectus  muscle  and  anterior  to  the  ophthalmic  artery. 

The  nerve-cells  within  the  ganglion  are  chiefly  multipolar  elements,  which 
closely  resemble  sympathetic  neurones  (Retzius)  and  send  their  axones  towards  the 
eye  by  way  of  the  short  ciliary  nerves. 

Roots. — All  of  these  enter  the  posterior  margin  of  the  ganglion.  The  motor 
or  short  root  (radix  brevls),  the  thickest  of  the  roots  and  sometimes  double,  is  an  off- 
shoot from  the  branch  of  the  oculomotor  nerve  which  supplies  the  inferior  oblique 
muscle.  It  is  short  and  comf>arativcly  robust  and  joins  the  postero-inferior  portion 
of  the  ganglion.  The  sensory  or  lonff  root  (radix  loni{a)  arises  from  the  nasal  branch 
of  the  ophthalmic,  leaving  the  latter  between  the  heads  of  the  external  rectus.  It  is 
long  and  slender  and  passes  forward  to  enter  the  upper  posterior  angle  of  the  gang- 
lion, occasionally  being  fused  with  the  sympathetic  root.     The  sympathetic  root  (radix 


THE  TRIGEMINAL  NERVE 


t237 


— ^..^  5,  a  tinv  filament  which  arises  from  the  cavernous  plexus  and  rims  forward  to 

rochms  Ite  ^^  ''^,'^,,!°'fLl  J^SkTS.  lo™™l  abo«.  and  Wo.  Ih.  optic 
nerve.     The  lower  set  is  uie  '"""=  ...  {  tg  const  luent  branches 

cervical  gangliated  cord  and  (*)  ^^^  "^'^f  ?*  "f-7?"Si^er   muscle  of  the  iris,  which,  while 
Fibres  suppl>-ing  the  chary  7"^'^!^ J;'^"^  "L™'*^^  the  axones  oJ  the  stellate 

in  a  sense  the  cominuat.on.s  »/ *»«=.^'°"'"X^   (1;  jS^al  fitaes  which  transmit  sensory 
f^XtrhTiSenro/^Ll^K  if  ^ni^^^^^^^  the  Ion,  ciliary  nerves. 

V.ri.tion..-The  motor  root  °«-'«5-"y  {"^^  fo^a 'c^mm^^^  f^nfofeTtran^ 
noted  above,  the  sensory  and  sympathetic  roots  frequently  !?.TJL"hlv  to  the  scattering  of  its 


lachrymal,  from  the  abducent  and  from  the  sP^^^J^lfblfihe  lone  ciliary  nerves  convey- 
'i^tTi^l^n  noted,  the  defiden^P^^Wyl^^^^  ^^^^         i„^ 

Sfl  iS^f  of  th™  fibres  a<io.S;anying  the  oculomotor  nerve. 

TT    The  MMillarv  Nerve  or  superior  maxillary  nerve  (n.  maxlUarjs)  is  purely 

^?-in?.Jm«l^te  in  size  between  the  ophthalmic  and  mandibular  divisions 

sensory  and  is  '"termed  ate  in  ^^^  '^^^"j^^        ^  ^^  ^^^  ^^^        j  ^^gi^„_ 

.u^  miHrllp  rranial  fossa  Iv  ne  be bw  the  cavernous  sinu    (Pig.  1053).      ine  nerve 
eav«thl  crinrm  Sgh  tL  foramen  rotundum.  trave.ses  the  spheno-maxillary 

""'t"?h^two  or  thr«  tpheno-p.l.«»e  branch.,  (no.  .|)li..w;l"I.O   (Fif- 


'^4: 


lajS 


HUMAN  ANATOMY. 


into  the  orbital,  posterior  nasal  and  palatine  branches.  White  in  neither  case  are  the 
trigeminal  fibres  interrupted  in  the  ganglion,  in  both  instances  they  receive  sympa- 
thetic fibres  from  the  ganglion,  which  accompany  the  trigeminal  ones. 

3.  The  posterior  superior  dental  nerve  (r.  alveolaris  rapcrior  posttrior) 
(Fig.  1060)  is  frequently  douUe.  It  passes  downward  and  forward  with  the  posterior 
dental  artery  through  the  pterygo-maxillary  fissure  to  reach  the  zygomatic  surface  of 
the  maxilla.  It  supplies  tiny  filaments  to  the  gum  and  adjacent  mucous  membrane  of 
the  cheek  and  enters  the  piosterior  dental  canals  to  supply  the  molar  teeth.  It  forms 
a  fine  plexus  (picins  deotalis  superior)  (Fig.  1059)  with  the  middle  and  anterior 
superior  dental  nerves. 

Variation. — In  the  absence  of  the  buccal  branch  of  the  fihh,  the  posterior  superior  dental 
has  been  observed  to  be  of  large  size  and  to  assume  the  distribution  of  the  buccal. 

4.  The  temporo-malar  or  orbital  nerve  (a.  z}'gomatlcuK)  (Fig.  1053)  after 
arising  from  the  maxillary  passes  from  the  spheno-maxillary  fossa  into  the  orbit 


Fig.  1059. 


DtaKrem  •howinc  plan  and  connactioiu  o(  Hcond  and  third  divltioni  of  Iricnnlnui  and  thrir  ganKlla. 

through  the  spheno-maxillary  fissure.  It  courses  along  the  external  orbital  wall  and 
divides  into  a  temporal  and  a  malar  branch.  The  temporal  branch  (0.  lygonuticotcm- 
poralis)  after  inosculating  with  the  lachrymal  nerve  paisses  through  the  spheno-malar 
foramen  to  enter  the  temporal  fossa.  It  then  runs  between  the  bone  and  the  temporal 
muscle  and  pierces  the  temporal  fascia  to  be  distributed  to  the  skin  of  the  anterior 
temporal  region.  It  communicates  with  the  temporal  branch  of  the  facial  nerve. 
The  malar  branch  (n.  zyKomaticofacialis)  traverses  the  malar  foramen  to  supply  the 
skin  of  the  malar  region.  It  joins  with  filaments  from  the  malar  branch  of  the 
seventh. 

Variatfona.— The  nerve  may  pass  through  the  malar  bone  before  It  divides,  both  branches 
may  pass  separately  throtifch  canals  confined  to  the  malar  bone,  or  the  temporal  branch  may  pass 


THE  TRIGEMINAL  NERVE. 


"39 


Fither  branch  may  be  absent  or  smaller  than  normal,  he 

^ ,  -— -        E«*"^  3^  ma^  te  replaced  in  its  dtetribution  by  the 

ilying  the  defiaency.  .  The  maUr  may^Jf.  ™^;..7;t:  laohrvmal. 


ihroueh  the  spheno-maxillary  fosure.    cun"  '"'!^""~'  ^  replaced  in  its  dteti 
£fel*i«"S.S?a{^-^'=S^^su  Jt^t^t^^a^^^^^^      the  lachrymal. 


5.  The  middle  superior  dental -n,e<r.^^^^^  T'SLI^SfyS 
U.e  .LxUlary  in  the  P^stenor  part  f  ^"^j^^^^^^^  i„  the  outer  wafl  of  the 
ra£^'a=rnSrSngi;{^w1th  the  other  twodentalnervessu^^^^^ 

^'^  T-^^S^rior  .uperior  ^V^^^^^^l.^.^'t^Z:^^:^^  £fSe 
lareest  of  the  three  supenor  dental  neryra.     It  f  ^'^^^       .^  ;„  ^  ainal   in  the 

Fig.  ia6a 


Mxnuiy 

dlvhloa  of  mudiliula' 
AiKkulo-wniwnl  a« 


Ert.ytwH"''''" 
Umgnti 

SartiMtitmfMi  turn- 

Inwnvl  inMllUfT  Mttnr 
Inl.  iMrytXd  n»»« 

EM.c<io«kl 


MiMqnMWMcb  oriahitot 

■ulimullUor  ■'•■<<' 


through  a  tiny  canal   in   the  otL^lelf'^aAtfth;  XbrnL^^^^^^ 
t^-i  Z  ="^rt:;;rin1  ^  rXr^r^dent.  piexu..  the  anterior 
I^rior  dental  supplies  the  canine  and  .nc.sor  teeth. 

Two  th.c..n.nn  a-  sometimes  found  in  »„»•« -P^^^^f  ,tSV-^^^ 
as  the ^v/w-  0/  /'«/«./.».  lies  above  the  t.p  °' '•^V^'l .'^n^e  other. sometimes  called 
WnctiofoJ^the  middle  and  P!«t«;"°«- »"P«-'°1  tSoriv^t  die  Junction  of  the  middle  and 

«r^dlSSurng  of  interlacing  bundle,  of  „erve-fibr«.. 


1340 


HUMAN  ANATOMY. 


7.  The  inferior  palpebral  branches  (rr.  palpebralcs  ioferiom)  (Fig.  1060) 
usually  two  in  number,  are  the  smallest  of  the  terminal  branches.  They  pass  upwara 
from  the  infraorbital  foramen,  pierce  the  origin  of  the  levator  labii  superioris,  pass 
around  the  lower  margin  of  the  orbicularis  ^pebrarum  and  supply  the  conjunctiva 
and  skin  of  the  lower  eyelid. 

8.  The  lateral  natal  branches  (rr.  naaalcs  eztemi)  (Fig.  1060),  from  two  to 
four  in  number,  pass  inward  under  the  levator  labii  superioris  alseque  nasi  and  supply 
the  skin  of  the  side  of  the  nose. 

9.  The  superior  labial  branches  (rr.  labiales  snperiores)  (Fig.  1060),  two  to 
four  in  number,  are  the  largest  of  the  terminal  branches.  They  pass  downward 
under  the  levator  labii  superioris  and,  after  supplying  the  anterior  portion  of  the 
skin  of  the  cheek,  terminate  in  the  mucous  membrane  and  skin  of  the  upper  lip. 

The  last  three  branches  inosculate  freely  under  the  levator  labii  superioris  with 
the  infraorbital  branch  of  the  facial,  forming  the  infraorbit€U plexus  (Fig.  1068). 

The  Spheno-Palatine  Ganglion. — ^The  spheno-palatine  ganglion  (((.  Bpheno> 
palattnam),  also  known  as  Meckel's,  the  spheno-maxillary  or  the  nasal  ganglion,  is  a 
small  triangular  reddish-gray  body,  with  the  apex  directed  posteriorly,  situated  in 
the  upper  portion  of  the  spheno-maxillary  fossa.  It  b  flat  on  its  mesial  surface, 
and  convex  on  its  lateral,  and  measures  about  5  mm.  in  length.  It  lies  in  close 
proximity  to  the  spheno-palatine  foramen  and  just  beneath  the  maxillary  branch  of 
the  trigeminal  nerve  (Fig.  1061).  The  ganglion  is  regarded  as  belonging  to  the 
series  of  sympathetic  nodes,  and  consbts  of  an  interiacement  of  nerve-fibres  in  which 
are  embedded  numerous  stellate  sympathetic  neurones. 

Roots.— The  sensory  root  consists  of  two,  sometimes  three,  short  stout 
filaments,  the  spheno-palatine  nerves  (on.  sphenopalatinn,  which  pass  direcdy 
downward  from  the  lower  mai^n  of  the  maxillary  nerve  to  the  upper  border  of  the 
ganglion.  While  some  few  of  the  fibres  of  this  root  are  axones  of  the  sympathetic 
ganglion-cells,  the  great  majority  are  dendrites  of  the  cells  of  the  Gasserian  ganglion 
which  pass  to  a  limited  extent  through,  but  mostly  around,  the  spheno-palatine 
ganglion  independenUy  of  its  cellular  elements.  They  are  continued  entirely  into  the 
various  trunks  that  are  usually  described  as  branches  of  distribution  of  the  ganglion 
(see  below). 

The  ptotor  root  is  the  great  superficial  petrosal  nerve  (a.  petnwus  soperficialis 
major)  which,  in  all  probability,  carries  sensory  as  well  as  motor  fibres.  It  arises  from 
the  facial  nerve  in  the  facial  canal,  passes  through  the  hiatus  Fallopii  and  a  groove  in 
the  petrous  portion  of  the  temporal  bone  and  then  under  the  Gasserian  ganglion  to 
reach  the  cartilage  occupying  the  middle  lacerated  foramen.  Here  the  great  super- 
ficial petrosal  nerve  is  join^  by  the  sympathetic  root,  the  great  deep  petrosal, 
(n.  petrostts  profundus),  which  is  a  branch  from  the  carotid  plexus.  The  two  great 
petrosal  nerves  fuse  over  the  cartilage  at  the  middle  lacerated  foramen  to  form  the 
Vidian  nerve  (n.  canalis  pteo'goidei  [Vidll])  (Fig.  io6i),  which  traverses  the  canal  of 
the  same  name  and  enters  the  spheno-maxillary  fossa  to  join  the  spheno-palatine 
ganglion.  In  its  course  through  the  canal  the  Vidian  nerve  gives  off  a  few  tiny 
nasal  branches,  which,  composed  of  trigeminal  and  sympathetic  fibres,  supply  the 
pharyngeal  ostium  of  the  Eustachian  tube  and  the  posterior  part  of  the  roof  of 
the  nose  and  the  nasal  septum.  While  in  the  canal,  the  Vidian  nerve  receives  a 
filament  from  the  otic  ganglion. 

In  addition  to  supplying  (accordinR  to  many  anatomists)  motor  fibres  to  the  levator  palati 
and  azygos  uvula  muscles,  some  of  the  facial  fibres  are  especially  destined  for  Klandular  struc- 
tures. Such  fibres  are  probably  interrupted  around  the  stellate  cells  of  the  spheno-palatine 
({anglion,  the  axones  of  which  then  complete  the  paths  for  the  secretory  impulses.  The  sensory 
constituents  of  the  great  superficial  petrosal  ner\e  are,  perhaps,  of  two  kinds :  {a)  fibres  from 
the  cells  of  the  geniculate  ^ganglion  of  the  facial  to  the  palatine  taste-buds,  and  (A)  recurrent 
trigeminal  fibres,  that,  by  way  of  the  maxillary,  spheno-palatine  and  great  superficial  petrosal 
nerves,  are  distributed  with  the  peripheral  branches  of  the  Vidian  or  of  the  facial  nerve. 

The  great  deep  petrosal  nerve  represents  the  association  cord  belttxcn  the  superior  cer\'!cal 
s>Tnpathetic  and  the  spheno-palatine  ganglion.  Many  of  Its  fibres  end  in  arborizations  around 
the  stellate  spheno-palatine  cells,  from  which,  in  turn,  axones  pass  to  blood-vessels  and  glands 
by  way  of  the  ganglionic  branches  of  distribution. 


THE  TRIGEMINAL  NERVE. 


1 341 


terior  palatine  nerves. 


Fig.  1061. 


liiHlliiikl 


int.  oradd  artery 


Po«t.lnr. 
poilerlovpBtettM 


GfMt  MpcrtcUl 
^petWMa  "err* 

GfcMrfcfppctrcMl 
serve  fnmi  canXld 
plexus 


Oik  gaagUoB.  ct4 

CMtlliC^af  EusUdliM 
tube,  cut 

.tBi.br.effitcendinK 
MViM  sup.  ccrv.  B^anl. 
Hit  tar.  of  sscenflinif 


^k  u«  .  »<  — —  ■• » 

rsnusof  »up.  cciv. 
gsatflkm 


Sup.rerv.  pumrlkto 
of  sywpatbctk 


iBt-  I  aroOd  utcrj 


Uvuls 


Superior  constttctoc 
I^vslor  paUt* 
Tensor  pelel* .  c  ut  above 


Dt««tlon  .howlng  .ph«o-p.l.lln.  and  oUc  (..«».  viCT«d  from  wi.hin. 


(„. ..-.« p~ur..r»  .-f.H.«.) .  which,  -^n^^t'^^x  rLruTriit  Kits: 

plate  of  the  palate  bone  enter  th«  nasaHo»a  and  su W  V  *«  ~  y^,^  ^„j  i^^. 

anterior  portion  of  the  inferior  turbinate  bone  and  '♦^^"°^°^';!^' for^^rf  )„  ,  groove  on  the 
nor  nasal  meatuses.  Emerging  from  its  «^»"f  \»^«  ^"\"  "^^^^P^ame^rof  the  naso-palatine 
inferior  aspect  of  the  hard  palate  ""^  'noscula^w  w.th  the  termi^^^^  ^  ^h^ 

nerve.    U  suppUes  the  hard  palate  and  its  mucous  rnembr^^^^^^^  ^^^  ^^^„ 

mam^nJI^Vcr^^hShThe^at^^r^^^^^^^  — ^  -'^  ^""^  ^  ™^ 

membrane  of  the  soft  palate  and  tonsil. 

They  are  :  (a)  the  AJJ/^nor  w/^r/or  «<iM/and  (*)  the  naso paiatwe  nc 


1243 


HUMAN   ANATOMY. 


c  Th«  posterior  superior  nasal  nerve  (rr.  Uteralo)  supplies  the  mucous  membrane  tA  the 
posteror  superior  portion  of  the  outer  wall  of  the  nasal  fossa. 

o.  The  naso-palatine  nerve  (■.  aastpalatliias)  (Fig.  1059)  crosses  the  roof  cA  the  nasal 
chnmber  and  passes  downward  and  forward  in  a  groove  in  the  vomer  and  septal  cartilage  to 
reach  the  anterior  palatine  canal.  It  then  passes  through  the  foramen  of  Scarpa,  the  left  nerve 
through  the  anterior  and  the  right  one  through  the  posterior  canal,  the  two  nerves  forming  in 
this  situation  a  fine  plexus.  Having  reached  the  inferior  surface  of  the  hard  palate,  the  naso- 
palatine inosculates  with  the  large  posterior  pakttine  nerve.  It  supplies  the  roof  and  septum  of 
the  nose  and  that  portion  of  the  hard  palate  which  lies  posterior  to  the  incisor  teeth. 

4.  The  posterior  branch  (Fig.  1059)  also  known  as  Htut  pharyngeal  ox 
ptery go-palatine,  leaves  the  spheno-maxillary  fossa  through  the  pterygo-palatine 
canal  and  supplies  the  mucous  membrane  of  the  naso-pharynx  in  the  r^ion  of  the 
fossa  of  Rosenmiiller. 

Variation*.— Branches  of  the  ganglion  have  been  described  as  passing  to  the  abducent 
nerve,  to  the  ciliary  ganglion  and  to  the  optic  nerve  or  its  sheath.  The  accessory  posterior 
palatine  nerve  is  sometimes  absent.  Quite  frequently  the  left  naso-palatine  nerve  passes 
through  the  posterior  foramen  of  Scarpa  and  the  right  nerve  through  the  anterior. 

III.  The  Mandibular  Nerve. — The  mandibular  or  inferior  maxillary  branch 
(n.  mandibnlaris)  of  the  trigeminal  nerve  is  the  largest  of  its  three  divisions  and,  being  a 
mixed  nerve,  consists  of  two  portions,  one  sensory  and  the  other  motor.  The  sensory 
part  is  the  larger  and  arises  from  the  lower  anterior  portion  of  the  Gasserian  ganglion. 
The  smaller  motor  part  is  the  motor  root  of  the  trigeminal  nerve,  which  contributes 
exclusively  to  this  division  of  the  fifth  nerve.  Although  these  two  portions  are  inti- 
mately associated  in  their  passage  through  the  foramen  ovale,  the  motor  bundle 
lying  to  the  median  side  of  the  sensory,  it  is  not  until  they  emerge  from  the  skull 
that  they  unite,  immediately  below  the  lower  margin  of  the  foramen  ovale,  to  form 
the  mandibular  nerve.  The  sensory  portion  supplies  the  skin  of  the  -side  of  the 
head,  the  auricle  of  the  ear,  the  external  auditory  meatus,  the  lower  portion  "'f  the 
face  and  the  lower  lip,  the  mucous  membrane  of  the  mouth,  tongue  and  .wastoid 
cells,  and  the  lower  teeth  and  gums,  the  salivary  glands,  the  temporo-roandibular 
articulation,  the  dura  mater  and  the  skull.  The  motor  portion  supplies  the  muscles 
of  mastication  (the  temporal,  the  masseter  and  the  external  andintenial  pterygoids), 
the  anterior  belly  of  the  digastric,  the  mylo-hyoid,  the  tensor  palati  and  the  tensor 
tympani  muscles.  By  union  of  the  two  constituents,  a  thick  common  trunk  is  formed, 
which,  after  a  course  of  from  2-3  mm. ,  separates  \in'  :r  cover  of  the  external  ptery- 
goid muscle  into  an  anterior  and  9^ posterior  division  (F'ig.  1063). 

Branches  and  Distribution. — ^The  branches  from  the  main  trank  of  the 
mandibular  nerve  are :  ( i )  the  recurrent  branch  and  (2)  the  internal  pterygoid  nerve. 

1.  The  recurrent  branch  (n.  splnosns)  arises  just  beneath  the  foramen  ovale 
and  accompanies  the  middle  meningeal  artery  into  the  cranium  through  the  foramen 
spinosum.  It  then  divides  into  two  branches,  the  anterior  of  which  supplies  the  greater 
wing  of  the  sphenoid  and  the  adjacent  dura  mater,  while  the  posterior  passes  through 
the  petro-squamous  suture  and  supplies  the  mucous  membrane  of  the  mastoid 
air-cells. 

2.  The  internal  pterygoid  nerve  (n.  pterygoidcns  internus)  (Fig.  1059) 
passes  downward  on  the  mesial  side  of  its  muscle  and,  in  addition  to  supplying  the 
pterygoid  muscle,  gives  off  the  motor  root  of  the  otic  ganglion  and  filaments  to  the 
tensor  tympani  and  tensor  palati  muscles. 

The  Anterior  Division  of  the  mandibular  nerve  (n.  masticatorlaB)  is  motor, 
with  the  exception  of  its  buccal  branch,  and  receives  almost  the  entire  motor  constit- 
uent of  the  trigeminal.  It  passes  downward  and  forward  for  a  short  distance  under 
the  external  pterygoid  muscle  and  then  breaks  up  into  its  branches. 

Branches. — These  are  :  (i)  the  masseteric,  (2)  the  external  pterygoid ,  (3) 
the  deep  temporal  and  (^4"!  the  dueeal  nerve. 

I.  The  masseteric  nerve  (d.  massetcricns)  (Fig.  1063)  passes  over  the 
upper  border  of  the  external  pterygoid  and  behind  the  posterior  mamn  of  the 
temporal  muscle.     It  takes  a  course  horizontally  outward  and  traverses  the  sigmoid 


THE  TRIGEMINAL  NERVE. 


1343 


notch  of  the  n«ndible  to  enter  thepo^terior  S^t::^^'lndtflarS^u,lion' 
masseter.     It  8"PP>'"  one  or  two  «an«nts  to  Uietemp^^^ 

,.  The  external  P*«W^*  ^'^iVtRKc^^^  It  fnten.  the 

usually  Ukes  its  origin  as  a  common  trunic  wun  uic 
deep  surface  of  the  exten^d  pterygojd  ^       ft,„di  „terlor  et  posterior) 

3.  The  deep  temporal  "erve*  t"  tempw-^    v  accompanies 

(F«.   -063).  are  "''*^>^'^'F^H5n   tLLeS^terygoid.afte^  ^ 

ihe  t     C3l  nerve  between  the  heacb  of  the  externa^^^^^  ^.^^^^  k^ 

upward  to  supply  the  anterior  F"^ ""  °*  J'^^^^Srg^W  ^^     then  upward'dose 
outward  across  the  "PPer.">«'^"  «*  ^''l  the  t^£ra7muscle.     It  often  fuses  with 

St£^ra.;^oroV5LS^^tTte"^^^^^^^ 


pklaHne 


tarn  Mkguw.Mchank  lympMl 
IM. 

Int.  pwrgoU  muKlc 


iDferUir  ilcaul  •*"' 

UmmiU.V.mtnt 


Di»«llon  .howint  Ut.nil  view  ot  .pheno-patatln.  and  Cic  pngli.. 


TU»  ^./^«r  freauently  accompanies  the  nerve  to  the  masseter  for 
STariaSe'^tanL'rfiThichTturn^s  u  J  along  the  bone  to  enter  the  deep 
surface  of  the  posterior  portion  of  the  musde.  sensory.     It 

•    ^^  '^^'^  '"TitrS::  ix^erXteC  ^  anda^Sr  de^p  te'mporal 'Jlerve. 
arises  in  common  with  ^^e  external  pi  n^g  ^^  ^^^  ^^^^^^^  pterygoid, 

and  is  accompan.ed  by  the  la"er  between  ^"^        j  j    j  ^es  the  outer 

Passing  downward  on  the  inner  f'^^^^^J^^^J^.X^vr^l  branches  which  form  a 
surface  of  me  buccinator,  where  it  b^eaJ"  "P  ^"^°  j,  ^f  ^^e  facial  nerve.  Some  of 
plexus  around  the  \^'^J«"?' ^^'^^'^^'Je "o  s"^p"y  ^'^^  •""'^''"'  membrane  of  the 
hr^'SrZZlrtL'^TX^orZ'^.lK  K  the  others  supply  the  sUm  of 

the  cheek. 

V.rUtlon..-1-tead  of  lying  .0  t^e  inne-icfe  jhe^rv-iay^^^^^^^^^  [JlS ^Irj^e 
L^i^tan'^'^SfeS  '^""^l^^r^rS^i'^r^^r^^^^^  foramen  in  the  alveolar  border 


!^ssr 


"44 


HUMAN  ANATOMY. 


of  the  mandible,  just  anterior  to  the  ramus.  It  has  been  seen  in  one  case  to  arise  directly  fiun 
the  Gasaerian  gai^ion  and  emerge  from  the  cranium  through  a  special  foramen  situated  between 
the  foramina  rotundum  and  ovale. 

The  Posterior  Division  of  the  mandibular  nerve  is  sensory,  with  the  exception 
of  the  mylo-hyoid  nerve.  It  passes  downward  beneath  the  external  pterygoid  and, 
after  givii^  on  the  two  roots  of  the  auriculo-temporal  nerve,  terminates  by  dividing 
into  tne  lingual  and  the  in/eriot  dented  nerve. 

Brandies. — These  are  :  (i)  the  auriculo-temporal,  (2)  the  lingual  and  (3) 
the  inferior  dental. 

1.  The  auriculo-temporal  nerve  (o.  aarkuloteaporalis)  (Fig.  1063)  arises  just 
below  the  foramen  ovale  by  two  roots  which  enclose  between  them  the  middle  meningeal 
artery.  It  passes  backward  beneath  the  external  pterygoid  muscle  and  between  the 
spheno-mandibular  ligament  and  the  neck  of  the  mandible,  and  then  turns  upward 
through  the  parotid  gland  between  the  tem|x>ro-mandibular  articulation  and  the  external 
ear.  Emerging  from  the  upper  margin  of  the  gland,  the  nerve  passes  over  the  root  of 
the  zygoma  and  ascends  to  the  temporal  region  behind  and  in  company  with  the 
superficial  temporal  artery. 

Branches.— These  are  :  («)  the  articular,  (i)  the  parotid,  (<■)  the  mea/al,  (d) 
the  anterior  auricular  and  (e)  the  superficial  temporal.  The  last  three  are 
terminal  branches. 

a.  The  articular  branches  (rr.  irticnlarcs)  are  one  or  two  delicate  filaments  which  enter 
the  posterior  portion  of  the  tempor-mandibular  articulation. 

*.  The  parotid  branches  (rr.  parotldci)  pass  to  the  gland;  they  arise  either  from  the 
auriculo-temporal  or  from  its  communicating  filaments  with  the  facial  nerve. 

c.  The  meaul  branches  (nn.  nieaiui  auditorll  exural)  are  two  in  number,  an  upper  and  a 
lower.  They  enter  the  external  auditory  canal  between  the  bone  and  the  cartilage  and  supply 
the  skin  covering  the  corresponding  parts  of  the  meatus,  the  upper  branch  in  addition  sending  a 
twig  (r.  Bcobranae  tynpaoi)  to  the  tympanic  membrane. 

d.  The  anterior  auricular  nerves  ( nn.  anricnlares  aateriores) .  usually  two  in  number,  supply 
skin  of  the  tragus  and  of  the  upper  anterior  portion  of  the  auricle. 

e.  The  superficial  temporal  nerve  (rr.  umporales  rapcrlkiain)  (Fig.  to68)  breaks  up  into 
a  number  of  fine  twigs  which  supply  the  skin  of  the  temporal  region  and  of  the  scalp  almost  to 
the  sagittal  suture. 

The  auriculo-temporal  communicates  by  its  roots,  close  to  their  origin,  with  branches  from 
the  otic  ganglion,  and  by  its  parotid  and  superficial  temporal  branches  with  the  facial  nerve. 
By  the  first  of  these  communications  secretory  fibres  of  the  glosso-pharyngeal  and  sympathetic 
fibres  are  carried  to  the  parotid  gland  ;  by  means  of  the  second  junction  sensory  trigeminal 
fibres  accompany  the  peripheral  motor  filaments  of  the  facial. 

Variations.— In  a  specimen  found  in  the  anatomical  laboratory  of  the  University  of  Pennsyl- 
vania, the  middle  meningeal  arter>',  instead  of  passing  between  the  two  roots  of  the  nerve, 
pierced  the  anterior  one. 

2.  The  lingual  nerve  (n.  lioKualis)  (Fig.  1079)  is  the  smaller  of  the 
terminal  branches  of  the  mandibular  nerve.  Lying  internal  and  anterior  to  the 
inferior  dental  nerve,  it  passes  downward  beneath  the  external  pterygoid  as  far  as  the 
lower  border  of  that  musc'e.  It  is  usually  connected  with  the  inferior  dental  nerve  by 
an  oblique  strand  of  fibris  which  occasionally  crosses  the  internal  maxillary  artery 
and,  close  to  its  origin,  it  is  additionally  joined  at  an  acute  angle  by  the  chorda 
tympani  nerve.  After  emerging  from  under  cover  of  the  external  pterygoid,  it  passes 
between  the  internal  pterygoid  and  the  ramus  of  the  mandible.  It  then  turns  inward, 
forward  and  downward  under  the  mucous  membrane  of  the  floor  of  the  mouth,  cross- 
ing over  the  superior  border  of  the  superior  constrictor  of  the  pharynx  and  the  deep 
portion  of  the  submaxillary  gland,  and  passes  under  the  submaxillary  duct  between 
the  mylo-hyoid  and  hyo-glossus  muscles.  Reaching  the  side  of  the  tongue  the  nerve 
continues  forward  to  the  apex.  lying  just  beneath  the  mucous  membrane. 

Branches.— The  lingual  nerve  supplies  small  filaments  to  the  subliagu.il  gland, 
the  floor  and  side  of  the  mouth,  the  side  of  the  tongue  and  the  lower  gum.  .  It 
gives  off  the  sensory  root  of  the  submaxillary  ganglion  and  its  terminal  filaments 
(rr.  lingualcs)  pass  upward  through  the  muscles  of  the  tongue  to  supply  the  mucous 


THE  TRIGEMINAL  NERVE. 


"45 


membrane  of  the  anterior  two-thirds  of  the  donwm.      Its  fibres  have  their  main 
termination  in  the  filiform  and  hii^form  papiUa.  ■      a  ,u    :„«-^, 

The  Ungual  nerve  commumcate*  with  the  chorda  tympani  and  the  inferior 
dental  and  in  its  anterior  portion  forms  loops  with  the  hypoglossal. 

\.  The  inferior  dentil  nerve  (n.  aWeotaris  Inferior)  (Fig.  1063)  is  the  larger 
of  the  terminal  branches  of  the  mandibular.  Lying  posterior  and  external  to  thi- 
Ungual,  to  which  it  is  connected  by  a  small  nerve  strand,  it  passes  downward  and 
foXrd  under  cover  of  the  external  pterygoid.  Living  the  lower  margin  of  hat 
musde  it  runs  between  the  ramus  of  the  mandible  and  the  spheno-mand.bular 
Ugament  and  enters  the  inferior  dental  canal,  along  which  it  courses  in  company 


Zy«(MMlfcr  pmtm 


Uatm  dhrMon  oT  mMdOMtar 


Deep  waipMal  briBcIni 


StMory  (llriflonornMiitHbiilavnnva, 
Intcnul  picrygtiiJ  ucnr«. 
CVtrda  tympaid 
Middle  iiienliiKcal  aitcry 


Aiirlado> 
icmporal  Bcrrc. 

SupwAcUl 
tcmpoTAl  «t«ry, 


tnavQIftry  utcry 

Conncctioa  between 

auric  ulo^cmponl 

and  facial  nrrvn. 

Facial 


laferior  dental 

Part  of  mawUblc 

Parotid  ffbod 


Submaxill-iry  gangHon 
IHgaitric  muw-lc. 
anierloc  belly 


KiUary  Klatul 


0_.„..  ..„..„.  n,.....«Ur  „«v.  .™.  .U  J.™„CH« .  ™na,«._J..  -  P--".  «-«-■  — «   '~ 

With  the  inferior  dental  artery,  and  supplies  filaments  to  the  t^^^;  "^ 'f  ^^  ^J^^^j^jl'^/h^j 
n.«p.n  Hprp  the  nerve  breaks  up  nto  ts  terminal  branches,  one  ol  whicti.  tne 
SSrconUnTes  wtthTnX  li^ndibl^  to  the  mid-line,  while  the  other  and  larger,  the 
mental,  emerges  at  the  mental  foramen.  .      .     . 

Branches.— These  are :  (a)  the  mjfiohyotd,  (*)  ihe  denial,  (.f ;  me  ii«:«<' 
and  (rf)  the  menial,  of  which  the  last  t«o  are  terminal  branches. 

a.  The  m,/<^A>»,V/  nerve  (n.  «yl.hy..d«..)  (Fig.  '«f 3) Js  the  onl^  m«or  strand^^  the 
posterior  division  of  the  mandibular  nerve.  It  ar««;  <™^  and  "ward  K  my7«^hyoid 
Wore  the  latter  enters  its  bony  canal  and  passes  <»°*"*f^'J"^  T*e^e^e  descends  into 
groove,  sometimes  a  -nal  for  part  ot^  way.  m  the^^^^^ 

the  digaslr  c  Ir  angle  and  reaches  Ihc  inferior  stmace  <m  ine  "'x'- ;■>  .    '    breaks  up  into 

bdnu  overlain  by  the  submaxillary  gland  and  the  facial  artenr  »"d  vein.    It  he«  breai^^  "P 
laments  which  supply  the  mylo-hyoid  muscle  and  ^^e -tenor  belly^f  the  d^-t"- ^^^  ,,, 

*.    The  denial  branchti   rr.  dentale.  iafcriorw)  are  given  ?Vj  *"^"^\/,.^    (,i„„ 
inferior  denul  canal.    They  combine  a.ui  unite  to  form  the  ^njenor  dental  plexus   ^n« 


\ 


134^ 


HUMAN  ANATOMY. 


4*aulia  l«brt»r)  which  supplies  filaments  to  the  molar  and  pfcmolar  teeth,  one  filament  to  each 
fanK,  and  the  adjacent  portion  of  the  gum.  ...... 

c.  The  incisor  hrcmck  (a.  olTMiarto  laftriM'  ■■ttricr)  is  the  smaller  of  the  terminal  divisKMis 
and  continues  forward  within  the  mandible  the  course  of  the  inferior  dental  nerve  from  the 
menul  foramen  to  the  mid-line.     It  supplies  the  canine  and  incisor  teeth. 

d  The  mental  nerve  (n.  mentalis)  (Fig.  1063)  is  much  the  larger  terminal 
branch  of  the  inferwjr  dental.  Emerging  from  the  mental  foramen,  it  breaks  up  under 
cover  of  the  depressor  anguli  oris  muscle  into  a  number  of  filaments  which  supply  the 
skin  of  the  chin  and  the  integument  and  mucous  membrane  of  the  lower  lip.  It  forms 
a  fa-ee  co-imunication  with  the  supramandibular  branch  of  the  facial  nerve. 

The  Otic  Ganglion.— The  otic  or  Arnold' i  ganglion  (%.  oticum  (Fig.  1064)  is 
one  of  the  two  ganglia  associated  with  the  mandibular  nerve.     It  is  a  small  flattened 

Fio.  1064- 

OpHkdak  «<Moa.V.  mm 

■■VlNMIi  Vi  BSffW 

Gm«t<i«  ir*Bf  tloa.  iaf.  tunacc 


TcBMT  tympuii,  cut      <lat»af  tympaai 
Br.  from  giic  ganslloo  to 


E- iMttcR.  tubt.  CM 

PMfOM  of  ttmpOfBl 


Small  tiipcff. 
prttonla«rve 
Br.  frr)«  guttfttba  to 
'     •   tynpftBf 


JKkkBr  mealac*^ 


•r.  toaiukulo^CBp.  Mm 
Int.  peerysoldBW 
Br.toieMarpaUtI' 


T«itior  paltfi.cvt 


[waU 


paUMboQc 


UBgwlaerTO 

'laC  dMttll  BCTV* 
■L  Muaiary  artery 
Tenporal  wtcry 


otic  c»i(lion  .nd  bnincha  iwn  from  m«tal  M|)«t.  "ctlonorrtiiU  beinc  not  ngitUl.  but  apprcchinR 
plane  o(  long  axis  ol  pelroaa. 

body,  of  irregularly  oval  or  stellate  outline  and  reddish-gray  color,  and  measures 
about  4  mm.  in  its  longest  or  antero-posterior  dimension.  It  lies  just  below  the 
foramen  ovale  on  the  mesial  side  of  the  mandibular  nerve  and  covers  or  even  encloses 
the  origin  of  the  internal  pteryj.:oid  nerve.  Internally  the  ganglion  is  in  relation  with 
the  tensor  p.->lati  muscle  and  the  cartilaginous  portion  of  the  Eustachian  tube  and 
pasteriorly  wi.h  the  middle  meningeal  artery.  It  is  a  sympathetic  ganglion  and  con- 
tains numerous  stellate  neurones  which  are  characteristic  of  such  structures. 

Roots.— Of  the  communications  that  the  otic  ganglion  receives  from  several 
sources,  some  are  regarded  as  its  roots,  of  which  the  sensory  root  is  contiTbiited  by 
small  superficial  petrosal  nerves  (n.  petrosus  saperficlalis  minor).  The  latter 
establish  connection  between  the  otic  ganglion  and  the  petrous  ganglion  of  the  K'"sso- 
pharyngeal  nerve  by  way  of  its  tympanic  branch  (page  1075)  on  the  one  hand  and, 
by  means  of  communicating  filaments,  between  the  otic  and  the  geniculate  ganglion 
of  the  facial  nerve  on  the  other.  As  the  continuation  of  the  tympanic  ner\e,  after 
union  with  the  filaments  from  the  geniculate  ganglion,  the  small  superficial  petrosal 
leaves  the  upper  and  fore  part  of  the  tympanic  cavity,  traverses  a  small  canal  in  the 
temporal  bone,  and  emerges  on  the  upper  surface  of  the  latter,  to  the  outer  side  of 
the  hiatus  Fallopii.  It  then  turns  downward,  passes  through  the  petro-sphenoidal 
fissure  or  through  a  special  canal  in  the  sphenoid  bone,  and  joins  the  otic  ganglion. 


THE  TRIGEMINAL   NERVE 


i»m 


•"^- m  mc^r  root  is  a  branch  from  the  '^^^^V^^^^^^  tT^- 
root  is  r«>r«ented  by  one  or  ^°.^^^^^^J^Z^^:^ir^  the  Vkto, 
meningeal  artery.     The  ganghon  also  receives  the  Ji^*««#«« 

"•■^  -         w  A  »..m>w.r  ol  delicate  strands  pa«)  trom  the  aoc  jjanglion  to  aci;:' 


Fir.,  ii^.s. 


Ophthatmk 


Masiliuy 


OccipiulU 
••Jor 

Occipiulio 
minor 


Mandibular. 
Maxittarjp 
MaadiboUr 


^Optithalmic 


Cirvical  picmus 


/  -.^ 


DiaKran,.  .how.n,  di«ribuUon  u.  c«an«.».  branch-  o.  .ri^.na.  and  ««i«.  apina.  nerv-. 


(Fig.  io6.,)  is  a  r«>d«h.tnangular  or  f.jform  tK^y,^^^^  connected  with 

its  Ireatest  length,  and  «  the  sm^lest  ^l^^^^^Jl^,  Lbmaxillary  gland  and 
the  fifth  nerve.  It  is  situated  above  the  de^  Submaxillary  duct  and  th.  lingual 
upon  the  hyo-glossus  -""^^  »"f  J^^^^^^^"  by  tTThort  sknder  filaments.  The 
nerve,  apparently  suspended  from  th^Jatter  oy  tw  ^^^  ^^^  ganglion 

proceeds  from  the  facial  by  ^ray  of  the  '^"""^ '7  .  I         ,  ^^  the  facial  artery. 

and  the  sympatMicrcon^  ^T"^,TmSSS^^^  a  number  of  fibres  which 
Br.nche..-The  branches  of  chstnbutm^^^^^^  ^^^^^  submaxillary 

rtSil^rrcoSmtratif'Shr^rX^ 


1348 


HLMAN  ANATOMY. 


the  Ungual  nerve  and,  after  accompanying  it  for  a  short  distance,  are  distributed  to 
the  sublingual  gland.  The  sensory  fibres,  processes  of  the  Gasserian  neurones,  tra- 
verse the  submaxilbry  ganglion  without  interruption  ;  the  secretory  fibres  from  the 
facial  end,  at  least  in  part,  around  the  stellate  sympathetic  neurones  of  the  ganglion, 
from  which  cells  axones  pass  to  the  alveoli  of  the  submaxillary  and  sublingual 
glands ;  while  other  sympathetic  filamenU  proceed,  as  the  axones  of  stellate  celb 
either  within  the  submaxillary  or  a  more  remote  sympathetic  ganglion,  to  supply  the 
^andular  tissue  and  ducts,  as  we'l  as  to  accompany  the  peripheral  branches  of  the 
lingual  nerve. 

Practical  Co-'aidentiona.— The  fifth  cranial  nerve  is  the  sensory  nerve  of 
the  face  and  the  motor  nerve  to  the  muscles  of  mastication.  It  is  more  frequently 
the  seat  of  excessively  painful  neuralgia  than  any  other  nerve  in  the  body.  Extra- 
cranial lesions  are  much  more  commonly  the  cause  of  such  neuralgia  than  intracra- 
nial. The  neuralgia  is  rarely  bilateral,  and  usually  does  not  involve  all  three  divisions 
of  the  nerve.  It  rather  atucks  one  or  two  divisions,  or  only  a  branch  of  one,  the 
first  and  second  divisions  being  most  frequentiy  involved.  Certain  tender  regions  can 
almost  always  be  found,  as  over  the  points  of  emergence  of  the  nerve  on  the  face,  at 
the  supraorbital,  infraorbital  and  mental  foramina,  where  in  an  interval  from  pain 
pressure  may  produce  a  paroxysm. 

The  supraorbital  notch  or  foramen  can  usually  be  lelt  at  the  junction  of  the  inner 
and  middle  thirds  of  the  supraorbital  margin.  The  mental  foramen  is  in  the  lower 
jaw,  below  and  between  the  two  bicuspid  teeth,  while  the  infraorbital  foramen  lies 
just  below  the  lower  margin  of  the  orbit  in  a  straight  line  between  the  supraorbital 
and  mental  foramina. 

When  the  first  division  is  the  seat  of  neuralgia,  the  disease  is  almost  always  con- 
fined to  the  supraorbital  branch.  Excision  of  this  branch  will  usually  give  relief  for 
alx>ut  two  years,  sometimes  permanently.  The  same  may  be  said  of  the  infraorbital 
nerve  when  the  disease  is  confined  to  the  second  division.  The  infraorbital  may  be 
excised  at  the  foramen,  through  the  mucous  membrane  of  the  mouth  or  by  an  in- 
cision in  the  skin  along  the  lower  margin  of  the  orbit.  Through  the  latter  the  orbital 
tissues  may  be  raised  and  the  nerve  reached  farther  back  in  its  canal,  which  in  its 
anterior  part  has  a  thin  bony  covering.  By  going  through  the  antrum  of  Highmore 
from  the  cheek,  just  below  the  infraorbital  foramen,  the  second  division,  with 
Meckel's  ganglion  attached  to  it  may  be  excised  at  its  emergence  from  the  skull. 
The  anterior  wall  of  the  antrum  is  opened  by  a  trephine  or  chisel  and  the  floor  of 
the  infraorbital  canal  in  the  roof  of  the  antrum  is  gouged  away  so  that  the  nerve  is  ex- 
posed and  followed  to  the  posterior  wall  of  the  antrum.  This  wall  is  then  opened, 
the  spheno-maxillary  fossa  exposed  and  the  ner^•e  is  divided  at  the  foramen 
rotundum  and  removed  with  the  ganglion.  The  bleeding  will  be  severe,  since 
large  and  numerous  branches  of  the  internal  maxillary  artery  surround  the  ganglion 
and  are  divided. 

When  the  neuralgia  is  confined  to  the  inferior  dental  nerve  the  mental  branch 
may  be  excised  at  its  foramen  through  the  mucous  membrane  of  the  mouth.  The 
inferior  dental  itself  is  more  frequenriy  attacked  through  a  trephine  opening  in  the 
ascending  ramus  of  the  lower  jaw.  It  may  with  greater  diflficult;^  be  reached  through 
the  mouth,  the  incision  being  made  along  the  anterior  niargm  of  the  descending 
ramus,  and  the  .soft  tissues  separated  from  the  inner  surface  of  the  ramus  until  the 
dental  spine  marking  the  dental  foramen  is  exposed;  the  inferior  dental  nerve  and 
artery  will  be  found  entering  the  canal.  The  nerve  may  then  be  exposed  and  ex- 
cised with  due  regard  for  the  accompanying  vessels  and  the  internal  maxillary  artery, 
from  which  the  inferior  dental  branch  has  just  been  given  off. 

The  buccal  ner\e  is  sometimes  the  seat  of  neuralgia,  and  may  be  reached  by  an 
incision  through  the  cheek  in  front  of  the  coronoid  process  and  the  insertion  of  the 
tendon  of  the  temporal  muscle  The  nerve  can  l>e  reached  irom  the  mouth  in  the 
same  situation. 

When  the  peripheral  operations  for  trigeminal  neural|{ia  (tic  douloureux)  have 
failed  to  effect  a  cure,  or  when  the  neuralgia  pi  imarily  shifts  from  one  branch  to  an- 
other, indicating  .-xn  extensive  central  involvement,  the  Gasserian  ganglion  must  be 


THE  ABDUCENT  NERVE. 


1249 


^oved  or  the  «~ory  root  resected  The  ^dl  is  o^-j^ jj^^il^yrr^Xr 
and  the  unopened  dura  (unless  unavoidably  t^^^^^  ^^^  ^^  ^j,^ 

of  the  skull  until  the  ganglion  lying  °"  »J^'f^*i3  „J^  and  r^oved.  The 
temporal  bone  between  the  twolayers  °« '*^^"j^v'y„^,PTit  comes  through  the 
midSe  meningeal  artery  is  ."P««  [y  «r^„  more"^ dangerous  hemorrhage,  how- 
foramen  spinosum.  A  P?^''''^^^"^^.  ^^u'^^t^"  gSion  is  intimately  «^ated 
SlJc  ^jLnTesT r  eyT  ar^t^ i^oJ'c^r  fr^m^  damage  to  the  first  di.^sion  o. 

*•=  "fflinpal  nerve  is  sometime  divid^  K^ilJ^a^strpifig  \^^^  To 

Se^r^e.!ltSe^rrrc;us^%x^^^^^^^       ™^»--  -^-y 

between  the  tongue  and  the  alveolus  o  the  lower  jaw.  ;   ;    ^^gin.  is  rare. 

:3ri»Yn<»e.Jl»ryi.x»«lexte™l  auditory  me.t».        • 
THE  ABDUCENT  NERVt 
The  sixth  or  abducent  nervej  •"-«".)  is  «c^^^^^^^ 
external  rectus  muscle  of  the  eyeball.  J^^  ^fJPiSfrof^ultipolar  neurones  which 
(nuctos  n.  abdacenUs)  (Fig.  933).  *™"rSJ^"Jand  under  Se  gray  matter  of  the 
lies  in  the  dorsal  part  of  the  te?™'"!"'",^  Vl%Cr  to  thrsSiL  a^^^        beneath  the 
floor  of  the  fourth  ventricle.     It  «  «t";^^f  »"»r™^  Sm^^  by  tS^fibres  of  the  facial 
eminentia  teres  and  ventral  to  »"d  wUhm  tl«  loop  form^^  ^   .^  ^.^^. 

nerve.     Leaving  the  nucleus  on  its  '""f^f  P^ J' ^'l^  X  "..ner  side  oi  the  superior 
which  pass  backward  and  ven^ro-U  eralj^. Jxjng  ^    he  nine  ^^  ^,^1^^^^^ 

'^^"""  ,    .  «  ..«—     A,  in  the  case  c'  the  third  and  fourth  nerves,  tne 

Centfl  «id  Cortieri  <^««'*»"'-;^,uJ"J^reri^low'tudinal  fasciculus,  some  of  the 
nucleus  of  the  sixth  receives,  by  way  of  ^e  I^J^"°[  '"^  establishment  of  a  reflex-path 
fibres  of  the  pedicle  of  the  ''"P«"o^ohve,  thus  con^pletin^^^ 

between  the  auditory  appa^tus  and  the  ^"'^ J^J^^,"f^Ludi„al  fasciculus  with  the  oculo- 
«M:ond  connection  is  effected  ^V  n^'""?"' *",h^XLrnudeus  is  brought  into  relation  with 
rmXra1.\t=x  by'way  oS^pV^mSt^t  of  the  opposite  side. 

Cour..  .nd  Di.tnbution,-After  leaving  the  s^^^^^^  SaSnt 

nerve,  which  at  its  superfaal  onpn  is  fla^.uul  oft^"JP;^y„'^  J  ,,^„,  ,5  „,„,., 
becomes  consolidated  and  ro"n«|«l' ''"^  .'^'^^1""^*™  l,^.„  over  the  sphenoid  bone 
the  lower  surface  o,  the  |K>n.     It  the^"^  ^^Ig  forThe'iifth  nerve^Fig  ,05a) 
at  a  po  nt  medial  and  slightly  P«*terior  to  ine  o,k:ii    k  •        ,;     j  j  process  and 

Thence  it  runs  forward  through  a  ""t^^';^^"^,?^'^^;^^^*^;"' L  a^ 
passes  to  the  outer  side  of  the  '"««"7^f  *;?^:;^  ",^^^  Here  it  lies  somewhat 

Kirtion  o.  the  temporal  bone  to  enter  t"^*;  ";•  y.  \"""*  ^'"„,,  eventually  reaching  the 
lielow  and  to  the  ..uter  side  o  the  l";;^-^"!"-^"';' ""^f^^S  throuRh  L  sphenoidal 
outer  wall  of  the  anterior  portion  of  the  simis.  cntcni  the  >rn.t  tr      g  ^^^    1^^^^^,,,,;^ 

muscle  which,  "^^^^-"'r,"^;^  i^  traverses  the  cavernous 

orbit   a  small  sensory  filament  from  the  ophthalmic  nerve. 

79 


125° 


HUMAN  ANATOMY. 


Variatioiu. — The  nerve  may  be  absent  on  one  side,  the  external  rectus  being  supplied  by 
a  branch  from  the  oculomotor.  It  may  have  its  superficial  origin  by  several  widely  separated 
strands,  the  accessory  fasciculi  emerging  from  between  the  fibres  of  the  pyramid  or  through 
the  lower  border  of  the  pons. 

THE  FACIAL  NERVE. 

The  seventh  or  feicial  nerve  (n.  facialis)  is  a  mixed  nerve  and  consists  of  two 
parts,  a  larger  motor  and  a  smaller  sensory.  The  former  supplies  with  motor  fibres 
the  muscles  of  expression,  the  extrinsic  and  intrinsic  muscles  of  the  external  ear, 
the  stylo-hyoki,  the  posterior  belly  of  the  digastric,  the  platysma  myoides  and  per- 
haps also  the  levator  palati  and  the  azygus  uvulse.  Certain  of  the  motor  fibres  are 
peculiar  and  as  secretory  fibres  are  destined  for  the  supply  of  the  submaxillary  and 
sublingual  glands.  The  sensory  part  of  the  facial  conveys  gustatory  fibres  to  the 
anterior  two-thirds  of  the  tongue. 

The  sensory  part  is  commonly  known  as  the^rf  intermedia  of  Wrisberg  (n. 
intermedias)  which,  instead  of  being  a  distinct  nerve,  may  with  propriety  be  regarded 
as  the  sensory  portion  of  the  seventh — a  view  strongly  supported  upon  morphologi- 
cal grounds.     The  sensory  fibres  are  processes  of  the  cells  situated  within   the 


Fir..  1066. 


Brain-fftem  with  nuclei  of  cranial  nervM  »hown  (liacrammatically ;  motor  nuckl  and  fibre*  are  bine;  acnaory 
nuclei  and  fihrefl  arc  red.  a,  oculomotor  nerve;  A.troi-hTear  nerve;  c,  motor  part  of  trijceminal  nerve;  </,  ienaory 
part  of  ;riBeminal  nerve ;  f,  spinal  loot  of  iiensory  part  of  trigeminal  nerve ;  /.  facial  nerve ;  jr.  abducens  nerve ;  A, 

01  auditory  nerve ;  y,  cloaao-pharyniceal  nerve ;  ik,  vagua 
M.  vagua  poftion  of  apinal  acccatory 


vestibuUr'portinn  of  i  uditory  nerve;  i.  cochlear  portion  olauditory  nerve;  j,  cloaao-pharvnifeal  nerve;  k,  vagua 
iier\'e,  ahowinK  also  the  nucleaa  ambiiuus  in  black ;  /,  hypocloaaal  nerve ; 


enlargement  on  the  facial  ner\'e  known  as  the  geniculate  ganglion,  which  is  situated 
within  tlie  facial  canal  ut  the  so-called  ktue.  Passing  through  the  proximal  part 
of  the  facial  canal,  the  axones  of  the  geniculate  ganglion  cells  enter  the  cranium 
through  the  iiUernal  auditory  meatus,  lying  alxive  the  auditory  nerve  and  below 
the  motor  root  of  the  seventh,  with  both  of  which  they  communicate.  Leaving  the 
meatus,  they  pass  inward  and  enter  the  brain-stem  at  the  superficial  origin, 
(Fig.  1046),  which  is  located  at  the  lower  border  of  the  pons,  between  tiie  motor 
root  of  the  seventh  and  the  auditory  nerve. 


Entering  the  suhstanff  "t  the  nii-dullii,  tlu  xensor)'  fibres  p.nss  either  through  or  dorsally  to 
the  spinal  root  of  the  trigeminal  iwrve  tu  reach  lh<- siijKTioi  jiartof  the  nmlfus  0/  reception, 
which  it  shares  with  the  glosso-pharyngt-iil  .iiul  vagus  nervts  (|)age  126J).  On  gaining  this 
nucleus,  the  sensory  fihrt-s  divide  into  short  ast  ending  and  much  longt-r  v'.  scending  branches, 
Ihiis  Ixrhnving  in  a  niani«-r  i<l»-ntiral  with  that  of  the  correspomling  fibres  of  the  trigeminus  and 
other  mixed  cranial  nertcs.  The  terminntlon  of  the  senst)ry  fibres  is  around  the  neurones 
of  the  reception-nucleUB,  from  which  nxones  jmss  to  the  mesial  fillet  of  the  opposite  side,  and 
evenm;tlly,  to  the  cerebral  cortex. 


THE  FACIAL  NERVE. 


125> 


The  motor  p«ti,  by  far  the  larger  o^ 'he  ^  a^d  con  t,^^^^ 
ieaUv  and  functionallphe  more  .mpo^m^^^  9,  )! an  oval  cI£tion^>f  soV 
of  the  motor  root  is  from  the  /'^«',  ™'"^^_li^-^l^^^^  measures  about  5  mm.  in 
half  dozen  groups  of  large  """'^'fj^^'  Z^^on  d  the  teZTntum  of  the  pons.  It 
length,  and  is  situated  m  the  posterior  P""^'""  soS  r^  of  the  trigeminal  nerve 
UesVl'  '^^  ^°"^'^  :r^"t^rSi  of  \he  c^ius  Spezoldes  ;  higher  up  it  is 
and,  in  its  lower  part,  dose  to  *«  ^^^  ™  ";'bv  the  superior  olive,  to  the  upper 
tilted  dorsally  ancf  separated  '^^.^J^^  JJ^ada/^uS".  situate;d  dose  to  the 

™£l  ^iVrtt^fr^fhl^^n^lSTforc^^^^^^^  descripUon  into  a 

radicular,  an  ascending  and  an  emergent  portion. 

Then.</^./«.A^^consis.s  of  "--'JS-i^t^uL^dr^^^^^^^ 
the  don»-lateraI  aspect  of  the  nucleus  o   °"^"  ■^.^'^^f^.'^^sTthe  abducent  nerve  and  then, 
upper  fibres  stream  over  the  dorso-lateralsuriaceo^^thenucl^^^  ^^  fourth  ventricle. 

«^the  other  fibres  o^  the  motor  ''^'•'^"^^^'^U^^^^Me  to  form  a  solid  strand,  the 
As  they  near  the  m  d-line  »hey  turn  starpl>^upward  jd  a^^^^^  ^^^  ^^^^  ^  ^^  ^^^  i„ 

ascending  porHon  of  the  seventh  nerve  l^'^'^^^j'^^fourth  ventricle,  beneath  which  it  runs 
this  situation  the  nerve  is  separated  from  the  ""^^  °  *f  T"  i„,„^iately  dorsal  to  the  p«s- 
within  the  funiculus  teres,  only  bv^h^ '•r^JTc^rnucleus  TlHe^  now  bends  abruptly 
tenor  longitudinal  bundle  and  mesial  to  the  f""^Vrr/^Wfo«  of  its  course,  during  which  it 
outward  at  a  right  angle  and  enters  "P°" 'j^^.^^'J^^'^^kward  and  vemrivlaterally,  be- 

whereby  the  nucleus  is  brought  under  the  """Xiu'd  nuXr  of  root-fibres  are  connected 
(«)  While  not  beyond  dispute,  it  ».?''*?"'=  ^^"heTvidence  adduced  from  clinical  observa- 
wiih  the  facial  nucleus  of  the  "PP°«"^»^f-,J*^J^^"of  a%^al  group  of  cells  from  which 
tions  and  pathological  findings  P«)mte  to  t»«f*'»^™^°'  dT!r,j,,i*  muscles.  These  fibres, 
arise  the  fib«s  ''"PP'vinK.the  "rbicuUns  ^pe^an^m^nd  fro^^^^^^ 

sometimes  called  the  "^^^Z-""' "^^'^'Xsuw^  by  he  seventh  n^ve'  (r)  The  latter, 
the  occurrence  of  paralysis  of  the  other  n*™ J^^Wneo    X  ^        j^s.  probably 

morever,  is  brought  into  association  w  th  \»»^^;*"»\""'^^^";|^„^^^^  to  the  impulses  o( 

within  the  posterior  longitudinal  '»«:'7'"''- »  ^  *^^^*;'^  the  e^  Ids     (rf )  Connection  with  the 

sight  and  hearing,  as  shown  by  «''«J'!'°"''\'^„"'r^^, "he  '  J^^^^  °'  '^  "'"*='•*  "* 

h^los«l  nerve  ha.s  been  '"^"n'f^  m  exp^ana  ion  o   the^™'^'^"^^^^  „„a,,  ,he  influence  of 

the  lips  with  those  of  the  t°np«-<fi7fi^  which  proSas  axones  from  the  motor  neurones 

of  tlie  same  side. 

The  .tiperfici.1  origin  of  the  motorrooUs  1^^^^;^^^^^,  teTnJ^Hor 
which  it  may  be  adherent,  ma  K«;oove  be  ^^een  J^t    "J^^^"^  often  as  several 

which  it  is  separated  by  the  sensc,rynK,t  of  the  seventn^^^  ^^^^^^^^    .^^ 

Emerging  from  the  «"^?.'^'^,  ^f  * J.\. ''i^'^^'J^  meatus,  through  which 

motor  and  sensory  roots  ununited  to  t*^^. '•^'3"'''\^X  tottom  of  the  meatus  the 
it  passes  alxne  and  anterior  to  the  ''"^'^  J.  .^,*^XrS  the  facial  canal,  whose 
sev'enth  and  tighth  nerves  part  ^.7P"y-.*''"J^7i;S:Sh..ri.ontan  outward, 
course  it  f..n<.ws  throughout.     At  f"\ '"^f  "^•'"*'  '^^^^^  tym,K,n(c  wall.     It 

between  the  cochlea  and.the  v«.t.bule^un  J   /each«  tj^e  mes       X    1^  ^^^^^^  ^,^^^^_ 

then  bends  abruptly  backward,  passes  ?»'"^'*^,/^,\ 'f  ,^"l,„ic  cavity,  to  end  at  the 
Lrd,  behind  the  pyramid,  in  the  P^^.^f  ^S^^lT^c^^  a  corre- 

stvlo-mastoid  foramen.     1  he  l>««nt.*',''f  ^ J*^  dissipation  is f.iund  the  jrmicuM^ 
StL^rhefe^«:irsKtXn  :t;rL^.     A^er  emerging  from 


1253 


HUMAN  ANATOMY. 


the  stylo-mastoid  foramen  the  nerve  passes  downward,  outward  and  forward  through 
the  parotid  gland,  and  divides,  just  posterior  to  the  ramus  of  the  mandible,  into 
its  terminal  branches,  the  temporo-facial  and  the  cervico-facial.  The  filaments  of 
these  branches  freely  join  with  one  another  and  form  the  fan-like  parotid  plexus 
(plezns  parotldan),  also  called  pes  anserinus. 

The  geniculate  gangUon  (g.  genicall)  is  a  small  oval  or  fusiform  thickening  on 
the  facial  nerve,  at  the  >  ,it  where  it  turns  backward  (genlculum  A.  facialis),  and 
contains  unipolar  neurones,  whose  axones  form  the  sensory  root  of  the  facial  n&rvc 
and  whose  dendrites  form  the  sensory  fibres  oA  distribution  of  the  seventh. 

The  so-called  branches  of  the  geniculate  ganglion— the  great  and  external 
superficial  petrosal  nerves  and  the  branches  to  the  tympanic  plexus — are  only  in  part 
comfKMed  of  fibres  connected  with  the  ganglion  cells  ;  they  are,  therefore,  more 
appropriately  regarded  as  branches  of  the  faci^  nerve. 

Branches  and  Distribution. — Within  the  facial  canal,  the  facial  nerve  gives 
off:  (i)  the  greai  suptrfidal  petrosal,  (3)  the  branch  to  the  tympanic  plexus,  (3) 
the  external  superficial  petrosal,   (4)  the  stapedial,   (5)  the  chorda  tympani  and 

Fio.  1067. 


k^^: 


Dtafnin  ihowliir  brudm  taA  eooiMctioiu  of  (ai:i«l  nervt  withia  taeU  canal. 

(6)  the  communicating  branch  to  the  vagus.  The  first  three  are  closely  connected 
with  the  geniculate  ganglion.  Outside  the  facial  canal  arise:  (7)  \he posterior  auric- 
ular, (8)  the  digastric,  (9)  the  stylo-hyoid,  (10)  the  temporo-/acial  Awi  (11)  the 
cervico-facial  nerve.  The  last  two  nerves  arise  in  an  uncertain  manner  from  that 
irregular  plexiform  expansion,  known  as  the  pes  anserinus,  into  which  the  facial 
broadens  within  the  substance  of  the  parotid  gland  after  emerging  from  the  stylo- 
mastoid foramen. 

I .  The  great  superficial  petrosal  nerve  (a.  petrosus  siipcrficialis  major)  (Fig. 
1063),  while  issuing  directly  from  the  gangliim,  contains  motor  fibres  in  addition  to  the 
scnsoty.  It  leaves  the  facial  canal  through  the  hiatus  Fallopii,  enters  the  middle  cranial 
foss;»  and  pa.sscs  forward  under  the  Gas-serian  ganglion  and  over  the  cartilage  of  the 
middle  lacerated  foramen.  The  nerve  then  crosses  the  outer  side  of  the  internal 
carotid  artery  to  reach  the  jxisterior  opening  of  the  Vidian  canril,  where  it  is  joined 
by  the  gre.1t  deep  petrosal  nerve  (page  1360)  from  the  carotid  sympathetic  plexus, 
with  which  it  unites  to  form  the  I'idian  nertr.  The  latter  traverses  the  Vidian 
canal  to  the  spheno-maxillary  fossa  and  there  enters  the  posterior  asjiect  of  the 
:ipheno-palatine  ganglion,  whose  motor  and  symi)athetic  roots  it  contributes.  The 
probable  relations  and  destination  of  these  fibres  have  been  considered  in  connection 
with  the  spheno-palatine  ganglion  (page  1340). 

3.  The  communicating  branch  to  the  tympanic  plexus  (r.  anactomoticiii 
enm  pirzn  tympfenico)  traverses  a  tiny  canal  in  the  tem[X)ral  bone  to  reach  the 
tympanic  cavity,  where  it  joins  the  main  continuation  of  the  tympanic  plexus  of  the 


THE  FACIAL  NERVE. 


"53 

the  parotid  gland.        .„^_«-j^  oetrosal  nerve  is  very  small  and  is  not  always 

4.  The  •t«P«*»?l»SS  LTwTOhbd  the  pyramid  in  the  posterior  wall  d 
ifZ^^rTc  S:i^!l.r^ '^^ntacc^s  to  the  muscle  by  pass.ng  through  a 
mbute  ^ce  in  the  base  of  the  pyramid. 

1068. 


TvMponl  bniKh  erf 

:4wtaid  branch  o( 
grtat  ftuflculai 


Mftlar  t<rAiKh  of  tacUl 

Triuiioral  »watK». 

of  facUl 

luftaorlMftl  brant  h. 

..r  fecial 

FacU)  nfT%*' 


HucuJ  braiKh  of  fiu-tal 
<iu|mmsn<tibu)«T  branch  of  fa*.UI 
UtoutUBilibuUr  brwch  of  fmiUI 

Smal)  MilpfU)  ner%r 

branch  nf  III.  c«nl«»l, 

Gml  kuiicuUr  nrrvc 


Supnorl4u)  •«%• 
Su|vatmchl«aT  nerve 

lofratroLhtcnr  nen  r 
Malar  bramhiif 

traivoro-nMlar 
InfraortiUl  nerve 
External  bran*  h  trf 
MMlner^e 


\  Sin«T*cW  ctnrkal  ner** 

5.  T1,e  chorda  tympani  ~- j-rse^ryT^^^^^^ 
motor  and  sensory  i"r''^vr"!^.rXhefacTaUsL.t  distance  above  th^ 
of  the  geniculate  ganglion.  It  arises  from  .Ji^'^^^V^  „  "^^  n„  chorda  posterius 
mastoiS  foramen  and  courses  upward  and  '"^^^J  t'^^^^'^e  fibrous  ancUucous 
to  enter  the  tympanic  cavity  (Fig.  1067).  P^^'^^jX^ensor  tympani  and  between 
layers  of  the  membrana  tympani.  «^.«^  ^'l^.I^f  ^j\„iv«  at  the  anterior  edge  of  the 
the  long  processes  of  the  incus  ""^  "?'J^"'';„\S^  reach  the  pterygo-maxiUary 
membrane.  It  then  traverses  he  iter  fJ^-^^^^^^J^^'^Vnglion,  take4  a  course  down- 
region,  and.  after  '•«=f"ving  a  hlament  from  the  otic  gang^  pt;rygoid  muscle,  it  unites 
ward  and  forward,  ^^er  whicb^under  cov^^^  ^    ,,, 

rj;t?iz:'=i;  ^^Pnh^'^  rT:.:'^^^i^X^^y 


«»M 


HUMAN   ANATOMY. 


fibres  of  the  chorda  tympani,  on  the  other  h:\nd,  are  distributed  to  the  mucous 
membrane  covering  the  anterior  two-thirds  of  the  side  and  dorsum  of  the  tongue, 
and  are  probably  concerned  in  transmitting  taste-impulses. 

6.  The  communicating  branch  to  the  auricular  branch  of  the  vagus 
(r.  aoastomoticns  c.  ramo  anriculari  n.  vagi)  is  given  of!  just  above  the  stylo-mastoid 
foramen  and  joins  the  auricular  at  the  point  where  the  latter  crosses  the  facial  canal. 

7.  The  posterior  auricular  nerve  (n.  auricalaris  posterior)  arises  just  outside 
the  stylo-mastoid  foramen.  It  passes  backward  and  upward  between  the  external 
ear  and  the  mastoid  process  and  divides  into  (a)  an  occipUal  branch,  which  supplies 
the  occipitalis  muscle  and  (p)  an  auricular  branch,  which  supplies  the  posterior  auric- 
ular muscle,  often  partially  the  superior,  and  the  transvers  is,  the  obliquus  and  the 
antitragicus  of  the  intrinsic  muscles  of  the  auricle. 

The  posterior  auricular  nerve  communicates  with  the  auricular  branch  of  the 
vagus,  the  small  occipital  and  the  great  auricular  nerve. 

8.  The  digastric  branch  (r.  digastricas)  arises  from  the  facial  below  the  pos- 
terior auricular  nerve  and  breaks  up  into  several  filaments  which  enter  the  posterior 
belly  of  the  digastric.  One  of  these  filaments,  after  passing  through  or  above  the 
digastric,  may  join  the  ^losso-pharyngeal  nerve. 

9.  The  stylo-hyoid  branch  (r.  stylohyoidcns)  is  a  small  twig  which  arises  in 
common  with  the  digastric  branch  and  passes  forward  to  enter  the  posterior  portion 
of  the  stylo-hyoid  muscle. 

ID.  The  temporo-facial  division  (r.  temporofacialis)  (Fig.  1087)  is  the 
larger  of  the  two  terminal  branches.  It  traverses  the  upper  portion  of  the  parotid 
gland  in  a  forward  and  upward  direction,  lying  superficial  to  the  external  carotid 
artery  and  the  temporo-maxillary  vein.  By  repeated  branchings  and  unions  the 
nerve  forms  an  intricate  looped  plexus  which  breaks  up  into  three  more  or  less  defi- 
nite groups. 

Branches. — These  are :  (a)  the  temporal,  (b)  the  mtlar  and  (f )  the  infraorbital. 

a.  The  temporal  branches  { rr.  tcmporain )  ptisa  upward  and  forward  over  the  zygomatic 
arch  and  supply  the  frontalis,  the  corrugator  supercilii,  the  upper  part  of  the  orbicularis  palpe- 
brarum, the  auricularis  superior  and  the  auricularis  anterior. 

The  temporal  branches  of  the  facial  coinraunicate  with  the  following  branches  of  the 
trigeminal :  the  auriculo-temporal,  the  supraorbital,  the  lachrymal  and  the  temporal  branch  of 
the  temporo-malar. 

6.  The  ma/ar  braiuhes  (rr.  xygamatld)  are  rather  small.  They  extend  forward  over  the 
malar  bone  and  are  sometimes  incorporated  with  the  temporal  or  infraorbital  branches.  They 
supply  the  lateral  part  of  the  orbicularis  palpebrarum  and  sometimes  the  zygomatic!  major 
et  minor. 

The  malar  branches  communicate  with  the  malar  branch  of  the  temporo-malar. 

c.  The  infraorbital  branches  { rr.  buccalti  rapcrlorea)  are  comparatively  large.  They  course 
horizontally  forward  across  the  masseter  muscle  in  comjviny  with  the  parotid  duct  and  supply 
the  lower  part  of  the  orbicularis  palpebrarum,  a  portion  of  the  buccinator,  the  zygomatici  major 
et  minor  and  the  muscles  of  the  nose  and  upper  lip. 

The  most  important  of  the  comrounicationt  i.s  the  one  between  the  infraorbital  and  the 
terminal  branches  of  the  maxillary  division  of  the  triKeniinal.  This  is  a  sensory-motor  plexus 
which  lies  below  the  infraorbital  foramen  and  under  the  levator  labii  su|>erioris'ant!  is  called  the 
infraorbital  plexus  (Fig.  1068).  The  nasal  and  infratrochlear  nerves  communicate  with  the 
infraorbital  at  the  side  of  the  nose. 


II.  The  cervico-facial  division  (r.  cervicofaclalls)  (Fig.  1087)  is  the  smaller 
of  the  terminal  branchts  of  the  facial  and  resembles  in  its  general  arrangement  the 
temporo-facial.  It  passes  downward,  outward  and  forward  through  the  parotid 
gland  and  finally  breaks  up  into  three  branches. 

Branches. — These  are  :  {a)  the  buccal,  {b)  the  supramandibular  and  (f)  the 
inframandibular. 

a.  The  bnccal  branch  (rr.  baccaln)  may  be  single  or  multiple.  It  crosses  the  masseter 
and  supplies  the  buccinator  and  orbicularis  oris  muscles. 

It  communicates  on  the  outer  surface  of  the  burcinator  muscle  with  the  sensory  buccal 
branch  of  the  mandibular  division  of  the  trigeminal  nerxe. 


THE  FACIAL  NERVE. 


Tr»n»ver«e  r«cial  artery 

Hranchcs  of  Iht  facial  ncm 

Superficial 
temporal  artery 


"55 

*   The  sui,ramindilmlar  branch  (r.  o,.,il~l».  »..dib«I.rl.)  passes  for* ard  between  the 

U,we*iip^^ch,„  and  ^^^^^^^^^^^'^^^^^^.^  of  the  inferior  dentai.        .^ 

Its  filaments  commwuct.  *''\"^°*M'°("  "^^ew  from  the  lower  margin  of  the  paroUd 

c.  The  inframandxbular  *~"^*J'i  "^'^  >/^'K'ST  jaw.    Piercing  the  deep  cervical 

£St  ifp^^^^forrSr^n'l.^a'^drJs^^  .^beneath  the  platysma  myoides 

^-S^:oSr^.  l\t-t^%^:^^S'^^ch  of  the  cerv^alp.... 

convtJsif)  or  of  P?r.^y^-.  J^J^^^rcoT/nSto  4^^  benches  it  usually  involves 
more  <=«'7'«°"/  t^he  evt  Ton ly  the  orbicularis  is  involved  it  is  ^led  bepharc 
the  muscles  about  t^f^y^,  "  .™  \^  involved,  stasmm  nictilans.    The  facial  nerve 

spinal  accessory.  i„^„-,mnn      If  the  r«t/ra/ lesion— as  a  tumor,  abscess 

nerve  will  result,  and  the  ,  p^j   ,069. 

paralysis  will  usually  be 
confined    to    the  lower 
branches  of  the  nerve  m 
the  face  and  neck,  the 
upper  branches  escaping 
probably  because  of  bi- 
lateral innervation  of  the 
upper    muscles    of    the 
face.    A  cortical  isolated 
paralysis  of  this  type  is 
exceedingly  uncommon. 
If  the  lesion,  as  an  apo- 
plectic hemorrhage,  is  in 
the  internal  capsule,  a 
hemiplegia  on  the  same 
side  as  the  facial  paral- 
ysis will   be  associated 
with  it,   and    this  also 
usually  occurs  when 
the  lesion  is  cortical.     A 
lesion  in  the  upper  part 
of  the  pons  will  give  rise 

to  a  similar  condition,  .    .  .u„  r.r.ns  tho  facial  nerve  will  be  paralyzed 

Lif  it  i-^'h«  middle  orlowerp^^^^^^^  ^  crossed  pard- 

on the  side  of  the  lesion   the  l'""  P'fK*^  .'^,V'^{°  :..  fibres  cross  to  the  opptJSite  side 
ysis).     This  is  explained  by  the  fact  f  ^'  ^J^  ™  and  trunk  cross  in  thrinodulla. 

andShere  wilMje  a  hemiplegia  of  the  jp^^^^^^^^^  .^^  ^^.^  ^^  „,^.  ,,  Us 

The  peripheral  P'f  7"  °\  ^'^'^  ^s^n  of  the  facial  nucleus  in  the  pons  givei  r  .c 
terminal  filaments  on  the  face,  but  a  IcMon  o  tne  i  ^^^  ^^^^^. 

to  much  the  .tme  ^V-l'^^-Xrhv    ut-rXs  5^^^^^^^^^     tumors,  Jtc.      In  its  long 
cranial  portion  may  be  myo.vtd  ^  tutKrcu^  \  m^    ^f  ,he  s.^fl  tissues, 

course  through  the  ^  »"°P'?,"/,;!"!;';;j"*f  ,t  ^^^^^^^  «kuU  in  the  middle  fossa. 


Parotid  gland 
Parotid  duct 
Maweter  muacle 


DiMection  ahowing  «"»"»";  "'Ij'i'l  "12 ' 
they  cTos»  maweter  mur.ci«- 


.lanches  a» 


^^^^■f- 


1356 


HUMAN  ANATOMY. 


When  all  branches  of  the  iacial  are  paralyzed  the  symptoms  are  characteristic. 
Only  one  side  of  the  forehead  wrinkles ;  the  tears  fail  to  enter  the  canaliculi,  and 
flow  over  the  cheek  ;  the  eye  cannot  be  doaec  •  foreign  bodies  on  its  surface  are  not 
removed  by  the  lid,  and  conjunctivitis  from  irritation  results.  The  affected  half  of 
the  face  is  expressionless,  and  the  comer  of  the  mouth  on  that  side  remains  partly 
open  and  hangs  down,  so  that  the  saliva  tends  to  run  out  The  mouth  is  drawn  to 
the  opposite  side ;  the  upper  lid  cannot  be  elevated,  and  whistling  b  impossible 
because  the  orbicularis  cannot  now  pucker  the  lips  ;  food  lodges  in  the  affected  side 
of  the  mouth,  because  the  buccinator  muscle  is  paralyzed,  and,  for  the  same  reason, 
the  mucous  membrane  often  gets  caught  between  the  teeth. 

In  those  cases  of  facial  paralysis  in  *hich  the  lesion  of  the  nerve  is  posterior 
to  ihe  styio-mastoid  foramen,  attempts  have  been  made  recently  to  restore  hmction 
to  the  peripheral  portion  by  dividing  the  trunk  posterior  to  the  parotid  gland, 
and  anastomosing  the  peripheral  end  to  a  neighboii  ig  cranial  nerve,  as  the  spinal 
accessory  or  the  hypoglossal.     The  results  have  not  been  entirely  satisfactory 

The  line  of  the  main  tru.ik  of  the  nerve  is  from  the  slight  depression  between  the 
banc  of  the  ear  and  the  mastoid  process,  forward  and  slighdy  downward.  It  passes 
through  the  deeper  portion  of  the  parotid  gfand. 

• 
THE  AUDITORY  NERVE. 

The  eighth  or' auditory  nerve  (n.  acnstictis)  is  not  only,  as  its  name  implies,  the 
nerve  by  which  sound  impulses  are  transmitted  to  the  brain,  but  also  the  nerve  of 
equilibration.  It  consists  of  two  portions,  the  cocUear,  the  true  nerve  of  hearing,  and 
the  vestibular,  which  is  concerned  with  equilibration. 

Traced  from  the  brain  toward  the  ear,  the  auditor)-  nerve  arises  at  its  super- 
ficial origin  by  two  roots,  a  mesial  (radix  vestibnlaris)  and  a  lateral  (radix  coch- 
learis),  which  embrace  the  inferior  cerebellar  peduncle,  the  mesial  passing  to  the 
inner  and  the  lateral  to  the  outer  side  of  the  peduncle.  The  nerve  thus  formed  by 
the  union  of  the.se  two  i.iots,  leaves  the  surface  of  the  brain-stem  at  the  postenor 
border  of  the  pons,  where  it  is  adherent  to  the  middle  cerebellar  peduncle.  To  its 
inner  side  and  closely  associated  with  it  are  the  motor  and  sensory  roots  of  the  facial 
nerve  (Fig.  1046),  which  lie  within  a  groove  on  the  mesial  surface  of  the  auditory 
and  with  it  enter  and  traverse  the  internal  auditory  canal.  Witl.in  the  latter,  the 
auditory  nerve  separates  into  two  divisions,  of  which  the  superior  and  larger  is  the 
vestibular  nerve  (n.  vestlbull)  and  the  inferior  and  smaller  is  the  cochlear 
nerve  (n.  cochleae).  Although  in  a  general  way  these  divisions  continue  the 
corresponding  roots,  this  agreement,  as  to  the  source  of  their  fibres,  is  not  complete, 
since,  as  will  be  more  fully  noted,  strands  of  vestibulai  fibres  are  incorporated  with 
the  cochlear  nerve. 

On  reaching  the  bottom  of  the  internal  auditory  canal,  the  facial  nerve  leaves 
the  meatus  and  enters  the  facial  canal,  while  the  fibres  of  the  auditory  nerve  dis- 
appear through  apertures  in  the  lamina  crihros.i  (Fig.  201)  to  gain  the  several 
parts  of  the  membranous  labyrinth  of  the  internal  ear.  During  their  joimey  through 
the  meatus,  the  vestibular  and  facial  trunks  arc  connected  (fila  anastouiica)  by  a 
branch  which  passes  from  the  pars  intermedia  to  the  vestibular  ner\'e,  and  by  one 
from  the  latter  to  the  geniculate  ganglion.  These  apparent  communications  between 
the  seventh  and  eighth  nerves  are,  in  fact,  only  aberrant  strands  of  facial  fibres  that 
return  to  the  seventh  after  temporary  association  with  the  auditory. 

The  vestibular  nerve  divides  into  three  terminal  branches  which  pass  through 
aper lures  in  the  cribriform  plate  above  the  falciform  crest  and  supply:  ( 1 )  the  utricle, 
(2)  the  superior  AnA  (3)  \)\k  external  semicircular  canal.  Not  all  the  fibres  of  the 
vestibular  root,  however,  are  included  in  these  branches  ;  of  the  three  branches  given 
off  by  the  cochle:ir  ner%e  two,  14)  those  to  the  saccule  and  ^5)  to  the  posterior  semi- 
circular  canal  arc  vestibular  fibres  incorporated  with  the  cochlear,  although  reem- 
ingly  derived  from  the  cochlear  nerve.  The  remaining  branch  of  the  cochlear  nerve 
contains  the  cochlear  fibres  proper,  which  traverse  the  numerous  foramina  of  the 
tractus  spiralis  foraminosus  and  the  central  canal  of  the  modiolus  to  supply  the  organ 
of  Corti  within  the  memhrenous  cochlea. 


THE  AUDITORY  NERVE. 


1257 

^  r'sLfo^V  a„iThSr'X4^'t.^t  they  ie  the  processes  ,axo„es)  ol 

SSfe-^s  situa^  somewhere  along  the  course 

driie  wrve.     It  is  necessary,  consequently,  to 

ik  thTJS  oripin  of  these  fibres  in  the  gangha 

^inKg  on   the  divisions  of  the  nerve      In 

^^iO^on  of  the  hmctional  differences  d  the 

^*L»  of  the  eighth  nerve,  .t  .s  desirable  to 

trace  separately  the  pathway  followed  by  the 

S^l^^veyed  by  Sch  of  these  components. 

P<Tif>hciml  Central  and  Corticml  Connection*  of 
U„  <KrN^e.-The  true  cochlear  fibres  anse 
^thin*e  internal  ear  (cochlea)  as  »o"«  «'  »^^ 
«^  of  the  wirri  fnglUm  or  gangUon  of  Corh  K%. 
^™i!t  (  FiK  ««>7*)-  Thb  structure  consKts  of  a 
^n"«  ^of^i^lar^neirones  which  .occupie^.  the  sp.r^ 

i::^r^elion^itMhe^roepithe.ial  cells  o.mpr^ 
^iSgtte  inner  and  outer  hair<ells  of  the  organ  d^Cortu 
I  Mvine  the  hair-cells  as  nonmedullated  fibres,  tney 
^^e,^  Z  foramina  nervosa  of  thelabium  tympa^.- 
™m  at  which  point  they  become  nwdu  lated.  flwy 
S  inteTace  to  form  an  elaborate  flat  fe  t-work  tha^ 

^^h^"w^he  laversoJ  the  lamina  st.iral.s  and  soon 
^mbuTTo  form  bundles  which  pass  to  the  cells  o 
;tr    .n%n  spirale.  each  fibre  probably  jommg  .N 

'd>viduf  cell."^  Leaving  the  ganglfon    the  axones  of 

K  ceUs  enter  the  bony  canals  withm  the  ir>Kliolus. 

foruhkh  they  emerge  at  the  tractus  spiralis  toram.- 

no^s  and  are^M  into  a  single  bundle,  the  aKh- 

tea  "^.^e  proper.    The  latter,  however,  soon  rece  ves 

uo^sionTone  of  which  consists  of  fibres  from 

he  Se  ^nd  the  other  from  the  ,K«tenor  sem,- 

^rcul^Tcanal     From  what  has  been  said,  it  is  -videm 

S  theS  accessions  are  ,«rt,  o' the  ve^ubular  -^^^^        ^  ^.^^  ^^  cochlear  root. 

and.  lieyond  their  temporary  ""^P^"'""!^;^;^,^^^^*"  into  relation  with  their  nucleus  ...  recep- 
Onreachli.K  the  medulla,  the  c.Khlear  fibres  come  mi  collectively  consl.tute  the 

tion.  which  includes  t.o  superfica  «K^^K~^S  omL  parts  (Fig.  93»)  of  whi.h  one. 
.couetic  nucleus  (n.Kle«.  «""'  "•^- nLle  jrr™  "coustu  n„c/eus  {n«cit^  .cc.Mor..»).  hes 
the  vertrul  cochlear  "«>««' "'''IS^^^nflpLd  the  ^r.  the  Uteral  cochlear  nudeu..  -r  tuber- 
ventral  to  the  interior  cerebellar  Pf  ""^^'^j  ""f  ,'„4^^^  neduncle  and  .«upies  the  .Mrem. 
culum  acatticum.  r.sts  upon  the  dorso-lateral  f"™"  J  ;^,  j^  „,  the  fl.x.r  of  the  fourt:,  ..  >v 
ovuer  part  of  the  triangular  acoustic  area  ^T" '"  L^Vfibres  T^  in  arb.>r;«a.i<.ns  around  th.  ste  - 
tricle  ^ge  1097  )■  The  greater  numl>er  ;^J,«^»;'7'i^[f  j^,  ^ution  with  the  more  elongatt-d. 
late  c  lls.f  thev.mr.il  ga.igWon.  wh.le  ''^^'-'r^  ^"^"^J^^  subdivisions  of  the  reception 
u^fo-n.  ceil,  of  the  lateral  nucleus.     From  the  "~XrSthe  axones  of  the  cells  of  the 

nucleus,  the  auditory  pathway  ,s  '^""t.^^^^^'^^/trthe^s^^^^^  »»>•=  ''P'"''  '""'  'i  T 

ventral  nucleus  passing  for  the  most  iK.rt  ^^n"  al  to  tne  re  ^^^^^  ^^,^^p  ^^,,^,„^  ,he 

trigeminus  t. form  the cor^s (^'''rt"- .^^'^^^^'X  ZZ  he  e,,endyma  of  the  flo..r  of  the 

*'^'^tfc„rpu.trap..oid...theconspic„oi«tmnsve.^ua.th^^^ 

,heventrarV?gion  of  the  ,«ns  m  ;t--3"";,P„7Jj'  ^jTum^  number  of  fibres  that  spring 
within  the  ventral  cochlear  ""^•'':".''- ''"PP  f„7^^^^^^^  ,,.,„  the  large  cells  found  within  the 

from  the  lateral  nucleus,  n  »f  f 'f " '' 5  l"*f^"^'o;stitute  the  nudeu.  trapeaoideu..  In  cU«e 
trapezoid  Ixxly.  on  each  side  of  themid-lme.  that  con  n  ^^^  ^^^^^._,^  ^,,^.^.       ,    „ 

relation  with  the  dors;,!  surface  of  th'Jo'pusJ^a^^K^^  ^    ^^,^^^  „,,^..^ 

either  side  of  the  median  raphe,  ''r'* ''^^  ""^f^e  Sear  fibres,  chiefly  from  the  opi^.site 
collection  of  nerve-cells  around  *»"'^^"«"yXh  thc^art  of  the  lateral  fillet  principally  take. 
hut  also  from  the  same  side,  end  and  from  which  tm.  tracx 


RMondruction  o«  left  memhrinouii  laby- 

!^i  >ra  Hen  dmukk  to  ampullat  ol  semi- 
""LlJr  cl^.  STd  to  macula  o(  utncl.  and 
ncculc.     X  M.     ^SIrrrtrr.) 


1258 


HUMAN   ANATOMY. 


origin  (Fig.  1079).  Not  all  of  the  fibres  arising  from  the  superior  olivary  nucleus,  however, 
enter  the  lateral  fillet.  A  considerable  number  leave  the  dorsal  surface  uf  the  nucleas  and,  as 
its  pedmule,  pass  to  the  abducent  nucleus  and,  by  way  of  the  posterior  longitudinal  fasciculu.s, 
to  the  nuclei  of  the  other  eye-muscle  nerves.  In  this  manner  reflex  paths  are  establisheil  by 
which  the  motor  nerves,  including  probably  the  facial,  are  brought  under  the  influence  of  audi- 
tor)' impulses.  Within  the  tract  of  the  fillet  and  a  short  distance  beyond  the  superior  olive,  Lh 
encountered  a  group  of  nerve-cells,  the  nnclcai  of  the  lateral  flUet  (nucleus  lenaiacl  lauralis). 
While  numerous  additions  to  the  fillet  are  received  from  these  cells,  their  relation  to  the  cochlear 
fibres  is  uncertain.  The  characteristics,  course  and  destination  of  the  lateral  fillet  have  been 
dsewhere  described  (page  io8a).  Sufllice  it  here  to  recall  that,  so  far  as  the  auditory  fibres  are 
concerned,  the  tract  terminates  chiefly  in  the  inferior  colliculus  of  the  quadrigemina  and  the 
median  geniculate  body. 

In  addition  to  its  constituents  through  the  corpus  trapezoides,  the  lateral  fillet  receives  con- 
siderable accessions  of  cochlear  fibres  by  way  of  the  atria  acuaticje.  These  strands  consist  of 
the  axones,  for  the  roost  part,  of  the  cells  lying  within  the  tuberculum  acusticum,  but  to  a  limited 

Fig.  1071. 


ni«ijiv.m  5iho'vinj{  rontiet.tion8  of  auditory  nerve ;  cochlear  fibre*  and  coniwctidw  are  in  black,  vcatibular  in  red ; 
C,  C'H  hit',  -  G^,  Kantflion  spirale  ;  lAC,  tnternai  auditory  canal  ,  I  C,  DC,  vential  and  doraal  cochlear  nuclei ;  Rfi^ 
rctttit>rni  iKidy;  jTO,  sujKrior  olive;  7*^.  trapeioid  hody;  .^r.S/,  aiiiustic  striae  ;  yt/,  nucleus  of  lateral  fillet  itF); 
MF,  nu'^ian  'fillet;  fO,  inferior  quadrifeminal  body;  ^(7.  mcdi.in  senicitlate  body;  ^^,  auditory  radiation ;  rC 
tempc'ai  cortei;  7;  thalamus;  SC,  aemicirrular  canal;  f ',  vestibule ;  Kf#,  veatibular  fanfflion;  My,  median 
veiiiljular  nucleua  ;  DN.  lateral  (Ueilera')  \rstibular  nuckui;  I'j/,  vealibulo-apmal  fibre;  O, cerebellum. 

extent  also  ui  the  axoi.es  of  the  ventral  cochlear  nucleus,  which  wind  over  the  latero-dorsal 
surface  of  the  inferior  cerebellar  ()eduncle,  pass  medially  beneath  the  ependyma  of  the  floor  of 
the  fourth  ventricle  as  far  as  the  median  groove,  and,  crossing  to  the  opposite  side,  then  sweep 
ventrally  thriitigh  the  dorsal  n-xiun  of  the  medulla  or  pons  to  join  the  tract  uf  the  lateral  fillet, 
and  so  proceed  in  company  with  the  other  cochlear  fibres  to  the  higher  levels.  By  no  means 
all  of  the  c(>m|x>nent  fibrtn  of  the  acoustic  strix  follow  the  lateral  fillet,  since  some  after  decussa- 
tion turn  brainward,  pos.sibIy  joining  the  mesial  fillet,  whilst  'ithers  may  enter  the  posterior 
longitudinal  fiisciculus  to  assist  in  establishing  reflex  paths  influx    ing  the  motor  nerves. 

The  auditory  path,  by  which  the  impulses  gathered  from  the  organ  of  Corti  by  the  cochlear 
fibres  are  conducted  to  the  cerebral  cortex,  includes  the  following  components  ( Fig.  1071 ) : 

I.  Peripheral  neurones  of  the  ganglion  spirale,  whose  axones  (the  cochlear  fibres)  pass  to 
the  reception-nucleus    -.entral  and  lateral  cochlear  nuclei). 

?.  Neurones  of  liio  cochlear  nuclei,  which  .send  their  axones  :  {,1)  by  way  of  the  corpus 
trap  les  to  the  superior  olivary  nucleus,  chiefly  to  that  of  the  opposite  side  but  also  to  that 
of  the  s.iine  side,  or  to  the  lateral  fillet  or  its  nucleus  without  interruption  in  the  olive  ;  (5)  by 
way  of  the  strix  aciisticx  through  the  tegmentum  to  join  the  trapezoidal  fibres. 

3.  Neurones  of  the  superior  olivary  nucleus  or  of  the  fillet-nucleus,  whose  axones  pa.ss  by 
way  of  the  lateral  fillet  i<i)  to  the  rells  within  the  inferior  collicuUis.  or  (A*  without  interruption 
through  the  inferior  brachium  to  the  cells  within  the  median  geniculate  body. 


THE  AUDITORY   NERVE. 


1259 


Fig.   107J. 
Ftoor  ol  IV.  ventricle 


.Superior  cerebelUt 


,Rupel 
pcdui 


luncle 


Inferior  cereheltar 
peduncle 

Lateral  vertllmUr 
■(Deiter'.l  nucleuit 
.Median  vertibular 

nucleuK       

'Cochlear  nbrea 

Doraal  cochlear  nucleua 

DescendluK  vertlbular 
root 


pas,,  M  the  4uMory  raJu,tw„,  »«/^ ''"""'^dUonrarea  i»  rtiH  uiKerUin,  the  most  imp-^rtant 

-"-sr^.^  «b«,  that  '^,:^^^;srr.t^':2t:ts^i^:^^^ 

the  preceding  account,  f^^"'  .     ^^       ^  ,u^ 

the  cochlea  of  the  opposite  side.  ^^,  „j  «•«  Vertibutar  Netve.-The  fibres  o<  the 

I>«iil>h«ral,  C««tna  and  Cortical  C<»"»«^/*^*  °^,,  .^e  bioolar  nerve-cells  situated  within 
v«rtiKr«n  6t  the  »';*«7^';^^;:^^or^r;i- J^S^^^  which  lie,  at  th.-  l«n«n 
,he  small  vatlbul-r  ,«.fUon  (■lV'^^Jj^^  ^'  theJcells  constitute  the  five  branches  of  d»- 
S.:S:;i:ri'::^ria;;::l.eT!S  ?Sro«Kh  the  vanous  openm^s  m  the  mner  wall  of  the 
bony  1  .byrinth.  in  the   manner   above 
S^bed    (page  «56 ).   to   reach    t^ 
spedaliKKl  areas,  the  mac«a-  atMshca 
S  the  saccule,  the  utncle  and  the 
:;;;jLll*of  the  semicircular  canals.«*e« 
the   nerve-filaments   end.   really  begin. 
„   intimate    relation    with    the    neun. 
epithelium.    While  the  centrally  directed 
akones  of  the  nettrones  ""PPly-ng  *e 
utricle  and  the  supenor   and   extena^ 
Lmicircular  canals  become  cons"''^^ 
to  form  the  vestibular  nerve  of  d««"Pt"^« 
anatomy,  those  from  the  sacctile  and  the 
pK««rior  semicircular  canal  Jointhe^h- 
tear  fibres  and  with  these  course  within 
t^  «K:hlear  nerve  umil  the  latter  and 
the  vestibular  nerve  unite  to  form  the 
common   aud.u.ry   tnmk.     Where    the 
common  trunk  separates  into  the  two 
roots    the   vestibular   hbres   leave   the 
cochlear  and  Pennanently  a.s>.umetheir 
natural  companionship  with  the  remain- 
ing fibres  of  the  veslibularroot. 

The  vestibular  fibres  enter  the 
brainstem  at  a  slightly  higher  level  than 
does  the  cochlear  root  l>'nK  "]«"»'»?^''; 
latter  and  the  ventral  c«K:hle«r  nucleus 
and  pass  dcrsally  within  the  pons  between 
the  inferior  cerebellar  peduncle  and  the  ^^  vestibular  fibres  divide 

spinal  trigeminal  root.  On  reiichmg  » '!^«' "T"^  ™  1^  ^.hjch.  after  condensing  into  an 
Soshort  upward  and  l"-?!^^  ,^"7'*»"^;r«„aTn  ^^^  the  cells  of  the 

ascending  and  a  d«K*ndinK  root  restive  y^  end  .^^^^^ 

vestibular  nucleus  of  reception.  T^'^^.^^'f'',, 'h\  "  tHde  (iMge  1097).  are  uncertain,  since  the 
u"  the  are.,   --custica  '" /he  floor  of    he  fourth^e^^^^^^ 

neurones  directly  related  to  *e  v«t^u^ar^bres  contn  >^^,|,^,.„,,  ^^..^^bly  have  only  an 

a  large  diffuse  complex  of  cells  ?"^\'''^' "'■*"*. hln  reconstructe. I  a-  has  been  successfully 
f„iirfct  connection  wi.h  .'^e  ve^  'bu^  jne^  \\hen^^^^^^^^^  ^.,„  .  ..,  ,,.„  „,  p^rts^ 
done  by  Sabin.  this  complex  has  the  form  '•n°« "  "  '•'«•      '  ^  ,       „  mesial  to  the  tract 

Sran  extended  irregulariytrian«u^^arnjassf^  j.,,^^  ^^  „>  „,„.,.„, 

lotted  by  the  ascending  ""'\;,'r^/'^'  "."J,;^^^^^  ,0  the  inner  ..,.1  partly  to  the  outer  side 

mass  of  cells  which  lies  alxjveihe  larger. m^^^  triangula-  mass  approaches  the 

^''•'  '^Sz:^  micro^opicaiiy  ^^^^^:^^:^^rt:::^^ 

a  taperixg  caudally  directed  ""'^'-^;^  « ^i^h  con  m^^^^^  ^^    ,  ^he  large 

vestibular  root.  (A)  .in  f ''»'^"'^'' .^T^'^Sus    ,•  fproU^       upward  the  superior  angle.  The  first 
mass  and  ( r)  an  .'r«K«'»M>yrannd..  nudeu^^^^^^  ^J^^,^^^  ,  „„^  ,,„    „    „.  vesUbular^.). 

of  these  suWi visions  (a1  is  '>™'« ";'*;"/ •P'.""     ,  .,„£   m,dlall..  n.  v.atibulnri»>.  als.>  as  the  ch,fj 

the  second  (*)  -^.^^l^^^Zi^l^"^^^^^^^  >  '""-'-  "P«''°'  ^"'*"'"  ""''~"  "  ' 

HUiliUiar  the  r-t"-.^ 


Nucleua  cunealus 
.Cloacd  part  of  medulla 


Veallbular  nuclei  a.  .hown^in^reconaimctlon  by  Dr.  Florence 


I260 


HUMAN  ANATOMY. 


nadaut  i>t  Bechtenw.  The  small  mass  corresponds  with  the  Utcial  veMibnlar  nucleus  (nac. 
latcnilU  a.  vestibolarto)  or  nucleus  of  Deiters.  The  fibres  of  the  descending  root  end  around  the 
neurones  within  the  spinal  nucleus  in  a  manner  similar  to  that  in  which  the  constituents  of  the 
spinal  root  of  the  trigeminus  terminate  in  relation  with  the  neurones  within  the  substantia 
gelatinosa,  whilst  those  of  the  ascending  vestibular  root  end  around  the  cells  within  the  remain- 
ing vestibular  nuclei. 

Although  much  uncertainty  and  conflict  of  opinion  exist  as  to  the  details  of  the  secondary 
paths  by  which  the  impulses  carried  by  the  vestibular  fibres  are  distributed,  it  may  be  accepted 
as  established  that  fibres  pass  from  the  nuclei  of  reception  :  (a)  to  the  cerebellum  (chiefly  to  the 
roof  nucleus  of  the  opposite  side  and,  possibly,  also  to  the  nuclei  globosus  and  emboliformis) 
as  coh5tituents  of  the  nucleo-cerebellar  tract,  by  which  the  impulses  of  equilibration  are  carried 
to  the  great  coordinating  centres,  {d )  as  arcuate  fibres  ventro-medially  into  the  tegmentum  of  the 
pons,  cross  the  mid-line  and  bend  upward  or  downward  to  pass  to  other  levels,  some  fibres, 
however,  remaining  on  the  same  side.  From  the  character  of  the  impulses  it  is  probable  that 
only  relatively  few  vestibular  fibres  join  the  median  fillet  to  ascend  to  the  optic  thalamus.  Other 
connections  of  the  nuclei  include :  (r)  commissural  fibres  between  Bechterew's  nucleus  of  the 
two  sides,  (rf)  fibres  to  the  abducent  nucleus,  (*)  crossed  and  uncrossed  fibres  '-om  Deiters' 
nucleus  to  the  posterior  longitudinal  fasciculus  and  (/)  fibres  from  the  same  nucleus  to  the 
spinal  cord. 

It  must  be  understood  that  by  no  means  all  of  the  neurones  of  Deiters'  nucleus  are  con- 
cerned in  transmitting  afferent  impulses  to  the  cerebellum,  for,  as  a  matter  of  fact,  many  are 
links  in  the  path  by  which  the  cerebellar  cells  exercise  coordinating  influences  over  the  root- 
cc-iia  of  the  spinal  nerves.  Starting  in  the  cerebellum,  such  efferent  impulses  are  carried  by 
efferent  fibres  which  descend  through  the  median  part  of  the  inferior  cerebellar  peduncle  and 
probably  end  around  certain  of  the  cells  within  Deiters'  nucleus.  From  these  cells,  in  turn, 
originate  the  fibres  of  the  vestibulo-spinal  tract,  which,  after  traversing  the  medulla,  enter  the 
antero-lateral  column  of  the  cord  and  end  in  relation  with  the  motor  root-cells.  A  shorter  and 
more  direct  path  for  vestibular  reflexes  is  probably  formed  by  the  collaterals  of  the  vestibular 
fibres  that  end  around  the  spinal  neurones  of  Deiters'  nucleus.  It  must  not  be  forgotten  that 
Deiters'  nucleus  is  the  origin  for  important  contributions  to  the  posterior  longitudinal  fasciculus 
(page  1 117),  by  which  the  vestibular  impulses  impress  the  nuclei  of  the  motor  and,  perhaps  to  a 
limited  degree,  also  those  of  the  sensory  nerves. 

Practical  Considerations. — The  auditory  nerve  is  rarely  the  seat  of  primary 
disease.  It  is  most  frequently  affected  consecutively  to  disease  of  the  middle  and  in- 
ternal ears.  It  is  sometimes,  though  seldom,  paralyzed  in  fractures  of  the  base  of  the 
skull.  Operations  on  this  nerve  have  been  performed  for  relief  from  pei'sistent 
and  annoying-  tinnitus. 

THE  GLOSSO-PHARYNGEAL   NERVE. 

The  ninth  or  glosso-pharyngeal  nerxe  (n.  glossopharyngcus)  is  a  mixed  nerve, 
containing  motor  and  sensory  fibres,  the  latter  including  those  transmitting  the 
impulses  of  the  special  sense  of  taste.  The  motor  element  is  quite  small  and  sup- 
plies only  the  stylo-pharyngeus  muscle  and  secretory  fibres  to  the  parotid  gland, 
while  the  sensory  fibres  are  distributed  to  the  mucous  membrane  of  the  middle  ear, 
fauces,  tongue  and  pharynx. 

The  Nuclei  of  the  Glosso-Pharyngeal,  Vagus  and  Accessory  Nerves. — 
In  the  description  of  the  medulla  (page  1073)  attention  was  called  to  the  presence  of 
nuclei  common  to  a  greater  or  less  extent  to  the  series  of  lower  lateral  nerves  including 
the  seventh,  nmth,  tenth  and  vagal  part  of  the  eleventh,  which,  with  the  exception  of 
the  last  named,  are  mixed  nerves.  The  motor  fibres  of  these  nerves  differ  from  those 
of  the  series  of  median  motor  nerves — the  third,  fourth,  sixth  and  twelfth — (a)  in  the 
more  lateral  situation  and  less  compact  grouping  of  their  cells  of  origin  and  (d)  in 
the  less  direct  course  they  follow  to  reach  the  surface  of  the  brain.  To  avoid  repeti- 
tion, the  general  arrangement  and  characteristics  of  the  nuclei  related  to  the  glosso- 
pharyngeal, vagus,  and  accessory  part  of  the  eleventh  nerve  will  be  here  described. 

The  Motor  Nuclei. — These  include  the  root-cells  within  the  dorsal  nucleus 
and  those  constituting  the  nucleus  ambiguus.  The  dorsal  nucleus  (nucleus  dorsalis), 
a  nucleus  both  of  origin  and  of  reception  for  the  fibres  of  the  ninth  and  tenth  nerves, 
is  a  narrow  elongated  tract  of  nerve-cells,  whose  upper  three-fourths  underlies  the 
floor  of  the  fourth  ventricle,  stretching  from  the  stria  acusticae  above  to  the  tip 
of  the  ventricle  below,  and  whose  lower  fourth  extends  into  the  closed  part  of  the 


THE   GLOSSOPHARYNGEAL   NERVE. 


1261 


Fig.  1073. 


«»H„lla  u.  the  level  of  the  nucleus  gracilis.  It  lies  immediately  lateral  to  the  lower 
^rt  o  the  S£  vSt  bul^  nudeuTand  the  upper  part  of  the  hvpogossd  nuc eus 
K. inner  tWrd  being  covered  by  the  spinal  vestibular  nucleus  and  its  lower  third 
Serffi  Se  hy^gt^  nuc  Js.  Its'^^.iddle  third  corresponds  to  the >'.«  r«^^ 
mg  ^9)  and  comes  into  intimate  relation  with  the  ventricular  fl««^  Jhen 
viminpd  in  cross^ctions  (Fig.  928)  the  nucleus  appears  pnsmatic  in  outiine  and 
r^n  to  ^nsSTTs^S^oupsd  cells,  of  which  the  median  contains  the  larger  and 
more  co^S^uous  elem^s  and  corresponds  to  the  dorsal  motor  n«<=^"f '  The 
remainSroups,  the  dorsal  sensory  nucleus,  are  composed  for  'he  most  j«r^  of 

of  the  pyramidal  decussation,  and 
is  best  developed  in  its  upper  part. 
In    transverse    sections    of    the 
medulla  (Fig.  927).  the  tract  is 
distinguishable  within  the  formaUo 
reticularis  grisea,  midway  between 
the    dorsal    accessory    olivary 
nucleus  and  the  substantia  gelaU- 
nosa,  as  a  small  and  inconspicuous 
group  of  cells.     Arising  as  axones 
of  the  latter,  the  loosely  grouped 
motor  fibres  at  first  pass  dorsally 
to  the  vicinity  of  the  ventricular 
floor,  then  bend  sharply  outward, 
and,  as  in  the  case  of  the  vagus, 
join  with  the  similar  fibres  preced- 
ing from  the  dorsal  motor  nucleus 
to  form  the  emergent  root  strands. 
The    Sensory   Nuclei. — 
The  nuclei  receiving  the  afferent 
fibres  of  the  lateral  mixed  nerves 
in  question   include  the  sensory 
part  of  the  dorsal  nucleus  (nu- 
cleus   alae    clnereae),   above    de- 
scribed, and  a  tapering  column  of 
gray  matter,  the  spinal  nucleus 
(nucleus  tractus  solitarii),  which 

resembles     the     corresponding  niamm showin. connection. ol root  fibra of  gloMO-ph«rynge«l 

nucleus  of  the  trigeminus.     The  .nd^'pl^^lgr.  ?.rv«^nd^.  .en^^^^^^^ 

spinal  nucleus  is  closely  associated  ^^'^:^J'TuinT^nA°lZ^^rP^^^^^  tsS."?.'  J^a' 

with  a  conspicuous  longitudinal  .tKn;S!"r^rr.rc^rrvigl".'^S«'iW^^^ 

tract  of  caudally  directed  nbres,  j^p^  moiian  Riiei. 

hrll  largest  constituent  of  the  fasciculus  ;  whilst  the  tTi.rd,  tKe  vagus,  adds  fibres 
that  course  within  the  lowest  segment  of  the  tract. 


1262 


HUMAN   ANATOMY. 


within  the  dorsal  nucleus  and  the  nucleus  ambicuus.  The  ninth  nerve  shares  these  motor 
nuclei  to  only  a  limited  extent,  such  of  its  fibres  as  are  efferent  arising  from  the  uppermost  part 
of  the  cell-columns.  Those  taking  origin  from  the  nucleus  ambiguus  pass  at  first  toward  the 
floor  of  the  fourth  ventricle  ;  they  then  abruptly  change  their  direction  by  bending  outward  and, 
joining  the  fibres  arising  from  the  dorsal  motor  nucleus,  proceed  ventro-laterally  through  the 
gray  reticular  formation,  just  ventral  to  or  across  the  spinal  root  of  the  trigeminus,  to  emerge 
at  their  superiK-ial  origin  along  the  bottom  of  the  postotivary  sulcus,  incorporated  with  the 
afferent  fibres  in  the  five  or  six  root-fasciculi  forming  the  entire  ninth  nerve.  The  cortical  con- 
nections of  the  motor  fibres  are  established  by  cortico-bulbar  fibres  that  arise  from  cells  situated 
within  the  gray  matter  of  probably  the  lower  part  of  the  precentral  gyrus.  After  traversing 
the  motor  path  through  the  corona  radiata,  internal  capsule,  cerebral  peduncle  and  pons,  the 
cortical  fibres  end,  on  reaching  the  upper  level  of  the  medulla,  in  arborizations  aroimd  the  motor 
root-cells  chiefly  of  the  opposite  side. 

Fig.  1074. 


Olbctorybulbf, 

OpMc 
iBtcnul  carotid  vtery 

Optic  cMum 

v.  BCrrc.  ftcnsocy 
fact- 

Ccfcfanl  p«duiicl<.J. 


Middle  peduncle  of 
ccrctjclluni' 


IX.JCudXI. 
Dcrve« 


Lachrynul  glaad 
Supratrochleu  Bene 
Superior  rectiM  muscle 
l.evalce  palpcbne  Mjperioria 
Lachrymal  Bctvc 

IV.  I 


Mandibular  nerve 

VII.  nerve,  motor  pan 

ParalntcnncdU 

VIII. 


Si^ieriar  peduncle  of 
cerebellum,  cut 


IX..X.aBdXI.nerve< 
Floor  of  IV.  ventricle 
'Spianl  portiona  of  XI.  nervet 


Interior  aspect  of  base  of  skull,  viewed  from  above  and  hehind.   showing  particularly  posterior  group  of  cranial 
nerves  passing  from  brain-stem  to  points  of  emergence  through  dura ;  posterior  part  of  skull  has  been  removed. 


Central  Connections  of  the  Sensory  Part  of  the  Olosso-Pharyngeal  Nerve. — ^The  afferent 
or  sensory  fibres  of  the  glosso-pharyngeal  nerve  are  the  axones  of  cells  within  the  jugular  and 
petrous  ganglia  situated  along  the  upper  part  of  the  nerve-trunk.  Entering  the  skull  through 
the  jugular  foramen,  the  sensory  fibres  approach  the  brain-stem  in  the  five  or  six  delicate  root- 
bundles  that  reach  the  medulla  along  the  groove  between  the  olivary  eminence  and  the  inierior 
cerebellar  peduncle.  Passing  to  the  ventral  side  of  the  spinal  root  of  the  triger->inus,  or 
traversing  this  field,  in  company  with  the  motor  fibres,  the  afferent  fibres  continue  dorso- 
mesially  through  the  formatio  reticularis  grisea  towards  the  dorsal  nucleus.  Just  before  reach- 
ing the  latter,  however,  the  sensorj'  fibres  separate  into  two  groups,  a  medial  and  a  lateral.  The 
fiist  and  smaller  of  these  continues  its  course  to  the  dorsal  sensory  nucleus,  around  the  cells 
of  which  its  fibres  end.  It  is  probable  that  the  cells  constituting  the  upper  groups  of  the  dorsal 
sensory  nucleus  are  particularly  concerned  in  receiving  the  impuls«»  giving  rise  to  gustatory 
impressions,  since  the  glosso-pharyngeal  is  recognized  as  the  ner\'e  of  taste.  Considering  the 
fact  that  the  afferent  fibres  of  the  facial  nerve,  which  constitute  the  pars  intermedia  of  VVrisberg, 
are  distributed  peripherally  chiefly  by  the  chorda  tympani,  are  also  concerned  in  conveying 
taste-impulses  and  end,  in  part  at  least,  in  the  same  nucleus  as  does  the  ninth,  the  sensory 
portion  of  the  seventh  nerve  may  be  regarded,  at  least  functionally,  if  not  from  a  morphological 
standpoint,  as  an  aberrant  strand  of  the  glusso-pharyngeal. 


THE  GLOSSOPHARYNGEAL   NERVE. 


1 26  J 


The  second  and  much  Urger  group  turns  outward  and  abruptly  downward  to  form  the 
chief  constituent  of  the  spinal  tract,  the  latctculm  •oUt«iu».  In  transverse  sections  ( Fig.  927) 
the  latter  appears  as  a  conspicuous,  compact,  rounded  bimdle,  that  lies  lateral  to  the  dorsal 
nucleus  and  behind  the  strands  of  root-fibres.  The  solitary  fasciculus  is  accompiinied  through- 
out its  course  by  a  slender  column  of  gray  matter,  which  lies  partly  on  the  surface  01  the  bundle 
and  partly  amongst  its  fibres  and  contains  numerous  ner%e-cells  of  small  size  which  constitute 
the  reception-staUon  for  the  greater  number  of  the  afferent  fibres  of  the  ninth  ner\  e.  Since  these 
fibres  ire  continually  ending  at  different  leveU  in  their  descent,  it  follows  that  both  the  fascic- 
ulus and  its  nucleus  gradually  diminish  in  size.  unUl,  at  about  the  level  of  the  sensory  decussa- 
tion, they  are  no  longer  distinguishable. 

Course  and  Distribution.— Leaving  the  superficial  origin  along  the  groove 
separating  the  olivary  eminence  from  the  inferior  cerebellar  peduncle,  the  isolated 
root-fasciculi,  about  half  a  dozen  in  number  and  in  series  with  those  of  the  vagus, 
assemble  to  form  a  single  trunk,  which  passes  outward  in  front  of  the  flocculus  of  the 
cerebellum  to  the  jugular  foramen.     As  it  traverses  thu,  foramen,  the  glosso-pharyn- 

FiG.  1075. 


Diagram  ihowing  tympanic  plexua  and  connections  o(  gloMo-pharyngeal  nerve. 


geal  lies  external  and  anterior  to  the  tenth  and  eleventh  nerves  and  in  its  own 
separate  dural  sheath.  It  occupies  a  groove,  or  sometimes  a  bony  canal,  in  the  fora- 
men and  in  this  situation  presents  two  thickenings,  t)\c  jugular  axiA  petrous  ganglta. 
Emerging  from  the  foramen,  the  nerve  passes  between  the  internal  carotid  artery 
and  the  internal  jugular  vein  and,  dipping  beneath  the  styloid  process,  follows  a 
downward  course  along  the  posterior  border  of  the  stylo-pharyngeus  muscle,  with 
which  it  passes  between  the  internal  and  external  carotid  artenes.  Turning  gradually 
forward,  it  reach^  the  outer  side  of  the  stylo-pharyngeus  muscle  and  stylo-hyoid 
ligament  and  disappears  beneath  the  hyo-glossus  muscle  to  break  up  into  its  terminal 
branchesto  the  tongue  (Fig.  1079). 

Ganglia  of  the  Glosso-Pharyngeal  Nerve.— In  the  course  of  the  nerve 
two  ganr'ia  are  found,  the  jugular  and  the  petrous.  They  contain  aggregations  of 
neurones  whose  dendrites  constitute  the  peripheral  sensory  fibres  and  whose  centrally 
directed  axones  form  the  sensory  root-fibres  of  the  nerve.  ... 

Thejugulai-  ganglion  (g.  superins)  which  may  be  regarded  as  a  detached 
portion  of  the  petrous  ganglion,  lies  m  the  upper  part  of  the  groove  occupied 
by  the  glossc  -^ryngeal  nerve  in  its  transit  through  the  jugular  foramen.  It  is 
variable  in  siz.  and  not  always  present  and  measures  only  from  1-2  mm.  m  length. 
The  gapglion  does  not  include  the  entire  thickness  of  the  nerve  but  only  the 
inferior  ijortion,  the  fibre*  of  the  superior  jwrtion  passing  umntemiptedly  over  it. 


1364 


HUMAN  ANATOMY. 


The  petrous  ganglion  (g.  pctrosam)  is  larger  than  the  jugular  and  involves 
the  entire  nerve.  It  is  oval  or  fusiform  in  shape,  n»easures  from  4-5  mm.  in  length, 
and  is  lodged  within  a  slight  depression  in  the  lower  part  of  the  groove  for  the 

nerve  in  the  jugular  foramen.  .    ,    .    ^,         .    ,  •.  c 

The  communications  of  the  petrous  ganglion  include  filaments  (a)  from 
the  superior  cervical  ganglion  of  the  sympathetic,  (6)  to  the  auricular  branch  of  the 
vagus  and  sometimes  (c)  to  the  ganglion  of  the  root  of  the  vagus. 

Branches.— The  branches  of  the  glosso-pharyngeal  nerve  are:  (i)  the  (ym- 
panic,  (2)  the  pharyngeal,  (3)  the  muscular,  (4)  the  tonsillar  and  (5)  the  lingual. 

I.  The  tympanic  nerve  (n.  tympanlcus)  or  Jacobsoris  nerve,  arises  from 
the  petrous  ganglion  as  its  most  important  branch  and  traverses  a  tiny  canal  in  the 
osseous  bridge  between  the  jugular  fossa  and  the  carotid  canal.  Entering  the  tym- 
panic cavity  and  receiving  fibres  from  the  carotid  plexus  of  the  sympathetic  by  way 
of  the  small  deep  petrosal  (n.  caroticotympanicus),  the  tympanic  nerve  pawes 
upward  and  forward  in  a  groove  on  the  promontory  and  breaks  up  in  this  situation 
to  form  the  tympanic  plexus  (plexus  tympanlcus  Oacobsonl] ).  After  distributing 
filaments  to  the  mucous  membrane  lining  the  tympanic  cavtty  and  the  associated 
air-spaces  (mastoid  cells  and  Eustachian  tube),  its  fibres  reassemble  and  join  with  a 
filament  from  the  geniculate  ganglion  to  continue  as  the  small  superficial  petrosal 
nerve  to  the  otic  ganglion  (Fig.  1075).  ,,.  ,     ,        . 

Branches.— These  are  :  (a)  the  small  superficial  petrosal  nerve,  (6)  the  trancA 
to  the  fenestra  oralis,  (c)  the  branch  to  the  fenestra  rotunda,  (rf)  the  branch  to  the 
Eustachian  tube,  {e)  the  branch  to  the  mastoid  cells  and  (/)  the  branch  to  the  great 
superficial  petrosal  nerve. 

a  The  stnall  superficial  petrosal  nerve  (n.  pctroms  raperficUlis  minor)  (Fig.  1075)  is  the 
continuation  of  the  tympanic  ner\e,  formed  by  a  reassembling  of  the  fibres  of  the  plexus,  sup- 
plemented by  a  filament  from  the  geniculate  ganglion  of  the  facial.  It  traverses  a  canal  which 
begins  at  the  anterior  superior  portion  of  the  tympanic  cavity,  passes  beneath  the  upper  end  of 
the  canal  for  tlie  tensor  tympani  and  appears  on  the  superior  surface  of  the  petrous  portion  of 
the  temporal  bone,  to  the  outer  side  of  the  cranial  opening  of  the  hiatus  Fallopii.  While  in  the 
canal  it  sometimes  receives  a  communicating  branch  from  the  great  superficial  petrosal  nerve. 
It  leaves  the  cranium  through  a  canal  in  the  greater  wing  of  the  sphenoid,  or  through  the  fissure 
between  the  greater  wing  and  the  petrous  portion  of  the  temporal  bone,  and  on  reaching  the 
bast  of  the  skull,  joins  the  otic  ganglion  as  its  sensory  root  (  Fig.  1075).  ..... 

b.  The  branch  to  the  fenestra  ovalis  supplies  the  mucous  membrane  in  the  neighborhood 
of  the  oval  window. 

c.  The  branch  to  the  fenestra  rotuuda  is  distributed  to  the  mucous  membrane  over  and 
around  the  fenestra.  ,.  ,. 

d.  The  branch  to  the  Eustachian  tube  supplies  the  mucous  membrane  lining  the  osseous 

portion  of  that  canal. 

e.  The  branch  to  the  mastoid  cells  supplies  the  mucous  lining  of  these  cells. 

/  The  branch  to  the  great  superficiat  petrosal  nerve  joins  the  latter  in  the  hiatus  Fallopii. 

2.  The  pharyngeal  branches  (rr.  pharyngel)  number  two  or  more,  of  which 
the  largest  descends  along  the  course  of  the  internal  carotid  artery  and  joins  the 
pharyngeal  branch (S  of  the  vagus  and  sympathetic  to  form  the  pharyngeal  plexus, 
which  supplies  the  mucous  membrane  and  muscles  of  the  pharynx.  The  smaller 
pharyngeal  branches  pierce  the  superior  constrictor  and  are  distributed  to  the 
mucous  membrane  lining  the  upper  portion  of  the  pharynx. 

3.  The  muscular  branch  (r.  stylopharyngeus)  enters  the  stylo-pharynegus, 
and,  after  giving  off  fibres  for  the  supply  of  that  muscle,  passes  through  it  to  be 
distributed  to  the  mucous  membrane  of  the  pharynx. 

4.  The  tonsillar  branches  (rr.  tonsillares)  are  given  off  near  the  base  of 
the  tongue.  They  are  slender  filaments  which  form  a  plexiform  ramification,  the 
circulus  tonsillaris,  around  the  tonsil.  From  this  plexus  filaments  are  distributed  to 
the  tonsil,  the  soft  palate  and  the  faucial  pillars. 

5.  The  lingual  branches  (rr.  linguales)  are  the  two  terminal  filaments  of  the 
nerve.  The  larger  posterior  branch  passes  upward  and  separates  into  a  nwnher  of 
filaments  which  supply  the  circumvallate  papillae  and  the  mucous  membrane  covering 


THE  VAGUS  NERVE. 


1265 


ihe  Dosterior  part  of  the  doreum  of  the  tongue,  the  glosso-epiglottic  and  phaiyngo- 
SgCc  fo  ds^and  Ihe  lingual  surface  of  the  epiglottis.  The  --"»"-; -ff-"''  ^^'"""^ 
!uppUes  the  mucous  membrane  of  the  side  of  the  tongue  half  way  to  the  Up. 


Fig.  1076. 


\ 


DteaMric.i 

bdly  in 


part 

[.  cer^kal  1 

Sptoat  acc«Mory  ncrrc  - 

Ocr^rfttUs  miBOc  nerv*  . 

II.  ccrvkal  n 

HypoKlawal(XlI'>  ■ 

Sup,  cerv.  nagl.  of  «ymr"thrtc- 

*^  Br.  Uon  II.  cerv.  atn»^ 

to  ip.  wcQtr^ 

III.  cervical  iier»«- 
CommtinicuM  IqrpoBloNl  - 

GcMtaufk.»iwliuperf.c«rv.n«r»«»- 
IV.  cervical  ntr 

V.  cervical  nerve 
Br.lBrfaomboldcl-. 


'  cxienal 
"plerjK'wi 

[.br.V.Bvrvc 

f)  Chorda 

I  f  lympanincrve 

k-Int.  pteryiioid 
r  t-dKrof  or^l  mu- 
(out  mcmtvane 

CloHO-phao  ngcal 

serve 

-Mental  nrrxr 
inf.  tirntal  nerrc. 
It«ta)  {Mirtioo 
iubtinKual  vlasd 

ibmasUlarr  uaaiX'- 

-Styto-|))uryiveu» 


•  TlijfO-hjotil  bt.  XII.  o«r<« 


h^/^A 


Cominunicatlag 

br.  tn  s|i.  acLcawry  - 

A  cutaneous  br._ 


^^//.£        111 


ndcM  hypogloMl 
■-til.tanr"*"'""*' 


rhnoic  ncrr« 

.ScalnusuUco 
jubda'iu  utny 


D«p  diMection  of  neck  .howln,  ninth,  tenth,  eleventh  .nd  twelfth  cfnial  nerve,  and  their  branch... 


THE  VAGI  ^  "NERVE. 
The  tenth  vaeus  or  pneumogastric  nerve  (n.  vagus)  is  the  longest  and  most 
widely  distributed  of  the  cranial  series.     Starting  in  the  cranium,  .t  passes  th^gh 
The  neck   thorax  and  upper  part  of  the  abdomen  before  breaking  up  mto  Us  terminal 
Irancht:      In  adSn^to  ceVmin  filaments  concerned  with  special  functions   distnb- 
Sio^he  heart  and  abdominal  viscera,  it  contains  both  motor  and  «e"««7y  Jfr^^;. 
Some  of  the  motor  constituents  of  the  nerve  arise  from  its  own  origin,  but  the  ma^or 
hv^rhaps  are  contributions  of  th^  arcessorius  va^i,  the  so-called  accessory  part  of 
h'L'^pinaraccLory  nerve.     The  vagu,  suppli«,  motor  fibres  to  the  mu^^f  j^J^^"^^^ 
soft  oalate  (with  the  exception  of  the  tensor  palati  and,  probably,  part  y  the  levator 
^irind  Sygos  uvute).  pharynx.  CBsoohagtis.  stomach  and  ^-^^^^^.f"^;"^^^^ 
exception  of  the  rectum),  and  to  those  of  the  larynx,  trachea,  and  bronchi  ^"d  their 
"ffiTons.     It  distributes  sensory  fibres  to  the  dura  mater,  externa  ear,  phar^  nx, 
^phagus,  stomach,  larynx,  trachea,  bronchi  and  subdivisions  and  pericardium. 

So 


ia66 


HUMAN   ANATOMY. 


Special  fibres  are  furnished  to  the  heart,  liver,  spleen,  pancreas,  kidneys,  suprarenal 
bodies  and  intestinal  blood-vessels. 

It  is  generally  admitted  that  the  bulbar  or  accessory  portion  of  the  eleventh  nePi'e  forms  an 
integral  part  of  the  motor  division  of  the  vagus,  and,  hepce,  should  be  included  with  the  efferent 
fibres  of  the  tenth.  As  to  the  ultir  ite  distribution  of  these  accessor)-  fibres,  and  conversely  of 
the  vagus  motor  fibres  proi>er,  much  discussion  and  many  conflicting  views  have  existed  and, 
even  at  present,  a  consensus  of  opinion  can  scarcely  be  said  to  have  been  reached.  After 
reviewing  the  evidence,  both  anatomical  and  experimental,  Van  Gehuchten '  concludes  that  the 
accessory  fibres  are  distributed  chiefly,  if  not  indeed  exclusively,  to  the  larynx  through  the  Infe- 
rior laryngeal  branch  of  the  vagus,  and  are  continued  neither  to  the  heart  nor  to  the  stomach. 
The  efferent  vagus  fibres  proceeding  to  the  heart  are  inhibitory  in  function  ;  whetfier  they  directly 
reach  the  cardiac  muscle  is  doubtful,  since,  reasoning  from  analogy,  it  is  probable  that  the  vagus 
fibres  end  around  sympathetic  neurones  whose  axones  are  the  filaments  coming  into  immediate 
relations  with  the  muscle-fibres.  Of  the  efferent  fibres  of  the  vagus  distributed  to  the  stomach 
and  other  parts  of  the  digestive  tract,  some  are  secretory,  while  others,  possibly,  influence  the 
caliber  of  die  blood-vessels,  in  both  cases  being  interrupted  in  sympathetic  ganglia  before  gain- 
ing their  destination. 

Deep  Origin  of  the  Motor  Portion. — As  stated  above,  the  efferent  fibres  of 
the  v^;us  consist  of  two  sets,  vagus  fibres  nroper  and  those  derived  from  the  acces- 
sory portion  of  the  spinal  accessory.  T'  -^  r  have  their  deep  origin  in  the  nu- 
cleus ambiguus  and  the  dorsal  motor ,  .'ries  with  the  motor  fibres  of  the 
ninth  nerve;  the  accessory  fibres  a~  •-.  nucleus  ambiguus  only.  The 
detailed  description  of  these  nuclei  ha  >  )age  1260).  The  fibres  arising 
from  the  nucleus  ambiguus  at  first  p.  ^~  toward  the  floor  of  the  fourth 
ventricle,  then  bend  sharply  outward  ...i,.,  idensed  into  compact  strands  that 
receive  the  fibres  originating  from  the  motor  cells  of  the  dorsal  nucleus,  proceed, 
ventro-laterally  in  company  with  the  sensory  fibres,  to  their  superficial  origin  along 
the  postero-lateral  groove  behind  the  olivary  eminence. 

Central  Connections  of  the  Sensory  Portion. — The  afferent  root-fibres  of 
the  vagus  are  the  axones  of  the  neurones  lying  within  the  ganglia  of  the  root  and 
of  the  trunk  situated  on  the  upper  part  of  the  nerve.  The  centrally  directed  processes 
jMss  into  the  medulla,  in  company  with  the  motor  strands,  and  divide  into  two  sets. 
Those  forming  the  larger  of  these  end  in  arborizations  around  the  cells  within  the 
lower  portion  of  the  dorsal  sensory  nucleus  ;  those  of  the  smaller  set  bend  downward 
and  enter  the  fasciculus  solitarius  to  terminate  in  arborizations  around  the  cells  of 
the  spinal  nucleus  of  reception.  (For  details  of  these  nuclei  see  page  1260).  As  in 
the  case  of  the  other  mi.xed  nerves — the  fifth,  seventh  and  ninth — the  secondary- 
paths  distributing  the  sensory  impulses  include  (a)  fibres  that  pass  from  the  recep- 
tion-nuclei to  the  tract  of  the  mesial  fillet,  and  so  on  to  the  great  brain,  and 
(b)  those  that  pass  to  the  cerebellum. 

Course  and  Distribution. — The  vagus,  disregarding  its  accessory  fibres 
which  at  first  are  incorporated  in  a  common  trunk  with  the  eleventh  nerve,  arises 
from  its  superficial  origin  by  a  row  of  twelve  or  fifteen  filaments  which  emerge 
from  the  surface  of  the  medulla  along  the  postero-lateral  sulcus  between  the  olivary 
eminence  and  the  inferior  cerebellar  peduncle.  These  fasciculi  lie  in  series  with 
those  of  the  ninth  nerve  above  and  of  the  eleventh  below  (Fig.  1046). 

After  leaving  the  surface  of  the  brain-stem,  the  converging  rootlets  of  the  vagus 
fuse  to  form  a  single  flattened  trunk,  which  passes  outward  beneath  the  flocculus  of 
the  cerebellum  to  the  jugular  foramen  (Fig.  1074).  The  trunk  leaves  the  cranium 
through  the  rear  division  of  the  middle  compartment  of  this  foramen,  invested  by  a 
dural  sheath  shared  by  the  spinal  accessory  nerve.  In  this  situation  it  presents  a 
ganglionic  enlargement  called  the  ganglion  of  the  root.  Emerging  from  the  jugular 
foramen,  the  vagus  bears  a  second  thickening,  the  ganglion  of  the  trunk,  and  enters 
the  carotid  sheath,  through  which  it  passes  downward  the  entire  length  of  the  neck. 
Within  the  carotid  sheath  the  nerve  lies  at  first  between  the  internal  carotid  arterj- 
and  the  internal  jugular  vein,  and  then  between  the  common  carotid  artery  and  the 
vein,  occupying  the  posterior  groove  between  these  vessels.     At  the  root  of  the 

'  Anatomic  du  Systfeme  Nerveux,  1906. 


THE  VAGUS   NERVE. 


1267 


KiG.  1077. 


nerv.,  .h.^.,^/«».  g: «' rrfh^i-^'T^^tJ^^  oMhe\.i;» "h.  greater 
part  of  the  jugular  foramen. 


ia68 


HUMAN   ANATOMY. 


The  cammttiiieatioiM  o(  this  ganglion  include  filaments  which  pass  between  the  ganglion 
ami  («)  the  facial  and  (4)  spinal  accessory  nerves,  (<  )  the  superior  cervical  ganglion  o<  the 
sympathetic  nerve  and  {d)  thp  petrous  ganglion  of  the  glosso-phar>-ngeal. 

The  ganglion  of  the  trunk  (g.  nodoram)  or  lower  ganglion  (Fig.  1077) 
is  a  reddish,  flattened,  fusiform  group  of  ner\'e-«.ells.  It  lies  beneath  the  jugular 
foramen,  about  i  cm.  below  the  ganglion  of  the  root,  and  measures  from  1.5-2  cm. 
in  length  and  about  4  mm.  in  diameter.  The  accessory  part  of  the  spinal  accessory 
nerve  passes  over  the  ganglion  on  its  way  to  fuse  with  the  vagtis,  which  it  does 
usually  immediately  beyond  the  ganglion. 

The  communications  of  this  ganglion  include  filaments  which  pass  between  the  ganglion 
and  (a)  the  hypoglossal  .ind  (A)  spinal  accessory  nerx'es,  (c )  the  loop  between  the  first  and 
second  cervical  nerves  and  (</)  the  superior  cervical  ganglion  of  the  sympathetic. 

Branches. — ^The  vagus  nerve  gives  of!  the  following  branches:  from  the 
ganglion  of  the  root,  (i)  the  meningeal  and  (2)  the  auriatlar ;  from  the  ganglion 


Fig.  1078. 


letRv. 


SCCM 


Diagnm  of  upper  pan  ot  rifht  vagus  nerve,  showinf  its  pharyngeal  and  laryngeal  branches  «ith  counectionB. 


ot  the  trunk,  (3)  ihe  pharyngeal  and  (4)  the  superior  laryngeal ;  in  the  neck,  (5) 
the  superior  cervical  cardiac,  and  (6)  the  inferior  cervical  cardiac ;  in  the  thorax, 
(7)  the  inferior  laryngeal,  (8)  the  thoracic  cardiac,  (9)  the  anterior  pulmonary, 
(10)  the  posterior  pulmonary,  (11)  the  esophageal  and  (12)  the  pericardial;  and 
in  the  abdomen,  (13)  the  abdominal. 

1.  The  meningeal  branch  (r.  meninKeus)  arises  from  the  ganglion  of  the 
root  and  follows  a  recurrent  course  upward  through  the  jugular  foramen  to  supply 
the  dura  mater  of  the  posterior  fossa  of  the  cranium,  especially  in  the  vicinity  of  the 
lateral  and  occipital  sinuses. 

2.  The  auricular  branch  (r.  auricularis)  is  given  ofl  from  the  ganglion 
of  the  root.  It  receives  a  filament  of  communication  from  the  petrous  ganglion 
of  the  ninth  nerve  and  follows  the  outer  margin  of  the  jugular  foramen  to  an 
opening  bctwcctJ  the  slylo-mastoid  and  jugular  foramina.  Entering  this  foran  ;n  -t 
traverses  a  canal  in  the  temporal  bone  which  crosses  the  inner  side  of  the  facial  canal 
and  terminates  between  the  mastoid  process  and  the  external  auditory   meatus. 


THE  VAGUS  NERVE. 


1369 


Leaving  the  canal  the  nerve  supphes  the  skin  of  the  posterior  part  of  the  .•>    "de  and 
of  the  posterior  inferior  portion  of  the  external  auditory  meatus. 

While  traversing  the  temporal  bone  the  auricular  nerve  communkatM  with  the  facial  and, 
after  reaching  its  area  of  distribution,  with  the  posterior  auricular  nerve. 

Variatioos.— The  auricular  nerve  may  be  absent  or  may  fuse  with  the  main  trunk  of  the 
iadaL  its  fibres  under  these  drcumsunces  probably  reachinn  their  destmation  through  the  pos- 
terior auricular  nerve.     Its  branch  of  communication  with  the  facial  may  l>e  alwcnt. 

1  The  pharyngeal  branchea  (rr.  pharyoKei),  usually  an  upper  and  a  lower 
but  sometimes  more  or  only  one,  are  given  of!  from  the  upper  portion  of  the  gang- 


FlG. 

LvMt  iMHl  •(  oMnri  MttM 


1079. 


PMutnocuIrk  ■•'« 

lafctioc  deMil ««"« 

Spinal  accccaory  BCn* 

Fart  o(  hdal  on 
HypoiloaMi 
Stylo-phaiyBCCua  nii«cl«' 
Olaaao-phaiyagaal  nerve 
I.  cervical  nerve 
PncumoKaatric  nerve 
-vupenor  cervkajganjllon  of 
ayui|flUMnc 
Superior  laffynffcal  nerve 
DannBitom  hypogloirt 
U.ccTTlcal 


III.  centcal  ntr.f 


Middl*  cenical  ff»OKli«ML 


Bnuichea  from  Inf. 
cervical  gasiflton 

Infartor  cervldl  cardfftc 
of  aympailhrtic 

Recurrent  laryngeal' 
nerve 
Internal  mammaij  artery    ,  ,   _. 
Cartilage  <if  I.  rib 

CUvkular  beet  of  ttetnua 

D«p  di»«tion  of  right  .id.  of  h«d  .nd  "^„*'j»^ovnng_Iin,».J.  .^ 

lion  of  the  trunk  and  include  to  a  considerable  extent  fibres  brought  thc^  ,s  by 
ite  accessory  portion.  They  pass  downward  and  mward  between  the  exter.wl  and 
ntemal^mtid  .arteries,  and  join  the  pharyngeal  branches  from  f  ^rlosso-pharyn- 
eeal  nerve  and  from  the  superior  cervical  ganglion  of  the  sympatnetic  to  form  tin- 
laryngeal  p/exus  (plexus  pharyngeus)  (Fig.  1078).     This  plexus  conUins  one  .^ 


-pharytiKcal,  pneuir 


laTO 


HUMAN  ANATOMY. 


more-  minute  sympathetic  ganglia  and  ramifies  over  the  middle  constrictor  of  the 
pharynx.  It  supplies  motor  libres  to  the  muscles  of  the  phar)-nx  and  of  the  soft 
palate,  with  the  exception  of  the  stylo-pharyngeus  and  the  tensor  palati.  F  om  the 
plexus  proceed  sensory  filaments  to  the  mucoi's  membrane  of  the  phar  x.  A 
filament  from  thb  plexus,  the  lingual  branch  of  the  vagus  (r.  llnr..  a  «  T»  U  com- 
posed of  fibres  from  both  the  ninth  and  tenth  nerves,  joins  the  h^  pogi  ^al  as  it 
hooks  around  the  occipital  artery. 

Variation.— A  slender  branch,  the  middle  laryngeal  .itrve,  is  described  as  arising  from  the 
pharynKeal  plexus  and  supplying  the  crico-thyroitT muscle,  after  which  it  pierces  the  crico- 
thyroia  membrane  and  supplies  the  mucous  membrane  of  the  lower  part  of  the  larynx. 

4.  The  auperior  laryngeal  nerve  (n.  Iar)-ngeus  superior)  (Fig.  1079)  arises 
from  the  middle  uf  the  ganglion  of  the  trunk  and  takes  a  downward  and  inward 
course  beneath  the  external  and  internal  carotid  arteries  toward  the  superior  tornu 
of  the  thyroid  cartilage.  It  divides  terminally  into  (<j)  the  external  and  (^)  internal 
laryngeal  branches. 

Communications. — Before  dividing,  the  superior  laryngeal  nerve  receives  filaments  frcim 
the  superior  cer\'ical  sympathetic  cardiac  and  from  the  pharyngeal  plexus. 

The  cardiac  twig  given  off  by  the  external  laryngeal  nerve  joins  with  the  superinr  ter\ical 
cardiac  branch  of  the  sym(>athetic.  In  thf  lower  part  of  the  larynx  the  external  laryngeal  nene 
inosculates  with  the  terminal  fibres  of  the  internal  laryngeal. 

At  the  inferior  portion  of  the  larynx,  the  internal  laryngeal  nerve  communicates  with  the 
terminal  filaments  erf  the  external  laryngeal,  and  in  this  way  supplies  sensory  'ibres  to  the 
mucous  membrane  lining  the  lower  part  of  the  larynx  and  to  the  muscles. 

Variation. — Instead  of  passing  to  the  inner  side  of  the  intern  '  carotid  artery  tin-  ncr\'e  .;.- 
lie  external  to  it. 

a.  The  external  laryngeal  branch  (r.  externns),  much  smaller  than  the  in- 
ternal, pa.sses  downward  ufion  the  inferior  constrictor  of  the  pharynx  and  beneath  the 
infrahyoid  muscles  to  the  crico-thyroid  muscle,  which  it  supplies.  It  sends  filaments 
also  to  the  inferior  pharyngeal  constrictor  and  gives  off  a  cardiac  twig  which  joins  the 
superior  cer\'ical  cardiac  branch  of  the  sympauetic. 

Variations — The  external  laryn^al  has  been  seen  to  send  filaments  to  the  thyroid  gland, 
the  pharyngeal  plexus,  the  stemo-hyoid,  stemo-thyroid,  thyro-hyoid  and  crico-arytenoideus  lat- 
eralis muscles  and  to  the  mucous  membrane  ot  the  vocal  cord  and  lower  portion  of  the  lar)-nx. 

b.  The  internal  laryngeal  branch  (r.  intcrnus),  larger  than  the  external, 
passes  downward  and  inward  between  the  middle  and  inferior  constrictors  of  the 
pharynx  and  enters  "the  larynx  by  piercing  the  thyro-hyoid  membrane  By  means 
of  its  epiglottic,  pharyngeal,  descending  and  communicating  branches,  it  supplies  the 
mucous  membrane  covering  the  internal  and  pharyngeal  sur^ces  of  the  larynx  and 
the  mucous  membrane  of  the  base  of  the  tongue. 

Variation. — Instead  of  pit-rcing  the  thyro-hyoid  membrane  the  nerve  may  obtain  entrance 
to  the  lar>'nx  through  a  small  foramen  in  the  thyroid  cartilage. 

5.  The  superior  cervical  cardiac  branch  (rr.  cardiaci  superiores — both  cervi- 
cal cardiacs)  arises  from  the  vagus  in  the  upper  part  of  the  neck.  It  either  joins 
a  cardiac  branch  of  the  vagus  or  passes  independently  down  the  neck  and  along  the 
side  of  the  trachea  to  end  in  the  deep  cardiac  plexus  (Fig.  1 132). 

6.  The  inferior  cervical  cardiac  branch  leaves  the  vagus  at  the  root  of  the 
neck.  On  the  right  side  it  courses  along  the  side  of  the  innominate  artery  and  either 
independently,  or  after  joining  one  of  the  other  cardiac  nerves,  enters  the  deep  car- 
diac plexus.  The  left  passes  in  front  of  the  arch  of  the  aorta  and  joins  the  superior 
cervical  cardiac  branch  of  the  left  sympathetic  to  form  the  superficial  cardiac  plexus 
(Fig.  1132). 

7.  The  inferior  or  recurrent  laryngeal  nerve  (n.  recnrrens)  (Fig.  1080) 
differs  on  the  two  sides  in  the  early  part  of  its  course.    The  right  nerve  is  given  oft  at 


'^mm 


mm 


"!¥» 


THE  VAGUS  NERVE. 


1271 


.h^  root  of  the  nee  •  aRUS  crosses  the  anterior  surface  of  the  subdavianartcr>-. 
I^whidiD^inr  ,  under  and  behind  the  artery  and  ascends.     The /r// ««^* 

STu  o  iJTn  »  '  ..^"crosses  the  anterior  a.s,>ec\  of  the  aortic  arch,  andafter 
Sne  Wow  andUhmdlhe  arch,  lateral  to  the  obliterate<l  ductus  arteriosus,  ascends 
E;1he  suSor  mediastinum  to  enter  the  neck.  After  entenn^  the  neck  the  further 
cmtL  !rf^e  .^r^  w  the  same  on  both  sides.  It  5>asses  upward  iH>stenor  o  he 
'3  shSu..  either  anterior  or  posterior  to  the  inferior  thyro.d  arterv-.  occup.es  the 

Fiu.  1080. 


,,.,,rt»  Mtvlal  «■*''"•■*•'"  ■*' 


Ififkffioff  cfTvh:*!  gmatfUs*. 


t,.,iKtM«  of  tym|»ttmlc 
!•  Jmooarr  bcUKb  o(M«<a 


SumHo  nrrlcal  arrite  t 

^^      of  n<"P«ll*^'^  ._    -     

s«|»tl<«  c«t.lc«l  raMtr  bnack  •(  n«w 
MIdill*  cwirkJ  funllal 


laf.  cfnkal  Of^t  I»mk» 

Miudic  LfT^kal  caHUc 
tmnth  ci(  v*nti» 

tit-tiiihof  vaniu 
I'hrenk  oen* 


rofeaidium 


margin  of  the  cricoid  cartil^e. 

becomes  the  arch  of  the  aorta,  and  on  the  nght  the  '"""'"T;^  ""  .^j^tions,  later  alter  their 

which  these  blood-vessels  undergo. 

Branches.-During  its  course  the  inferior  laryngeal  "^"^'^  f  Y«  " J  =  ^\.'^^^, 
cardScW^etracAea/f  (O  the  o'sopkageal,  (J)  the  muscu/ar  and  (.)  the  fermtnai 

branches. 


1372 


HUMAN   ANATOMY. 


a.  The  cardiac  bianchca  (rr.  cardiad  inferiora)  are  given  off  in  the  superior  mediastinum 
and  enter  th'-  deep  cardiac  plexus. 

b  and  .  Tracheal  and  oaophageal  branches  (rr.  trachealca  ct  otMpbagci)  are  given  off  as 
the  nerve  ascends  in  the  neck  between  the  trachea  and  oesophagus. 

d.  Muscular  branches  enter  the  inferior  constrictor  of  the  pharynx. 

e.  The  terminal  branches  (n.  laryngeal  inferior)  are  formed  at  the  point  where  the  ner\e 
breaks  up  on  the  inner  side  of  the  thyroid  cartilage.  They  supply  the  intrinsic  muscles  of  the 
larynx,  with  the  exception  of  the  crico-thyroid. 

As  it  turns  to  ascend,  the  inferior  laryngeal  nerve  communicates  with  the  inferior  cervical 
ganglion  of  the  sympathetic,  its  terminal  filaments  joining  with  those  of  the  internal  laryngeal. 

.Variations.— The  inferior  laryngeal  nerve  has  been  seen  to  supply  twigs  to  the  crico-thyroid 
muscle.  In  cases  m  which  the  subclavian  artery  arises  dorsally,  the  right  recurrent 
laryngeal  passes  directly  downward  and  inward  from  the  vagus  to  the  larj-nx. 

8.  The  thoracic  cardiac  nerves  (rr.  cardiaci  inferiores)  of  the  right  side  are 
derived  both  from  the  vagiis  as  it  lies  beside  the  trachea  and  from  the  inferior  laryn- 
geal. Those  of  the  left  side  arise  exclusively  from  the  inferior  laryngeal.  They 
help  to  form  the  deep  cardiac  plexus. 

9.  The  anterior  pulmonary  branches  (rr.  broachiales  anteriores)  are  two 
or  three  small  filaments  which,  on  the  right  side,  receive  communicating  fibres  from 
the  deep  cardiac  plexus  and,  on  the  left  side,  are  joined  by  filaments  from  both  car- 
diac plexuses.  These  unite  to  form  the  anterior  pulmonary  plexuses  (plexus 
pulmonales  anteriores)  (Fig.  1080),  which  communicate  with  each  other  and  with  the 
posterior  plexuses,  and  ramify  over  and  supply  the  anterior  aspect  of  the  bronchus 
and  root  of  the  lung. 

10.  The  posterior  pulmonary  branches  (rr.  bronchiales  posteriores)  are 
several  large  twigs  which  join  with  filaments  from  the  second,  third  and  fourth  tho- 
racic ganglia  of  the  sympathetic  to  form  the  posterior  pulmonary  plexus  (plexus 
pnlmonalis  posterior).  Fibres  from  this  plexus  cosnmunicate  with  the  corresponding 
structure  of  the  opposite  side  and  with  the  anterior  pulmonary  plexuses,  in  this  way  tach 
vagus  sending  fibres  to  both  lungs.  Branches  from  the  plexus,  bearing  tiny  ganglia, 
follow  the  subdivisions  of  the  bronchi  to  supply  the  ultimate  units  of  the  lung. 

11.  The  oesophageal  branches  (rr.  oesophat;ei)  are  given  ofT  in  two  situa- 
tions :  in  the  superior  mediastinum,  where  the  right  vagus  and  the  left  inferior 
laryngeal  distribute  oesophageal  branches,  and  in  the  posterior  mediastinum,  where 
the  oesophagus  is  surrounded  by  branches  from  the  oesophageal  plexus  or  plexus 
gtilce  (Fig.  1081).  This  plexus  is  composed  of  the  two  vagus  nerves,  after  they 
leave  the  posterior  aspect  of  the  bronchi,  in  conjunction  with  filaments  from  the 
great  splanchnic  nerves  and  from  some  of  the  lower  thoracic  ganglia.  Both  the 
muscular  and  mucous  coats  of  the  oesophagus  are  inner\'ated  from  this  source. 

12.  The  pericardial  branches  (rr.  pericardiac!)  are  given  of!  to  the  upper 
anterior  portion  of  that  membrane  by  either  vagus  and  to  the  posterior  portion  by 
the  jEsophageal  and  frequently  the  posterior  pulmonary  plexuses. 

13.  The  abdominal  branches  come  from  both  nerves.  On  gaining  the  pos- 
terior surface  of  the  stomach  after  following  the  corresponding  aspect  of  the  oesopha- 
gus, the  right  vagus  forms  the  posterior  gastric  plexus  along  the  lesser  cur\ature, 
from  which  gastric  branches  supply  the  posterior  surface  of  the  stomach  ;  the 
remaining  and  larger  part  of  the  plexus  is  continued  as  the  ca-liac  branches  to 
the  plexus  of  the  same  name  and,  thence,  in  company  with  the  sympathetic  strands, 
to  the  subsidiary  plexuses  supplying  the  spleen,  the  pancreas,  the  intestine,  the 
siii)rarenal  bodies  and  the  kidneys.  In  a  similar  manner,  along  the  lesser  curvature 
the  left  vagus  forms  the  anterior  gastric  plexus,  from  which  numerous  gastric 
brandies  are  distributed  to  the  anterior  surface  of  the  stomach,  the  continuation  of 
the  plexus  being  hepatic  branches,  which  join  the  sympathetic  filaments  accompany- 
ing the  hepatic  artery  to  supply  the  liver. 

Practical  Considerations.— The  pneumogastric  nerve  may  be  compressed 
or  displaced  by  tumors  in  the  neck,  or  it  may  be  injured  in  accidental  or  operative 
wouiuLs,  or  by  fracture  of  the  base  of  the  skull.      Its  division  is  not  always  fatal  ;  in 


THE  VAGUS  NERVE. 


1273 


fact  a  portion  of  it  has  been  deliberately  removed  with  success  In  those  cases  in 
which  the  nerve  was  divided,  difficulty  in  breathing  and  swallowing,  slowing  of 
the  respiration,  laryngismus,  changes  in  the  voice,  diminished  inspiratory  murmur, 
2th^  and  pneumonia  were  noticed  (Park).  In  cases  of  pressure  by  tumor^  _ 
the  pneumo^trics  of  both  sides,  lung  disturbances,  dyspntea,  weakening  01  the 
pulse,  and  a  ravenous  appetite  were  observed. 

Fig.  1081. 


Superior  cerrical  cardiac 
brmnch  of  aympathetic 

Vagus  nerve 

Middle  cervical  ganslion 

of  sympathetic 


Clavicle. 

Recurrent  laryngeal 

nerve,  displaced  outward 

loferioi  cervital  cardUc  of«ym|»-. 
thetlc.JolBiniE  superior  Inane  11 

Recurrent  laryngeal 

nerve 

Inferior  cervical  cardiac 

branch  of  vagus 

Innominate  arlei  y 

Aorta 

Combined  sympathetic 

and  vagal  inferioi 

cervical  cartiac  nerves 

Right  bronchus 

Pulmonary  arterj- 
Right  vagua- 


Thoracic  duct 
Vena  asygos 


Vena  cava  inferior, 
sectional  surface 


Liver,  under  surface- 


Branches  to  liver 
and  gall  bladder' 


Vagus  ner%-e 

Superior  cer%icalcardiacbrHncli 
subclavian  artery      [of  ^K"" 
Inferior  cer»ical  cardiac  branch 
Clavicle  ["'  ^"K"" 

I.  rib 

Inferior  cervical 
cardiac  branch  of 
sympathetic 
Recurrent  laryn- 
geal nerve 

Inferior  cervical 
cardiac  branch 
of  sympathetic 

Left  bronchus 

Pulmoiury  artery 

Lung,  mesial  surface 

CEsophagus 
_    rt  of  left  vagus 
about  to  aid  in 
formation  of 
plexus  gulo: 


Part  of  right  vagus 
about  to  paHs 
through  diaphragm 


Left  vagus 


Disacction  showing  lower  part  of  pncumogastric  nerves  and  their  blanches. 

Lesions  of  the  recurrent  larytifreal  branch  of  the  pncumogastric,  from  tumors, 
abscesses,  etc.,  are  comparatively  common.  Injury  to  this  nene  is  the  chief  danger 
to  be  feared  in  the  removal  of  the  thyroid  gland,  passing  as  it  does  so  close  to  the 
gland  and  to  the  inferior  thyroid  artery  where  the  latter  is  usually  ligated  preliminary 
to  or  during  the  excision  of  the  gland.     As  it  is  the  mam  motor  ncrvt:  of  the  larynx, 


'274 


HUMAN   ANATOMY. 


its  irritation  causes  spasm  of  the  laryngeal  muscles,  with  brassy  cough  and  stridulous 
breathing.  The  tendency  to  closure  of  the  glottis  is  sometimes  so  threatening 
as  to  demand  immediate  tracheotomy  or  intulMtion.  Paralysis  causes  hoarseness 
oi  loss  of  voice  (aphonia).  In  a  bilateral  paralysis  both  cords  fall  into  the  cadaveric 
position.  Loss  of  voice  results  and  marked  inspiratory  dyspnoea,  which  may  demand 
tracheotomy  or  intubation. 


THE  SPINAL  ACCESSORY   NERVE. 

The  eleventh  or  spinal  accessory  nerve  (n.  accessorius)  is  purely  motor.  It  con- 
sists of  two  portions,  a  spinal  and  an  accessor}',  which  differ  widely  in  origin,  course 
and  distribution.  The  spinal  portion  or  accessorius  spinalis  (r.  extemus)  is  so  termed 
because  it  arises  from  the  spinal  cord  and  the  accessory  portion  or  accessorius  vagi 
(r.  internus)  receives  its  name  in  recognition  of  the  fact  that  it  is  accessory  to  the 
vagus.  As  emphasized  in  connection  with  the  last-named  nerve  (page  1266),  the 
so-called  accessory  portion  of  the  eleventh  is,  in  reality,  an  integral  part  of  the  vagus 
and  the  description  of  its  deep  origin  and  distribution  has  been  included  with  those 
of  the  vagus.  There  remains,  therefore,  only  the  spinal  portion  of  the  nerve  to  be 
considered.  The  spinal  part — the  eleventh  nerve  proper — supplies  the  sterno- 
mastoid  ard  trapezius  muscles. 

Deep  Origin. — The  fibres  constituting  the  spinal  part  of  the  ner\e  arise  as  the 
axones  of  a  column  of  large  multipolar  neurones  which  is  situated  in  the  anterior 
horn  of  the  spinal  gray  matter  and  extends  from  the  lower  end  of  the  medulla  to 
the  fifth  or  sixth  cervical  segment  of  the  spinal  cord.  The  cells  of  this  column, 
known  as  the  accessory  nucleus,  occupy  a  dorso-lateral  position  in  the  horn,  lying 
posterior  to  the  cells  from  which  arise  the  fibres  of  the  anterior  roots  of  the  cer\'ical 
nerves.  Leaving  these  cells,  the  fibres  pass  dorsally  within  the  gray  matter  to  the 
vicinity  of  the  bay  between  the  anterior  and  postenor  horns,  where,  while  some  at 
once  curve  outward  and  traverse  the  white  matter  to  gain  the  lateral  surface  of  the 
cord,  the  majority  bend  abrupdy  brainward  and  pursue  a  short  ascending  path  before 
turning  (    tward. 

Course  and  Distribution. — The  superficial  origin  of  the  accessory  nerve 
is  marked  by  the  emergence  of  a  series  of  fasciculi  along  the  lateral  surface  of  the 
spinal  cord  between  the  anterior  and  posterior  roots  of  the  cervical  spinal  nerves,  the 
fasciculi  progressively  nearing  the  posterior  roots  as  they  issue  at  higher  levels. 
Consecutively  joining  shortly  after  they  escape  from  the  cord,  the  fasciculi  unite  to 
form  a  common  trunk,  which  gradually  increases  in  size  by  accessions  of  fibres  at 
each  succeeding  segment.  The  nerve-trunk  thus  formed  passes  upward  in  the  sub- 
dural space,  between  the  ligamentum  denticulatum  and  the  posterior  nerve-roots 
(Fig.  879),  to  the  foramen  magnum,  through  which  it  enters  the  cranium.  Upon 
reaching  the  side  of  the  medulla,  the  spinal  accessory  nerve  turns  outward  to  enter 
the  middle  compartment  of  the  jugular  foramen  and  to  unite  temporarily  with  the 
accessory  vagus.  It  occupies  the  jKisterior  part  of  the  middle  compartment  of  the 
jugular  foramen,  lying  within  a  dural  sheath  which  contains  also  the  vagus.  On 
reaching  the  lower  margin  of  the  foramen,  the  fibres  accessory  to  the  vagus  perma- 
nently leave  the  ele\  enth  nerve.  The  latter,  often  described  as  the  spinal  part, 
courses  downward  for  a  short  distance  in  the  interval  between  the  internal  carotid 
artery  and  the  internal  jugular  vein  and  then  passes  backward,  either  anterior  or  pos- 
terior to  the  vein,  until  it  reaches  the  deep  surface  of  the  stemo-mastoid  muscle, 
which  it  usually  enters.  While  within  the  substance  of  the  muscle,  the  spinal 
accessory  gives  off  faaments  which  unite  with  a  branch  from  the  second  cervical 
nerve  to  form  the  stemo-mastoid  plexus  (Fig.  1082)  for  the  supply  of  that  muscle. 
Emerging  from  beneath  the  posterior  edge  of  the  stemo-mastoid,  the  eleventh 
nerve  crosses  the  occipital  triangle  and  dips  under  the  anterior  margin  of  the 
trapezius  along  the  deep  surface  of  which  it  descends  almost  to  the  lower  margin 
of  the  muscle.  Under  the  trapezius  the  nerve  forms  a  plexus  of  varying  degrees 
of  intricacy  with  the  third  and  fourth  cervical  nerves.  This  is  called  the 
subtrapezial  plexus  ( Fig.  1082 ),  its  fibres  of  distribution  supplying  solely  the 
trapezius  muscle. 


THE   HYPOGLOSSAL   NERVE.  i275 

v.ri.t)«n.  —Considerable  deviation  from  the  normal  has  been  described  with  regard  to 
y"^**^?-7^^'*\^",er  limit  of  its  oriinn  has  been  observed  as  high  as  the  third  cerMcal 
the  8P>na'P"'^°";.,7l«!?irfarlwna^tfc  first  thoracic.  In  one  instance  the  nerve  left 
?hrsubduril°Z*  bjfow  t?fe  fi^t  cei^iiSl  H^rve'^and  re-entered  at  a  higher  level.  Quite  fre- 
Ihe  su'~"™,flf  "^j^rJi^  ,he  ,terno-mastoid  muscle.  In  one  reported  case  the  nerNe  ended  in 
ouentlyitfails  topierw  the^emo^mastow^^  ^  fourth  cervical  nerves. 

te'STfa^s  have  SX^id Wd^tiL  ^oom  of.the  University  of  Pennsylvania. 
R^ly  it  ^ves  off  a  filamem  which  joins  the  n.  descendens  cerv.calis. 

Practical  Considerations.— The  spinal  accessory  nerve  supplies  the  sterno- 
deido-mastoid  and  trapezius  muscles.  A  few  fibres  of  the  second  and  third  cer^'.cal 
ne?v«  enter  into  the  ^pply  of  the  stemo-mastoid.  but  the  muscle  is  almost  com- 
SeTefy  under  the  control  of  t^he  spinal  accessorj-^  The  cervical  nerves  take  a  greater 
part  in  the  supply  of  the  trapezius,  so  that  paralysis  of  the  spinal  accessory  does  not 

''"'^p^mWe'^r"pe"t  will^  the  head  backward  and  toward  the  affected 
side  anTwiU  pull  the  scapula  toward  the  spine.  In  spasm  of  the  f  erno^m^toid  as 
in  -'vry  neck,"  the  chin  will  be  turned  to  the  opposite  side  and  elevated,  whUe  the 
Lar  will  look  forward.  If  both  stemo-mastoids  are  m  contraction  the  chin  will  be  n 
the  med^  line  and  will  be  drawn  toward  the  sternum.  Paralysis  of  one  muscle  will 
JirXe  a  condition  somewhat  similar  to  that  produced  by  a  spasm  of  the  opposite 

°"^'  The  spinal  accessory  nerve  enters  the  under  surface  of  the  sterno-mastoid  muscle 
near  the  iuncUon  of  its  upper  and  middle  thirds,  where  it  may  be  reached  by  an 
TncTsiin  along  Ae  anterior  border  of  the  muscle.  The  nerve  emerges  from  the 
muscle  near  the  middle  of  its  posterior  border. 

THE   HYPOGLOSSAL  NERVE. 
The  twelfth  or  hypoglossal  nerve  (n.  hypoglossus)  is  a  purely  motor  nerve  and 
supplied  th^musculaturVof  the  tongue,  intrinsic  as  well  as  extnnsic,  with  the  excep- 
tion of  the  palato-glossus. 

Cntna  .nd  Coiticri  Conneetteni.-The  hypoglossal  nerve  takes  its  deep  origin  from 
severda^ia^wl  groups  of  neurones  called  the  hypoflo.«lnucleu.  (nuCu.  ..  hyPOfKo-n 
Tpig  949rwhkh  underiies  the  floor  of  the  fourth  ventricle.  This  n!«^'««  '«  »  """."^ 
elonKated  collection  of  large  multipolar  cells,  measuring  about  18  mm.  m  length  by  a  mm. 
fn  wWtiT  tharpartly  corresponds  in  position  to  the  tng^m  hypoglosst  in  the  floor  of  the 
ourthvCT  rice  The  entire  nudeusrhowever,  is  more  exteasive  than  the  tngonum  and 
Ixt^nds  C  the  level  of  the  stri^  acusticx  above  into  the  closed  part  of  the  m^^duHa  ».s  fa 

down  as  the  decussation  of  the  pyramids  (Fig^  9«7).  U  «-  ,yi"^^;"f  ^^e^^o^'^^h  v^^^^^^^^^^ 
to  the  central  canal  of  the  medulla  and  the  median  groove  in  the  floor  of  »•'«  fourth  ventncle^ 
r?ose  to  the  mid-line  and  its  fellow  of  the  opposite  side.  The  large  sire  and  branched  form 
o^he  neVle-^Hs  com^^  the  nudeus.  as  wdl  as  their  venttjil  position  m  relation  to 
the'tnUaT^a.  emp^siJ  the  close  co-espondence  of  thesej^m™^  ^.^  S^y'mattel 
the  motor  roots  of  the  spinal  nerves.  Indeed,  as  noted  later  (page  1380),  '"^P^V  "J;!^" 
;nci™?nethrhvpoKlossal  nucleus  is  the  morphological  equivalent  of  the  bases  of  the  antenor 
c'rir' tmSr^er  arising  and  beTore  leaving  the  ""^«-  /''f, /-'^^f'":^ 
into  a  number  of  fasciculi  which,  emerpng  from  the  ventral  aspect  of  the  nucleus,  take  a 
ventr"^  cour^Tnd  trTverse'  the  infernal  between  the  gray  and  white  ^etio^ar  formations^ 
From'his  situation  the  hypoglossal  fibres  continue  the  r  ~"«f;°  ^^ ''"^""V^j^^'^'^itt 
medulla  bv  oas-sine  for  the  most  part,  l)etween  the  nucleus  of  the  inferior  olive  and  the  mesial 
TcJlry  oC  nudJus.  althoug'J,  quite  a  number  of  the  strands  penetrate  tiie  ventral  portion 

°'  %tTn^r:onn^tnV of-  the  hypoglossal  nucleus  include :(«)  crossed  fibres  from  the 
nuclei  of  throprshrlde;  (*)  fibr^rom.  and  probably  also  to.  the  PO?»«""r '""P*"''": 
feSus  by  mearorwhich  the  nudeus  of  the  twdfth  is  brought  into  relation  with  the  nude 
Toth.r  cranial  nerves  •  and  (c\  fibres  which  join  the  dorsal  bundle  of  bchUtz.  a  system  of 
•iSudinTfibr^Tnderbing  the  floor  of  '-e  fourth  ventride  and  traceable  upward  beneath 
U.e%Man  aqueduct,  but'conceming  wha  lestina.ion  and  «""-"°- 'f '  :;:,^"„7:_,,,„ur 
The  cortical  centre  of  the  hypoglossal  nenje  P"'*^Wy ''*•*'''''" '^''".^^'^"^eKtl^h^ 
extremity  of  the  precentral  convolution.  The  fibres  arising  as  the  axones  oJ  the  «'"  wiinin 
*hTa™a  i^s,  over  ti^  upper  border  of  the  lenticular  nudeus  and  through  the  mtemal  capsule 
and  X^d  Tn  the  ^afn^tem  within  the  medten  part  of  the  pyramidal  tract  as  far  as  tiie 


1276 


HUMAN  ANATOMY. 


medulla.  The  cortko-nudear  fibres  then  bend  dorso-medially  and,  for  the  most  part  but 
not  entirely,  cross  llie  raphe  to  enter  the  ventro-tateral  surface  of  the  hypoglossal  nucleus  of 
the  opposite  side  and  end  in  arborizations  around  the  root-cells. 

Course  and  Distribution. — The  hypoglossal  takes  its  superficial  origin 
from  the  surface  of  the  brain-stem  in  the  form  of  from  ten  to  fifteen  slender  tasciculi, 
which  emerge  from  the  ventral  surface  of  the  medulla  in  the  groove  between  the 
olivary  eminence  and  the  pyramid  (Fig.  1046}. 

Fig.  1083. 


//^ 


1.  thoracic  ncrra 


l>iUA<ttric  muKlCtCut 
I.  crrvirkln 
Spteal  accessory  nerve- 
Small  occlpiul 

1 1,  cervical  ni 

Superior  CCTvical  gaQglioa- 
Hranch  of  II .  cervical  to  ipinal accenory • 
III.  cervical  at 
Communlcana  hjrFOf|:I 
Slumps  of  great  auricular  and  uiperiklal' 
cervical  nerves]  |\-   ctrvkal 


VI .  cervical  nerve . 
Brauk-h  of  communication  to 
sflnal  acceMory 
Cutancoui  brani 
VII,  cervical  nerv) 
Nerve  to  tubclaviu». 
VIII.  cervical  narvt 
rosterior  thurtctc 
nerve 
SupnicapiiUf 
nerve  ^' 


External  pterycoM  muscle 
Lingual  l>nuKh of  V.  nerte 

^  Chorda  tympani  nerve 
Internal  pterygoid  niuKlc 
Edge  of  oral  mucous  nieml>rane 

rlosso-pharyngeal  nerve 
Mental  nerve 
Inferior  dental  nerve,  cut 
uMlngual  gland 

laalllary  ganglion 
yto-h)iT>id  muscle 
'Thyfo-hyoldbranchof  XII.  nerve 
-Superior laryngeal  nerte 

.Descendens  hypoglossi ;  sympathetic 

cord  is  to  its  outer  »ide 

Vagus  Dcrve 

Cxteraal  laryngeal  nerve 

Omo-hyold  muv  1r.  >  ut 
Ffirenic  nerve 

Middle  cm  ical  ganglion  of  sy  ntpalheilc 
-Scalenus  anttcus  muscle 


5Uiclav(an  artery 


De«p  dissection  of  neck  showing  branches  of  vo^us,  spinal  accessory  and  h>-poglossal  nerves. 

These  root-bundles  pass  outward,  dorsal  to  the  vertebral  artery,  and  assemble 
into  two  groups,  which  pierce  the  dura  mater  separately  at  a  point  opposite  the 
anterior  condyloid  foramen.  Either  within  this  canal  or  as  they  leave  the 
cranium  through  its  external  opening  they  unite  into  a  single  trunk.  Arriving  at 
the  inferior  aspect  of  the  base  of  the  skull,  the  deeply  placed  hypoglossal  ner\'e 
descends  and  hooks  around  the  ganglion  of  the  trunk  o*  the  vagus,  to  which  it  is 
closely  attached  by  connective  tissue.  It  then  take:  downward  and  forward 
course  between  the  internal  carotid  artery  and  th"  internal  jugular  vein.  Arriving 
at  the  inferior  margin  of  the  posterior  belly  of  the  digastric,  the  nerve  winds  around 
the  occipital  artery  .md  cnitrses  downward  and  forward  to  the  otitcr  side  of  the 
external  and  internal  carotid  arteries.  It  then  continues  forward  above  the  hyoid 
bone  to  the  under  surface  of  the  tongue,  passing  beneath  the  tendon  of  the  digastric, 


THE    HYPOGLOSSAL   NERVE. 


1277 


under  the  stvlo-hyoid  and  mylo-hyoid  muscles  and  over  the  hyo-glossiis  (Fig.  1082) 
It  temS  by  piercing  tL  genio-hyo-glossus  and  breaking  up  into  a  number  of 
fibres  for  the  supply  of  the  lingual  muscles. 

C«nmimiction..-Immediately  after  emerging  from  the  anterior  ™"''y>°''*  ♦°™"*"',i,''] 
•inv^^n^n^ts  with  the  superior  cervical  ganglion  of  the  sympathetic  (4)  one  or  two 
a  tiny  '^'*J°""!!  jj^"" i^j^een  the  first  and  second  cervical  nerves  and  {c)  several  fibres 
•^'"Jll-I^te  thTnervI  wi  MhetSon  0I  the  trunk  of  the  vagus.  At  the  point  wljere  the  hypo- 
associate  the  3^  ^'"L'i'^A^^  cross,  id)  the  lingual  branch  of  the  vagus  joins  the  twelfth ; 
K  the  nerv"e  fes^-Th  SyWid  and  u4«  the  hyo-glossus  muscle,  it  communi- 
rates  with  (e)  the  lingual  branch  of  the  mandibular  nerve. 

Branches.— The  branches  of  the  hypoglossal  nerve  are  :    (i)  the  meningeal, 

( ,\  thi.  descendinir,  ( \)  the  thyro-hyoid and  (4)  the  Itngual.  . 

(2)  the  rf«««rf»«^   W  J^^^  J      „eninge«s)   consists  o   one  or  two   minute 

filaments^whic"  supply  the  dura  mater  of  the  posterior  cranud  fossa  and  the  d.ptoe 
S  the  .ScioilS  bone  As  the  hypoglossal  is  motor  in  hinction,  it  is  likely  that  these 
it  a^SribCted  to  the  ner^^^y  the  loop  between  the  first  and  second  cer^-lcal 

"*'^?'  The  descending  branch  (r.  descendens),  or  r.  descendens  hyfioghssi,^ 
in  realitv  only  to  rLited  extent  a  branch  of  the  twelfth,  since  the  greater  number 
"(  ^^fihr^  arc  accessions  to  the  hypogkjssal  from  the  first  and  second  cervical 
rl«  T^ere  is  r^n  however,  tobdieve  that  these  cervical  nerves  are  not  the 
SliveLurce  d  Sbf«  of  th^  descendens  hypoglc«si.  but  that  some  anse  fro. 
the^e  Is  oT^the  hypoglossal  nucleus.  The  descend  ng  branch  arises  near  the  point 
where  the  hyi^lS  nerve  hooks  around  the  occipital  ^^ery  »nd  runs  downwam 
rnd?nward  Wont  of  or  within  the  carotid  sheath.  It  gives  of!  a  branch  to  the  an- 
terior My  o  Sie  omo-hyoid  and,  about  the  middle  of  the  neck  joins  the  descend- 
n^ce^ica  nerve,  or  «.  cimmumcans  hypoglossi,  from  the  second  and  third 
ce^icalTer^es.  A  W  or  plexus,  termed  the  ansa  kypcglosn,  is  thus  formed  and 
^om?t  filamfnts  are  supplied  to  the  sterno-hyoid  and  stemo-thyroid  muscles  and  to 
the  posterior  b.Uy  of     -.omo^h^o^ 

..  \  f  »K»  Wn  «sal  as  its  fibres  can  be  traced  back  to  the  cervical 
Sus  1t  L  give^oh  t4t;eThe  ner^e'dips  beneath  the  stylo-hyoid  muscle  and 
P^  down  biwnd  the  greater  comu  of  the  hyoid  bone  to  reach  its  distribution  to 
the  thyro-hydd  muscle.  ^^^^^^  ^^^^^^^^  ^^^  --P'n/'^'rh  !l?d 

1  1i;ctrih„tion  of  the  hypogl(»sal.  As  the  nerve  lies  beneath  the  mylo-hyoid 
mtscle  £rts  LeVen  o^^  to  the  hyo-glo^us  the  stylo-glossus  a^d  the 
muscle    "l^^"""    ".      K  gen b-hyoid  are  in  aU  probability  de- 

^vl^'fSm  the  cervix  Ple^^^^  hyWo-^  origin.    After  giving 

off  the  above-named  branches,  the  hypoglossal  nerve  breaks  up  into  the  terminal 
fifamenu  wWch  pierce  the  genio-hyo-glossus  to  supply  it  and  the  l.ngualis  muscle. 

w.,i..i„n.  — Occasion.illy  the  hypoglossal  has  been  found  to  possess  a  posterior  root  bear- 
^"^V^^'lli^S-^  Si  is  to^regarded  as  a  persistence  of  the  temporary  embryonal 
ing  a  ganiflion.  .^n's  condition  is  "  ^ -^  .  ^  posterior  root  and  a  ganglion  of  Konep 
stage  during  which  «''f.  n^'^%;i'Xui  oridn  wasMwated  at  the  p«-:ut:.ior  aspect  of  theme- 
(page  1380).  In  one  case  the  ^"P*™"^' ®"S'"  *^  beUveen  the  rcotlets  of  orSn  and  in  rare 
d\;ila.    Quite  freq-jej^'y  ^^JL^m^'L  c?S  fSament   siTutted  eitV^^^^^  Se  genio-hyo- 

instances  behind  them.    Sometimes  a  crc«sniam«  i^  connects  the  two  hypoglossal 

glossus  a"d  Kjmio-h^o^u^^es  or  .^^^^^^  ^^  ^^^  mylo-hyoid.  tg  digas- 

nerves.  Rarely  the  "yPOK'"'***' ''~,^'' „„  ,i,p  r  Hem endens  hvpog'ossi  seems  to  be  derived, 
trie  or  the  "tylo-hyo.d  musde^ ,?«  ™tu\?n  iheSa^s  trLres  can  be  traced  back  to 

§?aTc?i\rprrbtderi:X^H^iri^^^  °^ f^'-  va^"-    The  r.  descen- 

dens hy^glo^i  may  send  a  b^ch  to  the  stemo-masto.d  muscle. 

Practical"  Considerations.— Involvement  of  the  hypoglo^al  nerve  usually 
.  ^^If^ith  other  cranial  nerves  is  frequent  in  bulbar  disease.  The  most  character- 
LT*  mjt^mt  aVe'i^^^        fongu'e,  when  protruded  to  the  affected  side,  caused 


137* 


HUMAN   ANATOMY. 


by  the  unopposed  action  of  the  muscles  of  the  opposite  side.  The  nerve  may  be 
injured  by  operative  or  other  wounds  in  the  submaxillary  region  or  in  the  mouf'  ,  as 
in  gun-shot  wounds.  It  can  be  easily  reached  in  the  submaxillary  region  by  the 
same  incision  as  that  used  for  ligating  the  lingual  artery  (page  736).  It  passes  for- 
ward to  the  tongue,  just  above  the  hyoid  bone,  and  forms  the  upper  boundary  of  the 
small  "lingual  triangle,"  which  is  exposed  when  the  submaxillary  gland  b  elevated. 

THE  SPINAL  NERVES. 

The  cranial  division  of  the  somatic  nerves  having  Ijeen  considered,  the  spinal 
group  next  claims  attention,  the  visceral  or  splanchnic  (sympathetic)  nerves  being 
reserved  for  a  final  and  separate  description. 

The  spinal  nerves  (nn.  spinales)  mclude  a  series  of  usually  thirty-one  pairs  of 
symmetrically  disposed  trunks  which  pass  laterally  from  the  spinal  cord  and  emerge 
from  the  vertebral  canal  through  the  intervertebral  foramina  (Fig.  880).  Elach 
nerve  arises  from  the  cord  by  a  dorsal  sensory  and  a  ventral  motor  root,  which  sepa- 
rately traverse  the  subarachnoid  and  subdural  spaces  and  evag^nate  or  pierce  the  pia 
mater,  arachnoid  and  dura  mater.  Within  the  intervertebral  foramina  the  roots  unite  to 
form  a  common  trunk,  which  carries  with  it  a  sheath  composed  of  the  three  membranes, 
the  contribution  of  the  arachnoid  and  pia,  however,  soon  ending,  whilst  the  dural 
covering  is  prolonged  to  become  continuous  with  the  epineural  sheath  of  the  nerve. 

Nomenclature. — ^The  spinal  nerves  are  designated  not  relative  to  the  position 
at  which  they  arise  from  the  cord,  but  according  to  their  point  of  emergence  from  the 
vertebral  canal.  They  are  divided,  therefore,  into  the  cervical,  thoracic,  lumbar, 
sacral  and  coccj-geal  groups.  With  the  exception  of  those  in  the  cervical  region, 
the  individual  nerves  are  named  according  to  the  vertebra  below  which  they  emerge 
from  the  vertebral  canal.  On  account  of  the  disprojxtrtion  between  the  eight  cer\'i- 
cal  ner\-es  and  the  seven  cervical  vertebrae,  this  arrangement  necessarily  can  not 
prevail  in  the  neck.  The  first  cervical  nerve,  often  called  the  suboccipital  nerve, 
emerges  between  the  occipital  bone  and  the  atlas  ;  the  second  emerges  below  the  first 
vertebra,  the  third  below  the  secopd  and  so  on  down  to  the  eighth,  which  traverses 
the  foramen  between  the  seventh  cervical  and  first  thoracic  vertebral  segments. 

Constitution. — Every  spinal  nerve  arises  by  two  roots,  a  posterior  sensory 
and  an  anterior  motor,  the  latter  being  composed  of  the  axones  proceeding  from  the 
motor  neurones  situated  within  the  gray  matter  of  the  anterior  cornu  of  the  spinal  cord, 
whilst  the  fibres  composing  the  posterior  or  sensory  root  are  the  axones  of  the  neurones 
within  the  ganglia  which  are  invariably  present  on  these  roots.  The  formation  of  the 
common  trunk,  by  the  union  of  the  two  roots,  affords  opportunity  for  the  two  varie- 
ties of  fibres  to  intermingle,  so  that  the  anterior  and  posterior  primary  divisions  into 
which  the  common  trunk  divides  contain  both  sensory  and  motor  fibres.  In  addition 
to  these  fibres,  which  are  destined  for  the  somatic  muscles  and  the  integument,  others 
are  added  from  the  sympathetic  neurones  for  the  supply  of  the  outlying  involuntary 
muscle  and  glandular  tissue  occurring  in  the  regions  to  which  the  spinal  nerves  are 
distributed.  It  is  evident,  therefore,  that  the  terms  "motor"  and  "sensory,"  as 
applied  to  the  somatic  blanches  of  the  spinal  nerves,  are  relative  and  not  absolute, 
since  in  all  cases  the  nerves  passing  to  the  muscles  contain  sensory  and  sympathetic 
fibres  in  addition  to  those  ending  as  motor  filaments  in  relation  with  the  striated 
muscle  fibres.  Likewise,  in  the  case  of  the  sensory  branches  distributed  to  the  integ- 
ument, sympathetic  filaments  (motor  to  the  involuntary  muscle  of  the  blood-vessels 
and  secretory  to  the  glands)  accompany  those  concerned  in  collecting  sensory 
impulses.  On  the  other  hand,  where  they  retain  their  typical  plan,  as  in  the  case  of 
the  thoracic  nerves,  the  spinal  ner\'es  contribute  motor  fibres  which  end  around  the 
sympathetic  neurones  to  supply  motor  impulses  either  to  the  involuntary  muscle 
of  the  organs,  by  way  of  the  splanchnic  efferents,  or  to  the  outlying  involuntary 
muscle  along  the  somatic  nerves  m  the  manner  above  described. 

The  sensory,  posterior  or  dorsal  roots  (radices  posteriores)  of  the  spinal 
ner\'«-  are  usually  larger  than  the  motor,  a  condition  due  to  the  increased  number 
of  tht.i  filaments  and  the  greater  size  of  those  filaments  (fila  radicularia).  The  fas- 
ciculi which  form  the  sensory  root  are  attached  to  the  cord  along  the  postero-lateral 


POSTERIOR   PRIMARY  DIVISIONS  OF   SPINAL   NERVES.     1279 
o.  o  «^ntinuous  series    called  the  posterior  root  zone  (Fig.   884).     These 

E?^^Skruas;sss.t'Sp:^^5i«'v£ 

spinal  ganglio|V  aggregations  of  ner^'e-cells  found  on  the 

The  "P'J**^  8""f '  .%,\^_,*^e°vM  a       852V    They  are  usually  ovoid  in  shape, 

Tn'^!^  'r^   in  length  Tdare^asto^ly  bifid  at  ^heir  proxiLl  ends      They 

?^^ist"tf  a  cluster  of  unipolar  neurones,  whose  centrally  directed  axones  form    he 

n!^.lro^t  of  the  spinal  nerve  a.id  whose  dendrites  e.xtend  peripherally  as  the 

L2      A^thoueh  s'ia^ed  ^^ond  the  dural  sheath  of  the  cord,  with  the  e.xcept.on 
ofthe  gang&of  the  ^SygLl  nerve,  they  are  invested  by  a  prolongation  of  it. 

terior  or  both  roots  of  one  of  the  nervw  ■""y^'O^f'^f^e  Srior  root  having  its  own. 
"'^"0iSiS*^J^ran.^n'*°deSch3'^5^^^^^^^^       Wna.  ganglia  <KCa^ona.ly  found 
along^lS^t^riST^te  of  the  upper  cervical,  the  lumbar  and  tte  .acral  nerves. 

The  motor,  anterior  or  ventral  roots  (radices  anteriores)  are  smMerJh^n 

srrr.^rTastsrLriSn^^^^^^^^^ 

'''*^°  Num^'l^^As  usually  found  the  thirty-one  pai«  are  grouped  as  follows:  -eight 
cervical  twelve  thoracic,  five  lumbar,  four  sacral  and  one  coccygeal. 

y«i.tion..-Shou1d  *- ^^J^y  TTh1^Je"ri'eI  ""^h^^'^eatr  Sion^'^^rs't'^t^e 
there  is  a  corresponding  "odificaUOT  ol  the  nenr^.      1  ^c  g  .^ 

^bSf  Tr^^^soT'j^^eX'S.^^'^Wcfa^V^rr^.-c^uda.  nerves,  may  be  found  in  the 
lilum  terminate. 

Size  —The  lareest  spinal  nerves  are  those  which  are  concerned  in  the  forma- 
tion of  S;  limb  pSS^rachial,  lumbar  and  sacral-and  are   therefore  ^hebwc 

-SnSeS^S£:JX£Se^'-^^ 

'''  '^;.^::-^^'^:o:  tTuTfrXtne  umon  of  the  two  roots.emerg^ 
from^tsntrertebrd  foramen  and  almost  immediately,  gives  off  a  --'•W  or 

^;^urco:^i^^'3tte:^;^^^^^ 

recurrent  twig,  each  trunk  soon  «?"'»  i"t°/*°  'ir^^^**:!' ^  "K-ukh  ts^^^^^^^ 
^sterior  firimary  divisions  (rr.  anterior  et  posterior),  each  of  «hich  is  composea 
fffibr«  from  both  roots  (Fig.  1085),  as  well  as  of  sympathetic  filaments. 

THE  POSTERIOR  PRIMARY     -IVISIONS  OF  THE  SPINAL  NERVES. 

The  posterior  primary  divisions  frr.  posteriores)  of  the  spinal  ner%'es  are  as  a 
rule  ImalKan  th'e  ant^ior  (rr,  anteriores).  They  ar«e  either  -  ^^;;g'^-^„;i 
from  the  trunk  formed  by  the  union  of  the  two  roots,  or  as  two  separate  stranos 


12S0 


HUMAN  ANATOMY. 


from  the  roots  themselves.     They  turn  dorsally  almost  immediately  and  divide  into 
an  internal  (r.  nwdialia)  and  an  external  branch  (r.   lateralis),  which  supply  the 

Fig.  X083. 


Third  occipital  ncrvr 

Cutaneous  bra.  of  IIL 
cervical,  dormt  div. 


Cutaneonii  bni.  of  IV.  and  V.f 
cervical,  dorial  division  ^ 


Cutaneous  brs.  of  dorsal 
divisions  of : — 
I.  thoracic 


Occipitalis  maior  nerve 


III..  IV..  v.,  VI..  VII.. 
VIII..  IX..  X.  and  XI. 
thoracic  ner\'es,  lateral 
cutaneous  branches 


I..  II.  and  III.  lumbar  ( 

nerves,  ext.  bn*.  of  •< 

dorsal  divisions  J 


Cutaneous  brs.  of  dorsal 

divisions  of  sacral< 

nerves 


XII.  thoracic,  lateral  cu- 
taneous br. 

Jlliac  br.  ilio>hyp<:^;astric 
nerve 

XII.  thoracic,  lateral  cu- 
taneous br. 


Superficial  dissection,  showinit  cutaneous  branrhe«  of  posterior  divi&inns  and  lateral  cutaneous  branches  of 

anterior  divisions  of  spinal  nerves. 

dorsal  muscles  and  integument.      At  the  two  extremities  of  the  spinal  series  the 
division  into  internal  'uid  external  branches  does  not  prevail^  the  first  cervical, 


THE  CERVICAL  NERVES. 


1281 


»K-  fo..rth  and  fifth  sacral  and  the  coccygeal  nerve  lailing  in  this  respect.     Down  to 

the  muscles  before  reaching  their  cutaneous  distnbuUon. 
THE  CERVICAL  NERVES. 

The  first  cervical  nerve  (n.  wbocclplUlls).  the  first  of  the  spinal  series,  « 
.v«S  in  sLver^lrra^  Its  posterior  rocit  is  either  insignifi«.nt  or  entirely  absent. 
fn^^D^t^rioriivtS^hich  does  not  divide  into  internal  and  external  branches.  » 
Urte?tC  the  anterior  and  usually  does  not  send  of!  any  direct  cutaneous  branch. 
S  nerTJa^  do^Uy  between  the  occipital  bone  and  the  Po^.^"-' «<=^' »^* 
It^  and  t.^^  the  suboccipital  triangle,  occupying  a  posUion  below  and  posterior 
to  die  vertebral  artery.     SupeHicial  to  it  is  the  complexus  muscle 

BrSSesi-rtese  are  :  (i)  the  muscular,  (a)  the  communuatxng  and  (3)  the 

"''"T^he  muscular  branches  supply  the  superior  and  inferior  oblique,  the  com- 

P'^^'ir  ^4.t^tTn^i^^tTxo^l  ?X3Te"^nd  cervi«d,  nerve.     It 

^Ue  to  tie  compSus!  amercing  which  muscle  it  communicates  w.th  the  great 
***^'tte^.^k  and  close  to  the  vertebra  is  a  series  of  loops  between  the  p<«terior 

'^  The  second  cervical  nerve  is  distinguished  by  the  size  of  its  posterior  division. 

^^^  Ths  Se  (Fig  1087)  passes  upward  over  the  inferior  oblique,  pierces 
The  complex^  and  ^^zius.  ^alid  accompanies  the  occipital  artery  to  the  s^p. 
5  the  ^sS  half  of  ^hich  it  is  the  main  -"-H-erve.     It  become  supe^^^^^^^ 

SpS  5s£rartrsprld\^r  i^nrmlr^^  b^^ci^^wth^^y  the 
scalp  as  far  forward  as  the  vertex. 

The  reat  occipital  nerve  communicte.  with  the  small  and  least  occipiul  and  the  posterior 
and  great  auricular  nerves. 

rxlrrK^h*i5:iyt-ora"cSrSi2'fiia^ 

The  third  cervical  nerve  has  a  smaller  posterior  division  than  has  the  second 
Passine  backward,  the  former  helps  to  form  the  postenor  cen-.cal  Pl«"^  ""^^^J'^J^ 
in^  eltS  and  internal  branches.  The  external  branch  (r.  Uitenilis)  supplira 
ac^^cS  i«  and  th"  .W/.W  branch  (r.  mcdiaUs),  known  a,  the  '^^  ^^  / W 
S3  Zrve  (a.  occipitalis  tertias),  pierces  the  complexus.  ^PlS^'"^,*"";.^?*""'  '° 
supply  the  skin  of  the  occipital  and  posterior  cervical  regions  (Fig.  1083). 


1382 


HUMAN   ANATOMY. 


In  addition  to  assisting  in  the  (ormation  o<  the  poatcrior  cervical  plextis  it  commanicatea 
with  tlie  gnat  occipital  nerve. 

The  fourth,  fifth,  sixth,  seventh  and  eighth  cervical  nervea  have  quite 
small  posterior  primary  divisions  (rr.  poatcrlorcs).  The  fourth,  fihh  and  sixth 
divide  mto  the  usual  external  and  internal  branches  (rr.  Uteralcs  ct  aMdiales),  which 
supply  respectively  the  adjacent  muscles  and  the  dorsal  integument.  The  seventh 
and  eighth  usually  have  no  cutaneous  branches  and  are  distributed  solely  to  the 
deeper  muscles  of  the  back. 

A  communicatinc  filament  from  the  foutth  may  aid  in  the  formation  of  the  posterior 
cervical  plexus. 

Variations. — The  cutaneous  branches  of  the  fifth  and  sixth  may  be  ver>-  small  or  absent 
entirely. 

THE  THORACIC  NERVES. 

The  posterior  primary  divisions  (rr.  posteriorcs)  of  the  thoracic  or  dorsal  ner\'es 
(nn.  tboracales)  follow  the  general  arrangement  of  dividing  into  external  and  internal 
branches.  Of  these  the  internal  branches  of  the  upper  six  are  mainly  cutaneous 
and  the  external  entirely  muscular.  In  the  lower  six,  on  the  contrary,  the  external 
branches  are  principmlly  cutaneous  and  the  internal  entirely  muscular. 

The  external  branches  (rr.  lateralcs)  gradually  increase  in  size  from  above 
downward.  They  pierce  or  pass  under  the  longissimus  dorsi  to  reach  the  interval 
between  that  muscle  and  the  ilio-costalis,  eventually  reaching  and  supplying  the 
erector  spinx.  Those  from  the  lower  half  of  the  thoracic  nerves  distribute  sensory 
fibres  for  the  supply  of  the  skm  overlying  the  angles  of  the  ribs  (Fig.  1083). 

The  internal  branches  (rr.  mediales)  of  the  upper  six  or  seven  pass  dorsally 
between  the  multifidus  spinae  and  semispinalis  muscles.  After  innervating  the  trans- 
verso-spinales  they  become  superficial  close  to  the  median  dorsal  line  and  supply  the 
skin  of  the  back,  sometimes  extending  laterally  beyond  the  vertebral  border  of  the 
scapula.  The  internal  branches  of  the  lower  nerves  traverse  the  interval  between 
the  longissimus  dorsi  and  the  multifidus  spinx  and  supply  the  latter  muscle. 

Variationa. — The  sixth,  seventh  and  eighth  thoracic  nerves  may  give  off  cutaneous  twigs 
from  both  external  and  internal  branches.  The  first  thoracic  nerve  may  have  no  cutaneous 
branch. 

THE  LUMBAR  NERVES. 

The  posterior  primary  divisions  (rr.  posteriores)  of  the  lumliar  nerves  (nn.  lum- 
bales)  divide  into  the  usual  external  and  internal  branches. 

The  external  branches  (rr.  laterales)  of  all  five  lumbar  nerves  enter  and  sup- 
ply the  erector  spinse,  those  of  the  lower  two  terminating  there.  From  the  external 
branches  of  the  first,  second  and  third  arise  cutaneous  offshoots  (nn.  clunium  supe- 
riores)  of  considerable  size  (Fig.  1083).  These  pierce  the  ilio-costalis  and  the 
aponeurosis  of  the  latissimus  dorsi  above  the  crest  of  the  ilium  and  supply  the  skin 
of  the  gluteal  region  as  far  forward  as  the  great  trochanter.  From  the  fifth  a  branch 
passes  downward  to  inosculate  with  a  similar  branch  of  the  first  sacral  nerve  to  aid  in 
the  formation  of  the  posterior  sacral  plexus. 

The  internal  branches  (rr.  mediales)  turn  directly  backward  and  supply  the 
multifidus  spinae  muscle. 

THE  SACRAL  NERVES. 

The  posterior  primary  divisions  (rr.  postciiores)  of  the  sacral  ner\-es  (nn. 
sacrales),  with  the  exception  of  that  of  the  fifth,  emerge  from  the  vertebral  canal 
through  the  posterior  sacral  foramina.  The  first,  second  and  third  pass  outward 
under  cover  of  the  multifidus  spinx  and  divide  into  external  and  internal  branches. 

The  external  branches  (rr.  laterales)  of  the  first,  second  and  third  sacral  nerves 
unite  over  the  upjjer  part  of  the  sacrum  with  a  similar  branch  of  the  fifth  lumbar  and 
with  the  fourth  sacra!  nerve  to  form  a  series  of  loops,  the  posterior  sacral  plexus 


THE   SACRAL   NERVES. 


1383 


I'rr- 


FiG.  1084. 


Part  of  maUilWii»  •p*n«  mi»cle 


Loom  of 

rommonicfttlon 

between  V.  luinbar. 

and  I  .  II.  *«m1  III. 

pottCTior  Mcral 

nerves' 

■  braiKlMtftMi 


From  XII." 
tlwrscic  iierw 


■V.  lumbar  nerve,  poftterior  divtekn 
X.  HcrmI  nerve,  po»terior  diviai. 
II.  Mtcral  nerve,  posterior  di 
111.  iacni!  nerve,  po*it 
IV.  Mctmlnervr 
Itviikm 

V.MCfmlixf" 

Coo  yi{««l  "> 

IV     M    .^^  » 


s««rferuT 


_  _-  '•f  "^  ■•*' 


fan  of  Ml 
•MKlHnMt 

— CuUMOuShr 
of  IV.ulcit^  ' 

hm  tMo  »"■•     ' 

levator  Mii 


!*■'  *"■ 


Dinection  thowing  Wt  posterior  sacral  pleM«. 

breaking  up  as  do  the  others  into  »>*"  7^"4'^^^i^^",7^  t^e  posterior  sacro- 
other  and  ujh^he  -cjea  -  ^^^^>^  ^^I^  ^^S  pl^e  the  ^^eat  sacro-sciatic 
fi^S  ale^giTe"  offrbJ  dSuted  to  the  integument  in  the  coccygeal  region 

(Fig.  1081). 


1384 


HUMAN  ANATOMY. 


THE  COCCYGEAL  NERVE. 

The  posterior  primary  division  (r.  po«tcrior)  of  the  coccygeal  nerve  (■.  coccy- 
gCM)  does  not  divide  into  internal  and  external  branches.  It  unites  with  the  fourth 
and  fifth  sacral  to  form  the  posterior  sacro-coccygeal  nerve,  whose  course  and  distri- 
bution are  described  above. 

THE  ANTERIOR  PRIMARY  DIVISIONS  OF  THE  SPINAL  NERVES. 

The  anteiior  primary  divbions  (rr.  anteriorcs)  of  the  spinal  nerves,  like  the 
posterior  (rr.  posuriorcs),  contain  fibres  from  both  the  anterior  and  posterior  roots 
and,  with  the  exception  of  those  of  the  first  and  second  cervical  nerves,  are  larger 
than  the  posterior.  After  liberation  from  the  main  trunk  at  the  intervertebral 
foramina,  they  pass  ventrally  and  supply  the  lateral  and  anterior  portions  of  the  neck 
and  trunk,  as  well  as  the  limbs. 

Shortiy  after  leavii^  its  foramen,  each  anterior  division  is  joined  by  a  slender 
bsciculus  from  the  gangliated  cord  of  the  sympathetic,  called  the  gray  ramus 
communicant  (page  1357).     Branches  to  the  sympathetic  system  are  given  off  from 

some  of  the  thoracic,  lum- 
Fio.  1085.  ijiy,  g„d  sacral  nerves,  in  the 

shape  of  small  fasciculi  of 
medullated  fibres,  called  the 
wUte  rami  communicanles. 
These  are  destined  for  the 
various  structures  of  the 
splanchnic  area  and  consti- 
tute the  visceral  or  splanch- 
nic distribution  of  tt<'>  spinal 
nerves.  The  remainder  of 
the  fibres  are  supplied  to 
the  body  wall  and  ex- 
tremities and  constitute  the 
somatic  distribution  of  the 
rferves. 

In  the  case  of  the 
cervical,  first  and  some- 
times second  thoracic,  lum- 
bar, sacral  and  coccygeal 
nerves,  plexuses  of  a  greater 
or  less  degree  of  intricacy 
are  interposed  between  the 
origin   and   distribution  of 


DiacTun  illustratinc  constitution  and  division  ol  typical  spinal  nerve ; 
'~    ■'X,  amcriot  and  poMerior  roots;  SG,  spinal  isnc- 

k;AD,  PD,  anterior  and  posterior  primary  divls- 

PC,   LC,  AC.  posterior,  lateral  and  anterior  ctttancons  biancbcs; 


5C,  spinal  cord;  .<*, /"i-. . 

lion ;  CT,  common  trunk ;  AD,  PD,  anterior  and 


RC,  ramus  communicans ;  Sy,  sympathetic  gaa(iioa  and  cord. 


the  nerves.  This  renders  the  tracing  of  anyrset  of  fibres  a  matter  of  extreme  difficulty, 
but  in  the  greater  portion  of  the  thoracic  region  the  original  segmental  and  less 
complex  arrangement  persists. 

A  typical  spinal  nen'e  (Fig.  1085),  such  as  one  of  those  in  the  mid-thoracic 
region,  is  arranged  as  follows.  The  constitution  of  the  main  trunk  (page  1278)  and 
the  distribution  of  its  posterior  branch  (page  1279)  have  already  been  described. 
The  anterior  primary  division  (r.  anterior)  leaves  the  intervertebral  foramen  and 
almost  immediately  is  connected  with  the  gangliated  cortl  by  gray  and  white  rami 
communicantes.  It  then  enters  an  intercostal  space  through  which  it  courses 
between  the  external  and  internal  intercostal  muscles,  both  of  which  it  supplies.  At 
the  side  of  the  chest  it  gives  off  a  lateral  cutaneous  branch  (r.  cutancus  lateralis), 
which  distributes  a  few  tiny  motor  twigs  and  then  pierces  the  external  intercostal 
muscle  to  supply  the  skin  over  the  kiteral  portion  of  the  trunk.  On  reaching 
the  superficial  Ktscia  it  usually  breaks  up  into  two  branches,  a  larger  anterior  (r. 
anterior)  and  a  smaller  posterior  (r.  posterior).  Havinp;  given  of!  the  lateral 
cutaneous  branch,  the  main  anterior  primary  division  continues  its  forward  course 
nearly  to  the  mid-line,  where  it  pier.t  -  the  muscle  and  becomes  superficial  as  the 
anterior  terminal  ctuaneous  branch  (         ineus  anterior). 


THE  CERVICAL  PLEXUS. 


1285 


•^±;.C^  andThe  aSfer^^^n  "«  Snd?  of  the  anterior  ..rima^ 
^ST^  -STmu^^  ierivrtheir  nerve-  •  "  "  fro...  both  .he  antenor  and  the 
poaterior  primary  divisions. 

THE  CEk  NERVES. 

^;S^:  TSc  J-CKument    and  diaph^^^  T^^^  ,='0.^  .^d 

fourth  c^nmumcatejrcdy  and  fo^^  ^^fP  jli,,,  ,he  fifth. 

*"l"':i.„^h  and  eSh°h  aid^^y  STfirst  and  sometimes  by  the  second  th«jracic 
form  U^  Sl;;*"/?^!^!^;   which  Wl-  the  upper  extrem.ty  and  the  Uteral 

thoracic  wall. 

THE  CERVICAL  PLEXUS. 

Th,  «rvical  Dlexus  (plexo*  cervicalta  )  is  formed  by  the  union  of  the  anterior 
priml^  dSiTn  «iJ^)  of  the  upper  four  cerv.cal  nerve,  (F.g.  to86). 
After    traversing    the  p,„    n^. 

intervertebral  foramina, 
they  pass   behind  the 
vertebral    artery    and 
emerge,    the   first   be- 
tween the  recttM  capiUs 
lateralis  and  the  rectus 
capitis    anticus    minor 
muscles,  and  the  others 
first  between  the  inter- 
transversales      muscles 
and  then  between  the 
rectiu    capitis    anticus 
major  and  scalenus  me- 
dius  muscles.     Each  is 
joined  bjr  a  gray  ramus 
communicans,    derived 
either  from  the  superior 
cervical  ganglion  of  the 

sympathetic    or    from 

the  association  cord  be- 
tween the  superior  and 

middle  cervical  ganglia. 

Under    cover    of    the 

stemo-mastoid  the  four 

nerves  are  connected  to 

form  the  cervical  plexus. 

The  second,  third  and 

fourth  each  divide  into 

an    ascending    and     a 

descending  branch ;  the 

first   does  not   divide. 


Dimgnm  lllostralint  plan  of  cervical  plexus. 


first   does   not    divide.  :rr«nilar  series  of   loops  that  constitute  the 


1286 


HUMAN  ANATOMY. 


and  the  diaphragm,  whilst  others  communicate  with  the  ninth,  eleventh  and  twelfth 
cranial  and  the  sympathetic  nerves. 

The  Cervical  Pi.Exrs. 


Superficial  Branches. 

A.  Ascending  branches  : 

1.  Small  occipital 

2.  Great  auricular 

B.  Transverse  branch  : 

3.  Superficial  cervical 

C.  Descending  branches  : 

4.  Suprasternal 

5.  Supraclavicular 

6.  Supraacromial 


II.     Deep  Branches. 

D.  External  branches  : 

7.  Muscular 

8.  Communicating 

E.  Internal  branches  : 

9.  Muscular 

10.  Phrenic 

11.  Communicating 


I.  The  superficial  branches  are  purely  sensory-.  They  become  superficial 
at  the  postti  ior  border  of  the  stemo-mastoid,  slightly  above  its  middle,  and  from  that 
point  radiate  in  all  directions  to  reach  their  cutaneous  destinations  (Fig.  1087). 

I.  The  small  occipital  nerve  (n.  occipitalis  minor)  (Fig.  10S7)  may  be  either 
single  or  double.  It  originates  from  the  second  and  third  cervical  nerves,  or  from 
the  second  only,  and  passes  backward  and  upward  beneath  the  deep  fascia  along  or 
overlapping  the  posterior  border  of  the  stemo-mastoid  muscle,  where  it  gives  of!  (a) 
the  cervical  branches.  It  pierces  the  deep  fascia  at  the  upper  angle  of  the  occipital 
triangle  and  breaks  up  into  its  terminal  branches  :  {b)  the  auricular,  (<•)  the  mastoid 
and  (</)  the  occipital . 

a.  The  cervical  branches  are  tiny  twigs  which  supply  the  skin  over  the  upper  part  of  the 
occipital  triangle. 

b.  The  auricular  branch  supplies  the  integument  over  the  cranial  aspect  of  the  posterior 
part  of  the  pinna. 

c.  The  mastoid  branch  supplies  the  scalp  overlying  and  above  the  mastoid  process. 

d.  The  occipital  branch  is  distributed  to  the  area  of  scalp  of  the  occiput  lying  between  the 
mastoid  process  and  the  distribution  of  the  great  rccipltal  nerve. 

The  small  occipital  communicates  with  the  posterior  and  great  auricular  nerves  and  with 
the  great  occipital. 

Variations. — ^The  small  occipital  varies  in  size  and  mav  be  so  small  as  to  be  distributed 
only  to  the  integument  in  the  neck.  In  such  an  event,  and  usually  in  case  of  any  deficiency, 
the  unsupplied  area  receives  fibres  from  the  great  occipital.  It  sometimes  passes  backward 
instead  of  upward  and  pierces  the  trapezius  near  the  upper  border  before  reaching  the  scalp. 

3.  The  great  auricular  nerve  (n.  auricularis  maenus)  (P'ig.  1087)  is  the  larg- 
est of  the  superficial  set  and  arises,  usually  with  the  superficial  cervical  ner\'e,  from 
the  second  and  third,  from  the  third  alone,  or  from  the  third  and  fourth  cervical 
nerves.  Turning  over  the  posterior  margin  of  the  stemo-mastoid  it  ascends  toward 
the  ear  between  the  platysma  and  the  deep  fascia.  Below  the  ear  it  gives  off  a  few 
{a)  facial  twigs  and  then  terminates  by  dividing  into  (^)  auricular  and  (f)  mastoid 
branches. 

a.  The  facial  twigs  pass  through  the  parotid  gland  and  over  the  angle  of  the  mandible, 
supplying  the  integument  over  the  parotiil  gland  and  masseter  muscle  and  communicating  with 
the  cervico-facial  division  of  the  seventh  cranial  nerve. 

b.  The  auricular  branches  ( r.  anterior )  supply  mainly  the  cranial  surface  of  the  posterior 
part  of  the  pinna.  One  filament  passes  tlirough  the  cartilage  by  means  of  a  cleft  between  the 
concha  and  the  antihelix  and  supplies  the  outer  surface,  while  a  few  twigs  are  distributed  to  the 
outer  surface  of  the  lobule.  The  auricular  branches  inosculate  with  the  small  occipital  and  pos- 
terior auricular  nerves. 

c.  The  mastoid  branch  ( r.  posterior)  is  distributed  to  the  skin  overlying  the  mastoid  process 
and  the  upper  part  of  the  stemo-mastoid  muscle.     It  inosculates  as  does  the  auricular  branch. 

Variation.—  The  mastoiil  branch  may  arise  independently  from  the  plexus  and  pass  upward 
to  its  destinatic    Ix  'ween  the  small  occipital  and  great  auricular  nerves. 


THE  CERVICAL  PLEXUS. 


1287 


3    The  .uperfici.1  cervical  nerve  (»   ™^-- ^l^hW  ^^f- ^-rt*^^ 
„o„U  the  g^t  auricular  from  th^""^,^,"^  t"l^^^^^^^^^ 

FliJ.  1087, 


Supf«orUul  Bcrvt 
Supratrochlear 


Tempunl  branch  of  bctal 


InfriorbiUl 
brantii  uf  ftcial 


'Buccal  branch 
offtKlal 

'Conmunicatioa  with 
bucral  hraach  of 
tnKDdibulai 
Suptamandibular 
bnach  at  fiicUl 


1 1  nframaatiaMiUr  bra&ch 
•J  of  facial 

SupTfidal  cenlcal  nenra 


'ttuperikUl  dMcending  braach 
^vfKMWraal  branch 


and  (/>)  a  /ower  set  of  branches. 

a.  The  upper  branch..  ( rr.  ,up.r.or«.)  fonn  an  «'X' o,it"ZfalK^^^^^^^^^^ 
ubr  branch  -fTe  facial  nerve,  »«'«;.  ^'"tlnd^'s'hruJasteTerioma^^^^^      the  mandible. 

of  the  iQwer  part  of  the  neck  to  the  mid-hne  as  tar  down  a»  llie  sternum. 


1388 


HUMAN  ANATOMY. 


Variation. — The  superficial  cervical,  instead  of  a  single  nerve,  may  arise  as  two  or  more 
filaments  from  the  cervical  plexus. 

The  descending  branches  (nn.  snpraclavictilares)  (Fig.  1A89)  arise  from  the 
third  and  fourth  cervical  nerves  and  pass  downward  in  the  anterior  margin  of  the 
occipital  triangle  along  the  posterior  edge  of  the  stemo-mastoid.  On  nearing  the 
clavicle  they  break  up  into  three  distinct  ;ets :  (4)  the  suprasUmal,  (5)  the  supra- 
clavicular and  (6)  the  supraacromial. 

Fig.  1088. 


Third  occipital  nerve  ^ 
Great  ocdpitat  nerve 

Bmndi  from  III.  cervical, 
donat  diviaion 


Branches  trom  IV.  cer- 
vical, donal  division 


Inosculation  between  facial  nerveand 
■mall  occipital  and  great  auricular 


Stemo-cleido-mastoid  muscle 

Great  auricular  nerve 
Small  occipital  nerve 

,  Superficial  cervical  nerve 
flnperilclal  descending  branch  of  cervical  plezuH; 
the  leader  crosses  the  suprasternal  brsncn 
^~^n«l  accessory  nerve 
Moacnlar  branch  to  trapezius 

branches 
Supraacromial  branches 


Dinection  showing  superficial  (^.anchcs  o(  cervical  plexus  and  posterior  cutaneous  branches. 

4.  The  suprasternal  branches  (rr.  supraclaviculares  anteriores)  are  the 
smallest.  They  pass  over  the  lower  end  of  the  stemo-mastoid  and  the  inner  end  of 
the  clavicle  and  supply  the  skin  of  the  chest  as  far  down  as  the  angulus  Ludovici. 
One  or  two  filaments  terminate  in  the  sterno-clavicular  articulation. 

5.  The  supraclavicular  branches  (rr.  supraclaviculares  mcdii)  pass  across 
the  middle  of  the  clavicle  and  supply  the  integument  of  the  chest  as  far  down  as  the 
third  or  fourth  rib,  inosculating  with  twigs  from  the  anterior  cutaneous  branches  of 
the  upper  thoracic  nerves 


Variation. — A  twig  may  perforate  the  clavicle. 


THE  CERVICAL  PLEXUS. 


1289 


fi  The  •uor.acromial  branchei  (rr.  wpnidaviailares  poateriorw)  cross  the  da- 

,„d  P^te^or  assets  of  the  sh^^^^^^^^^  ^^  ^^P^       -^^^Ki 

Both  arisUig  beneath  the  stemo-mastoid.  the  former  pass  away  from  and  the  latter 
toward  t^ -^^,"J- °'.?„^^^^^^^^  are  distributed  as  foUows:- 

,„.^xr=:::?in=:^tir^t^:^s^^ 

««no-mMtoid  plexus  p.e.  ,089.  \ 


MitfCuUrbvt.  10  compleaui  aiid 

Wvtatcr  from  occlp.  »^|or 

Third  ocdpitri  »ef  »• 

Fascial  ««ptui«  from  Hg»m«rtB«  nvt^m 
Gnat  occipital  oerrt 
Ractui  capMt  pnrticu 

Branch  to  obliquua 

Sfriacof  lI.carTkatT«rt<kn 

Cutaaaouabr.  ftwn  IH.  carrfcal 

Partofcomple«t»wi«h*''«'*'*' 

Third  ocdpltal  nerve 

Branch  to  corapleiua  from  II.  cerrtcal 

Bnnch  to  compleaua  ttom  III.  carrkal 


Intamal  br.  donal  dlvMon  o* 
Vl.carvicalnarve 

Vll.  cervical, dorsal  divUion 
Vin.  cervical,  dontl  dlviilon 
Intemal  br.  of  poal.  div.  of  V.  cwvical 

SiiinoiM  proGcas  oC  VI I .  cer»i'»l 


Obllquus  su|«riur 

Transverse  proirss 

of  atlas 

AnI.  dt*l*loB  I.  Lervi- 
,c«l.  ciitantous  l».    « 

dorsal  dlvltloa  pnsslnft 
II.  cervical  ner^e.^orsaldivirton       bKkward 
Levator  anguli  acapute 
.  Bnacfa  to  trachdo-maMoid 
III  carvical  nerve,  donal  diviakm 
ConS^Stia.  htiween  II.  and  U}-^^  *^'*t^* 
e!S^  brt.  of  III.  cervl<:al;do«l  dIvW  « 
IV.  canrtcal  nerve,  dorsal  dtviaion 
But.  bmndi  of  dorsal  rtWslon  V.  cervkal  nen« 


thoracic  veflei>ia 

Transverse  profew  II.  thoratic  vertcbrft 

I.evatar  anguH  Kapul^i; 

Trapezius 


Di«e.lio„  ol  right  »ld.  of  ■.«k,  Aowin,  d^r  retatlon.  »l  cmical  n«v». 

*.  The  «.p.«iu.  receives  fibres  from  t'ie^;;|^'^i  ^^.^  ".^^^^^^^^ 
and  acr.,mpany  the  descendmp  b™"f «  «   ^^e  supeM  ^t  tn^^^^^^^  ^^^    '^^^^  ^  ,^^,^ 

wHich^fiUmentsa^d^.^^^^^^^^ 

""''°j:?he":c'L«u.m.diu.and(.).c.l.nu.po«ticu.alsoreceivefibresfromthethir^ 

8.  The  communicating  branches  form  P«i"ts  of  contact  -^  "">-  J^ 

- ^rld-™he^air1;  ta-7;S  i^^^ 
stemo-mastoid  and  subtrapezial  plexuses. 


I390 


HUMAN   ANATOMY. 


9.  The  muscular  branches  are  dbtributed  to  (a)  certain  prevertebral  muscles 
and  to  {6)  the  genio-hyoid  and  the  infrahyoid  muscles. 


a.  The  rectus  capitis  amicus  major  and  minor  and  the  rectus  capitis  lateralis  are  supplied 
by  a  iilament  arising  from  the  loop  between  the  first  and  second  cervical  nerves.  The  intertrans- 
versales,  the  longus  colli  and  a  portion  of  the  rectus  capitis  anticus  major  receive  their  supply 
from  the  second,  third  and  fourth,  and  the  upper  part  of  the  scalenus  anticus  receives  a  twi^ 
from  the  fourth  cervical  nerve. 

6.  The  genio-hyoi<^  ^d  the  four  muscles  of  the  infrahyoid  group  are  innervated  by  the 
cervical  plexus  in  a  rather  roundabout  manner.  From  the  first  and  second  cervical  nerves  are 
given  off  one  or  more  branches  which  join  the  hypoglossal  nerve  shortly  after  its  appearance  in 
the  neck.  These  fibres  for  a  time  form  an  integral  portion  of  the  hypoglossal  and  eventually 
escape  from  it  as  the  nerve  to  the  genio-byoid,  the  nerve  to  the  thjrro-hsroid  and  the  n.  descen- 
dens  hypoglossi  (Fig.  1082).  The  last-mentioned  nerve  leaves  the  hypoglossal  at  the  point 
where  the  latter  crosses  the  internal  carotid  artery  and  then  descends  in  the  anterior  cervical 
triangle.  In  front  of,  or  sometimes  within,  the  carotid  sheath  it  forms  a  loop  of  communication, 
called  the  hypoglossal  loop  or  ansa  eervicalis  (anca  hypoglossi)  by  inosculation  with  the 
descending  cervical  nerve  (n.  deaceadens  eervicalis)  (Fig.  1082).  This  descending  cervical  nerve 
is  derived  from  the  second  and  third  cervical  nerves  and  at  first  consists  of  two  twigs  which  later 
unite  in  front  of  the  internal  jugular  vein.  From  this  point  it  passes  downward  and  inward  as  a 
single  trunk  to  reach  its  point  of  entrance  into  the  ansa  hypoglossi.  The  ansa  may  be  either  a 
simple  loop  or  a  plexus  and  is  situated  anterior  to  the  carotid  sheath  at  a  variable  point  in  the 
neck.  From  it  branches  are  given  off  to  the  stemo>hyoid,  the  stemo-thyroid  and  the  posterior 
belly  of  the  omo-hyoid  (Fig.  1076). 

10.  The  phrenic  nerve  (n.  phrenicus),  although  an  internal  muscular  branch 
of  the  cervical  plexus,  is  of  such  importance  as  to  merit  a  separate  description. 
Whilst  mainly  the  motor  nerve  to  the  diaphragm,  it  contains  some  sensory  fibres  ;  in 
this  connection  it  may  be  pointed  out  that  the  phrenic  is  not  the  only  motor  nerve 
to  the  diaphragm,  the  lower  thoracic  nerves  aiding  in  its  innervation.  The  phrenic 
arises  mainly  from  the  fourth  cervical  nerve  but  receives  additional  fibres  from  the 
third  and  fifth  (Fig.  1090).  It  passes  down  the  neck  on  the  scalenus  anticus,  which 
it  crosses  from  without  inward,  and  at  the  base  of  the  neck  accompanies  that  muscle 
between  the  subclavian  artery  and  vein.  At  the  entrance  to  the  thorax  it  passes 
over  the  root  of  the  internal  mammary  artery  from  without  inward  and  backward, 
occupying  a  position  behind  the  stemo-davicular  articulation  and  the  point  of  junc- 
tion of  the  subclavian  and  internal  jugular  veins.  It  then  follows  a  course  almost 
vertically  downward,  over  the  apex  of  the  pleura  and  through  the  superior  and 
middle  mediastina,  to  the  upper  surface  of  the  diaphragm. 

The  right  phrenic  (Fig.  1090)  is  shorter  than  the  left  on  account  of  its 
more  direct  downward  course  and  the  greater  elevation  of  the  diaphragm  on 
that  side.  It  crosses  the  second  part  of  the  ~  -bclavian  artery  and  accompanies 
the  right  innominate  vein  and   the  superioi  cava    on    tlieir   lateral    aspert. 

It    then    passes  in  front  of  the  root  of  th«  and  finishes  it*   course  by  de- 

scending between  the  lateral  aspect  of  the  pt  lum  and  the  .  -   'astinal  pleura. 

Nearing  the  diaphragm  it  breaks  up  at  the  antero-lat»ral  asjject  of  the  quadrate 
foramen  into  its  terminal  branches,  a  few  of  which  enter  the  abdomen  through 
this  opening. 

The  left  phrenic  (Fig.  1090),  having  to  wind  around  the  left  side  of  the 
heart  and  reach  the  more  inferior  half  of  the  diaphragm,  is  longer  than  its  fellow, 
about  one-seventh  longer  (Luschka).  Entering  the  thorax  between  the  subclavian 
artery  and  the  left  innominate  vein  it  crosses  the  anterior  face  of  the  left  vagus  ner\e 
and  continues  its  downward  course  by  passing  over  the  left  side  of  the  aortic  arch. 
Reaching  the  middle  mediastinum  it  courses  in  front  of  the  root  of  the  lung,  behind 
the  lower  left  angle  of  the  pericardium,  and  descends  to  the  diaphragm  between  the 
pericardium  and  the  mediastinal  pleura.  It  breaks  up  into  its  terminal  branches 
before  arriving  at  the  thoracic  surface  of  the  diaphragm,  which  it  enters  at  a  point 
further  frt)m  the  median  line  and  more  anterior  than  d-'ws  tho  right. 

Branches  of  the  phrenic  nerve  are  :  («)  the  p/eura/,{6)  the  pericardiac  and 
(f)  the  terminal. 


S5S 


THE  CERVICAL   PLEXl'S. 


1391 


Th-  „i«ir.lbnnche«   two  in  number,  are  almost  microscopic  in  size,  and  are  given 

tinal  pleura.  Mricardlacii.^  is  a  tiny  filament  which  is  usually  given  off 

the  t«^'^^-^^  ^^^,„,v  divides  antero-lateral  to  the  opening  for  the  inferior  vena  cava  mto  (<.<,) 
an  anterior  and  (A*),  a  R<«t«i°'^,'^^-  ^^^„  the  pleura  into  five  or  six  fine  twigs,  which  spread 
out  j:^:.::^^n'^^r::^T^r:LZ^TJn.,or  ^n  ^  ...  right  costal  portion  of  the 


Fig.  1090. 


ScBieniw  mediiM  mutel 
Vagus  ne 
V.  cervical  nerve' 
Scalenus  amicus  muscle- 
rnper  trunk  of  brachial  plema 
VII.  cervical  nerve 
Superior  intercostal  artery' 
VIII.  c«ivic«ii»itT«  — —  =■" 

I.  thoncic  nerre-  - 

Clavicle;: — — jv. 

phrenic  nerve 

Internal  mam*  —  _ 
mary  artery 


I  nnomlnate  vdM  "^ 

Yen*  c«v»  supetioi  — 

Uimg,  mcalal  lurlics 


^StenKxleidtvinastoid 

Vagus  nerve 
Internal  jugular  vein 
SubclaWan  artery 
Omo-hyoid  muscle 
Subclavian  vein 
Clavicle 

'SubcUvtusmoKte 


Lrib 


Pericardium  - 


lluutwliint  Mrml 
Vagus  nerve 

Phrenic  nerve 


Lunic,  mesial  uiriace. 
thowiniE  hilum 


_  IV.  rib 


Diaphragm,  up- 
t>er  surface 

VII.  rib 


Oissecion-iowlngphrenic  nerve..  P.pj---";--Jiil|S;X '«»—«' '  lung,  are  pun«i  aside; 

KhraVI.  and  to  the  fnlcifonn  lipment  of  the  liver  in  the  J-^J^  °*;'^^;,^^'  ^^^^  quadrate 

abdominalis  dexter ).    The  former  supplies  «"^  '""""r  J""'""  ^^....ent  branch  which  accompanies 
The  latter  traverses  the  quadrate  foramen  and  firstpvesoffarecurre^^^ 

the  inferior  vena  cava  back  to  the  right  auricle.    Aler  giving  oflth^s  branch  un^^ 

peritoneum  some  of  its  fibres  «"»«' ^t'''-^*''"''       ZroMhe  diaehrar^^        dUphr.gm.tic 


139* 


HUMAN  ANATOMY. 


laUral  bratuh  supplies  the  corresponding  part  of  the  left  costal  portion.  The  posterior  branch 
(r.  phreniCMbdcminalii  liiiiiUr)  is  distributed  to  the  left  lumbar  portion  of  the  mus'-le  of  the 
diaphragm  and  usually  either  a  filament  passes  to  the  left  semilunar  ganglion  or  seve.-al  small 
threads  to  the  coeliac  plexus,  one  of  which  can  be  traced  to  the  left  suprarenal  body. 

The  phrenic  nerve  communicate*  in  the  lower  part  of  the  neck  with  the  middle  or  inferior 
cervical  ganglion  of  the  sympathetic.  At  the  inferior  aspect  of  the  diaphragm  it  communicates, 
on  the  right  side,  with  the  diaphragmatic  plexus  of  the  sympathetic  and,  on  the  left  side,  with 
the  semilunar  ganglion  or  the  cceliac  plexus. 

Variations.— The  phrenic  may  receive  additional  roots  from  the  nerve  to  the  subclavius, 
the  nerve  to  the  stemo-hyoid,  the  second  or  the  sixth  cervical  nerve,  the  n.  descendens  cervi- 
calis  or  the  ansa  h)rpoglossi.  It  may  arise  exclusively  from  the  nerve  to  the  subclavius  or,  aris- 
ing normally,  may  give  a  branch  to  that  muscle.  It  sometimes  passes  along  the  lateral  border 
of  or  pierces  the  scalenus  anticus  muscle.  Instead  of  descending  behind  the  subclavian  vein  it 
may  pass  anterior  to  it  or  even  through  a  foramen  in  it.  . 

The  accetsory  phrenic  nerve  anses  either  from  the  fifth  alone  or  from  the  fifth  and  sixth 
cervical  nerves  and,  entering  the  thorax  either  anterior  or  posterior  to  the  subclavian  vein, 
joins  the  phrenic  at  the  base  of  the  neck  or  in  the  thorax. 

II.  The  eommunieating  branches  of  the  internal  set  effect  unions  with  (a)  the  sympathetic, 
ifi)  the  vagus  and  (<-)  the  hypoglossal 

a.  The  tuperior  cervical  ganglion  of  the  aympathetic  or  the  association  cord  connecting 
the  superior  and  middle  ganglia  sends  gray  rami  communicates  to  the  first,  second,  third  and 
fourth  cervical  nerves. 

b.  The  ganglion  of  the  trunk  of  the  vagus  is  sometimes  connected  by  means  of  a  tiny 
nerve  with  the  loop  between  the  first  and  second  cervical  nerves- 

c.  The  hypoglossal  nerve  receives,  just  below  the  anterior  condyloid  foramen,  a  good 
.si?  A  branch  from  the  loop  between  the  first  and  second  cervical  nerves.  This  communication 
f;  mishes  sensory  fibres  to  the  hypoglossal  nerve  which  subsequently  leaves  the  latter  as  its  men- 
ingeal branch  ;  other  spinal  fibres  leave  the  twelftii  as  the  n.de£cendens  hypoglossi  and  as  the 
nerves  to  the  genio-hyoid  and  thyro-hyoid  muscles. 

Practical  Considerations. — Of  the  motor  nerves  of  the  cervical  plexus  the 
phrenic  is  most  commonly  the  seat  of  trouble  and  this  may  result  in  or  be  associated 
with  spasm  or  paralysis  of  the  diaphragm.  The  involvement  of  the  diaphragm  may 
be  part  of  a  progressive  muscular  paralysis,  as  from  lead  poisoning,  or  from  injuries 
or  diseases  of  the  spine.  The  nerve  may  be  compressed  by  tumors  or  abscesses  of 
the  neck,  or  be  injured  in  wounds  of  the  neck.  It  passes  downward  under  the  stemo- 
mastoid  muscle  and  on  the  scalenus  anticus,  from  about  the  level  of  the  hyoid  bone. 
It  is  covered  and  somewhat  fixed  by  the  layer  of  deep  fascia  covering  the  scalenus 
anticus  muscle.  The  clonic  variety  of  spasm,  singultus  or  hiccough,  is  very  common, 
and  is  occasionally  though  rarely  dangerous  by  preventing  rest  and  sleep  ;  it  may 
complicate  apoplexy,  peritonitis  or  chronic  gastric  catarrh. 

If  only  one  phrenic  is  paralyzed  the  disturbance  of  function  is  slight  and  not 
easily  recognized.  In  a  bilateral  paralysis,  as  from  alcoholic  -.leuritis,  respiration 
depends  almost  entirely  on  the  intercostal  muscles,  since  the  diaphragm  is  completely 
paralyzed.  Dyspncea,  therefore,  occurs  on  slight  exertion.  The  epigastrium  is 
depressed  rather  than  prominent  and  the  lower  border  of  the  liver  is  drawn  upward. 

The  superficial  branches  of  the  cervical  plexus  emerge  together  through  the  deep 
fascia  near  the  middle  of  the  posterior  border  of  the  sterno-mastoid  muscle,  and  from 
this  point  pass  in  various  directions.  The  auricularis  magnus  passes  upw;ard  and 
forward  over  the  sterno-mastoid  to  the  ear  and  parotid  gland,  the  occipitelis  minor 
along  the  posterior  margin  of  the  same  muscle  to  the  scalp,  and  the  superficial 
cervical  branch  obliquely  forward  and  upward  to  the  submaxillary  region.  The 
descending  branches  are  three  in  number  and  {)ass  respectively  in  the  direction  of 
the  sternum,  clavicle  and  acromion.  They  gi\e  rise  to  little  or  no  disturbance 
when  wounded. 

THE  BRACHIAL  PLEXUS. 

The  brachi.^1  plexus  (plexus  brachialis")  is  a  somewh.at  intricate  interlacement  of 
the  anterior  primary  divisions  of  usually  the  lower  four  cervical  and  first  thoracic 
iier\'es.  To  these  are  sometimes  added  a  branch  from  the  fourth  cervical,  a  branch 
from  the  second  thoracic,  or  branches  from  both  of  these  nerves.     The  fasciculi  form- 


THE  BRACHIAL  PLEXUS. 


"93 


ina  this  Dlexus  emerRe  in  the  interval  between  the  scalenus  amicus  and  medius  and 

rSe.^      Afer  entering  the  axilla'its  component  parts,  whUe  ly'ng  nia.nly  to  the 

™i»  mEfSyrnd  before  dl,idmB>.o  iu  te™in.l  b™ch«  .<  l,e.enclo«<i  be»^ 

thp  nectoralis  minor  and  subscapularis  muscles.  .         ,  ,  _» _i„„-_,„ 

^oStoiion  and  Plan.-In  the  various  weavings  o  the  component  elements 

(Fig.  1091). 


Fig.  1091. 


Diagram  illustratinc  plan  o(  brachial  plexus. 

Emerging  from  the  interval  between  the  anterior  -"^  middle  s^enem^^^ 
than  the  otha«  because  the  first  thoracic  nerve  sends  ^^^^^X  f  ^^j^"  iiffe?Sy  to 


"<*4 


HUMAN   ANATOMY. 


'  -^^B 

;  -'^^^B^ 

'  .:i:' 

1:1 

ittl^l^H: 

iM£ 

^hH! 

their  position  as  regards  one  another,  while  the  cords  are  denominated  according  to 
their  relation  to  the  axillary  artery,  the  outer  lying  lateral  to,  the  inner  mesial  to,  and 
the  posterior  behind,  the  artery. 

V«ri«tion«.— Considerable  variety  exists  as  regards  the  length  of  the  component  nerve- 
bundles  in  their  several  portions,  division  and  union  taking  place  at  difierent  levels  in  dinerent 
individuals.  The  fifth  cervical  ner%e  may  pass  in  front  of  or  through  the  scalenus  anticus.  The 
sixth  though  not  so  frequentiv  as  the  fifth,  may  traverse  the  scalenus  anticus.  The  seventh 
cervical  nerve,  as  the  middle  trunk,  may  break  up  into  three  branches,  one  going  to  each  of 
the  three  cords.  The  fibres  of  the  posterior  cord  may  arise  from  only  the  seventh  and  eighth, 
or  the  sixth,  seventh  and  eighth  cervical  nerves.  Hlexuses  have  been  seen  m  which  only  two 
cords,  a  smaller  and  a  larger,  were  present,  the  latter  taking  the  place  of  either  the  mner  and 
outer  or  the  inner  and  posterior  cords. 

Communications.— The  five  nerves  comprising  the  source  of  the  plexus  are 
connected  to  the  sympathetic  system  by  gray  rami  communicantes  and  there  is 
|X)ssibly  a  white  ramus  communicans  passing  from  the  first  thoracic  nerve  to  the 
first  thoracic  ganglion  of  the  sympathetic. 

Fig.  1092. 


1.  cervical  nerve 
II.  cervical  nerve  ^^ 
in.  cervical  nerve 
IV.  cervical  nerve 

Vertebral  artery 

V.  cen^cat  nerve 

Scaleniifi  inedius  muKle 

VI.  cervical  nerve 

VII.  cervical  nerve 

VIII.  cervical  nerve 

I.  thoracic  nerve 

External  anterior  thoracic  nerve 

Supcalupulsr  ner,e 
I'pfier  tiilKcapular  nervr 
Outer  cord  of  plcxii> 
Posterior  cord  of  plexus 
Circumflex  ner\'e 
Deltoid  muacle      / 


Median  ner\-e  , 

I'liiar  nen'u  ^ 

MuscuIo-«*piral  nerve         /      , 

Internal  cutaneous  ner\'e       / 

Lesser  internal  cutaneous  ner\*e 


Internal  anterior 
thoracic  nerve 
Insertion  of 
scalenus  anticus 
.Posterior 
thoracic  nerve 

I.  rib 


n.  rib 
Inner  cord  of  plexus 


Middle  suhticapulnr  nerve 
Lower  subscapular  nerve 


Deep  dissection  of  neck,  showing  constitution  of  right  brachial  plexus. 

Practical  Considerations.— Sensory  disturbances  are  rather  rare  in  the 
distribution  of  the  brachial  plexus  of  nerves,  but  motor  troubles  are  comparatively 
common  and  are  sometimes  associated  with  disturbances  of  sensaUon.  The  whole 
plexus,  or  only  an  individual  branch,  may  be  involved.  The  most  common  cause 
IS  iniurv  such  as  dislocation  of  the  head  of  the  humerus,  a  fracture  of  the  clavicle, 
or  a  forced  apposition  of  the  clavicle  to  the  first  rib.  Other  causes  are  the 
pressure  of  tumors  or  the  constitutional  effects  of  poisons  and  infections.  I  he 
plexus  is  so  superficial  above  the  clavicle  that  it  can  be  felt  or  even  seen  in 
thin  people. 

Branches.— These  fall  naturallv  into  two  groups,  those  given  off  from  the 
fupraclavicular  and  those  from  the  infraclavicular  portion  of  the  plexus. 


THE  BRACHIAL   PLEXUS. 


1295 


I.    Supraclavicular  Branches 

,.     Suprascapular  4-      Muscular 


Posterior  scapular 
Posterior  thoracic 


Communicating  to  the  phrenic 
nerve 


II.    Infraclavicular  Branches 


From  Outer  Cord: 

6.  External  anterior  thoracic 

7.  Musculo-cutaneous 

8.  Median  (outer  head) 


H.   From  Inner  Cord  : 

9.     Internal  anterior  thoracic 
ID.   Lesser  internal  cutaneous 

11.  Internal  cutaneous 

12.  Ulnar 

13.  Median  (inner  head) 


C.   From  Posterior  Cord : 

14.  Subscapular 

1 5.  Circumflex 

16.  Musculo-spiral 

I.  The  Supraclavicular  Branchea.-These  are  given  ofi  at  various  levels 
while  the  plexus  is  still  in  the  neck.  „„„,«,iari«^   fFie     10Q2)   arises   from 

,.  The  suprascapular  nerve  (n.  ^-P^f^ff  ^.l/^ 'f ^n^in^  from  the  fifth 
the  posterior  surface  of  the  outer  trunk  most  «\ f^^^^^/^'^i^h'^'^rerior  cervical 
cerv  ioTl  nerve  and  the  remainder  from  Je  «.xth  It  trav«s«  U^  l^^^^.j,  y  ^^^ 
triangle  above  the  upper  border  of  the  P!^"^"^^*"^  ""{ .^e^ap^^  it  passes  through 
trapezius  muscles.  Reaching  the  superior  3"  fj^^f^f P^fj  ^mers  the  supra- 
the%rascapular  notch,.under  the  supras^puW^^ 

spinous  fossa.  After  giving  off  a  branch  forthe  ^"PP'^  *"^  ,  J  u^ment  of  the 
Ia  a  tiny  filament  to  *e  jH,.tmor  j^rUon  d  ^^^^  f^^^  ^^^ 

shoulder,  It  passes  through  the  g'^^!^*?""'!!^!^^^  "{ the  infripinous  fossa,  the 
scapular  artery  and  van.  Having  become  »"  *^P*"|  ?^  „"  ^  "branch  to  the 
ner^e  supplira  the  infraspinatus  muscle  and  often  gives    ott  a   orancn 

shoulder  joint. 

V«i.tion..-It  may  receive  additional  fibres  f™-"  ^Vou^h  cem-  '  ""es■m^no^or^^h^ 
entirelyTrom  ?he  fifth.    X  rare  anomaly  is  'he^PvineofloU  branch  to ^.         es  m^^^  ^^^^^.^ 

posterior  thoracic  nerve,  rom  the  dorsal  ^  -toSes  downward  and  backward 
Traversing  the  substance  of  the  «:alenus  medius  it  P»^^  *?™'p  ^^^.^^e  of  the 
toward  the  vertebral  border  of  the  scapula.  >•"«  "P^^'^'fi^i^S  "the  levator 
levator  anguli  scapulae  and  the  '>^«"^bo.de..     It  supphes  a  h  amemj^  ^.^^^ 

5Son;?t:r2- ^^^^^^^^^^  --  -' 

minor  muscles. 


Variation.— It  may  pierce  the  levator  anguli  scapula;. 


,    The    posterior    thoracic    (n.   thoracaUs   Iohrus)     also   called    the   lo;;^ 
=t"a1S«Kirirr?i5T'tnSSnT.r„i«a  ,he  „e,v.  descend,  on 


1396 


HUMAN  ANATOMY. 


the  inner  wall,  lying  posterior  lo  the  brachial  plexus  and  the  axillary  veasela,  and  upon 
the  lateral  aspect  of  the  serratus  magnus.  It  gives  ofi  successive  tw.gs  to  the  digita- 
tions  of  the  last-named  muscle,  which  alone  it  supplies  The  fibres  derived  «rom  the 
fifth  cervical  nerve  supply  the  upper  par,  those  from  the  sixth  the  middle  and  those 
from  the  seventh  the  lower  part  of  the  muscle. 


V«fimtk>M.-The  contribution  from  the  fifth  nerve  sometimes  fails  to  join  the  main  nerve 
»■*»■•""■•     *"."■   ....  -L    1:_;.-.: — .     T-k.  ..^^t  <r..m  the  seventh  nerve 

nerve. 


V«fimtk>ns.-The  contribution  from  the  mth  nerve  somenmes  laus  lo  join 
and  goes  directly  to  its  distribution  to  the  upper  digitations.  .The  root  from  Ui 
inay^nbsent    An  additional  root  may  be  contributed  by  the  eighth  cervical  i 


Practical  Conaiderations.— The  posterior  thoracic  nerve  may  be  paralyzed 
by  an  injury  in  the  suprascapular  region  or  in  the  axilla,  by  carrying  heavy 
weiehts  upon  the  shoulder,  or  as  a  result  of  infectious  disease,  cold  or  rheu- 
ma&m.  The  most  noticeable  sign  is  a  prominence  of  the  scapula  (winged  scapula), 
from  the  failure  of  the  paralyzed  serratus  magnus  muscle  to  hold  the  vertebral  border 
of  the  scapula  close  to  the  thorax.     That  border  and  the  inferior  angle  project  and 


Fig.  1093. 


AoonW  Mundc  atUir 


CapWk* 


Lcwcr  fnlrnul 

ciitiomiM  nerve' 
Loot  tbotacic  artwy 
iBtCTcMto-humcral  nvt.' 
Subecapulw  aitcrv  ' 

LatfeMiniM  dor<il 
Long  subacapular  nrrve 
fern  major^ 

PoMRfcii  Ihoradc 


Pcdonlin  ntem,  aH 


DiMnrtion  ol  ri«ht  axilta,  •bowins  reUtloni  o(  btmchimi  picxiu  to  blood-vessels. 


become  prominent.  When  the  arm  \i  in  froi:*^  -^f  the  chest  the  deformity  is  most 
marked  and  the  lower  angle  approaches  the  mi  '  ine  of  the  back.  The  patient  can- 
not lift  anything  heavy  with  the  affected  arm.  Since  the  incision  to  open  an  axillary 
abscess  is  made  vertically  in  the  middle  of  the  thoracic  wall  of  the  axillary  space,  to 
avoid  the  vessels  at  its  borders,  this  nerve  is  in  some  danger  as  it  passes  to  the 
serratus  magnus  muscle. 

4.  The  muscular  branches  supply  the  longus  colli,  the  scaleni  anticus, 
medius  and  posticus  and  the  subclavius. 

a  The  longu*  colli  and  »c«lenu»  anticut  are  supplied  by  small  twigs  which  arise  from 
the  anterior  surface  of  the  lower  four  cervical  nerves  as  they  leave  the  vertebral  column. 

6.  The  scaleni  medius  and  potticua  receive  fibres  given  of!  from  the  posterior  aspect  of 
the  lower  four  cervical  ner\'es  as  they  pass  through  the  inter\'ertebral  foramina. 

c  The  nerve  to  the  lubcUvius  (n.  sabclavius)  takes  its  origin  from  the  outer  trunk  ol  the 
plexus,  its  fibres  coming  mainly  from  the  fifth  cervical  nerve.  It  passes  through  the  subclavian 
triangle,  over  the  third  portion  of  the  subclavian  artery  and  behind  the  clavicle,  to  enter  the 
deep  surface  of  the  subclavius  muscle. 


THE  BRACHIAL  PLEXUS. 


1297 


tf..uttiM»«  —The  Dhrenic  ner\'e  may  itive  off  a  branch  to  the  subclavius  or  may  receive  a  fila- 
-^.TrS^SHervVto  th^bctevitts.  A  branch  <A  communication  with  the  external  antenor 
&*n.d  a  Sh  to  the  cUvicX  head  a<  the  stemocleido-nmtoid  have  been  noted. 

s  The  communicating  branch  to  the  phrenic  nerve  (Fir.  1090)  arises 
usually  from  the  fifth  cer^■ical  nerve,  sometimes  from  the  fifth  and  sixth.  OnginatinR 
at  the  outer  margin  of  the  scalenus  anticus  it  passes  mward  and  joins  the  phrenic.  II 
this  nerve  is  not  present  the  nerve  to  the  subclavius  usually  supplies  the  deficiency. 

II  The  Infraclavicular  Branches.— These  branches  comprise  those  Riven 
of!  by  the  three  cords  of  the  plexus  after  the  latter  has  passed  beneath  the  clavicle 
into  the  axilla. 

6.    The  External  Anterior  Thoracic  Nerve. 

The  external  anterior  thoracic  nerve  (n.  thoracalis  anterior  lateralis)  (FiR.  1093) 
receives  its  fibres  from  the  fifth,  sixth  and  seventh  cervical  nerves.  LeayinR  the  outer 
cord  beneath  the  clavicle,  it  passes  mcsially  over  the  axUlary  artery  and,  after  giving 


Fig.  1094. 


Mu»c.ilo-«piraI 
nerv 
Ulnar  nerve 


Lesaer  internal  cntaneon* 
ner^'e 


Common 
carotid  artery 


Phrenic  nem 


Scalenus 
'anticus  moacle 


Internal  cutaneoua  nerve 


Subclavian  artery         Subclavian  vela 


Dissection  o.  right  ..ilia,  showing  relatU™  o^btjchiaj^^exu,  to  subclavian  and  aai.lary  vessel,  , 

of!  a  filament  vi  hich  unites  with  a  similar  structure  from  the  internal  anterior  thoracic 
ner^e  SdiLo  two  branches  which  pierce  the  costo--raco,d  memb^^^^  and  en  e 
the  d^ep  suriace  of  the  pectoralis  major.     The  upper  branch  supplies   he  davicular 
portion'^!  the  muscle  and  the  lower  branch  the  upper  P«>^  °V  .Im^^^E  °^erces 

The  loop  between  the  anterior  thoracic  nerves  gives  off  a  filament  ^hich  p^ercra 
the  pectoralis  minor  and  ends  in  the  sternal  part  of  the  pectoralis  major,  to  both  of 
which  muscles  it  is  distributed. 

V.rUtlon..-This  nerve  may  supply  fibres  to  the  clavicular  portion  of  the  deltoid  and  to  the 
acromio-clavicular  articulation. 

82 


1398 


HUMAN  ANATOMY. 


7.    The  Muscuix)-Cutaneous  Nerve. 

The  musculo-cutaneous  nerve  (a.  niiKiilociiUiicm)  (Fig.  1098)  derives  its  fibres 
from  the  fifth  and  sixth,  and  sometimes  the  seventh,  cervical  ner\-es  and  is  a  branch 
of  the  outer  cord.  The  nerve  to  the  coraco-brackialis  muscle,  derived  from  the  seventh 
or  sixth  and  seventh  nerves,  is  usuall)  <ound  as  an  integral  part  of  it.  Leaving  the 
outer  cord  under  cover  of  the  pectoralis  minor  it  pierces  the  coraco-brachialis  and 
passes  obliquely  downward  and  outward  between  the  biceps  and  brachialis  anticus 
muscles.  Reaching  the  outer  margin  of  the  biceps  a  short  distance  above  the  elbow, 
the  nerve  pierces  the  deep  fascia  and  passes  under  the  median-cephalic  vein.  It  then 
becomes  superficial  (n.  CMtanciM  antebrachii  lateralis)  and  divides  into  its  terminal 
cutaneous  branches. 

Branches. — These  are  :  (a)  the  umsciUar,  (h)  the  humrral,  (<•)  the  articular  and  (</)  the 
ttrtHtnal. 

a.  The  muscular  branchra  supply  the  cor.ico-brachialis,  the  biceps  and  the  brachialis  anticus. 
The  nfn<e  lo  (tie  roraco-ttrarhialU,  which  commonly  has  an  independent  origin,  is  usually  doulilt- , 
one  fil  inient  going  U>  each  portion  of  the  tiuiscle.  The  nerves  to  the  biceps  and  brachialis  anticKs 
are  given  off  while  the  musculo-cuuneous  is  in  transit  between  thuse  muscles. 

b.  The  humeral  branch  accompanies  the  nutrient  branch  of  the  brachial  artery  into  the 
humerus. 

c.  The  articular  branch  aids  in  the  supply  of  the  elbow  joint 

d.  The  terminal  part  (n.  cataoeua  anubracUi  lauralU)  (Fig.  1103)  of  the  musculo-cutaneous 
divides  into  two  branches,  (aa)  an  anterior  and  (M)  a  posterior. 

aa.  The  anterior  branch  descends  in  the  antero-lateral  portion  of  the  superficial  fascia  of  the 
forearm  (Fig.  1104).  It  inosculates  above  the  wrist  with  the  radial  nerve  and  supplies  the  in- 
tegument of  the  antero-lateral  part  of  the  forearm.  It  also  distributes  fibres  to  the  skin  over  the 
thenar  eminence,  to  the  wrist  joint  and  to  the  radial  artery. 

bb.  The  posterior  bran  h  passies  downward  and  backward  and  supplies  the  skin  of  the 
postero-lateral  portion  of  the  forearm  down  to  or  slightly  beyond  the  wrist  joint  (Fig.  1103 ).  It 
inosculates  with  the  radial  nerve  and  with  the  inferior  extenukl  cutaneous  branch  of  &e  musculo- 
spiral. 

Variations.— Instead  of  piercing  the  coraco-brachialis  the  nerve  may  adhere  to  the  median 
or  its  outer  head  for  some  distance  down  the  arm,  and  then  either  as  a  single  trunk  or  as  several 
branches  pass  between  the  biceps  and  brachialis  anticus  muscles.  Sometimes  onl  v  a  part  of  the 
nerve  follows  this  course,  joining  the  main  trunk  aher  the  tatter's  transit  through  the  muscle. 
The  muscular  part  only  or  the  cutaneous  part  only  may  pierce  the  muscle.  The  nerve  may  be 
accompanied  tnrough  the  muscle  by  fibres  of  the  median  which  rejoin  the  latter  below  the 
coraco-brachialis.  The  nerve  may  remain  independent  and  fail  to  pierce  the  coraco-brachialis, 
either  passing  behind  it  or  between  it  and  the  associated  head  of  the  biceps.  It  may  perforate 
not  only  the  cnraco-brachialis  but  also  the  brachialis  antictis  or  the  short  head  of  uie  biceps. 
Rarely  the  entire  outer  cord,  after  giving  off  the  external  anterior  thoracic,  may  traverse  the 
coraco-brachialis.  Anomalies  in  dist...yution  include  a  branch  to  the  pronator  radii  terej,  the 
supply  of  the  skin  of  the  dorsum  of  the  hand  over  and  adjacent  to  the  first  metacarpal  bone, 
a  branch  to  the  dorsum  of  the  thumb  in  the  absence  of  the  mdial  nerve  and  the  givmg  off  cf 
dorsal  digital  nerves  to  both  sides  of  the  ring  finger  and  the  adjacent  side  of  the  little  finger. 

8.     The  Median  Nerve. 

The  median  nerve  (n.  medianus)  (Fig.  1098)  consists  of  fibres  which  can  be 
traced  to  the  sixth,  seventh  and  eighth  cervical  and  first  thoracic  ner\'es.  It  arises 
by  two  heads,  an  outer  and  an  inner,  which  are  derived  respectively  from  the  outer 
Ad  inner  cords  of  the  plexus,  the  former  containing  fibres  from  the  sixth  and 
seventh  cer\'ical  and  the  latter  fibres  from  the  eighth  cervical  and  first  thoracic 
ner\'es.  The  two  heads,  the  inner  of  which  usually  crosses  the  main  artery  of 
the  upper  extremity  at  about  the  point  where  the  axillary  becomes  brachial, 
unite  either  in  front  of  or  to  the  outer  side  of  the  artery.  From  the  point  of  fusion 
of  the  two  heads  the  nerve  passes  down  the  arm  in  close  relation  with  the  brachial 
artery,  usually  lyinj;;  Lateral  or  antero-lateral  to  the  artery  in  the  upjjer  part  of  the 
arm,  and  as  the  elbow  is  neared,  gradually  attaining  the  inner  side  by  crossing 
obliquely  the  anterior  surface  of  the  arter)-  (Fig.  1098).  It  passes  through  the 
cubital  fossa  beneath  the  median-basilic  vein  and  the  bicipital  fascia,  and  enters  the 
forearm  between  the  heads  of  the  pronator  radii  teres  muscle,  the  deep  head  of 


THE  BRACHIAL  PLEXUS. 


1299 


which  ieparatw  the  nerve  from  the  ulnar  artery.     It  follows  a  straiKht  amneikmu 
The  fo^S^  accom,«nied  by  the  median  artery,  lying  upon  the  flexor  prdundu, 

Fio.  1095. 


r«MaM. 


.  Median  nerve 
'  Brachial  artery 

.  Edge  of  Iricepa 


Sop.  ext.  cil<ane<Mi«  »ir.  raiwcuk>«UlraI- 
:nf.  emt.  coUnc«iu«  »ir.  miiacuUwpJtal- 


.UbMr  nerve 

-laferlor  profunda  artery 


>|n«cu!'""'""e""'>  IK  rve,  ant.  a     _ 
poat.  lira. 


MuwuloHipiral  1 

riiBierlor  Interomeooa  neT»«- 

Radiali 
Supinator  bre»ta- 

Pronator  imdii  tr 
Kxtenaor  carpi  nd.  longiat- 
Kxtennor  carpi  rad.  t>re»i<i»» 

Kadial  artery- 
Brachio-radiafli- 
Flexor  »ubl.  diKitomB 
radial  head 

rirxnr  carpi  radialto- 


Median  ner* 


ralinar  cutaneous  br.  of  mediaA- 

Ahductor  polllcia- 
li-Kitiii  lirs.  t>f  median  nerve* 


-BracUalla  aniicu* 

*Bicepa  tendon 

nator  radii  teren.  humeral  head 
-Articniar  branchea  of  median  nenre 


■  Flexor  carpi  radiali* 


-  Flexor  sublimia  digitomm 

-  Ulnar  nenre 

-Ulnar  artery 

-  Flexor  profundus  digitonim 

-  Flexor  carpi  ulnaria 

-  Palmar  cutaneous  br.  of  ulnar 

-DotMl  cntaneouj  br.  of  ulnar  nerve 

-  Flexor  sublimiR  dlgitorum 


.ridfoTm  hone 
-Oeep  br.  of  ulnar  nerve 
-Palmaris  bre\i»,  reflected 
-Abductor  minimi  digiti 

-Flexor  brevi»  minimi  digiti 
^Digital  bra.  of  ulnar  nerve 


0,»ecao„  or  right  upp.rextrem.,^o„mg^.;;^^^-,'S^c.^^^  .n«..,.  n...nt  h.  been 

diritorum   and   covered    by   the   flexor   sublimis   digitorum.      Near   the   wrist  the 
rSr^comes  more  superficial,  with  the  tendons  of  the  flexor  sublime  digitorum 


I300 


HUMAN   ANATOMY. 


and  palmaris  longus  lying  mesial  and  that  of  the  flexor  carpi  radiaiis  lateral  to  it 
(Fig.  1095).  It  passes  into  the  hand  beneath  the  anterior  annular  ligament,  at  the 
lower  margin  of  which  it  spreads  out  into  a  reddish  gangliform  swelling,  which  lies 
upon  the  flexor  tendons.     Below  this  point  it  breaks  up  into  its  terminal  branches. 

Branches. — The  median,  as  is  the  case  with  the  ulnar,  gives  ofi  no  branches 
in  the  arm.  In  the  forearm  the  branches  are  :  (a)  the  arlicular,  (i)  the  muscular. 
(f)  the  anterior  interosseous  and  (d)  the  pa/mar  cutaneous,  and  in  the  hand  :  (e)  the 
muscular  and  {/)  the  digital. 

a.  The  articular  branch  consists  of  one  or  two  tiny  twigs  which  supply  the  anterior  portion 
of  the  elbow  joint. 


Musciilo-spiral  nerve 

Cephalic  vein 

Posterior  interosseous  nerve 

Brachio-radialis  muscle 
Radial  nerW' 

Radial  recurrent  artery- 

Communications  1>etweeQ 

deep  and  superficial 

veins 


Cutaneous  branch  of  musculo- 
cutaneous nerve' 


Radial  vein. 


Radial  artery. 


Fig.  1096. 

Brachial  artery 


Median  nerve 

Brachial  vein 


Tendon  of  biceps 

Internal  cutancou*  nerve 

Bicipital  fascia 
-Median  nerve 

Pronator  radii  tere* 


Superficial  dii^cctlon  ol  right  arm,  showin:  •elalioni  of  nerves  to  blood-vestelt  on  front  of  elbow. 

b.  The  muscular  branchet  (rr.  muKulareti)  (Fig.  1095)  consist  of  a  fasces  of  nerv-e-bundles 
which  arise  from  the  median  a  short  distance  below  the  elbow.  They  are  distributed  to  the 
pronator  radii  teres,  the  flexor  carpi  radialb,  the  palmaris  longus  and  that  portion  of  the  flexor 
sublimis  digitorum  which  arises  from  the  inner  condyle  and  from  the  ulna.  Two  additional 
fllaments  from  the  median  supply  the  flexor  sublimis,  one  entering  the  radial  head  and  the 
other  that  (>ortion  which  flexes  the  index  flnger. 

c.  The  anterior  interosseoui  nerve  (n.  intcromeuR  antebrachii  volaria)  (Fig.  I098)  arises 
from  the  posterior  aspect  of  the  median  a  short  distance  below  the  elbow.  It  passes  down 
the  forearm,  accompanied  by  the  anterior  interosseous  artery,  on  the  anterior  surface  of  the 
interosseous  membrane  between  the  flexor  longus  polllcis  and  the  flexor  profundus  digitorum. 
At  the  upper  margin  of  the  pronator  qimdratus  muscle  it  dips  under  that  muscle  and  continue* 
down  for  some  distance,  Anally  entering  the  deep  surface  of  the  pronator  quadrattis. 


THE  BRACHIAL   PLEXUS. 


1 301 


It  supplies  the  flexor  longus  pollicis,  the  radial  half  of  the  flexor  profundus  digitonim 
ant!  'he  pronator  quadratus.  It  distributes  filaments  to  the  interosseous  membrane,  the  anterior 
intci  isseous  vessels,  the  shafts  of  the  radius  and  ulna  (the  twigs  to  these  bones  entering 
them  with  the  nutrient  arteries) ,  the  periosteum  of  the  radius  and  ulna  and  the  radio-can>al 
articulation. 

d.  The  palmar  cutaneous  branch  (r.  cuUneus  palmarU)  (Fig.  1097)  leaves  the  mechan 
at  a  var>'ing  distance  above  the  wrist.  It  becomes  superficial  near  the  upper  margin  of  the 
anterior  annular  ligament  by  piercing  the  deep  fascia  between  the  flexor  carpi  radialis  and  the 
palmaris  longus.  It  supplies  the  skin  of  the  palm  and  inosculates  with  the  palmar  cutaneous 
branch  of  the  ulnar  and  with  filaments  of  the  radial  and  musculo-cutaneous  nerves. 

e.  The  muscular  branch  in  the  hand  (r.  muscularis)  (Fig.  1097)  is  a  short  ner\'e  which 
arises  below  the  anterior  annular  ligament  and  curves  outward  toward  the  base  of  the  thumb. 
It  breaks  up  into  filaments  which  supply  the  abductor  pollicis,  the  opixinens  pollicis  and  the 
superficial  head  of  the  flexor  brevis  pollicis. 

/.  The  digital  branches  (Fig.  1097)  are  five  in  number  and,  with  the  exception  of 
the  twigs  supplying  the  two  outer  lumbricales,  are  purely  sensor)-.  They  arise  from  the 
median  a  short  distance  below  the  anterior  annular  ligament  of  the  wrist  (nn.  dinitalw  volares 
communes)  and  pass  c'istally  beneath  the  superficial  palmar  arch  and  over  the  flexor  tendons. 
As  they  approach  the  interdigital  clefts  they  pass  between  the  primar\-  divisions  of  the  median 
portion  of  the  palmar  fascia  and  become  more  superficial  as  they  continue  along  the  borders  of 
the  fingers  (nn.  digitales  volares  propril). 

The  ftrst  lies  along  the  radial  side  of  the  thumb  and  inosculates  around  its  radial  asspect 
with  the  radial  nerve. 

The  second  occupies  the  ulnar  side  of  the  thumb. 

The  third  gives  off  a  branch  to  the  first  lumbricalis  and  supplies  the  radial  side  of  the  index 

The  fourth  supplies  the  second  lumbricalis  and  then  divides  into  two  branches  w  hich  are 
distributed  to  the  adjacent  sides  of  the  index  and  middle  fingers. 

The  fifth,  after  being  connected  with  the  ulnar  nerve  by  a  stout  filament  (r.  anastomot- 
icus  cum  n.  aloare),  divides  for  the  supply  of  the  adjoining  aspects  of  the  middle  and  ring 
fingers.  .  j  •.     • 

In  the  fingers  these  nerves  lie  anterior  to  the  vessels  and  in  their  course  toward  the  tip 
of  the  finger  they  give  off  anterior  and  posterior  branches,  the  latter  supplying  the  skin  over  the 
middle  and  distal  phalanges  of  the  index,  middle  and  ring  fingers  and  over  the  distal  phalanx  of 
the  thumb.  Twigs  are  supplied  to  the  interphalangeal  articulations  and  near  the  end  of  the  finger 
each  of  the  five  breaks  up  into  two  terminal  branches,  one  of  which  is  destined  for  the  sensitive 
skin  over  the  anterior  portion  of  the  distal  phalanx  and  the  other  for  the  matrix  of  the  nail. 

Variations.— Some  of  these  are  described  on  page  im8.  The  fibres  usuallj,'  contributed  to 
the  median  nerve  by  the  first  thoracic  may  be  wanting.  Efither  the  outer  or  the  inner  head  may 
consist  of  two  nerve-bundles.  The  point  at  which  the  heads  unite  is  a  very  vanable  one  and 
has  been  found  as  far  down  as  the  elbow.  The  heads  may  enclose  the  axillary  vein  instead  of 
the  arter>'.  In  those  instances,  many  of  which  have  been  found  in  the  anatomical  rooms  of  the 
University  of  Pennsylvania,  in  which  a  .single  large  branch  of  the  axillary  artery  gives  off  the 
two  circumflex  artenes,  the  suliscapular  and  the  two  profunda  artenes,  this  trunk,  instead  of  the 
axillary  artery,  is  embraced  by  the  heads  of  the  median  nerve.  The  inner  hwd,  the  outer  head 
or  the  median  itself  may  pass  behind  the  axillary  artery  instead  of  in  front  The  outer  head  lias 
been  seen  to  arise  in  the  middle  of  the  arm  anci  pass  behind  the  artery  to  join  the  inner  head. 
One  instance  has  been  reported  in  which  the  median  entered  the  forearm  over  the  pronator  radii 
teres  instead  of  between  the  heads  of  that  muscle.  It  has  been  seen  lying  on  the  superficial 
surface  of  the  flexor  sublimis  digitonim.  The  median  may  be  cleft  for  a  short  distance  in  the 
forearm,  giving  passage  to  the  ulnar  artery  or  one  of  its  branches,  to  the  su|jerficial  long  head 
of  the  flexor  longus  pollicis  or  to  an  extra  palmaris  longus  muscle.  A  communication  m  the 
arm  between  the  median  and  ulnar  nerves  has  been  noted  in  one  instance.  A  similar  connectum 
in  the  forearm,  occurring  in  numerous  ways,  is  found  in  from  ao-as  per  cent,  of  cases  examined. 
A  connection  with  the  ulnar  in  the  hand  may  pass  either  from  the  ulnar  to  the  median  or  from 
the  median  to  the  ulnar.  The  anterior  interosseous  has  been  seen  to  receive  a  filament  Irom 
the  musculo-spiral  through  the  interos.seous  membrane,  and  inosculation  lietween  the  two 
interos.seous  ner\es  has  been  noted  at  the  lower  part  of  the  forearm  ;  according  to  Kaiiber, 
this  is  the  normal  arrangement  One  case  has  been  described  m  which  the  abductor  indicis 
was  supplied  by  the  median.  Fhiring  the  exchange  of  position  between  the  digital  bran^ 
of  the  median  nerve  and  the  digital  arteries  the  former  are  often  pierced  by  the  latter.  I  he 
fifth  digital  branch  may  arise  in  the  forearm  and  enter  the  hand  independently. 

Practical  Considerations. — A  pure  paralysis  of  the  median  nerve  is  rare,  and 
is  almost  always  traumatic  in  origin.  The  paralysis  is  more  commonly  a  part  of  a 
more  extended  invlvcment  of  the  brachial  plexus.  When  this  nerve  is  paralyzed 
above  there  is  inabi.ity  to  pronate  the  forearm  or  flex  the  wrist  properly,  smce  the 


1302 


HUMAN   ANATOMY. 


pronators  and  all  the  flexors  except  the  flexor  carpi  ulnans  and  the  ulnar  half  of  the 
flexor  prohindus  digitorum  are  supplied  by  it.  The  second  phalanges  of  the  middle 
and  index  fingers  cannot  be  flexed,  although  the  first  phalanges  can  be  flexed  and 
the  second  and  third  extended  in  all  the  fingers  through  the  interossei  muscles  ; 
flexion  of  the  third  phalanges  of  the  little  and  ring  fingers  can  be  accomplished  by 
the  ulnar  half  of  the  flexor  profundus,  which  is  supplied  by  the  ulnar  ner\e.     The 


Fig.  1097. 


BrachioradtaliH  tendon 
Branch  of  radial  nerve 


Palmar  cutaneous  br.  of 
median  nerve 


Median  nerve 
Flexor  carpi  radialis  tendon 


Abductor  pollidi 
Opponen*  potlida 

Abductor  polticia 

Digital  bra.  of 

median  nerve 

Adductor^ 

tiansversus  polUcia' 


Flexor  sublimit  diifitomm 

Flexor  carpi  ulnaris 
Palmai  cutaneous  )>r.  of  ulnal 
ner%e,  lying  upon  ulnar 
arter>' 
Ulnar  ner\'e 


Pisiform  bone 

-  Deep  branch  of  ulnar  nervr 
Abductor  minimidigiti 
Palmaria  bre\-is.  reflected 

Digital  brs.  of  ulnar  nerve 

pponen.4  minimi  d>Kiti 
.Flex,  brevis  minimi  digiti 


SuMHtdal  dlM«etlon  of  right  palm,  shewing  branches  of  median  and  ulnar  nerves ;  pan  of   anterior 
annular  ligament  hat  been  removed  to  expose  median  nerve. 


thumb  cannot  be  flexed  or  abducted,  although  it  may  be  adducted.  One  of  the 
most  characteristic  features  of  the  hand  is  lost— that  is,  the  ability  to  appose  the 
thumb  to  any  one  of  the  fingers,  as  in  picking  up  small  objects. 

In  wounds  of  the  axilla  the  median  is  the  nerve  most  frequently  injured,  the 
musculo-spiral  least  frequently,  as  the  median  lies  more  superficially  and  the  musculo- 
spiral  behind  the  vessels.  In  the  arm  the  median  can  be  easily  found  to  the  inner 
side  of  the  biceps  and  coraco-brachialis  muscles,  where  it  lies  on  the  brachial  vessels. 
At  the  elbow  it  is  found  to  the  inner  side  of  tne  brachial  artery,  the  guide  to 
which  is  the  biceps  tendon  which  in  turn  lies  just  to  the  outer  side  of  the  artery. 
At  about  the  middle  of  the  wrist  the  ner\'e  lies  under  the  palmaris  longus  tendon. 


THE   BRACHIAL   PLEXUS. 


1303 


9.  The  Internal  Anterior  Thoracic  Nerve. 
The  internal  anterior  thoracic  nerve  (n.  thoracaUs  anterior  m' Ualis)  (Fig. 
loqO  arises  h-om  the  inner  cord  and  consists  of  fibres  derived  frc.a  the  eighth 
cenfical  and  first  thoracic  nerves.  It  passes  forward  between  the  ax.Uary  artery  and 
vein  and.  after  giving  ofl  a  branch  which  forms  a  loop  with  a  similar  branch  from  the 
external  anterior  thoracic,  pierces  the  pectoralis  minor  in  which  some  of  'ts Jibrea 
terminate.  The  remainder  enter  the  deep  surface  of  the  pectoralis  major  to  supply 
the  lower  part  of  the  sternal  portion  of  that  muscle. 

v..^.fion.— The  fibres  which  supply  the  pectoralis  major  may  wind  around  the  lower 
bordeT^hrpJ^ctorallsiSr  Filaments  from  S  of  the  anterior  tLracic  nerves  may  supply 
the  integument  of  the  axillary  and  mammary  regions. 

ID.  The  Lesser  Internal  Cutaneous  Nerve. 
The  lesser  internal  cutaneous  nerve  (n.  cutoneiis  brachil  medialis)  (Fig.  1093). 
also  called  the  »frxe  of  Wrisberg,  can  be  traced  to  the  first  thoracic  nerve  It 
Seslrom  the  inner  cord  usually  in  common  with  the  internal  cutaneous.  After 
SgTtTpoint  of  origin,  it  descends  in  the  arm  along  the  inner  side  of  the  axillary 
and  bSilic  veins,  pierces  the  deep  fascia  about  the  middle  of  the  arm  and  supplier 
the  integument  of  the  inner  aspect  of  the  upper  extremity  as  ar  down  as  the  elbow. 
At  a  vanable  point  it  forms  a  loop  with  the  intercosto-humeral  nerve. 

v.ri«ion.  —The  lesser  internal  cutaneous  nerve  may  be  absent.     It  may  receive  fibres 

either  nerve  may  be  deficient,  the  other  usually  recompensing  for  the  deficiency. 
II.  The  Internal  Cutaneous  Nerve. 
The  internal  cutaneous  nerve  (o.  cutaneus  antebrachU  medialis)  (Fig.  1094) 
comDrfees  fibr«  from  the  eighth  cervical  and  first  thoracic  nerves.  It  has  its  origin 
She  inner  cord  of  the  plexus  usually  as  a  common  trunk  with  the  lesser  internal 
cu^eous  nerve.  After  distributing  some  small  filaments  to^^^e  integument  of  the 
.inner  arm  below  the  axilla,  it  runs  down  the  arm  between  the  brachial  artery  and 
SKrvSnTnd  at  about  the  middle  of  the  upper  arm  breaks  up  into  its  terminal 
branches,  (a)  the  anterior  and  (*)  the/wfewr. 

a.  The  .nterior  br«»ch  (r.  v.lari.)  passes  over,   sometimes  ""'»«;•»''«.  ™^?"-^";'^ 
vein  and  supplies  the  skin  of  the  ulnar  half  of  the  forearm  as  far  down  as  the  wnst  (Fig.  H04). 
It  inosculates  with  the  superficial  branch  of  the  ulnar  ner\-e.  ...       ,    ..      .  ...  „„__, 

4  The  pcterior  branch  (r.  ulnarl.)  turns  obliquely  around  the  inner  side  of  the  upper 
nart  of  the  foCm  and^pplies  the  integument  as  far  around  as  the  ulna  down  to  the  lower 
^hW  or  fourth  oHhrioS  It  unites  above  the  elbow  with  the  lesser  internal  cutaneoi« 
ne^elKe  fo«arwith  the  anterior  branch  of  the  internal  cutaneous  and  sometimes  with 
the  dorsal  ramus  of  the  ulnar. 

12.  The  Ulnar  Nerve. 
The  ulnar  nerve  (n.  ulnaris)    (Fig.   1092)  is  the  largest  branch  of  the  inner 
cord      Its  fibres  can  be  traced  to  the  eighth  cer^•ical  and  first  thoracic  nerves  and 
sometimS  by  a  root  from  the  outer  cord,  to  the  seventh  cervical.     Arising  from 
rinrcorVb^tween  the  axillary  artery  and  vein  and  posterior  to  the jn^^^' 
cutaneous  ner^'e  it  pursues  a  downward  course  in  front  of  the  tnceps  and  to  the 
inner  side  of  the  axillary  and  brachial  arteries.     Reachms;  the  middle  of  the  arm  it 
"Sows  an  inward  and  l^ckward  direction,  in  which  it  is  accompanied  bX  the  .deru, 
orofunda  artery   and  passing  either  over  the  inner  margin  of  or  through  the  interna 
fnSScuTar  i^'ptum  and  in^ont  of  the  inner  head  of  the  f  c^^- f  ,=^1  ^^'-^^^^^^^ 
between  the  internal  condyle  of  the  humerus  and  ^^e  olecranon  (Fig.  10^).     U 
becomes  an  occupant  of  the  forearm  by  passing  between  the  ^^ads  of  the  flexor  carpi 
uhiaris  muscle,  a  situation  the  nerve  shares  with  the  lufenor  prohmda  atid  posterior 


I3«H 


HUMAN   ANATOMY. 


ulnar  recurrent  arteries.     From  this  point  the  nerve  follows  a  straight  course  to  the 
wrist,  lying  in  the  forearm  upon  the  flexor  profundus  digitorum  and  covered  by  the 

Fig.  1098. 


Musculocutaneous  ner\-e 

Outer  hfatl  of  median  nenc 

Inner  head  of  median  nt:r\-« 

Long  head  of  bicepS' 

Short  head  of  biceps,  everted 
Coraco-brach  iat  is 


Musculocutaneous  ner\ 


Branchialis  anticu: 

Musculo-spiral  nerve' 
CtttaDcous  branches  of  niuscubxutancoi 


Brachio>fadiaUs 

Posterior  interosseous  nerve 

Biceps  tendon 

Radial  artery 

Supinator  brevis 

Ext.  carpi  radialis  longior 

Ext.  carpi  radialis  brevior 

Radial 


Prcmator  radii  teres,  cut 


Flexor  longus  polHcis- 


Palmar  cutaneous  branch  of  mtdian 


Opponens  pollici« 


Pectoralis  minor 


Internal  cutaneous 
Ulnar  nerve 


Interna]  cutaneous  branch  of 
musculo-spiral  nerve 


Inferior  profunda  artery 


Muscular  branch  f^  musculo-cutaneous 

>uperficial  flexots,  origin 
Articular  branches  of  median  nerve 


rticular  branches  of  ulnar  nerve 
Flexor  carpi  ulnaris 
Ulnar  artery 


interior  interosseous  nerve 
nterior  interosseous  artery 

Inar  nerve 
Flexor  profundus  (]ij{itorum,  cut 


Palmar  cutaneous  branch 
ronalor  quadratus,  cut 

'Dorsal  branch  of  ulnar  nerve 


Deep  brar  ch  of  ulnar  nervt 

Abductor  minimi  dlRiti 
Opponens  minimi  diiciti 

Flexor  brevis  minimi  digiti 

3rd  and  4th  flexor  tendons  with  ^rd  and  4th 
lumbricales,  turned  forward 


Dissection  of  right  upper  extremity,  showing  deeper  brmnchea  of  nerves  of  anterior  surface. 

flexor  carpi  ulnaris.     At  about  the  middle  of  its  course  through  the  lower  arm  it 
approximates  the  ulnar  vessels,  dose  to    the  inner  side  of  which  it  lies.     At  the 


THE  BRACHIAL   PLEXUS. 


1305 


wrist,  accompanied  by  the  ulnar  artery  it  pierces  the  deep  fasca  J^^f  ^bov^J^ 
TnnuUr  ligament,  to  the  outer  side  of  the  pisiform  bone,  and  enters  the  hand  b> 
Sing  su^rfici^  to  the  anterior  annular  ligament  (Fig  1097).  After  crossing 
ihe  ligament  it  divides  into  its  ..rminal  branches,  the  sufier/lna/  and  the  deep. 

Branches.-None  are  given  off  in  the  arm.  In  the  forearm  they  are  (a) 
the  articu/ar,  (d)  the  muscu/ar,  (c)  the  cuianecus  and  (rf)  the  '''';^''/ f  ^«^*  '^ '^ 
hand.    The  terminal  branches  in  the  hand  are  :  {e)  the  superjiaai  and  (/)  the  deep. 

a  The  wticulw  brwich  consists  of  one  or  two  filaments  which  leave  the  ulnar  as  it  lies  in 
the  interval  brtw^n  the  olecranon  and  the  internal  condyle.  They  pierce  the  internal  part  of 
the  capsular  ligament  and  supply  the  elbow  joint.  ...  ..  ,        .  .  ■ u-w^  «»  ♦!,» 

A  The  mu.cul«  branches  arise  from  the  ulnar  in  the  immediate  neighborhood  of  the 
elbow  and  supply  the  flexor  carpi  ulnaris  in  toto  and  the  ulnar  half  of  the  flexor  profundus 
dSor2    They  consist  of  severkl  fine  twigs  which  leave  the  ulnar  nerve  as  it  lies  between  the 

heads  of^he  fl;';^"^^'^-^^;.  are  two  small  filaments  which  arise  by  a  common  trunk  at 
about  ihe  r^iddle  of  the  forearm.  One.  which  is  inconstant,  after  piercing  the  deep  asc.a.  runs 
downward  to  inosculate  with  a  twig  from  the  internal  cutaneous.  The  other,  the  p.lm.r 
cut™u.  br^cMr.  c«ta«.us  palmari.)  (Fig.  1097  ).  lies  superficial  to  the  ulnar  artery,  which 
n^anirto  th;  hand  ataost  as  far  as%he  superficial  palmar  .'rh  It  sends  filaments  to 
rt™r  artery  and  breaks  up  into  a  number  of  tiny  threads  which  v  ,  -  -ly  the  '"^^Ktiment  of  the 
h^ttenar  re^on  and  inosailate  with  other  cutaneous  twigs  of  the  ulnar,  with  the  internal 
cutaneous  and  with  the  palmar  cutaneous  branch  oi  the  median.  ...  ,„,„t  ^hirh 

rf  The  dor.ia  branch  to  the  h«»d  (r.  dorMli.  manu.)  is  a  good  sized  trunk  which 
leavef  "the  ulnanTthe^pper  part  of  the  lower  half  of  the  forearm.  To  n=ach  the  dorsum  of  the 
htnTit  ^<^d^wnwa°d  andbackward  between  the  tendinous  portion  of  the  flexor  carp. 
uh"arii\K^e  ^aft  of  the  ulna,  giving  off  a  branch  over  the  dorsum  of  the  wnst  to  supply 
S^at  ^gton  and  inosculate  with  a  twig  from  the  radial  nerve.  Opposite  the  head  of  the  ulna^ 
^lits  into  three  branches  (nn.  dlglwles  dorMlw  for  the  supply  o  tl  e  fingers.  The  ulnar  or 
tenet  te«.ch  courses  along  the  inner  side  of  the  little  finger  to  ramify  m  its  integument  as  far  as 
^  w"  thfnaT  The  middle  br«.ch  follows  the  fourth  met^arsal  interval  and  divides  into 
wo  fil^ents.  one  extending  along  the  radial  side  of  the  little  finger  «  far  as  the  base  of  d^e 
naU  and  the  other  along  the  ulnar  side  of  the  ring  finger  as  far  as  the  proximal  side  of  the 
rnguarph^anT  The  radial  or  outer  branch  passes  toward  the  base  of  the  space  between^e 
rinS  middle  fingers  and  inosculates  with  the  branch  from  the  radial  ner^_e  for  he  same  ckft 
U  div^es  into  two  Lb-branches  and  in  connection  with  the  radial  supplies  the  advent  sides  o^ 
the  ringlnd  middle  fingers  (Fig.  l.oa).  At  the  lateral  aspect  of  the  fingers  all  of  these  bra..cnes 
innwiilate  with  the  palmar  digital  cutaneous  nerves.  .    ,„  »    t     •  .. 

inosculate  witntnep  terminal  branch  (r.  «.p.rficlali.  n.  nW^H»)  {Fig.  ,097)  furnishes 
small  w,'«  to  the  palmaris  brevis  muscle,  to  the  integument  of  the  ball  of  the  little  finger  and 
^metim^to  Ae  fourth  lumbricalis.  It  then  divides,  one  of  its  subdivisions  supplying  the 
Xr  swTrf  the  little  finger  while  the  other  breaks  up  into  two  portions  which  course  along 
the  adjoining  rides  of  the  litde  and  ring  fingers.  The  ultimate  distribution  of  these  filaments  is 
similar  to  that  of  the  digital  branches  ofthe  median  nerve  (page  1301.  „j  .u„, 

A  ^^  of  communication  passes  between  the  branch  for  the  little  and  nng  fingers  and  that 
from  thrrtLlian  for  the  ring  and  middle  fingers.  From  the  latter  Uny  threads  are  supplied  to 
the  inteeumcnt  and  vessels  of  the  palm.  »i._  j.„„ 

/•The  deep  terminal  branch  (r.  profondu.  a.  «ln.rU)  (Fig.  1099)  accompanies  the  deep 
branch  of  thf^narTrtery  and  sinks  deeply  into  the  palm  between  the  abductor  and  flexor 
mWmi  dieiti  muscles.  It  passes  internal  to  and  below  the  uncus  of  the  unciform  bone,  in  which 
™ve  for  Swerve  is  ^metimes  found,  crosses  the  palm  with  the  deep  Pflmar  arch  under 
thf  ^p  flexor  tendons  and  breaks  up  into  terminal  twigs  on  its  arrival  ?t  the  adductor  tmns- 
versus  oollicis  (Fig.  1199).  Muicular  branche.  rr.  masculare.)  are  furnished  to  the  abductor 
op^ne^s^d  flexor  minimi  digiti.  the  third  and  fourth  lumbricales,  the  pa  mar  and  dorsa^ 
interossei  the  adductores  obliquus  and  transversus  pollicis  and  the  deep  head  of  the  flexor  bre- 
"s  ^b.  ArticuUr  branche.  are  supplied  to  the  intercarpal  and  metacarpo-phalangea^  artic- 
uatC  and^ny  perforating  branche.  accompany  the  posterior  perforating  arteries  be  ween 
the  heads  of  the  s^ond.  thW  and  fourth  dorsal  interosseous  muscles  and  inosculate  with  the 
terminaltwiesof  the  posterior  interosseous  nerv-e  (Rauber). 
termi^p.  o. .     po  ^^^^^  communicates  freely  and  in  maijy  different  situahons  w^h 

the  m^"n  and  this  dose  imeriacing  is  paralleled  by  their  simi^ritj-  m  d«trib~„  Both  |^^^ 
off  no  branches  above  the  elbow,  both  supply  the  elbow  jomt,  between  them  they  supply  all  the 
mu^°^"thrflexor  surface  of  the  forearm,  both  send  filaments  to  the  wnst  ^.int  and  the  integ- 
IZrnt^  the  palm  and  between  them  all  U.e  mu.scles  of  the  hand,  the  palmar  aspect  of  all  the 
digits  and  the  interphalangeal  articulations  are  Innervated. 


iyif> 


HUMAN  ANATOMY. 


Further  description  of  the  communications  ol  the  ulnar  nerve,  in  addition  to  those  just 
mentioned,  will  be  found  in  connection  with  the  median  nerve  (page  1301). 

Variations.— The  ulnar  may  have  a  root  from  the  seventh  cervical  nerve  by  way  of  the  outer 
cord,  or  may  be  derived  from  the  eijchth  cervical  only  or  from  the  seventh  and  eigjhth.  It  may 
pass  in  front  of  the  internal  condyle  or  lie  behind  the  condyle  and  slip  forward  dunnt;  flexion  of 
the  elbow.  Connecting  twigs  have  been  seen  passing  from  the  ulnar  to  the  internal  cutaneous, 
to  the  median  in  the  upper  arm  and  to  the  musculo-spiral.  Frequently  there  is  an  associating 
branch  in  the  forearm  between  the  median  and  the  ulnar.  Muscular  twigs  have  been  noted  as 
passing  to  the  inner  head  of  the  triceps,  the  flexor  sublimis  digitorum,  the  first  and  second 
fumbncales  and  the  superficial  head  of  the  flexor  brevis  pollicis.  Deficiencies  in  the  branch  to 
the  dorsum  of  the  hand  have  been  observed  to  be  compensated  for  by  the  radial,  the  inferior 
external  cutaneous  branch  of  the  musculo-spiral  or  the  internal  cutaneous.  In  a  specimen  with 
absence  of  the  radial  nerve  all  four  fingers  were  supplied  by  the  ulnar.  The  dorsal  terminal 
filaments  of  the  ulnar  tend  to  encroach  on  the  radial  side  of  the  hand  and  in  one  ca.se  reached 
the  dorsum  of  the  first  phalanx  of  the  thumb. 

Practical  Considerations. — In  paralysis  of  the  ulnar  nerve,  flexion  of  the  wrist 
ii  impaired,  and  also  (on  account  of  the  flexor  carpi  ulnaris  paralysis)  lateral  motion 
toward  the  ulnar  side  (adduction).  There  is  difficulty  in  spreading  the  fingers,  as 
all  the  interossei  are  supplied  by  this  nerve.  The  hand  will  be  "  clawed"  from  the 
paralysis  of  the  interossei,  which  now  fail  to  resist  the  action  of  the  extensors  on 
the  proximal  phalanges,  and  of  the  flexors  on  the  distal  and  tnedial,  except  in  the 
middle  and  ring  fingers  where  the  flexor  profundus — its  ulnar  half  being  paralyzed— 
has  only  a  slight  influence  on  the  di-stal  phalanges.  Besides  the  flexor  carpi  ulna 'is, 
the  ulnar  half  of  the  flexor  profundus  and  the  interossei,  the  ulnar  ner\'e  supplies 
all  the  hypothenar  muscles,  the  adductor  pollicis,  the  inner  half  of  the  flexor  brevis 
pollicis  and  the  two  ulnar  lumbricales  ;  consequently  the  hypothenar  eminence  dis- 
appears and  the  thenar  eminence  shows  atrophy  in  ulnar  paralysis.  This  nerve  is 
involved  particularly  in  those  whose  occupations  require  them  to  press  their  elbows 
against  hard  objects  or  to  strike  blows  frequently  with  the  ulnar  border  of  the  hand. 
It  may  be  injured  in  fractures  of  the  elbow,  particularly  of  the  internal  condyle.  In 
the  forearm  and  wrist  it  is  the  nerve  most  frequentiy  injured.  It  is  found  on  the  inner 
side  of  the  brachial  artery  in  the  upper  half  of  the  arm,  but  in  the  lower  half  it  passes 
posteriorly  to  the  bony  interval  between  the  internal  condyle  and  the  olecranon, 
where  it  is  readily  located  by  pressure,  which  causes  a  tingling  sensation  down  the 
forearm.  The  same  sensation  is  often  produced  by  blows  on  the  elbow,  the  nerve 
being  compressed  between  the  internal  condyle  and  the  olecranon.  It  is  the  structure 
most  frequently  damaged  in  excisions  of  the  elbow.  In  the  lower  two-thirds  of  the 
forearm  it  lies  to  the  radial  side  of  the  flexor  carpi  ulnaris  muscle  and  to  the  ulnar 
side  of  the  ulnar  artery.  At  the  wrist  it  passes  over  the  anterior  annular  ligament  in 
the  same  relation  to  the  ..rtery  and  to  the  radial  side  of  the  pisiform  bone. 

14.     The  Subscapular  Nerves. 

The  subscapular  nerves  (nn.  subscapulares)  (Fig.  1092)  arise  from  the  posterior 
cord  and  are  usually  three  in  number.  Together  they  supply  the  three  muscles  which 
form  the  posterior  boundary  of  the  axillary  space. 

The  upper  or  short  subscapular  nerve  is  composed  of  fibres  which  are 
prolonged  from  the  fifth  and  sixth  cer\'ical  nerves.  It  often  is  either  double  in  origin 
or  divides  into  two  branches  shortly  after  leaving  the  posterior  cord.  It  arises 
behind  the  circumflex  nerve  and  after  a  short  course  enters  the  inner  surface  of  the 
f  ubscapularis  near  the  upper  margin  of  that  muscle. 

The  middle  or  long  subscapular  nerve  (n.  thoracodorsalis),  the  largest  of  the 
three,  arises  from  the  rear  aspect  of  the  posterior  cord,  behind  the  origin  of  the 
musculo-spiral  ner\'e.  Its  fibres  are  derived  from  the  sixth,  seventh  and  eighth 
cervical  nerves,  the  majority  of  them  coming  from  the  seventh.  It  takes  a  course 
downward  and  outward  on  the  posterior  axillary  wall  behind  the  axillary  artery,  and 
accompanies  the  subscapular  artery  to  the  deep  surface  of  the  latissimus  dorsi,  before 
entering  which  it  breaks  up  into  a  number  of  strands. 

The  lower  subscapular  nerve  obtains  its  fibres  from  the  fifth  and  sixth  cer- 
vical nerves.     It  arises  from  the  posterior  cord  behind  the  origin  of  the  circumflex 


THE   BRACHIAL   PLEXUS. 


•307 


and  passes  downward  and  outward  beneath  the  axillary  artery  and  the  circumflex 
and  musculo-spiral  nerves.  It  sends  fibres  to  th.-  inferior  p)rtion  of  the  subscap- 
ularis  muscle  and  terminates  in  the  substance  of  the  teres  major. 

Variation..-  As  retjards  oriifin  the  upper  may  arise  from  either  the  fifth  or  the  sixth  cervi- 
cal nenV^the  middle  from  the  seventh  alone  or  from  the  seventh  and  eiRluh  »r  rarely  by  an 
SduISna  filament  from  the  fifth,  and  the  lower  from  the  fifth,  sixth  and  seventh  or  tri.m  the 
fifth  or  sUth  alone.  As  regards  distribmion.  the  nerves  to  the  lower  part  of  the  sut«|capulans 
and  to  the  teres  major  mayproceed  separately  from  the  brachial  plexus  or  the  latter  nerve 
may  be  a  branch  of  the  circumflex 

15.     The  Circumflex  Nerve. 
The  circumflex  or  axillary  nerve  (n.  asillaris)  (Fig.  109O  is  .me  of  the  terminal 
branches  of  the  posterior  cord  and  contains  fibres  which  are  derivatives  of  the  fifth 

Fig.  1099. 


Median  nerve 

Flcxtir  Inngus  poUiciit 

Pulttuir  ctiUneoust  br.  of  median  nerve 


OppontfUit  iHilltcis- 


Adductor  obliquu»  pollicii, 


Flex.  l>rev.  poll., 
inner  head 

Flex.  hrev.  poll., 
outer  head 

Adductor  pollidii 

Adductor  tranftversuff 
poll. 


An  articular  branch 


Flex.  prof,  digitomni, 
in  part 

Ulnar  ner^-c 
Flex,  carpi  ulnaris 


Pisiform  bone 
Deep  br.  of  ulnar  nerve 
Articular  br.  of  ulnar 
l-nciform  hone       I '«"' 
Articular  bra.  of  ulnar 
nerve  [evcrtt-d 

Abductcr  minimi  Uigiti, 
Opponent  minimi  difEiti 
Second  palmar  inter- 
osseous 

Third  dorsal  interosseous 
Third  palmar  inter- 
Fourth  dorsal       [os-seous 
interosseous 
Flex,  brevis  minimi 
digit! 


Oi-«tionCr.,h.  P.-,-<^KJ^-:a°^:lSSiJX^^il^^^^  ""-  "^  "^^ 

and  sixth  cervical  nerves.  It  arises  near  the  lower  margin  of  the  subscapularis  and 
posterior  to  the  axiUarj-  artm-.  Accompanied  by  the  poster^r  circumflex  artery  it 
takes  a  backward  course  through  the  quadrilateral  space,  bounded  above  by  the 
subscapularis  and  the  teres  minor,  below  by  the  teres  major,   internally  by  the 


i3o8  HUMAN   ANATOMY. 

humeral  head  of  the  triceps  and  externally  by  the  humerus.  Having  tre versed 
thi>  s|)ace  it  winds  around  the  surgical  neck  of  the  humerus  and  reaches  the  outer 
aspect  of  the  shoulder. 

Branches. — These  are  :  (a)  the  articular,  (i)  the  cutaneous  and  (<•)  the 
muscu/ar. 

a.  The  articular  branchea  are  usually  two  in  number.  The  upper  arises  near  the  origin  of 
the  circumflex  and  the  lower  during  the  passage  of  the  nerve  through  the  quadrilateral  space. 
They  supply  the  anterior  inferior  portion  of  the  capsular  ligament  of  the  shoulder.  A  third 
articular  branch  is  described  as  passing  up  the  bicipital  groove,  supplying  a  twig  to  the  upper 
end  of  the  humerus  and  one  to  the  neighboring  portion  of  the  capsular  ligament  of  the  shoulder. 

*.  The  cutaneou*  branch  (n.  cuUncus  bractail  laUralU)  arises  as  a  common  trunk  with  the 
nen,-e  to  the  teres  minor.  It  becomes  superficial  between  the  long  head  of  the  triceps  and  the 
posterior  border  of  the  lower  third  of  the  deltoid  and  is  distributed  to  the  integument  over  the 
posterior  half  of  the  deltoid  and  the  posterior  suriace  of  the  upper  half  of  the  arm. 

One  or  two  cutaneous  filaments  are  derived  from  the  muscular  branches  to  the  deltoid. 
They  pierce  the  deltoid  and  are  distributed  to  the  skin  over  the  lower  portion  of  that  muscle. 

c.  The  muacular  branchea  (rr.  muacalares)  innervate  (aa)  the  teres  minor  and  (bb)  the 
deltoid. 

aa.  The  nerve  to  the  terea  minor  arises  from  the  circumflex  at  the  posterior  margin  of  the 
quadrilateral  space  and  enters  the  middle  of  the  posterior  inferior  border  of  the  muscle  which  it 
supplies. 

t>b.  The  deltoid  branchea  comprise  the  largest  portion  of  the  ner\e  and  consist  of  its  termi- 
nal fibres.  The  terminal  portion  of  the  circumflex  forms  a  bow,  with  its  convexity  in  contact 
with  the  deep  surface  of  the  deltoid,  extending  around  the  upper  part  of  the  humerus  almost  as 
far  forward  as  the  anterior  margin  of  the  deltoid  muscle.  It  grac'  illy  diminishes  in  size  as  the 
resuh  of  the  departure  of  a  series  of  twigs  which  enter  and  supply  tlie  fasciculi  of  the  deltoid. 

Variationa.— The  circumflex  may  receive  very  few  or  no  fibres  from  the  sixth  cervical  nerve. 
It  may  pierce  the  subscapularis  and  may  supply  that  muscle.  It  may  give  origin  to  the  nerve  to 
the  teres  major  and  has  been  observed  to  furnish  filaments  to  the  long  head  of  the  triceps  and 
to  the  infraspinatus. 

Practical  Considerations. — The  circumflex  nerve  is  frequendy  paralyzed 
from  injuries  to  the  shoulder,  as  in  birth  palsies  when  pressure  is  made  in  the  axilla. 
It  undergoes  special  strain  in  dislocations  of  the  shoulder,  the  nerve  being  stretched 
over  the  head  of  the  humerus  and  often  lacerated.  Other  branches  of  the  brachial 
plexus  may  be  injured  in  this  dislocation.  Since  the  circumflex  passes  around 
the  humerus  at  about  the  level  of  the  surgical  neck  it  is  sometimes  damaged 
in  fractures  in  that  situation.  The  most  prominent  symptom  in  paralysis  of  this 
nerve  is  loss  of  the  rotundity  of  the  shoulder  h^m  atrophy  of  the  deltoid  muscle. 
As  the  circumflex  winds  around  the  posteri>  r  surface  of  the  humerus  and  reaches 
the  anterior  part  of  the  deltoid  mus^':  from  behind,  incisions  for  reaching  the 
shoulder  joint,  as  in  excisions,  should  o^  made  anteriorly,  since  only  the  terminal 
branches  of  the  circumflex  will  then  be  divided  ;  paralysis  of  the  deltoid  is  thus 
prevented. 

i6.    The   Musculo-Spiral  Nerve. 

The  musculo-spiral  nerve  (n.  radialis)  (Fig.  iioo),  the  larger  terminal  branch  of 
the  posterior  cord,  is  in  fact  the  continuation  of  the  latter.  Its  component  fibres  are 
derivatives  of  the  sixth,  seventh  and  eighth,  and  sometimes  of  the  fifth,  cervical 
nerves  and  it  is  distributed  to  the  muscles  and  integument  of  the  extensor  surface  of 
the  arm,  forearm  and  hand.  After  separating  from  the  circumflex,  it  passes  down- 
ward behind  the  axillary  artery  and  over  the  surface  of  the  latissimus  dorsi  and  teres 
major  muscles.  Accompanied  by  the  superior  profunda  artery,  it  turns  backward  on 
the  inner  aspect  of  the  arm  and,  entering  the  musculo-spiral  groove  and  traversing 
the  interval  between  the  internal  and  long  and  the  external  head  of  the  triceps, 
reaches  the  lateral  a.spect  of  the  arm.  It  then  takes  a  forward  course  through  the 
external  intermuscular  septum  and  becomes  an  occupant  of  the  cleft  between  the 
brachioradiaiis  and  the  brachialis  anticus.  Continuing  in  this  space  as  far  as  the  level 
of  the  external  condyle  of  the  humerus  the  nerve  divides  into  its  terminal  branches, 
Xht posterior  interosseous  And  the  radial  {¥\^.  1095). 


THE   BRACHIAL   PLEXUS. 


1309 


Branches. — These  are  :  (a)  the  cutanfous,  (6)  the  muscular,  (r)  the  humeral, 
((/}  the  articular  and  {e)  the  terminal. 

Fig.  1 100. 


Scipulmr  head  of  triceps 

Superior  profunda  artery 

Portion  ol  ejrtenul  licad  of  iricepa,  everted 

Mnacular  branch 


Olecranon 

Anconeua 
Extensor  carpi  ulnaris 


Eztenior  loocui  pollicit 


Eztenaor  indicii 


Mucvloipiral  nerve 


Upper  external  cutancoui  nerve 
External  head  ol  iricepi 


Brachialii  anticus 

Lower  external  cutaneoua  nerve 


External  condyle 


Extensor  carpi  tadialis  kmgiar 


Extensor  carpi  radialis  brevior 

Supinator  brevis 

Posterior  inteioaseona  ner>'e 


Extensor  communis  digitonim 
Extensor  minimi  digiti 


Extensor  ossis  metacarpi  poUicIa 
Extensor  bre\'is  polHcia 


Kxtensor  longiis  poUicis 


nanKlifomi  enlargement  on 
posterior  interosseous  nerve 


Deep  dissection  of  extensor  surface  of  ri^^ht  upfier  extremity,  showing  conrse  and 
branches  of  musculo^piral  ner>-e. 

«.    The  cutaneous  branches  are  three  in  number,  an  internal  and  two  external. 

The  intemal  cuuneous  branch  frequently  arises  from  the  musculo^piral  in  common  with 


IJIO 


HUMAN  ANATOMY. 


the  branches  to  the  long  and  inner  heads  of  the  triceps.  It  phsses  tnckward,  posterior  to  the 
intercosto-humeral  nerve,  and  after  piercing  the  deep  fa.scia,  spreads  out  to  be  distributed  to  the 
integument  over  the  inner  head  of  tlie  triceps  to  within  a  short  distance  of  the  elbow  ( Fig.  i  lot ). 
It  is  accompanied  by  a  small  artery-. 

The  ■uparior  cstcmal  cutaneous  branch  (n.  couacu*  bracbil  posterior)  (Fig.  iioi)  arises 
from  the  musculo-spiral  posterior  to  the  external  intermuscular  septum  and  pierces  the  deep 
fascia  below  the  middle  of  the  arm,  between  the  external  head  of  the  triceps  and  the  brachialis 
anticus.  It  pasiies  down  with  the  cephalic  vein  and  is  distributed  to  the  integument  of  the 
external  anterior  portion  of  the  arm  down  to  or  slightly  below  the  elbow. 

The  inferior  external  cutaneous  branch  (a.  cutaocua  aatihrachii  dornatis)  (Fig.  iio3)  arises 
and  becomes  superficial  similarly  to  and  in  common  with  the  superior.    After  passing  down  the 


Fig.  iioi. 


'Cut:itiei>iu*  lirancheM  of  circumHrx  nerve 


Branch  of  InterttMto- 
humenil  nerve 


Int.  cutaneoufl  branch  of  mn*. 
culospiral  nerve 
L.eiwcr  internal  cutaneoitA, 
joine*!  below  the  leader  by 
branch  of  intervoato-hu- 
nicral  nerve 


Sup.  ext.  ciitaneoua  bnitch  of  inii!*. 
culo^piral  nt;rv»; 


inf.  ext.  cutaneoua  branch  of  niiiH. 
culo-apiral  nerve 


Post.  cutaneoiiH 
branch  of  musciilo- 
cutaiiei>U!t  nen>'e 


irom  pof«t.  branch  of  internal  cutaneous  nerve 


Superficial  dissection  of  right  arm,  showing  cutaneous  nerves  of  posterior  surface. 

arm  it  enters  the  forearm  by  crossing  the  dense  fascia  stretched  between  the  olecranon  and  the 
internal  condyle  of  the  humerus.  From  this  point  it  continues  its  downward  course  along  the 
posterior  aspect  of  the  forearm  as  far  down  as  the  wrist  or  even  onto  the  dorsum  of  the  hand. 
It  is  distributed  to  the  skin  of  the  posterior  portion  of  the  arm  between  the  areas  supplied  by 
the  other  cutaneous  branches  of  the  musculo-spiral  and  to  that  part  of  the  posterior  cspect  ot 
the  forearm  between  the  portions  supplied  by  the  posterior  branch  ol  the  internal  cutaneous 
and  the  posterior  branch  of  the  musculo-cutaneous.  In  the  neighborhood  of  the  wrist  it  inos- 
culates with  the  musculo-cutaneous  and  sometimes  with  the  branch  to  the  dorsum  of  the  hand 
from  the  ulnar. 

b.  The  muscular  branches  (rr.  muttcnUrtM)  are  given  off  (aa)  before  the  miLscnlo-spiral 
enters  the  musculo-spiral  groove  and  (bb)  after  leaving  the  groove. 

aa.  Before  entering  the  groove  branches  arise  for  the  supply  of  the  three  heads  of  the 
triceps  and  the  anconeus. 


THE  BRACHIAL   PLEXLS. 


13»« 


Int.  cuuneou*  ,(_^ 
branch  of  mu»-    ^^ 
Milu-Hpiral  nerv« 


Lcwrr  int.  c» 
tancouii  nerve 


thr  ulnar  nerve. 


Inf.  cxt.  cmanc'tiiiH 
branch  of  niuncuto- 
•piral  nerve 


Int.cutan^MM 

nerve,  poat. 

branch 


Post,  cutaneous 
far.  of  niuticiilu- 
cutaneuun  nerve 


The  branch  for  the  lonf  hc«l  of  the  trieep*,  before  its  entrance  into  the  miwcle,  breaks  up 
into  four  or  five  filaments.  .,      „        .  .  .         . 

The  nerve  supply  of  the  inner  head  of  the  triecpa  is  usually  effected  by  two  branches,  an 
upper  and  a  lower.  The  upper  is  short  and  enters  the  muscle  soon  after  kavinjt  the  musculo- 
spiral.  The  lower,  called  the  coUaUral  ulnar  branch,  is  longer  and  extends  for  a  considerable 
distance  along  the  inner  suriace  of  the  triceps  in  close  as.sorialion  with 
Posterior  to  the  internal  intermuscular 

septum  it  enters   its  muscle.     Tiny  r'"-  "oj. 

filaments  accompany  the  collateral 
ulnar  artery  to  the  capsular  ligament 
of  the  elbow. 

The  nerves  to  the  outer  head  of  the 
tricepa  and  to  the  anconeus  take  their 
origin  as  a  single  trunk.  The  former 
passes  directly  to  the  inner  surface  of 
the  outer  head,  while  the  latter  leaves 
the  musculo-spirnl  groove  and  tra- 
verses the  outer  portion  of  the  internal 
head  of  the  triceps  until  the  aiKoneus 
is  reached. 

bb.  After  leaving  the  groove  and 
while  lying  in  the  cleft  between  tlie 
brachialis  anticus  and  the  brachio- 
radialis,  twigs  are  given  off  for  the 
supply  of  the  brachio-radialis,  the 
extensor  carpi  radialis  longior  and  the 
brachialis  anticus. 

The  nerve  to  the  brachio-radialis 
enters  the  mesial  surface  of  that  muscle 
and  usually  supplies  a  filament  to  the 
capsule  of  the  elbow. 

The  nerve  to  the  extensor  carpi 
radialis  longior  may  arise  either  from 
the  posterior  interos-seous  or  directly 
from  the  musculo-spiral. 

The  nerve  to  the  brachialis  anti- 
cus, while  usually  present,  is  not  con- 
stant. It  enters  and  supplies  the  lateral 
portion  of  that  muscle. 

c.  The  humeral  branches  com- 
prise one  which  is  supplied  to  the 
periosteum  of  the  extensor  surface  of 
the  iiumerus  and  one  which  enters  the 
shaft  of  the  humerus  with  the  nutrient 
artery,  when  tlie  latter  arises  as  a 
branch  of  the  superior  profunda. 

d.  The  articnlar  branches  are  des- 
tined for  the  elbow.  They  arise  from 
the  musculo-spiral  as  it  lies  between 
the  brachialis  anticus  and  the  brachio- 
radialis,  from  the  ulnar  collateral  nerve 
and  from  the  nerve  to  the  anconeus. 

e.  The  terminal  branches  of  the 
musculo-spiral  arises  at  about  the  level 
of  the  external  condyle  and  in  the  fis- 
sure between  the  brachialis  anticus 
and  the  brachio-radialis.  They  com- 
prise (aa)  the  posterior  interosseous 
and  (W)  the  radial. 


Inf.  ext.  cutanemifl 
liranch  muwulo^piral 

I>om1  branch 
of  ulnar  ocrvc 


From  ulnar  nervi 


From 

niedinn 

nerve 


Superfirial  difuection  of  riifht  forearm,  showing  cutaneous  nerves 
of  posterior  surface. 


aa.  The  posterior  interosseous  nerve  (r.  profundus  n.  radialis)  (  Fig. 
iiDo)  is  the  larger  of  the  tcrtniiial  brunchea  and  is  mainly  motor  in  function.  Its 
fibres  can  be  traced  back  to  the  sixth,  seventh  and  sometimes  the  eighth  cervical 
nerve.  Shortly  after  its  origin  it  approaches  the  supinator  brevis,  through  a  fissure 
in  whose  substance  it  makes  its  way  to  the  lateral  side  of  the  radius,  in  this  way  reach- 


13" 


HUMAN  ANATOMY. 


ing  the  posterior  aspect  of  the  forearm.  Here  it  Ukes  a  po«ti«.>n  between  the  two 
layers  of  the  extensor  muscles  and  rapidly  decrcast's  in  size  by  giving  of!  in  quick 
succession  branches  to  the  neighboring  muscles.  As  a  much  attenuated  nerve  it 
reaches  the  posterior  surface  of  the  interosseous  membrane  at  the  junction  of  the 
middle  and  lower  thirds  of  the  forearm.     From  the  inter\'al  between  the  e.xtensores 

longus  and  brevis  pol- 
FiG.  1 103.  licis  it  courses  along 

sapnuicTomtai  bn.  ccrrkmi  pinna  the  membrane,   Cov- 

ered in  turn  by  the  ex- 
tensor longus  pollicis, 
the  extensor  indicis 
and  the  tendons  of 
the  extensor  longus 
digitorum,  finally 
reaching  the  dorsum 
of  the  wrist,  where 
it  presents  a  small 
gancliform  swelling. 
In  the  lower  fourth  of 
Its  course  it  is  son* 
times  called  the  t  ■ 
tern  al  interosseoi. : 
nerve. 

Branches  of 
the  posterior  interos- 
cuuncous  ner\e  seous  nerve  comprise 
two  sets:  those  given 
off  before  and  after 
traversing  the  supina- 
tor brevis. 


CuUneottfl  hr«. 
circumflex  nerrtt 


Sup.  cxt.  cuUneota 

br    ;  f  miwculo- 

spiral  ticrre 


Inf.  cxt.  cutaneon* 

br.  of  miMculo- 

spiral  nerve 

MusctiIo.^tttaneott. 
ner^'p.  post.  cuUn< 

brancb 

Muscuio-cutaneoiu 

nerve,  ant 

cutaneous  brancb 

Mu.sculo-cutaneo'U. 

post.  cutaneouB  br. 


:>"/<< 


Internal 
cutaneoua  nerve 


Those  arising  be- 
fore the  ner%'e  enters 
the  muscle  comprise  the 
nerves  for  the  extensor 
carpi  radialis  breinor 
and  the  supinator  brevis. 
The  latter  receives  two 
filaments,  which  supply 
the  two  strata  of  muscle 
consequent  upon  the  de- 
lamination  of  I  he  supin- 
ator brevis  by  the  pos- 
terior interosseous 
nerve.  Quite  frequently 
the  nerve  to  the  exten- 
sor carpi  radialis  long- 
ior  arises  from  this  por- 
tion of  the  posterior 
interosseous. 

The  branches  giv- 
en off  mfter  leaving  the 
muscle  include  the  sup- 
ply ot  the  extensor  car- 
pi ulnaris,  the  extensor 
I  >mtnunis  digitorum, 
the  extensor  minimi  digiii,  the  three  extensors  of  tlie  thumb    .\A  the  extensor  indicts. 

1  he  first  three  ot  these  muscles  are  supplied  by  a  branch  which  leaves  the  posterior  inter- 
osseous soon  after  its  emergence  from  the  supinator  brevis.  This  ner\'e  divides  intcj  two 
branches,  one  of  which  is  distributed  to  the  extensor  carpi  ulnaris  and  the  otb  f>  the  r.  main- 
ing  two  muscles.    The  extensor  communis  digitorum  receives  adrti'  n  fro>       twig 

which  arises  from  the  posterior  interosseous  further  down  the  fs 


Superficial  dissection  of  ri|{;ht  arm,  sbowlni;  cutaneous  nerves  of 
anterior  surface ;  cephalic  vein  is  seen  passing  up  to  delto-pectoral 
interval ;  basilic  vein  pierces  deep  fascia  at  lower  inner  aspect  of  arm. 


THE   BRACHIAL   PLEXLS. 


»3t3 


Inf.  exl.  cutanrowt 

br.  of  muncwlo- 

Bpinit  nerves 


Munculo-cuU 

ncf>u<*  tirrve.  anl 

ciitaneotui  hr 


Muftcnlo-cuta- 

Dcouft  nerve,  pout. 

cutaneous  br. 


lA"!»!»cr  internal 
cutaneouH  nr.  vo 

Internal  cutaneouii 
nerve 


Ant.  br.  internal 
frutaneoua  nerve 


The  extensor  ossis  nutacarpi  polHHt  and  the  extensor  bre,-is  pollUii  are  innervate.  I  hy  a 
branch  arising  below  the  precedinK.  which  breaks  up  into  two  dtTurrrnt  twigs,  one  of  which 

'^"^The*r«-/«u<^  W«-t  Pollicu  is  the  recipient  of  a  small  filan«nl.  wh.^h  arises  fron^  the 
posterior  interosseous  a  short  distance  below  the  preceding  ner\e. 

The  extensor  indiris  is  sup- 
plie<l  by  the  lowermost  mo«or 
filament  arisinx  from  the  poste- 
rior inten»seous. 

Terminal  twig*  are  ulstrib- 
iited  to  the  dorsal  portion  of  the 
wrist  joint,  the  intercarpal  and 
carpo-metacarpal  joints,  the  peri- 
osteum of  the  radius  and  ulna 
and  the  interosseous  membrane. 
One  of  the  filaments  supplyinK 
the  last-mentioned  structure  fre- 
quently inosculates  with  a  branch 
from  the  anterior  interosseous. 

The  filaments  to  the  carpus 
are  continued  through  the  meta- 
carpal spaces  and  are  joined  by 
twigs  from  the  deep  branch  of 
the  ulnar  (page  1305).  The  joint 
nerves  thus  formed  break  up  into 
two  branches  which  accompany 
adjoining  metacarpal  bones  to 
the  metacarpo-phalangeal  articu- 
lations. The  branch  to  the  first 
metacarpal  space  breaks  up  into 
seven  branches  ( Rauber). 

bb.  The  radial  nerve 
(r.  superficialis  n.  radialis) 
(Fig.  1095)  is  smaller  than 
the  posterior  interosseous 
and  is  purely  sensory  in  its 
function.  Its  fibres  originate 
from  the  sixth  cervical  ner\'e 
and  sometimes  from  the  fifth 
or  seventh.  From  the  end  of 
the  musculo-spiral  it  passes 
down  the  radial  side  of  the 
forearm  under  cover  of  the 
brachio-radialis  and  anterior 
to  the  supinator  brevis,  the 
pronator  radii  teres  and  the 
radial  head  of  the  flexor 
sublimis  digitorum.  It 
accompanies,  for  the  greater 
part  of  its  course,  the  radial 
artery,  to  the  radial  side  of 
which  the  nerve  lies.  At  the 
junction  of  the  middle  and 
lower  thirds  of  the  forearm 

it   begins   to   turn   gradually  ,    .     ,       ,  •         .•  i-    ,c" \ 

backward  over  the  radius  and  under  the  tendon  of  the  brachio-radiahs  (Pig.  1095). 
Reaching  the  extensor  surface  of  the  forearm  just  above  the  wnst  it  divides  into 
two  diverging  branches,  which  supply  the  back  of  the  hand  and  the  three  outer 

'^  Branches.— The  radial  nerve  divides  into  two  terminal  branches,  an  external 
and  an  internal. 

83 


Palmar  cuU- 
11COUS  br.  of  ul- 
nar nerve 

Palmar  cntane- 
oiia  br.  of  me- 
dian ner\'e 


DiKiUl  brs.  of 
ulnar  nerve 

Difdtal  bra.  of 
median  nerve 


Superficial  diwection  of  riiht  forearm  and  hand,  showing  cuuneoui 
naiAM  of  anterior  and  palmar  surface. 


I3I4 


HUMAN  ANATOMY. 


The  eztcmal  or  radial  branch  inosculates  with  the  musculo-cutaneous  oerv-e  and  dis- 
tributes filaments  to  the  intqcument  of  the  thenar  eminence  and  the  radial  side  ol  the  thumb  as 
far  out  as  the  base  of  the  nail. 

The  internal  or  ulnar  branch  splits  into  two  part^''.  The  inner  erf  these  likewise  under- 
goes dichotomous  division  and  supplies  the  dorsal  aspect  of  the  adjacent  surfaces  of  the  thumb 
and  the  index  finger.  The  outer  divides  similarly  to  the  inner  and  is  distributed  to  the  adjoining 
sides  of  the  index  and  middle  fingers.  It  gives  off  a  branch  which  inosculates  with  the  adjacent 
filament  from  the  dorsal  branch  of  the  ulnar  nerve,  so  that  the  contiguous  surfaces  of  the  middle 
and  ring  fingers  are  the  recipients  of  fibres  from  both  the  radial  and  ulnar  nerves. 

As  the  ulnar  side  erf  the  hand  is  approximated  the  digital  area  of  distribution  of  the  nidial 
nerve  gradually  recedes  toward  the  wrist  On  the  thumb  the  radial  extends  as  far  out  as  the 
base  of  the  nail,  on  the  index  finger  as  far  as  the  middle  of  the  second  phalanx  and  on  the 
middle  finger  only  over  the  proximal  portion  of  the  first  phalanx.  The  deficiency  in  these 
instances  is  supplied  by  twigs  from  the  digital  branches  of  the  median  nerve. 

Variations. — ^The  musculo-spiral  may  accompany  the  circumflex  nerve  through  the  quad- 
rilateral space.  It  may  communicate  with  the  ulnar  nerve  in  the  upper  arm.  Cases  are 
recorded  m  which  the  dorsal  digital  nerves  to  the  little  and  the  ulnar  side  of  the  ring  finger 
were  furnished  by  the  musculo-spiral  instead  of  by  the  ulnar  and  in  which  the  inferior  external 
cutaneous  branch  extended  to  the  first  phalanx  of  the  ring  finger  and  the  second  phalanx  of 
the  little  finger.  The  radial  nerve  may  supply  the  entire  dorsum  of  the  hand  and  the  dorsal 
aspect  of  all  the  fingers,  or  it  may  be  absent,  the  musculo-cutaneous  going  to  the  thumb  and 
the  ulnar  to  the  remainder  of  the  digits.  The  external  division  may  send  a  branch  to  the 
palm.  The  posterior  interosseous  may  pass  over  the  surface  of  the  supinator  brevis  and  may 
tumish  a  branch  to  the  anconeus  muscle.  Two  instances  are  reported  in  which  the  posterior 
interosseous  supplied  the  opposed  surfaces  of  the  middle  and  incfex  fingers. 

Practical  Considerations. — The  musculo-spiral  is  more  frequently  paralyzed 
than  any  of  the  other  branches  of  the  brachial  plexus.  Its  axillary  portion  ofter 
suffers  from  crutch  pressure ;  and  the  nerve  is  also  particularly  exposed  to  com- 
pression where  it  passes  between  the  triceps  muscle  and  the  humerus,  as  when  the  arm, 
during  sleep,  is  used  for  a  pillow.  It  has  been  injured  by  violent  contraction  of  the 
triceps  muscle,  as  in  the  act  of  throwing.  It  is  frequently  lacerated  by  the  fragments 
in  fractures  of  the  middle  of  the  shaft  of  the  humerus  When  the  lesion  is  in  the  axilla 
the  triceps  will  be  included  in  the  paralysis.  If  the  portion  in  the  arm  is  affected  the  tri- 
ceps and  anconeus  will  escape,  but  the  following  muscles  will  be  paralysed  :  the  supina- 
tors, the  extensors  of  the  hand,  the  extensor  communis  digitorum,  together  with  the 
extensor  indicis,  the  extensor  minimi  digiti  and  the  extensors  of  the  thumb.  The 
characteristic  symptom  is  the  inability  to  extend  the  hand  at  the  wrist  (wrist  drop), 
and  this  is  the  most  common  form  of  musculo-spiral  paralysis. 

THE  THORACIC  NERVES. 

The  thoracic  nerves  (nn.  thoracales)  (Fig.  1105)  consist  of  twelve  pairs  of  sym- 
metrical nerve-cords,  the  upper  eleven  of  which,  because  of  their  position  in  the 
intercostal  spaces,  are  called  intercostal  nerves,  and  the  twelfth,  which  lies  below  the 
twelfth  rib  and  is  an  occupant  of  the  abdominal  wall,  the  subcostal.  Since  only  seven 
ribs  reach  the  sternum,  the  upper  six  thoracic  nerves  alone  are  continued  throughout 
their  entire  course  in  intercostal  spaces.  The  lower  six,  with  the  exception  of  the 
twelfth,  after  traversing  their  respective  intercostal  spaces  proceed  within  the  abdom- 
inal wall,  through  which  they  course  to  within  a  short  distance  of  the  median  line. 
In  accordance  with  the  direction  of  the  ribs,  the  upper  nerves  lie  more  horizontally 
than  the  lower,  the  latter  becoming  more  and  more  oblique  as  the  lower  part  of  the 
abdominal  wall  is  reached.  As  they  advance  from  the  spine,  they  distribute  motor 
filaments  to  the  external  and  internal  intercostals,  the  subcostals,  the  levatores 
costarum,  the  serrati  postici  superior  et  inferior,  the  triangularis  stemi,  the  external 
oblique,  the  internal  oblique,  the  transversalis,  the  rectus,  the  pyramidalis  and  a  por- 
tion of  the  diaphragm.  Their  cutaneous  distribution  comprises  the  integument 
of  the  chest  and  abdomen  anterior  to  the  area  supplied  by  the  posterior  primary 
divisions  of  the  thoracic  nerves.  On  account  of  the  presence  of  the  shoulder  girdle, 
the  usual  nerve  distribution  is  modified  in  the  upper  thoracic  region  and  the  supra- 
clavicular branches  of  the  cervical  plexus  assiimf  a  function  belonging  to  the  thoracic 
nerves.     At  the  lower  portion  of  the  trunk  the  usual  arrangement  is  likewise  altered, 


THE  THORACIC   NERVES. 


1315 


the  area  immediately  above  Pouparts  ligament  and  the  pubes  bemg  mnervated  not 
bv  the  thoracic,  but  by  the  lumbar  nerves  (Fig.  1105).  The  supply  of  the  cutane- 
ous area  is  provided  by  two  rows  of  sensory  tw.gs,  which  become  superfiaal  by 
Seine  the  musculature  and  deep  fascia  of  the  trunk.  Each  of  the  thoracic  nerves, 
with  the  exception  of  the  first,  sends  out  a  lateral  cutaneous  branch  and.  wrth  no 
Mceptions.  an  anterior  cutaneous  branch.  The  upper  thoracic  nerves  deviate 
"riously  f^m  this  typical  arrangement,  the  first  haying  no  lateral  and  sometimes  no 
^[^ior  cutaneous  branch,  and  a  portion  of  the  lateral  cutaneous  branch  of  the 
Snd  called  the  intercosto-humeral  nerve,  leaving  the  thorax  to  be  distnbuted 
r°he  upper  extremity.  The  third  nerve  of  the  series  is  the  first  to  present 
a  typical^rangement.  although  it.  indeed,  sometimes  forms  a  loop  with  the 
Lser  internal  cutaneous  nerve  of  the  arm.  The  antenor  cutaneous  branches  are 
Eterm  nal  portions  of  the  thoracic  nerves  and  rre  constant  m  their  arrangemen 
and  distributfon.  with  the  exception  of  the  first,  which  is  either  very  small  or  absent 
and  a  filament  from  the  last,  which  passes  over  the  crest  of   the   ilium  to  the 


^  After  ^parating  from  the  posterior  primary  divisions,  the  anterior  primary 
divisions  of  the  thoracic  nerves,  with  the  exception  of  the  twelfth,  enter  the  mtei- 
costal  spaces  by  passing  between  the  antenor  costo-transverse  ligaments  and  the 
e^SLd^ntercost^  mu^les.  From  this  situation  to  the  angles  of  the  ribs  they  he 
Sw^  the  posterior  intercostal  membrane  and  the  external  intercosta  muse  es. 
AnTerior  to  th^poim.  they  are  situated  between  the  ^*o  sets  of  intercostal  muscles 
as  farTorward  as  the  termination  of  the  external  set  of  muscles  at  the  costo-chondral 
articulations,  from  which  point  forward  their  superficial  coyenng  is  the  anterior  inter- 
c^tal  membrane  and  the  deep  the  internal  intercostal  muscles.  At  first  they  lie  withm 
the  upper  part  of  the  intercostal  space,  but  as  they  advance  they  show  a  tendency 
to  occupy  the  middle  of  the  space.  WhUe  accompanymg  the  intercostal  ve^ls.  they 
lie  below  the  latter  and  at  a  greater  distance  from  the  nb  next  above.  The  upper 
two  nerves  extend  for  a  portion  of  their  course  along  the  mner  surface  of  the  corre- 
sponding ribs ;  the  twelfth  passes  in  front  of  the  quadratus  lumborum. 

The  upper  thoracic  nerves,  as  they  approach  the  margin  of  the  sternum,  tra- 
verse the  substance  of  the  internal  intercostal  muscles  and  hold  a  position  anterior 
to  the  internal  mammary  artery  and  the  lateral  portion  of  the  triangularis  sterni 
muscle  They  terminate  by  piercing  the  anterior  intercostal  membrane  and  the  pec- 
toralis  major,  and  ramify  in  the  pectoral  integument  as  the  anUrior  cutaneous  tunes 

TheTower  'fhoracic  nerves  pass  forward  and  at  the  anterior  ends  of  the  ribs 
take  up  a  deeper  position  in  the  trunk  wall  by  piercing  the  substance  of  the  interna 
interc<^tal  musclS.  They  then  traverse  the  intervals  between  the  dip:itat.ons  of 
the  diaphragm  and  enter  the  abdominal  wall,  the  seventh,  eighth  and  ninth  nerves 
lying  behind  the  cartilages  of  the  eighth,  ninth  and  tenth  ribs  r«pectively.  Prom 
this  point  their  course  is  ventral,  between  the  internal  oblique  and  the  transversalis. 
as  faTas  the  lateral  edge  of  the  rectus  sheath,  which  they  enter  by  piercing  its  pos- 
terior lamella.  They  ultimately  turn  forward  and  become  superficial  by  traversing 
the  rectus  and  its  anterior  aponeurotic  covering,  terminating  as  the  antertor  cutaneous 

nerves  0/ the  aMomen  (V'lg.  I lOi).  .  .   .     -.u  .u        „*!,».;-, 

Communications.— Each  thoracic  nerve  is  connected  with  the  sympathetic 
(raneliated  cord  by  one  or  two  rami  communicantes  (Fig.  1130).  Ordinarily  there 
fs  no  intercommunication  between  the  upper  intercostal  nerves,  but  in  rare  instance 
a  twig  passes  from  one  nerve  over  the  inner  surface  of  the  nb  next  below  to  the  sub- 
jacent nerve.  The  lower  three  or  four  thoracic  nerves,  while  lying  lietween  the  broad 
abdominal  muscles  are  occasionally  united  to  one  another,  sometimes  to  the  extent 

of  forming  a  small  plexus.  . . 

Peculiar  thoracic  nerves.— The  first,  second,  twelfth,  and  sometimes  the 
third,  thoracic  nerves  present  peculiarities  which  differentiate  them  from  the  others. 

The  first  thoracic  nerve  sends  a  large  portion  of  its  fibres  to  the  brach- 
ial plexus,  thus  suffering  great  reduction  in  its  size.  Ahhough  occasionally  a  very 
small  branch  to  the  axilla  is  fotmd,  .■»  lateral  cutaneous  branch  »  rare,  it  being 
generally  held  that  the  contribution  of  this  nerve  to  the  brachial  plexus  is  the 


I3i6 


HUMAN  ANATOMY. 


Suprmacromial 
branches  of  cvr> 
Fcctormlis  minor  mtiade      vical  plexus 

PcctonlU  major  mnscle    \  \^ 

Lesser  internal      V 
cutaneous 
nerve 


Fig.  1105. 


Descending  branch  of 

supcrticialis  colli 

Suprasternal  and  supra* 
clavicular  branches  of 
cervical  plexus 


Rectus  abdom- 
inis, cut 
Anterior 
branch  of  X. 
thoracic  nerve 

Anterior 
branch  of 
XI.  thoracic 


Anterior 
branch  of  XII. 
thoracic  nerve 

Hypofpiitric 
portion  of  ilit^ 
nypoKSStric 
uer\'e 

Aponeurosis 
of  external 
oblique  mus- 
cle, cut  edge 


Zlio-inguiual  nerve 
Dissection  Hhowmg  thoracic,  ilio-hypottmstric  and  illo-inguinat  nerves 

equivalent  of  a  lateral  cutaneous  branch.  In  addition  to  the  lateral  cutaneous,  the 
anterior  cutaneous  branch  may  albo  be  wanting,  the  area  typically  supplied  by 
the  absent  branch  being  served  by  the  descending  branches  of  the  cervical  plexus. 


THE  THORACIC   NERVES. 


1317 


The  second  thoracic  nerve  sometimes  contributes  fibres  to  the  brachial  plexus. 
The  posterior  ramus  of  its  lateral  cutaneous  branch  is  called  the  intercoslo-humeral  nerve. 

The  intercosto-humeral  nerve  (n.  intercostobrachialis)  (Fig.  1105)  is  quite 
large  and  pierces  the  inner  axillary  wall  betv^^en  the  second  and  third  nbs.  Enter- 
inir  the  axilla,  it  crosses  that  space  toward  the  arm  and  communicates  with  the  lesser 
internal  cutaneous  nerve  from  the  brachial  plexus.  After  piercing  the  deep  fascia, 
the  intercosto-humeral  nerve  supplies  the  internal  and  posterior  poUion  of  the  integ- 
ument of  the  upper  half  of  the  arm.  a  few  of  its  fibres  extending  slightly  beyt  :id  the 

margin  of  the  scapula.  •  .     \_     t  •  »        1 

The  third  thoracic  nerve  may  form  an  inosculation  with  the  lesser  internal 

cutaneous  nerve.  ,.      ,   ,         ,.     ,    ..    'u       a 

The  twelfth  thoracic  or  the  sub-ostal  nerve  lies  below  the  last  rib  and 
therefore  does  not  occupy  an  intercostal  space,  but  passes  outward  below  the 
external  arcuate  ligament  and  anterior  to  the  quadratus  lumborum  muscle.  It 
contributes  a  twig  to  the  lumbar  plexus  which  passes  down  to  )oin  the  first  lumter 
nerve  Its  lateral  cutaneous  branch  is  not  confined  in  its  distribution  to  the 
abdominal  wall,  since,  after  piercing  the  internal  oblique  and  sending  a  hlanient 
to  the  lower  digitation  of  the  external  oblique,  it  penetrates  the  substance  of  the 
latter  muscle  at  a  point  from  2-10  cm.  above  the  crest  of  the  ilium  and  supplies  the 
integument  of  the  gluteal  region  as  far  down  as  the  upper  mai^n  of  the  great 
trochanter ^^^g.  J  ^^3  -^^^^.^  ^^^.^  are  :  (i)  the  muscular  and  (2)  the  cutaneous. 

I.  The  muscular  branches  (rr.  muiculare*)  may  be  divided  into  two  groups:  (a)  the  thoracic 

"^  ^a^  The'thi^cta  muscular  branches  arise  from  the  first  to  the  seventh  inchisive  and  supply 
the  external  and  internal  intercostals,  the  subcostals,  the  levatores  coitarum.  the  serratus 
Dosticus  superior,  the  triangularis  stemi  and  the  rectus  abdominis.  .      , ,. 

The  branches  to  the  intercostal  and  siUicostal  muscles  are  distributed  throughout  the  course 
.f  each  nerve.  The  first  to  be  given  off  is  the  largest  and  courses  forward  for  some  distance 
along  the  lower  part  of  the  intercostel  space.    The  others  vary  greatly  in  number  and  size. 

The  branches  to  the  tevafores  costarum  consist  of  fine  threads,  one  arising  from  each  nerve 
beyond  the  anterior  costo-transverse  ligament.  They  pierce  the  external  intercostal  muscles 
and  enter  the  deep  surface  of  the  muscles  which  they  supply. 

The  branches  to  the  serratits  posticus  superior  arxe  from  the  upper  four  nerves.  After 
piercing  the  external  intercostal  muscles  they  pass  along  the  outer  margin  of  the  ilionrostalis  and 
suddIv  the  four  digitations  of  their  muscle. .u 

The  branches  to  the  triangularis  sterni  are  terminal  continuations  of  the  third  to  the  seventh 
intercostal  nerves.  After  piercing  the  internal  intercostal  muscles  they  pass  /o^^a/d  betvveen 
the  triangularis  stemi  and  the  internal  intercostals  or.  in  the  case  of  the  «^^''"«';:  »"t^.'l°V°  "^o 
transven«ilis  muscle.  In  addition  to  supplying  the  tri.ingulans  stemi  the  seventh  sends  fibres  to 
the  first  dieitation  of  the  transversalis.  3      .      .t.     j 

The  branches  to  the  rectus  arise  from  the  fifth,  sixth  and  seventh  and  enter  the  deep 

surfa^  °!^l^^^^  muscular  branches  arise  from  the  eighth  to  the  twelfth  inclusive  and  are 
distributed  to  the  intercostals,  the  subcostals,  the  levatores  costarum,  the  serratus  posticus  inferior, 
the  external  obique.  the  internal  oblique,  the  transversalis.  the  rectus,  the  pytamidalis  and  the 

'"'"''"'■ni^branches  to  the  intercostal,  subcostal  and  levatores  costarum  muscles,  with  the  excep- 
tion of  arising  from  the  lower  thoracic  nerves,  resemble  in  origin,  course  and  distribution  those 

'"^''Vh^hrllt'^^^ToxlTs^atusposticus  inferior  are  largerthan  those  to  the  serratus  posticus 
s«,,erior.  They  arise  from  the  ninth,  tenth  and  eleventh  nerves  and  pass  around  the  lateral 
maririn  of  the  ilio-costalis  to  reach  their  destination.  .    ,     , 

The  branches  ro\:t^ft  external  oblique,  X\^  internal o.lique  and  the /ni«^r  Wm  compnse 
numero.^  fine  twigs  which  supply  those  muscles  and  arise  from  the  lower  five  thoracic  nerves  as 
thev  course  forward  lietween  the  transversidis  and  the  internal  Ob  ique. 

they  ^^;;^J^^™  ^^  ^^  ,^^  ^^^f^  3ri^  from  .he  eighth  to  the  twelfth  nerves  inclusive  after  they 
have  entered  the  sheath  and  as  they  pierce  the  rectus  on  their  way  to  the  surface. 

The  brancht-  to  the  pyramidalis  are  derived  from  the  twelfth  thoracic  and  first  lumbar 

"'"'"^The  branche^  to  the  diaphragm  are  supplied  to  its  costal  portion  and  consist  <rf  tim. 
filaments  which  are  given  off  by  the  lower  six  thoracic  nerves  (Lur  nka). 


K 


I3i8  HUMAN  ANATOMY. 

2.  The  cutaneous  branche*  are  larger  than  the  muscular  and  consist  of  two 
sets  :  (a)  the  lateral  cutatuous  and  {b)  the  anterior  cutaneous. 


a.  The  Utenl  cutaneous  branches  (rr.  cntaoei  laterales)  consist  of  tn-o  series,  an  upper 
and  a  lower,  the  former  originating  from  the  first  to  the  sixth  and  the  latter  from  the  sixth  to  the 
twelfth  thoracic  nerves.  Those  of  the  upper  series  pierce  the  external  intercostal  mu.scles  and 
tho!;e  of  the  lower  the  external  oblique  in  a  line  situated  midway  between  the  mammary-  and 
mid-axillary  lines.  The  upper  seven  pass  between  the  digitations  of  the  serratus  magnus  and  the 
lower  between  the  digitations  of  the  latissimus  uorsi  and  the  external  oblique.  The  one  arising; 
from  the  twelfth  pierces  the  musculature  of  the  external  oblique.  Each  lateral  cutaneous  ner\'e 
divides  into  {aa)  an  anterior  and  {M)  a  posterior  branch  (Fig.  1083). 

aa.  The  posterior  branches  (rr.  posteriorcs)  are  smaller  than  the  anterior.  They  wind 
around  the  edge  of  the  latissimus  dorsi  and  supply  the  integument  of  the  lateral  area  of  the 
trunk  as  far  back  as  the  anterior  margin  of  the  region  supplied  by  the  posterior  primary  divi- 
sions of  the  thoracic  nerves.  The  branches  from  the  third  to  the  sixth  inclusive  have  fibres 
which  are  distributed  over  the  lateral  portion  of  the  scapula. 

66.  The  anterior  branches  (rr.  anterlorta  tpcctorales  et  abdomlnalcs] )  are  of  considerably 
greater  size  than  the  posterior.  Those  from  the  second  to  the  seventh  pass  toward  the  lateral 
margin  of  the  pectoralis  major  and  supply  the  integument  of  this  region  as  far  forward  as  the 
nipple.  Branches  (rr.  maaiiiiarii  laterales)  from  the  fourth,  fifth,  and  sixth  send  filamencs  ti> 
the  skin  and  substance  of  the  mammary  gland.  Those  from  the  seventh  to  the  eleventh  supply 
the  integument  of  the  abdomen  as  far  anterior  as  the  lateral  margin  of  the  rectus  The  anterior 
branch  from  the  twelfth  has  a  filament  which  passes  over  the  iliac  crest  to  the  integument  of  the 
gluteal  region,  usually  sending  a  branch  as  far  as  the  great  trochanter.  It  maintains  a  more  or 
less  even  balance  with  the  corresponding  branch  of  the  first  lumbar  nerve,  each  supplying  any 
deficiency  in  the  other. 

6.  The  anterior  cutaneous  Inanches  (rr.  cntaaei  anteriores)  are  the  terminal  fibres  of  the 
thoracic  nerves.  Those  from  the  upper  six  (rr.  cottnci  pcctoralea  anteriores)  pierce  the  pectoralis 
major  near  the  lateral  margin  of  the  sternum  and  supply  the  adjacent  integument  of  the  thorax. 
Filaments  (rr.  mammarii  mcdiales)  are  distributed  to  the  skin  of  the  mesial  portion  of  the  mam- 
mary gland.  The  anterior  cutaneous  branches  from  the  lower  six  (rr.  cutanei  aMomioales  ante- 
riores) vary  in  position.  They  consist  of  the  terminal  filaments  which  perforate  the  anterior 
portion  of  the  rectus  sheath  at  a  situation  anywhere  between  the  linese  alba  and  semilunaris. 
Those  from  the  seventh  become  superficial  near  the  ensiform  cartilage,  those  from  the  tenth 
supply  the  region  of  the  umbilicus  and  those  from  the  twelfth  are  distributed  to  the  area  located 
midway  between  the  umbilicus  and  the  pubic  crest  (Fig.  1105). 


Practical  Considerations. — Of  the  branches  of  the  thoracic  spinal  nerves, 
the  anterior  or  intercostals  suffer  most  frequently  from  sensory  disturbances,  and 
the  posterior  from  motor  disturbances.  Intercostal  neuralgia  may  result  from 
pressure,  as  from  aneurism  or  spinal  disease,  or  it  may  be  due  to  injury.  The  lower 
mtercostals  enter  into  the  supply  of  both  the  thoracic  and  the  anterior  .abdominal 
walls,  the  pleura  also  being  supplied  by  them.  Pain  referred  to  the  abdominal  wall 
and  rigidity  of  the  abdominal  muscles  may  therefore  be  due  to  diseases  within  the 
chest,  as  pleurisy.  Such  diseases  in  the  upper  part  of  the  chest  may  cause  pain  to 
extend  down  the  arm  along  the  intercosto-humeral  nerve,  which  is  the  lateral  cuta- 
neous branch  of  the  second  i.itercostal  nerve,  or  sometimes  of  the  second  and  third 
intercostals.  The  pain  of  intercostal  neuralgias  often  becomes  intense,  especially 
after  violent  expiratory  efforts,  as  in  couehing  and  sneezing ;  not  infrequently  after 
the  pain  ceases,  herpes  zoster  appears  in  tne  line  of  the  nerve  affected.  This  m../  be 
a  trophic  disturbance  or  an  extension  of  the  inflammation  along  the  nerve  endings 
to  the  skin.  Maslodynia,  or  the  so-called  "irritable  breast  of  Cooper,"  is  due  to 
intercostal  neuralgia,  and  occurs  in  the  female  during  the  child-bearing  period. 

The  lower  intercostal  nerves,  with  the  ilio-hypogastric  and  ilio-ingumal,  supply 
the  muscles  of  the  abdominal  wall,  and  are  frequently  injured  by  the  incisions  made 
in  abdominal  operations,  thus  leading  to  more  or  less  impairment  of  the  muscles  sup- 
plied and  favoring  the  later  development  of  hernia.  The  incision  should  therefore, 
so  far  as  possible,  be  made  in  the  line  of  the  fibres  of  the  muscles  (page   535). 

The  intercostal  nerves  continue  their  oblique  line  through  the  abdominal  mus- 
cles. The  pain  from  Pott's  disease  is  often  transferred  along  the  nerves  coming  from 
the  affected  segment  of  the  cord.     In  this  way  pain  in  the  abdominal  region  may 


THE  LUMBAR   PLEXUS. 


1319 


result  from  this  disease,  and  an  abdominal  lesion  may  be  suspected;  thus  has 
occurred  more  particularly  in  children.  A  feeling  of  tightness  is  sometimes  observed 
about  the  abdomen,  corresponding  to  the  course  of  one  or  more  pairs  of  these 
nerves  and  may  be  due  to  impaired  sensation  in  them.  Since  the  abdommal 
musdra  are  supplied  chiefly  by  the  seven  lower  intercostal  nerves,  they  are 
concerned  in  respiration.  When  they  are  contracted  as  m  general  peritonitis,  the 
lower  ribs  become  immobile,  and  breathing  Ukes  place  chiefly  in  the  upper  portion 
of  the  chest. 

THE  LUMBAR  PLEXUS. 

The  lumbar  plexus  (plexus  lumbalis)  lies  in  the  substance  of  the  psoas  magnus 
muscle  anterior  to  the  ti^nsverse  processes  of  the  lumbar  vertebra,  and  consists  of 
a  series  of  loops  formed  by  the  anterior  primary  divisions  of  the  first,  second  and 
third  lumbar  nerves,  the  smaller  subdivision  of  the  fourth  lumbar  and  sometimes  a 
branch  from  the  twelfth  thoracic  nerve.  The  remainder  and  major  portion  of  the 
fourth  lumbar  nerve  unites  with  the  entire  anterior  primary  division  of  the  fifth  to 
form  a  conjoint  trunk,  the  lumbo-sacral  cord  (tmncus  lumbosacralis),  which 
passes  into  the  pelvis  to  become  a  constituent  of  the  sacral  plexus  (Fig.  1106). 
The  lumbar  nerves  increase  in  thickness  from  above  downward,  the  first  being  only 
2  5  mm.,  while  the  fifth  attains  a  diameter  of  7  mm.  The  length  of  the  nerves  from 
their  exit  at  the  intervertebral  foramina  to  their  point  of  division  vanes  considerably, 
in  the  case  of  the  first  being  i  mm.  or  less,  of  the  second  10  mm.  and  of  the  third 

from  20-25  nim.  ,  ,„.  ,^     l    <=    ..  1      u 

Constitution  and  Plan.— In  forming  the  plexus  (Fig.  1106),  the  first  lumbar 
nerve  divides  almost  immediately  after  its  exit  from  the  vertebral  column  into  an 
upper  and  a  lower  branch.  The  upper, 
which  may  receive  a  contribution  from 
the  twelfth  thoracic  nerve,  becomes  the 
Hio-kypogastricdtnA  ilio-inguinal  nerves. 
The  lower  branch,  near  the  body  of  the 
second  lumbar  vertebra  joins  the  upper 
part  of  the  second  lumbar  nerve,  which, 
like  the  first,  divides  into  an  upper  and 
a  lower  branch.  The  union  of  the  lower 
branch  of  the  first  and  the  upper  branch 
of  the  second  results  in  the  formation  of 
the  genUo-crural  nerve.  Sometimes 
fibres  from  the  first  aid  in  the  formation 
of  the  anterior  crural  and  obturator 
nerves.  The  lower  branch  of  the  second, 
all  of  the  third  and  that  part  of  the 
fourth  which  enters  the  lumbar  plexus 
divide  into  smaller  anterior  and  larger 
posterior  trunks.  From  the  union  of 
the  anterior  branches  of  these  three  the 
obturator  nerve  is  formed,  and  from  the 
union  of  the  posterior  results  the  an- 
terior crural  nerve.  The  posterior  por- 
tions of  the  second  and  third  nerves 
give  off  from  their  dorsal  aspect  small 
branches  which  anite  into  the  external 
cutaneous  nerve.   The  accessory  obturator 


Fig.  1106. 


Uiatmm  IlliutnUnc  plan  of  lumbar  plexui. 


cutaneous  nerve.    inca«cjji»»^  •^i'.-'—"     .,,,,,.  ^.  .    „t 

nerve,  when  it  exists,  arises  from  the  third  and  fourth  lumbar  between  the  roots  ot 
the  anterior  crural  and  obturator  nerves. 

Communications.— All  of  the  lumbar  nerves  receive  gray  rami  communicantes 
from  the  gangliated  cord  of  the  sympathetic  ;  and  from  the  first  and  ^nd,  and 
possibly  the  third  and  fourth,  white  rami  communicantes  pass  to  the  lumbar  portion 
of  the  gangliated  cord. 


I320 


HUMAN  ANATOMY. 


Variations. — That  portion  of  the  fourth  lumbar  nerve,  mn.fitrcalis,  which  joins  the  lumbo- 
sacral cord,  is  usually  less  than  half  of  the  parent  truiik,  but  varies  from  one-twentieth  tu 
nine-tenths.  When  large,  it  may  be  joined  by  a  branch  from  the  third  lumbar,  and  when 
small  the  fifth  lumbar  may  contribute  to  the  lumbv  plexus,  the  fibres  going  to  the  ante- 
rior crural  alone  or  to  the  anterior  crural  and  obturator  nerves.  The  branch  to  the  lumbo- 
sacral cord  from  the  fourth  lumbar  mav  be  absent  and  in  such  an  event  the  fifth  is  the  only 
furcal  nerve  sending  fibres  to  both  the  lumbar  and  the  sacral  plexus.  It  is  thus  possible  to 
have  as  furcal  nerves  the  third  and  fourth,  the  fourth  alone,  the  fourth  and  fifth  or  the  fifth 
alone,  and  according  to  the  high  or  low  position  of  these  there  is  found  a  corresponding  origin 
of  the  branches  of  the  lumbar  plexus.  In  this  manner  are  accounted  for  the  ktgh  vaatow,  or 
prefixed  viA  postfixed  types  of  plexus. 

Branches  of  the  lumbar  plexus  are : 

1.  The  Muscular  5.  The  External  Cutaneous 

2.  The  Ilio-Hyf)ogastric  6.  The  Obturator 

3.  The  Ilio-Inguinal  7.  The  Accessory  Obturator 

4.  The  Genito-Crural  8.  The  Ante  w  >r  Crural 

I.     The  Muscular  Branches. 

The  muscular  branches  (rr.  musculares)  supply  the  quadratus  lumborum,  the 
psoas  magnus  and  the  psoas  parvus. 

The  branches  to  the  quadratus  lumborum  arise  from  the  upper  three  or  four 
lumbar  nerves,  and  sometimes  from  the  last  thoracic,  and  pass  directly  into  the 
quadratus. 

The  branches  to  the  psoas  magnus  arise  mainly  from  the  second  and  third  lumbar 
nerves,  there  sometimes  being  additional  ones  from  the  first  and  fourth.  They  pass 
directly  into  the  muscle. 

The  branches  to  the  psoas  parvus  consist  of  filaments  from  the  first  or  second 
lumbar  nerve  which  reach  the  muscle  by  piercing  the  underlying  psoas  magnus. 


2.     The  Ilio-Hvpogastric  Nerve. 

The  ilio-hypogastric  nerve  (n.  illohypoKastricus)  (Fig.  H07)  is  the  uppermost 
branch  of  the  plexus  and  is  somewhat  larger  than  its  associate,  the  ilio-inguinal.  Whilst 
it  derives  the  major  portion  and  sometimes  all  of  its  fibres  from  the  first  lumbar  nerve, 
it  usually  receives  others  from  the  twelfth  and  occasionally  the  eleventh  thorycic.  It 
emerges  from  the  lateral  margin  of  the  upper  portion  of  the  psoas  magnus  and  runs, 
below  and  parallel  with  the  twelfth  thoracic  nerve,  outward  and  downward,  posterior 
to  the  kidney  and  anterior  to  the  quadratus  lumborum.  Reaching  the  crest  of  the 
ilium,  it  pierces  the  transversalis  muscle  and  occupies  the  intermuscular  space  between 
the  internal  oblique  and  the  transversalis.  After  coursing  along  this  interval  as  far 
as  the  middle  of  the  iliac  crest,  it  divides  into  its  terminal  branches,  (a)  the  iliac  and 
(b)  the  hypogastric,  which  correspond  morphologically  with  the  lateral  and  anterior 
cutaneous  branches  of  the  thoracic  nerves.  There  are  also  some  (<■)  muscular 
branches. 

a.  The  iliac  branch  (r.  cutaneus  lattmlis')  pierces  the  internal  and  external  obliques  about 
the  middle  of  the  iliac  crest  and  is  distributed  to  the  integument  of  the  anterior  gluteal  region 
which  covers  the  gluteus  medius  and  the  tensor  fascis  femoris  (Fig.  1083).  It  forms  an 
inosculation  with  the  lateral  cutaneous  branch  of  the  twelfth  thoracic  nerve  and  maintains  an 
even  balance  with  it,  deficiency  in  the  development  of  either  being  recompensed  for  by  a  com- 
pensating increase  in  size  of  the  other. 

6.  The  hypogastric  branch  (r.  cutanea*  anterior)  continues  the  direction  and  course 
of  the  main  trunk  between  the  transver.s.ilis  and  the  internal  oblique  almost  to  the  linea  alba. 
Near  the  anterior  superior  spine  of  the  ilium  it  forms  an  inosculation  with  the  ilio-inguinal 
ner\'e.  As  it  approaches  the  region  of  the  internal  abdominal  riiig  it  begins  to  pu.sh  its  way 
gradually  through  the  internal  oblique  and  gain  the  interval  between  the  internal  and  the  exter- 
nal oblique  (Fig.  1 105).  A  short  distance  superior  and  internal  to  the  external  abdominal  ring 
it  traverses  a  tiny  foramen  in  the  aponeurosis  of  the  external  oblique  and  breaks  up  into  fibres 
of  termination  which  supply  the  integument  of  the  suprapubic  region. 

c.  Muscular  branchci  (it.  muacularca)  arise  from  the  hypogastric  branch  in  its  course 
through  the  abdominal  wall  and  supply  the  \  ansversalis,  the  internal  oblique  and  the  external 
oblique. 


THE  LUMBAR   PLEXUS. 


1331 


Variationa.— The  iliac  branch  luay  be  absent,  its  place  being  taken  by  the  lateral  cutaneous 
branch  of  the  twelfth  thoracic  nerve.  The  hypogastric  branch  may  inosculate  with  the  twelfth 
thoracic  and  may  supply  the  pyramidalis  muscle. 

3.    The  Ilio-Inguinai.  Nerve. 

The  iljo-inguinal  ner\'e  (n.  iUoinRuinalls)  (Fig.  1107)  is  the  second  branch  of 
the  lumbar  ple-xus  and  is  somewhat  smaller  than  the  ilio-hypogastnc.  Its  fibres 
usually  arise  from  the  first  lumbar  nerve,  with  accessions  from  the  twelfth  thoracic. 

Fig.  I 107. 


|: 


XII.  rib 
XII.  tbonck  nerve 


Qoadratus  lumboram 
Pioai  magnn* 

External  obliqtw 

LpStervl  culAneous  branch 

ol  XII.  doraal  nerve 

Internal  oblique 

Trantvenalis 

Ilio-hypogaatric  nerve 

Ilio-inguinal  nerve 

Iliac  branch  of 
ilio-hypogastric 


Lateral  cutancona  branch 
of  XII.  doraal  nerve 


External  culaneoua  nerve 

Anterior  crural  nerve 
Genital  branch  of 
genito<ruial  nerve 


Crural  branch  of 
genito^rural  nerve 


Branches  of  middle 

cutaneous  nerve 


I.  lumbar  ganglion 


Rami  communicanlei 


Aorta 

IV.  lumbar  nenre 

>V.  lumbar  ganglion 

V.  lumbar  nerve 
Pail  of  V.  lumbar  ganglion 

Genito.crural  ni'  ' 
I.  sacral  ganglion 

.  aacral  nerve 

n.  sacral  nerve 

IV.  sacral  ganglion 
Obturator  nerve 
,Accessor>-  obturator  n^'vt 


Hypogaatric  branches 
of  ifioniypogaatric  nerve 


Ilio-inguinal  nerve 


Branch  of  internal 
cutaneous  nerve 


Deep  dissection,  showing  nerves  arising  from  lumbar  plexus  and  lower  p.-irt 
uf  sympathetic  gangliated  cord. 

Sometimes  it  arises  entirely  from  the  twelfth  thoracic  or  from  the  second  lumbar  <>r 
from  the  loop  between  the  first  and  second  lumbar  nerves.  It  occasionally  forms  a 
common  trunk  of  considerable  length  with  the  ilio-hypogastric.     In  the  early  part 


1322 


HUMAN  ANATOMY. 


of  its  course  it  ftarallels  the  ilio-hypogastric,  appearing  at  the  edge  of  the  psoas 
magnus,  crossing  the  quadratus  lumboruin  behind  the  kidney  and  piercing  the  trans- 
versalis  to  reach  the  intermuscular  cleft  between  the  transversalis  and  the  internal 
oblique  (Fig.  1105).  While  in  the  last  situation  it  inosculates  with  the  ilio-hypo- 
gastric  and  continues  forward  to  enter  the  inguinal  canal,  from  which  it  emerges 
either  through  the  external  abdominal  ring  or  through  the  external  pillar  of  the 
ring,  infero-lateral  to  the  spermatic  cord. 

Some  of  the  branches  of  the  ilio-inguinal  supply  the  integument  of  the  u|^r  inner  portion 
of  the  thigh.  Other!  'no.  acrotain  antcriiircs)  are  distributed  tu  the  pubic  region  and  the  base 
of  the  penis  and  scrotum  or,  in  the  female  (na.  labUIn  anuriort*),  the  mons  Veneris  and  lahi.i 
majora.  Tiny  motor  filaments  ( rr.  mniculam)  are  given  off  in  the  course  of  the  nerve  to  the- 
transversalis,  the  internal  oblique  and  the  external  oblique. 

Variation*. — The  ilio-inguinal  may  be  small  and  terminate  near  the  iliac  crest  bv  joining 
the  ilio-hypogastric,  which  then  sends  off  an  inguinal  branch  with  the  course  and  distribution  of 
the  absent  portion  of  the  ilio-inguinal.  The  nerve  may  be  absent  entirely  and  replaced  by  either 
branch,  usually  the  genital,  of  the  genito-crural.  It  may  give  off  a  lateral  cutaneous  or  iliac 
branch  for  the  supply  of  the  integument  in  the  region  of  the  anterior  superior  spine  of  the  ilium. 
The  ilio-inguinal  may  partially  replace  the  genital  branch  of  the  genito-crural  or,  in  rare  in- 
stances, the  extem.<l  cutaneous. 

4.    The  Genito-Crural  Nerve. 

The  genito-crural  nerve  (n.  genitofemoralis)  is  formed  by  two  roots,  one  of  which 
arises  from  the  loop  between  the  first  and  second  lumbar  nerves  and  the  other 
directly  from  the  second  lumbar  ner\'e,  its  fibres  being  derivatives  of  the  first  and 
second  lumbar.  The  nerve  passes  obliquely  forward  through  the  musculature  of  the 
psoas  magnus,  near  the  inner  border  of  whose  anterior  surfetce  it  emerges  opposite 
the  body  of  the  third  lumbar  vertebra,  where  division  into  the  two  terminal 
branches,  (a)  the  g-enita/  and  (b)  the  crural,  takes  place  (Fig.  1107).  Occa- 
sionally division  occurs  earlier  in  the  course  of  the  nerve,  in  the  substance  of  the 
psoas,  and  under  these  circumstances  the  two  branches  emerge  separately  from  the 
muscle.    In  addition  to  the  terminal  branches  there  are  some  (f )  muscular  twigs. 

a  The  feniul  branch  (a.  •ptrmaticm  cxtaraoa)  obtairis  its  fibres  from  the  first  lumbar 
nerve.  Passing  downward  on  the  inner  margin  of  the  psoas  magnus,  it  cros.ses  the  external 
iliac  arter>-  and  bends  forward  toward  the  posterior  wall  of  the  inguinal  canal.  It  then  enters 
the  canal  either  by  piercing  the  infundibuliform  or  the  transversalis  fascia  and,  lying  internal  to 
and  below  the  spermatic  cord,  traverses  the  canal  and  enters  the  scrotum  (Fig.  1108).  It  sends 
a  filament  to  the  external  iliac  artery  and  supplies  the  cremaster  muscle,  the  skin  of  the  scrotum 
and  the  integument  of  the  thigh  immediately  adjacent  to  the  scrotum.  In  the  female  it  is 
smaller  and  accompanies  the  round  ligament  of  the  uterus  to  the  labium  majus,  to  whose  in- 
tegument it  is  distributed.  It  communicates  with  tlie  ilio-inguinal  nerve  and  with  the  spermatic 
plexus  of  the  sympathetic. 

*.  The  crural  branch  (n.  tamtmlnguinalis)  consists  of  fibres  from  the  second  lumbar  nerve. 
It  courses  down  on  the  anterior  surface  of  the  psoas  magnus,  lateral  to  the  genital  branch  and 
to  the  external  iliac  vessels,  and  enters  the  thigh  by  passing  beneath  Poupart's  ligament.  One 
of  its  filaments  traverses  the  saphenous  opening,  while  the  remainder  of  the  nerve  pierces  the 
fascia  lata  to  the  outer  side  of  the  opening  (Fig.  1107).  Its  branches  vary  considerably  in  size 
and  length  and  are  distributed  to  the  cuUneous  area  of  the  upper  an*;rior  part  of  the  thigh 
between  the  regions  supplied  by  the  external  cutaneous  and  ilio-inguinal  nerves,  sometimes 
extending  downward  as  far  as  the  middle  of  the  thigh.  It  furnishes  a  minute  branch  to  the 
femoral  artery  and  inosculates  with  the  middle  cutaneous  nerve. 

c.  Muscular  liranches  to  the  internal  oblique  and  transversalis  are  frequently  given  off  by 
the  genital  branch. 

Variations.— The  genital  and  crural  branches  may  arise  as  separate  offshoots  of  the  lumbar 
plexus  and  either  of  them  may  be  derived  entirely  from  the  first  or  the  second  lumbar  nerve. 
The  genital  branch  sometimes  contains  fibres  from  the  twelfth  thoracic.  Absence  of  the  genito- 
cnir.il  or  of  cither  hmnrh  m.iv  occur,  the  fibres  of  the  genital  branch  being  contamed  m  the  ilio-  ■ 
inguinal  and  those  of  the  crural  in  the  external  cutaneous  or  the  anterior  crural.  The  genittl 
branch  may  replace  or  reinforce  the  ilio-inguinal  nerve;  the  crural  branch  may  act  similarly 
toward  tlie  external  or  the  middle  cutaneous  nerve.  A  specimen  found  in  the  anatomical  labo- 
ratory of  the  University  of  Pennsylvania  showed  unusually  extensive  distribution  of  the  cnual 


THE  LUMBAR   PLEXUS. 


1323 


branch.    It  was  lareer  than  nonnal,  its  size  being  that  of  the  normal  external  cutaneous,  and  it 
emerged  from  the  deep  fascia  below  Poupart's  ligament  directly  anterior  to  the  femoral  vem.   It 

Kic.     108. 


Phu  parvm 
CWnilo-crunil  iwne 


Anterior  crural 
External  cuuncou*  nervi 

Gtniul  bianch  of  g«nito<ruiar 

Sartoriiu,  tum\ 

Branch  to  pcctlneur 

Branch  to  rectui  lemoria 

Branch  to  vaitus  extemiU' 


Rectus  (cmoril 
Middle  cutaneous  nerve- 


Reaui  frniorii 


Accenor)'  obturator 

Crural  branch  <A 

genlto-crural 
llio-inguinal  nerve 


Pectineus 
Adductor  longus 

Internal  saphenous 

nerve 
Intenuil  cutaneous 

ner\-e 


Muscular  branch  of 
superficial  divisiott 
of  obturator  nerve 


Branch  from  Irrtemal  saphenous 
to  subsartorial  plexus 


Anterior  branch  of  intenuil  cutaneous 


Cutaneous  branch  of  superficial  divisioa 
of  obturator  nerve 


Posterior  branch  of  internal  cutancoua 


From  posterior  branch  of  internal  cutaneous 


Articular  branch  from  nerve  to  vastus 
internus 

-Cutaneous  patellar  branch  of  internal 

saphenous  nerve 
Internal  saphenous  nerve 


Dissection  oi  right  thigh,  showing  branches  of  anterior  crural  nerve. 


divided  into  a  smaller  mesial  and  larger  lateral  branch  and  was  distributed  to  the  integument  oi 
the  thigh  as  far  down  as  the  junction  of  the  middle  and  lower  thirds. 


1324 


HUMAN  ANATOMY. 


5.    The  External  Cutaneous  Nervk. 

The  external  cutaneous  nerve  (n.  cutaaeus  femoris  lateralis)  (Fig.  1 109)  arises  at 
the  posterior  aspect  of  the  lumbar  plexus  from  the  second  and,  to  a  less  extent,  the 
third  lumbar  ner\'e.  It  may  arise  from  the  first  and  second,  from  the  second  alone 
or  may  derive  a  majority  of  its  constituent  fibres  from  the  third.  It  passes  obliquely 
downward  and  outward  beneath  the  lateral  margin  of  the  psoas  magnus  and  oyer  the 
iliacus  muscle,  through  the  iliac  fossa,  covered  by  the  iliac  fascia.  After  crossing  the 
deep  circumflex  iliac  artery  it  enters  the  thigh  beneath  Poupart's  ligament,  mesial 
to  the  anterior  superior  spine  of  the  ilium,  and  ^Msses  over,  sometimes  through  or 
under,  the  pointecl  tendinous  origin  of  the  sartonus.  The  ner\'e  then  descends  in 
the  thigh  beneath  the  fascia  lata  and  soon  divides  into  («)  an  anterior  and  (*)  a 
/Of /frwr  terminal  branch  (Fig.  1 1 10). 

a.  The  anterior  branch  (r.  aaterler)  follows  a  downward  course  in  the  thiRh  in  a  tiibulnr 
canal  in  the  fascia  lata,  from  which  it  emerges  at  a  point  10-15  cm.  below  the  anterior  superior 
iliac  spine.  It  continues  d< -v  ward  anterior  to  the  vastus  extemus  muscle  and  is  distributed  to 
the  inteKument  of  the  ante;  !j-,-<ieral  aspect  of  the  tliigh  as  far  as  the  knee.  Numerous  collateral 
branches  are  given  off,  the  majority  of  which  arise  from  its  lateral  edge  and  supply  the  skin  ovf  1 
the  ili'~  'ibial  band.  The  main  trunk  may  extend  quite  to  the  knee  and  become  a  participant  in 
the  f    I  '  tion  of  the  patellar  plexus. 

-  i'he  posterior  branch  (r.  poaUrior)  passes  obliquely  backward  through  the  fa.scia  lata 
ani'  jaks  up  into  several  branches  which  are  distributed  to  the  integument  over  the  tensor 
fas  ■_•  femoris  and  the  lower  portion  of  the  gluteal  region.  The  uppermost  filaments  are  crossed 
by  trtigs  from  the  lateral  cutaneous  branch  of  the  twelfth  thoracic  nerve. 

Variationa.— The  external  cutaneous  may  be  associated  with  the  anterior  crural  until  after 
Poupart's  ligament  has  been  pa.ssed.  A  branch  of  the  genito-crural  may  replace  the  posterior 
branch.     In  one  case  a  branch  of  the  ilio-inguinal  took  the  place  of  the  external  cutaneous. 

Three  siiecimens  found  in  the  anatomical  rooms  of  the  University  of  Pennsylvania  sh«)wed 
decided  anomalies.  In  one  the  nerve  passed  beneath  Poupart's  ligament  at  a  point  midway 
lietween  the  anterior  superior  spine  of  tne  ilium  and  the  femoral  artery.  In  another  the  nerve 
of  the  right  side  resembled  in  position  the  one  just  mentioned,  while  the  left  was  apparently 
absent,  its  place  being  taken  by  a  branch  of  the  anterior  crural.  In  the  third  the  posterior 
branch  emerged  from  f^eneath  Poupart's  ligament  5  cm.  to  the  inner  side  of  the  anterior  superior 
iliac  spine.  The  anterior  branch  formed  a  common  trunk  with  the  external  branch  of  the  mitl- 
dle  cutaneous  ner\e.  From  the  joint  trunk  a  small  branch  passed  to  join  the  internal  branch  of 
the  middle  cutaneous  after  the  latter  had  pierced  the  sartonus  muscle 

6.     The  Obturator  NER^  k. 

The  obturator  nerve  (n.  obturatorius)  (Fig  nor.)  is  composed  of  fibres  which 
arise  from  the  second,  third  and  fourth  lumbar  nerves,  the  fourth  supplying  the 
largest  and  the  second  the  smallest  contribution,  the  latter  sometimes  being  absent 
entirely.  Occasionally  additional  roots  are  derived  from  the  first  and  fifth  lumbar 
nerves,  and  sometimes  the  nerve  arises,  in  the  high  form  of  plexus,  from  the  first, 
second  and  third  lumbar  ner\'es. 

The  three  roots  having  united  in  the  substance  of  the  psoas  magnus,  the  nerve 
piisses  vertically  downward  and  emerges,  the  only  constant  branch  of  the  plexus  to 
do  so,  from  the  mesial  margin  of  the  psoas  muscle  opposite  the  brim  of  the  true 
pelvis.  Lying  posterior  to  the  common  and  lateral  to  the  internal  iliac  vessels,  the 
obturator  nerve  courses  along  the  antero-lateral  wall  of  the  pelvis  below  the  ilio- 
pectineal  line,  above  the  obturator  vessels  and  upon  the  inner  surface  of  the  pelvic 
fascia.  It  escape,  from  the  pelvis  through  the  obturator  canal  in  the  obturator  mem- 
brane and  divides  into  its  terminal  branches,  either  while  still  within  the  foramen  or 
shortly  after  emerging  from  it.  These  branches  are  separated  from  each  other  first 
by  the  anterior  fibres  of  the  obturator  externus  muscle  and  later  by  the  adductor 
brevis  muscle.  They  supply  the  adductor  muscles,  the  hip  and  knee  joints  and  the 
integument  of  the  mesial  aspect  of  the  thigh. 

Branches. — The  obturator  gives  of! :  (a)  a  branch  to  the  obturator  extemus 
muscle  and  then  divides  into  its  terminal  branches,  {b)  the  anterior  and  (f)  the 
posterior. 


THE   LUMBAR   PLEXUS. 


1325 


a.  The  branch  to  the  obmralor  •Btarnus  arises  within  the  pelvis  from  the  Inner  tuirface  of 
the  obturator  nerve.     It  accompanies  the  parent  trunk  through  the  foramen,  Immediately  after 

Kiu.  1109. 


Xn.  cuuncoiu  ncrvt 

ADt.  «up-  ipine  of  iliam 
Ant.  crural 

Br.  to  ncivm 

Sartorial - 

irtle.  br.  of  •cccwory  obturator  - 

Iliaou- 

Br.  to  Twtu*  ext.  and  cmtcu*  . 
Rrctui. 

Middle  cutancotu  nerve  - 

lat.  cutaneous,  ant.  branch  - 

Femoral  artery  - 

iDl  cutaneous,  post,  branch - 

Int.  saphenous  ncrrc 
Nerve  to  vastus  intemua 

Rcctna 


Artie,  br.  from  nerv« 
to  vastus  int. 


Ext.  iliac  artery 

Int.  iliac  artery 
A'.xewtorj-  obturator  nerve 

Obturator  nerve 

Pectineup* 

Obturator  nerve,  ant.  'livision 

Adductor  lonifus,  en: 

Obturator  nrr\'e.  poi"  iivi»ion 

Articular  br.  to  hip.Joint 

Adductor  brevis 


Pectineus 
Adductor  magnUK 

Adductor  brevis 

Gracilis 
Adductor  longus 

Tcfniin^  br.  ant.  dlvltlon  oNufator  utrrm 

Cutaneous  branch 

ft.  froa  iat.  ciitaac«Mi9  tu  nibnrtoriil  plniM 

Artie,  br.  to  knee-joint  from  obturator 

Br.  to  subiartorial  ptcznii  ana  femoral 

artery 


CuUneous  br.  to  inner  surface 
of  thigh  and  knee 


itemal  saphenous  nerve 
lUneous  patellar  br.  int.  saphenous 

SartoriuB,  insertion 

Post.  t>r.  int.  cutaneous 
Internal  saphenous 


Dissection  of  right  thign,  showing  branches  of  anterior  crural  and  obturator  nerves, 
escaping  from  which  it  dips  down  in  the  interval  between  the  obturator  membrane  and  the  obtur- 
ator extemus  muscle.    From  this  situation  its  fibres  pass  through  the  deep  surface  into  the 
substance  of  tlie  muscle. 


m 


tjtS 


HUMAN   ANATOMY. 


astular. 


the 


the 


ik»r 


ongus  and  e   tein  the  deep 


h  The  •mtrior  branch  y  r.  alcrlar),  the  more  Muierficiat.  dCM  ettds  in  fr<>m  of  the  obturatoi 
extern  ,->  atn'  adductor  l>revis  mu-v  les  and  '-etwijcn  the  pectineu<t  and  th  id<'-  'tor  K>ngt»> 
Having  reamed  the  interval  belwf  n  the  atkiin.tortr>  itrc\a  and  Urngmt  ii  .-{mi.  :es  into  ii> 
terminxil  branches. 

Ranches  ut  the  anterk>r  divwwm  are:    iaa)  tht    irHeular,     hi)  the  . 
c-tUaneout,  (Mi  the  wmmtimf a/tug  ainJ  iff)  the  rascu/     . 

aa.  The  articular  branch  leaves  the  obturatiMr  .i     the   inferior  xnaa%\ 
forntiien  and  passes  throuKh  the  cotyloid  notch  tt;  supply  the  hip  joint 

bi.  The  muacular  branchaa  supply  the  adduclores  e>'>:vis  and  l<    kus  and  the  gracit- -i. 

The  branch  to  the  a^awtor  ArrMJ  enters  the  mtiaclt  learthe"  -r  margt'i  ■(  the  anterior 
surf  are. 

The  branch  to  the  adductor  longus  aers  the  CKislrior  surf  a  e  i.  the  mu-  le  and  -iome- 
times  gives  off  the  cutanfous  braiu-k  of  t!  ■  i>bturator  ,  se«    >elow) 

The  branch  to  thr  groiilis  (Kuses  it>  -ard  behitf!  th«-     ikhirl 
surface  of  its  musrle. 

re.  The  cui~<ncoua  branch  •.-  cntaacaa)  (Fig.  iiu)  is  va<  tbit  in  size  and  maintains  an 
iipprosimately  e\.  '  balance  with  i,.-  internal  cutaneous  l-rancr  <jf  tne  anterior  crural.  Some- 
times arising  from  the  nerve  to  the  adductor  longm,  it  becomes  -uperticial  in  the  middle  of  the 
thigh  by  passing  between  the  adductor  lof-i'!i»  an<'  the  gract''--  It  su(>plies  the  integument  of 
the  lower  inner  portion  of  the  thigh  and  >>•  leath  the  sartcxius  tonri'  an  Inosculation  with 
branches  of  the  internal  rutaneous  and  inter  it  sapheiHHi^  nerves,  called  the  aubaartorial  or 
obturator  pleaut. 

dd.  'The  commumicating  branchesci  mtXd  iw'lgi,  viiac\t  .iiiiit  in  the  pelvis  with  theaccessory 
obturator  nerve  and  in  'he  thigh  anterior  to  the  cat>=Miar  U|;ament  f  the  hip  joint  with  the 
anterior  crural. 

ft.  The  vascular  bt     fh  enters  Hunter's  canal  akmK  t^  niesial  edt; 
and  spreads  m  '  over  tht   awer  portion  of  th"-  superficial  femoral  artery 

c.  The   p.     erior  branch  frntmUnj,   th-  deeper,    pierces  the 

obturator  exter     -  mnscle  '      discends  m  the    kit  be  ween  the  adductor 
and  in  the  lattt      ituation  >  into  its  tfrmin     'tin.. 

Branches'    t  the  pa  ;  diviN      :    re:^.        .\c  mms<  ^Utr    ivi  (bb)  \.l\e  articuiar. 

aa.  The  inutcutar  bianche*  sup)!-  the  obi  ator  externus.  the  adductor  magnus  and  the 
adductor  br.- .  i- 

The  111  ah  to  the oA//.-  itor .  -&•n«i<^  i.sadd>: 
obturator  wntch  supplies  that  mu  e.  It  arises 
division  and  enters  the  superfici.i !  ~  .  rface  of  tJie  mus- 

The  bran<  h  to  the  adducU    magttus  is  astioct' 
the  latter  as  th-  '-onjoinl  nerve  p;;  -ses  through  the  si 

The  brani      'o  the  adductor  brcvis  enters  the 


the  adductor  longus 

-rior  fibres  of  the 
<  brevis  and  magnus. 


present  only  wher  .he  usual 
bb.  The  arti-  ilar  bran 
The  branch  to  the  hip 

pectineus  to  be  distributPfl  t 
The  brani  h  tf  >  the    ».• 

division.      Vs-  « i    edwith 

f.tcetotht      iii  masmu 

l.ir fibres!   nnii  "1( 

The  ner\-.    cont 

finaliv  terminat' 


.il  tt>     tf  twig  tram  the  main  trunk  of  the 
m  the  poster  >r  surface  of  the  posterior 

=6. 

^  wit!-,   ;<e  branch  to  the  knee  and  leaves 
e  of  the  adductor  magnus. 
erior  surf^iie  of  the  muscle  and  Is 
>ranch  from  the  anterior  liivi-    >n  is  absent. 
^  are  destined  for  the  suppl>  of  the  hip  and  knee  joints. 

/  consists  of  otie  or  two  fine  twigs  which  pass  beneath  th< 

■  .tntero-median  portion  of  the  capsular  ligament. 

<>rthe  geniculate  branch  continues  the  course  of  the  posterim 

i-%'e  to  the  adductor  magnus,  it  courses  down  the  anterior  sur 

..  mch  it  pierces  at  the  lower  portion  of  the  thigh.     Here  its  muscu- 

<luctor  magnus  while  the  articular  portion  enters  the  popliteal  space. 

'.vard  on  the  popliteal  artery,  to  which  it  distributes  filaments,  and 

ig  the  knee  joint  through  the  posterior  ligament 


Variatit 
*pt  sometime- 

!ie»-f'.  iouiid  goi 
pa«   -.      In  a  c, 
vMUri  the  obturati 
bott   ■*  them  passt, 

waST    -*-«t      In  an. 
4)e        -B-;f<  r  extemi 


stances  the  root  from  the  second  lumbar  nerve  is  absent.  Branches 
the  obturator  intemus  and  to  the  pectineus.  Tiny  branches  have 
obturator  artery  and  to  the  periosteum  of  the  pelvic  surface  iif  the  os 
•sected  in  the  anatomical  laboratory  of  the  University  of  }'enn.syi 
right  side  divided  into  the  usual  anterior  and  |x)sterior  branrties,  bii> 
nor  to  the  adductor  brevis.  On  the  left  side  the  normal  arranifemen' 
specimen  In  the  same  laboratory  the  branch  from  the  m.'»'  tn?-* 
.luscle  lay  to  the  outer  instead  of  the  inner  side  of  the  oh*  '     -r 

7.     The  Accessory  Obturator  Nerve. 


imiimr  {jiejnifi.. 


accessory  obturator  nerve  is  an  inconstant  branch  of  th' 
v.nd  in  29  per  cent,  of  the  cadavers  examined  (Eislcr).      it: 
rd  and  fourth  lumbar  nerves,  with  an  occasional  root  from  the  fifth  :   i  may  be 
i'-        d  from  the  third  alone.     The  roots  of  origin  are  situated  rietw^een  th»«se  of  the 
ant( nor  crural  and  the  obturator,  and  the  nerve  may  be  intimately  associ^'ed  with 
either  of  these  two,  usually  the  former. 


THE  LUMBAR  PLEXl  S. 


«3a7 


The  accessory  obturator  courses  downward  mesial  to  the  pscKis  maj^us  ami 
beneath  the  iliac  fascia,  and  leaves  the  pelvis  by  passing  over  the  horizontal  ramus  .»! 
the  pub<  i  and  under  the  pectineus.  In  the  latter  situiition  it  breaks  up  in'  its 
branches,  one  of  which  (a)  supplies  the  pectineus,  anotler  (*)  the  hip  )oint,  nile 
ti  -!  tl'ird  (f)  inosculates  with  the  anterior  di^  -ion  of  the  obtur  ->r  mne.  Somi- 
times  it  ia  very  small  and  its  fibres  pass  only  to  i.ie  hip  joint  "    ins  of  its  in- 

o-     !ation  with  the  obturator  some  of  its  tibrt-s  may  reach  the  add     i.     -s  lon^us  and 
bit  m  and  gracilis  muscles,  as  well  as  the  integumfnt  of  the  inner  r  snon  ol  the  thigli 


8.     The  Ant       jr  Ciurai.  N   rve. 


The  anteri 
b'attch  oi  the  1 


crural  or  femoral  nei  ve  (  n. 
bar  plexus,  arises  from  tht-  t 


nerves,      it    as.-  s  obliquely  downward  md 


fenraralbi     t  Fig.    i  io8  .  the  largest 
-t,  secon   .  third  and  fourth  lumbar 


anfi  emerge> 
it      .nt  ^lIe5  it. 
'.acus,  covered  I 
■  become  an  oc 
■<■  side  of  the 


twar'l    (M^iterii     to  the  psoas  magnus, 

m  bineath  the  middle  <  i-iterai  iii.«rgin  nt  that  muscle.     Thence 

se  between  the  out         jre   ,t  the  p^       and  the  mesial  edge  of  the 

le  iliac  fascia,  as  far  .a.-,      jupart's     ^.i  lent,  under  which  it  passes 

ijant  of  the  anterior  portion  of  th'    thigh.     The  ner\e  lies  to  the 

ternal  iliac  and  femoral  v<-      Is,  m  the  abdomen  being  separatetl 


the 

■i.li- 


H.  m  by  the  psoas  magnus,  but,  as  the        ,h  is  reached,  gradually  nearing  them 
Scarpa's  triangle  the  nerve  lies  in  apposition  to  the  fenwral  sheath.     In 
ediate  neighborhood  of  Poupart's  ligament,  the  anterior  crural  nerve  rapidly 
'nto  a  number  of 

>chea,  which  may  be  grouped  into  {6)  a  superfici<d  division,  principally 
H\-  nd  (f)  a  deep  dit<ision,  mainly  motor.     In  addition  there  are  (« )  branches 

isii  .'/«  the  main  trunk. 

:.  The  branches  ftom  the  main  trunk  consist  of  (oa)  the  muscutar  branches  and  (W)  the 
nervf  to  the  femoral  artery. 

aa.  The  muacular  branches  supply  the  iliacus,  the  psoas  magnus  and  the  pectineus. 

The  branches  to  the  iliaeus  consist  of  two  to  four  lilaments  which  ari.se  in  the  abdomen, 
piiss  outward  and  enter  the  inner  margin  of  the  iliacus  muscle. 

The  branch  to  ySns  psoas  magnus  arises  in  the  lower  part  of  the  iliac  fossa  and  s^  iijilic-  the 


inferior  portion  of  that  muscle.     It  may  originate  in  comm< 
artery. 

The  branch  to  the  pectineus  leaves  the  anterior  crural 
inward  posterior  to  the  femoral  vessels  and  enters  the  anter 

bf>.  The  nerve  to  the  femoral  aiteiy  usually  takes  •  "^ 
aiises  higher,  sometimts  as  a  distinct  branch  from  the  t- 
interior  crural  as  far  as  Poupart's  ligament,  leaving  tli 
the  femoral  sheath.    At  the  ligament  it  gives  off  fine  twigs 
ot  the  femoral  vessels  and  from  them  tmy  filaments  jxiss 
twigs  are  distributed  to  the  deep  femoral  artery  anil 
traverses  the  nutrient  foramen  of  the  femur,  after  supp 

b.  The  anterior  or  auperficial  division  is  mainly 
sensory  twigs  to  the  anterior  and  mesial  surfaces  of  the  '■ 

Branches  of  this  division  are :    (aa)  the  middle  cut. 

aa.  The  middle  cutaneous  ner.fe  i  rr.  cataoci  anterieres ) 
m  external  and  an  internal,  both  iX  u  hich  contain  motor  as 

The  external  branch  passe^  i'i>wtiward  under  the  sartorii 
Si-fn  ofl  a  row  of  fine  twigs  which  enn-r  the  upper  portion  of 
the  nerve  pierces  the  sartoriu     U  '.he  junction  of  the  upper  and  mid<' 
way  throuph  the  fascia  lata  aiwi  splits  into  fine  filaments  which  sup| 
rectus  lemoris  as  far  as  the  knee. 

The  internal  branch  is  sometimes  united  in  the  upper  part  of  it 
It  supplies  twigp  to  the  saOorius  but  seldom  pierces  that  muscle,  u 
.interior.  This  f)ranch,  like  the  external,  is  distributed  to  the  anter 
as  far  down  as  the  knee  and  frequently  inosculates  with  the  crural  br.n 

Variations. — S«>niPtinies  the  middle  cutaneous  arises  from  th 
rural  or  from  the  lumbar  plexas  and  replaces  in  toto  or  in  pa 
i?enito-cnual. 


x'wV  'he  ner\e  to  tin 


ral 


.igs 


'  ^bb)  th- 
io)coii 
as  sens< 
.J  who<" 
emusi 


Ir 

■stcrior  ■%!:        e 

he  rontin.      -n 
K    I  hen  pii..ut- 
..ument  over 


.urse  »itl        e  e.i-  em. 
Uy  pa.s.sin.     ntenwl  inul 
integunuiit  of  the  thigh 
■!  oi  the  gciulo<rurat. 

ming  of  the  anterioi 
crural  branch  of  the 


1328 


HUMAN  ANATOMY. 


bb.  The  internal  cutaneous  nerve  (rr.  cuudcI  mcdialcs)  leaves  the  anterior  crural  in  th<^ 
neighborhood  of  Poupart' s  ligament  and  descends  in  Scarpa's  triangle,  at  the  apex  of  which  it 
crosses  obliquely  the  femoral  vesfcls  to  attain  their  mesial  side.  It  passes  superficial  to  or 
through  the  sartorius  muscle  and  divides,  cither  anterior  or  internal  to  the  superficial  femoral 
artery,  into  its  temyna!  branches,  the  anterior  and  the  posterior  ( Fig.  mo). 

Two  or  three  branches  are  given  off  by  the  main  trunk.  One  of  these  pierces  the  fascia 
lata  immediately  below  the  saphenous  opening  and  accompanies  the  internal  saphenous  vein 
down  to  the  middle  of  the  thigh,  supplying  the  integument  in  its  immediate  vicinity.    Another 

branch  pierces  the  fascia  lata 
Fig.  mo.  at  about  the  middle  of  the  thigh 

and  supplies  the  skin  of  the 
antero-median  aspect  as  far 
down  as  the  knee.  These 
branches  sometimes  arise  di- 
rectly from  the  anterior  crural, 
and  not  infrequently  the  nerw 
to  the  pectineus  gives  off  a 
branch  ulich  forms  a  loop  at 
thelinner  side  of  the  femoral 
artery  with  a  nerve  which  passes 
anterior  to  that  vessel. 

The  anterior  branch 
pierces  the  fascia  lata  in  the 
lower  third  of  the  thigh,  de- 
scends in  the  neighborhood  of 
the  tendon  of  the  adductor 
magnus  and  eventually  passes 
across  the  patella  to  reach  the 
lateral  region  of  the  knee.  It 
supplies  the  skin  in  the  vicinity 
of  the  adductor  magnus  tendon 
and  inosculates  at  the  knee 
with  a  branch  of  the  internal 
saphenous  nerve. 

The  posterior  branch  con- 
tinues down  beneath  the  pos- 
terior edge  of  the  sartorius 
and  becomes  superficial  by 
periorating  the  i;  ia  lata  at 
the  mesial  aspect  of  the  knee. 
Its  ultimate  filaments  supply 
the  integument  of  the  lower 
part  of  the  inner  side  of  the 
thigh  and  the  upper  portion  of 
the  leg.  Before  becoming  su- 
perficial it  inosculates  below 
the  middle  of  the  thigh  with 
the  obturator  and  internal 
saphenous  nerves  to  form  the 
Bubsaitorial  or  obturator  plexus 
(Fig.  1 109).  At  the  knee  and 
in  the  upper  part  of  the  leg 
it  again  forms  connections 
wi'h  the  internal  saphenous 
nerve. 

c.  The  posterior  or  deep 
division  of  the  anterior  crural 
nerve  consists  of  a  fasces  of 
ner\'e-bundles  which  furnishes 


Anterior  br.  of  inl. 
cuUincoiu  iierv-r 


From  lower  ( posterior) 
br.  int.  cutftneoiis  ner^'e 


Lower  ( posterior)  Itr. 
Int.  cutaneoui  nerve 

Cutaneous  patellar  br. 
int.  aaphenous  ner^-e 


rnt.  i«phenou.ii  nerve 


Int.  saphenoua  vein 


Superficial  iHmrtloii  of  right  thii^,  showing  cutaneous  nerves  of  inner 
anterior  aspect ;  km^  saphenous  vein  is  seen  disappearing  through  saphe- 
nous opening. 


inner\-ation  to  those  muscles  which  comprise  the  quadriceps  extensor  femoris  and  terminates 
as  the  internal  saphenous  nerve. 

Branches  of  this  division  are  :  (aa)  the  muscuiar,  (bb)  the  artienlar  and  (cc)  the 
intemat  saphenous. 

aa.  The  muscular  brasches  f  rr.  miuratarn)  supply  the  rectu.s  femori^  the  vastus  extcmus, 
the  crureus,  the  subcrureus  and  the  vastus  intemus. 


THE   LUMBAR   PLEXUS. 


I3»9 


Fio.  nil. 


Anterior  crural  nerve 

ItCCtMfelfMffta,  CU' 
Femoral  vdl 

Nerve  to  pectii... 

Femoral  artcr 

Articular  branc! 

Nerve  to  rect 

Exl.  circumflex  art 

Middle  cntan 
nerve 
Rectua  (emoria,  cut 

A  deacendinK  btancL 
of  ext.  circumflex  ait. 
Nerve  to  vaatua 
intemuH 


The  branch  to  the  rectus  femoris  usually  splite  into  three  twigs,  which  separately  enter  the 
posterior  surface  of  their  muscle.  It  furnishes  fine  twigs  to  the  antero-lateral  portion  of  the 
capsule  of  the  hip  joint.  . 

The  branch  to  the  vastus  externus  passes  over  the  rectus  and,  in  company  with  the 
descending  branch  of  the  external  circumflex  artery,  reaches  the  vastus  externus,  whose 
anterior  margin  it  enters  in  a  series  of  twigs.    It  sends  a  branch  down  to  the  knee  joint 

The  nerves  to  the  crureus  number  usually  either  two  or  three.  The  upper  branch  is  usually 
the  shortest  and  passes  directly  to  the  anterior  surface  of  the  crureus,  where  it  penetrates  the  sub- 
stance and  supplies  the  upper 
portion  of  the  miLscle.  A  sec- 
ond branch  pierces  the  vastus 
intemus  and  passes  down- 
ward under  the  anterior  bor- 
der of  that  muscle.  It  sup- 
plies the  lower  portion  of  the 
crureus,  the  subcrureus,  the 
periosteum  of  the  lower  an- 
terior part  of  the  femur  and 
the  capsular  ligament  of  the 
knee  joint.  A  third  branch  is 
distributed  to  the  lateral  por- 
tion of  the  crureus  and  by 
means  of  its  terminal  filaments 
aids  in  the  innervation  of  the 
knee  pint. 

The  branch  to  the  I'astus 
intemus  accompanies  the  in- 
ternal saphenous  nerve  along 
the  inner  side  of  the  vastus 
intemus,  under  cover  of  the 
strong  aponeurosis  which 
forms  the  roof  of  Hunter's 
canal.  It  sends  filaments  to 
the  upper  part  of  the  vastus 
intemus  and  then  enters  that 
muscle  about  the  middle  of 
the  thigh.  Its  continuation 
accompanies  the  deep  branch 
of  the  anastomotica  magna 
artery  and  supplies  the  cap- 
sule of  the  knee  joint. 

bb.  The  articular 
branehea  (rr.  artlcnlares) 
supply  the  hip  and  knee 
joints.  Those  filaments  which 
are  destined  for  the  hip  are 
derivatives  of  the  branch  to 
the  rectus  femoris.  Those 
which  aid  in  the  innervation 
of  the  knee  arise  from  the  in- 
ternal saphenous  and  from 
the  nerves  to  the  vasti  exter- 
nus and  intemus  and  the 
crureus. 

ec.  The  intamal  or  long 
■aphcnoui  ntrvt  ( a.  Hphcnui ) 
(Fig.  1 109)  is  the  continuation 
of  the  posterior  division  of 
the  anterior  crural  nerve.  It 
courses  down  the  thigh 
first  lateral  to  and  then  an 


Nerve  to 


Crurei 


Int.  oaphenona 

nerve 
Poat.  div.  int. 
cutaneoua 
nerve 

Aponeurotic 
'roof  of  Hunt- 
cr'a  canal 


A  br.  of  int.  sa- 
phenoua  nerve 
A  muscular  br. 
of  femoral 
artery 


Vaatua 
intemua 


Intertwl  aa phenoua  nerve 
Superflcial  br.  anaato- 
motica  mafna  art. 

Tendon  of  adductor 
magnua 


Diaaection  of  richl  thlfh.  ahowlnc  relation  of  anterior  crural  nerve 
to  bloodt-eaaela  and  to  Hunter's  canal. 


teiior  to  the  superficial  femoral  artery  under  cover  of  the  sartonus  muscle.  At  the  apex 
of  Scarpa's  triangle  it  enters  Hunters  canal  and  accompanies  the  vessels  therein  containef  « 
far  as  the  opening  in  the  adductor  magnus.  Departin,j  from  the  vessels  at  this  pomt  the  ners  e^ 
piercing  the  anterior  wall  of  Hunter's  canal,  continues  a  downward  course  between  the  vastus 


I330 


HUMAN  ANATOMY, 


hteraus  and  the  adductor  magnus.  At  tfie  inner  side  of  the  knee  it  becomes  supeifidal  by 
passing  between  the  tendons  ol  the  sartorius  and  gracilis  and  by  piercing  the  deep  fascia  in  this 
situation.  Thence  it  descends  in  the  leg  in  association  with  the  internal  saphenous  vein,  at  the 
ankle  passing  anterior  to  the  internal  malleolus  and  reaching  the  inner  a4>ect  of  the  foot,  on 
which  it  extends  only  as  far  as  the  metacarpo-phalangeal  articulation  of  the  great  toe  (Fig.  1 1 18) . 

Btanchea  of  the  internal  saphenous  are :  the  commmmcaimg,  the  infrapaUUar,  the  articu- 
lar and  the  terw  mal. 

The  commimicaHng  bnauk  arises  beneath  the  sartorius  at  about  the  middle  of  the  thigh 
and  inosculates  with  filiunents  from  the  obturator  and  internal  cutaneous  nerves  to  form  the 
subsarloricl  or  obturator  plexus. 

The  infrapatellar  branch  (r.  iafrapatelUrit)  (Fig.  1117)  arises  at  the  lower  part  of  the 
thigh.  It  perforates  the  sartorius  and  the  fascia  lata  and  spreads  out  beieath  the  integument 
of  the  knee,  where  it  inosculates  with  terminal  filaments  of  the  internal,  the  middle  and  some- 
times the  external  cutaneous  nerve  to  form  Hm  patellar  plexus  (Fig.  1117) . 

The  articular  brmneh  (r.  articalarla)  is  an  inconstant  twig  whidi  supplies  the  inner  portion 
of  the  capsule  of  the  knee  joint. 

The  termiual  branches  ate  distributed  to  the  integument  of  the  anterior  internal  portion 
of  the  leg  and  the  posterior  half  of  the  dorsum  and  mesial  side  of  the  foot 

Practical  Considerations. — All  the  branches  of  the  lumbar  plexus  have  motor 
and  sensory  fibres,  both  of  which  are  af!e<:ted  in  paralysis.  The  lesion  is  usually 
central,  involving  the  spinal  cord,  a3  in  tabes  dorsalis,  fracture  of  the  spine  or  Pott's 
disease,  and  involves  several  nerves,  or  all  of  them  below  the  seat  of  the  lesion  ;  the 
individual  branches  are  not  often  affected. 

The  ilio-kypo^astric  may  be  divided  by  the  incision  in  kidney  operations  or 
nuky  be  included  m  the  sutures.  This  nerve  and  the  ilw-inguinal  are  sometimes 
involved  in  operations  in  the  inguinal  region.    . 

The  genito-crural  sends  one  branch  through  the  inguinal  canal  to  the  cremaster 
muscle,  and  another  under  Poupart's  ligament  to  the  skin  of  the  inner  side  of  the 
thigh,  just  bdow  the  ligament  Gende  irritation  of  the  skin  here  will  cause  retraction 
of  die  testicle  (cremaster  reflex),  especially  in  children. 

The  anterior  crural  has  been  paralyzed  by  the  pressure  of  tumors  in  the  pelvis, 
has  been  involved  in  a  psoas  abscess,  and  has  been  injured  in  fracture  of  the  pubic 
ramus  and — rarely — in  fractures  of  the  femur.  If  the  lesion  involving  the  nerve  is 
within  the  pelvis  the  paralysis  would  afiect  the  ilio-psoas,  quadriceps  extensor  femoris, 
sartorius  and  pectineus.  If  the  lesion  is  outside  the  abdomen  the  ilio-psoas  will 
escape.  A  complete  jiaralysis  would  prevent  flexion  of  the  hip,  or  extension  of  the 
knee.  The  patient  is  then  compelled  to  avoid  flexion  of  the  knee  in  walking.  There 
will  be  anesthesia  in  the  parts  supplied  by  the  middle  and  internal  cutaneous,  and 
lonp;  saphenous  nerves,  that  is,  in  the  thigh  along  the  anterior  and  iner  surface 
(middle  and  internal  cutaneous),  except  in  the  upper  third  (crural  branch  of  the 
genito-crural),  and  along  the  inner  surface  of  the  leg  and  inner  border  of  the  foot  to 
the  ball  of  the  big  toe  (long  saphenous).  The  long  saphenous  vein  and  nerve  lie 
close  together,  about  a  finger's  breadth  behind  the  inner  border  of  the  tibia.  In  the 
thigh,  while  they  have  the  same  general  direction,  the  vein  lies  in  the  superficial 
fascia,  the  nerve  under  the  deep  fascia.  The  nerve  in  the  thigh  is,  therefore,  not  so 
liable  to  injury  as  is  the  vein. 

Since  the  anterior  crural  breaks  up  into  numerous  branches  just  below  Poupart's 
ligament,  its  trunk  in  the  thigh  is  very  short.  It  lies  slighdy  external  to  the  femoral 
artery  and  can  be  exposed  by  an  incision  extending  downward  from  the  middle  of 
Poupart's  ligament. 

Paralysis  of  the  obturator  nerve  would  interfere  with  adduction  of  the  thigh  as 
well  as  with  internal  and  external  rotation.  It  may  be  caused  by  pressure  within  the 
pelvis,  as  by  the  child's  head  in  difficult  labor,  by  a  tumor  or  by  an  obturatoi  hernia. 
Paralysis  of  the  obturator  is  usually  found  in  conjunction  with  paralysis  of  the  anterior 
crural.  The  nerve  may  be  irritated  in  coxalgia,  in  sacro-iliac  disease,  and  on  the  left 
side  in  carcinoma  or  faecal  impaction  in  the  sigmoid  flexure.  On  account  of  its  ter- 
minal distribution  pain  in  the  knee  is  usually  complained  of  whenever  this  nerve  or 
one  of  its  branches  is  involved. 


THE  SACRAL  PLEXUS. 


1331 


THE  SACRAL  PLEXUS. 
The  Moial  or  sciatic  plexus  (plexm  sacralU)  (Fig.  1 1 12)  is  formed  by  a  portion 
o(  the  fourth  lumbar  nerve,  all  of  the  hfth  lumbar,  the  entire  first  sacral  and  parts  of 
the  second  and  third  sacral  nerves.  As  previously  sUted  (page  1320)  the  fourth 
lumbar  nerve  or  n.  furcalis  splits  into  two  portions,  a  larger  upper  and  a  smaller 
lower  the  former  contributing  to  the  lumbar  plexus  and  the  latter  uniting  with  the 
fifth  lumbar  nerve.  The  lower  portion  of  the  fourth  lumbar  having  passed  downward 
behind  the  internal  iliac  vessels,  divides  into  anterior  and  posterior  branches,  which 
hue    respectively  with  similar 

branches  of  the  fifth  lumbar,  the  Fic.  ma. 

two  trunks  thus  formed  compris- 
ing the   lumbo-sacral   cord 
(tmncitt  lambosacralis).     This 
double  structure  emerges  from 
the  mesial  margin  of  the  psoas 
magnus,  passes  down  over  the 
brim  of  the  pelvis  and  constitutes 
the  lumbar  contribution  to  the 
sacral  plexus.      The  first   and 
second  sacral  nerves  leave  their 
foramina,  pass  laterally,  anterior 
to  the  pyriformis,  and  split  into 
anterior  and  posterior  branches. 
The  third  sacral  nerve  or  «.  bi- 
geminus  divides,  not  into  ante- 
rior and  posterior  branches,  but 
into  upper  and  lower,  the  upper 
becoming  a  constituent  of  the 
sacral  and  the  lower  a  portion 
of  the  pudendal  plexus.    Con- 
verging toward  the  lower  por- 
tion of  the  great  sacro-sciatic 
f«^ramen,   the  posterior  portion 
of  the  lumbo-sacral  cord  and  the 
posterior  branches  of  the  first 
and  second  sacral  nerves  hue 
and  form  the  external  fcpliteal 
or  pertmeal  and  some  voxaxttpos- 
tfriornerva.   The  anterior  por- 
tion of  the  lumbo-sacral  cord, 
the  anterior   branches  of   the 
first  and  second  sacral   nerves 


con* 


k«M«r  MMTi* 


D<agTmm  IHMtntinc  plan  ol  Hcnl  plnos. 


nrsi  anu  «:™..u  :«..-.  .....~  and  the  upper  part  of  the  third  sacral  unite  in 

the  internal  popliteal  or  tibial  nervf  and  some  small  anterior  branches  (  h  ig.  1 1 1 2 ). 
The  resulting  composite  structure,  the  sacral  plexus,  is  a  broad  triangular  felt-work 
of  nerve-strands,  whose  base  points  toward  the  sacrum  and  whose  apex  presents  at 
the  great  sicro-sciatic  i'  ramen.  The  plexus  is  an  occupant  of  the  pelvis,  on  whose 
postwior  wall  it  is  situated,  lying  upon  the  pyriformis  muscle  and  under  coyer 
ofthe  parietal  portion  of  the  pelvic  fascia.  In  relaUon  with  it  antenorly  are  the 
ureter,  the  pelvic  colon  and  the  internal  Uiac  artery  and  vei.. ,  The  ilio-lumbar  vessels 
pass  above  the  lumbo-sacral  cord  and  between  the  coid  and  the  hrst  sacral  nerv a  ^le 
found  the  superior  gluteal  vessels.  The  interval  between  the  second  and  third  «'cral 
nerves  is  occupied  by  the  sciatic  artery  and  vein. 

In  size  the  roots  of  the  sacral  plexus  vary  considerably,  the  largest,  ihe  Wt . 
lumbar  nerve,  measuring  about  7  mm.  in  diameter  and  the  smallest,  the  third  sacrai. 
3.5  mm.  As  regards  length,  the  contribution  from  the  fourth  lumbar  has  th-  long- 
est course  and  that  from  the  third  sacral  the  shortest.        ,    ^  .     ,      .,    .. 

Brancnet.— The  branches  of  the  sacral  piexua  and  their  clai«tficati<-n  ieni>« 
around  the  great  sciatic  nerve  and  its  distribution.     This  nerve  compnses  t-vo 


«332 


HUMAN  ANATOMY. 


essential  and  frequently  independent  elements,  the  internal  popliteal  or  tibial  and  thf 
external  popliteal  or  perone^.  Typically  the  sciatic  divides  into  these  two  ner\es 
in  the  lower  part  of  the  thigh  ;  very  often,  however,  they  are  distinct  from  the  outset, 
arising  independendy  from  the  plexus,  bein^  separated  in  the  great  sacro-sciatic  fora- 
men by  the  inferior  fibres  of  the  pyriformis  muscle  and  passing  through  the  thigh 
as  contiguous  but  ununited  structures.  Moreover,  even  when  the  sciatic  appears  tf> 
be  a  single  cord,  dissection  will  reveal  its  duality  in  origin  and  course.  The  branches 
of  the  sacral  plexus  may  be  grouped  as  follows  : — 


Collateral  Branches. 

A.  Anterior  branches : 

I.  Muscular 
3.  Articular 

B.  Posterior  branches : 

3.  Muscular 

4.  Articular 


II.  Terminal  Branches. 

A.  Anterior  branch : 

5.  External  p>oplit^-al 

B.  Posterior  branch : 

6.  Internal  popliteal 


COLLATERAL  BRANCHES. 

The  collateral  branches  comprise  two  sets,  designated  according  to  the 
portion  of  the  plexus  from  which  they  arise  as  the  anterior  and  the  fiostenor. 

The  anterior  collateral  branches  include  :  ( i )  the  muscular  branches  and 
(2)  the  articular  branches. 


Fig.  1 1 13. 


Superior  ctoteal  ncm,  giving  a  br.  to  pyrifonni* 


Paou  magntu,  cut- 
Ext.  ilUc  artery. 

Obturator  nerve 

Pubic  bone. 

meaial  aurface 

Obturator  internua 

••  White  line  "  of 

pelvic  faacia 


Nerve  to  obtcntor  internua  andgemellua  auperior 
Anterior  ,  " 

CTunI  nerve 


.  lumbar  nerve 


**-!.  aacral  nerve 

Bra.  to 
pyriformis 
U-  II.  aacral 
ganglion 
II.  aacral  nerve 
Visceral  br.  of 
II.  aacni)  nerve 


III.  aacral 
ganglion 
I V.  aacral  ganglion 

iV.  gaagltoalSMnlMlow) 


Levator  aui 


Coccygcus 
Br.  to  levator  ani 

Diaaeclkm  ot   right  half  of  pelvia. 


Viaccral  bn.  of  III.  and  IV.  aacral  nerves 
V.  aacral  nerve  (ventral  division) 

'Coccygeal  nerve  (ventral  division) 


Iridic  nerve ;  the  small  adatic  nerve  ia  juat  in  front 
Br.  to  sphincter  ani,  piercing  levator  am 

ahowing  aacral  and  pudcudal  pleanaea:  section  ia   not  meaial, 
but  to  left  of  mid-lme. 


I.  The  muscular  branches  supply  {a)  the  quadratus  femoris,  {b)  the  obtura< 
tor  intemus,  the  gemelli  and  (r)  the  hamstring  muscles  and  the  adductor  magnus. 

a.  The  nerve  to  the  quadratui  femoria  arises  from  the  anterior  surface  of  the  upper  portion 
of  the  plexus,  ite  fibres  coming  from  the  fourth  and  fifth  lumbar  and  first  sacral  nerves.  It  is 
frequently  united  in  the  first  part  of  its  course  with  the  nerve  to  the  obturator  Intemus.  Having 
traversed  the  great  sacro-sciatic  foramen  it  courses  downward  anterior  to  the  great  sciatic  nerve. 


COLLATERAL   BRANCHES. 


1333 


the  obturator  intemus  and  the  gemelli  and  posterior  to  the  capsular  ligament  of  the  hip. 
Reachine  the  upper  margin  of  the  quadratus  femoris  it  passes  anterior  to  that  muscle  and 
terminates  in  fibres  which  enter  the  anterior  sur  ice  of  the  muscle  for  which  it  is  desuned.  In 
addition  to  supplying  the  quadratus  femoris  it  sends  twigs  to  the  gemellus  tn/enor  and  to  the 
hip  Joint 

Variatiana.— The  nerve  to  the  quadratus  femoris  may  supply  the  upper  portion  of  the 
adductoTmagnus  and  may  send  filaments  to  the  superior  gemellus,  either  as  an  additional  or 
as  a  sole  supply. 

b  The  nerve  to  the  obturator  faitetnos  has  an  origin  one  step  lower  than  that  of  the 
preceding  nerve,  with  which  it  is  frequently  associated  for  a  short  d^tance.  It  arises  from  the 
anterior  Lpect  of  the  fifth  lumbar  and  first  and  second  sacral  nerves  and  leaves  the  pelvis  through 
the  ereat  Mcro-sciatic  foramen,  below  the  pyriformis  and  the  great  sciatic  nerve  and  lateral  to 
the  ^dic  ner%e  and  vessels  (Fig.  1.14).  Crossing  the  spine  of  *«  !«^hium  it  course  antenorly 
through  the  lesser  sacro-sdatic  foramen  and  enters  the  ischio-rectal  fossa,  where  it  termiMtes  by 
splitting  into  filaments  which  enter  the  posterior  surface  of  the  obturator  intemus.  A  small 
branch  of  this  nerve  supplies  the  gemellus  superior.  ,      ^     ^      .  av.  u-  1.  t„™,.  »i,» 

c  The  nerve  to  the  hamstring  muscles  consists  of  a  bundle  of  fibres  which  forms  the 
mesial'  edge  of  the  gluteal  portion  of  the  sciatic  nerve.  Arising  from  the  anterior  aspect  of  the 
plexus  and  deriving  its  fibres  from  the  fourth  and  fifth  lumbar  an-  Urst,  second  and  third  sacra^ 
nerves  it  descends  in  close  connection  with  the  sciatic,  lying  first  anterior  to  the  latter  aid  then 
to  the'inner  side  (Fig.  1115)-  In  the  thigh  the  nerve  breaks  up  into  two  «»  erf  fibres^  »" 
ul>ter  and  a  lower.  The  upper  set  leaves  the  sciatic  below  the  tuber  ischu  and  sendsfibres  to 
the  upper  portion  of  the  semitendiuosus  and  the  long  head  of  the  biceps /emons.  ">«  lower 
set  arisw  further  down  in  the  thigh  and  funishes  twigs  to  the  semunembraHosus,  the  addue/or 
magmu  and  the  lower  part  of  the  semilendinosus. 

2  The  articular  branches  are  derived  from  the  nerve  to  the  quadratus 
femoris  and  sometimes  from  the  anterior  aspect  of  the  sciatic.  After  descending 
between  the  capsule  of  the  hip  and  the  gemeUi  they  supply  the  postenor  porUon  of 
the  capsular  ligament  of  the  hip  joint.  ,  n   .u 

The  posterior  collateral  branches  comprise,  like  the  anterior,  (3)  the 
muscular  ind  {\)  Xhc  articular  branches.  .       •     .an  .u 

3  The  muscular  branches  include  («)  the  nerve  to  the  pyriformis,  (*)  the 
superior  and  (r)  the  inferior  gluteal  nerves  and  (rf)  the  nerve  to  the  short  head 
of  the  biceps. 

a  The  nerve  to  the  pyriformia  may  be  either  single  or  double.  It  arises  from  the  dorsal 
a.spect  of  the  second  or  first  and  second  sacral  nerves  and  enters  the  anterior  surface  of  its 
mi«cle.  There  may  be  an  additional  filament  from  the  root  to  the  superior  gluteal  nerve  con- 
tributed by  the  first  sacral  nerve.  ,     .       .^     ,  .    , 

b.  The  auperior  gluteal  nerve  (n.  gloutns  wperior)  (Fig.  1114)  arises  by  three  roots  from 
the  dorsal  surface  of  the  posterior  portion  of  the  lumbo-sacral  cord  and  the  first  sacral  nerve. 
Its  fibres  being  derivatives  of  the  fourth  and  fifth  lumbar  and  first  sacral  nerves.  After  passing 
alx>ve  the  pyriformis  muscle  in  company  with  the  superior  gluteal  artery  and  vein,  it  'eaves  the 
pelvis  through  the  great  sacro-sclatic  foramen  and  divides  into  (aa)  a  superior  and  (bb)  an 
inferior  branch.  ,    ,  .      t.        .1 

aa.  The  superior  branch  (Fig.  1114)  is  the  smaller  of  the  two,  and  after  passing  beneath 
the  gluteus  medius  and  along  the  upper  margin  of  the  gluteus  minimus  reaches  and  enters  the 
middle  of  the  inner  surface  of  the  former  muscle,  of  which  it  is  only  the  partial  nerve  supply. 

bb  The  inferior  branch,  larger  than  the  superior,  is  the  conUnuation  of  the  mam  trunk. 
After  a  forward  course  between  the  glutei  medius  and  minimus  in  company  with  the  lower 
branch  of  the  deep  portion  of  the  superior  gluteal  artery,  it  reaches  the  under  surface  of  the 
tensor  fascia:  femoris  (Fig.  1114).  It  supplies  the  glutei  medius  and  minimus  and  its  terminal 
fibres  constitute  the  supply  of  the  tensor  fascia  femoris.  . .  .      • 

c  The  inferior  gluteal  ntrv*  («.  glntaeu.  Inferior)  (Fig.  1114)  w  fonned  by  twigs  which  arise 
from  the  dorsal  surface  of  the  posterior  |>art  of  the  lumbo-sacral  cord  and  the  hrst,  and  s<»me- 
times  the  second,  sacral  nerve.  It  is  frequently  fused  in  the  eariy  part  of  its  course  with  the 
small  sciatic  nerve  and  not  infrequently  with  the  nerve  tt)  the  short  head  of  the  biceps.  It 
usually  sends  a  small  branch  down  to  join  the  small  sciatic  nerve.  Passing  beneath  the  nynformis 
it  emerges  from  the  pelvis  Into  the  gluteal  region  through  the  great  sacro-sciatic  foramen,  super- 
Icial  to  IIh:  great  sciatic  nerve.  Immediately  up-Mi  altering  the  Hittnck  it  breaks  up  fan-wise 
Into  a  number  of  twigs  which  enter  the  deep  surface  of  the  gluteus  maximus  about  midway 
Ijetween  the  origin  and  insertion. 


1334 


HUMAN  ANATOMY. 


d.  The  MTV*  to  Um  ahott  hnd  of  th*  biceps  (Fig.  1115)  apparently  arises  from  the  lateral 
margin  of  the  upper  part  of  the  great  sciatic  nerve.  The  fibres  comprising  it  can  be  traced  back 
to  the  fifth  lumbar  and  first  and  second  sacral  nerves,  sometimes  in  combination  with  the  roots 
of  the  inferior  gluteal  nerve.  Leaving  the  great  sciatic  in  the  middle  of  the  thigh,  often  as  a 
common  trunk  with  the  articular  branch,  it  enters  the  substance  of  the  short  head  of  the  biceps. 

Fig.  1 1 14. 


niuteiM 
niaximua 

Br.  from  V. 
Inmbarnerve 

I.  ucral  nev^r. 

r  dtviikHi 

Cufaacoythr. 

from  loop  of 

pMtcfior  ttCfah 

II.  Kscral 

liuslcTlor  dlvi»loa' 


major 
Narvt  to  quMkma 

femorls 
TcBdoB  of  otituntof  IntrrniM 
th  MfndluiftiipctlutdlKivc 
!>dUiul>(    ' 


Dcen  dincetlon  o(  rlfht  buttock,  showini  CTnergmce  ol  (rat  uAaXle  mrv*  below  pyrifomiLi  mnicte;  alio 
miucular  bnncfaM  and  poaterior  dlviaiona  oi  aacial  nenra. 

4.  The  articular  branches  supply  the  knee  and  are  usually  two  in  number. 
The  upper  arises  either  in  common  with  the  nerve  to  the  short  head  of  the  biceps  or 
independently  from  the  lateral  portion  of  the  great  sciatic.  Descending  on  the  pos- 
terior surface  of  the  femoral  head  of  the  biceps  it  passes  between  the  external  condyle 
of  the  femur  and  the  tendon  of  the  biceps  and  supplies  the  lateral  portion  of  the 
capsular  ligament  of  the  knee.  The  lower  arises  from  the  external  popliteal  nerve 
in  the  upper  portion  of  the  popliteal  space  and  divides  into  two  portions  which 
supply  the  lateral  and  posterior  portions  of  the  capsular  ligament  of  the  knee.  From 
the  branch  to  the  posterior  part  of  the  capsule  is  given  off  a  tiny  thread  to  the 
sup)erior  tibio-fibular  articulation. 

TERMINAL  BRANCHES. 

The  terminal  branches  of  the  sacral  plexus  are  the  external  and  the  iiUemaf 
popliteal,  and  these  are  usually  fused  in  tlie  upper  part  of  their  course  into  the  great 
sciatic  nerve. 


TERMINAL   BRANCHES. 


1335 


The  Great  Sciatic  Nerve. 
The  great  sciatic  nerve  (n.  Ischladlcns).  the  largest  nerve  of  the  entire  human  body, 
is  a  thick  bundle  of  nerve-fibres  derived  from  both  the  anterior  and  postenor  portions  of 

Fig.  1115. 


Gluten*  niHximiM' 
Gmt  aciattc  nerve 

Great  MCTD-sciatic  ligament 
Small  Kiatic  nerve 


Tuber  iKhli 
Great  itciatic  nctrc ' 

Br>.  to  nemitendlnoaua 

Adductor  magnu* 
BicejM,  long  head 

SemitendinoauH 
Scmimembranonia  ■ 

Br.  to  adductor  magnua, 

Br.  to  nemimembranoauii 

bcmimembranoMii 


Popliteal  artery 
Articular  liranch  .^ 

Poplitcnl  vein  «^ 
Communicauii  libialla— - 


Glttteua  medina 

PyrUorais 

Gcmellua  superior 

Obturator  internum 
Gemellus  inferior 
Obturator  eztcraus 
Trocbanter  major 

Quadratus  femoris 


Glutens  ntaaimus 
Br.  to  bleep* 


Bicepa,  short  head 
Int.  popliteal  nerve 

hJctemal  popliteal  ner»« 
Atttcnlar  branch 
Aiygoa  articular  branch 
Pcmnr,  popliteal  surface 

\  Muscular  branches 

Gastrocnemiua 

__  Commuoicans  tlbularis 


Deepdi«e«ion  of  posterior  siirtaceoj  right  thigh  '^"'F^^^^^Sm^'^I^^"^^^'" 
into  eitemal  popliteal  (peioneal)  and  rntemal  popliteal  (tibial)  nerves. 


the  sacral  olexus  (Fie.  1 1 12).     Properly  it  consists  of  two  elements  onlv,  the  ex- 
iern^l^SdSrtai  popliteal  nerves,  the  former  from  the  posterior  and  the  latter 


niK: 


1336 


HUMAN  ANATOMY. 


from  the  anterior  portion  of  the  plexus,  its  constituent  fibres  being  derivatives  of 
all  of  the  spinal  nerves  contributing  to  the  sacral  plexus.  Bound  up  with  it  and 
apparently  integral  portions  of  it,  are  the  nerve  to  the  hamstring  muscles  and  the 
nerve  to  the  short  head  of  the  biceps.  From  within  outward,  the  four  components 
are  arranged  in  the  following  order:  the  r,er\'e  to  the  hamstrings,  the  internal  popli- 
teal nerve,  the  external  popliteal  nerve  and  the  nerve  to  the  short  head  of  the  biceps. 
Arising  from  th '  apex  of  the  sacral  plexus  and  proceeding  as  its  direct  continua- 
tion, the  great  sc.  .c  leaves  the  pelvis  through  the  greater  sacro-sciatic  foramen 
below  the  pyriformis  muscle  and  above  the  geiv.t;llus  superior.  In  the  form  of  a  thick 
flat  trunk,  about  1.5  cm.  wide,  it  turns  downward  and  lies  aiiterior  to  the  gluteus 
maximus  and  posterior  to  successively  the  gemellus  superior,  the  tendon  of  the 
obturator  intemus,  the  gemellus  inferior,  the  quadratus  femoris  and  the  upper  portion 
of  the  adductor  magnus,  being  accompanied  in  the  upper  part  of  its  course  by  the 
sciatic  artery  and  the  arteria  comes  nervi  ischiadici.  Lying  external  to  the  nerve  is 
the  great  trochanter  and  internal  to  it  is  the  tuberosity  of  the  ischium  (Fig.  1 1 15 ). 
Entering  the  thigh  by  emerging  from  beneath  the  gluteus  maximus,  the  nerve  lies  under 
cover  of  the  hamstrings  and  at  a  varying  posiuon  in  the  thigh  it  splits  into  its  terminal 
divisions:  (5)  the  external popliUid  and  (6)  the  intemcU popliteal.  As  previously 
stated  (page  1333),  these  nerves  may  be  separate  from  their  origin. 

5.  The  External  Popliteal  Nerve. 

The  external  popliteal  or  peroneal  nerve  (n.  peronaens  comannis)  (Fig.  1115) 
is  homologous  with  the  musculo-spiral  of  »he  upper  extremity.  It  comprises  fibres 
derived  from  the  posterior  portionS;of  the  fourth  and  fifth  sacral  and  first  and  second 
lumbar  nerves.  As  a  part  of  the  great  sciatic,  it  follows  the  course  in  the  thigh  just 
described  and  after  the  bifurcation  of  the  sciatic  enters  the  popliteal  space  as  an  inde- 
pendent nerve.  In  the  upper  part  of  the  popliteal  space  it  lies  beneath  the  biceps  and 
later  inclines  gradually  outward  between  the  tendon  of  the  biceps  and  the  outer  head 
of  the  gastrocnemius.  Passing  over  the  lattor,  it  reaches  the  under  surface  of  the 
deep  fascia  posterior  to  the  head  of  the  fibula,  2-3  cm.  below  which  it  divides  into  its 
terminal  branches. 

Branches  of  the  external  popliteal  nerve  are  :'  the  cutaneous  and  the  terminal. 

The  cv  >neous  branches  axe:  (a)  the  sural  and  {b)  the  peroneal  communi- 
cating.- 

a.  The  im  .1  branch  (n.  cnuncas  rara*  lateralis)  (Fig.  11 19)  consists  of  one  or  more, 
usually  two,  filaii.ents  which  arise  in  the  popliteal  space,  frequently  in  common  with  the  peroneal 
communicatintf  nerve.  Becoming;  superficial  by  piercing  the  deep  fascia  overlying  the  outer 
head  of  the  gastrocnemius,  it  is  distrihuted  to  the  integument  of  the  upper  two  thirds  of  the 
lateral  aspect  oi  the  leg.  Its  degree  of  development  is  in  inverse  ratio  to  that  of  the  small  sciatic 
and  short  saphenous  nerves. 

b.  The  peroneal  communicating  nerve  (r.  aMttomoticas  peronaeat)  (Fig.  it  19),  also 
called  the  n.  commumcans  fibularis,  is  larger  than  the  preceding.  Leaving  the  peroneal  in  the 
popliteal  space,  often  in  combination  with  the  sural  nerve  or  nerves,  it  descends  beneath  the 
deep  fascia  and  over  the  lateral  head  of  the  gastrocnemius  to  the  middle  of  the  leg.  Here  it  is 
usually  joined  by  the  tibial  communicating  branch,  from  the  internal  popliteal  and  the  joint  trunk 
so  formed  (Fig.  1135)  is  called  the  external  or  short  saphenous  nerve  (page    ^42). 


The  terminal  branches  comprise:     (a) 
anterior  tibial  and  (c)  the  muscu  'o- cutaneous. 


the    recurrent  articular,    (6)    the 


a.  The  recurrent  articular  •^r  recurrem  tibial  branch  ( Fig.  ii  16)  is  the  smallest  of  the  three. 
Given  off  a  short  distance  below  ilv?  head  of  the  fibula  it  pa.sses  forward  under  the  peroneus 
longus  and  the  extensor  longus  digitonim,  courses  upward  in  the  musculature  of  the  tibialis 
amicus  and  divides  into  filaments  which  supply  the  upper  fibres  of  the  tibialis  anticus,  the 
anterior  portion  of  the  knee  joint,  the  superior  tibio-fibular  articulation  and  the  periosteum  of  the 
external  tuberosity  of  the  tibia. 

6.  The  Anterior  Tibial  Nerve. 

The  anterior  tibial  nerve  (n.  peronaens  profundas)  originates  below  the  head  of 
the  fibula  in  the  inter\'al  between  the  peroneus  longus  and  the  fibula.     After  winding 


TERMINAL  BRANCHES. 


J  337 


externally  around  the  head  of  the  fibula  beneath  the  peroneus  longus,  the  extensor 
proprius  hallucis  and  the  extensor  longus  digitorum  it  reaches  the  anterior  aspect  of 

Fig.  1 1 16. 


Eitemor  kHigiM  dlKitorum 

Antrrior  libtal  artery- 
Anterior  tibial  nervc- 
MuncalcxttiaiMOiis  ncrve- 

Pcrooens  lootu*.  laid  opat 

Tibialit  anticus- 
Ezteiuor  kHigiu  difitorum. 


Hnd  ol  fibula 

Peroneal  nerve 

Recurrent  tibial  branch 

Branch  to  eatcnaor  longiu  digitonim 


Muscular  branch  to  pcronci 


ftroneua  brevia 


External  braiKh  of  musculo-cutaneou* 


Peroneus  toiiKU*  tendon 
Peroneus  brevis  temlon 


riicin  of  extensor  brevis  digitorum 
.External  saphenous  ncr\-e 


Dissection  of  antero-hlrrsl  sarfare  of  tf^t  leg  "w!  of  .inmnni  nf  font,  shnarai;  antrrior 
tibial  and  musculo-cutaneous  nerves. 

the  leg.     Lying  on  the  anterior  surface  of  the  interosseous  membrane  it  joins  the 
anterior  tibial  vessels   8-12   cm.    below  its  origin  and  accompanies  these  vessels 


1338 


HUMAN  ANATOMY. 


down  the  front  of  the  leg  as  far  aa  the  ankle,  lying  first  to  their  outer  side,  then 
anterior  to  them  and  at  the  ankle  to  the  outer  side  again  (Fig,  i  Ii6). 

Branches  of  the  anterior  tibial  nerve  are  :  (aa)  the  muscu/ar,  {66)  the  articular. 
(<•<•)  the  external  and  {dd)  internal  terminal. 

aa.  The  mttMuUr  brancbM  are  distributed  to  the  tibialis  anticus,  the  extensor  lon^us 
digitonim,  the  extensor  proprius  hallucis  and  the  peroneus  tertius. 

The  nerves  to  the  tibialis  anticus  consist  of  two  twigs,  an  upper  and  a  lower.  The  upptr 
arises  at  the  orisin  of  the  anterior  tibial,  passes  beneath  the  peroneus  longus  and  the  extensor 
longus  digitoram  and  enters  the  upper  portion  of  the  muscle.  The  lower  arises  in  the  interval 
between  the  tibialis  anticus  and  the  extensor  longus  digitorum  and  passes  obliquely  downward 
into  the  substance  of  the  tibialis  anticus. 

The  nerve  to  the  extensor  longus  digUorum  arises  inunediately  below  the  preceding  and 
enters  the  inner  surface  of  the  muscle  which  it  supplies. 

The  nerves  to  the  extensor  proprius  hallucis,  usually  two  in  number,  arise  in  the  middle  ot 
the  leg  and  enter  the  substance  of  their  muscle. 

The  nerve  to  the  peroneus  tertius  is  usually  derived  from  the  nerve  to  the  extensor 
longus  digitonim. 

A*.  The  articular  branch  leaves  the  anterior  tibial  above  the  antenor  annular  ligament  and 
is  distributed  to  the  forepart  of  the  ankle-joint 

cc.  The  internal  terminal  branch  (Fig.  1117)  courses  forward  in  the  foot  under  the  inner 
tendon  of  the  extensor  brevis  digitorum  and  lateral  to  the  dorsalis  pedis  artery,  and  reacht  > 
the  base  of  the  first  digital  cleft.  Here  it  splits  into  two  branches  (nn.  digitaira  dorulea  balliKiH 
Uuralis  «t  digit!  tccundi  nedUlis),  which  supply  the  contiguous  sides  of  the  «reat  and  second 
toes  and  inosculate  with  branches  of  the  musculocutaneous  nerve.  In  the  region  of  the  tarsus 
it  sends  off  the  first  dorsal  interosseous  nerve,  which  supplies  the  first  dorsal  interosseoiis  musclt- , 
the  mesial  meUcarpal  articulations  and  the  first  and  second  metacarpo-phalangeal  joints.  Liki- 
the  other  interosseous  nerves,  it  sends  a  filament  between  the  heads  of  its  dorsal  interosseous 
muscle  for  the  supply  of  the  adjacent  articulations  (Ruge). 

dd.  The  external  terminal  branch  (Fig.  1118)  passes  laterally  over  the  tarsus  under  cover 
of  the  extensor  brevis  digitorum,  to  which  muscle  it  sends  branches.  From  it  are  given  off  two 
to  four,  usually  three,  dorsal  interosseous  branches,  which  decrease  in  size  from  within  outward, 
the  fourth  often  being  lacking  and  the  third  quite  rudimenUry.  These  interosseous  nerves  art 
distributed  to  the  adjacent  articulations  and  sometimes  to  the  second  and  third  dorsal  inter- 
osseous muscles.  The  fibres  from  the  anterior  tibial  to  the  dorsal  interosseous  muscles  are 
usually  not  their  sole  supply,  the  external  plantar  supplying  constant  branches  for  their  innerva- 
tion. From  the  latter  are  probably  derived  the  motor  innervation  and  frcim  the  occasional  ante- 
rior tibial  branches  some  extra  sensory  filaments.  This  branch  usually  ends  in  a  ganglifonji 
enlargement,  from  which  its  branches  are  distributed. 

Variations.— The  anterior  tibial  sometimes  supplies  the  mesial  side  of  the  great  toe  or  the 
adjacent  sides  of  the  second  and  third  toes.  In  one  case  the  anterior  tibial  supplied  the  outer 
three  and  one-half  toes,  the  inner  toe  and  one-half  Ijein^  innervated  by  the  musculo-cutoneons 
nerve.     Rarely  the  anterior  tibial  has  no  digital  distribution  whatsoever. 


c.    The  Musculo-Cutaneous  Nerve. 

The  musculo-cutaneous  nerve  (n.  peronaens  snperficialis)  (Fig.  11 16)  continues 
the  course  and  direction  of  the  external  popliteal.  Descending  through  the  leg  in  a 
fascial  tube  in  the  septum  between  the  peroneal  muscles  and  the  extensor  longus 
digitorum  it  becomes  superficial  by  piercing  the  deep  fascia  anterior  to  the  fibula  in 
the  lower  third  of  the  leg.  It  may  make  its  superficial  appearance  as  a  single  ner\e 
or  as  two  branches. 

Branches  of  the  musculo-cutaneous  are:  (a<i)  the  muscu/ar,  (bb)  the  internal 
and  (ff)  the  external  terminal. 

aa.  The  muscular  branches  (rr.  mmcnlarea)  are  destined  for  the  peronei  longus  and 
brevis. 

The  nerves  to  the  peroneus  lonfus  are  two  in  number,  an  upper  and  a  lower.  They  are 
given  off  at  the  upper  and  lower  portions  respectively  of  the  fascial  canal  occupied  by  the  parent 
nerve  and  enter  the  mesial  surface  of  their  muscle. 

The  nerve  to  the  peroneus  brevis  arises  with  the  lower  branch  to  the  peroneus  longtis  and 
enters  the  musculature  of  the  peroneus  brevis. 


TERMINAL   BRANCHES. 


1339 


From  mitUlle 


Kiom. 
peroneal  nerve 


pcroueftl  nenw 


MtMCulo-cuta* 
ncotM  nerve 


Ext.  Mphenous  J 
nerveS  ; 


Est.  terminal 
br.  muflcn1o>  * 
cutaneoua 
ner»« 


From  IntcriMl 
-ruiancoua 
uer^*e 


From  Imcmal 
-  cutaneous 
nerve 


I  CutaneouH 
F  patellar  br.  Int. 
^MaphenottH 
nerve 


.Int.  nphenona 
nerve 


M.  The  iataniiatafiBiaatbranch(a.caUMdsdM«alliM4lalit)  (Fig.  1117).  larger  than  the 
external,  passes  obliquely  inward  in  front  o<  the  ankle  and  then  forward  over  the  dorsum  of  the 
foot     Cutaneous  twigs  are  distributed 

to  the  anterior  aspect  of  the  lower  third  '"c  1  "7- 

of  the  leg  and  the  dorsum  of  the  foot. 
Just  below  the  anterior  annular  ligament 
the  nerve  breaks  up  into  an  inner,  a 
middle  and  an  outer  branch. 

The  inner  branch  inosculates  with 
the  internal  saphenous  nerve,  from  which 
it  receives  an  accession  of  fibres,  and 
passes  forward  to  supply  the  integument 
of  the  mesial  aspect  of  the  foot  and  great 
toe.  The  middle  branch  follows  the  first 
metatarsal  space  and  inosculates  with  the 
inner  branch  »f  the  anterior  tibial  nerve. 
The  outer  branch  courses  down  the 
second  metatarsal  space  and  divides  into 
ihe  two  dorsal  digital  nerves  (no.  dlgitatea 
doruln  pedis)  which  supply  the  contig- 
uous sides  of  the  second  and  third  toes. 
This  branch  is  sometimes  derived  from 
the  external  terminal  part  of  the  musculo- 
cutaneous. 

cc.  The  external  terminal  branch 
la.  calaacoa  dersalli  intcrmedius)  (Fig. 
1 1 1 7 )  courses  down  the  leg  anterior  to  the 
ankle  and  lateral  to  the  inner  branch, 
fciving  off  twigs  to  the  antero-lateral  por- 
tion of  the  integument  of  the  lower  part 
of  the  leg  and  dorsum  of  the  foot.  Having 
reached  the  foot  it  breaks  up  into  inner 
and  outer  branches. 

The  inner  branch  divides  into 
dorsal  digital  branches  for  the  supply  of 
the  adjacent  sides  of  the  third  and  fourth 
toes,  mA^'^  outer  branch,  after  receiving 
an  accession  of  fibres  through  inoscula- 
tion with  the  external  saphenous,  divides 
similarly  into  twigs  for  the  contiguous 
sides  of  the  fourth  and  fifth  toes.  The 
dorso-lateral  aspects  of  the  terminal 
phalanges  and  the  nails  receive  ?.ddi- 
tional  filaments  from  the  plantar  nerves- 
Variations.— Deficiencies  in  the  in- 
ternal branch  are  usually  supplied  by 
the  anterior  tibial  nerve  and  m  the  ex- 
ternal by  the  short  Siiphenous.  In  c.ise 
the  external  branch  ends  at  the  dorsum 
of  the  foot,  the  external  saphenous,  which 
would  fill  the  varnncy  at  the  digits,  has 
its  root  from  the  external  popliteal  more 
strongly  deve1o|)ed  than  usual,  and  thus 
the  toes  are  supplied  in  an  unusual 
manner  but  still  by  tibrLS  from  the  ex- 
ternal popliteal  ner\'e. 


-Crest  or  tiliia 


Int.  Maphrnoua 
"  nerve 


Int.  saphenolu 
'vein 


Int.  terminal 
br.  muAculo- 
'  cutaneous 
nerve 

Int.  terminal 
-  br.  ant.  tibial 
nerve 


6.    The  Internal  Popliteal 
Nerve. 
The  internal  popliteal  or  tib- 
ial nerve  fn.  tibialis)  (Fig.  11 15) 
is  of  greater  size  than  the  external 
and  corresponds  in  its  distribution 

to  the  combined  median  and  ulnar  nerves  of  the  arm.     Arising  from  the  anterior 
portion  of  the  sacral  plexus,  it  includes  fibres  derived  from  the  fourth  and  fifth  lumbar 


Superficial  diatection  a(  right  le*  and  tuul.diuwlug  cuuneons 
nerves  of  anterior  surface. 


IMO 


HUMAN  ANATOMY. 


and  first,  second  and  third  sacral  nerves.  Leavinjf  the  pelvis  through  -^  grtMr 
sacro-sciatic  foramen  below  the  pyriformis,  ;ind  fiassing  through  tb«-  gimesi  rejjinr 
and  upper  part  of  the  thigh  as  the  inner  portion  of  the  great  sdatk:  nwve.  h  kBcomc 
an  independent  trunk  at  the  point  of  bifurcation  of  the  sciatir  Eiinij|iwi  ium 
beneath  the  hamstring  musdea  and  descending  vertically  throtqeii  the  miimt  of  ttit 

Fig.  iiiS. 


MiMculo-caUncou*  ncnre 


Fibula 


ExirititorlofifftiH 
dixttorum  tendon 

Prronrm  tcrtina  tmdon 

Anterior  tlMal  nerve 
Articular  l)ninchc«  to  ankle  joint 

Peroneua  loogua  tendon 

External  aaphenooa  nerr* 

Muaculo  cutaneoua  nerve— 

external  diviaiaa 

External  division  of  anterior 

tibial  nerve 

Extenaor  brevia  digitorum 


Metalanal  liranchea  of  external 
division  of  anterior  titiial  nerve 


External  saphenous  nerve 

l>igital  limnches  of  external 

division  of  ntuaculo- 

cutaneoua  nerve 


.Eatensor  proprius 
"    "     '   tendon 


teacmalab'*    "»mi)*  .;v'^^^ 


Extensor  bievis  digitoram 


Internal  division 
of  musrolo* 
cutaneous  nerve 
Anterior  tiliial 
nerve— internal 
branch 


Dissection  of  dorsum  o{  right  foot,  showing  distribution  o<  anterior  tibial,  muaculo-cuuiieous,  and  inietiial  and 

external  saphenous  nerve*. 


popliteal  space,  it  gradually  attains  the  inner  side  of  the  jKipiiteal  vesstis,  crossing 
them  superficially  from  without  inward.  In  the  lower  part  of  the  space  the  nerve 
lies  posterior  to  the  popliteus  muscle  and  anterior  to  the  plantaris  and  the  gastroc- 
nemius. At  the  lower  border  of  the  popliteus  muscle  the  internal  popliteal  becomes 
the  posterior  tibial  nerve  (Fig.  1 1 19). 


TERMINAL    BRANCHES. 


134« 


r)  the  o 


at  the  intemai  popliteal  *f<  .  («)  the  articulmr,  (b)  the  musftUar, 
■MS  and  (rf)  itite  pmUriinr  tiimi 

Fig.  1119. 


TIIMI(IURm*0|.<''    >'>• 


liilwriMr  ciwnMl  kTrs.ulw  :wm^t% 


flualHta  auKto 

Ctt.  kni  «<li tiMii 

TMal  cwnnMiskUlBff 


TRMto  liaMkw 


nncctim  ol  tte  poMcrior  mrtec*  ol  rlghl  leg,  itaDwinc  poMcrior  libUl  nerve  and  iU 
bniKhci  and  part  o(  permieal  nerve. 

a   The   aitkular   bnnehM    (rr.    artkalarea)    supply   the   hip   and    knee   joints.      The 
one  destined  for  the  hip  has  been  described  on  page  1333.    The  branches  to  the  knee  are  ol 


,3^2  HUMAN  ANATOMY. 

«m.ll  ««•  and  of  varvine  number.  There  a.^  usually  two,  an  upper  and  a  Awrr  and  thes< 
SSi^intos.™!  fiZfentt"hich  inoculate  with  the  lower  articular  fibres  of  the  extern.-.! 
S.^?  fomhw  the  MliUaipUxta  of  Riidinger.  The  upper  or  azygot  bratuk  ^>s^iA\\^ 
SS5^thi3t^or  liSSSTof'the  Joint,  while  Ae  lower  accompanies  the  irfenor  mtern.,! 
SSr  art^  When  a  third  b  present  it  accompanies  the  superior  mtemal  ar^Kiular  arter> 
Sihe  Seal  plexus  a  number  of  fine  filaments  are  furnished  to  the  posenor  portion  ... 
fll^kne^  S  and  an  occasional  twig  enters  the  popllteu,  muscle  by  piercing  its  posterior 

'"*'«■  The  muwular  branche.  (rr.  m.Kalart.)  comprise  two  sets,  those  given  off  from  Ih. 
part  above  thTSon  of  the  sciatic  nerve  and  tho.e  given  off  below.  The  former  hav-e  bee., 
d^ted  on  w>  1333.  The  latter  consist  of  a  Kries  of  five  twigs  which  mnervate  the 
irastrocnemius  the  soleus,  the  plantaris  and  the  popliteus. 

■^  ^r^«to  the  gastrJnemiu,,  salens  and  plantaris  consist  of  two  stout  nerve  trunks, 
an  upp^  ^d  a  W-.  The  upper  arises  m  the  middle  of  the  popliteal  space  and  enters  the 
iTteKl^o"  thTinner  head  rfthe  gastrocnemius.  The  lower  anses  a  short  distance  below 
he  up^r^d  frequency  combined  with  the  nerve  to  the  plantaris.  divides  into  two  branches, 
a  shorter  for  Ae  outer  head  of  the  gastrocnemius,  and  a  longer,  which  enters  the  superior  bor- 
SeJ^of  The  soleus.  the  upper  part  of^which  muscle  it  supplies.    From  the  nerve  to  the  plantaris 

'''"™^1."rS"rtU°J:;^/"::^«'"a  complex  structure,  with  a  distribuUon  much  wider 

than  ^Tm^i^in  it.  naiT  Aiter  n^aching  the  lower  "J^f"  °' ♦^HKeTwa  and 
nerve  turns  forward,  ascends  between  the  antenor  aspect  of  the  muscle  and  «he  tmw,  and 
«^  Se  M  eri^?Vuria«  of  the  popliteus.  A  branch  supplies  the  periosteum  of  the  tibia  and 
AeHnters^he  nutrient  foramen  ofThat  bone  Another,  the  interosseous  hanch  (..  int.r«i^.. 
«^ri.TM^reSfiret  posterior  to  and  then  between  the  layers  of  the  nterosseous  membrane 
S^t  to  ^owe  mar^n.  Termi.-I  fibres  a.*  dUtributed  to  the  P*n«rteum  of  the  tibia  and 
toTe  ?nferiorSZ£  articulation.  Other  filaments  reach  the  Ubialis  posticus  muscle  an.l 
the  superior  tibio-fibular  prticulation. 

<:.  The  cutaneous  branch  is  the /»ia/rw»w<««««ir«Av«#ri'<r.  ,..  „«ii.ii.\ 

The  tibial  communicating  nerv.  or  n.  tibialis  commumuans  («.  cuu.ta.  wr.«  nwdUII. 
,  -ie  I  no  aJfees  in  the  uppeTportion  of  the  popliteal  .pace,  through  which  it  passes,  poster, 
o  The  inte<^p<^pl  teal  vTrve.  to  the  fissure  between  the  heads  of  the  gastrocnemius.  In 
company  whh  the  external  sa,rfienous  vein,  the  nerve  descends  in  thin  interva  tothe  tendo 
AcSs  a^d  aft«  piercing  thTdeep  fascia  at  about  the  middle  of  the  leg.  is  joined  by  the 
i^oneal  rommu^icS  nerve,  the  fusion  resulting  in  the  .xt.m.1  or  short  saphenou.  n.rv. 
^■^u™H.rTt^teb?ni  nerve  (Fig.  11.9)  courts  down  the  postero-lateral  aspect  of  the  lower 
tn^lL  l5  V^  ^erior^o  and  beneath  the  external  malleolus  in  company  wuh  he 
^remal  »ph^nor^in  and  follows  a  course  obliquely  downj""*  ""^  ---^^^.f  ,^«  J„^^ 
lateral  manrin  of  the  foot  to  the  dorsal  aspect  of  the  outer  side  of  the  fifth  toe,  at  the  tar  ena 
S  wh!rdi:Aalanrthe  nerve  terminat^  In  iu  ~"-?.'X"C''re^t;e  Sn  o^  h^ 
^nsory  twigs  to  the  postero-lateral  part  of  the  lower  third  of  the  leg.  *>«  J'^""^'',™ 
TxS  luieolus,  thVlateral  portion  of  the  heel  (rr.  calcd  l.wr.l..)  t^e  dorso-Uteral 
Sn  of  the  foot  (».  ««».«.  do".U.  lateralU)  and  the  outer  half  of  «h«  dorsum  o  the  fifth 
^  Twigs  are  furnished  to  the  ankle,  and  to  the  astragalo<alcanean  and  possibly  other  inter- 
tarsal  articulations.     In  the  foot  it  communicates  with  the  antenor  tibial  nerve. 

Variatioas.-The  point  of  union  of  the  two  tributaries  of  the  external  SfP"^"™* '^J|'''j^;' 
toulderariaUons,  somSimes  being  high  in  *^PoP««'tLf";^Zli«X7o^t  u'LtenlJ 
union  at  all,  in  the  latter  instance  the  nerve  which  reaches  am.  Mipplies  '"e  toot  usually  oein^ 
"he  n  conimunicans  tibialis.     In  one  specimen  found  in  the  anatomical  ,';?°"1*  °«„  ^^«,';^"^^f;^^ 

S^'SicKbiir^^^u^r^'^^^riny^ 
Si^rik^r^  oi^^j^i^^'x^^^^n^^f^i^  1 : 

UUs   irisfnethehiSier  and  piercing  the  inner  head  of  the  gastrocnemius  before  lo'n'ng  the  "• 

fibularis  usually  being  of  increased  size.    The  nerve  may  terminate  in  the  fx)t  and  not  nave  any 
diKital  distribution.  _  ^, 

d.  The  Posterior  Tibial  Nerve. 

The  poiterior  tibial  nerve  (n.  tibialis)  (Fij?.  11 19)  is  the  direct  continuation 
of  the  internal  ,K,pliteal  and  begins  at  the  lower  border  o'.''}^,?"?'"?"^/""*!*-  , '' 
extends  downward"^^  in  a  sheath  shared  by  the  posterior  tibial  vessels  between  the 
superficial  and  deep  muscles  of  the  posterior  portion  of  the  leg.     Antenor  to  it  are 


TERMINAL  BRANCHES. 


1313 


the  tibia  and  the  deep  leg  muscles  and  posteriorly  lie  the  soleus  and  gastrocnemius 
„  theTo^part  ofdie  Ik.     Above  the^kle  the  nerve  becomes  superficial,  and  is 

Srior  tiWal  vessl  the  nerve,  while  pursuing  a  straight  course,  changes  its  refa- 
^Stion  to  the  vesseb.  in  the  upper  part  of  the  leg  lying  to  the  inner  side,  lower 
dow^behind  and  above  the  ankle  attaining  the  outer  aspect  of  the  vessels  (Fig. 
?^r.)  P^ng  posterior  to  and  then  below  the  interna  malleolus,  the  po«enor 
til^nervedivTd^  under  cover  of  the  internal  annular  ligament,  into  its  terminal 
branches,  the  internal  and  the  external  plantar. 

Fig   II30. 


InMinml  cmlc«i»««n  iMyBch 
oi  pMUrior  tibial  tier 


Durttal  tmuichcs  ol 
Mwrnal  phwur  a*nr< 


Exlcnial  Mphenous  nerve 


External  Mphtnoui  nerve 


Diltita!  btanihrt  oC  external  plantar 
nerve 


Supcrflcial  dlMcction  oT  right  loot,  .howlng  cuUneou.  nrrvea  on  plantar  wirtace. 

Branches  o»  the  posterior  tibial  nerve  are  :  (aa)  the  muscular,  {bb)  the  internal 
cttkantan,  (r<r)  the  articular,  (,dd)  the  internal  plantar  and  {ee)  the  external  plantar. 

aa  The  muteulw  branch.,  (rr.  mttKuUret)  supply  the  tibialis  postiv^us,  the  solei.s.  thf 
flexor  longtis  hallucis  and  the  flexor  lonRUS  diKitorum.  i.„„.h  .r.  il,^.  rtexor 

The  nerve  to  the  Hbialis  posticus  supplies  that  muscle  and  sends  a  branch  to  llu-  Hexor 

Ion  J»rl  and  one  to  the  lower  part  of  the  soleus.    At  the  posterior  aspect  of  the  tibtahs 

S«  U  rive-  off  a  long  slender  branch  which  accompanies  the  peroneal  artery  nearly  to  the 

Imkte  ^p^yi^R  twiKS  to  the  artery,  to  the  periosteum  of  the  fibula  and  a  branch  whtch  enters 

"'  ''Sr:^^'Sl°the>''^.  lon^  kaiiucis  and  /«..«  di^lorun.  leave  the  posterior  tibial 
•iKJut  the  middle  of  the  leg  and  paf  ^  i' .ectly  to  their  muscles. 


1344 


HUMAN  ANATOMY. 


'•  -n 


bb  The  intamal  caleanMii  nerve  (rr.  cakaael  B«dUlM)  arises  from  the  posterior  tibial  at 
the  lower  part  of  the  leg  and  becomes  superficial  by  traversing  an  opening  in  the  intern  ! 
annular  ligament  Dividing  into  two  sets  of  twigs,  internal  ealcanean  and  caleanM-pUntar,  it  is 
distributed  to  the  integument  of  the  internal  aspect  of  the  heel  and  postenor  portion  of  the  solv. 

ec.  The  articular  branches  are  two  tiny  twigs,  given  ofl  beneath  the  wtemal  annular 
ligament,  which  supply  the  ankle  joint  .u     .v     _».     > 

rfrf/The  Internal  plantar  nerve  (o.  flaataris  Mdlalto)  ( Fig.  I m ),  larger  than  the  external, 
resembles  in  its  distribution  the  median  nerve  m  the  hand.  From  the  pomt  of  division  of  the 
posterior  tibial  nerve  it  courses  forward  in  the  foot  in  company  with  the  internal  plantar  artery. 
lyirat  first  above  the  internal  annular  ligament  and  the  ealcanean  head  of  the  abductor  hallucis 
Midthen  between  the  abductor  hallucis  and  the  flexor  brevis  digitorum.  Passing  thence  for- 
ward between  the  flexor  brevis  hallucis  and  the  flexor  brevis  digitorum  it  divides  into  two  ter- 

FlG.  lUI. 


C«lc«neo-pUnUt 
cutaneoiu  br.  of  tibial  nerve 

Articular  br.  (unualljr  ■  tw. 
of  tibial  nerve) 

Br.  to  aliductor  baltncia 


Int.  pUntar  nerve 
Bm.  to  Hex.  brevl«  digitorum 


I.  andll.lumbricales 
Digital  bm.  of  int.  plantar  nerve 


Flexor  btevia  digitorum 
Ext.  plantar  nerve 

Br.  to  abductor  minimi  digitl 

Abductor  minimi  digiti 

Flexor  acceiaoriui 

Br.  to  flex,  accewwrius 
Supcrftdal  br.  est.  ptanur  Mfvc 

Bra.  to  flex.  brev.  minimi  digiti 

Deep  br.  ext.  plantar  nerve 
Digital  branch 

Bra.  to  inlerosMi  of  fourth  upacr 
Digital  branch 


II.  and  IV.  lumbricalea 


Diweclion  o(  riglit  foot,  .h..wliig  liilernil  aud  external  planter  nervei  and  their  branchea. 
minal  branches,  an  inner  and  an  onter.     In  addition  to  the  terminal  branches  It  gives  oft  certain 

collateral^  TJlUteral  branches  are  muscular,  cutaneous  and  articular  in  distribution.  The 
muscular  supply  the  abtluctor  hallucis  and  the  flexor  brevis  diRitorum.  TX^f^  cutaneous  pass 
T^Z^r,  the  muscles  jtist  mentioned  to  1*  distributed  to  the  inteRument  of  the  inner  portion  of 
the  sole     The  articular  furnish  innervation  to  the  inner  tarsal  and  tarso-metatersal  Joints. 

The  terminal  branches  are  an  inner  or  mesial  and  an  outer  or  lateral.      .  ,  ,         , 

The  inner  ..r  mesial  terminal  branch  (Kig.  i  lai )  courses  forward  upon  the  under  surface  o 
the  abductor  hallucis,  pierces  the  plantar  fa.soia  ,x«terior  to  the  tarso-metttarsal  articulation  of 
he  gr^-tt  tol'  and  terminates  by  exlentlinR  along  the  mesial  side  of  that  toe  asUs  inner  planta 
digital  nerve.     In  its  course  it  furnishes  filaments  to  the  mner  surface  of  the  foot  and  a  twig  to 
the  mesial  head  of  the  flexor  brevis  hallucis. 


THE  PUDENDAL   PLEXUS. 


»345 


The  outer  or  l«t«niltennlii«lbtmiich  (Fig.  iiai)  U  larger  than  the  inner  and  U  simted 
below  the  distal  portion  of  the  flexor  brevis  digitorum  and  above  the  deep  plantar  fasaa.  After 
a  short  forward  course  it  splits  into  two  branches,  the  lateral  of  which  soon  divides  into  h«ro. 
There  are  thus  formed  three  plantar  digital  nerves  (an.  dlKiutea  plantare.  commnii*.),  e?jJi  of 
which  at  the  distal  end  of  its  n  ;tatarsal  space  divides  into  two  digital  nerves  { an.  diglule. 
,U>Ufts  pnprii),  the  inner  supplying  the  contiguous  sides  of  the  great  and  second  toes,  and  the 
middle  and  outer  being  distributed  similarly  to  respectively  the  second  and  third  and  third  and 
fomSTtoes  The  inner  of  the  three  sends  a  filament  to  the  first  lumbricalis,  the  middle  some- 
times to  the  second  lumbricalis.  while  the  outer  forms  an  inosoilation  with  the  external  plantar 
nerve  In  addition  to  innervating  the  muscles  enumerated  and  the  integument  erf  the  plantar  sur- 
bceof  the  mesial  three  and  one-half  toes,  each  of  the  digital  nerves  sends  tiny  filaments  toward 
the  dorsum  for  the  supply  of  the  naib  and  the  tips  of  the  to«.  

tt  The  external  plmntat  nerve  (a.  plaatarto  UtcralU)  ( Fig.  1121 )  is  a  smaller  nerve  dian  the 
internal  and  corresponds  in  its  arrangement  and  distribution  with  the  pataiar  branch  of  the  ulnar 
nerve.  After  string  from  the  internal  plantar  beneath  the  internal  annular  ''ipment.  it 
Stows  a  coursein  company  with  the  external  plantar  artery  obliquely  forward  "jd  o"tw»fd 
ab^the  flexor  brevis  digitorum  and  below  the  flexor  accessorius.Rwch.ng  the  mtenra^ 
between  the  abductor  minimi  digiti  and  the  flexor  brevis  digitorum  it  divides  near  the  head  of 
the  fifth  metatarsal  bone  into  superficial  and  deep  terminal  brancfaM.  „  ,      ,      ..       ■„, 

Bwach..  of  the  external  planter,  like  those  of  the  internal,  toclude :  colMerat  and  Urmxnal 

''"^tSJ  colUteral  bruichcs  comprise  muscular  and  cutaneous  twigs.  The  muicular  branches 
«e  given  of!  soon  after  the  origin  of  the  parent  nerve  and  supply  the  flexor  acc«ssonus  and  the 
Victor  minimi  digiti.  The  cutaneous  branches  ate  a  series  of  small  twigs  which  follow  the 
sentum  between  the  flexor  brevU  digitorum  and  the  abductor  minimi  dipu  and  become  super- 
fcial  by  piercing  the  deep  plantar  fasda.    They  supply  the  integument  of  the  lateral  poruon  of 

The  tcnninal  branches  are :  the  superficial  and  the  deep.  ....         u     .  .u 

The  anpetflcial  or  cutwieous  branch  (r.  wperidaUi)  inoscuUites  with  a  branch  of  the 
internal  planter  and  continues  forward  in  tiie  interval  between  the  flexor  brevis  digitorum  and 
the  abductor  minimi  digiti,  eventually  splitting  into  an  external  and  an  internal  branch. 

The  external  branch  (Fig.  iiai)  sends  filaments  to  the  flexor  minimi  digiU  and  the  inter- 
ossei  muscles  of  tiie  fourtit  metatarsal  space,  after  which  it  becomes  cutwieous  near  the  fifth 
metetarao-phalangeal  articuUtion  and  continues  forward  as  the  plantar  digital  nerve  for  the 

'"''"•Th^'^einal 'branch  (Fig.  iiai)  courses  forward  in  tiie  fourtii  metetersal  space,  at  whose 
distal  end  it  separates  Into  two  filaments  which  supply  tiie  opposed  surfaces  erf  tiie  /°"f*  "«<> 
fiftii  toes.    Thedigital  branches  send  filaments  dorsally  for  tiie  nails  and  tiie  \xi»  o  tiie  toes. 

The  d.«  or  muscular  branch  (r.  profaataa)  accompanies  the  external  planter  artery 
in  an  obliauelv  forward  and  outward  course  above  the  adductor  obliquus  halluas  and  the  flexor 
a^riSd  betow  tiie  interossei  muscles.  It  forms  an  arch  (Fig.  i»i)  whose  conve«ty  is 
directed  forward  and  outward,  and  terminates  in  tiie  region  of  tiie  base  of  the  great  toe.  h  rom 
the  convex  aspect  of  the  arch  are  given  off  tiie  filaments  which  innervate  the  interossei  muscles 
of  tiTfim.  ^Sond.  third  and  sometimes  tiie  fourti,  interosseous  space.  Otiier  muscular  twigs 
supply  tiie  adductiires  obliquus  and  transversus  hallucis  and  tiie  outer  three  lumbncales,  the 
branch  to  tiie  second  lumbricalis  first  passing  beneath  the  adductor  transversus  hal  ucis  The 
branches  to  all  of  tiiese  muscles  enter  their  deep  surface.  In  addition  to  the  muscular  distribu- 
tion, articular  twigs  are  furnished  to  tiie  tarsal  and  tetso-metetarsal  articulations. 

THE  PUDENDAL  PLEXUS. 

The  pudendal  plexus  (plexus  padendus)  is  the  downward  continuation  of  the 
sacral  plexus,  and,  whilst  each  retains  more  or  less  its  individuality  as  a  dwtinct 
structure,  there  is  no  sharp  line  of  demarcation  between  the  two.  Considerable 
interlacinff  and  overlapping  is  the  rule,  so  that  often  some  of  the  mii>ortant  branches 
of  the  pudendal  plexus  are  derivatives  to  a  large  extent  from  the  elements  giMng  rise 

to  the  sacral  plexus.  n    t  .u     .^1.;.. 

The  pudendal  plexus  (Fig.  1 122)  is  situated  on  the  posterior  wall  of  the  peUiij 
and  is  formed  by  contributions  from  the  anterior  primary  divisions  of  the  first,  second 
and  third  sacral  nerves,  from  the  entire  anterior  primary  divisions  of  the  fourth  and 
fifth  sacral  and  from  the  coccygeal  nerve.  ,  .       ,  „,      „.„; 

Communication«.— The  nerves  helping  to  form  the  plexus  receive  gray  rami 
communicantes  from  the  gangliated  cord  of  the  sympathetic,  which  join  them  shortly 
after  the  nerves  emerge  from  their  inter\ertebral  foramina. 

8S 


1346 


Branches. — Tb" 

FlO.    1 133. 


Diactmm  lllmlratiiiK  ptan  of  pudendal  and  roccy(cml 
plexiuei. 


HUMAN   ANATOMY. 

branches  of  the  pudendal  plexus  are  :  (i)  the  visceral,  (2) 
the  muscular,  (3)  the  perforating  cu- 
taneous, (4)  the  small  sciatic,  (5)  the 
pudic  and  (6)  the  satro-coaygeal. 

1.  The  visceral  branches  arc 
really  white  rami  communicantes.  They 
are  derived  from  the  second  and  third  or 
third  and  fourth  sacral  nerves  and  arc 
distributed  to  the  pelvic  viscera  by  way 
of  the  pelvic  plexus  of  the  sympathetic. 
The  details  of  these  nerves  are  des- 
cribed with  the  pelvic  plexus  of  the 
sympathetic  (page  1374)- 

2.  The  muscular  branches 
furnish  innervation  to  the  levator  ani, 
the  coccygeus  and  the  external  sphinc- 
ter ani.  They  arise  from  a  loop-like 
interlacement  of  nerve-fibres,  formed  by 
the  third  and  fourth  sacral  nerves,  with 
sometimes  the  addition  of  fibres  from  the 
second.  The  nerve  to  the  external 
spAincter  pierces  the  great  sacro-sciaiic 
ligament  and  the  coccygeus  muscle, 
sending  filaments  to  the  latter,  and  enters 
the  ischio-rectal  fossa,  lying  between  the 
edge  of  the  gluteus  maximus  and  the 
sphincter  ani  externus.     It  supplies  the 


Fig.  1123. 


From  II.  lumbar  ner%*e 
./  ^..'From  1.  lumbar 


From  III.  lumbar 
ncn-e 


Cutaneoua  br».  po»t. 
diviiiiona  of 
■acral  ncma 


CoccyiiMt  nenrM, 
poCcrW  diriaioni 

Coccymal  nerve 
anterior  dlTision 


From  ani.  V.  lacral 

FromnntlV.  «cTal 

Inferior  hemnr 

rhoidal  nerve» 


I  Iliac  hm.  of  ilio- 
'  hypogaitric 


Gluteal  brB.  <>( 
•mall  wiatic  ner^-e 


Inferior  pudendal 
nerve 


Superficial  diwecion  ol  right  buttock  and  adiucnt  regloni,  ihowlnr  cuunBJU.  nerv... 


THE  PUDENDAL  PLEXUS. 


'347 


An  est.  femoral  br. 
of  •mall  ndatic 


pcrterior  portion  oJ  the  external  sphincter  and  distributes  sensory   fibres  to  the 

mtnniment  over  the 

ba^  of    the    ischio-  ^'O-  ««*»• 

rectal  fossa  and  the  tip 

of  the  coccyx. 

Vartotkm.— This 
nerve,  inrtead  of  pierc- 
ing the  coccygeus,  may 
pass  between  that  mils 
cle  and  the  levator  anL 

The  nerve  to  the 
levator  ani  is  derived 
usually  from  the  third 
and  fourth,  sometimes 
the  second  and  third, 
sacral  nerves  and  en- 
ters the  muscle  by 
piercing  its  mesial 
surface. 

3,    The   perfo- 
rating    cutaneous 
nerve  (Fig.  11 26)  is 
an  inconstant  branch, 
being  found  in  about 
two    thirds    of    the 
bodies  examined.     It 
springs  from  the  dor- 
sal    aspect     of    the 
second  and  third  sac- 
ral nerves  and  at  its 
point  of  origin  may 
be  associated  with  the 
pudic   or    the   snail 
sciatic.         Passing 
downward  and  back- 
ward   it   pierces  the 
great  sacro-s  c  i  a  t  i  c 
ligament  in  company 
with    the    coccygeal 
branch  of  the  sciatic 
artery  and-  winds 
around  the  lower  bor- 
der of,  or  in  rare  in- 
stances   pierces,    the 
gluteus  maxim  us. 
Perforating  the  deep 
fascia  slightly  lateral 
to  the  coccyx,  it  be- 
comes superficial  and 
is  distributed   to  the 
integument  over  the 
inner  and  lower  por- 
tion  of   the    gluteus 
maximus. 

SomHIcUiI  dl.»ectlon  of  rluht  bullock  ai..l  ihiRh.  thowlng  cuuneoui 

Vwiatkm..  -In-  '«""  "^  ««*•'*'  ""*•"• 

&nf/S"n«^mpany  the  pudic  nene  or  pass  between  the  ligament  »~'^he  K,"Uju. 
maximus.     It  may  be  replaced  by  a  branch  of  the  small  saatic  or  by  a  nerve,  called  by  tisler 


From  CXI.  mta* 
ncoui  nerve 


1348 


HUMAN  ANATOMY, 


Ae  ».  perforan,  coccygrus  majcr,   which  arise,  from  the  third  and  fourth  or  fourth  and 
fifth  Mcral  and  pierces  the  coccygeus  muscle. 


Fig.  11J5. 


Friim  obturalpr  n«rv« 
From  inlemal  cuuiwooi 


Internal  uphcnoiu  n«r« 


liuier  malleolus 


External  1  .iliaiiMU  bramhes 


From  snull  Kiilic  mr^e 


Small  Kimtic  nerve 


Sural  from  peroneal  nerve 
Peroneal  communicating 


Pan  st  lural  branch 


Tibial  communicating 


Exii'tnal  saphenous  ner\e 


i:xt.  braiirh  <>l  muscukxutaneous 


Anlciior  branch  oJrxl   Mphelinn" 


Cut.ini'ii"  iier\es  ot  (Kwterior  lurface  of  right  leg. 

4.  Tm:   Smai.i.   S(  iatic   Nkrve. 
The  small  sciatic  nerve  (n.  cutancus  fcmorls  posterior)  (Fig.  tJI4)  js  a  purely 
sensory  structure.      It  originates  from  the  back  of  the  lirst,   setoiul  ami  thiril.   or 


Hi 


THE  PUDENDAL   PLEXUS. 


1349 


from  only  the  second  and  third,  sacral  nerves,  the  upper  root  usually  being  aMOCi- 
S^th  one  of  the  roots  of  the  inferior  gluteal  nerve  and  the  lower  root  with  the 
SoSng  cuuneous  or  the  pudic  nerve.  Leaving  the  pel vjs  through  the  gr«t 
S^^tk  foramen  below  the  pyriformis.  it  descends  m  the  gluteal  region  between 
thr^^  ischu  and  the  great  trochanter,  posterior  to  the  great  sciatic  nerve  and 
anterior  to  the  gluteus  miximus.  accompanied  by  the  inferior  glutei  nerve  and  the 
Stk  W  Emerging  into  the  tliigh  at  the  lower  border  of  the  gluteus  ma.x.rnus 
h  S,^thu.^downwaS  beneath  the  deep  fascia  and  9uperfic«l  to  the  hamstnng 
muS  to  a  short  distance  above  the  knee,  where  it  pierces  the  deep,  and  become 
r«^pant  of  the  superficial,  fascia.  Thence  it  pas-scs  downward  through  the  roof 
d  th^Ste^  space  and  through  the  upper  part  of  the  calf.  ,n  the  latter  situation 
accomSSing  the  external  saphenous  vein  and  inc^culating  with  the  external 
^^DhTnCs  ne?ve.  It  rarely  extends  beyond  the  middle  of  the  calf  tapering  off  into 
tiny  thr«d^  which  are  dis^buted  to  the  skin  of  the  posterior  surface  of  the  upper 
half  or  two  thirds  of  the  leg  (Fig.  1125.)  .      .     .     .  .  /i>  ,i,_ 

Branches  of  the  small  scnatic  nerve  are:  (a)  the  tn/ertor pudendal,  (6)  the 
gluteal,  (<■)  ihe  femoral  and  (d)  the  sural. 

a   The  Inferior  pudendal  or  perine.1  br.nch  (rr.  peri—ta)  (Fig.  11*8)  leaves  the  parent 

SBto^rlnS^^^^^^^^ 

„e^e1!S  withthr;irineal  and  inferior  hemorrhoid.1  bruKhes  of  the  pudic  nerve.    It  may 

•'"'n^-^nJ-urS'-STncbe.  (rr.  d-l^i  •-f.ri.r..)  (He.  ..^,4)  consist  of  two. 
three  or^or?  Stout  fiuTetS?  which  arise  W  the  small  sciatic  n  .Sort  d»tanj=  above  the 
nfcrior  margin  of  the  gluteus  maximus.  around  which  they  wind.  Piercing  ihe  fasr^  lata 
Sually  Uiey  turn  upward  over  the  lower  portion  of  the  gluteus  maximum  and  are  d.s- 
ribu  S  tc^^hTskin  of  the  inferior  gluteal  region,  as  far  exten«My  a,  the  great  trochanter  and 
ntSy  almost  to  tiae  coccyx.  The  outer  branches  oyeriap  the  t.-rmmal  twigs  of  the  p^enor 
hTAm-h  of  the  external  cutaneous  nerve  and  the  posterior  primary  divisions  of  the  first.  se«  ond 
!::;d  thii^  Ju^terTrv^^e  inner  branches  ^times  pierce  the  great  sacro-sciatic  liga- 
ment •  they  reinforce  or  may  replace  the  perforating  cutaneous  nerve.  .  ,        ,       . 

;   TTie  femoral  branch..  (Fig.  ,  1*4)  consist  of  two  series  of  twigs,  an  internal  and  an 
external,  which  pierce  the  fa.scia  laU  of  the  posterior  aspect  ol  the  thigh  and  supply  the  inttgu- 

"^"'rf'TheTS^rbranch..  (Fig.  1125)  are  usually  two  terminal  twigs  which  innervate  t.. 
a  vaiying  extent  the  integument  of  the  back  of  the  leg.  ''ometjmes  not  emending  beyoiK^ 
the  confines  of  the  popliteal  space  and  sometimes  continuing  all  the  way  to  the  ankle  They 
in^Xn-ith  the  «temal  sliphenous  nerve,  and  when  they  are  lacking  their  place  is  Uken  l.y 
the  external  saphenous. 

Variation*  —In  those  cases  in  which  the  internal  and  external  popliteal  nerves  are  separate 
from  Th"i^dpitn?y  the  small  sciatic  also  is  double.  The  ventral  portion  accompanies 
r^ntemal  Seal  and  gives  <.ff  the  inferior  pudendal  and  internal  femoral  branches  while 
^  Xr^l  iSrtion  accomr««nies  the  external  popliteal  «nd  gives  off  the  gluteal  and  externa 
-:  oraltraK  sSmeun.es  the  small  sciaticas  joined  in  the  thigh  by  a  branch  from  the  great 
? ,  uirfc. 

5.     The  Pudic  Nerve. 

(n.  pudcndus)  arises  from  thi-  front  of  the  second,  third  and 
as  main  root  coming  from  the  third  and  there  being  a  doubtful 
oot  irom  tne  nrs..  Leaving  the  pelvis  by  way  of  the  great  sacro-sciatic  foramen 
iietween  the  pyriformis  and  the  coccygeus  and  below  the  great  sciatic  nerve,  it  jias-ses 
forward  with  the  internal  pudic  artery  and  the  ner^e  to  the  obturator  liiternus,  over 
the  base  of  the  lesser  sacro-sciatic  ligament  to  the  spine  of  the  ischium  (  Pig.  U26). 
Rcachine  the  small  s^icro-sciatic  foramen  internal  to  the  internal  pudic  artery 
the  ner\e  traverses  thi?  opening  and  enters  the  ischio-rectal  fos.sa.  where  it  gives  of! 
the  inferior  hemorrhoidal  nerve.  The  main  trunk  coursi-s  forward  in  a  canal 
(Alcock's)    in  the  obturator  fascia  on  the  outer  wall  of  the  ischio-rectal  fossa 


The  pudic  iRT\v' 
•'  .'iih  sacral  nerves, 
ijot  from  the  first. 


I350 


HUMAN   ANATOMY. 


(Fig.  1126),  at  whose  anterior  portion  the  ner\e  appi caches  the  base  of  the  tri- 
angular ligament  and  divides  into  its  terminal  branches,  the  perineal  and  the  dorsal 
nerve  of  the  penis  or  ^litoris. 

Branchei  of  the  pudic  nerve  are  :  (a)  the  inferior  hemorrhoidal tierve,  (A)  the 
perineal  nerve  and  (c)  the  dorsal  nerve  of  the  penis  or  clitoris. 

a.  The  inicrior  hcmarThoiiUl  nerve  (na.  hcoMrrhoidalea  iaferiorts)  (Fig.  11 27)  is  usually 
given  off  by  the  pudic  upon  entering  the  ischio-rertal  fossa,  but  it  may  be  derived  directly  fr.mi 
the  plexus,  its  fibres  being  offshoots  of  the  third  and  fourth  satral  nerves.  In  company  with  tht 
iiiferior  hemorrhoidal  vessels  it  passes  mesially  across  the  base  of  the  Lschio-recul  fossa  toward 

Fig.  1136. 

CaccyfMl  Mm.  I 

CunaCMM  hffUKlMS  froMI  lonfM  .4  \'    luniliw 

4ad  1.  II.  Bad  HI.  mlysI  Bcfv**.  tMnl>;r.M 
dItWiaa 

Branch  of  IV.  flacral  ncnrc 
X      ^^(perforaiingcuuniou*) 

Levator  ■ni  and  anal 
fMcia 

^^^.Pttdic  npiA'c 

Ciit  edge  of  'obturator 
faacU 

Inferior  n...nor- 
— rhoiflnl  neive 
Intrmal  pwlic 

•rtrry 

Prrinnl  dlvlnioa  •( 
pudk  B<r>e 
Itanil  serve  ol 
cittart* 


VnlTi' 


lucimhikbtta  partly  n-n>ov"d  to  expuae  pudic  wrvc  and  accompanying  blood-v^iael.  in  ca.rtl  on  outer  wall  of 
lichiu-racul  lossa. 

the  anus,  oa  approximating  which  it  splits  into  a  numlier  of  filaments,  which  supply  he  external 
sphincter  and  ihe  iiit<  icimient  <•«  the  anal  rcRion,  and  inosculate  with  the  small  sciatic, 
pudic  and  fourth  s.icni!  iKives. 

6.  The  perineal  nerve  (■.  peilMl)  (Fig.  1126)  is  one  of  the  tenninal  branches  of  the  pudic 
and  arises  at  the  bifurcation  of  that  nerve  near  the  p<jsterior  margin  of  the  tnangular  ligament. 
Soon  after  its  origin  it  splits  .nio :  (aa )  a  superficial  and  ( W )  a  deep  branch. 

aa  The  lupcritcial  branch  is  entirely  sensory  :Jid  consists  of  two  parts,  a  lateral  or 
posterior  and  a  mesial  or  anterior.  These  pa.ss  forward  toward  the  bf-se  of  the  scrotum 
in  company  with  the  superficial  perineal  vessels.  ... 

The  fateral,  external  or  /wsterior  brtiHch  courses  along  the  lateral  mr.-gi".  of  the  pennemn 
distributing  twigs  in  this  region  ai.d  sometimes  sending  branches  to  the  inner  aspect  of  the  thigh 
and  a  filament  to  the  origin  of  the  ischio-cavemosus  muncle  ( .Schwalbe). 

The  mesial,  imtet-nal  or  anlerior  branch  is  larger  than  the  lateral  and  is  more  deeply 
placed.  It  pierces  the  posterior  margin  of  the  triangular  ligament  and  runs  forward  either 
benetith  or  through  the  transversus  perinei  muscle.  It  splits  into  two  or  more  branches 
(OD.  icrofalw  vel  labUlee  poaterloie.)  which  inosculate  freely  with  each  other  and  supply  the 
integtiment  of  the  scrotum  or  l.ibium  majus.  They  communicate  with  the  pudendal  branch  of 
the  small  sciatic  nerve  and  with  the  inferior  hemorrhoidal. 


THE  PUDENDAL   PLEXUS. 


I35« 


A*  The  dttp  brmnch  ol  the  perineal  nerve  U  mainly  muscular  and  consats  o<  a  iingte 
.™ak  «hich  S»  up  into  several  branche..  whose  main  destmation  is  themu«cl«  o 

CI   nerin^m     Pacing   forward  from  the  i8chi.^rectal  iosM    it   enters  the  deep  pennea. 

ntrsCT^'  «=nr  fila Jents  to  the  external  sphincter  ani.  the  levator  ani^  the  t^v^ 
nlri«i  ihe  ischio<avemosus.  the  bulbo-cavemosus  or  sphincter  vapn*  aiul  the  compressor 
K;  0«  b^ch!The  nerv.  ,o  th.  Wlb.  accompanied  by  the  artery  -^  *««"«. "^ 
eme«  the  talb.  supplying  its  tissue  and  that  of  the  corpus  spongiosum,  and  mnervating  the 

"^r  '^J^t^'^t  :irp^".'(..  -.r-U.  »«-.)  (Rk.  .-7)  a  terminal  branch  and  the 

Fic.  iiJ'. 


&»    ** 


Doraal  ncm 
o{  renin 

Cni»  pmi». 
dcUchrd 


l9chio-c«4-emoimii. 
dt-uchvd 


Nerve  to  isct  Jo- 

cavernora* 

Nerve  to  bullx>- 

cavemoms 
Nerve  to  hulb 
Nerve  to  trmn>- 

versiu  perinei 
MuKulu  be.  ol  l>nta«l 
di«l«t"fl  ot  \twUc  Btrvr 

Oomat  nerve 
of  peniH 

r.itxawtahr.  ofMrliwal 
(lhi>ionof  |)«<Uc  ncTvc 

Pudic  nerve 

i-uferlor  hemor- 
rhoidal  ncr\'e 


Sphincter  «ai . 
cztemui 


CoUeti*  fnacta, 
reflected 


Cms  penis  and 
ischto-cavernosaa 

Anterior  (intemali 
Huperfidat 
perineal  nerve 
Inferior  pudendal 
nerve 
Transvemns 

Prrinei 
osterior  miperfl- 
lislpeiineal  nerve 
llmal  rirvs  of  fwslr 

Perineal  diviMun 
of  pudic  «cr  i, 
muscutat  pcrxUm 
Piidic  nerve 


Inferior  hemof* 
I  hoidal  nerve 


('.ItitcnsnasimnB 

Ftmri  rv.  sacral 

ner\':  i 

Ferforatlnir  ciitineow  nerve  ami  a  b  inth  of  TV.  sacral  neiw 

'^rissSifoe';;^':?^v5s!srj2SS";S'orSst.;r^^^^^^ 

muscle.  Piercing  the  inferior  layer  of  the  triangular  ligament  and  the  "uspensory  ligament  of 
the  penis  it  reaches  the  dorsum  of  the  penis,  along  which  it  courses  as  far  as  he  glans^  It 
rivesoR  the  nrrv^  to  the  corpus  cavcmosum,  which  pierces  the  tnangular  ligament  a.id  suppl.« 
Sllrectile  tissue  of  the  cris  penis  and  corpus  cavemcjium  The  mam  nerve  "^"^J*?- *« 
aJiterioTtwo  thirds  of  the  penisVif«:ludinK  the  glans.  and  sends  off  ventral  bnmches  which  pass 
around  to  the  under  surface  of  the  organ.  „.„i,  .„„ii.,  .i,.n 

The  dorsal  nerve  of  the  clitoris  ( n.  dorsali.  clltoridU^(  Fig.  1128).  while  much  smaller  than 
the  dorsal  nerve  of  the  penis,  has  a  corresponding  course  and  distribution. 

The  dorsal  nerve  of  the  penis  or  clitoris  communicates  with  the  inferior  pudendal  branch 
of  the  small  sciatic. 

Variathma  -The  ou<!lc  may  receive  a  root  from  the  fifth  lumbar,  in  the  high  form  of  plexus. 
A  rooTf^  th"  fifth^CT^l  U  deirri^  by  Henlc.  The  Inferior  hemorrhoidal  may  pierce  either 
(heT^air^  thesmalfs^cro^^atic  ligament,  and  the  former  of  these  ligaments  may  be  perforated 
by  the  lateral  superficial  perineal  nerve. 


»35» 


HUMAN  ANATOMY. 


The  Coccygeal  Plexus. 

6  The  •«cro-coccyge«l  nerves  (nn.  anocaccyitei)  are  derived  from  a  small 
nerve  "inosculation  called  the  coccygeal  plexus  (plexn»  coccygeuB),  a  structure  formiM 
by  the  fifth  sacral  and  the  coccygeal  nerve,  with  a  contnbuUon  from  the  iourth  sacnil 
which  descends  over  or  through  the  great  sacro-sciatic  ligament  The  fifth  sacral, 
having  been  joined  by  this  twig  from  the  fourth,  descends  along  the  margin  of  th<- 
coccyx  and  is  joined  by  the  coccygeal  nerve,  the  resulting  nerve- bundle  constitutmjr 
the  coccygeal  plexus.  From  it  arise  minute  filaments  which  pierce  the  great  sacro- 
sciatic  ligament  and  are  distributed  to  the  intqfument  in  the  immediate  neighbor- 
hood of  Uie  coccyx  (Fig.  1084). 

Practical  Considerations.— Of  the  branches  of  the  sacral  plexus,  the  great 
sciaHc  nerve  is  the  most  importent,  owing  to  its  size,  its  extensive  distnbution  and 
its  exposed  position.     The  greater  part  of  the  sacral  plexus  is  continued  into  the 

Fio.  1128. 


■■lU.<«««nw«» 


lft<  hio-dlTfrsatuK 


lirfffkK  iwiiwU  Mm 

PflMcriOT  wipcrfictal 

(MffliM*)  ncrv« 

Anterior  iu|MrlklBl 

IMrincal  Berve 

Tnrarmus  l>«rlM4 

•ulxricUlK 

frrlncal  dlvbloll  of 
liudiciicrre 

iBfrfinr  hmurTlMld*] 
n«rvr 

SfWiKlcr  aai 


llcrt'fawU  <-f  iHittock 


Clau  clltatdk 


ntep  Uycr  of 
tHuvul^  lil,'4iiirnl 


Oorml  nrrvr  '-f  >  lit-*t« 
Supcrltclal  |M-nnrdl 


Frora  IV.  iKnl  mtm 


left 

linn) 


DitMciion  of  female  perineum,  r.h.«ring  nervei;  «iul  fawia  in  position  on  right  tide  of  body,  removrf  on 
{C^Mn-  (».scl«  removed  on  ri«hl  ».<le,  exi»«ini;  .uperlicial  prineal  inlerapace ;  luperior  layer  of  triangular 
iniv'!it,   denuded  of  muscular  tlaauc,  seen  on  left  sine. 


nLT\e.  Except  in  complete  lesions  of  the  spin.il  cord  this  nerve  is  rarely  1,.;  .  yzed 
in  all  its  branches.  The  paralysis  may  result  from  fractures  of  the  lumbar  \crtel>rae, 
of  the  sacrum  or  of  the  innominate  bone,  from  pressure  of  tumors  in  the  pelvis  or  of 
the  child's  head  in  labor  or  from  the  use  of  forccjis.  It  is  the  structure  in  greatest 
danger  in  dislocation  of  the  hip,  since  the  head  of  the  fcinur  in  the  most  frequent 
varieties  sweeps  backward  against  this  nerve.  In  the  reduction  of  these  (xistenor 
liisloc.itions  the  nerve  has  been  hooked  up  by  the  head  and  made  to  pass  across  the 
front  of  the  neck  of  the  bone.  From  its  close  relation  to  the  head  and  neck,  it 
may  l)e  injured  in  violent  movements  of  the  hip  joint  without  dislocation. 

It  passes  out  of  the  pelvis  through  the  greater  sacro-sriatic  foramen,  below  the 
pyriformis  muscle,  and  after  cur\inK  outward  and  downwarrl  under  the  gluteus  maxi- 
mus  muscle  it  continues  its  course,  approximately,  in  a  line  from  a  point  midway 


THE  SYMPATHETIC  SYSTEM  OF  NERVES 


1353 


beween  the  Rreater  trochanter  and  the  tuberosity  of  the  ischium  above  to  the  iniddle  of 
!^,«nUteal  soace  below.  At  about  the  unction  of  the  middle  and  lower  thirds  of 
t  tCh  kdiSintoX  internal  and  external  popiiteal  nerves.  Below  the  gluteus 
m^xS"iU9cle  it  is  comparatively  superficial,  so  thut  tenderne«  of  the  ner%e.  as 
S^ns^t^^iT  easily  eliJted  by  pn-siure.  At  the  point  where  it  emerges  rom 
uX^  S^te  :s  maiimus  it  b  Ldily  r«»ched  for  operation.  After  averucal  in^ 
S  trough  the  skin  and  fascia  at  this  level  the  bice,^  muscle  u  exposed  The 
tower  m3  of  the  gluteus  maximus  is  raised  and  Uie  biceps  drawn  inward  when 
Se  ne^n  be  easily  hooked  up  with  the  finger.  Because  of  the  great  importance 
erf  tKei^e  to  the  lower  extrei/iity  it  is  not  advisable  to  excise  or  div.de  it  as  this 
would  Sralyze  ts  whole  area  below.  Stretching  is  the  only  justifiable  operaUon. 
rithouiTSe  r«ulte  obtained  are  often  disappointing;,  and  the  operation  may  caus« 
a^ten«iritL  According  to  Trombetto.  it  wSl  reauS-e  a  tension  equal  to  the  weigh 
onsX  to  break  it.  and  it  is  more  likely  to  yield  at  its  attachment  o  the  spinal 
«H^  thS  el^X^e.  It  should,  therefore,  tolerate  a  stretching  torce  of  from  too  to 
^\T(T^»T  A  safe  working  rule  is  to  use  a  force  sufficient  to  r.«se  the 
affected  limb  from  the  table,  the  patient  lying  in  the  prone  position. 

UhTbeen  observed  that  when  the  paralysis  is  Jue  to  »«"'«=  F^»;^"jr.  '*"* 
„»r..«  of  the  sacral  olexus  within  the  pe  vis  it  is  often  confined  to  the  peroiual  or  ex- 
?^7  iJw  «^V  or  iTmost  marked  in  it.  This  has  been  explained  by  the  fact 
Shf2br«  forThe  ^oneal  nerve  lie  close  together  direcdy  on  the  pelvic  bones 
Lnd  a^  tSore.  pa&arly  exposed  to  pressure.  They  arise  for  the  most  par 
felX  luiX-Si^cral  cord,  formed  by  the  fourth  and  fifth  lumbar  and  first  sacral 
S"es  wS  He^lr^^on  the  innomWe  crest,  the  rest  of  the  plexus  lying  on  the 

•"^riSlS  d  the  external  popliteal  or  per^al  nene  the  extensors  of  the  foot 
and  toUTe  tibialis  anticus  and  the  peronei  muscles  are  involved.  The  foot  han^s 
dowi^m  its  own  weight  (foot  drop),  and  turns  in  from  paralysis  of  the  perone.. 
S^me  ^  the  anterior  tibial  muscle  escapes.  In  walking  t^^ .^nee  must  Ik=  un- 
dXflexS^  prevent  the  toes  from  dragging  on  the  ground  and  the  arch  of  the  foot 
1  tottenS  from  the  loss  of  the  support  given  to  the  arch  by  the  peroneus  U.ngus^ 
H  ?SS^  is  disturbed  it  will  be  only^to  a  slight  extent  oyer  the  anterior  part  of  the 
WatoutThe  shin,  and  outward  from  this  on  the  dorsum  o  the  foot  and  toes,  but  not 
?the  ^d«  of  the  foot.  The  peroneal  nerve  may  be  divideti  accidentally  in  a  sub- 
™4neoS  tenotomy^!  the  bice^tendon  for  contraction  at  the  knee,  the  nerve  lying 
dSe^TheTnner  Lder  of  the  tendon.  It  may  be  injured  by  external  violence.  ^ 
U^  around  the  head  and  neck  of  the  fibula,  where  if  necessary  an  incision  will 
S^S^  it ;  or  it  may  be  injured  by  pressure,  as  in  prolonged  knee hng. 

'^^n^>^iH  di  the  intemJ  popliteal  nene  all  the  other  muscles  of  the  leg.  in- 
cluding ^S^cid  and  deep  fleTors.  the  tibialis  jx)sticus  the  plantar  muscles  and 
inteSi  Ir^Ked.  Thellatient  cannot  extend  the  ankle  and  therefore  canriot 
iSnd^Thb  t<^.  The  toes  <^not  be  flexed  or  moved  sideways  Sensation  is  dis- 
tS^  on  the^ner  and  posterior  surface  of  the  leg.  the  outer  border  of  the  f.«t,  the 

"'"^  CWS^;"e':^^'S^-^  the  flexors  o,  the  knee  also  are  involve^ 

Lrul\1fo.;a?d\f  tU'iadnCp?^^^  which  is  supplied  by  the  anterior  .  n.ral 

nerve.  __.  ,„^ 

THE  SYMPATHETIC  SYSTEM  OF  NERVES. 

The  sympathetic  portion  (systema  nervorum  sympathetiaim)  of  the  peripheral 
ncrvmis  s;ffl£s  f^m  that  afready  de.crib«l-the  ^P;-'-^^']--^'  ^^^^ 
-in  beine  particularly  concerned  in  carrying  efferent  and  afferent  'm|>"f^  »«  and 
fnmX^th^racic  a  J  abdominal  organs  (collectively  termed  the  .punchmc  area\ 

Contrast  to  the  great  somatic  fskeletal)  masses  of  voluntary  muscle.  Whilst  tue 
Lhsf^the  afferent  or  sensory  impulses  conducted  from  the  splanchnic  area  differ 
CZ  in"  ,ortanrr«J;ct  from  those  formed  by  the  cerebro-spinal  nerves,  the  efferen 

IZr^Z  are  JLuliar  (.  )  in  supplying  the  involuntary  an<l  cardiac  muscle  ai.d 


1354 


HUMAN  ANATOMY. 


Fig.  1 1 39. 


the  gUndular  tissue  and  (6)  in  consisting  of  at  least  two,  sometimes  of  m<ire,  links  ue- 
tween  the  source  of  the  impulse  (the  spinal  cord)  and  the  structure  up..n  which  it  is 
expended.  It  is  these  interposed  links  that  constitute  the  sympathetic  elements 
proper— the  sympathetic  wiirotus.  The  cell-bodies  of  these  neurones  exhibit  a 
marked  disposition  to  become  aggregated  into  larger  or  smaller  collections,  which 
constitute  the  innumerable  ganglia  that  form  a  conspicuous  feature  of  the  sympathetic 
system,  whilst  their  axones  serve  to  connect  the  ganglia  with  the  terminal  structures 
(muscles  or  glands)  or  with  other  neurones.      It  is  evident,  therefore,   that  the 

sympathetic  system  consists  of 
a  complex  of  spinal  and  sym- 
pathetic fibres  intermingled 
with  groups  of  ganglion-cells. 
The  latter  are,  for  the  most 
part,  stellate  in  form  and  pro- 
vided with  axones  which,  while 
often  pursuing  a  long  course 
as  splanchnic  efferenls,  acquire 
only  partially  or  not  at  all  a 
medullary  coat  and  hence  may 
be  classified  usually  as  non- 
medullated  fibres.  Since  the 
spinal  fibres  are  provided  with 
this  covering,  the  bundles  of 
such  fibres  present  the  whitish 
color  distinguishing  medulhited 
strands,  in  contrast  to  the  gray- 
ish tint  of  the  strands  of  the 
nonmeduUated  sympathetic  fila- 
ments. It  is  upon  this  histolog- 
ical variation  of  their  predomi- 
tiating  fibres  that  the  difference 
recognized  in  the  white  and 
gray  rami  communicantes,  pres- 
ently to  be  described,  depends. 
Although  the  supply  of  the 
thoracic,  abdominal  and  pelvic 
organs  constitutes  an  important 
part  of  the  duty  of  the  sympa- 
thetic nerves,  it  is  by  no  means 
their  entire  concern,  the  inner- 
vation of  the  involuntary  muscle 
of  the  vessels  and  of  the  skin 
and  the  glands  throughout  the 
body  being  likewise  their  task. 
In  order  to  meet  their  obliga- 
tions to  the  structures  within 
the  liody  cavities,  the  sympa- 
thetic nerves  naturally  follow 
the  course  of  the  blood-vessels, 
with  the  result  that  every  artery 
of  consequence  within  these  re- 
gions is  surrounded  by  a  more  or  less  elaborate  net-work,  these  plexuses  in  most 
cases  bearing  the  names  of  the  arteries  which  they  accompany.  In  order  to  provide 
for  the  outlying  tracts  of  involuntary  muscle  contained  within  the  blood-vessels  outside 
the  body-cavities  and  within  the  skin,  as  well  as  for  the  glands,  the  sympathetic  fibres 
join,  by  way  of  the  gray  rami  communicantes,  the  somatic  spinal  nerves,  which 
they  accompany  to  all  parts  of  the  body.  For  this  reason  the  peripheral  somatic 
nerve-trunks  contain  three  varieties  of  fibres — afferent  and  efferent  spinal  and  efferent 
sympathetic. 


Diainmm  BhowinK  constitution  of  sympathetic  system ;  spjmil 
cficrenti  are  blsck ;  sympathetic  efferents  are  red ;  sympathetic  (vis- 
reral)  aflerents  are  blue:  SC,  spinal  cord:  AR,  PR,  anterior  and 
posterior  root  of  spinal  nerve ;  SG,  spinal  ganglion ;  AD,  ^Z;,antcrior 
and  posterior  primary  divisions;  WR,  GR,  white  and  gray  rami 
communicantes.  GC,  ffangliated  cord :  SvO,  sympathetic  ganglia ; 
'  etic  ganglion :  PvG.'SukG,  tVC  prevertebi   ' 


(7,   sympath        „ 
PvG,  SuiG,  JVG,  prevertebral, 

_ Spi\f,  splanchnic  efferents ;  .T 

somatic  eSerents ;  y,  veaaels  of  the  spinal  meninges;  /,  intestine, 


CG,  cervical  sympathetic  ganglion 

subsidiary  and  terminal  ganglia;  'Sfl\f,  splanchnic  ellerents;  So^, 


mmm 


"PIEiiHP>>n^"Hi9?IQPPi!PPP 


THE  SYMPATHETIC  SYSTEM  OF  NERVES. 


«355 


Constitution  and  General  Arrangement. — ^The  sympathetic  system  st  r\  es 
to  receive,  rearrange  and  distribute  the  visceral  filaments  of  the  cerebro-spinal  nervei;, 

Fig.  1130. 


latvuknitltoolc  cwd  of  tympaOmilk 
Thyroid  cutilacc  [tynpatfMtic 

Superior  cervical  cudUc  bnoch  of 
MkkDc  cervk«l  gaot^loa 


Infcilor  cerrkal  gaagUoa 

I.  tfMrack  gugUoa 

Right  recurrat  Urymgeal  man* 

CeoifaiDcd  cwlcal  cardtoc  brmwjwt 
RJtht  Ytgm  (of  aympMhetk 

Inlnior  cer%-icaJ  cardiac 

branch  of  va(i» 
Left  middle  aad  inferior  cervical 
cvtttacs  of  typatfceWc 


Diucction  thowins  right  gangiiatad  cord  of  Byaipathctic  and  itt  bnochat. 

and  to  complete,  by  the  interposition  of  one  or  more  of  its  especial  neurones,  the 
path  for  the  impulses  brought  by  such  tibres  to  the  objective  organs.     It  compriaei 


1356 


HUMAN  ANATOMY. 


two  principal  parts,  the  gangliated  cords  and  the  plexuses,  with  their  associated 

^""^The  gangliated  cord  (tnincus  sympatheticus).  one  of  a  symmetrically  placed 
pair  of  gangliated  trunks  situated  anterior  or  lateral  to  the  bodies  of  the  vertebr* 
(Fie.  1133),  begins  in  the  head  and  extends  through  the  neck,  thorax  and  abdo- 
men to  the  lowlr  portion  of  the  pelvis.  In  the  head  it  consists  of  a  P  exus  of 
fibres  continued  up  from  the  neck  in  an  intricate  interlacement  which  foUous  the 
internal  carotid  artery  ;  and  in  the  pelvis  it  terminates  by  the  two  cords  forming  a 
loop  or  fine  inosculation,  situated  anterior  to  the  coccyx  and  containing  the  coccygeal 
ganglion  or  ganglion  impar.  .  1       j-  »•     .       1 

The  plexuses  (plexus  sympathetlci)  are  a  series  of  more  or  less  disUnct  col- 
lections of  groups  of  nerve-cells  (gangli  )  and  fibres,  situated  mainly  in  the  axial  line 
and  giving  off  and  receiving  fibres  co-  lected  with  the  vanous  viscera  of  the  trunk. 
The  component  elements  of  the  p!  .uses  and,  indeed,  of  the  entire  sympathetic 
system,  are  the  ^awWia  and  the  «<•    e-fibres. 

The  ganglia,  whilst  foUowing  a  general  plan  of  arrangement  a.  .0  number,  size 
and  position,  are  subject  to  wide  individual  variations  and,  moreover,  where  they 
approach  a  segmental  type,  as  in  the  gangliated  cord,  there  is  considerable  deviation 
from  the  arrangement  presented  by  the  cerebro-spinal  system.  A  ^nglion  may  or 
may  not  be  connected  with  a  spinal  nerve,  but  it  is  always  ...iked  by  association 
cords  with  other  ganglia.  According  to  their  position,  three  varieUes  of  ganglia 
are  recognized.  One  group  includes  the  prevertebral  ganglia  (g.  tmnci  sym- 
patheUd),  those  found  as  nodes  in  the  gangliated  cord  ;  a  second  vanety  comprise 
the  collateral  or  intermediate  ganglia  (g.  plexuuin  sympathetlcorum),  which 
Ue  either  on  the  peripheral  branches  of  the  gangliated  cord  or  in  a  prevertebral 
plexus  ;  whilst  to  the  third  set  belong  the  innumerable  minute  terminal  ganglia, 
composed  of  nerve-cells  which  lie  at  or  Bear  the  visceral  distnbuUons  of  the  sympa- 
thetic fibres.  ,       ,  .     ,  .•  L 

Each  ganglion  consists  of  an  indefinite  number  of  mulupolar  neurones,  which 
possess  one  axone  and  a  number  of  dendrites,  the  whole  cluster  of  cells  being 
enclosed  in  an  envelope  of  fibrous  tissue.  The  axone  is  often  meduUated  in  the 
immediate  vicinity  of  its  cell,  but  usually  loses  this  sheath  as  it  gets  farther  and 
farther  away  from  its  origin.  The  course  taken  by  the  axone  of  a  prevertebral  gang- 
lion-cell may  be  one  of  three  :  (i)  it  may  pass  by  means  of  an  association  cord  into 
an  adjoining  prevertebral  ganglion,  (2)  it  may  proceed  as  a  constituent  of  a  gray 
ramus  communicans  to  join  a  spinal  nerve  or  (3)  it  may  follow  a  splanchnic  efferent 

toward  a  viscus.  . 

The  nerve-fibres  encountered  within  the  sympathetic  system  include  two  sets  : 
(a)  those  derived  from  the  cerebro-spinal  system,  which  are  usually  meduUated,  and 
(*)  the  sympathetic  fibres  proper,  for  the  most  part  nonmedullated,  although  as 
stated  above,  many  of  the  axones  possess  a  medullary  sheath  for  a  short  distance 
beyond  their  origin  from  the  nerve-cell.  This  distinction  between  meduUated  and 
nonmedullated  fibres  is,  however,  somewhat  indefinite,  since  the  meduUated  spinal 
fibres  often  become  nonmedullated  before  terminating,  whilst  the  sympathetic  fibres 
occasionally  are  meduUated  throughout  their  course. 

Rami  Communicantes.— Where  the  typical  segmental  arrangement  prevails, 
as  in  the  thoracic  region,  each  spinal  nerve  is  connected  with  the  adjacent  gangliated 
cord  by  a  pair  of  short  nerve-trunks,  known  as  the  rami  communicantes  (Fig.  1 129). 
These  are  divided  into  two  groups,  the  white  rami  and  the^ray  rami,  a  distinction 
de|)ending  primarily  upon  the  difference  in  the  appearance  of  the  strands  when  seen 
in  the  fresh  condition  ;  this  distinction,  moreover,  corresponds  with  the  histological 
difference  above  noted — white  rami  appearing  so  in  consequence  of  the  prepon- 
derance of  opaque  meduUated  fibres,  and  the  gray  rami  possessing  the  darker  tint 
on  account  of  the  absence  of  the  refracting  myelin  coat.  The  rami  communicantes 
pass  directly  between  the  spinal  ner\  ( s  and  the  gangliated  cord,  in  relation  to  the 
latter  joining  either  a  ganglion  or  an  association  cord  between  nodes. 

The  white  rami  communicantes  are  composed  almost  exclusively  of  the 
1  ■  :eral  branches  of  certain  of  ihc  spinal  nerves  which  use  the  sympathetic  system 
as  the  pathway  by  which  they  arrive  at  their  destination.     They  consist  of  fasciculi  of 


THE  SYMPATHETIC  SYSTEM  OF  NERVES. 


»357 


meduUated  nerve-fibres  derived  from  both  the  anterior  and  the  posterior  roots  ol 
the  spinal  nerves.  The  fibres  arising  from  the  anterior  root  are  called  the  splanch- 
nic efferent  fibres  and  those  from  the  posterior  root  the  splanchnic  afferent.  Not  all 
of  the  spinal  nerves,  however,  give  off  white  rami,  these  strands  of  communication 
forming  a  thoraco-lumbar  group,  from  the  first  or  second  thoracic  to  the  second 
or  tnird  lumbar  nerve  inclusive,  and  a  sacral  group,  derived  from  the  second  and 
third,  or  third  and  fourth  sacral  nerves.  The  cervical  nerves  do  not  give  off 
white  rami. 

The  splanchnic  efferent  fibres  are  the  axones  of  cells  located  within  the 
lateral  horn  of  the  gray  matter  of  the  spinal  cord.  They  furnish  motor  impulses  to 
the  unstriped  muscle  of  the  vessels  and  viscera,  and  secretory  ones  to  the  glands  of 
the  splanchnic  area  ;  they  also  convey  motor  impulses  to  the  heart.  Leaving  the 
spinal  cord  by  way  of  the  anterior  root,  they  pass  peripherally,  enter  a  white  ramus 
communicans  and  reach  the  gangliated  cord.  One  of  three  courses  is  then  pursued 
by  these  fibres  :  ( i )  they  may  end  at  once  by  forming  arborizations  around  cells  in 
the  ganglion  which  they  first  enter,  (2)  they  may  pass  through  this  ganglion,  thence 
up  or  down  through  an  association  cord  to  end  around  the  cells  of  a  node  of  the 
gangliated  cord  above  or  below  the  level  of  entrance,  or  (3)  they  may  course  through 
the  gangliated  cord  and  one  of  its  visceral  branches,  and  terminate  in  arborizations 
around  the  cells  of  a  prevertebral  or  of  a  collateral  ^glion.  It  is  possible  that  in 
some  cases  the  spinal  eflerents  may  continue  without  mterruption  through  the  several 
divisions  of  its  path  as  far  as  the  terminal  ganglia.  In  any  event,  whether  ending 
in  the  gangliated  cord,  the  prevertebral,  the  collateral  or  the  terminal  ganglia,  the 
cerebro-spinal  fibre  as  such  probably  never  actually  jains  the  tissue  of  the  oi^n,  the 
last  link  in  the  path  of  conduction  being  supplied  by  a  sympathetic  neurone. 

The  splanchnic  afferent  fibres  are  the  sensory  fibres  of  the  splanchnic  area 
and  consbt  of  the  dendrites  of  cells  situated  within  the  intervertebral  ganglia  on  the  pos- 
terior roots  of  the  spinal  nerves.  Whilst  the  greater  number  of  these  fibres  are  fotind 
in  the  white  rami,  a  few  are  thought  to  be  constituents  of  the  gray  rami.  Beginning 
in  the  viscera,  they  run  centrally,  without  interruption,  through  the  terminal  and 
collateral  ganglia,  through  the  gangliated  cord  and  the  white  (or  gray)  rami  to  the 
spinad  nerve,  and  thence  after  commg  into  relation  with  the  cells  of  the  ganglion  of 
the  posterior  root,  they  pass  by  way  of  the  posterior  roots  into  the  spinal  cord. 

The  gray  rami  comtnunicantes  are  bundles  of  axones  of  sympathetic  neu- 
rones which  pass  from  the  gangliated  cord  to  each  one  of  the  entire  series  of  spinal 
nerves.  The  reason  of  this  generous  provision  will  be  evident  when  the  purpose  of 
the  communications  effected  by  the  gray  rami  is  recalled,  namely,  to  provide  sympa- 
thetic filaments  to  the  outlying  muscles  and  glands  by  way  of  the  convenient  path 
afforded  by  the  distribution  of  the  somatic  nerves.  Mingled  with  the  gray  fibres, 
a  few  of  the  medullated  variety  are  often  encountered ;  these  are  probably  pardy 
splanchnic  afferent  fibres  and  partly  medullated  sympathetic  fibres.  Variation  in  the 
origin  of  the  gray  rami  from  the  gangliated  cord  is  not  uncommon  ;  they  may 
arise  either  from  a  ganglion  or  from  the  association  cord  between  two  ganglia ; 
after  leaving  the  gangliated  cord,  a  single  ramus  may  divide  and  supply  two  spinal 
nerves ;  or  the  reverse  may  happen,  two  or  more  rami  arising  independendy  and 
either  separately  or  after  fusing,  joining  a  single  spinal  nerve. 

The  hirther  course  of  the  sympathetic  fibres,  after  having  joined  the  spinal  nerves 
by  way  of  the  gray  rami,  is  as  follows  :  ( i )  they  may  course  peripherally  along  with 
the  anterior  or  posterior  primary  divisions  "f  the  spinal  nerve  and  convey  vasomotor, 
pilomotor  or  secretory  impulses  to  the  involuntary  muscle  and  glands  of  the  somatic 
area  ;  or  (2)  they  may  enter  the  spinal  canal  by  way  of  the  anterior  or  posterior 
nerve-roots  and  be  distributed  to  the  spinal  meninges,  but  tint  to  the  nervous  coluinn. 
According  to  Dogiel,  it  is  probable  that  a  small  number  of  axones  of  sympathetic 
neurones  enter  the  root-ganglia  of  the  spinal  nerves  to  end  in  arborizations  around 
cells  of  type  II  (page  1008). 

The  association  cords  (Fig.  1130)  are  the  longitudinally  disposed  bundles  of 
fibres  comprising  the  interganglionic  portion  of  the  ganjfliated  cord ;  they  contain  both 
white  .ind  gray  fibres.  The  gray  ones  are  the  axones  of  sympathetic  neurones  whi.h 
are  either  passing  between  adjacent  or  more  remote  ganglia,  or  taking  an  upward  or 


1358 


HUMAN  ANATOMY. 


downward  course  before  passing  distally  to  their  "!^^^ JP^^^^^^  distributioa 
The  white  fibres  are  either  spinal  splanchnic  efferent  or  afferent  hbres. 
The  ^J«  "^^^^  ^^  distribution  from  the  gangliated  cord  include  the  scma^tc 
and  the  visceral  The  somatic  branches  are  the  rami  comniuniamtes  ;  the  vis- 
ceral benches  comprise  the  splanchnic  efferents,  which  consist  of  both  white  and 
gray  efferent  fibres,  as  wdl  as  the  white  splanchnic  afierents. 

THE  CERVICO.CEPHALIC  PORTION  OF  THE  GANGLIATED  CORD. 

The  cervico-cephalic  portion  of  the  gangliated  cord  (Pf^**  "P***"*^/^,^;^^^^^^^ 
sjstematis  sympatheUci)  consists  of  a  series  of  ganglia,  "s^^^X /^^.*^' ^^^^^^^^^ 
two,  connected  by  composite  association  cords  (Fig.  1131)-     It  lies  postenor  to  the 

Fig.  II 31. 

Lower  head  of  cvtcnul  ptctygoM  irukIc 

Intenul  pierygow  muirlr  I  Buccal  ■ 

Aurfculo4tnipoi«l  oenw 
Intenul  carotid  artcnr     \ 


Fneuinofaftric  » 
Inferior  dental  ncnrv 


Spinal  acceaiory  nerve^^ 
Put  of  facial  nen- 

Stylo-pharyngeui.  n»»de 

<^o«o-|)haryiigeal  na've' 

I.  ccrvkal  nerve 

PneumoKastric  nerve. 

Supenrtr  cervkal  ganglfaa  of 

sympathetic 

Superior  larynieeal 

bcKcndens  hypogloaai 

lI.cenrtcaliierTe' 

111.  cervical  nerve 


IntervaniElloBlc  as' 

tord  of  i»yini>atbeiic 


Mfddit  ccrrical  gangUoo 


laferW  cervical 

■angUoa 


Branch  to  1 .  thoracic 


Inferior  cervical  cardUc  ^ 
of  sympathetic 


Ungual  nerva 
External  laryD|[eal  branch 


Superior  cervical  cardiac  ef 
•   sympathetic 


Middle  cervical  cardiac  of  sympathetic 
Rcrurtcn*  laryntfeal  nerva 


Middle  cerrRal  cardiac  ot 

Common  Ipneumotfaalric 

carotid  artery 
Infcrior  cervical  canUacof 

p— uaiunaitric 


Recurrent  laryngeal 
nerve 
lotemal  mammary  artery 

CartiUiceof  I.  rill  - 

Clavicular  fiuet  uf  sternum -^ 


Deep  dissec'Jon  of  neck,  showing:  cervical  portion  of  lympAthetlc  gangliAted  cord  »nd  its  conncctiom. 

caroti '  sheath  and  anterior  to  the  prevertebral  fascia  and  the  rectus  capitis  anticus 
major  and  scalenus  anticus  muscles.  Inferiorly  it  is  continued  into  the  thoracic 
portion  of  the  gangliated  cord,  and  superiorly,  at  the  base  of  the  skull,  it  forms  an 
intricate  plexus  around  the  internal  carotid  artery,  in  whose  company  it  enters  the 


mmgmfiimmwn!^i9mmimim''mmmm 


THE  SYMPATHETIC  SYSTEM   OF   NERVES. 


»359 


cranium.  The  small  ganglia  connected  with  the  trigeniinal  nerve — the  ciliary,  the 
spheno-palatine,  the  otic  and  the  submaxillary — are  regarded  as  outlying  nodes  be- 
longing to  the  cephalic  continuation  of  the  gangliated  cord. 

The  dominant  characteristic  of  this  portion  is  the  absence  of  white  rami,  the 
spinal  fibres  present  reaching  the  cervical  region  from  the  upper  thoracic  nerves  by 
way  of  the  association  cord  between  the  highest  thoracic  and  lowest  cervical  gang- 
lion, around  whose  cells,  as  well  as  those  of  the  higher  cervical  ganglia,  the  processes 
of  the  spinal  neurones  end. 

The  distribution  of  the  cervical  portion  of  the  cord  includes  pupillo-dilator 
fibres,  cardio-accelerator  fibres,  vasomotor  fibres  to  the  arteries  of  the  head,  neck  and 
upper  extremities,  pilomotor  fibres  to  the  integument  of  the  head  and  neck,  motor 
fibres  to  tlie  involuntary  muscles  of  the  orbit  and  eyelids  and  secretory  fibres  to  the 
glands.  The  branches  consist,  as  elsewhere,  of  two  groufs,  somatic  and  visceral,  the 
former  reaching  their  area  of  distribution  by  way  of  certain  cranial  and  spinal  nerves, 
and  the  latter,  either  alone  or  in  conjunction  with  other  nerves,  forming  plexuses 
which  accompany  blood-vessels  and  supply  various  viscera  and  vessels  of  the  head, 
neck  and  thorax. 

The  ganglia  of  the  cervical  portion  include  a  superior,  a  middle  and  an  inferior. 

The  Superior  Cervical  Ganglion. — The  superior  cervical  ganglion  (g.  cervi- 
cale  snperius)  (Fig.  1077)  is  the  largest  of  the  entire  sympathetic  series,  measuring 
2-3  cm.  in  length  and  4-6  mm.  in  width.  It  rests  posteriorly  on  the  rectus  capitis 
anticus  major  muscle  opposite  the  second  and  third  cervical  vertebrae,  with  the 
internal  carotid  artery  anterior  to  it  and  the  vagus  nerve  to  its  lateral  aspect.  \Vith 
the  typical  reddish-gray  hue  of  the  sympathetic  ganglia,  it  is  fusiform  in  outiine, 
although  it  may  present  constrictions,  usually  three,  which  indicate  its  composition  of 
four  fused  ganglia. 

The  somatic  branches  consist  of  (i)  rami  communicantes  and  (2)  some  of 
the  communicating:  branches  to  the  cranial  nerves. 

1.  The  rami  communicantes  consist  of  four  gray  rami  which  join  the  anterior 
primary  divisions  of  the  first  four  cervical  nerves. 

2.  The  communicating  branches  to  the  cranial  nerves  are  pfiven  off  from  the 
upper  portion  of  the  ganglion,  ( I )  one  joining  the  petrous  ganglion  of  the  glosso- 
pharyngeal, (2)  others  entering  the  ganglia  of  the  root  and  trunk  of  the  vagus  and 
(3)  another  joining  the  hypoglossal  nerve.  In  addition  to  these  there  is  frequently 
given  of!  from  the  lower  portion  of  the  ganglion  (4)  a  branch  which  joins  the  exter- 
nal laryngeal  ner\-e. 

The  visceral  branches  comprise  :  (i)  \.he pharyngeal ,  (2)  the  superior  cervi- 
cal cardiac ,  {,2))  ^^ '^''^^'^**^^^  ^^^^^^  ^^ ''■'^^^^^'^^• 

1.  The  pharyngeal  branch  or  branches  (rr.  lao'nsopharjnKei)  arises  from 
the  antero-mesial  aspect  of  the  ganglion  and  courses  obliquely  inward  and  downward 
posterior  to  the  carotid  sheath  to  reach  the  surface  of  the  middle  constrictor  of  the 
pharynx.  Here  it  unites  with  the  pharv'ngeal  branches  of  the  glosso-pharyngeal  and 
vagus  nerves  to  form  the  pharyngeal  plexus  (page  1269),  from  which  fibres  are 
distributed  to  the  muscles  and  mucous  membrane  of  the  pharynx,  a  few  filaments 
joining  the  superior  and  external  laryngeal  nerves. 

2.  The  superior  cervical  cardiac  nerve  (n.  cardiacus  superior)  (Fig.  1131) 
arises  as  two  or  three  twigs  from  the  ganglion,  with  sometimes  an  additional  filament 
from  the  association  cord  between  the  superior  and  middle  ganglia.  It  courses  down- 
ward anterior  to  the  longu ,  colli  muscle  in  the  posterior  part  of  the  carotid  sheath, 
crosses  the  anterior  or  the  posterior  surface  of  the  inferior  thyroid  artery,  and  then 
descends  in  front  of  the  inferior  laryngeal  nerve.  At  the  base  of  the  neck  the  course 
of  ihe  nerve  begins  to  differ  on  the  two  sides. 

The  right  nerve  enters  the  thorax  either  anterior  or  posterior  to  the  subclavian 
artery  and  accompanies  the  innominate  artery  to  the  aorta,  where  it  enters  the  deep 
cardiac  plexus,  a  few  fibres  passing  to  the  anterior  surface  of  the  aorta.  On  the  way 
down  a  few  twigs  join  the  inferior  thyroid  artery  and  with  it  enter  and  supply  the 
substance  of  the  thyroid  body. 

The  left  nerve  upon  entering  the  thorax  joins  the  common  carotid  artery,  alonpj 
whose  lateral  and  anterior  surfaces  it  courses  to  the  aorta,  upon  reaching  which  it 


1360 


HUMAN  ANATOMY. 


joins  the  superficial  cardiac  plexus.  In  some  instances  the  nerve  remains  behind  the 
carotid  artery  and  joins  the  deep  cardiac  plexus. 

A  pretracheal  branch,  derived  from  the  loop  between  the  superior  cer\ical 
cardiac  nerve  and  the  inferior  laryngeal,  descends  anterior  to  the  trachea  and  is  dis- 
tributetl  to  the  pericardium  and  the  anterior  pulmonary  plexus  (Drobnilc. ; 

The  superior  cervical  cardiac  nerve  communicates  freely  m  the  neck  with  the 
middle  cardiac  and  other  branches  of  the  sympathetic,  and  with  the  external  laryngeal 
and  superior  cervical  cardiac  branches  of  the  vagus.  In  the  thorax  it  mosculates 
with  the  inferior  laryngeal  nerve. 

Variations.— The  superior,  as  well  .^s  the  other  cardiac  nerves,  presents  a  considerable 
deirree  of  variation,  sometimes  to  so  grea:  an  extent  as  to  show  no  resemblance  to  the  accepted 
typical  plan  of  arraneement.  It  is  sometimes  absent,  especially  on  the  nght  side,  and  m  such 
event  appears  to  be  replaced  bv  a  branch  from  the  vagus  or  from  the  external  ljir>nKeal  ner\e. 
It  may  have  no  independent  course,  but  join  one  of  the  other  sympathetic  cardiac  nerves  and 
reach  its  destination  as  a  part  of  the  latter. 

3.  The  vascular  branches  comprise  plexiform  nerve-structures  which  accom- 
pany the  terminal  divisions  of  the  common  carotid  artery.  They  consist  of :  (a)  the 
external  carotid  branch  and  (*)  the  internal  carotid  branch. 

a.  The  external  carotid  branch  (n.  caroticus  extemns)  (Fig.  1061)  joins 
the  external  carotid  artery  and  furnishes  subsidiary  plexuses  which  accompany  the 
branches  of  that  vessel.  Iii  addition  to  supplying  vasomotor  fibres  to  the  external 
carotid  tree,  sympathetic  filaments  are  fumbhed  to  two  of  the  ganglia  of  the  trigem- 
inal ner\  e.  A  branch  (radix  g.  submaxillaris)  from  the  plexus  on  the  facial  artery 
(plexus  maxiUaris  externns)  joins  the  submaxillary  ganglion  as  its  sympathetic 
root,  and  one  or  more,  the  smallest  deep  petrosal  nerve,  from  the  plexus  on 
the  middle  meningeal  artery  (plexus  meoingeus),  forms  the  sympathetic  root  of  the 
otic  ganglion. 

Ganglia  of  microscopic  size  have  been  described  on  these  vascular  plexuses. 
The  most  important  of  these,  the  temporal  ganglion,  is  situated  on  the  external 
carotid  at  the  point  of  origin  of  the  posterior  auricular  artery  and  is  said  to  receive 
a  filament  of  communication  from  the  stylo-hyoid  branch  of  the  facial  nerve. 

b.  The  internal  carotid  branch  (n.  caroticus  internus)  is  apparently  an 
upward,  cranial  extension  of  the  superior  ganglion  (Fig.  io6i).  Ascending  beneath 
the  internal  carotid  artery,  it  accompanies  that  vessel  into  the  carotid  cand,  where  it 
divides  into  two  plexuses,  the  carotid  and  the  cavernous,  the  former  ramifying  on  the 
lateral  and  the  latter  on  the  mesial  aspect  of  the  artery.  While  the  individuality  of 
these  two  is  distinct,  there  are  numerous  fine  fibres  connecting  them  as  they  pass 
upward  into  the  cranium. 

The  carotid  plexus  (plexus  caroticus  internus)  is  located  on  the  lateral  or  outer 
surface  of  the  internal  carotid  artery  at  its  second  bend.  In  addition  to  supplying 
fine  plexuses  which  accompany  the  branches  of  the  artery  to  their  ultimate  ramifica- 
tions, the  following  arise  from  the  carotid  plexus  :  (aa)  the  carotid  branches,  (bb) 
the  communicating  branch  to  the  abducent  nerve,  (cc)  the  communicating  branches 
to  the  Gasserian  ganglion,  {dd  )  the  great  deep  petrosal  nerve  and  (<■<-)  the  small 
deep  petrosal  nerve. 

aa.  The  carotid  branches  consist  of  numerous  fine  twigs  which  are  supplied  to  the  internal 
carotid  arterj-. 

tib.  The  communicating  branch  to  the  abducent  nerve  consists  of  one  or  two  twigs  which 
join  the  nerve  as  it  lies  in  the  wall  of  the  cavernous  sinus  in  close  proximity  to  the  internal 
carotid  artery. 

cc.  The  communicating  branches  to  the  Oasserian  ganglion  comprise  several  small  fila- 
ments which  pass  to  the  ganglion ;  they  usually  arise  from  the  carotid  but  sometimes  are  deriv'< 
from  the  cavernous  plexus. 

dd.  The  great  deep  petrosal  nerve  courses  forward  to  the  posterior  end  of  the  Vidian  canal, 
where  it  joins  the  great  superficial  petrosal  to  form  the  I'idian  nerz'e  (page  1059),  finally  en- 
tering Meckel's  ganglion  as  its  sympatbetic  root. 

ee.  The  small  deep  petrosal  nerve  or  «.  tarotUo-tympanicUS  joins  the  tympanic  plexus 
(page  1075),  a  structure  formed  by  the  tympanic  branch  of  the  glosso-pharyngeal,  a  filament 
from  the  geniculate  ganglion  of  the  facial  nerv'e  and  the  small  deep  petrosal  nerve.     In  addition 


mm. 


pmn^Himp 


mmm 


w^rnm 


THE  SYMPATHETIC  SYSTEM   OF  NERVES. 


1361 


to  funiishinK  twigs  to  the  mucous  membrane  of  the  middle  ear  and  vicinity,  this  plexus  con- 
tributes a  large  part  of  the  sma/l  superficial  pel ic sat  nene,  which  joins  the  otic  ganglion  as  iu 
sensory  root  (page  1246)- 

The  cavernous  plexus  (plexus  caTernosus)  lies  inferior  and  internal  to  the 
internal  carotid  artery  and  in  intimate  relation  with  the  ravernoiis  sinus.  Its 
branches  are:  {aa)  the  carotid  branches,  (66)  the  communicatiiifr  branch  to  the  oculo- 
motor turve,  ice)  the  communicating  branch  to  the  trochlear  nerve,  {dd)  ihc  com- 
municating hranch  to  the  ophthalmic  division  of  the  trigeminus  nene,  (<•<•)  a  branch 
to  the  ciliary  ganglion  and  (,//)  hranchcs  to  the  pituitary  body. 

Fig.  1 132. 


SupcrtOT  cffrvkal  ctnliac  bnndi 

of  •ympathctk 
SupOTlor  ccrvkAl  canHac  bnach  of  vacw 
MIdillc  ccnrical  KanKliua 
MkUle  vCT\kal  canUac  bnach 

of  sylniMdMtic 


(of  iy>p«lkMH 
Inf.  «.er>i<:al  cardUc  braach 
oL  cenriul  gBimHoa 


Middle  ccnrkal  unttK 

faniKh  of  vawus 
Inf.  gcrvkal  unfiai. 

bniKh  of  vftgua 
illrmlc  oenre 


Lea  vacua  Mrv« 

Rccuimt  laryncral  Mwe 

I  -Ht  iMlmooary  aftcty 
-Pulmooary  vcina 


ilma«iar>-  orHka 

Masial  tut6..c  of  IM 
PcrkardiuM 


DiMection  showing  c««li«c  br«nch«  of  pneumogMtric  nerv«  and  or  sympathrtic  cord»;  aortic  arcli  and 
brenchc*  and  pulmonary  artery  partially  removed  ;  pericardium  laid  open. 

aa   The  carotid  branches  are  distributed  to  the  internal  carotid  artery. 

bb.  The  communicating  branch  to  the  oculomotor  nerve  joins  the  latter  about  at  the  point 
where  it  breaks  up  into  its  superior  and  inferior  divisions.  .  ,  ,  u 

cc.  The  communicating  branch  to  the  trochlear  nerve,  sometimes  deriscd  from  the 
carotid  plexus,  joins  the  trochlear  in  the  wall  of  the  cavernous  sinus. 

dd.  The  commun  ting  branch  to  the  ophthalmic  division  of  the  trigeminus  nerve  joins 
the  mesial  surface  of  that  nerve.  ...    ,  >  •     .1 

ee.  The  branch  to  the  ciliary  ganglion  (radices  sympathetlcae  g.  dllarls)  ^nses  in  the 
cranium  and  enters  the  orbit  through  the  sphenoidal  fissure,  either  as  an  independent  structure 
or  jointly  with  the  nasal  or  with  the  oculomotor  nerve.  As  the  sympathetic  root  (radix  media), 
it  enters  the  upper  posterior  angle  of  the  ciliary  ganglion  (Fig.  1058),  eiUier  alone  or  as  a 
common  trunk  with  the  sensory  root. 

86 


»362 


HUMAN  ANATOMY. 


ff.  The  branebM  to  th*  pituitary  body  consist  of  several  tiny  filaments  which  enter  the 
substance  of  that  body. 

4.  The  vertebral  branches  consist  of  two  or  three  filaments  which  pass 
baclcward,  pierce  the  prevertebral  muscles  ..nd  are  distributed  to  the  bony  and  lijja- 
mentous  structures  of  the  upper  portion  of  the  vertebral  column. 

The  Middle  Cervical  Ganglion.— The  middle  cervical  ganglion  (g.  cervicale 
medium),  a  structure  not  infrequently  absent,  consists  of  one  or  two  collections 
of  nerve-cells  situated  posterior  to  the  carotid  sheath  in  the  neighborhood  of 
the  inferior  thyroid  artery  (Fig.  1131).  It  lies  about  tJie  I  el  of  the  sixth  cer\'ical 
vertebra  and  represents  the  fusion  of  two  primitive  cervical  ganglia. 

The  BOtnatic  branches  are  :  ( i )  the  gray  rami  ctmimunicantes  and  ( i )  the 
subclavian  loop. 

I.  The  gray  rami  communicantes  arise  either  from  the  ganglion  or  from  its 
upper  or  lower  association  cord.  Tliey  consist  of  two  trunks  which  pass  backward 
and  join  the  anterior  primary  divisions  of  the  fifth  and  sixth  cervical  nervej. 

3.  The  subclavian  loop  (ansa  snbclavia  [Viettssenii] )  is  a  nerve,  frequently 
double,  which  passes  over  the  subclavian  artery  and  joins  the  inferior  cervical  gang- 
lion sending  twigs  (plexus  subclavius)  to  the  subclavian  artery  and  its  branches  and 
to  the  phrenic  nerve. 

The  visceral  branches  are:  (i)  the  thyroid  plexus  and  (2)  the  middle 
cervical  cardiac  nerve.  In  case  of  absence  of  the  middle  cervical  ganglion,  these 
branches  arise  from  the  intergaiiglionic  association  cord  between  the  superior  and 
inferior  ganglia. 

I.  The  thyroid  plexus  (plexus  thyreoldeus  inferior)  consists  of  several  fine 
inosculating  twigs  which  accompany  the  inferior  thyroid  artery  into  the  substance 
of  the  thyroid  body. 

3.  The  middle  cervical  cardiac  nerve  (a.  cardiacus  medius)  (Fig.  1131) 
differs  in  its  course  on  the  two  sides  of  the  body.  Descending  in  the  neck,  where 
it  inosculates  with  the  superior  cervical  cardiac  and  inferior  laryngeal  nerves,  it 
ftasses,  on  the  right  side,  either  anterior  or  posterior  to  the  subclavian  artery,  to 
the  front  of  the  trachea  where  it  receives  filaments  of  inosculation  from  the  interior 
laryngeal  nerve.  On  the  left  side  it  enters  the  thorax  between  the  common  carotid 
and  subclavian  arteries.  On  both  riirht  and  left  sides  it  terminates  posterior  to  the 
arch  of  the  aorta  by  entering  corresr    iding  sides  of  the  deep  cardiac  plexus. 

Variations. — ^The  Kangliated  cord,  in  the  region  of  the  middle  g;anglion,  may  lie  posterior 
to  the  inferior  thyroid  artery  or  may  be  bifurcatra,  the  artery  lying  between  the  two  portions. 

The  Inferior  Cervical  Ganglion. — The  inferior  cervical  ganglion  (g.  cervicale 
infenus)  (Fig.  1079)  is  situated  at  the  root  of  the  neck,  over  the  first  costo-central 
articulation,  between  the  neck  of  the  first  rib  and  the  transverse  process  of  the 
seventh  cervical  vertebra.  In  shape  it  is  irregular,  being  flat,  round  or  cres- 
centic,  and  it  is  often  fused  with  or  only  partially  separated  from  the  first  thoracic 
ganglion.  Situated  in  the  external  angle  between  the  subclavian  and  vertebral 
arteries  it  is  usually  connected  above  with  the  middle  ganglion  by  an  association  cord 
and  by  the  subclavian  lo<ip,  the  former,  passing  posterior  to  the  vertebral  artery, 
but  sometimes,  especially  on  the  left  side,  forming  a  nervous  ring  around  that  vessel. 

The  somatic  branches  consist  of:  (i)  the  gray  rami  communicantes,  (2)  the 
subclavian  loop  and  (3)  a  communicating  branch  to  the  inferior  laryngeal  nerve. 

1.  The  gray  rami  communicantes  consist  of  two  nonmedullated  trunks 
which  join  the  anterior  primary  divisions  of  the  seventh  and  eighth  cer\'ical  ner\'es. 

2.  The  subclavian  loop  (ansa  subdavia  [Vieussenii] )  has  already  been  de- 
scribed, as  a  branch  of  the  middle  cervical  ganglion. 

3.  The  communicating  branch  to  the  inferior  laryngeal  nerve  frequently 
accompanies  the  inferior  cervical  cardi  j  nerve  ;  it  joins  the  inferior  laryngeal  pos- 
terior to  the  subclavian  artery. 

The  visceral  branches  comprise  :  ( i )  the  vertebral  plexus  and  (  2)  the  inferior 
cervical  cardiac  nerve. 


"mHUPMiPiPBn 


■HP!" 


^pnnaHP 


THE  SYMPATHETIC   SYSTEM   OF   NERVES. 


•363 


I.  The  vertebral  plexua  (pkxuH  vertebraliH)  is  a  cUwely  woven  net-work  ol 
tibres  which  follows  the  course  and  distribution  of  the  vertebral  artery  in  the  neck 
and  cranium. 

Fio.  1133. 


II.  thoncic  nenrt 
IntercofiUI  artery 
III.  thoracic  atm 


IntercnKtal  artery 
V*.  tbonick  nerre 


XI.  thoracic  KaiiKlion  ;  Immedi- 
ately below  it  is  the  XII. 


.\II.  rib 

Diaphmfm 

I.  lumbar  ganglion. 


nio-hypoga»tric 
nerve 
II.  and  III.  lumbar 

fraiiKlia.  fused 
llio-inguinal  nerve 

IV.  lumbar 
ganglion        / 

IV.  lumbar  nerve 

V.  lumbar  ganglion  — ^ 

lnten{.inKllonk  _J^ 
auocfatlon  cord 
1.  sacral  ganglion  — 

Antcriur  cniiml  ncnrc 

II.  aacral  ganglion 
III.  aacral  nerve 
IV.  sacral  ganglion 


I.  Ui(>rai-|c  if*'    "    1  pwtMly 

bl«IMle«i  wKh  ii  (rr4af 
cervical  fantflloa 

II.  thoracic  gangUon 


Dissection  showing  thoracic,  lumbar  and  sacral  portions  of  riKht  gangliated  corj  anil  their  branches. 

2.  The  inferior  cervical  cardiac  mrvr-  (n.  cardiacus  Inferior)  (Fig.  1132), 
sometimes  arising  from  the  first  thoracic  ganglion,  descends  in  the  thorax  posterior  to 


«364 


HUMAN  ANATOMY. 


the  subclavain  artery,  inosculates  with  the  middle  cen  ical  cardiac  and  inferior  lar>nRtal 
lerves  and  terminatesi  in  the  dctp  cardiac  plexus. 

THE  THORACIC  PORTION  OF  THi:  GANGLIATED  CORD. 

The  thoracic  portion  of  the  gangliated  curd  (pars,  thoracalis  syitematlM  sympa- 
thrtlcl)  consists  of  a  series  of  eleven,  twelve,  ten  or  even  fewer  irrejjularly  triangular, 
fusiform  or  oval  ganglia  (rk.  thomealla),  situated  lateral  to  the  bodicfc  of  the  thoraci.- 
vertebne,  covered  by  parietal  pleura  and  interconnected  by  association  cords  which 
lie  anterior  to  the  intercostal  blood-vessels  (Fig.  1133).  The  largest  of  the  ganglia 
is  the  first,  which  is  situated  at  the  mesial  end  of  the  first  intercostal  space  and  is 
not  infrequently  hised  with  the  inferior  cer\'ical  ganglion.  The  location  of  tho 
thoracic  ganglia  corresponds  usually  to  the  heads  of  the  ribs,  the  lowest  being  placed 
anterior  to  the  head  of  the  twelfth  rib  and  at  the  upper  margin  of  the  twelfth  thoracic 
vertebra. 

A  characteristic  of  the  thoracic  ganglia  is  the  almost  wnvaiym^  presence  0/  uhit,- 
rami  communicantes,  all  of  the  series,  with  the  poM'We  exception  of  the  first,  receiving 
these  rami  from  the  thoracic  spinal  nerves.  They  consist  of  an  upper  and  a  Iffiter 
series,  the  former  coming  from  the  upper  five  nerves  and  coursing  head-ward  to  enter 
and  be  distributed  mainly  by  way  of  the  cervico-cephalic  portion  of  the  gangliated 
cord  ;  and  the  lower  arising  from  the  lower  seven  and  being  distributed  to  certain 
thoracic  and  abdominal  structures.  As  elsewhere,  so  here  from  each  of  the  ganglia 
b  given  of!  a  gray  ramus  communicans  to  a  thoracic  spinal  nerve. 

The  somatic  branches  of  the  thoracic  portion  of  the  gangliated  cord  are 
chiefly  the  gray  rami  communicantes.  These  arise  from  each  of  the  thoracic  pnglia 
and,  m  close  proximity  to  the  white  rami,  pass  backward  and  join  the  anterior  pri- 
mary divisions  of  all  the  thoracic  spinal  nerves. 

The  visceral  branches  "rise  from  the  ganglia  and  their  association  cords  and 
consist  of  gray  splanchnic  efferent  and  white  splanchnic  efferent  and  afferent  fibres. 

The  splanchnic  afTerent  fibres  have  no  sympathetic  connections,  and  consist 
merely  of  tracts  which  ciny  impulses  from  the  splanchnic  area  through  the  thoracic 
and  spinal  ganglia  to  the  postenor  roots  of  the    -nnal  thoracic  nerves. 

The  splanchnic  efferent  fibres,  afit-r  priS:>ing  through  the  gangliated  cord  or 
its  peripheral  branches,  form  links  with  the  ceUs  of  the  collateral  or  terminal  ganglia, 
from  which  nonmeduUated  axones  are  derived  for  the  supply  of  various  visceral  or 
vascular  structures.  Those  of  the  upper  series  are  distributed  mainly  as  branches  of 
the  cervical  ganglia ;  while  those  of  the  lower  series,  from  the  sixth  to  the  twelfth  thoracic 
nerves  inclusive,  in  the  thorax  supply  the  aorta  and  lungs  with  vasomotor  fibres. 
Beloxv  the  thorax  their  distribution  is  quite  extensive,  including,  in  conjunction  with 
the  vagus,  viscero-inhibitory  fibres  for  the  stomach  and  intestine,  motor  fibres  for  a 
portion  of  the  circular  muscle  of  the  rectum,  vasomotor  fibres  for  the  abdominal  aorta 
and  its  branches  and  secretory  and  sensory  fibres  for  the  abdominal  viscera.  The 
thoracic  gangliated  cord  is  peculiar  in  containing,  along  with  the  visceral  fibres  dis- 
tributed by  its  splanchnic  eflerents,  many  efferents  proceeding  from  the  spinal  cord 
destined  for  regions  supplied  by  way  of  the  limb  nerves  arising  from  the  cervical  and 
lumbo-sacral  segments  of  the  spinal  cord.  In  order  to  provide  gray  rami  at  appro- 
priate levels  to  join  the  spinal  nerves  the  spinal  efferents  course  both  up  and  down 
m  the  gangliated  cord  beyond  the  thoracic  region.  In  this  manner  the  thoracic 
nerves,  in  addition  to  giving  off  the  splanchnic  efferents,  provide  vasomotor,  pilo- 
motor and  secretory  filaments  for  the  greater  part  of  the  lower  half  of  the  body. 

The  visceral  branches  comprise  :  (i)  Has pulnumary  branches,  (2)  the  aortic 
branches  and  {y)  the  splanchnic  nerves. 

1.  The  pulmonary  branches  (rr.  pulmonates)  are  derived  from  the  second, 
third  and  fourth  ganglia  and  proceed  forward  to  join  the  posterior  pulmonary  plexus. 

2.  The  aortic  branches  arise  from  the  upper  four  or  five  ganglia  and,  after 
furnishing  a  few  fine  twigs  to  '  ■  vertebrae  and  their  ligaments,  inosculate  around 
the  thoracic  aorta  in  the  for  a  fine  plexus  (plexus  aorticus  thoracalis). 

3.  The  splanchnic  nerves  ( nn.  sptaachnici)  (Fig.  u^.'i")  are  three  tnink.s 
which  anse  from  the  lower  part  of  the  thoracic  cord  and  are  distributed  to  structures 
situated  in  the  abdominal  cavitv. 


^mmmmmmmmm 


iVnVMB**PIK*MP<P 


rmmmm 


mmm 


THE  SYMPATHETIC  SYSTEM  OF  N    .<VES. 


•365 


The  great  splanchnic  nerve  ( n.  •plaocboicns  major ,  ises  by  a  series  (./  roots 
from  the  gangliated  cord  from  the  fifth  to  the  ninth  gannlia  inclusive.  Dcscendingr 
along  the  antero-lateral  aspect  of  the  vertebral  column,  thiH  ner>e  pierces  the  cms  of 


the  diaphragm  and  enters  the  upper  end  of  the  semilunar  ganglion,  some  of  its 
fibres  being  traceable  to  the  suprarenal  body  and  the  renal  plexus.  In  the  thoracic 
portion  of  its  course  is  developed  the  greai  splanchnic  ganglion  (g.  splanchnicum )  from 


1366 


HUMAN  ANATOMY. 


which,  as  well  as  from  the  nerve  itself,  are  given  off  filamei.ti  for  the  supply  of  the 
oesophagus,  the  thoracic  aorU  and  the  vertebra.  Sometimes  m  the  thorax  it  s 
divided  and  forms  a  plexus  with  the  small  splanchnic  and  m  this  event  several  sni.ul 
ganglia  are  present.  This  nerve  consists  mainly  (four-fifths,  accordmg  to  Rudmger ) 
of  meduUated  fibres,  which  are  direct  continuations  of  white  rami  from  as  far  up  as 
the  third  thoracic  nerve  or  even  higher.  l      •    l       ■ 

The  small  splanchnic  nerve  (n.  splanchnicus  minor)  arises  from  the  ninth  and 
tenth,  or  tenth  and  eleventh  gangua  or  from  adjacent  portions  of  interganglionic  cords. 
Entering  the  abdomen  by  piercing  the  cms  of  the  diaphragm  either  in  association  with 
or  in  close  proximity  to  the  great  splanchnic,  it  terminates  in  that  portion  of  the  semi- 
lunar ganglion  called  the  aoriico-renal  ganglion. 

The  least  splanchnic  nerve  (n.  splanchnicus  imus)  arises  from  the  lowest  of 
the  thoracic  ganglia  and  may  receive  a  filament  from  the  small  splanchnic,  from  which 
it  occasionally  takes  origin.  Piercing  the  diaphragm  in  company  with  the  gangli- 
ated  cord  it  terminates  in  the  renal  plexus.  ..,,,.. 

A  fourth  splanchnic  nerve  is  rarely  Resent  It  is  described  by  Wnsberg  as 
having  been  found  in  eight  cadavers  out  of  a  large  number  examined.  It  is  formed 
by  filaments  from  the  cardiac  nerves,  aided  by  twigs  from  the  lower  cervical  and 
upper  thoracic  ganglia. 

THE  LUMBAR  PORTION  OF  THE  GANGLIATED  CORD. 

The  lumbar  portion  of  the  gangliated  cord  (pars  abdominalis  systematis  sympa- 
thetici)  (Fig.  1 134)  consists  usually  of  four  small  oval  ganglia  connected  by  association 
cords.  There  may  be  a  decided  increase  in  the  number  of  the  ganglia,  as  many  as 
eight  having  been  found,  and,  on  the  other  hand,  occasionally  there  are  fewer  than 
four,  there  being  under  these  circumstances  a  compensatory  increase  in  the  size  of  the 
ganglia  present.  The  lumbar  portion  of  the  sympathetic  lies  nearer  the  median  line 
than  does  the  thoracic,  the  cords  being  placed  anterior  to  the  bodies  of  the  lumbar 
vertebra  and  the  lumbar  vessels,  along  the  mesial  border  of  the  psoas  magnus,  on 
the  left  side  being  partially  concealed  by  the  aorta  and  on  the  right  by  the  inferior 
vena  cava.  It  is  connected  with  the  thoracic  portion  by  a  small  association  cord, 
which  passes  either  through  or  posterior  to  the  diaphragm,  and  with  the  sacral  portion 
by  a  cord  which  descends  behind  the  common  iliac  artery.  White  rami  communi- 
cantes  are  received  from  the  first,  the  second  and  sometimes  the  third  lumbar  nerve, 
additional  white  fibres  being  derived  from  the  lower  thoracic  nerves  by  way  of  the 
gangliated  cord. 

The  somatic  branches  comprise:  (i)  the  white  and  (2)  the  gray  rami 
comtnunicantes.  These  are  the  longest  to  be  found  in  the  body,  on  account  of  the 
distance  between  the  ganglia  and  the  intervertebral  foramina.  They  accompany  the 
lumbar  vessels  and  pass  teneath  the  fibrous  afches  from  which  the  psoas  magnus 
takes  origin. 

1.  The  whitt  rami  communicantes  are  derived  from  the  upper  two  or 
three  lumbar  nerves  and  join  the  upper  ganglia  or  the  adjacent  portion  of  the  inter- 
ganglionic cord.  They  contain  splanchnic  efferent  and  afferent  fibres,  which  continue 
downward  the  distribution  of  the  thoracic  portion  of  the  gangliated  cord,  including 
vasomotor  and  secretory  fibres  for  the  lower  extremities,  pilomotor  fibres,  vaso- 
motor fibres  for  the  abdominal  vessels,  motor  fibres  for  the  circular  musculature 
of  the  rectum  and  inhibitory  fibres  for  the  longitudinal  muscle  of  the  rectum.  Fibres 
peculiar  to  the  lumbar  region  include  vasomotor  ner\'es  of  the  penis  and  motor  fibres 
tor  the  bladder  and  uterus,  those  to  the  bladder  supplying  the  sphincter  as  well 
as  the  circular  and  longitudinal  muscle-fibres,  those  to  the  last-mentioned  group 
being  inhibitory. 

2.  The  gray  rami  communicantes  are  irregular  in  number  and  arrange- 
ment, sometimes  a  single  one  dividing  rnd  joining  two  lumbar  nerves  and  sometimes 
two  to  five  passing  to  a  single  spinal  nerve. 

The  visceral  branches  vary  c<insiderably  in  their  distribution,  some  joining 
the  hypogastric  plexus  (plexus  hypoKastricus),  others  the  aortic  plexus  (plexus  aorticus 
abdominalis)  and  still  others  supplying  the  vertebrse  and  their  ligaments. 


THE  SYMPATHETIC  SYSTEM  OF  NERVES. 


1367 


THE  SACRAL  PORTION  OF  THE  GANGLIATED  CORD. 

The  sacral  portion  of  the  gangliated  cord  (para  pelvina  systematis  sympathetici) 
consists  of  four  ganglia  interconnected  by  association  cords,  there  being  a  consider- 
able degree  of  variation  in  both  the  number  and  the  size  of  the  ganglia  (Fig.  1133)- 
Lying  anterior  to  the  sacrum  and  internal  to  the  anterior  sacral  foramina,  it  is  con- 
nected above  with  the  lumbar  portion  by  a  single  or  double  association  cord  which 
lies  posterior  to  the  common  iliac  artery,  and  below  it  gradually  approaches  the 
median  line  and  is  united  in  front  of  the  coccyx  with  its  fellow  of  the  opposite  side  by 
a  loop  or  fine  plexus  in  which  is  situated  the  single  coccygeal  ganglion  or  gang- 
lion impar. 

While  this  portion  of  the  gangliated  cord  receives  no  white  rami  communicantes, 
in  the  sense  of  trunks  passing  from  the  sacral  spinal  nerves  to  the  sacral  ganglia,  the 
visceral  brai.ches  of  the  pudendal  plexus  pass  directiy  to  the  pelvic  plexus  without 
traversing  ganglia,  and  are  considered  as  being  homolc^ous  with  white  rami.  In 
addition  to  these,  white  fibres  reach  the  sacral  from  the  lumbar  portion  of  the 
gangliated  cord.  _  .  •      t 

The  somatic  branches  a»^  the  gray  rami  communicantes.  They  arise  from 
the  sacral  ganglia  and  pass  dorsally  to  join  the  anterior  primary  divisions  of  the  sacral 
and  coccygeal  spinal  nerves. 

The  visceral  branches  are  distributed  through  the  medium  of  the  pelvic 
plexus  (page  1374)  and  furnish  motor  fibres  to  the  longitudinal  and  inhibitory 
fibres  to  the  circular  musculature  of  the  rectum,  the  chief  motor  fibres  to  the  bladder 
(probably  to  the  longitudinal  muscular  fibres),  motor  fibres  to  the  uterus,  the  nervi 
erigentes  or  vaso-dilators  of  the  penis  and  secretory  fibres  to  the  prostate  ^land. 

Additional  strands,  the  parietal  branches  unite  and  ramify,  anterior  to  the 
sacrum,  with  similar  twigs  from  the  opposite  side  and  furnish  filaments  to  the  sacrum 
and  coccyx  and  their  ligaments,  and  to  the  coccygeal  body. 

THE  PLEXUSES  OF  THE  SYMPATHETIC  NERVES. 

The  tendency  of  the  sympathetic  nerves  to  form  intricate  and  elaborate  plexuses 
(plexus  sympathetici)  is  a  marked  feature  of  this  portion  of  the  nervous  system. 
They  lie,  in  the  main,  anterior  to  the  plane  of  the  gangliated  cord  and  consist  of 
fibres  alone  or  of  fibres  and  ganglia,  from  which  smaller  plexuses  or  branches  pass 
to  the  viscera.  Some  of  them  are  of  sufficient  importance,  size  and  individuality 
to  merit  separate  descriptions ;  such  are  the  cardiac,  the  pulmonary,  the  oesophageal, 
the  solar  and  the  pelvic.  The  pulmonary  and  oesophageal  plexuses  have  been 
described  in  connection  with  the  vagus  nerve  (page  1272). 

The  Cardiac  Plexus. 

The  cardiac  plexus  (plexus  cardiacus)  consists  of  an  interlacement  of  nerve-fibres, 
containing  one  well-marked  ganglion,  to  which  accessions  are  brought  by  the  vagus 
and  sympathetic  nerves  and  from  which  fibres  are  furnished  to  the  heart  and,  to  a 
slight  degree,  the  lungs.  It  comprises  two  portions:  (i)  the  superficial  cardiac 
plexus  and  (2)  the  deep  cardiac  plexus.  „        r    . 

1.  The  superficial  cardiac  plexus  (Fig.  1135)  »  much  the  smaller  of  the 
two  and  consists  of  a  fine  inosculation  of  nerve-fibres  in  the  meshes  of  which  is  con- 
tained a  small  ganglion,  the  ganglion  of  WHsberg  (g.  cardiacum  [WrisbefRi]). 
It  is  situated  in  the  concavity  of  the  arch  of  the  aorta,  between  the  obliterated  ductus 
arteriosus  and  the  right  pulmonary  artery.  Tributary  to  it  are  the  superior  cervical 
cardiac  branch  of  the  left  gangliated  cord  and  the  inferior  cervical  cardiac  branch 
of  the  left  vagus,  whilst  ite  fibres  of  distribution  contribute  to  (a)  the  right  coronarj- 
plexus,  (b)  the  left  half  of  the  deep  cardiac  plexus  and,  along  the  left  pulmonary 
artery,  (f)  the  left  anterior  pulmonary  plexus. 

2.  The  deep  cardiac  plexus  (Fig.  1135).  considerably  larger  than  the  su- 
perficial, is  located  above  the  bifurcation  of  the  pulmonary  artery,  posterior  to  the 
arch  of  the  aorta  and  anterior  to  the  lower  end  of  the  trachea.     It  comprises  two 


1368 


HUMAN  ANATOMY. 


distinct  portions,  a  right  and  a  left,  united  by  numerous  fibres  around  the  lower  end 
of  the  trachea.  The  right  portion  receives  as  tributaries  all  of  the  cardiac  branches 
of  the  sympathetic,  vagus  and  inferior  laryngeal  nerves  of  the  right  side.  The  left 
portion  receives  all  of  the  cardiac  branches  of  the  left  vagus  and  sympathetic  ner\es. 
except  the  two  which  enter  the  superficial  plexus  (the  superior  cervical  cardiac  branch 
of  the  left  gangliated  cord  and  the  inferior  cervical  branch  of  the  left  vagus),  with  the 
addition  of  filaments  from  the  left  inferior  laryngeal  nerve  and  from  the  superficial 
cardiac  plexus. 

Fig.  1135. 


•Thyroid  body 

Superior  cervical  cardiac 
branch  of  sympathetic 


Clavicle 

Conibinffi  cerviall 

cardiac  bn.  u( 

HtiYa  sympathetic 

".  rib 


SuiNtlor  ccnfcal  cardiac  t"  ■"■  h  of 
ivmisthetic 

ympathetic  nerve 

agus  nerve 
Saperlof  cervical  cardiac  bran.:!)  uf  vagu^ 
Middle  cervical  ganglion 
Scalenus  anticua 


Middle  cervica]  cardiac  of  sympathrtij 

Brachial  plexus 

Inferior  cervical  ganjrlirn 
Inf.  cervical  cardiac  br.  of  syin|«thrtit,  tmss 
Pltiwoic  ner%-e  1    iny  vrrtrfarai  artery 

Subclavian  artery  to  Join  middle  br. 

^^Inf.  cervical  cardiac  branch  of  vagus 

^  ^..Recurrent  laryngeal  nerve 


-^Phrenic  nerve 


Recurrent  laryngeal  nerve 

Supertitial  cardiac  piexua,  ihowinij  ^anf  lion 
cf  Wr<st«r( 


Pulmonary  artery 
Left  coronary  artery 


Dissection  showing  constituents  of  superficial  cardiac  plexus,  other  cardiac  nerves  and  right 

coronary  plexus. 

From  the  right  portion  of  the  plexus  arises  the  right  or  anterior  coronary 
plexus  (plexus  coronarius  cordis  anterior),  to  which  fibres  are  sent  from  the  superficial 
plexus.  This  plexus  reaches  the  heart  by  coursing  along  the  ascending  aorta  and 
then  follows  the  right  coronary  artery,  in  whose  course  it  distributes  fibres  to  adjacent 
portions  of  the  heart.  Other  branches  from  the  right  portion  join  the  superficial 
cardiac  plexus  and  the  right  anterior  pulmonary  plexus. 

From  the  left  portion  originates  the  left  or  posterior  coronary  plexus  (plexus 
coronarius  cordis  posterior)  which,  reinforced  by  fibres  from  the  superficial  plexus, 
follows  the  course  and  distribution  of  the  corresponding  artery.  The  left  portion 
contributes  filaments  to  the  superficial  cardiac  and  left  anterior  pulmonary  plexuses. 

The  Solar  Plexus. 
The  abdominal  and  pelvic  cavities  arc  innervated  by  the  solar,  hypogastric  and 
pelvic  plexuses,  composed  of  the  visceral  branches  of  the  lower  thoracic,  lumbar  and 
upper  sacral  portions  of  the  gangliated  cord,  in  conjunction  with  the  central  nervous 


THE  SYMPATHETIC  SYSTEM   OF   NERVES. 


'369 


axis  by  means  of  the  rami  communicantes  of  the  lower  thoracic  and  upper  lumbar 
nerves  and  the  visceral  branches  of  the  pudendal  plexus. 

The  solar  or  epigastric  plexus  (Fig.  1136),  the  largest  of  the  series,  is  situated 
in  the  upper  abdominal  region,  posterior  to  the  stomach,  anterior  to  the  aorta  and 
the  crura  of  the  diaphragm,  superior  to  the  pancreas,  between  the  suprarenal  bodies 
and  around  the  origins  of  the  coeliac  axis  and  the  superior  mesenteric  artery.  It  is 
continuous  above  with  the  diaphragmatic  plexus,  laterally  with  the  suprarenal  and 

Fio.  1136. 


cn«rTv| 


DiaphiacBiatic  gmnglimi 

Gnat  tplanchalc  BCfve 

Rigbt  wmlluBar  gaaKltaa, 

Snill  spUtK^hnic  nerve 


Spcnutic  utOTy 

til.  lumbar  Kanglioo 

Aortic  plaiua 

IV.  lumbar  gaogtloa 
I'reler 

Uypogastric  plczua 

tMac  between  V.  Itimbar 
vertebra  and  sairun 

1.  lacral  ganglfoa 


Diuectioa  of  abdominal  sympathetic  nerves,  showing  solar,  hypogastric  ami  secondary  plexuses. 


renal  plexuses,  below  with  the  superior  mesenteric  and  aortic  plexuses  and,  by 
means  of  the  aortic  and  hypogastric  plexuses,  with  the  two  pelvic  plexuses.  Con- 
tributory to  it  are  the  right  vagus  and  the  great  and  small  splanchnic  ner\'es.  The 
fully  formed  plexus  consists  of  two  portions:  (i)  the  semilunar  ganglia  and  (2) 
the  cceliac  plexus. 

I.  The  semilunar  ganglia  (kk.  coeliaca)  (Fig.  1136),  the  hirg<st  of  the 
ganglionic  elements  in  the  solar  plexus,  are  situated  upon  the  crura  of  the  aphragm 
at  the  superior  and  lateral  portions  of  the  plexus,  pairtly  overlapped  by  the  suprarenal 
bodies  and  separated  from  each  other  by  the  rceliac  axis  and  the  superior  mesenteric 
artery  ;  the  right  one  is  partially  covered  by  the  superior  vena  cava  and  the  two  are 


I370 


HUMAN  ANATOMV. 


connected  by  cords  which  pass  transversely  above  and  below  the  root  of  the  cceliac 
axis.  The  upper  end  of  each  is  expanded  and  receives  the  termination  of  the  great 
splanchnic  nerve,  while  the  lower  portion,  the  aortico-renal  ganglion,  is  partially 
detached  and  receives  the  small  splanchnic  nerve.  A  third  portion,  located  below 
and  to  the  right  of  the  root  of  the  superior  mesenteric  artery,  is  called  the  superior 
mesenteric  ganglion  (g.  mesentericum  superius).  From  each  semilunar  ganglion 
branches  emerge  in  all  directions  to  join  those  plexuses  which  are  continuous  with 
the  solar. 

2.  The  coeliac  plexus  (plexus  coeliacus)  embraces  the  coeliac  axis  and  consists 
of  a  dense  felt-work  of  ner\'e-fibres,  in  which  are  embedded  numerous  small  ganglia, 
and  which  is  joined  by  branches  from  both  semilunar  ganglia  and  from  the  right 

Fir..  11.^7. 


hnsiforiii  caitiia,^ 


ploic  artery 
and  ntexus 


■Liver.  SfilifelUii 
kit>« 

'Left  v»iiut  nert  e 
Right  va);u«  nf-r\  e 
Aorti 


•Branches  of  Jefl 
vagus 


Dissection  showing  gastric  mnd  hepatic  plexuses. 

vagus.  Inferiorly  it  is  continued  into  the  superior  mesenteric  and  aortic  plexuses 
and  from  it  arise  the  coronary,  hepatic  and  splenic  plexuses. 

The  gastric  plexus  (plexus  gastricus  superior)  accompanies  the  gastric  artery 
along  the  lesser  curvature  of  the  stomach,  inosculates  with  both  vagus  nerves  and 
distributes  branches  which  run  for  a  short  distance  beneath  the  peritoneum  and  then 
enter  and  supply  the  deeper  coats  of  the  stomach. 

The  hepatic  plexus  (plexus  hepaticus)  traverses  the  lesser  omentum  in  company 
with  the  bile  duct,  the  hepatic  artery  and  the  portal  vein  and,  after  inosculating  with 
fibres  of  the  left  vagus,  enters  the  liver,  in  which  it  ramifies.  In  addition  to  its 
terminal  distribution  it  contributes  filaments  to  the  right  suprarenal  plexus  and 
furnishes  offshoots  which  follow  the  collateral  branches  of  the  hepatic  artery,  sup- 
plying the  areas  to  which  these  arteries  are  distributed. 

The  splenic  plexus  (plexus  lienalis),  which  surrounds  the  splenic  artery, 
receives  accessions  from  the  left  semilunar  ganglion  and  the  right  vagus  and  enters 
the  spleen.  Branches  of  the  plexus  accompany  the  branches  of  the  splenic  artery 
and  are  distributed  similarly. 


THE  SYMPATHETIC  SYSTEM  OF   NERVES. 


1371 


The  diaphragmatic  or  phrenic  plexus  (plexus  phrenicus)  is  derived  from  the 
upper  portion  of  the  semilunar  gan^^lion  and  accompanies  the  phrenic  branch  of  the 
abdommal  aorta  to  the  diaphragm,  the  right  being  larger  than  the  left.  After 
supplying  some  filaments  to  the  suprarenal  body,  it  enters  the  musculature  of  the 
diaphragm  and  there  unites  with  the  phrenic  ner\e  from  the  cervical  spinal  plexus. 
At  the  point  of  inosculation,  on  the  right  side  only,  near  tli  suprarenal  Ixxly  and  on 
the  under  surface  of  the  diaphragm,  is  a  small  ganglion  call  the  phrenic  ganglion 
(g.  phrenicum).  From  it  are  given  of!  branches  to  the  supi, 'renal  body,  the  inferior 
vena  cava  and  the  hepatic  plexus. 

The  suprarenal  plexus  ( plexus  suprarenalis)  arises  from  the  lateral  aspect  of 
the  semilunar  ganglion  and  is  joined  by  tilaments  trom  the  diaphragmatic  and  renal 


Fig.  1138. 


t  ~>sstin>«p4plalc» 
itextra  ^th  |ilcxub' 


Pyloric  artery 
with  plexus' 

(.iastro-d  u  odeiul 

artery  wtth  plexus. 

Hepatic  artery 

with  plexus, 

Ittf.  rancreatico 

duodenal  artery 

Sup.  pancreatlco- . 

duodenal  artery 

Hancreai,  cut' 

Sup.  tnrsRiteric 

ulary  with  plexus' 

Duodenum 


Stninach, 

lurnrd  up 


r.astro-*^ploif.T 

'     lira  with  pir^us 

Ri|{htva)Oi"  nerve 
<  iMtric  artery 
with  plcxtis 
.Sfilenic  artery 
with  plexus 


Sple< 


Diwection  showing  j^astric,  hepatic  ftnd  splenic  plexuKi;  Btomai-h  has  been  tunied  up  ami  part  of  pancrcoB  removed- 


plexuses.  It  ronsists  mainly  of  mcdullated  fibres  and,  while  very  short,  is  made  up 
of  a  number  of  filaments  and  is  of  considerable  size.  Numerous  tiny  ganglia  are 
scattered  throughout  ihe  meshes  of  this  plexus. 

The  renal  plexus  (plexus  renalis)  is  derived  mainly  from  the  aortico-renal 
ganglion,  additional  fibres  being  contributed  by  the  smallest  splanchnic  nerve,  some- 
times by  the  small  splanchnic,  and  by  the  aortic  and  suprarenal  plexuses  ;  there  is 
occasionally  present  a  twig  from  the  first  lumbar  ganglion.  Entering  the  hilum  of 
the  kidney  with  the  ••  lal  artery,  the  plexus  splits  up  and  ramifies  in  the  renal  sub- 
stance. In  its  couri>c  along  the  artery  a  number  of  ganglia  of  varying  size,  called 
the  renal  ganglia  are  found.  In  addition  to  supplyincc  the  kidney,  filaments  .ire 
furnished  to  the  spermatic  plexus  and  to  the  ureter,  and  on  the  right  side  to  the 
inferior  vena  cava. 


13.72 


HUMAN  ANATOMY. 


The  spermatic  plexus  (plexus  spennaticus)  follows  the  course  of  the  spermatic 
artery  through  the  abdomen,  inguinal  canal  and  scrotum,  inosculating  with  filaments 
which  arise  in  the  pelvis  and  accompany  the  vas  deferens  and  its  artery  to  the 
scrotum.  It  is  derived  from  the  renal  and  aortic  plexuses,  a  small  spermatic  gang- 
lion being  situated  at  the  point  of  origin  of  the  fibres  contributed  by  the  aortic  plexus. 

The  ovarian  plexus  (plexus  ovaricus),  arising  similarly  to  the  spermatic, 
accompanies  the  ovarian  artery  and  is  distributed  to  the  ovary,  the  oviduct,  the 
broad  ligament  and  the  uterus.  In  the  broad  ligament  it  inosculates  with  ♦»•" - 
pelvic  fibre«;  which  constitute  the  uterine  plexus. 


those 


Fig.  1 139. 


Hepatic 

artery  and 
plcxu9 


Superior 
mesenteric 
arterj- 

Termination 
of  ileum 


-Transverse  coloD 

Splenic  artery 

.Jejunum 

Duodenum 

Superior  mesen- 
teric artery  and 
plexus 


Dissection  showing  hepatic  and  superior  mesenteric  plexuses ;  transverse  colon  has  been  turned  up. 

The  superior  mesenteric  plexus  (plexus  mesentericus  superior)  (Pig.  1139), 
firm  in  texture  aiu'  "ontaining  a  large  admixture  of  meduUated  fibres,  is  continuous 
with  the  ccEliac  1  s  above  and  with  th^  aortic  below.  Its  fibres  are  derived  from 
the  semilunar  g.  .j;lia,  the  coeliac  plexus  and  the  right  vagus.  Situated  in  the  root 
of  the  plexus  and  lying  below  and  to  the  right  of  the  origin  of  the  superior  mesen- 
teric artery  is  the  superior  mesenteric  ganglion. (g.  mesentericum  superius), 
from  which  a  number  of  the  fibres  of  the  ple.xus  arise.  Accompanying  the  superior 
mesenteric  artery,  the  plexus  gives  off  subdivisions  which  correspond  to  and  follow 
the  course  of  the  branches  of  that  artery,  supplying  filaments  to  the  small  intestine, 
the  ccecum,  the  vermiform  appendix  and  the  ascending  and  transverse  coloi        As 


THE  SYMPATHETIC  SYSTEM  OF  NERVES. 


«373 


the  fibres  approach  the  distal  ed^^e  of  the  mesentery  some  of  them  leave  the  vessels 
and  form  minute  independent  plexuses  from  which  filaments  pass  to  the  gut. 

The  aortic  plexus  (plexus  aortlcus  al  'ominalis)  (Fig.  1136)  is  the  direct 
downward  extension  of  the  solar.  Embracing  the  aorta,  it  extends  from  the  origin 
of  the  superior  mesenteric  artery  above  to  that  of  the  inferior  mesenteric  below,  and 
is  connected  with  the  semilunar  ganglia  and  with  the  renal  and  superior  mesenteric 
plexuses  superiorly  and  with  the  hypogastric  inferiorly.      It  consists  of  a  pair  of 

Fig.  114a 

Aorta       Renal  mnKlion 

Onrian  artery 
Mrrveirom  aortic  plesiM.  .  MH^  /      /  ,y^   ^flvarian  vein 

Ovarian  veiii^\. 
Ovarian  artery.. 


Uretet  - 


Right  ovaty- 

Falkfilaa  ttifa*- 

Usament  of_ 
ovary 


Diiaectlon  thowlnf  hypogaitrie  and  pelvic  plezuaes. 

symmetrically  placed  nerve  trunks  situated  at  the  sides  of  the  aorta  and  connected 
with  each  other  by  several  branches  which  lie  anterior  to  that  vessel ;  filaments  from 
the  lumbar  ganglia  join  the  main  cords  of  the  plexus.  It  gives  of!  the  inferior  mes- 
enteric plexus,  sends  contributions  to  the  suprarenal,  renal  and  spermatic  or  ovarian, 
supplies  filaments  to  the  aorta  and  inferior  vena  cava  and  terminates  in  the  hypo- 
gastric plexus. 

The  inferior  mesenteric  plexus  (plexus  mesenterlcus  inferior)  is  derived 
from  the  left  portion  of  the  aortic  plexus  and  follows  the  course  and  distribution 
of  the  artery  for  which  it  is  named.  Situated  a  short  distance  beyond  its  origin 
is  the  small  inferior  mesenteric  ganglion.     From  this  plexus  branches  arc 


»374 


HUMAN  ANATOMY, 


distributed  to  the  descending  and  sigmoid  colons  and  to  the  upper  portion  of  the 
rectum.  .        . 

The  hypogastric  plexus  (plexus  hypoRastrictis)  (Fig.  1 140),  the  contmuation 
of  the  aortic,  lies  on  the  posterior  wall  of  the  pelvis  in  the  angle  between  the 
common  iliac  arteries,  and  enclosed  in  a  firm  investment  of  fibrous  tissue.  In 
addition  to  the  fibres  derived  from  the  aortic  plexus,  others  are  contributed  by 
the  lumbal  ganglia,  and  the  resulting  intricate  interlacement,  in  which  there  are 
no  ganglia,  constitutes  the  hypogastric  plexus.  It  supplies  the  pelvic  contents 
and  at  its  lower  end  divides  into  the  two  pelvic  plexuses. 

The  pelvic  plexuses  (plcsns  hypoRastrlci  inferiores),  (Fig.  1140)  the  terminal 
divisions  of  the  hypog;istric,  are  situated  lateral  to  the  rectum  and  to  the  vagina 
in  the  female.  They  comprise  fibres  derived  from  the  hypogasstric  plexus  and  from 
the  upper  part  of  the  sacral  portion  of  the  gangliated  cord,  aided  by  the  visceral 
branches  0/  the  pudendal  plexus,  all  of  these  forming  an  elaborate  net-work,  in  which 
are  dotted  numerous  small  ganglia.  The  completed  structure  follows  the  course 
of  the  internal  i!  .ic  artery,  around  whose  branches  it  sends  derivatives  for  the 
supply  of  the  peUic  contents. 

The  hemorrhoidal  plexus  (plexus  hemorrhoidalis  medius)  arises  from  the 
upper  portion  of  the  pelvic  plexus  and  after  inosculating  with  the  superior 
hemorrhoidal  branches  (nn.  hemorrholdales  superiores)  of  the  inferior  mesenteric 
plexus,  are  distributed  to  the  rectum. 

The  vesical  plexus  (plexus  vesicalis)  consists  of  branches  of  the  pelvic  which 
accompany  the  vesical  arteries  to  the  lateral  and  inferior  portions  of  the  bladder, 
after  reaching  which  they  leave  the  vessels  and  split  into  small  twigs  for  the  supply 
of  the  bladder,  some  filaments  going  to  the  ureter,  the  vas  deferens  and  the  seminal 
vesicle. 

The  prostatic  plexus  (plexus  prostaticus)  comprises  a  number  of  nerves  of  con- 
siderable size  and  is  situated  between  the  lateral  aspect  of  the  prostate  gland  and 
the  mesial  surface  of  the  levator  ani  muscle.  After  furnishing  twigs  to  the  prostatic 
urethra,  the  neck  of  the  bladder  and  the  seminal  vesicle,  it  continues  forward  as  the 
ca  vemous  plexus. 

The  cavernous  plexus  (plexus  cavernosus  penis)  extends  forward  through  the 
triangular  ligament  and  the  compressor  urethra  muscle  to  the  dorsum  of  the  base  of 
the  penis,  where  it  receives  some  communicating  filaments  from  the  pudic  nerve. 
After  supplying  branches  to  the  apex  of  the  prostate  gland  and  the  membranous 
urethra,  the  plexus  terminates  by  breaking  up  into  (1)  the  small  and  (2)  large 
cavernous  nerves  of  the  penis. 

1.  The  small  cavernous  nerves  (nn.  cavernosi  penis  minores)  pierce  the 
fibrous  envelope  of  the  crus  penis  and  end  in  filaments  which  supply  the  erectile 
tissue  of  the  corpus  cavernosum. 

2.  The  large  cavernous  nerve  (n.  cavernosus  penis  major),  consisting  mainly 
of  medullated  fibres,  passes  directly  along  the  dorsum  of  the  penis,  giving  off  fila- 
ments which  enter  the  substance  of  the  corpus  cavernosum.  At  about  the  middle  of 
the  body  of  the  penis  it  inosculates  with  the  dorsal  nerve  of  the  penis,  both  of  these 
nerves  sending  twigs  to  the  corpus  spongiosum. 

The  utero-vaginal  plexus  (plexus  uterovaginalis)  corresponds  to  the  prostatic 
plexus  of  the  male  and  consists  of  two  portions  :  (i)  the  uterine  plexus  and  (2)  the 
vaginal  plexus. 

1.  The  uterine  plexus  (plexus  uterinus)  is  derived  from  the  pelvic  plexus  and  is 
supplemented  in  its  distribution  by  the  visceral  branches  from  the  pudendal  plexus. 
These  fibres  accompany  the  uterine  vessels  along  the  side  of  the  uterus,  most  of  them 
entering  the  cervix  and  the  lower  portion  of  the  body  of  the  uterus.  They  inoscu- 
late with  fibres  from  the  ovarian  plexus  and  in  their  meshes  are  found  many  small 
ganglia,  a  collection  of  which  is  located  near  the  cer^•ix  uteri  and  is  called  the  gang- 
lion cervicale. 

2.  The  vaginal  plexus  (plexus  vaKinalls)  arises  from  the  lower  part  of  the 
pelvic  and  comprises  mainly  fibres  derived  from  the  visceral  branches  of  the  puden- 
dal plexus.  It  supplies  the  vagina  and  the  urethra  and  continues  forward  as  the 
cavernous  plexus  of  the  clitoris  (plexus  cavernosus  clitoridis). 


DEVELOPMENT  OF   PERIPHERAL  NERVES. 


«375 


Practical  Considerations. — The  cervical  sympathetic  may  be  injured  by  deep 
wounds  of  the  neck,  or  may  be  compressed  by  tumors,  abscesses  or  aneurisms.  It 
supplies  motor  fibres  to  the  involuntary  muscles  of  the  orbit  and  eyelids,  vasomotor 
filM'es  to  the  face,  neck  and  head,  dilator  fibres  to  the  pupil,  accelerator  fibres  to  the 
heart  and  secretory  fibres  to  the  salivary  glands.  If  it  is  irritated,  some  or  all  of  the 
following  symptoms  will  be  present :  the  palpebral  fissure  will  open  wider,  the  eyes 
will  be  protruded,  the  skin  of  the  face  and  neck  will  be  pale  and  cold,  the  pupils 
dilated,  and  the  sweat,  nasal  secretion  and  saliva  diminished.  Section  or  destruction 
of  the  cervical  sympathetic  will  give  the  opposite  symptoms. 

The  cervical  sympathetic  has  been  removed  for  epilepsy,  glaucoma  and  exoph- 
thalmic goitre.  The  greatest  success  has  been  obtained  in  the  last  condition,  espe- 
cially by  Jonnesco,  who  advises  this  procedure  in  hysteria,  chorea,  and  tumors  of  the 
brain,  as  well  as  in  the  above-mentioned  conditions.  It  may  be  excised  through  an 
incision  anterior  to  the  stemo-ma.stoid,  as  it  lies  f)osterior  to  the  carotid  sheath 
on  the  prevertebral  fascia.  The  smK-rior  cervical  ganglion  is  the  largest  and  lies 
oppojte  the  transverse  processes  of  ;he  second  and  third  vertebra-.  Branches  of  it 
go  upward  along  the  external  and  internal  carotid  arteries,  the  ascending  branch 
passing  along  the  internal  carotid  artery  through  its  bony  canal  in  the  basie  of  the 
skull  to  form  the  carotid  and  cavernous  plexuses,  both  of  which  arc  n  illy  parts  of 
one  plexus  arranged  around  this  artery.  Other  branches  communicate  with  the 
cranial  nerves,  the  pharyngeal  nerves  and  the  superficial  cervical  cardiac  nerve. 
The  middle  cervical  ganglion  is  the  smallest,  lies  on  the  inferior  thyroid  artery  oppo- 
site the  sixth  cervical  vertebra  and  is  in  danger  in  the  ligation  of  that  artery.  The 
inferior  ganglion,  intermediate  in  size  between  the  other  two,  lies  in  a  depression 
between  the  neck  of  the  first  rib  and  the  transverse  process  of  the  seventh  cer\'ical 
vertebra. 

The  branches  of  the  upper  four  or  five  thoracic  ganglia  of  the  sympathetic  enter 
into  the  supply  of  the  thoracic  viscera,  but  the  branches  of  the  lower  seven  or  eight 
form  the  splanchnic  nerves  and  go  to  the  supply  of  the  abdominal  viscera  through  the 
solar  plexus  and  its  extensions  into  other  sympathetic  plexuses  of  the  abdomen.  It 
is  of  interest  and  importance  to  observe  that  those  intercostal  nerves  corresponding  in 
their  origin  from  the  spinal  cord  with  the  ganglia  giving  off  the  splanchnics,  together 
with  the  first  two  lumbar  nerves,  the  ilio-hypogastric  and  ilio-mguinal,  supply  the 
abdominal  wall  with  motor  and  sensory  branches.  In  this  way  the  same  segments 
of  the  spinal  cord  supply  the  abdominal  viscera  as  well  as  the  skin  and  muscles  over 
them.  A  similar  arrangement  of  the  nerves  is  seen  in  the  joints,  where  the  same 
nerves  supply  the  skin  covering  the  joint,  the  muscles  which  move  it,  and  the  joint 
structures.  As  a  result  of  this,  when  necessary,  all  parts  of  the  joint  act  in  sympa- 
thy. In  an  inflammation  of  the  joint  the  skin  becomes  sensitive,  tending  to  ward  of! 
interference,  and  the  muscles  become  rigid,  preventing  motion  and  favoring  rest.  In 
a  similar  manner  the  abdominal  muscles  become  rigid  to  protect  inflamed  viscera 
underneath,  the  muscles  of  one  side  only  if  the  inflammation  is  localized  to  one  side, 
but  the  muscles  of  both  sides  if  a  general  peritonitis  is  present. 


DEVELOPMENT    OF    THE    PERIPHERAL    NERVES. 

The  manner  in  which  the  nerve-fibres  composing  the  peripheral  nervous  system  develop 
from  the  primary  cells,  the  neuroblasts,  has  been  indicated  in  the  previous  sketch  of  their 
histogenesis  given  on  page  loii.  It  remains,  therefore,  to  describe  briefly  at  this  place  the  more 
important  features  of  their  morphogenesis.  The  fundamental  fact  has  been  repeatedly  empha- 
sized, that  efferent  or  motor  fibres  are  outgrowths  from  neurones  situated  within  the  cerebro- 
spinal axis,  whilst  all  afferent  or  sensory  fibres  arise  from  cells  placed  outside  this  axis  and 
within  the  ganglia  located  along  the  course  of  the  ner\'es.  It  is  evident,  furthermore,  that  the 
efferent  constituents  of  the  peripheral  nerves  have  their  nuclei  of  origin  within  the  spinal  cord 
or  brain  and  grow  outward,  as  axones,  to  their  destinations.  The  afferent  fibres,  on  the  other 
hand,  proceed  in  Ixjth  directions,  the  axones  early  growing  centrally  to  join  the  nerx-ous  axis, 
hence,  having  usually  a  short  course,  being  represented  by  the  entering  sensory  roots.  The 
dendrites  grow  in  the  opposite  direction  and  contribute  the  sensory  fibres  that  extend  often  to 
remote  parts  of  the  body.  Whilst  in  the  lowest  vertebrates,  the  amphioxus  and  the  cyclos- 
tomes,  the  ventral  and  dorsal  roots  of  the  spinal  nerves  remain  distinct,  in  the  higher  types 
they  join  to  form  the  mixed  nerve,  which  typically  divides  into  the  anterior,  posterior  and 


1376 


HUMAN  ANATOMY. 


visceral  divisions.  .Such  t>-pical  divisioii.  however,  is  displayed  only  by  «»»«f  ."P?"' "^*  ^r"- 
tSd  to  that  part  of  the  trunk  in  which  the  primary  seRmentation  is  retained.  nan«1y.  the 
thS  «X.^^re  the  skeletal  muscular,  and  vascular  segments,  a.  well  as  thenerves, 
SLKnUty.  In  the  other  parts  of  the  spinal  «:ri^  the  cervical  and  Uie  '««"bo-sacral, 
wtere^ovision  ik  made  for  the  supply  of  the  highly  differentiated  musculature  of  the  ex- 
SiSm  a  number  of  cord-segnients.  the  nerves  early  unite  to  form  plexuses  from  v^hich 
&e~  t^nks  pow  out.  an  arr^gement  well  adapted  for  the  dutribut.on  «^ Jb^H Jro.,. 
different  sources  without  undue  multiplication  of  nervous  paths.  Concerning  the  factors  which 
pUrthe^oung  nerve  to  its  destination  with  such  remarkable  constancy,  nothing  »  known. 
STt  it  n«y  be  alsumcd  that  these  are  probably  influences  of  a  physical  character,  the  developing 
nerve  Sklng  the  path  offering  least  resistance.  The  visceral  division  of  the  spmal  nerve,  to 
which  refeAnce  tas  been  mlde,  corresponds  to  the  white  ramus  ^T'T"'^.  P^™  °f  ,^^ 
certain  of  the  thoracic  and  lumbo^cral  nerves.  These  splanchnic  fibres  differ  from  the 
»matic  efferent  ones  in  Uking  their  origin  fmm  cells  which  occupy  a  "'"^ '»t«^,  P«?'""" 
within  the  gray  matter  of  the  spinal  cord  than  do  the  root-cells  giving  rise  to  the  motor  fibres 
d»ttaed  fofthe  skeletal  muscl^.  WhiUt  the  great  majority  of  the  f'«'<^h"«Lfi^res  reach  the 
i«mus  of  communication  by  way  of  the  anterior  root,  some  few  perhaps  traverse  the  posterior 
or  sensory  toot  and  its  ganglion  before  continuing  their  course  to  the  s>-mp.-»thetic  The  senjor) 
fiL^T^bed  within  the  anterior  root. of  the  spinal  nerv«i  are  not  »«»»» ^""^"^  "'^r! 
roots,  which  are  exclusively  motor,  but  recurrent  meningeal  twigs  destined  for  the  membranes 

*^  ^'•^Jcranial  Nenre^-From  the  preceding  account  of  these  nerves,  it  is  evident  that  the 
optic  nerve  differs  morphologically  widely  from  an  ordinary  nerve,  since  1»  "V'V  ^^K^^''^^';;'; 
aWlified  outlyin;;  j^rtion  of  the  brain.    Its  development  may  be  omitted,  therefore,  from 
this  series  and  appropriately  considered  in  connection  with  the  development  of  the  eye  (page 
148a).    There  is  sufficient  reason,  as  will  appear  later,  for  regardmg  the  hypoglossal  nerve  as  a 
cranially  displaced  member  of  the  spinal  series.    Of  the  remaming  nerves,  only  the  olfactory 
and  auditory  are  purely  sensory ;  the  third,  fourth,  sixth  and  eleventh  are  exclusively  motor ; 
and  the  ftfth,  seventh,  ninth  and  tenth  are  mixed,  the  motor  strands  taking  ongin  from  the  neu- 
rones within  the  brain-stem,  while  the  sensory  ones  are  derivations  from  the  neurones  lying 
within  the  ganglia  connected  with  the  afferent  fibres.    Although  at  first  sight  the  tngeminus 
closely  corresponds  to  a  spinal  nerve  in  the  pos.session   of   ai   g^ghated  sensory  Md  a 
motor -root,  critical  examination  of  the  origin  of  its  motor  fibres  discloses  an  important  differ- 
ence, liamely  that  they  arise  from  the  lateral  nuclei  and  not  from  the  mesial,  which  correspond 
to  collections  of  ventral  root-cells.     A  similar  difference  also  appears  between  the  efferent 
trigeminal  fibres  and  those  of  the  eye-muscle  nerves,  the  latter  arising  from  groups  of  root<ells 
occupying  a  position  close  to  the  mid-line.    In  order  to  appreciate  the  significance  of  this  differ- 
ence reference  must  be  made  to  the  primarj-  division  of  the  musculature  of  the  head  already 
referred  to  in  connection  with  the  grouping  of  the  muscles  (page  47»  )•     IJ  was  there  pointed 
out  that  it  may  be  assumed  that  the  segmented  condition  of  the  trunk  musculature,  as  expressed 
by  the  metemeres,  is  continued  into  the  cephalic  region  but  with  subsequent  suppression  of  the 
middle  members  of  the  possible  nine  or  ten  segments  which  constituted  the  original  quota  of 
head-metameres.    Of  those  persisting  two  groups  are  recognized-one  includmg  the  firet  three 
metameres.  giving  rise  to  the  ocular  muscles  and  being  supplied  by  the  third,  fourth  and  sixth 
nerves ;  the  other  including  the  last  three  or  four,  producing  the  tongue-muscles,  and  being  sup- 
plied by  the  twelfth  nerve.     To  these  groups  of  cephalic  metameres  is  added  a  third,  the 
branchiomeres.  which  are  regarded  as  representing  a  supplementary  senes  connected  with  the 
branchial  arches  and  not  present  in  the  trunk.    The  branchiomeres  receive  the  mixed  cranial 
nerves  whose  motor  filaments  supply  muscular  masses  surrounding  the  visceral  tubes  (digestive 
and  respiratory),  and  arise  from  the  lateral  motor  nuclei.    It  follows  that  none  of  the  cranial 
nerves  contain  fibres  from  all  these  sources,  in  the  case  of  the  fifth,  seventh,  ninth  and  tenth,  the 
fibres  being  derived  from  the  lateral  motor  and  the  sensory  nuclei,  and  in  the  case  of  the  third, 
fourth  and  sixth,  from  the  mesial  (ventral)  nuclei  alone.     From  the  primary  conditions,  as 
revealed  by  studies  on  the  lower  vertebrates,  it  is  probable  that  the  dorsal  fibres  also  are  by  no 
means  of  similar  morphological  value,  since  some  represent  a  somatic  sensory  system,  as  those 
distributed  to  the  integument,  and  others  belong  to  a  visceral  sensory  one.  as  those  distnbuted 
to  the  walls  of  the  mouth,  pharynx  and  lar>-nx.     Following  the  pnraple  already  emphasized 
the  motor  fibres  of  the  cnmial  nerves  grow  from  the  brain  outward,  while  the  sensory  ones  extend 
centrally  from  the  ganglia  of  the  nerves  associated  with  the  brain.    The  cranial  and  spinal  nerves 
appear  on  the  surface  of  the  neural  tube  at  a  very  eariy  period,  their  presence  being  conspicuous 

by  the  end  of  the  fourth  week  (Fig.  901).  

The  olfactory  nerve  is  developed  in  connection  with  the  epithelial  lining  of  the  primary 
olfactory  pit  (page  1429).  As  early  as  the  end  of  the  first  fcetal  month,  in  the  human  embrjo, 
cells  corresponding  to  neuroblasts  appear  in  'he  anlage  of  the  olfactory  organ.  1-rom  these 
elements  processes  soon  grow  brainward,  nucleated  tracts  indicating  the  formation  of  the  later 
olfactory  fibres.    The  cell-bodies  of  the  younj  neurone  migrate  so  that  for  a  time  their  position 


DEVELOPMENT  OF  PERIPHERAL  NERVES. 


«377 


b  no  kMiger  within  the  prinutfy  epithelium,  but  deeper  and  within  a  cell  aggregation  known 
ai  the  olfattory  gangHoH.  The  neurones,  however,  retain  connection  with  the  olfactory  epithe- 
lium by  means  of  their  peripherally  directed  procesfies,  which  correspond  to  dendrites,  and  with 
the  brain  by  means  of  their  axooes.  With  the  thickening  of  the  olfactory  epithelium  which  sub- 
sequently occurs,  the  peripheral  fibres  and  their  nuclei  comes  to  lie  entirely  within  the  epithelial 
stratum  and  persist  as  the  olfactory  cells,  whose  centrally  directed  processes  form  the  olfactory 
filaments  that  end  as  arboriiations  within  the  characteristic  olfactory  glomeruli.  The  first 
cranial  nerve  Is  peculiar  in  the  superficial  position  of  its  cell-bodies  and  in  the  extreme  shortness 
of  iu  dendrites,  whkh  are  represented  b>'  the  rod-like  fibres  of  microscopic  length  extending 
from  the  cell-bodies  toward  the  free  suriace  of  the  olfactory  mucous  membrane.  This  superficial 
position  of  the  olfactory  neurones  is  regarded  as  an  unusual  persistence  of  the  primary  condition 
of  all  sensory  elements  and  as  evidence  of  the  archaic  nature  of  the  olfactory  nerves. 


Fig.  II4I. 


Sapcrior  oolliculi 
Mid-fanin. 


Ibody 


inferior  coUlculiu 

Oculomotor  ncnrc 

Trachlcmr  ncrrc 


Cerebellum 
TriKeminal  nerve 
Auditory  nerve 


GtoMo-pharynf^Rl  nerve 
Vaffus  nerve 


Spinal  acccMory  nenre 


lencephalon 

Median  geniculate  body 
Pallium 


Rhinencephalon 

Optic  Malk 
nferior  part  of  III.  ventricle 
Facial  .lerve 


Hypaglaaaal  nerrt 


Reconstruction  of  brain  of  human  embryo  of  four  and  one  half  wceki  (io.j  mm.);  outer  iuriace,  thowiag 
devalopinc  nervef.    X  »•    Drawn  from  Hi*  model. 

The  optic  nerve  is  so  inherently  a  derivative  of  the  cerebral  and  optic  vesicle,  that  its  develoj)- 
ment  is  appropriately  considered  with  that  of  the  eye  (pa-  "  •  moreover,  its  morpholoiacul 

significance  being  so  at  variance  with  that  of  the  other  may  be  omitted  from  further 

discussion  in  the  series  now  being  described. 

The  oculomotor  nerve  being  strictly  a  motor  nerve  much  in  common  in  its  mode  of 
formation  with  the  ventral  root  of  a  spinal  nerve,  with  which  it  is  homologous.  The  nerve 
originates  as  an  outgrowth  from  a  group  of  neuroblasts,  which  occupies  the  ventral  zone  about 
the  middle  of  the  mesencephalon.  From  these  neurones,  visible  in  the  fourth  wep'  In  the 
human  embryo,  the  axones  proceed  as  a  converging  group  of  fibres  which,  piercing  i  c  .all  of 
the  brain-tube  close  to  the  mid-line,  appear  on  the  ventral  suriace  of  the  brain-stem  as  the  fibres 
of  the  thiid  nerve.  Although  by  some  regarded  as  possessing  a  transient  rudimentary  dorsal 
root  that  early  entirely  disappears,  thus  bringing  the  nerve  of  a  cranial  myomere  into  close 
correspondence  with  those  of  the  spinal  series,  it  is  doubtful  whether  such  structure  is  usually 
present,  the  suppression  of  the  dorsal  portion  of  the  nerve  being  complete.  Soon  after  its  for- 
mation, the  main  trunk  undergoes  division  into  a  smaller  upper  and  a  larger  posterior  limb, 
which  foreshadow  the  superior  and  inferior  divisions  of  the  mature  nerve. 

The  trochlear  nerve,  although  springing  from  a  central  group  of  neuroblasts  in  clo?« 
proximity  with  those  giving  rise  to  the  third,  is  peculiar  in  the  course  of  its  axones.  Instead 
of  maintaining  a  ventral  course,  these  proceed  dorsally  and  become  superficial  on  the  upper 
f  dorsal)  aspect  of  the  hind-brain,  piercing  the  plate  which  later  becomes  the  superior  medul- 

87 


1378 


HUMAN  ANATOMY. 


Urv  velum  As  in  the  case  of  the  third,  so  lor  the  trochlear  an  abortive  transient  dorsal 
gantdion  aiid  root  have  been  described  (Martin).  If  present  these  must  be  regarded  as  ex- 
ceptional and  not  constant  features.  .  .     j.«         ■    ,      • 

The  uicemlnal  nerve  is  a  mixed  nerve  and  therefore  takes  its  ongin  differently  for  its 
two  roots.  The  motor  one  is  developed  from  a  series  of  neuroblasts,  which  he  at  some  distance 
from  the  mid-line  within  the  wall  of  the  neural  tube,  at  a  position  corresponding  to  the  junction 
of  the  dorsal  ind  ventral  zones  of  the  mid-l)rain  and  metencephalon.  The  axones  of  these 
neuroblasu  grow  forward  and  converge  to  the  surface  of  the  later  pons  at  a  position  close  to 
where  the  ingrowing  sensory  fibres  join  the  neural  tube.  The  sensor>-  fibres  are  the  axones  of 
neurones  located  within  the  Gasserian  ganglion  The  latter  is  derived  as  a  ventrally  dir«^«l 
outgrowth  from  the  ectoblast  of  the  roof  of  the  hind-br;un,  with  which  it  remains  attached  for  a 
short  time,  but  later  becomes  entirely  separated.  The  neuroblasts  acquire  a  bipolar  form,  one 
set  of  processes,  the  axones,  growing  centr.illy  to  establish  secondary  connections  with  the 
hind-brain  as  the  large  sensory  root,  while  the  others,  the  dendrites,  extend  peripherally  into 
the  substance  of  the  fronto-nasal  and  maxillary  processes  to  form  the  ophthalmic  and  maxillary 
nerves  anil  into  the  mandibular  process  to  form,  in  conjunction  with  the  smaller  motor  root. 

Fig.  1142. 


Reconstruction  of  brain  and  cranial  nervet  of  pig  tmbn-oj  cranial  nerves  indicated  byfigures;  ci<3.  cerv|ca1 
spinal  nerves ;  in  connection  with  seventh  nerve.,/  J.^.larp  superficial  petroaal ;  chp.,  chorda  tympani : /a.,  facial , 
/.  a.,  vagus  KiiiKlia  of  root  and  trunk;  tow.,  commisi.ttral  extension  01  ganglion  01  root;  t,  I- roriep  s  hypoglossal 
ganglion.    (F.  T.  Lrwii.) 

the  mandibular  division  of  the  trigeminus  from  the  ganglion  ridge.  Provision  for  the  ciliary 
ganglion  is  made  early  by  the  migration  of  cells  from  the  major  ganglion  along  the  de- 
veloping ophthalmic  division.  Similar  migrations  along  the  other  divisions  give  rise  to  the 
spheno-palatine,  the  otic  and  the  submaxillary  ganglia.  The  later  histological  characteristics 
of  these  cells,  as  well  as  their  mode  of  origin,  warrant  the  view  that  the  ciliary  ganglion,  as  well 
as  the  otiiers  connected  with  the  trigeminus,  belong  to  the  -ympathetic  system.  On  entering 
the  wall  of  the  brain-tube,  the  bulk  o*  the  sensory  trigeminal  fibres  assume  a  longitudinal  course 
and  early  establish  the  tract  of  the  spinal  cord. 

The  atHlucent  nerve  developes,  in  a  manner  identical  with  the  third  and  fourth,  from  a 
median  group  of  cells  occupying  the  ventral  zone  of  the  upper  part  of  the  hind-brain.  In  the 
human  embryo  of  about  four  and  a  half  weeks  (Fig.  1141),  the  nerve  appears  at  its  super- 
ficial origin  mesial  to  the  Gasserian  ganglion.  The  root-fibres  early  consolidate  into  a  compact 
strand. 

The  facial  nerve  being  a  mixed  one  also  arises  from  a  double  source,  its  motor  fibres 
taking  origin  from  efferent  neuroblasts  situated  in  the  ventro-lateral  wall  of  the  metencephalon. 
In  contrast  to  the  direct  ventral  course  of  the  axones  of  the  mesial  motor  nerves,  those  of  the 
facial  pursue  a  path  to  the  surface  of  the  brain-stem  even  more  indirect  than  that  taken  by  the 
lateral  motor  fibres  of  the  other  mixed  nerves.  Proceeding  as  the  axones  of  neuroblasts  lying 
within  the  lateral  part  of  the  ventral  zone  of  the  wall  of  the  hind-brain,  they  are  directed  dor- 
sally,  then  grow  forward,  turn  outward  and,  finally,  ventrally  to  gain  emergence  from  the  brain. 
The  sensory  portion  of  the  facial  is  topographiciUly  closely  connected  during  its  development 
with  the  auditory,  the  nuclei  of  the  two  nerves  often  being  designated  the  facial-acoustic  com- 
plex. The  three  components  of  this  aggregation— the  geniculate,  the  cochlear  and  the  vestibu- 
lar ganglia — are  primarily  derived  from  an  ectoblastic  cell-mass  in  the  vicinity  of  the  otic  vesicle. 


DEVELOPMENT  OF  PERIPHERAL  NERVES. 


"379 


Th«  neuroblast  of  the  facial  cunstituetit,  the  Kenkulate  KaiiKlion,  hmmJ  their  centrally  tlirccte.l 
processes  tu  the  brain-stem  as  the  pars  intermedia,  whilst  their  (leripherally  KrowinK  tlemlritt^ 
contribute  the  sensory  fibres,  pay-^inK  by  way  of  the  chortia  tympani  ami  the  greater  ami  lesser 
superficial  petrosal  nerves.  The  geniculate  KaoKlion  and  the  (lars  intermedia  curres|Miiid, 
therefore,  to  a  dorsal  root 

The  auditory  nerve,  althouich  for  a  time  closely  related  in  {losition  (Fiij.  1103)  with  the 
facial  (geniculate)  ^anKlion,  developes  entirely  independently  and  at  notinte  has  more  than  an 
incidental  relation.  The  primary  auditory  nucleus  is  defined  in  human  eml>r>-o«  by  the  beKin- 
ning  of  the  fourth  week  as  an  elongated  ellipsoidal  ma.ss  in -contact  with  the  anterior  wall  of  the 
otic  vesicle.  According  to  Streeter',  the  nucleus  very  shortly  exhibits  a  diflerentiation  into 
a  superior  and  an  inferior  part,  from  the  latter  of  which  soon  appears  a  third  portion.  This 
third  portion,  the  later  ganglion  spirale,  early  manifests  •  tendency  to  coil  in  conse(|uence  of 
its  close   relations  with  the 

Fio. 


114.^. 


V*f«a  root  gans. 


AcccMorjr  root  K*ng. 

/4 


IX.  nM  (ang. 


KroHcp 


Gang,  nodos. 
N.  laryg.  tup. 


XII.  with  r.dcwcnil.' 


ductus  cochlearis.  The 
major  part  of  the  primary 
acoustic  complex,  including 
the  superior  and  most  of 
the  inferior  part,  becomes 
the  vestibular  ganglion, 
from  the  neuroblasts  of  which 
centrally  directed  axones 
pass  to  the  young  brain- 
stem as  the  vestibular  nerve, 
while  the  dendrites  become 
connected  at  certain  places 
with  the  semicircular  canals, 
the  utricle  and  the  saccule. 
The  grouping  of  the  vestibular 
rami  seen  in  the  adult  is  early 
foreshadowed  in  the  develop- 
ing nerve,  since  from  the 
upper  pan  of  the  vestibular 
ganglion  grows  out  the  su- 
perior division  of  the  vestib- 
ular nerve  which,  supplies 
the  utricle  and  the  ampulizs 
of  the  superior  and  external 
semicircular  canals  (Fig. 
1070) .  The  lower  part  of  the 
ganglion,  in  addition  to  fur- 
nishing the  anlage  for  the 
cochlear  nerve,  gives  off  the 
inferior  division  of  the  vestib- 
ular nerve,  by  which  the 
saccule  and  the  posterior 
canal  are  supplied.  During 
the  subsequent  growth  of  the 
structures,  the  neurones  of 
the  spiral  ganglion  send  ax- 
ones towards  the  brain  which  become  the  cochlear  nerve,  whilst  their  dendrites-grow  peripherally 
into  the  ductus  cochlearis  and  are  represented  by  the  minute  filaments  extending  from  the 
cells  of  the  spiral  ganglion  to  the  auditory  cells  of  Corti's  organ. 

The  glosso-pharyngcal  nerve  is  a  mixed  nerve  and  has,  therefore,  a  double  origin.  Its 
motor  fibres  arise  from  neuroblasts  situaied  in  the  dorsal  part  of  the  ventral  zone  of  the  wall  of 
the  hind-brain  just  posterior  to  the  otic  vesicle.  The  sensory  part  of  the  nerve,  along  with 
that  erf  the  vagus,  ofTers  greater  complexity,  since  it  is  developed,  as  shown  by  Streeter*,  from 
two  sources.  The  ganglion  of  the  root  (g.  superius  or  jugular  ganglion)  arises  very  eariy  as 
a  small  mass  of  cells  derived  from  the  ganglion-crest  of  the  land-brain.  It  varies  in  size  and 
soon  ceases  to  grow,  which  behavior,  in  connection  with  the  preponderating  ingrowth  of  the 
motor  fibres,  accounts  for  the  well-known  inconstancy  of  the  structure.  The  ganglion  of 
the  trunk  (g.  petrosum)  arises,  according  to  Streeter,  not  from  the  neural  crest  but  in 
relation  with  the  ectoblast  of  the  second  visceral  furrow.  M  first  ununited  with  the  smaller 
ganglion  superius,  the  ganglion  of  the  root  subsequently  becomes  joined  to  it,  the  two  nodes 

•  Amer.  Jour,  of  Anatomy,  vol.  vi.,  1907. 
'Amer.  Jour,  of  Anatomy,  vol.  iv.,  1904. 


Sympathetic 


Vasna 

Reconatruction  of  peripheral  nervea  of  human  embryo  of  five  weeks 
(14  mm.)  >;  13.    (Slrtrler.) 


1380 


HUMAN  ANATOMY. 


being  later  closely  related,  both  as  to  position  and  fibres.    An  outgrowth  of  distally  directed 
fibres  establishes  the  main  trunk  of  the  ner%e,  while  a  forwardly  growing  strand  represents  the 

later  tympanic  branch.  .  ,  .  j  •    .1.  •   j      1 

The  v«fu»  and  ipinal  accesiory  nerve*  are  so  mseparably  related  m  their  development 
that  their  origin  must  be  regarded  as  proceeding  from  a  common  vagus  complex.  The  latter 
comprises  three  elements :  (a)  a  series  of  motor  roots,  which  arise  from  the  ventral  zone  of 
the  hind-brain  and  extend  from  near  the  glosso-pharyngeal  anlage  m  front  as  far  as  the  third  or 
fourth  spinal  segment  below ;  (*)  a  partially  subdivided,  but  at  first  contmuous,  ganglionic 
mass,  which  arises  from  the  ganglion-crest  of  the  hind-brain  and  represents  the  root-ganglia ; 
(c)  a  secondary  ventral  cell-mass,  the  primitive  ganglion  of  the  trunk,  which,  as  in  the  case  of 
the  glosso-pharvngeal  nerve,  is  developed  in  close  relation  with  the  ectoblast  of  the  posterior 
branchial  furrows.  Whilst  the  motor  rootlets  persist  and  become  the  efferent  root-fibres  of  the 
later  vagus  and  aci-essory  nerves,  the  dorsal  or  crest-ganglia  soon  exhibit  differences  in  their 
growth,  the  one  situated  farthest  forward  outstripping  the  others  and  becoming  the  vagal  gang- 
lion of  the  root,  and  the  remaining  ones  becoming  the  accessory  root-ganglia.  These  latter 
constitute  a  chain  which  below  meets  with  the  spinal  dorsal  ganglia.  Primarily,  therefore,  the 
entire  length  of  the  vagus  complex  is  occupied  by  a  series  of  mixed  nerve  strands  possessing 
both  motor  and  sensory  elements.  The  head-end  of  the  series  later  becomes  predominatingly 
sensory,  while  in  the  tail-end  of  the  same  the  motor  character  prevails.  The  ventral  vagus 
nucleus  is  attached  secondarily  to  the  dorsal  nucleus  by  centrally  growing  fibres,  while  from  its 
distal  end  extend  the  dendritic  processes  which  constitute  the  trunk  of  the  vagus  and  11 . 
branches.  In  consequence  of  the  intergrowth  of  these  afferent  and  efferent  fibres,  the  definite 
tenth  ner\'e  in  the  usual  sense,  with  its  two  ganglia,  becomes  established.  Although  for  a  short 
period  the  accessor)-  part  of  the  complex  is  provided  with  both  motor  and  sensory  parts,  the 
latter  are  subsequently  overpowered  by  the  efferent  fibres,  so  that  the  presence  of  the  rudimen- 
tary ganglionic  elements  within  the  accessorius  can  be  demonstrated  only  by  microscopic  exam- 
ination ( Streeter) .  From  the  preceding  facts  it  is  evident  that  the  estimate  of  the  eleventh  nerve 
as  an  integral  part  of  the  vagus  is  well  founded. 

The  hypoglossal  nerve  appears  in  the  human  embryo,  towards  the  close  of  the  third  week, 
as  several  strands  which  grow  from  the  ventral  zone  of  the  wall  of  the  hind-brain  and  are  in 
series  with  the  ventral  root-fibres  of  the  upper  cervical  spinal  nerves.  Soon  the  separate  root- 
lets converge  and  consolidate  into  a  common  trunk,  from  which,  by  the  end  of  the  fifth  week, 
the  chief  branches  of  distribution  arise.  The  production  of  the  wide-meshed  net-work  which 
distinguishes  the  communications  between  the  upper  cervical  and  hypoglossal  nerves  results 
from  the  separation  of  fibres  which  are  at  first  closely  adjacent,  the  subsequent  migration  of  tho 
growing  tongue-muscles  drawing  the  hypoglossal  fibres  away  from  the  spinal  nerves,  except  at 
such  points  where  they  have  become  enclosed  in  a  common  sheath.  There  is  good  reason  for 
regarding  the  hypoglossal  nerve  as  representing  the  ventral  roots  of  trunk-nerves,  which  have 
been  cephalicly  displaced  and  drawn  within  the  cranium.  Moreover,  the  observations  of 
Froriep  and  others  upon  adult  mammals  and  of  His  upon  the  human  embryo  have  shown  the 
presence  of  a  rudimentary  dorsal  ganglion  and  abortive  dorsal  root-fibres.  The  occasional 
presence  of  a  rudimentary  ganglionic  mass,  known  as  Froriep's  ganglion,  attached  to  the 
fibres  of  the  adult  hypoglossal  nerve  in  man  is  to  be  interpreted  as  the  persistent  dorsal 
element  which  ordinarily  disappears.  ...  .    j  , 

From  the  preceding  sketch  it  is  evident  that  in  no  instance,  as  observed  in  the  usual  adult 
condition  in  man,  is  there  complete  correspondence  between  the  members  of  the  cephalic 
series  and  those  of  the  trunk.  The  group  of  purely  sensory  nerves— the  olfactory,  optic  and 
auditory— includes  one,  the  optic,  which  is  so  exceptional  in  its  fundamental  relations  as  to  lie 
without  the  pale  of  peripheral  nerves  in  their  strict  sense.  The  remaining  two  sensory  nerves 
are  held  to  be  primarily  the  equivalents  of  constihients  of  a  peculiar  system  of  sensoo' 
organs,  best  developed  in  fibres,  known  as  the  organs  of  the  lateral  line.  The  third,  fourth, 
sixth  and  twelfth,  the  ventral  motor  nerves,  are  undoubtedly  associated  with  head-somites, 
although  the  exact  number  and  nerve  relations  of  such  mesoblastic  segments  are  uncertain ; 
in  fundament?'  nificance,  therefore,  these  nerves  agree  with  (hose  of  the  trunk-series, 
although  moilii.  .  by  the  suppression  of  their  dorsal  or  sensory  constituents.  The  mixed 
nerves— the  fifth,  seventh,  ninth  and  tenth  (the  eleventh  being  reckoned  as  part  of  the  vagus)— 
are  unrepresented  in  the  spinal  series  and  belong  to  the  branchiomeres  represented  by  the 
visceral  arches.  Of  these  ner\es,  the  trigeminus  most  nearly  accords  in  constitution  with  a  typical 
spinal  ner\e,  since,  with  the  exception  of  ventral  motor  constituents  which  are  wanting,  it  pos- 
sesses as  does  the  typical  spinal  nerve,  both  somatic  (general  cutaneous)  sensory  and  visceral 
sensory  fibres.  A  further  resemblance  is  found  in  the  ch.iracter  of  the  gray  matter  constituting 
the  reception-nucleus  for  the  sensory  fibres  of  the  trigeminus,  since  this  column  is  comixjsed  of 
substantia  gelatinosa  continuous  with  the  Rolandic  substance  capping  the  posterior  co;nu  of  the 
cord.  A  similar,  although  less  imim.itc,  arrangement  is  seen  in  the  column  of  ijray  matter  accom- 
panying the  descending  root  (funiculus  solitarius)of  the  facial,  glosso-pharyngeal  and  vagus  nerves. 


THE  ORGANS  OF  SENSE. 

The  cells  directly  receiving  the  stimuli  producing  the  sensory  impressions  of 
touch,  smell,  taste,  sight  and  hearing  are  all  derivations  of  the  ectoblast — the  great 
primary  sensory  layer  from  which  the  essential  parts  of  the  organs  of  special  sense 
are  differentiations.  The  olfactory  cells — nervous  elements  that  correspond  to 
ganglion  cells  —  retain  their  primary  relation,  since  they  remain  embedded  within 
the  invaginated  peripheral  epithelium  lining  the  nasal  fossse,  sending  their  dendrites 
towards  the  free  surface  and  their  axones  into  the  brain.  Usually,  however,  the 
nerve  cells  connected  with  the  special  sense  organs  abandon  their  superficial  position 
and  lie  at  some  disUnce  from  the  periphery,  receiving  the  stimuli  not  directly,  but 
from  the  epithelial  receptors  by  way  of  their  dendrites.  In  the  case  of  the  most 
highly  specialized  sense  organs,  the  eye  and  the  ear,  the  percipient  cells  lie  enclosed 
within  capsules  of  mesoblastic  origin,  the  stimuli  reaching  them  by  way  of  an 
elaborate  path  of  conduction. 

THE  SKIN. 

Since  the  extensive  integumentary  sheet  that  clothes  the  exterior  of  the  entire 
body  not  only  ser\es  as  a  protective  investment,  an  efficient  regulator  of  body 
temperature  and  an  important  excretory  structure,  but  also  contains  the  special  end- 
organs  and  the  peripheral  terminations  of  the  sensory  nerves  that  receive  and  convey 
the  stimuli  producing  tactile  impressions,  the  skin  may  be  appropriately  considered 
along  with  the  other  sense-organs  of  which  it  may  be  regarded  as  the  primary  and 
least  specialized.  On  the  other  hand,  the  correspondence  of  its  structure  with  that 
of  the  mucous  membranes,  with  which  it  is  directly  continuous  at  the  orifices  oil  the 
exterior  of  the  body,  emphasizes  the  close  relation  of  the  skin  to  the  alimentary  and 
other  mucous  tracts. 

This  general  investment,  the  tegmentum  commune,  includes  ihe  skin  proper, 
with  the  ppecialized  tactile  corpuscles,  and  its  appendages — the  hairs,  the  nails  and 
the  cutaneous  glands.  Its  average  superficial  area  is  approximately  one  and  a  half 
square  meters. 

The  skin  (cutis),  using  the  term  in  a  more  restricted  sense  as  applied  to  the 
covering  proper  without  its  appendages,  everywhere  consists  of  two  distinct  portions 
— a  superficial  epithelial  and  a  deeper  connective  tissue  stratum.  The  formci ,  the  epi- 
dermis, is  devoid  of  blood-vessels,  the  capillary  loops  of  which  never  reach  f  .rther  than 
the  subjacent  corium,  as  the  outermost  layer  of  the  connective  tissue  stratum  is  called. 

The  thickness  of  the  skin,  from  .5-4  mm.,  varies  greatly  in  different  parts  of 
the  body,  being  least  on  the  eyelids,  penis  and  nympha,  and  greatest  on  the  palms 
of  the  hands  and  soles  of  the  feet  and  on  the  shoulders  and  back  of  the  neck.  In 
general,  with  the  exception  of  the  hands  and  feet,  the  skin  is  thicker  on  the  extensor 
and  dorsal  surfaces  than  on  the  opposite  aspects  of  the  body.  Of  the  entire  thick- 
ness, the  proportion  contributed  by  the  epidermis  is  variable,  but  in  most  localities 
it  is  about  .  i  mm.  Where  exposed  to  unusual  pressure,  as  on  the  palms  of  laborers 
or  on  habitually  unshod  soles,  the  epidermis  may  attain  a  thicknes.s  of  4  mm. 

As  seen  during  life,  the  color  of  the  skin  results  from  the  blending  of  the  in- 
herent tint  of  the  tissues  with  that  of  the  blood  within  the  superficial  vessels.  When 
the  latter  are  empty,  as  after  death,  the  skin  assumes  the  characteristic  pallor  and 
ashen  hue.  Where  the  capillaries  are  numerous  and  the  overlying  strata  thin,  the 
skin  exhibits  the  pronounced  rosy  color  of  the  lips,  cheeks,  ears  and  hands.  Where, 
on  the  contran,',  the  contents  of  fewer  vessels  shimmer  through  the  epidermis,  the 
paler  tint  of  the  limbs  and  trunk  is  produced. 

In  certain  localities — especially  over  the  mammary  areoUe  after  pregnancy,  the 
axillw,  the  external  jiiniul  organs  and  around  the  anus — the  .skin  presents  a  more  or 
less  pronounced  brownish  color  owing  to  the  unusual  quantity  of  pigment  within  the 

1,181 


1382 


HUMAN   ANATOMY. 


Fig.  I 144. 


Imprint  of  dorsal  surface  of  left  hand  near  ulnar  border; 
radiatiiiK  lines  are  produced  by  creases  connecting  points  at 
which  hairs  emerge. 


epidermis.     The  amount  of  skin-pigment  not  only  differs  permanently  among  races 

^  (white,  yellow  and  black)  and  indi- 

viduals (blond  and  brunette),  but 
also  varies  in  the  same  person  witli 
age  and  exposure,  as  contrasted  by 
the  rosy  tint  of  the  infant  and  the 
bronzed  tan  of  the  weather  beaten 
mariner. 

Unless  bound  down  to  the 
underlying  tissues,  as  it  is  over  the 
scalp,  external  ear,  palms  and  soles, 
the  skin  is  ireely  movable.  Its 
physical  properties  include  con- 
siderable extensibility  and  marked 
elasticity.  By  virtue  of  the  latter  the 
temporary  displacement  and  stretch- 
ing produced  by  movements  of  the 
joints  and  muscles  is  overcome  and 
the  smoothness  of  the  skin,  so  con- 
spicuous in  early  life,  is  maintained. 
With  advancing  age  the  elasticity 
becomes  impaired  and  folds  are  no 
longer  effaced,  resulting  in  the  perma- 
nent wrinkles  seen  in  the  skin  of  old 

people.    Certain  folds  and  furrows,  however,  are  not  only  permanent  and  ineffaceable. 

appearing  in  the  foetus,  but  are  fairly  constant  in  position  and  form.     One  group, 

produced  by  fle.xion  of  the  joints,  includes  the  conspicu-  ^^^ 

ous  creases  on  the  flexor  surface  of  the  wrist,  palm  and 

fingers,  and  the  similar  markings  on  the  soles  of  the  feet. 

The  other  group,  more  extensive   but  less  striking, 

includes  the  fine  grooves   that  connect  the   points  of 

emergence  of  the  hairs  and  cover  the  trunk  and  extensor 

surface  of  the  limbs  with  a  delicate  tracery  (Fig.  1 144). 
The  surface  modelling  of  the  skin  covering  the 

palms,  soles  and  flexor  aspects  of  the  digits  is  due  to 

the  disp<3sition  of  numerous  minute  ridges  ( cristae  cutis) 

ami  furrows  (sulci  cutis).     The  cutaneous  ridges,, A\v3\ii 

.  2  mm.  in  width,  correspond  to  double  rows  of  papilla 

which  they  cover,  the  sweat  glands  opening  along  the 

summit  of  the  crests.     The   patterns   formed  by  the 

cutaneous  ridges  (Fig.    1145)  remain   throughout  life 

unchanged  and  are  so  ilistinctive  for  each  indiviilual 

that  they  afford  a  reliable  and  practical  means  of  identi- 
fication.' In  addition  to  the  various  longitudinal,  trans- 
verse and  oblique  ranges  of  ridges  that  cover  the  greater 

part  of   the  hand,  groups  of   concentrically  arranged 

ridges  occupy  the  volar  surface  over  the  distal  phalanges, 

the  pads  between  the  metacarpo-])halangeal  joints  ami 

the  middle  of  the  hypothenar  eminence.     These  highly 

chari.  teristic  areas^  the  so-called  tactile  pads  (tonili 

tactilcs)  are  most  strikingly  developed  over  the  bulbs 

of  the  fingers,  where  the  ridges  are  often  tlisposed  in 

whorls  rather  than  in  regular  o\als.     The  markings  of 

corrcspontling  areas  of  the  two  hands  are  symmetrical 

antl  sometimes  identical. 

Structure.— The  two  parts  of  which  the  skin  is 

everywhere  composed— the  epidermis  and  the  connec- 
tive tissue  stratum — are  derivatives  of  the  ectoblast  and 

of  the  mesoblast  respectively.     The  connective  tissue  portion  includes  two  layers. 


'■ijS0** 


Imprint  of  palmar  surface  of  Ml 
middle  finger,  showing  iirr  iiigcment 
of  cutaneoua  ridges;   transverse  in 

tcrruptians  arc  produce!  by  firxi'-t* 
creases  over  joints. 


THE   SKIN. 


1383 


the  corinm  and  the  tela  subcutanea,  which,  however   are  so  blended  with  each  other 
as  to  be  without  sharp  demarcation. 

The  corium  or  derma,  the  more  superficial  and  compact  of  the  connective 
tis:;ue  strata,  lies  immediately  beneath  the  epidermis  from  which  it  is  always  well 
defined.  With  the  exception  of  within  a  few  localities,  as  over  the  forehead,  external 
ear  and  perineal  raphe,  the  outer  surface  of  the  corium  is  not  even  but  beset  with 
elevatiois,  ridges,  or  papillae,  which  produce  corresponding  modelling  of  the  opposed 
undev  .surface  of  the  overlying  epidermis.  The  pattern  resulting  from  these  eleva- 
tions varies  in  different  regions,  being  a  net-work  with  elongated  meshes  over  the 
ktck  and  front  of  the  trunk,  with  more  regularly  polygonal  fields  over  the  extremi- 


FiG.  1 146. 


Fig.  I 147. 


Portion  of  corium  from  palmar 
surface  of  hand  after  removal  of  epi- 
dermis ;  each  ran^e  includes  a  double 
row  of  papillae,  which  underlie  the 
superficiat  cutaneous  ridxes  and  en- 
close openings  of  sweat  glands ;  latter 
appear  as  dark  points  along  ranges 
01  iKipillse.    X  5. 


Small  portion  of  preceding;  specimen, 
showing  papillae  under  higher  mai^Tiifica- 
tton ;  orifices  of  torn  sweat  glands  are  seen 
between  papillae.    X  24. 


ties  and  with  small  irregular  meshes  on  the  face  (Blaschko).  The  best  developed 
papilUe  are  on  the  flexor  surfaces  of  the  hands  and  feet,  where  they  attain  a  height 
of  .2  mm.  or  more  and  are  disposed  in  the  closely  set  double  rows  that  underlie  the 
cutaneous  ridges  on  the  palms  and  soles  above  noted.  The  papilla  afforil  favorable 
positions  for  the  lodgement  of  the  terminal  capillary  loops  and  the  special  organs  of 
touch  and  are  accordingly  grouped  as  vascular  and  taiiilc. 

In  recognition  of  the  elevations,  which  in  vertical  sections  of  the  skin  appear 
as  isolated  projections,  the  corium  is  subdivided  into  nn  outer  papillary  stialiim 
(corpus  paplllare),  containing  the  papillae,  and  a  deeper  reticular  stratum  (tunica 
r-opria),  composed  of  the  closely  interlacing  bundles  of  fibrous  and  elastic  tissue 
aiat  are  continued  into  the  more  robust  and  loosely  arranged  trabecuhe  of  the  tela 
subcutanea.  These  two  strata  of  the  corium,  however,  are  so  blended  that  they 
pass  insensibly  and  without  definite  boundary  into  each  other.  Although  coir;,  jsed 
of  the  same  histological  factors — bundles  of  fibrous  tissue,  elastic  fibres  and  con- 
necti\e  tissue  cells — the  disposition  of  these  constituents  is  much  more  compact  in 
the  dense  reticular  stratum  than  in  the  papillary  layer,  in  which  the  connecti\-e 
tissue  bundles  are  less  closely  interwoven. '  While  the  general  course  of  the  fibrous 
bundles  within  the  corium  is  parallel  or  oblique  to  the  surface,  some  strands, 
continued  upw.ird  from  the  underlying  subcutaneous  sheet,  are  vertical  and 
traverse  the  stratum  reticulare  either  to  bend  over  and  join  the  horizontal  bundles 
or  to  break  up  and  disappear  within  the  papillary  stratum.     The  elastic  tissue. 


1384 


HUMAN  ANATOMY. 


which  constitutes  a  considerable  part  of  the  corium,  occurs  as  fibres  and  net-works, 
which  within  the  reticular  stratum  form  robust  tracts  corresponding  in  their 
disposition  with  the  general  arrangement  of  the  fibrous  bundles.  Towards  the 
surface  of  the  corium,  the  elastic  fibres  become  finer  and  more  branched  and  beneath 
the  epidermis  anastomose  to  form  the  delicate  but  close  subepithelial  elastic  net-work 
that  IS  present  over  the  entire  surface  of  the  body  with  the  exception,  possibly,  of 
the  eyelids  (Behrens). 

The  tela  subcutanea,  the  deeper  layer  of  the  connective  tissue  portion  of  the 
skin,  varies  in  its  thickness,  and  in  the  density  and  arrangement  of  its  component 
bundles  of  fibro-elastic  tissue,  with  the  amount  of  fat  and  the  number  of  hair-follicles 
and  glands  lodged  within  its  meshes. 

The  latter  are  irregularly  round  and  enclosed  by  tracts  of  fibrous  tissue,  some 
of  which,  known  as  the  retinacula  cutis,  are  prolonged  fron  e  corium  to  the  deepest 
parts  of  the  subcutaneous  stratum.  Here  they  often  bk  a  into  a  thin  but  definite 
sheet,  t\x  fascia  subcutanea,  which  forms  the  innermost  boundary  of  the  skin  and  is 


Fig.  1 148. 


Epidermis 
Papillary  stratum 

Reticular  stratum 


Hair  follicle 


Retiiuculum 


Fat 


Section  of  skin,  showing  its  chief  layers— epidermis,  corium  and  tela  subcutanea.    X  17. 


connected  with  the  subjacent  structures  by  strands  of  areolar  tissue.  Where  such 
loose  connection  is  wanting,  as  on  the  scalp,  face,  abiiomen  (linea  alba),  palms  and 
soles,  the  skin  is  intimately  bound  to  the  underlying  muscles  or  fascia  ancl  lacks  the 
independent  mobility  that  it  elsewhere  enjoys.  The  integument  covering  the  eye- 
lids and  penis  is  peculiar  in  retaining  to  a  conspicuous  degree  its  mobility  although 
devoid  of  fat.  VVhere  the  latter  is  present  in  large  quantity,  the  term  panniculus 
adiposns  is  often  applied  to  the  tela  subcutanea. 

In  places  in  which  the  skin  glides  over  unyielding  structures,  the  interfascicular 
lymph-spaces  of  the  tela  subcutanea  may  undergo  enlargement  and  fusion,  resulting 
in  the  production  of  the  subcutaneous  mucous  bursae.  These  are  found  in  many 
localities,  among  the  most  constant  bursa  being  those  over  the  olecranon,  the  patella 
and  the  metatarso-phalangeal  joints  of  the  little  and  the  great  toe.  The  bursje  in 
the  latter  situation,  when  abnormally  enlarged,  an-  familiar  as  bunions. 

In  addition  to  the  strands  of  involuntary  muscle  associated  with  the  hairs  as  the 
arrectores  pilorum,  unstriped  muscular  tissue  is  incorporated  with  the  skin  in  the 
mammary  areola?  and  over  the  scrotum  and  penis  (tunica  dartos).  The  facial 
muscles  having  largely  cutaneous  insertions,  the  skin  covering  the  face  is  invaded 
by  tracts  of  striated  muscular  tissue  that  penetrate  as  far  as  the  corium. 


THE   SKIN. 


i3«5 


The  epidermis  or  cuticle,  the  outer  portion  of  the  skin,  consists  entirely  of 
epithelium  and,  being  partly  horny,  affords  protection  to  the  underlying  corium  with 
its  vessels  and  nerves.  The  thickness  of  this  layer  varies  in  different  parts  of  the 
body.  Usually  from  .08-.  10  mm. ,  it  is  greatest  on  the  fle-xor  surfaces  of  the  hands 
and  feet,  where  it  reaches  from  .^-.g  mm.  and  from  1.1-1.3  mm.  respectively 
(Drosdofi).  .      . 

The  cuticle  consists  of  two  chief  layers,  the  deeper  stratum  frcrmtnaltvum,  con- 
taining the  more  active  elements,  and  the  stratum  corneum,  the  cells  of  which  undergo 
cornification.     Between  these  layers  lies  a  third,  the  stratum  internudium,  that  is 


Fig.  II49- 


Stratum  conicum 


Spiral  duct  of 
sweat  gland 


Stratum  lucidum 


stratum 
gcrmmativum 


Corium 


(Ion  of  section  of  skin  ,'mm  sole  of  foot,  showing  layere  of  epidermis.    X  70. 

ordinarily  lepresented  by  only  a  single  row  of  cells  to  which  the  name,  stratum 
granulosum,  is  usually  applied.  This  layer  marks  the  level  at  which  the  conversion 
of  the  epithelial  elements  into  horny  plates  begins  and  also  that  at  which  the 
separation  effected  by  blistering  usually  occurs. 

On  the  palms  and  soles,  where  the  epidermis  attains  not  only  great  thickness 
but  also  higher  differentiation,  four  distinct  layers  may  be  recognized  in  vertical  sec- 
tions of  the  cuticle.  From  the  corium  outward,  these  are:  (i)  the  stratum  germina- 
tivum,  (2)  the  stratum  granuhsum,  {3)  the  stratum  lucidum  and  (4)  the  stratum 
corneum.  The  first  two  represent  the  portion  of  the  epidermis  endowed  with  the 
greatest  vitality  and  powers  of  repair  and  the  last  two  the  horny  and  harder  part. 

The  stratum  germinativum,  or  stratum  Malpighi,  rests  upon  the  outer  sur- 
face of  the  corium,  by  the  papiilic  of  which  it  is  iinpri:s3t;d  and,  hence,  when 
viewed  from  beneath  after  being  separated,  commonly  presents  a  more  or  less 
evident  net-work  of  ridges  and  enclosed  pits,  the  elevations  corresponding  to  the 


Ill 


1386 


HUMAN   ANATOMY. 


Stratum  corneum 


Stratum  lucidum 


Stratum 

granulosum 


Stratum 

germinativum 


Deepest  cells 

of  epidermis 

Corium 


Pi.rtion  of  preceding  preparation,  sliowinn  in  more  detail  layers  of  epidermis; 
only  deeper  part  of  stratum  corneum  is  represented.     >  2ho. 


interpapillary  furrows  and  the  depressions  to  the  papilla?.  In  recognition  of  this 
reticulation  the  name,  rete  Malpighi,  is  sometimes  applied  to  the  deepest  layer  of 
the  epidermis.    As  in  other  epithelia  of  the  stratified  squamous  type,  the  deepest  cells 

are  columnar  and  lie  with 
Fig.  1 150.  their  long  axes  perpen- 

dicular to  the  supportinjf 
connective  tissue.  The 
basal  ends  of  the  colum- 
nar cells  are  often  slijiht- 
ly  serrated  and  fit  into 
corresponding  indenta- 
tions on  the  corium. 
Their  outer  ends  are 
rounded  and  received 
between  the  super- 
imposed cells.  Succeed- 
ing the  single  row  of 
columnar  elements,  the 
cells  of  the  stratum 
germinativum  assume  a 
pronounced  polygonal 
form,  but  become  some- 
what flatter  as  they 
approach  the  stratum 
granulosum.  The  num- 
ber of  layers  included 
in  the  germir  al  stratum 
is  not  only  uncertain, 
but  varies  with  the  rela- 
tion to  the  papillae,  being  greater  between  than  over  these  projections.  The  finely 
granular  cytoplasm  of  the  cells  of  the  stratum  germinativum  contains  delicate  but 
distinct  fihrilla,  which,  longitudinally  disposed  in  the  deep  columnar  cells,  in  the 
polvgonal  elements  (Fig.  1151),  radiate  from  the  nucleus  towards  the  periphery 
(Kromaycr).  The  fibrillse  are  not  confined  to  the  cells,  but  extend  beyond  and  pass 
across  the  intercellular  lymph-clefts  as  delicate  protoplasmic  bridges  that  connect 
the  units  of  the  \arious  layers  of  the  stratum  and  confer  upon  them  the  character- 
istics of  the  so-called  ' '  prickle  cells. 

The  stratum  granulosum  is  e.xceptionally  well  marked  on  the  palms  and  soles 
and  in  these  localities  includes  from 
two  to  four  rows  of  polygonal  cells, 
SDint'what  horizontally  compressed, 
that  stand  out  conspicuously  in  stained 
sections  by  reason  of  the  intensely 
colored  particlcswithin  theircytoplasm. 
The  nature  of  the  peculiar  substance, 
deposited  within  the  body  of  the  cells 
as  |)articles  of  irregular  form  and  size, 
is  still  uncertain.  To  it  R.invier  gave 
till"  name  of  cicidin  and  Waldeyer  that 
of  keraiohyalin.  .Since  the  nuclei  of 
the  cells  in  which  the  deposits  occur 
always  exhibit  e\idences  of  degenera- 
tion, it  is  probable  that  keratohyalin 
is  in  some  way  derived  from  disintegra- 
tion of  the  nucleus  (Mertsching)  ancl 
represents    ■\    tr.insitinn   st.^s^p    in    the 

process  ending  in  cornification  of   the  succeeding  layers  of  the  cuticle   (Brunn). 

The  stratum  lucidum,  usually  wanting  in  other  localities,  in  the  palm  and 

sole  appears  as  a  thin,  almost  homogeneous  layer,  separating  the  corneous  from  the 


Fihrillje 


Portion  of  horizontal  section  of  skin,  shciwinjf  intracellular 
fihrilla*  within  cells  of  stratum  Rerminativum.     -"  Soo. 


m^ 


THE   SKIN. 


1387 


PiKmenlal 
epidertniH 


granular  layer.  With  the  latter  it  constitutes  the  stratum  intermetlium.  As  indicated 
by  its  name,  the  stratum  lucidum  appears  clear  and  without  distinct  cell  lK)undaries. 
although  suggestions  of  these,  as  well  as  of  the  nuclei  of  the  component  elements,  arc 
usually  distinguishable.  The  cells  of  tha  stratum  lucidum  are  uniformly  cornified 
and  differ,  therefore,  from  those  of  the  overlying  layers  in  which  the  process  is  often 
confined  to  a  mantle  zone.  ... 

The  stratum  corneum  includes  the  remainder  of  the  epidermis  and  consists 
of  many  layers  of  horny  epithelial  cells  that  form  the  exterior  oi  the  skin.  Where 
no  stratum  lucidum  exists,  as  is  usually  the  case,  the  corneous  layer  rests  uixin  the 
stratum  granulosum,  from  which  its  horny  elements  arc  being  continually  recruited. 
During  their  migration  towards  the  free  surface,  the  cells  lose  their  vitality  and 
become  more  flattened  until  the  most  superficial  ones  are  converted  into  the  dead 
homy  sc.iles  that  are  being  constantly  displaced  by  abrasion. 

The  pigmentation  of  the  skin,  which  even  in  white  races  is  conspicuous  in 
certain  regions  (page  1381),  depends  upon  the  presence  of  colored  j)articles  chiefly 
within  the  epidermis,  although,  when  the  dark  hue  is  pronounced,  a  few  small 
branched  pigmental  connective 

tissue  cells  may  appear  within  '"'*'■  ' 

the  subjacent  corium.  The  dis- 
tribution of  the  pigment  particles 
varies  with  the  intensity  of  color, 
in  skins  of  lighter  tints  being 
principally,  and  sometimes  en- 
tirely, limited  to  the  columnar 
cells  next  the  corium.  With 
increasing  color  the  pigment 
particles  invade  the  neighlxaring 
layers  of  epithelium  until,  in  the 
dark  skin  of  the  negro,  they 
are  found  within  the  cells  of  the 
straivnn  corneum  but  always 
in  diminishing  numbers  towards 
the  iree  surface.  Even  when 
the  cells  are  dark  and  densely 
packed,  the  colored  particles 
never  encroach  upon  the  nuclei, 
which,  therefore,  appear  as  con- 
spicuous pigment  free  areas.  _  i.  ■  t  a 
The  source  of  the  pigment  within  the  epidermis  is  uncertain,  bv  some  being  found 
in  an  assumed  transference  of  the  colored  particles  from  the  corium,  by  means 
of  wandering  cells  or  of  the  processes  of  pigmented  connective  tissue  cells  that 
penetrate  the  cuticle,  and  by  others  ascribed  to  an  independent  origin  »w  siOt 
within  the  epithelial  elements.  While  it  may  be  accepted  as  established^  that  at 
times  the  connective  tissue  cells  are  capable  of  modifying  pigmentation  (Karg),  it 
is  equally  certain  that  the  earliest,  and  probably  also  later,  intracellular  pigmenta- 
tion of  the  epidermis  appears  without  the  assistance  of  the  connective  tissue  or 
migratory  cells. 

The  blood-vessels  of  the  skin  arc  confined  to  the  connective  tissue  portion 
and  never  enter  the  cuticle.  The  ar/trics  are  derived  either  from  the  trunks  of  the 
subjacent  layer  as  special  cutaneous  branches  destined  for  the  integument,  or  indi- 
rectly from  muscular  vessels.  When  the  blood  supply  is  generous,  as  in  the  palms 
and  soles  and  other  regions  subjected  to  unusual  pressure  or  exposure,  the  arteries 
ascend  through  the  subdermal  layer  to  the  deeper  surface  of  the  corium  where, 
having  subdivided,  thev  anastomose  to  form  the  subcutaneous  plexus  (rcte  artcriosum 
cutaneum).  P>om  the  latter  some  twigs  sink  into  the  subdermal  layer  and  contribute 
the  capillary  net-works  that  supply  the  adii>ose  tissue  antl  the  sebaceous  glands. 

Other  twigs,  more  or  less  numerous,  pass  outward  through  the  deeper  part  of 
the  corium  and  vvithin  the  more  superficial  stratum  unite  into  a  second,  subpapillary 
plexus  (rete  arteiiosum  subpapillare),  that  extends  parallel  to  the  free  surface  and 


Section  of  skin,  surroundinK  anus.  showinR  pigmentation  of  deeper 
layer  of  epidermis.    >  50. 


w^m 


1388 


HUMAN   ANATOMY. 


Fig.  1 153. 


1 
ui 


Papilla  r> 
loops 


beneath  the  bases  of  the  papilke.  The  latter  are  supplied  by  the  terminal  twigs  whicli 
ascend  vertically  from  the  subpapillary  net-work  and  break  up  into  capillary  loops 
that  occupy  the  papillae  and  lie  close  beneath  the  epidermis  (Fig.  11 53).  With  the 
exception  of  the  loops  entering  the  hair-papilla,  the  capillaries  enclosing  the  hair- 
follicles  arise  from  the  subpapillary  plexus. 

The  arrangement  of  the  cutaneous  veins,  more  complex  than  that  of  the  arteries, 
includes  four  plexuses  (retes  veoosum)  lying  at  different  levels  within  the  corium  and 

extending  parallel  to  the 
surfaces.  The  first  and 
most  superficial  one  is 
formed  by  the  union  of 
the  radicles  returning  the 
blood  from  the  papilla-. 
The  component  veins  lie 
below  and  parallel  to  the 
rows  of  papillx  and  im- 
mediately beneath  the 
bases  of  the  latter.  At 
a  slighdy  lower  level,  in 
the  deeper  part  of  the 
stratum  [>apillare,  the  ve- 
nous channels  proceeding 
from  the  subpapillary  net- 
work join  to  form  a  second 
plexus  with  polygonal 
meshes.  A  third  occurs 
about  the  middle  of  the 
corium,  while  the  fourth 
shares  the  position  of 
the  subcutaneous  arterial 
plexus  at  the  junction  of 
the  corium  and  subdermal 
strata.  The  deepest  plexus 
receives  many  of  the 
radicles  returning  the 
blood  from  the  fat  and 
the  sweat  glands,  the  re- 
mainder being  tributary* 
to  the  veins  accompany- 
ing the  larger  arteries 
as  they  traverse  the  tela 
subcutanea. 

The  lymphatics  of 
the  skin  are  well  repre- 
sented by  a  close  super- 
ficial plexus  within  the 
papillary  stratum  of  the 
corium  into  which  the 
terminal  lymph-radicles  of 
the  papilla;  empty.  The 
relation  of  these  channels  to  the  interfascicular  connective  tissue  spaces  is  one  only 
of  indirect  comiminication,  since  the  lymphatics  are  provided  v/ith  fairly  complete 
endothelial  walls.  It  is  probable  tliat  the  lymph-paths  within  the  papillae  are  closely 
related  to  the  intercellular  clefts  of  the  epidermis,  according  to  Unna,  indeed,  direct 
communications  existintr.  Mieratory  leucocytes  often  find  their  way  into  the  cuticle 
where  they  then  appear  as  the  irregulariv  stellate  cells  of  Lans^crhans  seen  between 
the  epithelial  elements.  A  wiile-ineshed  deep  plexus  of  lymphatics  is  formed  within 
the  subdermal  layer,  from  which  the  larger  lymph-trunks  pass  along  with  the 
subcutaneous  blood-vessels. 


5>ection  of  injected  skin,  showinj^  general  arrangement  ot  bIoo<l- vessels.    X  40. 


THE   HAIRS. 


1389 


The  numerous  nerves  within  the  highly  sensitive  integument  are  chiefly  the 
peripheral  processess  of  sensory  neurones  which  terminate  in  free  arborizations  between 
the  ephithelial  elements  of  the  cuticle,  or  in  relation  with  special  endings  located,  for 
the  most  part,  within  the  corium  or  subdermal  connective  tissue.  Some  sympathetic 
fibres,  however,  are  present  to  supply  the  tracts  of  involuntary  muscle  that  occur  within 
the  walls  of  the  blood-vessels  or  in  association  with  the  hairs  and  the  sweat  glands. 

On  entering  the  skin  the  medullated  nerves  traverse  the  subdermal  layer,  to 
which  they  give  ofl  twigs  in  their  ascent,  and,  passing  into  the  corium,  within  the 
papillary  stratum  divide  into  a  number  of  branches.  Those  destined  for  the  epidermis 
beneath  the  latter  break  up  into  many  fibres  which,  losing  their  medullary  substance, 
enter  the  cuticle  and  end  in  arborizations  that  ramify  between  the  epithelial  cells  as  far 
as  the  outer  limits  of  the  stratum  germinativum.  The  ultimate  endings  of  the  librillx, 
whether  taperingorslightlyknobbed,  always  occupy  the  intercellular  channels  and  are 
never  directly  connected  with  the  substance  of  the  epithelial  elements.  According  to 
Merkel,  special  tacUle  cells,  (Fig.  867)  occur  in  the  human  epidermis,  particularly 
over  the  abdomen  and  the  thighs.  These  cells,  spherical  or  pyriform  in  shajx;  and 
composed  of  clear  cytoplasm,  occupy  the  deeper  layers  of  the  cuticle  and,  on  the  side 
directed  towards  the  corium,  are  in  contact  with  the  end-plate  or  meniscus  of  the  nerve. 

The  nerve-fibres  particularly  concerned  with  the  sense  of  touch  terminate  within 
the  connective  tissue  portion  of  the  skin,  either  within  the  corium  in  special  end-organs 
—the  tactile  bodies  of  Meissner,  the  end-bulbs  of  Krause,  the  genital  corpuscles  and 
the  end-organs  of  Ruflini,  or  within  the  subdermal  layer  in  the  Vater-Pacinian  cor- 
puscles, or  their  modifications,  the  Golgi-Mazzoni  corpuscles.  The  structure  of  these 
special  end-organs  is  elsewhere  described  (pages  1018,  1019),  their  chief  locations 
being  here  noted. 

Meissner's  corpuscles  (Fig.  872)  are  especially  numerous  in  the  tactile 
cushions  on  the  flexor  surface  of  the  hands  and  feet.  While  much  more  plentiful  in 
all  the  tactile  pads  than  in  the  intervening  areas,  the  touch  corpuscles  are  most 
abundant  in  those  on  the  volar  surface  of  the  distal  phalanges,  where  they  approxi- 
mate twenty  to  the  square  millimeter  (Meissner).  Their  favorite  situation  is  the 
apex  of  the  papill<e,  where  they  appear  as  elongated  elliptical  botlies,  sometimes  in 
pairs,  whose  outer  pole  lies  immediately  below  the  epidermis.  These  corpuscles  are 
additionally,  although  sparingly,  distributed  on  the  dorsum  of  the  hand,  the  flexor 
surface  of  the  forearm,  the  lips,  the  eyelids,  the  nipple  and  the  external  genital  organs. 

The  Vater-Pacinian  corpuscles  (  Fig.  874)  are  well  represented  in  the  hands 
and  feet  and  usually  occupy  the  subdermal  tissue,  although  sometimes  found  within  the 
corium.  Their  distribution  corresponds  closely  to  that  of  Meissner's  corpuscles,  they 
being  most  numerous  beneath  the  tactile  cushions  in  the  order  above  described. 

The  Golgi-Mazzoni  corpuscles  are  modifications  of  the  Pacinian  bodies  and, 
like  the  latter,  are  found  within  the  subdermal  tissue. 

The  end-bulbs  of  Krause  (Fig.  869)  occur  within  the  corium,  either  slightly 
below  or  within  the  papilla,  on  the  lips  and  external  genital  organs,  :is  well  as 
probably  in  other  regions. 

The  genital  corpuscles  (Fig.  870)  lie  within  the  corium  of  the  modified  skin 
covering  the  glans  penis  and  the  prepuce  and  the  clitoris  and  surrounding  parts  of 
the  nymphie. 

The  end-organs  of  Ruffini  resemble  the  sensory  terminations  in  tendons 
(page  1017)  and  lie  within  the  deeper  parts  of  the  corium,  often  associated  with  the 
Pacinian  bodies. 

The  mode  of  ending  of  the  nerves  supplying  the  hairs  and  sweat  glands  will  be 
described  in  connection  with  those  structures  (pages  1394.  1400). 


THE  HAIRS. 

The  appendages  of  the  skin — the  hairs,  nails  and  cutaneous  glands — are  all 
specializations  of  the  epidermis  and  are.  therefore,  cxchisivety  of  ertnbl.nstic  origin. 

The  hairs  (pill)  are  present  over  almost  the  entire  body,  the  few  localities  in 
which  they  are  absent  being  the  flexor  surface  of  the  hands  and  feet,  the  extensor 
aspect  of  the  terminal  segment  of  the  fingers  and  toes,  the  inner  surface  of  the 


»390 


HLMAN  ANATOMY. 


prepuce  and  of  the  nymphs  and  the  glans  penis  and  clitoridis.  With  the  exception  of 
those  regions  in  which  the  growth  is  sufficiently  long  to  constitute  a  complete  cover- 
ing— the  scalp,  bearded  parts  of  the  face  in  the  male,  aAillx  and  mons  pubis — the 
hairs  are  for  the  most  part  short  and  scattered,  although  subject  to  great  individual 
variation  and  sometimes  to  remarkable  redundance. 

The  hairs  in  various  locations  are  known  by  special  names  ;  those  of  the  scalp 
being  capil/i ;  of  the  eyebrows,  supercilia  ;  of  the  eyelashes,  cilia  ;  of  the  nostrils, 
vibrissa;  of  the  external  ear,  tragi ;  of  the  beard,  barba  ;  of  the  axillje,  hirci ;  of 
the  pubes,  pubes  ;  while  the  fine  downy  haire  that  cover  other  parts  of  the  body  are 
designated  lanugo. 

The  closest  set  hairs  are  on  the  scalp,  where,  according  to  Brunn,  on  the  vertex 
they  number  from  300-320,  and  in  the  occipital  and  frontal  regions  from  200-240 
per  square  centimeter.     On  the  diin  44  were  counted,  on  the  mons  pubia  30-35, 


Epidermis 


Sdiueoiu  fbiixl 


Erector  miucle 


Sweat  gland 


Hair-papilla 


Paniculua 
adipotua 


Section  of  Kalp,  showing  longitudinally  cut  hair-follicles.    X  14. 


on  the  extensor  surface  of  the  forearm  24  and  on  the  back  of  the  hand  18  for  like 
areas.  Even  where  their  distribution  is  seemingly  uniform,  close  inspection  shows 
the  hairs  to  be  arranged  in  groups  of  from  two  to  five. 

The  length  of  the  hairs  includes  the  extremes  presented  by  the  lanugo,  only  a 
few  millimeters  long,  on  the  one  hand,  and  by  the  scalp-growth,  sometimes  measur- 
ing 150  cm.  (loS  in.)  or  more,  on  the  other.  Their  thickness,  likewise,  shows 
much  variation,  not  only  in  different  races,  individuals  and  regions,  but  also  in  the 
same  person  and  part  of  the  body,  as  on  the  scalp  where  fine  and  coarse  hairs  may 
lie  side  by  side.  The  thickest  scalp-hairs  have  a  diameter  of  .162  mm.  and  the 
finest  one  of  .011  mm.,  with  all  intermediate  sizes.  The  hairs  of  the  beard  vary 
from  .101-.203  mm.  and  those  on  the  pubes  from  .054-.  135mm.  (Falck).  In  a 
general  way  hairs  of  light  color  are  finer  than  dark  ones,  the  respective  diameters  of 
blond,  brown  and  black  hairs  being  .047,  .054  and  .067  mm.  (Wilson).  On 
at^aining  their  full  growth  without  mutilation,  hairs  do  not  possess  a  uniform  thick- 
ness throughout  their  length,  since  they  diminish  not  only  towards  the  tip,  where  the 
shaft  ends  in  a  point,  but  also  towards  the  root.  This  feature  is  most  evident  in 
short  hairs,  as  in  those  of  the  eyebrows. 

The  color  of  the  hair,  which  varies  from  the  lightest  straw  to  raven  black,  is 
closely  associated  with  racial  and  individual  characteristics,  being  usually,  but  by  no 


THE   HAIRS. 


"3y« 


means  always,  in  harmony  with  the  degree  of  general  pigmentation.  The  lattet  is 
commonly  uniform  throughout  the  length  of  the  hair,  hut  in  rare  c;tses  it  may  \k-  so 
variable  that  the  shaft  presents  a  succession  of  alternating  light  and  dark  zones 
(Brunn).  The  straight  and  curly  varieties  of  hair  ilefiend  chicHy  u|M>n  diflercmes  in 
the  curvature  of  the  follicle  '  and  the  form  of  the  hair.  In  the  ciise  of  straight  hairs 
the  follicle  is  unbent  and  the  shaft  is  cylindrical,  and  therefore  circular  in  cross- 
section  ;  hairs  that  are  wavy  or  curly  spring  from  follicles  more  or  less  IkiU  and  are 
flattened  or  grooved,  with  corresponding  oval,  reniform,  irn-gularly  triangular  or 
indented  outlines  when  transversely  cut. 

Arrangement  of  the  Hairs. — Since  the  buried  part  of  the  hair,  the  root,  is 
never  vertical  but  always  oblique  to  the  surface  of  the  skin,  it  follows  that  the  free 
part,  the  sJia/t,  is  also  inclined.  The  direction  in  which  the  hairs  jwint,  however,  is 
by  no  means  the  same  all  over  the  body,  but  varies  in  different  regions  although 
constant  for  any  given  area.  This  disposition  depends  upon  the  peculiar  placing 
of  the  hair-roots  which  in  certain  localities  incline  towards  one  another  along 
definite  lines,  an  arrangement  that  results  in  setting  the  shafts  in  opposite  directions. 
As  these  root-lines  are  not  straight  but  spiral,  on  emerging  from  the  skin  the  hairs 
diverge  in  whorls  (vortict.  -ilorum),  the  position  and  number  of  which  are  fairly 
definite. 

Such  centres  include :  (i )  the  coaspicuous  vertex  whorl  on  the  head,  usually  single  but 
sometimes  double;  (a)  Hu:  facial  whorls  surrounding  the  openings  of  the  eyelids;  (3)  the 
auricular  whorls  at  the  external  auditory  meatus  ;  (4)  the  axillary  whorls  in  the  armpits  ;  and 
(5)  the  inguinal  whorls,  just  below  the  groin  ;  additional  (6)  but  less  constant  lateral  whorls 
.nay  be  located,  one  on  each  side,  about  midway  between  the  axilla  and  the  iliac  crest  and 
(Kjmewhat  beyond  the  outer  border  of  the  rectus  muscle. 

These  whorls,  all  paired  except  the  first,  apportion  the  entire  surface  of  the  body  into 
certain  districts,  each  covered  by  the  hairs  proceeding  from  the  corresponding  vortex.  The 
whorl-dlstricts,  moreover,  are  irregularly  subdivided  into  secondary  areas  by  lines,  the  hmir- 
rangea  (flumlna  pilontm),  along  which  the  hairs  diverge  in  opposite  directions.  Additional  lines, 
the  converging  hair-rangca,  mark  the  meeting  of  tracts  pointing  in  different  directions  and  in 
places  also  assume  a  spiral  course.  In  consequence  of  these  peculiarities  the  body  is  aivered 
with  an  elaborate  and  intricate  hair-pancm,  that  is  most  evident  on  the  fcetus  towards  the  close 
of  gestation  ;  later  in  life  the  details  of  the  pattern  are  uncertain  owing  to  its  partial  eflfacement 
by  the  constant  rubbing  of  clothing. 

Structure.— Each  hair  consists  of  two  parts,  the  shaft,  which  projects  beyond 
the  surface,  and  the  root,  which  lies  embedded  obliquely  within  the  skin,  the  deepest 
part  of  the  root  expanding  into  a  club-shaped  thickening  known  as  the  bulb.  The 
root  is  covered  with  a  double  investment  of  epithelial  cells,  the  inner  and  outer  root- 
sheaths,  which,  in  turn,  are  surrounded  by  a  connective  tissue  envelope,  the  theca. 
Th  'ntire  sac-like  structure,  consisting  of  the  hair-root  and  its  coverings,  constitutes 
the  hair-follicle  (folliculus  pili).  At  the  bottom  of  the  latter,  immediately  beneath 
the  bulb,  the  wall  of  the  follicle  is  pushed  upward  to  give  place  to  a  projection  of 
connective  tissue,  the  hair-papilla',  which  cames  the  capillary  loops  into  close  relation 
with  the  cells  ■  "wt  active  in  the  production  of  the  hair.  Save  in  the  case  of  the 
finest  hairs  ('  ugo),  which  are  limited  to  the  corium,  the  hair-follicles  traverse  the 
latter  and  end  at  varying  levels  within  the  fat-laden  subdermal  layer  (panniculus 
adiposus).  In  a  general  way  the  follicle  may  be  regarded  as  a  narrow  tubular  invagi- 
nation of  the  epidermis,  at  the  bottom  of  which  the  hair  is  implanted  and  from  the 
entrance  of  which  the  shaft  projects.  The  most  contracted  part  of  the  follicle,  the 
neck,  lies  at  the  deeper  end  of  the  relatively  wide  funnel-shaped  entrance  to  the  sac. 
Closely  associated  with  the  hair-follicle,  which  they  often  surround,  are  the  sebaceous 
glands  that  pour  their  oily  secretion  at  the  upper  third  of  the  follicle  into  the  space 
between  the  shaft  and  the  wall  of  the  sac. 

The  Hair-Shaft. — In  many  thick  hairs,  but  by  no  means  in  all,  three  parts 
can  be  distinguished — the  cuticle,  the  cortex  and  the  mfdvlla.  The  latter,  however, 
is  usually  wanting  in  hairs  of  ordinary  diameter,  being  often  also  absent  in  those  of 
large  size. 

'  Frederic  :  Zeitschr.  (.  Morph.  u.  Anthropol.,  Bd.  ix.,  1906. 


1393 


HUMAN   ANATOMY. 


Fic.  ii5j. 


The  Ctttid*  of  the  hair  appears  as  a  transparent  outermost  layer  marked  by  a  net-work  of 
fine  sinuoai  lines,  the  irregular  meshes  ot  which  have  their  kNigest  diameter  placed  obli(|ut-!y 
transverse.    These  lines  corresp»jnd  to  the  free  borders  of  extremely  thin  glassy  cuticle-platfs 

that  overlie  the  hair  as  tiles  on  a  roof,  the  imbrication  involv- 
inK  from  four  to  six  layers.  Seen  in  profile  (Kig.  1155).  th«^ 
contour  of  the  hair-«haft,  therefore,  is  not  smooth  Init  serratrd, 
the  minute  teeth  formed  by  the  free  margins  of  the  scales 
lieinK  directed  towards  the  tip  of  the  hair.  After  isolation  by 
suitable  reagents,  the  cuticular  elements  appear  as  transparent 
structureless  cslls,  quadrilateral  in  outline  and  curved  to  con- 
form to  the  hair-shait  which  they  cover. 

The  cortical  substance,  often  indeed  constituting  practi- 
cally the  entire  shaft,  consists  ot  elongated  fusiform  cells  so 
compactly  arranged  that  the  individual  elements  are  only  dis- 
tinguishable after  the  action  of  disassociating  reagents.  In 
addition  to  the  remains  of  the  shrunken  nuclei  the  Aair- 
spindlfs,  as  these  modified  epithelial  cells  are  called,  possess 
fibrillx  that  pass  between  adjacent  cells  similar  to  the  inter- 
cellular bridges  in  the  epidermis.  A  variable  amount  of 
pigment,  present  either  as  a  diffuse  tint  of  the  spindles,  or  as 
granules  within  or  between  the  same,  is  -x  mn  ,t.nnt  ccn-titucnt 
of  the  cortical  substance.  In  blond  hair  the  color  is  chiefly 
diffuse,  the  pigment  granules  being  often  entirely  wanting  ;  in 
hair  of  darker  shades,  the  granules  predominate  and  increase  in  intensity  of  color  as  well  a.s 
in  qiuintity.  As  the  hair  grows  ou*ward  from  the  bulb,  it  loses  much  of  its  moisture,  and  in 
consequence  later  contains  minute  air-vesicles  that  replace  the  fluid  previously  occupying  the 
clefts  between  the  hair-spindles.  Even  when  conspicuous,  the  medulla  does  not  extend  the 
entire  length  of  the  hair,  often  being  interrupted  and  always  disappearing  before  reaching  the  tip. 
The  medulla,  when  well  represented,  is  seen  as  an  axial  stripe,  somewhat  uneven  in  outline, 
that  varies  with  illumin'  'ion,  with  transmitted  light  appearing  as  a  dark  band  and  with  reflected 
light  as  a  light  one.  Thi.-.  pf-culiarity  depends  upon  the  presence  of  air  imprisoned  between  the 
shrunken  and  irregular  »w  dntlary  <•<•/&— -dried  and  comified  epithelial  elements  which  are  con- 
nected by  branching  proc'sses  into  a  net-work  incompletely  filling  the  medulla.  The  air  within 
the  shaft  is  a  factor  modifying  the  color  of  the  hair,  since  the  resuking  reflex  tends  to  lessen  the 
intensity  of  the  tint  direcdy 


Portion  o(  ibaft  of  hair:  h,  ihatt 
covered  witli  cuticle;  j,  cuticle  re- 
moved to  expose  cortical  aubatance; 
M,  medulla  .-135.  a,  d,  iiolatcd  cella 
of  cuticle  and  of  cortical 
respectively.   X  340. 


referable  to  the  pigment ; 
this  diminution  affects  par- 
ticular)' the  lighter  shades, 
as  in  dark  hairs  the  large 
amount  of  pigment  masks 
the  reflex. 


Fig.  1 1 56. 


Uuter  rtnt'Sheaih 


Hair  surrounded  by 
inner  root-sheatli 


Adipose  tissue 


The  Hair-Folli- 
cle.— This  structure 
consists  essentially  of 
( I )  a  connective  tissue 
sheath,  the  theca,  con- 
tributed by  the  cerium ; 
( 2)an  epithelial  lining, 
the  outer  rovl-sheath, 
continued  from  the 
deepest  layer  of  the 
epidermis;  and  (X)  the 
inner  root-sheath,  an 
epithelial  investment 
probably  differentiated 
within  the  follicle,  and 
not  a  direct  prolonjra- 
tion  from  the  cuticle. 

The  theca  folliculi  includes  three  strata  :  an  outer,  composed  of  loosely  db- 
posed  longitudinal  bundles  of  fibrous  tissue  with  few  cells  and  elastic  fibres  ;  a  middle 
one,  made  up  of  closely  placed  circular  bundles ;  and  a  very  thin,  homogeneous 
inner  coat,   the   ii^lassy  membrane,  which  represents  an  unusually  w'.'U   developed 


Fibrous  tissue 


Horizontal  section  of  scalp,  showing  iroup  of  transveraely  cut 
hair-lollicles,     X  65. 


THE  HAIRS. 


«39.^ 


basement  membrane  separating  corium  from  cuticle,  (jreatly  attenuated,  it  is 
prolonged  over  the  hair-papilla,  which,  as  a  special  vaiicularized  thickfninjj  of  the 
connective  tissue  of  the  follicle,  carries  nutrition  to  the  bulb  of  the  growing;  hair. 

The  outer  root-theath  is  the  continuation  of  the  stratum  gcrminativunt  alone, 
the  other  layers  of  the  epidermis  thinning  out  and  disapptarinR  iK-forc  reaching  the 
neck  of  the  follicle.  Its  cells  present  the  characteristics  of  those  of  the  germinating 
layer,  with  exceptionally  well  marked  fibrilKe.  On  approaching  the  lc\el  of  the 
papl'^a,  the  outer  root-sheath,  which  farther  above  consists  of  numerous  layers, 
rapidly  diminishes  in  thickness  until,  on  the  sides  of  the  papilla,  it  is  reduced  to  a 
single  row  of  low  columnar  cells. 

The  inner  root-theath,  which  b  best  developed  over  the  middle  third  of  the 
hair-root  and  fades  away  on  reaching  the  upper  third,  includes  three  layers.  The 
outer,  known  as  Henle's  layer,  consists  of  a  single  row  of  flat  polygonal  cells,  often 
partially  separated  by  ovaf  spaces.      Their  nuclei  are  very  indistinct  or   invisible 


Fio.  1157. 


Thcca  funiculi 


Middle  layer 


Hcnie't  layer 
oi  inner  root-sheath 


Outer  root-sheath 


Tranaverse  lection  of  hairfollicle,  showing  hair  ■urronnded  by  internal  and  external  root-sheaths.    :■  285. 

within  the  comilied  cytoplasm.  The  middle  or  Huxley's  layer,  also  hoi^ny  in 
nature,  often  comprises  only  one  stratum  of  nucleated  cuboid;il  cells,  but  in  the 
thicker  hairs  two  or  even  three  rows  of  irregularly  interlocked  cells  may  be  preseiit. 
The  third  layer,  known  as  the  sheath  aiHcle,  resembles  the  external  coat  of  the  hair, 
against  which  it  lies,  in  being  extremely  thin  and  composed  of  flat  horny  plate-.,. 
The  latter,  however,  are  always  nucleated  and  so  disposed  that  they  are  opposed  to 
the  serrations  of  the  thicker  hair-cuticle. 

Traced  towards  the  bottom  of  the  follicle,  the  root-sheaths  and  the  hair,  which  above  are 
sharply  defined  from  one  another,  become  more  and  more  alike  until,  in  the  immediate  vicinity 
of  the  hair-papilla,  they  blend  into  a  still  imperfectly  differentiated  mass  of  cells.  The  deepest 
elements  of  this  complex,  however,  are  cutioidal  or  low  columnar  and  form  an  uninterrupted 
tract  over  the  papilla,  continuous  with  the  outtmnost  crlts  of  tlie  outer  root-sheath.  It  is  fmtn 
the  proliferation  of  these  deepest  cells  that  the  formative  material,  or  matrix,  is  provided 
to  meet  the  requirements  of  growth  and  replacement  of  the  hairs.  Without  anticipating  the 
account  of  the  detailed  changes  described  in  connection  with  the  development  of  the  hair 
(page  1401 ),  it  may  be  here  noted  that  of  the  three  parts  of  the  hair,  the  medulla  is  produced  by 

88 


^ 


1394 


HUMAN   ANATOMY. 


the  cells  overlying  the  summit  of  the  papilla,  while  those  converted  into  the  cortical  substance, 
cuticle  and  inner  root-sheath  occupy  the  sides  of  the  papilla  and  deepest  part  of  the  follicle. 

With  few  exceptions,  the  hair  follicles  are  associated  with  two  or  more 
sebaceous  glands,  rarely  with  only  one,  the  ducts  of  which  open  into  the 
sac  in  the  vicinity  of  the  neck.  The  glands  usually  lie  on  the  side  towards  which 
the  hair  inclines,  but  sometimes,  especially  in  the  case  of  the  smaller  hairs,  they  may 
completely  surround  the  follicle.  Since  these  glands  are  outgrowths  from  the  srme 
tissue  that  lines  the  follicles,  their  ducts  pierce  the  outer  root-sheath,  bringing  their 
oily  secretion  into  direct  relation  with  the  hairs. 

The  structure  of  the  sebaceous  glands  is  described  with  the  cutaneous  glands 
(page  1397). 

Most  of  the  larger  hair-follicles,  particularly  those  of  the  scalp,  are  provided  with 
ribbon-like  bundles  of  involuntary  muscle,  called  the  arrectores  pilonim  in  recog- 
nition of  their  effect  on  the  hairs.    They  arise  from  the  superficial  part  of  the  corium, 

passobliquelydownwardto  be  inserted 


Fig.  1 158. 


W^^ 


mto  the  sheath  of  the  hair-follicle  near 
the  junction  of  corium  and  subdermal 
tissue  and  on  the  side  corresf>onding 
with  the  inclination  of  the  hair  and 
the  situation  of  the  sebaceous  glands. 
Since  the  latter  are  closely  embraced 
by  the  muscular  bands,  contraction  of 
the  muscles  exerts  pressure  u[)on  the 
glands  and  facilitates  the  discharge  of 
their  secretion  (^sebum) — hence  these 
muscles  are  sometimes  also  designated 
expressores  sebi.  The  effect  of  con- 
traction of  the  arrectores  pilorum  is 
often  conspicuously  seen  on  the  surface 
in  the  condition  known  as  "goose- 
flesh"  {cutis  anseriHd),'>K\i&[e.the  hairs 
and  surrounding  tissue  appear  to  be 
unusually  elevated  owing  to  the 
upward  pull  on  the  hair-follicles  and 
the  consequent  erection  of  the  hairs 
in  the  opposite  direction. 

The  blood-vessels  supplying 
the  hair-follicle,  which  in  a  sense  con- 
stitute a  special  system  for  each  sac,  include  the  capillary  loops  ascending  within  the 
hair-papilla  and  the  net-work  of  capillaries  surrounding  the  follicle  immediately  outside 
the  glassy  membrane.  The  first  are  derived  from  a  small  special  twig  that  ascends 
to  the  follicle,  and  the  second  from  the  subpapillary  net-work  of  the  corium.  With 
the  exception  of  those  draining  the  papilla,  which  are  tributary  to  the  deeper  stems, 
the  veins  join  the  subpapillary  plexus. 

The  nerves  distributed  to  the  follicles  follow  a  fairly  definite  arrangement.  As 
shown  by  Retzius,  usually  each  hair-sac  is  supplied  by  a  single  fibre,  sometimes  by 
two  or  more,  which  approaches  the  follicle  immediately  below  the  level  of  the  mouth 
of  the  sebaceous  glands.  After  (jenetrating  the  fibrous  sheath  as  far  as  the  glassy 
membrane,  the  nerve-fibre  separates  into  two  divisions  that  encircle  more  or  less 
completely  the  follicle  and  on  the  opposite  side  break  up  into  numerous  fibrillae 
constituting  a  terminal  arborization.  The  nerve-endings  usually  lie  on  the  outer 
surface  of  the  glassy  membrane  within  the  middle  third  of  the  follicle  and  only 
exceptionally  are  found  within  the  outer  root-sheath  or  the  hair-papilla. 

THE  NAILS. 

The  nails  (untpies),  the  homy  plates  overlying  the  ends  of  the  dorsal  surfaces  of 
the  fingers  and  toes,  correspond  to  the  claws  and  hoofs  of  other  animals  and,  like 
them,  are  composed  exclusively  of  epithelial  tissue.     They  are  specializations  of  the 


Plpillary 


Portion  of  section  of  injected  tcalp,  show'i  j-  rapil!ary 
net-works  surrounding  liair-fotticles  and  twigA  enteriflf 
papilUc.     <  20. 


THE    NAILS. 


1395 


epidermis  and,  therefore,  may  be  removed  without  mutilation  when  the  cuticle  is 
taken  off  after  maceration. 

The  entire  nail-plate  is  divided  into  the  body  (corpus  unguis).  whii.n  includes 
the  exposed  portion,  and  the  root  (radix  unguis),  which  is  embedded  beneath  the 
skin  in  a  pocket-like  recess,  the  nail-groove  (sulcus  unguis).  The  modified  skin 
supporting  the  nail-plate,  both  the  body  and  the  root,  constitutes  the  nail-bed 
(solum  unguis),  the  cutaneous  fold  overlying  the  root  being  the  nail-wall  (vallum 
unguis). 

The  side°  of  the  quadrilateral  nail-plate  are  straight  and  parallel  and  at  their 
distal  ends  connected  by  the  convex  free  margin  (margo  liber)  that  projects  for  a 
variable  distance  beyond  the  skin.  The  proximal  buried  border  (margo  occultus)  is 
straight  or  slighriy  concave,  more  rarely  somewhat  convex,  and  often  beset  with 
minute  serrations  (Brunn).  Both  surfaces  of  the  transversely  arched  nail  are  smooth 
and  even,  with  the  exception  of  the  longitudinal  parallel  ridges  that  often  mark  the 
upper  aspect.  Inspection  of  the  latter  during  life  shows  color-zones,  the  translu- 
cent whitish  crescent  formed  by  the  projecting  portion  of  the  nail  being  immediately 
followed  by  a  very  narrow  yellow  band  that  corresponds  to  the  line  along  which  the 
stratum  comeum  of  the  underlying  skin  meets  the  under  surface  of  the  plate.     The 


Diatal  pontons  o(  fingen,  ahowinK  rctations  o(  nail ;  A  wu  drawn  from  livins  rabject ;  B  mnd  C  are  lateral  and 
under  vei«n  respectively  of  Inner  surface  of  cuticle  with  nail ;  nothing;  but  the  epidermal  structures  are  present,  the 
cuticle  and  nail  having  been  removed  together,  a.  A.  distal  and  proximal  borders  of  nail ;  r,  under  surnce  of  nail ; 
rf,  nail  in  section ;  e,  Ibie  of  dellectioii  of  cuticle  to  under  surface  of  nail ;  /,  lunula ;  g,  nail-wall ;  h,  cuticle  in  section. 

succeeding  and  larger  part  of  the  nail  is  occupied  by  the  broad  pink  zone  which  owes 
its  rosy  tint  to  the  blending  of  the  color  of  the  blood  in  the  underlying  capillaries 
with  that  of  the  horny  substance.  On  the  thumb  constantly,  but  on  the  fingers  often 
only  after  retraction  of  the  cuticle,  is  seen  a  transversely  oval  white  area,  the 
so-called  lunula,  which  marks  the  position  of  the  underlying  matrix.  Additional 
white  spots,  irregular  in  position,  form  and  size,  are  sometimes  seen  as  temporary 
markings. 

The  thickness  of  the  nail-plate — greatest  on  the  thumb  and  large  toe  and  least 
on  the  last  digits — diminishes  towards  the  sides,  but  in  the  longitudinal  direction, 
between  the  lunula  and  the  free  margin  of  the  nail,  is  fairly  uniform  ;  beneath  the 
white  area,  however,  the  under  surface  of  the  nail  shelves  of!  towards  the  buried 
border,  where  it  ends  in  a  sharp  edge. 

Structure. — The  substance  of  the  nail-plate  (stratum  comeum  unguis)  consists 
entirely  of  flattened  homy  epithelial  cells,  very  firmly  united  -tntl  containing  the 
remains  of  their  shrunken  nuclei.  These  cornified  scales  are  1.  isposed  in  lamellx, 
which,  in  transverse  section,  pursue  a  course  in  general  parallel  with  the  dorsal  sur- 
fact;.  In  nails  which  pos.sess  the  longitudinal  rid>;i:s,  however,  the  latter  coincide 
with  an  upward  arching  of  the  lamellae  dependent  upon  the  conformation  of  the 
nail  matrix  (Brunn).     In  longitudinal  section  the  lamellation  is  oblique,  extending 


1396 


HUMAN  ANATOMY. 


from  above  downward  and  forward,  parallel  to  the  shelving  under  surface  beneath  the 
white  area  that  rests  upon  the  matrix.  Minute  air- vesicles,  imprisoned  between  the 
horny  scales,  are  constant  constituents  of  the  nail-substance.  When  these  occur  in 
unusual  quantities,  they  give  rise  to  the  white  spots  in  the  nail  above  mentioned. 
Corresponding  respectively  to  the  colored  zones— the  white,  rosy  and  yellow— 
the  dorsal  surface  of  the  nail,  the  nail-bed  is  divided  into  a  pro.ximal. 


seen  on 


Fig.  ii6o. 


Subculineoiu  tinuc 
Stratum  germinativum 
Stratum  comeum 


Transformation 
zone 


Matrix 


Longitudinal  Mction  of  proximal  part  of  nail  lying  within  the  nail  groove.    X  3». 

a  middle  and  a  distal  region,  each  of  which  exhibits  structural  differences.  The 
most  important  of  these  regions  is  the  proximal,  known  as  the  matnx,  which  lies 
beneath  the  white  area  and  alone  is  concerned  in  the  production  of  the  nail. 

The  corium  of  the  nail-bed  varies  in  the  different  regions  in  the  arrangement  and  size  of  its 
elevations  Within  the  proximal  third  of  the  matrix,  these  elevations  occur  in  the  form  of  low 
papilla;  which  decrease  in  height  and  number  until  they  disappear,  a  smooth  field  occupying 
the  middle  ot  the  matrix.  This  even  field  is  succeeded  by  one  possessing  closely  set,  low, 
narrow  longitudinal  ridges,  that  at  the  distal  margin  of  the  lunula  suddenly  give  place  to  more 
pronounced,  but  less  numerous  broader,  linear  elevations.  These  continue  ^  far  as  the  distal 
end  of  the  nail-lxd  and  are  then  replaced  by  papillae.  Owing  to  the  strong  fibrous  bands  and 
the  absence  of  the  usual  layer  of  fatty  subdermal  tissue,  the  corium  of  the  nail-bed  is  closely 
attached  to  the  bone.  The  fibrous  reticulum  formed  by  the  interfacing  of  the  longitudinal  with 
the  vertical  bundles  contains  few  elastic  fibres,  since  these  are  entirely  wanting  beneath  the  body 
of  the  nail  and  only  present  in  meagre  numbers  within  the  matrix. 

In  view  of  its  genetic  activity,  the  relations  of  the  epidermis  underlying  the  nail  are  of 
especial  interest.  While  the  stratum  germinativum  of  the  skin  covering  the  finger  tip  passes 
directly  and  insensibly  onto  the  nail-bed,  the  entire  extent  of  which  it  invests  (atratum  wrmina- 
tivum  unRuU),  the  stratum  corneum  ends  on  reaching  the  under  suriace  of  the  nail-plate,  the  line 
of  apposition  corresijonding  to  the  narrow  yellow  zone  which  defines  the  distal  boundary  of  the 
rosv  area  Beneath  the  latter,  therefore,  the  epidermis  of  the  nail-bed  consists  of  the  stratum 
eemiinativum  alone,  which,  without  comification  of  any  of  its  cells,  rests  against  the  under  sur- 
face of  ihtr  nail.  Beneath  the  white  zone,  that  is,  within  the  matrix,  the  epidermis  includes  a  half 
dozen  or  mor.  layers  of  the  usual  elements  of  the  stratum  germinativum,  surmounted  by  a  like 
number  of  strata  of  cells  distinguished  by  a  peculiar  brownish  color.  On  reaching  the  "«"  these 
moflified  epithelial  elements,  which  appear  white  by  reflected  light,  are  not  circumscribed,  but 
pass  over  into  the  substance  of  the  nail,  into  the  ron,stitucnt  cells  of  which  they  are  dinrtly  con- 
verted Their  cytoplasm  presents  a  marked  fibrillation  to  which,  according  to  Brunn.  the  light 
appearance  of  the  cells  is  referable  as  an  interference  phenomenon  and  not  as  a  true  pigmente- 
tion.     ThU  peculiarity  of  the  celU,  coupled  with  the  relatively  small  size  of  subjacent  capillaries. 


THE   CUTANEOUS   GLANDS. 


1397 


Nail-bed        Nail-plale 


Stratum  corneiim 

and 

Stratum 

germinativum 

of  nail-wall 


Eponychium 
Margin  of  nail 


probably  accounts  for  the  tint  distinguishing  the  white  area.  Since  the  transformation  of  tlie 
cells  of  the  stratum  germinativum  into  those  of  the  nail-plate  is  confined  to  the  matrix,  it  is  evi- 
dent that  the  continuous 

growth  of  the  nail  Ukes  Fig.  1161. 

place  along  the  floor  and 
bottom  of  the  nail-groove, 
the  last  formed  increment 
of  nail-substance  pushing 
forward  the  previously  dif- 
ferentiated material  and 
thus  forcing  the  nail  to- 
wards the  end  of  the  digit. 
The  relation  of  the  epi- 
dermis of  the  nail-wall  to 
the  substance  of  the  plate 
is  one  of  apposition  only, 
production  of  the  nail  oc- 
curring in  no  part  of  the 
fold.  Over  the  greater 
extent  of  the  latter  all  th- 
typical  constituent 
cntide  are  represen' 
within  the  most  p 
portion  the  stratum ,' 
nativum  alone  is  present, 
the  stratum  comeum  fad- 
ing away,  ^^^^ere  the 
homy  layer  exists,  it  rests 
directly  upon  the  nail,  but 
is  differentiated  from  the 
latter  by  being  less  dense 
and   by   its    respoase   to 

stain-s.  As  the  nail  leaves  the  groove,  a  part  of  the  stratum  germinativum  of  the  nail-wall  is 
prolonged  distally  for  a  variable  distance  over  the  dorsal  surface  of  the  nail-plate  as  a  delicate 
membranous  sheet,  the  eponychium,  which  usually  ends  in  a  ragged  abraded  border. 


Corium 


Trantvenc  section  of  nail- wall  and  adjacent  part  of  nail-plate  and  nail-bed.     v  qo. 


THE  CUTANEOUS  GLANDS. 

These  structures  include  two  chief  varieties,  the  sebaceous  and  the  sweat 
glands,  together  with  certain  modifications,  as  the  ceruminous  glands  within  the 
external  auditory  canal,  the  circumanal  glands,  the  tarsal  and  ciliary  glands 
within  the  eyelid  and  the  mammary  glands.  In  all  the  epithelial  tissues — the 
secreting  elements  and  the  lining  of  the  ducts — are  derivatives  of  the  ectoblast 
and,  therefore,  genetically  related  to  the  epidermis. 

The  Sebaceous  Glands. 

Although  these  structures  (glandulae  scbacae)  are  chiefly  associated  with  the 
hair-follicles,  in  which  relation  they  have  been  considered  (page  1394),  sebaceous 
glands  also  occur,  if  less  f-  ^quently,  independently  and  in  those  parts  of  the  skin  in 
which  the  hairs  are  wanting,  as  on  the  lips,  angles  of  the  mouth,  prepuce  and  labia 
minora.  The  size  of  these  glands  bears  no  relation  to  that  of  the  hairs,  since  among 
the  smallest  (.2-.4  mm.)  are  those  on  the  scalp.  The  largest,  from  .5-2.0  mm., 
are  found  on  the  mons  pubis,  scrotum,  external  ear  and  nose.  Conspicuous  aggre- 
gations, modified  in  form,  occur  in  the  eyelid  as  the  Meibomian  glands. 

Depending  upon  the  size  of  the  glands  their  form  varies.  The  smallest  ones  are 
each  little  more  than  a  tubular  diverticulum,  dilated  at  its  closed  end.  In  those  of 
larger  size  the  relatively  short  duct  subdivides  into  several  expanded  compartments, 
which,  in  the  largest  glands,  may  be  replaced  by  groups  of  irregular  alveoli,  with 
uncertain  ducts  that  converge  into  a  short  but  wide  common  excretory  pas-sage. 

Structure'. — The  structural  components  of  these  glands  include  a  fibroits 
envelope,  a  membrana  propria  and  the  epithelium,  the  first  two  being  continuous 
with  the  corresponding  crverings  of  the  hair-follicle.      Tho  epithelium  continued 


1398 


HUMAN   ANATOMY. 


Alveoli 


Sebaceous  glands  from  skin  covering  nose. 


into  the  ducts  and  alveoli  of  the  sebaceous  glands  is  directly  prolonged  from  the 

outer  root-sheath  of  the  epidermis,  where  associated  with  the  hair-follicles,  or  from 

the  epidermis  where  the  hairs 
Pig.  1162.  are  wanting.     The   periphery 

of  the  alveolus  is  occupied  by  a 
single,  or  incompletely  double, 
layer  of  flattened  and  imper- 
fectly defined  basal  cells,  that 
rest  immediately  upon  the  mem- 
brana  propria  and  are  distin- 
guished by  their  dark  cytoplasm 
and  outwardly  displaced  oval 
nuclei.  Passing  towards  the 
centre  of  the  alveolus,  the  next 
cells  contain  a  number  of  small 
oil  drops  which,  with  each  suc- 
cessive row  of  celb,  become 
larger  and  appropriate  more 
and  more  space  at  the  expense 
of  the  protoplasmic  reticulum 
in  which  they  are  lodged.  In 
consequence,  the  cells  occupy- 
ing the  axis  of  the  alveoli,  which 
are  completely  filled  and  with- 
out a  lumen,  contain  little  more 
than  fat  As  the  cells  are 
escaping  from  the  glands  they 
lose  their  nuclei  and  individual 
outlines  and,  finally,  are  merged 

as  debris  into  the  secretion,  or  sebum,  with  which  the  hairs  and  skin  are  anointed. 

The  necessity  for  new  cells,  created  by  the  continual  destruction  of  the  glandular 

elements  that  attends  the  activity  of  the  sebaceous 

glands,  is  met  by  the  elements  recruited  from  the  Fig.  1163. 

proliferating  basal  cells,  which  in  turn  pass  towards 

the   centre    of   the   alveolus   and   so   displace   the 

accumulating  secretion. 

The  Sweat  Glands. 

These  structures  (Klandulae  sudoriferae),  also 
called  the  sudoriparous  glands,  are  the  most  important 
representatives  of  the  coiled  glands  (glandulae  glomi- 
formes)  often  regarded  as  constituting  one  of  the  two 
groups  (the  setaceous  glands  being  the  other)  into 
which  the  cutaneous  glands  are  divided.  They 
occur  within  the  integument  of  all  parts  of  the  body, 
with  the  exception  of  that  covering  the  red  margins  of 
the  lips,  the  inner  surface  of  the  prepuce  and  the  glans 
penis.  They  are  es-  ecially  numerous  in  the  palms  and  soles,  in  the  former  locality 
numbering  more  than  iioo  to  the  square  centimetre  (Horschelmann),  and  fewest  on 
the  back  and  buttocks,  where  their  number  is  reduced  to  about  60  to  the  square 
centimetre  ;  their  usual  quota  for  the  same  area  is  between  two  and  three  hundred. 

Modified  simple  tubular  in  type,  each  gland  consists  of  two  chief  divisions,  the 
bodv  (corpus)  or  gland-coil,  the  tortuously  wound  tube  in  which  secretion  takes 
place,  and  the  exrretor}'  duct  (ductus  sudoriferns)  which  opens  on  the  surface  of  the 
skin,  exceptionally  into  a  hair-follicle,  by  a  minute  orifice,  the  sweat  pore  (poms 
tiuduriferus),  often  distinguishable  with  the  unaided  eye. 

The  body  of  the  gland,  irregularly  spherical  or  flattened  in  form  and  yellowish 
red  in  color,  consists  of  the  windings  of  a  single,  or  rarely  branched,  tube  and  com- 
monly occupies  the  deeper  part  of  the  corium,  but  sometimes,  as  in  the  palm  and 


Cells  from  alveoli  of  sebaceous  gland . 
showing  reticulated  protoplasm  due  to 
presence  of  oil  droplets.    X  Too. 


THE  CUTANEOUS  GLANDS. 


1399 


S.genninativum 


scrotum,  lies  within  the  subdermal  connective  tissue.  The  coiled  jM)rtion  of  the 
gland  is  not  entirely  formed  by  the  secretory  segment,  since,  as  shown  by  the  recon- 
structions of  Huber,  about  one  fourth  is  contributed  by  the  convolutions  of  the  first 

part  of  the  duct. 

On  leaving  the  gland-coil,  in  close  pro.\imity  to  the  blind  end  of  the  gland,  the 
duct  ascends  through  the  corium  with  a  fairly  straight  or  slightly  wavy  course  as 
far  as  the  epidermis.  On  entering  the  latter  its  further  path  is  marked  by  conspicu- 
ous cork-screw-like  windings,  which,  where  the  cuticle  is  thick  as  on  the  palm,  are 
close  and  number  a  dozen  or  more  and  terminate  on  the  surface  by  a  trumpet-shaped 
orifice,  the  sweat-pore. 

In  its  course  through  ^*°-  "^ 

the  corium  the  duct 
never  traverses  a 
papilla  or  ridge,  but 
always  enters  the  cuti- 
cle between  these  ele- 
vations. On  the  palms 
and  soles,  where  the 
pores  occupy  the  sum- 
mit of  the  cutaneous 
ridges,  the  ducts  enter 
the  cuticle  between  the 
double  rows  of  papillae. 

Structure. — The 
secreting  portion  of 
the  gland-coil,  called 
theampu/ia  on  account 
of  its  greater  diameter, 
possesses  a  wall  of 
remarkable  structure. 
The  thin  external 
sheath,  composed  of  a 
layer  of  dense  fibrous 
tissue  and  elastic  fibres, 
supports  a  well  defined 
membrana  propria. 
Immediately  within  the 
latter  lies  a  thin  but 
compact  layer  of  invol- 
untary muscle  whose 
longitudinallydisposed 
spindle  -  shaped  ele- 
ments in  cross-section 
appear  as  a  zone  of 
irregularly  nucleated 
cells  that  encircle  the  secreting  epithelium  and  displace  it  from  its  customary  position 
against  the  basemt  li  membrane.  This  muscular  tissue  enjoys  the  distinction,  sharing 
it  with  the  muscle  of  the  iris,  of  being  developed  from  the  ectoblast.  The  secreting 
cells  constitute  a  single  row  of  low  columnar  epithelial  elements,  that  lie  internal  to 
the  muscle  and  surround  the  relatively  large  lumen.  Their  finely  granular  cytoplasm 
contains  a  spherical  nucleus,  situated  near  the  base  of  the  cell,  and  in  certain  of  the 
larger  glands,  as  the  axillary,  includes  fat  droplets  and  pigment  granules.  These 
are  liberated  with  the  secretion  of  the  gland  and  when  present  in  unusual  quantity 
account  for  the  discoloration  produced  by  the  perspiration  of  certain  individuals.  In 
the  case  of  the  ceruminous  glands,  the  amount  of  oil  and  pigment  is  constantly  great 
and  confers  the  distinguishing  characteristics  on  the  ear-wax. 

The  sudden  and  conspicuous  reduction  in  the  size  of  the  tube  which  marks  the 
termination  of  the  secreting  segment  and  the  beginning  ./  tl:"  duct,  is  accompanied 
by  changes  in  the  structure  of  its  wall.     In  addition  to  a  leduction  of  its  diameter  to 


Fat-cells 


Coiled  p«rt  at 
•weat-gUiid 


Section 


of  »kin  (rom  palm,  showing  diHerent  pans  of  sweat-glands  extending  from 
surface  into  tela  subcutanea.    X  6;. 


I400 


HUMAN   ANATOMY. 


one-half  or  less  of  that  of  the  ampulla,  the  duct  loses  the  layer  of  muscle  and 
becomes  flattened,  with  corresponding  changes  in  the  form  of  its  lumen.  The  single 
row  of  secreting  elements  is  replaced  by  an  irregular  double  or  triple  layer  of 
cuboidal  cells,  which  exhibit  an  homogeneous  zone,  sometimes  described  as  a 
cuticle,  next  the  lumen.  On  entering  the  epidermis,  the  duct  not  only  loses  its 
fibrous  sheath  and  membrana  propria,  but  the  epithelial  coastituents  of  its  wall  are 
soon  lost  among  the  cells  of  the  stratum  germinativum,  so  that  its  lumen  is  continued 
to  the  surface  as  a  spiral  cleft  bounded  only  by  the  comilied  cells  of  the  cuticle. 

Apart  from  mere  variations  in  size,  certain  glands — the  circumana/,  the  ciliarv 
and  the  ceruminous — depart  sufficiently  from  the  typical  form  of  the  coiled  glands  to 
entitle  them  to  brief  notice.  The  circumanal  glands,  lodged  chiefly  within  a 
zone  from   12-15  ^^-  ^^^^  *"<!  about  the  same  distance  from  the  anus,  are  not 

all    the  same,    but   include, 
Fig.  1 165.  according    to    Huber,    four 

varieties.  In  addition  to  ( i ) 
the  usual  sweat  glands  and 
(2)  some  (Gay's)  of  excep- 
tional size,  (3)  others  have 
relatively  straight  ducts  that 
end  in  expanded  saccules, 
from  which  secondary  alveoli 
arise  ;  finally  (4)  branched 
glands  of  the  tubo-alveolar 
type  are  present.  The  cili- 
ary glands  (Moll's)  of  the 
eyelid  are  not  typical  coiled 
structures,  but  belong  to 
the  branched  tubo-alveolar 
groups.  The  ceruminous 
glands,  distinguished  by 
the  large  amount  of  oil  and 
pigment  mingled  with  their 
secretion,  are  likewise  refer- 
able to  the  branched  tubo- 
alveolar  type. 

The  blood-vessels  of 
the  sweat  glands  include 
arterial  twigs  given  off  from 
the  cutaneous  rete,  a  capillary 
net-work  outside  the  mem- 
brana propria,  best  developed 
within  the  coiled  portion  of  the  tube,  and  the  veins  that  join  the  deeper  plexus 
within  the  corium.  „       .  .     • 

The  nerves  are  especially  numerous  and  consist  of  nonmedullated  sympathetic 
fibres  that  traverse  the  fibrous  sheath  and  form  a  close  plexus  on  the  outer  surface 
of  the  membrana  propria.  From  this  net-work  fibrillae  penetrate  the  basement 
membrane  and  end  in  close  apposition  with  the  gland-cells  and  muscle-elements. 
Their  termination  on  the  secreting  cells  is,  according  to  Amstein,  in  the  'onn  of 
peculiar  endings  consisting  of  groups  and  clusters  of  minute  terminal  knobs  with 
which  the  nerve  fibrillar,  without  or  after  division,  are  beset. 

THE  DEVELOPMENT  OF  THE  SKIN  AND  ITS  APPENDAGES. 

The  Skin.— The  integument  consists  of  two  genetically  distinct  parts— the 
epithelium  (epidermis)  developed  from  the  ectoblast,  and  the  connective  tissue 
(corium  and  tela  subcutanea)  from  the  mesoblast.  During  the  earliest  stages  of 
development  the  ectoblast  is  represented  by  a  single  layer  of  cells,  which,  by  the  end 
of  the  first  month,  is  in  places  reinforced  by  an  external  second  layer,  that  by  the 
seventh  week  has  appeared  over  the  entire  surface.     This  doyble  layer  now  consists 


Farts  of  coiled 

Mcntinf 

•egment 


Miucle.cellt 


Section  of  deeper  coiled  portion  of  swe«t-(l*nd.    X  3>S- 


DEVELOPMENT  OF  SKIN   AND  APPENDAGES. 


1401 


Fiu.  1 166. 


Sections  of  developing 
Rkhi.showinfc  earliest  stafcrs 
in  formation  of  hair-follicles; 
in  D  epithelial  cylinder  is 
invading  mesoblast.     >   90. 


of  a  deeper  row  of  cuboid  or  low  columnar  cells,  covered  by  a  superficial  sheet, 

known  as  the  epitrichium,  composed  oi'  flattened  elements  often  lacking  in  definition, 

and  nuclei.     During  the  succeeding  weeks  the  cpitrichial  cells  become  swollen  and 

vesicular  and  differentiated  from  the  underlying  elements,  which  meanwhile  are 

engaged   in   producing    the   epidermis.     The   epitrichium 

persists  until  the  sixth  month,  when  it  becomes  loosened  and 

IS  cast  off.     During  the  third  and  fourth  months  the  ectoblastic 

cells  have  so  multiplied,  that  from  four  to  five  layers  are 

present,  those  next  the  mesoblast  being  columnar  and  rich  in 

protoplasm,    while   the  more   superficial   are   irregular  and 

clearer.     By  the  middle  of  the  fifth  month,  by  which  time 

the  layers  have  increased  to  almost  a  dozen,  the  outer  cells 

become  horny  and  assume  the  characteristics  of  a  stratum 

comeum,  while  the  deepest  ones  represent  the  stratum  germi- 

nativum,  with  an  intervening  transitional  zone.     About  the 

sixth  month  desquamation  of  the  surface  cells  begins,  the 

discarded  epitrichial  and  other  scales  mingling  with  the  secre- 
tion from  the  sebaceous  glands,  which  meanwhile  have  been 

developed,  as  constituents  of  the  white  unctuous  coating,  the 

vernix  caseosa  (smegma  embryonnm),  that  covers  the  surface 

of  the  foetus,  especially  in  the  folds  and  creases.     Ehiring 

the  last  weeks  of  gestation  the  epidermis  acquires  considerable 

thickness  and  a  sharper  differentiation  of  its  c  .mponent  strata. 
The  connective  tissue  part  of  the  skin  is  developed  as 

a  superficial  condensation  of  the  mesoblast,  that  during  the 

first  month  consists  of  closely  placed  spindle  cells.     Coinci- 

dently  with  the  appearance  of  the  fibrous  fibrillae,  in  the 

third  month,  differentiation  takes  place  within  the  condeiised 

mesoblastic  tissue,  which  so  far  exists  as  a  uniform  zone,  into 

a  superficial  and   more  compact  layer  and  a   deeper  and 

looser  one ;  the  former  becomes  the  corium  and  the  latter  the  tela  subcutanea. 

Within  the  last  layer  soon  appear  larger  or  smaller  groups  of  round  cells  in  which 

oil  drops,  at  first  minute  and  then  of  increasing:  diameter,  indicate  the  beginning 

of  their  conversion  into  adip>ose  tissue.     By  the  sixth  month  the  panniculus  adiposus 

is  established.     About  the  fifth  month  the  line  marking  the  junction  of  cuticle 

and  corium  becomes  uneven  in  consequence  of  the  development  of  the  papill^p 

and  ridges  of  the  corium  and  the  attendant  invasion  of  the  epidermis.     Certain  of 

the  mesoblastic  cells  are  transformed  into  the  component  elements  of  the  involuntary 

muscle  that  occurs  either  associated  with  the  hair  follicles  as  the  arrectores  pilorum, 

or  as  i'le  more  extended  tracts  of  the  dartos. 
The  Hairs. — ^The  primary  development 
of  the  hair  begins  about  the  end  of  the  third 
month  of  foetal  life  as  localized  proliferations 
of  the  epidermis.  In  section  these  appear  as 
lenticular  thickenings  and  on  the  surface  as 
slight  projections.  Very  soon  solid  epithelial 
cylinders  sprout  from  the  deeper  surface  of 
these  areas  and  invade  the  subjacent  corium 
to  form  the  anlages  of  the  hair-follicles.  The 
original  uniform  outline  of  these  processes  is 
early  replaced  by  a  flask-shaped  contour  in 
consequence  of  the  enlargement  of  their  ends 
which  in  their  growth  surround  connective 
tissue   processes   to   form  the  hair-papillee. 

The  embryonal  connective  tissue  immediately  surrounding  the  epidermal  ingrowth 

diflerenliates  into  iht;  fibrou.s  xhealh  and  the  glassy  membrane. 

Meanwhile  and'even  before  the  formation  of  the  papilla  the  epithelial  contents  of 
the  young  follicles  differentiate  into  an  axial  strand  of  spindle  cells  that  later  undergo 
keratinization    and  become   the  hair-shaft  that  grows   by  subsequent   additions 


Fio.  1 167. 


Halr-follide 


Papilla 


Developing  skin,  showing  later  stages  of  (orma- 
tion  of  halr-K>nicles ;  surrounding  mesoblast  is 
forming  hal^-papina  and  fibrous  sheath  of  follicle. 
■   90- 


I402 


HUMAN   ANATOMY. 


from  the  matrix  surmounting  the  piipiUa.  In  addition  to  forming  the  outer  root- 
sheath  the  peripheral  elements  contribute  the  matnx-cells  that  occupy  the  furidus  of 
the  follicle  and  surround  the  papiUa.  The  cells  covering  the  summit  and  adjacent 
sides  of  the  papilla  are  converted  into  elongated  spindles  that  later  gradua|ly  l)ecomf 
horny  and  assume  the  characteristics  of  the  cortical  substance  of  the  hair.  VV  hen 
present,  the  medulla  is  developed  by  the  transformation  of  the  cells  occupying  the 
summit  of  the  papilla,  which  enlarge,  become  les.s  granular  and  grow  upward  as  an 
axial  strand  that  invades  the  chief  subsUnce  of  the  hair  and  accumulates  kerato- 
hyalin  within  its  cells.  At  first  present  as  minute  drops,  this  substance  increases 
in  quantity  until  it  occupies  the  cells  in  the  form  of  large  vesicles.  The  subsequent 
disappearance  of  these,  followed  by  shrinkage  of  the  cells  and  the  introduction  <.f 
air,  completes  the  differentiation  of  the  medulla.  The  pigment  particles,  w-hich 
appear  later,  are  first  evident  in  the  hair-bulb  and  probably  arise  within  the  epithelia 
tissue.  The  elements  of  the  hair-cuticle  and  of  the  inner  root-sheath  are  differentiated 
from  the  matrix-cells  at  the  sides  of  the  papilla.  The  tall  columnar  elements  become 
eloneatpd  and  converted  into  the  cornihod  plates  of  the  cuticle  both  of  the  hair  and 

of  the  inner  root-sheath.     The  layers 
1168.  of  Huxley  and  of  Henle  are  derived 

from  cells  that  soon  exhibit  granules  of 
keratohyalin,  so  that  on  reaching  the 
level  of  the  summit  of  the  papilla  the 
process  of  cornification  has  been  estab- 
lished. This  is  especially  marked  in 
the  elements  of  Henle' s  layer,  in  which 
the  deposit  takes  the  form  of  a  longi- 
tudinal fibrillation. 

The  growth  of  the  hair  takes 
place  exclusively  at  the  lower  end  of 
its  bulb,  where,  so  long  as  the  hair 
grows,  the  conversion  of  the  matrix- 
cells  into  the  substance  of  the  hair  is 
continuously  progressing.  By  this  pro- 
cess the  sutetance  already  differentiated 
is  pushed  upward  by  the  cells  under- 
going transformation  and  these  in 
turn  are  displaced  by  the  succeeding 
elements.  In  this  way,  by  the  addition 
of  new  increments  in  its  bulb,  the  hair  is  forced  onward  and,  in  the  c^  of  those 
first  formed,  through  the  epidermis  that  still  blocks  the  mouth  of  the  follicle.  This 
eruption  begins  on  the  scalp  and  regions  of  the  eyebrows  about  the  fifth  fcetal  month 
and  on  the  extremities  about  a  month  later. 

The  hairs  covering  the  Jirtus  are  soon  shed,  durinR  the  last  weeks  of  gestation  and  immedi- 
ately following  birth,  and  are  replaced  by  the  stronger  hairs  of  childhood.  These  latter,  too,  .irt- 
continually  falling  out  and  being  renewed  until  puberty,  when  in  many  localities,  as  on  the  scalp, 
fiice  axillx  and  external  genital  organs,  they  are  gradually  replaced  by  the  much  longer  and 
thicker  hairs  that  mark  the  advent  of  sexual  maturity.  Even  .ifter  attaining  their  mature  growth, 
the  individual  life  of  the  hairs  is  limited,  those  on  the  scalp  probably  retaining  their  vitahty  for 
from  two  to  four  years  and  the  eyelashes  for  only  a  few  months  ( Pincus). 

During  the  years  of  greatest  vitality  not  only  are  the  discarded  hairs  replaced  by  new  ones, 
but  the  actual  number  of  hairs  may  increase  in  consequence  of  the  development  of  additional 
follicles  from  the  epidermis  after  the  manner  of  the  primary  formation.  When  from  age  or  other 
cause  the  hair-follicles  loose  their  productive  activity  and,  therefore,  are  no  longer  capable  of 
replacing  the  atrophic  hairs,  more  or  less  conspicuous  loss  of  hair  results,  whether  only  tem- 
porary or  permanent  evidently  depending  upon  the  recuperative  powers  of  the  follicles. 

The  change  of  hair  that  is  continually  and  insensibly  occurring  in  man,  in  contra-st  to  the 
conspicuous  periodic  shedding  of  the  coal  seen  in  other  animals,  includes  the  atrophy  of  the  old 
hair  on  the  one  hand,  and  the  development  of  the  new  on  the  other.  ,    .     .    . 

The  eariiest  manifestations  of  this  atrophy,  as  seen  in  longitudinal  sections  of  the  hair- 
follicle  are  reduction  in  the  size  an<l  differentiation  of  the  mass  of  matnx<ells  at  the  bottom  ot 
the  follicle  and  the  diminution  of  the  hair-papilla.    The  progressive  reduction  of  the  matnx  is 


Sebaceous  gland 


Hair 


Koot-sheath 


Bulb 


Papilla— 


Developing  sliiii,  allowing  later  stage  of  hair-follicle;  liair 
is  now  dltferentlaled.    X  80. 


DEVELOl'MENT   OF   SKIN   AND   APPENDAGES. 


•403 


Kiu.  1 169. 


Papilla 


Section  of  fiiul  skin,  show- 
ing sebftccoiu  K^AnA  developing 
from  haiMollicie.     ■   90. 


accompanied  by  the  pt  jducUon  of  a  dub-shapeU  enlargement  of  the  hair,  between  which  ami 

the  shrunken  matrix  a  strand  of  atrophic  epithelial  cells  for  a  time  remains.    With  the  continued 

progress  of  these  changes,  the  root  of  the  club-hair,  as  the  degcneratinK  hair  is  termed,  shortens 

so  that  the  bulbus  enlargement  recedes  from  the  bottom  of  ihe 

hair-sac,  until  it  lies  just  below  the  narrow  neck  of  the  follicle, 

where  it  remains  for  a  longer  or  shorter  period  until  the  hair 

is  dislodged  and  finally  discarded.    A  hair  that  has  fallen  out 

in  consequence  of  these  atrophic  changes  presents  well-marked 

differences  in  the  appearance  and  structure  of  its  root  from  a 

growing  hair  removed  by  force.     In  the  discarded  hair  the  root 

possesses  the  characteristic  club  shape,  with  contours  broken  by 

irregular  proces.ses  composed  of  the  splintered  cortical  substance, 

which  alone  forms  the  terminal  bulb  that  is  always  solid  and  has 

neither  cuticle  nor  medulla. 

While  the  old  hair  is  still  lodged  in  the  upper  part  of  the 
follicle,  the  first  steps  towards  its  replacement  are  initiated  by  the 
stratum  germinativuri  of  the  old  hair-sac.  Whether  surrounding 
a  new  papilla,  as  held  by  many,  or  capping  the  revived  original 
one  (Brunn),  the  deepest  follicle-cells  contribute  by  proliferation 
the  material  from  which  the  new  hair  is  developed  in  a  manner 
agreeing  essentially  with  that  in  which  its  predecessor  was  evolved. 

The  Nails. — The  first  appearance  of  a  definite  nail- 
area  on  the  dorsum  of  the  distal  phalanx  is  seen  towards  the 
end  of  the  third  fcetal  month  (Kolliker),  although  Zander 
has  described  a  local  thickening  of  the  epidermis  covering 
the  tip  of  the  digit  a  the  ninth  week.  By  the  fourth  month  the  nail-area  shows 
as  a  slightly  depressed  field  that  is  defined  proximally  and  laterally  by  a  curved 
swelling,  the  earliest  suggestion  of  the  nail-wall.  Distally  the  field  is  limited  by  a 
transverse  elevation.  Shortly  after  the  nail-area  has  been  thus  defined,  the  outer 
cells  of  its  stratum  germinativum  exhibit  deposits  of  keratohyalin  which,  by  the  end 
of  the  fourth  month,  lead  to  the  formation  of  a  thin  overlying  layer  of  nail-substance. 
For  a  time  this  gains  in  thickness  by  additions  to  its  under  surface  alone,  the  primary 
nail  being  produced  by  the  progressive  conversion  of  the  cells  of  the  stratum  granu- 
losum,  which  is  present  throughout  the  nail-area. 

At  this  stage  the  young  nail  lies  completely  buried  within  the  epidermis,  lying 
between  the  most  superficial  elements  of  the  epidermis  and  the  epitrichial  cells  above, 
and  the  deeper  layers  of  the  cuticle  below.  The  overlying  epithelial  mass,  compose*! 
of  the  epidermal  and  epitrichial  elements,  constitutes  the  eponyckium,  the  remains 

of  which,  after  the  disapf>earance  of  its  middle  and 
distal  [)arts,  are  subsequently  seen  as  a  thin  mem- 
brane covering  the  proximal  part  of  the  nail-plate. 
As  yet  the  young  nail-plate  has  not  come  into 
relation  with  the  epidermis  of  the  nail-groove,  since 
it  is  still  confined  to  the  primitive  area.  But  during 
the  fifth  month  the  proximally  growing  root  invades 
more  and  more  the  sulcus  until  it  attains  its  definite 
relations  with  the  nail-wall.  Meanwhile  the  nail-bed 
beneath  the  developing  root  undergoes  thickening 
and  becomes  the  matrix,  while  the  cells  containing 
keratohyalin  gradually  disappear  from  the  distal 
region  of  the  nail-area  in  consequence  of  their  com- 
pleted conversion  into  the  nail-substance.  Subse- 
quently these  cells  are  limited  to  the  proximal 
nail-producing  zone  of  the  matrix  from  which,  after 
the  initial  formation  of  the  primary  nail-substance, 
the  nail  alone  receives  the  additions  necessary  for  its 
continued  growth.  In  consequence  of  the  resulting 
forward  growth  the  nail  pushes  its  way  through  the  elevated  distal  boundary  of  the 
nail-field,  the  epithelium  lying  above  the  nail-plate  being  lost,  while  that  below  remains 
as  the  representative  of  the  sole-plates  that  are  well  marked  in  many  other  animaU. 


1 IG.  11701. 


t; 


?^'  ,  .,'J .1     ,  i, 


Section  of  ftetal  skin,  showing  develop* 
ing  sweat-Klands ;  a.  is  less  advanced  than 

b  and  c.    X  itx). 


1404 


HUMAN  ANATOMY. 


The  Sweat  Glands. — The  development  of  these,  the  most  important  members 
of  the  group  of  coiled  glands,  begins  during  the  fifth  foetal  month  as  solid  epithelial 
sprouts  from  the  under  surface  of  the  epidermis.  At  first  cylindrical  in  form, 
these  processes  soon  acquire  a  club-shaped  lower  end  and  .'jr  a  time  resembii.- 
developing  hair-follicles.  The  terminal  segment  of  the  gland-anlage  enlarges  in 
diameter  and  thus  early  differentiates  the  later  ampulla.  With  subsequent  increase 
in  length,  the  characteristic  coils  soon  appear,  after  which  a  lumen  makes  its 
appearance  in  the  ampullary  segment  and  gradually  extends  to  the  surface. 

Practical  considerations  of  the  skin  find  mention  in  connection  with  the 
various  regions,  to  which  the  reader  is  referred. 

THE  NOSE. 

Although  only  a  si  part  of  the  nasal  chambers  is  occupied  by  the 
periphp'al  olfactory  or^ap  man,  the  greater  part  forming  the  beginning  of  the 
respiratory  tract,  comparative  anatomy  and  embryology  establish  the  primary 
significance  of  the  nasal  groove  and  its  derivations  as  the  organ  of  smell,  the 
relation  of  the  nose  to  respiration  being  entirely  secondary.  The  nose,  therefore, 
is  appropriately  grooped  with  the  organs  of  special  sense,  notwithstanding  its  relation 
to  the  proper  production  of  voice  and  to  taste  and  the  rdle  that  it  plays  in  varying 
facial  expression. 

The  nose  consists  of  two  portior.:,  the  outer  nose  (nasiis  ezternus)  and  the  inner 
chamber  (cavnm  nasi),  which  is  divided  by  the  median  partition  into  the  right  and 
left  nasal  fossae 

The  outer  nose  forms  the  prominent  triangular  pyramid  that  projects  from  the 
glabella  forward  and  downward,  supported  by  a  bony  and  cartilaginous  framework 
and  covered  by  muscles  and  integument.  Its  upper  end  or  root  (radix  nasi)  springs 
from  below  the  glabella  from  the  frontal  bone,  with  which  it  usually  forms  an  angle 
and  from  which,  in  consequence,  it  b  separated  by  a  groove.  When  the  latter  is 
wanting  and  the  rounded  median  ridge,  or  dorsum,  of  the  nose  continues  the  plane 
of  the  forehead,  the  nose  is  said  to  be  of  the  Grecian  type.  The  dorsum  ends  below 
in  a  free  angle  or  point  (apex  nasi),  the  upper  or  bony  part  of  the  dorsum,  often 
termed  the  bridge,  in  the  aquiline  type  of  nose  forming  a  more  or  less  conspicuous 
angle  with  the  cartilaginous  part. 

The  sides  of  the  nose  (partes  laterales  nasi)  descend  from  the  root  with  increas- 
ing obliquity  until  they  reach  the  broadest  part  of  the  nasal  pyramid,  or  base,  which 
is  pierced  by  the  openings  of  the  nostrils  or  anterior  nares  (nares).  Just  before 
meeting  the  base,  each  lateral  surface  expands  into  the  mobile  and  rounded  xving  (ala 
nasi)  that  forms  the  outer  wall  of  the  nostril  and  is  limited  above  by  a  shallow 
groove,  the  alar  sulcus.  Under  the  influence  of  the  attached  muscles,  the  alae  are 
subject  to  dilitation,  compression,  elevation  and  depression  and  thereby  participate 
in  modifying  facial  expression. 

In  addition  to  the  endless  minor  variations  of  form  that  the  outer  nose  presents, 

which,  apart  from  individual  distinction,  have  little  significance,  the  relation  of  its 

greatest  breadth  across  the  alae  to  its  total  length,  from  root  to  tip,  is  of  sufficient 

anthropological  inlportance  to  receive  attention  in  the  classification  of  the  races  of 

,.,_,,.,.        ,  ,   ,  .  ...      /greatest  breadth    X  ioo\ 

mankmd.    This  relation,  the  cephalometnc  nasal  index  I — , — — r ) 

^  \        greatest  length        / 

varies  with  different  races,  according  to  Topinard  the  index  of  the  white  races  being 

below    70   {leptorhines),    that  of   the   yellow   and  red   races  between   70  and  85 

{mesorhines) ,  and  that  of  the  black  races  above  85  {plafyrhines'). 


THE  CARTILAGES  OF  THE  NOSE. 
The  cordiform  nasal  opening  ('apertiir.'j  pyriformis)  of  the  f.-jcLi!  skeleton,  hounded 
by  the  free  margins  of  the  nasal  and  superior  maxillary  bones,  is  enclosed  and 
continued  to  the  anterior  nares  by  the  nasal  cartilages  and  contiguous  fibrous  tissue. 
These  cartilages  are  usually  considered  as  including  five  chief  plates,  the  unf>aired 
septal  and  the  paired  upper  and  lower  lateral,  and  a  variable  number  of  smaller 


THE  CARTILAGES  OF  THE   NOSE. 


>405 


supplemental  pieces  (cartilaKines  minoreii).  The  conventional  di«-ision  of  the  iin»t 
three,  however,  is  unwarranted,  since  embryologically  and  niorpholoKically  they 
constitute  one  piece  (cartllaso  mediana  nasi),  which  even  in  the  adult  iii  represented 
by  the  connected  septal  anil  upper  lateral  plates. 

The  cartilage  of  the  leptum  (cartilagu  scpti  nasi)  (Fi^.  1171)  completes  the 
median  partition  that  divides  the  right  and  left  nasal  fossa?  from  each  other  and 
represents  the  anterior  extremity  of  the  primordiid  cartilaginous  cranuni.  It  is 
irregularly  rhomboidal  in  form  and  so  placed  that  its  superior  angle  lies  al}<i\e, 
received  between  the  nasal  bones  and  the  median  plate  of  the  ethmoid,  and  its 
inferior  angle  below,  resting  upon  the  incisor  crest  of  the  maxillae.  The  anterior 
angle  is  directed  forward  and  the  posterior,  much  the  more  pointed,  is  prolonged 
as  the  sphenoidal  process  (processus  sphenoidalis  sep'.i  cartilaKinei)  for  a  variable 
distance  between  the  mesethmoid  and  the  vomer  to'vards  the  body  of  the  sphenoid, 
which  exceptionally  it  may  reach.  The  antero-superior  margin  of  the  septal  carti- 
lage, thickest  above,  is  attached  to  the  under  suriace  of  the  internasal  suture  for  a 

Fig.  ii;i. 


Frontal  •iniu 


Septal  cartilage 


Mesial  crus  of  left 

lower  lateral  cartilage 


Vomerine  cartilage 


Perpendicalar  plate  of  ethmoid 


Sphenoidal  ainua 


Pfwterlor  naris 

A     \ 

Sphenoidal  process  Vomer 

Nasal  septum  viewed  from  left  side ;  mucous  membrane  uas  been  partially  removed. 

distance  of  from  12-15  ro™-  Bviow  the  nasal  bones,  the  margin  of  the  septal 
cartilage  is  continuous  with  the  upper  lateral  cartilages  which  form  ring-like  expian- 
sions  (alae)  of  the  median  plate.  Still  lower,  the  free-margin  of  the  latter  extends 
between  the  lower  lateral  cartilages  to  within  about  a  half  inch  from  the  tip  of  the 
nose  which,  however,  it  does  not  reach,  the  medial  crura  of  the  lower  lateral  plates 
intervening.  The  postero-superior  margin,  the  thickest  part  of  the  cartilage,  is 
attached  to  the  free  margin  of  the  perpendicular  plate  of  the  ethmoid  bone.  The 
postero-inferior  margin  rests  upon  the  anterior  part  of  the  upper  margin  of  the 
vomer  and  the  incisive  crest  as  far  as  the  anterior  nasal  spine,  where  the  border 
passes  into  the  rounded  anteroinferior  margin  that  joins  the  nasal  spine  with  the 
anterior  angle.  This  border  is  always  convex  and  does  not  reach  the  lowest  part  of 
the  partition  between  the  nostrils,  which  being  devoid  of  septal  cartilage,  is  freely 
movable  and  constitutes  the  septum  mobile. 

The  upper  lateral  cartilages  (cartilagines  nasi  lateralcs^  (Fig.  ii72)  are  iwo 
triangular  plates,  one  on  either  side,  that  by  their  med'an  and  longest  border  are 
attached  to  the  septal  can;ilage,  with  which  in  their  upper  part  they  are  directly 
continuous.  The  tipper  margin  of  oarh  is  joined  to  the  free  Imrder  of  the  na.sal  bone, 
which  it  slightly  underlies,  and,  exceptionally,  the  adjacent  edge  of  the  maxilla,  l"hc 
lower  margin  is  embedded  in  fibrous  tissue  which  connects  it  with  tlio  adjoining  plates. 
The  median  parts  of  the  cartilages  are  markedly  convex  and  separated  by  a  slight 
groove  that  is,  for  the  most  part,  obliterated  by  fibrous  tissue. 


I4u6 


HIMAN   ANATOMY. 


Fig.  II7J. 


rpprr  lalrnil 
cartilage 


Nual  bone 


SepUl 
carlilagt 


I.owcr  lateral 
cartilage 

NanI 
aperture 

Caitilaxe 
at  tip 


Bony  and  cartilaginous  framework  of  noae,  front  aspect. 


The  lower  lateral  cartilages  (cartilagiocs  alares  aajores)  (Fij;.  1172)  are  a 
pair  of  thin  curvetl  plates  that  encircle  the  apertures  of  the  nostrils  anteriorly  an«l 
constitute  the  framework  cif  the  tip  of  the  nose.     Each  cartilage  consists  of  an  intitr 

plate(cn»  mcdiale).  from  6-7  mm. 
broad,  which,  with  its  fellow  of 
the  opposite  side,  embraces  the 
lower  and  anterior  part  of  the 
septal  cartilage  and  aids  in  com- 
pleting the  partition  separating 
the  nares.  In  front  it  narrows, 
bends  sharply  outward,  and  piisses 
more  or  less  abruptly  iiitt)  a 
hroAAtr  outer  plate  (cms  laterate), 
which  is  of  very  uncertain  fonn 
and  size,  although  of  a  general 
elongated  oval  shape  and  some 
12  mm.  broad.  The  triangular 
space     between     the     varyingly 

Crolonged  posterior  end  of  the 
tteral  plate,  the  maxilla  and  the 
upper  lateral  cartilage  is  tilleu 
out  by  fibrt)us  tissue  in  which 
are  embedded  two,  three  or 
more  small  cartilaginous  pieces 
(cartilSKines  alares  minores).  These  vary  greatly  in  size  and  form,  but  in  a  general 
way  tend  to  complete  the  ring  of  cartilage  surrounding  the  lateral  wall  of  the 
nares.  They  do  not,  however,  reach  the  lower  border  of  the  nas.il  ring,  which, 
as  well  as  the  remaining  part  of  the  lower  boundary  of  the  aperture  of  the  nostril, 
is  devoid  of  cartilage  and  composed  of  integument  and  fatty  connective  tissue. 
The  rounded  anterior  angles  of  the  lower  lateral  cartilages  occupy  the  tip  of  the 
nose,  close  together  when  this  is  fKiinted,  but  separated  by  a  space  that  shows 
e.xternally  as  a  more  or  less  evident  groove  when  the  tip  of  the  nose  is  blunt 
and  broad.  The  median  plates  approach  the  septal  cartilage  closer  in  front  than 
behind,  where  they  curve  outward  to  end  in  a  rounded  and  upward  curving  hook. 
The  fibrous  tissue  uniting  the  median  borders  of  the  lower  lateral  plates  with  the 
anterior  edge  of  the  septal  cartilage  usually  contains  two  small  sesamoid  cartilages 
(cartilagines  sesamoideae  nasi)  that  pardy  fill  the  triangular  intervals  on  either  side  of 
the  median  line. 

The  vomerine  cartilages  (cartilaKines  vomeronasales)  are  two  narrow  strips, 
from  1-2  mm.  wide  and  from  10-15  "i""-  long,  that  lie,  one  on  either  side,  along  the 
lower  border  of  the  septal  cartilage 
in  the  vicinity  of  the  nasal  crest. 
They  are  attached  to  the  carti- 
lage and  bone  by  fibrous  tissue 
anil  'situated  beneath  the  mucous 
membrane  lining  the  n.isal  fossa?. 
Their  chief  interest  is  their  rela- 
tion to  the  rudimentary'  organ 
of  Jacobson  fpage  1417)  below 
which  they  lie.  In  animals  in 
which  the  organs  are  well  devel- 
oped these  cartilages  form  protect- 
ing and  supfKjrting  scrolls  ;  in 
man.  however,  both  organ  and 
cartilage  are  so  feebly  developed 
that  they  loose  their  close  relation. 

The  integument  covering  the  outer  nost  is  in  general  thin  and  closely  bound 
down  to  the  underlying  fibrous  tissue,  being  piirticularly  unyielding  over  the  tip  and 
alae.     With  the  exception  of  within  the  alae  and  lateral  borders  of  the  nostrils,  the 


Fig    1173 


L^nrer  lateral 

cartila]^ 

Upp-r  lateral 
cartilage 

Small  alar  . 
cartilaKe 


^Cartilage  of  tip 

Lateral  cru»("<'°,^r 
*•     •  ,    _     -,  lateral 
Mesial  cms  (canilage 


.  Nasal  apertare 
.SeptRl  cartilage 


/'I 


t 


Cartilages  of  nose,  viewed  (rom  below. 


PRACTICAL  CONSIDERATIONS:   THE    KXTERNAL   NOSH.     1407 

fatty  tissue  is  very  meagri-.  The  sebaceous  Kluntls,  on  the  other  haml,  art-  well 
developed  and  o|)en  in  maii>'  instances  in  conjunction  with  the  follicles  of  the  delir.ite 
hairs  that  cover  all  parts  of  tl  <;  surface.  On  the  alie  the  closely  ]>lucctl  ((lands  are  of 
exceptional  size  and  oir'H  tiy  dints  readily  seen  as  minute  depressions. 

Vessels. — In  order  to  compensate  for  the  e.xposed  [)osition,  the  external  nose 
is  generously  supplied  with  aritfies,  derived  chiefly  from  the  facial  and  ophthalmic, 
which  are  united  by  numerous  anastomoses  with  each  other  as  well  as  with  branches 
from  the  infraorbitit.  The  veins  are  all  tributary  to  the  angular  vein,  which  U-jjins 
at  the  inner  canth<  >nd  descends  along  the  side  of  the  nose  to  the  facial  trunk, 
receiving  in  its  course  the  dorsal,  lateral,  and  alar  branches.  The  angular  vein 
communicates  with  the  ophthalmic  and  the  veins  of  the  nasal  fossa. 

The  lymphatki  are  arranged  in  three  sets  (Kiittner).  The  first,  beginning  at 
the  root  of  the  nose,  passes  above  the  upper  eye-lid  and  along  the  supraorbital  ridge 
to  the  jiarotid  nodes.  The  second  group,  formed  by  the  superficial  and  deep  lym- 
phatics at  the  nasal  root,  skirts  the  lower  margin  of  the  orbit  and  ends  in  the  lower 
parotid  nodes.  The  third  and  most  important  set  includes  from  6  to  10  trunks  that 
follow  the  blood-vessels  and  end  in  the  submaxillary  nodes. 

The  nerves  supplying  the  outer  nose  include  the  motor  branches  of  the  facial 
to  the  muscles  and  the  sensory  twigs  from  the  trifacial  to  the  skin,  distributee!  by  the 
infratrochlear  and  nasal  branches  of  the  ophthalmic  and  by  the  infraorbital  of  the 
superior  maxillary. 

PRACTICAL  CONSIDERATIONS    T'.,.  EXTERNAL  NOSE. 

The  Nose  may  be  congenitally  absent,  or  bifid,  or  imperfect,  as  from  absence 
of  the  septum  or  of  one  nostril,  or — very  rarely — of  both  nostrils.  As  to  its  external 
aspect  it  may  be  of  various  types,  e.g. :  Grecian,  when  the  dorsum  is  on  a  practi- 
cally continuous  straight  line  with  the  forehead,  with  no  marked  naso-frontal  groove ; 
aquiline,  with  the  dorsum  slightly  arched  ;  rounded,  with  the  arch  much  more 
pronounced;  foetal — "pug" — with  the  bridge  depressed  and  the  nostrils  directed 
somewhat  forward. 

The  foetal  type  is  simulated  in  the  new  bom  by  the  subjects  of  inherited 
syphilis  in  whom  the  bridge  of  the  nose  is  often  much  depressed  as  a  result 
either  of  (a)  imperfect  development  following  the  severe  specific  coryza  that 
affects  the  nasal  mucosa  and,  through  the  close  apposition  of  the  latter  to  the 
periosteum  of  the  fragile  nasal  bones,  interferes  with  their  nutrition  ;  or  {b)  by 
actual  caries  or  necrosis  of  those  bones  or  of  the  septum  favored  by  the  same 
conditions.  In  acquired  syphilis  the  similar  nasal  deformity  is  practically  always 
the  result  of  the  destruction  of  the  septum,  or,  less  frequently,  of  the  nasal  bones,  by 
late  (tertiary)  lesions. 

As  a  consequence  of  faulty  development  in  the  anterior  mid-portion  of  the 
frontal  bone  the  membranes  of  the  brain  may  protrude,  forming  a  meningocele, 
which  is  more  common  at  the  naso-fiontal  junction  than  elsewhere.  Occasionally 
the  defect  permitting  the  protrusion  exists  in  the  cribriform  plate  of  the  ethmoid, 
and  the  meningocele  occupies  the  nasal  fossa,  having  under  these  circumstances 
been  mistaken  for  a  nasal  polyp  and  removed,  death  resulting  from  subsequent  septic 
meningitis 

The  cosmetic  importance  of  the  nose  is  so  great,  the  diseases  producing 
deformity  so  frequent,  and  the  susceptibility  of  the  organ  to  injury  so  marked,  that 
much  ingenuity  has  been  expended  upon  devices  to  restore  it  when  lost,  or  to 
improve  its  appearance.  In  the  Tagliacotian  operation  a  cutaneous  flap  is  taken 
from  the  arm  »-hich  is  held  close  to  the  nose  by  a  complicated  dressing  until  the  flap 
is  firmly  united  in  its  new  position,  when  its  pedicle  is  detached  from  the  arm.  The 
Indian  method  is  more  particularly  anatomical,  since  the  flap  taken  from  the  fr)re- 
head  is  50  fashioned  that  ii  rviuivcs  intact  the  blood  froiti  thr  fr;;::lul  branch  of  t'lc 
ophthalmic  artery  *rom  the  internal  carotid,  the  ophthalmic  receiving  at  the  origin 
of  the  frontal  an  important  anastomosis  from  the  angular  b-  inch  1  if  the  facial  arterv, 
which  is  given  off  from  the  external  carotid  artery.  Fo  -rtia!  deformities  flai)s 
may  be  taken  from  the  sides  ac<'      ling  t-  the  size  and  si         >m  .•(  the  deficiency. 


■:^kk 


1408 


HUMAN   ANATOMY. 


As  upon  other  parts  of  the  face,  plastic  operations  are  very  successful  owing  to 
the  free  blood  supplyT  Acne  rosacea  is  common  on  account  of  the  ready  response 
"  vSarity  of  the  nose  to  external  irriuting  influences,  and  to  internal  disturbances 
of  the  circulation,  as  from  heart  and  lung  disease  chronic  gastritis,  and  alcoholism. 
Furuncles  and  superficial  infections  are  frequent  because  of  the  number  of  sebaceous 
and  sweat  g'  -nds  present.  Lupus  and-in  the  alar  sulcus-rodent  ulcers  are  com- 
mon because  of  the  constant  exposure  of  the  nose  to  external  irritation  and  to 
Lering  of  temperature,  depressing  its  vital  res  stance.  Frost-bite  of  the  nose  is 
also  common,  eslJecially  about  the  tip.  because  of  its  exposed  position  and  the  lack 
of  protection  to  the  delicate  vessels  from  overlying  tissues.  . 

The  nerve  supply  to  the  nose  is  likewise  very  free,  as  is  shown  m  a  practical 
manner  by  the  min  which  accompanies  inflammatory  conditions,  espeaaUy  those 
involving  the  lower  cartilaginous  portion  where  the  skin  and  subcutoneous  tissues 
are  ver^  adherent  Thrresulting  exudate  is  therefore  much  confined,  pressing 
upon  the  nerves  ;  thb  accounts  also  for  the  frequency  with  which  gangrene  occurs 

under  these  circumstances.  ,  .  u  j  »t. 

Watering  of  the  eyes  from  irritation  of  the  skin  or  mucous  membrane  of  the 
nose  is  due  to  the  free  nerve  supply,  and  to  the  fact  that  the  same  nerve,  the  tri- 
eeminal.  supplies  the  nose  and  the  lachrymal  apparatus  ;  as  a  porUon  of  the  nasal 
chamber  is  supplied  by  a  branch  of  the  ophthalmic  nerve,  raising  the  eyes  to  the  sun 
will  often  give  the  added  irritation  necessary  to  precipitate  a  sneeze  when  the  nasa 
stimulus  suggests  one,  but  is  not  quite  strong  enough  unaided.  Cough  and  bronchial 
asthma  have  resulted  from  nasal  affections  due  to  the  indirect  relations  between 
the  fifth  cranial  nerve  and  the  pneumogastric.  As  the  olfactoiy  portion  of  the 
nasal  fossa  is  in  the  upper  portion  of  the  cavity,  an  earnest  effort  to  recognize 
an  odor  or  to  enjoy  one  to  the  utmost,  is  accompanied  by  a  deep  inspiration 
through  the  nose  with  dilatation  of  the  nostril.  In  paralysis  of  the  facial  nerve 
the  involvement  of  the  dilatores  naris  has  been  thought  to  explain  the  lessening  of 
the  olfactory  sense  sometimes  seen  in  this  condition.  Paralysis  of  the  levatores 
al£e  nasi  muscles  has  permitted  the  nostrils  to  close  during  inspiration,  causing  stridor 
and  mouth-breathing.  The  loss  of  the  sense  of  smell  is  a  not  uncommon  result 
of  severe  blows,  especially  on  the  forehead,  and  may  be  due  to  (a)  concussion  of 
the  olfactory  bulbs  ;  (6)  fracture  of  the  cribriform  plate  of  the  ethmoid  ;  (f)  injury 
to  the  olfactory  roots  where  they  cross  the  lesser  wing  of  the  sphenoid  ;  or  (rf) 
lesion  of  the  olfactory  nerves  where  they  traverse  the  cribnform  foramina.  Sneezing 
from  irritation  of  the  nose  is  probably  due  to  the  indirect  relationship  between  the 
fifth  pair  and  the  vagus  and  may  be  so  violent  that  serious  injury  may  result,  as  in 
cases  in  which  a  subcoracoid  luxation  of  the  shoulder,  a  fracture  of  the  ninth  nb, 
and  the  rupture  of  all  the  coverings  of  a  large  femoral  hernia  were  produced  by 

this  act  (Treves).  ,    .      ,       , .      i    .  »  » 

The  abundant  sweat  and  sebaceous  glands  in  the  skin  of  the  nose  account  for 
the  frequency  with  which  acne  vulgaris  attacks  it.  The  alae,  the  only  movable  por- 
tions, take  part  in  the  movements  of  expression,  as  in  contempt  and  scorn. 

Fractures  of  the  nose  are  common  because  of  its  exposed  position,  and  of  the 
frequency  of  blows  and  other  forms  of  violence  applied  to  the  face.  Their  chief 
importance  depends  upon  the  prominence  of  the  nose  as  a  feature  of  the  face,  any 
change  in  its  shape  attracting  general  attention.  The  h^cture  occurs  most  com- 
monlv  in  the  lower  part,  because  of  the  greater  weakness  of  the  bones  and  their  greater 
prominence  at  that  level.  In  its  upper  part,  the  relative  depression  of  the  dorsum, 
the  greater  thickness  of  the  bones,  and  their  more  firm  support,  make  fracture  less 
common.  On  the  other  hand,  the  higher  fractures  are  more  dangerous  because  of 
their  possible  relation  with  the  cribriform  plate  and  sinuses  of  the  ethmoid  bone.  tJie 
frontal  sinuses  and  the  nasal  duct.  Involvement  of  the  cribriform  plate  is  m  effect  a 
compound  fracture  of  the  base  ©f  the  skull,  exposing  the  meninges  to  the  danger  of 
infection.  Fractures  of  the  nose  are  almost  always  compound,  because  of  the 
intimate  adhesion  of  the  mucous  membrane  to  the  bone,  with  little  intervening 
tissue,  so  that  when  the  bone  breaks  the  overiying  adherent  tissue  la  torn  through 
This  accounts  for  the  practically  uniform  occurrence  of  epistaxis,  on  account  of  which 
it  is  often  difficult  to  detect  the  presence  of  escaping  cerebro-spinal  fluid  when  the 


THE   NASAL   FOSS/E. 


1409 


cribriform  plate  is  also  fractured.  On  the  other  hand,  the  rich  glandular  supply  of 
the  mucous  membrane,  which  makes  the  usual  mucous  secretion  exceptionally  free, 
may,  in  a  post-traumatic  coryza,  result  in  a  watery  discharge  of  such  quantity  as  to 
suggest  the  f'scape  of  the  cerebro-spinal  fluid.  Emphysema  within  the  orbit  and 
under  the  skin  may  result  from  the  communication  of  the  nose  with  the  ethmoidal  or 
frontal  siniises.  In  the  effort  to  keep  the  nose  clear  of  blood  by  blowing,  the  air  is 
forced  into  the  sulxrutaneous  tissues. 

In  fractures  at  the  lower  part,  the  deformity  is  frequently  lateral,  because  of 
the  greater  exposure  to  side  blows,  and  the  tendency  of  the  cartilaginous  ahe  and 
septum  to  avoid  crushing.  In  the  upper  part  depression  is  more  likely,  because  of 
the  tendency  to  escape  any  but  forces  from  in  front,  »he  greater  force  necessary  to 
produce  the  fracture,  and  the  presence  of  a  bony  septum  underneath,  which  crushes 
rather  than  bends. 

When  the  deformity  has  been  replaced  there  are  no  strong  muscles  to  repro- 
duce it,  so  that  litde  or  no  effort  is  necessary  to  maintain  the  fragments  in  position. 
The  deformity  must  be  reduced  early  and  the  reduction  maintained,  because  owing 
to  the  free  blood  supply,  union  is  usually  rapid,  sometimes  occurring  in  a  week. 
One  must  bear  in  mind  in  reducing  the  deformity  that  the  roof  of  each  nasal  fossa  is 
not  more  than  2-3  mm.  wide,  and  that,  therefore,  a  narrow  rigid  instrument  is 
necessary  to  press  die  fragments  upward  into  their  normal  positions. 


THE  NASAL  FOSSi€. 

The  cavity  of  the  nose  is  divided  by  the  median  septum  into  two  nasal  fossae 
which  extend  from  the  anterior  to  the  posterior  nares,  or  choono!,  through  which 
they  open  into  the  naso-pharynx.  They  comn  unicate  more  or  less  freely  with  the 
accessory  air-spaces  within  the  frontal,  ethmoid,  sphenoid  and  maxillary  bones,  into 
which,  as  a  lining,  the  mucous  membrane  of  the  nasal  fosss  is  directly  continued. 

Seen  in  frontal  section  (  Fig.  1176),  each  fossa  is  triangular  in  its  general  outline, 
the  apex  being  above  at  the  narrow  roof  and  the  base  below  on  the  floor.  The 
smooth  median  wall  is  approximately  vertical  and  meets  the  floor  at  almost  a  right 
angle,  while  the  sloping  lateral  wall  is  modelled  by  the  projecting  scrolls  of  the  three 
turbinates,  which  overhang  the  corresponding  meatuses.  In  sagittal  sections 
(Fig.  1 174)  the  contour  of  the  fossa  resembles  an  irregular  parallelogram  from  which 
the  upper  front  corner  has  been  cut  off,  so  that  in  front  the  upper  border  slopes 
downward  to  correspond  with  the  profile  of  the  outer  nose.  1  he  greatest  length  of 
the  fossa,  measure^  along  the  floor,  is  from  7-7.5  cm.  (23^-3  in. )  and  its  greatest 
height  from  4-4.5  cm.  The  width  is  least  at  the  roof,  where  it  is  less  than  3  mm., 
and  greatest  in  the  inferior  meatus  a  short  distance  above  the  floor,  where  it  expands 
to  from  15-18  mm. 

The  Vestibule. — The  anterior  part  of  the  fossa,  immediately  above  the  open- 
ing of  the  nostril  and  embraced  by  the  outer  and  inner  plates  of  the  lower  lateral 
cartilage  and  adjoining  portion  of  the  septum,  is  somewhat  expanded  and  constitutes 
the  vestibule  (vestibulum  nasi),  a  pocket-like  recess  prolonged  towards  the  tip  being 
the  ventricle  (recessus  apicis).  These  spaces  are  lined  by  delicate  skin,  directly  con- 
tinuous with  the  external  integument  and  tighdy  adherent  to  the  underlying  cartilage, 
and,  in  the  lower  half  of  the  vestibule,  containing  numerous  sebaceous  glands  and 
hairs.  In  the  vicinity  of  the  nostril  the  hairs,  known  as  vibrissa,  are  coarse  and 
long  and  curved  downward  to  afford  protection  to  the  nasal  entrance.  Over  the 
upper  part  of  the  vestibule,  the  skin  is  smooth  and  closely  attached  to  the  lower 
lateral  cartilage,  the  upper  margin  of  the  outer  plate  projecting  as  a  slightly  arching 
ridge,  the  limen  vestibuli,  which  forms  the  superior  and  lateral  boundary  of  the  vesti- 
bule and  marks  the  line  of  transition  of  the  skm  into  the  mucous  membrane  that  lines 
the  remaining  parts  of  the  nasal  fossa. 

Above  and  beyond  the  vestibule,  the  nasal  fossa  rapidly  expands  into  a 
triangular  space,  the  atrium  nasi,  that  lies  in  advance  of  the  entrance  into  the  middle 
na«al  meatus.  Above  and  in  front  the  atrium  is  bounded  by  a  low  and  variable 
ridge,  the  (if^gcr  nasi,  that  represents  a  rudimentary  naso-turbinate,  which  in  many 
mammals  attains  a  large  size.     The  space  lying  in  front  of  the  agger,  extending 

89 


I4IO 


HUMAN  ANATOMY. 


from  the  limen  to  the  cribriform  plate  of  the  ethmoid  and  roofed  in  by  the  forepart 
of  the  arched  upper  boundary  of  the  fossa,  is  long  and  narrow  in  consequence  of 
the  approximation  of  the  median  and  lateral  walls.  It  leads  from  the  nasal  aperture 
to  the  summit  of  the  nasal  fossa  and  to  it  Merkel  applied  the  name  carina  nasi. 

The  Nasal  Septum. — The  median  wall  consists  of  the  partition  formed  chiefly 
by  the  perpendicular  plate  of  the  ethmoid,  the  vomer  and  the  septal  cartilage,  cov- 
ered on  both  sides  by  mucous  membrane.  The  extreme  lower  and  anterior  part  of 
the  septum,  consisting  of  the  alar  cartilage  and  the  integument,  is  flexible,  and  there- 
fore called  the  membranous  portion,  or  septum  mobile  ;  the  terms  bony  and  cartilagi- 
nous portions  are  applied  to  the  remaining  parts  of  the  septum  supported  by  bone 
and  cartilage  respectively. 

While  during  early  childhood  its  position  is  median,  in  the  great  majority  of 
adults  the  septum  presents  more  or  less  asymmetry  and  lateral  deflection,  most  often 

Fig.  1 174. 

Frontal  sinus 

^Superior  tutWnate 

Sphenoethmoidal  rvccM 

Opening  of  sphenoidal  sinus 

Superior  meatus 


Fossa  nf 
Rosenmiiller 


OpeninK  o! 
Eustachian  tube 


to  the  right.  Thiji  deviation  may  affect  the  septal  cartilage  alone,  may  be  limited  to 
the  bones  (in  53  per  cent,  according  to  Zuckerkandl),  or  may  be  shared  by  both. 
The  most  common  seat  of  the  deflection  is  the  junction  of  the  ethmoid  and  vomer,  in 
the  vicinity  of  the  spheno-ethmoidal  process,  or  along  the  union  of  the  vomer  and 
the  septal  cartilage.  The  asymmetry  may  involve  the  entire  septum,  which  then  is 
oblique  ;  or  it  may  take  the  form  of  a  simple  bulging  towards  one  side,  a  double  or 
sigmoid  projection  ;  or  be  an  angular  deflection  resembling  a  fc'd,  crest  or  spur  that 
projects  into  one,  sometimes  both,  of  the  fossae  (Heymann). 

Although  the  mucous  membrane  covering  the  nasal  septum  is  generally  smooth 
and  of  fairly  constant  thickness,  its  surface  is  marked  by  inequalities  caused  chiefly 
by  variations  in  the  amount  and  development  of  the  glandular  and  vascular  tissue, 
(ine  such  accumulation,  the  tuberndum  septi,  is  relatively  constant  and  on  the  septum 
about  opposite  the  anterior  end  of  the  middle  turbinate.  During  early  life  a  series 
of  from  four  to  six  or  more  oblique  ridges,  plicte  septi,  often  model  the  lower  and 
posterior  part  of  the  septum,  extending  from  below  upward  and  forward.  Slightly 
above  the  anterior  nasal  spine,  the  septal  mucosa  presents  the  minute  openings  lead- 
ing into  the  rudimentary  oi^an  of  Jacobson.  Behind,  the  margin  of  the  bony  septum 
is  covered  by  mucous  membrane  of  unusual  thickness  which,  therefore,  forms  the 
immediate  free  edge  of  the  partition  separating  the  posterior  nares. 

The  Lateral  Wall.— The  lateral  wall  of  the  na.snl  fossa:  is  characteris>..;a!!y 
modelled  by  the  projecting  scrolls  (conchae  nasi)  of  the  three  turbinates.  The  latter 
partly  subdivide  each  fossa  into  three  lateral  recesses,  the  superior,  middle,  and 


THE   NASAL   FOSSAE. 


1411 


inferior  meatuses.  These  are  overhung  by  the  correspo  Jing  bony  concha,  the 
superior  meatus  being  roofed  in  by  the  upper  turbinate  and  the  inferior  lying  between 
the  lower  turbinate  and  the  floor  of  the  fossa.  That  part  of  the  nasal  fossa  between 
the  conchae  and  the  septum,  into  which  the  recesses  open  medially,  is  sometimes  called 
the  meatus  nasi  communis.  The  details  of  the  nasal  fossa  as  seen  within  the  macerated 
skull  have  been  described  in  connection  with  the  skeleton  (.page  223).  In  the  recent 
condition,  when  the  soft  parts  are  in  place,  while  their  general  contour  is  preserved, 
the  compartments  of  the  fossae  are  materially  reduced  in  size  by  the  thickness  of  the 
mucous  membrane  and  the  erectile  tissue  that  cover  the  bony  framework. 

The  Superior  Meatus. — Corresponding  to  the  small  size  of  the  upper  turbinate, 
the  superior  meatus  (meatus  nasi  snperior),  or  ethmoidal  fissure,  is  narrow  and 
groove-like  and  littie  more  than  half  the  length  of  th..  middle  one.  It  is  directed 
downward  and  backward  and  is  floored  by  the  convex  upper  surface  of  the  middle 
concha.  When  the  upper  turbinate  is  r^laced  by  two  scrolls  (conchae  superior 
et  suprema) — a  condition  that  Zuckerkandl  regards  as  very  frequent,  if  indeed,  not 
the  more  usual — the  meatus  is  accordingly  doubled.  Into  the  upper  and  front  part 
of  the  superior  meatus  the  posterior  ethmoidal  air-cells  open  by  one  or  more  orifices 

Fig.  1 1 75, 


Frontal  liniu 

Probe  in  infundibulum 

Middle  turbiraie,  partly. 
removed 


Hiatua  aemilanarb' 
Ethmoidal  bulla^       -''''-' 


Jl>eiiiii(pi         A({»erna»i. 

of  maxiHarv  %\nn% 

into  infundibu.um- 

Ventrici 

LI  men  nasi' 

VeuibulC' 


Probe  in  nMo-lachrymol 
duct 


Opcnin(  of  middle  ethmoidal  cells 

Superior  turbinate,  partly  removed 

Opening  into  sphenoethmoidal  rcceia 

^      -i^^,^..^SphenoidaI  sinus 

Openins  of  posterior 
rthmolrl  cells  into 
superior  meatus 
Naso.phar>-nx 


Opening  of  Eustach- 
ian lube 


Inferior  meatua 


Inferior  turbinate, 
partly  renovcd 


Middle  meatua 


Lateral  wall  of  naaal 


;  portlona  of  tnrMnale  bones  have  been  removed  to  eapose 
openings  into  air  spaces. 


of  variable  size.  Above  and  behind  the  upper  turbinate  and  in  front  of  the  body  of 
the  sphenoid  bone  lies  a  diverticulum,  the  ^heno-ethmoidal  recess,  into  the  posterior 
part  of  which  opens  the  sphenoidal  sinus. 

The  Middle  Meatus. — The  recess  beneath  the  middle  turbinate  (meatus  nasi 
medius)  is  spacious  and  arched  to  conform  with  the  contour  of  the  middle  and 
inferior  conchae  which  constitute  its  roof  and  floor  respectively.  On  elevating, 
or  still  better  removing  close  to  its  attachment,  the  middle  turbinate  bone,  a  deep 
crescentic  groove,  the  infundibulum,  is  seen  on  the  outer  wall  of  the  fossa  overhung 
by  the  anterior  half  of  the  concha.  The  crescentic  cleft  leading  from  the  middle 
meatus  into  the  infundibulum  is  the  hiatus  semilunaris,*  which  t-xtends  from  above 
downward  and  backward,  with  its  convexity  directed  forward.  Its  anterior  boundary 
is  a  sharp  crescentic  ridge  due  to  the  uncinate  process  of  the  ethmoid  covered 
with  thin  mucous  membrane,  while  behind  it  is  limited  by  a  conspicuous  elevation 
produced  by  the  corresponding  underlying  bony  projection  of  the  ethmoidal  bulla. 

'  Some  confusion  exist?;  in  tlie  use  of  this  term,  siiicc  It  Is  ofttm  applied  to  the  tnitire  grno^x  and 
not  merely  to  the  cleft  which  leads  from  the  meatus  into  the  btoovp.  The  name  is  here  employed 
a-H  indicating  the  lunate  cleft  and  not  the  Rroove  (which  is  the  infimdihiilnm ),  as  oriKinally  used 
by  Zuckerkandl,  who  introduced  it.    See  Antomie  der  Nasenhohle,  Wien,  i88»,  page  39. 


^;,!-*X:k 


141 2 


HUMAN  ANATOMY. 


When  the  infundibnlum  does  not  end  blindly  above,  which  it  often  does  (page 
194),  its  upper  extremity,  usually  somewhat  expanded,  receives  the  openmg  of  the 
frontal  sinus,  ostium  frontaU.  The  sinus  is,  however,  not  dependent  upon  the 
infundibulum  for  its  communication  with  the  middle  meatus,  smce,  as  pomted  out 
by  Zuckerkandl,  between  the  front  of  the  atUchment  of  the  middle  turbinate  bone 
and  the  uncinate  process  of  the  ethmoid  there  exists  a  passage  which  leads  to  the 
ostium  frontale.  Into  the  upper  part  of  the  infundibulum  usually  open  some  of  the 
anterior  ethmoidal  air-cells  ;  lower  in  the  groove  lies  the  oval  or  slit-like  ostium 
maxillare  the  chief  communication  of  the  antrum  of  Highmore.  When  the  latter 
is  provided  with  an  additional  orifice,  as  it  is  in  10  per  cent.  (Kallius),  the  smaller 
accessory  communication  opens  into  the  inhindibulum  a  few  millimeters  behmd 
the  principal  aperture.  Above  the  hiatus  semilunaris,  either  on  or  above  the 
bulla  •*  usually  seen  tlie  slit-like  opening  through  which  the  middle  ethmoidal  cells 
com>nuiicate  with  the  meatus. 

The  Inferior  Meatus.— T\(\%  passage  (meatus  nasi  inferior),  the  largest  of  the 
three,  measures  from  4.5-5.5  cm.  in  length,  its  anterior  end  lying  from  2.5-3-5  "«. 
behind  the  tip  of  the  nose.     At  first  relatively  contracted,  it  abrupdy  expands,  not 


Fir.    ii7< 


Scalp 


Cerebral  hemiipherc. 


Superior  longitudinal  ainot 
Bone 


'alx  cerebri 


Ethmoidal  cella 

Lower  end  of  probe 

lying  in  liiatus 

semilunaris 


Middle  turbinate. 

Probe  passim  from 

antrnni  into. 

intuiidibulum 


Inferior  turbinate 


Nasal  septum 


Right  eyeball 

Hiatus  semilunaris 
Middle  meatus 

Maxillary  sinna 

Inferior  meatut 
Floor  of  na!<al  fossa 
Oral  mucous  membrane 


Tongue 


Frontal  section  of  head,  viewed  from  behind,  showing  nasal  foss«  and  communiiaiions 
with  fronul  and  maxillary  sinuses. 

only  in  height,  in  correspondence  with  the  arched  attached  border  of  the  lower 
turbinate,  but  also  in  width.  Farther  backward,  it  gradually  diminishes  and  is  again 
reduced  at  its  choanal  end.  On  the  lateral  wall  of  the  inferior  meatus,  usually  from 
3-3.5  cm.  behind  the  posterior  margin  of  the  nostril,  after  removal  of  the  lower 
turbinate,  niay  be  seen  the  opening  of  the  naso-lachrymal  duct.  The  position  and 
fonn  of  the  orifice  are  subject  to  much  variation.  When  close  to  the  arching  attached 
border  of  the  concha,  the  aperture  is  usually  oval  or  even  round  ;  when  its  pos't'"" 
is  lower,  it  is  narrow  and  slit-like,  obliquely  vertical,  and  often  guarded  by  a  fold  ol 
mucous  membrane,  the  so-called  valve  of  Hasner. 

The  arched   roof  of  the   nasal   fossa   is  divisible   into  a  naso-frontal,  an 
ethmoidal  and  a  sphenoidal   part  in  accordance  with  the  bones  over  which  the 


THE  NASAL  MUCOUS  MEMBRANE. 


•4IJ 


mucous  membrane  stretches.  The  lower  part  of  the  naso-frontal  division,  below  the 
nasal  bone,  is  cutaneous  and  cartilaginous.  Anteriorly  the  roof  is  reduced  to  little 
more  than  a  groove  on  account  of  the  approximation  of  the  lateral  aiid  median 
walls,  but  posteriorly  broadens  towards  the  choana.  The  median  part  of  the  roof, 
foimed  by  the  cribriform  plate  of  the  ethmoid,  is  very  thin  and  makes  a  sharp  angle 
with  the  steeply  descending  sphenoidal  division.  Between  the  latter  and  the  superior 
turbinate  bone  lies  the  spheno-ethmoidal  recess. 

The  floor  of  the  nasal  fossa,  much  broader  than  the  roof  and  supported  by 
the  palatal  process  of  the  maxilla  and  the  horizontal  plate  of  the  palate  bone,  from 
before  backward  is  approximately  horizontal,  but  from  side  to  side  is  distinctly  con- 
cave. Anteriorly  this  wall  is  robust,  but  rapidly  diminishes  in  thickness  as  it  passes 
backward.  About  2  cm.  behind  the  posterior  margin  of  the  nostril  and  close  to  the 
septum,  the  floor  of  each  nasal  fossa  presents  a  slight  depression,  sometimes  narrow 
and  funnel-shaped,  that  leads  into  a  small  canal  lined  with  a  prolongation  of  mucous 
membrane.  This  canal  converges  towards  the  septum  with  its  fellow  of  the  opposite 
fossa,  descends  almost  vertically,  and  passes  through  the  incisive  foramen  in  the  hard 
palate  to  end  on  the  roof  of  the  mouth  as  a  minute  slit  at  the  side  of  the  incisive  pad 
or  papilla  f>alatina.  Although  the  two  tubes  of  mucous  membrane  may  join  to  form 
a  single  incisive  canal,  they  usually  retain  their  independence  (Leboucq,  Merkel). 
They  are  often  closed  and  impervious  ;  sometimes,  however,  even  in  the  adult 
communication  is  retained  betweer  the  nasal  and  oral  cavities. 

The  posterior  nares  or  choante,  the  apertures  through  which  the  nasal  fossie 
communicate  with  the  naso-pharynx,  one  on  either  side  of  the  septum,  resemble  in  form 
somewhat  a  Gothic  arch  (Fig.  1354).  They  are  relatively  much  lower  in  the  new- 
bom  child  than  in  the  adult,  in  which  they  measure  about  3  cm.  in  height  and 
'1.5  cm.  in  breadth  (Zuckerkandl),  although  individual  variation  is  considerable. 
Each  ofiening  is  bounded  below  by  the  horizontal  plate  of  the  palate  bone  ;  laterally 
by  the  inner  surface  of  the  internal  pterygoid  plate  of  the  sphenoid  ;  above  by  the 
vaginal  process  of  the  sphenoid  and  the  ala  of  the  vomer ;  and  mesially  by  the 
vertical  posterior  borders  of  the  vomer.  Over  this  bony  arch  the  nasal  mucous 
membrane  is  continuous  with  that  lining  the  pharynx.  Laterally  the  posterior 
limit  of  the  nasal  fossa  in  the  recent  condition  is  indicated  by  a  furrow  (sulcus  nasalis 
posterior)  that  extends  from  the  under  surface  of  the  sphenoid  downward  to  about 
the  junction  of  the  hard  and  soft  palates.  Behind  this  furrow,  about  on  a  level  with 
the  lower  border  of  the  inferior  turbinate,  lies  the  opening  of  the  Eustachian  tube 
(Fig.  1 174).  Since  the  turbinates  end  approximately  i2  mm.  in  advance  of  the 
choanae,  the  outlines  of  these  optenings  are  unbroken  by  the  scrolls  that  model  the 
lateral  wall  of  the  nasal  fossae,  all  three  conchse,  however,  being  visible  through  the 
posterior  nares. 


THE  NASAL  MUCOUS  MEMBRANE. 

Beyond  the  limen  that  marks  the  limit  of  the  integument  clothing  the  vestibule 
(page  1409),  the  nasal  fossa  is  lined  by  mucous  membrane  continuous  with  that  of  the 
naso-pharynx  through  the  choanje.  Since  in  addition  to  lining  the  tract  over  which 
the  respired  air  passes  the  nasal  mucous  membrane  contains  the  cells  receiving  the 
impressions  giving  rise  to  the  sense  of  smell,  it  is  appropriately  divided  into  a  respir- 
atory and  an  olfactory  part. 

The  Olfactory  Region. — The  highly  specialized  regio  olfactoria  is  quite 
limited  in  extent  and  embraces  an  area  situated  over  the  middle  of  the  upper  tur- 
binate and  the  corresponding  Jjart  of  the  septum.  According  to  Brunn,  '  whosr 
conclusions  are  here  presented,  the  olfactory  area  of  each  fossa  includes  only  about 
350  sq.  mm. ,  the  septum  contributing  something  more  than  one-half  of  the  entire  surface. 
Accordingly  the  specialized  field  is  by  no  means  coextensive  with  the  upper  turbinate 
bone,  as  it  reaches  neither  its  lower  nor  posterior  border  (Fig.  1 177).  The  anterior 
margin  of  the  area,  which  lies  about  I  cm.  behind  the  front  wall  of  the  nasal  fossa,  is 
irregular  in  outline  owing  to  the  invasion  of  the  specialized  region  by  the  adjacent 

'  Archiv  f.  mikros.  Anat.,  Bd.  39,  1893. 


HH 


HUMAN   ANATOMY. 


Fig.  1177. 


respiratory  mucous  membrane,  tongues  or  even  islands  of  the  latter  projecting  into 
or  being  surrounded  by  the  former.  Upon  the  evidence  derived  from  careful  dissection 
of  the  olfactory  mucous  membrane,  however,  it  is  difficult  to  avoid  the  conclusion 

that  Brunn's  areas  are  too  limited,  as  nerve-fila- 
ments clearly  attached  to  the  olfactory  bulb  are 
usually  traceable  onto  the  upper  part  of  the  middle 
turbinate  bone.  In  fresh  preparations  the  olfactory 
area  usually,  but  not  always,  can  be  approximately 
mapped  out  by  the  yellowish  hue,  lighter  or 
darker,  that  distinguishes  it  from  the  respiratory 
region  in  which  the  mucous  membrane  exhibits 
a  rosy  tint. 

The  epithelium  contains  two  chief  con- 
stituents— the  supporting  and  the  olfactory  cells. 
The  supporting  cells  are  tall  cylindrical  elements, 
about  .06  mm.  in  height,  that  extend  the  entire 
thickness  of  the  epithelium.  Their  outer  and 
broader  ends  are  of  uniform  width  and  contain 
the  oval  nuclei  which,  lying  approximately  at 
the  same  line  and  staining  readily,  form  a 
deeply  colored  and  conspicuous  nuclear  stra- 
tum at  some  distance  beneath  the  free  margin. 
Between  the  latter  and  the  row  of  nuclei,  the 
epithelium  presents  a  clear  zone  devoid  of 
nuclei.  The  inner  part  of  the  supporting  cells 
is  thinner  and  irregular  in  contour  and  often' 
terminates  by  splitting  into  two  or  more  basal  processes  that  rest  upon  the  tunica 
propria.     Between  these  ends  lie  smaller  pyramidal  elements,  the  basal  cells,  that 


... Hptum  (s)  ha«   been 

partiany  separated  and  turned  upward ;  dark 
field  shows  olfactory  area  on  lateral  and  meswl 
walls  of  fossa,  as  mapped  out  by  Hrumn.. 


Right  nasal  fossa, 
any 


Fig.  I 178. 


Outer  zone 
Nuclear  layer  of 
supporting  cells 

Olfactory  cell* 


Blood-vessel  - 
Glands, 


Bundle  of 

olfactory  nerves  « 


.;ii?STii'5^S;;jsi^^M<'^ 


^^mmm 


A^M.L 


^% 


Section   of  olfactory  mucous  membrane ;   epithelium  displays  outer  nuclei-free  and  nuclear  layers  formed   by 
supporting  cells  and  broad  stratum  containing  nuclei  of  olfactory  cells.     ■   300. 

probably  represent  younger  and  supplementary  forms  of  the   sustentacular  cells. 
The  granular  protoplasm  of  the  basal  processes  often  contains  pigment  particles. 

The  olfactory  cells,  the  perceptive  elements  receiving  the  smell-stimuli,  con- 
sist of  a  fusiform  body,  lodging  a  spherical  nucleus  enclosed  by  a  thin  envelope  of 
cytoplasm,  and  two  attenuattnl  processes,  a  peripheral  and  a  central.  The  olfactory 
cells  are  in  fact  sensory  neurones  that  have  retained  their  primitive  position  within 
the  surface  epithelium,  as  in  many  invertebrates,  instead  of  receding,  as  is  usual  ir- 


THE  NASAL  MUCOUS  MEMBRANE. 


1415 


the  higher  animals,  to  situations  more  remote  from  the  exterior.  The  slender 
peripheral  process  of  the  olfactory  cell,  which  corresponds  to  the  dendrite  of  the 
neurone,  is  of  uniform  thickness  and  ends  at  the  surface  in  a  small  hemispherical 
knob  that  projects  slightly  beyond  the  general  level  of  the  epithelium  and  bears  from 
6-8  minute  stiff  cilia,  the  olfactory  hairs.  The  length  of  the  peripheral  pr.icesses. 
being  dependent  upon  the  position  of  the  nuclei,  vanes,  since  the  latter  occupy 
dif!e-ent  levels  within  the  epithelium  in  order  to  accommodate  their  greater  numlxT— 
about  60  per  cent,  in  excess  of  those  of  the  supporting  cells  (Brunn ).     The  central 


Fig.  ii8a 


Fig.  1179. 


Ulfactoo'  cell 
Suppoitlnc  cell 


Nerve-fibre 


Section  of  human  olfactory  mucoui 
membrane,  silver  pre|iaration ;  two 
olfactory  cells  are  seen,  one  of  which 
sends  nerve-libre  towards  brain.  X  jjs- 
(Btunn.) 


Isolated  elements  of  epithelium  of  olfactory 
mucous  membrane ;  0,  olIactor>-  cells  ;  *,  sup- 
porting cells.    X  looo.    (Ariuu).) 


processes  of  the  olfactory  cells,  much  more  delicate  than  the  peripheral,  are  directly 
continueti,  as  the  axis-cylinders,  into  the  subjacent  nonmedullated  nerve-fibres  within 
the  tunica  propria,  from  which  they  pass  through  the  cribriform  plate  to  enter  the 
brain  and  end  in  the  arborizations  within  the  olfactory  glomeruli  of  the  bulbus 
olfactorius  (page  1152). 

The  tunica  propria  is  differentiated  into  a  superficial  and  a  deep  layer  by 
the  adenoid  character  of  the  stratum  immediately  beneath  the  epithelium.  The 
superficial  layer,  from  .015-. 020  mm.  thick,  consists  of  closely  packed  irregularly 
round  cells,  resembling  lymphocytes,  and  meagre  bundles  of  delicate  connective 
tissue.  The  deep  layer,  on  the  other  hand,  contains  robust  bundles  of  fibro-elastic 
tissue  and  relatively  few  cells.  A  distinct  membrana  propria  is  wanting  within  the 
olfactory  region. 

The  glands  of  Bowman  ( glandulae  olfactoriae)  are  characteristic  of  the  olfactory 
region  and  probably  elaborate  a  specific  secretion  (Brunn).  They  open  onto  the 
free  surface  by  very  narrow  ducts  that  lead  into  saccular  fusiform  dilatations,  into 
which  the  tubular  alveoli  open.  The  ducts  possess  an  independent  lining  of  flattened 
cells  that  extend  as  far  as  the  surface  and  lie  between  the  surrounding  epithelial  ele- 
ments. The  dilatations  are  clothed  with  flattened  or  low  cuboidal  cells,  which  are 
replaced  by  those  of  irregular  columnar  or  pyramidal  form  .  "n  the  tubular 
alveolar.     From  th-j  character  of  their  secretion  the  glands  of  Bov  are  probably 

to  be  reckoned  as  serous  and  not  mucous  (Brunn,  Dogiel). 

The  Respiratory  Region. — The  mucous  membrane  lining  of  the  respiratory 

region  differs  greatly  in  thicknc-ss  in  various  parts  of  the  nasal  fossa.      In  situ.-itinns 

where  the  contained  cavernous  tissue  is  well  represented,  as  over  the  inferior  turbinate, 

:  may  reach  a  thickness  of  several  millimeters,  while  when  such  tissue  is  wanting,  as 

on  the  lateral  wall,  it  is  reduced  to  less  than  a  millimeter. 


I4I6 


HUMAN  ANANOMY, 


The  epithelium  is  stratified  ciliated  columnar  in  type,  from  .050-. 070  mm. 
thick,  and  includes  the  tall  surface  cells,  bearing  the  cilia,  betweer*  the  inner  ends  of 
which  lie  the  irre^larly  columnar  basal  cells.  Numerous  elements  exhibit  various 
stages  of  conversion  into  mucous-containing  goblet  cells.  The  current  produced  by 
the  cilia  is  toward  the  posterior  nares. 

Beneath  the  epithelium  stretches  the  membrana  propria  or  basement  membrane, 
that  varies  greatly  in  thickness  ;  although  in  certain  localities  feebly  developed,  it  is 
usually  well  marked  and  measures  from  .010-. 020  mm.  in   thickness  (Brunn). 


Fig.  1181. 


Eptthelium 


GUuidi 


Section  of  respiratory  mucous  membrane  covering  nasal  septum,     x  75. 

Under  pathological  conditions  its  thickness  may  increase  fourfold  or  more.  In  many 
places  the  membrana  propria  is  pierced  by  minute  vertical  channels,  the  basal  canals, 
in  which  connective-tissue  cells  and  leucocyctes  are  found,  but  never  blood-capillaries 
(Schiefierdecker). 

The  tunica  propria  consist:^  of  interlacing  bundles  of  fibro-elastic  tissue  which 
are  most  compactly  disposed  towards  the  subjacent  periosteum.  The  looser  super- 
ficial stratum  is  rich  in  cells  and  here  and  there  contains  aggregations  of  lymphocytes 
that  may  be  regarded  as  masses  of  adenoid  tissue  (Zuckerkandl).  In  certain  parts 
of  the  nasal  fossa  the  stroma  of  the  mucous  membrane  contains  vascular  areas  com- 
posed of  numerous  intercommunicating  blood-spaces  that  confer  the  character  of  a 
true  cavernous  tissue.  These  specialized  areas,  the  corpora  cavernosa,  as  they  are 
called,  are  especially  well  developed  over  the  inferior  and  the  lower  margin  and 
posterior  extremity  of  the  middle  conchae,  and  less  so  over  the  posterior  end  of 
the  upper  turbinate  and  the  tuberculum  septi.  When  typical,  they  occupy  practically 
the  entire  thickness  of  the  mucous  membrane  from  periosteum  to  epithelium,  the 
interlacunar  trabecuhf  containing  the  glands  and  blood-vessels  destined  for  the  sub- 
epithelial stroma.  The  blood-sinuses,  the  general  disposition  of  which  is  vertical 
to  the  bone  (Zuckerkandl),  include  a  superficial  reticular  zone  of  smaller  spaces 
and  a  deejjer  one  of  larger  lacimoe.  The  engorgement  and  emptying  of  the  cavernous 
tis.sue  is  controlled  by  nervous  reflexes  and  probably  has  warming  of  the  inspired  air 
as  its  chief  purpose  (Kallius). 

The  glands  of  the  respiratory  region  are  very  numerous,  although  varying  in 
size,  tubo-alveolar  in  form  and,  for  the  most  part,  mixed  mucous  in  type.  The 
chief  ducts  open  on  the  free  surface  by  minute  orifices  barely  distinguishable  with  the 
unaided  eye.  Their  deeper  ends  branch  irregularly  into  tubes  that  bear  the  ovoid 
terminal  alveoli.     The  latter  are  lined  with  mucous-secreting  cells,  between  which  lie 


Fig.  1 183. 


PRACTICAL  CONSIDERATIONS:   THE  NASAL  CAVITIES.     1417 

the  crescentic  groups  of  serous  cells  that  sump  the  Rlaiuls  is  mixed  (Stohr). 
Exceptionally  exclusively  serous  glands  are  also  encountered  (Ka'.ius). 

JacolMon'8  Organ.— Mention  has  been  made  of  the  r.  .mentary  »t«;««^<"''e 
(orwmod  vomeronasale)  found  in  man.  almost  constantly  in  the  new-b<)rn  child  and 
frequentiy  in  the  adult,  as  a  represenutive  of  the  organ  of  Jacobson  that  is  present, 
in  varying  degrees  of  perfection,  in 
all  amniotic  vertebrates  (  Peter).  1  n 
many  animals  possessing  in  high 
degree  the  sense  of  smell  (macros- 
matic),  the  oi^n  is  well  developed 
and  hinctions,  serving  possibly  as  an 
accessory  and  outlying  surface  by 
which  the  first  olfactory  impressions 
are  received  (Seydel). 

In  man  the  organ  is  represented 
by  a  laterally  compressed  tubular 
diverticulum,  from  1.5-6  mm.  in 
length,  that  passes  backward  and 
slighdy  upward  to  end  blindly  be- 
neath the  mucous  membrane  on  each 
side  of  the  septum.  The  entrance 
to  the  tube  is  a  minute  aperture 
situated  near  the  lower  border  of 
the  septum,  above  the  anterior  nasal 
spine  and  the  rudimentary  vomerine 
cartilage.  The  median  wall  of  the 
diverticulum  is  clothed  with  epithe- 
lium composed  of  tall  columnar  cells 
resembling  those  of  the  olfactory 
region,  but  the  characteristic  olfac- 
tory cells  are  wanting.  The  epithe- 
lium covering  of  the  lateral  wall 
corresponds  to  that  of  the  respiratory  region.  In  macrosmatic  animals  branches  oi 
the  olfactory  nerve  are  traceable  to  Jacobson' s  organ  in  which  are  found  olfactory  cells. 

PRACTICAL  CONSIDERATIONS  :  THE  NASAL  CAVITIES. 

The  nasal  cavities  have  certain  important  clinical  relationships  which  may  be 
classified  as  (i)  physiological— (a)  respiratory,  phonatory  and  olfactory  ;  (*)  sexual ; 
(2)  topographical— (a)  the  nasal  chamber  and  the  vestibule  ;  (*)  the  premaxillary, 
maxillary,  and  palatal  portions  ;  (r)  the  septum,  and  the  turbinate  bones. 

I.  (a)  The  air  passing  out  from  the  pharynx,  being  confined  to  the  plane  of 
the  posterior  nares,  is  not  carried  up  to  the  olfactory  region,  so  that  the  odors  on  the 
expired  breath  are  not  appreciated.  When  the  communication  between  the  respira- 
tory and  olfactory  portions  is  cut  off,  as  by  swelling  of  the  mucous  membrane  at 
the  region  of  union  of  these  portions,  loss  of  smell  supervenes.  Discharge  which  may 
accumulate  about  the  middle  turbinate  bone  or  in  the  upper  portion  of  the  vestibule 
cannot  be  removed  by  the  act  of  blowing  the  nose,  for  the  reason  above  assigned  that 
the  air  of  expiration  cannot  pass  within  the  olfactory  portion.  The  act  of  blowing 
the  nose,  or  the  process  of  washing  out  the  nose  by  a  current  thrown  in  from  the 
naso-pharynx,  will  wash  out  the  inferior  meatus  with  ease,  provided  the  discharge  is 
not  inspissated,  and  the  parts  of  the  floor  of  the  nose  are  normal  (Allen).  An 
abnormal  width  or  patency  of  the  respiratory  portion  of  the  fossa — especially  of  the 
inferior  meatus — due  to  imperfect  development  of  the  inferior  turbinates,  has 
been  thought  (Lack),  by  diminishing  the  vis  a  tersro  in  blowing  the  nose  and  thus 
favoring  the  retention  and  decomposition  of  the  nasal  mucus,  to  contribute  to  the 
occurrence  of  atrophic  rhinitis  (oz«na).  The  value  of  the  nose  as  an  accessory 
organ  of  phonarion  consists  in  its  action  as  a  resonating  cavity  which  adds  quality, 
color  and  individuality  to  the  voice.     This  hincrion  of  the  nose  becomes  strikingly 


Portion  of  Ironul  section  through  nual  fontr  of  liittcn,  (howint 
orgmn  of  Jacobson.    X  ao. 


I4i8 


HUMAN  ANATOMY. 


apparent  when,  as  durinjj  an  acute  coryza,  the  fossae  are  more  or  less  completely 
obstructed  and  the  voice  becomes  flat  and  entirely  without  resonance- 

(6)  The  relations  between  the  nasal  chambers  and  the  sexual  apparatus  are  of 
practical  importance  and  have  as  an  anatomical  basis  the  analO|{y  between  the  mucosa 
covering  much  of  the  turbinates  and  part  of  the  septum,  and  the  erectile  tissue  of  the 
penis,  and  the  sympathy  between  the  erectile  portions  of  the  generative  tract  and 
erectile  structures — e.  g. ,  the  nipple — in  other  parts  of  the  body. 

2.  (a)  The  distinction  between  the  nasal  chamber  and  the  vestibule  is,  in  the 
main,  based  upon  the  difference  in  their  lining  membrane,  that  of  the  vestibule 
being  simply  a  continuation  inward  of  the  external  integument  to  the  line  (limeti 
nasi)  at  which  the  nasal  fossa  proper  begins.  The  vestibular  cavity  is  provided  with 
rigid  hairs  (to  aid  in  arresting  foreign  particles  carried  in  with  the  air  current),  and 
sebaceous  glands,  and  is  especially  susceptible  to  eczematous  or  furuncular  affections. 
Diseases  of  the  vestibule  may,  therefore,  be  dealt  with  as  though  they  were  affections 
of  the  skin  ;  while  diseases  of  the  mucosa  of  the  nasal  chambers  are  to  be  treated  on 
the  same  principles  as  those  of  the  mucous  membranes  generally,  with  special  refer- 
ence to  its  erectile  character  and  to  its  close  relation  to  the  underlying  periosteum 
and  bone. 

(*)  Thesutural  lines  of  the  premaxilla,  of  the  maxilla,  and  of  the  palatal  bones 
aid  in  determining  the  boundaries  of  the  subdivisions  of  the  nasal  chamber,  which 
are  indicated  to  some  degree  by  the  production  of  the  planes  of  the  su*-  res  of  the 
roof  of  the  mouth,  vertically  upward  through  the  nasal  chambers. 

(f)  The  morphological  significance  of  the  septum,  placed  as  it  is  !  .e  median 
line  of  the  face  of  the  embryo,  with  the  turbinate  bones  lodged  to  its  ■  ijht  and  left 
sides,  remains  the  same  in  the  skull  of  the  adult,  notwithstanding  the  ..  Jt  that,  with 
cultivated  races  at  least,  the  septum  is  usually  deflected  through  the  greater  part  of 
its  course  from  the  median  line.  This  deflection  has  been  said  to  be  due  to  the 
persistent  growth  of  the  septal  bones  in  a  vertical  plane  after  their  edges  have 
united — the  apex  of  the  deflection  being  often  found  at  the  junction  of  the  ethmoid 
and  vomer  ;  any  preponderance  in  strength  of  one  of  these  bones  w  ill  cause  bending 
of  the  weaker — usually  the  perpendicular  plate  of  the  ethmoid.  The  usual  direction 
of  the  deflection  is  to  the  left,  and  this  has  been  thought  to  be  due  to  the  habit  of 
using  the  right  hand  in  blowing  the  nose.  Asymmetry  of  the  nasal  chambers  is  a 
result  of  the  deflection.  One  of  these  chambers,  commonly  the  left,  is  much  smaller 
than  its  fellow  of  the  opp  te  side,  and  may  be  occluded,  when  the  right  chamber 
will  be  larger  than  normal  and  possess  both  osseous  and  erectile  structures  which 
have  undergone  physiological  hypertrophy.  Care  should  be  taken  to  distinguish 
between  such  hypertrophy  and  the  effects  of  diseased  action  (Allen). 

The  anterior  nares  are  directed  downward  and  are  on  a  lower  plane  than  the 
floor  of  the  nose.  To  examine  the  interior  of  the  nose  the  movable  nostril  must 
therefore  be  elevated  and  the  head  thrown  backward.  The  speculum  shaped  for  the 
purpose  should  not  be  passed  beyond  the  dilatable  cartilaginous  portion.  With  good 
light  one  mav  see  the  anterior  part  of  the  middle  turbinate  bone,  a  larger  portion  of 
the  inferior  turbinate,  the  beginning  of  the  middle  meatus,  and  get  a  freer  view  of  the 
inferior  meatus,  the  septum  and  the  floor  of  the  nose.  The  lower  orifice  of  the  nasal 
duct  cannot  be  seen,  although  it  is  only  about  an  inch  from  the  orifice  of  the  nostril, 
and  three-fourths  of  an  inch  above  the  floor  of  the  nose.  This  is  due  to  the  fact 
that  it  is  concealed  behind  the  attached  and  depressed  anterior  end  of  the  inferior 
turbinate. 

To  expose  better  the  structures  in  the  external  wall  of  the  narrow  and  rigid 
nasal  fossa,  various  procedures  have  been  adopted.  Rouge  made  an  opening  into 
the  anterior  nares  from  the  mouth,  by  incising  in  the  angle  between  the  upper  lip  and 
the  gum.  By  separating  the  alar  cartilages  from  the  bones  and  dividing  the  cartilag- 
inous septum  the  movable  anterior  portion  of  the  nose  can  be  turned  upward,  giving 
a  full  exposure  of  the  nasal  fossa;,  without  leaving  an  unsightly  scar. 

To  permit  a  freer  exploration  with  the  finger,  Kocher  divided  the  septum  as  far 
back  as  possible  with  scissors.  He  also  divided  the  roof  of  the  nose  near  the  septum, 
turning  the  divided  parts  aside.  An  osteoplastic  flap  may  be  made  by  extending  this 
incision  upward,  dividing  the  bone  in  this  line  and  making  a  second  incision  around 


PRACTICAL  CONSIDERATIONS:  THE  NASAL  CAVITIES.     1419 

the  ake  and  along  the  side  of  the  nose,  again  dividing  the  bone.  The  Hup  thus 
formed  can  be  turned  upward,  after  breaking  the  bridge  of  bone  between  the  up|)er 
ends  of  the  two  incisions,  exposing  the  na^  fossa. 

The  finger  can  be  passed  backward  through  the  nostril  far  enough  to  meet  the 
finger  of  the  other  hand  passed  tu  the  posterior  nares  through  the  mouth. 

The  posterior  nares  can  be  examined  by  the  rhinoscopic  mirror  or  by  the  finger 
introduced  through  the  mouth.  Posterior  rhinoscopy,  like  laryngoscopy,  is  carried 
out  with  difficulty,  because  the  region  of  the  naso-pharynx  ia  sensitive  and  is  intol- 
erant of  intrusion.  In  the  act  of  swallowing,  the  epiglottis  protects  the  larynx  by 
closing  the  laryngeal  '  .pening,  and  the  soft  palate  rises  against  the  posterior  wall  of 
the  pharynx,  preventing  regurgitation  into  the  nose.  When  the  rhinoscopic  mirror 
is  used  the  same  thing  occurs,  so  that  the  view  of  the  larynx  and  naso-pharynx  is 
shut  of!.  Considerable  difficulty  is  sometimes  ex|>erienced  in  training  the  patient  to 
overcome  this  tendency.  The  employment  of  the  nasal  douche  is  based  upon  the 
same  mechanism.  When  the  stream  of  fluid  passed  through  one  nostril  reaches  the 
posterior  part  of  the  nose,  its  progress  toward  the  mouth  is  obstructed  by  the  elevated 
soft  palate,  and  it  therefore  passes  around  the  posterior  edge  of  the  septum  and  back 
through  the  opposite  nasal  fossa. 

With  the  rhinoscopic  mirror  in  good  position,  and  the  soft  palate  quiet,  one 
may  see  the  posterior  nares  divided  by  the  septum,  the  turbinated  bones,  and  the 
meati  (especially  the  middle  turbinate  and  the  middle  meatus),  the  roof  of  the  naso- 
pharynx and  the  orifices  of  the  Eustachian  tubes.  The  finger  introduced  through 
the  mouth  can  feel  the  same  structures,  and  can  recognize  naso-pharyngeal  adenoids, 
tumors,  or  abscesses. 

The  mucous  membrane  over  the  turbinates,  owing  to  the  presence  of  a  rich 
venous  plexus,  is  one  of  the  most  vascular  in  the  body,  and  resembles  erectile  tissue 
(page  1968).  This  and  the  general  vascularity  of  the  nose  partly  explain  the  great 
frequency  of  epistaxis.  The  excessive  supply  of  blood  to  the  mucosa  may  be  {a)  for 
the  purpose  of  enabling  it  to  raise  the  temperature  and  add  to  the  moisture  of  the 
inspired  air :  (i)  to  favor  the  activity  of  the  numerous  mi'^ius  glands,  the  free  secre- 
tion of  which  together  with  the  acdon  of  the  cilia  of  the  epithelial  cells  is  required  to 
remove  the  dust  and  the  micro-organisms  that  are  filtered  from  the  air  during  inspi- 
ration by  the  \abrissae  and  the  cilia  themselves  ;  (f )  to  endow  it  with  sufficient  vitality 
to  resist  the  pathogenic  action  of  such  micro-organisms.  In  spite  of  this  defensive 
quality,  the  constant  exposure  to  atmospheric  irritants  often  leads  to  congestions  and 
coryzas,  which  if  long  continued  and  frequently  repeated  result  in  hypertrophy  of 
the  mucous  membrane.  This  may  require  removal  by  cauterization  or  excision  to 
relieve  the  consecinent  obstrucdon.  The  mucous  membrane  is  somewhat  less  closely 
attached  to  the  septum  than  to  the  neighboring  parts,  and  hence  hfematomata  of  the 
septal  submuco?  I  are  not  infrequent  after  an  injury  to  the  nose.  Such  hsmatomata 
are  almost  invariably  infected  and  proceed  to  suppuration  forming  septal  abscesses, 
the  constitutional  symptoms  (toxaemia)  of  which  may  give  rise  to  anxiety  if  their 
local  cause  is  overlooked. 

Epistaxis  is  common  not  only  because  of  (a)  this  vascularity  of  the  mucosa,  but 
also  by  reason  of  (6)  the  frequency  of  trauma  to  the  nose  ;  the  relation  of  its  veins 
(f )  to  the  general  venous  current  so  that  they  may  be  congested  in  cardiac  or  in  pul- 
monary disease,  or  in  straining,  or  in  paroxysms  of  coughing,  as  in  whooping  cough  ; 
and  (d)  to  the  intracranial  sinuses,  so  that  nose-bleed  may  be  a  symptom  of  cerebral 
congestion  or  tumor  ;  (e)  the  bleeding  may  be  vicarious,  as  in  cases  of  suppressed 
menstruation  (an  illustration  of  the  sexual  relations  of  the  nasal  apparatus);  (/) 
it  not  uncommonly  follows  ulceration — simple,  tuberculous  or  syphilitic — and  in 
obstinate  cases  such  ulcers  should  always  be  sought  for. 

The  source  of  hemorrhage  from  the  nose  is  most  frequendy  in  the  anterior  part, 
particularly  on  the  septum,  and  is  then  onlinarily  controlled  with  ease.  Usu.-illy  the 
ptient  should  be  kept  upright,  with  the  head  back,  (not  in  the  usual  iwsitiun  icu:i 
ing  over  a  basin,  increasing  the  tension  of  the  vessels  of  the  neck  and  head)  and 
should  be  made  to  take  deep  breaths  with  the  arms  raised,  thus  fr'ly  expanding  the 
thorax  and  depleting  the  cervical  veins  and,  indirectly,  the  faci:i'.  ind  ophthalmic  into 
which  the  veins  of  the  nose  empty.     If  ordinary  means  fail,  and  this  is  more  likely 


I420 


H  MAX   ANATOMY. 


if  the  bleeding  point  is  ,',nor,  iht-  posterior  iiares  may  be  [dug^ed.  For  this 
purpose  a  loiig  silk  lig  n  is  ju.vwi  through  the  nose  to  the  phar>nx  and  out 
through  the  mouth,   b>     i.raiis  of  .    lltllo.q's  r  mnula  i»r  a  soft  cathet  T  >  the 

middle  of  the  ligature  i  it'achwi  a  :.!uk  o<  gau.  slightly  larger  than  the  posterior 
nares,  which  is  Uien  drawi;  h.  tiie  \i.ii  rior  end  oi  the  ligature  into  the  nasal  lossii, 
which  it  should  tightly  fill. 

Postnasal  adrnoids  orij;.  latein  tii',-  loimidly  excessive  lymphoid  tissue — pharj  n- 
geal  tonsil — of  the  postnasal  sj/aci-,  nl  whi'  !i  tissui  they  are  a  simple  hypertropliy. 
The  growth  forms  a  mass  m  the  vault  oi  tlie  naso-jilwrynx  and  often  extends  down- 
ward and  forward,  filling  tip  RosenmuUer's  toss;r  and  involving  the  orifices  of  the 
Eustachian  tubes.     The  tonsils  are  a)mmonly  ilx.  enlarijed. 

The  symptoms  proiluced  are  :  (a)  obstn  ted  nasai  respiration,  more  marked 
during  sleep,  when  the  mouth  is  closed  by  tlic  approximation  ui  the  tongue  to  the 
palate  ;  (^)  asa  result  of  this,  broken  rest  and  "  night  terrors"  .  and  i  r)  as  a  further 
consequence  (and  also  from  deficient  oxygenation),  deterioration  of  the  genera  1 
health,  delayed  or  arrested  growth,  and  anemia  ;  (d)  intermittent  partial  deafni  ^ 
and  recurrent  attacks  of  catarrhal  or  suppurati\  e  otitis  media  ;  *  >' )  pigeon-breast  from 
inecjuality  of  intra-  and  extra-thoracic  atmosphtric  pressure. 

The  early  removal  of  adenoids  that  product  iiny  or  all  ^  f  these  symptoms  is 
usually  indicated,  and  is  facilitated  l/V  their  friabilit\  and  by  the  toughness  and  <len- 
sity  of  the  submucosa  on  which  they  lie,  circumstances  which  permit  of  their  usually 
easy  enucleation  either  with  the  fingers  or  with  the  adenoid  forceps  and  curette. 

Naso-pharyngeal  growths  may  be  either  simple  fibromata  or  fibro-sarcomata. 
They  are  usually  dense,  and  contain  large  venous  channels,  which  have  no  definite 
sheath  and  thus  do  not  retract  when  severed.  Incision  into  them  may  therefore  be 
followed  by  sewre  hemorrhage  with  no  tendenv  y  to  sjwntaneous  arrest.  Ulcera'^^i 
or  ubrasion  of  the  surface  of  3»ese  growths  is  not  inirequent,  and  is  also  attendee!  y 
repeated  and  often  dangerous  loss  of  blood. 

The  nasal  fossae,  already  very  narrow,  are  frequently  further  obstructed  by  •  h- 
olugical  conditions,  such  as  deviations  of  the  septum,  hypertrophy  of  the  mi  us 
membrane  covering  the  turbinates,  spurs  on  the  septum,  polypi  and  tumors  Ihe 
septum  is  rarely  straight  after  the  seventh  year,  in  about  seventy-five  per  it.  of 
cases  being  turned  to  one  or  the  other  -jide,  most  frequently  the  left  (vide  sHftra). 
Both  the  bony  and  cartilaginous  jxirtions,  more  especially  the  anterior  cartilaginous, 
are  involved.  The  deflection  is  sometimes  due  to  a  fracture  from  blows  or  falls.  The 
whole  nose  usually  deviates  more  or  less  tn  one  side.  Spurs  on  the  septum  c  'i- 
monly  occur  at  the  junction  of  the  bony  and  cartilaginoii -.  portions.  A  deviation  .  i 
the  septum  does  not  necessarily  mean  that  the  narrowed  nasal  fossa  is  serious!.- 
obstructed.  It  frequently,  however,  comes  in  contact  w  'h  the  surface  of  the  turbii,- 
ates,  and  may  result  in  an  adhesion  or  synechia  from  the 
is  set  up.  Operations  are  often  necessary  to  correct 
deviation  of  the  septum.  The  concavity  on  the  opposite 
a  tumor. 

Hypertrophy  of  the  ethti     'lal  labyrinth,  or  bulla  eihtintidali-,  is  som 
far  advanced  as  to  obstruct  the  nasal  fossa  on  thatsiui 
lies  and  yields  before  this  expanded  cell,  and  retax  e.\> 
to  such  an  e.xtent  as  to  make  it  bend   and    ob^"  ict 
a  greater  or   lesser   degree.     T'  e  remo\al  of  tl.      in 
practiced  in  these  ca.ses  (Taylor   .  or  the  bulla  itself  m;i 
the  cutting  forceps  or  curette.     Over-development  ■ 
times  be  so  great  as  to  occasion  ol)struction  of  the  upp 
nasal  fossa. 

The  floor  of  the  nose  is  the  widi-st  part,  and  si      is  gradu  ,il  and 

downward  in  the  upright  position,  so  that  collecting      •jcu'*  tend-,  u  Kward 

and  drop  ii'lii  the  throat.     Rliinuiillis.  wlneii  are  incrn»i..rtjOii-    •"•:  i  loreign 

bodv.  are  most  frequently  found  in  i  o  inferior  meatus,  whic  st.     The 

jKisterior  nares  are  below  the  level  of  the  respiratory  portion  discharge 

above  the  middle  turbinate  cannot  be  blo«     from  the  nose.  r  portion  of 

the  inferior  turbinate  slopes  downward  an'    forward,  and  its  am  .loi      .d  is  attached 


itative  inflammation  which 
diffit  ulties  arising  from 
'  will  differentia     it  :ro"i 

tme 

The  middle  turbin-^te  o> 

(j.-ess  agai   St  the 
ue    oppoHte   nasal   ii 
He  turbiiHi     is   somei 
be  oHite i.ti-      hy  mear. 
he  bul'-      thH.  -idaJis  may 
portif         the.     Ti-rspondini. 


THE    ACCESSORY     MR-SPACKS. 


1421 


so  neai 


thi"  nosi-  that  H^'  roomiest  |h»rtion  of   i  ,.    inferior  nw-atiw  is 
the  •  nirance  ih  air  into  the  lower  [»art  oi  the  nasal  U>-iSii  is 


the  fkior    >f 
postern  1!       Thercfi  '< . 

(,hstriut<l.  ami  is  iivorctl      wii.  I  the  upptr—- respiratory  "—iK)rtion.  «-sjh.    illy 
through  the  wide  anterior  "j    mu^  of  the  iniildle  ineiUUs,  which  reaches  .s  hi^h  .is 


the  tendo  'iculi.     This  anato   =ir:al  arn»ni 
mentions     that  odors  on  ex|    re<l  air  a 
The  I   lations  of  the  nasai  '  hiMnfx 
rymafion.     v  aflectinjj  the  tesi      4ct,  1 
by  extendi!  -'  to  the  pH  irynx  1      way  ■ 


'lent  is  the  e.xplainuion  of  the  tut  already 
;iot  recoffnized. 


xplain  V     ■  a  corvza  ma-    ■  ;    se  (a)  lach- 

nial  Si'      tnd  conjunctiva  dysph-i^ia, 

c  p<)»t«      r  nares  ;  (,f  i  hoiii       ,«*  nr  eolith. 

act  :  ( rf        >ntal  heaiLirhe,  1  v  involving  the 

l)y  implicating         antrum  ;  (  /)  gr.ve  iitraorhiul 

ither  the  ethmoi-      cells  or  the  sphei   >idal  r-inur-es 

ng  the  perineur.i,  or  perivascular  s  leaths,   or  '-v 

through  I  If  cribriform  foramina  to  the  fl(H>r  i.i  the  anter^  -r 

tension  to  the  retnipharyngeal  lymph  node     [wge  <»5=  1,  11=    • 

isal  lymphatics  empty,  may  result  in  a  retrophar^  igt    I  ao- 

sces-  .  I'T  (A  I  infe-tion  (pyogenic  or  tuberculous)  of  'he  submaxillary   preaur      iar. 

r  de«t)  cervical  nxles  may  follow  nose  diseases.     Tht  /raver  of  tht      ■    mf)licaUoi! 


bv  tun  her  e  tension  t 
frontai  sinu^  ■»  :  (f) 
or  intracranial  disea^ 
basal  ni«Mim>f.tis  by 
way  of    he  '    !iph.i» 
cranial  uwsa  ,    (,  ,t 
whi«-h  rrrtain  erf  lae 


'he  resf>iratory 
e  ache 
,  !■    way  1 
xti  nding  a. 


M-     oi  course,    .^MKiatui  with  the  severer  infective  l.tms  .1 
p    ivths — comnsonly  sarcomatous — may  begin  in    'e  nasal  cha 
in  .my  of  the   iirccttons  above  mentioned. 

THE  ACCESSORY  AlR-SPAf    :S. 

The  I  isal  toss.1   co    muiicate  with  a  number  of  rei 
■  Hrt  within  the  -iurroun^  bones,  which  are  filled  with 

membrane  dir<i  tly  conti       us  with  that  of  the  meatu^-s. 
in.  !  =de  fHe  maxillaty,  thr  /rontai,  the  sphenoidal  an     '' 


itis.     Maligna: 
uul  may  extei 


hollowed 
mucous 


:  spaces 
and  the 


Fio.  1 183. 


eifti  rartilaxe 


Risi.l 


Mas-setermusctt 

Internal 
ptrryjjoid 


Rnnf  of  inferior  meatus 


Inferior  turbinate 


Kail  >>i 
naM>-|>har>'nv 
TefnfK>ral  muscle 
MasftettT  nnisi  le 

Internal 
pteryguiil  mUM  Ic 

KuMarhian  tulw 

ConHvle  iif 
man.lible 


Internal  carotid  arter> 


Portion  of  tninsver«  sect,  .n  of  head  passinc  ^;s7;«»tb  nastst  - 
of  the  section  has  been  drawn  -.u<^  iw  aasal  \am 


LKterna,  ^cT>jioid  muscle 

jgaiK  ,A  jtoHMnmuUer 

-jar  jaat  brio*  umldle  turtnnates  :  tht-  inferior  surface 
'  mud  either  sfiAces  if^  view«l  from  below. 


ethmoidal  air-cells,  all  paitt'  ai»<-  «ithifl  rhe  orrespoortmc  ^>ones.  -Sinct-  llu- 
mucous  membrane  is  thin  and  sntirr  ?wlv  adh»-««*  ■  the  bof=«-  tlw  form  of  the  cavi- 
ties as  obser\'ed  in  tht-  rcc-nt  rimditton  cor»*5«rtrfids  rlosely  to  that  seen  in  tlu- 
macerated  skull.     The  r.tzea«d  <-xt«)t  of  tbespuw-'es  var\'  not  on;      t  different  j>eriods 


■  423 


HUMAN  ANATOMY. 


of  life,  but  also  often  on  the  two  sides  of  the  same  individual ;  their  communications 
with  the  nasal  fossx,  however,  are  fairly  constant. 

The  Maxillary  Sinus.— This  space,  (sinus  maxillaris),  or  the  atUrum  of 
Highmore,  the  largest  of  the  pneumatic  cavities,  lies  to  the  outer  side  of  the  nasal 
fossa  and  resembles  in  its  general  form  a  three-sided  pyramid  (FIr.  1184).  It 
occupies  the  greater  part  of  the  superior  maxillary  bone,  so  that  its  walls,  with  the 
exception  of  the  postero-inferior  one,  are  very  thin  and  often  in  jjlaces  of  paper)- 
delicacy  (Fig.  256).  The  median  wall,  or  base,  is  directed  toward  the  iiasal  fossa,  from 
which  it  is  separated  by  a  thin  osseous  partition  in  the  formation  of  which  the  vertical 
plate  of  the  palate  bone,  the  uncinate  process  of  the  ethmoid,  the  maxillary  process 
of  the  inferior  turbinate  and  a  small  part  of  the  lachrymal  bone  assist.  The  apex  lies 
at  the  zygomatic  process  of  the  maxilla.     The  upper  or  orbital  wall  is  thin  and  often 


Fig.  1184. 


Vestibule 


Anterior  ethmoidal  cclli 


Left  imxillan'  ■iniu 


Inferior  meatus 
Place  wliere  f  ronul  sinus  was  attaclied 


Anterior  ethmoidal  cells 


Maitillary  sinus 
Posterior  ethmoidal  cells 


Left  sphenoidal  cell 


Right  sphenoidal  cell 


Naso-pharynx  . 


Cast  of  nasal  fossae  and  accessory  airspaces,  viewed  from  above ;  casU  of  froaul  sinuses  have  been  removed ; 

natural  aiie.    (KalKiu.) 

modelled  by  the  ridge  containing  the  infraorbital  canal.  The  anterior  wall  presents 
towards  the  face  and  is  varyingly  impressed  by  the  canine  fossa.  The  postero- 
inferior  wall  is  normally  the  thickest,  but  is  sometimes  reduced  by  extension  of  the 
sinus  into  the  adjacent  alveolar  border.  The  sinuses  are  often  so  modified  by  local 
enlargements  that  the  typical  pyramidal  form  is  lost  and  their  dimensions  materially 
influenced.  As  an  indication  of  the  size  of  the  average  sinus,  a  sagittal  diameter  of 
35  mm.  (ij<  in.),  and  a  vertical  and  frontal  one  of  27  mm.  (about  i  in.)  each 
'(  kallius),  may  be  uken  as  approximate  measurements.  Not  infrequently,  however, 
considerable  asymmetry  exists  even  to  the  extent  of  one  antrum  being  almost  twice  as 
large  as  the  other.  The  usual  cajiacity  of  the  antrum  is  between  12-18  cc.  (i}i-4H 
fl.  dr. )  with  an  averse  of  approximately  15  cc,  or  4  fl.  dr.  (Braune  and  Clasen). 

The  antrum  communicates  indirectly  with  the  middle  meatus  by  means  of  an 
aperture  (ostium  maxillare)  that  pierces  the  upper  and  anterior  part  of  the  base  to 
open  into  the  infundibulum.  and  thence  by  way  ol  the  hiatus  semilunaris,  into  the 


THE   ACCESSORY  AIR-SPACES. 


>t23 


meatus.  The  ostium,  which  is  usually  in  the  lateral  wall  of  the  infundibulum, 
about  one  centimeter  from  the  upper  end  of  the  hiatus,  is  an  oval  or  elliptical  cleft 
of  variable  size,  with  extremes  (A  length  from  3-19  mm.  (Zuckerlcandl),  and  from 
2-5  mm.  in  width.  An  additional  communication  (ostinm  accessorium),  present 
in  about  10  per  cent.,  likewise  opens  into  the  infundibulum,  lying  behind  the  chief 
aperture.  It  is  ordinarily  small,  its  diameter  being  only  a  few  millimeters.  The 
mucous  membrane  lining  the  maxillary  sinus  is  directly  continuous  with  that 
covering  the  lateral  wall  of  the  nasal  fossa.  With  the  exception  of  being  thinner,  it 
corresponds  in  structure  with  the  mucous  membrane  of  the  respiratory  region,  being 
invested  with  ciliated  columnar  epithelium  and  possessing  numerous,  although  small 
and  scattered,  tubo-alveolar  glands. 

VarUtiona.— The  investigations  of  Zackerkandl  (Kallius)  have  shown  that  enlarj^ment  of 
the  maxillary  ;'iiis  may  be  produced  by:  (i)  hollowing  out  of  the  alveolar  process  (alveolar 
recess)  ;  (2)  excavation  of  the  floor  of  the  nasal  fossa  by  extension  of  the  alveolar  recess 
between  the  plates  of  the  hard  palate  (palatal  recess);  (3)  encroachment  of  the  sinus  into  the 
frontal  process  of  the  maxilla  ;  4)  hollowing  out  of  the  zygomatic  process  of  the  malar  bone 
(malar  recess) ;  (5)  extension  to  and  appropriation  of  an  air-cell  within  the  orbital  process  of 
the  palate  bone  (palatal  recess).  Contraction  of  the  maxillar>-  sinus,  on  the  other  hand,  may 
follow :  ( I )  imperfect  absorption  of  the  cancellated  bone  on  the  floor  of  the  sinus,  or  secondary 
thickening  of  its  walls  ;  (i)  encroachment  due  to  approximation  of  the  facial  and  nasal  wiills, 
unusual  depression  of  the  canine  fossa,  excessive  bulging  of  the  lateral  nasal  wall,  or  imperfectly 
erupted  teeth. 

The  crescemic  projections  which  quite  commonly  are  seen  protruding  from  :he  walls  into 
the  interior,  occasionally  are  replaced  by  septa  that  completely  divide  the  sinus  into  two  cavities, 
each  having  its  independent  opening  into  the  nasal  fossa,  but  not  being  in  communication  with  each 
other.  These  partitions  vary  in  position  and  direction,  sometimes  subdividing  the  antrum  into  an 
anterior  and  a  posterior  compartment,  and  at  others,  into  an  upper  and  a  lower  chamber.  In 
the  last  case  the  lower  space  may  communicate  with  the  inferkir  meatus  (Zuckerkandl,  Briihl). 


Fig.  I 185. 


Right  frontal  sinus 


(.eft  frontml  sinus 


Pastasc  leftdinK  into 
^        infundibulum  and 
f       middle  meatus 


Nasal  _eptum 


Portion  jf  frontal  section  exposinn  frumal  sinuses  which  ai^  asymmetncal. 


The  Frontal  Sinus. — The  air-spaces  between  the  outer  and  inner  tables  of 
the  frontal  bones  (sinns  fnintales)  are  very  variable  in  extent  and  form.  The  relative 
development  and  general  position  of  these  cavities  are  usually  indicated  by  the 
degree  of  prominence  of  the  superciliary  ridges,  but  by  no  means  invariably,  since 
numerous  exceptions  to  this  correspondence  occur.  The  sinuses  are  frequently 
t|uite  asymmetrical  (Fig.  1 185),  one  cavity  being  enlarged,  somelliitcs  at  the  expense 
of  the  other,  with  accompanying  displacement  of  the  intervening  septum.  The 
latter,  usually  approximately  median  in  position,  is  often  very  thin,  but  only  rarely 


1424 


HUMAN  ANATOMY. 


incomplete,  so  that  the  spaces  very  seldom  communicate.  Numerous  instances  have 
been  observed  in  which  one  sinus  was  entirely  wanting.  The  average  dimensions  of 
the  frontal  sinus,  as  given  by  A.  L.  Turner,  mclude  a  height  of  31  mm.  (i>^  in.),  a 
width  of  30  mm.,  and  a  depth  of  17  mm.  The  capacity  varies  from  3-8  cc.  (Bruhl). 
These  spaces  are  not  recognizable  in  the  new-bom  child,  first  appearing  about  the 
seventh  year,  after  the  absorption  of  the  cancellated  bone.  It  is  not  until  after 
puberty,  however,  that  they  atuin  their  full  size.  They  are  usually  larger  in  the 
male  than  in  the  female. 

The  typical  pyramidal  form  of  the  space  is  often  modified  by  the  enlargement 
of  the  sinus  beyond  its  usual  limits,  since  when  exceptionally  developed  it  may 
extend  into  the  orbital  plate  of  the  frc  ntal  bone,  at  times  reaching  as  far  as  the 
lesser  wing  of  the  sphe.ioid,  or  into  the  median  orbital  wall,  or  laterally  into  the 
external  angular  process,  or,  exceptionally,  into  the  nasal  spine  beneath  the  root  of 
the  nose.  On  the  other  hand,  the  frontal  sinus  may  be  encroached  upon  by 
projecting  ethmoidal  cells. 

The  frontal  sinus  communicates  with  the  middle  nasal  meatus  through  either  the 
infundibulum,  or  a  passage  between  the  anterior  attachment  of  the  middle  turbinate 
and  the  uncinate  process,  or  both.  Its  aperture  (ostium  frontalis)  lies  from  2-10 
mm.  from  the  upper  end  of  the  hiatus  semilunaris.  The  frontal  sinus  is  lined  by  a 
prolongation  of  the  respiratory  nasal  mucous  membrane,  diminished  in  thickness  but 
otherwise  of  its  usual  structure. 

Fig.  n86. 


Sphenoidal  tinui 


Frontal  sinus 


Superior  meatus 


Middle  meatus 
Naso-pharynx 


Choana  (poMerior  naria) 

Maxillary  sinua 
Cast  at  naaat  foMae  and  accestor)'  airtpacci,  viewed  from  riKhl  tide :  lutuial  size. 


(AViMrMJ.) 


The  Ethmoidal  Air-Cells. — These  spaces  Ccellulae  ethmoidales)  include  a 
series  of  pneumatic  cavities,  very  variable  in  number  and  size,  that  from  birth  lie 
between  the  upper  part  of  the  nasal  fossae  and  the  orbits,  from  which  they  are  se{)arated 
by  osseous  plates  of  papery  thinness.  They  are  all  lined  with  mucous  membrane 
which  rovers  the  thin  bony  partitions  that  separate  the  spaces  from  one  another. 
When  these  partitions  are  deficient,  as  they  often  are  in  old  subjects,  the  intervening 
septa  are  entirely  membranous.  The  ethmoidal  air-spaces,  completed  by  the  articu- 
lation of  the  ctfimoid  with  the  frontal,  maxillar>',  Iachr>'mal,  sphenoid  and  palate 
bones,  usually  form  three  groups,  the  anterior,  the  middle  and  the  posterior  cells. 
Every  space  communicates  with  the  nasal  fossa,  either  directly  by  means  of  an 
inde|>enaent  aperture,  or  indirectly  through  one  or  more  cells  of  the  same  group. 
Sometimes  the  cells  are  «o  fused  that  two  general  cavities,  an  anterior  and  a  poste- 
rior, repliice  the  corresponding  groups.  When  typically  arranged,  the  anterior  cells 
communicate  with  the  middle  meatus  by  means  of  apertures  that  open  into  the 
upper  part  of  the  infundibulum.     The  middle  cells  also  open  into  the  middle  meatus, 


THE  ACCESSORY  AIR-SPACES. 


1425 


usually  by  a  crescentric  cleft  upon  or  above  the  ethmoidal  bulla,  but  sometimes  into 
the  infundibulum.  The  posterior  cells  communicate  with  the  superior  meatus  by  one 
or  more  openings  overhung  by  the  upper  concha.  Very  exceptionally  the  ethmoidal 
cells  may  communicate  with  the  sphenoidal  or  the  maxillary  sinuses,  or  may  extend 
into  the  substance  of  the  middle  turbinate  bone.  The  mucous  membrane  clothing 
the  ethmoidal  cells  is  exceedingly  thin,  but  corresponds  in  its  general  structure, 
even  in  possessing  glands,  with  that  lining  the  respiratory  region  of  the  adjacent 
nasal  fossae. 

The  Sphenoidal  Sinus. — The  paired  air-spaces  (sinus  sphenoidales)  produced 
by  the  absorption  of  the  cancellated  tissue  within  the  body  of  the  sphenoid  bone  are 
separated  by  an  osseous  p.irtition  and  seldom  communicate.  They  are  very  variable 
in  size  and  often  asymmetrical,  with  corresponding  displacement  of  the  septum.  A 
length  of  22  mm.,  a  width  of  15  mm.,  and  a  height  ci  12  mm.,  are  the  approximate 
dimensions  of  the  averse  sinus.  The  capacity  of  the  latter,  as  determined  by  Briihl, 
is  from  1-4  cc.  When  large,  the  spaces  may  appropriate  not  only  a  lai^e  part  of 
the  sphenoid,  extending  into  both  wings,  the  pterygoid  processes  and  the  rostrum, 
but  also  include  the  boalar  process  of  the  occipital  bone.     Not  infrequently  one  or 


Fig.  1187. 


Anterior  cUimoidal  celU 


Probe  puecs  to  middl*  mekto* 


Sphenoidal  sinuaes 


Piluiury  body 


Op«iln(«  ol  •phenoldal  •iniu 
and  poaterior  ctlimoidal  cell* 

Intenial  carotid  artery 


I'union  of  Mction  of  fronn  formalin-hardened  head,  expoainx  ethmoidal  and  ipbenoidal  air-apacea; 

viewed  from  above. 

more  of  the  jxisterior  ethmoidal  air-cells  projects  or  opens  into  the  sphenoidal  sinuses. 
Very  exceptionally  these  spaces  may  come  into  close  relations  with  or  even  open  into 
the  maxillary  antrum  (Zuckerkandl) — a  condition  normally  found  in  some  apes. 
The  sphenoidal  sinus  of  each  side  communicates  with  the  nasal  fossa  by  means  of 
the  spheno-ethmoidal  recess,  above  the  superior  turbinate  and  close  to  the  roof  of 
the  fossa,  by  an  aperture  that  pierces  the  upper  part  of  the  anterior  wall  of  the  sinus. 
Through  .this  opening,  redu'«d  in  the  recent  condition,  the  respiratory  mucous 
membrane  is  prolonged  into  the  sinus  which  it  lines. 

The  palatal  sinus,  the  small  air-space  within  the  orbital  process  of, the  palate 
bone,  communicates  indirectly  with  the  nasal  fossa  by  either  the  posterior  ethmoidal 
cells  or  the  sphenoidal  sinus  into  which  it  opens. 

Vessels.— Of  the  arteries  supplying  the  nasal  fossa  the  spheno-palatine  branch 
of  the  internal  maxillaf)'  is  the  largest  and  most  important.  Entering  the  nose 
through  the  spheno-palatine  foramen,  it  divides  into  external  (posterior  nasal)  and 
internal  (naso-palatine)  branches,  which  supply  an  extended  tract  reaching  from  the 
posterior  to  the  anterior  nares.    The  external  branches  are  distributed  to  the  turbinate 

90 


I42( 


HUMAN  ANATOMY. 


bones  and  the  mucous  membrane  of  the  meatuses,  indudine  the  lower  part  of  the 
olfactory  region,  and  in  addition  send  twigs  to  the  ethmoidal  cells  and  the  frontal 
and  maxillary  sinuses.  The  naso-palatine  artery  supplies  the  septum  and  upper  part 
of  the  olfactory  region.  Numerous  smaller,  and  for  the  most  part  collateral,  twigs 
derived  from  the  anterior  and  posterior  ethmoidal  branches  of  the  ophthalmic  pass  to 
the  upper  part  of  the  fossa;  from  the  descending  palatine,  branches  are  distributed 
to  the  posterior  part;  and  from  the  lateral  nasal  and  septal,  branches  from  the  facial 
twigs  supply  the  nostril.  In  addition  to  those  from  the  posterior  nasal,  the  antrum 
receives  branches  h-om  the  infraorbital.  The  sphenoidal  sinus  is  supplied  chiefly 
by  the  pterygo-palatine  artery.  The  ultimate  distribution  is  effected  by  capillary 
net-works  which  supply  the  periosteum,  the  glands  and  the  tunica  propria. 

The  veins  returning  the  blood  from  the  rich  venous  plexuses  and  the  cavernous 
tissue  within  the  nasal  mucous  membrane  follow  three  chief  paths  passing  (a)  forward 
to  the  facial  vein,  (*)  backward  to  the  spheno-palatine,  and  (f)  upward  into  the 
ethmoidal  veins.  The  latter  communicate  with  the  ophthalmic  vein  and  the  veins 
and  superior  sagittal  sinus  within  the  dura  mater.  A  communication  of  greater 
importance,  however,  is  established  by  a  vein  that  accompanies  the  anterior  ethmoidal 
artery  through  the  cribriform  plate  into  the  anterior  central  fossa  and  empties  either 
into  the  venous  plexus  of  the  olfactory  tract  or  into  one  of  the  larger  veins  on  the 
orbital  surface  of  the  frontal  lobe  (Zuckerkandl). 

The  lymphatics  within  the  mucous  membrane  are  represented  by  an  irregular 
plexus  of  lymph-vessels  in  addition  to  perineural  lymph-sheaths  surrounding  the 
olfactory  nerve-bundles.  Both  sets  may  be  filled  by  mjection  from  the  subarachnoid 
space.  The  larger  lymphatics  pass  backward  toward  the  posterior  nares  and  join 
two  trunks,  one  of  which  is  continued  to  the  prevertebral  node  and  the  other  to  the 
hyoid  nodes.  According  to  Schiefferdecker,  the  basal  canals  (page  951)  communi- 
cate with  the  lymphatics  and  probably  hcilitate  the  escape  of  fluid  which  aids  the 
glands  in  keeping  moist  the  epithelium  lining  the  nasal  fossae. 

The  nerves  include  the  special  olfactory  fibres  concerned  in  the  sense  of  smell, 
and  those  of  common  sensation  derived  from  the  ophthalmic  and  superior  maxillary 
divisions  of  the  trigeminal  nerve.  The  lateral  wall  of  the  nasal  fossa  is  supplied  from 
several  sources,  including  the  upper  posterior  nasal  branches  from  Meckel's  ganglion 
and  the  lower  posterior  nasal  branches  from  the  larger  palatine  ner\'c-  behind,  and, 
in  front,  the  external  division  of  the  nasal  nerve  and  the  nasal  branch  of  the  anterior 
superior  dental,  which  also  distributes  twigs  to  the  floor  of  the  fossa.  The  septum 
receives  its  chief  supply  from  the  naso-paladne  nerve,  supplemented  by  branches 
from  Meckel's  ganglion  behind  and  by  the  internal  division  of  the  nasal  nerve 
in  front.  The  mucous  membrane  lining  the  antrum  receives  filaments  from  the 
infraorbital  nerve  by  means  of  its  supenor  dental  branches.  The  frontal  sinus  is 
supplied  by  twigs  from  the  supraorbital  and  the  nasal  nerves  ;  the  ethmoidal  air-cells 
by  minute  branches  from  the  nasal,  and  the  sphenoidal  sinus  by  filaments  from  the 
spheno-palatine  ganglion. 

PRACTICAL  CONSIDERATIONS  :  THE  ACCESSORY  AIR-SPACES. 
Trauma  of  the  accessory  sinuses — with  the  exception  of  the  maxillary  antrum, 
which  may  be  involved  in  extensive  (crushing)  fractures  of  the  face— usually  takes 
the  form  of  perforating  wounds,  commonly  from  falb  on  sharp  objects.  The 
thinness  of  their  walls,  and  the  ease  with  which  they  may  het  traversed  by  such  a 
vulnerating  body,  are  well  illustrated  by  a  case  in  which  a  fall  forward  on  to  the  tip 
of  an  umbrella  resulted  in  a  wound  which  began  on  the  face  above  the  bicuspid 
teeth,  passed  through  the  maxillary  sinus,  the  sphenoidal  sinus,  and  entered  the 
cranium,  the  ferrule  of  the  umbrella  being  found  embedded  in  the  pons  (Treves). 
Inflammation  of  the  accessory  sinuses  is  not  infrequent,  on  account  of  the  con- 
stant exposure  of  the  nasal  mucosa  to  atmospheric  sources  of  infection.  It  has  a 
tendency  to  become  chronic  because  (a)  the  openings  of  the  sinuses  are  small  and — 
with  the  exception  of  the  frontal— are  badly  placed  for  drainage ;  {b)  the  ciliated 
epithelium,  on  the  activity  of  which  the  removal  of  the  sinus  contents  depends,  is  apt 
to  be  so  damaged  by  the  primary  inflammation  that  retention  of  secretion  occurs ; 
(f)  the  mucosa  around  the  different  ostia  is  so  loosely  atUched  that  it  readily 


PRACTICAL  CONSIDERATIONS:  ACCESSORY  AIR-SPACES.  1427 

becomes  oedematous  and  is  thrown  into  folds  which  later  are  obstructive  ;  (rf)  foreign 
bodies  (as  a  carious  tooth,  in  the  case  of  the  antrum)  have  little  chance  for  (»cape, 
and  mucous  cysts,  polyps,  and  lesions  of  the  sinus  walls  (pyogenic,  syphilitic  or 
tuberculous  caries  or  necrosis)  are  not  uncommon  ;  (<•)  one  cavity  may  be  infected 
from  another,  pus  from  the  frontal  sinus  entering  the  ethmoidal  cells,  or  pus  from 
either  of  these  entering  the  antrum  through  its  normal  opening,  or  through  a 
perforation  of  its  wall  in  the  vicinity  of  the  infundibulum  (Lack). 

In  the  greater  number  of  cases,  the  chief— often  the  only— symptom  of  chronic 
suppuration  of  the  accessory  sinuses,  is  a  purulent  nasal  discharge.  Spontaneous 
recovery  is  practically  impossible,  and  in  the  great  majonty  of  cases,  operaUon— for 
disinfection  and  drainage— becomes  necessary.  The  cavities  (as  one  may  act  as  a 
reservoir  of  pus  coming  from  another)  may  have  to  be  attacked  in  a  definite  order. 
Ordinarily  it  is  possible  to  determine  whether  the  pus  comes  from  the  sinuses  that  open 
into  the  same  passage  within  the  middle  meatus— the  anterior  group— or  from  those 
which  open  more  posteriorly,  above  the  middle  turbinate  bone— the  posterior 
group  If  no  definite  evidence  can  be  obtained  as  to  which  of  the  anterior  group  is 
involved,  it  would  be  well  to  attack  first  the  antrum,  then  the  ethmoidal  cells,  and 
then  the  frontal  sinus.  If  the  posterior  group  is  affected  it  is  usually  proper  to 
remove  the  posterior  portion  of  the  middle  turbinate  and  open  the  posterior  ethmoidal 
cells,  later,  if  necessary,  opening  the  sphenoidal  sinus.  Occasionally,  as  in  ozxna 
(on  account  of  the  width  of  the  inferior  meatus  and  the  atrophy  of  the  inferior  and 
middle  turbinates),  the  opening  of  the  sphenoidal  sinus  can  be  seen  from  the  front, 
and  then  this  sinus  may  be  explored  first  (Lack). 

The  frontal  sinuses  do  not  appear  as  distinct  spaces  until  about  the  seventh 
year,  and  are  developed  by  a  separation  of  the  two  tebles  of  the  skull,  with  more 
or  less  resulting  prominence  above  the  superciliary  ridges.  There  may  be  a 
greater  relative  bulging  toward  the  interior  of  the  cranium,  so  that  the  prominence 
of  the  superciliary  ridges  is  no  indication  of  the  size  of  the  cavities  of  the  sinuses. 
They  are  often  very  irregular  in  size,  one  being  larger  at  the  expense  of  the  other, 
the  septum  deviating  to  one  or  the  other  sido  accordingly.  It  'u  therefore,  difficult, 
at  times,  to  decide  which  side  is  involved  by  disease. 

Fracture  of  the  skull  over  a  frontal  sinus  does  not  imply  that  the  cranial  cavity  is 
opened,  even  when  depression  exists.  The  frequent  presence  in  these  fractures  of  em- 
physema within  the  orbit  and  in  the  subcutaneous  tissue,  results  from  the  entrance  of  air 
through  the  communication  with  the  nose,  when  the  latter  is  blown.  The  dependent 
position  of  its  opening  into  the  middle  meatus  or  the  infundibulum,  provides  better 
drainage  for  discharges  than  is  the  case  in  the  other  sinuses,  and  probably  accounts  for 
the  relative  infrequency  of  empyema  of  this  sinus,  although  this  advantage  is  partly  off- 
set by  the  length,  narrowness,  and  tortuosity  of  the  canal,  which  render  it  easily  liable 
to  obstruction.  Swelling  of  the  mucous  lining  of  the  oudet  of  the  frontal  sinus  may 
thus  occlude  the  canal,  and  result  in  abscess  (empyema).  If  this  remains  undrained  the 
pus  would  tend  to  burrow  through  the  weakest  point  of  the  wall,  which  usually  leads  it 
through  the  floor  of  the  cavity  into  the  orbit,  giving  rise  to  an  orbital  cellulitis,  and  to 
displacement  of  the  eyeball.  It  later  tends  to  escape  through  the  inner  portion  of  the 
upper  eyelid.  In  some  cases  it  extends  through  the  posterior  wall  of  the  sinus  into 
the  cranial  cavity,  causing  a  septic  meningitis,  or  an  extradural  or  brain  abscess. 

Extensive  necrosis  of  the  frontal  bone  may  follow  sinus  disease,  as  the  frontal 
diploic  vein,  which  empties  into  the  frontal  vein  at  the  supraorbital  notch,  receives 
blood  from  the  sinus. 

If  free  drainage  ij  maintained  these  complications  are  very  rare,  but  if  drainage 
is  defective  it  is  imperative  to  open  the  sinus  early.  This  may  be  done  externally, 
the  anterior  wall  being  removed  by  a  chisel  or  trephine.  The  incision  may  be  verti- 
cal or  along  the  superciliary  ridge  from  the  inner  end  to  the  supraorbital  notch, 
sometimes  dividing  the  supraorbital  vessels.  The  thinness  of  the  nasal  portion  of 
the  floor  of  the  sinus  is  marked — as  well  as  that  of  the  orbital  portion — and  therefore 
frontal  sinus  suppuration  is,  as  a  rule,  associated  with  infection  of  some  of  the  anterior 
ethmoidal  cells,  which- surgically — may  perhaps  be  considered  as  forming  a  part 
of  that  sinus  (Lack),  although  Kiimmel  notes  that  he  has  seen  the  ethmoidal  cells 
perfectly  intact  in  a  series  of  cases  of  frontal  sinusitis. 


1428 


HUMAN   ANATOMY. 


i 


Attempts  have  been  made  to  pass  a  probe  into  the  ostium  frontale  from  the  nose, 
but  this  is  exceedingly  difficult  because  of  the  concealed  position  of  its  orifice  behind 
the  anterior  end  of  the  middle  turbinate  bone,  and  sometimes  because  of  its  tortuous 
course.  Efforts  to  reach  the  sinus  through  the  nose  are  usually  made  by  removing 
the  anterior  end  of  the  middle  turbinate  bone,  at  the  same  time  opening  the 
anterior  ethmoidal  cells  which  are  frequently  involved  by  the  same  inflammatory 
process.  By  this  method  an  aperture  is  left  for  the  permanent  discharge  of  the 
sinus  into  the  nose,  whereas  by  the  e.xtemal  method  the  opening  into  the  nose  may 
remain  closed. 

The  maxillary  sinus,  or  antrum  of  Highmore,  is  the  largest  and  most 
important  of  the  accessory  sinuses  of  the  noso.  It  is  most  frequently  the  seat  of 
pathological  processes,  as  infections  and  tumors. 

Infection  may  reach  it  from  the  nose  through  the  opening  in  the  middle  meatus, 
when  it  may  be  secondary  to  disease  of  the  frontal  and  anterior  ethmoidal  sinuses, 
the  opening^  into  all  three  being  closely  associated  ;  or  it  may  be  caused  by  caries  of 
the  teeth,  especially  of  the  first  and  second  molars,  the  roots  of  which  frequently 
produce  prominences  in  the  floor  of  the  antrum,  or  may  very  exceptionally  extend 
mto  its  cavity.  Occlusion  of  the  small  orifice  with  retention  of  the  pus  frequenth 
causes  great  pain  from  pressure  on  the  infraorbital  nerve  in  the  roof  of  the  antrum. 
The  pus  may  burrow  into  the  nose,  the  ethmoidal  cells,  or  the  orbit. 

The  normal  orifice  is  too  high  on  the  internal  wall  for  drainage,  and  is  too  small 
for  effective  irrigation,  which  may  be  provided  for  (a),  if  the  cause  is  a  carious  tooth, 
by  removing  a  tooth  and  making  an  opening  through  the  roof  of  the  socket  into  the 
antrum  ;  this  affords  dependent  drainage,  but  permits  the  entrance  of  food  from  the 
mouth  ;  (*)  by  perforating  the  bony  wall  between  the  antrum  and  the  inferior  meatus 
with  or  without  removing  the  anterior  end  of  the  inferior  turbinate  ;  or  (r)  by 
making  an  opening  through  the  thin  anterior  wall,  above  the  roof  of  the  second 
bicuspid  tooth,  at  the  level  of  the  canine  fossa. 

A  tumor  of  the  maxillary  sinus  may  be  either  benign  or  malignant.  Its  growth 
will  lead  to  enlargement  of  the  cavity,  and  to  the  following  symptoms,  one  or  more 
of  which  will  predominate,  according  to  the  direction  it  takes  :  (a)  inward,  through 
the  thin  inner  wall  of  the  sinus,  causing  epistaxis,  obstructed  respiration,  epiphora 
from  pressure  on  the  na.sal  duct ;  (6)  inward  and  backward,  involving  the  naso- 
pharynx and  interfering  v.ith  both  respiration  and  deglutition  ;  ic)  forward,  pushing 
the  anterior  wall — also  thin — before  it  and  obliterating  the  inframalar  depression  in 
the  cheek;  (rf)  upward,  causing  infraorbital  neuralgia  (as  the  infraorbital  nerve 
runs  in  the  roof  of  the  sinus),  toothache  from  compression  of  its  middle  and  anterior 
superior  dental  branches,  face  ache  from  involvement  of  the  other  branches  of  the 
superior  maxillary,  and  later  exophthalmos  and  diplopia  ;  (e)  downward,  pushing 
down  the  arch  of  the  hard  palate  so  that  the  roof  of  the  mouth  on  the  affected  side 
becomes  convex,  and,  by  pressure  on  the  superior  dental  nerves,  causing  se\ere 
odontalgia  in  the  upper  teeth,  which  later  become  loosened.  Benign  growths  may 
be  removed  through  an  opening  made  by  cutting  away  the  anterior  wall.  Malignant 
growths  necessitate  excision  of  the  superior  maxilla. 

In  diseases  of  the  sphenoidal  sinuses  their  intimate  relation  with  the  brain 
above,  the  optic  ner\e  and  ophthalmic  artery  abo\e  and  to  the  outer  side,  and,  along 
the  outer  wall,  with  the  internal  carotid  artery,  the  cavernous  sinus  and  the  nerves 
passing  through  the  sphenoidal  fissure,  should  be  borne  in  mind.  Such  diseases 
may  lead  to  (a)  optic  neuritis  and  blindness,  if  the  optic  ner\e  is  involved;  (b) 
to  general  ophthalmoplegia  if  the  third,  fourtii,  tiie  ophthalmic  division  of  the  fifth, 
the  sixth,  and  the  symiwthetic  filaments  fri>ni  the  cavernous  plexus  (all  transmitted 
through  the  sphenoidal  fissure)  arc  implicateti  ;  (r)  to  cavernous  sinus  thrombosis 
if  the  ophthalmic  \ein — passing  through  the  same  fissure — is  infected. 

Tumors  of  the  pituitary  b<xly — resting  in  the  pituitar>'  fossa  in  the  sella  turcica 
and  just  almvf  the  roof  nf  the  sintis — m.-iy  penetrnte  its  c.ivity.  The  ojiening  of  each 
sinus  is  in  the  upper  part  of  the  anterior  wall,  a  very  unsuitable  position  for  drainage, 
in  the  presence  of  infection.  Encroachment  on  any  of  the  surrounding  structures 
might  lead  to  serious  results.  The  anterior  wall  may  be  exjxised  and  attacked  by  the 
surgeon,  but  only  with  consitlerable  difficulty,  l)ecause  of  its  deep  situation  and  its 


DEVELOPMENT  OF  THE  NOSE. 


1429 


restricted  avenue  of  approach  through  the  nasal  fossa.  The  chief  obscar  is  the 
middle  turbinate  bone,  which  must  be  removed  before  the  orifice  can  be  seen  or  the 
anterior  wall  removed.  Any  efforts  at  cleaning  pathological  tissue  from  the  sinus 
must  be  made  with  due  regard  for  the  important  structures  just  outside  and  the  thin 
intervening  bone. 

Inflammation  of  the  ethmoidal  cells  is  most  frequently  associated  with  the 
presence  of  myxomatous  polypi  within  the  nose.  Infection  may  extend  (a)  upward 
to  the  cranial  cavity,  either  directly  or  by  way  of  the  ethmoidal  veins,  or  into  the 
cavernous  sinus  via  the  ophthalmic  vein,  or  to  the  longitudinal  sinus — especially  in 
children — by  the  small  vein  traversing  the  foramen  ciecum  ;  (*)  outward  to  the 
orbit,  causing  an  orbital  cellulitis;  (c)  to  the  lachrymal  sac  (on  account  of  the 
contiguity  of  the  lachrymal  bone)  causing  dacryo-cystitis. 

A  valuable,  but  not  always  reliable,  sign  of  involvement  of  the  ethmoidal  cells, 
is  localized  pain  at  the  inner  canthus  of  the  eye  (Kiimmel),  and  swelling  of  the 
mucous  membrane  around  the  middle  turbinate  may  in  this — as  in  infection  of  the 
other  sinuses — be  considered  an  imptortant  symptom.  In  order  to  evacuate  the 
diseased  cells,  the  middle  turbinate  (as  in  the  case  of  the  sphenoidal  sinus)  must  be 
removed  before  the  ethmoidal  cells  can  be  exposed.  As,  in  the  large  majority  of 
cases  at  least,  the  condition  is  coincident  with  similar  infection  of  the  frontal  sinus, 
the  anterior  cells  may  be  easily  reached  from  the  floor  of  the  latter  after  it  has  been 
opened.  The  optic  nerve,  the  trochlear  nerve,  the  superior  oblique  ocular  muscle 
and  the  anterior  and  posterior  ethmoidal  arteries,  are  the  most  important  structures 
endangered  during  this  operation. 

DEVELOPMENT  OF  THE  NOSE. 

The  earliest  trace  of  the  nasal  aniage  appears  about  the  beginning  of  the  third 
week  of  foetal  life  as  a  thickening  of  the  ectoblast  to  form  the  nasa/  area  at  each 
side  of  the  anterior  portion  ol  the  head.  About  one  week  later  the  convexly  cres- 
centic  outline  of  this  area  gives  place  to  a  slight  depression  that  deepens  into  the 
ol/actorv  pit  or  fossa  in  consequence  of  the  increased  thickness  of  the  surrounding 
mesoblast.  The  encircling  ridge  thus  produced  is  best  marked  on  the  mesial  and 
lateral  boundaries  of  the  fossa  (Kallius),  where  the  resulting  elevations  foreshadow 
the  developme.it  of  the  inner  and  outer  nasal  processes.  With  the  forward  growth 
and  union  of  the  maxillary  process  of  the  first  visceral  arch  with  the  median  nasal 
process,  or  processus  globularis,  to  complete  the  upper  boundary  of  the  primitive 
oral  cleft  (page  62),  the  margin  of  the  entrance  of  the  nasal  pit  becomes  closed  in 
below.  Subsequently,  howe\-er,  the  lateral  n  -sal  process  extends  medially  above 
the  maxillary  process  until  it  meets  the  median  aasiil  process  and  thus  becomes  the 
immediate  lower  and  lateral  boundary  of  the  opening  of  the  fossa.  The  latter  grows 
and  deepens  chiefly  upward,  towards  the  brain,  and  backward  and  in  consequence 
the  olfactory  organ  for  a  time  consists  of  two  blind  pouches,  separated  by  the  frontal 
prtKess,  lying  above  the  primitive  oral  cavity.  These  pouches  invade  the  mesoblast 
until  their  blind  posterior  ends  reach  the  primitive  oral  cavity  between  which  rnd  the 
olfactory  diverticula  a  thin  ijartition,  composed  of  the  two  abutting  layers  of  epithe- 
lium, alone  intervenes.  This  septum,  bucco-nasal  membrane  of  Hochstetter,  iMjcomes 
attenuated  and  finally  ruptures,  the  resulting  openings,  the  primitive  choaiite,  estab- 
lishing communication  between  the  nasal  fossa;  and  the  primitive  oral  cavity.  That 
part  of  the  roof  of  the  latter  which  extends  from  the  choans  to  the  nasal  apertures 
constitutes  the  primitive  palate,  and  contributes  not  only  the  anterior  portion  of  the 
definite  palate,  but  also  the  tissue  forming  the  lips  (Hochstetter).  The  primitive 
palate  includes  contributions  from  different  sources,  its  middle  portion  being  from  the 
median  nasal  process  and  its  lateral  portions  being  derived  from  the  lateral  nasal 
process  in  front  and  from  the  maxillary  process  behind  (Peter). 

Subsequent  to  the  formation  of  the  primitive  palate,  about  the  fifth  week,  the 
primitive  nasal  fossa?  increa.se  in  size,  sink  deeper  into  the  head  between  the  metlian 

1)lane  and  the  eye,  and  come  into  closer  relation  with  the  brain.  The  nasal  fossa-, 
lowcver,  in  acquiring  their  definite  expansion  additionally  appropriate  a  considerable 
portion  of  the  primitive  oral  cavity  which  becomes  separated  from  the  remainder  of 
that  space  by  the  formation  of  the  definite  palate. 


Mb 


143° 


HUMAN   ANATOMY. 


Nasal  area 


Fore-brain 


Nasal  area 


Forc-brain 


The  first  step  in  the  production  of  the  latter  is  the  appearance,  about  the  ninth 
week,  of  the  palatal  ridges,  wedge-shaped  elevations  that  grow  downward  and  in- 
ward from  the  maxillary  processes.  In  front  these  ridges  begin  at  the  primitive 
choanx,  where  they  are  continuous  with  the  primitive  palate,  and  extend  backward 
as  far  as  the  tympanic  pouches.  At  first  almost  sagittal  in  their  plane,  the  palatal 
ridges  become  gradually  converted  into  horizontal  plates  that  come  into  contact 

and  finally   unite   along    their 
Fig.  ii8H.  opposed  median  edges  to  com- 

Fore4>rain  plete  the  roof  of  the  mouth  am. 

the  floor  of  the  nasal  fossae  and 
the  definite  or  secondary  ckoante, 
this  fusion  being  accomplished 
by  the  end  of  the  third  month. 
Coincidently  with  these 
changes  the  pnmitive  choana- 
elongate  and  come  to  lie  on 
either  side  of  the  posterior  por- 
tion of  the  nasal  septum  to 
which  the  frontal  process  has 
now  become  reduced.  The 
union  of  a  pair  of  outgrowths 
from  the  palatal  plates,  beyond 
their  point  of  fusion  beneath 
the  choanae,  produces  the  uvula, 
while  the  remaining  ununited 
portions  of  the  ridges  give  rise 
to  the  palato-pharyngeal  arches. 
For  a  time  the  nasal  sep- 
tum is  still  incomplete,  since  it 
has  not  yet  reached  the  palate, 
and  the  nasal  fossx  communi- 
cate by  means  of  a  cleft  between 
the  septum  and  the  palate. 
With  the  downward  gi-  vth  of 
the  partition  this  con.  •  lica- 
tion  is  obliterated,  the  itum 
joining  the  f>alate  along  thi  line 
of  the  median  suture. 

The  formation  of  the  ante- 
rior part  of  the  floor  of  the  nasal 
fossa:  is  more  complex  since, 
according  to  Peter,'  in  this 
region  the  palatal  processes  do 
not  come  in  contact  with  each 
other  owing  to  the  interposi- 
tion of  a  portion  of  the  partition 
that  separates  the  primitive 
choanae.  The  palatal  plates, 
however,  fuse  with  this  wedge 
of  tissue  along  the  line  of  appo- 
sition except  at  one  point  on 
each  side,  where  the  epithelium  persists  as  a  solid  strand  leading  downward  and  inward 
from  the  fore  part  of  the  floor  of  the  nasal  fossa  to  the  roof  of  the  oral  cavity.  These 
strands  acquire  a  lumen  and  become  the  incisive  canals  (page  1413 )  that  may  persist 
thrnsighntit  life  and  establish  communication  between  the  nasal  and  oral  chambers. 

The  further  differentiation  of  the  nasal  fossae  of  man  follows  the  same  funda- 
mental plan  that  applies  to  other  mammals,  but  is  modified  by  the  reduction  that 


Lateral  nasal 
proceu 


Nasal  fossa 


Fore-brain 


Nasal  fossa 


Naso-fronlal  proceis     Procnsus  globularis 


Frontal  sections  <if  f^re-brain  of  rabbit  efnbr>-os.  illustrating  early 
staKes  in  ilevelopment  of^nose ;  in  A.  nasal  area  shows  as  Ihirkeiiinir 
of  ectoblast ;  in  11,  nasal  area  is  slightly  depreaaed ;  in  C  and  D,  nasal 
fosfat  are  forming,    x  30, 


'  Anatom.  Anxeiger,  Bd.  xx.,  1902. 


DEVELOPMENT  OF  THE  NOSE. 


1431 


Cartilajtinout  captuli* 
EthnKMurMnal 


Fig.  1189. 


Maxill»turbiiial 
NmwHoi 


>>alaul  ;>rocan' 
Onl  c«vtt; 


TOBKtK 


Frontal  Mctlon  through  dcvelopinf  naial  f« 

communicate;  palaulproccaaet  are  forminK, 


and  onl  cavity  which 
X15- 


occurs  in  the  production  of  the  relatively  feebly  developed  human  olfactory  apparatus. 
With  this  differentiation  is  associated  the  formation  of  the  turbinates  and  the 
intervening  clefts  (the 
meatuses)  and  of  the  acces- 
sory air-spaces.  Thestud- 
iesof  Zuckerkandl,  Killian, 
Schoenemann,  Peter'  and 
others  have  shown  that 
the  tvpical  development  of 
the  conchae  proceeds  from  jacobaon'iorgaa 
three  primary  outgrowths 
from  the  lateral  nasal  wall  in 
regions  later  correspond- 
ing to  the  maxilla,  ethmoid 
and  nasal  bones.  These 
elevations,  appropriately 
known  as  the  maxillo-tur- 
binal,  the  elhmo-turbinal 
and  the  naso-turbinal,  un- 
dergo differentiation  that 
lea&  to  the  simple  or  com- 
plex definite  arrangement 
of  the  conchae  found  in 
various  animals. 

In  man  the  maxillo-turbinal,  later  the  inferior  turbinate,  first  appears  and  pre- 
cedes the  ethmo-turbinal  plate  that  later  is  supplemented  by  a  second  scroll,  thus 
producing  the  middle  and  superior  turbinates  respectively.  The  naso-turbinal, 
alwavs  nidimentary  in  man,  is  represented  by  a  small  ridge  that  appears  in  front  of 
the  ethinti-turbinal  and  above  the  maxillo-turbinal  plates  and  persists  as  the  agger 
nasi.  The  ethmo-turbinal  is  most  intimately  related  to  the  true  olfactory  area  and 
undergoes,  even  in  man,  conspicuous  subdivision.  Although  finally  reduced  to  two 
(the  upper  and  middle  turbinates),  in  the  human  foetus,  just  before  birth,  five  ethmo- 
turbinal  plates  defined  by  six  grooves  are  present  (Killian).  Persistence  in  excess 
of  the  usual  complement  accounts  for  the  presence  of  the  supernumerary  ethmoidal 
turbinates  so  often  observed. 

As  interpreted  by  Killian,  the  subsequent  modifications  of  the  ethmo-turbinab 
and  the  intervening  furrows,  either  by  further  expansion  or  by  fusion,  are  not  only 
intimately  concerned  in  producing  details  modelling  the  lateral  wall  of  the  nasal  fossa, 
as  the  uncinate  process,  ethmoidal  bulla,  hiatus  semilunaris  and  infundibulum,  but 
also  associated  with  the  first  appearance  of  the  accessory  air-spaces.     The  earliest 

establishment  of  these  spaces  pre- 
Kici.  1 190.  cedes  the  appearance  of  the  carti- 

lage that  later  encloses  them,  their 
relations  to  the  skeleton  being, 
therefore,  secondary  (Kallius). 
The  ethmoidal  air-cells  and  the 
sphenoidal  sinus  are  primarily  con- 
strictions from  the  nasal  fossae,  while 
the  maxillary  and  frontal  sinuses 
are  more  or  less  direct  extensions 
from  the  same  cavities. 

The  maxillary  sinus  ap- 
pears about  the  middle  of  the  third 
foetal  month  as  a  minute  epithe- 
lium-lined sac  within  the  mcsoblast  at  the  side  of  the  nasal  fossa,  from  which  if 
has  been  evaginated  ;  by  the  ixth  month  it  measures  some  5  mm.,  and  at  birth 
has  acquired  the  size  of  a  pea.     Until  the  eruption  of  the  milk  teeth  provides  the 

'  in  Hertwig's  Handbuch  d.  Entwikelungslehre,  Lief.  4  and  5,  1902. 


Fore-lnain 


Nanal  aperture 
Lateral  naaal  proceas 

Maxillary  process 
Primitive  choana 


Palatal  process 


Part  o(  head  of  fortus  15  mm.  in  length,  showing  primitive  choanw 
and  palate,     v  8.    1  Pfter.) 


iMi 


1432 


HUMAN  ANATOMY 


U 


Fig. 


1 191. 

Fon-brain 


Infnrua]  «•• 


MUalfoua 


•Lstciml  nasal  proceu 
•Median  naial  process 

'ProccMiLH  globularis 
Maxillaiy  proctia 

Mandibubr  proccis 

Anterior  end  of  head  ol  (oetui  10.3  nun.  in  len(tli, 
slmwinK  early  devciopment  of  external  iioee.  X  H. 
iPrlrr.) 


necessary  room  for  expansion,  its  growth  is  retarded.  Aher  the  sixth  year,  when 
the  eruption  of  the  permanent  teeth  begins,  the  antrum  loaes  its  general  spherical 
outline  and  gradually  acquires  the  definite  pyramidal  fomi. 

The  frontal  sinua  formed  as  an  extension  of  tlie  nasal  foaaa  during  the  third 
fuetal  month,  is  for  a  time  so  small  that  it  is  usually  regarded  as  absent  at  birth. 
Although  indistincdy  seen  during  the  third  year,  not  until  about  the  seventh  is  the 

sinus  a  definite  sfnce ;  it  remains  small,  how- 
ever, untn  puberty,  after  which  its  adult 
proportiotu  are.  gained. 

The  sphenoidal  sinus,  primarily  arises 
by  the  constriction  and  partial  isolation  of  a 
part  of  the  primitive  nasal  fossa.  Although 
its  development  begins  during  the  thirti 
foetal  month,  the  space  remains  so  rudimt.i- 
tary  that  not  until  the  seventh  year  has 
absorption  of  the  cancellous  bone  progressetl 
sufficiently  to  make  the  sinus  apfiarent. 

Notwithstanding  its  rudimentary  condi- 
tion in  man,  the  organ  of  Jacobson  devel- 
ops at  a  very  early  period,  beginning  as  a 
groove-like  depression  on  the  median  wall  of  the  nasal  pit.  This  groove  is  con\'erted 
into  a  tubular  pouch  that  soon  becomes  laterally  compressed  and,  by  the  middle  of 
the  third  month,  measures  about  .5  r  .n.  in  length  and  receives  twigs  from  the  olfac- 
tory nerve  ( Kallius).  After  the  fifth  foetal  month  the  organ  suffers  regression  and 
becomes  rudimentarv  and  variable  in  comparison  with  the  perfection  it  attains  in 
animals  possessing  olfactory  sense  in  a  high  degree. 

The  development  of  the  outer  nose  is  closely  associated  with  the  changes 
affecting  the  median  and  lateral  nasal  processes — prommences  considered  in  connection 
with  the  formation  of  the  upper  boundary  of  the  primitive  oral  cleft  (page  62), 

Reference  to  Fig.  1 192  shows  the  median  nasal  processus,  separated  by  a  distinct 
furrow  that  soon  Ixcomes  filled  and  partially  obliterated  by  ingrowth  of  young 
connective  tissue,  as  does  likewise 
the  groove  between  the  globular  and 
maxillary  processes.  At  first  sepa- 
rated by  a  relatively  wide  interval, 
the  infranasal  nasal  area  of  His,  the 
nasal  apertures  are  brought  nearer 
togetlier  by  the  rapid  narrowing  of 
the  iiiterpost'd  portion  of  the  frontal 
process.  E\pntually  the  tissue  be- 
tween theglobular  processes  bocomes 
the  philtrum  ol  the  upper  lip  and 
that  b- tween  the  nasal  opt-.ings 
■  )ersisth  as  the  partition  between  the 
nostrils.  By  the  end  of  the  second 
month  the  external  nose  is  defined, 
but  is  verj'  broad  and  flat  and  lim- 
ited above  by  an  arched  furrow  that 
separates  the  convex  nasal  margin 
(His)  from  the  forehead.  The  nos- 
trils, originally  placed  high  and  for 
a  long  time  directed  forward,  grad- 
ually descend  and  assume  a  hori- 
zontal plane  as  the  middle  of  the  arched  nasal  margin  grows  downward  and  forward 
to  become  the  p«oint  of  the  nose.  These  changes,  however,  are  not  accomplished 
until  near  the  end  of  gestation  and  at  birth  the  bridge  of  the  nose  is  still  small  and 
flat  which,  in  connection  with  tlif  general  breadth  of  the  organ,  imparts  to  the 
infantile  nose  its  peculiar  stumpy  api)earance.  Not  until  long  after  birth,  and,  indeed, 
not  until  after  puberty,  does  the  outer  nose  acquire  its  definite  individual  form  in 


Fig.  I 193. 


Forc^wain 


Head  of  fcrtni  of  about 


Infranasal  area 
Nasal  aperture 
Lateral  nasal  process 
Medial  nasal  uroceKs 
Processua  globularis 

Mandibular  process 


3n  da\-it.  showing  de\-eloping  nose. 
13.     IK.ibl.) 


THE  ORGAN  OF  TASTK. 


U33 


which  family  and  racial  characteri»tics  are  often  so  strikingly  ri-produced.  From  the 
second  until  the  sixth  month  the  nostrils  are  occluded  by  epithelial  plugs  which 
subsequently  undergo  >;radual  resolution,  so  that  before  birth  the  niisal  a|>ertures  are 
unobstructed.  The  catiiiages  of  the  outer  nose  are  derived  from  the  common  carti- 
laginous capsule  that  constitutes  the  primary  nasal  skeleton.  Subdivision  into  the 
individual  plates  is  probably  effected  by  ingrowth  of  the  surrounding  connective 
tissue  ( Mihalkovics,  Kallius). 

THE  ORGAN  OF  TASTE 

In  the  description  of  the  tongue  and  its  papillx  (page  1575),  reference  is  made 
to  the  presence  of  specialized  epithelial  structures,  the  tatte-budt,  that  ser\e  for  the 
reception  of  gustatory  stimuli.  These  bodies  collectively  constitute  the  peripheral 
sense-organ  of  taste  and  as  such  will  be  here  considered. 

As  implied  by  their  name,  the  taste-buds  (calyculi  gustatorii)  are  irregular  ellip- 
soidal or  conical  bodies,  sometimes  broadly  oval  but  more  often  slender  in  outline, 
and  in  the  adult  mea.sure  from  .070-.  080  mm.  in  length  and  about  half  as  much  or 

Fiu  up  J. 


Lyiaphoid  nodulct 
Foramen  cKCiun 


Anterior  palatine 
arch 

Folia  lingnc 


rungiform  papilU 


Pan  01  doraum  ot  tonpie,  showinx  papilUe. 

less  in  breadth.  Since  they  lie  entirely  within  the  epithelium  clothing  the  mucous 
membrane,  the  necessary  access  to  the  interior  of  the  buds  is  afforded  by  minute 
pore-canals,  each  of  which,  beginning  on  the  free  surface  at  the  outer  taste-pore,  \eads 
through  the  intervening  layer  of  epithelium  to  the  inner  pore  that  caps  the  subjacent 
pole  of  the  bud.  By  means  of  these  canals  the  sapid  substances  dissolved  in  the 
fluids  of  the  mouth  reach  and  impress  the  gustatory  cells  within  the  taste-buds. 
Pore-canals  are  not,  however,  invariably  present,  since,  as  pointed  out  by  Graberg, 
certain  taste-buds  remain  immature  and  retain  their  embryonal  form  and  relations, 
being  broad  and  conical  and  in  contact  with  the  free  surface.  In  such  buds  the 
gusUtory  cells  are  few,  onlv  two  or  three,  and  so  superficially  placed  that  a  dis- 
tinct canal  is  absent  Occa.>tionally  double  buds  are  encountered  in  which  two 
(fustatory  bodies  are  implanted  by  a  common  base,  but  partly  retain  their  inde- 
pendence in  having  separate  distal  poles,  each  provided  with  its  separate  taste-pore 

and  canal.  .      •.       « 

The  chief  position  of  the  taste-buds  is  within  the  epithelium  lining  the  sides  of 

the  annular  groove  on  the  circumvallate  papilla,  the  buds  being  more  numerous  and 

closely  placed  on  the  median  than  on  the  lateral  wall  of  the  furrow.     Their  number 


1434 


HUMAN  ANATOMY. 


has  been  variously  estinuted,  but  it  it  probable  that  from  loo  to  150  represents  the 
maximum  for  a  single  pafHlla,  in  many  cases  the  quoU  being  less  than  one  half 


Fio.  1 194. 


Annu'ar 

wall  tvr- 

round  inir 

IMpilla 


MuKleof  loncuc 


Section  of  citviunvmllalc  papilla  (rum  Uwigne  o(  child.     K  70. 


Fig. 


"95- 


of  these  fibres  (Grabei^).  The  locality  of  next  importance  numerically  is  the 
papillx  foliatse  on  the  sides  of  the  tongue  in  the  furrows  of  vhich,  even  in  man, 
the  taste-buds  are  plentiful. 

Additional  situations,  in  which,  however,  the  taste-buds  are  very  sparingly  and 
uncertainly  distributed,  include  the  fungiform  papillae,  the  soft  palate,  the  posterior 
surface  of  the  epiglottis  and  the  mesial  surface  of  the  arytenoid  cartilages.     Within 

the  fungiform  papillx  a  few  buds  may  be  found  on 
the  free  surface,  where  the  epithelium  is  thinnest. 
Over  the  soft  palate  their  distribution  is  irregular 
and  uncertain,  while  in  the  larynx  the  buds  are  lim- 
ited to  the  areas  covered  by  squamous  epithelium. 
According  to  Davb,  between  fifty  and  sixty  taste- 
buds  of  varying  size  may  be  counted  on  the 
epiglottis  within  an  area  3  mm.  in  diameter. 

Structure. — Wherever  found,  the  taste-buds 
consist  exclusively  of  epithelial  tissue  and,  in  cor- 
resjjondence  with  other  sense  organs,  include  two 
chief  varieties  of  elements — the  supporting  cells 
and  the  more  highly  specialized  neuro-epithelium, 
the  gustatory  cells,  among  which  lie  the  terminal 
fibrills  of  the  nerve  of  taste. 

The  supporting  cells  are  represented  prin- 
cipally by  elongated  epithelial  elements  that  occupy 
both  the  superficial  and  deeper  parts  of  the  taste- 
buds  of  which  they  contribute  the  chief  bulk.  They 
vary  in  their  individual  contour,  being  lanceolate, 
wedge-shaped  or  columnar,  according  to  the  model- 
ling to  which  they  are  subjected  by  the  neighboring 
cells.  They  possess  large,  clear,  vesicular  nuclei 
that  contain  litde  chromatin  and,  therefore,  stain 
faintly.  The  position  of  the  nucleus  is  inconstant,  in  some  cells  being  near  the 
base  and  in  others  in  the  middle  or  nearer  the  apex.     The  peripheral  ends  of  the 


Taste-bud 


Taste-pore  < — ~ 


Epithelium 


Taste^bttd 


Taste-buda  in  section ;  upper  one  siiowa 
gustatory  hairs  ptofecting  into  pore-canal. 


rms:  wmojm  of  t^^ste. 


1435 


i.a'j  I i.i  1.' 


Fig.  1196. 

(  )Ut«T  tllKtV-pi 


si^>purting  cells,  somewhat  bhRit««<'  ami  HmHmkH  a«d  hesrt  with  a  namw  cutiouUir 
cone,  are  closely  grou|>nl  in  b<«i««  ttw  nmmuimr  ipenii^  <■•  the  inner  ta«te-pi>rt', 
through  which  project  the  stiff  tsur  mtttxmm^  (if  rJK-  tfustai*"-  cells.  Thmr  det'|xT 
or  central  ends  are  prolonged  wma  mw  or  ammv  f»rf»topl»sinir  i^iicesses  which  unite 
with  simitar  extensions  u«  the  IjnmI  ceils,  as  iAm?  pet-^iar  supporting  cells  .tr  tlte  base 
of  the  bud  are  called. 

The  6asa/  ceils  are  madiAed  «aM«macuiar  •■It-mertts.  pr(>babi>  epithelial  in  iMiure, 
which  occupy  the  lower  iourth  '  the  buds,  resting  i«pon  thf  sufijacent  epithelium 
and,  in  turn,  affording  support  Vi,yr  the  eiongatvd  celi«*  Although  differing  111  siz«- 
and  details  of  lorm,  th«-  basal  <•»-!»*  ^re  provided  wit!'  >val  nuclei  and  are  gen«Tally 
more  or  less  branched,  by  iiwbw»<  of  their  protopl"«'«nir  processes  they  are  unite<l 
with  the  central  entis  of  the  lot»gsturt«»all\'  dispon**!  suprwrting  and  gustatory  <-lls 
with  one  another  and  with  tlie  s«rrtMmding  epithelial  i  ''lis.  The  mmiber  of  lasal 
cells  in  each  bud  is  small,  uiten  iil»  two  iir  thrr^'  ami  !ield<«m  more  than  half  a 
dozen  being  present  (Graberg*,  Katiiiw')- 

The  percipient  elements,  the  gnatatory  c^a.  are  irreipibrtv  arranged  bet\v.-t;n 
the  more  deepiv  placed  sapporting  cell*  and  enclosed  within  a  snell  formed  by  liie 
more  superficial  ones.     Thr  long  and  fusiform    reaching  from  the  Ijase  of  tiw 

bud  to  the  inner  t.»ste-porr  ■ ,  i,  hich 

e  stifi  hair-like  processes  . 
outer  ends  project.    Their  si. . 
rich  in  chromatin  and   deqii'. 
occupy  the  thickest   part»  of 
whicn  beyond  the  nucl'"j»  at  ,■..•',•-.! 

in  either  direction  i»s  thin  pr-  >ccsms  i'l«e 
peripheral  ones,  as  noted,  extend  not  only 
as  far  as  the  inner  tiiste-jxtre,  but  through 
the  latter  and  into  the  ainal  by  meais  of 
the  gustatory  hairs  into  which  the  taste 
cells  are  prolonged.  The  centrally  directed 
ends  are  usually  much  the  shorter  and 
join  the  processes  of  the  basal  cells.  The 
number  of  gustatory  cells  within  a  single 
tast'  bud  varies,  in  exceptional  cases  only 
two  )r  three  being  present,  but  more 
often  they  are  almost  as  numerous  as  the 
suppf>rting  cells  (Grabcrg). 

The  capi'.lary  clefts  observed  within 
and  around  'he  taste-buds — the  intra-  sub-  and  peri-bulbar  juice-spjices  described 
by  Grabcrg — are  regarded  by  some  as  existing  during  life  and,  therefore,  not  as 
artefacts.  To  these  intercellular  clefts  the  last-named  authority  attributes  the  func- 
tion of  insuring  and  facilitating  an  active  lymph-circulation  within  and  around 
the  taste-buds,  .liiereby  is  effected  the  prompt  removal  of  foreign  substances  that 
might  prove  delett  .ioiis  if  too  long  retained  in  close  relation  with  the  delicate 
sensory  elements. 

Hermann  has  shown  that  the  taste-buds  are  the  seat  of  continual  degeneration 
and  repair,  sometimes,  indeed,  entire  buds  undergoing  regression.  Whether  such 
destructive  processes  are  to  be  ascribed  directly  to  the  invasion  of  leucocytes,  al- 
though the  latter  are  nornwlly  found  in  insignificant  numbers  within  the  buds,  is  still 
a  subject  of  discussion. 

The  nerves  distributed  to  the  gustatory  l>odies  are  the  fibres  of  the  glosso- 
pharyngeal, the  nerve  of  taste.  From  the  rich  subepithelial  plexus  numerous  twigs 
ascend  into  the  epithelium,  one  set  going  directly  into  the  taste-buds  and  the  other 
ending  within  the  surrounding  tracts  of  epithelium.  Since  the  last  set —the  intrr- 
bulbar  fibres — probably  have  no  concern  with  the  impressions  of  taste  and  serve  to 
convey  sensory  stimuli  of  other  value,  it  suffices  to  note  that  after  repeated  division 


(  eiitnil 


vniph-space 


Hani  cell 


DiaKTamnulU:  MHrtiofi    illnstratinK  architecture   of 
taate-hud      \l»tahetgA 


'  Anatomische  Hefte,  Bd.  xii.,  Hf.  2,  1890. 

•  Bardeleben's  Handbuch  d.  Anatomic  des  Menschen,  Lief.  13,  1905. 


1430 


HUMAN  ANATOMY. 


\''V^., 


F-'ic;.  1 197. 


Partial))'  sepaimled  cells  of  UUr- 
bud  with  tenninal  filaments  uf  gusu- 
tory  nerve.    X  Jio.    lAnutetm.) 


the  ultimate  fibriUae  terminate  in  minute  bead-like  endings  that  lie  free  between  the 
epithelial  cells,  either  near  the  free  surface  or  at  a  deeper  level. 

The  ner\es  distributed  to  the  taste-buds— the  intrabulbar  fibres — enter  at  the 
basal  pole.  Usually  numbering  from  two  to  five  for  each  bud,  on  gaining  the 
interior  of  the  latter  they  undergo  rapid  division  and  become  numerous.    A  majority 

of  the  resulting  fibrillx  ascend  in  tortuous  windings 
towards  the  apex  of  the  bud  in  the  vicinity  of  which 
some  end,  while  others  recurve  and  end  at  lower  levels. 
The  fibrilliE  terminate  in  free,  usually  minute  knob-like 
endings,  that  lie  between  and  often  in  close  contact  with 
the  supporting  and  gustatory  cells.  It  is  probable  that 
in  no  instance  do  the  nerve-fibrillse  actually  unite  with 
the  gustatory  cells,  the  relation  being  one  of  appKMition 
and  not  of  continuity. 

Development. — ^The  earliest  evidences  of  the 
taste-buds '  appear,  about  the  third  foetal  month,  within 
the  deepest  stratum  of  the  immature  epithelium  as  groups 
of  cctoblastic  cells  that  are  distinguished  by  their  large  size  and  elongated  form  from 
the  surrounding  v.pithelial  elements.  The  anlage  tends  to  become  conical,  the  ape.x 
gradually  reaching  the  free  surface  and  the  base  resting  or  slightly  encroaching  u|K>n 
the  subjacent  connective  tissue,  from  which  it  is  only  indistinctly  defined.  The 
primary  slender  form  of  the  developing  bud  is  later  replaced  by  one  of  broad  conical 
proportions  in  which  the  wide  base  is  supported  directly  by  the  connective  tissue 
without  the  interposition  of  epithelium. 

For  a  time  the  height  of  the  young  taste-bud  equals  the  entire  thickness  of  the 
epithelium,  the  position  of  its  apex  being  marked  by  a  slight  depression  on  the  free 
surface.  In  consequence  of  the  rapid  increase  of  the  surrounding  epithelium,  thb 
depression  gradually  deepens  until  the  bud,  which  meanwhile  has  grown  but  slightly, 
lies  at  the  bottom  of  a  narrow  funnel-shaped  passage,  the  pore-canal  (Gral^rg). 
Previous  to  the  fifth  month,  the  constituents  of  the  taste-bud  are  apparently  of 
the  same  character  and  not  until  towards  the  end  of  gestation  is  the  differentiation 
between  the  supporting  and  gustatory  cells  clearly  established.  The  definition  of 
the  tastc-t>uds  from  the  surrounding  tissue  is  sharpened  by  the  apfiearance  of  the 
so-called  fxlrabulbar  cflls,  flattened  protecting  epithelial  ejements  in  which  partial 
cornilicatiun  probably  takes  place  (  Kallius).  Coincidently  many  of  the  conical 
embryonal  buds  gradually  assume  their  more  slender  and  ovoid  mature  form.  Before 
birth  the  taste-buds  are  j)resent  not  only  on  the  sides  but  also  over  the  summit  of 
the  circumvallate  papilUe.  While  exceptionally  some  of  ihose  in  the  latter  situation 
may  rt-main,  as  a  rule  they  disappear  and,  hence,  in  the  adult  the  gustatory  bodies 
an-  usually  confined  to  the  sides  of  the  papilhe.  Likewise  the  complement  of  taste- 
buds  on  the  fungiform  papilla;  is  much  larger  at  birth  than  later  (StahrM,  giving  to 
these  papilhe  an  importance  during  early  childhood  that  subsequently  is  lost 

THE  EYE. 

.Although  the  organ  of  sight  (orKanitn  visus),  strictly  regardcKl,  consists  only  of 
thi-  f\i-l)all  or  inlolx-  of  the  eyi  it  is  closely  asst>ciatetl  with  other  structures,  as  the 
eyelids,  the  lachrymal  apiKiratus,  the  t)rbital  fascia  and  fat  and  the  ocular  muscles, 
which  scr\e  for  its  {)rotection,  support  and  change  of  axis.  The  description  of  some, 
at  U'ast,  of  these  accessory  structures  therefore  appropriately  here  finds  place. 

THE  ORBIT  AND  ITS  FA.SCI/F-. 

The  walls  of  the  orbit  h.i\e  l>een  described  in  connection  with  the  skull  (page 
232 ) ;  suffici-  it  here  to  iMiint  out  that  in  its  general  form  the  orbital  r.ivity  resembles 
a  pyramid,  ^M)  modified  by  the  rounding  of  its  angles  that  it  approximates  an  irregu- 
lar cone.     The  base  corresponds  with  the  orbital  opening  on  the  face  and  the  apex 

'Gmbert; :  S<hw;iltie's  Morj>hol(>K.  Arbeiten,  Bd.  vlii.,  1898. 
'/eits<-hr.  f.  Moriihul.  u.  Anthropol.,  Bd.  4,  igui. 


THE  ORBIT  AND  ITS  FASCIA. 


1437 


with  the  optic  foramen.  The  median  walls  of  the  two  orbits  are  slightly  divergent 
behind,  but  almost  parallel  with  the  sagittal  plane  au.l  with  each  other  ;  the  lateral 
wails  are  obliquely  placed  and  with  the  sagittal  plane  form  an  angle  of  about  48° 
and,  therefore,  with  each  other  one  of  something  more  than  a  right  angle.^  The  axis 
of  the  orbit  is  directed  inward  and  upward,  forming  an  angle  of  from  :  s'-so"  with 
the  horizontal  plane,  and  one  of  about  45°  with  the  orbitel  axis  of  the  op|)osite  side, 
which  it  intersects  in  the  vicinity  of  the  sella  turcica.  The  width  of  the  orbital  en- 
trance is  about  4  cm.  and  the  height  about  5  mm.  less,  while  the  depth  of  the  orbit  is 
approximately  4  cm.  The  space,  therefore,  is  much  more  capacious  than  necessary 
to  accomodate  the  eyeball  and  the  associated  muscles,  blood-vessels  and  nerves. 
The  interspaces  thus  left  are  occupied  by  the  orbital  fat  (corpus  adiposum  orbitae ),  sup- 
ported by  a  framework  of  connective  tissue  lamellae  prolonged  from  the  orbital  fascia 
which,  in  turn,  is  continuous  with  the  periosteum  lining  the  orbit.  The  latter,  also 
known  as  the  periorbita,  is  thin  but  resistent  and  at  the  various  openings  in  the  walls  of 
the  orbit  continuous  with  the  periosteum  covering  the  adjacent  surfaces  of  the  skull. 

Fig.  1198. 


Niial  loiM-. 
Anterior  ethmoidal  cell*. 

Meiitt  orbiul  wmIL 
'.ntenuil  rectus  mu«cl« 
Potterior  ethmoidal  cell 


Conlnnrtival  lac 
Anterior  chamber 
Corncn 
Lent 

Vitreoiu  chamber 

Check  liKsment 
Orbiul  wall 


Eatemal  racHu  muclc 
Sclera 


Orbital  (at 
Optic  na\t 
HoriionUl  •cctloa  ol  ri(ht  orbit  ahowing  eye  in  poaition. 

The  eyeball  does  not  rest  directly  in  contact  with  the  fatty  cushion  fonning  the 
walls  of  the  cup-shaped  recess  in  which  it  lies,  but  is  separated  from  the  surrounding 
adipose  tissue  t)V  a  fascial  investment,  the  captule  of  Tenon  'jwge  504).  This 
sheet  covers  tlic  posterior  three-fourths  of  the  eyeball  and  encloses,  between  it  and 
the  eye,  the  space  of  Tenon.  The  latter  in  front  begins  beneath  the  conjuctival 
sac.  close  to  the  corneal  margin,  and  behind  ends  in  the  vicinity  of  the  optic  nerve. 
It  <loes  not,  however,  quite  reach  the  latter,  but  terminates  where  the  eyeball  is 
pierced  by  the  posterior  ciliary  vessels  and  nerves,  thus  leaving  an  irregular  oval  aret 
uncovered  (Merkel ).  Farther  backward  the  space  of  Tenon  communicates  with  the 
subdural  lymph-channel  prolonged  along  the  optic  nerve  and  thus  establishes  relations 
with  the  intercranial  lymph-piiths  (page  949). 

The  eye  muscles,  which  together  with  the  elevator  of  the  upper  lid  have  been 
descrilxxl  (page  502),  are  invested  by  fascial  sheaths  prolongttl  from  the  orbitiil 
periosteum.  These  sheaths  increase  in  thickness  its  they  approach  the  eyelxiU  until, 
at  the  points  where  the  tendons  tif  the  ocular  muscles  meet  the  fascial  sheet  investing 
the  posterior  part  of  the  eve — the  capsule  of  Tenon — the  muscle  sheaths  blend  with 
this  capsule  on  the  one  hand,  and,  on  the  other,  are  at»achetl  at  certain  points  to  the 
orbital  wall  as  robust  pointed  processes  of  consideral  le  strength.     One  such  prtKess, 


1438 


HUMAN  ANATOMY. 


'  '  flu  1  '  '  .  1 


attached  to  the  upper  lateral  wall,  is  formed  by  the  fusion  of  the  fascial  lamellx  con- 
tributed by  the  sheaths  of  the  levator  palpebrje  superioris  and  of  the  superior  ami 
externa!  straight  muscles.  Another  and  broader  process,  inserted  along  the  median 
wall,  includes  the  blended  extensions  from  the  investments  of  the  internal  rectus  and 
superior  oblique  ;  whilst  a  third  process,  formed  by  the  union  of  prolongations  from 
the  fasciae  covering  the  inferior  and  internal  recti  and  the  inferior  oblique,  is  attached 
to  the  lower  and  median  orbital  wall.  These  fascial  extensions,  passing  as  they  do 
from  the  tendons  of  the  eye-muscles  to  the  orbital  wall,  restrain  excessive  muscular 
action  and  hence  the  name,  cAec/i  iigamenls,  has  been  applied,  especially  to  those 
limiting  the  action  of  the  internal  and  external  recti.  The  processes  also  materially 
assist  in  maintaining  the  position  of  the  eyeball  within  the  orbit.  This  function  is 
particularly  exercised  by  the  robust  fascial  expansion  which  stretches  across  the  orbit 
below  the  eyeball  and  as  the  suspensory  ligament  of  Lockwood  serves  to  support  the 
bulbus  oculi. 

The  orbital  fat  is  prevented  from  projecting  forward  l)eyond  a  certain  limit  and, 
therefore,  from  encroaching  unduly  upon  the  eyelid,  by  a  sheet  of  fibrous  tissue,  the 


Fig.  1 199. 

I'ppcr  uml  plate 


Lachrymal  r'land 

Palpebral  faicia.  cut 
Lateral  palpebral  lixament 


Lower  laraal  plaie 


.Palpebral  iaacia 


Lachr>inal  1 


Median  palpebral  linainem 

l.achrymal  punrtum  and 
catialiculua 


Nasal  duct 


^  Opening  of  nani  durt  in 
inferior  naial  mcatua 


Maxillary  sinui 
Diiacction  of  orbit  and  ad|acem  atructuret.  >howinK  palpebral  faacia,  liichr>'mal  Mc  and  naial  duct. 

palpelral  fascia  or  septum  orbHale  (Hcnle),  which  stretches  across  the  orbital 
entrance  and  materially  strengthens  and  aids  the  eyelid  in  closing  this  aperture. 
Above,  the  septum  is  attached  to  the  border  of  the  orbit,  just  behind  the  margin, 
from  which  it  extends  downward  to  become  firmly  united  with  the  common  fascial 
investment  of  the  levator  pal|>ebne  superioris  and  superior  rectus  and,  still  loner, 
with  the  up|)er  convex  border  of  the  superior  tarsal  plate.  On  each  side  the  septum 
blends  with  the  corresponding  |)alpebral  ligament,  while  Ix^low  it  passes  from  the 
orl)itril  margin  to  the  mlorior  tarsal  plate,  after  becoming  united  with  the  8h<  ith 
of  the  iiifiTior  rectus.  The  septum  orbital  is  not  of  uniform  thickness,  but  is 
strongest  above,  especially  towards  the  sides,  and  wejikest  l)eneath  the  lower  eyelid  ; 
further,  in  a  general  way,  the  sheet  is  more  robust  ne:ir  its  [x-ripheral  bony  attach- 
ment than  where  it  joins  the  tarsal  plates.  In  conjunction  with  the  [lalpebral  liga- 
ments, it  is  so  strong  behind  the  angles  of  the  eye  that  in  these  localities,  particularly 
medially,  it  is  very  unyielding  and  capable  of  resisting  forward  displacement.  The 
int'-rnai  union  of  the  lev.aor  palpebr^  superioris  with  the  septum  orbitale  enables 
this  inuscif  when  it  contracts  to  tens^  the  fascial  diaphragm. 

Practical  Considerationa. — The  orbital  cavity  is  somewhat  pyramidal  in 
shape  and  its  anterior  or  ba-sal  portion  is  cKxupied  chiefly  by  the  eyel>all,  which  lies 
slightly  nearer  the  r(M)f  and  the  outer  wall  than  the  lower  and  inner  walls.    Its  diameter 


PRACTICAL  CONSIDERATIONS:    ORBIT   AND   FASCIit.      i439 

is  greatest  just  back  of  its  anterior  margin,  which  is  thickened  and  offers  the  best 
protection  to  the  eye  from  injury.  The  upper  margin  is  most  market!  and  with  the 
eyebrow  offers  a  good  protection  to  the  eye  in  that  direction.  The  inner  margin  is 
not  prominent,  but  is  well  reinforced  by  the  bridge  of  the  nose.  The  outer  edge  is 
least  prominent,  and  on  that  side  palpation  is  possible  as  far  back  as  the  equator  of 
the  globe.  For  this  reason,  and  because  the  outer  walls  converge  backward  while 
the  inner  •valla  are  parallel,  incisions  for  reaching  the  interior  of  the  orbit  are  Ijest 
made  on  the  outer  side.  The  walls  are  thin  and  easily  fractured  by  direct  violence, 
as  from  canes  and  similar  objects,  which  sometimes  enter  the  adjacent  cavities,  as 
the  ethmoidal.  Tumors  may  encroach  upon  the  orbital  space  either  by  causnig  the 
absorption  of  the  thin  intervening  bone,  or  by  growing  through  one  or  more  of  the 
openings  in  its  wall,  as  through  the  optic  foramen  and  sphenoidal  fissure  from  the 
cranial  cavity,  the  nasal  duct  from  the  nose,  or  the  spheno-maxiUary  fissure  from  the 
temporal  or  zygomatic  ioaax. 

The  eyeball  occupies  about  one-fifth  of  the  orbital  cavity,  the  remainmg  space 
being  filled  by  nerves,  vessels,  muscles,  the  lachrymal  gland,  fat,  and  a  system  of 
fasciae.  In  the  ordinary  case  a  straight  edge  placed  against  the  upper  and  lower 
margins  of  the  orbit  will  just  touch  the  closed  lids'  covering  the  apex  of  the  cornea, 
but  will  not  compress  the  eye.  A  straight  line  between  the  two  lateral  margins 
would  pass  back  of  the  cornea,  on  the  outer  side  posterior  to  the  ora  serrata  and  on 
the  inner  side  at  the  junction  of  the  ciliary  body  and  iris. 

An  exophthalmos  is  a  protrusion  forward  of  the  ball,  and  is  usually  due  to 
pressure  from  behind,  more  rarely  to  paralysis  of  the  recti  muscles.  Some  of  the 
more  common  causes  of  retrobulbar  pressure  are  orbital  cellulitis  or  abscess,  tumors, 
distension  of  the  orbital  vessels,  and  excess  of  fat. 

Rnophthalmos,  due  to  exhausting  disease,  is  more  apparent  than  real,  but  a  true 
sinking  of  the  globe  may  be  due  to  paralysis  of  Miiller's  muscle  due  to  lesion  of  the 
sympathetic,  to  atrophy  of  the  retro-bulbar  cellular  tissue  caused  bv  trophic  dis- 
turbance, to  fracture  and  depression  of  the  orbital  bones  with  cicatricial  adhesion 
and  contraction,  and  to  injury  of  Tenon's  capsule  and  the  check  ligaments. 

InJIammation  of  the  capsule,  or  Tenonitis,  may  be  due  to  constitutional  poison 
or  to  infection  following  operations  involving  it,  as  in  tenotomy  of  the  ocular 
muscles.  It  may  be  an  extension  from  an  inflammation  of  the  eyeball.  The  inflam- 
matory exudate  in  the  capsule  and  adjacent  tissues  will  sometimes  cause  a  slight 
exophthalmos,  and  the  eye  will  be  immobile.  All  the  extrinsic  muscles  of  the  eye 
pierce  the  capsule  about  the  equator  of  the  globe  to  reach  their  insertions  in  it. 
Each  muscle  receives  a  tubular  investment  from  the  capsule,  which  fuses  with  the 
proper  sheath  of  the  muscle  and  leaves  a  small  bursa  on  the  anterior  surface  of 
each.  To  open  the  capsule  for  a  tenotomy,  the  incision  is  made  just  back  of  the 
cornea,  and  goes  through  only  the  conjunctiva  and  outer  layer  of  the  capsule.  The 
desired  tendon  is  easily  found  and  brought  out  with  a  hook,  when  it  is  divided.  The 
capsular  prolongation  about  the  tendon  prevents  retraction  of  the  stump  after  the 
division,  and  so  preserves  the  function  of  the  muscle.  This  is  aided  by  expansions 
of  the  capsule  passing  to  the  margins  of  the  orWt  and  continuous  with  the  perios- 
teum. Those  passing  from  the  internal  and  external  recti  are  stronger  than  the 
others  and  are  called  the  internal  and  external  cheek  ligaments.  They  are  uniti-d 
by  a  layer  of  fascia  (suspensory  ligament  of  the  cyelwU)  passing  under  the  eyeball 
so  that  the  eye  is  supported  after  the  bony  floor  of  the  <Mhit  has  been  removed,  as 
after  excision  of  the  superior  maxillary  bone.  If  the  outer  layer  of  the  glol)e  is  left 
after  enucleation  of  the  eye,  the  muscles  will  still  have  an  attachment  and  be  cajwble 
of  moving  an  artificial  eye  fitted  to  the  stump. 

While  the  movements  of  the  eyeball  arc  free  in  all  directions,  as  in  a  ball  and 
socket  joint,  no  change  in  position  of  the  eyeball,  as  a  whole,  takes  place,  as  the 
centre  of  rotation  is  about  in  the  centre  of  the  globe.  By  these  movements  the 
image  of  the  object  to  be  especially  seen  Ls  fixed  upon  the  most  sensitive  part  of  the 
retina. 

The  internal  rectus  draws  the  ball  directly  inward  and  the  external  rectus 
directly  outward.  The  other  four  muscles,  the  superior  and  inferior  recti  and  the 
two  oblique,  have  a  complicated  action.     The  upward  and  downward  movements 


I440 


HUMAN  ANATOMY. 


are  controlled  chiefly  by  the  superior  and  inferior  recti  respectively,  but  each  has  a 
slight  adducting  and  a'slight  rotating  movement — i.e.,  the  superior  rectus  will  move 
the  upper  extremity  of  the  vertical  meridian  slightly  inward  (intorsion),  and  the 
inferior  rectus  will  move  the  same  part  slightly  outward  (extorsion).  The  superior 
oblique  is  attached  to  the  globe  behind  the  equator,  and  lower  than  its  pulley,  so  that 
in  addition  to  its  chief  or  internal  rotating  action  upon  the  upper  limit  of  the  ball  it 
has  also  an  elevating  effect  upon  the  posterior  portion,  the  cornea  moving  down- 
ward. Since  its  pull  is  inward,  the  cornea  also  moves  outward.  The  chief  move- 
ment of  the  inferior  oblique  is  rotary  in  the  opposite  direction  ( extorsion  of  the  upper 
part).  It  is  likewise  inserted  into  the  posterior  half  of  the  globe,  which  is  depressed 
by  it,  and  the  cornea  is  raised  and  moved  outward.  In  elevation  of  the  cornea  by 
the  superior  rectus  the  internal  rotation  of  this  muscle  is  counteracted  by  the  inferior 
oblique,  and  in  a  similar  manner  when  the  cornea  is  moved  downward  by  the  inferior 
rectus,  its  external  rotation  is  opposed  by  the  superior  oblique.  The  upward  and 
outward  movement  is  produced  chiefly  by  the  sufterior  and  external  recti,  the  infe- 
rior oblique  opposing  the  intorsion  o,  the  superior  rectus.  Motion  downward  and 
outward  is  due  to  the  external  and  inferior  recti,  the  superior  oblique  opposing  the 
outward  wheel  action  of  the  inferior  rectus.  The  downward  and  inward  motion  is 
due  to  the  internal  and  inferior  recti,  the  superior  oblique  opposing  the  inferior 
rectus. 

When  one  muscle  is  weaker  or  larger  than  its  opposing  muscle,  the  eye  is  turned 
to  the  side  of  the  stronger,  producing  strabistnus  or  squint.  It  b  usually  tume<l 
laterally,  most  frequently  to  the  inner  side  producing  internal  or  convergent  strabis- 
mus. All  the  recti  except  the  external  are  suppli^  by  the  oculomotor  nerve.  If 
that  nerve  is  paralyzed  only  the  external  rectus  can  act,  and  an  e.xtemal  squint  will 
result.  If  the  sixth  cranial  nerve  (abducens)  which  supplies  the  external  rectus  is 
paralyzed,  the  eye  will  turn  inward,  the  superior  and  inferior  recti  opposing  each 
other. 

Paralysis  of  one  or  more  muscles  may  occur.  If  a  single  muscle  is  involved  it 
is  usually  the  superior  oblique  or  external  rectus,  as  each  of  these  is  supplied  by  a 
sepiirate  cranial  nerve,  the  fourth  and  sixth  respectively. 

Although  the  third  ur  oadomotor  has  a  much  wider  distribution  than  these,  sup- 
plying all  the  other  extrinsic  muscles,  as  well  as  the  ciliary  muscle  and  sphincter  of 
the  iris,  when  it  is  completely  paralyzed  the  clinical  picture  is  definite.  Ptosis  is 
present  and  is  due  to  paralysis  of  the  levator  palpebne.  External  strabismus  and 
slight  depression  of  the  eye  are  produced  by  the  unopposed  action  of  the  external 
rectus  and  superior  oblique,  while  the  eye  is  otherwise  motionless.  The  pupil  is 
dilated  from  paralysis  of  the  sphincter  of  the  iris,  and  accommodation  for  near  objects 
is  lost  from  paralysis  of  the  ciliary  muscle.  Slight  exophthalmos  appears  from  paral- 
ysis of  all  but  one  of  the  recti  muscles. 

The  fourth  nrrve  alone  is  rarely  paralyzed.  There  will  be  little  disturbance 
of  function,  since  the  motion  of  the  superior  oblique  is  j)erfonned  partly  by  the 
other  muscles.  The  eye  will  turn  inward  when  the  object  l(K>ked  at  is  lowered, 
and  ujjward  only  when  the  object  is  turned  far  toward  the  healthy  side.  One  eye 
must  be  closetl  to  prevent  double  vision  or  diplopia. 

Of  the  single  paralyses,  that  of  the  sixth  nervf  is  most  frequent  on  account  of 
its  extended  course  from  its  origin  in  the  brain  to  its  peripheral  termination  in  the 
external  rectus,  rendering  it  liable  to  involvement  by  adjacent  |>athological  processes, 
as  meningitis,  tumors,  or  hemorrhages.  .Such  lesions  may  invoKe  it  alone,  or 
together  with  a  series  of  cerebral  ner\'es,  paralyzed  one  after  another  from  a  progrcss- 
inv;  pathological  condition,  which  would  then  probably  l)e  at  their  central  origin,  or 
in  the  wall  of  the  cavernous  sinus,  where  they  are  close  together.  The  sixth  ner\e 
may  Ik-  {laralyzed  by  a  fracture  of  the  base  of  the  cranium  in  the  middle  f<>s.sa. 

When  the  ophthaimir  divi'sion  of  the  /i/th  »ert'f  is  paralyze*!,  there  follows 
anesthesia  of  the  conjiinctix'a  of  the  globe  and  upper  lid,  and  of  the  other  piirts  8upplie<l 
l)v  this  n<'r\e.  The  lids  jIo  not  respond  reflexly,  as  usual,  for  protection  of  the 
c<irne:i,  which  is  liable  then  to  troublesome  ulceration. 

The  irnical  ssiiipathitir  supplies  the  dilatator  muscle  of  the  iris,  and  reaches  the 
cranium  along  the  internal  carotid  artery.   When  the  cer\'ical  symjiathctic  is  jmraly/ed 


THE  EYELIDS  AND  CONJUNCTIVA. 


1441 


the  pupil  contracts.  There  will  be  some  drooping  of  the  upper  lid  due  to  paralysis 
ot  the  superior  palpebral  muscle  of  Miiller  which  passes  from  the  under  surface  of  the 
levator  palpebrae  muscle  to  the  upper  nuu^in  of  the  upper  tarsal  cartilage,  and  is 
supplied  by  the  cervical  sympathetic.  There  will  be  slight  enophthalmos  from  paral- 
ys»  of  a  thin  layer  of  unstriped  muscle  passing  across  the  spheno-maxillary  nssure 
(orbitaiis  muscle  of  Miiller). 

The  normal  pupil  will  contract  for  accommodation  and  convergence  to  near 
objects  and  from  stimulation  by  a  bright  light.  An  Argyll-Robertson  pupil  is  one 
which  does  not  react,  either  directly  or  indirectly  (consensually)  to  the  influence  of 
light,  but  contracts  promptly  on  convergence  of  the  visual  axes.  The  exact  situation 
of  the  lesion  is  uncertain  ;  it  may  involve  the  fibres  which  pass  from  the  proximal 
end  of  the  optic  nerve  to  the  oculomotor  nuclei ;  it  may  be  nuclear  in  its  position  ; 
or  it  may  be  in  the  spinal  end  of  the  floor  of  the  fourth  ventricle. 

Owing  to  the  relatively  large  amount  of  fat  and  loose  connective  tissue  in  the 
orbit,  infection  may  lead  to  an  extensive  orbitai  abscess,  so  that  an  early  ofKnin^  is 
imperative  to  prevent  disturbance  or  loss  of  sight  The  muscles  may  be  impaired 
by  the  process,  leading  to  the  lessened  mobility  of  the  eye.  The  optic  nerve  may 
be  inflamed  with  resulting  atrophy  and  permanent  impairment  of  sight,  and  the  other 
ocular  nerves  may  also  be  paralyzed.  From  the  exophthalmos  the  optic  ner\'e  may 
be  stretched,  although  the  degree  of  stretching  permitted  without  disturbing  sight  is 
often  remarkable.  Pus  may  enter  the  cranial  cavity  through  the  optic  foramen,  and 
set  up  a  meningitis  or  a  brain  abscess. 

Injuries  of  the  orbital  tissues  are  usually  the  result  of  penetration  by  foreign 
bodies.  The  eye  has  been  pried  out  by  the  finger,  or  thumb,  on  the  outer  side  by 
insane  people,  or  in  fights,  the  finger  being  readily  forced  back  of  the  equator  of 
the  globe.  There  are  cases  in  which  the  eye  has  been  refdaced  and  vision  regained 
after  such  accidents,  although  it  is  usually  lost. 

Fracture  of  the  bony  wall  of  the  orbit  ordinarily  leads  to  hemorrhage  into  the 
soft  tissues,  showing  later  under  the  conjunctiva  of  the  ball  (subconjunctival  ecchy- 
mosis).  If  the  neighboring  air  cavities,  si  the  ethmoidal  and  sphenoidal  sinuses,  are 
involved,  emphysema  of  the  orbit  may  result.  The  exophthalmos  from  air  behind 
the  eye,  can  be  reduced  by  backward  pressure,  the  air  beinj;  forced  back  into  the  air 
sinuses.  A  collection  of  blood  would  not  disappear  by  such  pressure.  In  cases  of 
emphysema  the  patient  should  be  instructed  not  to  blow  the  nose,  as  by  that  at 
additional  air  is  forced  into  the  orbit 

Tumors  of  the  orbit  are  comparatively  common.  They  may  begin  in  the  adja- 
cent cavities  and  invade  the  orbit  secondarily.  The  most  important  symptom  in  all 
cases  is  exophthalmos.  Pain  and  paralysis  from  pressure  on  the  nerves,  and  con- 
gestion and  edema  of  the  lids  from  pressure  on  the  veins  frequently  occur. 


THE   EYELIDS  AND   CONJUNCTIVA. 

The  eyelids  (palpebrac)  are  two  movable  folds  of  integument — an  upper 
and  a  lower — strengthened  along  their  free  margins  by  a  lamina  of  dense  fibrous 
tissue,  the  tarsal  plate,  and  modified  on  their  deeper  aspect  so  that  this  surface 
resembles  a  mucous  membrane,  the  conjunctiva.  When  in  apposition  or  closed  they 
completely  cover  the  orbital  entrance  and  the  eyeball  ;  at  other  times,  when  open, 
they  cover  the  periphery  of  the  orbit  but  allow  a  variable  portion  of  the  anterior  part 
of  the  eye  to  remain  exposed. 

The  palpebral  fisiure  (rima  palpcbramm)  is  bounded,  above  and  below,  by 
the  free  margins  of  the  lids  and  at  the  ends,  where  the  lids  join,  by  two  fibrous 
bands,  the  median  and  lateral  palpebral  ligaments.  Of  these  the  inner  and 
stouter  springs  from  the  nasal  process  of  the  superior  maxillary  bone  and  the  narrow 
outer  one  is  attached  to  the  malar  bone.  The  palpebral  fissure  is  an  oval  cleft  of 
not  quite  symmetrical  form,  since  the  curvature  of  its  upper  boundary  is  somewhat 
greater  than  that  of  the  lower  ;  further,  the  points  marking  the  summit  of  the 
two  curves  neither  correspond  to  the  middle  of  the  arches  nor  lie  opposite  each 
other,  that  of  the  upper  arch  lying  nearer  the  mid-line  and  that  of  the  lower  nearer 
the  lateral  wall.     Neither  is  the  palpebral  fissure  strictly  horizontal,  since  the  inner 

9» 


1442 


HUMAN  ANATOMY. 


Fig.  i2aa 


of  its  ends,  the  angles  or  canthi,  lies  slightly  (from  4-6  mm. )  lower  than  the  other  one. 
The  free  borders  of  the  lids  meet  at  the  outer  canthus  without  change  of  curvature, 
but  on  approaching  the  inner  canthus  they  alter  their  direction  and  extend  medially 
for  several  millimeters  before  meeting.     In  this  manner  immediately  external  to 

the  inner  canthus  the  lids  bound  a  shallow 
D-shap>ed  recess,  about  5  mm.  long,  known 
as  the  lachrymal  lake  (lacus  lacrimalis). 
The  palpebral  fissure,  which  possesses  an 
average  length  of  30  mm.  and  a  height  of  from 
12-14  mm. ,  is  subject  to  considerable  individ- 
ual variation  in  size,  thereby  exposing  a  vari- 
able amount  of  the  eyeball.  In  consequence, 
the  appearance  of  a  larger  or  smaller  eye 
is  produced,  an  impres.sion,  however,  that 
depends  upon  the  size  of  the  opening  between 
the  lids  and  not  upon  differences  in  the  eyeball 
itself,  the  diameters  of  which,  under  normal 
conditions,  are  practically  constant.  The 
height  of  the  palpebral  fissure  in  young 
children  is  relatively  greater  than  in  the  adult, 
a  jjeculiarity  that  confers  the  characteristic 
wide-eyed  appearance  in  early  life. 

The  upper  lid  is  not  only  much  the 
broader,  its  height  being  about  double  that 
of  the  lower  one,  but  also  the  more  movable 
and  the  chief  agent  in  closing  the  palpebral 
opening.  When  the  latter  is  closed  the  free 
edges  of  the  two  lids  are  in  contact  through- 
out their  length,  the  anterior  margin  of  the 
upper  one  overlapping  slightly  the  corre- 
s|X)iiding  edge  of  the  lower.  The  line  of 
apposition  is  somewhat  arched,  with  the 
convexity  directed  downward,  and  falls  below 
a  horizontal  line  passing  through  the  inner 
canthus.  '  When  the  eyeli<ls  arc  separated 
to  the  usual  extent,  the  free  edge  of  the 
upper  lid  lies  just  below  the  upper  margin 
of  the  cornea,  a  narrow  crescentic  area  of 
which  it  masks,  while  the  corresponding 
border  of  the  lower  lid  falls  slightly  below 
the  inferior  corneal  margin.  The  jxisition 
of  the  pupil  is  about  midway  lx,'twpen  the 
two  canthi.  When  the  eyelids  are  closeil, 
the  upper  fold  covers  the  entire  cornea,  its 
lower  border  lying  opposite  the  correspond- 
ing margin  of  the  cornea. 

Viewed  in  sagittal  seclion  (Fig.  1201 ), 
the  free  Ixirder  of  the  lid  presents  a  well- 
(lefine<l  |).:sterior  margin,  along  which  open 
the  minute  ducts  of  the  tarsal  glands, 
whilst  the  .interior  margin  is  roundetl  anil  passes  insensibly  into  the  adjoining 
external  skin-surface  and  is  beset  with  the  eyelashes.  The  latter,  the  cilia,  are  .stiff 
outwardly  cur\-ing  hairs,  which  numtx;r  from  icx>-i5o  in  the  upper  lid  and  alniut  half 
as  many  in  the  lower.  With  the  exception  of  about  5  mm.  next  the  inner  angle, 
where  the  lids  lx)rdor  the  lachrymal  lake  and  the  eyelashes  are  alwent,  the  cilia  are 
arranged  in  a  double  or  triple  row,  with  the  longest  (8-12  nmi.  )  in  the  centre  of  the 
upper  Ht'iies,  Although  their  follicles  occupy  a  zone  of  from  1-2  mm.  in  width,  the 
free  enils  of  the  cilia  lie  practically  in  a  single  row  the  longer  and  more  closely  set 
upper  lashes  either  crossing  or  overlying  the  shorter  ones  of  the  lower  lid. 


'Con>uncHva 


Tliree  views  i»t  hvtiiK  eye.  showi'iif  relntlotiit  of 
eyeltall  to  |)a)pebr:il  fissure  aii<l  tietails  of  inner 
ranthus. 


THE  EYELIDS  AND  CONJUNCTIVA. 


'443 


Skin 


Fig.  laoi. 

Subcutancouii  tiuuc 

Orbicularis  palpebranim 
Kit 


Tarsol  miiwlc 

Levator  palpcbrK 

supcrioriii 


Blood-vcwcl 


Henlc's  ((laod 


The  palpebral  fis!«ure  leads  into  the  conjunctival  sac,  which,  when  the  lids  are 
in  contact,  is  a  closed  capillary  space  between  the  lids  atid  the  anterior  surface  of  the 
eyeball.  When  the  cleft  is  open,  the  conjunctival  sjKice  becomes  an  annular  groove 
of  unequal  depth,  its  height  being  from  22-25  "i™-  behind  the  upper  litl  and  only 
about  half  as  much  behind  the  lower,  and  being  shallowest  at  the  inner  angle. 
That  part  of  the  sac  which  covers  the  posterior  surface  of  the  lid.s  constitutes  the 
palpebral  conjunctiva  and  that  reflected  onto  the  eye  ball  is  the  bulbar  con- 
junctiva, while  the  bottom  of  the  groove,  where  these  two  portions  are  continuous, 
is  known  as  the  fornix  conjunctivK,  the  superior  and  inferior  being  distinguished. 

The  lachrymal  lake  (lacas  lacrimalis)  is  the  shallow  bay  into  which  the  con- 
junctival sac  is  prolonged  for  about  5  mm.  between  the  medial  ends  of  the  eyelids.  It 
contains  an  irregularly  oval  or  comet-shaped  elevation,  the  lachrymal  caruncle. 
The  latter  (caruncula  lac- 
rimalis) consists  of  an  is- 
let of  modified  skin  from 
which  project  usually 
about  a  dozen  minute 
and  scarcely  visible  hairs, 
provided  with  large  seba- 
ceous and  sm.iUer  sweat 
glands  and  embedded  in 
a  cushion  of  fatty  tissue. 
Just  to  the  outer  side  of 
the  caruncle,  a  vertical 
crescentic  fold,  the  plica 
semilunaris,  indicates 
the  limit  of  the  bulbar 
conjunctiva.  The  fold  is 
of  interest  as  probably 
representing  in  a  very 
rudimentary  way  the 
nictitating  membrane,  or 
third  eyelid,  of  the  lower 
animals.  The  semilunar 
fold  frequently  contains 
a  minute  plate  of  hyaline 
cartilage  as  the  vestige  of 
the  stronger  l>;ir  in  the 
nictitating  membrane. 
Likewise  the  small  group 
of  alveoli  sometimes 
(ouml  within  the  base  ot 
the  foil!  is  regarded  as 
the  homologue  of  the 
Harderian  gland  of  the 
lower  types.  The  [>oints 
at  which  the  slightly 
curvetl  iMJundarieii  of  the 
lachrymal  lake  pass  into 
the  more  architl  «?dges  of  the  eyelids  arc  er.i|)himi/<d  I  y  liiile  e)>  .-.ii.i  ins,  the  lach- 
rymal papillae,  each  of  which  is  piert(.'tl  hy  a  inin-it.'  apc'ratiin-  the  punctum 
lacrimalis,  th.nt  marks  the  Ixginning  of  the  canals  l>y  which  the  tears  are  normals- 
carried  off  from  thi.'  conjunctival  s;ir. 

Structure  of  the  Eyelids. — The  eyelid  comprises  five  layers  which,  from 
without  inward,  .ire:  (i)  the  sh'n,  (2^  the  siihiHlaneoHS  lissiw,  ( ,V)  the  rUH.uii/ur 
layer,  (4)  \\wi  tarso-fmdal layer  VimX  (5)  ihf  ronjiinrliva. 

The  skin  covering  the  outer  surface  of  the  eyelids  is  distinguished  hy  its  unusual 
delicacy,  being  thin  and  l)esel  with  very  fine  downy  and  widely  scattered  hairs,  pro- 
vided with  sehirivHis  f.  .Hicles  ;  small  sweat  glands  also  (K-cur.      It  presents  numerous 


Mriliomiati  iliK-t 


Clandu  of  Moll  Cilia  'r:l].<ry 

Vertical  wctioj:  of  up|ict  eyrlid  ■»!  ciiil 


j^^  HUMAN  ANATOMY. 

ineffaceable  transverse  creases  which,  with  advancing  years,  are  supplemented  by 
vertical  furrows.  Towards  the  inner  canthus.  particularly  in  the  lower  lid  pigment 
exists  in  variable  quantity,  often  in  amount  sufficient  to  confer  a  distinct  brownish 

hue  to  the  intt^-nent.  .  .  i  «  .   •..    i 

The  subcutaneous  tissue  is  distinguished  by  the  entire  absence  of  fat.  its  loose 
texture  and  great  extensibility  :ind  elasticity.  In  consequence  of  these  properties,  it 
sometimes  becomes  the  seat  of  extensive  swelling  after  edema  or  hemorrhage. 

The  muscular  layer,  for  the  most  part  consisting  of  the  annular  bundles  of  the 
orbicularis  palpebrarum,  is  in  fact  so  blended  with  the  subcutaneous  tissue  as  to  be 
practically  Embedded  within  the  latter.  Reference  to  the  description  of  the  orbicu- 
laris pali^brarum  (page  484)  wUl  recall  the  ^ener^  division  of  the  muscle  into 
an  orbitaUnd  a  pali^Tbral  portion,  and  the  relaUons  of  the  deeper  or  lachrymal  s  ip 
(tensor  tarsi)  to  the  tear-sac  and  the  tarsal  plate.  In  vertical  sections  of  the  eyelid 
(Fie  1201)  the  cirrulariy  arranged  bundles  of  the  palpebral  portion  show  as 
transversely  cut  groun*  of  muscle-fibres  enclosed  by  condensations  of  the  surround- 
ing areolar  tissue.  A  distinct  annular  tract,  known  as  the  ciliary  bundle  (m  altans 
Rioiani)  lies  close  to  the  free  border  of  the  lid.  chiefly  between  the  tarsal  plate  and 
the  hair  follicles,  but  in  part  often  also  between  the  conjunctiva  and  the  tarsus.  In 
the  upper  lid,  in  addition  to  the  circular  bundles  of  the  orbicularis  palpebrarum,  the 
terminal  strands  of  the  longitudinal  fibres  from  the  levator  palpebrae  superions 
descend  along  the  deeper  suriace  of  the  (irst-ramed  muscle  Some  of  these 
penetrate  between  the  circular  bundles  and  end  in  the  deeper  layer  of  the  skm  ; 
others  descend  more  vertically  to  find  their  insertion  in  the  upper  border  of  the 

Under  the  name,  tarsal  muscles  or  muscles  of  AfiiUer,  are  described  the  un- 
certain bundles  of  involuntary  muscle  that  are  found  in  the  vicinity  of  the  convex 
border  of  the  tarsi.  Those  within  the  upper  lid  arise  from  the  tendon  and  inter- 
mingle with  the  fibres  of  the  levator  palpebrarum,  with  the  course  of  which  they 
a<  .«fe,  and  end  eiHier  by  insertion  into  the  upper  border  of  the  tarsal  plafe.  or  ;.ito 
the  adjacent  fibrous  tissue.  In  the  lower  lid.  they  are  less  numerous  and  regular, 
and  extend  from  the  for.ix  conjunctiva  to  the  adjacent  border  of  the  tarsus  The 
tarso-fascial  layer  is  represented  next  the  margins  of  the  lids  by  the  tarsal  plates  ana 
beyond  the  latter  by  the  septum  orbitele.  .   .         ^,  •         u 

The  Ursal  plates  (tarsi)  are  two  lamella  of  dense  fibrous  tissue,  one  in  e^ch 
lid  that  occupy  the  margins  of  the  eyelids,  to  the  maintenance  of  whose  form  they 
largely  contnbute.  1  hey  are  crescentic  in  outline,  the  borders  next  the  lid-cleft 
being  only  slightly  curved  and  almost  straight  and  the  thinner  distal  borders  mark- 
edly convex.  Their  ends  are  joined  to  the  pali>ebral  ligaments  which  branch  into 
upper  and  lo\ver  limbs  for  the  attachment  of  the  tarsal  plates  The  upper  tarsus  is 
the  more  arched  and  br(«der,  measuring  about  10  mm.  or  about  double  the  lower 
t)late  in  both  cases  the  median  ends  of  the  crescents  being  blunted  and  less  pointed 
than  the  lateral.  The  plates  are  approximately  i  mm.  in  thickness  and  consist  01 
d..astlv  felted  fibrous  tissue,  and  are  blended  in  front  and  below  with  the  subcu- 
tan<.(.us  tissue,  above  with  the  septum  orbitale  and  the  insertion  of  the  lid-niuscles, 

and  behind  with  the  conjunctiva.  ,    1       ,1, 

In  addition  »o  preserving  the  cur^•ature  of  the  lids,  the  tarsal  pl.ttcs  lod^e  tb. 
linear  series  of  the  Meibomian  or  tarsal  glands  ( glandulae  tarsalcs).    The»e  stru. 
tures,  between  thity  and  forty  in  number  in  the  upper  lid  and  about  one-third  less 
in  the  lov  er  one,  consist  of  a  chief  tubular  duct,  placed  vertically  ami  lined  by  stratified 
squamous  epithelium,  which  is  Inset  with  numerous  simple  or  branched,  irregr  ar, 
flask-shaped  alveoli.     The  latter  contain  cuboidal  epithelial  elements  that  resemble 
in  appearance  and  condition  those  found  in  sebaceous  follicles,  to  which  class,  in  fact 
the  tarsal  glands  belong.    They  secrete  an  oily  substance,  sebum  palpebrarum,  which 
is  .lischarged  through  the  minute  punctiform  orifices  of  the  ducts  that,  on  everting 
the  edires  of  the  lids,  are  seen  as  a  row  of  dark  iK>ints  just  external  to  the  sharp  con - 
juncti^l  Uirder  of  the  eyelid.     In  this  manner  the  latter  is  kept  lubricated,  and  thus, 
'indci-  usual  conditions,  maintains  an  effective  barrier  against  the  overflow  of  the 
tears  from  the  conjunctival  sac.     Within  the  free  edge  of  the  evehds.  just  in  advance 
of  the  ur..,al  plates  lie  the  glands  Of  Mcll.  and  the  glands  of  Zeiss.    The  former 


THE  EYELIDS  AND  CONJLNCTIVA.  1445 

are  coileci  tubules,  resembling  moditied  swoat  glands,  the  latter  sebaceous  jtland:;, 
the  ducts  of  >vhich  usually  open  close  to  or  into  the  mouths  of  the  follicles  of  the 
eye-lashes. 

The  palpebral  conjunctiva  lines  the  ocular  surface  of  the  eyelids.  Slme  the 
latter  are  developed  as  integumentary  folds,  at  first  the  conjunctiva  resembles  the 
skin,  but  after  the  temporary  closure  of  the  lids,  from  the  middle  of  the  third  month 
until  shortly  before  birth,  it  loses  its  original  character,  and  later,  Ixithed  continu- 
ously with  the  secretion  of  the  tear-gland,  assumes  the  translucently  rosy  tint  and 
general  appearance  of  a  mucous  membnjnc,  as  which  the  conjuncti\a  is  often 
regarded.  Over  the  tersi  the  )>alpebral  conjunctiva  is  so  tightly  adherent  to  the 
underlying  fibrous  plate,  that  the  tunica  propria  i^!  re<hi<-»;d  to  an  insignificant  layer 
and  the  Meibomian  glands  shimmer  through  the  smooth  translucent  conjunctiva  and 
appear  as  parallel  yellowish  stripes.  On  gaining  the  reiroiarml  fossa,  along  the 
convex  border  of  the  tarsal  plates,  the  conjunctiva  bccomtj  loosi-  and  mov  ible  and 
marked  by  circular  folds  since  the  tunica  propria,  which  here  connects  the  epithelium 
with  the  underlying  fascial  tissue,  is  plentiful.  The  small  tubular  glands  of  Henle 
often  occupy  the  subepithelial  tissue  of  this  part  of  the  conjunctiva.  In  the  fornix 
and  its  vicinity  minute  lymph-nodules  occur  normally,  either  ciiscrete  or  in  small 
groups.  In  the  same  locality  and  at  the  convex  borders  of  the  tarsi,  small  nest.s  of 
serous  alveoii,  known  as  accessory  tear-glands,  ox  glands  of  Krause,  arc  found,  being 
much  more  numerous  in  the  upper  than  in  the  lower  lid. 

The  bulbar  conjunctiva  «es  from  the  fornix  onto  the  anterior  jiart  of  the 
eyeball,  over  which  it  extends,  i  *rinkled  but  gradually  thinning,  as  far  as  the 
corneal  margin,  at  which  point  {limbus  cormec)  the  tunica  propria  ends  anil  the 
epithelium  alone  continues  uninterruptedly  over  the  cornea.  During  it-s  passage  from 
the  free  etlge  of  the  eyelid  io  the  cornet'  the  character  of  the  conjunctival  epithelium 
varies  in  differen*  pa;ts  of  the  sac.  Thus,  at  the  border  of  the  lids  and  for  a  few 
millimeters  over  the  tarsi,  it  resembles  the  epidermis., in  being  stratified  sf4uamous. 
Towards  the  convex  border  of  the  tarsal  plates  the  squamous  type  gives  way  to  the 
cyliiidiical  ;  in  the  retrotarsal  fossa,  throughout  the  fornix  and  for  a  short  distance 
(.5-1  mm.;  over  the  eyeball,  the  epithelium  is  exclusively  columnar,  varying  in 
thickness  and  in  the  number  of  its  layers  ;  whilst  o\cr  the  cornea  and  adjacent  parts 
of  the  sclera,  the  epithelium  is  again  stratified  squamous. 

Vetsels  of  the  Eyelids. — The  arteries  chiefly  supplying  the  eyelids  arc  the 
superior  and  inferior  palpebral  branches  from  the  ophthalmic  and  from  the  lachrymal 
arteries.  These  form  the  first  source,  the  internal  p.-lpebral,  which  arise  either  sepa- 
rately, or  by  a  short  common  stem,  pierce  the  septum  orbital.-  a  siiort  distance  above 
or  immediately  below  the  internal  palpebral  ligament,  and,  hi  .i<i(lition  to  sending 
twigs  to  the  lachrymal  caruncle,  canals  and  sac,  pursue  a  tortuous  cours«*  near  the 
free  margin  of  the  lids  towards  the  externa!  cantlius.  ')u  nearing  the  latter  the 
superior  and  inferior  internal  branches  join  tiie  corresponding  bianchcs  froni  the 
external  pidpebral  and  from  the  lachrymal,  a.*  well  .us  anatomosing  with  »wigs  from  the 
superficial  tempoi  tl  and  transverse  f.icial  arteries  !n  this  mannur  a  larsa'  arch  is 
formed  in  each  lid  along  the  base  of  each  tarsus,  'elwccii  the  iaUir  and  the  orbicu- 
laris niusHe,  from  which  perfor^tinj;  twigs  penetrate  the  tarsal  plates  for  the  supply  of 
the  Meibomian  inlands  and  the  adjacent  conjunctiva.  In  the  upper  lid  a  less  regular 
secondary  tarsal  arch  is  formed  along  the  convex  boriler  of  the  tarsus  by  the  anasto- 
mosis of  the  palpebrals  and  the  fronUil  and  supraorbital  branches.  A  similar,  hut  less 
constant  anil  complete,  arch  occurs  in  the  lower  lid. 

In  consequence  of  the  double  path  of  csca|)e  of  the  blooil  from  the  orbit— through 
the  ophthalmic  and  the  facial  veins — the  veins  of  the  eyelids  a.'c  tributaries  of  two 
systems.  Those  from  the  deeper  structures  (conjunctiva,  Meiljomian  glands),  the 
retrotarsal  veins.  empt\  in'.i  the  branches  of  the  ophthalmic,  while  those  draining  the 
more  superficial  jwrts  ot  the  vyi^WiX.  pretarsah'cins.  are  tributary  to  the  frontal  and  facial 
veins  medially  and  to  the  su|)raorbital  and  superficial  temporal  laterally.  Sinci'  not 
only  the  supraorbital,  but  also  the  frontal  veins  communicate  with  the  oi)hthalmic 
system,  the  IjIikkI  is  carried  off  by  way  l)oth  of  the  orbital  and  f.i;i,il  ihannels. 

The  lymphatics  of  the  eyeliils  are  arrangetl  in  two  sets,  a  pret.irsid  and  a  jxisi- 
tiirsiil.  the  net-works  uf  which  are  connectii'  by  vessi  Is  uhich  \>ierce  the  tarsi.     The 


li0^iM'^i 


1446 


HUMAN   ANATOMY. 


m 


former  receives  lymph  from  the  skin  and  muscles,  the  latter  from  the  Meibomian 
glands  and  the  conjunctiva.  The  larger  vessels  on  tin  rwiter  side  pass  to  the  pre- 
auricular and  parotid  lymph-nodes,  and  those  on  the  inner  or  mesial  side  follow  the 
tributaries  of  the  facial  vein  and  enter  the  subtnaxillary  lymph-nodes. 

Nerves  of  the  Eyelids. — The  sensory  nenes  are  branches  of  the  ophthalmic 
and  superior  maxillary  divisions  of  the  trigeminal.  The  upper  lid  is  supplied  mainly  by 
the  frontal  and  supraorbital  nerves,  the  lower  lid  by  the  infraorbital  nerve.  On  the 
nasal  side  these  nerves  are  supplemented  by  twigs  from  the  supra-  and  infratrochlear 
branches  of  the  ophthalmic,  and  on  th«  outer  side  by  terminal  filaments  from  the 
lachrymal  nerve.  The  main  branches  lie  between  the  tarsi  and  the  orbicularis 
muscle,  sending  branches  forward  to  the  skin  and  l>ackward  through  the  tarsi  to  tht- 
conjunctiva  and  Meifxjmian  glands.  In  .nddition  a  marginal  plexus  is  formed  near 
the  edge  of  each  lid,  which  supplies  the  adjacent  [larts  and  the  follicles  of  the  cilia. 

The  motor  nerve  to  the  levator  palpebrae  is  a  branch  of  the  superior  division  nt 
the  oculomotor  ner\'e ;  the  orbicularis  palpebrarum  is  supplied  by  the  facial,  and  tlu- 
involuntary  muscle  of  the  lids  by  fibres  from  the  sympathetic. 

Practical  Considerations. —  The  Eyebrows. — ^The  hair  of  the  eyebrows  may 
be  absent,  dark  brows  may  show  white  patches  (piebald  eyes),  or  they  may  hi- 
entirely  white,  as  in  albinos.  Incisions  in  this  area,  as  for  neurectomy  in  supra- 
orbital neuralgia,  should  be  made  in  the  line  of  the  brow  and  within  the  limits  of  thi- 
hair,  so  that  the  scar  which  results  may  be  hidden. 

Dermoid  cysts  occur  in  the  line  of  the  orbito-nasal  fissure  of  the  fa-tus,  and  are 
most  frequent  near  the  outer  end  of  the  brow,  under  the  orbicularis  palpebrarum, 
next  to  the  periosteum.  Usually  they  art  no  larger  than  a  cherry,  and  in  some 
instances  lie  deep  in  the  orbit,  when  they  would  be  difficult  of  diagnosis.  More 
rarely  they  occur  at  the  inner  angle  of  the  orbit,  when  they  may  be  connected  with 
the  tlura.  In  such  cases  they  would  be  difficult  of  removal  and  might  be  confused 
with  meningocel  s. 

F.piranlhus  is  a  crescentic  fold  of  skin  lying  over  the  inner  canthus  and  the 
inner  end  of  the  palpebral  fissure.  It  m:iy  be  associated  with  a  congenital  defect  in 
the  briilge  of  the  nose.  In  many  children  a  slight  tendency  to  it  is  seen  before  the 
briflgc  of  the  nose  has  reached  its  full  development,  while  in  those  races  which  have 
little  or  no  bridges  to  their  noses,  a  slight  epicanthus  is  normal.  Until  this  condition 
is  suspected,  these  children  are  often  thought  to  have  convergent  squint,  l)ecausi- 
the  cornea  is  ne.iri-r  f)  the  skin  than  in  a  normal  eye. 

Very  rarely  the  lids  may  fail  to  develop  (ablcpharia )  ;  less  rarely  a  cleft  in  the 
margin  of  the  lid  is  seen,  usually  to  the  median  side  of  the  centre  of  the  lid  (colo- 
bonia),  and  most  frequently  in  llie  upper  lid.  5>ometini<s  the  eye  has  a  uniform 
covering  of  skin  which  replaces  the  lids,  no  palpebral  ii>Mire  fx-ing  present.  This 
is  probably  due  to  a  persistence  of  the  early  foetal  condition,  in  w'ln  ;i  the  two  lids 
are  adherent.      It  is  called  ankylo-blcpharon. 

Lagophthahnus  is  an  incomplete  closure  of  the  lids,  and  is  -ometmes  congenital, 
sometimes  the  result  of  paralysis  of  the  facial  nerve  which  supplies  the  orbicularis 
muscle.  Voluntary  contraction  of  this  muscle  will  usually  close  the  lids  in  the  les>,er 
degrees  of  the  congenital  variety,  but  in  uleep  they  arc  not  closed.  Since  the  eye 
turns  up  as  the  lids  are  brought  together,  the  cornea  is  concealetl. 

Ptosis  is  a  drooping  of  the  upper  lid,  and  when  congenital  is  usually  associate<l 
with  epicanthus,  and  is  bilateral.  The  forehead  is  t)ftcn  wrinkled  from  the  effort  of 
the  occipito-frontalis  mus'  1p  to  aid  the  orbicularis  in  lifting  the  lid.  The  head  is 
usually  thrown  back  and  tlu  eyes  dcjjressed  to  bring  the  sensitive  part  of  the  retina 
and  pupil  in  line  with  the  object  to  be  seen. 

Blepharospasm  is  an  irritable  spasm  of  the  orbicularis  closing  t'le  lids,  and  is 
usually  due  to  disease  of  other  parts  of  the  eye. 

The  skin  of  the  lids  is  the  thinnest  in  the  body  and  is  very  Ifm^ely  applied, 
through  the  loose  areolar  subcutaneous  tissue.  It  therefore  wrinkles  easily,  is  readily 
deformed  by  scars,  and  is  a  favorable  field  for  plastic  operations.  If  cicatricial  con- 
traction everts  the  lower  lid,  as  it  often  does,  the  condition  is  known  as  ectropion. 
More  rarely  contraction  of  the  conjunctiva  after  ulceration  or  injury-  inverts  a  lid. 


THE   EYEBALL. 


1447 


producing  entropion.  The  eyelids  become  cedematiiUii  or  ecchyuiotic  from  slight 
causes,  and  in  erysipelas  are  markedly  swollen,  clobin^^  the  lids,  or  i.i  severe  cases 
may  become  gangrenous,  the  exudate  interfering  with  the  blood-supply. 

Herpes  zoster  is  sometimes  seen  alon-;  the  cutaneous  distribution  of  the  frontal 
and  nasal  branches  of  the  trigeminal  nerve.  It  is  found  on  the  forehead,  lids,  nose, 
and  even  the  cornea.  The  iris,  ciliary  body,  or  choroid  may  be  involved,  since 
through  the  lenticular  ganglion,  the  nasal  nerve  supplies  these  j'.ructures.  The 
cause  is  an  inflammation  of  the  trunk  of  the  trigeminal  nerve,  the  Gasserian  ganglion, 
or  the  lenticular  ganglion. 

Hordeolum  or  stye  is  a  suppuration  of  one  of  the  sebaceous  glands  ( Zeiss' s 
glands)  associated  with  the  follicles  of  the  eyelashes.  A  ckalaxion  is  an  affection  of 
one  of  the  Meibomian  glands,  with  occlusion  of  the  duct  and  retention  of  the  secre- 
tion. There  is  often  no  inflammation  present.  For  this  reason,  and  because  of 
its  situation  on  the  under  surface  of  the  tarsal  cartilage,  it  is  often  not  noticed 
until  it  reaches  considerable  size  and  shows  through  the  lid.  Normally  the  cilia  or 
eyelashes  curve  away  from  the  surface  of  the  eyeball.  Sometimes  from  inflammation, 
most  commonly  in  trachoma  or  granular  lids,  they  take  the  opposite  direction  and 
irritate  the  cornea  (trichiasis  or  wild  hairs). 

Tike  Conjuiutiva. — Congenital  fatty  growths  occur  rarely  in  the  outer  part  of 
the  upper  conjunctival  sac.  Dermoids  and  navi  have  also  been  seen  in  the  con- 
junctiva. This  membrane  covers  the  anterior  third  of  the  eyeball,  and  where  it  passes 
to  the  lids  forms  the  fomices.  Because  the  upper  fornix  is  deeper  than  the  lower, 
being  therefore  turned  less  easily,  foreign  bodies  are  removed  from  the  upper  sac 
with  greater  difficulty.  These  particles  strike  first  on  the  surface  of  the  globe,  and 
are  usually  brushed  down  into  the  lower  sac  by  the  upper  lid.  They  frequently, 
however,  catch  in  the  conjunctiva  of  the  ball  or  of  the  upper  lid,  and  are  held  in  the 
conjunctival  sac  only  when  they  get  above  the  upper  retro-tarsal  fold,  where,  if  not 
removed,  they  may  set  up  a  chronic  inflammation,  or  remain  unnoticed.  They 
have  been  found  there  months  or  even  years  afterward,  entirely  embedded  in  the 
outgrowths  of  the  inflamed  conjunctiva  (Fuchs). 

A  pterygium  is  an  elevated  layer  of  conjunctiva  and  subconjunctival  tissue, 
triangular  m  shape  with  its  apex  near  the  edge  of  the  cornea,  and  its  base  usually 
tc wards  the  inner  canthus.  It  tends  to  progress  towards  the  pupil,  but  may  stop 
anywhere  short  of  it. 

A  Pinguecula  is  a  yellowish  elevation  of  conjunctiva,  to  the  inner  side  of  the 
cornea,  sometimes  to  the  outer  side.  It  corresponds  to  the  part  of  the  conjunctiva 
consUntly  exposed  in  the  interpalpebral  fissure,  which  therefore  undergoes  a  change 
in  structure.  That  at  the  inner  side  is  most  marked  and  may  become  a  pterygium  later. 

The  scleral  portion  of  the  conjunctiva  is  loosely  applied  to  permit  of  free  motion 
of  the  ball.  Near  the  margin  of  the  cornea  it  becomes  more  fixed,  and  should  be 
caught  there  by  the  forceps  in  the  effort  to  fix  the  eye  when  operating  upon  it.  The 
palpebral  portion  is  more  firmly  attached,  especially  at  the  back  of  the  tarsal  plates 
where  it  is  more  vascular,  and  where  paleness  is  taken  to  indicate  a  general  anxmia. 

In  fractures  of  the  base  of  the  skull  involving  the  roof  of  the  orbit  the  hemor- 
rhage into  the  orbital  tissues  shows  first  under  the  conjunctiva  of  the  globe  (subcon- 
junctival ecchymosis ).  It  finds  its  way  under  the  conjunctiva  of  the  lids  later  because 
that  is  more  firmly  attached,  and  iiiili'ss  the  lid  is  lifted,  it  will  first  be  noticed  at  the 
margin  of  the  lid,  after  which  it  may  grow  upward  under  the  skin.  This  is  due  to 
the  fact  that  the  orbito-tarsal  or  palpebral  ligament  passes  between  the  manon  of  the 
orbit  and  the  upper  edge  of  the  tarsal  plate  like  a  curtain  and  prevents  the  progress 
of  the  blood  forward  to  the  skin  until  it  has  first  passed  down  behind  the  tarsal  plate 
and  under  its  lower  margin.  Owing  to  the  thinness  of  the  conjunctiva,  oxygen  per- 
meates it  more  rt-adily  than  it  does  the  skin,  so  that  blood  under  it  retains  its  redness 
instead  of  becoming  dark,  as  under  the  skin  of  the  lid  in  ordinary  "black  eye." 

THE    EYEBALL. 
The  eyeball  is  situated  in  the  anterior  part  of  the  orbit,  about  2  mm.  nearer 
the  lateral  than  the  nasal  wall,  and  slightly  nearer  the  superior  than  the  inferior 
waii.     .\  line  dr;-i-.vn  from  the  superior  margin  of  the  orbit  to  the  iftfcfiu:  :r.  lurr^cnt  to 


1448 


HUMAN   ANATOMY. 


the  surface  of  the  cornea.  The  axes  of  the  eyeballs  are  practically  parallel,  when 
fixed  on  a  distant  object,  but  the  optic  nerves  converge  considerably,  so  that  they 
enter  the  eyeball  from  2-3  mm.  to  the  nasal  side  of  the  posterior  pole  ot  the  eye. 
The  general  form  of  the  eyeball  is  that  of  a  sphere,  but  in  sagittal  section  it  is  found 
to  be  composed  of  the  segments  of  two  spheres,  an  anterior  smaller  segment,  corre- 
sponding to  the  transparent  cornea,  which  has  a  radius  of  from  7-8  mm.  and  a  pos- 
terior opaque  segment,  corresponding  to  the  sclera,  with  a  radius  of  la  mm.  The 
junction  between  the  two  segments  is  marked  externally  by  a  broad,  shallow  groove, 
the  sulcus  sclera,  which  is  filled  by  the  scleral  conjunctiva. 

The  diameters  0/ the  eyeball  measure  approximately  as  follows :  the  antero-pos- 
terior,  24.2  mm.  ;  the  vertical,  23.2  mm.  ;  and  the  transverse,  23.6  mm.  Its  shape 
is,  therefore,  that  of  a  spheroid  somewhat  flattened  from  above  downward,  and  from 


Fig.  1 302. 


Lens 
Sntpenaory  Ugmment  of  lens       \ 
Canal  of  Schlemin 
ClUan' proccin 

Conjunctiva 


Cornell 

'       Anterior  chamber 
/        Iri* 

/      Posterior  chamber 

/    Scletocomeal  juncture 


Tendon  of  in-       'ti 
temal  rectus-- 
muflcle 

Vena  vorticoaa 


Tendon  of 
-external  rectus 
muscle 


A'itreouB 


Ciliary  nerve 

Posterior  ciliary  vessels 

Hyaloid  can.il     J»fr/l'n 
optic  nerve     <J*fcs 
Central  retinal  vesseU   t'T^Tv/Vj 


Choroid 


Retina 
Fovea  centralis 


Optic  papilla 


DIagiammatic  horiionul  section  of  right  eye.    X  i\i. 

side  to  side.  The  diameters  are  slightly  greater  in  the  male  than  in  the  female,  and 
vary  according  to  the  refractive  power,  being  longer  in  nearsighted  or  myopic,  and 
shorter  in  oversighted  or  hyperopic  eyes. 

The  eyeball  consists  of  three  concentric  coats  or  tunics :  ( • )  the  external  or 
fibrous  tunic,  com|X)sed  of  the  sclerotic  and  the  cornea  ,•  ( 2 )  the  middle  or  vascular 
tunic,  which  is  pigmented  and  partly  muscular,  and  is  composed,  from  behind  for- 
ward, of  the  choroid,  the  ciliary  body,  and  the  iris;  and  (3)  the  inner  or  nervous 
tunic,  the  retina,  an  expansion  of  the  brain,  which  contains  beside  the  ner\e-cells 
and  the  nerve-fibres  the  specialized  neuroepithelium  for  the  reception  of  visual  stimuli. 

Within  these  tunics  are  enclosed  the  refracting  media,  the  crystalline  lens,  the 
aqueous  humor  and  the  vitreous  body. 

Practical  Considerations. — Congenital  anomalies  may  affect  the  whole  eye, 
the  apjjendages,  or  the  individual  structures  of  the  eye. 

The  eye  may  be  congenitally  absent,  on  one  or  both  sides  (anophthalmos).  In 
some  cases  of  appjircnt  absence  the  eyeK-tU  h.ns  been  found  to  be  exceedingly  small 


mmpipfpnapipi" 


^ipPRm 


THE  FIBROUS  TUNIC. 


1449 


(microphthalmos)  and  situated  deep  in  the  orbit  near  the  optic  foramen.  The  piitient 
may  otherwise  be  entirely  normal ;  or  other  developmental  errors,  as  hare-lip  or 
cleft-palate  may  be  present.  In  some  instances  where  no  eyeball  was  found,  the 
optic  nerve  had  not  entered  the  orbit,  and  in  others  the  chiasm  had  not  formed,  the 
primary  optic  vsicle  having  failed  to  develop. 

Multiple  eyes  occur  in  some  monsters.  As  digits  sometimes  bifurcate  to  form 
supernumerary  digits,  so  the  cephalic  end  of  the  embryo  may  divide,  giving  rise  to 
two  heads.  These  may  fuse,  when,  according  to  the  extent  of  fusion,  there  will  be 
four,  three,  or  two  eyes ;  or  if  both  the  orbits  and  the  eyes  fuse  there  may  be 
only  one  eye  (cyclopia). 

The  actual  size  of  the  eye  in  man  varies  little,  the  apparent  size  depending 
chiefly  upon  the  projection  from  the  orbit  and  the  part  exposed  between  the  lids. 
Tht  variation  in  different  animals  depends  rather  upon  the  necessity  for  acuteness  of 
vision  than  upon  the  size  of  the  animal.  The  larger  the  globe  the  farther  the  cornea 
and  lens  from  the  retina,  and 

therefore  the  larger  and  '^^"  '*°3- 

more  distinct  the  image  on 
the  retina  of  the  object  seen. 
The  more  active  the  animal 
the  greater  is  the  necessity 
for  acuteness  of  vision,  and 
therefore  the  larger  the  eve. 
The  eyes  of  birds  are  pro 
portionally  larger  than  those 
of  other  animals.  Nocturnal 
animals,  such  as  the  owl, 
have  large  eyes.  The  large 
retinal  image  probably  com- 
pensates for  the  scarcity  of 
light,  to  which  they  are 
accustomed. 


Fibre  layer 
Ganglion  cells 
Bipolar  cells 
Visual  cells 

PlKment  layer 
stroma 
Large  vein 


Lamina  fusca 


Fibrous  I  issue 
of  sclera 


Episcleral 

endothelium 
Space  of  Tenon 
betwern  sclera 
and  ca|Hiule 
of  Tenun 


Section  of  three  coats  of  eyeball,  about  five  millimeters  from  optic  papilla; 
capsule  of  Tenon  seen  below  sciera.    X  40. 


The  Fibrous  Tunic. 

The  Sclera.— The 
sclera,  or  sclerotic  coat,  is 
a  firm,  dense  fibrous  coat 
which  forms  the  posterior 
four-fifths  of  the  outer  coat 
of  the  eye,  being  closely  con- 
nected with  the  sheaths  of 
the  optic  nerve  posteriorly, 
and  joining  in  front  with 
the  cornea.  In  the  neigh- 
borhood of  the  optic  nerve  it  measures  i  mm.  in  thickness,  and  gradually  becomes 
thinner  toward  the  equator,  until,  just  postiirior  to  the  attachment  of  the  tendons 
of  the  ocular  muscles,  it  measures  only  .4  mm.  After  receiving  the  expansions 
of  these  tendons  it  again  becomes  thicker  and  reaches  a  thickness  of  .6  mm.  In 
children  and  in  individuals  who  have  thin  sclerie  and  dce|)ly  pignientetl  eyes, 
the  sclera  possesses  a  bluish  white  color,  while  in  old  age  it  assumes  a  yellowish 
t''ige.  The  optic  nerve  passes  through  this  tunic  at  a  position  i  mm.  below  and 
t..!in  3-4  mm.  to  the  inner  side  of  the  {wsterior  pole  of  the  eye;  the  canal  is 
partially  bridged  over  by  interlacing  fibrous  bundles,  the  lamina  crihrosa,  which 
are  intimately  associated  with  the  supporting  tissue  of  the  nerve,  tlrouped  around 
the  nerve  entrance  are  small  openings  for  the  ciliary  nerves  and  posterior  ciliary 
arteries,  and  toward  the  equator  four  or  five  for  the  vena  vortinna  which  emerge 
from  the  choroid. 

Structure  of  the  Sclera. — The  sclera  is  composetl  of  interlacing  bundles  of 
white  fibrous  tissue,  which  on  the  outer  and  inner  surface  have  chiefly  a  nifridional 
direction,  while  the  centra!  bundles  form  a  fairly  regular  alternation  of  circular  and 


I450 


HUMAN  ANATOMY, 


Epithelium 

Anterior 
limiting: 
racmbrene 


I 


meridional  lamellae.  The  tissue  yields  gelatine  on  boiling.  With  the  fibrous  bundles 
is  associated  a  rich  net-work  of  fine  elastic  fibers.  The  clefts  between  the  lamellie 
contain  irregularly  stellate  connective  tissue  cells — the  scleral  corpuscles.  On  the 
inner  surface  of  the  sclera  many  of  these  cells  are  pigmented  and  give  it  a  brownish 
color.  This  layer — the  lamina  fusca — forms  with  the  underlying  choroid  a  narrow 
lymph-space,  the  suprachoroidal  lymph-space,  both  walls  of  which,  together  with  the 
fine  connective  tissue  trabecula;  which  cross  it,  are  lined  with  endothelial  cells.  The 
outer  surface  of  the  sclera,  from  the  optic  nerve  entrance  to  the  attachment  of  the 
ocular  muscles,  is  similarly  covered  with  endothelial  plates,  and  forms  part  of  the  lining 
of  Tenon's  lymph-space.  Anterior  to  the  muscle-insertions  it  is  covered  with  a 
loosely  meshed  connective  tissue,  the  episcleral  tissue,  which  is  richly  supplied  with 

blood-vessels,   nerves  and   lymph- 
FJo.  1304.  vessels,    and    is    continuous    with 

the   subconjunctival  tissue  of  the 
conjunctiva  sclerte. 

The  blood-vessels  of  the  sclera 
arise  from  the  arteries  which  per- 
forate it  to  supply  the  vascular  coat 
of  the  eye,  viz :  the  anterior  and 
posterior  ciliary  arteries.  They 
form  a  wide  meshed  net-work  on 
the  surface  of  the  sclera,  which 
sends  anastomosing  vessels  to  a 
deeper  lying  set  in  the  substance  of 
the  membrane.  In  the  neighbor- 
hood of  the  optic  nerve  entrance 
the  branches  of  the  short  posterior 
ciliary  arteries  form  an  arterial 
circle,  the  circulus  Zinni,  which 
sends  branches  to  the  optic  ner\'e 
and  choroid,  and  is  therefore  of 
great  importance  in  establishing 
an  anastomosis  between  thf  cho- 
roidal circulation  and  the  arteria 
centralis  retinae  which  supplies  the 
retina. 

The  veins  of  the  sclera  empty 
into  the  anterior  and  posterior 
ciliary  veins,  and  into  the  venx 
vorticosae.  At  the  junction  of  the 
cornea  and  sclera  is  an  important  circular  venous  channel,  the  canal  of  Schiemm, 
which  will  be  described  later.  The  lymphatics  of  the  sclera  are  represented  by 
the  intercommunicating  cell-spaces,  which  communicate  with  the  suprachoroidal 
and  suprascleral  lymph-spaces,  and  anteriorly  with  the  spaces  of  Fontana,  at  the 
corneo-scleral  angle. 

The  nerves  of  the  sclera  are  derived  from  the  ciliary  nerves  during  their  course 

between  the  sclera  and  the  choroid,  their  terminal  filaments  being  distributed  to  the 

vessels,  and  also  as  a  fine  tortuous  net-work  betwee;  the  bundles  of  the  scleral  tissue. 

The  relations  of  the  sclera  to  the  optic  nerve  sheaths  will  be  considered  in  the 

description  of  the  optic  nerve  entrance  (page  1470). 

The  Cornea. — The  cornea  forms  the  anterior  one-fifth  of  the  ftbrous  tunic  of 
the  eyeball,  and,  although  composed,  like  the  sclera,  of  bundles  of  connective  tissue, 
is  transparent  and  allows  rays  of  light  to  enter  the  eyeball.  Its  anterior  surface 
is  nearly  but  not  quite  circular,  measuring  11. 9  mm.  in  its  greatest  transverse 
diameter,  and  1 1  mm.  in  its  vertical  diameter.  The  posterior  surface  is  circular  and 
measures  13  mm.  in  diameter.  The  sclera  therefore  encroaches  n  ore  upon  the  cornea 
anteriorly  than  posteriorly,  .so  that  the  cornea  fits  into  a  groove  '.n  the  sclera.  The 
radius  of  curvature  of  the  anterior  corneal  surface  is  about  7. 7  mm. ,  that  of  the  hori- 
zontal meridian  being  slightly  greater  (7.8  mm.)  than  that  of  the  vert-.cal.     The 


Section  of  human  cornea.    X  85. 


THE  FIBROUS  TUNIC. 


1451 


radius  of  curvature  of  the  posterior  surface  is  only  6  mm. ;  the  cornea  is  consequently- 
thicker  in  the  periphery  than  at  the  center,  in  the  projwrtion  of  1. 1  mm.  to  ..S  mm. 
The  degree  of  curvature  varies  in  different  indi\''duals  and  at  different  periotls  t)f  life, 
being  greater  in  youth  than  in 


KiiJ.   1205. 


Corneal  corpuwlcs  (conucctiv<  tiwuc  cella).  lurface  view.     -  .150. 


old  age.  As  the  radius  of  curva- 
ture of  the  sclera,  with  which  its 
bundles  arc  continuous,  is  12 
mm. ,  the  cornea  rests  upon  the 
sclera  as  a  watch-glass  upon  a 
watch.  At  the  junction  of  the 
two  membranes,  on  the  outer 
surface,  is  the  shallow  grot)ve, 
the  sulcus  sclera". 

Structure  of  the  Cor- 
nea.— The  cornea  is  composed 
of  five  distinct  layers,  which 
from  without  in  are:  (i)  the 
anterior  epithelium,  (2)  tTie  an- 
terior limititif;  membrane,  (3) 
the  substantia  propria,  (4) 
the  posterior  limiting  mem- 
brane, and  (5)  the  posterior 
endothelium. 

The  anterior  epithelium 
of  the  cornea  is  continuous 
with  that  covering  the  surface 

of  the  adjacent  conjunctiva  sclerse.  It  is  of  the  stratified  squamous  variety,  usually 
five  cells  deep  in  man,  and  measures  .045  mm.  in  thickness  at  the  center,  and 
.080  mm.  at  the  periphery.  The  deepest  cells  are  columnar  in  form,  with  broad 
basal  plates  resting  upon  the  anterior  limiting  membrane,  to  which  they  are  firmly 
attached  by   means  of   minute   projections  which  roughen  the  anter  ..  surface  of 

the  latter.  The  outer  parts  of  the  liasiil 
cells  contain  the  nucleus  and  fit  into  corre- 
sponding depressions  in  the  cells  of  the 
superimposed  layers.  The  middle  layers  are 
composed  of  irregular  polyhedral  cells, 
which  usually  present  tine  protoplasmic 
denticulations,  and  resemble  prickle  cells. 
The  superficial  layers  consist  of  flattened 
cells  which  lie  parallel  to  the  free  surface 
and  contain  well-staining  nuclei. 

The  anterior  limiting  membrane,  or 
Bowman's  membrane,    is  situated    immedi- 
l^_^g^  ^^.  WC      ately  below  the  epithelium,  and  appears  as  a 

T^^tlnf  ^^Bft^'^     w      homogeneous  band,  alxiut  .02  mm.  in  thick- 
_  m^A^       ^SBm  %.  "^^  *'  ^^^  center  and  thinner  at  the  periph- 

'S^flMin^Sr.jdi^SSSvHd^       ^'^'  ^''^''^  '^  terminates  without  extending 
Jnw^^^^iSUf^^  into  the  conjunctiva  of  the  sclera.    The  niem- 

"  ^\t  brane    may    be  split   into    fine    fibrilhe    by 

Corneal  spaces,  after  artlon  o(  aricentic  nitrate ;         (^g    ysg    ,jf    suitable    reagents,    is    connected 

jjo.  firmly   with   the  cornea  proper   by   delicate 

filaments,  and  is  to  be  considered  a  special  condensation  of  the  latter.  It  contains 
no  elastic  tissue. 

The  substantia  propria  constitutes  the  main  portion  of  the  cornea,  and  is 
made  up  of  interlacing  bundles  of  connective  tissue,  which  are  directly  continuous 
with  those  of  the  adjacent  sclera.  The  bundles  are  composed  of  fine  fibrillie,  have 
a  flattened  form,  and  are  so  disposed  as  to  produce  regular  lamellae,  about  sixty 
in  number,  running  parallel  with  the  surface.  The  alternating  lamell*  have  a  direction 
iipp''oximately  at  right  angles  to  each  other  and  arc  frequently  joined  together  by 


Fig.  iao6. 


1452 


HUMAN  ANATOMY. 


Fig.  1207. 
Canal  of  Schlemm 


bands,  which  are  especially  numerous  in  the  anterior  lamellae,  to  which  the  name 
fibrtg  araiatte  has  been  given.  The  fibrillse  and  bundles  are  held  together  by  an 
amorphous  cement  substance,  and  embedded  in  it  are  the  cellular  elements,  the 
corneal  corpuscles.  These  are  flattened  connective  tissue  cells,  with  faintly  granular 
protoplasm,  the  nuclei  of  which  in  the  adult  are  irregular  and  show  nucleoli.  The 
cells  are  provided  with  branching  processes  which  anastomose  with  those  of  other 
cells  both  on  the  same  level  and  with  those  between  adjacent  lamellx,  and  so  con- 
stitute a  continuous  net- work  of  protoplasm,  upon  which  the  nutrition  of  the  cornea 
largely  depends.  They  have  been  described  as  occupying  part  of  a  regular  system 
of  cell-spaces  and  canaliculi,  but  most  recent  investigations  seem  to  indicate  that 
during  life  they  fill  out  the  spaces  completely,  and  leave  no  gaps  through  which 
fluid  can  pass.  Occasionally  leucocytes  or  wandering  cells  are  found  between  the 
fibrous  elements. 

The  posterior  limiting  membrane,  also  known  as  Descemet's  membrane,  the 
membrane  of  Demours,  or  the  posterior  elastic  membrane,  is  a  practically  homo- 
geneous band,  which  varies  in  thickness  from  .006^.012  mm.  at  the  center  and 
at  the  periphery  respectively.  It  is  less  firmly  united  to  the  substantia  propria  than 
is  the  anterior  limiting  membrane,  and  is  less  easily  affected  by  acids,  alkalies,  boiling 

water  and  other  regents.  It  resembles 
elastic  tissue  and  is  very  firm  and  resist- 
ant to  injury  or  perforation  from  inflam- 
mation. At  the  periphery,  Descemet's 
membrane  splits  up  into  bundles  of  fine 
fibres,  which  are  gradually  strengthened 
and  form  a  series  of  firm  connective 
tissue  trabeculje,  some  of  which  form 
the  point  of  attachment  of  the  ciliary 
muscle ;  others  run  into  the  iris,  and  still 
others  constitute  the  outer  wall  of  a 
circularly  disposed  venous  channel,  the 
sinus  circuiaris  iridis,  or  canal  of 
Schlemm.  These  fibres  are  known  as 
the  ligamentum  pectinatum  iridis 
and  form  the  outer  boundary  of  the  angle 
of  the  anterior  chamber.  They  are 
incompletely  covered  with  endothelial 
cells  and  enclose  between  their  loose  meshes  the  spaces  of  Fontana.  These, 
better  developed  in  lower  animals  than  in  man,  directly  communicate  with  the  aqueous 
chamber,  and  thus  form  an  important  path  for  filtration  of  fluid  from  the  interior  of 
the  eye,  by  way  of  the  canal  of  Schlemm,  into  the  anterior  ciliary  veins. 

The  posterior  endothelium  covers  the  inner  surface  of  Descemet's  membrane 
It  is  composed  of  a  single  layer  of  flattened  polygonal  cells,  the  nuclei  of  which  often 
e.xtend  above  the  level  of  the  eel!  body.  The  cells  are  connected  together  by  deli- 
cate protoplasmic  processes  and  are  continuous  with  the  cells  lining  the  spaces  of 
Fontana  and  the  anterior  surface  of  the  iris.  With  Descemet's  membrane  they  con- 
stitute a  barrier  to  the  filtration  of  fluid  from  the  anterior  chamber  into  the  cornea, 
although  its  passiige  by  diffusion  is  possible. 

The  blood-vessels  of  the  norm.- 1  cornea  are  limited  to  a  j)eripheral  zone, 
from  1-2  nun.  in  width,  where  the  terminal  twigs  of  the  episcleral  branches  of 
the  anterior  ciliary  arteries  end  in  loops  (Fig.  I2i,s),  from  which  the  blood  is 
carried  to  th-  anterior  ciliary  veins.  The  remainder  of  the  cornea  is  free  from 
blood-channels. 

Tiie  ncnrs  of  the  cornea  are  exccctiingly  numerous.  They  are  branches  of 
the  long  and  short  ciliary  nerve,  from  40  to  45  in  number,  and  form  a  plexus  which 
surrounds  the  margin  of  the  cornea  (plexus  annularis).  Those  which  supply  the 
anterior  part  of  the  cornea  anastomose  first  with  the  conjunctival  ner\'es.  Entering 
the  cornea,  they  are  accompanied  for  a  distance  of  i  mm.  by  a  perineural  lymph- 
sheath,  and  then  losini;  thi^  and  their  medullary  sheath,  they  form  within  the  corneal 
stroma  a  number  of  plexuses  at  various  depths.     A  few  of  the  fibres  pass  backward 


Traheculte  of 

pectinate 

liKament 


Bundles  of  ciliary  muscle 

Nferidional  section  throuKh  angle  of  anterior  chamber 
showing  spaces  of  Fontana  between  relaxed  fibres  of 
pectinate  ligament  and  canal  of  Schlemm.     x  65. 


wmmm 


PRACTICAL  CONSIDERATIONS:    THE  FIBROIS  TUMC.     1453 

and  supply  the  posterior  layers.  Fully  two-thirds,  however,  after  forming  a  funda- 
mental plexus,  push  forward  and  ^nA  perforating  branches  through  Bowman's  mem- 
brane and  form  on  its  surface  a  subepithelial  plexus,  the  minute  fibres  of  which  |wss 
in  a  radial  manner  toward  the  center  of  the  cornea.  From  this  ple.xu.i  fine  fibrils 
ascend  between  the  epithelial  cells,  and  end  either  as  varicose  fibrils,  or  in  connection 
with  ipecial  end-bulbs  (the  intraepithelial  plexus).  In  the  substantia  propria  the 
branches  from  the  fundamental  plexus,  after  forming  complex  secondary  plexuses, 
end  as  naked  fibriilx  between  the  lamell<e,  probably  in  close  connection  with  the 
corneal  corpuscles. 

Practical  Considerations — The  external  or  fibrous  covering  of  the  eyeball 
consists  of  the  sclera  and  cornea,  and  is  the  protective  covering.  The  posterior  five- 
sixths  is  made  up  of  sclera,  which  in  some  animals  becomes  cartilaginous  or  even 
bony.  In  the  human  eye  the  average  normal  tension  within  the  globe  is  etjuivalent 
to  a  column  of  mercury  26  mm.  high.  Excessive  intraocular  tension  occurs  under 
pathological  conditions  (glaucoma)  and  may  reach  70  mm.  or  more.  The  more 
delicate  structures  then  suffer  severely  and  unless  the  pressure  is  relieved  they  are 
functionally  destroyed.  The  sclera  is  thickest  and  strongest  posterioriy  and  grad- 
ually grows  thinner  as  it  passes  forward.  Immediately  behind  the  insertions  of  the 
recti  muscles  it  is  thinnest  (.4  mm.).  Here  bulging  is  most  likely  to  occur  from 
internal  pressure  (anterior  scleral  or  ciliary  staphyloma),  or  pus  within  to  burrow 
through.  In  front  of  this  zone  it  is  reinforced  by  expansions  from  the  insertions  of 
the  muscles,  and  would  seem  therefore  to  be  stronger,  although  it  is  in  this  region, 
just  back  of  the  margin  of  the  cornea,  that  ruptures  are  most  likely  to  occur  from 
external  violence. 

Ruptures  of  the  sclera  occur  close  to — within  3  mm.  of — the  corneal  margin  and 
concentric  with  it,  because  in  most  cases,  as  Fuchs  points  out,  the  application  of  the 
force  does  not  lie  in  the  centre  of  the  cornea,  but  in  the  sclera  below  and  to  the  outer 
side  of  the  cornea.  The  greatest  expansion  of  the  sclera  takes  place  in  its  upper  half 
near  the  margin  of  the  cornea,  at  which  place,  therefore,  the  sclera  ruptures. 

This  region  is  the  so-called  dangerous  zone  of  the  eyeball,  because  th'^ '  ^u 
ciliary  body  correspond  to  it,  and  in  wounds  involving  these  structures,  symj  ...?tic 
ophthalmia  frequently  results,  often  leading  to  destruction  of  both  eyes.  Besides  the 
anterior  slaphylomata  of  the  sclera,  we  may  have  the  equatorial  and  the  posterior. 
The  equatorial  develops  at  the  spots  where  the  venae  vorticos^e  penetrate  and  thus 
weaken  the  sclera  about  the  equator  of  the  globe. 

The  posterior  is  assumed  to  be  the  result  of  a  congenital  weakness  of  the  sclera. 
The  anterior  or  equatorial  can  be  seen  or  palpated,  while  the  posterior  is  recognized 
only  by  demonstrating  the  existence  of  a  high  degree  of  short-sightedness,  which  is 
due  to  an  increase  of  the  sagittal  axis  of  the  eyeball. 

Rupture  of  the  sclera  is  usually  the  result  of  a  blow  on  the  eye.  The  ciliary  body 
and  anterior  portion  of  the  choroid  are  frequently  forced  into  the  wound,  the  vitreous 
and  aqueous  chambers  contain  blood,  while  the  lens  may  find  its  way  through  the 
rent  and  lie  under  t!  conjunctiva,  which  may  or  may  not  be  torn.  Rarely  the  rup- 
ture will  be  in  the  )>  >sterior  portion  of  the  globe. 

Congenital  opacities  of  the  conua  may  occur  and  may  be  completp  or  partial. 
In  some  of  the  ca-ses  reported  of  the  complete  variety  the  anterior  elastic  lamina 
was  absent,  and  the  anterior  layers  of  the  stroma  were  not  laminated  as  usual,  but 
crossed  each  other,  and  among  them  were  found  blood-vessels.  The  partial 
varieties  may  consist  of  a  dense  white  opaque  ring  at  the  margin  of  the  cornea, 
as  though  the  sclera  had  extended  into  the  cornea,  or  they  may  resemble  an  arcus 
senilis  in  which  a  perfectly  clear  strip  of  cornea  divides  the  opaque  line  from  the 
margin  of  the  sclera. 

The  cornea  in  health  is  transparent,  and  almost  all  pathological  lesions  render  it 
opaque.  It  is  the  most  exposed  and  therefore  the  most  frequently  injured  part  of  the 
eye.  Wounds  of  the  cornea  heal  readily  under  favorable  circumstances,  showing  that 
its  nutrition  is  good,  although  there  are  no  vessels  in  it,  except  within  1-2  mm.  of 
its  margin.  When  the  cornea  is  inflamed,  however,  new  vessels  may  form  from 
those  at  the  margin  and  extend  a  variable  distance  inward.     Under  the  influence  of 


1454 


Hill 


HUMAN   ANATOMY. 


initating  conditions  a  superficial  inflammation  may  develop,  covering  the  comea  with 
a  new  vascular  tissue  ( pannus).  the  deeper  layers  still  being  bloodless.  Owing  to  a 
very  free  nerve-supply  the  cornea  is  very  sensitive. 

.  As  in  the  sclera,  weakness  of  the  cornea  leads  to  bulging,  from  internal  pressure. 
The  c;i  ses  of  weakness  may  be  congenital  and  acquired.  Congenital  conical  cornea 
or  kerataconus  may  occur,  and  it  is  believed  that  some  congenital  defect  predisposes 
to  the  same  condition  that  occurs  in  the  adult.  It  is  not  due  to  weakening  from  pre- 
vious ulceration  or  injury  of  the  cornea,  and  the  exact  cause  is  not  known. 

A  staphyloma  of  the  cornea  is  a  similar  condition  in  which  the  protuberance  is 
due  to  the  distention  of  a  cicatrix,  to  the  posterior  surface  of  which  the  iris  may  be 
attached  (anterior  synechiae  of  the  iris).  The  cicatrix  involves  all  the  layers  of  the 
cornea,  and  is  the  result  of  a  perforating  ulcer.  If  the  ulcer  had  been  a  non-per- 
forating one,  and  the  iris  did  not  adhere  to  its  posterior  surface,  the  protrusion  of  the 
comea  would  then  be  called  a  keratectasia. 

If  all  the  layers  of  the  comea  to  the  posterior  elastic  lamina  had  been  destroyed 
by  the  ulcer,  and  this  layer  had  bulged  through  the  weakened  spot  like  a  hemial 
pouch  it  would  be  rolled  a  keralocele.  . 

ArcHS  senilis  is  usually  a  sign  of  old  age.  Modern  investigation  indicates  that  it 
is  due  to  a  fatty  Hz^eneration  of  the  substantia  propria,  the  exact  nature  of  the  fatty 
material  being  .    -  It  first  appears  as  a  crescent  above,  then  below,  and  finally 

a  complete  cii  •    1.     It  never  interferes  with  sight.     It  is  occasionally  seen 

in  children. 

The  Vascular  Tunic. 

The  midoi  ocular  coat  of  the  eye  (tunica  vasctilosa  ocuH),  or  uveal  tract, 

consists  of  a  vascular  connective  tissue  sheath,  which  lies  internal  to  the  outer  fibrous 

Fig.  i2u8. 


Anterior  cliamber 

Pupil 

Circulua  arteriosus  minor 

Artery  joining  ring 


Vena  vorticosa 


Short  ^lost.  ctliary 
.irtery 


Ciliary  nerve 
I^ong  posterior  ciliary  artery 


Circulua  arteriosus  major 

Anterior  ciliary  artery 

Ciliary  nerres 


■Venous  whorl 


Optic  nerve 


Injected  eyeball,  showing  arrangement  of  ciliary  arteries  and  of  choroidal  %'eins.    X  3.    Drawn  from 
preparation  made  by  Professor  Keitter. 

tunic.  It  extends  from  the  entrance  of  the  optic  nerve  to  the  pupil  and  includes 
three  portions,  which  from  behind  forward  are  the  choroid,  the  ciliary  body  and  the 
iris.     The  choroid  and  ciliary  body  are  in  contact  with  the  sclera,  but  the  iris  bends 


IHE  VASCULAR  TUNIC. 


>455 


sharply  inward  and  floats  in  the  aqueous  humor,  incompletely  dividinK  the  spiice 
anterior  to  the  crystalline  lens  into  a  posterior  and  an  anterior  i  hamlier. 

The  Choroid. — The  choroid  (tuoica  choriuidca)  forms  the  [KKiterior  two-third* 
of  the  vascular  coat.  It  lies  between  the  sclera  and  the  retina  and  e.\tends  from  the 
optic  nerve  entrance  to 

the  anterior  limit  of  the  ^'°-  '*°9- 

visual  part  of  the  retina 
at  the  ora  serrata,  its 
main  function  being  to 
supply  nutrition  to  the 
nervous  tunic.  It  is 
a  delicate  coat,  which 
has  a  thickness  of  .1 
mm.  near  the  nerve  and 
gradually  diminishes  in 
thickness  towards  the 
ora  serra*-.,  where  it 
measures  only  .06  mm. 
The  tntter  surface  is 
roughened  by  the  tra- 
becule of  connective 
tissue  which  cross  the 
suprachoroidal  lymph- 
space  and  connect  the  choroid  with  the  overlying  sclera.  The  connection  is  main- 
tained partly  also  by  the  larger  vessels  and  nerves,  which  lie  within  this  space 
during  their  course  forward  and  send  branches  to  supply  the  choroid.     The  inner 

Fig.  1210. 


SecticMi  vA  choroid,    y.  275. 


Large  vein 


Artery 


Surface  view  o(  injected  liuman  choroid,  thowinfi  venous  radicles  converging  to  (orm  larger  veins,    x  iS. 


surJacenX  the  choroid  is  smooth  and  covered  by  the  pigiv  ed  cells  of  the  retina, 
which  are  so  closely  attached  that  they  frequently  adher.  ^  the  choroid  when  the 
membranes  are  separated.  Posteriorly,  the  choroid  helps  to  form  the  lamina  crib- 
rosa,  the  fenestrated  membrane  through  which  the  optic  nerve-fibres  pass  ;  anteriorly 
it  is  continuous  with  the  ciliary  body. 


■vqMWiiinHi 


mifi^mmmimm 


1456 


HUMAN  ANATOMY. 


Fig.  121 1. 


Portion  o(   iii)«cted   chorioc»pillari»  layer  ol 
human  choroid.     X  130. 


Structure  of  the  Choroid The  choroid  consists  of  four  layers,  which  from 

without  inward,  are  :  (i )  the  /amtHa  suprathorioidea,  (2)  the  choroid pr^r,  which 
contains  the  larger  vess<ls,  (3)  the  ckoriocapillaris,  or  layer  of  fine  capillanes,  and 

( 4 )  the  membrmia  vitera.  ,    .        l       •  j      j 

'  The  lamina  supr^chorioidea  forms  the  outer  boundary  of  the  choroid  and 
connects  it  with  the  sclera.  It  is  composed  of  interlacing  bundles  of  fibrous  connec- 
tive tissue,  which  are  strengthened  by  a  nch  net- 
work of  elastic  fibres.  The  cellular  elements 
consist  of  (a)  flattened  endothelial  plates,  which 
line  the  lymph-clefts  and  cover  the  connective 
tissue  trabeculae  connecting  the  choroid  and  the 
sclera  by  traversing  the  suprachoroidal  lymph- 
space  ;  and  (b)  large,  irregularly  branched  con- 
nective tissue  cells,  the  chromatopkores,  which 
are  conspicuous  on  account  of  their  deeply 
pigmented  protoplasm.  The  lamellae  of  the 
suprachoroid  continue,  without  definite  boun- 
dary, into  the  subjacent  choroidal  stroma. 

The  choroid  proper,  as  the  choroidal 
stroma  is  called,  hxs  the  same  general  structure 
as  the  suprachoroidal  layer,  but  the  connective 
tissue  elements  are  denser  and  support  a  large 
number  of  blood-vessels,  between  which  are 
placed  the  stellate  chromatophores.  The  largest 
vessels  occupy  the  outer  part  of  the  coat,  and 
are  chiefly  venous.     They  are  surrounded  with 

perivascular  lymph-sheaths,  and  converge  in  peculiar  whorls  to  form  four  or  five 

large  trunks  the  vena  vorticosa,  which  pierce  the  sclera  in  the  equatorial  region  and. 

running  obliquely  backward,  drain  not  only  the  choroid,  but  partly  also  the  ciliar,, 

body  and  iris.     The  arteries  are  derived  from  the  short  ciliary  ves.sels,  «hich  pass 

through    the   sclera   near  the  optic  nerve. 

They   lie   internal   to   the  veins  and   their 

walls  contain  longitudinally  disposed  muscu- 
lar fibres  in  addition  to  the  customar  cir- 
cular ones. 

The  choriocapillaris,  or  membrane  of 

Ruvsch,  is  com{x)sed  of  the  fine  capillaries 

of   the  choroidal    vessels,    which    fomi   an 

extremely  fine  mesh-work  embedded  within 

a    homogeneous,    nonpigmented    matrix. 

Between  the  choriocapillaris  and  the  layer  of 

larger  vessels  is  a  narrow  boundary  zone  of 

closely  woven  fibro-elastic  strands,  which  is 

nearly  free  from  pigment.     In  some  animals 

this  layer  possesses  a  peculiar  metallic  reflex 

and  is  known  as  the  tapetum  fibrosum  ;  in 

carnivora  its  iridescent  appearance  is  due  to 

the  presence  of  cells  containing  minute  crys- 
tals (tapchim  cellulosum). 

The  membrana  vitrea,  or  membrane 

of  Bruch,  the  innermost  layer  of  the  choroid, 

measures  only  .002  mm.   in  thickness.     It 

separates   the    choriocapillaris    from   the 

retina  and  is  composed  of  two  strata,  an 

inner  homogeneous  one,  probably  an  exu- 

dation  product  of  the  retinal  pigment  cells,  and  an  outsr  highly  elastic  portion. 
The  lymphatics  of  the  choroid  are  represented  ( 1 )  hj  vessels  which  bc-„nn  m  the 

lymph-spaces  between  large  blood-vessels,  and  are  in  communication  with  the  spaces 

between  the  suprachoroidal  lamella,  and  (2)  by  the  perivascular  lymph-spaces  oi 


Fig.  1313. 


Sclera 


Cornea 


Ciliary 
"processes 


Anterior  part 


showing  iris 
serrau.    X  3. 


.--  of 
ciliary 


Ciliary  ring 


■  Retina 

sagitully  aectioned  eyeball. 
processes  and  ring  and  ora 


mm^mmmmmmm^mm 


wmmtft 


THE  VASCULAR  TUNIC. 


«457 


the  veins,  which  begin  between  the  meshi-s  of  th    v:huriocapillaris.  the  two    ••sti-ms 
being  separate. 

The  nerves  ol  the  choroid  arise  from  the  long  and  short  ciliary  nerves  during 
their  course  on  the  inner  surface  ol  the  sclera.  They  form  a  plexus  withm  the 
lamina  suprachorioidea,  which  contains  grou[)s  of  ganglion  cells,  and  sends  numerous 
nonmedullated  fibres  chiefly  to  the  muscular  coiiis  of  the  arteries.  A  few  ganglion 
cells  are  found  along  the  blo«Kl-ve8.sels.    The  choroid  contains  no  sensory  ncrve-tibres. 

Kii;.  iai3. 


Choroidal  itronu— 
PiKincnted  ccllk. 

Clear  cell* 
Blood-T«ml» 

Sectioni  ol  ciliary  pr'      ••tn 


A,  trom  ftiH«rior ;  f 
at  pRr^    iikui*  rcti 


The  Ciliary  Body.— The 
the  vascular   tunic,  extends   from 
Sections  through  the  eyebaJI  ir  i 
a  triangular  form.     The  outer  Mil' 
by  the  pigmented  extension  ot  thi 
to  the  outer,  extends  inward  fron 

The  ciliary  body  presents  tl 
eesses  and  the  cil'nry  muscle. 


Clear  cclli 


from  poMcriar  part ;  two  cpitbcllal  laytrt,  pignwntad  and  clear, 
'  cover  choroidiil  Mroma.    X  So. 

V  bo<l .  (corpus  cillare),  the  middle  portion  ol 
•  ora  serrata  to  the  sclero-corneal  junction, 
ridional  direction  (Fig.  1 2 14)  show  that  it  has 

*  apposition  to  the  sclera,  the  inner  is  covered 

•  t   and  tl>    short  anterior  side,  at  right  angles 
lie  ligament  toward  the  lens. 

'Ir.  i^ns  ;  the  ciliary  ring,  the  cil    ry  pro- 


1214. 


Cuifica 


Canal  ol  Schlen 


it«  liipiinHmt 


niiarf  mnsi  k-  (radial  Kbrcai 
Silcri 

Meridional  fibrvs 


Ci1iar>-  proccaaes  Circular  fibres  Choroi*' 

Meridional  section  of  ciliary  rCKion,  showing  ciliary  biv         i  «<-s» 

The  ciliary  ring,  or  orbiculus  ciliaris,  <        sts        1  ^aiiooth 
mm.  in  width,  in  advance  of  the  ora  serrata.  '^-•■'        stnicturL  , 

in  the  absence  of  the  choriocapillaris,  its  vessti  m  a  lortfjis 

and  returning  the  blood  from  the  iris  and  cili.ir     bou        ■  the  vena- 
its  inner  surface,  delicate  meridionally  placetl  i<>i'  Is  mak' 
union  of  which  the  ciliary  processes  are  forme* : 

The  ciliary  processes  constittitc  the  ^^-tnainder  rf.  th?-  \r.rtfr  p 
ciliary  body.  They  form  an  annular  series  of  folds,  about  seventy  in  m 
surround  the  lens  and  act  as   points  of  attachment   to   its    suspend 

92 


1  of  tissue,  4 

'  he  choroid 

U.1I  directton 

ticosse.     Ofi 

their  ajjpf.ii  ince,  by  th«^ 

^  of  the 

^)er,  which 

.   ligament. 


^■■li! 


mmmmmt^KK^ 


145* 


HUMAN  ANATOMY. 


Commencing  by  the  union  of  several  plicationa  of  the  orbiculus  ciliaris,  they  rapidly 
increase  in  height  and  breadth,  until  they  reach  an  elevation  of  from  .8-1  mm.,  and 
then  fall  suddenly  to  the  iris  level.  They  consist  c '  a  rich  net-work  of  vessels  em- 
bedded in  a  pigmented  connective  tis-sue  stroma,  lik'  >hat  of  the  choroid.  The  inner 
surface  is  covered  with  a  homogeneous  - 1<  ubrar  ,  which  is  continuous  with  the 
membrana  vitrea  of  the  choroid,  on  the  inn< :  sur'  .e  of  which  is  placed  the  double 
layer  of  cells  representing  the  ciliary  portion  ui  the  retina  (pars  ciliaris  retina). 
Each  ciliary  process  Ls  composed  of  a  number  of  irregularly  projecting  folds  «  'icli 
increase  in  height  as  the  u'.i  is  approached. 


Fig. 


Coinca 


1315. 


r.mtcr  aitniil  tint 
lri( 

Lmmt  aitarU  rinc 

Ciliary  proccu' 


Canal  of  Schlcmni 

^Corneal  loop 


Pnfotal.'nc  branch 

Conjunctival  v««a*li 


Anterior  ciliary  w     1 


Communication  between  Retinal  ve»ael»' 

choroidal  and  optic  vessels 
Central  retinal  vessels 


Vena  vortlcoaa 

Sapplylng  choroid 

Short  posterior  ciliary  artery 

.Loiif  post'    or  ciliary  artery 
CommunicatinK  twig 
Inner  sheath  vessels 
Outer  sheath  vessels 


Communication  between  optic 
'and  sheath  vessels 


Diagram  illustrating  circulation  of  eyeball.    (Lettr.) 


The  ciliary  muscle  occupies  the  outer  portion  of  the  ciliary  body,  lying 
between  the  sclera  and  the  ciliary  processes.  It  forms  an  annular  prismatic  band 
of  involuntary  muscle,  which  in  meridional  sections  has  the  form  of  a  right-angled 
triangle,  the  hypothenuse  being  the  outer  side,  next  to  the  sclera,  and  the  right 
angle  facing  the  lens.  Its  main  fibres  arise  from  the  sclera  and  pecti>  te  ligament, 
at  the  corneo-scleral  junction  internal  to  the  canal  of  Schlemm,  and  run  in  a 
meridional  direction  backward  along  the  sclera  to  be  inserted  into  the  choroidal 
stroma  (hence  their  name,  tensor  chorioidete).  The  inner  angle  of  the  triangle,  at 
the  base  of  the  iris,  is  occupied  by  a  band  of  circularly  disposed  fibres,  which  consti- 
tute the  circular  ciliary  muscle  of  Afiiller.  Belween  the  circular  and  meridional 
portions,  the  fibres  assume  a  radial  direction  and  arc  separated  by  considerable 
connective  tissue,  which  in  the  deeply  pigmented  races  may  contain  many  branched 


f^mmmmmmifmi^mimiKm 


mmmffmm 


PRACTICAL  CONSIDERATIONS:  THE  VASCILAR  Tl  NIC.     1459 

^  ;ginented  celb,  but  in  the  white  races  n  free  from  pigment.  In  hyperopic  eyes  the 
.ircular  bundlea  are  usually  better  developed  than  in  myopic  or  ■«. 

The  blood-vessels  d  the  ciliary  body  arise  from  the  anterior  and  the  long  ciliary 
arteries.  They  form  a  ring  around  the  root  of  the  iris,  the  circulus  arlrriosus  iridis 
major,  from  which  vessels  arc  sent  inward  to  supply  the  iris,  ciliary  'iusc!e  and 
ciliary  processes.  The  veins  from  the  ciliary  muscle  empty  chiefly  into  the  anterior 
ciliary  veins;  those  from  the  ciliary  processes,  ..nd  a  few  from  the  ciliary  muscle  pass 
backward  and  become  tributary  to  the  venie  voriirostr. 

The  nerves  of  the  ciliary  Ixxly  are  derived  from  the  anterior  branches  of  the  long 
and  short  ciliary  nerves,  which  form  an  annular  plexus  within  the  ciliary  muscle. 
Four  iets  of  fibres  probably  exist :  ( i )  sensory  fibres,  largely  subscleral  in  distribu- 
tion ;  (2)  vasomotor  fibres  runni  j  to  the  blood-vessel  walls  ;  (3)  motor  fibres  sup- 
plying; the  muscle  bund'  s ;  (4)  fibres  terminating  within  the  interfascicular  tissue  of 
the  ciliary  muscle. 

Practical  Considerationa. — Congenital  coioboma  of  the  choroid,  as  of  the 
iris,  usually  occurs  in  the  lower  part,  along  the  line  of  the  foetal  ocular  cleft.  In  tht 
defect  the  sclera  r  .ows  pearly  white  through  the  ophthalmoscope,  with  here  and 
there  a  little  pigm  .it  and  a  few  ciliary  vessels.  The  retina  is  frequently  absent,  but 
its  occasional  presence  explains  why  this  area  is  not  always  blind. 

In  acute  exudative  inflammation  of  the  choroid,  foci  of  inflammation  are  seen 
scattered  over  th**  fundus,  and  are  characteristic.  They  form  yellowish  spots  between 
the  choroid  and  retina,  and  are  later  convened  into  connective  tissue,  binding  the 
choroid  and  retina  together.  The  two  iayent  become  atrophic  finally,  the  layers  of 
rods  and  cones  disappearing.  The  exudate  may  extend  into  the  retina  ard  even  into 
the  vitreous,  producing  opacities. 

Sarcoma  is  the  common  tumor  of  the  choroid  and  is  usually  pigmented. 

Carcinoma  of  the  choroid  is  always  a  metastatic  gro"-th,  usually  a  metastasis  from 
a  carcinoma  of  the  breast.  Adenoma,  angioma,  and  enchondroma  of  the  choroid 
have  been  described. 


FupllUry  iMryiii        AnMriw  entlotlwlluiii 


Stroma  or  Irta 


The  Iris. — The  iris  forms  the  anterior  segment  of  the  vascular  tunic  and  is 
visible  through  the  cornea.  Slighdy  to  the  inner  side  of  its  centre  is  placed  an 
approximately  circular 

opening,  the  pupil.   The  Fig.  iai6. 

periphery  of  the  iris,  or 
ciliary  border,  is  attached 
to  the  ciliary  body  behind 
and  receives  tibres  from 
the  pectinate  ligament  an- 
teriorly. The  free  border, 
which  forms  the  margin 
of  the  pupil,  rests  upon 
the  anterior  surface  of  the 
lens.  The  iris  measures 
II  mm.  in  diameter  and 
about  .4  mm.  ir.  thick- 
ness. The  pupil  varies  from  1-8  mm.  in  diameter.  The  color  of  the  iris,  viewed 
from  in  front,  varies  in  different  individuals  and  g^ves  the  color  to  the  eyeball.  It  is 
dependent  partly  upon  the  amount  of  pigment  within  the  iris  stroma,  and  pardy 
upon  the  density  of  the  pigmentation  of  the  cells  on  its  posterior  surface.  In  light 
blue  eyes,  the  stroma  contains  very  little  pigment  and  the  posterior  pigment  layer, 
seen  through  it,  gives  it  a  bluish  tint ;  whereas  in  brown  eyes  the  stroma  contains  so 
much  pigment  that  the  posterior  pigment  layer  is  totally  obscured  and  the  iris  appears 
brown.  The  anterior  surface  is  marked  by  a  number  of  fine,  radiating  lines,  or  ridges, 
which  indicate  the  position  of  the  blood-vessels.  Concentric  to  the  pupillary  margin, 
at  a  distance  of  from  1-2  mm.,  is  an  irregular  ridge,  the  circulus  arteriosus  iridis 
minor,  which  divides  the  iris  into  a  pupillary  and  a  c'Hary  zone  which  are  often  differ- 
ently colored.     The  pupil  is  surrounded  by  a  narrow  black  border.     The  posterior 


Sphincter  nuKle  nvmcntcd  [«n  lrl<lka  tvtiUB 

Section  of  pupilliry  end  o(  iilj.    X  ii; 


! 


1460 


HUMAN  ANATOMY. 


PupiMary  border  of  iris' 


Lesier  arterial  circle^ 


Ciliary  artery — 


surface  of  the  iris  presents  a  series  of  delicate  converging  folds,  which  are  intersected 
by  concentric  lines. 

Structure  of  the  Iris. — Radial  sections  of  the  iris  show  the  stroma  to  be  com- 
posed of  numerous  thick-walled  blood-vessels,  running  in  a  radiating  manner  from  the 
ciliary  border  toward  the  pupil.  They  are  supported  by  a  delicate  connective  tissue 
framework,  which  contains  irregularly  shaped,  branching  pigmented  cells,  many 
nerves  and  lymph-spaces.  The  anterior  surface  is  covered  with  a  single  layer  of  polyg- 
onal endothelial  cells,  continuous  with  those  lining  Descemet's  membrane.  Beneath 
these  cells  is  a  condensation  of  the  connective  tissue  stroma — the  anterior  boundary 
layer,  in  which  the  cells  are  closely  placed.  Minute  clefts  in  the  tissue  form  a  direct 
communication  between  the  anterior  chamber  and  the  interfascicular  lymph-clefts. 
In  very  dark  irides  pigment  is  found  not  only  within  the  branched  cells,  but  heaped 
in  irregular  masses  within  the  stroma.     The  muscular  tissue  of  the  iris  consists 

of  two  distinct    masses,    the 
•-''«■  "'7-  sphincterpupilla;  An<\l\\c  dila- 

tator pupilla. 

The  sphincter  muscle,  is 
a  band  of  involuntary  muscle 
measuring  about  .7  mm.  in 
width,  which  surrounds  the 
pupil  and  is  situated  in  the 
vascular  stroma,  back  of  the 
blood-vessels,  and  separated 
from  the  pupil  edge  by  the 
narrow  border  constituted  by 
the  posteriorpigmented  layer. 
The  dilatator  muscle  is 
formed  by  a  sheet  of  smooth 
muscle-fibres  in  the  position 
formerly  described  as  the 
posterior  limiting  lamella,  or 
membrane  of  Bruch.  The 
investigations  of  Grynfeltt 
and  Heerfordt  have  settled 
definitely  the  question  of  its 
existence,  and  shown  that  its 
fibres  arise  from  the  outer  cells 
of  the  retinal  pigment  layer, 
on  the  posterior  surface  of  the 
iris.  They  do  not  reach  quite 
to  the  pupillary  border. 

The  posterior  surface  of 
the  iris  is  covered  by  the  pig- 
mented layer,  which  morphologically  represents  the  anterior  segment  of  the  atrophic 
nervous  tunic,  or  pars  iridica  retinte.  This  is  continuous  with  the  pigmentary  layer 
covering  the  ciliary  processes,  but  the  cells,  disposed  as  a  double  layer,  are  so  deeply 
pigmented  as  to  be  indistinguishable  without  bleaching  the  tissue.  "Wvt  dilatator 
muscle  is  developed  from  the  outer  layer  of  fusiform  cells,  so  that  it  represents  an 
epithelial  (ectoblastic)  muscle.  The  inner  cells  are  larger  jwlygonal  elements,  which 
gradually  lose  their  pigment  as  they  approach  the  ciliary  processes.  Over  the  latter 
they  contain  no  pigment,  whereas  the  outer  cells  remain  pigmented. 

The  blood-vessels  of  the  iris  pass  radially  inward  from  the  circulus  arteriosus  iridis 
major  at  the  periphery.  Near  the  pupillary  border,  they  form  a  second  ring,  the  cir- 
culus arteriosus  iridis  minor,  branches  from  which  supply  the  sphincter  muscle  and  the 
pupillary  zone.  The  venous  radicles  unite  to  form  trunks  which  accompany  those 
from  the  ciliary  processes  to  empty  into  the  venee  vorticosee. 

The  lymphatics  are  represented  by  the  interfascicular  clefts  which  communicate 
with  the  anterior  chamber,  with  the  spaces  within  the  ciliary  body,  and  with  the 
spaces  of  Fontana. 


Vascular  plexus  in 
ciliary  proceasM 


Veins  draining 
ciliary  procesiies 


Choroidal  veins' 


Injected  ciliary  processes  and  iris;  vessels  are  seen  from  th* 
posterior  surface,    X  y>. 


PRACTICAL  CONSIDERATIONS:     THE   IRIS. 


1 46 1 


The  nen'cs  of  the  iris  are  branches  of  the  ciliary  nerves.  They  follow  the  course 
of  the  blood-vessels  and,  branching,  form  a  plexus  of  com'T>iinicating  nonmedullated 
fibres,  which  supply  sensory,  motor  and  vasomotor  imr  .0.  The  human  iris  i)n)b- 
ably  contains  no  ganglion  cells. 

Practical  Considerations. — ^The  iris  may  be  partially  or  completely  absent, 
when  by  bringing  down  the  eyebrows  and  partially  closinjr  the  lids,  the  p;itient 
will  make  an  effort  to  shut  off  the  excess  of  light,  as  in  albinism,  and  the  eye  will 
frequently  be  nystagmic. 

A  congenital  coloboma  or  deficiency  in  the  iris  is  usually  in  the  lower  pi»rt,  and 
may  be  associated  with  a  corresponding  defect  in  the  ciliary  bcxly  and  choroid.  The 
pupil  may  be  eccentric  in  position  (corectopia),  unusually  small  (microcoria), 
irregular  in  shape  (discoria),  or  it  may  be  represented  by  several  pupils  (iMilycoria). 
The  pupillary  membrane  of  the  icetus,  covering  the  pupil,  not  infrequently  persists 
for  a  short  time  after  birth.  A  portion  of  it  persisting  permanently  is  one  of  the 
commonest  congenital  anomalies  of  the  eye. 

The  color  of  the  iris  varies  according  to  the  amount  and  location  of  the  pigment 
in  it.  When  the  coloring  matter  is  absent  from  the  stroma,  and  present  only  in  the 
posterior  layer  of  epithelium,  the  eye  is  blue.  If  such  an  iris  is  thicker  than  usual 
the  opacity  will  be  greater  and  the  eye  will  tend  to  be  grayish.  When  there  is  pig- 
ment only  in  slight  amount  in  the  stroma,  the  eye  is  greenish,  and  when  in  marked 
quantity  in  the  stroma,  the  eye  is  brown  or  even  black,  as  in  negroes.  The  deepest 
tints  of  brown  are  usually  called  black. 

In  albinism  there  is  an  absence  of  pigment  in  the  iris,  and  in  the  other  parts  of 
the  body  where  pigment  is  usually  found.  The  eyes  are  pinkish  in  color,  because 
the  light  enters  through  the  tunics  and  is  not  absorbed  by  the  choroid  and  retina, 
owing  to  the  absence  of  pigment  in  it.  The  retina  is  therefore  intolerant  of  light, 
so  that  the  patient  tries  to  shut  it  out  by  screwing  up  the  eyebrows  and  lids,  and  by 
contraction  of  the  iris.  He  will  frequently  show  nystagmus  or  oscillation  of  the 
eyeball,  and  amblyopia,  or  subacuteness  of  vision. 

The  two  eyes  are  not  always  of  the  same  color,  and  even  in  the  same  eye,  one 
part  of  the  iris  may  be  blue  and  another  brown  (piebald  iris).  One  eye  may  have 
Its  color  permanently  changed  as  the  result  of  inflammation,  so  that  the  difference  in 
color  may  be  an  important  diagnostic  sign  of  previous  disease 

The  iris  acts  as  a  colored  curtain  to  shut  off  excess  of  light,  as  more  or  less 
light  is  necessary  for  the  definition  of  images.  Too  much  light  impairs  the  defini- 
tion and  injures  the  retina.  The  pupils  are  usually  of  equal  size  in  health,  and  any 
marked  inequality  has  a  pathological  significance.  The  iris  does  not  hang  in  a  verti- 
cal plane,  but  is  pushed  slightly  forward  and  supported  at  its  pupillary  margin  by  the 
lens.  If  the  lens  is  absent  or  dislocated,  the  pupillary  margin  of  the  iris  may  tie 
seen  to  quiver  with  the  movement  of  the  eyes.  The  ins  in  spite  of  its  great  vascu- 
larity may  not  bleed  much  when  wounded,  probably  because  of  the  contraction  of 
its  abundant  muscular  fibres.  The  iris  is  continuous  with  the  ciliary  body,  and 
through  the  latter  with  the  choroid,  the  three  taken  together  making  up  the  uveal 
tract,  or  middle  tunic  of  the  eye.  Any  inflammation  of  the  one  may  easily  spread 
to  the  others.  This  usually  occurs,  but  as  the  inlammation  is  predominant  in 
one,  we  speak  of  an  iritis,  a  cyclitis,  or  a  choroiditis,  and  not  of  the  whole  pro- 
cess as  a  uveitis.  In  an  iritis  the  exudation  which  affects  the  stroma  as  well  as 
the  anterior  and  posterior  aqueous  chambers  can  be  studied  by  inspection.  It 
thickens  and  discolors  the  iris,  renders  the  aqueous  fluid  turbid,  and  leaves  a 
deposit  on  the  contiguous  surfaces  of  the  cornea  and  lens.  Since  the  pupillary 
margfin  of  the  iris  is  in  confcict  with  the  lens  on  the  posterior  surface  the  exudate 
causes  adhesions  of  this  margin  to  the  lens  (f)osterior  synechia;).  Since  the  pupil 
is  contracted  in  inflammation,  when  these  adhesions  form,  dilatation  of  the  pupil 
normally  or  under  the  influence  of  atropine,  gives  rise  to  a  very  irregular  pupil, 
the  unattached  portion  dilating,  the  attached  portions  not.  Sight  need  not  be 
affected  if  the  pupil  is  large  enough.  If  the  whole  margin  of  the  pupil  is  attached 
to  the  lens,  or  the  pupil  is  occluded  by  exudate,  the  normal  flow  of  fluid  from 
the  posterior  to  the  anterior  chamber  cannot  take  place,  and  glaucoma  (vide  supra), 


1462 


HUMAN   ANATOMY. 


a  disease  due  to  increased  intraocular  tension  from  retention  results.  It  is  neces- 
sary, therefore,  in  iritis  to  keep  the  pupil  dilated,  so  as  to  prevent  such  adhesions 
as  far  as  possible. 

The  Nervous  Tunic. 

The  Retina. — The  retina,  the  light  perceiving  portion  of  the  eye,  with  its  con- 
tinuation, the  optic  ner\'e,  in  contrast  to  the  other  sense  organs  represents  a  portion 
of  the  brain  itself,  and  develops  in  close. connection  with  it.  It  is  a  delicate  mem- 
brain,  which  extends  from  the  optic  nerve  entrance  to  the  pupillary  border.  The 
functionating  portion,  or  pars  optica  retina,  reaches  as  far  forward  as  lY\eoraserrata, 
where  it  termmates  as  an  irregular,  wavy  line  ;  anterior  to  this  the  retina  is  repre- 
sented by  an  atrophic  portion,  consisting  of  the  double  layer  of  cells  co\ering  the 


Fibre  layer 
Ganglion  cells 

Inner  plexifortn  layer 


Cerebral  layer 


Sustentacular  cell 


Neuroepithelial  laj'er 


Pigmented  layer 


Inner  nuclear  layer 
(bipolar  nerve-cells) 


Outer  plexiform  layer 


1  Outer  nuclear  layer 
(bodies  of  visual  cells\ 


Rods  and  cones 


Pigmented  layer 


Choroid 
Diagram  illustrating  structure  ot  retina  and  relations  of  three  fundamental  layers.    (Gteeff.) 

ciliary  body  and  the  iris,  already  referretl  to  in  the  description  of  these  structures, 
and  known  respectively  as  the  pars  ciliaris  retina,  and  pars  iridica  retina. 

The  pars  optica  retinae  is  closely  ap]>lied  to  the  inner  surface  of  the  choroid 
and  is  in  contact  with  the  hyaloid  membrane  investing  the  vitreous  body.  It  grad- 
ually diminishes  in  thickness  from  .4  mm.  at  the  posterior  pole  to  .1  mm.  near  the 
ora  serrata.  During  life  the  membrane  is  transparent  and  possesses  a  purplish  red 
color,  owing  to  the  presence  in  its  outer  layers  of  the  so-called  visual  purple ;  after 
death  the  retina  rapidly  becomes  opaque  and  has  the  appearance  of  a  grayish  \cil. 
The  inner  surface  is  smooth  and  presents  at  the  posterior  pole  of  the  eye,  a  small 
circular  or  transversely  oval  yellow  spot,  the  maatla  lutea,  from  1-2  mm.  in  diam- 
eter. At  the  centre  of  the  macula  is  a  small  depression,  the  fovea  centralis,  fron 
.2-.  4  mm.  in  diameter,  in  which  position  the  retina  is  reduced  in  thickness  to  .  i  mm. 

The  entrance  of  the  optic  nerve  forms  a  conspicuous  spot  of  light  color,  situatetl 
3  mm.  to  the  na.sal  side  of  the  macula  lutea.  This  area,  called  the  optic  papilla  or 
porus  opticus,  is  in  form  of  a  vertical  oval,  about  1.5  mm.  in  its  horizontal  and 


THE   NERVOUS  TUNIC. 


1463 


1.7  mm.  in  its  vertical  diameter.  At  its  centre  is  often  seen  a  well-marked  excavation, 
the  optic  cup,  from  the  bottom  of  which  emerge  the  blood-vessels  which  supply  the  retina. 
Bein)^  insensible  to  visual  impulses,  the  optic  entrance  corresponds  to  the  ' '  blind-spot. 

Structure  of  the  Retina. — The  retina  is  composed  of  nervous  elements  which 
are  supported  by  a  specialized  sustentacular  tissue  or  neuroglia.  Morphologically  it 
must  be  considered  as  composed  of  two  lamellx,  which  correspond  to  the  outer  and 
inner  walls  of  the  optic  vesicle  (page  1482)  from  which  it  is  developed.  These  fun- 
damental divisions  of  the  retina  are :  ( i )  the  external  lamella,  the  pigmented  layer 
on  the  outer  surface  ;  and  (2)  the  internal  lamella,  which  includes  the  remaining  layers 
of  the  retina.  The  inner  lamella  may  be  subdivided  further  into  the  neuroepithelial 
and  the  cerebral  layers.  Sections  of  the  retina,  made  perpendicularly  to  its  surface 
(Fig.  1 220),  show  under  the  microscope  from  without  inward  the  following  layers : — 


I.  OirrRK  I.AVKR  OV  OPTIC 
VESICLK 


IR  INNBR  LAYER  OF  OrTIC 
VBSICLB 


{•■ 


Layers  of  the  Retina. 

Pig^mented  layer 


I  Pigmented  layer 


J.  Layer  of  rods  and  cones 

3.  Layer  of  bodies  of  visual  cells  or  outer  nuclear 

layer 

4.  Outer  plexiform  layer 

5.  Layer  of  bipolar  cells,  or  inner  nuclear  layer 

6.  Inner  plexiform  layer 

7.  Layer  of  ganglion  cells 

8.  Layer  of  nerve-fibres 


Ncuro- 
'  epithelial 
layer 

Cerebral 
layer 


To  these  nervous  layers  must  be  added  two  delicate  membranes,  ( i )  the  membrana 
limitans  interna,  which  bounds  the  inner  surface  of  the  retina,  and  (2)  the  membrana 
limitans  externa,  which  lies  between  the  outer  nuclear  layer  and  the  layer  of  rods 
and  cones.  These  membranes  represent  the  terminal  portions  of  the  supporting  neu- 
rogliar  fibres,  ox  fibres  of  Miiller. 

The  pigmented  layer,  formed  of  deeply  pigmented  cells,  constitutes  the  most 
external  layer  of  the  retina  and  represents  the  xjuter  wall  of  the  foetal  optic  vesicle. 
It  is  composed  of  hexagonal  cells,  from  .012-.018  mm. 
in  diameter,  the  protoplasm  of  which  is  loaded  with  fine, 
needle-shaped  crystals  of  pigment  (fuscin).  The  outer 
portion  of  the  cells  is  almost  free  from  pigment  and  con- 
tains the  nucleus.  From  the  inner  border  fine  proto- 
plasmic processes  extend  inward  between  the  rods  and 
cones  of  the  neuroepithelial  layer.  Under  the  influence 
of  light,  the  pigment  particles  wander  into  these  processes 
and,  under  such  conditions,  the  pigmented  cells  may 
remain  attached  to  the  retina  when  the  latter  is  separated 
from  the  choroid.  Ordinarily,  the  pigmented  layer  ad- 
heres to  the  choroid  and,  hence,  was  formerly  considered 
to  be  a  part  of  that  membrane.  The  pigmented  cells  are 
separated  by  a  distinct  intercellular  cement  substance  and  in  some  of  the  lower 
animals  contain  colored  oil  droplets  and  particles  of  a  highly  refracting  myelin-like 
substance  {myeloid granules  of  Kiihne). 

The  layer  of  rods  and  cones,  although  usually  described  as  a  distinct  stratum, 
is  only  the  highly  specialized  outer  zone  of  the  layer  of  visual  cells  and,  therefore, 
constitutes  the  outer  portion  of  the  neuroepithelial  division  of  the  retina.  It  is  com- 
posed, as  its  name  indicates,  of  two  elements,  the  rods  and  the  cones,  which  arc  the 
outer  ends  of  the  rod  and  cone  visual  cells.  They  are  closely  set,  with  their  long 
axes  perpendicular  to  the  surface  of  the  retina.  The  rods  far  outnumber  the  cones, 
except  in  the  f<  i  centralis,  in  which  location  cones  alone  arc  found.  In  the  macula 
each  cone  is  sui :  unded  by  a  layer  of  rods  ;  elsewhere  the  cones  are  separated  by 
intervals  occupied  by  three  or  four  cones. 

The  rods  of  the  human  retina  (Fig.  1221)  have  an  elongated,  cylindrical  form, 
and  measure  approximately  .060  mm.  in  length  and  .020  mm.  in  diameter.    Each  rod 


Pigmented  cells  from  outer  layer  of 
retina ;  lurface  view.    X  250. 


1464 


HUMAN  ANATOMY. 


Fig.  ijjo. 
Fibre  o(  Miiller 


is  composed  of  an  outer  and  an  inner  segment,  of  about  equal  length.  The  outer 
segment  possesses  a  uniform  diameter,  is  doubly  refracting,  and  readily  breaks  up  into 
minute  disks.  It  is  invested  with  a  delicate  covering  of  neurokeratin,  contains 
myeloid  (Kuhne)  and  is  the  situation  of  the  visual  purple  or  rhodopsin.  The  inner 
rod  segment  is  somewhat  thicker  and  has  an  ellipsoi.  lal  form.  It  is  siri'  refracting, 
homogeneous  in  structure  (rapidly  becoming  granular  after  death)  and  im  its  inner 
extremity  sends  the  delicate  rod-fibre  through  the  external  limiting  mciMbrane  into 
the  outer  nuclear  layer  where  the  nucleus  of  the  rod  visual  cell  is  found. 

The  cone  visual  cell  is  composed  of  the  same  general  divisions  as  the  rod-cell, 
including  the  specialized  outer  part,  the  cone,  and  the  body  within  the  external  nu- 
clear layer.  The  cones  are  shorter  than  the  rods,  and,  except  in  the  fovea,  have  a 
length  of  .035  mm.  Elach  one  (Fig.  1221)  is  comjxjsed  of  an  outer  narrow  cone- 
shaped  segment,  and  an  inner  broader  segment,  which  is  distinctly  ellipsoidal  in 
form,  with  a  diameter  of  .060  mm.     The  inner  segment  is  double  the  length  of  the 

outer,  and  is  continued  inward  as 
the  conefibre  with  its  nucleus  in 
the  outer  nuclear  layer.  In  the 
fovea,  where  the  cones  alone  are 
found,  they  are  of  approximately 
the  same  length  as  the  rods,  and 
possess  about  one  half  the  usual 
diameter. 

The  outer  nuclear  layer, 
the  inner  portion  of  the  neuroepi- 
theleal  layer,  is  composed  of  the 
bodies  of  the  rod  and  cone  visual 
cells,  which  show  chiefly  as  the 
nuclei,  the  so-called  rod-  and  cone- 
granules.  The  rod-granules  oc- 
cupy an  elliptical  enlargement  of 
the  attenuated  rod-fibres.  They 
exhibit  a  transverse  striation  and 
are  placed  at  varying  levels  within 
the  layer.  The  rod-fibres  are  con- 
tinued as  a  thin  protoplasmic  pro- 
cess into  the  outer  reticular  layer, 
where  they  form  small  end-knobs 
which  are  associated  with  the  outer 
terminals  of  ihe  small  nerve-cells, 
the  rod-bipolars.  The  cone-gran- 
ules are  less  numerous  than  those 
of  the  rods,  display  no  transverse 
markings,  and  are  found  only  in  the 
outer  portion  of  the  nuclear  layer, 
near  the  external  limiting   mem- 


litternal  limitinR 
membrane 


Ganglion  cell 


Fibres  of  Miiller 


Bipolar  nerve 
cells 


Blood-vesMi 


Layer  of  visual 
cells 


Nucleus  of  cone- 
cell 


Cone- 
Rod 


Pigment  layer 
Section  of  human  retina  from  near  posterior  pole. 

brane.  The  cone-fibres,  the  attenuated  bodies  of  the  cone  visual  cells,  are  broader 
than  the  corres|K)nding  parts  of  the  rods  and  are  continued  through  the  outer  nuclear 
layer  as  far  as  the  outer  portion  of  the  external  plexiform  layer,  where  they  end  with 
a  broad  base,  from  which  delicate  processes  extend  inward  to  interlace  with  the 
terminal  arborizations  of  the  cone-bipolars.  The  outer  nuclear  layer  is  about  .05 
mm.  in  thickness. 

The  outer  plexiform  layer  is  a  narrow  granular  looking  stratum,  between  the 
outer  and  the  inner  nuclear  layer,  and  constitutes  the  first  of  the  cerebral  layers 
of  the  retina.  It  is  composed  of  ie  dendritic  arborizations  of  the  bipolar  nerve-cells 
of  the  succeeding  layer,  which  lie  1  «  close  relation  with  the  centrally  directed  proces- 
ses from  the  foot-plates  o-  the  cone-cells  and  with  the  end-knobs  of  the  ro«i-fibres. 
In  addition  to  these  constituents  of  the  plexiform  layer,  numerous  fibres  arising  from 
the  protoplasmic  processes  of  the  horizontal  cells  of  the  inner  nuclear  layer  also  take 
part  in  its  formation. 


THE  NERVOUS  TUNIC. 


•465 


Fig.  1 221. 


The  inner  nuclear  layer,  the  most  complicated  of  the  retinal  strata,  measures 
.035  mm.  in  thickness  near  the  optic  disc.  It  contains  nervous  elements  of  three 
main  types — the  horizontal  cells,  the  bipolar  cells,  and  the  amacrinc  cells — and, 
associated  with  these,  the  nuclei  of  the  sustcntacular  cells. 

The  horizontal  cells  form  the  external  layer,  and  were  formerly  included  in  die 
outer  plexiform  layer.  They  have  flattened  cell-bodies  and  send  out  from  five  to 
seven  dendrites,  which  divide  into  innumerable  branches  and,  passing  into  the  outer 
plexiform  layer,  terminate  in  close  association  with  the  Ixises  ot  the  rotl  and  rone 
visual  cells.  Each  horizontal  cell  possesses  also  an  axone,  which  is  directed  outward 
through  the  outer  plexiform  layer,  and  ends  in  a  richly  branched  arborization  alxiut 
the  visual  cells.  A  second  type  of  large  horizontal  cells 
is  also  described,  some  of  which  send  axis-cylinder  pro- 
cesses through  the  inner  nuclear  layer  to  form  terminal 
arborizations  in  the  inner  plexiform  layer.  The  function  of 
the  horizontal  cells  is  not  well  understood,  but  they  prob- 
ably serve  as  a.ssociation  fibres  between  the  visual  cells. 

The  bipolar  cells,  the  ganglion  cells  of  this  layer, 
are  of  two  chief  varieties,  the  rod-bipolars  and  the  cone- 
bipolars.  They  are  oval  cells,  each  sending  an  axone 
inward  toward  the  inner  plexiform  layer,  which  ends  in 
communication  with  the  large  nerve-cells  of  the  ganglion 
cell  layer,  and  a  dendrite  outward  which  is  associated  with 
the  end  terminals  of  the  visual  cells  and  with  the  arboriza- 
tions of  the  horizontal  cells.  The  dendrites  of  the  rod- 
bipolars  form  an  arborescence  of  vertical  fibrils,  which 
enclose  from  three  to  twenty  end  knobs  of  the  rod -fibres, 
whilst  their  axis-cylinders  pass  entirely  through  the  inner 
plexiform  layer  and  usually  embrace  the  cell-body  of  one 
of  the  lai^e  ganglion  cells.  The  dendrites  of  the  cone- 
bipolars,  on  the  other  hand,  bear  horizontal  arborizations 
"•hich  interlace  with  the  fibrils  from  the  foot-plates  of  the 
.le-cells.  Their  axones  penetrate  less  deeply  into  the 
.ner  plexiform  layer  than  do  those  of  the  rod-bipolars, 
coming  in  contact  at  various  levels  with  the  peripherally 
directed  dendrites  of  the  ganglion  cells. 

The  amacrine  cells  are  placed  in  the  inner  portion  of 
the  nuclear  layer.  Formerly  considered  as  sustentacu- 
lar  elements,  they  are  now  recognized  as  nerve-cells, 
although,  as  their  name  indicates,  no  distinct  axone  can 
be  demonstrated.  They  pr-ssess,  however,  richly  branched 
dendritic  processes,  which  ramify  in  the  inner  plexiform 
layer  and  end  either  as  the  brush-like  arborizations  of  the 
disuse  amacrines,  or  as  the  horizontally  branching  arborizations  of  the  stratiform 
amacrines.  A  third  type,  known  as  association  amacrines,  is  also  described.  They 
connect  widely  separated  amacrine  cells  of  the  same  layer  (Cajal). 

The  nuclei  of  the  sustentacular  cells,  the  fibres  of  Muller,  will  be  described  later 
(page  1466). 

The  inner  plexiform  layer,  .04  mm.  in  thickness,  appears  granul.ir,  similar 
to  the  corresponding  outer  zone,  and  is  composed  of  the  interlacing  axones  of  the 
bipolar,  amacrine  and  horizontal  cells  'rom  the  inner  nuclear  layer  and  the  dendrites 
of  the  large  ganglion  cells  in  the  sub'acent  retinal  layer.  Intermingled  with  them 
arc  also  the  fibres  of  Miiller,  which  form  conspicuous  vertical  strise,  with  lateral 
offshoots  within  the  stratum. 

The  layer  of  ganglion  cells,  consists,  throughout  the  greater  part  of  the 
retina,  of  a  single  row  of  large  multipolar  neurones,  each  with  a  cell-body  containing  a 
vesicular  nucleus  and  nucleolus  and  showing,  like  many  other  ganglion  cells  of  the 
central  nervous  system,  typical  NissI  bodies  and  a  fibrillar  structure.  Near  the 
macular  region,  the  ganglion  cells  are  smaller  but  more  numerous  and  arranged  as 
several  superimposed  layers;  toward  the  ora  serrata,  on  the  contrary,  the  individual 


Visual  cells  Irom  human  ret- 
ina, A,  cone.€c11;  B,  rodH-t;U,  tj, 
b,  outer  and  inner  segments ;  c, 
attenuated  bodies  (Ahres).  with 
nucleus  [d)  and  central  ends  («*); 
em,  position  of  external  limiting 
membrane.    X  750.    (Grteff.) 


1466 


HUMAN  ANATOMY. 


Fig.  1232. 


cells  are  .separated  by  considerable  intervals.  Their  axones,  or  a.xis-cylinder  pro- 
cesses, pass  inward  and  become  the  nerve-fibres  of  the  fibr  layer.  Converging  toward 
the  optic  entrance,  they  become  consolidated  into  the  optic  nerve  and  pass  to  the 
brain.    The  dendrites  of  the  ganglion  cells,  one  to  three  in  number,  run  outward  into 

the  inner  plexiform  layer  and  end  as  richly  branched 
arborizations.  These,  like  those  of  the  amacrine  cells, 
terminate  either  difiusely,  or  in  horizontal  ramifica- 
tions limited  to  definite  strata,  in  connection  with  the 
centrally  directed  processes  from  the  bipolar  cells. 

The  nerve-nbre  layer  is  composed  silmost 
entirely,  but  not  exclusively,  of  the  axones  of  the 
ganglion  cells  of  the  preceding  layer.  The  individual 
fibres,  from  .005-.  05  mm.  in  diameter,  are  collected 
into  bundles  of  varying  size,  which  take  a  horizi  'ntal 
course  and  converge  toward  the  optic  disc.  The  are 
normally  devoid  of  medullary  sheaths,  but  acquire 
them  after  passing  through  the  lamina  cribrosa  of  the 
sclera.  A  few  of  the  fibres  are  centrifugal,  arising 
from  ganglion  cells  within  the  brain,  and  terminate 
apparently  in  connection  with  the  association  amacrines 
of  the  inner  nuclear  layer. 

In  the  macular  region,  the  nerve-fibres  are  prac- 
tically absent,  those  from  the  retinal  area  lying  direcriy 
to  the  temporal  side  of  the  macula  arching  above 
and  below  the  yellow  spot.  From  the  macula  itself, 
a  special  strand,  known  as  the  maculo-papillary  bundle 
and  composed  of  about  twenty-five  fasciculi,  passes 
directly  to  the  nerve-disc. 

The  suBtentacular  tissue,  the  neuroglia  of  the 
retina,  exists  in  two  forms — as  \}as.  fibres  0/ Miiller  and 
as  the  spider  cells. 

The  fibres  of  Miiller  are  modified  neuroglia 
fibres  which  pass  vertically  from  the  inner  surface  of 
the  retina  through  the  succeeding  layers  as  far  as  the 
bases  of  the  rods  and  cones  (Fig.  1222).  The  inner 
extremities  of  the  fibres  possess  conical  expansions, 
which  are  in  apposition  and  form  an  incomplete  sheet, 
known  as  the  membrana  limitans  interna.  As  the  fibres  traverse  the  retmal  layers, 
they  give  off  delicate  lateral  oflEshoots,  which  break  up  into  a  fine  supjxjrting  reticu- 
lum. Within  the  inner  nuclear  layer  each  fibre  presents  a  broad  expansion,  in  which 
is  situated  the  oval  nucleus  of  the  sustentacular  cell,  the  fibre  of  Miiller.  After 
traversing  the  outer  nuclear  layer  their  broadened  peripheral  ends  come  into  contact 
and  form  a  continuous  sheet,  the  membrana  limitans  externa.  From  the  latter  deli- 
cate offshoots  continue  outward  and  embrace  the  bases  of  the  individual  rods  and 
cr  ,es.  In  addition  to  the  robust  fibres  of  Muller,  neuroglia  cells,  in  the  form  of 
spider  cells,  are  found  in  the  nerve-fibre  and  ganglion  cell  layers.  These  cells  send 
out  long  delicate  processes  which  extend  between  the  processes  and  cells  and  thus 
help  to  support  them. 

The  Macula  Lutea. — The  structure  of  the  retina  undergoes  important  modifi- 
cations in  two  areas,  at  the  macula  lutea  and  at  the  ora  serrata.  In  the  former  the 
ganglion  cells  increase  rapidly  in  number  as  the  macula  is  reached,  so  that  instead 
of  forming  a  single  layer  they  are  distributed  in  from  eight  to  ten  strata.  The  inner 
nuclear  layer  is  also  increased  in  thickness.  Within  the  fovea  centralis,  however, 
in  order  to  reduce  to  a  minimum  the  layers  traversed  by  the  light-rays,  the  cerebral 
layers  are  almost  entirely  displaced,  only  the  absolutely  essential  retinal  strata — the 
pigment  cells  and  the  visual  cells  with  their  necessary  connections — being  retained 
within  the  area  of  sharpest  vision  (Fig.  1223).  On  approaching  the  fovea,  the 
ganglion  cells  rapidly  decrease  in  number,  until  at  the  centre  of  the  depression,  they 
are  entirely  absent  and  the  ner\'e-fibre  layer,  therefore,  disappears.     The  bipolar 


Supporting  fibres  of  Muller  from 
retina     of     ox;     Golei     preparation. 


THE  NERVOUS  TUNIC. 


1467 


cells  are  present  as  an  irregular  layer  within  the  fused  remains  of  the  two  plexiiurni 
layers.  The  most  conspicuous  elements  are  the  visual  cells,  which  in  this  position  are 
represented  solely  by  the  cones,  which  have  about  twice  their  usual  length  and 
thickness,  the  increase  in  length  being  contributed  by  the  outer  segments.  The 
cone-cell  nuclei  become  removed  from  the  external  limiting  membrane ;  the  cone- 
fibres  are  therefore  lengthened,  pursue  a  radial  direction,  and  constitute  the  so-callctl 


Iiilcrnal  limiting 
membrane 


Inner  plexiform  layer 

Ganglion  cells 


Bipolar  cells        Outer       Pigmented    Cone        Cones 
plesiform  layer     layer     visual  cells 

Section  of  human  retina  through  fovea  centralis.    ^  Ho. 

fibre-layer  of  Henle.  Opposite  the  centre  of  the  fovea,  the  choroid  is  thickcneil  by 
an  increase  in  the  choriocapillaris.  The  yellow  color  of  the  macula  is  diie  to  a 
diffuse  coloration  of  the  inner  retinal  layers. 

The  Ora  Serrata. — The  visual  part  of  the  retina  ends  anteriorly  in  an  irregu- 
lar line,  the  ora  serrata.  Within  a  zone  of  about  i  mm.  in  width,  the  retina  dimin- 
ishes in  thickness  from  .50  to  .15  mm.,  in  consequence  of  the  abrupt  disappearance 
of  its  nervous  elements.  The  rods  disappear  first ;  then  the  cones  become  rudimen- 
tary, and  finally  cease  ;  the  ganglion  cells,  nerve-fibre  layer  and  inner  plexiform  layor 
fuse,  and  the  two  nuclear  layers  unite  and  lose  their  characteristics,  most  of  the 
nuclei  present  being  those  of  the  supporting  fibres  of  Miiller,  which  are  here  highly 
developed.    These  elements  p^^    ^ 

continue  beyond  the  ora 
serrata  (Fig.  1224)  as  the 
transparent  cylindrical  cells 
composing  the  inner  layer  of 
the  pars  ciliaris  retinte,  the 
densely  pigmented  cells  of 
the  outer  layer  being  a  direct 
continuation  of  the  retinal 
pigmented  cells.  These  two 
strata  of  cells  are  prolonged 
over  the  ciliary  body  and  the 
iris  as  far  as  the  pupillary  margin,  over  the  iris  constituting  the  pars  iridica  reiinie. 
As  the  columnar  cells  pass  forward,  they  gradually  decrease  in  height,  and  at  the 
junction  of  the  ciliary  body  and  the  iris  the  cells  of  both  layers  become  deeply  pig- 
mented, with  consequent  masking  of  the  boundaries  of  the  individual  elements. 
The  cells  of  the  anterior  layer  are  of  additional  interest  as  gi\  ing  rise  to  the  dilatator 
muscle  of  the  iris. 

The  aggregation  incident  to  the  convergence  of  the  nerve-fibres  from  all  parts  of 
the  retina  produces  a  marked  thickening  of  the  fibre-layer  around  the  optic  disc, 
and  as  the  fibres  turn  outward  to  form  the  optic  nerve  the  other  layers  of  the  retina, 
together  with  those  of  the  choroid,  suddenly  cease.  On  the  temporal  side  a 
narrow  meshwork  of  intermediate  tissue  separates  the  nerve-fibres  from  the  other 
retinal  strat  but  at  the  nasal  side  this  tissue  is  absent.  The  ganglion  cells  dis- 
appear first  whilst  the  pigmented  cells,  with  the  lamina  vitrea  of  the  choroid, 
extend  furthest  inward. 

The  blood-vessels  of  the  retina  are  deri"'a  from  .-  single  artery,  the  arleria 
centralis  retina,  which  enters  the  optic  nerve  at  a  point  from  15-20  mm.  behind 
the  eveball,  and,  with  its  accompanying  vein,  runs  in  the  axis  of  the  nerve  and 


IHpoluceUt' 


VlsiuU  cellsi 


Pitfilienlfd  ,jm 
Layer 

Section  of  human  retina  through  ora  serrata.  showing  transition  of  pars 
optica  into  pars  ciliaris.    x  165 


1468 


HUMAN  ANATOMY. 


emerges  slightly  to  the  nasal  side  of  the  centre  of  the  optic  disc.  Here  the  artery 
divides  into  two  main  stems  (Fig.  1225),  the  superiorand  inferior  papillary  branches, 
each  of  which  subdivides  at  or  near  the  disc-margin  into  superior  and  inferior 
nasal  and  temporal  branches  which  run  respectively  mesially  and  laterally,  dividing 
dichotomously  as  end  arteries,  no  anastomosis  existing.  The  macular  region  is 
supplied  by  special  macular  branches,  the  center  of  the  fovea,  however,  being  free 
from  blood-vessels.  The  larger  branches  from  the  central  artery  course  within  the 
nerve-fibre  layer,  and  send  fine  twigs  peripherally  inward  to  form  an  inner  and  an 
outer  plexus,  the  former  on  the  outer  surface  of  the  inner  plexiform  layer,  and  the 
latter  within  the  inner  nuclear  layer.  Beyond  the  outer  plexiform  layer  the  vessels 
do  not  penetrate,  the  visual  cells  being  dependent  for  their  nourishment  upon  the 
choriocapillaris  of  the  choroid.  At  the  nerve  entrance  an  indirect  communication 
exists  between  the  arteria  centralis  and  the  posterior  ciliary  arteries,  through  the 
medium  of  the  small  branches  which  constitute  the  circulus  arteriosus  Zinni. 

Fig.  laas. 


I'eniporHl 


-Vusal 


Normal  fundus  of  right  eye  as  seen  with  ophthalmoscope ;  central  retinal  vessels  seen  emerxing  from  optic 
aerve;  arteries  are  lighter,  veins  darker  vessels;  fovea  centralis  shows  as  light  point  in  macular  region,  which 
lies  in  temporal  field  and  is  devoid  of  large  vessels. 

The  l)nnphatics  of  the  retina  are  represented  chiefly  by  the  perivascular  lym- 
phatic spaces  which  surround  all  the  veins  and  capillary  blood-vessels.  These  spaces 
may  be  injected  from  the  subpial  lymph-space  of  the  optic  ner\'e,  and  by  the  same 
method  communications  may  be  demonstrated  between  (i)  this  space  and  the 
interstices  between  the  nerve  bundles  which  converge  toward  the  optic  papilla, 
( 2 )  a  space  between  the  membrana  limitans  interna  and  the  hyaloid  membrane  of 
the  vitreous,  and  (3)  a  narrow  cleft  between  the  pigmented  cells  and  the  layer  of 
rods  and  cones. 

Practical  Considerations. — All  pathological  conditions  of  the  retina  ap- 
pear as  opacities,  and  thus  interfere  with  sight.  The  medullary  sheaths  of  the  optic 
nerve-fibres  end  at  the  lamina  cribrosa.  Rarely  the  sheaths  around  these  may 
extend  some  distance  into  the  retina,  showing  as  a  white  striated  margin  around 
the  optic  disc  and  continuous  with  it.  Sometimes  the  blood-vejascls  of  the  retina 
may  enter  at  the  margins  of  the  optic  disc,  instead  of  at  its  centre,  as  usual,  which 
IS  then  free  of  vessels  and  very  pale.  At  the  entrance  of  the  optic  nerve,  the 
fiinsparency  of  the  retina  is  lessened  by  the  thickening  of   its   fibre-layer 


PRACTICAL   CONSIDERATIONS:    THK   RETINA. 


1469 


The  integrity  of  the  central  artery  of  the  retina  is  necessary  to  the  preservation 
of  sight.  The  branches  of  this  vessel  are  distributed  to  the  retina  only,  and  have 
no  communication  with  those  of  the  other  coats,  nor  do  they  anastomose  with  one 
another.  If  the  main  artery  or  one  of  its  branches  is  plugged  with  an  embolus,  the 
area  supplied  by  the  blocked  vessel  is  then  deprived  of  sight. 

The  retina  may  undergo  inHammatory  change  in  nephritis,  syphilis,  diabetes, 
and  other  constitutional  diseases.  Of  all  these  inriammations  of  the  retina,  that  tlue 
to  kidney  disease  (albuminuric  retinitis)  is  the  most  characteristic.  Besides  the 
signs  of  general  intiammation,  as  haziness  of  the  retina,  choked  disc,  distended 
retinal  arteries,  or  hemorrhages  into  the  retina,  pure  white  or  even  silvery  patches 
often  occur  ;  they  are  due  to  fatty  degeneration.  Retinitis  without  these  charac- 
teristic changes  may  occur  from  albuminuria,  so  that  the  urine  should  be  examined  in 
all  cases  of  retinitis. 

The  retina  between  the  optic  nerve  and  the  ora  serrata  is  held  in  apposition  to 
the  choroid  only  by  the  support  afforded  by  the  vitreous  body.  It  may  be  readily 
detached  from  the  choroid  by  such  causes  as  injury,  e.xtravasaiion  of  blood  or 
serum  between  the  two  layers,  or  by  tumors  of  the  choroid. 

In  contusions  of  the  eye  the  retina  is  sometimes  torn  alone,  although  this  is 
rare.  The  retina  does  not  tear  as  easily  as  the  choroid,  as  is  shown  by  the  fact  that 
in  ruptures  of  the  choroid  the  retina  is  generally  not  lacerated. 

Glioma  is  the  only  tumor  found  in  the  retina,  and  occurs  exclusively  in  children, 
usually  under  three  years  of  age. 

A  rare  tumor  arising  from  the  pars  ciliaris  retinse  has  been  described,  to  which 
the  name  teralo-tieuroma  has  l)een  applied  by  Verhoeff. 

The  Optic  Nerve. — The  extraocular  portion  of  the  optic  nerve  has  been  de- 
scribed elsewhere  (page  1 223).    Likewise,  the  three  sheaths — the  dural,  the  arachnoid 


Fig.  1226. 

Phyaiologicml  cxca%-ation 


Lamina  cribroMa 


Fibre-layer ^^-j^Jr  .j; 


Subarachnoid  AfMce 
Subdural  space 


Pial  aheath 


Central  retinal  veaaela  within  optic  nerve 
Section  d  eyeball  through  entrance  of  optic  nerve.    X  ». 

and  the  pial — which,  with  the  subdural  and  the  subarachnoid  lymph-spaces,  are  con- 
tinued over  the  nerve  as  prolongations  of  the  corresponding  brain-membranes  (page 
949).  On  reaching  the  eyeball,  the  dural  sheath  bends  directly  outward,  its  fibres 
commingling  with  those  of  the  outer  third  of  the  sclera  (Fig.  1226)  ;  the  arachnoid 
ends  abruptly  on  the  inner  wall  of  the  intervaginal  space ;  whilst  the  pia  arches 
outward  to  form  part  of  the  inner  third  of  the  sclera,  but  sends  longitudinal  fibres  as 
far  as  the  choroid.  As  the  nerve-fibres  enter  the  eyeball,  for  convenience  assuming 
that  they  are  passing  from  the  brain  toward  the  retina,  they  traverse  a  fenestrated 


I470 


HUMAN  ANATOMY. 


Bkmd-vraicl 


Bundini  '*f 
nrr\x-librr> 


IntFTfaadaiter 
connective  liMue 


TtamverK  Mction  o{  part  of  oMic  nerve.  ahowin(  Mvcnl  taKkuli  of 
nerve-nbrei.    X  125. 


membrane,  the  lamina  cribroaa.  which  is  formed  by  interkcinu  bundles  from  the 
inner  third  of  the  sclera  and  from  the  pial  sheath.  As  they  penetrate  the  lamina 
cribrosii  they  lose  their  medullary  sheaths  ;  in  consequence  the  optic  nerve  is 
reduced  one  third  in  diameter.     The  intervaginal  lymph-space  ends  abruptly,  bemg 

separated  from  the  choroid 
Fio.  1 217.  by  the  fibres  of  the  pia  which 

arch  outward  to  join  the 
sclera.  The  nerve  projects 
slightly  into  the  eyeball  on 
account  of  the  thickness  of 
the  layer  of  arching  nerve- 
fibres  and  forms,  therefore, 
a  circular  elevation,  known 
as  the  optic  papilla  or 
optic  diac,  about  1.5  mm. 
in  diameter,  the  center  of 
which  is  occupied  by  a  fun- 
nel-shaped depression,  the 
so-called  physiological  exca- 
vation. The  axis  of  the  nerve 
is  occupied  by  the  central 
artery  of  the  retina,  which 
gives  off  minute  branches  for 
the  nutrition  of  the  nerve, 
that  anastomose  with  the 
pial  vessels,  and,  through  the  circulus  arteriosus  Zinni,  with  branches  of  the  posterior 
ciliary  arteries.  When  seen  in  transverse  sections  (Fig.  1227).  'he  optic  ner\e 
appears  as  a  mosaic  of  irregula/  polygonal  areas  composed  of  bundles  of  medullated 
nerve-fibres  surrounded  by  connective  tissue  envelopes.  Although  provided  with 
medullary  sheaths,  the  optic  fibres  are  devoid  of  a  neurilemma,  in  this  respect 
agreeing  with  the  nerve-fibres  composing  the  central  nervous  system.  The  entire 
nerve  corresponds  to  a  huge  funiculus,  the  perineurium  being  represented  by  the 
pial  sheath,  and  the  endoneurium  by  the  interfascicular  septa  of  connective  tissue 
prolonged  from  the  pia  between  the  bundles  of  fibres.  Numerous  connective 
tissue  cells  occur  along  the  strands  of  fibrous  tissue. 

Practical  Considerations.  Any  disturbance  of  the  optic  nerve-fibres  passing 
from  the  retina  to  the  cortex  of  the  brain  (page  1225)  will  cause  disturbance  of 
vision,  and  within  certain  limits  the  lesion  may  be  localized  by  the  character  of 
the  symptoms  produced. 

The  most  characteristic  symptom  from  a  lesion  on  one  side  '  ^  the  chiasm 
is  a  homonymous  lateral  hemianopsia, — that  is,  the  right  or  the  le.  ich  eye  will 

be  blind.  This  is  explained  by  the  fact  that  the  optic  tracts  a.  .  up  of  fibres 
coming  from  the  corresponding  lateral  halves  of  both  retinae, — ....,  the  fibres  from 
the  right  half  of  each  retina  pass  to  and  make  up  the  right  optic  tract,  and  pass 
therefore  to  the  right  half  of  the  brain.  It  will  thus  be  seen  that  anything  com- 
pressing the  optic  fibres  of  the  right  side  behind  the  chiasm,  for  instance  a  hemorrhage, 
would  produce  a  blindness — more  or  less  complete  according  to  the  extent  of  the 
fibres  involved — of  the  right  half  of  each  eye. 

Since  most  of  the  optic  fibres  enter  the  lateral  geniculate  bodies,  a  lesion  there 
always  causf-5  hemianopsia,  or  half-eye  blindness.  Lesions  of  the  optic  thalamus, 
or  of  the  superior  quadrigeminal  body,  may  also  by  compression  of  the  adjacent 
optic  tract  produce  hemianopsia. 

In  the  optic  radiation  are  other  than  optic  fibres,  so  that  hemianopsia  may  or 
may  not  follow  lesions  in  that  tract,  according  to  whether  optic  fibres  are  involved 
or  not.  The  exact  course  of  the  visual  fibres  in  the  optic  radiation  is  uncertain. 
If  the  visual  area  of  the  brain  cortex  is  involved  by  the  lesions,  no  other  symptoms 
will  be  present,  but  the  hemianopsia  will  be  complete  and  homonymous — that  is,  the 
corresponding  halves  of  the  two  eyes  will  be  blind. 


THE  CRYSTALLINE  LENS 


I47« 


-n()u> 
'he  • 


•he 
ht'inui ' 


nostitis 

'•ssure 

half 

Ma). 
this 


nee 


«t,  u-     distun 

lit'  blH"ltM.'ss  >'l      le 

-that  I     ol  « he  opiit  A.- 


^cope 
arkfd  ' 
.s\»ollci, 
Aol  "di. 


ii. 


i  .Hidition  ro 

.1     j»r«tnides 

li.i*.      iwc  urt'- 

'>ptiv  rHiintis. 

Ilv  No  per 

Vpend 

»,*»   ol    the 

.«{ th*-  brain. 

.-.urh     irciim- 

on  \\y.  whole, 

v-eption, 

-f        has  no 

thr    various 

\\  t!  c  form  of 


If  the  lesion  affect  the  chiasm,  as  from  tumor;!  of  ti  try  fNxly. 

d  the  body  of  the  sphenoid  bone,  tuberculous  or  sypli.  iiv,  •-  uMJn 

on  the  mesial  portion  of  the  chiasm  involving  the  decu 
of  each  eye  supplied  by  these  fibres  will  be  blind  (h 
Since  the  nasal  half  of  each  eye  perceives  the  temporal 
variety  ot  half-blindness  is  called  bitemporal kemianopiir 

If  the  optic  fibres  of  one  side  in  front  of  the  chiasn 
of  vision  will  affect  one  eye  only,  so  that  the  occurreno 
eye,  without  other  ktiown  cause,  with  good  sight  in  the 
in  front  of  the  chiasm. 

Inflammation  of  the  intraocular  end  of  the  optic  m 
or  papilla— ^\\ei  rise  to  the  condition  to  which  the  nar- 
is  applied,  which  is  then  recognizable  with  the  ophth 
or  independently  of  the  signs  of  inflammation  there  are 
and  the  evidence  of  mechanical  compression,  so  that  t! 
into  the  vitreous-  beyond  ^  to  ^  mm.,  the  phenomc 
sent.     This  variety  of  papillitis,  as  well  as  more  mo< 
constitutes  one  of  the  important  symptoms  of  brain       a 
cent,  of  the  cases.     The  development  of  the  papilbuK  dot 
upon  the  size  of    the  growth,  nor  upon  its  situ    -  -•n,  ex' 
medulla  are  less  apt  to  originate  optic  neuritis  th.       iiose  ii 
Usually  a  bilateral  condition,   it    is  sometimes  un.  ateral,  dei 

stances  it  suggests  that  the  cerebrum  is  the  seat  o!  the  grow  is. 

in  favor  of  the  tumor  being  on  the  same  side  as  the  neuriti- 
however,  optic  neuritis,  although  an  important  symptom 
localizing  significance.     Other  intracranial  causes  of  optic  ii'  u 
types  of  meningitis  (when  the  ophthalmoscopic  picture  oft'  •'  ^y^, 
the  so-called  "descending  nearitis  "  ),  abscess  and  soft- 
ening of  the  brain,  cerebritis,  hydrocephalus  and  aneu-  •^■c-.  ijjii. 
rism.  In  addition  to  the  intracranial  causes  of  papillitis, 
this  phenomenon  may  arise  from  a  general  infection — 
for  example,  influenza,  syphilis,  rheumatism,  smaU-pox, 
etc. — and  is  then   known  as  infectious  optic  neuritis. 
It  is  also  caused  by  various  toxic  agents,  by  anaemia,  by 
menstrual  disturbances,  nephritis,  and  other  constitu- 
tional disorders  (de  Schweinitz). 

Injuries  of  the  optic  nerve  are  most  frequently  the 
result  of  fractures  of  the  base  of  the  skull  at  the  optic 
foramen,  the  nerve  being  injured  by  the  fragments. 
It  may  be  wounded  by  foreign  bodies  entering  the  orbit, 
with  or  without  injury  of  the  eyeball. 

The  Crystalline  Lens. 


The  lens,  the  most  important  part  of  the  refractive 
apparatus  of  the  eye,  is  a  biconvex  body  situated  on  a 
level  with  the  anterior  plane  of  the  ciliary  body,  from 
which  it  is  suspended  by  the  suspensory  lif^ament,  or 
zonule  of  Zinn.  Its  anterior  surface  supports  the  pu- 
pillar>-  margin  of  the  iris,  and  its  posterior  surface  rests 
m  a  depression,  the  patellar  fossa,  on  the  anterior  sur- 
face of  the  vitreous  body.  It  is  completely  transparent  and  enclosed  in  a  transparent 
elastic  membrane,  the  lens  capsule.  Together  with  the  capsule,  the  lens  measures 
from  9-IO  mm.  in  its  transverse  diameter,  and  about  4  mm.  in  thickness  from  pole 
to  pole.  The  convexity  of  its  two  surfaces  is  not  the  same,  that  of  the  posterior 
being  greater  than  that  of  the  anterior.  Neither  are  these  convexities  constant,  since 
they  &re  continually  changing  with  the  variations  in  lens-[X)wer  incident  to  viewing 
distant  or  near  objects.  The  radius  of  curvature  of  the  anterior  surface  is  approxi- 
mately 9  mm.  and  that  of  the  posterior  surface  6  mm.  when  the  eye  is  accommodated 


Meridional  lection  of  human  lens 
and  its  cafMule;  anterior  epithelium 
and  transitional  sonc  are  seen,  v  7- 
(Babuchin.) 


'472 


HUMAN  ANATOMY. 


Fio. 


FracnicnU  of  iaoUicd  l«»-flbrM;  A.  from 
superficial  laycri;  B.  fiom  dL'cpcr  laycni  C, 
young  fibres  with  nuclei.    X  275. 


for  disUnt  objects ;  these  radii  are  reduced  to  about  6  and  5  mm.  respectively  in 
accninmodation  for  near  objects.  The  anterior  surface  is  therefore  more  afft-ctwl  in 
the  act  of  accommodation,  the  lens  becomes  more  convex  and  its  aniero-posterior 
diameter  increases  from  4  to  4.4  mm.  The  superficial  portion  of  the  lens  beneath 
the  capsule  is  compf)sed  of  soft  c«>mpres8ible  material,  the  substantia  (ortUalis ;  the 
consistency  gradually  increases  toward  the  centre,  especially  in  later  life,  so  that  the 
central  portion,  the  hmcUhs  lentis,  is  much  firmer  and  dryer. 

The  atructure  of  the  lens  includes  the  capsule  and  its  epithelium  and  the  lens 
subsunce.  The  capsule,  which  entirely  surrounds  the  lens,  is  a  transparent,  struc- 
tureless, highly  elastic  membrane,  which,  while 
resistent  to  chemical  reajjents,  cuts  easily  and 
then  rolls  outward.  It  is  thickest  on  the  anterior 
surface,  where  it  measures  from  .010-.015  mm., 
and  thinnest  at  the  posterior  pole  (.005-. 007 
mm. ).  In  the  adult  the  lens  b  devoid  of  Uood- 
vessels,  but  during  a  part  of  fcetal  life  it  is 
surrounded  by  a  vascular  net-work,  the  tunica 
vascuiosa  lentis,  which  is  supplied  chiefly  by  the 
hyaloid  artery.  This  temporary  vessel  is  the 
terminal  branch  of  the  central  artery  of  the  r  ina 
and  passes  from  the  optic  disc  forward  thr  ...j^h 
the  hyaloid  canal  or  canal  of  Cloquet  in  the  vit- 
reous to  the  posterior  surface  of  the  lens.  The 
vascular  lens  tunic  and  the  hyaloid  artery  are 
temporary  structures  and  usually  disappea  be- 
fore birth.  Exceptionally  they  may  persist, 
the  tunic  being  rfnresented  by  the  pupillary 
membrane  and  the  artery  by  a  fibrous  strand  within  a.d  vitreous,  stretchmg  from 
the  optic  disc  towards  the  lens.  The  capsule  probably  represents  an  exudation 
product  t\  the  cuticular  elemedts  from  which  the  lens- 
substance  is  developed. 

The  anterior  portion  of  the  capsule  is  lined  by  a  sin- 
gle layer  of  flat  polygonal  cells,  the  epithelium  of  the  lens 
capsule,  which  represents  morphologically  the  anterior 
wall  of  the  original  lens-vesicle  (page  1480).  On  ap- 
proaching the  equator  of  the  lens,  these  cells  become 
elongated,  and  gradually  converted  into  the  young  lens- 
fibres,  the  nuclei  of  which  form  a  curved  line,  with  its 
convexity  forward,  in  the  superficial  part  of  the  lens. 

The  lens-substance  is  composed  of  long  flattened  fibres,  the  cross-sections  of 
which  have  a  compressed  hexagonal  outline,  from  .005-.  01 1  mm.  broad  and  from 

.002-.004   mm.  thick,  held 
Fig.  1231.  together  by  an  interfibrillar 

cement  substance.  These 
fibres  are  modified  epithelial 
elements,  which  develop  by 
the  elongation  of  the  original 
ectoblastic  cells  of  the  poste- 
rior layer  of  the  lens-vesicle. 
The  subsequent  growth  of 
the  lens  depends  upon  a 
similar  modification  of  the 
anterior  capsule-cells,  the  re- 
gion where  this  transforma- 
tion occurs  being  known  as 
the  transitional  zone.  The  individual  lens-fibres  vary  greatly  in  length,  those  form- 
ing the  outer  la-  ■  -^  being  longer  and  thicker  than  those  which  constitute  the  nucleus 
of  the  lens.  T^i  edges  of  the  fibres  are  finely  serrated,  and,  as  the  points  of  the 
serrations  of  a  '-    nt  fibres  are  in  contact,  fine  intercellular  channels  are  left  for  the 


Fig.  IJ30. 


Lens-fibres  seen  in  transverse  section. 
X  s8o. 


Adult  crystalline  lens,  showinic  Iciia-stars;  A,  anterior;  *.  posterior 
surface ;  radiating  lines  of  juncture  meet  at  central  area.    X  4-   (Arnold.) 


THE  VITREOUS  BODY. 


U73 


paatage  of  nutritive  fluid.  The  fibres  are  su  arranged  that  their  ends  terminate  alun^ 
definite  radiating  stria?,  or  /ens-stars,  which  in  the  yuun>;  lens  are  three  in  number 
on  each  surface.     In  the  adul'  lens  additional  rays  incre;u>e  the  number  ti)  from  six  to 


stinct  but  distinguishable  with  the  ophthalmoscope.  The 
I  the  [X)le  of  one  surface  of  the  lens  terminate  at  the  end  of 
I  the  other,  and  conversely ;  the  intervening  fibres  take  up 
In  adult  life  the  lens-fibres  become  more  condensed,  the  lens 
loses  its  clear  ;.  v>arance,  and  assumes  a  yellowish  tint.  This  change  affects  the 
nucleus  first  and  the  periphery  later,  coincidently  the  lens  becoming  less  elastic  as 
the  result  of  its  loss  of  water. 


nine,  the  stri^  bein) 
lens-fibres  which  cf->'- 
one  of  the  ra.'' 
intermediate  [» 


Practical  Contiderationa. — The  lens  may  be  congenitally  absent  (aphakia), 
or  it  may  be  abnormal  in  size,  shape,  position,  or  transparency.  Its  anterior  or 
posterior  surface  may  be  abnormally  convex  (lenticonus).  Congenital  anomalies  of 
position  (ectopia  Icntis)  occur  rarely.  The  lens  may  remain  in  its  fa-tal  position  in 
the  vitreous  chamber,  or  it  may  be  displaced  in  an  equatorial  direction  from  faulty 
development  and  weakness  of  some  part  of  the  suspensory  ligament.  This  weakness 
usually  occurs  below  so  that  the  lens  moves  upward.  The  ligament  may  be  absent  in 
its  whole  circumference,  when  the  lens  may  be  protruded  into  the  anterior  chamber. 

Cohboma  or  parti^  deficiency  of  the  lens  is  very  rare.  It  is  with  comparative 
frequency  associated  with  a  similar  defect  in  the  iris,  ciliary  body  and  choroid,  and, 
like  it,  is  usually  in  the  lower  portion.  A  defect  of  the  corresponding  part  of  the 
suspensor)'  ligament  is  occasionally  present. 

Traumatic  luxation  of  the  lens  may  take  place  into  the  vitreous  or  aqueous 
chamber.  It  may  occur  laterally  through  the  coats  of  the  eyeball  into  the  capsule 
of  Tenon  or  under  the  conjunctiva.     That  into  the  vitreous  is  most  frequent. 

The  capsule  of  the  lens  is  strong  and  elastic.  It  is  at  the  same  time  brittle, 
breaking  like  thin  glass  when  torn  as  by  a  sharp  instrument  For  this  reason  it  is 
sometimes  called  the  vitreous  membrane.  The  anterior  layer  of  the  capsule  is  con- 
siderably thicker  than  the  posterior,  and  is  more  liable  to  pathologic'  changes,  pro- 
ducing  opacities.  Wounds  of  the  capsule  f)ermit  the  aqueous  fluid  lu  reach  the  lens 
fibres,  which  then  become  swollen,  opaque,  and  finally  disappear  from  the  dissolving 
action  of  the  aqueous.  Advantage  of  this  is  taken  in  the  needling  operation  (dis- 
cission )  for  the  removal  of  a  cataract. 

In  chil'* Hi    ''e  'ens  substance  is  of  nearly  equal  consistency  throughout,  but  as 
age  advan  ei  thf. 
the  nude  ■■■      ^^ 
old  age  tit 
are  inte'fe 
reflection 
older  peo,.i' 

A  cai  I) 
much  more  c 


■•la!  portion  becomes  gradually  more  condensed,  and  is  called 

wtr.-!i»?r't-d  nucleus,  however,  does  not  exist  until  adult  life.      In 

L.T!  '')sti:  its  i'Jits'icity  so  that  the  changes  neces-sary  for  accommodation 

.  d  '.V  ith,  and  "^iijjht  :  i  disturljed.      The  hardened  nucleus  permits  a  greater 

li  -it  'iv;n  ••  (.•  (>i  ler  portion,  so  that  the  lens  is  more  readily  seen  in 

a.;-.i  tV  pu;  !l  ii!  es  more  or  less  its  blackness. 

V  is  an  op,vii  V  of  the  lens,  or  its  capsule,  but  that  of  the  lens  is  so 
ii  !ion  tli.i.'  •  !k.  of  the  capsule,  that  by  the  word  cataract  the  lenticular  is 
usually  meant  ■,;!'-;■:>  i^-  iv  .d  is  otherwise  qualified.  All  cataracts  are  at  .sometime 
partial,  and  the  ^  ^ita  according  to  their  location,  anterior  polar  or  capsular, 

posterior  polar  or  capsular,  centnil  or  nuclear,  lamellar,  perinuclear  and  cortical. 
Cataract  occurs  sometimes  in  the  young,  and  is  then  soft ;  that  is,  the  lens  has  no 
nucleus. 

The  ViTREors  Body. 

The  vitreous  body  (corpus  Titreum)  fills  the  space  between  the  lens  and  the 
retina,  being  in  close  contact  with  the  retina  and  acting  as  a  support  to  it  a»  far 
forward  as  the  ora  serrata.  Here  it  becomes  ser""ited  from  the  retina  and  passes  to 
the  posterior  surface  of  the  lens,  presenting  a  ; :  How  depression,  the  fossa  hya- 
loidea  or  patellar  fossa,  on  its  anterior  sur&ce  for  the  reception  of  the  lens.  The 
fresh  vitreous  is  a  semifluid,  perfectly  transparent  mass  which  const  ^s  of  about  98. 5 
per  cent,  of  water. 

The  structure  of  the  vitreous  has  been  a  subject  of  protracted  dispute,  but 
recent  investigations  have  established  beyond  question  that  it  possesses  a  framework, 

93 


>474 


HUMAN   ANATOMY. 


Portion  of  adult  vitreous  body,  showinf?  felt-work  of  fibres 
and  atrophic  traces  of  cells.    X  450.    (Retzims.) 


composed  of  delicate,  apparently  unbranched  fibrils,  which  pass  in  all  directions 
through  the  vitreous  space  and  form  the  meshes  in  which  the  fluid  constituents  of 
the  mass  are  held.  The  surface  of  the  vitreous  is  enclosed  by  a  delicate  boundary 
layer,  called  the  hyaloid  membrane,  formed  by  condensations  of  the  fibrils, 
which  are  here  arranged  parallel  to  the  surface,  and  closely  felted.      It  is,  however, 

not  a  true  membrane,  but  only  a  con- 
FiG.  1J32.  densation  of  the  vitreous  fibres.     The 

vitreous  is  attached  firmly  to  the  retina 
at  the  nerve  entrance  and  at  the  ora 
serrata,  iK'tween  these  points  the  hya- 
loid being  indistinct.  As  the  vitreous 
leaves  the  retina,  the  Ixjundary  layer 
becomes  thicker,  in  some  cases  to  lie- 
come  thin  again  or  absent  in  the  region 
of  the  patellar  fossa. 

The  central  part  of  the  vitreous  is 
occupied  by  a  channel,  the  hyaloid 
canal,  also  known  as  the  canal  of  Stil- 
ling or  the  canal  of  Cloqiiet,  which  is 
about  one  millimeter  wide  and  extends 
from  the  optic  entrance  toward  the  pos- 
terior pole  of  the  lens.  During  fcetal 
life  this  canal  lodges  the  arieria  hya- 
loidea,  the  continuation  of  the  central 
artery  of  the  retina,  which  passes  to 
the  lens  and  assists  in  forming  the  embryonal  vascular  envelope  surrounding  the  lens. 
Usually  the  embryonal  connective  tissue,  together  with  the  blood-vessel,  disappears  ; 
occasionally,  however,  delicate  remnants  of  this  tissue  can  be  detected. 

The  normal  adult  vitreous  ordinarily  contains  no  cells,  but  some  are  occasionally 
seen  near  the  surface,  beneath  or  on  the  hyaloid  membrane.  They  are  amicboid, 
often  contain  vacuoles  and  are  to  be  considered  as  modified  leucocytes.  In  addition 
a  few  branched  connective-tissue  cells  may  be  present. 

Practical  Considerations. — Congential  abnormalities  of  the  vitreous  are  due 
either  to  a  persistence  of  some  part  of  its  foetal  vascular  apparatus  or  to  an  atypical 
development  of  the  tissue  from  w  hich  it  is  formed.  The  remains  of  these  structures 
may  occasionally  be  seen  as  a  filamentous  band,  free  at  one  end,  which  floats  in  the 
vitreous,  the  other  end  being  attached  to  the  optic  disc  behind,  or  the  posterior  sur- 
face of  the  lens  in  front.  The  strand  may  be  attached  at  both  ends,  with  or  without 
a  patent  arterj-.  Small  rounded  gray  bodies,  apparendy  cystic  and  attached  to  the 
disc,  are  occasionally  seen.  They  are  in  some  way  the  remains  of  the  foetal  vascular 
ap])aratus.  The  congenital  opacities  sometimes  seen  at  the  posterior  pole  of  the  lens 
are  probably  derived  from  the  posterior  fibro-vascular  sheath  of  the  lens.  Materials 
from  the  blood  are  readily  absorbetl  by  the  vitreous,  as  the  bile  in  jaundice. 

Miiscee  volitantes  are  the  flocculi,  seen  liy  the  patient  as  black  spots  be- 
fore the  eyes,  and  are  sometimes  made  up  of  inflammatory  e.xudate  from  inflam- 
mation of  the  internal  or  middle  coat  of  the  eye.  They  may  be  due  to  blood  from 
traumatic  or  s|X)ntaneous  hemorrhage  into  the  \itreous.  Musca*  \-olitantcs  arc  often 
seen  independently  of  any  vitreous  disease  and  are  due  to  the  shadows  thrown  upon 
the  retina  by  naturally  formed  elements  in  the  vitreous  body,  perhaps  the  remains 
of  embryonic  tissue.  Some  of  the  vitreous  may  be  lost  and  rapidly  replaced  with- 
out seriously  disturbing  sight.  In  the  removal  of  cataract,  the  suspensory  ligament 
may  lie  diviikxl  and  an  embarra.ssing  loss  of  vitreous  may  result. 

.•\  foreign  body  in  the  vitreous  chamber  generally  gi\es  rise  to  a  serious  inflam- 
mation, which  may  destroy  the  eye.  If  loose,  it  tencls  by  gravity  to  settle  in  the 
lower  portion,  and  usually  rests  on  the  posterior  part  of  the  ciliary  Ixidy  ( T.  Collins). 
Rarely,  in  the  absence  of  infection,  it  has  remained  for  years  without  setting  up 
inflammation.  The  rule  is,  hi.wever,  to  remf)ve  them,  when  recent,  as  early  as 
possible,  as  inflammation  may  set  in  at  any  time.     In  most  cases  the  foreign  body 


SUSPENSORY  APPARATUS  OF  THE  LENS. 


'475 


Cornea 
Canal  of  Srhlemm, 


can  be  exactly  localized  by  the  X-ray,  and  if  of  iron  or  steel,  may  often  be  removed 
by  a  magnet.  The  accident  is  always  serious  and  may  Ik-  followed  by  a  virulent 
inflammation,  demanding  an  excision  of  the  globe  to  prevent  a  sympathetic  involve- 
ment of  the  other  eye.  Because  of  the  risk  of  infection  and  loss  of  fluid,  operative 
interference  in  the  vitreous  chamber  is  usually  to  be  avoidetl. 

Sympathetic  ophthalmitis y  or  more  accurately,  infective  irido-cycUtis,  or  uveitis, 
is  an  inflammation  of  one  eye,  usually  called  the  "  sympathizer,"  owing  to  injuiy  or 
disease  of  the  fellow  eye,  usually  called  the  "exciter."  Traumatisms  of  the  ciliary 
region  (danger  zone)  which  have  set  up  an  irido-cyclitis  or  uveitis  are  responsible 
for  fully  80  per  cent,  of  the  cases  of  so-called  sympathetic  inflammation.  This 
disease  was  formerly  supposed  to  be  due  to  reflex  action  through  the  ciliary  nerves, 
and  this  theory  in  a  modified  form  is  sti'  .laintained  by  a  few  clinicians.  The  ' '  mi- 
gration theory"  propounded  by  Leber  and  Deutschmann  that  the  inflammation  is  a 
progressive  process  in  the  continuity  of  the  tissue  of  one  eye  to  the  other  by  way 
of  the  optic  nerve  apparatus  and  is  of  bacterial  origin,  has  not  been  proved.  It  is 
believed  by  some  investigators  that  the  bacteria  which  enter  the  primarily  affected 
eye  produce  a  toxin  which  causes  the  disease,  and  by  others  that  it  represents  an 
endogenous  infection  produced  by  invisible  bacteria,  that  is,  that  it  is  a  metastasis 
(de  Schweinitz). 

The  Suspensory  Apparatus  of  the  Lens. 

The  lens  is  held  in  position  by  a  series  of  delicate  bands,  wiiich  pwss  from  the 
vicinity  of  the  ora  serrata  over  the  ciliary  processes  to  be  attached  to  the  [leriphery 
of  the   lens.      These 

fibres  collectively  con-  Fig.  1*33. 

stitute  the  suspen- 
sory ligament,  or 
zonula  of  Zinn,  a 
structure  of  impor- 
tance not  only  for  the 
support  of  the  lens 
but  also  in  assisting 
the  ciliary  muscle  in 
effecting  the  changes 
in  the  curvature  of 
the  lens  incident  to 
accommodation.  The 
zonula  is  not,  as  for- 
merly believed,  a  con- 
tinuous membrane, 
but  is  composed  of  a 
complicated  system 
of  fibres.  The  latter, 
varying  in  thickness 
from  .005-. 022  mm., 
arise  chiefly  from  the 
cuticular  membrane 
covering  the  pars  ciliaris  retina  in  the  vicinity  of  the  ora  serrata.  The  investigations 
of  Retzius,  Salzmann  and  others  indicate  that  some  fibres  arise  also  from  the  mem- 
brana  limitans  interna  of  the  pars  optica  retina,  whilst  others  pass  into  and  end 
within  the  vitreous  body.  The  greater  number  of  the  fibres  pass  forward  chiefly  in 
the  depressions  between  the  ciliary  processes,  and  along  the  sides  of  the  latter,  closely 
applie<l  to  the  surface  ;  they  then  proceed  outward  across  the  circumlental  sjiace  to 
be  attached  to  the  capsule  of  the  lens.  Some  of  the  fibres  are  inserted  anterior  to 
the  equator,  others  posterior  to  the  equator,  and  some  directly  into  the  lers  margin. 
Those  inserted  anteriorly  arise  behind  and  chiefly  from  the  valleys  between  the  ciliary 
processes,  whilst  those  inserted  back  of  the  equator  come  from  the  ciliary  processes 
in  front.  As  they  diverge  to  gain  their  insertion  in  the  lenaea|)Sii!c,  the  ciossiiig 
fibres  enclose  an  annular  space,  triangular  in  section,  whose  base  is  directed  toward 


Meridional  section  of  ciliar>-  reKlon,  showing  ciliary  processes  anil  suspensory 
ligament  of  lens,     v  20. 


1476 


HUMAN  ANATOMY. 


the  lens  equator.  The  fibres  are  so  closely  interlaced  that  it  is  possible  to  inject  air 
between  them  and  so  produce  a  beaded  ring  surrounding  the  lens.  This  appearance 
was  long  interpreted  as  demonstrating  the  presence  of  a  delicate  channel,  the  canal 
of  Petit  encircling  the  lens.  The  existence  of  a  definite  channel,  however,  is  no 
longer  accepted,  the  sj-ace  capable  of  inflation  being  part  of  the  larger  circumlental 
space,  which  is  filled    /ith  fluid  and  communicates,  by  means  of  fine  clefts,  with  the 

posterior  chamber.  t     u-  u 

In  addition  to  the  chief  zonular  fibres,  accessory  bands  occur,  some  of  which 
pass  from  the  ciliary  processes  to  the  long  zonular  fibres,  whilst  others  extehd  from 
point  to  point  on  the  ciliary  processes. 

The  origin  of  the  vitreous  body  and  of  the  suspensor>-  ligament  has  long  been  and  still  is  a 
matter  of  dispute.  The  fact  that  these  structures  are  very  closely  connected,  that  fibres  from  the 
suspensory  ligament  pass  through  the  vitreous,  and,  in  some  cases  at  least,  end  in  that  body, 
renders  it  probable  that  the  two  structures  have  a  common  genesis.  Anatomiste  are  divided, 
however  in  their  views,  some  believing  the  structures  in  question  to  be  denved  from  the 
mesoblast  which  enters  the  choroidal  cleft  with  the  blood-vessels,  whilst  others  assign  to  them 
an  ectoblastic  origin,  either  from  the  lens-vesicle,  or  from  the  retina  (inner  wall  of  the  second- 
ary optic  vesicle).  In  many  of  the  lower  animals  the  vitreous  contains  no  blood-vessels,  and, 
further,  since  the  vitreous  is  formed  without  the  presence  of  embryonal  connective  tissue, 
the  prwumption  is  strong  that  the  vitreous  arises  from  the  retina.  That  the  ectoblast  in  mam- 
mals, however,  is  the  sole  source"  of  the  vitreous  has  not  been  proven ;  moreover,  the  close 
histological  resemblance  of  the  vitreous  to  embryonal  connective  tissue  suggests  with  mu'-h  force 
the  probability  that  the  mesoblast  has  at  least  some  share  in  the  formation  of  thevitrtoi    body. 

The  Aqueous  Humor  and  its  Chamber. 

The  aqueous  humor  is  the  transparent  fluid  which  fills  the  space  between  the 
anterior  surface  of  the  vitreous  body  and  the  posterior  surface  of  the  cornea.  In 
chemical  composition  it  closely  resembles  water,  containing  only  traces  of  albumin 
and  extractives,  and  differing  from  lymph  in  its  low  percentage  of  albumin.  It  is 
produced  chiefly  by  the  blood-vessels  of  the  ciliary  processes,  the  ins  taking  probably 
little  or  no  part  in  the  process.  The  albumin  of  the  blood  is  separated  by  the  action 
of  the  double  layer  of  cells  covering  the  pars  ciliaris  retina,  which  act  either  as  a  filter- 
ing medium  (Leber),  or  as  a  secreting  epithelium  (Treacher  Collins).  The  aque- 
ous humor  is  constantly  being  produced  and  is  carried  off  through  the  spaces  of 
Fontana  into  the  canal  of  Schlemm,  and  also  through  the  lymph-spaces  in  the  ins, 
its  quantity  being  an  important  factor  in  determining  intraocular  tension.  With  the 
exception  of  a  few  migratory  leucocytes,  the  aqueous  humor  is  devoid  of  morpho- 
logical elements.  __  .■••...       u 

The  space  occupied  by  the  aqueous  humor  is  incompletely  subdivided  by  the 
iris  into  two  compartments,  the  anterior  and  posterior  chambers.  The  anterior 
chamber  (camera  ocull  anterior)  is  bounded  in  front  by  the  cornea,  and  behind  by 
the  iris  and  lens,  and  has  a  depth  at  its  centre  of  from  75-8-5  mm.  The  posterior 
chamber  (camera  oculi  posterior)  is  the  small  annular  space,  triangular  m  cross-sec- 
tion, which  has  for  its  anterior  boundary  the  iris,  and  is  limited  laterally  by  the  ciliary 
processes,  and  medially  and  posteriorly  by  the  lens  and  the  vitreous  body.  The 
spaces  betweT  the  fibres  of  the  suspensory  ligament  communicate  with  the  poste- 
rior chamb  ,  are  filled  with  aqueous  humor,  and  are,  therefore,  only  a  part  of  the 
posterior  chamber. 

Practical  Considerations. — When  the  cornea  is  perforated  as  by  a  wound 
or  by  ulceration,  the  aqueous  is  forced  through  the  opening  so  rapidly  that  the  iris 
is  swept  along  by  it,  and  unless  great  care  is  observed  it  will  become  adherent  to  the 
margin  of  the  corneal  opening  (anterior  synechia). 

The  aqueous  humor  is  of  importance  in  the  removal  of  foreign  matter.  Blood 
will  often  lie  removed  in  a  few  days.  Suppuration  of  the  adjacent  tissue  may  lead 
to  the  collection  of  pus  in  the  anterior  chamber  (hypopion).  Hyphaemia  is  a  collec- 
tion .  blood  in  this  chamber,  and  of  itself  is  not  a  grave  condition,  although  it  may 
be  a  sign  of  a  more  serious  disease. 


LACHRYMAL   APPARATUS. 


1477 


Glaucoma  is  a  disease  due  to  excessive  intraocular  tension  which,  u  iless  re- 
lieved, progressively  increases  until  the  eye  is  destroyed,  and  which  almost  always 
involves  the  other  eye.  The  abnormal  tension  is  the  result  of  disturbance  in  the 
outflow  of  the  intraocular  fluid.  This  fluid  is  an  exudation  from  the  blood-vessels  of 
the  ciliary  body.  From  the  posterior  chamber  the  fluid  passes  through  the  pupil  to 
the  anterior  chamber.  It  then  escapes  in  the  angle  formed  by  the  iris  and  cornea 
by  passing  through  the  lym_.h-spaces  in  the  ligamentum  pectinatum  and  by  diffusion 
reaches  the  canal  of  Schlemm.  Thence  it  passes  out  by  the  anterior  ciliary 
veins.  Obstruction  in  the  path  of  this  current  oc-.rs  usually  either  in  the  lymph- 
channels  of  this  region,  or  at  the  pupil  from  adhesion  of  the  whole  pupillary  margin 
to  the  lens,  or  from  occlusion  of  the  pupil  by  inflammatory  exudate,  in  iritis. 

Iridectomy  frequently  gives  relief  in  both  varieties  ;  in  the  former  by  opening 
up  the  lymph-spaces  near  the  corneal  angle  of  the  anterior  chamber,  the  incisions 
being  carried  well  into  this  angle  ;  in  the  latter  by  making  a  new  opening  for  the 
current  between  the  posterior  and  anterior  chambers. 

The  symptoms,  like  the  cause,  may  be  explained  largely  u[>on  an  anatomical 
basis.  The  venae  vorticosae  pass  obliquely  through  the  sclerotic  and  are  therefore 
compressed  and  obstructed  by  the  distension.  Their  blood  is  then  compelled  to 
escape  through  the  anterior  ciliary  veins,  which  penetrate  the  sclerotic  more  at  a 
right  angle,  and  are  consequently  distended.  CEdema  of  the  cornea  results  causing 
a  superficial  haziness.  The  cornea  is  insensitive  from  paralysis  of  the  anterior  ciliary 
nerves.  Usually  the  anterior  chamber  is  shallow  because  the  lens  and  iris  are  pushed 
forward  by  the  obstructed  fluid  behind,  and  the  ciliary  nerves  being  paralyzed  the 
pupil  is  dilated  and  immobile,  giving  a  staring  expression.  The  optic  disc  is  at  first 
hypersemic,  and  is  consequently  markedly  depressed  from  the  intraocular  tension, 
giving  rise  to  one  of  the  most  important  symptoms,  pathological  cupping  of  the  disc, 
or  the  glaucomatous  cup.  The  great  pain  in  glaucoma  is  due  to  compression  of  the 
sensory  nerves  of  the  ciliary  body  and  iris  against  the  unyielding  sclera.  The 
distended  retinal  veins  can  be  seen  through  the  ophthalmoscope. 

A  condition  analogous  to  glaucoma,  hydrophthalmos,  occurs  in  children,  and  is 
either  congenital  or  acquired  very  early  in  life.  Unless  relieved  it  almost  always 
produces  blindness. 

THE   LACHRYMAL  APPARATUS. 

The  lachrymal  apparatus  consists  of  the  gland  secreting  the  tears,  situated  in  the 
anterior  and  outer  portion  of  the  orbital  cavity,  and  the  systenv  of  canals  by  which 
the  tears  are  conveyed  from  the  mesial  portion  of  the  conjunctival  sfic  to  the  inferior 
nasal  meatus. 

The  lachrymal  gland  (glandula  lacrimalis),  resembling  in  shape  and  size  a 
small  almond,  con.ists  of  two  fairly  distinct  parts — the  superior  orbital  portion  and  the 
inimor  palpebral  or  accessory  portion.  The  former  occupies  the  fossa  lacrimalis  in 
the  frontal  bone  and  is  the  larger  portion.  It  mea.sures  20  mm.  in  length,  12  mm. 
in  breadth  and  reaches  from  the  edge  of  the  superior  palpebral  muscle,  along  the 
upper  margin  of  the  orbit  to  the  suture  between  the  frontal  and  malar  bones.  The 
upper  convex  border  is  attached  to  the  periosteum  of  the  fossa  by  means  of  a  number 
of  bundles  of  connective  tissue,  which  are  inserted  into  its  capsule.  Below,  it  rests 
upon  a  fascial  arch,  which  runs  from  the  trochlea  to  the  fronto-malar  s\iture. 

The  lower  or  palpebral  portion  of  the  gland,  glandula  lacrimalis  inferior,  is 
somewhat  smaller  than  the  upj)er  and  separated  from  the  latter  by  the  fascial 
expansion  already  mentioned.  Its  lower  concave  surface  rests  upon  the  fornix  of 
the  conjunctiva,  extending  laterally  almost  to  the  outer  canthus. 

The  ducts  from  both  pun  ions  of  the  gland  are  exceedingly  fine,  those  from  the 
upper  portion,  from  three  to  six  in  number,  passing  downward  through  the  inferior 
portion.  Some  of  the  ducts  from  the  lower  gland  join  those  coming  from  above ; 
others  run  independently,  in  all  about  a  dozen  ducts  opening  into  the  conjunctival 
sac  along  a  line  just  in  front  of  the  fornix.  In  structure  the  glands  correspond  to 
the  tulx)-alveolar  type,  and  resiMnblc  the  serous  glands  in  their  general  rhamrtcr. 
The  acini  of  the  lower  portion  are  separated  by  robust  septa  of  connective  tissue, 
which  contain  considerable  lymphoid  tissue. 


1478 


HUMAN   ANATOMY. 


The  arteries  of  the  gland  are  derived  from  the  lachrymal,  and  the  veins  enij)!  • 
into  the  ophthalmic  vein.  The  nerves  include  sensory  fibres  from  the  lajhrymai 
branch  of  the  ophthalmic,  as  well  as  secretory  fibres  from  the  sympathetic. 

Accessory  lachrymal  glands  Arc  found  in  both  the  upper  and  Icwer  fornices,  from 
eight  to  thirty  being  present  in  the  upper  lid  and  from  two  to  four  in  the  lower. 
They  are  very  small  and  situated  chiefly  near  the  outer  angle  of  the  palpebral  fissure. 


Fig.  IJ34. 


Alveoli 


Ducts 


Beginning  o{  duct 


Section  of  lachrymal  gland,  under  low  magnification,  showing  general  arrangement  of  alveoli.    X  ao. 


Fig.   IJ35. 


The  lachrymal  passages  (  Fig.  1 236)  begin  by  minute  openings,  the  lachrymal 
puncta,  which  are  usually  placed  at  the  summit  of  the  conical  lachrymal  papilla:. 
The  latter  occupy  the  margins  of  the  eyelids,  near  the  mesial  e.xtremity,  at  a  point 

where  the  arched  palpebral  borders  passes  over  into  the 
approximately  horizontal  boundaries  of  the  lachrymal 
lake.  The  upper  punctum  is  situated  6  mm.  from  the 
inner  canthus ;  the  lower  one  is  slightly  larger  and  a 
trifle  farther  removed  from  the  canthus. 

The  puncta  open  into  the  lachrymal  canaliculi, 
which  at  first  are  vertically  directed,  then  bend  abruptly 
icsi^illy  and,  taking  a  nearly  horizontal  course  parallel 
th  the  borders  of  the  lachrymal  lake,  run  as  far  as  the 
ntr  canthus,  ••  1  •■re  they  empty  usually  b\  a  common 
anal  into  the  lai  al  and  slightly  posterior  wall  of  the 
lachrymal  sac.  Occasionally  the  two  canaliculi  do  not 
unite  but  open  separately  into  a  diverticulum  of  the  sac, 
known  as  the  sinus  of  Maier.  Elach  canaliculus  is  from 
8-10  mm.  in  length.  The  lumen  of  the  canal  measures 
only  .  I  mm.  in  diameter  at  the  punctum,  presents  a  diverticulum  I  mm.  in  diameter 
at  the  bend,  anil  continues  with  an  appro.ximately  uniform  calibre  of  .5  mm.  in  its 
horizontal  portion. 

The  Structure  of  the  canaliculi  includes  a  lining  of  stratified  .squamous 
epithelium,  which  rests  upon  a  delicate  tunica  propria  rich  in  elastic  fibres,  muscular 
fibres  from  the  orbicularis  palpebrarum  affording  additional  support.  The  muscle 
bundles  run  parallel  to  the  horizontal  portion  of  the  canaliculi,  but  are  arranged  as  a 
circular  sphincter  about  the  vertical  portion. 

The  lachrymal  sac  (saccus  lacrimalis )  may  be  regarded  as  the  uppt-r  diiaieti 
portion  of  the  naso-lachrymal  duct,  the  lower  part  of  which  passes  through  a  bony 
canal  and  opens  into  the  inferior  nasal  meatus  leneath  the  lower  turbinate  Imne, 


AK-eoli  of  larlir^'mal  gland  more 
liishly  magnified.     X  235. 


PRACTICAL  CONSIDERATIONS  :   LACHRYMAL  APPARATUS.  1479 


Cast  of  tear-psiaa«ces ;  C, 
canaliculi ;  .V,  lachrymal  sac; 
/},  iiaso-lachrymal  duct ;  nat- 
ural size.    {Dii'ight.) 


The  sac  is  about  15  mm.  lonjj,  and  5-6  mm.  in  diameter  when  distended.  It  is 
situated  near  the  inner  canthus  and  lies  within  tlie  deep  lachrymal  jjr<M)\e  Ix'tween 
the  superior  raa.\illar>'  and  the  lachrymal  bone.  Its  dosed  upper  end,  or  /loiifi/s. 
e.\tends  beneath  the  internal  tarsal  ligament  and  some  of  the  fibres  of  the  orbicularis 
palpebrarum,  whilst  its  orbital  surface  is  covered  by  the  fibres  of  the  liUer  muscle, 
which  spring  from  the  lachrymal  bone  and  are  known  as  the  Ifiisor  tarsi  or  Hormr' s 
muscle.  The  lower  end  of  the  sac  narrows  where  it  passes  into  the  nasal  iluct.  The 
wall  is  lined  with  a  tiouble  layer  of  columnar  epithelial  cells,  which  in  part  are 
provided  with  cilia.  It  is  composed  of  libro-elastic  tissue  and  is  loosely  connectetl  with 
the  periosteum. 

The  nasal  or  naso-lachrymal  duct,  the  lower  portion  of  the  tear-jiassage,  is 
situated  within  the  bony  canal  formed  by  the  superior  ma.xiliary,  lachrymal  and  infe- 
rior turbinate  bones.  It  varies  in  length  from  12-24  nmi. .  according  to  the  position 
of  the  lower  opening,  and  is  from  3-4  mm.  in  diameter.  Its 
direction  is  also  subject  to  individual  variation,  but  is  slightly 
backward,  as  well  as  downward,  and  is  usually  indicated  by 
a  line  drawn  from  the  inner  canthus  to  the  anterior  edge  of 
the  first  upper  molar  tooth.  The  duct  opens  into  the  lower 
nasal  meatus,  at  a  point  from  30-.^5  mm.  behind  the  poste- 
rior margin  of  the  anterior  nares.  The  aperture  may  be 
imperfectly  closed  by  a  fold  of  mucous  membrane,  the  so- 
callt?d  valve  of  Hastier  {^Xka  lacrimalis).  The  structure 
of  the  duct  includes  a  lining  of  mucous  membrane  which  is 
clothed  with  columnar  epithelium  and  may  contain  glandular 
tissue  in  the  lower  portion.  The  mucous  membrane  is  sep- 
arated from  the  periosteum  by  areolar  tissue  and  a  venous 
ple.xus ;  it  may  present  additional  folds,  resembling  valves, 
the  best  marked  of  which  is  situated  at  the  junction  of  the 
sac  and  the  duct. 

The  arteries  supplying  the  lachrymal  duct  are  from  the 
nasal  and  the  inferior  palpebral.  The  large  and  numerous  veins  mostly  join  the 
nasal  plexus  and  empty  into  the  ophthalmic  and  facial.  The  nerves  are  derived  from 
the  infratrochlear  division  of  the  nasal  branch  of  the  ophthalmic. 

Practical  Considerations. — The  most  fretjuent  congenital  error  of  develoj)- 
ment  in  the  lachrymal  apparatus  is  found  in  connectitm  with  the  canaliculus.  It 
may  be  entirely  absent,  or,  what  is  more  common,  may  appear  only  as  a  groo\e, 
the  edges  having  failed  to  unite.  This  union  of  the  edges  may  occur  only  in  part, 
so  that  the  canaliculus  may  have  two  or  more  openings. 

The  lachrymal  gland  is  rarely  the  seat  of  inflammation.  Hypertrophy  or 
enlargement  may  be  con^i  nital  or  syphilitic.  Prolapse  or  dislocation  forward  may 
occur  so  that  the  gland  can  l)e  seen  or  felt  below  the  upp-r  outer  margin  of  the  orbit  ; 
it  has  been  excised  in  extreme  cases.   Cysts  are  due  to  occlusion  .  t  one  or  more  ducts. 

The  ducts  of  the  gland  open  into  the  outer  third  of  the  upper  conjunctival 
fornix,  and  the  tears  sweep  over  the  front  of  the  eye  towards  the  puncta  untler  the 
influence  of  gravity  and  the  contractions  of  the  orbicularis  muscle.  The  lower 
punctutn  is  frequently  everted  so  that  it  no  longer  dips  into  the  lacus  lacri  nails,  and 
the  tears,  instead  of  finding  their  w.iy  into  the  normal  pass.ige,  flow  over  the  lower 
lid  on  to  the  cheek  (epiphora).  Tliis  is  usually  the  first  step  in  the  development  of 
ectropion  or  turning  out  of  the  lid  (  vide  supra).  When  thi  eversion  cannot  be  cor- 
rected, the  canaliculus  is  usually  slit  up  on  its  posterior  siile  so  as  to  form  a  groove 
dipping  into  the  lacus,  from  which  the  tears  may  again  l)e  taken  up  by  the  natural 
passages.  The  most  (winmon  cause  of  epipiiora  is  obstruction  of  the  lachrymal 
passages.  This  occurs  most  frequently  at  the  junction  of  the  lachrymal  sac  and 
nasal  duct,  which  is  the  narrowest  part  of  the  duct.  The  method  of  correcting  su.h 
an  obstruction  is  by  the  use  of  sountls,  which  are  passed  from  the  punctum  with  or 
without  first  slitting  the  canaliculus.  The  rule  is  to  A\x.  the  c.ina'iculus  when  the  sound- 
ing is  to  be  kept  up  for  any  length  of  time,  hut  if  it  is  performed  for  diagnosis  only, 
the  slitting  is  not  done.     The  upper  canaliculus  is  shorter  but  narrower  than  the  lower, 


■■Ml    :,    i% 
Mil 


1480 


HUMAN  ANATOMY. 


which  is  usually  selected,  as  there  is  less  danger  of  laceration  of  the  lining  mucous 
membrane  leading  to  narrowing  or  occlusion  of  the   canaliculus  by  scar   tissue. 

Congenital  fistulte  sometimes  result  from  non-closure  of  the  groove  from  which 
the  sac  and  nasal  duct  are  formed.  The  lachrymal  sac  is  situated  at  the  inner  side 
of  the  inner  canthus,  behind  the  inner  palpebral  ligament,  which  is  the  best  guide  to 
it,   and  crosses  about  the  junction  of  the  upper  and   middle  thirds  of  the  sac. 

A  collection  of  mucus  or  pus  in  the  lachrymal  passage  is  usually  in  the  sac,  and 
when  not  otherwise  relieved,  it  tends  to  discharge  itself  through  the  skin  below 
the  tendo-oculi,  and  frequendy  lower  than  the  level  of  the  sac.  The  abscess  is 
therefore  opened  below  the  tendon  and  external  to  the  inner  edge  of  the  lachrymal 
groove. 

The  line  of  the  sac  and  duct,  taken  together,  is  approximately  from  the  inner 
canthus  to  the  space  between  the  second  premolar  and  first  molar  teeth.  It  opens 
below  into  the  inferior  meatus  of  the  nose,  just  below  and  behind  the  anterior  end  of 
the  inferior  turbinate  bone,  which  conceals  it  from  view  at  the  anterior  naris.  The 
sac  and  duct  form  a  slightly  curved  line  with  its  convexity  backward,  and  its  course 
downward,  backward  and  slightly  outward.  To  pass  a  probe  along  the  lachrymal 
passage,  the  lower  lid  is  everted  by  the  thumb  so  that  the  punctum  may  be  seen. 
The  probe  should  be  entered  into  the  punctum  vertically.  It  should  then  be  turned 
horizontally  and  passed  through  the  canaliculus  to  the  inner  wall  of  the  lachrymal 
sac.  It  is  then  made  vertical  and  passed  along  the  duct — i.e.,  downward,  slightly 
backward,  and  outward  to  the  nose. 


DEVELOPMENT  OF  THE  EYE. 

The  development  of  the  eye  begins  as  a  lateral  diverticulum  which  very  early  appears  on 
either  side  of  the  fore-brain  (Fig.  911).  These  outgrowths,  the  primary  optic  vesicles,  are 
hollow  and  directly  communicate  with  the  general  cavity  of  the  primitive  brain  by  means  of 
the  optic  stalks,  which  are  at  first  broad,  but  later  become  narrowed.  As  the  development 
proceeds,  the  transver-ely  placed  optic  stalks  gradually  assume  a  more  oblique  axis,  and,  after 
the  differentiation  of  the  fore-brain  into  its  two  subdivisions,  open  into  the  diencephalon  or 
inter-brain.  The  primary  optic  vesicle  expands  until  it  comes  into  contact  with  the  surface 
ectoblast.  The  next  important  step  is  a  thickening  of  the  wall  of  the  vesicle  where  it  is  in  con- 
tact with  the  ectoblast  (Fig.  1338).  In  consequence  of  the  rapid  multiplication  of  its  cells, 
this  portion  of  the  wall  becomes  invaginated  and,  as  a  result,  the  cavity  of  the  primary  optic 

vesicle  is  gradually  obliterated,  the  application  ot 
FlG.  1237.  the  invaginated  portion  of  the  wall  to  the  inner  sur- 

face of  the  uninvaginated  part  of  the  vesicle  biinging 
about  the  formation  of  a  cup-shaped  structure  pro- 
vided with  a  double  wall.  This  cup  is  called  the 
secondary  optic  vesicle  and  from  it  the  retina  is 
developed,  which  must  be  considered,  therefore,  as  a 
modified  portion  of  the  brain  itself. 

Coincidentally  with  the  invagination  of  the  optic 
vesicle,  the  overlying  ectoblast  undergoes  active 
proliferation  and  pushes  into  the  space  vacated  by 
the  receding  invaginated  wall,  thus  producing  a 
depression  known  as  the  lens-pit.  The  lens-pit  ( Fig. 
1238)  deeix-ns  and  becomes  cup-shaped  ;  the  edges 
of  its  anterior  walls  approacli  each  other  and  then 
fuse,  and  In  this  manner  form  a  closed  sac,  the  lens- 
vesicle.  This  remains  for  a  time  connected  with  the 
surface  ectoblast,  but  later  becomes  separated  from 
it  and  forms  an  Isolated  sac  of  epidermal  tissue,  which, 
hy  the  proliferation  of  its  cells,  becomes  converted  into  a  solid  structure  and  constitutes  the 
rrystalline  lens.  At  first  the  lens-vesicle  fills  the  cavity  of  the  optic  cup  completely,  but  with 
till.-  deepening  ot  the  latter,  a  space  appears  l)etween  Its  anterior  wall  and  the  lens-vesicle, 
which  gniclually  widens  and  forms  the  vitreous  cavity.  The  space  between  the  lens-vesicle 
and  the  ectoblast  is  imaded  by  a  prwess  from  the  surrounding  mesoblast,  which  pushes  in 
from  l!ie  side.  Kruti»  liiis  liij;rowth  is  <leve!oi)ed  the  cornea,  with  the  exception  of  the  surf.ire 
epithelium,  and  the  stroma  of  the  iris. 

Almost  from  the  first  appearance  of  the  Invagination  of  the  primary  optic  vesicle,  the 
invaginated  portion  of  the  wall  exhibiis  a  marked  tendency  to  proliferation  of  its  cells.    The 


Part  of  frontal  net-tion  of  head  of  early  rabbit 
embryo,  showing  optic  veKicIes  evagiiiated  from 
braiii-vcsictc.         30. 


DEVELOPMENT   OF   THE   EYE. 


1481 


Fig.  1J38. 


Brain-rniclc 


UnlnvaKiiMlcit 
wall 

InvHKinatcd  wall 
Optic  stalk 

Optic  vesicle 
Lens- pit 


Lens-pit  shows  as  depressed  area  of  thickened 
ectoblast ;  anterior  wall  of  optic  vesicle  beKiniiing 
to  be  invaginated ;  optic  stalk  narrowing.    ,-  30. 


uninvafonated  portion  of  the  wall,  on  the  contrary'i  KTudiiatly  becomes  thinner,  until  it  is  repre- 
sented by  a  single  layer  of  cubical  cells.  These  soon  assume  a  dark  color  in  consequence 
of  the  appearance  within  their  protoplasm  of  fine  pigment  particles.  From  this  wall,  there- 
fore, the  layer  of  pigmented  cells  composing  the  outermost  stratum  of  the  retina  is  developed, 
whilst  from  the  rapidly  augmenting  layers  of  the  inner  wall,  the  essential  nervous  elements 
of  the  retina,  together  with  the  supporting  neurogliar  tissue,  are  fonneii. 

The  invagination  of  the  optic  vesicle  is  not  confined  to  its  outer  wall,  but  also  affects  its 
lower  wall,  in  consequence  of  which  a  groove,  the  fietal  ocular  clefi,  appears  in  this  position 
(Fig.  1340).  This  is  continued  backward  to  and  along  the  under  surface  of  the  optic  stalk,  in 
the  form  of  a  furrow.  By  means  of  this  slit  a  com- 
munication is  established  between  the  cavity  of  the 
secondary  optic  vesicle  and  the  centre  of  the  optic 
stalk,  and  through  it  blood-ves.sels  from  the  sur- 
rounding mesoblast  gain  entrance  to  the  interior  of 
the  ner\'e  and  the  eyeball.  The  walls  of  this  fit-tal 
cleft  gradually  approximate  and  become  fused.  The 
imprisoned  vessel,  the  hyaloid  artery,  later  gives 
rise  to  the  arteria  centralis  retinje.  The  vitreous 
body  has  been  usually  considered  as  a  derivative 
exclusively  of  mesobtastic  tissue  which  entered  the 
eye  in  company  with  the  blood-vessels.  According 
to  the  recent  investigations  of  Schon,  Kolliker  and 
others,  however,  this  view  is  inadequate,  since  at 
least  the  anterior  or  ciliary  portion  of  the  vitreous 
is  a  product  of  the  cells  of  the  inner  wall  of  the 
secondary  optic  vesicle.  The  choroid  and  the 
sclera  are  differentiated  from  the  mesoblast,  which 
surrounds  the  eyeball. 

Development  of  the  Lens. — Soon  after  the  iso- 
lation of  the  primitive  lens-vesicle  from  the  surface  ectoblast,  the  cells  in  the  posterior  wall 
begin  to  proliferate  actively,  while  those  on  the  anterior  wall  are  reduced  to  a  single  layer. 
The  latter  persists  as  the  lining  epithelium  of  the  adult  lens-capsule.  By  the  growth  of  the 
cells  of  the  posterior  wall  and  their  elongation  into  lens-fibres,  the  hollow  vesicle  is  gradually 
converted  into  a  solid  mass  of  lens-substance,  the  fibres  extending  forward  until  they  come  in 
contact  with  the  anterior  wall.  Subsequently  the  growth  of  the  lens  proceeds  by  the  application 
of  additional  layers  of  fibres  to  the  surface  of  the  primary  nucleus,  the  new  fibres  developing 

from  the  cells  lining  the  anterior  capsule.  Their  con- 
version takes  place  .it  the  equator  of  the  lens,  where 
the  nuclei  of  the  elongating  lens-fibre  are  arranged  in 
a  convex  line  known  as  the  nuclear  zone  (Fig.  1 228 ). 
The  capsule  of  the  lens  apjiears  very  early, 
even  before  the  closure  of  the  lens-vesicle,  and  long 
liefore  the  appearance  of  blood-vessels  around  the 
lens.  It  forms  a  sharp  boundary  line,  at  first  along 
the  (josterior  border,  which  gradually  thickens  and 
finally  surrounds  the  entire  lens.  The  capsule  is  to 
•Jl^^n^     WS'T— #f-o  f     Ilk  be  considered  as  a  secretion  product  of  the  lens-cells. 

i^H^HHk    ^^^IBK:      i*  '   ^  °  xhe  rapid  early   growth   of   the   young  lens 

.JUP^^^BI^^teilfc- ,~  ^icn"™*'"       requires  an  adequate  1)1chk1  supply.     This  is  insured 
^^J^Sf  \ \  by  the  development  if  a   vascular   net-work,  the 

.j._    :•.-        ■;  tunica  vasculosa  lentis,  which  completely  surriiuiuls 

'■'■  ■    ■■!.•'".-"•         i  the  lens  from  the  .second  month  until  the  close  of 

.■    ■  fii-tal   life,  when  this  temporary   membrane  is  ab- 

.sorbed.  The  chief  supply  of  this  vascular  net-work 
is  derived  from  the  vessels  of  the  vitreous,  which, 
as  already  noted,  enter  the  eye  through  the  cleft  in 
the  optic  ner\e.  Passing  fiirward  through  the  canal  of  Clo(|iut  in  the  centre  of  the  vitreous 
cavity,  the  chief  vessel,  the  hyaloid  artery,  reaches  the  (xislirior  (lole  of  the  lens,  when  it  dixitles 
into  numerous  branches.  These  branches  pass  around  the  etiuator  of  the  lens  onto  the  aiilerior 
surface,  where,  joined  by  vessels  from  the  mes(il)lastic  tissue  which  is  to  constitute  the  ttilure 
iris  and  ciliary  body,  they  pn>ceed  to  the  centre  of  the  pupil  and  liieak  up  into  their  terminal 
loops.  The  portion  of  the  net-work  covering  the  pupillary  area  is  (  Mlletl  the  membrana  pupil- 
laris,  whilst  the  remainder  is  known  as  the  membrana  capsularis.  Tiiis  v;iscui.ir  sheet  is  usually 
entirely  at)Sorl)«l  Ixjfore  birth,  but  occasionally  portions  of  it  may  be  seen  |>ersisling  in  tlie 
form  of  fine  threads  in  the  pupillary  space,  or  on  the  posterior  pole  of  the  hns.  The  retenlioii 
of  such  strands  is  sometimes  associated  with  the  |)ersistence of  portions  of  the  hyaloid  .irtery. 


Fio.   1239. 


■—  Ectoblast 
1 

Outer  layer 

.ip  of  optic  cup 
Inner  layer 
Anterior  wall 
Optic  stalk 

Posterior  wall 
uf  Icnh-Kac 


Lens-sac  closed  ;  outer  and  inner  layers  of  sec- 
ondary oplic  vesicle  now  almost  in  contact.    .•  30. 


I4i>3 


HUMAN  ANATOMY. 


Fio.  1240. 


■~~  MeNoblast 

—  Lipof  opticcup 


FccUl  cleft 


Sagittal  s«rtion  of  dpvelopitiK  eye  at  same 
staae  as  precvdinK  specimen,  showing  invagi- 
tiatTon  of  optic  vesicle  along  ftctal  cleft.     X  30. 


Development  of  the  Retina. — As  already  pointed  out,  the  retina  develops  fn>in  the  walls  <if 
the  optic  vt^icle,  the  piunifnted  layer  being  derived  from  the  uninva)(inated  outer  wall,  thu  pi^;- 
nient  nppearinK  early  and  first  near  the  anterior  margin  of  the  optic  cup;  the  remainder  of  tht- 
retina  comes  from  the  rapidly  gnminK  cells  of  the  inner  wall.  The  first  cells  to  be  differentiated 
in  the  nervous  portion  of  the  retina  are  the  spongioblasts  which  develop  into  the  supporting 

neurogliar  fibres,  the  fibres  of  AriiHer.  These  are 
strengthened  by  the  addition  of  mesoblastic  elements, 
which  enter  the  inner  layers  along  with  the  blooil- 
vessels.  The  neuroblasts  develop  from  cells  whit  h 
correspond  in  position  to  those  of  the  external  nu- 
clear layer.  As  they  divide,  the  cells  are  displaced 
inward,  so  that  the  ganglion-cells  represent  the  oldest 
descendents.  When  seven  or  eight  layers  have  been 
differentiated,  the  ganglion-cells  send  out  axones, 
which  form  the  fibre-layer  and  converge  toward  the 
optic  nerve.  The  visual  cells  are  the  last  to  appear, 
the  layer  of  rtxls  and  cones  developing  as  cuticular 
outgrowths  from  the  cells  of  the  external  nuclear  layer. 
Anteriorly  the  walls  of  the  secondary  optic  vesicle 
are  reduced  to  a  double  layer  of  cells.  For  a  certain 
distance,  corresponding  to  the  position  of  the  future 
ciliary  body  (pars  ciiiaris  retinae),  the  outer  cells  are  pigmented,  whilst  the  inner  ones  are  trans- 
parent. Still  farther  forward,  the  rudimentary  portion  of  the  nervous  tunic  is  continued  over 
the  posterior  surface  of  the  iris  (:«irs  Iridica  retinx)  as  a  double  layer  of  deeply  pigmented 
cells  which  extends  as  far  as  the  pupil'  try  margin  which  thus  corresponds  to  the  anterior  lip  of 
the  secondary  optic  vesicle. 

The  optic  nerve  is  developed  secondarily  and  in  close  association  with  the  early  optic  stalk, 
which  is  at  first  hollow,  and  later  becomes  grooved  along  its  inferior  surface.  The  walls  of 
this  /a;tal  cleft  become  approximated  and,  after  the  entrance  of  the  blood-vessels,  the  lips 
of  the  cleft  fuse,  the  ves.sels  being  thus  enclosed.  Since  the  fibres  of  the  optic  nerve  are  for 
the  most  part  axones  of  the  ganglion-cells  of  the  retina,  it  is  evident  that  they  are  not  developed 
within  the  nerve,  but  invade  the  latter  as  outgrowths  of  fibres  from  the  retina,  pushing  along 
the  optic  nerve  and  tract  to  reach  their  cerebral  connections.  In  addition  to  these  centripetal 
fibres,  a  certain  number  of  centrifugal  ones  appear  later  as  outgrowths  from  cells  within  the 
brain.    The  supporting  tissue  is  developed  by 

proliferation  of   the  cells  of  the  optic  stalks  Fig.  1241. 

and  their  differentiation  into  neurogliar  ele- 
ments, assisted  by  the  mesoblastic  elements 
from  the  surrounding  pia  and  the  portion 
which  enters  the  cleft  with  the  blood-vessels. 
The  nerve-fibres  are  at  first  naked  axis-cylin- 
ders, which  later  acquire  medullary  sheaths. 
Development  of  the  Fibrous  and  Vascular 
Tunics. — With  the  separati.->n  of  the  lens- 
vesicle  from  the  overlying  ectc  iliUxst,  the  meso- 
blast  insinuates  itself  fwtueen  these  structures, 
in  addition  to  surrounding  tliC  entire  ecto- 
blastic  optic  vesicle.  The  portion  surrounding 
the  optic  vesicle  posteriorly  thickens  rapidly 
and  becomes  differentiated  into  the  vascular 
tunic,  or  choroid,  whilst  the  outer  layer  Ije- 
comes  the  fibrous  tunic,  or  sclera.  The  choroid 
ap|)ears  first,  the  pigmentation  of  its  cells  being 
evident  by  the  seventh  month.  The  meso- 
blastic process  tietween  the  lens  and  the  ecto- 
blast  is  very  thin  at  first,  but  subse<|Uently 
splits  into  two  layers.  The  anterior  of  these 
becomes  the  substantia  propria  of  the  cornea  and  its  lining  endothelium.  The  latter  produces 
tiK-  membrane  of  Descemet.  The  ixjsterior  mesoblastic  la>er  carries  blood-vessels  which  help 
to  form  the  capillary  net-work  surrounding  the  lens.  The  s|)ace  between  the  two  mesoblastic 
layers  represents  the  future  anterior  chamber  of  the  eye.  .About  the  fourth  f(Ltal  month  the  aii- 
tt'rior  lip  of  the  optic  vesicle  pushes  forward  in  advance  of  the  lens  and  carries  with  it  additioii.il 
mesoblastic  tissue.  From  this  the  iris  is  developed,  the  stroma  being  formed  by  the  mesoblast, 
whilst  the  posterior  pigmented  portion  represents  the  anterior  part  of  the  optic  vesicle,  from 
which  the  dilatator  muscle  (and,  according  to  some  authorities,  also  the  sphincter  pupilla!)  is 
derived.     The  ciliary  processes  are  produced  by  the  rapid  lateral  expansion  of  the  walls  of  the 


t'pper  eyelid 
Outer  pigmented 
retinal  layer 
Inner  retinal 
layer 
Meaoblant 

Lens,  now  solid 

Optic  nerve 

Vascular  vitreous 

tissue 

Ectoblast 

Lipof  retinal  co:i  t 


Much  later  stage,  showing;  lens  now  solid  ;  lavers  of 
optic  vesicle  converted  into  retinal  coat :  vascular  vitreous 
tissue;  condensation  and  invasion  of  mesoblast.      '   20. 


THE   EAR. 


I4«.^ 


optic  vesicle,  about  the  fourth  or  fifth  month,  in  consequence  of  which  folds  in  the  nieinlir.iiu- 
ariiie,  into  which  blood-vessels  and  other  mesodermic  elements  extend.  The  corneal  stroma 
becomes  blended  with  the  sclera,  thenceforth  the  two  forminK  a  continuous  tunii-. 

Development  of  the  Vitreous  Body. — As  already  stated,  the  vitreous  liody  is  at  present  re- 
garded as  developing  chiefly  by  proliferation  of  the  cells  of  the  inner  w.ill  of  the  optic  vesicle, 
especially  from  its  anterior  or  ciliary  portion.  The  suspensory  ligament  ot  the  lens  is  ilerived 
from  the  same  source.  The  cells  develop  into  the  fibres  which  iorm  the  line  net-work  of  the 
vitreous  bo<ly;  at  the  periphery  these  become  condensed  and  form  the  Ixiuiulary  layer  or 
hymloid  membrane.  The  vitreous  is  supplied  with  IiUmxI  by  branches  oi  the  hyaloid  artery, 
which  sprinKS  from  the  head  of  the  optic  nerve.  An  especially  complete  net-work  is  found  at 
the  periphery  of  the  vitreous  and  these  ves-sels  pass  forward  to  the  eoMator  of  the  lens  ami 
assist  in  forming  the  tunica  vasculosa  lentis.  The  retinal  ves.sels  are  formed  later  as  branches  of 
the  central  artery,  the  vitreous  vessels  usually  undergoing  complete  absorption  before  birth. 

The  development  of  the  eyelids  begins  with  the  priKluction  of  folds  of  integument,  which 
appear  above  and  below  the  cornea  during  the  second  f(ttal  month.  The  folds  approach  each 
other  and  th«  epidermal  cells  fuse  about  the  third  month,  the  eyelids  remaining  united  until 
shortly  before  birth.  The  Meiliomian  and  other  glands  of  the  lids  are  produced  by  ingrowths 
of  the  surface  ectobla.st.  The  lachrymal  gland  arises  during  the  third  month  as  a  solid  ingrow  th 
from  the  conjunctival  epithelium  close  to  the  upper  lid.  The  lachrymal  canal  begins  as  a  solid 
process  of  epithelial  cells  from  the  lid,  which  dips  inward  along  the  lachrymal  furrow,  between 
the  superior  ma.villary  and  nasal  processes.  This  cord  of  cells  l)ecomes  isolatetl  from  the  sur- 
face, and  later  acquires  a  lumen,  connecting  by  means  of  the  canaliculi  with  the  conjunctival  sac 
above.    The  duct  establishes  communication  with  the  nasal  fos.sa  just  before  birth. 

THE  EAR. 

The  ear  (orKanon  auditus)  may  be  conveniently  studied  under  its  three  natural 
subdivisions,  which  are  conventionally  described  as  the  e.xternal,  middle  and  the 
internal  ear — structures  lodged  entirely  or  in  part  within  the  temporal  bone.     The 


Fig.  1242. 


Rone 
Malleus 
Incus 


SUipc!! 


Inner  car 

Semicircular  canal 


Internal  auditory  canal 
Auditory  nrrvc 

Endolymphatic  sjic 


Cirtilagi- 


Oiagnim  ihowing  relationa  of  three  subdivisions  of  ear 


CO 

{Mwli/ieii /torn  Sihu 


externa/  ear  includes  the  auricle  and  the  external  auditory  canal  ;  the  middle  car 
the  tympanum,  the  Eustachian  tube  and  the  mastoid  cells  ;  and  the  inUntal  ear 
the  labyrinth,  with  the  peripheral  ramifications  of  the  auditory  ner\'e. 

Such  division,  moreover,  is  justified  by  the  developmental  history  of  the  organ, 
since  tlie  internal  ear  is  developed  es-sentially  from  the  hijrhly  differentiatt^l  otic  vesicle 
which  gives  rise  to  the  complicated  membranous  labyrinth  ;  the  middle  ear  largely 
from  the  first  pharyngeal  |)ouch  ;  whilst  the  external  ear  represents  the  deepened 
and  modified  boundaries  of  the  first  external  visceral  furrow. 


1484 


HUMAN  ANATOMY. 


Foua  helids 


THE  EXTERNAL  EAR. 

The  external  ear.  the  outennost  subdivision  of  the  auditory  orf^n,  indudi-s 
( I )  the  auricle,  the  funnel-shaped  appendage  attached  to  the  side  of  the  head  for  the 
collection  of  the  sound-waves,  and  (2)  the  external  auditory  canal,  which  conveys 
these  stimuli  to  the  tympanic  membrane,  the  flexible  partition  closing  the  canal  and 
separating  it  from  the  middle  portion  of  the  ear. 

The  Auricle. 

The  auricle  (anrlcnla),  also  called  the  pinna,  is  attached  to  the  side  of  the  head 
around  the  opening  of  the  external  auditory  canal,  midway  between  the  forehead  and 
the  occiput.  It  presents  two  surfaces,  an  external  and  an  internal.  The  angle  which 
its  internal  surface  forms  with  the  head,  the  cephcdo-auricular  angle,  is  usually  about 
30°,  but  varies  from  20-45'*.  The  circumference  of  the  auricle  is  somewhat  pyriforni 
in  outline,  with  the  broadest  part  of  the  fi^  .e  above.  The  external  surface  of  the 
aurice  is  irregularly  concave  and  presents  for  examination  several  well-marked 
depressions  and  elevations,  which  depend,  for  the  most  part,  upon  the  corresponding 
modelling  of  the  underlying  cartilage.  The  concha,  the  largest  and  deepest  of  the 
concavities,  surrounds  the  entrance  or  meatus  to  the  external  auditory  canal.  This 
funnel-like  fossa  is  subdivided  by  an  obliquely  transverse  ridge,  the  crus  helicis, 
continuous  with  the  helix,  into  the  upper  and  smaller  part,  the  cymba  con- 
chsc,  and  a  lower  and  larger  part,  the  concha  proper  or  cavum  conchae.     The 

tragus    is    an    irregular 
Fig.  1*43.  eminence  in  front  of,  and 

slightly  overlapping,  the 
meatus.  At  the  upper 
extremity  of  the  tragus, 
just  below  a  notch,  the 
incisura  anterior,  that 
separates  the  tragus  from 
the  upper  part  of  the 
auricle,  is  sometimes  seen 
a  small  elevation,  the 
tuberculum  supratrag- 
icum.  The  antitragus 
is  an  eminence  behind  the 
tragus  and  separated  from 
it  by  a  deep  notch,  the 
incisura  intertragica. 
The  lobule  contributes 
the  rounded  lower  ex- 
tremity of  the  auricle.  In 
contrast  to  other  parts  of  the  ,>inna,  it  possesses  no  framework  of  cartilage  and,  hence, 
is  soft  and  inelastic.  The  helis  forms  the  scroll-like  margin  of  the  ear,  sweeping  from 
the  upper  part  of  the  tragus  in  front  to  the  lobule  behind.  It  is  more  or  less  rolled 
upon  itself  so  that  its  margin  looks  forward.  On  the  anterior  edge  of  the  heli.x.  near 
the  junction  of  its  upper  and  middle  thirds,  is  sometimes  found  a  small  triangular  ele- 
vation, the  car-point  or  tubercle  of  Darwin,  which  is  of  interest  as  representing,  ac- 
cording to  the  last-named  authority,  the  erect  pointed  extremity  in  the  expanded  ears 
of  certain  (juatirupeds.  It  is  said  to  l)e  constant  in  the  foetus  of  about  the  sixth  month 
and  to  be  more  common  in  the  male  than  in  the  female.  In  front  of  and  p.irallel  to 
the  helix,  is  a  curved  ridge,  the  antihelix  which  tx-gins  at  the  antitragus  below, 
forms  the  concave  posterior  boundary  of  the  concha,  and  divides  above  it  into  a 
siipi-rinr  and  an  inferior  rnis  tx-twoen  which  lies  the  fossa  of  the  antihelix  or  the 
fossa  triangularis.  .\  narrow  groove  between  the  helix  and  the  antihelix  marks 
the  fossa  of  the  helix  or  the  scaphoid  fossa. 

The  elevations  on  the  external  surface  of  the  auricle  are  represented  by 
depressions  on  the  cranial  surface,  and  conversely  the  depressions  on  the  external 


Cavum  coiichi 


Antitragus 


Foua  triangularin 


Cnini  antihcHcifi 

'Cymba  conchw 
Crus  heliciA 
Incisura  anterior 
Tragus 


^incisura 
intertragica 


Lobillus 


Ri'hl  auricle,  outer  aspect. 


THE  EXTERNAL  EAR. 


«4»5 


surface  are  represented  by  eminences.  Thus,  th?  concavity  oi  the  conchu  is 
represented  on  the  cranial  surface  b^  the  eminentia  conchae;  the  antihi-lix  by 
the  fosaa  antihelicis ;  the  fossa  triangularis  by  the  eminentia  fosase  triangu- 
laria ;  the  scaphoid  fossa,  by  the  eminentia  tcaphK.  The  other  elevations  and 
depressions  corresjKjndinjf  to  those  of  the  outer  surface  are  not  sten  on  the  cranial 
surface,  except  in  the  dissected  cartilage  denudetl  of  the  inte>;unient. 

Structure  of  the  Auricle. — The  auricle  consists  of  integument  and  an  enclosed 
plate  of  yellow  elastic  cartilage  continuous  with  that  of  the  meatus.  It  is  also  provided 
with  several  unimportant  ligaments  and  muscles.  The  lobule,  however,  contains  no 
cartilage,  but  only  fibrous  tissue  and  fat  enclosed  within  the  intek>umentary  fold. 

The  skin  of  the  auricle  is  thin  and  closely  adherent  to  the  cartilage,  es|>ecially 
on  the  outer  jurface.  In  certain  parts  it  contains  fine  hairs  and  sebaceous  and  sweat 
glands.  The  hair  follicles  are  especially  abundant  over  the  tragus,  antitragus  and 
the  notch  lying  between  them,  the  hairs  guarding  the  entrance  into  the  external 
auditory  canal,  known  as  tragi,  being  exceptionally  long.  The  sebaceous  glands 
are  espiecially  well  developed  in  the  cavity  of  the  concha. 

Cartilage  of  the  Auricle. — The  cartilage  of  the  auricle  may  be  divided  into 
two  parts :  (a)  the  scroll-like  plate  forming  the  tragus  and  external  auditory  canal, 
and  {6)  the  large  irregular  plate  forming  the  main  cartilage.     These  two  clivisions 


Fig.  1344. 


s 


Itucitioii  of  •urlcularis  nipcrior  Obllquiu 


Helkii  major 


Tragicui 


IMale  of  tragus 

ami  estrmal 

auditory  canal 


auda  hclicia 


Cartilaginous  framework  oi  right  auricle,  with  intrinsic  auricular  muscles;  A,  outer,  B,  inner  surface. 

are  connected  by  a  cartilaginous  isthmus  lying  between  the  incisura  intertragica  on 
its  outer  side  and  the  deep  fissure,  (Incisura  terminalis  auris),  which  in  the  isolated 
cartilage  is  seen  between  the  posterior  wall  of  the  outer  meatus  and  the  anterior 
border  of  the  lower  part  of  the  concha,  on  its  inner  side.  Two  smaller  clefts,  the 
fissures  of  Santorini,  are  found  between  the  three  plates  which  form  the  carti- 
laginous scroll  supporting  the  tragus  and  outer  end  of  the  external  auditory  canal. 
The  cartilage  of  the  tragus  is  an  irregular  plate  and  subject  to  considerable  variation. 

The  depressions  and  elevations  of  the  cartilage  proper  corrtspond  in  general  to 
the  surface  modelling  of  the  auricle,  but  are  sharply  marked,  especially  on  the  cranial 
aspect.  A  deep  notch,  the  fissura  antitragohelicina,  separates  the  lower  part  of 
the  helix  from  the  antitragus,  thus  defining  the  caudal  process  (cauda  belicis),  as 
the  lower  extremity  of  the  cartilage  forming  the  helix  is  called. 

The  spina  helicis  is  a  small  conical  projection,  directed  forward  and  down- 
ward, opposite  the  first  bend  of  the  helix.  This  serves  for  the  attachment  o*  the 
anterior  ligament.  The  upper  end  of  the  tragus-plate  fits  into  an  angle  formed  by 
the  junction  of  the  beginning  of  the  helix  and  the  upper  end  of  the  anterior  border  of 
the  concha.  In  addition  to  the  elevations  and  depressions  already  referred  to,  on 
the  mesial  surface  is  found  a  ridge,  the  ponticulus,  which  extends  downward 
and  forward  over  the  eminence  of  the  concha  and  serves  for  the  attachment  of  the 
posterior  auricular  muscle  (Fig.  1244,  B). 


I486 


HUMAN   ANATOMY. 


Ligaments  of  the  Auricle. — The  extrinsic  ligaments  of  the  auricle,  thnae 
which  attach  the  auricle  to  the  temporal  bone,  (orm  a  more  or  less  continuous  mass 
of  fibres.  These  are  separated  somewhat  arbitrarily  and  de»cribetl  as  the  anterior 
and  posterior  ligaments.  The  anterior  ligament  extends  from  the  helix  and  the 
tragus  to  the  root  of  the  zygoma.  The  posterior  ligament  extends  from  the  emi- 
nence of  the  concha  and  ponticulus  to  the  anterior  jwrt  of  the  mastoid  process.  A 
number  of  bands  of  fibrous  ti-s-sue,  the  instrinsic  ligaments,  bind  the  parts  of  the 
cartilage  tr^cthcr. 

The  Muscles  of  the  Auricle. — These  include  the  extrinsic  and  the  intrinsic 
muscles. 

The  extrinsic  muscles  of  the  auricle,  those  which  extend  from  the  head  to  the 
auricle  and  move  it  as  a  whole,  have  been  described  under  the  muscular  system 
(page  483).     They  are  the  anterior,  superior  and  posterior  auricular  muscles. 

The  intrinsic  muscles,  six  in  numl)er,  consist  of  small  strands  of  muscle-fibres 
attacheil  to  the  skin,  which  extend  from  one  part  of  the  auricle  to  another  and  are 

confine<l  to  the  auricle  itself.  Of  these, 
four  arc  on  the  external  surface  of  the 
auricle  and  two  on  the  cranial. 


Fig.  1245- 


Pint 


ItHtsurx 
Santorini 


OttUlaginouA, 
canal 


1.  The  ■mailer  motel*  of  the  helix 
{ill.  kflids  minor)  lies  upon  the  cms  helicis 
and  the  beginning  uf  the  helix,  its  fibres 
running  obliquely  upward  and  forM'ard. 

2.  The  greater  muscle  of  the  helix 
(»«.  hclifis  major)  arises  from  the  spine  of 
the  helix  and  extends  upward  along  the 
anterior  border  of  the  helix  and  is  inserted 
into  the  eminence  of  the  triangular  fossa. 

3.  The  muscle  of  the  tragus  {m.  tragi- 
cus)  is  a  flat  muscle  on  the  outer  surface  uf 
the  tragus ;  usually  only  its  vertical  fibres 
are  distinguishable.  Occasionally  a  'separate 
bundle  of  muscular  fibres  (in.  pyramidalis) 
extends  from  the  tragus  to  the  spine  of  the 
helix.  Likewise  another  band,  the  m.  in- 
cisum  San/orini,  somedmes  called  the 
ifi/a/a/or  roncheF,  bridges  the  greater  incisura 
Santorini.  Both  of  these,  however,  belong 
to  the  system  of  the  tragus  muscle. 

4.  The  muscle  of  the  antitragus  ( in. 
aniitragicus)  is  attached  to  the  outer  surface 
of  the  antitragus.  Its  fibres  run  obliquely 
from  the  antitragus  upward  and  backward 
and  are  inserted  into  the  caudate  process  of 

the  helix.    On  the  cranial  surface  of  the  auricle  are  the  transverse  and  the  oblique  muscles. 

5.  The  transverse  muscle  (;«.  Iransversus)  bridges  over  the  fossa  antihelicis  and  extends 
from  the  eminence  of  the  scaphoid  fossa  to  the  eminence  of  the  concha. 

6.  The  oblique  muscle  (>«.  obli</uus),  considered  by  Gegenbauer  as  a  part  of  the  trans- 
verse muscle,  extends  from  the  back  of  the  concha  to  the  eminence  of  the  triangular  fossa. 

Actions.— Duihenne  and  Zienissen  found  tliat  by  stimulating  the  muscles  of  the  tragus  and 
antitragus  the  external  auditorj-  canal  was  narrowed.  Duchenne  further  demonstrated  that  the 
greater  and  lesser  muscles  of  the  helix  were  antagonistic  to  those  of  the  tragus.  The  transverse 
muscle  and  the  oblique  muscle  by  their  contraction  are  said  to  cause  a  slight  flattening  of  the 
auricle. 


lony  canal 


Dissection  showinK  l)onv  ami  carlilajcinous  fmrtionsof 
rtRht  external  autlitorv  canal :  seen  from  in  front. 


Vessels  of  the  Auricle. — Arteries. — The  auricle  receives  its  blood  supply 
from  branches  of  the  superficial  temporal  artery  and  the  posterior  auricular  artery, 
and  thus  indirectiy  from  the  external  carotid.  Tlie  superficial  temporal  sends  three 
branches  to  the  outer  surface  of  the  auricle:  (a)  the  artery  of  the  helix  to  the 
ascending  part  of  the  helix,  fossa  triangularis  and  the  superior  crus  of  the  anti 
helix;  (*)  the  artery  of  the  crus  helieis  to  the  region  of  the  crus  helicis;  (r)  the 
arterv  of  the  tragus  to  the  region  of  the  tragus  and  lobule,  the  lobule  receiving 


THE  EXTERNAL  EAR. 


1487 


a  branch,  the  OHlerior  artery  of  the  lobule,  fr<im  the  artery  of  the  tragus.  The  |m>s- 
terior  auricular  artery  suimlies  a  variable  number  «>f  branches  to  the  auricle.  I'sually 
two  of  theiie  are  jjiven  oft  Ik-Iow  and  one  above  the  |)osterior  auricular  muscle.  These 
branches  are  lar^;er  and  longer  than  those  from  the  superficial  tem|H>ral.  After  rami- 
fyinn  over  the  cranial  surface  of  the  auricle,  they  reach  its  outer  surface  bv  piercing; 
the  aur'cle  or  by  [Kt-ssinK  over  its  free  margin.  They  supply  the  posterior  part  of 
the  outer  surface  and  anastomose  with  the  bnmches  of  the  su|>erticial  teniiHiral. 

The  veins  of  the  auricle  accompany  the  arteries  and  include:  («)  tlit'  anterior 
auricular,  which  empties  into  the  su|H'rficial  tcminiral  ;  (^)  the  |H>sterior  auricular, 
three  or  four  in  numl>er,  which  join  a  ple.xus  Ix-hind  the  ear  which  empties  nrincipally 
into  the  e.xternal  jugular  vein,  but  .ilso  unites  with  the  jx>sterior  facial  veni.  Com- 
munications with  the  mastoid  emissiiry  vein  of  the  lateral  sinus  also  fr<.'<iueiitly  e.xist. 
The  Lymphatics. — The  lymphatics  of  the  auricle  form  a  close  net-work  within  the 
dee|)er  layers  of  the  intejjument,  from  which  lymphatic  stems  jkiss  in  three  jjeneral 
groups.  Those  from  the  outer  surface  are  aflerents  chiefly  of  the  anterior  auricular 
mxles,  which  are  placed  immediately  in  front  of  the  tragus  and  In-neath  the  parotid 
fascia  ;  a  few,  however,  b>?nd  backward  over  the  helix  to  end  ir.  the  jxwterior  auricu- 


Fic.  1246. 


A.  perforan^ 
'foftaaf  triaiiKularis 

A.  helicts 


A.  atiricul^riK 
imst.  ftij|i. 


A.  temporalis  .     ,  ro»l"ior 

*^  aiiru-ular  muscle 


A.  perforans_ 
cymb» 

A.  candle  heliciv 


A.  trati 


TaroiUl  branch 
Arteriea  of  right  auricle,  .4.  Literal  surface;  B,  postero-meaial  surlace.    KSckicathr.) 

lar  nodes  that  overlie  the  insertion  of  the  sterno-mastoid  muscle.  Those  from  the 
upper  pjirt  of  the  cranial  surface  piiss  mainly  to  the  posterior  auricular  nodes,  some 
being  tributary  to  the  e.xternal  jugular  nodes.  A  number  of  stems  frt)ni  the  lower 
part  of  the  auricle  and  from  the  lobule  terminate  in  the  parotid  nodes. 

Nerves  of  the  Auricle. — The  motor  nen'es  supplying  the  intrinsic  muscle's 
of  the  auricle  are  from  the  temporal  and  posterior  auricular  branches  of  the  facial 
nerve,  the  former  l)eing  distributed  to  the  muscles  of  the  helix,  tragus  and  antitragus, 
whilst  the  ptwterior  auricular  supplies  the  tranverse  and  oblique  muscles.  The  sen- 
sory nenrs  includi;  branches  from  :  (a)  the  great  auricular  nerve,  which  supplies  the 
integument  of  the  lower  three-quarters  of  the  inner  surface  of  the  auricle,  with  the 
exception  of  a  small  portion  near  the  meatus,  and  sends  filaments  to  the  outer  surface 
of  the  lobule  and  adjacent  area  ;  (6)  the  small  occipital  nerve,  which  supplies  the 
upper  one-quarter  of  the  inner  surface  ;  ( r)  the  auricular  branch  of  the  vagus,  w  hich 
supplies  the  small  muscles  on  the  back  of  the  concha  and  a  limited  cutaneous  area 
near  the  meatus  ;  and  ((/)  the  auriculotemporal  nerve,  which  tlivides  at  the  level  of 
'he  tragus,  and  sends  filaments  from  its  auricular  branches  to  the  outer  surface  of  the 
.luricle. 

The  External  AuniroRV  Canal. 

The  external  auditory  canal  (meatus  acusticus)  leads  from  the  cavity  of  the 
concha  to  the  tympanic  membrane,  which  closes  its  inner  extremity.  Although  the 
adult  meatus  \aries  considerably  in  size  and  direction,  it  is  usually  tortuous. 

In  a  general  way,  in  its  external  jwrtion  the  canal  extentis  somewhat  forward 
and  inward,  perhaps  slightly  upward  ;  then,  in  its  middle  portion,  almost  directly 


^ 


1488 


HUMAN    •N-TOMY. 


Internal  auditory 
canal 


inward,  possibly  slightly  backward  ;    and  finally,  in  its  internal  portion,  forward, 
downward  and  inward.      Its  supcro-posterior  wall  measures  about  25  mm.  (i  m.)  m 

length,  and  the  anterior 
wall  about  35  mm.  ( i  -)« 
in.),  the  greater  length 
of  the  anterior  wall  be- 
ing due  to  the  obliquity 
of  the  drum-head  and 
the  outward  protrusion 
of  the  tragus.  The 
canal  is  almost  as  long 
in  the  infant  as  in  the 
adult. 

Structure.— The 
external  auditory  canal 
is  composed  of  an  outer 
cartilagino-membranous 
(cartilaginous)  and  of  an 
inner  bony  portion,  both 
of  which,  as  well  as  the 
external  surface  of  the 
tympanic  membrane,  are 
lined  by  skin.  The  car- 
tilagino-  membranous 
part  contributes  something  more  than  one-third  of  the  entire  length  of  the  canal, 
and  is  a  continuation  of  the  cartilage  of  the  auricle.  The  cartilage  of  the  canal, 
histologically  of  the  elastic  type,  does  not  form  a  complete  tube,  but  is  deficient  at 
its  upper  back  part,  where  ii  is  filled  in  by  fibrous  tissue.  On  approaching  the 
bony  portion,  this  deficiency  in  the  cartilage  is  more  marked  and  the  fibrous  tissue 
correspondingly  increased. 

Two  or  more  slit-like  apertures,  the  fissures  of  Santorini  (incisurae  cartiiaK- 
inis  meatus  acustici  esterni)  are  usually  found  traversing  the  cartilagino-membranous 

Fig.  1248. 


Lateral  (inu* 


Frontal  section  paaiini  through  right  ear,  showing  external,  middle, 
and  internal  divisions;  section  is  seen  from  in  front. 


Condyle  of  Jaw 


Cartilaginous  canal 


Tymjianic  membrane 


External  audiuiry  canal 


Maatoid  cells 


^  Bony  canal 


'Eustacliian  tube 

Internal  carotid  artery 
ympanic  cavity 


Lateral  sinus 


Horitontal  section  puslng  through  right  ear,  viewed  from  tielow. 

canal  nearly  at  right  angles  (Fig.    Ii45);  ^  ll»«=y  are   filled   with  fibrous   tissue, 
they  permit  the  anastomosb  between  the  vessels  of  the  anterior  and  posterior  surfaces 


THE   EXTERNAL   EAR. 


1489 


Seban  ous  ^I-'tni! 


CartilaKc 


of  the  ear.  At  its  inner  end  the  cartilajjino-membranous  meatus  is  attached 
to  the  inferior  and  lateral  edges  of  the  osseous  meatus,  the  fibrous  part  Ix'iiij; 
continuous  superiorly  and  posteriorly  with  the  periosteum  lining  of  tlie  osseous 
1  anal.  The  osseous  portion  of  the  tulw,  about  14  mm.  in  length,  is  longer 
and  narrower  than  the  cartilagino-membranous  part.  At  its  inner  end  it  ])resents 
a  narrow  groove,  the  sulcus  tympanicus,  for  the  insertion  of  the  tympanic 
membrane.  The  sulcus  e.xtends  around  the  sides  and  floor  of  the  canal,  but  is 
deficient  above. 

The  skin  lining  the  external  auditory  canal  is  closely  attachetl  to  the  untlerlying 
cartilaginous  portion  of  the  tube,  the  skin  me.isures  alxtut  1.5  mm.  in  thick- 
ness, but  is  much  thinner  within  the  bony  canal,  e.xcept  along  the  roof,  where  it 
remains  relatively  thick.  Over  the  outer  surface  of  the  tympanic  membrane  the 
skin   is   reduced  to 

a  very  delicate  and  *'*^-  '*49- 

smooth  investment, 
covered  by  a  corre- 
spondingly attenu- 
ated epidermis,  and 
a  suggestion  of  sub- 
cutaneous tissue. 
Numerous  fine  hairs 
and  large  sebace- 
ous glands  occur 
in  the  cartilagfinous 
portion,  but  dimin- 
ish in  size  and  fre- 
quency towards  the 
bony  canal,  in  which 
they  are  entirely 
wanting.  Within  the 
cartilaginous  meatus 
and  along  the  roof 
of  the  bony  tube,  the 
skin  is  closely  be- 
set with  the  large 
coiled  ceruminous 
glands,  which  re- 
semble in  structure 
modified  sweat 
glands.  Like  the 
latter,  the  cerumin- 
ous glands  consist  of 
a  deeper  and  wider 
coiled  portion,   the 

secretory  segment,  and  a  long  narrow  excretory  duct,  which  ends  in  most  c;ises  inde- 
pendently on  the  free  surface  of  the  skin,  but  sometimes,  particularly  in  the  very 
young  child,  it  opens  into  the  duct  of  a  sebaceous  gland.  The  cuboidal  secreting 
cells  contain  yellowish  brown  pigment  particles  and  granules  resembling  fat.  The 
ear-wax  or  cerumen  is,  as  usually  found,  the  more  or  less  dried  mixture  of  the 
secretions  derived  from  both  varieties  of  glands,  together  with  discarded  squamous 
epidermal  cells. 

Vessels. — The  arteries  distributed  to  the  external  auditory  canal  are  irom  three 
sources:  (a)  anterior  branches  of  the  superficial  temjMjral  supply  the  external  por- 
tion of  the  meatus  ;  (b)  the  deep  auricular  artery,  a  branch  of  the  internal  maxillary, 
passes  to  the  deeper  portions  ;  whilst  (f)  the  posterior  auricular  provides  branches 
for  the  jxjsterior  and  sujjerior  surfaces.  The  arteries  destined  for  the  interior  of  the 
?anal  pierce  the  membranous  roof  of  the  cartilaginous  meatus,  the  fissures  of  Santo- 
r'sij  .Tid  the  fibrous  tissue  connecting  the  cartilaginous  with  the  bony  portion  of  the 
i  ibe.     They  form  capillary  net-works  within  the  j)erichondrium  and  periosteum  and. 


Cartilage 


Hair  fonicle 


Corium 


Transverse  section  of  skin  lininK  cartiUiRinous  portion  of  external 
auditory  canal,    v  30. 


:490 


HUMAN   ANATOMY. 


Concha 
External  auditory  canal 
Memhrana  flaccida 
Depression  for 
malleus    \ 


within  the  skin,  around  the  glands  and  the  hair  follicles,  some  extending  on  to 
the  upper  part  of  the  membrana  tympani.  The  deeper  veins  of  the  meatus, 
which  drain  the  bony  and  a  small  part  of  the  cartilaginous  meatus,  empty  into  the 
venous  plexus  behind  the  articulation  of  the  lower  jaw,  those  from  the  upjjer 
wall  of  the  meatus  extending  upward  to  join  the  venous  plexus  which  spreads  out 
over  the  skull. 

The  lymphatics  of  the  external  auditory  canal  arise  from  a  cutaneous  net-work 
from  which  trunks  pass  in  three  general  groups,  as  do  those  of  the  auricle.  ( i ) 
The  trunks  of  the  posterior  group  arise  in  the  posterior  wall  of  the  external  meatus 

and  empty,  for  the  most  part,  into 
Fig.  lajo-  the   posterior  auricular   (ma.st<-.id) 

nodes.  Some,  however,  avoid  this 
first  station  and  join  the  efferent 
vessels  of  the  upper  nodes  of  the 
superior  deep  cervical  chain.  (2) 
The  inferior  group  includes  a  vari- 
able number  of  trunks  coming  from 
the  lower  wall  of  the  external  audi- 
tory meatus,  some  of  which  pass  to 
the  nodes  placed  along  the  course 
of  the  external  jugular  vein  at  its 
exit  from  the  parotid,  whilst  others 
end  in  the  mastoid  nodes.  (3) 
The  anterior  group  is  from  the 
concha  and  the  anterior  wall  of  the 
meatus.  These  vessels  are  tribu- 
tary to  the  parotid  nodes,  more 
particularly  to  the  anterior  auricular 
nodes  situated  immediately  in  front 
of  the  tragus. 

Nerves. — The  sensory  nerves 
supplied  to  the  external  auditory  canal  are  derived  from  the  auriculo-temporal 
branch  of  the  trigeminus  and  from  the  auricular  branch  of  the  pneumogastric.  The 
latter,  also  known  as  Arnold's  nerve,  perforates  the  wall  of  the  meatus  and  supplies 
its  lining  membrane. 

Practical  Considerations  :  The  Auricle. — The  auditory  mechanism  may 
be  said  to  consist  of  two  portions — that  which  conducts  the  sound  and  that  which 
receives  it.  The  former  is  represented  by  the  external  and  the  middle  ear  :  the 
latter,  by  the  internal  ear.  The  function  of  the  auricle  is  to  collect  and  intensify 
the  sound-waves  and  to  direct  them  into  the  external  auditory  canal.  That  it 
does  not  play  a  very  important  part  in  hearing  is  shown  by  the  fact  that  its 
removal  has  been  followed  by  comparatively  little  loss  in  the  acuteness  of  hearing 
(Treves).  Complete  absence  of  the  auricle  is  exceedingly  rare  ;  partial  defect 
( microtia)  is  more  frequent ;  while  congenital  fistulse  are  comparatively-  common. 
These  fistula  are  considered  to  be  due  to  defective  closure  of  the  first  branchial 
cleft.  According  to  His,  however,  they  are  due  to  deficient  union  of  the  crus  helicis 
and  the  crus  r.iipratragicus.  If  a  fistula  closes  at  its  orifices,  a  retention  cyst, 
sometimes  dermoid,  may  result.  The  ear  may  be  abnormally  large  (macrotia),  or, 
as  a  result  of  defective  union  of  the  rudimentary  tubercles  from  which  the  auricle 
is  developed,  auricular  appendages  ( polvotia)  may  l)e  met  with.  A  supernumerary 
auricle  may  very  rarely  be  found  on  the  side  of  the  neck  at  the  orifice  of  one  of 
the  lower  branchial  clefts. 

Owing  to  the  rich  blood-supply  of  the  auricle,  wounds  heal  rapidly.  When, 
however,  they  occur  near  the  external  auditory  meatus  and  are  large,  cicatricial 
closure  of  the  canal  must  be  guarded  against. 

Frost-bite  is  frec|uent  l5ecai..ie  of  the  exposure  to  cold  and  the  lack  of  protec- 
tion to  the  blood-vessels  from  overlying  tis.sues,  since  little  more  than  skin  covci-s 
them.     An  intense  reactive  congestion  follows,  and  frequently  leads  to  gangrene. 


I'mljo 
Tympanic  membrane 


Cast  of  right  external  auditory  canal,  seen  from  be- 
hind ;  natural  siie.  Drawn  from  cast  made  liy  Profeasor 
Randall. 


PRACTICAL   CONSIDERATIONS:    THE   EXTERNAL   EAR.     1491 

The  skin  is  closely  adherent  to  the  underlying  tissues,  especially  on  the  anterior 
surface,  so  that  the  exudate  is  under  much  ten?  m,  interferinti  with  the  bl<x)d- 
supply.     The  nerves  are  also  compressed,  accounti.ijj  for  the  j;reat  pain. 

Htematomata  of  the  auricle  are  due  to  effusions  of  blootl  l)etween  the  cartilage 
and  its  perichondrium.  They  occur  usually  on  the  concavity  of  the  auricle  from  a 
blow,  as  in  boxers,  or  foot-ball  players.  They  may  occur  rarely,  without  traumatism, 
as  in  the  insane,  although  some  believe  that  injury  is  the  exciting  cause  in  these 
cases  ;  or  even,  in  very  exceptional  instmces,  may  appear  without  precedent  traimia 
or  mental  disease.  In  those  cases  in  which  there  is  great  tension,  it  may  be  neces- 
sary to  incise  and  drain  to  prevent  necrosis. 

Of  the  tumors,  keloid,  following  punctures  for  ear-rings,  is  common  in  the 
negro ;  capillary  nievi  are  frequent,  whilst  cirsoid  aneurism  may  occur.  Cysts  in 
connection  with  the  first  branchial  cleft  have  already  been  mentioned. 

The  External  Auditory  Canal. — Congenital  atresia  is  rare  and  is  often 
associated  with  malformations  of  the  auricle,  the  middle  and  the  internal  ear,  so 
that  correction  of  the  external  condition  will  usually  fail  to  restore  the  hearing. 

The  length  of  the  external  meatus  is  about  i '%  inches,  about  3^  '"ch  of  which 
is  bony  and  about  J^  inch  cartilaginous.  In  the  new-born  it  consists  of  skin  and 
cartilage  only,  and  its  lumen  is  very  small.  Owing  to  the  obliquity  of  the  tympanic 
membrane,  that  structure,  in  the  new-born,  is  in  close  contact  with  the  floor  of  the 
canal,  so  that  the  latter  must  be  drawn  away  from  the  membrane  to  expose  it.  For 
this  purpose  the  auricle  should  be  drawn  downward  and  backward.  The  skin  of 
the  cartilaginous  portion  is  supplied  with  hair,  sebaceous  and  ceruminous  glands. 
Furuncles  are  frequent,  the  infection  passing  along  the  hair-follicles  to  the  asso- 
ciated sebaceous  glands.  In  some  persons,  one  boil  follows  another  from  successive 
glandular  infection.  The  skin  of  the  bony  portion  is  thinner  than  that  of  the  car- 
tilaginous, e.xcept  in  the  posterior  part  of  the  roof,  where  a  thicker  wedge-shaped 
piece  containing  glands  extends  as  far  as  the  drum-head. 

Ceruminous  masses  often  collect,  and  frequently  contain  pathogenic  bacteria. 
They  may  press  upon  the  tympanic  membrane,  and  through  intralabyrinthine  pres- 
sure may  produce  vertigo,  or  may  lead  to  vomiting  or  convulsions.  Interference 
by  the  mass,  with  air  conduction,  may  result  in  loss  of  hearing. 

A  diffuse  infection  of  the  meatus  may  be  primary,  but  it  is  more  apt  to  Ix;  a 
secondary  result  of  otitis  media.  In  severe  cases  the  pus  may  extend  to  the  bone 
separating  the  periosteum.  It  may  then  pass  to  the  parotid  region  through  the 
anterior  bony  wall,  but  it  is  more  likely  to  do  so  through  the  fissures  in  the  cartilag- 
inous portion.  Abscesses  in  the  parotid  region  more  frequently  extend  by  the  same 
route  in  the  reverse  direction. 

The  general  direction  of  the  car.a!  is  from  without  inward,  downward,  and 
slightly  for\vard.  The  auricle  and  cartilaginous  meatus  are  suspended  from  the 
margin  of  the  bony  portion  so  that  an  angle  is  formed  opening  downward.  For 
a  short  distance  from  the  external  orifice  the  meatus  inclines  forward.  In  the  remain- 
ing cartilaginous  portion  it  turns  backward,  while  in  the  bony  portion  it  is  again 
deflected  forward.  Therefore,  to  examine  the  tympanic  niembrane  the  cartilaginous 
meatus  must  be  drawn  upward  to  correct  the  vertical  curve,  and  backward  to 
straighten  the  antero-posterior  curve. 

The  diameter  of  the  canal  is  greater  at  the  two  extremities  than  in  the  centre. 
The  smallest  diameter  in  the  bony  portion  is  at  the  inner  third,  where  foreign  bodies 
most  frequently  lodge,  which  have  been  known  to  remain  in  the  canal  for  years 
without  much  discomfiture,  or  even,  in  some  cases,  without  their  presence  being 
known.      Care  is  necessary  in  their  removal  lest  the  tympanit  membrane  be  injured. 

The  anterior  ivall  of  the  meatus  is  in  rel,Ttion  with  the  temporo-maxillary  articu- 
lation, and  its  bony  portion  has  been  fractured  from  blows  upon  the  lower  jaw.  The 
parotid  gland  is  in  relation  with  this  wall  as  well  as  with  the  floor,  so  that  tumors  of 
the  gland  may  narrow  or  occlude  the  canal  by  pressure.  Parotid  abscesses  opening 
into  the  canal  are  likely  to  pass  through  the  deficiencies  in  the  cartii.ige  (fissures  of 
Santorini).  Since  the  lower  jaw  is  in  relation  with  the  cartilaginous  as  well  as  with 
the  btiny  portion  of  the  meatus,  the  former  is  drawn  forward  when  the  mouth  is 
opened.     Hence  the  mouth  is  usually  opened  when  one  listens  intently. 


1492 


HUMAN   ANATOMY. 


l\ic  posterior  7vall  is  separated  from  the  mastoid  process  by  the  tympano-mas- 
toid  fissure.  The  auricular  branch  of  the  pneumogastric  (Arnold's  nerve;  passes 
through  this  fissure  to  the  jjosterior  wall  of  the  canal.  The  coughing,  sneezing,  or 
vomiting  that  sometimes  follows  irritation  of  the  canal,  as  from  cleaning  the  ear,  or  ex- 
amining it  with  instruments,  is  said  to  be  due  to  a  refle.x  effect  upon  the  pneumogastric 
through  this  branch.  The  auriculo-temporal  branch  of  the  trigeminal  nerve  enters 
into  its  supply,  and  may  explain  the  earache  in  cancer  of  the  tongue  or  disease  of  the 
lower  teeth.  Between  the  posterior  wall  of  the  meatus  and  the  mastoid  cells  is  a 
thin  plate  of  bone  one  or  two  millimeters  in  thickness.  The  sigmoid  portion  of  the 
lateral  sinus  is  usually  about  12  mm.  back  of  this  wall,  and  the  mastoid  antrum 
about  S  mm.  posterior  to  its  deeper  portion. 

The  superior  wall,  which  is  from  4-5  mm.  in  thirkness,  often  contams  air- 
cells  between  two  plates  of  compact  bone.  Pus  may  burrow  through  it  from  the 
canal  to  the  interior  of  the  cranium.  At  the  posterior  superior  angle  of  the  canal  are 
a  number  of  small  openings  for  blood-vessels  and  some  connective  tissue  fibres, 
through  or  along  which  pus  may  find  its  way  from  the  mastoid  antrum  to  the  under 
surface  of  the  periosteum  in  the  meatus. 


EAR. 

the  tympanic  cavity ,  the  Eustachian 


THE  MIDDLE 

The  middle  ear  includes  three  subdivisions  ; 
tube,  and  the  mastoid  cells. 

It  is  an  irregular  air-chamber,  beginning  on  the  lateral  wall  of  the  naso-pliarynx 
with  the  Eustachian  tube,  which  leads  upward,  backward  and  outward,  for  about 
one  inch  and  a  half  into  the  temporal  bone.  Opposite  the  external  auditory  canal, 
it  widens  into  the  tympanic  cavity  and  continues  backward  into  the  mastoid  cells. 

The  Tympanic  Cavity. 
The  tympanic  cavity  (cavnm  tympani),  also  called  the  tympanum,  is  an  irregu- 
lar space  within  the  temporal  bone,  lying  between  the  internal  ear  and  the  extern.il 


KiG.   I 25 I. 

Superior  ligament 

Head  of  malleus 
Tendon  of  tensor  tympani 

Posterior  semicircular  canal  > 
Facial  nervc^ 

Vestibul 


Internal  aurtitorj'  canal' 
Cochlea 


Articular  surface  for  incus 

Epitympanic  space 

Lateral  ligament 


Handle  of  malleus 
External  auditory  canal 
Tympanic  membrane,  cut 


Prohc  In  Eust^achian  tube 


Promontory 
tympanic  cavity 


Frontal  section  Ihrouub  right  ear.  viewed  from  behind.      ■'  ^%. 

auditory  canal.  It  is  lined  with  mucous  membrane  and  contains,  in  addition  to  the 
air  which  enters  by  way  of  the  Eustachian  tube,  the  chain  of  ear  ossicles.  Its  short- 
est diameter,  that  between  the  middle  of  the  tympanic  membrane  and  the  wall  of  the 
labyiinlh,  is  iilxjul  2  nun.  The  antero-postcrior  diameter  is  about  12  n  •  :.,  whilst 
the  distance  from  the  roof  (tegmen  tympani)  to  the  floor,  the  supero-inferior  diam- 
eter, is  about  1 5  mm. 


THE   MIDOLK   KAR. 


1493 


The  cavity  of  the  tympanum  is  subdivided  into_  three  parts  :  ( i )  the  a/riiim  or 
tympanic  cavity  proper;  (2)  the  cavum  epilympcnicum,  the  upper  part  of  tlie  space 
which  ovp'lies  the  atrium  ;  and  (3)  the  antrum,  which  leads  into  the  mastoid  cells. 

The  atrium  (Fijj.  1251)  resembles  in  shape  a  short  cylinder  with  concave 
ends,  the  outer  end  beinjj  formed  by  the  tymp;mic  mentbranc  and  its  Ixmy  marj^in, 
whilst  the  inner  end  is  formed  by  the  outer  wall  of  the  labyrinth. 

The  cavum  epitympanicum  or  attic  occupies  the  space  between  the  atrium 
and  the  roof  and  constitutes  approximately  one-third  ( about  5  mm.  )  of  the  supero- 
inferior  diameter.  It  contains  the  head  of  the  malleus  and  the  Ixxly  of  the  incus 
(Fig.  1252).  It  extends  considerably  over  the  external  auditory  canal  anil  is 
bounded  laterally  by  a  wedge-shaped  jxjrtion  of  the  temporal  bone,  called  the  scutum. 

The  antrum  tympanicum  is  an  irregularly  pyramidal  space  commimicating 
with  the  upper  back  part  of  the  tympanicum  by  a  triangular  orifice.  Its  dimensions 
vary,  but  its  average  length  is  about  1 2  mm. ,  its  height  8. 5  mm. ,  and  its  width  6. 7 
mm.  It  is  larger  in  the  infant  than  in  the  adult,  and  its  lumen  is  frequently  lessened 
by  bands  of  mucous  membrane  which  stretch  across  it  and  thus  encroach  upon  the 
space.  Its  roof  is  formed  by  the  tegmen  tympmni  sometimes  called  the  tegmcn 
antri  in  this  location.     Its  external  w?  '  '0  formed  by  the  squamous  portion  of  the 

Fig.  lasi. 


Superior  liKament  of  incus 
'  of  mall 
mallftui 


Superior  liKament  of  malltus 
Head  of—"--    ^ 


Chorda  tjmipani  nerve. 


Tensor  tympani' 
Processus  cochlea riformiS' 

Eustachian  tulje 


«"Epitynipantc  space 
^—IncuK 

rbi»  iilar  prot'ess,  for  staphs 
'Handle  of  malleus 

—Tympanic  membrane 


Inner  aspect  of  outer  wall  of  rii;ht  tympanic  cavity,  Aiowlnn;  incus  and  malleas  and  tympanic 
menibrane  in  position.  X  2K. 

temporal  bone,  and  on  its  internal  one  is  seen  the  outer  wall  of  the  horizontal  semicir- 
cular canal.  The  thin  mucous  membrane  of  the  antrum  is  closely  united  with  the 
periosteum  and  possesses  a  layer  of  low  nonciliated  squamous  epithelium. 

The  walls  of  the  tympanic  cavity  present  many  irregularities  and  depres- 
sions and  the  boundaries  are  not  sharply  defined.  As  the  direction  of  the  supero- 
inferior  axis  of  the  cavity  is  not  perpendicular  but  oblique,  it  follows  that  the  outer 
wall,  composed  of  the  tympanic  membrane  and  its  Iwny  margin,  is,  accurately 
speaking,  the  infero-lateral  wall,  whilst  that  formed  by  the  labyrinth  is  the  dorso- 
mesial  wall.  For  convenience  of  •description,  however,  there  may  be  recognized 
with  advantage  an  external  and  an  internal,  a  superior  and  an  inferior,  and  an 
anterior  and  a  posterior  7. '<?//. 

The  outer  wall  (paries  membranacea)  of  the  tympanic  cavity  proper  (the 
atrium)  is  formed  by  the  drum-head  and  the  maigiii  of  Ijone  into  which  it  is  inserted, 
whilst  the  outer  wall  of  the  epitympanic  space  is  formed  by  the  scutum.  In  the  infant 
the  btjny  external  auditory  canal  consists  of  a  ring  of  bone,  the  annulus  tympani- 
CUS.  This  ring,  incomplete  at  its  upper  anterior  part  at  the  notch  of  Rivinus, 
pos.sesses  a  well-marked  groove,  the  sulcus  tympanicus,  for  the  reception  of  the 
tympanic  membrane.  At  the  notch  of  Rivinus,  the  tympanic  membrane  is  attached 
to  the  bony  margo  tympanicus  and  the  external  lateral  ligament  of  the  malleus,  and 
is  continuous  with  the  skin  lining  the  bony  auditory  canal. 


■■■iii 


1494 


HUMAN  ANATOMY. 


The  Membrana  Tympani. — The  tympanic  m<:.ibrane  or  drum-head  is  a 
delicate  transparent  disc,  irregularly  oval  or  ellipsoidal  in  outline  and  concave  on  its 
outer  surface.  It  is  placed  obliquely  with  the  horizontal  plane,  forming  an  angle  i)f 
;ilx)ut  55°,  opening  outward.  As  the  middle  jxjrtion  of  the  membrane  is  drawn  m- 
ward,  the  inclination  of  its  several  parts  differs.  The  obliquity  of  the  membrane 
is  about  the  same  in  the  infant  as  in  the  adult.  With  the  upper  back  wall  of  the 
external  auditory  canal  the  drum-head  forms  a  very  obtuse  angle,  whilst  with  the 
antero-inferior  wall  it  encloses  an  angle  of  about  27°.  The  longest  diameter  of  the 
membrane  is  directetl  from  above  and  behind,  forward  and  downward,  and  measures 
from  9.5-10  mm.  ;  the  shortest  is  from  8.5-9  mm.  The  membrane  is  about .  10  mm. 
thick,  except  at  the  periphery,  where  it  is  thickenetl.  Like  the  rest  of  the  tympa- 
num and  the  labyrinth,  it  is  practically  as  large  in  the  infant  as  in  the  adult. 

The  handle  of  the  malleus  is  embedded  in  the  tympanic  membrane  (Fig. 
1252),  and  extends  from  a  point  near  the  middle,  upward  and  forward  toward  the 
periphery,  to  end  at  the  short  process.  At  its  lower  end,  the  handle  of  the 
malleus  is  flattened  laterally  and  broadened  at  the  umbo,  which  corresponds  to  the 
deepest  part  of  the  concavity  of  the  membrane.  The  short  process  of  the  malleus 
forms  a  conspicuous  rounded  projection  at  the  antero-superior  part  of  the  drum- 
head. Extending  from  the  short  process  of  the  malleus  to  the  anterior  and 
posterior  ends  of  the  tympanic  ring  are  two  .straight  stria.  The  part  of  the 
drum-head  included  between  these  strise  and  the  Rivinian  notch  is  known  as  the 
membrana  flaccida  (pars  tlaccida)  or  Shrapnell's  membrane.  It  is  thinner 
and  less  tense  than  the  remaining  larger  part  of  the  drum-head  which  is  called  the 
membrana  tensa  (pars  tcnsa). 

The  inner  aspect  of  the  drum-head  presents  two  folds  of  mucous  membrane  which 
stretch  horizontally  backward  and  forward  to  the  annulus  and  form  an  anterior  and  a 
posterior  inverted  pocket.  The  anterior  pocket  contains  in  its  wall,  in  addition  to  the 
mucous  membrane,  the  long  process  of  the  malleus,  the  chorda  tympani  nerve  and 
the  inferior  tympanic  artery,  the  nerve  continuing  along  the  lower  border  of  the 
posterior  fold. 

The  •tructure  of  the  tympanic  membrane  includes  three  main  layers:  (i)  the  middle 
fibrous  stratum,  or  metnbrana  propria;  (a)  the  external  cutaneous  layer,  the  prolonRation  of 
the  skin  lining  the  external  auditory  canal ;  and  (3)  the  internal  mucous  membrane,  a  continua- 
tion of  the  mucous  membrane  clothing  other  parts  of  the  tympanic  cavity. 

The  fibrous  layer  or  membrana  propria  represents  the  mesoblastic  portion  of  the  drum-head 
and  consists  of  an  outer  stratum  of  radially  disposed  fibres  which  diverge  from  the  malleus 
towards  the  periphery  of  the  membrane,  and  an  inner  stratum  of  circular  fibres,  concentrically 
arranged  and  best  developed  near  the  periphery  of  the  membrane  but  absent  at  the  umbo.  The 
radiatint  fibres,  on  the  contrary,  become  more  dense  at  the  umbo,  parth  'hrough  accumulation 
and  partly  through  splitting  (Gerlach).  Between  the  fibres  of  the  two  layers  are  seen  connect- 
ive tissue  corpuscles  which  are  spindle-shaped  in  longitudinal  and  stellate  in  cross-section. 

The  membrana  propria  is  absent  within  the  pars  flaccida  or  Shrapnell's  membrane.  At  the 
periphery  of  the  membrana  propria,  the  fibres,  especially  those  of  »he  radial  stratum,  are  con- 
nected with  those  of  a  rii./  of  thick  connective  tissue,  the  annulus  fibrosus  which  occupies  the 
sulcus  tympanicus.  The  nbres  of  the  annulus  fibrosus  run  in  various  directions,  but  for  the 
most  part  converge  toward  the  tympanic  membrane  proper  (Fig.  1253)-  Round  cells  are 
found  between  these  fibres.  .    ,  »  .u 

The  cutaneous  layer  consists  of  a  thin  epidermal  stratum,  composed  of  two  or  three  rows 
of  cells  and  a  delicate  sheet  of  connective  tissue,  but  neither  a  definite  corium  nor  papillae  are 
present.  A  thickened  hand  of  subepithelial  connective  tissue  extends  across  Shrapnell's  mem- 
brane and  along  the  handle  of  the  malleus  and  contains  the  large  vesssels  and  nerves  which  pass 
from  the  meatus  to  the  membrana  tympani. 

The  mucous  membrane  covering  the  inner  surface  of  the  drum-head  consists  oj  a  scanty 
layer  of  connective  tissue,  invested  with  a  sheet  of  large  low  no-  ciliated  epithelial  cells. 

The  vessels  of  the  tympanic  membrane  include  arteries  which  are  arranged  as  an  outer  and 
inner  set,  separated  by  the  membrana  propria.  The  former  set  is  derived  from  the  deep  auricu- 
lar branch  of  the  internal  maxillary  artery  ;  the  latter  from  the  tymiwnic  branch  of  the  internal 
maxilL-iry  and  from  the  stylo-ma-stoid  branch  of  the  posterior  auricular.  Each  of  these  sets 
forms  a  plexus  of  vessels  with  a  large  branch  extending  downward  along  the  malleus  handle, 
and  another  around  the  periphery  of  the  membrane,  these  two  branches  being  connected  by 
numerous  radiating  twigs.    Perforating  vessels  connect  the  two  sets  of  arteries,  especially  along 


THE  MIDDLE  EAR. 


>495 


the  malleus  handle  and  at  the  periphery  of  the  membrane.  The  ileitis  are  most  numerous  at  the 
handle  of  the  malleus  and  periphery  of  the  membrane  and  communicate  with  those  of  the  exter- 
nal meatus  and  tympanic  cavity. 

The  lymphatics  are  arranjjed  similarly  to  the  blood-vessels  in  two  sets,  one  under  the  skin 
and  the  other  under  the  mucous  membrane.  They  communicate  freely  with  each  other  and 
probably  empty  partly  into  the  lymph-nodes  situated  over  the  mastoid  process  and  in  the 
region  of  the  tragus,  and  partly  into  the  lymph-tracts  of  the  Eustachian  tulie  and  thence  event- 
ually into  the  retropharyngeal  and  deep  cervical  nodes. 

Fig.  IJ53. 


Epithelium  of  tympanic 
surface 


Tympanic  cavity 
MucouH  memlirane      '*' '  ,  .'.?"'^'!£-.f^'^>-fH' 


'Jj-.')j]''' Epidermis  of  canal 


Blood-vessels' 


Epidermis  of  drum-head 

V  '-  O-^^J-i^^ Subepidermal  layer 

External  auditory  canal 


Corium  of  skin  lining 
canal 

Epidermis  passing  outo 
'drum-head 


Bone 


Radial  fibres  of  annulus 
fihrosus 


-   '    -     ■       ''-V^X -'.■.. ^^v»       ' 

Section  through  attached  margin  of  tympanic  membrane,  showing  continuation  of  skin  and  mucous  membrane 
over  its  outer  and  inner  surtaces  respectively.     <  75.    Drawn  from  preparation  made  by  Dr.  Ralph  Butler. 


The  nerves  supplying  the  tympanic  membrane  are  derived  chiefly  from  the  auriculo-tem- 
poral  branch  of  the  trigeminus,  supplemented  by  twigs  from  the  tymp.inic  plexus  and  by  the 
auricular  branch  of  the  vagus.  They  accompany,  for  the  must  part,  the  blood-vessels  and,  in 
addition  to  supplying  the  latter,  form  both  a  sulx:utaneous  and  a  submucous  plexus. 

The  inner  wall  (paries  labyrintlu^a)  of  the  tympanic  cavity  separates  it  from 
the  internal  ear.     It  presents  for  examination  a  number  of  conspicuous  features. 

The  promontory  appears  as  a  well-marked  buljjinn  of  the  inner  wall  near  its 
middle  (Fig.  1254)  and  corresponds  to  the  first  turn  of  the  cochlea.  The  branches 
of  the  tympanic  plexus  arc  found  in  the  mucous  membrane  co\ering  it.  At  the 
biittom  of  a  niche,  whose  anterior  Ixirder  is  formed  by  the  lower  posterior  margin 
of  the  promontory,  lies  the  round  window  (fenestra  cochlea).  It  is  closed  by 
the  secondary  tympanic  membrane  (membrana  tympani  secundaria),  which 
separates  the  tympanic  cavity  from  the  scala  tympani  of  the  cochlea  (Pig.  1259). 
The  membrane  is  attached  in  an  obliquely  placed  groove,  is  slightly  concaA-e 
toward  the  tympanum,  and  measures  from  1.5-3  mm.  in  diameter.  The  oval 
window  (fenestra  vestibull)  lies  at  the  Ijottom  of  a  depression,  the  fossula 
vestibuli,  in  the  upper  back  part  of  the  inner  wall,  above  the  round  window,  and 
leads  into  the  vestibule.  It  is  somewhat  kidney-shaped,  its  upper  border  being 
concave,  its  lower  slightly  convex.  In  the  recent  state  the  oval  window  is  closed 
by  the  foot-plate  of  the  stapes  and  ll.e  ligament  which  connects  the  os-siclc  with 
the  sides  of  the  window  (Fig.  1260).  The  longest  diameter  of  the  latter  is 
about  3  mm.   and  its  shortest   1.5  mm.     Abov"  the  oval  window  a  well-marked 


_. 


1496 


HUMAN   ANATOMY. 


ridjje  indicates  the  position  of  the  facial  canal  or  aquednctits  Fallopii.  This 
ridge  is  bordered  posteriorly  and  su{)eriorly  by  tlie  ele\ation  which  corres])on<ls  to 
the  wall  of  the  horizontal  semicircular  canal  ( prominentia  canalis  semicircularis  latcr- 
a!i»^  The  sinus  tympani,  a  well-marked  depression,  is  behind  the  promontory, 
Ixjtween  the  niche  of  the  round  window  and  the  pyramid,  below  and  beiund  the 
oval  window.  It  is  separated  from  the  fossuhe  of  the  two  windows  by  l)ony  ridges. 
It  varies  in  depth  from  2-5  mm  ,  with  a  \ ertical  iliameter  of  from  2-6  mm. 

The  superior  wall  (paries  teKmenUlis)  is  formed  by  a  plate  of  bone,  the  teg- 
men  tympani,  which  forms  part  of  the  upper  and  anterior  surface  of  the  i)etrous 
jHjrtion  of  the  temporal  l»ne.  I'osteriorly  it  forms  the  roof  (jf  the  antrum  tympani- 
cum,  and  anteriorly  contributes  the  roof  of  the  canal  for  the  tensor  tympani  muscle 
and  of  the  adjoining  part  of  the  Eustachian  tube.  It  varies  in  thickness  and  may  l)e 
defective  to  a  large  extent  from  atrophy  or  arrested  development. 

The  inferior  wall  (paries  jugularis),  narrower  than  the  superior,  separates  the 
typanum  from  the  jugular  fossa.  Its  bony  plate  may  be  incomplete  and  may  lie 
considerably  below  the  level  of  the  membrana  tympani. 

The  anterior  wall  (paries  car^tica)  separates  the  tympanum  from  the  carotid 
artery  and  at  times  presents  a  fissure.  At  its  upper  part  is  the  irregular  trian- 
gular opening  of  the  Eustachian  tube  and  above  this  opening  lies  the  small  canal  for  the 


Outer  end  of  horiiontat 
part  of  facial  canal 


Stapes  lying  in 
oval  winoow 


Stapedius  muscU 
Ruuiid  window 


Facial  canat 


Promontory 

Tensor  tympani 


^Eustachian  tube 


^^♦^^?S?^ 


Outer  aspect  ol  inner  wall  of  right  tympanic  cavity;  itapes  lies  within  oval  window.    X  i%. 

tensor  tympani  muscle.  The  canaliculus  caroticus  tympanicus  perforates  the  anterior 
wall  just  below  the  mouth  of  the  Eustachian  tube,  and  transmits  the  tympanic  branch 
of  the  internal  carof'd  artery  and  carotico-tympanic  nerves. 

The  posterio  wall  (paries  mastoidea)  of  the  tympanum  at  its  upper  part  is 
occupied  by  the  antrum  tympanicum,  which  leads  into  numerous  irregular  cavities, 
the  mastoid  cells.  At  the  lower  border  of  the  antrum  is  a  saddle-shaped  notch,  the 
fossa  incudis,  which  lodges  the  short  process  of  the  incus.  E.xtending  for\yard 
from  the  posterior  wall,  on  a  le\el  with  the  lower  border  of  the  oval  window,  projects 
the  small  bony  elevation,  the  pyramid  (eminentia  pyramidalis),  which  encloses  the 
stapedius  muscle  ("Fig.  1254).  Its  ape.x  is  inerccd  by  a  small  round  opening  for 
the  e.xit  of  the  stapedius  tendon.  The  canal  within  this  eininence  communicates 
posteriorly  \.ith  the  facial  canal.  On  a  level  with  the  eminentia  pyramidalis,  close 
to  the  posterior  margin  of  the  drum-membrane,  lies  the  apertura  tympanica  canaliculi 
chordae  tympani,  the  oiiening  through  which  the  chorda  tympani  nerve  enters  the 
middle  ear. 

THK  CONTENTS  OF  THE  TYMPANUM. 

The  Auditory  Ossicles. — Three  small  bones  (ossicula  auditus)  iorm  a  chain 
extending  across  the  upper  part  of  the  tymprtnum  from  the  tyinpanic  membrane  to 
the  labyrinth.  The  outermost  of  th^-se,  the  malleus  (hammer),  is  attached  to  the 
tympanic  membrane  ;  the  innermost,  the  stapes  (stirrup),  is  fixed  in  the  oval  window, 
and  between  these  two  bones  and  conuected  with  both  of  them,  lies  the  third  hnk  m 
the  chain,  the  incus  (anvil). 


THE   MIDDLE   EAR. 


"497 


The  malleui  (hammer)  is  about  8  mm.  lone  and  nmsists  of  a  head,  a  nt-ck  and  three 
processes.  The  head  is  the  upper  chih-shapetl  portion,  lyinn  in  thf  tpitynipanii-  sikut  ;  lh<- 
constricted  portion  just  l)elow  the  head  is  the  neit,  and  Ih-Iow  this  is  a  prominenct-  to  uhirh 
the  three  processes  are  attached.  The  (Kisterior  surface  of  the  hi-a<l  iH-.irs,  for  the  articulation 
with  the  incus,  an  oblong  depressed  surface  with  prominent  marKins  rxtendiny;  in  a  spiral 
manner  downward  and  inward  to  the  neck.  This  articular  surface  consists  of  two  prim  ipal 
facets  separate<l  l)y  an  obliiiue  ritlge,  the  upner  facet  IiM)kinK  backward,  tin-  lower,  iMwar<l. 
The  .ixis  of  the  head  forms  with  that  of  thi  handle  an  aUKle  of  alKiut  I4u°,  upeniuK  upward 
and  inward. 


Fig.   1255. 


Hend 


Artictilar 
.Hitrfac«  for 
incuA 


IIea<l 


Point  of  InMi-tion  tif 
lattrral  ligamt-nt 


Manubrium 


PrtxYMNUft  ffraciliN 


Manubrium 


Right  inalletta;/4,  teen  from  lieliind;  /?,  M,-n  from  In  front.  X  ^\^. 

The  manubrium  (handle),  a  taperinR  proces.s  extending  downward,  backward  and  inward, 
is  embedded  in  the  substance  of  the  tympanic  membrane  (Fiji.  1 J55 ).  Near  the  up|)er  part 
of  the  iimer  anterior  surface  of  the  handle  is  sometimes  found  a  slij;ht  projection  for  the 
insertion  of  the  tensor  tympani  muscle.  The  lower  end  of  the  manubrmm  is  s|Kitula  shaped, 
flattened  transversely.  The  long  process  is  directed  toward  the  Glaserian  fissure,  whilst  the 
short  process  looks  toward  the  external  meatus. 

The  processus  breins  (short  process)  is  a  small  conical  elevation  situated  at  the  up|)er  end 
of  the  handle,  lx;low  the  neck  of  the  malleus.  Like  the  handle  it  is  attached  to  the  tympanic 
membrane  and  covered  by  a  layer  of  cartilage,  notably  on  its  external  surface. 

The  processus  gracilis  ( long  prcx-ess )  arises  from  the  anterior  angle  of  the  internal  surface 
of  the  neck,  close  to  the  base  of  the  short  process,  and  extends  downward  and  forward  to  the 
Gla-serian  fis.sure.  It  is  well-  developed  in  the  fictus  and  in  young  children,  but  is  often  rudi- 
mentary in  the  adult 

Fig.  1J56. 
A  K 


Proceasua 
longus 


I^uc«s.sus  lon^us' 


rrocrasua 
orlnuilaria 


Right  incus;  A,  lateral;  B,  anlerior  aspect.    X  4^. 


The  incus  (anvil)  resembles  a  molar  tooth  with  two  widely  sejiarated  fangs,  rather  than  an 
anvil.  It  consists  of  a  body,  a  long  process  and  a  short  process.  The  body  of  the  incus  has 
two  main  facets  on  its  anterior  and  antero-extemal  surfaces,  which  correspond  to  those  on  the 
head  of  the  malleus  and  articulate  with  them.  The  processus  brevis  (short  process)  is  conical 
in  shape,  flattened  laterally  and  projects  nearly  horizontally  backward  to  a  depression  in  the 
posterior  wall  of  the  tympanum  at  the  entrance  of  the  antnim,  where  its  a|)ex  is  attached.  The 
processm  lonsus  (long  process)  runs  downward  and  backward,  behind  ami  nearly  parallel  with 
the  handle  of  the  malleus,  and  ff>rms  nearly  a  right  angle  with  the  short  process.  At  its  lower 
end  it  is  I)ent  sharply  inward  and  con.stricted  into  a  neck,  which  terminates  in  a  rounded 
tnt)ercle,  the  processus  orbicularis^  that  articulates  with  the  head  of  the  stap  -.  In  the  futus 
this  process  is  separated  from  the  rest  of  the  long  process. 


1498 


HUMAN   ANATOMY. 


The  lUpn  (stirrup),  as  its  name  im|>licrs,  is  stirrup-shaptxl  and  consists  of  a  head,  neck, 
two  crura  and  a  base  ur  foot-plate.  The  external  surface  of  the  small  rounded  head  is  hollowed 
out  for  articulation  with  the  orbicular  process  of  the  incus.  Just  below  this  is  the  constricted 
ntck,  from  which  the  two  crura  diverge  to  become  attached  to  the  foot-plate  near  its  lower 


Fig.  1257. 


Heact. 


Aniirior  cni" 


I'pper  edge 


Posterior 
"Lower  edge 


Koot-pltitc 
Right  itapct,  A,  cceii  front  .-ibove;  B,  mesUI  surface  of  foot-plate.  X  iVi. 

margin.  The  anterior  crus  is  shorter  and  straighler  than  the  posterior,  both  being  .slightly 
curved.  The  fool-plate  consists  of  a  lamina  of  bone  .-ind  corresponds  to  the  bean-shape  of  the 
oval  window,  into  which  it  nearly  fits.  The  upper  edge  of  the  foot-plate  is  convex  ;  its  lower 
edge  is  almost  straight,  being  slightly  hollowed  out  near  its  middle. 

Articulationi  of  the  Osiidei.— In  the  malleo-incudal  joint,  both  articular  surfaces  are 
covered  with  a  thin  layer  of  hyaline  cartilage.  The  fairly  well-develoi>ed  capsular  ligament, 
reinforced  mesially,  is  fastened  to  the  depres.sed  margins  of  the  articular  surfaces.  A  wedge- 
shaped  meniscus  of  fibro-cartilage  projects  from  the  upper  wall  of  the  capsule  between  the  sur- 

FiC.  tjjS. 


Sup.  ligament 


Hend  of  malleus 
External  ligament 
Mem.  Aacciila  or 
Shrapiiell's  membrane 
Pnissak's  space 
Neck 

'Short  process 

Chorda  tympani 

Tendon  of  tensor 
tympani 


artilage 
'Epidermis 
Menibrana  propria 


^fucous  membrane 


Menibrana  tensa 


.\nnulus  tendinosns 


Frontal  section  passing  through  malleus  and  tympanic  membrane. 
X  60.    Drawn  from  preparation  made  by  Dr.  Ralph  Butler. 


manubrium  handle  moves  inward,  its 
lower  cog  catches  the  rorres|X)nding  rog 
of  the  incus  and  the  long  process  of  the 
latter  must  follow.  If  the  handle  moves 
outward,  the  lower  cog  moves  away 
from  the  incus  and  the  latter  moves  but 
little"  (Politzer). 

The  articulation  of  the  incus  and 
•tape*  is  a  very  delicate  but  true  joint. 
Both  the  slightly  convex  surface  of  the 
lenticular  process  of  the  incus  and  the 
slightly  concave  surface  of  ihe  head  of 
the  sta|x»  are  covered  with  hyaline  car- 
tilage and  united  by  a  capsular  ligament 
made  up  largely  of  elastic  fibres  and 
thickened  on  the  posterior  surface. 
So  etimes  a  meniscus  of  fibro-cartilage 
separates  the  two  articular  surfact.i. 

The  articulation  of  th£  stapes  and 
oval  window  is  effected  by  the  margins 
of  the  window  and  the  foot-plate  of  tht^ 
stapes.  These  surfaces,  as  well  as  the 
vestibular  aspect  of  the  stapes,  are  cov- 
ered with  a  layer  of  hyaline  cartilage. 
The  cartilage  of  the  foot-plate  and  that 
of  the  window^  are  connected  by  a  liga- 
ment of  elastic  fibres,  forming  a  syn- 
chondro.-iis. 

In  addition  to  the  ligaments  con- 
cerned in  the  foregoing  articulations, 
four  bands  attach  the  ossicles  to  the  tym- 
panic walls  and  prevent  their  excessive 
movement ;  of  these,  three  connict  the 
malleus  and  one  the  incus. 


1.  The  superior  ligament  of  the  malleus  extends  from  the  tegmen  tympani  to  the  head  of 
the  malleus.     (Figs.  1253  and  1258.) 

2.  The  interior  ligament  of  the  malleus  is  a  strong,  bro;id,  fibrous  band  arising  from  th» 
anterior  part  of  the  head  and  neck  of  the  malleus.  Some  of  its  fibres  are  attached  to  the  ante- 
rior end  of  the  annulus  tympanicus  (spina  tympanica  major)  and  other  fibres  pass  through  the 
Glaserian  fissure  to  become  attached  to  the  spine  of  the  sphenoid.  These  fibres  correspond  to  the 
remains  of  the  embryonic  process  of  Meckel  of  the  malleus  and  envelop  the  processus  gracilis. 


THE   MIDDLE   EAR. 


14yV 


3.  The  latml  ligament  of  th«  mallaua  is  somewhat  fan-shii|>e<l  and  extemlx  t)etwet-n  the 
roUKheneil  neck  o(  the  malleus  and  the  external  wall  of  the  tym|ianum  aUive  the  Kivinian  notch. 
The  |)ostcrior  fibres  of  this  liKament  are  callfd  the  poitcrior  ligament  of  thf  malleus  (  Hflmholt/) , 
ami,  tottether  with  the  fit)res  of  the  anterior  liKament  lyins  in  the  same  plane,  form  the  "  axis- 
liKanient  of  the  malleus,"  since  the  axis  on  which  the  malleus  turns  (kisscs  through  thi-  attach- 
ment of  these  two  fibrous  structures. 

4.  The  poiterior  ligament  of  the  incut  extends  from  the  n\yex  of  the  short  process  of  the 
incus  to  the  tympanic  wall  at  the  lower  part  of  the  mouth  of  the  antrum.  It  Ls  fan-shapetl,  the 
incudal  attachment  heinf;  les.s  extensive  than  that  of  the  tympanic.  Th-j  eupcrioT  ligament 
of  the  incue  is  variable  and  consists  chiefly  of  a  fold  of  mucous  membrant-. 

The  Inuatympanie  Mutcle*. — The  muscles  within  the  tympimum  connected  with  th< 
os.sicles  (muKuli  oMiciilomn  audltas)  are  :  (1 )  the  tensor  fytHf>am  Mv\  (a)  the  s/afifiiius. 

The  tenaor  tympani  Ls  a  diminutive  spindle-shaped  muscle,  al)out  1.25  cm.  Iouk.  lyin*;  in  the 
bony  canal  directly  above  the  osseous  part  of  the  Eustachian  tulie,  from  which  it  is  ixirtly 

Fig.  1259. 


FaciHl  iirr\-e 


kainu!*  titrictihlft 
ampulla  rift 


riricle 


Foot  of  atapa 


Secoiulnry  tym- 
pantc  memtiratie 


F.xtrrnal 
auditury  canal 


Promontory 


Drnm-heacI  or 

tympanic 

membrane 


Tympanic  cavity 


Vertical  Hction  through  human  middle  and  internal  ear.    X  i%i.  Drawn  from  preparation  made  by  Dr.  Ralph  Butler. 

separated  by  the  bony  scroll,  the  processus  coch/eariformis.  The  posterior  fibres  ari.se  from 
the  top  of  the  cartilage  of  the  Eustachian  tube  and  the  adjoininj;  part  of  the  g^reat  wing  of  the 
sphenoid.  Some  of  the  fibres  are  connected  with  the  tensor  palati  muscle  and  others  arise 
from  the  wall  of  the  canal  which  the  muscle  tKCupies.  The  fibres  converge  in  a  feather-like 
manner  to  the  tendon,  which  begins  within  the  muscle  about  the  middle  ni  lie  canal,  and,  pass- 
ing through  the  tympanic  opening  of  the  canal,  turns  at  nearly  a  right  aii^le  over  the  end  or 
rostrum  of  the  processus  ctKhleariformis  to  be  inserted  into  the  anterior  part  of  the  inner 
margin  of  the  malleus-handle  just  below  the  short  process.  The  tendon  is  almost  per- 
pendicular  to  the  plane  of  the  tympanic  membrane,  is  oblique  to  the  long  axis  of  the  manu- 
brium and  is  enveloped,  along  with  the  muscle-belly,  in  a  fibrous  sheath.  The  tensor  tympani 
and  tensor  palati  muscles  receive  their  nerve  supply  from  the  same  source,  namely,  the  trigem- 
inus, through  the  otic  ganglion 

The  stapedius  muscle  lies  within  the  triangular  canal  of  the  eminentia  pyramidalis,  arising 
from  its  floor  and  sides.  Its  fibres  converge  to  the  tendon,  which,  passing  through  the  opening 
at  the  apex  of  the  canal,  extends  forward,  slightly  upward,  and  outward,  to  he  inserted  into  the 
lower  posterior  part  of  the  head  of  the  stapes.    Some  of  the  fibres  of  the  tendon  also  pass  to  the 


1500 


HUMAN   ANATOMY. 


lenticular  priM-css  and  the  capmilnr  liKament.  Theteiui.iii  :s  ire<|uently  fnvelo|>ed  in  a  fold  oi 
iiiiicoUH  nienibranr.  A  branch  of  the  fm  i.'l  nerve  ji.issi  ihroufth  a  small  oritice  Iwtwtfn  tlic 
Fallopian  canal  and  the  canal  for  the  sta|iedius  to  sii|)|>lv  tiii>  mus«-|e. 

Movement*  of  the  Oitides.— When  the  tyni|Kinic  menihrane  and  malleus-handle  are  nu>\  eil 
inward,  the  lonjt  priness  of  the  incus  is  also  moved  ir.w.ird  and  pushes  the  head  of  the  sta|>es 
inuard,  anil  sliKhtly  upward.  This  cans^-s  pressure  u|H>n  the  li(|uid  within  the  labyrinth,  and, 
since  the  bony  walls  ot  the  labyrinth  are  ineliistic,  the  membrane  of  the  round  window  is  bulged 
outward.  As  the  tym|>iinic  membrane  rt  .■  ,;  its  normal  |iusition,  these  movements  are  re- 
versed. When  on  the  other  hand  the  tympai.:,-  membrane  is  moved  outward,  the  movement  of 
the  lonK  pr>K:ess  of  the  incus  is  very  sdifht  liecause  of  the  untiH-kint;  of  the  malleo-incudal  articu- 
lation. Contraction  of  the  tensor  tympimi  rnusclc  draws  the  centre  of  the  tympanic  membrane 
inward  and  in  this  way  increa,se>»  the  tensi  Ml  of  the  membrane  and  of  the  posterior  part  of 
the  axial  ligament  of  the  malleus,  especially  of  »s  external  |)ortion.  Ci  mtraction  of  the  stapedius 
muscle  pulls  the  hea»l  of  the  -.ta|ies  Ixickward,  thus  liltinR  the  anterinr  end  of  the  foot-plat--  out- 
uaril.  the  posterior  end  acting  as  a  fulcrum. 

The  Mucous  Membrane  of  the  Tympanum. — The  tympanic  cavity  is 
lined  by  a  thin  transparent  mucous  membrane,  closely  adherent  to  the  periosteum 
and  continuous  with  that  of  the  Eustachian  tube  and  naso-pharyn.x  anteriorly,  and 


Fig.  126"  1 


posterior  cniH  of 
!»tapcA 


Lower  end  of 
iucuH 


Malleus  handle 


Interiml  ftiidito- 
ry  canal 


Cocliltar  nerve 


'Hsal  turn  of 
C€x:hlea 


Tympanic  cav-it  j 


(lorizontal  wction  through  human  mi  MIe  atid  intenial  ear :  stapes  occludes  oval  window,     v  5U.     Drawn  from 
preparation  made  by  l3r.  Ralph  Butler. 

with  that  of  the  mastoid  cells  posteriorly.  It  covers  the  ossicles  and  their  liKiiments, 
the  muscle's,  the  tendons  ,ind  the  chtirda  tympani  ner\e,  and  ff)rms  a  number  of  folds 
e.\tending  across  the  cavity.  These  folds  vary  in  location,  direction  and  number, 
and  form  pouches  within  the  tympanum. 

The  attic  is  divided  into  an  external  and  an  internal  compartment  by  the  incus, 
the  head  of  the  malleus,  the  sup'^rior  lijjament  of  tlic  malleus  and  the  superior  malleo- 
incudal  fold  of  mucous  membrane.  The  external  compartment  is  bounded  on  the 
;. liter  .side  by  the  external  tympanic  v.  ,;;,  and  i;;  itself  sui.dividcd  inio  a  super;  r  ant; 
an  inferior  space  by  the  externil  lii;.unent  of  the  malleus.  The  inferior  divi-  "ii  i;s 
called  Prussak's  space  and  is  xmnded  externally  '      Shrapnell's  membram  i- 

nally  by  the  neck  of  the  inalleiis,  inferior'-    '      •'■      ■         pnv      ■;  of  the  hammt 


superiorly  by  the  external  ligament 


id 
'ig.    1 258).     A  numbci    of 


THK    MIDDI.K   KAR. 


ISO  I 


inconstant  folds  of  mucous  incinbranc,  extern!  from  the  will  of  tfie  tviniMiium  u> 
tl>e  malleus  and  the  incus.  The  most  consta  of  these  is  the  unti  r  nialK  >-inciiii.il 
plica,  which  stretches  iMckward  to  the  |>osterioi  ligament  ot  llie  inii;s.  Ailuitioiial 
folds  frecjuentlv  extend  l)etween  the  cura  of  the  stapes  and  from  tli  in  lo  tile  wall 
of  the  tyin|)itnuni. 

The  epithelium  of  the  tympanic  mucosal  vari<-  in  ditTereiu  pans  .f  the  civity. 
Over  the  proinontt)ry,  the  ossicles  and  the  tympanic  membrane,  it  conMstsvi  .1  -.iiinle 
layer  of  low  cuboidal  nonciliate<l  cells,  whilst  over  the  other  parts  the  cells  arc  ciliated 
columnar  in  type.  Small  tubular  glands  occur  within  the  linin^j  of  the  anterior  part 
of  the  cavity.  The  sulx-pithelial  connective  tissue,  which  supports  the  vessels  and 
nerves,  comprises  two  layers,  the  outer  forminj;  the  periosteum  of  the  fx>nv  wall. 

The  secondary  tympanic  membrane  closing  the  fenestri  cmhliie,  bulges 
somewhat  toward  the  cochlea  and  is  attached  to  the  bony  crest  or  ridge  of  the  win- 
dow by  its  widened  rim.  It  onsists  of  three  layers,  of  which  tin-  middle  one  is  a 
I'.i-linct  fibrous  lamina  propria,  which  is  covered  on  the  tvmpinic  surface  bv  nuicou-. 
membrane,  and  on  the  other  side  by  an  extension  of  the  lining  of  the  perilymphatic 
S|>ace.  The  lamina  propria  is  composetl  of  radially  disposed  buntlles  c>f  fibrous 
tissue.  The  outer  mucous  stratum  is  formed  of  a  thin  fibr.ous  tunica  propria, 
invested  by  a  single  layer  of  flattened  nonciliated  epithelial  cells,  similar  to  those 
covering  the  neighboring  promontory.  The  innermost  stratum  of  the  membrane 
includes  a  thin  layer  of  subendothelial  fibrous  tissue,  over  which  stretches  a  layer  of 
endothelial  plates. 

Vessels  and  Nerves  of  the  Tympanun..-  The  arteries  supplying  the 
tympanic  cavity  are  from  five  sources. 

1.  The  stylo-mastoid  branch  of  the  posterior  auricula-  artery  passes  through  the 
stylo-mastoid  foramen  and  the  Fallopian  aqueduct,  and  sends  a  iKanch  to  the  sta- 
{ledius  muscle  and  three  branches  to  the  posterior  part  of  the  tympanic  cavity.  One 
of  these  passes  to  the  floor,  one  through  the  canal  for  the  chorda  tympani  nerve,  and 
one  to  the  posterior  part  of  the  oval  window. 

2.  The  tympanic  branch  of  the  ir^ternal  maxillary  artery  enters  the  tympanic 
cavity  through  the  Glaserian  fissure  and  supplies  the  anterior  part  of  the  cavity, 
including  the  anterior  ligament  of  the  malleus,  the  pr<Kessus  gracilis  and  the  tympanic 
membrane. 

3.  The  middle  meningeal  branch  of  the  internal  maxillary  artery  sends  a  branch 
through  the  hiatus  P'allopii  to  anastomose  with  the  stylo-mastoid  artery,  a  branch 
through  the  canaliculus  tympanicus  to  the  promontory,  and  a  branch  to  the  tensor 
tympani  muscle. 

4.  The  ascending  pharyngeal  sends  branches  to  the  floor  and  the  promontory, 
one  of  them  accompanying  Jacobson's  ner\-e. 

5.  The  internal  carotid  artery  in  its  passage  through  the  carotid  canal  gives  off 
branches  to  the  anterior  wall  of  the  tympianic  cavity. 

The  veins  follow,  in  a  general  way,  the  course  of  the  arteries.  They  are  tribu- 
tary to  the  middle  muningeal,  the  pharyngeal  plexus  and  the  jugulars. 

The  lymphatics  ari.se  from  a  net-work  within  the  mucous  membrane  and  end 
chierty  in  the  retropharyngeal  and  the  parotid  nodes. 

'I'he  nerves  supplying  the  inuc(jus  membrane  of  the  tympanum  are  branches 
from  the  tympanic  plexus  formed  by  the  tympanic  branch  of  the  glosso-pharyngeal 
ner\  e,  in  conjunction  with  sympathetic  filaments  from  the  net-work  accom|>anying  the 
carotid  artery.  The  tensor  tympani  nwscle  receives  its  supply  from  the  trigeminus: 
the  stapedius  muscle  from  the  facial.  Although  the  chorda  tympani  nerve  has  an 
intimate  topographical  relation  to  the  sjiace,  which  it  traverses  close  to  the  outer 
wall,  it  gives  no  filaments  to  the  structures  within  the  tympanum. 


The  EisTACHiAN  Tube. 

The  Eustachian  tube  Ctnba  auditiva)  is  a  canal,  partly  bony  and  partly  cartilagi- 
nous, extending  from  the  Literal  wall  of  the  naso-pharynx  backward,  upward  and  out- 
ward to  the  anterior  part  of  the  tympanum,  fn  the  adi-'.t  it  measures  about  37  mm. 
{xYi  m.)  in  length,  of  which  approximately  the  upper  third  (tympanic  portion^ 


^*v»| 


I502 


HUMAN  ANATOMY. 


belongs  to  the  bony  division,  whilst  the  remainder  is  contributed  by  the  cartilaginous 
division  of  the  tube.  With  the  sagittal  plane  it  forms  an  angle  of  45«',  and  with  the 
horizontal  plane  one  of  about  3.°.  With  the  long  axis  of  the  external  auditory 
canal  it  forms  an  angle  of  from  las'-US".  opening  outward.  The  cartilaginous  and 
bony  divisions  of  the  tube  do  not  lie  exactly  in  the  same  plane,  but  join  at  a  very 
obtuse  angle  opening  outward.  The  tube  has  somewhat  the  shape  of  an  hour  glass, 
being  wider  at  the  ends  and  narrowed  at  the  junction  of  the  cartilaginous  and  bony 
portions  into  the  isthmus,  where  its  height  is  about  3  mm.  and  its  breadth  about  half 
as  much. 

The  osseous  or  tympanic  portion  (pars  ossca)  about  12  mm.  long,  is  bounded 
above  by  the  tegmen  tympani  and  the  canal  for  the  tensor  tympani  muscle,  from 
which  it  is  incompletely  separated  b)r  the  processus  cochleariformis.  Below  and 
internal  to  it  lies  the  canal  for  the  carotid  artery.  Its  lumen  is  irregularly  triangular 
in  cross-section. 


Fig.  1261. 


Tvmpanic  membrane 
Tympanic  cavity 
Antrum 
Condyle  of  jaw 


Baailar  proccM 


Internal  auditory  canal 

Right  internal  carotid  artery 


External  audi-, 
tory  canal 
Parol  id  eland- 

FiKMof  KOMn-- 

CartlliKC  ol_ 
Euftlai-hUn  tube 
husuchUn  tub«- 


l-evator  palati- 
Tenaor  palati- 

Huiiulu  pnce 


— Tympuik  memhianr 

_Extenial  auditory 
meatus 

-Parotid  gland 
^External 

pterygoid  muscle 

-Ramus  of  jaw 

Internal  pter>'goid 
'muscle 


-Soft  palate 
-Masacter  muscle 


Palatal  raphe 


^Vestibule 


Palatal  nigte- 


(fi*" 


Incisor  canal  - 


^Buccinator  muscle 


Incisive  pad' 

Anterior  part  of  section  through  head  at  plane  shown  in  small  outline  liitnre,  viewed  from  below;    left 
Eustachian  tube  exposed  throughunt  iu  length.    Drawn  Irom  preparation  made  by  Professor  Dwight. 

The  cartilaginous  or  pharyngeal  portion  (pars  cartila){iaea)  is  about  25 
mm.  (I  in.)  in  lenjfth  and  attached  to  the  rough  oblique  margin  of  the  anterior 
end  of  the  osseous  portion  of  the  tube. 

Its  posterior  wall  is  formed  by  a  plate  of  cartilage  rcartllago  tubae  aaditivae),  the 
upper  margin  of  which  is  curled  outward  upon  itself  to  form  a  gutter,  which  appears 
on  transverse  section  as  a  hook,  whose  inner  and  outer  plates  are  known  as  the 
mesial  and  lateral  lamina  respectively.  The  interval  between  the  margins  of  this 
cartilaginous  groove  presents  outward  and  forward  and  is  filled  up  with  a  strong 
fibrous  membrane,  thus  completing  the  canal.  Therefore  part  of  the  anterior  wall 
and  the  posterior  superior  wall  of  the  tube  are  formed  by  this  cartilage  and  the  rest 
of  the  anterior  wall  and  all  of  the  inferior  by  fibrous  tissue.  The  cartilage  is  attached 
to  the  base  of  the  skull  and  frequently  is  deficient  in  places,  sometimes  being 
divi'led  into  se\<'ral  pieces.  At  birth  the  cartilage  is  entirely  of  the  hyaline  variety, 
but  later  this  is  more  or  less  extensively  replaced,  jiarticulary  in  the  pharyngeal 
division,  by  fibrocartilage,  except  iu  the  upper  part  where  the   hyaline  cartilage 


THE  MIDDLE  EAR. 


»503 


persists.  It  is  this  cartilage,  covered  by  the  cushion  of  mucous  membrane,  thai 
confers  the  characteristic  Gothic  arch  contour  to  the  lower  opening,  the  osteum 
pharyngeum,  of  the  tube. 

The  Mucous  Membrane  of  the  Eustachian  Tube. — The  Eustachian 
tube  is  lined  throughout  its  length  with  mucous  membrane,  which  differs  some- 
what in  the  cartilaginous  and  osseous  portions.  That  in  the  former  resembles  the 
mucous  membrane  of  the  naso-pharynx,  with  which  it  is  directly  continuous,  whilst 
that  of  the  osseous  division  resembles,  to  some  extent,  the  mucous  membrane  of  the 
tympanic  cavity.  The  epithelium  of  both  divisions  consists  of  the  ciliated  stratified 
columnar  type,  with  some  goblet  cells,  but  the  cells  in  the  pharyngeal  division, 
especially  in  the  lower  part,  are  taller  than  those  of  the  tympanic  portion,  which  are 
low  cuboidal. 

In  the  tympanic  portion  ihe  mucous  membrane  is  closely  united  with  the  perios- 
teum and  contains  very  few  mucous  glands  and  little  or  no  adenoid  tissue.  In  the 
cartilaginous  division,  on  the  contrary,  the  epithelium  overlies  a  layer  of  adenoid 

Fig.  1363. 


Lateral  lamina 


oblique  ntuKle-fibres' 


Lumen  of  tube 


Tetisor  palati  (dilator  tuba.)— 


.Mesial  lamina  of  cartilage 
of  tube 


™l^¥'' 

Levator  palati^ 

Tmniverve  section  of  cartilaginous  Eustachian  tube,    .v  7. 


tissue,  often  called  the  tubal  tonsil.  This  tissue  is  especially  abundant  in  children, 
and  beneath  it  are  found  numerous  mucous  glands  which  open  on  the  free  surface  of 
the  tube.  These  glands  extend  nearly  to  the  perichondrium  and  sometimes  can  l)e 
traced  even  through  the  Assures  in  the  cartilage  into  the  surrounding  connective  tissue. 
A  considerable  amount  of  adi{X)se  tissue  often  occupies  the  submucosa  of  the  lower 
and  lateral  walls.  The  submucous  layer  is  well  developed  in  the  cartilaginous 
division  of  the  tube,  particularly  in  the  outer  membranous  wall.  It  consists  of 
loosely  arranged  tibro-clastic  tissue,  ^hich  supports  the  mucous  glands  and  the 
larger  vessels  and  nerves. 

The  muscles  of  the  Eustachian  tube  are  the  levator  and  the  tensor  palati ,  the 
contractions  of  which  not  only  affect  the  palate,  but  also  produce  changes  in  the 
position  of  the  floor  and  in  the  lumen  of  the  tube.  These  muscles  are  described  in 
connection  with  the  palate  Tpage  159.^),  suffice  it  here  to  note  their  close  relations  to 
the  Eustachian  tube,  beneath  and  to  the  inner  side  of  which  the  levator  lies,  and  to  the 
outer  side  of  which  the  tensor  extends.  By  reason  of  the  intimate  attachment  which 
both  muscles  have  to  the  cartilage  of  the  tube,  since  both  take  partial  origin  from  this 
structure,  contraction  of  their  fibres  tend  to  draw  apart  the  walls  of  the  canal  and  they 
thus  serve  as  dilators.     Such  action  is  particularly  true  of  the  tensor  palati,  many  of 


'504 


HUMAN  ANATOMY. 


whose  fibres  are  inserted  into  tibrous  tissue  completing  the  lateral  wall  of  the  tube 
(Fig.  1262),  this  part  of  the  muscle  being  designated  the  dilator tubte.  In  addition 
to  opening  the  tube,  the  levator  palati  elevates  its  floor. 

The  blood-vessels  of  the  Eustachian  tube  include  the  arteries,  which  arise  from 
the  ascending  pharyngeal  and  from  the  middle  meningeal  and  the  Vidian  branches  of 
the  internal  maxillary;  and  the  veins,  which  communicate  with  those  of  the  tym- 
panum and  of  the  pharynx  and  also  form  a  plexus  connecting  with  the  cavernous 
sinus. 

The  nerves  are  supplied  from  the  tympanic  plexus  and  from  the  pharyngeal 
branches  from  the  spheno-(>alatine  ganglion. 


The  Mastoid  Cells. 

The  antrum  tympanicum  communicates  posteriorly  with  a  variable  number  of 
irregular  pneumatic  cavities,  the  mastoid  cells  (cellulae  mastoideae),  so  called  because 
the  majority  of  these  sjiaces  occupy  the  mastoid  process.  Unlike  the  antrum,  these 
cells  are  not  developed  at  birth.  As  the  mastoid  process  develops,  the  original 
diploetic  structure  is  usually  more  or  less  replaced  by  larger  cavities  forming  the 
pneumatic  type.  In  a  study  of  one  thousand  bones,  Randall  found  that  scarcely  two 
per  cent,  of  mastoids  could  be  classed  as  diploetic,  and  only  some  ten  per  cent,  as 
combining  a  notable  amount  of  diplne  with  pneumatic  spaces  ;  further,  that  no  mastoid 
is  absolutely  pneumatic,  although  some  senile  bones  show  a  single  thin-walled  cell 
occupying  the  greater  part  of  the  process.  The  pneumatic  cells  of  this  region  may 
extend  to  the  sigmoid  portion  of  the  lateral  sinus  ;  into  thr  occipital  bone  ;  into  the 
squamous  portion  of  the  temporal  bone  and  above  the  external  auditory  canal  ;  into 
the  root  of  the  zygomatic  process  ;  into  the  floor  of  the  Eustachian  tube  close  to  the 
carotid  canal,  .  ii'  occasionally  as  far  as  the  apex  of  the  petrous  portion  of  temporal 
bone.     Th'  "^  are  lined  by  a  very  thin  mucous  membrane,  which  is  continu- 

ous with     ■  J  antrum  and  of  the  tympanic  cavity.     It  is  closely  united  with 

the  perios  u  possesses  a  layer  of  low  nonciliated  squamous  epithelium. 

The  I-  '.  essels  supplying  the  mastoid  cells  are  the  arteries  derived  from 
the  stylo-n  i.  ■..  and  the  middle  meningeal,  and  the  veins,  which  communicate  with 
those  of  the  tympanum  and  the  external  wall  of  the  mastoid  process.  Some  of  the 
veins  are  tributary  to  the  mastoid  emissary  and  the  lateral  sinus,  whilst  others  puss 
beneath  the  superior  simicircular  canal  through  the  cranial  wall  to  join  the  dural  veins. 

The  nerves  are  the  mastoid  ramifications  of  the  tympanic  plexus. 

Practical  Considerations  :  The  Tympanum. — This  cavity  is  continuous 
anteriorly  with  the  nasopharynx  by  way  of  the  Eustachian  tube,  and  posteriorly 
with  the  mastoid  antrum  and  air  cells  by  way  of  the  attic,  so  that  infection,  which 
is  very  common  in  the  pharynx,  may  extend  throughout  this  whole  tract.  The 
tympanic  cavity  extends  above  the  limits  of  the  membrane  about  5-6  mm.  as  the 
attic,  and  about  2-3  mm.  below  as  the  "cellar"  or  hypotympanic  recess.  Secre- 
tions on  the  floor,  therefore,  may  not  be  seen  through  the  membrane.  The  defective 
drainage  which  results  from  the  lower  level  of  the  floor  of  the  tympanum,  as  com- 
pared with  that  of  the  external  meatus,  is  one  of  the  causes  of  the  frequency  of 
chrcnic  otitis  media  with  purulent  discharge,  even  after  the  early  evacuation  of 
the  products  of  inflammation  in  the  acute  stage. 

On  the  internal  wall  the  facial  nerve  passes  in  a  curve  over  the  vestibule  in  the 
angle  between  the  roof  and  inner  wall  of  the  tym|ianum,  then  downward  in  the 
slightly  projecting  Fallopian  canal  with  a  concave  turn  above  and  behind  the  oval 
window,  continuing  its  course  downward  at  the  junction  of  the  posterior  and  inner 
wall  to  emerge  below  from  the  skull  at  the  stylo-mastoid  foranien.  This  canal 
offers  considerable  resistance  to  caries  in  its  immediate  neighborhood,  although  the 
disease  not  infrequently  communicates  itself  to  the  nerve.  Such  involvement  of 
the  nerve  is  often  the  prodromal  symptom  of  a  fatal  cerebral  affection  (Politzer). 
At  birth  this  portion  of  the  Fallopian  canal  is  very  thin  and  translucent,  and  is 
deficient  as  it  arches  over  the  oval  window,  so  that  involvement  of  the  nerve  is 
much  more  common  in  children  than  in  adults. 


PRACTICAL  CONSIDERATIONS:    THE  MIDDLE   EAR.        1505 

Roofing  in  the  antrum  and  the  passage  leading  into  it  from  the  attic  is  a  thin 
layer  of  bone  (tegmen  antri),  which  is  particularly  thin  over  the  antrum  and 
separates  these  spaces  'rom  the  middle  fossa  of  the  skull.  Not  infrequently  there 
are  membranous  defects  in  the  tegmen,  upon  which  the  dura  rests  (Macewen). 
Pus  frequently  passes  through  this  bony  plate,  or  its  deficiencies,  to  the  temporo- 
sphenoidal  region  of  the  brain,  which  is  the  most  frequent  seat  of  brain  abscess. 

Fractures  of  the  base  of  the  skull  in  the  middle  fo«sa  may  pass  through  the 
tegmen,  rupturing  the  adherent  dura,  and  permitting  cerebro-spinal  fluid  to  pass  into 
the  tympanum.  If  there  is  coincident  rupture  of  the  tympanic  membrane,  the  fluid 
will  likely  appear  at  the  external  auditory  meatus,  or  if  the  membrane  remains  intact, 
the  fluid  may  pass  to  the  pharynx  through  the  Eustachian  tube. 

Often  the  hearing  in  chronic  plastic  otitis  media  is  better  during  a  great  noise 
than  when  the  surroundings  are  more  quiet,  because  the  stiffened  ossicles  transmit 
additional  ordinary  sounds  more  readily  after  they  have  been  loosened  by  the  more 
violent  vibrations;  or  it  may  be  because  the  auditory  nerve,  owing  to  the  greater 
irritation,  becomes  more  sensitive  (Urbantschitsch). 

The  various  relationships  of  the  tympanum  as  involved  in  infectious  disease 
should  be  understood  from  the  standpoint  of  etiology  and  from  that  of  sequelae  or 
complications. 

Infection  may  reach  the  tympanum  from  (a)  the  naso-pharjrnx  through  the 
Eustachian  tube  (scarlatina,  diphtheria,  pharyngitis,  tonsillitis,  rhinitis);  or  (6)  the 
mastoid  antrum  and  cells  posteriorly,  't  may  extend  from  the  tympanum  (a) 
upward,  by  perforation  of  the  tegmen,  often  deficient  at  places,  leading  tD  external 
pachymeningitis,  or  to  subdural  abscess  ;  the  dura,  arachnoid,  and  pia  mater  at 
this  level  are  fused,  so  that  when  the  dura  is  ulcerated  through,  a  diffuse  meningeal 
infection  does  not  ensue,  but  the  process  tends  rather  to  spread  into  the  brain  along 
the  perivascular  lymphatic  sheaths  of  the  pial  vessels,  resulting  in  an  abscess  in 
the  temporal  lobe  (Taylor);  (*)  to  the  internal  jugular  vein  through  venules  that 
penetrate  the  fundus  tympani  to  empty  into  the  jugular  bulb,  and  thence  to  the 
lateral  sinus  ;  (<•)  to  the  superior  petrosal  sinus  and  the  dura  mater  of  the  middle 
fossa  of  the  skull  by  the  structures  (veins  and  areolar  tissue)  passing  through  the 
petro-squamous  suture  ;  (</)  to  the  facial  canal  either  through  congeniul  defects  in 
hs  walls,  or  through  carious  openings,  or  along  the  course  of  the  stylo-mastoid 
artery  ;  facial  paralysis  may  follow,  or  infection  may  travel  along  the  internal  auditory 
meatus  and  give  rise  to  a  diffuse  leptomeningitis  in  the  cerebellar  fossa  (Taylor); 
(<■)  to  the  labyrinth  by  way  of  the  fenestra  ovalis,  or  through  the  membrana 
tympani  secondaria,  which  closes  the  fenestra  rotunda  opening  into  the  scala 
tympani ;  permanent  deafness  may  result  from  destruction  of  the  labyrinth,  and  the 
infection  may  pass  along  the  cochlear  branch  of  the  auditory  nerve  and  the  nerve 
itself  to  the  cerebellar  fossa  ;  (/)  to  the  ossicles  causing  caries  and  deafness  ;  {g) 
to  the  mastoid  antrum  (y. I'.).  .     . 

The  Tympanic  Membrane. — The  tympanic  membrane  is  oblique  in  its 
lateral  as  well  as  in  its  vertical  direction,  so  that  the  inferior  wall  of  the  auditory 
canal  is  longer  than  the  superior,  and  the  anterior  wall  longer  than  the  posterior. 
The  firm  attachment  of  the  handle  of  the  malleus  to  the  membrane  causes  it  to 
assume  the  shape  of  a  hollow  cone  with  its  convexity  pointing  internally.  The 
innermost  point  of  the  cone  is  at  the  lower  end  of  the  handle  of  the  malleus  and 
is  called  the  um6o.  The  distance  between  it  and  the  promontory  on  the  internal 
wall  of  the  tympanic  cavity  is  only  about  2  mm. 

Retention  of  the  products  of  inflammation  within  the  tympanum  may  decrease 
the  inward  bulging  of  the  membrane  or  even  cause  it  to  protrude  outward.  When 
the  Eustachian  tube  is  obstructed,  the  air  then  confined  within  the  middle  ear,  may 
become  partly  absorlietl,  allowing  the  external  atmospheric  pressure  to  increase  the 
inward  bulging,  and  to  press  the  base  of  the  stapes  more  firmly  into  the  fenestra 
ovalis,  giving  rise  to  a  ringing  in  the  ears. 

If  an  imaginary  line  in  the  axis  of  the  handle  of  the  malleus  is  continued  to  the 
lower  margin  of  the  membrane,  .-jnd  .-»  second  at  right  angles  to  this  is  carried  through 
the  um6o,  the  membrane  will  be  divided  by  the  vertical  line  into  a  lesser  anterior  and 
a  greater  posterior  portion,  and  by  the  h-.rizontal  line  into  a  greater  upper  and  a  lesser 


iriiliiiiMa 


i5o6 


HUMAN   ANATOMY. 


lower  portion,  the  umbo  being  slightly  below  the  middle  of  the  membrane.  By  the 
two  lines  the  membrane  is  divided  into  unequal  quadrants.  This  arrangement  into 
quadrants  is  a  very  important  one  since  the  pathological  apfiearances  occurring  in 
each  differ  greatly. 

The  antero-superior  quadrant  corresponds  to  the  tympanic  ofjening  of  the  tube,  the 
canal  for  the  tensor  tymfxini  muscle,  and  the  anterior  pouch  of  the  drum-head.  The 
antero-inferior  quadrant  corresponds  to  the  carotid  canal.  The  postero-superior  quad- 
rant contains  the  long  prr  -ess  of  the  incus,  the  stapes,  and  the  articulations  of  these 
bones,  the  oval  window,  the  pyramid,  and  sta[>ed)us  muscle,  the  posterior  pouch  lA 
the  drum-head,  the  chorda  tympani,  and  the  fwsterior  fold  (pathologic).  The/Vf/rro- 
inferior  quadrant  contains  the  round  window,  the  tympanic  cells  in  the  floor  of  the 
tympanic  cavity  and  the  bulb  of  the  jugular  vein.  The  flaccid  portion  or  Shrapnell's 
membrane  corresponds  to  the  neck  of  the  malleus  and  Pnissak's  space  (Briihl-Politzer). 
The  bulb  of  the  jugular  vein  may  be  larger  than  usual  in  which  case  it  may 
encroach  upon  the  posterior  half  of  the  membrane.  Moreover,  it  may  have  an 
imperfect  bony  covering  when  it  will  be  in  danger  during  paracentesis  tympani, 
the  place  of  election  of  which  is  in  this  portion  of  the  membrane.  For  the  same 
reason,  pus  in  the  middle  ear  may  more  readily  encroach  upon  the  vein.     The 

posterior  inferior  quadrant  is 
selected  for  openings  to  evac- 
uate effusions  in  the  tympanum, 
because  it  is  less  sensitive  and 
vascular  than  the  rest  of  the 
membrane  and  corresponds  to 
less  important  structures.  The 
opening  also  gives  better  drain- 
age than  through  any  other 
portion.  It  should  be  borne 
in  mind  that  the  floor  of  the 
tympanum  is  2-3  mm.  below 
the  mferior  margin  of  the  drum 
head,  so  that  in  the  upright 
position  perfect  drainage  can- 
not be  obtained.  The  tym- 
panic membrane  has  an  internal 
mucous  lining,  an  external 
cutaneous  and  an  inter\'cning 
fibrous  layer.  It,  therefore,  has 
lii'i-  elasticity,  so  that,  while 
smj...  openings  often  heal  rap- 
A  permanent  opening,   however. 


I^ottcricrMd 

1'rull,ih'»fold 


PiMterkw 

lilfamCBt 
MFnilirslu 
lUalda 
Anl*rior 

lent 

malleus 
^ntertof  (old 


KouBd 

window 


rroinontorv 


Light  reflea 


Normal  dnitn.heac]  of  right  tide  ai  m«ii  with  mirror.    X  6. 


idly,   large  openings  close  slowly,  or  not  at  all. 
does  not  of  necessity  produce  deafness. 

With  an  aural  speculum  and  good  light,  one  may  locate  the  various  structures 
as  follows  :  Above  and  in  front  is  seen  the  short  process  of  the  malleus  as  an  ap[>ar- 
ently  prominont  point.  From  this  point  two  streaks  pass  to  the  periphery,  showing 
the  division  between  the  tense  portion  of  the  membrane  and  its  flaccid  portion 
(Shrapnell's  membrane),  seen  only  in  a  roomy  meatus.  E.xtending  backward  and 
downward  from  this  point  is  seen  a  whitish  streak  ending  at  thv;  umbo.  This  is  the 
long  process  or  handle  of  the  malleus.  Directed  downward  and  forward  from  the 
umbo  is  an  area  of  li^ht  with  its  apex  at  the  umbo  and  its  base  near  the  periphery  of 
the  membrane.  It  is  triangular  in  shape  and  is  due  to  the  funnel  shape  of  the 
membrane  and  the  resulting  light-reflex.  Above  and  in  front  of  the  short  process  of 
the  malleus  is  the  membrane  of  Shrapnell.  Through  the  grayish  translucent  tym- 
panic membrane  the  contents  of  the  tympanum  may  sometimes  be  seen,  changing 
apparently  the  coloi  of  the  membrane.  Its  conical  shape  has  been  proven  by  trial 
and  mathematically  to  be  the  most  favorable  for  the  reception  of  sound  waves.  The 
vibrations  are  traiisinilted  thi'uugh  the  oasiclt»i  l<i  the  labyrinth  by  way  of  the  oval 
window.  The  malleus  rests  in  the  membrane,  the  stapes  occupies  the  oval  window 
and  the  incus  lies  between  and  articulates  with  the  two. 


PRACTICAL   CONSIDERATIONS:    THE   MIHIM-E   EAR.        1507 

The  Eustachian  Tube. — The  superior  orifice  of  the  Eustachian  ui\x-  is  in 
the  upper  part  of  the  anterior  wall  of  the  tympanum,  and  is  therelori-,  not  well 
adapted  for  drainage  of  that  cavity.  The  tube  is  directed  downward,  I'nrward,  and 
inward  to  the  side  of  the  naso-pharynx,  where  it  is  on  a  level  with  tin-  [ntstf-rior  en<l 
of  the  inferior  turbinate  bone.  In  children  it  is  wider,  shorter,  and  niort'  horizontal, 
so  that  in  infection  of  the  middle  ear  drainage  in  them  is  better,  but.  for  ''e  same 
anatomical  reasons,  otitis  media  is  more  likely  to  follow  pharyngeal  antl  tonsillar 
infections.  The  pharyngeal  orifice  is  bounded  above  and  at  the  inner  side  by  the 
prominent  cartilaginous  arch  which  encloses  a  funnel-shaped  o|XMiing.  The  mucous 
membrane  over  this  projection  is  thickened  by  a  cushion  of  adenoid  tissue,  hyper- 
trophy of  which  is  frequently  a.ssociated  with  pharT.ngeal  adenoids  and  enlarged 
tonsils,  and  may  occlude  the  tube,  ultimately  causing  deafnessi.  The  upper  Ixtriler 
of  the  pharyngeal  opening  of  the  tube  is  a  half  inch  above  the  soft  palate,  and  the 
sama  distance  below  the  basilar  process,  below  the  hinder  end  of  the  inferior  turbi- 
nate bone  and  in  front  of  the  posterior  pharyngeal  wall  (Tillaux).  Immediately 
behind  this  orifice  is  the  *ell-marked  de|>ression  called  Rosenmiiller's  fossa,  the 
depth  of  which  is  increased  in  cases  of  enlargement  of  the  pharyngeal  tonsil  and 
which  may  then  lead  to  difficulty  in  the  passage  of  a  catheter  into  the  Eustachian 
tube.  It  may  also,  when  recognized,  serve  as  a  useful  guide  to  the  orifice  of  the 
tube.  Injury  to  the  orifice  of  the  tulje  during  operations  in  the  naso-pharynx, 
or  at  the  posterior  ends  of  the  turbinates,  may  lead  to  cicatricial  contraction  and 
occlusion,  thus  causing  defective  hearing.  Ulcerations  in  the  naso-pharynx  may 
produce  a  like  effect.  The  length  of  the  tube  is  about  37  mm.  ( i  ys  in.  )  and  its 
pharyngeal  opening  is  about  2;,  mm.  ( i  in. )  lower  than  the  tympanic.  Its  i:pper 
third  (12  mm.)  is  bony,  and  its  lower  two- thirds  (25  mm.)  cartilaginous.  The 
narrowest  part,  the  isthmus,  is  at  the  junction  of  these  two  jxartions.  The  kimtn 
of  the  cartilaginous  portion  forms  a  somewhat  S-shaped  slit,  the  walls  being  in 
actual  contact,  except  during  the  act  of  swallowing,  when  the  slit  opens  so  that 
air  may  reach  the  tympanum  and  equalize  the  atmospheric  pressure  on  the  two 
sides  of  the  tympanic  membrane.  In  the  bony  portion,  though  the  lumen  is 
smaller,  it  is  open.  In  cases  of  obstruction  of  the  tube  at  its  pharyngeal  end — 
as  by  pressure  from  a  growth,  or  from  a  thickened  mucosa — the  outside  pres- 
sure predominates,  the  tympanic  membrane  is  pushed  inward,  and  buzzing  or 
"singing  in  the  ears"  results.  Whenever  the  palate  is  raisetl  or  deglutition 
takes  place,  the  tensor  palati  and  palato-pharyngeus  contract,  and  in  so  doing 
open  the  Eustachian  tube  by  traction  on  the  fibrous  tissue  which  unites  the  outer 
borders  of  the  fibro-cartilaginous  scroll  of  which  the  tube  is  composed.  Concussion 
of  the  tympanic  membrane  from  loud  reports,  as  from  the  firing  of  great  guns, 
is  minimized  by  breathing  with  the  mouth  open,  thus  elevating  the  soft  palate, 
opening  the  Eustachian  tube,  and  equalizing  the  pressure  on  the  two  sides  of  the 
membrane. 

Inflation  of  the  tympanum  is  accomplished  through  the  Eustachian  tube,  and  is 
employed  for  diagnostic,  prognostic,  and  therapeutic  purposes.  Several  methotls 
are  in  use.  Valsalva's  consists  of  a  vigorous  expiratory  effort  while  the  nose  and 
mouth  are  kept  closed.  Politzer  inflates  the  tympanum  through  one  nostril  by  a 
vigorous  compression  of  a  rubber  air-bag,  while  the  patient  is  in  the  act  of  swallow- 
ing. The  opposite  nostril  and  mouth  are  closed.  The  most  satisfactorj'  methoti  in 
difficult  cises  is  by  means  of  the  Eustachian  catheter.  The  instrument  is  jiassed  tip 
downward  ilong  the  floor  of  the  nose  until  it  drops  into  the  post  nasal  space  and 
the  ()osterior  wall  of  the  pharynx  is  reached.  The  tip  is  then  turned  gently  outward 
and  withdrawn  about  i  cm.  when  the  slight  resistance  of  the  cartilaginous  rim  is 
felt.  After  gliding  forward  over  this  prominence,  it  will  engage  in  the  orifice  of  the 
tube.  The  ring  at  the  proximal  end  of  the  catheter — which  is  in  the  plane  of  the 
the  curve  of  the  beak  and  thus  shows  the  position  of  the  latter — is  then  directed 
toward  the  external  meatus  of  the  same  side  (Bonnafont).  The  catheter  may  lie 
withdrawn,  and  the  tip  at  the  same  time  l)e  turned  to  the  opposite  side  from  the 
one  to  be  catheterized,  so  that  the  lieak  of  the  instrument  catches  on  the  edge  of 
the  vomer.  It  is  then  turned  upward  through  180',  and  thus  enters  the  tubal 
opening  (Frank,  l.owenbergj. 


l5o8 


HUMAN   ANATOMY. 


Foreign  bodies  may  lodge  in  the  tube  during  vomiting,  or  a  broken  piece  of  the 
bougie  may  be  left  in.  They  will  usually  esca|je  during  vomiting  or  hawking,  or 
they  may  be  removed  by  an  instrument  if  visible. 

If  the  tube  is  normal,  a  bougie  I  >2  mm.  in  diameter  will  easily  pass  the  isthmus, 
the  narrowest  part.  Strictures  may  be  dilated  or  applications  made  by  bougies. 
Narrowing  of  the  lumen  may  occur  near  the  isthmus  from  chronic  inflammation  or, 
at  the  pharyngeal  orifice,  from  the  pressure  of  pharyngeal  adenoids,  tumors,  or  polypi. 

Mastoid  Process  and  Cells. — The  mastoid  process  which  is  formed  by  the 
posterior  extremity  of  the  petrous  bone,  is  relatively  small  at  birth  and  contains  no 
air  cells  except  the  antrum.  The  antrum  is  almost  constant,  although  its  size  varies. 
In  the  infant  it  will  hold  a  small  pea,  while  in  the  adult  its  average  len^h  is  from  12- 
15  mm.  (one-half  inch  or  slightly  more),  its  height  8-10  mm.,  and  its  width  about 
7  mm.  (Briihl).  It  is  the  means  of  communication  between  the  tympanum  and  the 
mastoid  cells,  so  that  infection  finds  an  easy  passage  from  the  former  to  the  latter. 
Its  distance  from  the  external  surface  of  tht  r,astoid  process  will  depend  upon  the 
size  of  its  cavity.  This  is  usually  from  12-14  mm.  Anteriorly  the  antrum  opens 
into  the  attic  portion  of  the  tympanum,  and  is  in  almost  a  direct  line  through  that 
cavity  with  the  Eustachian  tube.  A  probe  passed  up  the  tube  from  the  pharynx 
would  pass  through  the  attic  into  the  antrum  and  would  strike  the  joint  between  the 
incus  and  the  stapes.  The  axis  of  the  external  canal  would  strike  the  line  at  an  angle 
of  about  thirty  degrees. 

The  floor  of  the  antrum  ii  below  the  level  of  the  entrance  into  the  attic,  so  that 
pus  in  the  antrum  tends  rather  to  enter  the  mastoid  cells.  Sometimes  nearly  all  the 
ma.stoid  cells  are  pneumatic  ;  more  frequently  they  are  diploetic  at  the  tip  of  the 
mastoid  process,  and  pneumatic  above  (page  148).  Pus  in  the  air  sf>aces  may 
reach  the  diploetic  region  by  breaking  down  the  thin  intervening  septa.  Those 
cases  in  which  there  are  no  mastoid  spaces  are  probably  sclerotic  from  pathological 
causes.  Thus  a  chronic  inflammation  of  the  mastoid  may  give  rise  to  new  bone 
formation,  filling  the  diploe  and  causing  eburnation.  This  would  tend  to  prevent 
the  outward  progress  of  pus  and  would  favor  its  extension  toward  the  interior  of 
the  cranium. 

The  suprameatal  spine  is  about  10-12  mm.  above  the  floor  of  the  antrum, 
which  corresponds  to  a  point  about  half  way  up  the  posterior  wall  of  the  bony  meatus, 
and  lies  about  5  mm.  posterior  to  the  inner  end.  Thus  bulging  of  the  pc»terior  wall 
of  the  meatus  may  result  from  disease  in  the  antrum.  The  squamo-mastoid  suture  is 
frequendy  seen  on  the  surface  of  the  mastoid  process  in  children,  and  may  give  pas- 
sage to  pus  from  the  antrum  to  the  surface.  Through  deficiencies  in  the  mastoid 
process  near  its  tip  pus  may  find  its  way  into  the  sheath  of  the  sterno-cleido-mastoid 
muscle,  or  along  the  large  blood-vessels  into  the  neck. 

The  bony  wall  between  the  antrum  and  posterior  fossa  of  the  skull  is  thin  and 
cancellous,  and  may  show  deficiencies  through  which  pus  may  reach  the  posterior 
fossa.  In  the  fossa  on  the  posterior  surface  of  the  mastoid  process  is  the  groove 
for  the  sigmoid  sinus,  which  is  frequently  infected  from  disease  of  the  antrum.  Such 
infection  may  extend  from  the  antrum  to  the  posterior  or  cerebellar  fossa  of  the  skull, 
causing  meningitis,  septic  thrombus  of  the  lateral  sinus,  or  a  subdural  or  cerebellar 
abscess. 

The  [X)ssible  lines  of  extension  of  nia.stoid  inP.animation  may  be  summarized  as 
follows  (after  Taylor)  :  (i )  Upward,  from  absorption  of  the  thin  tegmen  antri,  or 
through  the  veins  passing  up  through  foramina  in  the  tegmen  (causing  external 
pachymeningitis  in  the  floor  of  the  middle  cranial  fossa),  or  through  the  remains  of 
the  petro-squamous  suture  (causing  thrombosis  of  the  superior  petrosal  sinus).  (2  ) 
Downward,  by  emissary  veins,  or  through  a  sinus  at  the  lower  part  of  the  mastoid  in 
the  digastric  fossa  (causing  cellulitis  lieneath  the  sterno-niastoid,  or  travelling  aloni^ 
the  stvlo-glossus,  stylo-pharyngeus  and  stylo-hyoid  to  the  retro-pharyngeal  region). 
(3)  Forward,  through  the  thin  bony  layer  separating  the  external  auditory  meatus 
from  the  antrum  .ind  the  mastoid  cells  f  causing  discharge  from  the  meatus  if  the 
perforation  is  complet',  or  if  it  remains  subperiosteal,  directing  the  pus  outward  to 
a  point  just  back  of  th.-  pinna).  (4)  Outward — especially  in  children — through  the 
thin   post-auditory  process  of  the  squamous  bone,   or  through  the  open  masto- 


PRACTICAL   CONSIDERATIONS:    THE   MinOLE   EAR.         i5<>9 

squamous  suture  (causing  a  fluctuating  adenomatous  postauricular  swelling,  pushing 
the  pinna  forward  and  ntaking  it  unduly  prominent).  (5)  Inward,  either  through 
venules  passing  to  the  sigmoid  sinus,  or  through  caries  of  the  wall  of  the  sigmoid 
groove  (causing  external  pachymeningitis,  or  subdural  absces.s,  <>r  suppurative  basal 
meningitis,  or  cerebellar  abscess — by  way  of  the  cerebellar  veins  emptying  into  the 
lateral  sinus— or,  most  frequently,  sigmoid  sinus  thrombosis). 

The  sigmoid  sinus  is  usually  about  i  cm.  behind  the  suprameatal  spine,  but  is 
occasionally  so  far  forward  as  to  lie  just  beneath  the  external  surface  of  the  mastoid 
process,  and  immediately  behind  the  bony  wall  of  the  meatus. 

Owing  to  its  close  relation  to  the  mastoid  antrum  and  cells,  no  other  cranial 
sinus  is  so  frequently  the  seat  of  infective  inflammation.  In  infants,  however,  it  is 
seldom  seen,  owing  »o  the  foUow^ig  facts  ;  First,  the  mastoid  cells  are  not  developed 
in  them,  though  the  antrum  exists  ;  secondly,  the  squamous  covering  of  the  antrum 
is  not  yet  soldered  to  the  mastoid,  and  therefore,  purulent  matter  finds  a  reatiy  exit, 
not  being  enclosed  in  a  ccmj;!t:te  oony  casing  ;  thirdly,  more  numerous  exits  for 
the  venous  blood  exist  in  infants  than  in  adults  ;  and  fourthly,  the  sigmoid  sinus 
rests  on  a  flatter  osseous  surface  than  in  adults,  the  bony  gutter  which  imbeds  the 
adult  sinus  being  not  yet  fully  formed.  In  infants  the  internal  ear  is  more  exposed 
than  in  adults  to  pathological  encroachments  from  the  middle  ear,  hence  in  them 
leptomeningitis  is  apt  to  ensue,  which  frequently  ends  fr  ally,  and  that  so  rapidly  as 
to  prevent  the  formation  of  sigmoid  sinus  thrombosis  (Macewen). 

When  the  sigmoid  sinus  is  infected,  extension  may  occur  to  the  venous  channels 
associated  with  it,  esp>ecially  to  th'.  internal  jugular,  anterior  condylar,  and  deep  veins 
of  the  neck  into  which  the  anterior  condylar  empty  themselves.  Evidence  of  involve- 
ment of  these  may  be  found  in  two  areas, — along  the  internal  jugular,  and  in  the  upper 
third  of  the  posterior  cervical  triangle.  Pain  on  pressure  over  the  inflamed  veins  may 
be  elicited  even  when  the  patient  is  deeply  somnolent  or  semi-conscious.  Thrombosis 
of  the  internal  jugular  when  marked,  is  very  easy  of  detection,  as  it  lies  so  super- 
ficially. The  finger  perceives  a  cord-like  formation  to  the  inner  side  of  the  sterno- 
mastoid  on  the  outer  side  of  the  artery,  though  the  latter  is  sometimes  overlapped  by 
it.  This  may  extend  the  whole  length  of  the  internal  jusrular,  but  it  is  f.  .'^uendy 
confined  to  the  upper  third.  The  entire  thrombus  may  oe  disintegrated  and  its  par- 
ticles carried  by  the  current  to  the  lung,  where  they  may  set  up  >..ective  infarction. 
They  may  be  carried  to  the  lungs  by  the  veins  passing  into  the  posterior  cervical 
triangle  which  flow  through  the  vertebral  and  other  channels  to  the  subclavian 
(Macewen). 

The  complication  most  to  be  feared  in  middle  ear  disease  is  the  spread  of  the 
infection  to  the  interior  of  the  cranium.  This  may  occur  by  direct  extension  of 
the  carious  process  through  the  bone  :  more  rarely  through  me  labyrinth  and  internal 
auditory  canal  or  the  aqueducts  ;  or,  still  more  rarely  along  the  small  blood-vessels 
or  connective  tissue  fibres  which  pass  through  the  bone  between  the  middle  ear  and 
the  dura.  Very  exceptionally  the  pus  may  find  its  way  through  the  thin  anterior 
wall  into  the  carotid  canal  and  along  this  to  the  cranial  cavity. 

Although  otitis  media  appears  to  occur  on  both  si'les  with  equal  frequency,  the 
right  side  of  the  head  has  been  said  to  be  more  frequently  affected  by  intrarraiiial 
sequelae.  If  so,  this  is  probably  due  to  the  greater  size  of  the  lateral  sinus  and  the 
sigmoid  sinus  on  the  right  side.  Consequently  the  right  sigmoid  sinus  encroaches 
more  upon  the  petrous  and  the  ma.stoid  portions  of  the  temporal  bone,  es|)ecially  at 
the  sigmoid  knee,  and  the  distance  between  the  lower  border  of  the  tympanum  and 
the  antrum  on  the  one  hand  and  the  sigmoid  sinus  on  the  other,  is  less  than  between 
the  corresponding  points  on  the  left  side  (Macewen). 

Involvement  of  the  internal  ear  from  otitis  media  is  comparatively  rare.  This 
portion  of  the  ear  is  developetl  independently  of  the  rest,  and,  after  necrosis,  may  be 
extruded  in  sequestne,  in  which  may  be  recognized  the  structure  t)f  the  labyrinth. 
If  the  pus  associated  fails  to  escape  externally,  there  is  danger  of  its  passing  through 
the  internal  auditory  meatus  and  aquitductus  vestibuli  to  the  brain.  Affections  of  the 
semi-circular  canals  produce  disturbances  of  equilibrium. 

The  sinus  is  in  danger  in  operations  on  the  antrum,  the  external  opening  for 
which  should  be  immediately  behind  the  meatus,  and  the  centre  of  the  opening  2-3 


^aam 


15IO 


HUMAN   ANATOMY. 


mm.  below  the  level  of  its  upper  wall.  If  the  sinus  is  in  an  abnormally  anterior  posi- 
tion, the  posterior  wall  of  the  meatus  must  be  removed  to  gain  more  nwm. 

The  facial  nerve  is  also  in  great  danger  in  these  o|>erations,  and  has  frequently 
been  injured.  It  lies  in  the  inner  wall  of  the  mouth  of  the  antrum,  and  is  therefore, 
in  front  of  it.  The  antrum  is  appro.ximately  about  12  mm.  (one-half  inch)  in  a  direc- 
tion very  slightly  inward,  forward,  and  upward  from  a  point  on  the  external  surface, 
5  mm.  (josterior  to  the  suprameatal  spine.  The  anterior  edge  of  the  opening  made 
to  reach  the  antrum,  should  be  at  this  point,  and  its  upper  edge  3  mm.  below  the 
spine.  It  should  never  be  carried  deeper  than  i  '2  cm.  ( ^g  in. )  from  the  anterior 
edge  of  the  external  opening,  for  fear  of  injuring  the  facial  nerve  or  external  semi- 
circular canal. 

As  the  situation  of  the  mastoid  antrum  is  the  key  to  the  position  in  all  o[)erations 
upon  either  the  antrum  itself  or  the  mastoid  cells,  Macewen  has  noted  three  points  in 
the  anatomy  of  the  mastoid  that  may  govern  the  surgeon  in  reaching  the  antrum 
without  (a)  ojjening  the  sigmoid  groove  and  injuring  its  enclosed  sinus;  (b) 
encroaching  upon  the  Fallopian  canal  and  destroying  the  facial  nerve  ;  (f )  invading 
the  middle  cerebral  fossa  ;  (</)  injuring  the  semicircular  canals. 

1.  The  suprameatal  triangle — the  lower  border  of  which  corresponds  with 
the  level  of  the  roof  of  the  antrum,  and  is,  therefore,  a  few  lines  below  the  level  of  the 
biise  of  the  temporo-sphenoidal  lobe — is  bounded  above  by  the  posterior  root  of  the 
zygoma,  below  by  the  postero-superior  segment  of  the  bony  external  meatus,  and 
behind  by  a  line  uniting  these  two  and  drawn  vertically  from  the  posterior  border  of 
the  meatus  to  the  zygomatic  root.  The  opening  is  made  within  this  triangle  and 
close  to  the  last  line — the  base  of  the  triangle. 

2.  The  excavation  of  the  bone  is  carried  inward  and  a  little  forward,  in  the  direc- 
tion of  the  posterior  wall  of  the  bony  meatus,  as  shown  by  a  probe  passed  into  it  from 
behind  between  the  skin  and  the  osseous  wall.  The  more  oblique  the  direction  of 
this  wall  from  behind  forward,  the  more  anterior  the  situation  of  the  antrum. 

3.  The  depth  of  the  inner  wall  of  the  tympanic  cavity  from  the  level  of  the 
skull  at  the  bony  external  meatus  should  be  determined  by  introducing  a  probe 
through  the  external  ear  (and  through  the  tympanic  membrane  previously  per- 
forated by  patholc^cal  processes)  until  it  touches  the  inner  wall  of  the  tympanum. 
If  this  cavity  lies  deeply,  the  more  superficial  mastoid  antrum  will  be  relatively 
deep  also. 

Of  forty  brain  abscesses,  the  bone  was  diseased  directly  to  the  dura  in  thirty-seven 
(92  |>er  cent.),  the  bone  was  diseased,  but  not  the  dura,  in  one  (2.5  per  cent. ),  and 
the  bone  was  healthy  in  two  ( 5  per  cent. )  (  Korner). 

It  follows  from  this  list  of  cases,  that  after  a  thorough  exposure  of  the  antrum  antl 
the  ear  cavities,  the  carious  process  should  be  followed  inward  to  the  dura  or  brain. 
In  case  an  abscess  in  the  temporo-sphenoidal  lobe  cannot  be  reached  in  this  way  the 
skull  may  be  opened  by  a  trephine,  or  by  an  osteo-plastic  resection  immediately  above 
the  ear.  A  cerebellar  abscess  might  be  reached  by  an  opening  one  and  one-half 
inches  behind  the  centre  of  the  bony  meatus  and  one  inch  below  Reid's  base  line. 


THE  INTERNAL  EAR. 

The  internal  ear  consists  essentially  of  a  '.lighly  complex  membranous  sac,  con- 
nected with  the  |)eripheral  ramifications  of  the  auditory  nerve,  and  a  bony  capsule, 
which  encloses  all  parts  of  the  membranous  structure  and  is  embedded  within  the 
substance  of  the  petrous  portion  of  the  temporal  bone.  These  two  parts,  known 
respectively  as  the  membranous  and  the  bony  labyrinth^  are  not  everj-where  in  close 
apposition,  but  in  most  places  are  separated  by  an  interx-ening  space  filled  with  a 
fluid,  the  perilymph,  the  inner  sac  lying  within  the  osseous  capsule  like  a  shrunken 
cast  within  a  mould.  The  membranous  labyrinth  is  hollow  and  everywhere  filled 
with  a  fluid,  called  the  endotymph,  which  nowhere  gains  access  to  the  cavity 
occupied  by  the  perilymph.  The  internal  ear  is  closely  related,  on  the  one  side, 
with  the  Ixjttom  of  the  internal  auditory  canal,  which  its  inner  wall  contributes,  and 
with  the  inner  wall  of  the  tympanic  cavity  on  the  other.  Its  entire  length  is  about 
20  nmi. ,  and  its  long  axis  corresponds  closely  with  that  of  the  pyramidal  or  petrous 


THE   INTERNAL    K    R. 


»5>« 


poitiun  of  the  temporal  bone.  The  position  of  approximately  its  posterior  third 
»  indicated  by  the  transverse  ridge  that  crosses  the  upper  surface  of  the  temp>ral 
bone  a  short  disUnce  Iwhind  the  internal  auditory  meatus.  The  irregular  cavity  of 
the  bony  labyrinth,  hi  Slowed  out  in  the  temporal  bone,  comprises  three  subdivis- 


FiG.  1264. 


Tytnimitic  cavity 
Facial  canal 

Cuchlea- 


ScniicirciiUir  canaW 


Vcatibule 

Internal  auditory  cmnal 

Right  temporal  bon«,  upper  part  ol  petroni  panion  hat  bam  removed  to  show  bony 
labyrinth  lying  In  position. 

ions  :-  a  middle  one,  the  vestibule,  an  anterior  one,  \\\e  cochlea,  and  a  posterior  one, 
the  semicircular  canals.  Both  the  front  and  hind  divisions  communicate  freely  with 
the  vestibule,  but  neither  communicates  with  the  membranous  labyrinth  nor,  in  the 
recent  condition,  with  the  tympanic  cavity.  Although  corresponding  in  its  general 
form  with  the  bony  compartments  of  the  cochlea  and  semicircular  canals,  the 
membranous  labyrinth  less  accurately  agrees  in  its  contour  with  the  bony  vestibule, 
since,  instead  of  presenting  a  single  cavity,  it  is  subdivided  into  two  unequal 
compartments,  known  as  the  saccule  and  the  utricle,  which  are  lodged  within  the 
bony  vestibule.  The  divisions  of  the  membranous  labyrinth  are,  therefore,  four, 
which  from  before  backward  are  :  the  membranous  cochlea,  the  saccule,  the  utricle 
and  the  membranous  semicircular  canals. 

The  Osseous  Labyrinth. 
The  Vestibule. — The  vestibule  (vestlbulum),  the  middle  division  of  the  lx)ny 
labyrinth  lies  between  the  cochlea  in  front  and  the  semicircular  canals  behind  and 
communicates  freely  with  both.     It  is  an  irregulariy  elliptical  cavity,  measu'ing  about 

5   mm.    from   before    back- 

•^  •  Fk;.  1265. 


Superior  ampulla 
Common  cru»>^ 


Superior  canal 


Horizontal 


Lodges  utricle 
Lodges  saccul 


Cochlea 


Posterior  canal 


ward,  the  same  from  above 
downward ,  and  from  3-4  mm. 
from  without  inward.  The 
lateral  (outer)  wall  separates 
it  from  the  tympanic  cavity, 
and  contains  the  oval  window 
with  the  foot-plate  of  the 
stapes.  The  medial  (inner) 
wall,  directed  toward  the 
bottom  of  the  internal  audi- 
tory canal,  presents  two 
depressions   separated  by  a 

ridge,  the  crista  vestibuli,  .^   ,.     ^l  j 

the  upper  pointed  end  of  which  forms  the  pyramidahs  vestibuli.  The  anterior  and 
smaller  of  these  depressions  is  the  spherical  recess  ( recessus  sphaericus)  and  lodges 
the  saccule.  In  the  lower  part  of  this  fossa,  about  a  dozen  minute  peiforations  mark 
the  position  of  the  macula  cribrosa  media  for  the  passage  of  branches  of  the  vestibu- 
lar iier\e  from  the  bottom  of  the  internal  auditory  canal  to  the  saccule.  The  posterior 
and  larger  depression  is  the  elliptical  recess  (recessus  ellipticus).    Behind  the  lower 


Pnftterior  ampulla 
Cast  of  right  lioiiy  labyrinth,  mesial  aspect.     ■.  l. 


1513 


HUMAN   ANATOMY. 


Cnw  cummnnc- — ., 


AqiurductiiM 

WHtilmli 

Kecnwuw 

<IMplicU!l 

MacuW    .t^criur 


Crista  vcatibuli 

KcccMuw  ph:eri- 

cuH  with  macula 

■rrdia 


Ampulla 


part  of  the  spherical  recess,  the  crista  vestibuli  divides  into  two  limbs  between  which 
IS  the  recetsus  cocblearit,  which  lodges  the  bej^inning  of  the  ductus  cochlearis  and 
is  pierced  by  u  number  of  small  openings  for  the  passage  of  nerve  filaments  to  this 
duct     The  numerous  minute  holes  piercing  the  crista  (pyramid)  and  the  elliptical 

recess    collectively     form 
Fig   1366.  the   macula    cribroaa 

■upcrior(Fig.  1266)  and 
transmit  branches  of  tht- 
vestibular  nerve  to  the 
utricle  and  to  the  ampulhe 
of  the  superior  and  hori- 
zontal semicircular  canals. 
Below  and  behind  the  re- 
cessus  ellipticus  lies  a 
groove,  the  fossula  sul- 
ciformis,  which  dctpens 
posteriorly  into  a  very 
small  canal,  the  aqueduct 
of  the  vestibule  (aquae- 
ductus  vestibuli )  which  runs 
in  a  slightly  curved  course 
to  the  posterior  surface  of 
the  petrous  portion  of  the 
temporal  bone,  where  it 
ends  in  a  slit-like  opening, 
the  apertura  externa  aquaeductus  vestibuli,  situated  between  the  internal 
opening  of  the  internal  auditory  canal  and  the  groove  for  the  lateral  sinus.  The 
canal  transmits  the  ductus  endolymphaticus  and  a  small  vein.  The  anterior  wall  of 
the  vesdbule  is  pierced  by  the  large  opening  leading  into  the  scala  vestibuli  "*  the 
cochlea.  Near  this  aperture  is  seen  the  beginning  of  the  lamina  spiralis  ossea  which 
lies  on  the  floor  of  the  vestibule  below  the  oval  window.  Posterioriy  the  vestibule 
directhr  communicates  with  the  semicircular  canals  by  five  round  openings. 

The  Semicircular  Canals. — The  three  bony  semicircular  canals— the  superior, 
the  posterior  and  the  horizontal— \\e^  behind  the  vestibule  and  are  perpendicular  to 
one  another  (Fig.  1 265).     Their  disposition  is  such  that  the  planes  of  the  three  canals 


" )  Macula  crilv 
/roaa  aupenor 

Facial  canal 


Oval  window 


Lamina  spiralis 


Section  o(  riitht  hony  labyrinth  paasinc  throuch  plane  of  sii(irrior  Mmi- 
circular  caual :  anterior  wall  of  veuibule  it  mii  Ironi  behind.    ;<  4. 


correspond  with  the 
sides  of  the  comer  of  a 
cube,  suggestively  re- 
calling the  relations  of 
the  three  cardinal 
planes  of  the  body — 
the  sagittal,  frontal  and 
transverse.  Each  canal 
possesses  at  one  end  a 
dilatation,  called  the 
osseus  ampulla.  The 
superior  canal  ( ca- 
nalis  superior)  lies  farth- 
est front  and  in  a  nearly 
vertical  plane  at  right 
;in>;les  to  the  long  axis 
of  the  (letrous  portion 
of  the  temporal  bone, 
whilst  the  plane  of  the 
longest  canal,  the  pos 


Fig.  1267. 


Small  mil  i:r 
posterior  canul 


Cms  commune 


Facial  canal 

Oval  (vestibular) 
window' 


Lamina  !«|firalis - 


Round  (ctjchlear)  window 


Small  end  df 
horizontal  canal 


Ampulla  nr 
posterior  canal 


Section  of  riffht  bony  lahyrinth  passinfp  through  plani 

canal ;    posterior  wall  of  vestibule  is  seen  from  bctore. 


of  sniierior  semicircular 
4- 


terior  (canalis  posterior)  is  approximately  parallel  to  it.  The  external  portion  of 
the  horizontal  semicircular  canal  forms  a  prominence  on  the  inner  wall  of  the  middle 
ear  aljove  the  facial  canal,  while  the  upper  part  of  the  superior  semicircular  canal 
produces  the  conspicuous  elevation,  the  eminentia  arcuata,   seen  on  the  superior 


THE   INTERNAL   EAR. 


»5«3 


surface  of  the  petrous  bone.  The  semicircular  canals  open  into  the  fxisterior  part  of 
the  vestibule  by  five  apertures  (Fig.  1267),  the  undilatcd  ends  of  the  superior  and 
posterior  canals  joining  to  form  a  common  limb  (Qru»  communej.  The  horisontal 
can^  (canalis  lattralis)  alone  communicates  with  the  vestibule  by  two  distinct  oyxn- 
ings.  Its  ampulla  is  at  its  outer  end  and  lies  at  the  upper  part  of  the  vestibule  above 
the  oval  window,  from  which  it  is  separated  by  a  groove  corres|x)nding  to  the  facial 
canal.  Lying  above  and  close  to  this  opening  is  placed  the  anipuUary  end  of  the 
superior  canal.  The  ampullary  end  of  the  postenor  canal  lies  on  the  ffotir  of  the 
vestibule,  near  the  opening  of  the  no.>-diIated  end  of  the  horizonkil  canal  and  of  the 
canalis  communis.  In  the  wall  of  the  ampulla  of  the  posterior  canal,  a  number  of 
small  openings  (macula  cribroaa  inferior)  provide  for  the  entrance  of  the  sjiecial 
branch  of  the  vestibular  nerve  destined  for  this  tube. 

The  Cochlea. — The  bony  cochlea  a>nstitute3  the  anterior  |)art  of  the  labyrinth 
and  appears  as  a  short  blunt  cone,  about  5  mm.  in  height,  whose  ba.se  forms  the  an- 
terior wall  of  the  inner  end  of  the  internal  auditory  meatus.     Its  apex  is  directed  hori- 


Fio.  116.S. 


Sca1«  v«»tib«li 


Scala  tympan' 


Modiolus 
Am  cochlnrb 
Area  veHtibuIarid  inferior. 


Internal  auditory  canal 

Foramen  ningularc 


HamuluH,  overlyinK 

hclii-iHrrnia 


1-aminu  KpiraliH 

Canalis  spirMliM  niiMHuli 

Facial  cniuil 
C'-'hla  falciformi;* 

Area  veHtibularit 
huliertiir 


Cochlea  and  bottom  of  internal  auditorj-  canal  exposed  by  vertical  section  p«MinK  parallel  with  «ycoma  ;  prejara- 
lioii  hal  been  turned  so  that  cochlea  rests  with  its  base  downwanl  and  apex  pouiiiiiu  upwaul.     X  5. 

zontally  outward,  somewhat  forward  and  downward,  ami  reaches  almost  to  the  Eusta- 
chian tube.  Its  large  lower  turn  bulges  into  the  tympanic  cavity  and  produces  the 
conspicuous  ele\ation  of  the  promontory  seen  on  the  inner  wall  of  the  middle  ear 
(Fig.  1269).  The  bony  cochlea  consists  essentially  of  a  tapering  central  column, 
the  modiolus,  around  which  the  bony  canal,  about  30  mm.  long,  makes  something 
more  than  two  and  a  half  spiral  turns,  the  dasa/,  middle  and  apical.  The  conical 
modiolus  has  a  broad  concave  base  which  forms  part  of  the  base  of  the  cochlea  (basis 
cochlea),  and  a  small  apex  which  extends  nearly  to  the  apex  of  the  cochlea,  or 
cupola  (cupula).  It  is  much  thicker  within  the  lowest  turn  of  the  canal  than  above, 
and  is  piercetl  by  many  small  canals  for  the  nerves  and  vessels  to  the  spiral  lamina 
(Fig.  1268).  The  axis  of  the  motliolus,  from  base  to  apex,  is  traversed  by  the 
central  canal,  whilst  a  more  peripherally  situatetl  channel,  the  canalis  spiralis, 
encircles  the  modiolus  and  contains  th-  spiral  ganglion  and  a  spiral  vt-in.  Prtiject- 
ing  at  a  right  angle  from  the  modiolus  into  the  canal  of  the  bony  cochlea  is  a  thin 
shelf  of  bone,  the  lamina  spiralis  ossea,  which  is  made  up  of  two  delicate  bony 
plates  between  which  are  fine  canals  containing  the  branches  of  the  cochlear  nervx'. 
The   spiral   lamina   begins  between  the  round  window  and  the  lower  wall  of  the 


I    u 


HI  MAN    ANATOMY. 


vi»iibulc    (F'lK.    uf^),    and    after   wiin  injf  spintUy   »roun<l    thi'    modictlus   to   the 
ajx-x  of  tlif      >chlca,  ciuls  in  a  h(H>k-lik<    prt)ces^    th<    hamulus    which  forms  jKirt 


of  the  th«-  \i>    indary  ..(  thf  lulicotrema     Fig.    i    ->y,>.     The- 
canal  'if  the  !    .ny  cochlea  effe(  —tl  by  the  usscouh     H-ral  lanr 
membranous  spiral  lamina    which  str»-tches  u  ,m  the  i 
l.iininu,  to  whii  li   it  is  attachci      to  the  outer  vml         the 
upper  diviL^iun  <.f  the  caivd  is      illt-d  the  scala  v      ubu! 
the  vestibule,  whilst  the  !•  iwer     ivision,  tl      scala  tympai 


fxiitial  division  of  the 
is  completed  by  the 
edge  ot  the  ossi-niiH 
1  (Vn:  .71).  The 
!  conr  nicates  with 
would  '.-n  into  the 
tympanic  cavity,  were  it  t,<<t  se] -rated  fr.  that  sp:i<-e  by  uie  seconi  tym|)anic 
meinbrane.  Thew  scake  onin -tnicate  au;  each  ■  ler  thmujfh  an  .ning,  the 
helicotrema,  at  >  ajHix  »i  tht  cochlea  i  lose  to  i  e  beginning  of  tl  scala  tyni- 
|wni  at  the  round  •  mdow  is  the  jiner  ontice  of  the  aquaeductus  cochlec  (dacttis 
|)erilyaphati«is),  1  i.uter  ..(.rni  Vxin-  m  a  depri  .ion  on  the  lower  surface  of 
the  i>v  inii<i  near  ii-.  posteri'ir  tM%e.  t  transmits  a  small  vein  and  >-stablishes  a 
coinniiuiicati  "1  lietween  the  -viiKirachP'tii  >  lace  and  the  scala  tympani. 

Ihc  internal  auditory  canal  c<   nmuiiicates  with  the  cranial  cavity  by  an  o\ at 
ofxiiing  on  the  jiost.  nor  surface  of  rh<     .vramidal  portion  of  the  tem|>oral  bin      from 
whirh  it  exteiuls  0111*     <l   ui  the  inti    ii.-l  lar.      Its  outer  or  lateral  end.  the  fundus, 
is  divided  into  a  smailt      ^iperior  .md  a  iar>;er  inferior  fossa  by  a  transv       i'  ridv;*-.  th' 
crista  falciform^s.     l^i  the  inter  .r  f>,in  nf  the  superior  fossa  ( area  Li.ialls 
ojK-ning  of  tht   fa<.ial  canal     iMpMArductus  FalUipii)  lor  the  transmission  of  th« 
ner\  In  its  posterior  part  ti  <■  openi    j:3  (area  vestibularis  soperior)   1 

brai    !ies  of  the  vestibular  ner\     -winch  -.upi       the  utricle  and  the  ampulhe 
sup    ior  and   horizontal  semicir.  iilar  can.us.  >,ese  oixnin^s  apix.ar  in  the  n. 

>ril)ii>s.i  ,iH«ri«>r  on    ;i.>  inner  surl.u    if  the  1j         labyrinth  (page  15:2).      The 
rior  part   .1  she  inferior  1"-^  is  -alletl  the  area  cochlearis  and  is  (K-rforated 
y  the  oiM-ninf         th.    ce'tral  can;d  of  the  modiolus.     Surroundiii 
Tous     1,  II  aj         es  of  1  le  tractus  spiralis  foraminosus  for  s 
bran'  es  of  i    ••  cochlear  licrve  to  the  two  lower  turns     •'  th- 
he  are.i      K-hlea     ml  siparaled  from  it  by  a  ridge,  lies  tli         <t 


inidd' 
the 

n»iss.    n 
Ik-hind 
the  ve> 
ner\es  i< .  th 
these  ojaMii 
lare,  which 


th. 
aciu 

■  th, 


ire 

.iis- 

iilea. 


>ul< 


area   vvsCibu= 
.cculc.     Th 

,:-       Behind  •  .. 

ieads  into  a  t. 


iafi 

.iru 

'S8ul 


of  the  maciii.i  cribrosii  inferioi 
tined  fur  the  ampulla  of  the  p.i 


«r)  wit!;   its  small  openings  for 
.   cribr<.^,i  nietlia,  described  alxive, 
ferior  is  a  large  opening,  the  fort 

■  H    other  end   of  which  are  the  .sn;   il 
transmit-,  the  branch  of  the  vt-stibiilar  nerve  des- 
>r  semicii.  iilar  canal. 


•sag 

ine(i  ifv 
singu- 
lenings 


Tm.  MKMBRANors  Labyrinth. 

n  mbranous   i.ibyrinth   ( labyrinthus   membranaceus)  lies  .    me  bony 

kbvrii:  iiich  it  resembles   in   general  form.      This   agreement         least   inarkeit 

v»Tthin      n    st-stibule,   since  here  the  single  division  of  the  bony  capsule  is  occupied 
'\    v.  comi>artments  of  the  membranous  sac,   the  utricle  and   the  s.i<cule.     The 
mous  labyrinth  comprises:    (  i)  the  n/ric/f  and  the  saccule,  which,  witi,  the 
rndolymphaticus,   lie  within  the  vestibule;   (2)  the  three  membranotis  se^ii' 
canals    lodged    within   the    Ixmy   semicircular  canals ;  and    1 3 )   the   tuem 
cochlea  enclosed   within  the   Ixjny   cochlea.      The    memhranous    labyrinth 
ched,  especially  in  certain  places,  by  connective  tissue  to  th-  inner  waif  of  the 
capsule.     The  interval  between  the  membranous  and  iwny     ilnnntb-^.  largest 
n  scate  tympani  and  vestibuli  of  the  cochl<-a  and  in  th,-  v-stib'''".  uunsututss  the 

pe       inphatic  space  (spatium  perilymphaticum  )  and  crwt    ins    .  »,^  Ivmisnatic 

thi  u,  the  perilymph.  The  fluid  within  the  membrai.»ato  iaijyr  h.  .tf^iropri.itely 
called  the  endolymph,  can  pass  from  one  part  ol  di.  -,  ^i-rmth  t.  -«i»ott.er,  although 
the  saccule  and  utricule  are  only  indirectly  com  a  '  >•  M^i\  cii»  ductus  etk^ 
lymphaticus  and  a  narrow  channel,  the  canalis  uiricui&-«accu<«m 

The  Utricle. — The  utricle  (utriculus)  occup.t-s  thr  rctesMus  4ii^*icus  in  the 
u|)|)er  back  part  of  the  vestibule.  It  is  larger  tlu-ai  the  ^ccule  and  communicates 
with  the  three  membranous  semicircular  caruls.  Att.4cb.-<l  to  the  upper  and  inner 
walls  of  the  vestibule  by  connective  tissue,  it  extends  from  the  roof  ot  the  vestibule 


THK    INTKRNAL    KAR 


«5I5 


backward  and  downward  to  thi-  ••[KrninK  o!  the  |»o»UTii)r  aminilla,  a  clistancf  of  fruin 
S.5-6  mm.  The  utricle  in  madt-  up  ot  three  sutxlivisions,  tin-  u|>|H-nn<)st  of  whieh  is 
rcspresentetl  by  a  blinil  sac,  (ruin  -3.5  mm.  in  U-UKtli  i<l  bre.ultii.  called  the 
recessna  utriculi,  whilst  the  two  lov  t-r  divisions  together  ..irm  the  utrirulus  pro- 
priua.  which  measures  ,^  '^i.  by  from  1.5  nun.  The  lower  [la't  of  the  utricle 
pn)i)er  is  prolon^etl  into  live  iabe-sha|i«l  ain  p  aterior,  which  lonniit.s  thi'  am- 
pulla o.  the  posterior  semicircular  can<d  with  t       i    ricle. 

The  openings  of  the  semicircular  c    nala  into  the  i"ricle  are  dis|>«>sf<l  as 
follows:  into  the  '      sshs  uti.,uti  >  i>en  f  i  )  tin-  ampulla  of  th.     in>erior  semicircular 

anal  and  (.2)  '  of  the  horiz'-ntid  canal,  /nto  the  utricn.iis  /»o/>nii.f  »\Kn  t  ^) 
the  sinus  superi>  hicli  ies  withi.  he  crus  Cf)mmune  and  receives  in  turn  the 
nonampullatetl  ei  >l  thi  ,ii!>erior  -id  posterior  semicircular  canals:  i4»  thi  non- 
ampullated  end  of  the  hn  /..utal  s<  licircular  canal;  and  (5)  the  ani)mlla  of  the 
posterior  semicircul.ir  ca 'li  through  tlie     'lus  posterior.      On  the  anterolateral  wall 

•f  the  recessus  ut'      li   ,,  p|,i,.t(.i  the  m.ti  ula  acustica  of  the  utricle,  whilst  from  its 


Fic;.   ijli/. 

Ilaniiiln«  Hrllnrtrema 


I'actat  cBtinl 
Vr*tilnilar(iivHl  iwimlow 


1  yiiilMiilii'  cavily 


Promi.mon.- 

ProlKT  l»a«.M*s  thruUKH  cochlear  t  round 

RiKht  hony  i-tKhlea  (tartially  expo^*' 


Scala  tynijinni 


antero-mesial  w.ill  sprinjjs  I. 
utricle   that   joins    even    a    suutu 
iiulolymphaticus. 

The  Saccule. — Thes,i. 
3  bv  2  mm.  in  size,  which  o 
pait  (jf  the  vestibule,  10  whii  i>> 

flattened  laterally  and  at  its  li  iii.illv 

reuniena,  vhich  connects  the  with 

bulges  Kirk. v.ird  forminj,' the  sir.  triculans, 

that    of     he    utricle.       The    small         iial, 
the    ductus    (.nilolyinphaticiis,   ari>       froir 
ductus  endolymphaticus  ])asses  thn 
blind  ■iilateil  extremity,  the  saccus  en 
of  the  dura  i  inter  below  the  openinj.:  ■ 
the    recessus  sphericus   branches   of    tli. 
macuii  acustica  .siiccnli  on  the  anterior  v 
is  the  -ery  small  tulx-  passing  from  tlii 
wall  of  the  cochlear  duct  near  the  csecuri: 
is  called. 

The   Membranous  Semicircul 
lares     oci  upy  alxjut  "iie  thinl  of  the  di 


\ytr- 


-..su 

if;  t.s  u        .      lul 

,U  c. '■!  coi       t  with 

lied  linj;      >   fonii 

''  >.iccii  T'lf 

rill!     to  tnc!   in  a 
'wfii  the  Liyrs 
'  ih  "he  ooeninj}!^   tn 

eiui  r    ami    |.-.:"    to    tlw- 
The  canaas  reunicns 
iccule  inl- 


uiy    lilt 

iMfSterio;       ' 
'!'•    .iq»a-<t 
haticus, 

e  „  i_,ed     -f.       ' 
estibular      or\ 
of  th>-  sa     ule. 
ivver  part  of  the 
vestibulare,  as  its  blind  vi-stibui.. 

inals. — These  tul)es  (ductus  sem 
uT  of  the  osseous  canals  and  coi' 


i* 


t 


I5i6 


HUMAN  ANATOMY. 


FiO. 


Trahectllic 


Memhranoutt 

canal 


to  them  in  number,  name  and  form.     They  are  closely  united  along  their  convex 
margins  with  the  bony  tube  (Fig.  1270),  whibt  their  opposite  wall  lies  free  in  the 

perilymphatic      space, 
"'*'•  being  attached  only  by 

irregular  vascular  con- 
nective tissue  bundles, 
ligamenta  labyrin- 
thi  canaliculorum, 
which  stretch  across 
this  space.  Like  the 
bony  canals,  each  of 
the  membranous  tubes 
possesses  an  aftipulla, 
which  in  the  latter  is 
relatively  much  larger 
than  in  the  former, 
being  about  three  times 
the  size  of  the  rest  of 
the  tube.  The  part  of 
the  ampulla  corre- 
sponding to  the  con- 
vexity of  the  semicir- 
cular canal  is  grooved 
on  the  outer  surface  at 
the  entrance  of  the 
ampullary  nerves.  On 
the  corresponding  in- 
ternal surface  is  a  pro- 
jection,   the    septum 


Pelitymphatic, 
spflce 


TrmhcculK 


Bony  wall 


Truuvene  wctlon  of  ■nperior  ntnidreular  canml.  thowiiiK  Riationi  o( 
mcmbnuia  to  bony  tube.     >:  3$. 


transversum,  which  partially  divides  this  space  into  two  parts  and  is  surmounted 
by  the  crista  acustica,  which  contains  the  endings  of  the  vestibular  nerves.  The 
crescent-shaped  thickening  beyond  each  end  of  the  crista  is  called  the  planum 
semilunatum. 


Structure  of  the  Utricle,  Saccule  and  Semicircular  Caaalt  -The  veatibule  and  the  bony 
■emicircular  canals  are  lined  by  a  very  thin  periosteum  composed  of  a  felt-work  of  resistant 
fibrous  tissue,  containing  pigmented  connective  tissue  cells.  Endothelium  everywhere  lines  the 
perilymphatic  space  between  the  membranous  and  osseous  canals,  covering  the  free  inner  sur- 
face of  the  periosteum,  the  fibrous  trabeculse,  and  the  outer  or  perilymphatic  surface  of  this 
part  of  the  membranous  labyrinth. 

The  walls  of  the  utricle,  saccule  and  membranous  semicircular  canals  are  made  up  of  (a) 
an  outer  fibrous  conn f dive  /issue  lamella  and  («)  an  inner  epithelial  lining,  the  latter  consisting 
throughout  the  greater  part  of  its  extent  of  a  single  layer  of  thin  flattened  polyhedral  cells.  Be- 
neath the  epithelium,  especially  in  the  region  of  the  maculse,  is  (r)  a  thin,  almost  homogeneous 
hyaline  tnembrane,  with  few  cells.  This  middle  layer  presents  in  places  on  its  inner  surface 
small  papillary  elevations  covered  by  epithelium.  On  the  concave  side  of  each  of  the 
.semicircular  canals  is  a  strip,  the  raphe,  of  thickened  epithelium  in  which  the  cells  become  low 
cylindrical  in  type.  In  the  plana  semilunata  they  are  cylindrical  in  type.  Over  the  regions 
receiving  the  nerve-fibres,  the  maculx  actisticae  and  the  crista;  acusticx,  the  epithelium 
undergoes  a  marked  alteration,  changing  from  the  Indifferent  covering  cell*  into  the  highly 
specialized  neuroepithelium. 

The  macula  acusticK  are  about  3  mm.  k)ng  by  3  mm.  broiul,  the  macula  of  the  saccule 
bemg  a  little  narrower  { i. 5-1.6  mm.-)  than  that  of  the  utricle  (2  mm. ).  At  the  margin  of  these 
areas  the  cells  are  at  first  cuboldal,  next  low  columnar,  and  then  abruptly  increase  in  length,  until 
they  measure  from  .030-.035  mm.,  in  contrast  with  their  usual  height  of  from  .cx)3-.ocj4  mm.  The 
acoustic  area  includes  two  kinds  of  elements,  the  sustentacular  or  fibre-cells  and  the  hair-cells. 
The  sustentacHlar  cells  are  long,  rather  narrow,  irregulariy  cylindrical  elements  and  extend  the 
entire  thickness  of  the  epithelial  layer,  resting  upon  a  well-developed  basement-membrane  by 
their  expanded  or  divided  basal  proces.ses.  At  a  variable  distance  from  the  ba.se,  they  present  a 
swelling  etielosmg  an  oval  nucleus  and  terminate  at  the  surface  in  a  culicular  zone.  The  cylin- 
drical hair'cells  are  broader  but  shorter  than  the  SKstentacular  cells,  and  reach  from  the  free 
surface  only  as  far  as  the  middle  of  the  epithelial  layer,  where  each  cell  terminates  usually  in  a 


THE   INTERNAL   EAR. 


1S17 


rounded  or  somewhat  swollen  end  containing  a  spherical  nucleus.    The  central  end,  next  to  the  ' 
free  surface,  exhibits  a  differentiation  into  a  cuticular  zone,  similar  to  that  covering  the  Inner 
ends  of  the  sustentacular  elements.    From  the  free  border  of  each  hair-cell,  a  stiff  robust  hair 
(.oao-.o25  mm.  long)  projects  into  the  endolymph.    This  conical  process,  however,  is  resolv- 
able into  a  number  of  agglutinated  finer  hairs  or  rods. 

The  free  surface  of  the  neuroepithelium  within  the  saccule  and  the  utricle  is  covered  by  a 
remarkable  structure,  the  so-called  otolith  mcmtiranc.  This  consists  of  a  gelatinous  membrane 
in  which  are  embedded  numberless  small  crystalline  bodies,  the  otoliths  or  ear-stones.  Between 
it  and  the  cuticular  zone  is  a  space,  about  .030  mm.  in  width  and  filled  with  endolymph,  through 
which  the  hairs  project  to  the  otolith  membrane.  The  otoliths  (otoconia)  are  minute  crystals, 
usually  hexagonal  in  form,  with  slightly  rounded  angles,  and  from  .009-.011  mm.  in  length. 
They  are  composed  of  calcium  carbonate  with  an  organic  basis. 

On  reaching  the  macula  the  nerve-fibres  form  a  subepithelial  plexus,  from  which  fine 
bundles  of  fibres  pass  toward  the  free  surface.  The  fibres  usually  lose  their  medullary  substance 
in  passing  through  the  basement  membrane  and  enter  the  epithelium  as  naked  axis-cylinders. 
Passing  between  the  sustentacular  cells  to  about  the  middle  of  the  epithelium,  they  break  up 
Into  fine  fibrillae,  which  embrace  the  deeper  ends  of  the  hair-cells  and  give  oS  fine  threads  that 
pass  as  free  axis-cylinders  between  the  cells  to  higher  levels. 

The  criau  acuatica  and  the  planum  aemilunatum  are  covered  with  neuroepithelium  similar 
to  that  of  the  maculse.  The  hairs  of  the  hair<ells.  however,  are  longer  and  converge  to  and  are 
embedded  within  a  peculiar  dome-like  structure,  known  as  the  cupola,  which  probably  does  not 
exist  during  life,  but  b  an  artefact  formed  by  coagulation  of  the  iuld  in  which  the  ends  of  the 
hairs  are  bathed.    Otoliths  probably  do  not  exist  in  the  cristx  acusticae. 

The  Cochlear  Duct. — ^The  membranous  cochlea  (ductus  cochlearis)  lies 
within  the  bony  cochlea,  and  like  it  includes  from  two  and  one-half  to  two  and  three- 
quarter  turns,  named  respectively  the  basal,  middle  and  apical,  the  latter  being 


Fic.  1271. 


Oi^n  of  Corti' 


Corti'n  mrmbranr 

Ganglion  apiralc 

Sola  votihuli 


Ductus 
cochin  rift 


Ligamcn- 
turn  iipinle 


Basilar  membrane 

Ganglion  spirmle' 


trochlear  ner^■e  in  interal 
auditory  canal 


Modiolus 
Section  of  human  cochlea  paiaing  'hrough  axis  ot  modiolus.     '    12. 

three-fourths  of  a  turn  at  the  apex  of  tl  -hlea.  The  taperinR  tube  of  the  bony 
cochlea,  winding  spirally  around  the  m  ..olus,  is  subdivided  into  three  compart- 
ments by  the  osseous  spiral  lamina  and  two  membranes,  namely,  the  membranous 
spiral  lamina  and  Reissner's  membrane.  The  membranous  spiral  lamina 
(lamina  twsilaris)  or  basilar  membrane  extends  from  the  free  border  of  the  lamina 
spiralis  ossea  to  the  outer  wall  of  the  cochlea,  where  it  is  connected  to  an  inward 
bulging  of  the  periosteum  and  subperiosteal  tissue,  called  the  spiral  ligament. 
The  lower  of  the  two  tubes  thus  formed  is  the  scala  tympani  and  communicates,  in 
the  macerated  skull,  with  the  tympanum  through  the  round  window.  The  upper 
tube  is  subdivided  into  two  compartments  by  an  exceedingly  delicate  partition, 
known  as  Reissner's  membrane  (membrana  vestibularis)  whicj  extends  from  the 
upper  surface  of  the  osseous  lamina  near  its  outer  end,  obliquely  upward  and  outward, 
to  the  external  wall  of  the  cochlea.     The  comr-xrtment  above  this  membrane  is  the 


I5«8 


HUMAN   ANATOMY. 


'  scala  vestibuli  and  communicates  with  the  perilymphatic  space  of  the  vestibule.  The 
scalx  tympani  and  vestibuli  communicate  only  at  the  apex  of  the  cochlea  throujjh 
the  helicotrema.  They  contain  p>erilymph  and  are  brought  into  relation  with  the 
subarachnoid  space  through  the  aquaeductus  cochlex.  They  are  lined  by  a  delicate 
(ibrous  periosteum,  usually  covered  on  the  surface  which  is  in  contact  with 
the  enclosed  perilymph,  by  a  single  layer  of  endothelial  plates.  In  some  localities, 
however,  as  on  the  tympanic  surface  of  the  basilar  membrane,  the  lining  cells 
retain  their  primitive  mesoblastic  character  and  never  become  fully  differentiated  into 
endothelium. 

The  third  compartment,  the  ductus  cochiearis,  is  triangular  on  cross-sectiun 
(Fig.  1 271),  except  at  its  ends,  and  bounded  i>y  Reissner's  membrane  above,  by 
the  basilar  membrane  and  a  part  of  the  osseous  spiral  lamina  below,  and  by  the 
outer  wall  of  the  bony  cochlea  externally.  Save  for  the  narrow  channel,  the 
canalis  reuniens,  by  which  it  communicates  with  the  saccule,  the  cochlear  duct  is 
a  closed  tube  and  contains  endolymph.  It  begins  below  as  a  blind  extremity,  the 
cscum  vestibulare,  lodged  within  the  recessus  cochiearis  of  the  vestibule  and, 
after  making  two  and  three-quarter  turns  through  the  cochlea,  ends  above  at  the 
cupola  of  the  cochlea  in  a  second  blind  extremity,  the  caecum  cupulare,  or 
lagena,  which  is  attached  to  the  cupwia  and  forms  a  part  of  the  boundary  of  the 
helicotrema. 


Architecture  and  Structtire  of  the  Cochlear  Duct. — Reittner'a  membrane  (membrana  vctitih- 
ularls),  the  delicate  partition  separating  the  cochlear  duct  from  the  scala  vestibuli.  befrins  on 
the  upper  surface  of  the  lamina  spiralis,  about  .2  mm.  medial  to  the  free  edge  of  the  iHjny 
shelf,  and  extends  at  an  angle  of  from  40-45"  with  the  lamina  spiralis  os.sea  to  the  outer  wall  of 
the  cochlea,  where  it  is  attached  to  the  periosteum.  Notwithstanding  its  excessive  thinness 
( .003  mm. ),  it  consists  of  three  layers :  (a)  a  ver)-  delicate  middle  slratum  of  connecHi'e  tissue, 
(b)  the  endothelium  covering  the  vestibular  side,  and  (c)  the  epithelium  derived  from  the  coch- 
lear duct,  and  contains  sparingly  distributed  capillary  blood-vessels. 

The  outer  wall  of  the  cochlear  duct  (Fig.  1372)  is  bounded  by  a  part  of  a  thickened  cres- 
centic  cushion  of  connective  tissue,  whose  convex  surface  is  closely  united  with  the  bony  wall 
and  whose  generally  concave  surface  looks  toward  the  cochlear  duct.  This  structure,  the  liga- 
mentum  tpirale,  extends  slightly  above  the  attachment  of  Reissner's  membrane  and  to  a  greater 
dist.ince  below  the  attachment  of  the  b<-isilar  membrane,  thus  forming  part  of  the  outer  walls 
of  the  scala;  vestibuli  and  tympani.  At  its  junction  with  the  ba.silar  membrane  it  presents  a 
marked  projection,  the  crista  basilaris,  whilst  a  very  slight  elevation  marks  the  (wint  of  attach- 
ment of  the  membrane  of  Reissner.  The  part  of  this  ligament  lying  between  these  projections 
corresponds  to  the  outer  wall  of  the  cochlear  duct.  Its  concave  free  inner  surface  is  broken  by 
a  third  elevation,  the  prominentia  spitalia,  or  accessory  spir  '  ligament,  distinguished  usually  by 
the  presence  of  one  large  (vas  prominems)  or  several  smaii  blood-vessels.  The  lower  and 
smaller  of  these  two  divisions  of  the  outer  wall  is  called  the  lulcus  spiralis  extcmus  and  is  lined 
by  cul)oidal  epithelium,  whilst  the  larger  upper  division  is  occupied  by  a  peculiar  va.scular 
structure,  the  stria  vascularis,  which  contains  cipillary  blood-vessels  within  an  epithelial  struc- 
ture. Its  surface  is  covered  with  pigmented  irregular  polygonal  epithelial  cells,  and  its  deeper 
strata  consist  of  cells  which,  especially  in  the  superficial  layers,  resemble  the  surface  epithelium, 
but  in  the  deeper  layers  assume  more  and  more  the  character  of  connective  tissue.  t)ver  the 
prominentia  spiralis  the  cells  become  flat  and  polyhedral. 

The  ligamentum  spirals  is  composed  of  a  peculiar  connective  tissue,  rich  in  ceils  and  blood- 
vessels. Its  thin  outer  layer  forms  the  jHjriosteum  and  is  denser  than  the  adjacent  loose  con- 
nective tissue.  The  latter  is  broiidest  opposite  the  scala  tympani,  where  its  fibres  converge 
towards  the  crista  biisilaris.  Opposite  the  outer  wall  of  the  cochlear  duct  it  again  becomes 
more  conipjict  and  is  rich  in  cells  and  blood-vessels.  An  internal  layer  extending  from  near  the 
prominentia  spiralis  to  the  basilar  membrane  consists  of  ,.  hyaline,  noncellular  tissue.  Some 
authors  claim  to  have  found  smooth  muscle-fibres  in  the  ligamentum  spirale. 

The  tympanic  wall  or  floor  of  the  cochlear  duct  (Fig.  127a)  comprises  the  basilar  mem- 
brane, extending  from  the  basilar  crest  to  the  outer  end  of  the  bony  spiral  lamina,  and  the  limbus 
laminie  spiralis,  which  includes  this  wall  from  the  attachment  of  Reissner's  membrane  to  the  end 
of  the  bony  lamina.  The  limbus  (crlma  *plrali*)  is  a  thick  mass  of  connective  tissue  upon  the 
upi>er  surface  of  the  outer  end  of  the  os.seous  lamina  spiralis.  Its  outer  extremity  is  deeply 
gr(K)ved  to  form  a  gutter,  the  sulcus  spiralis  intemus,  the  projections  of  the  limbus  above  ami 
below  the  .sulcus  forming  rcspccti > cly  its  superior  (vestibul.ir)  .ind  inferior  (tjmpanir)  labia. 
The  up(>er  surface  of  the  limbus  is  marked  by  clefts  and  furrows  which  are  most  conspicuous 
near  the  outer  margin  of  the  upper  lip  ( labium  vestibulare ) ,  where  the  irregular  projections  l>etween 


THE   INTERNAL   EAR. 


•5«9 


the  furrows  form  the  so-called  auditory  teeth,  because  of  their  fancied  resemblance  to  incisor 
teeth.  The  lower  Up  (lablun  lympaakum )  is  continuous  externally  *ii'  the  liasilar  membrane 
and  is  perforated  near  its  outer  end  by  some  4000  apertures  (foramina  ntrvou)  trinsmittinK 
minute  branches  of  the  cochlear  nerve.  The  epithelium  covering  the  elevated  portions  of  the 
limbus,  includiuK  the  auditory  teeth,  is  of  the  flat  polyhedral  variety,  the  intervt- niiiu  furrows  an<l 
clefts  bcinjt  lined  by  columnar  cells.  The  epithelium  of  the  sulcus  spiralis  consists  of  a  sihsle 
layer  of  low  cuboidal  or  flattened  cells,  continuous  with  the  epithelium  of  the  auditory  teeth 
above  and  with  the  highly  specialized  elements  of  Corti's  or^an  below. 

The  baailar  membrane  consists  of  a  median  (inner)  and  a  lateral  (outer)  part.  The  former, 
known  as  the  «ona  arcuaU,  is  thin  and  supports  the  modified  iieuroepitheli'  -ii  constituting  the 
organ  of  Corti;  the  outer  part,  named  the  sona  pectinata,  is  the  thicker  divisi  .  and  lies  external 
to  the  foot-plates  of  the  outer  rods  of  Corti.  The  basilar  membrane  is  madi  jn  of  three  distinct 
layers,  the  epithelium,  the  oAsUuUia  propria  and  the  tympanic  lamella.  1  ne  substantia  propria 
is  formed  of  an  almost  homogeneous  connective  tissue  with  a  few  nuclei  and  fine  fibres,  which 
radiate  toward  the  out  edge  of  the  ppiral  lamina.  The  fibres  of  the  zona  arcunta  are  very  fine 
and  interwoven,  appeu.>ng  to  be  an  extension  of  those  of  the  lower  lip  of  the  limbus,  whilst 
straight  and  more  distinct  fibres  stretch  from  the  outer  rods  of  Corti  to  the  spiral  ligament  and 
coastitute  the  so-called  auditory  atringa.    According  to  the  estimate  of  Ketzius,  there  are  24,. 100 

Fig.  \rj». 


■stria  viiKoilariH 


'KelMiirr's  memhrant? 


Pmmincntin  *p4rali« 
Membrana  tectoria 


S|>iral  lixament 


Criiita  iHiHitariH 


Nerve-fibm« 


Vas  spiralii  Uuiic 

Cioai-icctian  of  d"..-liu  cochleai U  from  human  cochlea.    \  ^u.     Uiawn  frDm  prapara'ioii  made  by  Dr.  Ralph  Butler. 


of  these  special  fibres.  Their  length  iVicrea.ses  from  the  Iwse  toward  the  apex  of  the  cochlea,  in 
agreement  with  the  corresponding  increase  in  breadth  of  the  basilar  membrane.  The  tympanic 
lamella  contains  numbers  of  fusifonn  cells  of  immature  character  interspersed  with  fibres.  In 
this  location  the  differentiation  of  the  m  -soblastic  cells  lining  the  tympanic  c.inal  has  never 
a  vanced  to- the  production  of  typical  end>>thelial  plates,  the  free  surface  of  the  lamella  being 
inver>te<i  by  the  short  fusiform  cells  alone.  The  inner  zone  of  this  layer  contains  capillaries 
which  empty  into  one,  or  sometime.^  two,  vein",  frequently  seen  under  the  tunnel  of  Corti  and 
known  as  the  vas  spirale.  The  epithelium  covering  the  inner  zone  of  the  t>asilar  membrane 
forms  the  organ  of  Corti,  the  highest  example  of  specialization  of  ncuro-epithelium. 

The  Organ  irf  CortL — The  organ  of  Cork  (organon  B|iiralr)  consists  in  a  general  way  of  a 
series  of  epithelial  arches  formed  by  the  interlocking  of  the  upper  ends  •  jf  uonvir^jing  and  greatly 
modified  epithelial  cells,  the  pillaraor  rodaof  Corti,  uiv>n  the  inner  ,in.'  .mli-i  -iji..^  01  wLith  rrst 
groups  of  neuroepithelial  elements — the  auditory  and  the  auatentscular  ceils,  t'lio  triangui:'.r 
space  included  between  the  converging  pillars  of  Corti  ^ilwve  and  ihe  b.i.s;'^  miivbr^ne  tx.-low 
constitutes  the  tunnel  of  Corti,  which  is,  therefore,  only  an  intercellular  spar.  ..:  unusu  il  size.  It 
contains  probably  a  st>ft  semifluid  intercellular  substance  serving  i'>si)i>port  ihe  nerve-fib  ils 
traversing  the  space  (Fig.  127,,).     The  pillara  or  roda  of  Corti,  cxiin;;;.'LHl  in  -.let,- 1!.  j)mv<   to  K- 

composed  of  two  jwns,  the  ilensei  substance  of  the  |)illur  proper,  aiiJ  a  llni \\>  <)'<.'  pioi.. 

plasmic  envelope,  which  presents  atridug-ularthickeningat  the  base  dircc.ed  tow. ird  the  -aviiy  oi 
the  tunnel.    Each  pillar  possesses  a  slender  slightly  sigmoid,  longitudinr.'A  strir\;cd  hody.  vhuse 


tS20 


HUMAN  ANATOMY. 


upper  end  terminates  in  a  triangular  kead,  and  whose  lower  extremity  expands  into  the  /oo/ 
resting  upon  the  basilar  membrane.  The  inner  pillar  is  shorter,  more  nearly  vertical  and  less 
curved  than  the  outer  ;  its  head  exhibits  a  single  or  double  concave  articular  facet  for  the  recep- 
tion of  the  corresponding  convex  surface  of  the  head  of  the  outer  rod.  The  cuticular  substance 
of  lx>th  pillars  adjoining  the  articular  surfaces  is  distinguished  by  a  circumscribed,  seemingly 
homogeneous  oval  area  of  different  nature.  The  upper  straight  border  of  the  head  of  each  pil- 
lar is  prolonged  outwardly  into  a  thin  process  or  head-plate,  that  of  the  inner  lying  uppermost 
and  covering  over  the  head  and  inner  part  of  the  plate  of  the  outer  pillar.  The  head-plate  of  the 
latter  is  longer  and  projects  beyond  the  termination  of  the  plate  of  the  inner  rod  as  the  phalan- 
geal process,  which  unites  with  the  adjacent  phalanges  of  the  cells  of  Deiters  to  form  the  mem- 
brana  reticularis.  The  inner  pillars  of  Corti  are  more  numerous,  bui  narrower  than  the  outer 
elements,  from  which  arrangement  it  follows  that  the  broader  outer  rods  articulate  with  two  and 
sometimes  three  of  the  inner  pillars,  the  number  of  the  latter  in  man  being  estimated  by  Retzius 
at  5600,  as  against  3850  of  the  outer  rods. 

Immediately  medial  to  the  arch  of  Corti,  resting  upon  the  inner  rods,  a  single  row  of  spe- 
cialized epithelial  elements  extends  as  the  inner  auditory  or  hair-celU.  These  elements,  little 
more  than  half  the  thickness  of  the  epithelial  I'/er  in  length,  possess  a  columnar  body  contain- 
ing an  oval  nucleus.     The  outer  somewhat  constricted  end  of  each  hair-cell  is  limited  by  a 


Ouier  hair- 
cells 
Hensen's  cells 


Celb  of  Deiters 


Fig.  1273. 


Niiel*  apace  Inner  liair-cellii 


MembniiM  tectoriit 


Section  showing  details  of  Cortl's  ornan  from  human  cochlea ;  owinx  to  slight  obliquity  of  section,  width  is  some- 
what exaggerated,    x  375.     Drawn  from  prefiaration  made  by  Dr.  Ralph  Butler. 


sharply  defined  cuticular  zone,  from  the  free  surface  of  which  project,  in  man,  some  twenty-five 
rods  or  hairs.  The  inner  hair-cells  are  less  numerous  (according  to  Retzius  about  3500),  as  well 
as  shorter  and  broader,  than  the  corresponding  outer  elements.  Their  relation  to  the  inner  rods 
of  Corti  is  such,  that  to  every  three  rods  two  hair-celli  are  applied.  The  inner  auctcntacular 
cells  extend  throughout  the  thickness  of  the  epithelial  layer  and  exhibit  a  slightly  imbricated 
arrangement  as  they  pass  over  the  sides  of  Corti's  organ  to  become  continuous  with  the  lower 
cells  of  the  sulcus  spiralis. 

The  cells  covering  the  basilar  membrane  from  the  outer  pillar  to  the  ba.silar  crest  comprise 
three  groups:  (a)  those  composing  the  outer  part  of  Corti's  organ,  including  the  outer  hair- 
cells  and  cells  of  Deiters  ;  (*)  the  outer  supporting  cells,  or  cells  ofHensen;  (f )  and  the  low 
cuboidnl  elements,  the  cells  of  Oaudius,  investing  the  outermost  part  of  the  basilar  membrane. 

The  outer  auditory  or  hair-celli  are  about  five  times  more  numerous  ( approximately  1 8,000 
according  to  Waldeyer)  than  the  corresponding  inner  elements,  and  in  man  and  apes  are  dis- 
posed in  three  or  four  rows.  They  alternate  with  the  peculiar  end-plates  or  "  phalanges  "  of 
Deiters'  cells,  which  separate  the  ends  of  the  hair-cells  and  join  to  form  a  cuticular  mesh-work,  the 
membrana  reticularis,  through  the  openings  of  which  the  hair-cells  reach  the  free  surface.  The 
inner  row  of  these  cells  lies  directly  upon  the  outer  rods  of  Corti,  so  placed  that  each  cell,  as  a 
rule,  rests  upon  two  rods.  The  cells  of  the  second  row,  however,  are  so  disposed  that  each  cell 
lies  opposite  a  single  rod,  whilst  the  third  layer  repeats  the  arrangement  of  the  first  In  conse- 
quence o(  ihls  grouping,  these  elements,  in  conjunction  with  the  "  phalanges,"  appear  iti  surf;!Ce 
views  like  a  checker-board  mosaic,  in  which  the  oval  free  ends  of  the  auditory  cells  are  included 
between  the  peculiar  compres.sed  and  indented  octagonal  areas  of  the  end-plates  of  Deiters'  cells 


THE   INTERNAL   EAR. 


1521 


Cells  oi  Hnncn 


Deitert'  cella 


Outer  hair-cells 


Plate-like  processes  ol 
hair-cell 


Outer  pillar  cella 
Inner  hair-cells 


(Fig.  1374).  The  outer  hair-cells  are  cylindrical  in  their  general  fomi,  tenniiiatinK  about  the  mid- 
dle of  the  epithelial  layer  in  slightly  expanded  rounded  ends,  near  which  the  spherical  nuclei  are 
situated.  The  outer  sharp'  defined  ends  of  the  cells  are  distinguished  by  a  cuticular  border  su|>- 
porting  about  twenty-five  rigid  auditory  rods  or  hairs  which  project  beyond  the  level  of  the  nieni- 
brana  reticularis.  The  deeper  end  of  each  outer  hair-cell  contains  a  dense  yellowish  enclosure, 
known  as  the  body  o/Kelzius,  which  is  triangular  when  seen  in  profile.  The  bodies  are  absent 
in  the  inner  hair-cells. 

The  cella  of  Deiter*  have  much  in  common  with  the  ruds  of  Corti,  like  these  being  special- 
ized sustentacular  epithelial  cells  which  extend  the  entire  thickness  of  the  epithelial  stratum  to 
terminate  in  the  peculiar  end-plates  or  phalanges.  It  follows,  that  whilst  the  free  surface  of  Corti's 
organ  is  composed  of  both  auditory  and  sustentacular  cells,  the  elements  rtsting  upon  the  basi- 
lar membrane  are  of  one  kind  alone — the  cells  of  Deiters.  The  bodies  of  the  latter  consist  of 
two  parts,  the  elongated  cylindri- 
cal <"A;V//or/io«  of  the  cell,  con-  Fig.  1174. 
taining  the  spherical  nucleus  and 
resting  upon  the  basilar  mem- 
brane, and  the  greatly  attenuated 
pyramidal  phalangeal  process. 
A  system  of  communicating  in- 
tercellular clefts,  the  spaces  of 
Nuel,  lie  between  the  auditory 
and  supporting  cells ;  like  the 
tunnel  of  Corti,  these  spaces  are 
occupied  by  a  semifluid  intercel- 
lular substance.  The  cells  of 
Deiters  are  arranged,  as  a  rule, 
in  three  rows,  although  in  places 
within  the  upper  turns  four  or 
even  five  alternating  rows  are 
sometimes  found.  Each  cell 
contains  a  fine  filament,  theyC&r; 
ofRetztHS,  which  begins  near  the 
middle  of  the  base  with  a  conical 
expansion,  and  extends  through 
the  cell-body  to  the  apex  of 
the  phalangeal  process,  where, 
according  to  Spee,  it  splits  into  .seven  or  more  fine  end-fibrils,  that  extend  into  the  cuticular 
superficial  layer  under  and  about  the  phalanges. 

The  membrana  tectoria  or  Corti's  membrane  stretches  laterally  from  the  upper  lip  of  the 
llmbus,  above  the  sulcus  spiralis  and  Corti's  organ,  as  far  as  the  last  row  of  outer  hair-cells. 
The  membrane  is  a  cuticular  production,  formed  originally  by  the  cells  covering  the  rt^ion  of 
the  auditory  teeth  and  the  spiral  sulcus.  Medially  it  rests  upon  the  epithelial  cells,  but  farther 
outward  it  becomes  separated  from  the  free  edge  of  the  auditory  teeth  and  a.s.sumes  its  conspic- 
uous position  over  the  organ  of  Corti.  The  membrane  seems  to  be  composed  of  fine  resistant 
fibres,  held  together  by  an  interfibrillar  substaiKe.  During  life  the  membrane  is  probably  soft 
and  gelatinous,  and  much  less  rigid  than  its  appearance  indicates  after  the  effect  of  reagents. 
The  lower  surface  of  the  free  portion  of  the  membrane,  opposite  the  inner  hair-cells,  is  mod- 
elled by  a  shallow  furrow,  which  indicates  the  position  of  a  spirally  arranged  band  known  as  the 
stripe  of  Hensen.  Like  the  basilar  membrane,  the  membrana  tectoria  increases  in  width  from 
the  base  towards  the  apex  of  the  cochlea. 

The  outer  sustentacular  cells  or  cells  of  Hensen  form  an  outer  zone  immediately  external  to 
the  last  Deiters'  cells.  These  elements  resemble  the  inner  sustentacular  cells,  but  differ  somewhat 
in  form  and  arrangement.  In  coivsequence  of  their  oblique  position,  the  bodies  are  not  only 
greatly  elongated,  but  also  imbricated.  They  do  not  contain  the  fibres  of  Retzius.  The  cells  ol 
Claudius  are  the  direct  continuations  of  Hensen's  cells,  and  laterally  pass  uninterruptedly  into 
the  low  columnar  elements  covering  the  remaining  part  of  the  basilar  membrane.  They  consist  of 
a  simple  row  of  cuboidal  cells  possessing  clear,  faintly  granular  protoplasm  and  spherical  nuclei. 

The  Nerves  of  the  Cochlea. — The  branches  of  the  cochlear  division  of  the 
auditory  nerve  enter  the  base  of  the  cochlea  through  the  tradus  spiralis  foramhiosus 
(page  1514),  those  destined  for  the  apical  turn  traversing^  the  central  canal  of  the 
modiolus.  From  the  modiolus  a  series  of  stout  lateral  branches  diverge  at  quite 
regular  intervals  through  canals  which  coiuinuiiicate  uith  the  peripheral  spiral  canal 
within  the  base  of  the  bony  spiral  lamina.  Within  the  peripheral  canal  the  nerve- 
fibres  jo'n  numerous  aggregations  of  bipolar  nerve-cells,  which  continue  along  the 


Corti's  organ  viewed  from  above,  showing  mosaic  formed  by  rillats 
and  Deiters'  cells ;  outer  ends  oi  auditory  cells  occupy  mesihes  of  cuticula r 
net-work.    {Xelximsi. 


m^ 


kW 


m 


1533 


HUMAN  ANATOMY. 


'i^ 


spiral  canal  and  collectively  constitute  the  ganglion  tpirale.  From  these  cells 
numerous  dendrites  are  given  of!,  which  pass  ^ong  the  canals  within  the  spiral 
lamina  towards  its  margin,  the  twigs  meanwhile  subdividing  to  form  an  extensive 
plexus  contained  within  corresponding  channels  in  the  bone.  At  the  edge  of  the 
spiral  lamina  bundles  of  fine  fibres  are  given  of!,  which  escape  at  the  foramina  ner\'ina 
of  the  labium  tympanicum  and  enter  the  epithelial  layer  close  to  the  inner  rod  of  Corti. 
During  or  before  their  passage  through  the  foramina,  the  nerve-fibres  lose  their  med- 
ullary substance  and  proceed  to  their  destination  as  fine  naked  axis-cylinders.  The 
radiating  bundles  pass  within  the  epithelium  to  the  mesial  side  of  the  base  of  the  inner 
pillar  ;  here  they  divide  into  two  sets  of  fibrillse,  one,  the  mesial  spiral  fasciculus, 
going  to  the  inner  hair-cells  and  the  other,  the  lateral  spiral  fasciculus,  passing 
between  the  inner  pillars  to  reach  the  tunnel  of  Corti.  Within  this  space  fibnllae  are 
given  off  which,  after  crossing  the  tunnel,  escape  between  the  outer  rods  into  the 
epithelium  lying  on  the  lateral  side  of  the  arch.  The  further  course  of  the  fibrilla; 
seems  to  be  such  that  some  extend  between  the  outer  pillar  of  Corti  and  the  first  rows 
of  hair-cells,  whilst  succeeding  groups  of  fibrillae  course  between  the  rows  of  Deitcrs' 


Fici.  1275. 


'Stiperuir  canal 


RnHiIar 
membrane 


Branches  of  cochlear  nerve  to 

Corti'8  organ  Membranous  cochlea 

Canalis  rcunienn  opening  into  cochlear  duct 


mterior  canal 
Blinil  Mac  of  ductus  cuchlearis 
Branch  of  veatibular  nerve  to  p* 


Membranous  labyrinth  of  five  months  ftctus.  fjostero-mesial  aspect :  u,  utricle ;  jj,  */,  sujierioi  .md  )K»stcrinr  utric- 
ularsinus;  j,  saccule;   hj,  utriculo-saccular  canal ;  cr,  canalis  reuntens;  pa,  posterior  ampulla.    X  6.     ^/tetzins). 

cells  to  reach  the  remaining  hair-cells.  The  relation  between  the  nerve-fibrils  and 
the  auditory  cells  is  in  all  cases  probably  close  contact  and  not  actual  junction  with 
the  percipient  elements.  The  p.-iths  by  which  the  impulses  collected  from  the  audi- 
tory cells  are  conveyed  to  the  cochlear  nucleus,  and  thence  to  the  higher  centres,  are 
descrilxid  in  connection  with  the  Auditory  Nerve  (page  1258). 

Blood- Vessels  of  the  Membranous  Labyrinth. — The  arteries  supplying 
the  internal  ear  arise  from  the  internal  auditory  artery,  supplemented  to  a  limited 
extent  by  branches  from  the  stylo-mastoid.  The  auditory  artery,  a  branch  of  the 
kisilar,  after  entering  the  internal  auditory  meatus  divides,  according  to  Sicbenmann, 
into  three  branches  : — ( i )  the  anterior  vestibular,  ( 2 )  the  cochlear  proper,  and  ( ^ ) 
the  vestibulo-cochlear  artery. 

1.  The  vestibular  artery  accompanies  the  utriculo-ampullary  nerve  and  sup- 
plies the  upper  part  of  the  vestibule,  including  the  posterior  part  of  the  utricle  with 
its  macula,  the  saccule  and  the  crista  of  the  upper  and  outer  ampullae  of  the  corre- 
sjxjnding  semicircular  canals. 

2.  The  cochlear  artery  pursues  a  spiral  course.  It  gives  of!  three  branches, 
two  of  which  are  distributed  t<i  the  lower  turn  of  the  cochlea,  whilst  the  third  sup- 
plies the  middle  and  apical  turns. 

3.  The  vestibulo-cochlear  artery  arises  either  from  the  cochlear  artery  or 
independendy  and  divides,  within  the  spiral  lamina,  into  a  cochlear  and  a  vestibular 


9i 


DEVELOPMFNT  OF  THE   EAR. 


1523 


branch.  The  cochlear  branch  is  dfatributed  to  the  lower  turn  of  the  cochlea  and 
anastomoses  with  the  cochlear  artery  proper.  The  vestibular  branch  'i  distributed 
to  the  lower  part  of  the  vestibule,  including  the  lower  part  of  the  saccule  and  utricle, 
to  the  crus  commune  and  part  of  the  semicircular  canals,  and  to  the  lower  end  of  the 
cochlea.  According  to  Siebenmann,  the  macula  of  the  saccule  receives  its  arterial 
supply.from  a  blood-vsssel  which  usually  arises  from  the  common  stem  of  the  vestilv 
ulo-cochlear  artery,  01 ,  more  rarely,  runs  independently  through  the  whole  internal 
meatus.  A  similar  origin  applies  to  the  artery  supplying  the  nerve  of  the  posterior 
ampulla.  In  the  base  of  the  spiral  lamina  the  arteries  are  connected  by  capillary 
loops  especially  in  the  lower  turn  of  the  cochlea.  As  mentioned  above,  one  or  more 
spiral  vessels  are  often  seen  under  the  tunnel  of  Corti  within  the  tympanic  covering 
of  the  basilar  membrane.  The  region  of  the  stria  vascularis  and  prominentia  spiralis 
are  especially  well  supplied  with  blood-ves-sels.  Those  seen  in  the  scala  tympani  are 
principally  veins,  while  a  larger  numlx;r  of  arteries  are  found  in  the  scala  vestibuli. 
The  blood-supply  of  the  lower  turn  of  the  cf>chlea  is  mucR  more  generous  than  that 
of  the  others. 

The  veins  by  which  the  blwxl  escai)es  from  the  cochlea  include  :  ( I )  the  vein 
of  the  vestibular  aqueduct,  which  empties  into  the  superior  petrosal  sinus  ;  (2)  the 
vein  of  the  cochlear  aqueduct,  which  empties  into  the  internal  jugular  and  (3)  the 
venous  ple.xus  of  the  inner  au<litory  canal,  which  empties  either  into  the  t.ansverse  or 
inferior  petrosal  sinii  The  first  of  these  channels  collects  the  blood  from  the  semi- 
circular canals;  the  second  from  the  whole  cochlear  canal  through  the  anterior,  pos- 
terior and  middle  spiral  veins  and  from  most  of  the  vestibule  through  the  anterior 
and  posterior  vestibular  veins.  The  veins  of  the  internal  auditory  canal  form  collat- 
erals to  the  other  veins  of  the  labyrinth  and  receive  the  large  central  cochlear  vein 
(Siebenmann ),  which  leaves  the  cochlea  near  the  border  of  the  central  foramen  of  the 
modiolus,  as  well  as  tributaries  corresponding  to  the  branches  of  the  acoustic  nerve. 


THE   DEVK1.0PMENT  OF  THE  EAR. 

The  development  of  the  ear  incliid"  s  the  formation  of  two  morphologically  distinct  divis- 
ions, the  membranous  labyrinth,  the  ess<iuial  auditor>-  structure,  and  the  accessory  parts,  com- 
prising the  middle  ear,  with  its  ossicles  iiiiU  a.ssociated  cavities,  and  the  external  auditor)'  canal 
and  the  auricle.   The  developmental  history- 


Fig    1276. 


Hind-ttrahl 


Auditory  pit 


Dorvi!  aorta 


Orophar>-nx 

I  visceral  fiirniw 


of  the  organ  of  hearing  pro|)er  in  its  early 
stages  is  largely  an  account  of  the  growth  .nnd 
differentiation  of  the  ectoblastic  otic  vesicle, 
since  from  this  is  produced  the  imix)rtant 
membranous  tube,  the  enveloping  fibrous 
and  osseous  structures  being  com|Kiratively 
late  contributions  from  the  mesoblast. 

Development  of  the  I-abyrinth.— The 
internal  ear  appears  as  a  thickening  .ind 
soon  afte'  depression  of  the  ectoblast  within 
a  small  area  on  either  side  of  the  cephalic 
end  of  die  neural  tube,  at  a  level  correspond- 
ing to  alxjut  the  middle  of  the  hind-brain 
(Fig.  1276,. 

This  depression,  the  auditory  pit,  is 
widely  o|)en  for  a  considerable  time  -.wA 
distinguished  by  the  greater  thickness  of 
its  depressed  wall,  which  contrasts  strongly 
with  the  adjacent  ectoblast.  After  a  time 
the  lips  of  the  pit  approximate  until,  by 
their  final   union,  the  cup-like  depression  is  converted   into  a  closed  sac,  the  otic  vesicle. 

This  sac,  after  severing  all  conne<-tion  with  the  ectoblast,  gradually  recedes  from  the  sur- 
face in  consequence  of  the  growth  o*  the  inter\-ening  mesobUustic  layer  ;  it  next  loses  its  sphe- 
roidal form  and  becomes  somewhat  pe,nr-sha|ied.  with  the  smaller  end  directed  tlorsally.  The 
smaller  end  rapidly  elongates  into  a  clul>shaped  diverticulum,  the  receiius  endolymphaticus, 
which  later  becomes  the  ductus  and  the  saccus  endolymphaticus.  The  remainder  of  the  otic 
S.1C  soon  exhibits  a  subdivision  into  a  larger  dilatation,  the  vestibutar  pouch,  and  a  smaller 
ventral  om,  \Yiv  cochlear  poHch  {Vxfi.  1297). 


Frontal  section  of  early  rabbit  embryo, 
<>l!f  pits.     V,  40. 


I5H 


HUMAN  ANATOMY. 


1 1 


Fig.  1277. 


Hinil-brain 


Otic  sac 


The  Minieircular  canals  differentiate  from  three  folds  which  grow  from  the  vestibular 
pouch  opposite  the  attachment  of  the  ductus  endolymphaticas.  The  central  parts  of  the  two 
walls  of  each  fold  unite  and  undergo  absorption,  while  the  peripheral  part  of  each  fold  remains 
open,  thus  forming  a  semicircular  tube,  one  end  of  which  becomes  enlarged  to  form  the 
ampulla.  The  superior  vertical  canal  appears  first,  and  the  horizontal  or  external  last.  The 
growth  of  the  epithelial  diverticula  is  later  accompanied  by  a  condensation  of  the  surrounding 
mesoblast,  which  differentiates  into  an  external  layer,  the  future  cartilaginous  and  later  bony 
.psule  ;  a  layer  internal  to  this  becomes  the  perichondrium  and  later  periosteum.  A  second 
mesoblastic  layer  Is  formed  from  the  cells  immediately  surrounding  the  otic  vesicle,  whilst  the 
space  between  these  fibrous  layers  is  filled  by  a  semi-gelatinous  substance  which  later  gives 
place  to  the  perilymph  occupying  the  perilympnatic  space.  Within  the  ampullx,  which  early 
develop,  the  epithelial  lining  undergoes  specialization,  accompanied  by  thickening  of  the  meso- 
blastic wall  wittiin  circumscribed  area.s,  to  form  the  cristae  acusticx. 

Coincidently  with  the  development  of  the  semicircular  canals,  a  diverticulum,  the  cochlear 
canal,  appears  at  the  lower  anterior  end  of  the  membranous  sac.    This  tube,  oval  in  section, 

grows  forward,  downward,  and  inward,  and  represents 
the  future  cochlear  duct.  After  attaining  considerable 
length,  further  elongation  is  accompanied  by  coiling 
and  the  assumption  of  the  permanent  disposition  of 
the  tube.  The  epithelium  of  the  cochlear  tube  early 
exhibits  a  distinction,  the  cells  of  the  upper  suri.ice 
of  the  somewhat  flattened  canal  becoming  attenuated, 
whilst  those  on  the  lower  wall  undergo  thickening  and 
further  differentiation.  The  flattened  cells  form  the 
epithelial  covering  of  Reissner's  membrane  and  of  the 
outer  wall,  and  the  taller  elements  are  converted  into  the 
complicated  structures  of  the  tympanic  wall  of  the  ductus 
cochlearis,  including  the  crista,  the  sulcus,  and  the 
organ  of  Corti. 

The  development  of  these  structures  includes  the 
differentiation  of  two  epithelial  ridges ;  from  the  inner 
and  larger  of  these  is  derived  the  lining  of  the  sulcus 
spiralis  and  the  overhanging  membrana  tectoria.  The 
outer  ridge  is  made  up  of  six  rows  of  cells,  the  inner 
row  becoming  the  inner  hair-cells,  the  outer  three 
rows  becoming  the  outer  hair-cells,  whilst  the  two 
rows  between  these  two  groups  form  the  rods  of 
Corti.  The  cristii  appears  between  the  sulcal  cells  and 
the  cochlear  axis  a<;  a  thickening  of  the  spiral  lamina. 

The  cochlear  outgrowth  of  the  primary  otic  vesicle-  forms  the  membranous  cochlea,  or 
scala  media,  alone,  the  walls  of  the  adjacent  divisions,  the  scala  vestibuli  and  seals  tympani, 
resulting  from  the  changes  within  the  surrounding  mesobla-st.  The  latter  differentiates  into  two 
zones,  an  outer,  which  becomes  the  cartilaginous,  and  finally  os.seou.s,  capsule,  and  an  inner, 
lying  immediately  around  the  membranous  can.-il,  which  for  a  time  constitutes  a  stratum  of  deli- 
cate connective  tissue  between  the  denser  capsule  and  the  ectoblastic  canal.  Within  this  layer 
clefts  appear,  which  gradually  extend  until  two  large  spaces  bound  the  membranous  cochlea 
above  and  below. 

These  spaces,  the  scala  vestibuli  and  tht-  scala  tympani,  are  separated  for  a  time  from  the 
scala  media  by  a  robu.st  septum  consisting  of  a  mesoblastic  layer  of  considerable  thickness  and 
the  wall  of  the  ectoblastic  tube.  With  the  further  increa.se  in  the  dimensions  of  the  lymph- 
spaces,  the  partitions  separating  them  from  the  co-  .lear  duct  are  correspondingly  reduced, 
until,  finally,  the  once  broad  layers  are  represented  by  frail  and  attenuated  structures,  the 
membrane  of  Rcisuner  and  the  basilar  membrane,  which  consequently  include  an  ectoblastic 
stratum,  the  .r,  thelial  layer,  strengthened  by  a  mesoblastic  lamina,  represented  by  the  sub- 
stantia propria  .md  its  endothelioid  covering. 

Thv-  main  sac  of  the  otic  vesicle  from  which  the  foregoing  diverticula  arise  constitutes  the 
primitive  ni?mbrancus  vestibule,  and  later  subdivides  into  the  saccule  and  utricle.  This  separa- 
tion begins  as  an  annular  constriction  of  the  primitive  vestibule,  incompletely  dividing  the  vesicle 
into  two  compartments.  The  still  relatively  large  ductus  endolymphaticus,  the  direct  successor 
of  the  recessus  endolymphaticus,  unites  with  the  narrow  canal  connecting  these  vesicles  in  such 
a  manner  that  each  space  receives  one  of  a  pair  of  convergi:!-;  limbs,  an  arrangement  foreshad- 
owing the  permanent  relations  of  the  parts. 

Even  before  the  subdivision  of  the  primitive  vestibule  Is  established,  the  vestibular  end 
of  the  cochlear  canal  becomes  constricted,  so  that  communication  Ixrtween  this  tube  and  the 
future  sacCTile  is  maintained  by  only  a  narrow  passage,  later  the  canalis  reunicns.  The  dex-el- 
opment  of  the  maculae  acustica:  of  the  saccule  and  utricle  depends  upon  the  specialization  of 


Part  of  frontal  KCtioR  ci  bead  o{  rahbit 
cffibrvo ;  otic  sac  is  svparatcti  from  ectoblast 
and  beginning  ku  elunsatc.    X  40. 


DEVELOPMENT  OF   THE   EAR. 


«525 


Well  of 
brmin-vciiicle' 


Endolymphatic 
Trwtm 


Vcitihiiter 
]xiiich 


Otic  vesicle  ibowi  dillemitialion  into  three  subdiviiioa*,  endo- 
lymphatic, vestibular  and  cochlear.    X  4o- 


the  epithelium  within  certain  areas  associated  with  the  distribution  of  the  auditory  ner\'es. 

The  ner\e-fibres  form  their  ultimate  relations  with  the  sensor)'  areas  by  secondary  growth  into 

the  epithelial  structures. 

Development  of  the  Auditory  Nerve*. — The  vestibular  and  cochlear  ner\-es,  according  to 

Streeter',  develop  from  a  KanKlion-ma.ss  first  seen  at  the  anterior  edge  of  the  otic  vesicle.    This 

consists  of  an  upper  and  lower  part 

from  the  dorsal  and  ventral  portion  Pic.  ,  j-g. 

of  which  peripheral  ner\'e  branches  , 

are  developed,  whilst  a  single  stem 

connects  it  with  the  brain. 

The  nerves   destined  for  the 

utricle  and  the  superior  and  external 

ampulla   develop  from   the   upper 

part  of  the  ganglionic  mass,  while 

the  nerves  which  supply  the  saccule 

and  posterior  ampulla  develop  from 

the  lower  part  of  this  ma.ss.    The 

stem  extending  centrally  from  the 

ganglion  toward  the  brain  beconns 

the  vestibular  nerve. 

The  spiral  ganglion  begins  its 

development  at  the  ventral  border 

of  the  lower  part  of  this  mass,  the 

cochlear  nerve  growing  toward  the 

brain  while  the  peripheral  division 

containing  the  ganglion  extends  into 

the   membranous    cochlea.     From 

the  foregoing  sketch,  it  is  evident 

that  the  membranous  labyrinth  is 

genetically  the  oldest  part  of  the  internal  ear,  and  that  it  U,  in  fact,  only  the  greatly  modified 

and  specialized  closed  otic  vesicle  surrounded  by  secondary  mesoblastic  tissues  and  spaces. 

Development    of   the 
Fig.  IJ79.  Middle  Ear.— The  tympanic 

cavity  and  the  Eustachian 
tube  are  formed  essentially 
by  the  backward  prolonga- 
tion and  secondary  expansion 
of  the  inner  entoblastic  por- 
tion of  the  first  branchial  fur- 
row, the  pharyngeal  pouch. 
The  dorsal  part  of  the  latter, 
in  conjunction  with  the  adja- 
cent part  of  the  primitive 
pharynx,  gives  rise  to  the  sec- 
ondary Mo-fymfianic  space 
(fuchs);  the  posterior  end 
of  this  becomes  dilated  to 
form  the  tympanic  cavity, 
while  the  segment  interven- 
ing between  the  tympanic 
diverticulum  and  the  pharynx 
is  converted  into  the  Eusta- 
chian tube.  The  first  and 
second  branchial  arches  con- 
tribute the  roof  of  the  tym- 
panic cavity. 

The  ear  oaiides  are  de- 
veloped in  connection  with 
the  primitive  skeleton  of  the 
visceral  arches.   The  ntallrus 


Endolymphatic  duct 


Wall  of  brain- 


Canalicular 

recCM 


■Utricnlo- 
Haccular  pouch 


Surface 


Cochlear  duct 


Further  diBerentiation  of  otic   vesicle  into  endolymphatic  duct,  utriculo- 
•accular  pouch  and  cochlear  duct. 

and  incui  represent  specialized  parts  of  the  cartilaginous  rod  of  the  first  arch,  the  tensor  tynv 
pani  being  developed  from  the  muscular  tissue  of  the  same  arcli.      nie  ilafit^i  is  develoix^  trom 
the  second  arch.    The  mesoblast  which  surrounds  the  structures  of  the  tympanic  cavity  during 
their  development  becomes  spongy  nnd  finally  degenerates  toward  the  end  of  furtal  life. 
'Amer.  Jour,  of  Anatomy,  Vol.  VI.,  1907. 


1536 


HUMAN  ANATOMY. 


Th«  air-ctUs  of  the  temporal  bone,  includiBg  those  of  the  mastoid  process,  are  formed 
later  by  a  process  of  absorption. 

The  qrmpanie  membrane  results  principally  truni  chants  which  take  place  in  die  first 
branchial  arch ;  it  is  originally  thick  and  consists  of  a  niesoblastic  middle  stratum,  covered  on  its 
outer  sur&KX  by  the  ectobiast  and  on  its  inner  surface  l>y  the  entoblast. 

Development  of  the  Estamal  Bar. — The  median  p«>rtion  of  the  ectoblastic  groove  of  the 
fimt  branchial  furrow  becomes  deepened  to  form  the  outer  part  vk  the  estemal  aaditoiy  canal. 


lOlAHMS  •». 


Di«Knim  inmntint  devdopnwnt  of  human  membranous  cochic* ;  primiry  otic  vesicle  subdivides  into  vcMibular 
and  cochlear  pouches  and  endolymphatic  appendage ;  cochlear  pouch  becomes  ductus  cochlearis ;  from  vestibular 
pouch  are  derived  utricle,  saccule  and  aemicirciilar  canals ;  whilst  endolymphatic  appendage  gives  rise  to  endo- 
lymphatic sac  and  duct,     (^retler. ) 

white  the  surrounding  parts  of  the  first  and  second  arches  <1evelop  into  the  auricle.  About  the 
fourth  week  of  foetal  life,  the  thickened  posterior  mar^n  of  the  first  arch  is  broken  up  into  three 
tubercles  by  two  transverse  furrows.  Similarly  on  the  adjoining  margin  of  the  second  arch,  a 
second  vertical  row  of  three  tubercles  is  fonned  and,  in  addition,  behind  these  a  longitudinal 
groove  appears  marking  off  a  posterior  ridge.  From  these  six  tubercles  and  the  ridge  are  differ- 
entiated the  various  parts  of  the  auricle,  the  lowest  nodule  of  the  first  arch  becoming  the  tragus, 
the  remaining  f)nes  with  the  ridge  giving  rise  to  the  helix,  whilst  from  the  three  tul)ercles  oi 
the  second  arch  are  developed,  from  above  downuard,  the  antihelix,  the  aiiHtragus  and  thr 
lobule 


1 


THE  GASTRO-PULMONARY 
SYSTEM. 


GENERAL    CONSIDERATIONS. 

The  fnod-stuffs  required  to  compensate  the  continual  loss  occasioned  by  the 
tissue-changes  within  the  body  are  temporarily  stored  within  the  digestive  tube. 
During  this  sojourn  the  food  is  subjected  to  the  digestive  processes  whereby  tht-  sub- 
stances suiuble  for  the  nutritive  needs  of  the  animal  are  separated  by  absorption  frtjm 
the  superfluous  materials  which,  sooner  or  later,  are  cast  out  as  excreta.  Closely 
associated  with  digestion,  and  in  a  sense  complementary  to  it,  is  the  respiratory  func- 
tion by  which  the  supply  of  oxygen  is  assured.  In  the  lowest  vertebrates  these  two 
life-needs,  food  and  oxygen,  are  obtained  from  the  water  in  which  the  animal  lives, 
this  medium  containing  both  nutritive  materials  and  the  air  required  for  the  perform- 
ance of  the  respiratory  interchange  of  gases  (oxygen  and  carbon  dioxide). 


Fig.  1 381. 

Wainsn  body 

'        NMucberd 


Oral  cavity    Pharyngeal   / 


poiichi.      Heart     L""*!    '        *-'"' 


\        \ 
Stomach       l^nct«a> 


Cloacal  orifice 


*•"*«"'      HindKW 
Saxiital  Kction  of  ichcnatlc  vertebral*     ( Motlijifi'  from  FIrisckmamm  1 

Since,  therefore,  in  these  animals  both  food  and  oxygen  are  secured  from  the 
same  source,  the  water,  the  digestive  and  respiratory  organs  form  parts  of  a  single 
gastro-pulmonary  apparatus.  This  close  relation  is  seen  in  the  lower  vertebrates 
(fishes),  in  which  the  anterior  segment  of  the  digestive  tube  is  connected  on  either 
side  with  a  series  of  pouches  and  apertures,  the  branchial  clefts,  bordered  by  the 
vascular  gill-fringes  by  means  of  which  the  blood-stream  is  brought  into  intimate 
relation  with  the  air-containing  water. 

When  the  latter  element  is  forsaken  as  a  permanent  habitat  and  the  animal 
becomes  terrestrial,  a  more  highly  specialized  apparatus,  suited  for  aerial  respiration, 
becomes  necessary.  This  need  results  in  the  development  of  the  lungs.  The  latter, 
however,  retain  the  intimate  primary  relation  to  the  digi-stive  tract,  and  are  formed 
as  direct  ventral  outgrowths  from  the  gut-tube. 

The  vertebrate  digestive  tract  early  becomes  differentiated  into  three  divisions  : 
fore-gut,  mid-gut,  and  hind-gut.  The  first  includes  the  mouth,  pharynx,  oesopha- 
gus, and  stomach,  and  serves  for  the  mechanical  and  chemical  preparation  of  the  food 
materials.  The  second  comprises  the  longer  or  shorter,  more  or  le?s  convoluted 
small  intesiine,  and  forms  the  segment  in  which  absorption  of  the  nutritive  materials 
chiefly  takes  place.  The  third  embraces  the  large  intestine,  and  contains  the  super- 
fluous remains  of  the  ingested  materials  which  are  discarded  from  the  body  at  the 

i$>7 


I52« 


HUMAN   ANATOMY 


anal  opening.  Aaaociated  with  the  mid -gut  are  t»<<  iti^«M<!i«t  jjiidi.  tine  liver  anH 
the  pancreas.  Greater  cumpiexity  in  the  character  o*  ttbf  ti^uMi  ani'  in  %hf  mannrr  t  >\ 
securing  it  necessitates  incrt-ased  specialization  in  tkr  ttmn  w^nein'  <>f  th*-  diKL-stivc 
tube  ;  hence  the  addition  o(  acressory  organs,  as  ctw  liiiw,  orai  glands,  ii>ngue,  and 
teeth,  the  latter  often  serving  as  (prehensile  as  w»ill  as  taaiiBicatury  uruuns. 

Reference  to  the  early  relations  of  the  emteryn  to  t*e  vtteliiiu-  site  |rt^  ja) 
recalls  the  important  fact  that  the  greater  pan  ot  the  )pt(  tract  at  tormed  W  tht:  con- 
striction and  separation  of  a  p«irtion  of  the  yoik-sac  by  the  appmximatK^n  ami  ducmrc 
of  two  ventral  folds,  the  splanchnopleura.  Swcr  the  li«»«T  coniiist.s  of  two  linj-rs,  the 
entoblast  and  the  visceral  lamitu  of  the  nies«»blast,  the  rwu.-  resultiiii,'  fr»>m  tit"  union 
of  the  splanchnopleuric  folds  possessc-s  a  lining  directly  tien«ed  from  the  inner  j^eriii- 
layer,  supplemented  externally  by  mesobtast.  The  iattrr  nrfitribuies  iln-  oonn-ctixe 
tissue,  muscular  and  vascular  constituents  of  the  digestiv-  mtw,  whilt  the  c^pitbetiuni 
and  the  associated  glandular  elements  are  the  products  ol  iie  «ntoblaM. 


MUCOLS    MEMBRANES. 


The  apiertures  <.  the  digestive,  respiratory,  ar. 
tions  at  which  the  ini  ument  becomes  continHo  ' 
passages  communicatinj^  with  the  exterior.     The 

t'lo.  laSi. 


i:   r>i«     Mrinary  tracts  mark  loca- 
witt\   u.     V,  tUs  of  cavities  and 

>ti,>s  of  I'll!    spaces  cnflstitute 


Kpilh,*';um 


Papilla  ot  lunica 
propria  «ki  !i- 
pM^  b>-  bkMHt- 
vnMls 


Coniw<iive- 
tisAUf  fttroma 


Section  "t  oral  mucous  membrane.    >'  t.so. 


mucous  membranes.  The  latter,  however,  not  cnly  form  the  free  surface  of  the 
chief  tracts,  but  also  that  of  the  ducts  and  lubes  continued  into  the  glands  which  are 
developed  as  outgrowths  from  the  mucous  membranes. 

Temporarily  in  the  higher  types  and  permanently  in  such  of  the  lower  animals 
as  possess  a  common  cloacal  space,  all  the  ir.iicous  membranes  of  the  body  are  con- 
tinuous. After  acquiring  the  definitive  arrangemint  whereby  the  uro-genitiil  tract 
becomes  separated  from  the  digesti\e  tube,  these  membranes  in  man  and  mammals 
(except  monotremata)  form  two  great  tracts,  the  gastra-pulmonary  and  the  genito- 
urinary. 

The  free  surfaces  of  the  mucous  membranes  are  kept  continuallv  moist  by  a 
viscid,  somewhat  tenacious  secretion,  the  mtu7is,  derivetl  from  the  glands  ;  they  are 
thus  protected  from  the  drying  and  irritating  influences  of  the  air,  foreign  substances, 
and  secreted  or  excreted  matters  with  which  they  .-jre  hn-.-.jtjh!  into  contact. 

Structure. — Every  mucous  membrane  comprises  two  distinct  parts  :  the  epi- 
thelium, which  forms  the  immediate  free  surface  and  furnishes  protection  for  the  more 
delicate  tissues  beneath  ;  and  the  tunica  propria,  a  connective-tissue  layer  which 
constitutes  the  stroma  and  gives  place  and  support  to  the  terminal  branches  of  the 


MICOUS  MEMBRANKS. 


15J9 


Fto.  11S3. 


EiJithclium 


Btrrves  and  the  hlno(f-v»!s<«<4s  and  the  btyinninn^i  of  tlic  lymph-nuliclL-s.  Thus  i<  -aIII 
be  s«!en  thar  the  )i<?i»tTiti  siruct»r«-  of  .1  inuoms  intrtni'rant-  airrf»|»<)nds  cUimI'  ih 
that  of  the  i«ite({uiiiwM,  liie  prmrrtinn  epidenr.is  oi  tiie  latter  litin);  reuri-^enti  :>y 
tlie  epkbeliunn  of  the  former,  wkdf  fjoth  the  coriuin  nd  tb»-  tiinira  pn  i^a  i^  tiiKk- 
che  coin»»^'tive-twi»u«f  basis  over  wiMrh  thi-  e?pithelial  ..lyer  stretches.  .A  strai-.mi  o< 
atdmucims  tissue,  corre^ipondin);  ««h  the  subcutaneous  layer  in  the  sk  .onmrts 
the  mucoiiH  membnuM'  with  the  sumionding  ^ttructures. 

The  epithelium  iiiay  be  stquatnous  or  columnar,  sMinple  or  jaratitied.  Its  char- 
acter is  usiuilly  determined  Iw  the  crNidittuns  ti>  which  it  is  subjected  ;  thus,  where 
ciwerinK  surfaces  exp«i«e<t  to  imechawcal  inHiiences  of  ii<reif{n  bodies,  it  is  commonly 
stmtitied  squiwnous,  m,  in  the  upper  part  oi  Uie  digtaMivc  tract  Where,  on  the  other 
hand,  the  mucoiM  membrane  is  concxsme  in  facilitating'  absorption,  as  in  the  inti-stiiial 
tube,  the  epithelium  is  simpk-  i-«>lumnar  in  trpe.  in  kKsdities  in  which  the  existence 
of  <  current  favors  the  iunclton  of  un  orKUW  either  as  a  means  of  freeing  the  surface 
from  secretion  or  particles  of  foreign  maOer.  #s  in  the  respiratory  tract,  «)i"  of  propul- 
sion through  a  tube,  as  in  the  epididymis  or  the  oviduct,  the  epithelium  i.-*  of  the 
ciliated  columnar  variety.  Mcxlitications  of  ti»e  epithelial  cells,  diw  to  (he  pro-t-nce 
of  pigment  or  of  secretion,  distinguish  certain  qiucimis  membranes,  as  those  clolhirikj 
the  oiacr»»ry  region  and  the  lai^e  intestine  rc»ptrcti\ '-ly. 

The  limutt  propria  or  stroma  consists  fjf  interlai  mg  bundles  of  fibro-eUistic  tis.sue 
which  support  spindle  or  stek^te  connective-tissue  celb.  The  latter  usually  lie  within 
thj  uncertain  clefts  betueen  the 
stroma  bundles,  which  may  be  re- 
gi'rded  as  lymph-spaces.  In  many 
localities  the  surface  of  the  tunica 
profjria  is  beset  with  numerous  cle- 
vatntis  or  papitltr.  nver  which  th- 
epitbeliuan  extend.s.  Such  irregu- 
larities. wiM3i  slight,  may  not  modify 
the  free  surface  of  the  mucous  mem- 
brane, sinc»-  the  epithelial  layer  com- 
pletely tills  the  depressions  between 
the  ele\ations :  when  more  pro- 
nounced, the  papilla-  or  folds  of  the 
connective  tis.sue  produce  the  con- 
spicuous modelling  of  the  surface 
seen  in  the  papilla-  of  the  tongue 
or  the  ruga?  of  the  vagina.  The 
papillse  contain  the  terminal  loo|)s 
of  the  blood-vi-.-sels  and  the  ner\'es 
supplying  the  mucour  i!r:'in'<rane. 
Where  especially  coni-crifd  in  ab- 
sorption, the  mucous  me^nhranes  often  gain  increase  of  surface  by  cylindrical  eleva- 
tions, or  villi,  as  conspicuously  seen  in  the  small  intestine.  These  projections, 
consisting  of  the  stroma  covered  by  epithelium,  contain  the  absorbent  vessels,  or 
lacteals.  in  addition  to  the  blood-capillaries. 

A  more  or  less  well-defined  line  separates  the  epithelium  from  the  .subjacent 
tunica  propria.  This  demarcation  is  the  basement  membrane,  or  membrana  propria, 
a  detail  which  h-ts  been  variously  interpreted.  I'sually  the  basement  membrane 
appears  as  a  mere  line  beneath  the  epithelium,  and  is  then,  probably,  formed  by  the 
apposition  of  the  ba.sal  processes  of  the  epithelial  cells.  When  surroimding  glandular 
tissue  it  is  better  developed,  presenting  a  distinct  and  much  more  robust  structure.  In 
these  positions  the  basement  membrane  is  probably  a  product  of  the  tunica  propria  and 
occurs  in  two  types,  sometimes  being  homogeneous,  at  other  times  reticular  (Flint ' ). 
In  many  localities  the  deepest  part  of  the  mucous  membrane,  next  the  submu- 
cous tissue,  is  occupied  bv  a  narrow  layer  of  involuntary  muscle,  the  muscularis 
mucosa.  While  not  ever\nvhere  present,  it  is  especially  well  developed  in  the  intes- 
tinal tract  from  the  gullet  to  the  anus,  and  in  places  consists  of  two  distinct  layers, 

'  American  Joumal  of  Anatomy,  vol.  ii..  No.  i,  190J. 


Sectiim  ot  mucous  membrane  <A  utuiphagus.     <.  55. 


^:i: 


i 


>5JO 


HUMAN  ANATOMY. 


■  circular  and  a  lo,ip?udinal.  The  inner  surface  of  the  stratum  is  often  broken  by 
processes  of  muscular  tissue  which  penetrate  the  tunica  propria  well  towards  the 
epithelium.  The  muscularis  mucosae  belongs  to  the  mucous  membrane,  and  there- 
fore must  be  distinguished  from  the  muscular  coat  proper,  which  is  frequently  a 
conspicuous  additional  layer  in  the  digestive  tract. 

Mucous  membranes  are  atuched  to  the  surrounding  structures  by  a  submucous 
layer  of  areolar  tissue.  The  latter  varies  in  thickness  and  density,  consequently  the 
firmness  of  the  union  between  the  mucous  and  submucous  straU  differs  greatly  in 
various  localities.  Usually  the  atuchment  is  loose,  and  readily  permits  changes  in 
position  and  tension  of  the  mucosa,  which,  in  the  relaxed  conditior.  is  often  thrown 
mto  temporary  folds  or  ruga,  as  in  the  oesophagus  and  stomach.  In  other  places 
the  folds  are  permanent  and  not  effaced  by  distention  of  the  organ  ;  a  conspicuous 
example  of  such  arrangement  is  seen  in  the  valvule  conniventes  of  the  small  intestine, 
in  which  the  submucous  tissue  forms  the  basis  of  the  elevation. 

The  blood-vessels  supplying  mucous  membranes  reach  the  latter  by  way  of  the 
submucous  tissue,  in  which  the  larger  branches  divide  into  the  twigs  which  pass  into 


Fig.  1184 


Voa-vast'ular  rpithelium 
Tcrmina!  capillary  loopa 

Tunk-a  propria 


Larnr  branclm  withia 
•unmut'OM 


Section  u(  iiiJevtcU  or;il  muc-.ut  ni«nitifane 


the  mucosa.  Within  the  deefier  parts  of  the  tunica  propria  the  smaller  arterial 
branches  bi'tak  up  into  the  capillaries  forming  the  subepithelial  and  papillary  net- 
works, the  vascular  loops  being  limited  to  the  connective  tis.sue  stroma  and  never 
entering  the  epithelium.  The  venous  stems  usually  follow  the  arteries  in  their  gen- 
eral course.  When  glands  arc  present,  the  capillaries  surround  the  tubules  or  alveoli 
with  ritii  net-works  in  close  relaticm  to  the  basement  membrane. 

The  lymphatics  within  mucous  membrares  are  seldom  pn-sent  as  definite  chan- 
nels, since  they  begin  as  the  uncertain  interfascicular  clefts  l)etwcen  the  bundles  of 
stroma-tissue.  Towards  the  deeper  parts  of  the  mucosa  the  lymph-paths  becf)me 
more  definite,  and  exist  as  delicately  walled  varicose  paiHa^es  which  converge  towards 
the  submucous  tissue.  Within  the  latter  the  lyiiiph-ves-sels  form  net-works  richly 
providefl  with  valv«-s  and  the  accompanying  dilatations. 

The  Htrtrs  distributed  to  mucous  membranes  include  cerebral  or  spina;  and 
sympathetic  branches,  the  latter  supplying  especially  the  involuntary  muscle  of  the 


GLANDS. 


«53t 


stroma  and  of  the  blood-vessels.  Surfaces  highly  endowed  with  general  and  tactile 
sensibility  are  proxnded  with  a  generous  supply  of  twigs  containing  medulbted  tibres. 
As  the  latter  pass  towards  their  ultimate  destination  ( for  convenience  aiuuming  that 
all  are  peripherally  directed)  they  lose  their  medullated  character  and,  as  naked  axis- 
cylinders,  form  the  subepithelial  plexuses,  from  which  delicate  tilaments  ()ass  into  the 
papillae,  where  they  terminate  either  as  free  club-shaped  or  special  sensory  endings. 
It  IS  probable  that  in  places  the  nerves  penetrate  between  the  epithelial  cells  forming 
the  layers  next  the  basement  epithelium  and  terminate  in  varicose  free  endings. 

GLANDS. 

Certain  of  the  epithelial  cells  lining  the  mucous  membranes  of  the  body  become 
modified  to  assume  the  rAle  of  secretion-forming  organs  or  glands,  the  products  of 
which  are  poured  out  upon  the  free  surface  and  keep  the  latter  moist.  The  latter 
purpose  is  secondary  in  the  case  of  many  important  glands,  as  the  parotid,  pancreas, 

Fio.  taSs. 


Diagram  >huwtnKtyp«  of  (land*.    a.«,  tubular;  /■•,  alveolar  ur  lactrular     a.  limplc;  b,  colled;  c-d,  iiicreaiiiigh 
complex  compound  tubular;  t,  iubo«iv«olar ;  /,  simple ;  ^  *-i.  profreMively  complex  compound  alveolar. 

or  liver,  since  these  organs  supply  special  secretions  for  particular  ends.  Aggrega- 
tions of  the  secreting  elements  vary  greatly  in  size,  form,  and  arrangement,  as  well 
.«  in  the  character  of  their  prcxiucts. 

The  simplest  type  is  the  unicellular  gland  UwnA  in  the  lower  forms;  in  principle 
this  is  represented  in  man  and  the  higher  animals  by  the  goblet-cills  soi-n  in  pro- 
fusion in  mucous  membranes  covered  with  columnar  epithelium.  The  secrc-tion 
poured  out  by  these  goblet-cells  serves  to  protect  and  lubricate  the  surface  of  tin- 
mucous  membranes  in  which  they  occur.  The  term  "gland,"  houiver,  usu:illy 
implies  a  more  highly  developed  organ  composed  of  a  collection  of  serrt'ting  epithe- 
lial elements. 

Glands  are  classified  according  to  their  form  into  two  chief  groups,  the  tubular 
and  the  alveolar,  each  of  which  occurs  as  simple  or  compound.  It  sh)uKl  !«.■  empha- 
sized that  °n  many  instances  no  sharp  distinction  tietween  these  conventional  groups 


':i'<  ; 


Wk 


1532 


HUMAN  ANATOMY. 


opening  on 
tnucoua  mcinbranc 


Eiurctory  duct 


exists,  some  important  {glands,  as  the  salivary,  being  in  fact  a  blending  of  the  two 
types  ;  such  glands  are,  therefore,  appropriately  termed  tubo-alveolar. 

In  the  least  complex  type,  the  simple  tubular,  the  gland  consists  of  a  cylindrical 
depression  lined  by  epithelium  directly  continuous  with  that  covering  the  adjacent  sur- 
face of  the  mucous  membrane,  as  an  outgrowth  of  which  the  gland  originally  devel- 
oped. In  such  simple  gland  the  two  fimdamental  parts,  tYic  fundus  and  the  duct,  are 
seen  in  their  primary  type.  The  fundus  includes  the  deeper  portion  of  the  gland  in 
which  the  epithelium  has  assumed  the  secretory  function,  the  cells  becoming  lai^er  and 
more  spherical  in  form,  while  in  structure  the  distinction  between  the  spongioplasm  and 
hyaloplasm  is  usually  marlcxl  in  consequence  of  the  particles  of  secretion  stored  up 
within  the  meshes  of  the  s()on^ioplastic  net-work,  which  is  often  sharply  displayed. 
The  duct  connects  the  fundus  with  the  free  surface  and  carries  off  the  products  elabo- 
rated within  the  gland.  It  is  lined  with  cells  which  take  no  part  in  secretion  and 
hence  retain  for  some  distance  the  character  of  the  adjacent  surface  epithelium. 
Dilatation  of  the  fundus  of  the  primitive  type  produces  the  simpK;  alveolar  or  saccular 

gland  ;  division  of  the  fundus  and  part  of 
the  duct  gives  rise  to  the  compound  tubu- 
lar variety  ;  repeated  cleavage  and  subdivi- 
sion of  the  duct,  with  moderate  expansion 
of  the  associated  terminal  tracts,  lead  to 
the  production  of  the  tubo-alveolar  type. 
Simple  tubular  glands  may  be 
minute  cylindrical  depressions  of  practi- 
cally uniform  diameter,  as  the  crypts  of 
Lieberkuhn  in  the  intestine,  or  they  may 
be  somewhat  wavy  and  slighdy  expanded 
at  the  fundus,  as  often  seen  in  the  gastric 
glands  towards  the  cardiac  end  of  the 
stomach.  When  the  torsion  becomes 
very  pronounced,  as  in  the  sweat-glands, 
the  coiled  variety  results. 

Compound  tubular  glands  pre- 
sent all  degrees  of  complexity,  from  a 
simple  bifurcation  of  the  fundus  and  a<l- 
jacent  part  of  the  duct,  as  in  the  pyloric 
or  uterine  glands,  to  the  elaborate  duct- 
system  endmg  in  terminal  divisions  either 
of  a  tubular  form,  as  in  the  kidney  and  tes- 
ticle, or  of  a  modified,  somewhat  dilated, 
alveolar  form,  the  tubo-alveolar  type,  as 
in  the  salivary  glands. 

Tubo-alveolar  glands,  modified 
compound  tubular,  constitute  a  very  im- 
portant group,  since  they  embrace  many 
of  the  chief  secretory  organs  of  the  body. 
They  are  made  up  by  re|)etition  of  similar  structural  units,  differences  in  the  size  of 
the  organ  depending  upon  the  number  of  those  associated  to  compose  the  gland. 
These  units  correspond  to  the  groups  of  terminal  compartments,  or  alvtoii,  con- 
nected w  ith  A  single  ultimate  division  of  the  duct-system.  The  alveoli  or  acini  contain 
the  secreting  cells,  and  are  limited  externally  by  a  Ixtsement  membrane,  often  well 
devel()|)etl.  which  su|)ports  the  glandular  e|)ithelium  and  separates  the  latter  from  the 
blo<Kl-  and  lymph-vessels  that  surround  the  acinus. 

The  alveoli  belonging  to  the  same  intermediate  duct,  held  together  by  delicate 
connective  tissue,  constitute  a  pyramidal  mass  of  glandular  tissue,  \.\\ii primary  Mu/cs. 
The  latter  are  assembled  into  larger  groups,  or  strondary  lobules,  which  in  turn  are 
united  by  interlobular  connective  tis.sue  mto  the  lobes  composing  the  entire  gland. 
The  loin's  are  held  together  more  or  less  firmly  by  the  i!iterlob;»r  areolar  tissue 
i^oniinuous  with  the  general  fibrous  envelope,  which  furnis  ;i  ca|)sule  for  the  entire 
organ  and  separates  it  from  the  surrounding  structures. 


Diagram  Hhuwinfr  rclaliiMiH  ii{  various  pnn  mhim  of  duct- 
tivalrm  in  Klantls  of  tubu-alveutar  type. 


GLANDS. 


1533 


The  interlobar  tissue  and  its  interlobular  continuations  contain  the  blood-vessels, 
lymphatics,  and  nerves  supplying  the  gland  and,  in  addition,  the  major  |K>rtion  of 
the  excretory  ducts.  In  the  larger  glands  the  latter  form  an  claUirate  system  of  pas- 
sages arranged  after  the  general  plan  shown  in  the  accom|Kuiying  diagram  (  Fig. 
1285).  Traced  from  the  terminal  compartments,  or  alveoli,  of  the  gland,  the  duct- 
system  begins  as  a  narrow  canal,  the  intermediate  duct,  lined  by  low  culx>idal  or  flat- 
tened cells  directly  continuous  with  the  glandular  epithelium  of  the  alveoli.  After  a 
short  course  the  tube  increases  in  diameter  and  becomes  the  intralobular  duct,  which 
is  often  conspicuous  on  account  of  its  tall  and  sometimes  striated  or  rod-epithelium. 
The  further  path  of  the  excretory  tubules  lies  within  the  connective  tis.sue  sepai[ating 
the  divisions  of  the  glandular  suljstance,  and  embraces  the  interlobular  and  the  inter- 
lobar ducts,  the  latter  joining  to  form  a  single  main  excretory  duct  which  o|)ens  ujK>n 
the  free  surface  of  the  mucous  membrane.  The  last-named  {Passage  is  linetl  for  some 
distance  by  cells  resembling  th<>8e  covering  the  adjacent  mucous  membrane  ;  w  here 
these  are  stratified  squamous  in  type,  this  character  is  maintained  for  only  a  limited 

Fio.  laS;. 


Mucous  alveoli 


Serous  alvtoll 


Sevtion  of  |K»ietiot  part  o(  (oiikuc.  showinR  »lv«ili  «>!  Mfoui  uiul  mu«MU  lypn  of  glandi. 


extent,  Ixfore  the  interlobar  ducts  are  reached  gradually  giving  place  to  a  simple, 
sometimes  at  first  ilouhle,  layer  of  columnar  oj)ith<lium  which  exteiuls  as  far  as  the 
intralobular  tubules.  The  walls  of  the  larger  <liicts  consist  of  a  fibro-elastic  coat,  linetl 
by  epithelium,  and  somctinu-s,  in  the  case  of  the  large  glands,  as  the  jKirotid,  liver, 
jwncreas,  or  tt-sticle,  are  strengtheni-d  externally  by  a  layer  of  inv<>luntar\-  nniscle. 
In  the  case  of  the  large  ducts  the  latter  is  usually  dis|)oseil  as  a  tr:insvers«-  and  longi- 
tudinal layer,  to  which,  as  in  the  hc|>atic  duct '(  Hendrickson).  a  thinl  oblicjue  one 
may  Ik-  atldt-tl.      Hiflerential  stains  show  the  presence  of  a  large  amount  of  elastic.!. 

"  The  glandular  epithelium  lining  the  aivtoii  rests  u|)on  the  limiting  l«s.inent 
membrane  .is  a  single  laver  of  irregularly  spherical  or  |X)lygonal  secreting  cells  ;  these 
do  not  completelv  Jill  the  alveolus,  but  leave  an  intercellular  deft  into  which  the 
proihict  ot  the  cells  is  (Kuiretl  .nml  in  which  the  system  of  excretory  ducts  Ingins 
r)e|H'nciiiig  ii|M>n  the  iKciiliaritit-s  of  the  ceiis  and  the  character  of  their  secretion, 
glands  are  divided  into  serous  and  mucous. 


»534 


HUMAN  ANATOMY. 


Fig.   1266. 


The  serous  glands  are  distinguished  by  cells  which  are  distincdy  granular, 
generally  pyramidal  in  form,  with  nuclei  situated  in  the  vicinity  of  the  centre.  The 
secretion  elaborated  by  such  glands  is  thin  and  watery.  The  general  appearance  of 
the  cells  dejiends  upon  the  number  and  size  of  the  granules  stored  within  their  cyto- 
pla.sm,  and  changes  markedly  with  the  variations  of  functional  activity  of  the  gland. 
When  a  serous  gland  is  in  a  condition  of  rest,  the  cells  are  loaded  with  secretion, 
and  appear,  therefore,  larger  and  coarsely  granular.  After  active  secretion,  on  the 
contrary,  the  cells  are  exhausted  and  smaller  and  contain  little  of  their  product,  often 
e.xhibiting  differentiation  into  a  clear  outer  zone,  free  from  granules,  and  a  darker 
innet.zone,  next  the  lumen,  in  which  the  granules  still  remain. 

The  mucous  glands  elaborate  a  clear,  viscid,  homogeneous  secretion,  which, 
when  present  in  considerable  quantity,  as  during  rest,  distends  the  cells,  crowding 
the  nuclei  to  the  periphery  against  the  basement  membrane,  and  gives  to  the  glandu- 
lar epithelium  a  clear  and 
transparent  appearance  in 
marked  contrast  to  the 
granular  character  of  the 
elements  of  a  serous  gland. 
During  rest,  when  loaded 
and  distended  with  mucoid 
secretion,  the  transparent 
cells  possess  well-defined 
outlines,  and  present  a  nar- 
row peripheral  zone  con- 
tiining  the  displaced  nuclei 
and  granular  protoplasm. 
After  prolonged  activity  the 
exhausted  cells  contain  rela- 
tively Utile  mucoid  secre- 
tion, and  hence  the  threads 
of  spongioplasm  are  im 
longer  widely  sejwratetl,  but 
lie  closely  ;  in  consequence 
of  these  changes  the  cells 
lose  their  former  transjwr- 
ency  and  resemble  the 
elements  of  serous  glands, 
becoming  smaller,  d^irker, 
and  more  granular  than 
th.'  cells  of  the  quiescent 
mucous  gland 

The  alveoli  of  mucous 
glands  often  contain  small 
crescentic  groups  of  sin.iU 
granular  cells  lying  iK-twecn 
the  usual  larger  clear  ele- 
ments and  the  l)a.scincnt 
membrane ;  these  are  the 
interpretation  of  which  has 
as  groups  of  cells 


serou!)  cells 


Duct 


Mucous  cdls 


neniilune 


H-rttnii  ul  hutiiai)  »iuhliiiKua1  Klancl.  Khowinje  Mrrous  cells  ftrrangeil  as  demi- 
luneH.     •  300. 


rrtsfents  of  Gianuzsi,  or  demilunes  of  Heidrnhain,  the 
caused  nuuh  discussion.  The  older  view  rj-ganUtl  the  cn-scent 
(iilTcring  from  the  surrounding  ones  only  in  their  st.nge  of  activity  and  not  in  their 
I'ssential  characters,  all  the  cells  within  the  alveolus  Ix-ing  of  the  same  nature.  The 
iippusite  view,  advanced  by  Ebner  over  a  quarter  of  a  century'  ago,  has  received  sup- 
port from  more  recent  critical  studies  by  Kiichenmeister.  Sojger,  Op[H-l,  R.  Krause, 
.mil  others,  who  have  shown  that  the  cells  composing  the  crescents  ditTer  from  the 
mucus-containing  elements,  elaborate  a  sfx-cial  secretion,  and  are  similar  to,  if  not 
identical  with,  those  tilling  the  alveoli  f>f  serous  glands.  According  to  thj'se  obsen-ers, 
the  crescents  are  groups  nf  serous  cells  compressed  and  tlisplaced  by  the  pre<lomi- 
n.iting  innrous  elements,  but  not  excluded  from  the  lumen  of  the  alveolus,  as  was 


GLANDS. 


•  5M 


Fig.  1289. 


S«rlion  of  «rvrral«?vrt>ti  of  Hubmmx- 
illary  Kl»i>d  of  dofE.  sliouiiiK  u-rmitia) 
ifuctH  aiid  sci'rrtion-t'.i|iillaiit>  iiiissiiiK 
to  iTwcrntic  (Ktimilt-ttk  K^'^^ufis  of  !*rou» 
cclln.     ^  joo.     {KrUims.) 


formerly  thought  to  be  the  case,  since  extensions  of  the  lumen  pass  between  the 
mucous  cells  to  reach  the  demilunes. 

In  addition  to  the  main  alveolar  lumina,  always  narrow  in  st-rous  and  wider  in 
mucous  acini,  the  existence  of  intercellular  passa^^es,  or  secretion-capillaries,  has  been 
established  for  marw  glands,  especially  by  the  employment  uf  the  Golgi  and  other 
special  methods.  These  clefts  penetrate  laterally  be- 
tween the  glandular  epithelium  frt>ni  the  a.xial  lumen 
towards  the  basement  membrane,  partially  enclosing 
the  secreting  cells  with  a  branching  system  of  minute 
canals.  Alveoli  containing  exclusively  mucous  cells 
do  not  possess  these  intercellular  canaliculi,  the  axial 
lumen  alone  being  present.  In  acini  of  ihe  serous 
type  the  accessory  channels  are  represente<l  by  minute 
branching  [)assages  which  penetrate  between  the  cells, 
but  seldom  roach  the  liasement  membrane.  The  most 
conspicuous  of  the  secretion-capillaries  occur  in  aKe- 
oli  c«)ntaining  the  demilunes,  the  product  of  the 
serous  cells  escaping  into  the  main  lumen  by  means 
of  the  lateral  intercellular  canals  which  pass  between 
the  mucous  elements  to  reach  the  perii)heral  group  of 
serous  cells  composing  the  crescent.  The  view  that 
the  secretion-capillaries  normally  extend  into  the  cyto- 
plasm of  the  glandular  epithelium,  and  are,  therefore, 
also  intracellular,  must  be  regarded  as  doubtful  and  still  undecided,  although  sup- 
ported by  many  able  histologists. 

Depending  upon  the  distribution  of  the  two  varieties  of  alveoli,  the  lulio- 
alveolar  glands  may  be  divided  into  four  groups  ( Ebner) : 

1.  Pure  serous  glands,  in  which  only  serous  alveoli  occur,  as  the  jiarotid. 

2.  Mixed  serous  glands,  in  which  a  few  mucous  alveoli  are  intermingled  with  the 
serous,  as  the  submaxillary. 

3.  Mixed  mucous  glands,  in  which  the  serous  cells  occur  as  crescentic  groups  or 
demilunes,  as  the  sublingual  and  buccal. 

4.  Pure  mucous  glands,  without  serous  alveoli  or  demilunes,  as  the  palatal. 
Simple  alveolar  or  saccular  glands  in  their  ty|>ical  fl:isk-like  form,  as  seen 

in  the  skin  of  amphibians,  art-  not  found  in  man.  The  dilated  sphericiil  fundus  is  iiiutl 
with  clear  and  distended  secreting  cells,  in  which  the  nuclei  are  displaced  towards  the 
periphery  by  the  mucus  elalxiratetl  within  the  ejiithelial  elements.  In  the  higher 
animals  this  type  of  gland  is  represented,  somewhat  nunlifietl,  by  the  simple  sebaceous 
follicles. 

Compound  alveolar  or  saccular  glands  constitute  a  group  much  less  exten- 
sive than  formerly  supposed,  sinc-e  careful  study  of  the  form  and  arrangement  of  many 
organs,  as  the  salivary  glands,  pancreas,  etc.,  has  sh.iwn  that  these  are  more  appro- 
priately regardetl  as  tubo-alveolar  than  as  brancheil  siiccular  glands.  The  latter, 
nowever,  still  have  representitives  in  the  larger  sebaceous  and  Meilximian  glands. 
The  most  conspicuous  example  of  the  compound  s;iccular  or  racemose  typi'  is  the 
lung,  which  in  its  devclojiment  and  the  arrangement  of  the  air-tubes  and  the  s;u-like 
terminal  cjimpartments  corrt-sponds  tJ)  this  variety. 

The  blood-vessels  distributed  to  glands  are  always  numerous,  since  secretory 
activity  implies  a  generous  blood-supply.  In  the  case  of  the  smaller  and  simpler 
glands,  the  capillaries  within  the  mucosa  form  a  mesh-work  outside  the  basi'menl 
membrane  enclosing  the  glandular  epithelium.  The  large  cotupmmd  glands  ;ire  pro- 
vided with  a  vascular  system  which  usually  corres[M)ncls  in  its  (general  arrangem»-nt 
to  that  of  the  excretory  ducts,  following  the  tM  ts  of  the  intcrlolKir  .uxl  iiiKriolnilar 
areolar  tissue  and  its  extensions  In-tween  the  p..  iips  of  the  alveoli.  ()>i  reaching  the 
individual  acini,  the  capillaries  form  net-works  which  surround  the  hisj-ment  mem- 
brane enclosing  the  alveoli,  thus  bringing  the  bioiHl-current  into  close,  but  ni>t  direct, 
relation  with  the  secreting  cells,  an  arrangement  favoring  the  stiection  by  tile  proto- 
plasm of  the  particular  substances  icfiuired  for  the  function  of  the  gland.  V\'hen  tiie 
relation  between  the  glandular  epithelium  and  the  capillaries  is  unusually  intimate. 


i4? 


>» 


1536 


HUMAN  ANATOMY. 


as  in  the  case  of  the  liver,  a  distinct  basement  membrane  is  sometimes  wanting,  a 
delicate  sup]x(rtinjj  reticulum  alone  inter\^ening  between  the  blcxni-stream  and  the 
protoplasm  of  the  cells.  Although  subject  to  local  deviations,  conspicuously  excep- 
tional in  the  liver,  the  veins  follow  in  general  the  coun>c  of  the  arterial  branches,  the 
larger  bkxKi-vessels,  together  with  the  main  excretory  ducts,  the  lymphatics,  and  the 
nerves,  occupying  the  principal  extension  of  the  connective  tissue  into  the  glandular 
mass. 

The  lymphatics  are  represented  by  the  larger  trunks  which  follow  the  excretory 
ducts  and  freely  anastomose  within  the  interlobular  areolar  tissue.  After  the  intra- 
lobular portion  of  the  vessel  is  reached,  its  definite  character  is  gradually  lost  until  the 
lymphatic  channels  are  to  be  recognized  only  as  the  clefts  between  the  bundles  of 
connective  tissue  separating  the  alveoli. 


Fig.  1 290. 


Fig.  1391. 


lnjc»tc<I  Rastric  iniiCiHis  iiicnt- 
!>r;iiie,  shtmiiiK  cnpilLiry  nel-wurk 
^utioutKlingtubiilarjitatKis.     '   ^s. 


Section  of  siibma  Rfft««-^  tfland  of  rabbit :  umier 
half  >'i  tiKUre  shown  rftstrinuiioii  trf  iieive-fibres 
to  .ilv  roti ;  luwrr  half  sho^K's  terminal  f1il<  ts  aiul 
Mrcrtrtii>i)-ia|Hllalics.     X  390-     \,Hft.ti4s.i 


The  nerves  supplying  the  larger  glands  include  fil)res  from  two  sources,  the 
cranial  or  s])inal  nerves  and  the  syin{)athetii-.  They  follow  the  interlobular  excretory 
ducts,  around  which  plexuses  are  formed,  ganglion-cells  being  frequent  at  the  jwunts 
of  junction.  The  stronger  twigs  contain  a  prefKuulerating  projjortion  >[  ihi-lc 
medullated  fibres,  which  l>ecoMie  progressively  less  in  size  and  num'nr  in  iheir  course 
towards  the  alveoli.  I'pon  reaching  the  latter  the  nerves  consist  uimos;  <-',!inlv  of 
nonmedullate<l  fibres,  and  in  the  end-plexuses  around  the  alveoli  .such  filjres  alone 
are  present.  The  termin.il  distribution,  as  demonstrated  by  the  (iolgi  and  nwthskiie 
bine  methods,  incluiles  ffiilrmmar  and  hypolemmar  fibrillte,  the  former  lying  upon 
and  the  latter  beneath  the  basement  membrane.  The  hyiK)lemmar  fibrilla;  pass  into 
the  acini  from  the  extra  alveolar  plexus  formed  by  the  filaments  surrounding  the  base- 
ment membrane.  The  ultimate  relation  between  the  terminal  fibrillar  and  the  glandu- 
lar epithfiiuni  is  stili  tmn-rfain,  but  it  mav  Ih'  regarded  .is  i-stablishrd  that  the  nerves 
extend  iH-twecn  and  .iroiiiid  the  cflls  ;  an  intracellular  termination,  on  the  contrary, 
is  doiibtfui.  Ket/iiis,  Kbaer,  and  others  agree  in  piituring  the  delicate  ptrialveolar 
[)lexus  as  consisting  of  tortuous  and  convoluted  filaments  which  end  in  occasional 


GLANDS. 


»537 


Fio. 


lagt. 


delicate  varicosities.  Amstein '  has  described  a  special  minute  plate-like  end-organ 
as  a  widely  occurring  mode  of  nerve-ending  in  glands.  W.  Krause'  has  noted  in 
certain  glands  a  form  of  end-capsule  resembling  a  simplified  Pacinian  corpuscle.  The 
sympathetic  fibres  are  distributed  especially  to  the  involuntary  muscle  of  the  blood- 
vessels and  the  ducts,  the  peristaltic  wave  within  the  muscular  coat  of  the  latter  facili- 
tating emptying  of  the  secretion. 

Development. — Since  glands  are  only  extensions  of  the  mucous  membrane  or 
integument  upon  which  they  open,  their  development  begins  as  an  outgrowth  or 
budding  from  the  epithelium  covering  such  suriaces.  In 
the  simple  tubular  glands  the  minute  cylinders  are  closely 
placed  and  composed  of  densely  packed  cells.  In  the 
case  of  the  larger  compound  glands,  as  the  .salivary  or 
pancreas,  the  first  anlage  consists  of  a  solid  cylindrical 
plug  which,  [jenetrating  into  the  mesoblast,  soon  begins 
to  branch.  The  ends  of  the  terminal  divisions  enlarge 
and  eventually  become  the  alveoli.  Meanwhile  the  sur- 
rounding mesoblast  undergoes  condensation  and  forms 
the  interlobular  and  other  septa,  as  well  as  the  general 
envelope,  or  capsule,  thereby  giving  definite  form  to  the 
general  glandular  aggregation.  The  iscular  and  other 
structures  usually  found  within  the  interparenchymatous 
tis,sue  are  secondary  and  later  formations.  The  develop- 
ment of  the  gland  involves  a  double  process  of  active 
growth, — not  only  the  extension  of  the  epithelial  pro- 
cesses, but  also  a  coincident  invasion  and  subdivision  of 
the  latter  by  the  mesoblast  to  form  the  constituent  units 
of  the  organ.  The  lumen  of  the  gland  appears  (it'st  in 
the  main  excretory  duct,  from  which  it  extends  into  the 
secondary  tubes  and,  finally,  into  the  alveoli.  Growth, 
separation,  and  more  regular  arrangement  of  the  cells 
cor.iposing  the  epithelial  cylinders  are  the  chief  factors  in  producing  the  lumen.  In 
the  early  condition  of  the  glands,  before  the  assumption  of  functional  activity,  the 
cells  later  constituting  alveoli  of  the  serous  or  mucous  type  are  similar  and  without 
histological  distinction.  Upon  the  establishment  of  their  difierent  rAles,  however, 
the  characteristics  distinguishing  the  '.-urieties  of  glands  appear,  'he  differences  de- 
pending upon  physiological  rather  than  upon  inherent  anatomical  variation. 

'  An.ntom.  Anzei^r,  Bd.  x.,  1895. 
*Zeitschriftf.  raUonal.  Med.,  Bd.  xxiii.,  1865. 


Section  of  1rrit\  oral  mucous 
membrane,  &howin<  develo(»ng 
tubo^lveolar  gland.    X  yi. 


Vl 


SI  ■  *,  vl 


THE  ALIMENTARY  CANAL 


This  is  a  long  and  complicated  tube  extending  from  the  mouth  to  the  anus. 
Excepting  the  two  ends,  each  of  which  is  at  first  a  pouch  from  the  ecu.blast,  it  is 
developed  from  the  entoblast  with  a  mesoblastic  envelope.  It  consists  of  the  mouth, 
pharynx,  and  oesophagus  above  the  diaphragm,  and  of  the  stomach  and  small  and 
large  intestines  below  it.  There  are  many  accessory  organs  connected  with  it  wliose 
primary  function  is  to  assist  in  the  process  of  nutrition.  The  chief  ones  above  tiie 
diaphragm  aje  the  teeth,  the  tongue,  and  the  salivary  glands ;  those  ijelow  it  aie 
glands  of  various  kinds,  mostly  so  small  as  to  be  contam«l  in  the  mucous  membraiit. 
But  two  distinct  organs,  the  liver  and  the  pancreas,  belong  to  this  class,  both  being 
originally  outgrowths  from  the  gut.  The  trachea  and  lungs  have  a  similar  origin, 
but  their  physiological  hinction  is  so  different  that  they  are  treated  of  under  a  separate 
heading. 

The  general  structural  plan  of  the  digestive  tube,  presenting  in  places  great  mod- 
ifications, is  :  ( I )  a  lining  of  mucous  membrane  ;  ( 2 )  a  submucous  layer  of  areolar 
tissue,  into  which  glands  may  penetrate  from  the  former  ;  (3)  a  double  layer  of  non- 
striped  muscular  fibres,  of  which,  as  a  rule,  the  inner  is  ci'  "ilar  and  the  outer  lon^ji- 
tudinal ;  (4)  below  the  diaphragm,  a  serous  covering  fron  he  peritoneum,  which, 
although  originally  complete,  is  in  the  adult  wanting  m  certain  parts. 

The  length  of  the  alimentary  canal  is,  on  the  average,  not  far  from  9  m.  ( ap- 
proximately 30  ft.),  of  which  not  more  than  45  cm.  (about  18  in.)  is  above  the 
diaphragm.  A  preliminary  sicetch  of  the  d'visions  above  the  diaphragm  may  be  con- 
venient. The  vestibule  of  the  mouth  is  tht  space  between  the  lips  and  cheeks  exter- 
nally and  the  jaws  and  teeth  internally.  The  (potential)  cavity  of  the  mouth  is  within 
the  arches  of  the  gums  and  teeth.  It  is  bounded  above  by  the  hard  palate  and  its 
backward  continuation  the  soft  palate.  The  greater  part  of  the  floor  is  occupied  by 
the  tongue.  There  is  a  free  horseshoe-siiap«l  sjiace  beneath  the  tongue  within  the 
lower  jaw,  called  the  alveolar-lingual  groove  or,  better,  the  sublingual  space.  The 
pharynx  joins  the  mouth  at  the  anterior  pillar  0/  the  fauces,  a  fold  passing  outward 
and  downward  from  the  soft  palate  to  the  tongue.  The  pharynx  extends  from  the 
base  of  the  skull  to  the  lower  border  of  the  lar>;nx.  The  upper  part,  the  naso- 
pharynx, is  behind  the  nasal  chambers  which  open  into  it,  the  oropharynx  is  L<jliind 
the  mouth,  and  the  laryngo- pharynx  behind  the  larynx.  At  the  lower  border  of  the 
larynx  it  is  followed  by  the  oesophagus,  a  long  tube  which,  piercing  the  diaphragm, 
opens  into  the  stomach. 

THE  MOUTH. 

The  framework  of  the  mouth  is  made  by  she  hard  palate  and  tho  ai\eoiar 
processes  of  the  upper  jaw,  by  the  greater  part  of  the  hoAv  (including  the  .Jvcjlat 
processes)  of  the  lower  jaw  and  part  of  the  ramus,  and  I)y  the  hyoid  bone,  to  which 
m  .'   l>e  added  the  mylo-hyoid  muscle  forming  the  floor. 

When  the  lips  are  opened  and  the  lower  jaw  dropped,  the  mouth  is  a  true  cavity 
extending  to  the  pharynx  ;  when  these  parts  are  closed,  the  tongue  fills  practically  the 
whole  space.  It  is  convenient,  however,  to  speak  of  the  cavity  of  the  mouth.  This 
space  is  subdivided  into  the  vestibule  or  preoral  cavity  and  that  of  the  oral  cavity  or 
mouth  proper.  The  former  is  the  region  between  the  closed  lips  and  cheeks  in  front 
and  the  closed  jaws  and  teeth  behind.  When  the  lips  are  closed,  it  communicates  with 
the  mouth  proper  only  by  a  small  passage  behind  the  wisdom-teeth,  in  front  of  the 
ramus  of  the  jaw. 

THE   LIPS,  CHEEKS,  AND   VESTIBULE. 

The  orifice  of  the  mouth  (rima  oris)  is  a  transverse  slit  of  variable  length 
bounded  by  projecting  folds,— the  lips.     These,  like  the  cheeks,  with  which  they  arc- 
continuous,  are  composed  of  complicated  layers  of  muscle,  covered  externally  Dy 
skin  and  internally  by  mucous  membrane. 

153S 


BOH 


K.ifliil 


THE  LIPS,  CHEEKS,  AND  VESTIBILE. 


1539 


Fat  is  found  irregularly  dispowd  anions  the  muscles  of  the  cheeks  in  varying 
quantity,  but  in  the  depression  in  front  of  the  maibeter  and  superiiciiil  to  the  tniccinator 
there  is  a  distinct  ball  of  fat  enclosed  by  a  ca|)sule,  which  is  the  remnant  of  the  so- 


Fic. 


PfOlUI  ll 


'idal  tiniu 


OrbJvularitDns 


Gcni 


.Orifice  ot  Euilachiui 
labc 


Gcnio-hj-oid 


Mylo  hyoii 

Hyoid  bone' 


XKfW)phai^us 


Sagitul  iwtiian  of  hratt  nf  ytiuiiKxluU,  ihrrc-luunhii  tmlunil  itiae. 

called  "button"  of  infanc)-  —a  collection  which  ^ivcs  resistance  to  the  cheek  and  pre- 
vents it  from  beinjj  flatteneil  by  atmospheric  pressure  during  nursing.  The  mucous 
membrane  is  reflected  from  the  cheeks  onto  the  jaws,  where  it  covers  the  gums. 
This  line  of  reflection  at  the  middle  of  the  lower  jaw  is  7  or  S  mm.  from  the  alveolar 


m. 


m 


I540 


HUMAN  ANATOMY. 


border  and  about  twice  as  far  from  it  in  the  upper.  In  botfj  jaws,  but  especially  in 
tlie  lower,  the  line  approaches  the  teeth  as  it  |>asses  tiackward.  There  is  a  distinct 
fold  or  frenum  of  mucous  membrane  passing;  from  the  anterior  nasu]  spine  to  the 
middle  of  the  upper  lip.  The  free  ed^e  is  often  irregular,  and  may  have  a  nodular 
enlargement.  A  much  smaller  fold  is  often  found  on  each  side  in  the  region  of 
the  bicuspids.  A  median  fold  to  the  lower  li|>  is  small  and  inconstant.  Extr:rnally 
the  lips  present  a  red  region  of  modified  mucous  membrane,  intermediate  between 
the  skin  of  the  face  and  the  mucous  membrane  of  the  mouth.  A  sagittal  section 
through  either  lip  shows  these  three  parts.  In  the  new-bt)rn  the  intermediate '  part 
is  subdivided  into  two,  of  which  the  inner — rather  the  broader — more  closely  resem- 
bles true  mucous  membrane  than  the  latter.  After  death  in  the  young  child  it 
assumes  a  brownish  color,  which  has  been  mistaken  for  the  effect  of  acid.  In  the 
adult  these  two  subdivisions  lose  their  distinctness.     The  lower  lip  is  the  larger  and 


Fto.  iaQ4. 


-^ — Nasal  M'ptum 

MaxillaT\ 
ainus 


" — Mucous  mfm- 
brati«*iiMT 
iliK  Jkilatt* 


Mylo-hyoid 
Plat  ysilKi 

Antriior  belly  of  ili^itriC' 

GcniO'hyoiU'^ 

(^•■nio-KloflBUS 

Frortal  section.  showinK  oral  cavity  and  lower  part  of  nasal  Iosmf  ;  plane  of  section 

xypMia.    Three-fourths  natural  sise. 


— ■ — Submental  artery 


throuKh  anterior  end  of 


fuller,  showing  more  red  except  towards  the  angles  of  tli(  mouth,  where  it  disap- 
pears. Its  lower  border  is  slightly  indented  in  the  middh  The  upper  lip  shows  a 
more  marked  indentation  below  a  little  gutter,  the  philtrmn.  running  down  from  the 
nasal  septum.  A  slight  median  prominence  of  the  lower  «lge  of  the  upper  lip  is  the 
tubercle,  which  interrupts  the  straightness  of  the  cleft  when  the  lips  are  closed,  making 
the  line  resemble  a  Cupid's  bow. 

The  muscles  of  the  lips  an-  a  complicated  interlacement  from  many  sources. 
The  orbicularis  oris,  formerly  supposed  to  form  a  sphincter,  has  no  separate  exist- 
ence. The  general  plan  is  as  follows.  The  upper  fibres  of  the  buccinator  enter  the 
lower  lip  and  pass  out  at  the  opjx)sitc  ringle  to  ascend  into  the  upper  part  of  the  other 
buccinator.  Those  of  the  lower  part  traverse  the  upper  lip  in  a  similar  manner. 
The  layer  formed  by  the  buccinator  lies  under  the  mucous  membrane  near  the  border 
of  the  lips,  and  bends  forward  so  that  its  cdjjc  is  nearest  the  skin  at  about  its  junction 

'  Gttu  Nc--tattcr  :  Ucbcr  den  Lippcnsaum,  etc.,  I::a;:g.  :>is:>crt.,  Munich,  1894. 


THE  LIPS.  CHEEKS.  AND  VESTIBULE. 


154' 


with  the  free  red  surface.     In  the  lower  lip  the  qmadraiHs  (depressor  labii  inferioris) 
runs  upward  under  the  skin  to  breiik  up  into  fibres  ending  in  the  lips.     The  tri- 

angularit  (de]>rf«M)r  an^uli  oris)  passes 


Pio.  tigs. 


rhiiti 


Tabcfcic 


Labial  ration,  from  life,  reduced  one-fiftli. 


nt  the  angle  vk  the  mouth  into  the  up|ier 
lip  and  ends  as  a  series  of  sciKtrate  fibres 
inserted  into  the  mucous  membrane,  many 
of  them  crossing;  the  middle  line.  This 
muscle,  before  it  breaks  up,  is  in  the  same 
plane  as  the  buccinator,  but  farther  from 
the  edge  of  the  lips.  Some  (^rman  au- 
thors, by  grouping  together  the  various 
muscles  of  the  upper  lip,  have  made  a 
utperior  quadratus  and  triangularis 
which  are  dis|>osed  in  a  similar  manner 
to  the  lower  ones.  Besides  these  there 
.ire  two  muscles,  the  zygomaticus,  de- 
scending, and  the  risorius,  ascending, 
which  meet  at  the  oral  angles  and  end 
there  in  the  skin  or  mucous  membrane, 
or  in  both.  There  are  also  numerous 
fibres,  seen  only  with  the  microscope  in 
sagittal  sections,  passing  from  the  skin 
to  the  mucous  membrane  ;  these  consti- 
tute the  rectus.* 


Labial  (landi 


Fibres  of  orbicularis, 
oris 


Ttansitiuii  into  true, 
mucous  membrane 


Modified  mucouii  membrane 


InteKumcnt 


.Sebaceous  gland 


Tratisition  into 
modified  skin 


Sagittal  section  of  lip  of  young  child.     X  30. 

The  mucous  membrane,   which   is  siiii«jth,  is  so  closely  attachfd  to  the 
muscles  that  it  follows  the  movements  of  the  latter.      Mucotis  glands  are  lodged  in  its 
'  Aeby  :  Archiv  f.  mikro.  Anat.,  Bd.  xvi.,  1879. 


'iHr 


"11 


k^ 


1542 


mmmm 


HUMAN  ANATOMY. 


deeper  parts  and  in  the  scanty  submucous  tissue.  They  are  named  iadia/,  bticcal, 
and  molar,  according  to  their  situation.  The  labial  glands  are  gathered  into  a  series 
of  groups  near  the  inner  border  of  the  lips,  the  buccal  glands  are  smaller  and  scattered, 
and  the  molar  glands  are  well-defined  groups  opposite  the  molar  teeth.  The  duct 
of  the  parotid  gland  {q.v.)  opens  into  the  vestibule,  the  space  between  the  lips  and 
cheeks  externally,  and  the  teeth  and  alveolar  processes  internally.  Separating  the 
vestibular  space  from  that  of  the  mouth  proper  behind  the  alveolar  processes  is  a 
prominent  fold  of  mucous  membrane  over  the  pterygo-maxillary  ligament.  This  fold 
appears  at  the  inner  side  of  the  last  upper  molar  and  runs  downward  and  outward  to 
that  of  the  lower.  The  space  behind  the  teeth  when  the  mouth  is  closed  is  small, 
but  a  tube  some  5  mm.  in  diameter  can  be  passed  through  it. 

Vessels.^The  arteries  supplying  the  lips,  which  are  very  vascular,  are  chiefly 
the  coronary  branches  of  the  facial  arteries,  each  of  which  forms  an  arch  meeting  ite 
fellow  in  each  lip.  The  vessel  lies  between  the  muscles  and  the  glands  of  the  mucous 
membrane,  n».arly  opposite  the  line  of  junction  of  the  latter  and  the  intermediate  por- 
tion. The  pulsation  is  easily  felt  through  the  mucous  membrane.  The  veins,  less 
regular,  lie  on  the  outer  side  of  the  muscles.  The  lymphatics  empty  into  the  glands 
at  the  angle  of  the  jaw,  excepting  those  near  the  median  line  of  the  lower  lip,  which 
run  into  the  suprahyoid  glands. 

Nerves. — The  mucous  membrane  of  the  cheek  is  supplied  by  the  buccal  branch 
of  the  inferior  maxillary  division  of  the  fifth  cranial  nerve,  the  lips  by  the  terminal 
branches  of  its  second  and  third  divisions. 


THE  TEETH. 

In  form  the  teeth  present  three  parts, — the  body  or  crown,  coated  with  enamel  ;  a 
somewhat  constricted  part,  the  neck,  covered  by  the  gums  ;  and  the  root  or  fang, 
which,  covered  by  the  cementum,  is  fixed  in  the  socket.  The  greater  part  of  the 
tooth  is  composed  of  the  dentine  and  surrounds  the  pulp-cavity,  to  which  minute 
openings  in  the  root  or  roots  transmit  vessels  and  nerves. 

The  shape  of  the  crowns  is  the  basis  of  classification.  Thus,  in  the  front  teeth 
the  crown  is  flattened  so  as  to  have  a  chisel-like  shape,  adapted  to  cutting,  hence 
these  are  termed  incisors  ;  the  canine  teeth  have  the  crown  forming  a  single  point  or 
cusp  ;  the  bicuspids  have  two,  and  the  multicuspids,  or  molars,  several  cusps.  The 
crowns  of  all  the  teeth  may  be  considered  as  modifications  of  a  simple  cone,  or  as 
combinations  of  several  cones.' 

In  man  the  teeth  come  in  two  sets,  the  temporary  or  milk  and  the  permanent 
teeth  ;  the  total  number  of  the  former  is  twenty,  that  of  the  latter  thirty-two.  The 
number  and  arrangement  of  the  teeth  of  any  animal  is  expressed  in  its  dental  formula  ; 
this  for  man,  for  the  left  half  of  the  mouth,  may  be  written  as  follows  : 

Temporary  Teeth  :  i*  f  '  »fi '  ^^  ?  X  a  =  aoV 


Permanent  Teeth  :  i?  f  '  W'  m^  ( 
21      »      3  V 


8 


It  will  thus  be  seen  that  in  the  milk-teeth  there  are  no  bicuspids  and  one  molar  les« 

Since  the  typical  mammalian  dental  formula  \%  i\  c ^  bi-  m  ■',  it  may  be  assumed 

3143 
that  in  man  three  pairs  have  been  suppressed.     These  suppressed  teeth  are  occasion- 
ally represented  by  supernumerary  ones  ;  from  the  position  of  the  latter  it  is  probable 
that  the  missing  teeth  are  the  second  incisors  and  the  first  and  fourth  bicuspids. 

To  avoid  confusion  in  the  nomenclature  of  the  teeth  from  the  cur\'e  of  the  jaws, 
it  is  customary  to  speak  of  the  labial  and  lingual  surfaces  of  the  incisors  and  canines, 
and  of  the  facial,  or  buccal,  and  //'«^«<i/ surfaces  of  the  bicuspids  and  molars.  The 
sides  against  the  other  teeth  are  often  called  the  median  and  distal,  supposing  the 
teeth  to  be  implanted  in  a  straight  transverse  line.     This  is  not  satisfactory  in  all 

•See  Homolcfi^es,  page  1566. 


THE  TEETH. 


I '^43 


cases.  We  shall  speak  instead  of  the  inner  and  outer  sides  of  the  incisors  and 
canines  and  of  the  anterior  and  posterior  sides  of  the  bicuwpids  and  molars.  If  the 
position  of  the  tooth  in  the  jaw  be  remembered,  no  confusion  is  jxMisible. 

The  Incisors. — The  crowns  are  characterized  by  slightly  convex  quadrilateral 
labial  surfaces,  rather  broader  than  the  lingual  ones,  and  ending  in  straight  cutting 
edges,  slightly  concave  lingual  surfaces  slanting  forward  and  bevelled  at  the  edge, 
triangular  lateral  surfaces,  and  single  roots.  The  labial  and  lingual  surfaces  of  the 
crowns  are  bounded  at  the  root  by  curved  lines,  the  convexity  being  towards  the 
gums.     At  the  sides  these  borders  are  continued  as  straight  lines  towards  the  free 

Fig.  1397. 


Partly  developed  fangs  of  laM  molar. 


Crown  of  last  molar. 


PennanenI  teeth,  ahowinK  thair  forma  and  relationa ;  outer  surface  o(  jawL  partly  removed. 

partially  formed. 


Last  molara  arc  only 


edge,  and  meet  at  an  acute  angle.  The  enamel  is  continued  farther  on  the  lingual 
surface,  especially  in  the  lateral  incisors  of  both  jaws.  The  cutting  edge  shows  three 
small  scallops  on  its  first  appearance,  but  they  speedily  wear  away  ( Fig.  1298). 

The  superior  median  incisors  are  much  the  largest.  The  labial  surface  of 
the  crown  is  nearly  square.  The  inner  half  of  this  surface  is  more  strongly  convex 
than  the  lateral.  Traces  of  three  swellings  are  often  found  on  the  labial  sitle  of  the 
lower  half  of  the  crown  extending  to  the  three  primitive  scallops  on  the  edge.  The 
free  edge  meets  the  internal  border  at  nearly  a  right  an^le,  but  the  outer  angle  is 
rounded.  The  lingual  surface,  narrower  than  the  labial,  is  a  little  concave.  Some- 
times the  edges  are  raised  so  as  to  leave  a  distinct  V-shaped  depression,  in  the 
middle  of  which  runs  a  vertical  ridge,  the  cingvlvm,  which  ends  below  in  a  tubercle. 


1544 


HUMAN  ANATOMY. 


Often  the  cingulum  of  the  incisors  is  represented  merely  by  the  tubercle.  There  are 
all  kinds  of  intermediate  stages  between  this  and  a  nearly  plane  surfoce.  Sometimes 
the  tubercle  is  triple.  The  fang  is  nearly  conical,  and  usually  has  an  outward  sknt. 
The  superior  lateral  incisors  are  more  cusp-shaped,  the  angles,  especially  the  outer, 
tending  to  be  rounded.  The  lingual  surface  is  less  plane  than  in  the  median  inciso-^ 
and  the  cmgulum  larger.  Sometimes  it  is  ahnost  a  distinct  cusp.  The  fang  is  also 
conical,  with  an  outward  inclination. 

The  inferior  incisors  are  smaller  than  the  superior,  and  the  median  ones  the 
smallest  of  all.  The  crowns  broaden  from  the  neck  to  the  e<%e.  This  feature  is 
more  marked  in  the  lower  races,  and  still  more  in  apes.  The  labial  surface  is  more 
nearly  plane  than  in  the  upper  op  s;  the  lingual  surface  is  more  even.  The 
cingulum  IS  small,  often  not  very  e\  lent  The  angles  of  the  free  edge  are  sharper 
than  those  of  the  upper  jaw,  exc<  ang  the  outer  one  of  the  lateral  tooth,  which  is 
generally  rounded.  The  fangs  a  j  compressed  from  side  to  side  a'  d  their  tips  turn 
a  little  away  from  the  median  line.     This  is  particularly  true  of    ne  lateral  one  but 


Fio.  1398. 


Unworn  antfaces  of  upper 
»nd  lower  uermanent  inciwr 
teeth,  lingual  aipect.    X  2. 


Median  inciaor  teeth 
of  left  aide,  labial  (A) 
and  lateral  (B)  aapecta. 


Fio.  1300. 

A  B 

n 

Temporary  incisor 
teeth  of  left  side.  A, 
median;  B,  lateral  in- 
cisors.   ( Leidv.) 


IS  a  constant  feature  of  neither.     The  sides  of  the  fangs  are  often  grooved.     The 
external  groove  is  the  deeper,  and  when  only  one  is  present  it  is  on  that  side. 

Ttxe  pulp-cavity  is  relatively  large  in  the  superior  medfan  incisors,  in  which  it 
presents  three  expansions  towards  the  free  edge.  It  is  smaller  in  the  others,  and  has 
usually  but  two  distinct  diverticula.  The  canal  of  the  lower  teeth,  especially  when 
the  roots  are  deeply  grooved,  often  divides  below  the  pulp-cavity  into  an  anterior 
and  a  posterior  branch,  which  usually  reunite  before  reaching  the  tip  of  the  fang.' 

The  upper  inci.sors  occupy  in  all  more  space  than  the  lower,  which  is  due  chiefly 
to  the  great  size  of  the  upper  median  ones.  In  the  lower  jaw  the  median  incisors 
are  the  smaller,  but  there  is  no  great  difference  between  them  and  the  kterals.  The 
supenor  laterals  are  but  slightly  larger  than  those  below  them. 

The  temporary  incisors  differ  only  slighdy,  save  in  size,  from  the  permanent 
ones.  The  edges,  however,  are  originally  straight,  except  those  of  the  inferior  median 
ones,  which  show  the  irregularities.' 

The  Canines.— These,  called  bv  the  Geimans  the  "  corner  teeth"  as  marking 
the  point  where  the  alveolar  arch  changes  direction  most  suddenly,  are  characterized 
by  a  crown  with  a  single  cusp,  a  long  conical  root  somewhat  compressed  laterally  and 
marked  by  a  groove  on  each  side.     The  crown,  convex  on  the  labial  side,  expands 

'  Muhlreiter :  Anatomie  des  Menschllchen  Gebisses,  Leipzig  1891 
Wien  18^,  •     ■  ^"''*°™*  '^  Mundhohle.  mit  besondere  BeriicksichtigunK  der  Uhnt, 


THE  TEETH. 


1545 


Fio. 


Caniiw  iceth  of  left  aide, 
kbial  (A)  and  lateral  (A)  as- 
pects.    C ,  temporary  canines. 


from  the  root  and  suggests  that  of  an  incisor  with  the  angles  taken  off.  The  lingual 
side  of  the  crown  of  the  upper  tooth  tends  to  be  convex,  often  having  a  ridge  running 
down  to  the  small  tubercle  at  the  base.  In  the  lower  tooth  this  side  is  plane  or  con- 
cave, with  a  distinct  tubercle,  which  exceptionally  is  enlarged 
so  as  to  hint  at  a  secondary  cusp.  The  sides  of  the  crown 
are  triangular.  The  borders  of  the  enamel  are  convex  to 
the  gum  on  the  labial  side,  less  so  on  the  lingual,  and  slightly 
concave  laterally.  The/ang  of  the  upper  tooth  is  the  longer 
and  the  less  compressed  ;  it  very  rarely  ends  in  a  bifurcation, 
but  this  is  less  uncommon  in  the  lower.  The  direction  of  the 
end  of  the  fong  is  uncertain.  The  whole  tooth  is  brotidcr 
on  the  labial  than  on  the  lingual  side.  The  pulp-cavity  is 
most  marked  in  antero-posterior  sections,  which  show  an  en- 
largement of  its  continuation  at  the  Ix-ginning  of  the  root, 
just  beyond  the  neck. 

The  milk  canines  are  much  like  the  second  ones, 
only  smaller.  The  labial  surface  of  the  upper  tends  to  divide 
into  an  outer  and  an  inner  facet.  The  root  is  approximately 
triangular  on  section,  with  rounded  edges. 

The  Bicuspids  or  Premolars. — These  teeth,  of  which 
the  second  is  the  larger  in  both  jaws,  are  characterized  by 
crowns  with  two  cusps,  one  on  the  buccal  and  one  on  the 
lingual  side.  The  upper  ones,  being  very  much  the  more 
typical,  will  be  used  for  the  general  description.  Both  the 
labial  and  the  lingual  aspects  of  the  crowns  are  convex  ;  they 
exfiand  laterally  from  the  neck,  and  each  ends  in  a  pointed 
cusp  of  which  the  anterior  border  is  the  shorter.  This  is 
used  in  determining  the  side,  but  we  agree  with  Testut  that 
the  guide  is  often  useless.  The  buccal  cusp  is  the  larger.  The  cus|>s  are  separated 
by  a  furrow  from  which  small  ramifications  often  run  onto  the  buccal  one.  The  lin- 
gual cusp  has  an  unbroken  surface.  The  buccal  cu.sp  of  the  first  bicuspid  is  more 
prominent  than  the  lingual,  but  in  the  second  they  reach  the  same  plane.  The  bor- 
der of  the  enamel  is  convex  towards  the  root  on  both  the  buccal  and  lingual  aspects, 
the  ends  of  these  curves  meeting  on  the  other  sides.  The  fang  is  compressed  with 
a  groove  on  the  sides  next  its  neighbors.  That  of  the  second  is 
often  bifid  just  at  the  tip,  but  that  of  the  first  is  very  often,  per- 
haps usually,  divided  into  two  throughout,  having  a  buccal  and 
a  lingual  root.  Sometimes  the  former  is  subdivided,  so  that  it 
has  three  like  a  molar.  The  root  has  in  general  a  backward 
slant. 

The  lower  bicuspids  have  smaller  grinding  surfaces  on 
the  crowns  than  the  upper,  but  the  roots  are  longer,  and  the 
crowns,  .seen  from  the  side,  are  at  least  as  large.  The  first  has 
a  well-developed  buccal  cusp,  curving  in  from  the  buccal  surface, 
and  a  very  small  lingual  one  connected  to  the  former  by  a  ridge 
interrupting  the  fissure  between  them,  which  gives  the  tooth 
something  of  the  effect  of  a  small  canine.  The  second,  like  that 
of  the  upper  jaw,  has  the  two  cusps  in  one  plane  ;  the  lingual 
one  is  sometimes  double,  and  the  plane  is  often  obscure.  The 
flattened  fang  is  but  faintly  grooved,  if  at  all,  and  is  rirely 
bifid. 

Th^  Pulp-cavity  vX  the  bicuspids  ends  in  an  expansion  below 
each  cusp,  that  under  the  buccal  being  the  larger.  In  the  upper 
teeth  the  cavity  is  much  compressed  from  side  to  side  in  the 
root.  In  the  first  upper  bicuspid  there  are  usually  two  pro- 
longations to  the  point  of  the  fang,  even  when  the  r  jot  is  not 
split.  In  the  second  the  cavity  generally  agrees  with  the  conformation  of  the  r(M>t. 
In  the  lower  teeth  the  cavity  is  less  compressed  and  is  tolerably  roomy  as  it  enters 
the  root.     It  is  usually  single,  but  may  split. 


First  premolar  teeth 
left   side,   labial    l.-)) 

and  lateral  \H\  asiieits. 

(AWrfv.) 


of 


1546 


HUMAN  ANATOMY. 


The  Molars. — ^These  teeth — three  on  each  side— are  distineuished  by  the  large 
crown,  into  which  the  neck  expands,  the  number  of  cusps  on  tne  surface,  and  the 
greater  subdivision  of  the  root.  Those  of  the  lower  jaw  are  the  larger  ;  and  in  both 
jaw 3  the  first  is  the  largest  and  the  last  (called  from  its  late  appearance  the  wisdom- 
tooth)  the  smallest.  The  crowns  are  convex  on  both  the  buccal  and  lingual  sides, 
but  nearly  plane  on  the  others.  The  enamel  ends  in  a  nearly  straight  line  all  the  way 
round.  The  grinding  surfaces  are  four-sided  ;  those  of  the  upper  are  somewhat  dia- 
mond-shaped, the  buccal  anterior  angle  being  rather  in  front  ;  those  of  the  lower  are 
learly  parallelograms,  the  long  diameter  being  antero-posterior.  Typical  upper 
molars  have  four  cusp>s  at  the  angles  ;  typical  lower  ones  have  an  additional  cusp  at 
the  posterior  border  ;  but  in  the  upper  jaw  the  first  is  the  only  one  that  can  be  called 
typical. 

In  the  upper  molars  the  largest  cusp  is  the  anterior  lingual,  which  is  connected 
by  a  ridge  (the  cingulum)  to  the  posterior  buccal.  The  posterior  lingual  cusp  is  the 
smallest.  A  minute  rudimentary  cusp  is  found  on  the  lingual  surface  of  the  anterior 
lingual  cusp,  usually  too  small  to  reach  the  grinding  surface,  and  often  hard  to  recog- 
nize. Not  counting  this,  the  first  upper  molar  has  four  cusps  ii  more  than  90 
per  cent.  Owing  to  the  cingulum,  the  grooves  on  the  grinding  surface  are  best 
described  as  two  oblique  ones,  the  first  from  the  anterior  border  to  the  middle  of  the 


Fio.  J  303. 


Firat 


Fig.  1304. 

Upper  molmrs 


Til 


Another  first 
Lower  molars 


Sccood 


^^iMrrr^i 


First 


.*>*^j 


Another  first 


Second 


Second  molar  teeth  of  left 
side,  labial  M)  ftod  laterml 
(A)  aspects.     (Uidy.) 


Triturating  surfaces  of  molar  teeth  of  right 
side.  The  upper  margin  of  the  figures  corresponds 
to  the  labial  surface.    ( Lridy. ) 


buccal,  the  second  from  the  lingual  border  to  the  middle  of  the  buccal.  They  are 
deepest  at  the  middle.  They  appear  on  the  buccal  and  lingual  sides,  deeper  on  the 
former  but  rarely  reach  the  gum.  They  may  end  in  a  pit,  a  favorite  seat  of  caries 
(Tomes).  The  crown  of  the  second  upper  molar  presents  three  chief  forms  (Miihl- 
reiter).  It  may  have  four  cusps  and  differ  but  slightly  from  the  first  molar.  The 
lingual  surface  is  relatively  narrower  and  the  posterior  lingual  cusp  smaller.  In  the 
second  form  the  last-mentioned  cusp  is  wanting.  The  cingulum  persists  and  the 
g^rinding  surface  is  approximately  triangular.  The  third  form  is  compressed  from 
side  to  side  into  a  very  narrow  diamond,  with  the  anterior  buccal  cusp  in  front  and 
the  posterior  lingual  behind.  Three  and  four  cusps  are  about  equally  common  in  this 
tooth  in  Caucasians,  but  the  lower  races  have  more  often  four.  The  crown  of  the 
upper  wisdom-tooth  presents  many  remarkable  variations.  The  fKJSterior  lingual 
cusp  is  wanting  in  about  two-thirds  of  the  cases.  The  crown  may  be  strongly  com- 
presse  .  as  has  been  described  for  the  second  molar,  but  with  greater  variation.  In 
size  th    wisdom-tooth  may  be  very  large  or  very  small. 

The  crowns  of  the  lower  molars  are  divided  by  a  crucial  fissure,  the  main  line 
running  antero-posterioriy.  The  hind  part  of  this  splits  so  as  to  enclose  the  fifth 
cusp,  which  is  ntrar  or  actually  at  the  buccal  side.  The  cfTcct  of  this  is  to  form  a 
cavity  at  the  crossing  of  the  lines  in  the  middle  of  the  crown.    The  lines  on  the  sides 


mmmm 


THE  TEETH. 


1547 


of  the  crowns  are  leas  deep  than  in  the  upper  jaw.  Sometimes  the  fifth  cusp  is  wanting, 
in  which  case  the  posterior  part  of  the  furrow  does  not  divide  and  the  arrangement  is 
remarkably  symmetrical.  Very  rarely  the  first  molar  has  a  sixth  cusp  on  the  lingual 
side.  The  first  molar  has  five  cusps  m  more  than  90  per  cent. ;  the  second  four  only 
in  more  than  80  per  cent. ;  the  third  four  rather  more  often  than  five.  The  buccal 
cusfis  of  the  lower  molars  are  worn  down  earlier  than  the  lingual  ones. 

The  following;  tables  from  the  independent  researches  of  Rose '  and  of  Zuckerkandl  show 
the  percentage  of  frequency  of  different  groupings  of  cusps.  Although  there  is  some  discrepancy 
in  the  percentages,  both  agree  as  to  the  most  and  least  common  arranKement  in  both  jaws. 
These  statistics,  like  those  of  the  separate  teeth,  anpty  to  Europeans.  (It  is  to  l)e  remembered 
that  a  certain  percentage  of  teeth  cannot  be  includiea.) 


Urraii  Jaw. 
Molara. 
•     «     i 

Percent. 
Rom.        Zttck. 

LoWBH  Jaw. 
Molan. 

'      '     i 

Per  Cent. 
R6m.        Zoek 

Cusps.   . 
Cusps  .   . 
Cusps  .   . 

■    -4     4    4 

•  -4    4    3 

•  -4     3    3 

19.9           9.6 
28.9         28.7 
37-9        601 

Cusps  .   . 
Cusps  .   . 
Cusps  .   . 

•  5    5    5 
•545 

•  5    4    4 

19.8         11. 5 
304         305 

404         500 

Fig. 


'30S- 


Ths/angs  of  the  first  and  second  upper  molars  are  two  buccal  and  one  lingual, 
which  latter  is  much  the  largest.  It  is  often,  especially  in  the  first  molar,  grooved 
on  the  lingual  side.  It  is  conical  and  strongly  divergent.  It  often  shows  a  tendency 
to  subdivision,  which  may  actually  occur,  although  rarely.  The  two  buccal  ones  are 
compressed  antero-posteriorly  and  nearly  vertical.  The  front  one  is  the  broader,  and  is 
grooved  before  and  behind.  This  is  often  tl.e  case  with  the  other.  The  roots  of  the 
upper  wisdom-tooth  are  smaller  ;  the  lingual  is  less  divergent,  and  may  be  connected 
by  a  plate  with  one  of  the  buccal  ones.  AH  may  be  fused  more  or  less  completely  into 
one.  The  roots  of  the  inferior  molars  are  two  :  an  anterior  and  a  (x>sterior,  of  which 
the  former  is  rather  the  larger,  both  compressed  from  before 
backward  and,  especially  the  first,  deeply  grooved,  suggesting 
the  fusion  of  two.  Sometimes,  again  especially  in  the  first, 
each  root  is  bifid.  Those  of  the  wisdom-tooth  are  usually 
nearer  together,  and  are  frequently  fused  into  a  common  coni- 
cal root.  A(>art  from  their  position  in  the  jaws,  the  roots  of 
the  molars,  excepting  the  upper  wisdom-tooth,  have  a  back- 
ward slant  of  varying  degree.  Their  twbts  and  curves  are 
ren^arkably  uncertain.  Sometimes  they  converge  and  some- 
times diverge  unduly,  hooking  in  either  case  under  bone,  so 
as  to  make  extraction  difficult  or  impossible.  The  pu/p- 
cavify  of  the  molars  is  large,  especially  at  the  level  of  the 
neck.  In  the  upper  teeth  it  is  distincdy  wider  transversely 
than  from  before  backward.  It  has  as  many  prolongations 
towards  the  surface  as  there  are  cusps.  There  is  a  canal  in 
each  root  of  the  upper  teeth.  Those  in  the  buccal  fangs  are 
compressed,  that  in  the  lingual  cylindrical.  The  anterior 
fong  of  the  lower  molars  has  two  canals  which  develop  from 
a  single  one.     The  posterior  fang  has  but  one. 

The  milk  molars  are  hi'o  m  number.  Like  the  perma- 
nent ones,  the  lower  are  the  larger ;  but,  unlike  them,  the 
second  tooth  is  larger  than  the  first  in  both  jaws.  The  crown 
of  both  first  molars  presents  a  prominence  on  the  buccal  sur- 
face near  the  root.     The  crown  of  the  first  upper  molar  is 

rather  su^estive  of  a  bicuspid,  although  there  are  two  buccal  cusps  and  one  lingual. 
The  first  mferior  molar  is  relatively  narrow  and  long  from  before  backward.  The 
length  of  the  buccal  side  is  greater  than  that  of  the  second  permanent  one.  The 
second  molars  resemble  very  closly  the  first  permanent  ones.  The  upper  has  four 
cusps  and  a  cingulum,  the  lower  five  cusps.  The  hollow  in  the  crown  of  the  tem- 
porary molars  is  relatively  deeper  than  that  of  the  permanent  ones,  but  smaller  and 
more  divergent.     They  straddle  the  crowns  of  the  developing  bicuspids. 

*  Anatom.  Anzeiger,  Bd.  vii.,  1892. 


WW 

Tempormry  molar  lerth 
{A,  first;  B,  second)  of  left 
side.  TrtturalitiK  surfaces  of 
crowns  also  shown.    {IMdv.) 


iH*^  1 1 


le' 


'548 


HUMAN  ANATOMY. 


TOOTH-STRUCTURE. 

In  principle,  and  among  the  lower  vertebrates,  in  fact,  as  well,  teeth  may  be 
regarded  as  hardened  papillae  of  the  oral  mucous  membrane  ;  they  consist,  therefore, 
of  two  chief  parts, — the  connective-tissue  core  and  the  epithelial  capping.  Of  the 
three  constituents  present  in  typical  mammalian  teeth,  the  enamel  is  the  derivative  of 
the  ectoblastic  epithelium,  the  dentine,  with  the  pulp,  and  the  cementum  being  con- 
tributions of  the  embryonal  connective  tissue. 

The  Enamel. — This,  the  hardest  tissue  of  the  body,  covers  the  crown,  being 
thickest  on  the  cutting  edge  or  grinding  surface  of  the  tooth.    It  gradually  thins  away 


Fig.  1306. 


iripcsof  Ret2iui  (longitudinal) 


Contour  lii 

SchrcKcr's  lines 

Prism-stripes  oJ  Schreger  (light  and 
^.___^_,    ,^^„_^_  dark) 

.Gum 

Pulp-tiuue 

Dentine 


Cementum 
Alveolar  periosteum 

Osseous  tissue  of  jaw 


Root-canal 


'  Sagittal  section  of  canine  tootti  m  sttm.    Semi-diagrammatic. 

towards  the  neck,  around  which  its  terminal  border  appears  as  a  more  or  less  distinct 
and  often  serrated  edge.  The  external  surface  of  the  enamel,  especially  in  young 
teeth,  often  e.xhibits  a  line  striation  composed  of  horizontally  disposed  lines.  Under 
a  hand-glass  these  lines  are  seen  to  be  minute  elevations,  the  enamel-ridges,  which 
encircle  the  crown.  The  remarkable  hardness  of  this  tissue  is  due  to  the  large  amount 
(97  per  cent. )  of  earthy  material  and  the  small  proportion  of  organic  matter,  which 
latter  in  adult  enamel  averages  only  about  3  per  cent. ;  in  infantile  enamel  the  amount 
of  animal  material  is  from  five  to  six  times  greater  (Hoppe-Seyler). 


STRUCTURE  01    THE  TEETH. 


>549 


Fio. 


1307. 


The  enamel — the  product  of  epithelial  cells,  the  amelobiasis — consists  of  an  a(;gre- 
eation  of  five-  or  six-sided  columnar  elements,  the  enamel-prisms,  which  measure 
from  .0035-.0045  mm.  in  diameter  and  from  3-5  mm.  in  len^h.  Their  genera! 
disposition  is  at  right  angles  to  the  surface  of  the  dentine  u|X)n  which  they  rest,  on 
the  one  hand,  and  to  the  exterior  of  the  crown  on  the 
other.  They  usually  extend  the  entire  thickness  of  the 
enamel,  and  are  of  slightly  larger  diameter  at  the  surface 
of  the  tooth  than  next  the  dentine,  in  this  manner  com- 
pensating for  the  increase  in  the  external  circumference 
of  the  crown.  The  assumption  that  additional  prisms 
are  intercalated  at  the  periphery  is  not  supported  by  the 
manner  of  the  production  of  the  enamel-columns.  The 
latter  run  for  a  short  distance  almost  at  right  angles  to 
the  surface  of  the  dentine,  then  bend  laterally  for  a 
considerable  {lart  of  their  course,  but  assume  a  vertical 
disposition  on  approaching  the  external  surface.  In 
addition  -.o  these  general  curves,  the  ranges  of  enamel- 
columns  possess  a  spiral  arrangement,  in  consequence 
of  wh'"'  he  t  irallelism  of  the  prisms,  as  seen  in  ground- 
irbed  and  their  bundles  are  apparendy 


sect' 
intPi 


Grouiid-sectiofi  o<  enamel,  showing 
ranset  of  ciunwl-prl«iia.    x  yio. 


;■'    itely  transverse  sections  enamel  pre- 
sen'  which  the  hexagonal  areas  represent 

the  ti  ne  ii.dividual  prisms.     Critically  examined,  the  areas  consist  of  a  darker 

central  portion  surrounded  by  a  narrow  lighter  peripheral  zone.  The  interpreta- 
tion of  the  latter  has  been  various,  many  observers  regarding  such  lines  as  cement- 
substance  holding  together  the  prisms.  According  to  Walkhof!,'  however,  what  is 
usually  regarded  as  cement-substance  is  a  cortical,  apparently  homogeneous  layer  of 
less  thoroughly  calcified  material  which  encloses  the  denser  central  portion  of  the 
prism  and  acts  as  a  cushion,  thereby  reducing  the  effect  of  pressure.  After  the 
decalcifying  action  of  acids,  the  prisms  may  be  ouUined  by  stains  which  color  the 
very  meagre  amount  of  true  cement-substance  which  exists  between  the  enamel- 
columns  and  appears  as  delicate  lines  defining  the  prisms. 

Under  favorable  conditions,  especially,  but  not  only,  after  the  action  of  acids,  the 
enamel-prisms  exhibit  alternate  light  and  dark  transverse  markings.  The  true  rela- 
tions of  these  bands  are  to  be  appreciated  only  by  accurate  focusing  in  thin  sections 
passing  exactly  parallel  to  the  axes  of  the  prisms  ;  otherwise  the  obliquity  of  section 
produces  the  optical  distortions  often  represented  in  the  assumed  wavy  contour  of  the 
enamel-rods.  The  varicose  appearances  commonly  seen  def)end  upon  the  beaded 
form  and  consequently  scalloped  border  of  the  denser  central  portion  of  thf  prisms, 
which  give  a  corresponding  arrangement  to  the  lighter  cortical  substance  which  fills 
the  minute  inequalities  of  that  portion  ;  the  true  oudine  of  the  enamel-prism,  how- 
ever, is  smooth  and  straight,  and  not  varicose,  as  the  optical  impressions  lead  one 
to  believe  and  as  usually  pictured.  According  to  Williams,  the  apparent  varicosities 
depend  upon  the  spherical  form  of  the  enamel-globules  of  which  the  prisms  are  built  up. 

When  an  axial  longitudinal  section  of  a  tooth  is  examined  by  reflected  light,  the 
enamel  displays  a  series  of  alternate  dark  and  light  bands,— the /mw-j/r/]^«  ^ 
Schreger.  These  markings  extend  generally  vertical  to  the  surface  of  t^^e  enamel, 
and  depend  upon  the  relation  of  the  ranges  of  the  enamel-prisms  to  the  xes  of  the 
light-rays.  Rotation  of  the  illuminating  pencil  through  180°  effects  the  change  of 
the  dark  stripes  to  ligf"*  ones  and  7nce  versa.  Each  stripe  includes  from  ten  to  twenty 
enamel-prisms,  and  ii.  .nvisible  by  transmitted  light. 

In  addition  to  the  foregoing  markings,  the  enamel  often  presents,  in  radial  longi- 
tudinal sections,  brownish  pandlel  lines,  the  stripes  of  Retsius,  which  run  in  the 
general  direction  of  the  contour  of  the  tooth,  but  at  an  angle  of  from  1 5°  to  30°  with 
the  free  surface.  Seen  in  sections  cut  at  right  angles  to  the  tooth-axis,  these  stripes 
appear  as  a  series  of  concentric  lines  encircling  the  crown  |}arallel  to  and  near  the 
surface ;  in  the  middle  and  deeper  parts  of  the  enamel  they  are  less  evident  or  entirely 
I  Normale  Htstologie  mensch.  Zahne,  1901. 


iliPWniipMippippipi! 


'550 


HUMAN  ANATOMY. 


Fig.  1308. 


Umgiludinal  ground  Kct ion  d 
enamel,  treated  with  acid,  showing 
disposition  of  range*  of  enamel-prismt 
(*./')  in  .stripes  of  Schreger.  Left 
thin)  of  figure  shows  alternate  light 
(s)  and  dark  (I'l  bands  as  seen  by  re- 
flected light.    X  aoo.    (£tnrr.) 


absent.  The  interpretation  of  the  stripes  of  Retzius  !s  still  a  Subject  of  di.^pute.  The 
brown  appearance  of  the  stripes  by  transmitted  light  only,  by  reflected  light  appear- 
ing bluish  white,  disproves  the  assumption  that  they  depend  upon  the  presence  uf 
pigment  within  the  enamel.  The  widely  accepted  view  of  Ebner,  that  the  stripes  are 
due  to  air  contained  in  the  interfascicular  clefts,  has  been  modified  by  Walkhofi,  who 

regards  the  markings  as  due  to  local  diminution  in  the 
calcification  of  the  enamel-prisms  during  certain  periods 
in  the  growth  of  the  tissue  when  the  central  as  well  as 
the  cortical  substance  of  a  great  number  of  columns 
fails  to  take  up  sufficient  lime  salts. 

The  enamel-cuticle,  or  membrane  of  Nasmylh, 
forms  a  continuous  investment  of  the  crown  of  the 
newly  erupted  tooth.  In  the  course  of  time  it  dis- 
appears from  the  areas  exposed  to  wear,  but  over  the 
protected  surfaces  it  may  persist  during  life.  The 
membrane  (.009-.0!8  mm.  in  thickness)  is  transparent 
and  remarkably  resistant  to  the  action  of  acids,  less 
so  to  alkalies,  affording  admirable  protection  to  the 
underlying  enamti.  After  separation  from  the  latter 
by  acids  it  appears  structureless,  or  at  most  granular. 
The  inner  surface  of  the  membrane  presents  markings 
and  slight  irregularities  which  correspond  to  the  free 
ends  of  the  subjacent  enamel-prisms. 

The  origin  of  the  enamel-cuticle  has  been  much 
discussed,  and  even  now  is  not  without  some  uncer- 
tainty. It  may  be  regarded  as  established  that  it  rep- 
resents the  remains  of  part  of  the  tissue  once  concerned 
in  the  production  of  the  enamel.  The  latter  is  formed, 
as  more  fully  described  on  page  1561,  through  the 
agency  of  the  epithelial  cells  constituting  the  inner 
layer  of  the  enamel-organ.  With  the  completion  of  their  task  as  enamel  builders, 
these  cells  produce  a  continuous  cut'jular  envelope  which  persists  as  Nasmyth's 
membrane,  the  epithelial  elements  o'  fte  enamel-organ,  so  far  as  they  are  concerned 
in  forming  enamel,  subsequently  u>-generating.  The  enamel-cuticle  is  continuous 
with  the  cortical  substance  of  the  prisms,  with  which  it  agrees  in  opti(^  and  chemical 
properties, — a.  relation  which  confirms  the  identity  of  origin  of  Nasmyth's  membrane 
and  the  enamel-columns. 

The  Dentine. — The  dentine  or  ivory  resembles  bone  both  in  its  genesis  and 
chemical  composition,  being  a  connective  tissue  modified  by  the  impregnation  of  lime- 
salts.  Dentine  exceeds  bone  in  hardness,  containing  a  larger  proportion  (72  per 
cent.)  of  earthy  matter  and  a  smaller  amount  (28  per  cent.)  of  organic  substance. 
When  decalcified  by  acids,  the  reniaining  animal  material  retains  the  previous  form 
of  the  dentine  and  yields  gelatin  on  prolonged  boilitig.  Dentine,  like  bone,  is  formed 
through  the  agency  of  specialized  connective-tissue  cells,  the  odontoblasts,  but  differs 
from  osseous  tissue  in  the  small  number  of  these  cells  which  become  imprisoned  in 
the  intercellular  matrix.  When  this  occurs,  as  it  exceptionally  does  in  normal  human 
dentine  and  more  frequently  in  pathological  conditions  or  in  the  lower  animals,  the 
dentine-cells  correspond  to  the  bone-corpuscles,  both  being  connective-tissue  elements 
lying  within  lymph-spaces  in  the  calcified  intercellular  substance. 

Examined  in  dried  sections  under  low  magnification,  the  dentine  presents  a  radial 
striation  composed  of  fine  dark  lines  which  extend  from  the  pulp-cavity  internally  to 
th»  enamel  or  the  cementum  externally.  These  dark  lines  are  the  dentinal  tubules, 
filled  with  air,  which  are  homologous  with  the  lacunae  and  canaliculi  of  bone,  and 
contain  the  processes  of  the  odontobli...ts.  In  the  crown,  as  seen  in  longitudinal 
sections,  the  course  of  the  dentinal  tubules  is  radial  to  the  pulp-cavity  ;  in  the  root 
their  disposition  is  horizontal  and  almost  parallel.  The  canals,  however,  are  not 
straight,  but  sigmoid,  the  first  convexity  being  directed  towards  the  root,  the  second 
towards  the  crown.  In  addition  to  these  primary  curves,  which  are  especially  marked 
in  the  crown,  the  dentinal  tubules  present  numerous  shorter  secondary  curves  which 


STRUCTURE  OF  THE  TEKTH. 


'55» 


impart  to  the  individual  canaliculi  a  spiral  course.  The  cause  of  the  latter  Kollinann 
refers  to  the  more  rapid  growth  of  the  dentinal  fibres  than  of  the  slowly  forming 
dentinal  matrix.  In  consequence  of  the  correspondence  of  the  cur\aturc  of  the  di-n- 
tinal  tubules,  the  tooth-ivory  exhibits  a  series  of  linear  markings,  Sthreget'  i  /ines, 
which  nm  parallel  to  tht>  inner  surface  of  the  dentine.  These  markings  nnist  not  l)e 
confounded  with  the  contour  lines  of  Owen  (pwge  1552),  also  within  the  dentine,  or 
with  Schreger's  prism-stripes  within  the  enamel  (Fig.  1306). 

The  dentinal  tubules  are  minute  canals,  from  .OD13-.002  mm.  in  diameter,  which 
begin  at  the  pulp-cavity  with  the  largest  lumen  and  extend  to  the  outer  surface  of 
the  dentine,  to  end  beneath  the  enamel  or  cementum.  Each  spirally  coursing  canal 
undergoes  branching  of  two  kinds,  a  dichotomous  division  at  an  acute  angle  in  the 
vicinity  of  the  pulp-cavity,  resulting  in  two  canaliculi  of  equal  diameter,  and  a  lateral 
branching  during  the  outer  third  of  their  course  whereby  numerous  twigs  are  given  of! 
with  a  corresponding  dimi- 
nution in  the  size  of  the  cana-  Fig.  1309. 
liculi ;  the  terminal  tubes, 
often  reduced  in  diameter  to 
mere  lines,  frequently  anas- 
tomose with  one  another  or 
form  loops.  The  dentinal 
tubules  are  occupied  by  the 
delicate  dentinal  fibra,  the 
processes  of  the  odonto- 
blasts, which  in  the  young 
tooth  constitute  a  net-work  of 
protoplastic  threads  through- 
out the  dentine  of  importance 
for  the  nutrition  of  the  tis- 
sue. The  relation  of  the  den- 
tinal tubules  on  the  external 
surface  of  the  dentine  varies 
on  the  crown  and  root.  In 
the  former  situation  the  free 
surface  of  the  dentine  pre- 
sents crescentic  depressions, 
filled  by  the  enamel,  in  which 
the  tubules  appear  as  ab- 
ruptly terminating  or  cut  of!  ; 
on  the  root,  on  the  contrary, 
where  the  dentinal  surface  is 
smooth,  the  tubules  stop  in 
curved  ends  or  loops  beneath 
the  cementum,  only  in  very 
exceptional  cases  communi- 
cating with  the  canaliculi  of 
the  latter. 

The  immediate  wall  of  the  dentinal  tubules  is  formed  by  a  delicate  membrane, 
the  sheath  of  Neumann,  which  in  appropriate  transverse  sections  appears  as  a  con- 
centric ring.  On  softening  the  decalcified  dentine  by  acids  or  alkalies,  the  sheaths 
may  be  isolated,  since  they  resist  the  action  of  the  reagents  which  attack  the  sur- 
rounding intertubular  substance.  The  sheaths  of  Neumann  are  formed  through  the 
agency  and  at  the  expense  of  the  dentinal  fibres,  the  latter  being  smaller  in  old  than 
in  young  dentine.  The  sheaths,  therefore,  may  be  regarded  as  specialized  parts  of 
the  intertubular  matrix,  distinguished  by  less  complete  calcification  and  greater 
density. 

The  intertubular  ground-substance  of  ien'.ine  resembles  that  of  bone  in  being 
composed  of  bundles  of  extremely  delicate  fibrilLx  of  fibrous  connective  ti.ssuc.  The 
latter,  best  seen  in  decalcified  tissue,  swell  on  treatment  with  water  containing  acids 
or  alkalies,  and  yield  gelatin  after  prolonged  boiling.    The  disposition  of  the  bundles 


Ground-section  of  dried  tooth  including  adjacent  enamel  and  denline. 

-  300. 


m 


i? 
I 


1 55" 


HUMAN  ANATOMY. 


uf  fibrillse — more  regular  in  dentine  than  in  bone  -is  longitudinal  and  parallel  to  the 
primary  surfaces  of  the  dentine.  In  addition  to  the  fibres  which  extend  lengthwise, 
others  run  obliquely  crosswise  in  the  layers  of  dentine.  The  bundles  of  fibrillse 
measure  from  .003-.  003  mm.  in  diameter,  and  appear  in  transverse  sections  as  small 
punctated  fields.  The  librillie  are  knit  together  by  the  calcified  organic  matrix,  in 
which  the  lime  salts  are  deposited  in  the  form  of  spherules,  the  interstices  between 
which  are  later  filled  and  calcification  thus  completed.  When,  as  often  happens,  the 
latter  process  is  imperfect,  irregular  clefts,  the  interglobular  spaces,  remain,  the  con- 
tours of  which  arc  formed  by  the  spheres  or  dentinal  globules  of  calcareous  materia!. 
The  interglobular  spaces  are  of  irregular  form  and  uncertain  extent,  being  usually 
largest  in  the  crown.  At  the  border  between  the  dentine  and  the  cementum  there 
exists  normally  a  distinct  zone,  \^i^  granular  layer  of  Tomes  (Fig.  1311),  composed  of 

Fig.   1310. 


Plllp^iisuv 


Oranular  layer  of  denliiu- 


Ccmctitum 


Alveolar  periosteum 


Transverse  section  of  root  of  lower  canine  tooth.    X  30. 


closely  placed  interglobular  sjiaces  of  small  size  ;  under  low  magnification  in  ground- 
sections  the  spaces  appear  as  dark  granules,  hence  the  designation  of  the  zone.  Since 
the  existence  of  these  spaces  depends  upon  imperfect  calcification  of  the  intertubular 
Rround-substance,  the  dentinal  tubules  are  unaffected  and  pass  through  the  spaces  on 
their  course  to  the  surface  of  the  dentine,  several  of  the  canals  traversing  the  larger 
spaces.  The  contour  lines  of  Owen,  or  the  incremental  lines  of  Salter,  appear  as 
linear  markings,  which  usually  run  obliquely  to  the  surface  of  the  dentine  (Fig.  1 306). 
They  probably  depend  upion  v  '  'ions  in  calcification  incident  to  the  growth  of  the 
dentine,  and  resemble  the  i  ,iobular  spaces  in  their  origfin.  The  contour  lines 
are  best  marked  in  the  crown  and  are  only  exceptionally  seen  in  the  fang.  As 
pointed  out  by  Walkhoff,  the  lines  of  Owen  and  those  of  Retzius  in  the  enamel  are 
usually  present  at  the  same  time,  since  both  are  expressions  of  iin|jerfect  calcification. 
The  Cementutn. — The  cement,  or  crusta  petrosa  of  the  older  writets,  forms 
an  investment  of  slightly  modified  osseous  tissue  from  the  neck  of  the  tooth  to  its 


STRICTURE  OF  THE  TEETH. 


«553 


l)«uin 


Ginnular  layer 
of  TomcR 


« 

u 


A 


1^' 


apex.  Beginnini;  where  the  enamel  ceases,  or  overlapping;  the  latter  to  a  small 
extent,  as  a  layer  only  .02-.03  mm.  thick  the  cement  gradually  increa-ses  in  thick- 
ness until  over  t'le  root,  t^peciall)  hetweei  ihe  fanKs  of  the  molars,  its  deptli  reaches 
sevaral  millimetres.  When  well  i'-  .lope  the  cement  u.sually  presents  two  layers, — 
an  inner,  almost  homogeneous  straium  '-  .t  the  dentine,  in  which  the  cement-cells  are 
absent,  and  an  outer  supplemental  layer  which  exhibits  the  appearance  of  true  bone- 
tisaue.  The  ground-substance  of  cemen- 
tum  differs  from  that  of  ordinary  bone 
in  containing,  according  tt>  Bibra,  slightly 
less  organic  matter  and  a  great  number 
of  fibre-bundles  that  extend  vertically  to 
the  lamellae,  corresponding  to  Sharpey's 
fibres.  The  lacunx  are  larger  than  those 
of  bone  and  vary  greatly  in  their  number 
and  form  ;  their  processes,  the  canaliculi, 
are  unusually  long  and  elaborate.  As  in 
bone,  so  these  lymph-spaces  contain  con- 
nective-tissue cells,  the  cetnent-corpMsiles. 
The  lamella*  are  so  disposed  that  the 
lac  \xat  lie  generally  parallel  with  the  long 
axis  of  the  tooth,  their  processses  extend- 
ing vertically  to  the  free  surface.  While 
connecting  with  one  another  by  means 
of  the  canaliculi,  the  lacuna?  very  rarely 
communicate  with  the  'lentinal  tubules, 
the  latter  terminating  ■  blind  endings. 
The  union  between  the  outer  surface  of 
the  cement  and  the  pericementum  is  in- 
timate, since  the  latter  is  in  »act  the  alve- 
olar periosteum  from  which  the  cement 
was  derived  ;  this  close  relation  is  indi- 
cated by  the  roughness  which  the  outer 
surface  of  the  cement  presents  when 
macerated.  Although  at  times  feebly 
developed  under  normal  conditions,  typical  Haversian  canals  are  found  only  in  con- 
ditions  of  hypertrophy. 

The  Alveolar  Periosteum. — The  periosteum  investing  the  jaws  likewise  lines 
the  sockets  receiving  the  roots  of  the  teeth,  which  are  by  his  means  securely  held 
in  place.  The  name  pericementum  is  often  applied  to  this  special  part  of  the  peri- 
osteum, which  clothes  the  alveoli  on  the  one  hand  and  covers  the  cement  on  the 
other,  thereby  fulfilling  the  double  r6le  of  periosteum  and  root-membrane.  The 
latter  consists  of  tough  bundles  of  fibrous  tissue,  elastic  tissue  being  almost  want- 
ing, which  are  prolonged  into  the  penetrating  fibres  characterizing  the  cementum 
on  one  side  and  into  the  fibres  of  Sharpey  of  the  alveolar  wall  on  the  other.  The 
fibrous  bundles  run  almost  horizontally  in  the  upper  part  of  the  root,  but  become 
more  oblique  towards  the  apex  of  the  fang.  In  the  latter  situation  the  pericemen- 
tum loses  its  dense  character  and  becomes  a  loose  connective  tissue  through  which 
the  blood-vessels  and  nerves  pass  to  reach  the  tooth.  The  less  dense  portions 
of  the  root-membrane  between  the  penetrating  bundles  of  fibrous  tis.sue  contain, 
in  addition  to  the  vessels  and  nerves,  irregular  groups  of  epithelial  cells  which 
appear  as  cords  or  net- works  within  the  connictive-tissue  .  oma.  These  groups 
are  the  remains  of  the  epithelial  sheath  which  surrounded  the  young  tooth  during 
its  early  development.  They  have  sometimes  been  described  as  glands,  lymphatics, 
and  other  structures,  their  true  nature  being  unrecognized.  At  the  alveolar  mar- 
gin the  pericementum  is  directly  continuous  with  the  tissue  composing  the  gum, 
the  fibrous  bundles  being  so  disposed  immediately  beneath  the  enamel-border  that 
they  form  an  encircling  band  of  dense  fibrous  tissue,  the  ligamentum  circulare 
dentis  of  Kolliker,  which  aids  in  maintaining  tirmer  union  between  the  tooth  and 
the  alveolar  wall. 


Lacuna 


Ground-Kctfon  of  root  of  dri«i1  tnolh  including  adjacent 
drntine  and  ccmentum.     X  300. 


:r  1 1 


*. 


1554 


HUMAN  ANATOMY. 


Fio. 


131a. 


The  Pulp. — ^The  contents  of  the  pulp-cavity  is  the  modified  tissue  of  tl 
mesoblastic  dental  papilla  remaining  after  the  completed  formation  of  the  dentine. 
The  major  part  of  the  adult  pulp  consists  of  a  soft,  very  vascular  connective  tissue 
containing  tew  or  no  elastic  elements,  but  numerous  irregularly  distributed  cells  of 
uncertain  form.  The  general  type  of  the  tissue  resembles  the  embryonal,  both  in  the 
character  of  the  fibrous  tissue  and  of  the  cells,  which  are  round,  oval,  or  stellate  with 
long  processes.  The  fibrous  bundles  and  the  more  elongated  cells  are  most  regu- 
larly disposed  around  the  blood-vessels  and  nerves,  which  they  invest  in  delicate 
fibrous  sheaths. 

The  peripheral  zone  of  the  pulp,  next  the  dentine,  presents  the  greatest  special- 
ization, since  in  this  situation  lie  the  direct  descendants  of  the  dentine-producing 
cells,  the  odontoblasts.     In  this  locality  the  pulp,  especially  in  older  teeth,  presents 

three  layers.  The  outer  ( .  04-.  08  mm.  thick  ) 
consists  of  several  rows  of  large  cylindrical 
elements,  of  which  the  most  sufterificial  are 
arranged  vertically  to  the  free  surface  of 
the  pulp,  after  the  manner  of  an  epithelium. 
These  are  the  odontoblasts,  now  no  longer 
active,  about  .025  mm.  in  length  and  .005 
mm.  broad,  which  send  out  long,  delicate 
processes  (the  dentinal  fibres)  into  the  den- 
tal tubules  externally,  and  shorter  ones 
towards  the  pulp-tissue.  When  very  young 
they  probably  possess  also  lateral  processes. 
The  deeper  cells  of  the  odontoblastic  layer 
are  less  regularly  disposed  and  less  cylindri- 
cal in  form.  The  second,  or  U'eil's  layer, 
best  seen  in  older  teeth,  is  characterized 
by  absence  of  cells,  the  fibrous  tissue  and 
the  cell-processes  forming  a  clear,  cell-free 
zone  which  separates  the  striking  layer  of 
odontoblasts  from  the  subjacent  third  or  in- 
termediate layer.  The  latter  consists  of  nu- 
merous small  round  or  spindle-cells,  closely 
placed,  but  irregularly  disposed,  which  grad- 
ually blend  with  the  ordinary  pulp-tissue. 
The  blood-vessels  supplying  the  pulp  are  from  three  to  ten  small  arteries  which 
soon  after  entering  the  pulp-cavity  break  up  into  very  numerous  branches  from  which 
a  rich  capillary  net-work  is  derived.  In  human  teeth  the  capillaries  usually  do  not 
invade  the  layer  of  odontoblasts,  although  at  times  the  vascular  loops  may  extend 
between  these  cells.  The  venous  radicles  form  larger  veins  which  follow  the  course 
of  the  arteries.     Distinct  lymphatics  have  not  been  demonstrated  within  the  pulp. 

The  nerves  are  numerous,  each  fang  receiving  a  main  stem  and  several  additional 
smaller  twigs,  which  in  a  general  way  accompany  the  blood-vessels  in  their  coarser 
distribution.  On  reaching  the  crown-pulp  the  larger  twigs  are  replaced  by  finer 
branches,  which  divide  into  innumerable  interwoven  fibres.  The  latter,  on  reaching 
the  margin  of  the  pulp,  form  a  peripheral  plexus  beneath  the  layer  of  odontoblasts, 
from  which  terminal  non-medullated  fibrillae  are  given  off.  Some  of  these  end 
beneath  the  odontoblasts  in  minute  knot-like  swellings  ;  others  penetrate  the  odonto- 
blastic layer  to  terminate  in  pointed  free  endings.  There  is  no  trustworthy  evidence 
supporting  the  view  that  the  nerves  directly  communicate  with  the  odontoblasts  or 
enter  the  dentine. 


Section  o{  periphery  of  pulp-tinue  of  young  tooth. 
X  175. 


IMPLANTATION  AND  RELATIONS  OF  THE  TEETH. 

The  Permanent  Teeth. — Elach  fang  is  implanted  in  a  socket  corresponding 
to  it  in  shape,  so  that  the  pressure  is  transmitted  from  the  surface  of  the  conical  fang 
throughout,  except  at  the  very  tip,  which  has  a  hole  for  the  vessels  and  nerves.  A 
corresponding  hole  in  the  socket  communicates  with  the  dental  canals.     The  human 


IMPLANTATION  AND  RELATIONS  OF  THE  TEETH. 


1555 


teeth  are  all  in  contact  with  their  neighbors,  there  being  no  break  or  diastema  in  the 
upper  jaw  between  the  incisors  and  canines  for  the  points  of  the  canines  of  the  lower 
jaw.  The  canines  project  very  little  beyond  the  line  of  the  free  edges.  The  crowns 
increase  in  size  from  the  incisors  to  the  first  molars  and  then  decrease.  The  ver- 
tical distance  from  the  gum  to  the  free  edge  regularly  diminishes  from  the  median 
incisors  backward,  with  the  exception  of  the  canines.  The  lines  of  the  teeth  above 
and  below  are  practically  of  the  same  length.    When  the  mouth  is  closed  the  superior 

canines  lie  to  the  outer  side  of  the 
Fio.  1313.  inferior  ones,  opposite  the  ends  of 

"  *     '  '  the  lips ;  thus  the  median  upper 

incisors  impinge  on  both  the  lower 
ones  of  the  same  side,  and  the 
upper  lateral  incisors  strike  both 
the  lower  lateral  and  the  canine. 
In  the  same  way  the  point  of  the 
cusp  of  the  upper  first  bicuspid 
rests  between  the  points  of  both 
the  inferior  ones,  and  that  of  the 
second  on  both  the  second  lower 
and  the  first  molar.  The  first 
upper  molar  has,  perhaps,  a  quar- 
ter of  its  grinding  surface  on  that 
of  the  inferior  second  molar,  but  a 
smaller  part  of  the  second  upper 
molar  rests  on  the  lower  wisdom- 
tooth.  The  smaller  size  of  the 
upper  wisdom-tix>th  brings  its  posterior  border  into  line  with  that  of  the  lower.  This 
arrangement  causes  the  opposed  crowns  to  interlock  to  a  certain  extent,  but  not  so 
closely  that  grinding  movements  cannot  occur  between  them.  The  advantage  of  each 
tooth  coming  in  contact  with  two  is  evident  after  the  loss  of  a  tooth,  as  the  one  cor- 
responding to  it  is  not  rendered  useless.     In  the  upper  jaw  the  incisors  have  a  marked 


Dental  arches  seen  from  before.  Letters  in  thi<i  and  subicquent 
cuts  indicate  the  j^roupt  of  teeth :  t,  incisors ;  c,  canines ;  b,  bicus- 
pids ;  M,  molars. 


Fig.  13 14. 


'  i| 


Dental  arches  seen  from  behind. 


forward  inclination,  and  overlap  the  lower,  concealing  nearly  a  third  of  their  crowns,  the 
mouth  being  closed.  The  crowns  of  the  upper  bicuspids  look  pretty  nearly  downward 
and  those  of  the  molars  slant  outward.  This  is  very  marked  in  the  wisdom-tooth  and 
may  he  very  slight  in  the  first  molars.  The  low r  inrisnrs  have  th'-  front  surfaces  nearly 
vertical ;  the  molars  have  an  inward  slant,  so  as  to  bring  their  .i.xi  ■<  into  the  same  line 


,v  '   ^ 


m 


1556 


HUMAN  ANATOMY. 


Dental  arches  seen  from  the  side,  showing  relations 
of  upper  and  lower  teeth. 


as  those  of  the  upper  ones  ;  hence  it  follows  that  the  alveolar  arches  of  the  upp«r  and 
lower  teeth  are  in  different  curves,  the  latter  having  a  great  transverse  disUnce 
between  the  necks  of  the  wisdom-teeth. 

The  right  half  of  the  jaw  is  usually  the  stronger  and  the  teeth  form  a  smaller 
curve.  It  has  been  pointed  out  in  the  section  on  the  motions  of  the  lower  jaw  that 
the  line  between  the  molars,  and  probably  the  bicuspids,  is  a  part  of  the  circumference 
of  a  circle  the  centre  of  which  is  near  the  top  of  the  lachrymal  bone  ;  it  may  now  be 
added  that  the  line  of  the  cutting  edges  of  the  lower  incisors  is  a  part  of  a  transverse 
curve  with  the  convexity  upward.  There  is  no  corresponding  concavity  in  the  line 
of  the  edges  of  the  upper  incisors,  for  the  lower  do  not  naturally  meet  them  ;  but  the 
convexity  plays  along  the  lingual  surfaces  of  the  upper  ones.  The  position  and  shape 
of  the  superior  incisors  make  their  inner  surface  a  part  of  a  vault.  A  transverse 
section  of  this  is  necessarily  a  curve  with  an  upward  convexity.  The  wearing  ui  the 
outer  corners  of  the  lateral  incisors  is  evidence  of  this  action.     The  fact  that  there  is 

no  purely  lateral  motion,  but  an  oblique 
one,  modifies,  without  invalidating,  this  con- 
ception. 

The  relations  of  the  roots  of  the  su- 
perior teeth  to  the  antrum  are  very  impor- 
tant. The  incisors  have  no  relation  with  it 
whatever.  The  long  fang  of  the  canine  is 
opposite  the  wall  between  the  antrum  and 
nose,  and  separated  by  diploe  from  the 
former.  The  first  bicuspid  is  usually  sepa- 
rated in  the  same  manner.  The  second  is 
very  close  to  its  front  wall  and  may  indent 
the  floor.  The  first  and  second  molars 
always  do  this.  The  wisdom-tooth  also  in- 
dents it  at  the  junction  of  the  floor  with  the 
posterior  wall.  Its  relation,  owing  in  pai 
to  its  varying  development,  is  less  certain.  Exceptionally  the  first  bicuspid  an^ 
even  the  canine  may  be  in  contact  with  the  antrum.  Thus  caries  of  the  roots  <<t 
any  of  the  molars,  but  especially  of  the  first  and  second,  sometimes  of  the  second 
bicuspid  and  exceptionally  of  the  first,  or  even  of  the  canine,  may  lead  to  inflamma- 
tion of  the  antrum.     In  certain  cases  pus  may  pass  directly  into  it  from  the  root. 

The  Temporary  Teeth. — In  the  first  dentition  the  dental  arches  differ  from 
the  permanent  ones  in  showing  a  broader  curve,  more  nearly  approaching  half  a  circle, 
symmetrical  on  both  sides,  in  having  the  upper  incisors  less  slanting,  and  the  molars 
of  >>ach  row  more  nearly  vertical.  This  implies  less  difference  in  curve  between  the 
jaws.  The  line  of  meeting  of  the  teeth  is  more  horizontal.  The  crowns  increase  in 
size  from  the  incisors  backward.  In  the  young  child  the  antrum  is  but  a  small  pouch, 
and  the  roots  of  the  first  teeth  and  the  sacs  of  the  second  lie  in  diploetic  tissue.  The 
first  permanent  molar,  as  its  fangs  grow,  is  nearest  the  antrum,  having  extended  above 
it  by  the  end  of  the  second  year.  In  its  early  stages  the  first  bicuspid  is  too  far  forward 
to  have  any  relation  to  the  antrum,  and  the  second  reaches  only  its  extreme  anterior 
border.  The  second  permanent  molar  is  at  first  behind  rather  than  below  it,  and  the 
third  is  still  higher.  As  these  descend  they  swing  around  the  antrum.  Thus  the  roots 
of  only  the  first  permanent  molar  are  in  approximately  the  same  relation  to  the  antrum 
throughout. 

DEVELOPMENT  OF   THE  TEETH. 

About  the  beginning  of  the  seventh  week  of  foetal  life  the  ectoblastir  epithelium 
presents  a  thickening  along  the  margins  of  the  oral  cavity.  The  ridge-like  epithelial 
proliferation,  or  labio-dental  strand,  so  formed  grows  into  the  surrounding  mesoblast 
and  divides  into  two  plates  which,  while  still  continuous  at  the  surface,  diverge  almost 
at  right  angles  at  the  deeper  plane.  The  lateral  or  outer  plate  is  vertical,  and  cor- 
responds to  the  plane  of  separation  which  soon  occurs  in  the  differentiation  of  the 
borders  of  the  lips  and  jaw.  The  median  or  inner  plate  grows  more  horizontally  into 
the  mesoblast,  and  is  the  one  intimately  concerned  in  the  tooth  development ;  for  this 


DEVELOPMENT  OF  THE  TEETH. 


1557 


reason  it  is  termed  the  dental  ledge.  It  will  be  seen  that  the  formerly  described  pri- 
mary stage  of  the  dental  groove  is  unfounded,  since  the  furrow  that  does  exist  is 
secondary  and  not  directly  related  to  the  formation  of  the  teeth,  but  to  the  differ- 
entiation of  the  lips.  During  the  third  fcetal  month  the  anlages  for  the  entire  set  of 
milk-teeth  become  evident  along  the  dental  bar,  coincidcntly,  by  the  eleventh  week, 
the  completion  of  the  labial  furrow  separating  the  lip  from  the  original  epithelial 
strand  with  which  the  dental  ledge  alone  for  a  time  remains  attached. 

The  anlages  of  the  milk-teeth  are  indicated  by  club-shaped  epithelial  outgrowths 
which  grow  down  from  the  deeper  surface  of  the  dental  ledge  to  form  the  enamel- 

Flo.  1316. 


Keconstructioni  of  oral  ectoblast  of  human  embryos ;  only  epithelium  of  lips,  mouth,  and  cnamelorffans  shown. 
A,  embryo  ol  2.5  cm.  length;  m,  oral  opeuinx;  ^,  labial  epithelium;  /</,  reverse  of  labiOKJental  groove;  i/j,  dental 
ledge,  /f,  embryo  of  4  cm. ;  /a,  projection  caused  hy  labio-aental  groove;  1/5,  dental  letlgc.  C,  embryo  of  11.5  cm., 
or  01  about  fourteen  weeks ;  « '.  eiiamel.organ  of  hrst  molar  tootn.  D,  embryo  of  18  cm.,  or  of  atmut  seventeen 
weeks  ;  i*  m  ^  enamet.orBans  of  second  incisor  and  of  first  molar  teeth.     ( Urawn/rom  ffdtr*s  moitf'f. ) 

organs  and  to  meet,  and  later  cap,  the  mesoblastic  elevations  or  dental papilur.  With 
the  rapid  growth  and  expansion  of  the  extremity  of  the  epithelial  plug,  a  differentia- 
tion of  the  latter  into  the  typical  t|iree-layered  enamel-organ  takes  place,  the  pro- 
jecting dental  papilla  apparently  invaginating  the  overlying  epithelial  structure.  At 
first  connected  by  a  broad  band  of  cells,  the  attachment  of  the  enamel-organ  with  the 


1558 


HUMAN  ANATOMY. 


dental  ledge  becomes  more  and  more  attenuated  until  finally  it  is  broken  ;  its  remains 
appear  for  some  time  as  nests  or  islands  of  epithelial  cells  embedded  within  the  young 
connective  tissue  of  the  alveolar  border. 

The  Dental  Papilla. — This  structure  first  appears  shortly  after  the  beginning 
expansion  of  the  club-shaped  de^  eloping  enamel-organ  as  a  condensation  of  the  meso- 

Fio.  1317. 


,Dcntal  ledge 


Thickened 
onl  epitbelinm. 


Inner  layer 
of  enamel- 
organ 


Dtnt»\ 
papilla 


.Epithelial 
sheath 


Frontal  sections,  showing  (our  eurly  stages  u(  tooth-development.    .-I,  ff,  X  100 


C.  D.  ■  60. 


blast  beneath  the  epithelial  ingrowth.  The  papilla  consists  for  a  time  of  a  close 
^Rgregation  of  small,  round,  proliferating  cells  ;  with  the  differentiation  of  the  layers 
of  the  enamel-organ,  the  elements  occupying  the  periphery  of  the  dental  papilla 
become  elongated  and  arranged  as  a  continuous  row  of  cylindrical  cells  over  the  api- 
cal portion  of  the  papilla  beneath  the  capping  enamel-organ.  These  cylindrical  meso- 
blastic  cells  are  the  odontoblasts,  the  active  agents  in  the  formation  of  the  dentine. 


DEVELOPMENT  OF  THE  TEETH. 


"559 


Fio.  1318.. 


When  engag^  in  the  latter  process  the  cells  measure  from  .035-.  050  mm.  in  length 
and  from  .C05-.010  mm.  in  breadth,  but  over  the  sides  of  the  papilla  they  gradually 
become  lower  until  towards  the  base  they  blend  with  and  become  indistinguishable 
from  the  deeper  cells  of  the  mesoblastic  <  Icvation.  So  lont'  s  the  tooth  grows, 
division  proceeds  and  odontoblasts  are  differentiated  in  the  vii  ;y  of  the  last-formed 
parts  of  the  root ;  after,  however,  the  odontoblasts  are  engageu  in  forming  dentine, 
mitosis  is  no  longer  to  be  observed  in  these  elements. 

The  formation  of  the  dentine  is  accomplished  through  the  agency  of  the 
odontoblasts  much  in  the  same  manner  that  the  osteoblasts  produce  the  matrix  of 
bone.  The  earliest  trace  of  the  dentine  appears  as  a  thin  homogeneous  stratum,  the 
membrana  pra;/ormativa,  overlying  the  coincidentiy  forming  layer  of  odontoblasts. 
Although  separable  by  certain  reagents  as  a  cuticular  structure,  the  membrane  is  only 
a  part  of  the  general  dentinal  ground -substance  with  which  it  blends  ;  later  it  is  prob- 
ably absorbed  when  brought  into  contact  with  the  enamel.  The  dentinal  matrix, 
deposited  through  the  influence  of  the  odontoblasts,  is  for  a  time  without  fibrous 
structure  and  uncalcitied,  the  deposition  of  the  lime  salts  occurring  first  near  the  apex 
of  the  papilla  and  next  the  enamel,  a  zone  of  uncalcified  matrix  around  the  pulp- 
cavity  marking  the  youngest  dentine.  The  calcareous  material  is  first  deposited  in 
the  form  of  globules,  the  dentinal  spheres,  the  calcification  being  completed  by  the 
subsequent  invasion  of  the  interstices  between  the  spherical  masses.  When  for  any 
reason  calcification  is  incomplete  these  clefts  remain 
lime  free,  a  condition  seen  in  the  interglobular  spaces 
already  described.  The  spherical  form  of  the  calca- 
reous deposits  is  indicated  by  the  uneven  condition  of 
the  inner  surface  of  the  dentine  in  macerated  teeth,  the 
wall  of  the  pulp-cavity  presenting  numerous  minute 
hemispheriad  projections  which  correspond  to  the 
globular  masses  of  lime  salts.  The  scalloped  border 
and  pitted  outer  surface  of  the  dentine,  together  with 
the  extension  of  the  dentinal  tubules  as  far  as  or  into 
the  enamel,  point  to  the  absorption  of  the  primary 
dentine  constituting  the  preformed  membrane,  proba- 
bly through  the  influence  of  the  enamel.  As  empha- 
sized by  Ebner,'  the  formation  of  the  fibrillse  of  the 
ground-substance  takes  place  independently  of  the 
direct  influence  of  the  dentine-cells,  since  the  general 
disftosition  of  the  earliest  fibrillae  is  at  right  angles  to 
that  of  the  odontoblasts  and  their  processes.  The 
dentinal  matrix  differs  from  that  of  bone  in  being  the 
production  of  a  single  set  of  cells,  while  the  osseous 
tissue  is  the  collective  work  of  different  elements, 
many  of  which,  after  contributing  their  increment,  be- 
come surrounded  by  the  ground-substance  to  form 
the  bone-corpuscles  within  the  lacunae.  In  human 
dentine,  on  the  contrary,  the  odontoblasts  are  only 
rarely,  under  nonnal  conditions,  imprisoned  within  the 
ground-substance  which  they  have'  formed.  The  de- 
mands made  upon  the  odontoblasts  during  their  active  r61e  as  dentine  producers  are 
met  by  the  nutrition  supplied  by  the  rich  vascular  supply  of  the  dentinal  papilla,  so 
that  for  a  time  the  cells  are  enabled  not  only  to  increase  the  dentinal  matrix,  but  also 
to  extend  their  processes,  which  they  send  into  the  tubules  of  the  dentine  as  the  den- 
tinal fibres,  without  diminution  in  size.  With  the  completion  of  dentine  production, 
and  the  consequent  de  ease  in  the  area  upon  which  they  rest,  the  odontoblasts 
become  narrower  and  sm  .Her  (Walkhoff)  ;  later  they  exhibit  evidences  of  impaired 
vitality  and  degeneration,  their  dentinal  processes  likewise  growing  thinner  and  less 
flexible  and  assuming  the  characteristics  of  the  fibres  of  Tomes  of  the  adult  tissue. 
According  to  Walkhoff,  the  dentinal  fibres  suffer  in  size  as  the  result  of  their  activity 
in  the  production  of  the  sheath  of  the  tubules. 

'  In  Kolliker's  Gewebelehre  des  Menschen,  6te  Auf.,  1899. 


IsolalM  odontobluts  from  incisor 
tooth  of  iiew-tmni  child,  a.  A,  frotn 
upper  part  of  crown  ;  r,  d,  e,  from  lat- 
crml  region.    X  400.    \,Ebney.) 


llH 


Mil 


■•fi 


HI 


1560 


HUMAN  ANATOMY. 


After  the  entire  dentine  has  been  formed,  the  odontoblasts  remain  as  the  periph- 
erally situated  pulp-cells,  retaining  their  connection  with  the  dentine  by  means  of  the 
dentinal  fibres.  The  other  portions  of  the  dental  papilla  become  converted  into  the 
pulp-tissue,  which  reuins  the  embryonal  type  throughout  life  and  later  receives  the 
larger  vascular  and  nervous  trunks. 

The  Enamel-Organ. — The  extremity  of  the  cylinder  of  ectoblastic  epithelium 
which  early  marks  the  position  of  the  future  tooth  by  its  ingrowth  from  the  dental 
ledge  soon  broadens  out  and  becomes  invaginated  to  form  the  young  enamel-organ 
overlying  the  apex  of  the  mesodermic  dental  papilla.  In  contrast  to  the  latter,  which 
as  the  pulp-tissue  remains  as  a  |)ermanent  structure,  the  enamel-organ  is  but  embry- 
onal and  transient,  and  later  entirely  disappears.  When  fully  developed,  the  enamel- 
organ  consists  of  three  principal  parts, — the  outer,  middle,  and  inner  layers.  Since 
the  organ,  originally  pyriform,  is  converted  into  a  cap  by  the  invagination  of  its 
broader  and  deeper  surface,  it  follows  that  the  external  and  internal  layers  are 
directly  continuous  at  the  margin  of  the  inverted  area. 


Fio.  1319. 


Sublingual  space 


Fibres  of^ 

fenio-(los5us    ^ 


JLOni  epithelium 


Developing 

gland 
,Dental  papilla 


Muscular  fibres 


Sagitul  section  through  mandible  and  surrounding  structures  o(  eighteen-weeks  fcrtus.    X  jo. 

The  outer  layer  consists  of  larger  and  smaller  epithelial  cells  of  flattened  form 
and  about  .010  mm.  average  diameter  ;  these  cell?  send  numerous  processes  into  the 
surrounding  vascular  connective  ti.ssue  forming  the  tooth-sac  which  invests  the  dental 
germ,  whereby,  in  conjunction  with  the  vascular  tufts,  the  sac  and  the  enamel-organ 
are  intimately  united 

The  middle  la  of  the  enamel-organ  consists  apparently  of  mucoid  tissue, 
since  it  presents  a  1  .work  of  stellate  cells  separated  by  large  clear  spaces.  Critical 
examination,  however,  shows  that  this  tissue  consists  of  epithelial  elements  which 
have  become  modified  in  consequence  of  an  enormous  distention  of  the  intercellular 
spaces  by  fluid  and  a  corresponding  elongation  of  the  intercellular  bridges,  the  epi- 
thelial plates  in  this  manner  being  reduced  to  stellate  cells  connected  by  long,  delicate 
processes.  The  inner  border  of  the  highly  characteristic  middle  layer  forms  a  tr  .nsi- 
tion  zone,  known  as  the  inter mediale  layer,  in  which  gradations  from  the  modifie>,  to 
the  ordinary  type  of  stratified  epithelium  are  seen.  The  intermediate  layer  is  best 
marked  over  the  upper  part  of  the  crown,  at  the  sides  thinning  out  and  entirely  dis- 


DEVELOPMENT  OF  THE  TEETH. 


1561 


appearing  at  the  margin  of  the  enamel-organ,  v  ere  the  outer  and  inner  layers  of  the 
latter  are  continuous.  The  modified  epithelial  tissue  of  the  middle  layer,  sometimes 
called  the  enamel-pulp,  is  greatest  in  amount  just  prior  to,  or  during  the  t)eginning 
of,  active  tooth-formation,  about  the  fifth  or  sixth  fcctal  month. 

The  inner  layer  of  the  enamel-organ  comprises  a  single  row  of  closely  set,  tall, 
cylindrical  elements,  the  enamel-cells,  adamanloblasts,  or  ameloblasts,  through  the 
active  agency  of  which  the  enamel  is  produced.  The  ameloblasts  are  liest  developctl 
where  they  cover  the  apex  of  the  dental  papilla,  the  location  of  the  earliest  formed  den- 
tine ;  in  this  situation  the  cells  measure  from  .025-.040  mm.  in  length  and  froni 
.004-.007  mm.  in  breadth.  They  possess  an  oval  nucleus  about  .010  mm.  long, 
which  usually  lies  close  to  the  outer  end  of  the  cell,  embeddtd  in  cyto|)lasm  exhibit- 
ing a  reticulum  and  often  minute  granules.  The  ameloblasts  are  united  with  one 
another  by  a  small  amount  of  cement-substance,  and  are  define*!  fnu  ;  the  interme- 
diate layer  by  a  fairly  distinct  border.  Opf)osite  the  sides  of  the  den  li  papilla,  cor- 
responding to  the  limits  of  the  future  crown,  the  ameloblasts  gradually  diminish  in 
height  until  they  are  replaced  by  low  cubical  cells  which,  at  the  margin  of  the  enamel- 
organ,  are  continuous  with  the  epithelium  of  the  outer  layer.  Preparatory  to  the  for- 
mation of  the  dentine  of  the  tooth-root,  this  margin  grows  downward  towards  the 
base  of  the  elongating  dental  papilla,  which  is  thus  embraced  by  the  extension  r>f  the 


Fig. 


1320. 


Oral  epithelium 


Atrophic  epithelial  net-work 


Dental  groove 


Enamel_  ,j,4 
Dentine ., 

Epithelial  iheath 


Position  of  mesoblaslic  dental  papilla 


Reconstruction  of  developing  lower  incisor  tooth  from  embryo  of  30  cm.  length,  about  twenty-four  weeks. 

{Drawn  from  Host's  modtl.) 


enamel-organ.  The  investment  thus  formed  constitutes  the  epithelial  sheath  (Fig. 
1320),  a  structure  of  importance  in  determining  the  form  of  the  tooth,  since  it  serves 
as  a  mould  in  which  the  young  dentine  is  subsequently  deposited  ;  there  is,  however, 
insufficient  evidence  to  regard  the  epithelial  sheath  as  an  active  or  necessary  factor  in 
the  production  of  the  dentine. 

The  formation  of  the  enamel,  in  contrast  to  that  of  the  dentine,  results  fiom 
the  activity  of  ectoblastic  epithelium,  and  may  be  regarded  as  a  cuticular  development 
carried  on  by  the  ameloblasts.  The  earliest  stage  in  the  production  of  enamel  is 
the  appearance  of  a  delicate  cuticular  zone  at  the  inner  end  of  the  ameloblast  ;  this 
fuses  with  similar  structures  tipping  the  adjoining  cells  to  form  a  continuous  homo- 
geneous mass.  The  latter  soon  exhibits  differentiation  into  rod-like  segments,  the 
enamel-processes,  or  processes  of  Tomes,  which  are  extensions  from  the  ameloblasts 
and  are  the  anlages  of  the  enamel-prisms,  and  the  interprismatic  substance.  The 
latter  becomes  greatly  reduced  in  amount  as  the  development  of  the  enamel-columns 
progresses  ;  the  major  part,  becoming  incorporated  with  the  processes  of  Tomes, 
forms  the  cortical  jxjrtion  of  the  enamel -prisms,  while  the  remainder  persists  as  the 
cement-substance  which  exists  in  meagre  quantity  between  the  mature  prisms.  The 
enamel-processes  are  for  a  time  uncalcified,  but  with  the  more  advanced  formation  of  the 
enamel-prisms  the  calcareous  material,  which  is  deposited  as  granules  and  spherules, 
appears  first  in  the  axis  of  the  prism,  later  invading  the  periphery  (Ebner).     The 


1 

■ 

1 

■R 

i 

■ 

1 

^^1 

1 

1562 


HUMAN  ANATOMY. 


enamel  increases  in  thicknejis  by  the  addition  of  the  last-formed  increments  at  the 
inner  ends  of  the  ameloblasts,  the  same  cells  sufficing  for  the  deposit  of  the  entire 
mass.     Owing  to  the  expansion  of  the  external  surface  of  the  crown,  the  diameter  of 

Fio.  13J1. 


Intermediate  layer  ai 
enamel-urgaii 


meloblaats 


.YouiiK  enamel  with 
Tumcs's  proceiM* 


Dentine 


Laat-formed  dentin* 
Odontoblasts 


.  Embr>-unal  pulp-tissue 
Section  of  developing  tooth  through  junction  of  enamel  and  dentine.     ^  400. 


Fig. 


1323. 


the  enamel-prisms  augments  towards  their  outer  ends  to  compensate  for  the  increased 
area  which  they  must  fill,  since  no  additional  prisms  are  formed. 

The  complex  curvature  of  the  enamel-prisms  and  the  oppositely  directed  ranges 
of  the  latter,  producing  the  appearance  of  Schreger's  stripes,  result  from  changes  in 
the  position  of  the  enamel-cells  incident  to  the  growth  of  the  crown,  since  the  axes 
of  the  newly  formed  prisms  correspond  with  those  of  the  ameloblasts,  variations  in  the 
direction  of  which  affect  the  disposition  of  the  enamel-columns. 

The  earliest  formed  enamel  lies  in  close  apposition  with  the  oldest  dentine  con- 
stituting the  membrana  praeformativa ;  the  last  devel- 
oped immediately  beneath  the  ameloblasts.  The  enamel, 
therefore,  is  deposited  from  within  outward,  or  in  the 
reversed  direction  followed  by  the  growth  of  the  dentine. 
The  oldest  strata  of  both  substances  lie  in  contact ;  the 
youngest  on  the  extreme  outer  and  inner  surfaces  of  the 
tooth. 

After  the  requisite  amount  of  enamel  has  been  pro- 
duced, differentiation  into  prisms  ceases,  in  consequence 
of  which  the  last-formed  enamel  remains  as  a  continu- 
ous homogeneous  layer  investing  the  free  surface  of  the 
crown,  known  as  the  membrane  of  Nasmyth. 

The  Tooth-Sac. — Coincidently  with  the  develop- 
ment of  the  enamel-organ  and  the  growth  of  the  dental 
{>apilla,  the  surrounding  mesobiast  undergoes  differen- 
tiation into  a  connective-tiiBue  envelope  known  as  the 
dental  or  tooth-sac.  The  latter  not  only  closely  invests  the  enamel-organ,  but  is 
intimately  related  to  the  base  of  the  dental  papilla,  with  which  it  is  continuous.  In 
contrast  to  the  epithelial  enamel-organ,  which  is  entirely  without  blood-vessels,  the 


Isolated  ametohlasts  from  in- 
cisor of  new'bom  child,  a,  basal 
plate ;  d,  ciiticiilar  border ;  f,  pro. 
cesses  of  Tomes;  d,  homogeneous 
mass  still  covering  process.    X  400. 


DEVELOPMENT  OF  THE  TEETH. 


»5*3 


inner  port  of  the  tooth-sac  is  richly  provided  with  capillaries,  and  therefore  is  an 
important  source  of  nutrition  to  the  developing  dental  germ.  The  i>art  of  the  sac 
opposite  the  root  of  the  young  tooth  is  at  first  prevented  from  cummg  into  direct 
contact  with  the  dentine  by  the  double  layer  interpu!>ed  by  the  epithelial  sheath. 
This  relation  is  maintained  until  the  development  of  the  cement  begins,  when  the 
vascular  tissue  of  the  dental  sac  breaks  through  the  epithelial  sheath  to  reach  the 
surface  of  the  dentine,  upon  which  the  cementum  is  deposited  by  the  mesoblast.  In 
consequence  of  this  invasion,  the  epithelial  sheath  is  disrupted  mto  small  groups  or 
nests  of  celb  which  f>ersist  for  a  long  time  as  epithelial  islands  within  the  fibrous 
tissue  of  the  alveolar  periosteum  into  which  the  dental  sac  is  later  converted. 

The  formation  of  the  cementum  takes  place  through  the  agency  of  the 
mesoblastic  tissue  in  a  manner  almost  identical  with  the  development  of  subperiosteal 


Fig.  1323. 


Jtwi  o(  child  of  six  years,  showing  all  tcmporao'  teeth  in  place  with  permanent  teeth  in  various  stages  of 

development. 


bone,  the  active  cement-producing  cells,  or  cementoblasts,  corresponding  to  the  osteo- 
blasts which  deposit  the  osseous  matrix  upon  the  osteogenetic  fibres  of  the  periosteum. 
A  conspicuous  feature  of  cementum  is  the  unusual  number  of  transversely  disposed 
bundles  of  fibrillae,  or  Sharpey's  fibres,  among  which  many  are  imperfectly  calcified. 
The  cementum  appears  first  in  the  vicinity  of  the  neck  of  the  tooth,  and  progresses 
towards  the  apex  of  the  root  as  the  dentine  of  the  fang  is  deposited.  After  the  tooth 
is  fully  formed,  the  layer  of  cement  continues  to  grow  until  thickest  at  the  apex,  which 
it  completely  invests,  with  the  exception  of  the  canal  leading  to  the  entrance  of  the 
pulp-cavity.  The  cement  being  deposited  directly  upon  the  homogeneous  layer  con- 
stituting the  external  surface  of  the  dentine,  the  firm  connection  between  the  two 
portions  of  the  teeth  is  one  of  adhesion  rather  than  of  union.  Later  secondary 
changes  may  exceptionally  bring  the  canaliculi  of  the  cement  into  communication 
with  the  terminations  of  the  dentinal  tubules.     During  the  changes  incident  to  the 


'564 


HUMAN  ANATOMY. 


completed  tooth-development  the  tissue  of  the  dental  sac  becomes  denser,  the  part 
opposite  the  root  persisting  as  the  pericementum  which  intimately  connects  the 
cementum  with  the  alveolar  wall,  while  the  more  superficial  part  blends  with  the 
tissue  forming  the  gum. 

The  development  of  the  permanent  teeth  is  early  provided  for  by  the  dif- 
ferentiation of  the  anlagcs  of  the  secondary  denul  germs  during  the  growth  of  the 
first.  This  provision  includes  the  thickening  and  outgrowth  of  the  dental  bar  to  form 
the  enamel-organ  of  second  dentition,  and  later  the  appearance  of  a  new  dental  p;i- 
pilla  beneath  the  epithelial  cap.  The  enamel-organ  for  the  first  permanent  molar 
appears  about  the  seventeenth  week  of  ftetal  life,  followed  soon  by  the  corresponding 
dental  papilla.  The  germs  of  the  permanent  incisors  and  canines,  including  the 
papillie,  are  formed  about  the  twenty-fourth  week  ;  those  for  the  first  bicuspids  are 
seen  at  about  the  twenty-nintli  week,  and  those  for  the  second  bicuspids  about  one 
month  later.  The  interval  between  the  formation  of  the  enamel-organ  and  the  asso- 
ciated dental  papilla  increases  in  the  case  of  the  last  two  permanent  molars.  While 
the  enamel-germ  of  the  second  molar  appears  about  four  months  after  birth  and  the 
corresponding  papilla  two  months  later,  the  enamel-organ  for  the  third  molar,  or 
wisdom-tooth,  which  is  visible  about  the  third  year,  precedes  its  papilla  by  almost 
two  years. 

The  First  and  Second  Dentition  and  Subsequent  Changes.— At  birth 
the  jaws  contain  the  twenty  crowns  of  the  milk-teeth,  the  still  separate  cusps  of  the 
first  permanent  molars,  one  of  which  has  begun  to  calcify,  and  the  uncalcified  rudi- 
ments of  the  permanent  incisors  and  canines  behind  and  above  the  corresponding 
milk-teeth  of  the  upper  jaw,  behind  and  below  those  of  the  lower.  At  birth  the  bony 
plate  above  the  alveoli  of  the  upper  jaw  is  separated  by  a  littie  diploe  from  the  floor 
of  the  orbit.  The  milk-teeth  come  through  the  gum  in  five  groups  at  what  are  called 
dental  periods,  separated  by  intervals  of  rest.  The  grouping  is  more  regular  than  the 
time  of  eruption.  The  teeth  of  the  lower  jaw  have  a  tendency  to  precede  their  fellows 
of  the  upper. 


TABLE  OF  ERUPTION  OF  MILK-TEETH.' 


I. 

II. 
III. 
IV. 

V. 


Denial  Pcriodi. 
Six  to  eight  months. 
Eight  to  ten  months. 
Twelve  to  fourteen  months. 
Eighteen  to  twenty  months. 
Twenty-eight  to  thirty-two  months. 


Groups  of  Teeth. 

Two  middle  lower  incisors. 

Four  upper  incisors. 

Two  lateral  lower  incisors  and  four  first  molars. 

Four  canines. 

Four  second  molars. 


The  inter\'al  between  the  first  and  second  periods  is  practically  nothing.  It  is 
very  common  to  have  the  first  two  groups  appear  together.  After  this  every  inter\  al 
IS  longer  than  the  preceding  one.  In  the  matter  of  time  no  part  of  development  is 
more  irregular  than  that  of  the  teeth.  The  first  incisors  occasionally  appear  earlv  in 
the  fifth  month  and  sometimes  not  till  the  tenth,  or  even  later.  The  first  dentition  is 
sometimes  complete  at  or  shortly  after  the  close  of  the  second  year.  The  roots  are 
not  fully  formed  when  the  crowns  pierce  the  gums.  The  first  set  of  teeth  is  in  its 
most  perfect  condition  between  four  and  six  years. 

Calcification  of  the  second  set  begins  in  the  first  molar  before  birth,  in  the  incisors 
and  canines  at  about  six  months,  the  bicuspids  and  the  second  upper  molar  in  the  third 
year,  the  second  lower  molar  at  about  six,  and  the  wisdom-tooth  at  about  twelve. 

The  first  permanent  molars  come  into  line  with  the  milk-teeth,  piercing  the  gums 
before  any  of  the  latter  are  lost.  Before  eruption  the  upper  first  molars  lie  nearer  the 
median  line  and  farther  forward  than  the  lower.  The  roots  of  the  incisors  are  absorbed 
and  the  crowns  fall  out  to  make  way  for  their  successors.  The  molars  do  the  same 
for  the  bicuspids  which  grow  between  their  roots.  The  permanent  superior  canines 
are  developed  above  the  interval  between  the  lateral  permanent  incisors  and  the  first 
bicuspid,  which  are  almost  in  contact.  An  expansion  of  the  jaw  is  necessary  for  them 
to  come  into  place.  The  inferior  ones  have  more  room.  Both  are  somewhat  external 
to  their  predecessors.     The  second  upper  molar  comes  down  from  abovo  and  behind, 

"  From  Rotch's  Pediatrics. 


DEVELOPMENT  OF  THE  TEETH. 


1565 


and  so  does  the  wiadom-tooth  much  later.  The  inferior  second  molar  is  formed 
almost  in  the  angle  between  the  body  and  ramus.  The  inferior  wisdom-tooth,  Ix-fore 
it  cuts  the  gum,  faces  forward,  inward,  and  slightly  upward.     To  the  table  from 


Pio.  13*4. 


PcnwiiMnt  midani, 


Prrmancnt  mola 


I'emunetit  canine 
Iticuspidii 

.rrrmanent  in*-f^>r» 

Ti'tn|>orary  caninr 
rt'miMiran  inohirs 

IVimaiieiit  incisurs 
TfniiMirary  canine 

Permanent  canine 
Hicuspids 


Jaws  of  child  of  ten  years.  thowinK  partially  erupted  permanent  teeth  with  temporary  canines  and  molars  Mill  in 

place. 

Rotch  we  add  one  from  Livy,'  who  made  observations  -ral  thousand  children 

of  English  and  Irish  operatives. 

TABLE  OF  ERUPTION  OF  PERMANENT  TEETH." 

Years.  Groups.  Years.  Croups. 

6  Four  first  molars.  10  Four  second  bicuspids. 

J  Four  middle  incisors.  II  Four  canines. 

Four  lateral  incisors.  la  Four  second  molars. 

9  Four  first  bicuspids.  17  to  25  Four  wisdom-teeth. 

TABLES  SHOWING  TIME  OF  ERUPTION  OF  PERMANENT  TEETH.' 

Bo  vs. 

Ag«s.  9  10  II  '!  13  '4  15  I*        ToUI. 

Lateral  incisors    ....      i  42  9  4  i           i       .   .       .   .  59 

First  bicuspids i  76  12  i         9° 

Second  bicuspids .....  59  i^  5  '  "" 

Canines 18  28  25  8        .   .       .   .       .   .  79 

Second  molars 5  4a  6?  VS        184       78        12  663 

•  British  Medical  Journal,  1885.  «  From  Rotch.  •  From  Livy. 


1566 


HUMAN  ANATOMY. 


GlKU. 

*«•••  »  lo  II  11  ij  14  I)  16       ToUI. 

lateral  incixors 34         8         4        j6 

First  bictiHpidx 56        i^^i         j  1  1       .   .       .   '.         73 

SccoikI  bicuspids ji        16         2  a        .   .  71 

Second  molars 5       44       8u       j88        149       66        14       ^46 

( It  seems  possible  from  the  method  employed  that,  especially  in  the  case  o<  the  second  molars, 
the  tables  may  err  on  the  side  of  overstatinK  the  age. )  Livy's  researches  show  that  in  the 
first  dentition  the  first  molars,  incisors,  and  canines  come  through  first  in  the  lower  jaw.  In 
miwt  cases  the  bicuspids  come  first  in  the  upper.  The  second  molars  come  first  in  the  lower  jaw, 
unless  their  appearance  is  delayed,  in  which  case  the  order  is  uncertain.  The  date  of  the  appear- 
ance of  the  second  molar  can  be  only  an  approximate  guide  to  the  age.  VVhen  it  is  present  the 
child  is  unlikely  to  be  under  twelve.  The  change  in  the  shape  of  the  jaw— namely,  the  lengthening 
necessary  for  a  longer  row  of  larger  teeth,  as  well  as  the  widening  required  to  make  room  for  the 
canines— t>egin>  in  the  course  of  the  second  dentition  and  continues  after  its  close,  as  the  second 
molar  doe.>  not  at  once  assume  its  permanent  position  in  regular  line  with  the  rest.  It  w.xs 
pointed  out  in  the  section  on  the  growth  of  the  face  that  the  greatest  activity  of  growth  Likes 
place  at  the  paiis.s  of  dentition.  The  roots  of  the  permanent  teeth  are  by  no  means  fully 
developed  at  their  eruption.  With  their  perfection  the  sockets  are  formed  around  them  by  the 
harmonioun  moulding  of  the  parts  involved. 

Homolofies — Tnerf  are  two  chief  evolutioniiry  theories  of  the  origin  of  the  mammalian 
teeth  :  one,  the  concres<  -nee  theory,  is  that  they  are  formed  by  the  growing  together  „.'  originally 
separate  rones,  the  primuive  reptilian  teeth.  This  view  is  supported  by  Kiise '  and  Kukenthal." 
at  lea.st  for  the-  bicuspids  and  molars.  Cope,*  whom  Osborn*  has  followed,  advanced  the 
differentiation  theory,  according  to  which  the  many  cusps  of  the  molars  have  arisen  as  outgrowths 
from  a  primitive  cone.  This  is  based  on  comparative  anatomy  and  paieontolog)-.  According  to 
this,  there  was  first  the  ctmf,  in  the  upper  jaw  called  yJne  prolocone  and  in  the  lower  the/»ro/o- 
(.■OHid.  Two  secondary  cusps  next  appeared  respectively  before  and  behind  it  \.\\e  paraione 
and  tnetacone  of  the  upper  teeth  and  \.\\k  faraeonid  ana  metaconid  ol  the  lower.  The  next 
change  is  for  these  to  move  to  the  labial  side  in  the  upper  jaw  and  to  the  lingual  in  the  lower. 
Thus  the  primitive  cone  and  these  two  secondary  ones  Jorm  the  points  of  a  triangle  with  the  base 
outward  in  the  upiier  jaw  and  inward  in  the  tower.  A  prolongation,  the  talon  or  heel,  is  next 
developed  on  the  posterior  end  of  the  tooth,  and  rises  into  a  single  cusp,  the  hypocone  in  the 
upper  jaw  and  the  hffoconid  in  the  lower.  The  last,  however,  has  Iwo  secondary  cusps  spring 
from  it,  Ihe  enlocontd  and  the  hypoconid.  According  to  this  theory,  the  fiararonid  ol  the  lower 
teeth  has  disappeared  in  the  human  molars  owing  to  want  of  room  consequent  on  the  develop- 
ment of  the  talon  of  the  upper  teeth.  The  following  table  shows  the  homologies  of  the  cusps 
of  the  hiunan  luolars  acxordiog  to  Osborn. 

Upper  MotARs. 

Anterior  lingual .  Protocone. ) 

Anterior  buccal Paracone.    V  Forming  the  triangle. 

Posterior  buccal Metacone.  ) 

Posterior  lingual Hypocone.    The  talon. 

Lower  Molars. 

Anterior  buccal Protoconid.     1  „  .    r  ^ 

Anterior  lingual Metaconid.      1  '*^'""''"*  °'  tnangle. 

Posterior  buccal H)poconici.     ) 

Posterior  lingual Entoconid.       }  The  talon. 

Posterior Hypoconulid.  J 

R.ise  has  advanced,  in  support  of  his  theory  of  concrescence,  thai  calcification  begins  sepa- 
rately for  each  cusp.  Osborn  jxiints  out  that  R.ise  has  shown  that  they  ossify  ver\-  nearlv  in 
the  order  of  their  alleged  evolution.  Schwalbe'  professes  himself  un.ible  to  deci'de  on  the 
relative  merits  of  the  two  theories. 

Variations.  -Variations  of  the  cusps  and  of  the  fangs  have  been  descril)ed  with  the  teeth. 
Those  of  niinil)er  affect  chiefly  the  incisors  and  molars.  An  additional  incisor  may  occur  on 
one  or  both  sides  in  either  dentition,  not  verv  rarely  in  the  upper  jaw,  but  extrem<"ly  so  in  the 
lower,  the  condition  in  the  latter  being  more  stable.  Extra  upper  incisors  are  often  more  or  less 
displaced  to  the  rear  and  implanted  obliquely-.  Thev  are  particularly  common  in  cases  of  cleft 
pal:ite ;  not  impossibly  the  presence  of  additional  teeth  predisposes  to  the  non-union  of  the 

'  Anatoni.  Anzeiger.  Hd.  vii.,  iHq2. 

'  Jenaische  Zeitschrift,  Ikl.  xxviii..  1893. 

'  Journal  of  .\torpholog>'.  i8,SS.  i.S.St). 

♦  .Vmerican  Naturalist,  i8S,S,  and  International  Dental  Journal,  1895. 

'  Anatoni.  -Xn/eiger,  Bd.  ix.,  1894. 


THE  GUMS. 


IS67 


pictiMxilUry  and  the  maxillonr  bones,  or  to  the  non-union  oi  two  parts  al  the  fiHmer,  su|)piMinK 
that  two  Mich  parts  really  exM.  The  extra  inciitor  nviy  a|>piireiitlv  a|>t)enr  on  the  meUun  •■itfe 
of  the  first,  between  the  nret  and  second,  or  between  the  lattrr  and  the  ranintr.  Tu  aicnuiit  for 
this  Rosenberg'  asserts  that  the  typical  number  h  five,  a»  in  the  oiHMKum,  of  which  the  iiecond 
and  fourth  are  the  two  persistent  ones,  and  that  either  the  first,  tnircl,  or  fifth  nviy  occasionully 
present  itself.  Th.  Ktilliker  *  records  a  case  of  rieht  cleft  (talate  in  which,  besidcH  the  fiHir  regular 
iiK'isurs,  three  were  found  between  the  cleft  ami  the  rixht  canine.  Ah  cases  of  exces.s  of  incisors 
are  much  more  common  titan  of  deficiency,  the  diHii|)|)earance  of  the  U(>|>er  lateral  one  does  not 
seem  imminent ;  still,  there  are  signs  of  deitetterativn.  The  crown  is  less  s<|iiare  than  that  of  the 
central,  it  is  occasionally  pointed,  often  unusually  smill,  sometimes  not  reachiiiK  the  line  <if  the 
other  crowns.  It  may  be  absent,  and  then  a  series  of  cases  can  be  made  ran^ini;  from  those  in 
which  the  remainine  incisor  is  separated  both  from  its  fellow  of  the  other  side  and  from  the 
canine  beside  it  by  lar^e  ^aps  to  those  in  which  the  teeth  are  reeular  and  continuous.  Very 
rarely  one  of  the  lower  incisors  is  wantingi  and,  according  to  Rosenberg,  either  i.iay  fail. 

A  fourth  molar  is  very  uncommon  ;  but  not  at  all  rarely  the  wisdom-t<H>th  is  late  in  coming 
through  the  gum,  and  occasioiully  it  never  does.  It  seems  sometimes  to  be  wanting  and  often 
is  ruuimentary.  It  has  t>een  seen  represented  by  three  detached  cusps,  an  apimrent  confirmation 
of  K(>se's  views  of  the  homology  of  the  teeth. 

The  entire  dental  series  may  be  unusually  large  or  small.  In  the  former  case  the  fare  is 
prognathous,  probably  as  a  result  oi  the  increase  cI  space  required  for  the  teeth.  The  up|>er 
central  incisors  are  occasionally  very  large  without  increase  in  size  of  the  other  teeth.  Thes;ime 
is  true  of  the  molars ;  in  which  case  the  number  oi  cusps  is  generally  greater,  but  the  converse 
does  not  occur  when  the  molars  are  unusually  small.* 

The  points  of  the  canines  may  project  beyond  the  line  of  the  other  teeth  am  1  e  molars  may 
increase  in  size  from  the  first  to  the  third. 

Teeth  are  sometimes  remai  kably  displaced.  The  superior  canines,  owing  to  their  hii;h  origin 
in  the  setond  dentition,  are  particularly  subject  to  it.  They  may  appear  on  the  front  of  the  jaw, 
in  the  antrum,  the  nose,  or  the  back  oi  the  mouth.  The  molars,  and  especially  the  wisdom-teeth, 
are  also  erratic. 

THE  GUMS. 

This  term  b  used  rather  vaguely  to  indicate  the  mucous  membrane  aitd  sub- 
mucous tissue  covering  the  alveolar  processes  and  closely  attached  to  the  necks  of 
the  teeth.  Whether  the  neck  is  entirely  surro-  ded  by  it  varies  in  different  indi- 
viduals as  the  teeth  are  not  in  all  equally  close  ;  as  a  rule,  owing  to  the  ordinary 
expansion  of  the  crown  from  the  neck,  at  lea.st  a  little  of  the  gum  is  found  l:)etween 
the  teeth.  It  is  some  3  mm.  thick,  dense,  firmly  fastened  to  the  bone,  and  is  neither 
very  vascular  nor  very  sensitive. 

In  structure  the  gums  resemble  other  parts  of  the  oral  mucous  membrane,  con- 
sisting of  the  epithelium  and  the  connective-tissue  layer.  The  latter,  directly  con- 
tinuous with  the  periosteum  of  the  alveolar  border  and  the  pericementum,  is  comjiosed 
of  closely  fitted  bundles  of  fibrous  tissue  and  beset  with  numerous  papilbe.  On 
young  teeth  the  epithelium  is  prolonged  for  from  .5-1  mm.  over  the  enamel  and  often 
for  a  short  additional  distance  over  the  cement,  ending  in  an  abrupt  margin.  In  the 
immediate  vicinity  of  the  tooth  the  papillae  sometimes  exhibit  infiltrations  of  lym- 
phoid cells.  The  gums  are  without  glands.  The  structures  sometimes  described  as 
such,  as  the  "  glands  of  Serres,"  consist  of  nests  of  epithelial  cells  derived  from  the 
remains  of  the  atrophic  embryonal  epithelial  sheath  (page  1563). 


THE   PALATE. 

The  Hard  Palate. — ^The  shape  and  proportions  of  the  hard  palate  have  been 
discussed  with  the  bones  (p^e  228),  so  we  ha\e  here  to  do  only  with  its  mucous 
covering.  This  is  very  firmly  fastened  to  the  rough  surface  of  the  bones  by  dense 
connective  tissue  which  is  particularly  thick  at  the  sides,  doing  much  to  fill  up  the 
angle  between  the  roof  and  the  alveolar  process.  On  either  side  near  the  front, 
extending  onto  the  inner  surface  of  the  alveolar  processes,  is  a  series  of  raised  ridges 
(  Fig.  1 325  ) ,  in  the  main  transverse,  although  slightly  convex  anteriorly,  the  analogues 
of  the  palatal  ruga  of  most  mammals.  They  never  extend  behind  the  first  molar 
tooth,  are  numerous  and  prominent  in  childhood,  but  much  reduced  in  middle  age, 
and  occasionally  wht>lly  lost. 

'  Morphol.  Jahrbuch.  Bd.  xxii.,  1895. 

Nova  Arte  des  Leopold.  Carol.  Akad.  der  Naturforscher,  Bd.  xliii.,  i88a. 
•  Magitot  :  Traits  des  Anomalies  du  Syst^me  Dentaire,  1887. 


■■it 


1568 


HUMAN  ANATOMY. 


Just  behind  the  incisors,  at  or  before  the  incisor  canal,  there  is  a  small  raised 
pad  or  fold  of  mucous  membrane,  on  either  side  of  which  the  orifice  of  the  incisor 
canal  is  often  found.  When  pervious,  it  is  very  minute,  admitting  merely  a  bristle. 
Behind  this  the  palate  presents  a  median  rc^he  of  paler  color  than  the  resc,  which  may 

Fio.  1325. 


OrtficM  of  palatine  glands 


Inclwr  pad  with  orifice  of  inciaor 
canal 


Raphe 


Mucous  membrane  removed  to 
show  layer  of  glands 


Soft  palate 


Superior  dental  arch  and  lalate ;  palatal  rugsc  occupy  aiilerii)r  (art.    Soft  palate  partially  cut  away. 


run  to  the  root  of  the  uvu'a  or  may  stop  short  of  it,  bt-injf  often  deflected  to  the  left. 
A  little  behind  the  pad  this  line  may  be  interruptetl  by  a  pale  oval  elevation  or  more 
often  a  depression.  The  membrane  of  the  roof  of  the  mouth  is  nowhere  bright  red  ; 
that  of  the  hard  palate,  however,  is  paler  than  the  rest.  There  are  no  glands  in  the 
o\al  white  space,  but  there  is  a  continuous  layer  on  either  side  of  it.  The  orifices  of 
the  glands  are  easily  seen  with  a  lens,  sometimes  with  the  naked  eye.     A  little  in 

Fig.   1.136. 


"i^Krtfe^: 


Muscular  fibres  of  tongue 


Dorsal  sitr 


"  tongue  f/    ^^' 


Anterioi  pillar  of  fauces 

iMica  triangularis'^ 


Tonsil 


-Soft  palate 

.Supratonsillar  tons 
Uvula 

Posterior  pillar  of  fauces 


Epiglottis 


Sagittal  section  through  palate,  uvula,  and  tongue,  showing  right  lateral  wall  of  fauces;  tongue  has  been  pulled 

downwani  by  hook. 

front  of  the  origin  of  the  soft  palate  the  mucous  membrane  becomes  deeper  colored. 
These  differences  in  color  are  more  striking  in  children. 

The  Soft  Palate.— This  structure  consists  of  a  fold  of  mucous  membrane,  con- 
tinuous with  the  hard  palate,  enveloping  seveml  l.iyprs  of  interlacing  muscular  fibres. 
at  least  i  cm.  in  thickness  at  iu  origin.     Its  lower  border  is  the  edge  of  the  fold. 


THE  PALATE. 


I5«9 


This  is  concave  on  each  side,  and  presents  a  median  elongation,  the  uvula,  which 
varies  from  a  short  prominence  to  a  cord  2  cm.  in  length.  Thus  the  palate  has 
a  lower  surface  lookmg  downward  and  forward  and  an  upper  one  looking  upward 
and  backward.  When  the  mouth  is  closed  the  palate  and  uvula  rest  against  the 
tongue  ;  when  open  they  hang  free,  but  the  muscles  inside  can  modify  their  shape 
and  position.     Median  sections  show  the  tip  of  the  uvula  often  reaching  within  half 


Fio. 


1337- 


Pharynfml  miicoat  mcfflbran* 


endon  o(  tenaor  pkUtI 
Levator  palati     PalXopharj-ngciu 


Masses  of  glands  Oral  mucous  membrane 

Transverse  section  of  soft  palate  near  its  anterior  attachment.    X  4. 


an  inch  of  the  tip  of  the  epiglottis.  Possibly  muscular  relaxation  allows  it  to  descend 
somewhat  farther  than  in  life,  but  it  is  certain  that  no  very  great  elongation  is  neces- 
sary for  it  to  touch  that  organ  and  give  rise  to  great  discomfort.  The  soft  palate  can 
be  raised  so  as  to  touch  the  back  of  the  pharynx  and  close  all  communication  between 
the  nose  and  the  mouth.  Two  folds,  the  pillars  of  the  fauces,  each  the  reflection  of 
the  mucous  membrane  over  a  muscular  bundle,  start  from  the  palate  on  either  side. 
The  anterior  pillar,  enclosing  the  palato-glossus  muscle,  arises  from  the  front  of  the 
palate  near  the  uvula,  some  distance  anterior  to  the  edge,  and,  curving  downward, 
runs  to  the  tongue  at  the  junction  of  the  middle  and  posterior  thirds,  separating  the 
mouth  from  the  pharynx  and  forming  the  posterior  border  of  the  sublingual  space. 
The  posterior  pillar  starts  from  the  lower  border  of  the  palate  on  either  side  of  the 
uvula,  covering  the  palato-pharyngeus,  and  runs  down  the  throat  to  the  superior  cornu 
of  the  thyroid  cartilage,  the  lower  part  being  indistinct.  Some  of  the  muscular  fibres 
within  it  go  to  the  upper  border  of  the  thyroid  cartilage  in  front  of  the  horn,  but  the 
fold  is  not  often  found  so  low,  except  in  frozen  sections,  in  which  it  appears  at  the 
sides  of  the  back  of  the  pharynx. 

A  deep  triangular  recess  on  either  side,  between  the  anterior  and  posterior 
pillars,  contains  the  tonsil.  This  region  is  often  vaguely  described  as  the  isthmus  of 
the  fauces,  one  being  left  in  doubt  whether  it  belongs  to  the  pharynx  or  to  the  mouth. 
In  the  preceding  pages  the  pharynx  is  described  as  beginnmg  at  the  anterior  pillar. 

The  reasons  for  this  divi- 
Fio.  1328. 

Fibres  of  azygos  uvulie  Phar>'ngeal  mucous  membrane 


Fibres  of 
palato-pharynj^us 


lands 


sion  are  developmental, 
morphological,  and  phys- 
iological. The  part  of 
the  tongue  anterior  to 
this  fold  is  of-  mandibular 
(buccal)  origin,  while  the 
part  behind  it  comes  from 
the  pharynx.  The  sur- 
face of  the  former  is  sup- 
plied by  the  mandibular 
ner\e,  the  third  division 
of  the  fifth,  and  the  latter  by  the  glossopharyngeal.  The  mucous  membrane  of  the 
posterior  third  does  not  bear  papillse  (except  the  circumvallate  papillae  near  the  junc- 
tion of  the  two  regions),  but  is  rich  in  adenoid  tissue  and  glands,  differing  in  both 
respects  from  the  part  in  front  of  it.  The  arrangement  of  the  transverse  fibres  of  the 
glosso-palati  muscles  in  the  substance  of  the  tongue  suggests  a  sphincter  at  the 
entrance  of  the  ph-irynx.  Ftn.illy,  in  degltttition  it  is  in  passing  this  line  that  the 
bolus  ceases  to  be  under  the  control  of  the  will. 

99 


Masses  of  glands  Oral  mucous  membrane 

Transverse  section  of  soft  palate  near  base  of  uvula.     X  4. 


i?i> 
m 


.'*§-*  I 


•a  -i  i 


t57o 


HUMAN  ANATOMY. 


The  following  layers  compose  the  soft  palate  from  above  downward  :  ( i )  The 
pharyngeal  mucous  membrane.  (2)  A  fibro-muscular  iayer.  The  fibrous  portion 
IS  the  expansion  of  the  tendons  of  the  tensor  palati  muscles.  It  is  strong  and  tense 
near  the  hard  palate,  gradually  dwindles  lower  down,  and  joins  the  pharyngeal 
aponeurosis  at  the  sides.  Below  this  is  the  complex  of  the  muscles.  (3)  A  glan- 
dular layer  opening  into  the  mouth.  This  is  soiiit;  5  mm.  thick  at  its  origin  and 
{}ractically  continuous  throughout  most  of  the  palate.  It  is  interrupted  at  the  median 
line  near  the  hard  palate  by  a  septum  of  muscular  and  fibrous  tissue,  is  wanting  near 
the  free  edge  of  the  palate  a  littie  on  either  side  of  the  root  of  the  uvula,  and  is  con- 
tinued down  the  uvula  as  a  cylindrical  string  of  glands  nearly  to  the  tip,  through  and 
about  which  run  the  fibres  of  the  azygos  uvulae  muscle.  Irregular  glandular  collections 
are  found  near  the  latter,  especially  at  the  base  of  the  uvula.  (4)  A  lower  layer  of 
mucous  membrane. 

The  mucous  membrane  of  the  soft  palate  is  red  on  the  pharyngeal  and  pale  on 
the  buccal  surface ;  on  both  sides  it  presents  papillae,  those  on  the  upper  surface 


Fig.  1339. 


Glandi 


AponcurMic  tissue 


Oral  mucous  membrane 


Sagitto-lateral  Mction  of  soft  palate.    X  15. 

especially  being  near  the  base.  The  most  common  form,  slender  and  elongated,  is 
scattered  over  the  entire  buccal  surface  and  the  front  of  the  uvula  (Riidinger). 
Thicker  short  papillae  are  also  found  near  the  beginning  of  the  pharyngeal  surface. 
Small  adenoid  collections  occur  on  the  upper  surface,  as  well  as  small  glands  situated 
in  the  depth  of  the  mucous  membrane.  The  orifices  of  the  chief  glandular  layer 
pierce  the  inferior  palatal  surface. 

The  Muscles  of  the  Soft  Palate.— Some  of  the  muscles  arise  in  the  soft 
palate  ;  others  run  into  it.  Isolation  of  the  individual  sets  of  fibres  is  not  always 
possible. 

The  tensor  palati  ( dilatator  tuba)  {  Fig.  1 330)  arises  from  the  scaphoid  fossa  at 
the  root  of  the  internal  pterygoid  plate,  from  the  spine  of  the  sphenoid,  and  from  the 
outer  membranous  part  of  the  Eustachian  tube.  It  descends  vertically  along  the 
internal  pterygoid  plate  as  a  round,  red,  and  distinct  muscle,  which  becomes  tendinous 
as  it  turns  inward  under  the  hamular  process  at  right  angles  to  its  previous  course, 
after  which  it  broadens  into  the  fibrous  expansion  in  the  soft  palate  already  described, 
above  the  other  muscles.     A  bursa  lies  between  the  tendon  and  the  hamular  process. 


THE  PALATE. 


»57« 


The  levator  palati  (Fig.  1330)  arises  from  the  base  of  the  skull  at  the  apex 
of  the  petrous  portion  of  the  temporal  bone  and  from  the  cartilaginous  part  of  the 
Eustachian  tube  beside  it.  At  first  thick,  it  passes  downward,  forward,  and  inward 
with  the  tube,  and,  leaving  it,  expands  into  a  layer  which  spreads  out  through  the 
soft  palate.  Some  of  the  anterior  fibres  from  the  tube  go  to  the  back  of  the  hard 
palate,  con  cituting  the  salpingo-palatinus,  while  others  descend  in  the  lateral  wall  of 
the  pharynx,  covered  by  mucous  membrane,  beneath  the  salpingo-pharyngeal  fold. 
The  great  body  of  the  fibres  crosses  the  middle  line  in  the  front  part  of  the  soft 
palate.  Most  of  them  descend  in  the  opposite  side.  Some  seem  to  form  loops  with 
an  upward  concavity  with  fibres  from  the  fellow-muscle.  Near  the  hard  palate  this 
decussation  completely  divides  the  glandular  layer  (Fig.  1327). 

The  azygOB  uvulae  (Fig.  1331),  although  probably  a  double  muscle  originally, 
soon  (even  at  birth)  becomes  practiodly  a  smgle  one.  Arising  from  the  tendinous 
fibres  of  the  tensor  palati  just  behind  the  postenor  nasal  spine,  it  soon  becomes  mus- 
cular and  increases  in  size.  Its  course  b  downward  into  the  uvula,  but  on  reaching 
the  base  it  is  already  broken  up  into  separate  bundles  which  pass  about  and  through 

Pio.  1330. 

Hmid  |»bt* 


HamuUr 

Tensor  palati 
Levator  palati 


palate  (rut) 

External  pterygoid  plate 

Posterior  nares 

.Opening  ot  Kustachian  tufa* 


Cut  edge  of  pharynx 
Mass  of  t»  Jcnoid  tissue 


Fossa  of  Rosenmiiller 
(opened) 

Styloid  process 


Occipital  condyle 
Inferior  surface  o(  skull  with  upper  part  of  opened  pharynx  and  palaul  muscles  attached  ;  viewed  from  behind. 

the  glandular  core  of  the  uvula.  The  belly  of  the-  muscle  lies  near  the  dorsal  surface, 
between  the  fibrous  expansion  of  the  tensor  palati  and  the  levator  palati,  which  decus- 
sates on  its  oral  surface. 

The  palato-pharyngeus  (Fig.  1331)  has  a  complicated  origin  in  mure  than 
or.  .yer  from  the  Iwrder  of  the  hard  palate,  from  the  lower  surface  of  the  apo- 
.urosis,  and  perhaps  from  fibres  of  the  levator  palati.  Certain  fibres,  either  arising 
in  the  middle  line  or  coming  from  the  other  side,  pass  downward  and  outward 
over  the  azygos  uvulae  ;  others  lie  beneath  the  glandular  layer.  Some  of  the  fibi.-* 
seem  to  continue  the  course  of  the  salpingo-pharyngeus  of  the  opposite  side,  witii- 
out  being  directly  continuous.  The  muscle  passes  down  near  the  edge  of  the  soft 
palate  and  then  in  the  posterior  pillar  into  the  side  of  the  pharynx,  where  it  min- 
gles with  the  stylo-pharyngeus.  A  part  is  inserted  into  the  upper  border  of  the 
thyroid  cartilage,  and  sometimes  into  the  superior  horn.  It  also  expands,  together 
with  the  stylo-pharyngeus,  into  a  thin  layer  just  beneath  the  mucous  membrane 
of  the  back  of  the  pharynx,  which  meets  its  fellow  in  the  median  line  where  it  is 
inserted  into  the  pharyngeal  aponeurosis.  Its  lower  limit  is  a  curved  line  with  the 
concavity  looking  upward  and  outward,  behind  the  larynx  (Fig.  1361).    (This  fnirt 


1572 


HUMAN  ANATOMY. 


of  the  muscle  must  be  dissected  from  behind,  after  removing  the  constrictors  of 
the  pharynx. ) 

The  palato-glosBUS  (Fig.  1339)  is  a  small  bundle  arising  from  near  the  middle 
line  of  the  oral  side  of  the  lower  part  of  the  soft  palate,  forming  by  its  projection  the 
anterior  pillar  of  the  fauces,  in  which  it  runs  to  the  tongue,  where  it  joins  the  trans- 
verse fibres.  The  pair  of  muscles  act  as  a  sphincter  tending  to  close  the  passage  from 
the  mouth  to  the  pharynx.    A  thin  expansion  from  this  muscle  passes  over  the  tonsil. 

Vessels. — The  arteries  of  the  palate  (both  hard  and  soft)  come  chiefly  from 
the  descending  palatine,  which,  emerging  from  the  posterior  palatine  canal,  runs  for- 
ward along  the  inner  side  of  the  base  of  the  alveolar  process.     It  sends  a  few  branches 


Fio.  1331. 


Nasal  Mptum 


Eustachian  tube 


SalpifiRO- 
pharyiiKcu: 

l.i.-\:it(ir  iialatl 


Falato-pharyni 


I'jtuto-pharyngel 


Stylo-phao'ngi 


i Poslerior  surface  of  tongue 


Posterior  cri«>«ryteiK>id 


.(Esophagus 


Muscles  o(  palate  and  phannx,  seen  from  behind  ;  pharynx  laid  open. 

inward  and  backward  to  the  front  of  the  soft  palate,  which  is  supplied  on  the  side  by 
a  branch  either  from  the  facial  or  from  the  ascending  pharyngeal.  It  is  to  be  noted 
that  no  vessel  is  likely  to  interfere  with  the  division  of  the  tensor  palati  at  the  inner 
side  of  the  hamutar  process. 

The  veins  of  the  hard  palate  follow  in  the  main  the  arteries.  Those  of  the  upper 
side  of  the  soft  palate  join  the  plexus  of  the  zygomatic  fossa.  The  larger  ones  of  the 
under  side  connect  with  the  veins  of  the  tonsil  and  the  root  of  the  tongue. 

The  lymphatics  n\  the  h.ird  palate  ani  of  the  tindor  side  of  the  soft  palate  form 
a  rich  plexus.  Those  on  the  upper  side  of  the  latter  are  small.  The  chief  current  is 
to  the  deep  glands  of  the  neck. 


THE  TONr.lE. 


«57.T 


Nerves. — The  tensor  palati  is  supplied  by  the  mandibulai  iivision  of  the  fifth 
pair,  the  other  muscles  by  the  pharyngeal  plexus.  The  mucous  membrane  of  the 
hard  palate  is  supplied  by  the  anterior  palatine  nerve  and  terminal  branches  of  the 
naso-palatine.  That  of  the  soft  palate  is  supplied  by  the  other  palatine  nerves 
and  by  branches  from  the  glosso-pharyngeal. 

THE  TONGUE. 

The  tongue  is  a  median  muscular  organ  attached,  to  the  floor  of  the  mouth, 
the  symphysis  of  the  jaw,  and  the  body  and  both  horns  of  the  hyoid,  covered  with 
mucous  membrane,  which  when  the  mouth  is  closed  it  practically  fills  (Fig.  1339). 
The  root  is  the  attached  f)ortion,  extending  from  the  hyoid  to  the  symphysis,  com- 
posed of  the  genio-glossi  and  the  hyo-glossi  muscles.  The  tip  is  the  free  anterior 
end,  flat  both  above  and  below  when  extended,  and  surrounded  by  mucous  mem- 
brane. Behind  this  the  tongue  is  a  solid  mass.  The  dorsum  in  its  anterior  two- 
thirds  is  convex  from  side  to  side,  and  rests  against  the  hard  and  sofl  palates  ;  the 
[wsterior  third,  nearly  vertical,  looks  backward,  forming  the  front  wall  of  the  pharynx 
when  the  mouth  is  closed.  There  is  a  median  groove  in  the  upper  part  of  this  pos- 
terior third,  continued  for  a  little  distance  onto  the  top,  in  which  the  uvula  rests. 
This  hind  portion  is  so  broad  that  the  edges  of  the  tongue  reach  quite  to  the  sides 


Fig.  1332. 

Anterior  tongue  anlage 


II  arch 

III  arch 


Larynx 


Reconstruction  of  floor  of  primitivt  oro-phar>'njt  of  embryo 
12.J  mm.  in  length.    X  l&     \Hit.) 


Under  surface  of  tongue  of  new-bom  chilfl 


of  the  pharynx.  In  the  anterior  two-thirds  the  edges  of  the  tongue  are  prominent, 
overhanging  the  sides. 

Developme- '  -hows  that  the  tongue  has  a  double  origin,  the  posterior  third 
arising'  from  I  .  of  the  pharynx  and  overlapp'ng  on  each  side  the  anterior  two- 

thirds,  which  rom  a  median  ir> hss,  the  tuberculum  impar.  of  buccal  origin  (  Fig. 

1332).  The  /(_  lossal  duct  co.  •  to  the  surface  at  the  junction  of  these  parts, 
which  in  the  infant  are  separated  by  th»  sulcus  terminalis.  As  will  later  be  evident, 
the  manner  of  development  is  of  much  significance. 

The  mucous  membrane  of  the  lateral  and  inferior  surface  is  thin  and  smooth 
with  small  papillae  at  the  tip.  In  the  middle  it  forms  a  fold,  the  frtnum,  running 
from  near  the  tip  to  the  floor  of  the  mouth.  In  infancy  this  is  occasionally  so 
short  as  to  restrain  the  tip  of  the  tongue  from  the  motions  necessary  for  nursing. 
Often  it  is  hardly  visible.  The  plica  fimbriata  and  the  plica  sublingualis  are  two 
folds  on  either  side  of  the  front  part  of  the  under  surface,  of  which  the  former  with 
ragged  edges  is  the  outer,  the  longer,  and  the  larger.  Both  are  distinct  in  the  infant 
and  (especially  the  latter)  lost  or  poorly  marked  later.  The  plicx  fimbriate  bound 
a  triangular  space  which  Gegenbaur  considers  a  rudiment  of  the  undcr-tongue  of  some 
mammals.  The  mucous  membrane  of  the  dorsum  is  divisible  into  two  wholly  differ- 
ent regions  :  the  one  comprising  the  anterior  two-thirds,  the  other  the  posterior  ver- 
tical third.  The  line  of  .separation,  or  sulats  terminalis,  is,  however,  not  transverse, 
but,  starting  at  the  side  from  the  anterior  pillar  of  the  fauces,  runs  backward  and 
inward  to  meet  its  fellow.     This  is  not  usually  visible  in  the  adult  ;  but  its  place  is 


1574 


HUMAN   ANATOMY. 


easily  recognized,  as  just  before  it  is  a  V-shaped  arrangement  of  circumvallate  papillx, 
the  median  apex  being  at  or  near  a  small  depression,  the  foramen  cacum,  which 
marks  the  termination  of  the  foetal  duct  through  the  tongue  from  the  thyroid.  In 
the  adult  this  may  be  a  short  tunnel  or  a  depression,  into  which  the  ducts  of  several 
glands  open.     According  to  Miinch,'  it  is  always  behind  the  hindmost  circumvallate 


Fig.  1334. 


Cut  o'goma 

Pterygoid 
plates 
Euatachian 
tnbe 


Cut  and  reflected 

s4)tt  palatt 


Anterior  poitioii  of  head  has  been  removed  by  frontal  section  passing  through  plane  of  posterior  nares :  the  soft  palate 
cut  in  mtd-line  and  turned  aside,  exposing  posterior  wall  of  phar"'  x ;  tongue  drawn  forward  and  downward. 


papilla.  The  mucous  membrane  covering  the  dorsum  of  the  tongue  is  closely  beset 
with  elevations,  ox papillee,  of  which  there  are  three  varieties,  the  filiform,  fungiform, 
and  circumvallate.  In  general  they  consist  of  a  core  of  connective-tissue  stroma  cov- 
ered with  stratified  squamous  epithelium  ;  the  projection  formed  by  the  connective 
tissue  bears  minute  secondary  papillae,  which,  however,  do  not  model  the  free  sur- 

'  Morpholog  Arbeiten,  Bd.  vi.,  1896. 


THE  TONGUE. 


«575 


lace  of  the  mucous  membrane.  The  anterior  two -thirds  of  this  surface  are  rough 
with  fungiform  and  filiform  pafnlla ;  the  lormer,  less  numerous,  appear  as  red 
points  chiefly  near  the  edges,  while  the  filiform  are  everywhere,  but  arranged  in  par- 
allel rows  continuing  forward  the  lines  of  the  circumvallate  papillx.  At  the  edges  of 
the  tongue,  just  in  front  of  the  end  of  the  anterior  pillar  of  the  fauces,  close  inspec- 
tion, especially  with  a  lens,  will  generally  show  a  small  series  of  minute  transverse 
parallel  ridges,  corresponding  to  the  papilla  foliatte  of  rodents  in  a  rudimentary  con- 
dition. The  papUlct  circumvallcUa  are  fungoid  papillae  surrounded  by  a  depression 
bounded  externally  by  a  low  annular  wall.  The  usual  number  of  these  papilla-  is 
from  nine  to  ten,  rangmg  from  six  to  sixteen  (Miinch).  The  sides  of  the  V  in  which 
they  are  disposed  are  not  very  symmetrical.  Usually  there  is  at  lea.st  one  median 
papilla  behind  the  apex,  and  very  rarely  one  or  two  before  it.  The  circumvallate 
papillae  are  of  especial  interest  as  being  the  most  important  seat  of  the  gustatory  end- 


F«o-  1335- 


Filiform  papilla. 


Surface  epithelium  coveririK 
fungiform  papilla 

Projections  of  tunica  pro- 
pria coiutituting  basis  o( 
papilla 


•2^„Conneciive-tissue  stroma  of 
mutous  membrane 


.Muscular  tissue  of 
t(.  -.gue 


Section  of  lingual  mucous  membrane,  showing  filiform  and  fungiform  papills.    X  Tj. 


organs,  or  taste-buds,  which  lie  embedded  within  the  epithelium  lining  the  groove 
encircling  the  central  elevation.  A  detailed  description  of  the  tasie-buds  is  given 
with  the  organs  of  special  sense  (page  1433). 

The  surface  of  the  vertical  posterior  third  of  the  tongue  is  smooth,  in  the  sense 
that  there  are  no  papillae  nor  roughnesses,  but  it  is  studded  with  masses  of  lymphoid 
tissue,  sometimes  called  the  lingual  tonsil  (Fig.  1334),  which  make  numerous  eleva- 
tions on  its  surface.  The  mucous  membrane  of  the  back  of  the  tongue  is  continued 
in  a  thinner  layer  onto  the  front  of  the  epiglottis.  It  presents  the  median  glosso- 
epiglottic  fold,  containing  fibro-elastic  tissue  and  muscular  fibres  of  the  genio-glc^i, 
which  separate  two  little  depressions,  the  glosso-epiglottic  fossa.  These  may  be  with- 
out any  definite  lateral  boundary,  or  may  be  embraced  by  the  small  lateral  glosso- 
epiglottic  folds,  the  internal  borders  of  which  are  concave.  The  mucous  membrane 
is  firmly  attached  to  the  subjacent  muscles  in  the  anterior  two-thirds  of  the  tongue, 
but  less  firmly  behind. 

Glands  of  the  Tongue. — The  lingual  glands  include  both  serous  and  mucous 
varieties,  which  are  distributed  as  three  group  :  (i)  serous  glands,  (2)  posterior 
mucous  glands  and  (3)  anterior  mucous  glands. 


IS7* 


HUMAN   ANATOMY. 


The  tubo-alveolar  glands  surrounding  the  circumvallate  and  the  foliate  papillx 
are  the  only  ones  of  a  purely  serous  type  ;  their  thin,  watery  secretion  is  no  doubt  an 
important  medium  in  conveying  sapid  substances  to  the  taste-buds  situated  in  this 


Epithelium  coverinir 
Bliform  papilla 


CBplllary  loops  within 
connective-tissue  basis 
of  papilla 


HK-    Mucous  membrane 


Muscular  tissue 


Injected  mucous  membrane  and  subjacent  areolar  and  muscular  tissue  from  upper  surface  of  tongue.    X  60. 

Fio.  1337. 


Annular  wall 


1^ Serotu  gland 


Muscular  tissue  »••  >■!>   »      •- 

Section  across  circumvallate  papilla  from  child's  tongue,  showing  central  portion  and  encircling  fold.    X  w. 

vicinity.  The  glands  encircling  the  circumvallate  papillse  constitute  an  annular  group 
some  4  mm.  wide  and  about  twice  as  deep.  Those  about  the  papillae  foliata  form  an 
elongated  group,  about  3.5  mm.  in  width,  which  extends  from  8-15  mm.  in  front  of 


THE  TONGUE. 


«577 


the  base  of  the  palato-glossal  fold.  Anteriorly  towards  the  dorsum  the  serous  glands 
remain  isolated  ;  posteriorly  they  come  into  contact  with  the  mucous  glands,  so  that 
alveoli  of  both  varieties  may  be  included  within  a  single  microscopical  hold  (  Fig.  1 287  ). 

The  posterior  third  of  the  dorsum,  from  the  circumvaltate  papilla-  backward, 
possesses  a  rich,  almost  continuous  layer  of  mucous  glands,  5  mm.  or  more  in  thick- 
ness, which  lie  beneath  the  mucous  membrane  and  mingle  with  the  lymphoid  tissue. 
Since  the  alveoli  lie  among  the  muscles  at  some  depth,  the  excretory  ducts  often 
attain  a  length  of  from  10-15  mm.,  and  open  on  the  free  surface  in  close  asstKiation 
with  the  lymph-follicles. 

The  anterior  mucous  glands  (Fig.  1287)  are  disposed  principally  as  two  elon- 
gated groups,  glandula  linguaUs  anteriores,  or  glands  of  Nuhn,  or  of  Blandin 
(from  15-20  mm.  in  length,  7-9  mm.  in  width,  and  somewhat  less  in  thickness), 
which  lie  on  either  side  of  the  mid-line,  near  the  tip  of  the  tongue,  among  the  mus- 
cular bundles.     They  meet  in  front,  but  diverge  behind,  where  they  may  be  con- 


Fic.  1338. 


LympliHiodct 


Clandi 


itterlacin|(  fibrous  and 
muscular  bundles 


Section  from  posterior  third  of  child's  tongue,  showin);  lymph-nodea  constituting  a  part  of  lingual  tonsil,    y  jo. 


tinned  backward  by  additional  collections  of  mucous  glands  along  the  edges  of  the 
tongue.  The  ducts — five  or  six  in  number— open  on  the  folds  occupying  the  under 
surface  of  the  tongue  near  the  frenulum. 

Muscles  of  the  Tongue.— These  include  two  groups,  the  extrinsic  and  the 
intrinsic  muscles.  The  former  pass  from  the  skull  or  hyoid  bone  to  the  tongue  ;  the 
latter  comprise  the  particular  muscles  both  arising  and  ending  within  the  organ.  Their 
general  arrangement  is  as  follows.  Under  the  mucous  membrane  is  a  dense  sheath 
of  longitudinal  fibres,  surrounding  the  others  completely  near  the  apex,  and  farther 
back  wanting  at  the  middle  of  the  under  surface  where  the  fibres  of  the  genio-glossi 
and  hyo-glossi  enter  the  organ.  This  outer  layer  is  the  cortex.  The  inner  part  is 
divided  into  two  by  a  vertical  median  septum  of  areolar  tissue,  which  is  quite  dense 
in  its  upper  part.  It  is  sickle-shaped,  with  the  point  in  front  and  not  reaching  the 
apiex.  The  inner  jwrtion,  or  medulla,  is  composed  of  transverse  muscle-fibres  inter- 
posed between  layers  of  those  called  vertical,  which  in  fact  present  many  degrees  of 
obliquity. 

The  extrinsic  muscles  are  the  genio-glossus,  the  kyo-glossus,  the  stylo-glossus, 
and  the  palato-glossus,  to  which  may  be  added,  from  its  jx)sition,  the  genio-hyoid. 
All  of  these  are  in  pairs  and  symmetrical. 


1378 


HUMAN  ANATOMY. 


The  (enio-hyoid  (Fig.  1339)  is  a  coller-tion  of  fleshy  fibres  extending  cluae  to 
the  median  line,  from  the  iniFerior  genial  tubercle  to  the  anterior  surface  of  the  body 
of  the  hyoid  bone.  It  is  a  thick  band,  four-sided  on  transverse  section,  with  rounded 
angles,  and  expands  laterally  on  approaching  its  insertion.  A  layer  of  areolar  tissue 
separates  it  from  its  fellow. 

Nerve. — ^The  nerve-supply  is  from  the  hypoglossal,  but  probably  consists  of 
fibres  derived  from  the  cervical  nerves. 

ActioH. — ^To  draw  the  hyoid  forward  and  upward ;  or,  when  fixed  below,  to 
depress  the  mandible. 

The  genio-glouus  (Fig.  1339)  arises  just  above  the  preceding  by  short  ten- 
dinous fibres  from  the  superior  genial  tubercle.  Its  inferior  fibres  run  horizontally 
backward  to  the  base  of  the  tongue,  passing  over  the  hyoid  bone  to  the  base  of  the 
epiglottis  ;  the  fibres  above  these,  inserted  successively  into  the  mucous  membrane  of 

Fio.  1339. 


Stinnp  of  nuMder 


Hatnul; 

•"«■"»    SlyToid. 

Superior  constrictor 
Plerygo-mandibuUr  ligament 

Stylo-KlOMtu. 


Hvoid  bone, 
Thyro-hyotd 

Inferior  conitrictor. 


Phar)!!!^!  and  extrinsic  lingual  muacle* 


the  dorsum  of  the  tongue  near  the  middle  line,  are  at  first  oblique,  then  vertical,  and 
finally  concave  anteriorly  as  they  approach  the  apex,  so  tliat  the  muscle  is  fan-shaped 
when  seen  from  the  side.  Each  muscle  is  separated  from  its  fellow  by  the  median 
septum. 

Nerve. — The  hypoglossal. 

Action. — ^The  complex  action  of  this  muscle  includes  retraction  of  the  tongue  by 
the  anterior  fibres,  drawing  forward  and  protrusion  by  the  posterior  fibres,  and  depres- 
sion, with  increased  concavity,  of  the  dorsum  by  its  middle  part. 

The  hyo-glo8Sus  (Fig.  1339),  external  to  the  preceding,  from  which  it  is  sepa- 
rated by  areolar  tissue,  arises  from  the  side  of  the  body  of  the  hyoid,  the  whole  of  the 
greater  horn,  and  the  lesser  horn.  The  last  portion,  rather  distinct  from  the  rest,  is 
described  sometimes  separately  as  the  chondro-glosbus.  The  whole  muscle, 
applied  to  the  side  of  the  tongue,  forms  a  layer  of  fibres  directed  upward  and  for- 


THK  TONC.UE. 


»579 


ward  ;  towards  the  front  its  fibres  are  almost  longitudinal.  The  fibres  from  the  lesser 
horn  run  on  the  dorsum  beneath  the  mucous  membrane,  forming  a  part  of  the  super- 
ficial longitu.'inal  system. 

Nerve. — The  hy|x»t{l(>ssal. 

Actum. — To  depress  the  sides  of  the  tongue,  thereby  increa.sing  the  transverse 
convexity  of  the  dorsum  ;  the  muscle  also  retracts  the  protruded  tongue. 

The  ttylo-glOMut  (Fig.  1339)  arises  from  the  tip  of  the  styloid  process  and 
from  the  beginning  of  the  styio-maxillary  ligament  It  is  a  small  ribbon-like  muscle 
with  an  anterior  and  a  posterior  surface,  but  as  it  descends  it  twists  so  as  to  lie  along 
the  outer  side  of  the  tongue,  which  it  reaches  in  the  region  of  the  circumvallate 
papills.  On  joining  the  tongue  the  fibres  divide  into  an  upper  and  a  lower  bundle, 
both  of  which  are  chiefly  longitudinal,  although  some  fibres  blend  with  the  transverse 
scries.     It  is  soon  lost  in  the  sheath  of  longitudinal  fibres. 

Nerve. — The  hypoglossal. 

Action. — To  retract  the  ton"".-  and  to  elevate  the  sides,  thus  aiding  in  pro- 
ducing transverse  concavity  of  the  uorsum. 

The  palato-glosaus  (Fig.  1339)  arises  from  the  anterior  or  buccal  aspect  of 
the  palate,  and  descends  within  the  fold  forming  the  anterior  pillar  of  the  fauces  to 
the  tongue,  where  it  joins  the  transverse  fibres,  passing  between  the  two  parts  of  the 
stylo-glossus. 

Nerve. — From  the  pharyngeal  plexus,  the  motor  fibres  coming  probably  from 
the  spinal  accessory  nerve. 

Action. — To  elevate  the  tongue,  to  depress  the  soft  palate,  and,  with  its  fellow 
by  approximating  the  anterior  pillars,  to  close  the  fauces. 


Lonyitodinml  fibres 


Fio.  1340. 


TranivrrM  fibn* 


Plio  fimbriata 


Glandi 
Trantverse  Mctioo  of  ton(iie  of  child,  near  tip. 


Vertical  fibrea 


The  intrinsic  muscles  are  the  lingualis,  the  transversus,  and  \.\\e  perpendicu- 
laris  (Fig.  1340). 

The  lingualis,  sometimes  divided  into  a  superior  and  an  inferior,  comprises  the 
greater  ni  .Tiber  of  »Vf  longitudinal  fibres, — all,  in  fact,  that  do  not  come  from  the 
extrinsic  muscles.      '  ;»e  thickness  of  this  layer  is  some  5  mm. 

The  transversus  furnishes  nearly  all  the  transverse  fibres,  the  most  important 
extrinsic  contribution  being  from  the  palato-glossus.  It  arises  from  the  septum  and 
runs  outward  to  the  mucous  membrane  ;  as  it  approaches  the  cortex  the  fibres  break 
up  into  bundles,  among  which  pass  groups  of  the  fibres  of  the  lingualis.  The  trans- 
versus is  arranged  in  a  series  of  vertical  layers,  between  which  pass  layers  of  the 
vertical  set.  Thus  a  horizontal  section  has  the  effect  of  a  series  of  transverse  fibres 
like  the  bars  of  a  gridiron  with  the  cut  ends  of  the  vertical  fibres  between  them  and 
the  longitudinal  fibres  cf  the  lingualis  at  either  side.  Near  the  apex  fibres  of  this 
system  run  directly  from  the  mucous  membrane  of  one  side  to  that  of  the  other. 

The  perpendicularis  is  the  name  given  to  the  few  vertical  fibres  that  do  not 
come  from  the  extrinsic  muscles.  They  occur  chiefly  at  the  tip  and  sides,  passing 
from  the  lower  to  the  upper  mucous  membrane. 

Nerve. — All  the  intrinsic  muscles  are  supplied  by  the  hypoglossal. 

Action. — The  tongue  is  protruded  chiefly  by  the  action  of  the  posterior  fibres  of 
the  genio-glossus,  drawing  the  posterior  part  of  the  tongue  forward,  assisted,  perhaps, 
by  the  contraction  of  the  transversus.     It  is  withdrawn  by  its  own  weight.     The 


r5«o 


HUMAN  ANATOMY. 


lon^tudiiul  system,  the  various  paits  of  which  can  act  separately,  turns  the  tip  in 
any  direction.  The  styio-f^loMus  and  palato-glos.sug  raise  the  posterior  portion, 
paitiirularly  at  the  edges,  but  the  latter  probably  acts  more  on  the  palate  than  on  the 
tongue. 

VcMeU. — The  principal  arteries  supplying  the  tongue  are  branches  of  the 
lingual,  elsewhere  described  (page  735).  Although  there  may  be  a  trifling  ana.sto- 
mosis  at  the  tip  between  the  vessels  of  the  opposite  sides,  there  is  no  communication 
sufficient  to  re-establish  the  circulation  at  once,  so  that  ligation  of  either  artery 
will  render  that  half  of  the  tongue  bloodless  for  an  operation.  The  veins  consist  of 
four  sets  on  each  side,  communicating  freely  with  one  another.  They  are  (  i  )  the 
dorsal  veins  forming  a  submucous  plexus  on  the  back  of  the  tongue  above  the  larynx 
and  joining  those  of  the  tonsil  and  pharynx,  (2)  two  veins  accompanying  the  artery 
and  iiometimes  forming  a  plexus  about  it,  (3)  two  with  the  lingual  nerve,  (4)  two 
with  the  hypoglossal  nerve.  Of  these  latter,  the  one  below  the  ner\e  is  the  larger 
and  is  the  ranine  vein,  running  on  the  under  surface  of  the  tongue  on  either  side  of 
the  frenum.  The  lymphatics  present  a  rich  net-work  on  the  anterior  two-'hirds  of 
the  dorsum.     The  multitude  of  spaces  throughout  the  organ  communicate  with  ly.n- 


Fio.   1341, 


Lonjcitudinal  fibre* 


Glandi 


Ponion  ol  sublingual  glatid 


Vcrlira!  libreii 


Traii!.\crsf  (ilires 


Septum       Gcnio-glossua      Hyo-Klossua 


Tnnfvcne  Mction  of  tongue  of  child,  throuKh  middle  third.     ■  j. 

phatics.  Some  from  the  median  part  empty  into  the  suprahyoid  glands,  but  most 
go  to  the  submaxillary  and  to  the  deep  cervical  glands. 

Nerves. — The  motor  fibres  are  supplied  by  the  hypoglossal,  aided  probably  by 
the  facial  through  the  chorda  tympani.  Those  of  common  sensation  are  from  the 
lingual  branch  of  the  fifth  for  the  anterior  two-thirds  and  from  the  glosso-pharyngeal 
for  the  remainder,  excepting  the  region  just  in  front  of  the  epiglottis,  which  is 
supplied  by  the  superior  laryngeal  from  the  vagus.  The  glosso-pharyngeal  area 
somewhat  overlaps  the  posterior  third,  as  it  supplies  the  circumvallate  and  foliate 
papillae.  The  chief  fibres  of  special  sense  are  derived  from  the  glosso-pharyngeal, 
their  principal  distribution  being  to  the  taste-buds  on  the  circumvallate  papillae.  Re- 
garding the  source  of  the  taste-fibres  to  the  anterior  parts  of  the  tongue  opinions 
still  differ.  According  to  many  anatomists,  these  fibres  reach  their  destination 
through  the  chorda  tympani,  since  the  latter  nerve  is  supposed  to  receive  taste- 
fibres  from  the  ninth  by  way  of  the  pars  intermedia  of  Wrisberg,  which  accompanies 
the  facial.  According  to  Zander,' Dixon,' Spiller,' and  others,  however,  the  view 
attributing  fibres  of  special  sense  for  the  anterior  part  of  the  tongue  partly  to  the 
fifth  nerve  is  correct. 

Growth  and  Changes. — At  birth  the  tongue  is  remarkable  chiefly  for  its  want 
of  depth,  as  shown  in  a  median  section,  which  depends  on  the  undeveloped  condition 
of  the  jaws.     This  is  gradually  corrected  coincidently  with  the  growth  of  the  face. 

'  Anatomischer  Anzeiger,  Bd.  xiv.,  1897. 

•  Edinburuh  Medical  Journal,  1897. 

'  University  of  Pennsylvania  Medical  Bulletin,  March,  1903. 


THE  SUBLINGUAL   SPACE. 


15*1 


The  drcumvallate  papilla '  are  imperiectly  developed  lor  some  time  aher  birth,  so 
much  so  that  it  w  not  easy  to  recognize  them.  The  foliate  papilla-  arc  al^M)  rtlativily 
undeveloped.  On  the  other  hand,  the  funKif«>rm  papilla-  are  proiK>rtionatcly  both 
larger  and  more  numerous  than  in  the  adult.  The  development  of  the  adenoid  tiswuc 
at  the  bat'-  of  the  tongue  occurs  during  the  last  two  months  of  Icctal  life.  In  places 
the  connective  tissue  surrounding  the  ducts  of  the  mucous  glands  l)ecomes  infiltrated 
with  leucocytes  and  is  transformed  into  lymphoid  tissue  (Stohr). 

THE    SUBLINGUAL    SPACE. 

This  space  is  between  the  lower  jaw  and  the  tongue,  above  the  mylohyoid,  and 
bounded  behind  by  the  fold  of  the  anterior  pillar  of  the  fauces  pas.sing  to  thi-  tongue. 
It  is  lined  with  thin,  smooth  mucous  membrane  reflected  from  the  mandible  to  the 
tongue  and  attached  lightly  to  the  parts  beneath.  With  the  mouth  closed,  this 
space  is  filled  by  the  tongue.  It  is  best  examined  in  the  living  subject  when  the  tip 
of  the  tongue  is  against  the  upper  incisors.     A  fold  of  mucous  membrane,  the/rr«««», 


Fio.  134a. 


Plica  fitnbriata 


■SublitifTual  riMjfr 
.OriAcra  (if  submaxillary  and 
sublingual  duct-t 


Sublingual  space,  tongue  pulled  up. 


if  well  developed,  passes  in  the  middle  line  from  the  tongue  to  end  over  the  floor  of 
the  mouth.  Close  to  its  termination  on  either  side  is  a  smooth  elevation  caused  by 
the  sublingual  gland,  which  in  the  present  position  is  drawn  upward  under  the 
tongue.  A  varying  number  of  gland-ducts  perforate  the  mucous  membrane  with 
orifices  hardly  visible  to  the  naked  eye.  Internal  to  these  swellings  at  the  lower  end 
of  the  frenum  is  a  small  enlargement  on  each  side  of  the  median  line,  so  closely 
blended,  however,  as  to  seem  but  one  ;  these  elevations,  the  caruncula  sahvares, 
mark  the  point  at  which  the  duct  of  the  subma.xillary  gland  opens  on  each  side 
This  duct  runs  along  the  floor  of  the  sublingual  space  between  the  mylo-hyoid 
muscle  and  the  mucous  membrane,  a  smalt  part  of  the  gland  usually  accompanying 
the  duct  a  short  distance  over  the  muscle,  forming  a  prominence,  the  sublingual 
ridge  (plica  snbHnKtialis^.  \  constant  group  of  inlands  is  found  in  the  mucous 
membrane  below  the  incisors.' 

•  Stahr:  Zeitschrift  fur  Morph.  und  Anthrop.,  Bd.  iv..  Heft  2,  1902. 

•  The  sublingual  bursa  alleRcd  to  exist  on  either  side  of  the  frenum  has  not  been  described, 
since  it  is  at  most  extremely  uncommon. 


1582 


HUMAN   ANATOMY. 


THE  SALIVARY  GLANDS. 

These,  besides  the  mucous  follicles  of  the  mouth,  are  the  parotid,  the  submax- 
illary, and  the  sublingual  glands  of  the  two  sides.  They  are  all  reddish  gray  in 
color  and  of  about  the  same  firmness,  excepting  the  parotid,  which  is  denser. 

The  Parotid  Gland. — The  parotid  is  the  largest  of  the  salivary  glands,  weigh- 
ing from  20-30  gm. ,  with  a  considerable  range  beyond  these  limits.  It  is  situated 
behind  the  upper  part  of  the  ramus  of  the  lower  jaw,  which  it  overlaps  both  within 
and  without.  Its  limits  in  both  directions  are  very  variable.  The  prolongation  for- 
ward over  the  masseter  muscle  may  become  nearly  distinct  from  the  rest  of  the  gland, 


F'o-  1343- 


.Facial  artery 


Rxtemal  jugular, 
vein 


Mylo-hyoid 
^'DigaHtric,  anterior  belly 

^Submaxillary  gland 


Superficial  dissection,  showing  parotid  and  submaxillary  glands  undisturbed. 

and  is  then  known  as  the  socia  parotidis.  The  sheath  of  the  parotid  is  a  strong  fibrous 
envelope  continuous  with  the  cervical  fascia  in  front  of  the  sterno-mastoid,  closely 
applied  to  the  glandular  substance  and  continuous  with  the  partitions  that  pass 
through  the  organ,  so  that  it  can  be  dissected  off  from  the  gland  only  with  difficulty. 
The  parotid  is  divided  into  many  small  compartments  or  lobules  by  these  resisting 
septa  of  ♦'ibrous  tissue,  the  quantity  of  which  gives  it  toughness.  The  shape  of  the 
p-arotifl,  as  well  as  its  size,  is  variable,  since  it  grows  where  it  can  among  more  or  less 
rosii-ting  structures.  Its  f^hape  and  relations,  therefore,  may  be  considered  together. 
Relations. — The  parotid  nmipies  a  ravity  bounded  in  front  by  the  ramus  of 
the  jaw,  covered  by  the  masseter  and  internal  pterygoid  muscles  ;  behind  by  the 


THE   SALiVrt.^V     .LANDS. 


1583 


external  auditory  meatus,  the  tympanic  plate,  the  base  of  the  styloid  process,  and  t'  f 
front  of  the  adas  These  two  walls  meet  above  at  the  Glaserian  tissure.  The  pos- 
terior wall  is  prolonged  laterally  by  the  posterior  belly  of  the  digastric,  the  stylo- 
hyoid, and  more  externally  by  the  stemo-mastoid  muscles.  The  styloid  process  as 
it  descends  becomes  internal,  and  the  stylo-glossus  and  stylo-pharyngeus,  together 
with  the  fascia  known  as  the  stylo-maxillary  ligament,  bound  the  posterior  part  of 
the  gland  internally.  In  front  of  the  styloid  process  there  is  no  wall  to  the  space 
occupied  by  the  parotid  the  gland  resting  against  the  areolar  tissue  mixed  with  fat 
that  lies  on  the  outer  wall  of  the  pharynx.  The  widest  part  of  this  cavity  is  at  the 
surfekce,  where  the  foscia  is  connected  with  the  capsule  of  the  gland.  The  largest 
expanse  of  the  parotid  is,  therefore,  external.  It  overlaps  the  jaw  and  may  reach 
down  to  the  angle  and  be  separated  merely  by  fibrous  tissue  from  the  submaxillary 
gland.  A  constant,  but  very  variable,  prolongation  on  the  face  below  the  zygoma 
accompanies  the  duct  The  parotid  gland  reaches  upward  between  the  joint  of  the 
jaw  and  the  external  auditory  meatus  and  tympanic  plate.  Internally  it  lies  against  the 
structure:  above  described,  always  resting  on  the  inner  side  of  the  internal  pterygoid 
muscle  and  extending  to  the  great  vessels  and  nerves  which  separate  it  from  the 
side  of  the  pharynx.  There  may  or  may  not  be  a  higher  prolongation  inward 
through  the  space  in  front  of  the  styloid  process.  The  internal  carotid  artery,  inter- 
nal jugular  vein,  and  pneumogastric  nerve  are  close  against  the  lower  part  of  the  inner 
surface  of  the  gland.  The  external  carotid  artery  enters  the  gland  from  the  Inner 
side  and  divides  into  its  temporal  and  internal  maxillary  branches,  besides  giving  of! 
the  posterior  auricular,  and  sometimes  the  occipital  arteries,  within  its  substance. 
The  external  jugular  vein  is  formed  within  the  gland  and  emerges  from  its  lower  side. 
Near  the  skull  the  great  vessels  and  nerves  are  separated  from  the  gland  by  the  styloid 
process.  The  faciS  nerve  enter?  the  gland  on  its  posterior  side  and  passes  through 
It  obliquely  so  as  to  become  more  superficial  as  it  travels  forward,  lying  external  to  the 
external  carotid  artery  and  jugular  vein.  Before  emerging  from  the  gland  the  facial 
nerve  breaks  up  into  its  two  great  divisions,  the  branches  of  which  begin  to  subdivide 
within  the  glandular  mass.  The  auriculo-temporal  nerve  also  pa.sses  through  the 
upper  part  of  the  gland,  emerging  on  its  outer  aspect.  A  varying  number  of  lym- 
phatic glands  lie  in  the  substanr'i  of  the  parotid,  mosdy  in  the  more  superficial  part. 
They  are  small  and  not  easy  to  find.  A  larger  one,  said  by  Sappey  to  be  constant, 
b  in  the  gland  just  in  front  of  the  ear. 

The  parotid  or  Stenson's  duct  is  formed  by  two  chief  tributaries,  and  emerges 
from  the  front  of  the  gland,  above  its  middle,  running  forward  and  a  little  down- 
ward across  the  masseter  muscle  to  turn  in  sharply  at  its  anterior  border.  It  then 
crosses  a  collection  of  fat  and  runs  obliquely  through  the  buccinator  muscle  and 
the  oral  mucous  membrane  to  empty  into  the  vestibule  of  the  mouth  opposite  the 
second,  often  the  first,  superior  molar  tooth.  The  length  is  some  40  mm.  and  the 
diameter  3  mm.  The  termination  is  a  mere  slit.  Its  walls  are  firm  and  resistant. 
The  general  direction  of  the  duct  is  that  of  a  line  from  the  lower  side  of  the  concha 
of  the  ear  to  midway  between  the  border  of  the  nostril  and  the  red  edge  of  the  lip. 
The  transverse  facial  artery  lies  above  it,  on  leaving  the  gland,  and  a  plexus  of  veins 
surrounds  it. 

Vessels. — The  arteries  of  the  parotid  gland  are  derived  from  several  sources  ; 
although  numerous,  none  of  them  is  large.  Besides  several  small  branches  from 
the  external  carotid  itself  while  in  the  gland-substance,  there  are  twigs  from  the 
temporal,  especially  from  its  transverse  facial  branch,  from  the  posterior  auricular, 
the  mtemal  maxillary,  and  probably  from  an  occasional  branch  that  may  pass  through 
the  gland.  The  veins  form  quite  a  plexus  through  the  gland  and  open  into  the  sys- 
tem of  the  temporo-maxillary  and  of  the  external  jugular.  Of  the  lymphatics  much 
remains  to  be  learned,  but  they  probably  empty  into  both  the  deep  and  the  -iper- 
ficial  cervical  nodes. 

Nerves  are  from  the  facial,  auriculo-temporal,  and  great  auricular,  besides  sym- 
pathetic fibres  from  the  carotid  plexus. 

The  Submaxillary  Oland.— This  gland,  weighing  from  7-10  gm.,  lies 
largely  under  cover  of  the  lower  jaw.  just  before  the  angle,  in  a  fosM  on  the  inner 
side  of  the  bone.     As,  however,  the  skin  is  carried  inward  under  the  jaw  at  this 


1584 


HUMAN   ANATOMY. 


point,  the  gland  appears  on  the  surface.  It  projects  but  little,  if  at  all,  on  the  outer 
side  of  the  jaw,  but  curls  around  the  posterior  border  of  the  mylo-hyoid  muscle 
and  extends  for  some  distance  in  the  floor  of  the  mouth,  under  the  mucous  mem- 
brane, in  the  angle  between  the  mylo-hyoid  and  the  hyo-glossus,  sometimes  reach- 
ing the  sublingual  gland  (Fig.  1344).  It  lies  in  a  capsule  derived  from  the  cervical 
fascia,  which  is  so  loosely  attached  that  the  gland  can  easily  be  isolated.  The 
anterior  end  of  the  posterior  belly  of  the  digastric  and  of  the  stylo-hyoid  pass  behind 
and  beneath  it.  The  hypoglossal  nerve  and  the  lingual  vein  lie  beneath  it,  as  does 
the  first  part  of  the  lingual  artery,  until  the  latter  f>asses  under  the  hyo-glossus. 
Its  sublingual  branch  runs  along  the  inner  side  of  the  prolongation  of  the  gland. 

Fig.  1344. 


Buccinator 


Parutid  gland 


Internal  pterygoid' 

(cut) 

Superior  constrictor. 

Digastric. 

Stylo-hvoid- 

Stylo-glo'ssUB- 

Stylo-pharyngeus. 

Occipital  artery 

Internal  carotid 

Middle  constrictor 

Facial  artery 

External  carotid 

Lingual  artery 


Superior  thyroid, 
artery 

Inferior  constrictor 


Oral  mucous 
lembrane 


Dc«ppr  pofUua  of  9iit>- 
ntaxllI«ry^Un(l 

ut  mandible 
ubmaxlllary  duct 
Sublingual  gland 


G«n{o«iossus 
Mylo-hyoVd  (cut) 
inio-hyoid 
Stump  of  digastric,  anterior  belly 
ibmental  artery 
•ubmaxillary  gland,  superficial  part 


Great  comu  of  hyoid  bone 
Hyo-glossus 
rhyro-hyoid 
Deeper  dissection,  showing  rehilions  of  salivary  glanda. 


to  which  it  sends  vessels.  The  facial  artery  lies  beneath  the  gland  before  reaching 
the  border  of  the  jaw.  The  facial  vein  is  superficial  to  it.  The  lingual  nerve  lies 
above  the  prolongation. 

The  submaxillary  or  Wharton's  duct  runs  from  the  front  of  the  main  body 
of  the  gland  aloiijr  the  floor  of  the  mouth  under  the  mucous  membrane,  often  accom- 
panied f.xtcrnally  by  the  prolonjration  of  the  gland.  It  is  from  4-5  cm.  long,  with  a 
diameter  of  3  mm.  Its  walls  are  decidedly  thinner  than  those  of  the  parotid  duct. 
Anteriorly  it  rises  to  open  into  the  mouth  by  a  little  papilla  on  the  side  of  the  frenum 
linguae,  the  last  few  millimetres  running  in  a  fold  of  mucous  membrane.  The  lingual 
norvc  passes  under  the  duct  from  without  inward  soon  after  it  leaves  the  gland. 
The  sublingual  artery  is  beside  it  and  a  plexus  of  veins  around  it. 


STRUCTURE   OF  THE   SALIVARY   GLANDS. 


1585 


Vettels. — The  arteries  of  the  sublingual  gland  are  derived  from  the  facial  and 
the  sublingual  branch  of  the  lingual.  The  veins  are  from  the  corresponding  ones. 
The  lymphatics  go  to  the  submaxillary  glands. 

Nerves. — ^The  gland  receives  filaments  from  the  sympathetic  plerus  accompa- 
nying the  facial  artery,  from  the  lingual  nerve,  and  from  the  submaxillary  ganglion. 

The  Sublingual  Gland. — This  differs  from  the  two  preceding  glands  in  having 
no  capsule.  It  lies  in  loose  areolar  tissues  on  the  mylo-hyoid  muscle,  at  the  front 
part  of  the  sublingual  space.  Its  weight  is  3  or  4  gm.  Each  gland  rests  internally 
against  the  genio-glossus,  and  anteriorly  they  touch  one  another.  They  are  more 
readily  separated  into  lobes  than  the  others.  Testut  regards  them  as  aggregations  of 
separate  glands.  The  sublingual  glands  are  covered  by  the  mucous  ii.^  iibrane  of  the 
floor  of  the  mouth,  which  they  press  upward  into  rounded  swellings  on  either  side 


Fig.  1345. 

••^„l.!,llllllll'llU)ll)l)i)i,ir..> 


Openinfr  of  anterior. 
linKual  glands 

Frenum. 


.Caruncle  and  openinK  of 
submaxillary  duct 


Gcnio-hyoid 
ylo-hyoid 

Cut  fibres  of  difastric 

Section  acrou  anterior  part  of  floor  o(  month,  itaowing  relationi  ol  sablingual  gland*  to  mucons  membrane  and 

muKlcs. 


of  the  beginning  of  the  h-enum.  The  lingual  nerve  and  the  submaxillary  duct  are 
on  the  inner  side.  The  sublingual  or  Rivini's  ducts  vary  in  number  from  four 
to  twenty  or  more.  They  open  for  the  most  part  in  the  floor  of  the  mouth,  but 
some  may  join  Wharton's  duct.  Bartholin's  dud  is  an  inconstant  one,  larger 
than  the  others,  that  usually  opens  close  to  the  outer  side  of  Wharton's  duct,  which 
it  follows. 

Vessels. — The  arteries  are  from  the  sublingual  branch  of  the  lingual  and  the 
submental  branch  of  the  facial,  which  latter  sends  minute  twigs  through  the  mylohyoid 
muscle.  The  blood  escapes  into  '  e  ranine  vein.  The  lymphatics  run  to  the  sub- 
maxillary nodes. 

Nerves  are  from  the  sympathetic,  the  lingual,  the  submaxillary  ganglion,  and, 
according  to  some,  from  the  chorda  tympani. 


STRUCTURE  OF  THE  SALIVARY  GLANDS. 

The  three  chief  salivary  glands  possess  in  common  the  tubo-alveolar  type  of 
structure;  depending  upon  the  character  of  their  secreting  cells  and  products,  the  func- 
tionating organs  represent  both  the  serous  and  mucous  varieties.  The  parotid  is  a 
pure  serous  gland  ;  the  submaxillary  is  a  mixed  one,  the  alveoli  containing  serous  cells 
predominating  ;  the  sublingual,  also  a  mixed  gland,  consists  chiefly  of  mucous  alveoli, 
the  serous  cells  being  limited  to  the  marginal  groups  con»tit«iting  the  demilunes  of 
Heidenhain. 

100 


1586 


HUMAN   ANATOMY. 


The  parotid  gland  consbts  entirely  of  serous  alveoli,  although  mucus-pro- 
ducing acini  may  occur  in  the  accessory  lobules  situated  along  the  duct  of  Stenson. 
The  primary  lobules  are  made  up  of  alveoli,  from  .015  to  .020  mm.  in  diameter,  lined 
with  epithelial  cells,  which  are  somewhat  pyramidal  in  form,  since  they  are  broader 
next  the  basement  membrane  and  narrower  towards  the  cleft-like  lumen.  The  rest- 
ing cells,  fresh  and  examined  without  the  addition  of  reagents,  appear  filled  with 
numerous  minute,  glistening  granules  which  lie  embedd^  within  a  less  strongly 
refracting  substance.  The  granules,  however,  are  readily  affected  by  reagents,  often 
undergoing  partial  or  comphte  solution;  hence  the  reticulated  appearance  of  the  pro- 
toplasm frequendy  obser\'eii  in  glandular  epithelium  after  fixation.  The  nuclei  of 
the  serous  cells  are  usually  of  spherical  form  and  contain  distinct  nucleoli  and  delicate 

Fig.  1346, 


iMerlobular  duct 


Aiteo'. 


Interlobular  septum 


Section  of  small  lobule  of  parotid  gland,    y  80. 


chromatm  net-works.  The  sptem  of  excretory  canals  begins  at  the  alveoli  as  the 
intermediate  tubules,  which  in  the  parotid  are  relatively  long,  about  .010  mm.  in 
diameter,  and  lined  with  low,  flattened  cells,  directly  continuous  with  the  taller  alveolar 
epithelium,  on  the  one  hand,  and  with  that  of  the  intralobular  ducts  on  the  other. 
The  latter,  or  salivary  tubules  of  Pfluger,  of  langfer  diameter  (about  .035  mm.)  than 
that  of  the  immediately  preceding  or  succeeding  segments  of  the  canal^  are  clothed 
with  a  single  layer  of  columnar  cells,  some  .014  mm.  in  height,  which  present  a 
peculiar  differentiation  into  an  inner  and  an  outer  zone.  The  former,  next  the 
lumen  of  the  tube  and  containing  the  nucleus,  appears  finely  granular  or  almost 
homogeneous,  while  the  outer  or  basal  zone  exhibits  a  longitudinal  striation  composed 
of  rows  of  minute  granules.     After  treatment  with  certain  reagents,  the  striated  zone 


STRUCTURE  OF  THE   SALIVARY   (.LANDS. 


15*7 


breaks  up  into  delicate  rod-like  processes,  in  recognition  of  which  the  cells  lining  the 
intralobular  tubules  are  often  designated  rotl-epitheliuin.  An  active  secretory  r61e 
has  been  ascribed  to  these  cells,  R.  Krause'  having  succeeded  in  demonstrating  an 
excretory  function  by  means  of  sodium  sulphindigotate.  The  interlobular  and  inter- 
lobar ducts  gradually  increase  in  size  and  possess  a  lining  of  columnar  cells  which  are 
usually  arranged  as  a  single  layer.  In  the  larger  canals,  however,  the  epithelium 
consists  of  two  imperfect  rows,  since  smaller  cells  lie  ne.\t  the  basement  membrane, 
w«idged  in  between  the  larger  typical  elements.  The  columnar  cells  continue  until 
near  the  termination  of  the  main  excretory  duct,  where  they  give  place  to  the  stratified 
squamous  epithelium  prolonged  from  the  oral  mucous  membrane. 

Fio.  1347. 

Intermediate  duct  ^ 

Tubular  alveolus 


Alveolar  lumen 


Interlobular  duct 


Connective  ttatw 


Section  of  parotid  xtand,  showing  serous  alveoli.    X  270- 


The  submaxillary  gland  differs  in  structure  from  the  parotid  in  possessing 
both  serous  and  mucous  alveoli,  the  latter  forming  approximately  one-fifth  of  the 
entire  organ.  The  alveoli  containing  serous  cells  correspond  closely  with  those^  "J 
the  parotid,  being  from  .020  to  .030  mm.  in  diameter  and  filled  with  elements  loaded 
with  minute  granules.  Not  infrequently  the  cells  exhibit  differentiation  into  an  inner 
granular  and  an  outer  almost  granule-free  zone.  The  mucous  alveoli  are  often  some- 
what lai^er  than  the  serous,  reaching  a  diameter  of  .040  mm.  or  more.  The  mucus- 
protlucing  cells  present  the  usual  appearance  and  share  the  acinus  with  typical  demi- 
lunes consisting  of  cells  identical  with  those  lining  the  serous  alveoh.  The  mucous 
acini  are  direcUy  connected  with  those  of  the  serous  type. 

Intermediate  tubules  connect  alveoli  of  both  kinds  with  the  intralobular  cana^; 
those  beginning  in  mucous  acini  are  shorter  (.035-. 060  mm. )  and  less  nchly  branched 
than  the  tubules  originatifH;  in  serous  alveoli.  The  latter  measure  from  .060-^  140 
mm.  in  length,  and  repeatedly  divide  ;  they  are  lined  with  low  cubical  cells  which  are 
gradually  transformed  from  the  alveolar  epithelium  in  contrast  to  the  abrupt  transition 
seen  in  the  tubules  connected  with  mucous  acini.  The  cells  lining  the  intralobular 
tubules  of  the  submaxillary  gland  exhibit  the  characteristic  rod-like  striation  seen  in 
the  parotid,  the  rod-epithelium  sometimes  containing  yellowish  pigment  RT^""'^- 
The  interlobular  and  interlobar  ducts  resemble  those  of  the  parotid  gland.  The 
chief  excretory  duct  possesses,  in  addition  to  a  subepithelial  elastic  layer,  a  weakly 
developed  stratum  of  longitudinally  disposed  involuntary  muscle.  Goblet-cells  appear 
between  the  columnar  elements  lining  the  duct. 

The  sublingual  gland,  being  of  the  mixed  mucous  type,  resembles  in  striicture 
the  labial  and  buccal  glands,  and  consists  of  a  series  of  individual  lohules,  opening  by 
half  a  dozen  or  more  separate  ducts,  rather  than  a  compact  single  orj^an.     In  com- 
'  Archiv  f.  mikro.  Anat.,  Bd.  xlix.,  1897. 


1588 


HUMAN   ANATOMY. 


mon  with  other  mucous  glands,  the  sublingual  lobules  do  not  possess  intralobular 
tubules  lined  with  the  characteristic  rod-epithelium.  The  interlobular  ducts  subdi- 
vide into  smaller  canals  which  extend  within  the  primary  lobules  and  give  of!  wider 
passages  lined  with  cubical  epithelium.     Towards  the  end  of  these  terminal  canals 


Duct 


.MucouB  alvcoH 


Sefous  klveoll 
Section  of  lubnuxillary  gland,  ihowing  Mroiu  and  mucoua  alveoli.    X  rjo. 

the  mucous  cells  appear,  at  first  isolated  or  in  groups,  increasing  in  numbers  until 
they  form  the  entire  lining  of  the  passage  and  become  the  secreting  elements  occupy- 
ing the  tubular  alveoli  of  the  gland.  The  latter  vary  from  .030-.060  mm.  in  diam- 
eter, and  are  clothed  with  cells  averaging  .015  mm.  high.     The  condition  of  the 

Fio.  1349. 


-Mucous  cells 


Duct. 


Crescents  ol  serous  cells 


Section  of  sublingual  gland,  showing  serous  cells  grouped  as  crescents.    X  370. 


alveoli  as  regards  the  mucus-bearing  cells  varies  greatly  even  in  the  same  lobule.  At 
times  .m  entire  primary  lobule  is  composed  of  acini  filled  with  mucous  cells  ;  at  others 
empty  and  gorged  alveoli  alternate,  or  the  depleted  acini  may  predominate.  Uncer- 
tainty as  to  the  presence  of  the  demilunes  also  exists,  since  these  may  be  absent  in 


PRACTICAL   CONSIDERATIONS:    THE   MOUTH. 


1589 


certain  well-developed  alveoli  filled  with  larj^e  mucous  cells,  or  they  may  be  present 
in  considerable  numbers.  Mucous  celb  are  much  less  numerous  m  the  sublin}{ual 
glands  of  young  infants  tlian  in  the  adult  organ.  The  relatively  wide  lumen  of  the 
alveoli  and  the  more  reticulated  appearance  of  their  epithelium  serve  to  distinguish 
the  exhausted  sublingual  gland  from  the  parotid  of  similar  condition. 

The  normal  secretions  of  the  oral  glands,  mucous  as  well  as  serous,  contain  no 
formed  elements  ;  occasionally  accidental  granules  or  cell  remains  arc  present.  The 
characteristic  spherical  so-called  salivary  corpuscles  which  occur  in  varying  numbers 
in  the  mixed  oral  secretion  have  no  relation  to  the  salivary  glands,  since  they  are 
only  modified  leucocytes  escaped  from  the  lymphoid  tissue  of  the  faucial  and  Imgual 
tonsils.  On  gaining  the  oral  cavity,  these  cells  are  affected  bv  the  saliva  and  liecome 
greatly  swollen,  the  granular  remains  of  their  cytoplasm  exhibiting  molecular  motion 
m  a  marked  degree.  ,    ,  ,. 

Development  of  the  Oral  Glands.— The  earliest  traces  of  the  saltvary 
glands  are  seen  during  the  second  foetal  month.  The  anlage  for  the  submaxillary 
gland  first  appears  about  the  sixth  week;  next  that  for  the  parotid  about  the 
eighth  week  ;  a  little  later  that  for  the  sublingual.  The  parotid  anlage  develojis 
from  the  oral  ectoblast  along  the  lateral  groove  separating  the  upper  and  lower  jaws 
The  submaxillary  and  sublingual  glands  arise  from  a  ridge-like  anlage  of  the  bucca 
epithelium  occupying  the  hirrow  marking  the  angle  between  the  tongue  and  the  flooi 
of  the  mouth,  the  anlage  for  the  sublingual  lying  nearer  the  tip  of  the  tongue.  At 
first  the  parotid  and  submaxillary  lie  about  equally  removed  from  the  oral  opening, 
but  later  migration  occurs,  the  former  passing  backward  and  the  latter  forward. 

The  development  of  the  gland  in  each  case  begins  as  a  solid  cylindnral  out- 
growth from  the  deeper  layer  of  the  oral  epithelium,  which  presents  a  local  thicken- 
ing The  cylinder  rapidly  lengthens  and  branches,  so  that  by  the  eighth  or  tenth 
w^k  the  submaxillary  and  parotid  glands  respectively  consist  of  a  mam  stalk  and 
terminal  buds.  The  anlage  of  the  sublingual  gland  gives  off  epithelial  buds  on 
acquiring  a  length  of  about  i  mm.  The  primary  sprouts  of  the  anlage  subdivide  and 
eventually  become  the  smaller  ducts  and  the  glandular  tissue.  Meanwhile  the  imme- 
diately surrounding  mesoblast  undergoes  condensation,  and  contributes  the  connective- 
tissue  envelope  with  its  prolongations  between  the  lobules  and  acini  supporting  the 
blood-vessels  and  ner\es.  Towards  the  close  of  the  third  month,  whUe  the  gland- 
tubules  are  still  solid,  the  lumen  of  the  hiture  main  .xcretory  duct  appears  «"  the 
epithelkl  cylinder,  extending  from  the  free  suriace  towards  the  alveoli.  The  latter 
acquire  their  lumen  during  the  fifth  month. 

The  smaller  oral  glands,  including  those  of  the  lips,  cheeks,  tongue,  and  palate, 
develop  much  later  than  the  larger  salivary,  since  their  anlages  appear  during  the 
fourth  month.  The  details  of  their  development  correspond  m  general  with  those 
attending  the  formation  of  the  larger  oral  glands. 

PRACTICAL  CONSIDERATIONS  :  THE  MOUTH. 

The  chief  congenital  deformities  of  the  mouth  are  harelip  and  cleft  palate. 
Harelip  results  from  a  failure  of  the  developmental  procedures  concerned  in  forming 
and  differentiating  the  nasal  and  buccal  cavities.  These  processes  have  already  been 
described  in  connection  with  the  formation  of  the  face  (page  59).  Upon  the  down- 
growth  of  the  fronto-nasal  process  depends  the  formation  of  the  vomer,  the  perpen- 
dicular plate  of  the  ethmoid  and  the  external  nose,  and  of  the  intermaxillary  bone 
and  that  portion  of  the  upper  lip  corresponding  to  the  four  incisors.  The  partiUon 
separating  the  nasal  from  the  oral  cavity,  later  the  hard  and  soft  palates,  is  formed 
by  the  union  of  the  horizontal  palatal  plates  from  the  buccal  aspect  of  the  two  maxillary 
processes  (Fig.  76).  When  the  frontal  and  maxillary  processes  fail  to  unite  on  one 
side,  single  harelip  results,  the  cleft  in  one  side  of  the  lip  lying  opposite  the  space 
between  the  upper  canine  and  lateral  incisor,  or  between  the  latter  and  the  central 
inci-sor  When  union  between  the  maxillary  and  the  frontal  processes  fails  on  both 
sides  double  harelip  follows,  the  lateral  incisors  often  being  absent  and  the  inter- 
maxiilary  bone  with  the  central  incisors  and  the  median  portion  of  the  lip  occupying 
a  position  beneath  the  nasal  septum. 


I590 


HUMAN   ANATOMY. 


Fig.   1350. 


New-l>orn  i-liiUI  with  duuble  haKlip. 


Cleft  palate  is  caused  by  faulty  union  between  the  palatal  processes  of  the  maxillary 
arches.  The  cleft  is  always  in  the  middle  line,  and  may  involve  only  the  uvula  and 
soft  palate,  may  extend  to  the  |X)sterior  margin  of  the  intermaxillary  bone,  or  may 
diverge  from  that  point  on  one  or  both  sides  and  run  forward  through  the  alveolus, 

being  then  associated  with  single  or  double  hare- 
lip, the  cleft  or  clefts  in  the  alveolus  corresponding 
in  position  to  the  deficiencies  in  the  lip  (page  63). 

The  Lips. — The  mucous  membrane  of  the 
lips  and  the  adjacent  skin  are  often  affected  by 
herpes  labialis,  which  may  be  associated  with 
gastro-intestinal  disturbance,  or  may  be  purely 
neurotic  in  its  origin,  following  mentd  depression 
or  anxiety.  It  is  found  in  the  distribution  of  the 
second  and  third  divisions  of  the  fifth  pair  which 
supply  sensation  to  the  upper  and  lower  lips  re- 
s|)ectively.  The  vascularity  of  the  lips,  while  it 
leads  to  excessive  exudate  and  large  swelling  after 
contused  or  lacerated  wounds,  favors  rapid  heal- 
ing and  the  avoidance  of  infection  after  surgical 
wounds.  In  few  places  equally  exposed  to  con- 
tact with  infectious  organisms  was  healing  by  "first 
intention' '  so  common  before  the  intrcxluction  of 
antisepsis.  The  coronary  arteries  run  between  the  mucous  membrane  and  the  orbicu- 
laris oris.  They  are  therefore  more  often  severed  by  wounds  extending  from  within 
outward — usually  made  by  the  teeth— than  by  those  beginning  externally.  The  coro- 
naries  anastomose  very  freely.  In  arresting  hemorrhage  from  them  by  direct  ligature 
b<)th  ends  should  be  tied.  If  a  wound  of  the  lips  is  united  by  pins  and  figure-of- 
eight  sutures,  the  pins  should  be  passed  close  to  the  inner  edges  of  the  wound  so  that 
the  coronaries  may  be  compressed  between  the  pins  and  the  sutures.  The  vascu- 
larity of  the  lips  renders  chancres  of  that  region,  like  those  of  the  face,  exceptionally 
large  both  in  depth  and  in  superficial  area.  It  also  adds  greatiy  to  the  extent  of 
furuncular  or  carbuncular  infection  in  this  region,  the  occurrence  of  which  is  favored 
by  the  large  number  of  hair  and  sebaceous  follicles  present.  The  danger  of  infective 
sinus  thrombosis  (intracranial)  as  a  result  of  such  infection  here  or  elswhere  on  the 
face  is  much  increased  by  the  free  anastomosis  between  the  valveless  facial  vein  and 
its  tributaries  and  the  ophthalmic  vein,  which  is  also  without  valves.  As  might  be 
expected,  nsvi  are  frequent  in  the  lips.  In  the  male  the  lower  lip  is  the  favorite  seat 
of  epithelioma.  Either  infection  or  diminished  tissue  resistance  from  minor  trauma- 
tisms, or  from  tobacco-irritation  in  smokers,  is  supposed  to  explain  this  clinical  fact. 
The  mucous  glands  of  the  lip  are  not  rarely  the  seat  of  retention-cysts  from  obstruc- 
tion of  their  ducts. 

The  Gums.— The  mucous  membrane  of  the  lips  is  continuous  with  that  cover- 
ing the  fibrous  tissue  of  the  gums,  but  the  latter  is  slightly  less  vascular  and  much  less 
sensitive.  The  gums  are  sometimes  congenitally  hypertrophied  ;  the  condition  is 
usually  associated  with  defective  or  aberrant  developmental  processes  often  affecting 
the  mentality.  They  are  also  often  found  hypertrophied  in  edentulous  old  persons  or 
m  persons  with  badly  fitting  artificial  dentures.  They  are  the  frequent  seat  of  inflam- 
mation from  various  causes,  the  most  common  of  which  are  the  decomposition  of 
food  and  the  deposition  of  calcium  salts— tartar— about  the  necks  of  the  teeth.  Infec- 
tion frequendy  follows  the  liyperaemia  produced  by  these  forms  of  irritation.  When 
it  is  confined  to  the  space  between  the  mucous  membrane  and  the  fibrous  tissue,  it 
causes  a  limited  superficial  abscess, — "gum-boil;"  if  it  gains  access  to  the  sub- 
periosteal space,  it  may  cause  a  form  of  alveolar  abscess,  the  usual  variety  of  which 
IS,  however,  due  to  infection  secondary  to  dental  caries,  and  is  situated  about  the  root 
of  a  tooth  {x>ide  infra). 

Tartar  is  found  most  abundantly  near  the  openings  of  the  submaxillary  and  sub- 
lingual ducts,— «>.,  near  the  inner  surfaces  of  the  lower  incisor  teeth.  Mercury  and 
lead  cause  gingivitis  probably  by  the  actual  presence  of  their  salts  in  quantity  suffi- 
cient to  act  as  irritants,  their  deposition  from  terminal  capillaries  being  favored  by  the 


PRACTICAL   CONSIDERATION'S  :    THK   MOUTH.  1591 

frequent  hyperaemia  due  to  the  vascularity  and  the  warmth  and  moisture  of  the  region, 
together  with  slight  but  repeated  trauma  during  m;»stic:itii.n.  The  gingivitis  of 
scur\y  or  of  purpura  is  merely  a  local  evidence  of  a  constitutional  condition,  iuul  is 
hemorrhagic  rather  than  inflammatory. 

During  dentition  the  resistance  of  the  gums  may  cause  backward  pressure  Ujxin 
the  nervous  and  vascular  supply  of  the  pulp  of  the  tooth,  giving  rise  to  some  |)ain  and 
sometimes  to  grave  reflex  disturbances,  especially  in  infants.  The  insensitive  gum 
then  becomes  exceedingly  tender  and  is  swollen  and  cedematous.  The  wiik-sprcad 
relations  of  the  fifth  nerve  render  long-continued  irritation  of  its  dental  branches  dan- 
gerous. "Lancing"  the  gums  is  the  obvious  remedy.  It  is  especuiUy  apt  to  be 
needed  over  the  molars  and  cuspids,  and  the  lines  of  incision  should  be  planned  so  as 
to  release  fully  the  presenting  surfaces  of  those  teeth. 

The  Teeth. — Alveolar  Abscess. — The  line  of  penetration  in  dental  caries  is 
often  in  the  direction  of  the  pulp,  through  which  infection  extends  to  the  "apical 
space"  between  the  root  of  the  tooth  and  its  socket,  containing  the  ves.sels  and  nerves 
and  some  loose  connective  tissue.  This  space  soon  becomes  filled  with  pus,  the  cavity 
enlarges,  and  reaches  the  compact  bone  on  the  surface  of  the  alveolus  (the  density 
of  which  impedes  the  process  somewhat)  ;  but  finally  the  bone  is  perforated,  usually 
through  the  thinner  external  or  buccal  wall  of  the  alveolus.  The  periosteum  usually 
yields  opposite  the  gum  immediately  over  the  apex  of  the  tooth,where  it  is  reinforced 
by  mucous  membrane  only.  If  the  root  of  the  tooth  is  a  long  one  or  the  abscess 
has  gone  deeply  into  the  bone,  the  pus  may  reach  the  periosteum  at  a  point  where  it 
is  supported  by  the  muscular  uid  fibrous  tissues  of  the  cheek.  The  pus  may  then 
strip  the  periosteum  from  the  jione  so  as  to  cause  extensive  necrosis.  This  is  less 
likely  to  (Kcur  in  the  alveolus  of  the  upper  jaw  or  in  the  hard  palate,  on  account  of 
their  free  blo«xl-supply  derived  from  several  sources.  In  cases  of  this  type  in  either 
jaw,  a  sinus  followed  by  a  depressed,  adherent,  and  disfiguring  cicatrix  is  liable  to 
result  (Roughton).  Alveolar  abscess  is  also  influenced  in  its  course  by  the  situation 
of  the  particular  tooth  involved.  In  the  maxilla,  abscesses  connected  with  the  canines 
or  incisors  may  point  into  the  nasal  cavity  or  on 

the  under  surface  of  the  hard  palate.    The  pus 

is  more  likely,  however,  to  descend  by  gravity 

alongside  of  the  root  to  the  edge  of  the  gum,  or 

to  follow  the  canal  of  the  root  into  the  pulp-cavity. 

Abscesses  connected  with  the  upper  molars,  es- 
pecially the  first,  or,  more  rarely,  those  in  relation 

to  the  cuspids,  maj  point  in  the  antrum.     They 

occasionally  o-^n  on  the  face  in  front  of  the  an- 
terior bor-'er  of  the  masseter.     The  relation  of 

the  apex  .   the  root  to  the  mucous  membrane  of 

the  gum  often  determines  the  point  of  opening. 

If  the  apex  in  the  case  of  the  lower  teeth  is  above, 

or  in  that  of  the  upper  teeth  is  below  the  line  of 

reflection  of  the   mucous   membrane  from  the 

cheek  to  the  gum,  the  abscess  tends  to  point  in 

the  mouth.    If  the  contrary  is  the  case,  pointing 

on  the  face  or  neck  may  result. 

In  syphilis  the  first  teeth  exhibit  mdforma- 

tions  characteristic  of  perversions  of  nutrition  or 

of  inflammation  of  the  gums  sufficiendy  severe  to 

affect  the  blood-supply  to  the  tooth-sacs.     The 

enamel  may  be  deficient,  opaque  or  chalky,  the 

dentine  soft  or  friable,  the  teeth  irregular  in  size 

and  uneven  in  position.  ...  u      j 

The  permanent  teeth  may  show  the  same  general  aberrations  as  to  growth  and 

nutrition  that  are  produced  bv  stomatitis  from  digestive  derangements  or  from  lo<al 

irritation.     After  mercurial  stomatitis,  for  example,  the  teeth  are  irregularly  outlined, 

horizontally  seamed,  scraggy,  malformed,  deficient  in  enamel,  separated  too  widely. 

and  dirty  yellow  in  color. 


Fig.  i35t. 


j^4.^  */i^_ 


Chancteristic  teeth  of  inherited  syphilis. 
A.  upper  pemunent  cenlnil  incisors  deeply 
notched ;  lateral  inrisors  show  no  delect ;  rixht 
canine  has  deep  notch;  exposed  dentine  has 
become  discolored.  B,  upper  incisors  onlv  re- 
cently erupted ;  central  notch  marked  out  but 
not  yet  cleared  out  by  breaking  away  o(  unprf>- 
tected  dentine ;  lour  lower  incisors  present  peg* 
like  excrescences  due  to  loss  of  enamel  and 
cxpoanre of  dtrtine.    {HutckmtoH.) 


Hi 


1592 


HUMAN  ANATOMY. 


The  typical  (and  pathognomonic)  syphilitic  teeth—"  Hutchinson's  teeth"-^«c 
the  upper  permanent  central  incisors.  The  type  is  observed  in  its  pe-fection  soon 
after  the  extrusion  <rf  these  teeth.  The  essential  characteristic  is  a  crescentic  notch 
u  *ii  'iS'.-^)  in  the  free  edge  of  the  tooth,  the  anterior  border  of  the  notch  being 
bevelled  from  above  downward  and  from  before  backward,— »>. ,  at  the  expense  of 
the  anterior  suriace  and  border  of  the  tooth.  Typical  Hutchinson's  teeth  are.  fur- 
thermore, reduced  m  length  and  narrowed,— "  stunted  ;"  their  angles  are  rounded 
oft,  the  lateral  and  inferior  borders  merging  in  a  curved  line  ;  they  deviate  from  nor- 
mahty  in  direction,  their  axes  being  obliquely  convergent,  or  more  rarely  divergent 
instead  of  parallel.  /  8      . 

The  other  surgical  relations  of  the  teeth  and  of  the  dental  tissues  which  are  of 
chief  importance  are  concerned  wit      '-e  new  growths  originating  in  dental  elements 
The  odontomaia  are  divided  by  S        i  as  follows,  and  the  classification  should  be 
remembered  in  studying  the  anatomical  development  of  the  teeth  : 

(i)  Persistent  portions  of  the  epithelial  sheath  (page  1561),  taking  on  over- 

E)wth,  may  give  rise  to  an  epithelial  odontome  (multilocular  cystic  tumor).  (2) 
pansion  of  the  tooth-follicle  with  retention  of  the  crown  or  root  of  an  imperfectly 
developed  tooth  results  in  9l  follicular  odontome  (dentigerous  cyst).  (3)  Hyper, 
trophy  of  the  fibrous  tooth-sac  causes  a  fibrous  odontome ^  especially  frequent  ii 
nckets,  ^-hich  usually  affects  the  osteogenctic  fibrous  membranes.  (4)  If  the  fore- 
going hypertrophy  occurs  and  the  thickened  capsule  ossifies,  a  cementome  results.  ( 5 ) 
If  this  takes  place  irregulariy,  small  malformed  teeth— "  denticles"— may  form  in 
large  num'..'.-s  and  occupy  the  centre  of  the  tumor  (compound follicular  odontome ) . 
(6)  Tumors  of  the  root,  after  the  full  formation  of  the  crown,  are  of  necessity  com- 
posed of  dentine  and  cementum  only,  enamel  not  entering  into  them  (radicular 
odontomaia).  (7)  Tumors  composecl  of  irregular  conglomerations  of  enamel,  den- 
tine, and  cementum,  and  often  made  up  of  two  or  more  tooth-germs  fused  together, 
constitute  composite  odontomaia.  All  these  growths  can  be  understood  only  by 
^reful  study  of  the  normal  development  of  the  teeth.  They  are  rarely  diagnosed 
before  operation,  which  is  therefore  in  some  cases  needlessly  severe.  Sutton  says 
very  truly,  "  In  the  case  of  a  tumor  of  the  jaw  the  nature  of  which  is  doubthil,  par- 
ticulariy  in  a  young  adult,  it  is  incumbent  on  the  surgeon  to  satisfy  himself,  before 
proceeding  to  excise  a  jjortion  of  the  mandible  or  maxilla,  that  the  tumor  is  not 
an  odontome,  for  this  kind  of  tumor  only  requires  enucleation.  In  the  case  of  a 
follicular  odontome  it  is  usually  sufficient  to  excise  a  portion  of  its  wall,  scrape  out  the 
cavity,  remove  the  tooth  if  one  be  present,  stuff  the  sac,  and  allow  it  to  close  by  the 
process  of  granulation. ' ' 

The  Roof  of  the  Mouth  and  the  Palate.— The  mucous  membrane  cov- 
ering the  hard  palate  is  so  fused  with  the  periosteum  as  practically  to  be  inseparable 
from  it  It  is  dense,  resistant,  and  comparatively  insensitive.  A  vertical  trans- 
verse section  of  the  roof  of  the  mouth  (Fig.  1294)  shows  the  mucous  membrane  to 
be  thickest  laterally  and  thinner  in  the  median  line. 

Cleft  palate  (page  1590)  results  from  imperfect  fusion  between  the  horizontal 
palatal  plates  of  the  maxillary  processes  of  the  first  visceral  arch.  It  is  always  in  the 
middle  line.  It  may  involve  the  soft  palate  and  uvula.  If  it  extends  forward  as  far 
as  the  alveolus,  it  follows  the  line  between  the  maxilla  and  the  premaxillary  bone, 
usually  terminating  in  a  harelip  (page  1589)  opposite  the  interval  between  the  lateral 
mcisor  and  canine  teeth.  If  it  separates  the  maxillae  on  both  sides  from  the  pre- 
maxillary bone,  it  is  almost  always  associated  with  double  harelip. 

The  toughness  of  the  muco-periosteum  of  the  hard  palate  facilitates  ths  forma- 
tion of  flaps  in  operations  for  the  closure  of  such  a  cleft.  In  dissecting  uo  the  flaps 
it  b  well  to  keep  close  to  the  bone  and  to  avoid  the  descending  or  posterior  pala- 
tine branches  of  the  internal  maxillar>'  artery.  These  vessels,  on  which  the  nutri- 
tion of  the  flaps  as  well  as  of  the  bone  depends,  emerge  from  the  posterior  palatine 
canal  at  a  point  on  the  line  of  junction  of  the  hard  and  soft  palates  8  mm.  (>^  in.) 
anterior  to  the  hamular  process  and  a  little  to  the  inner  side  of  the  last  molar  tooth. 
They  run  forward  in  a  shallow  groove  just  internal  to  the  outer  border  of  the  hard 
palate.  They  are  nearer  to  the  bone  than  to  the  mucous  surface,  but  their  pulsa- 
tions can  often  be  felt  by  the  finger.     For  these  reasons  incisions  in  uranoplasty 


PRACTICAL  CONSIDERATIONS:  THE  MOUTH. 


1593 


should  be  made  close  to  the  alveolus  and  the  bone  should  be  hugged  as  the  flaps 
are  raised.  In  troublesome  bleeding  from  these  arteries  the  posterior  palatine  canal 
may  be  plugged  by  a  sharpened  stick,  which  should  previously  be  sterilizeti. 

When  the  clelt  involves  only  the  soft  palate,  staphylorrhaphy  is  required. 
The  muscles  that  tend  to  pull  the  edges  apart  are  the  tinsor  palati  and  levator 
palati.  The  former  turns  atound  the  hamular  process  and  passes  almost  horizon- 
tally towards  the  median  line,  the  latter  lies  close  to  the  posterior  surface  of  the 
soft  palate  and  runs  obliquely  from  above  downward  and  inward.  These  muscles 
may  be  divided  by  various  incisions,  the  simplest  being  a  section  of  the  velum  near 
its  lateral  border  and  parallel  with  the  cleft. 

The  hamular  process  may  be  felt  behind  and  a  little  intf  rnal  to  the  last  molar 
tooth.  The  pterygo-mandibular  ligament  may  be  felt  passing  from  the  hamular 
process  to  the  posterior  end  of  the  mylo-hyoid  ridge  of  the  lower  jaw  just  behind  the 
last  molar  tooth.  The  fold  ol  mucous  membrane  covering  it  may  be  seen  when  the 
}aws  are  separated  widely.      The 

lingual   branch  of   the   fifth   nerve  Fig.  135a. 

may  be  felt  between  the  mucous 
membrane  and  the  bone  anterior  to 
the  base  of  the  pttrygo- mandibular 
ligament  and  below  the  last  molar. 
With  a  finger  passed  behind  the 
last  molar,  the  swell  of  the  alveolar 
ridge  can  be  recognized  as  it  nar- 
rows to  pass  into  the  ramus.  The 
nerve  is  below  and  parallel  with 
that  ridge.  It  is  sometimes  divided 
for  the  relief  of  the  unbearable  pain 
of  carcinoma  of  the  tongue.  Thit; 
may  be  done  by  entering  the  point 
of  a  curved  bistoury  a  little  less 
than  three-quarters  of  an  inch  be- 
hind and  below  the  last  molar  and 
cutting  on  the  bone  towards  the 
tooth. 

The  Floor  of  the  Mouth. 
— ^The  mylo-hyoid  muscle,  extend- 
ing from  the  symphysis  to  the  last 
molar  tooth,  separates  the  buccal 
cavity  from  the  neck.  Infections 
or  neoplasms  beginning  above  this 
muscle  are  first  recognized  through 
the  mouth  ;  those  below  it  in  the 
neck.  The  sublingual  gland,  for 
example,  lies  altogether  above  it 
and  directly  beneath  the  mucous 
membrane  of  the  floor  of  the  mouth  ;  the  duct  of  the  submaxillary  gland  occupies 
a  similar  position.  Affections  of  these  structures,  therefore,  manifest  themselves 
in  the  mouth.  The  submaxillary  gland,  however,  lies  partly  beneath  the  poste- 
rior border  of  the  mylo-hyoid.  Accordingly,  disease  of  this  gland  is  apt  to  show 
most  markedly  beneath  the  jaw  (Fig.  267,  page  247).  "  Ludwig's  angina  "  (page 
553)  may  spread  to  the  loose  connective  tissue  between  the  my'.o-hyoid  muscle 
and  the  mucous  membrane  of  the  floor  of  the  mouth.  That  membrane  is  reflected 
from  the  under  surface  of  the  tongue  to  the  alveoli  and  is  divided  anterioriy  by 
the  frenum  lingua.  On  either  side  of  this  may  be  seen  the  ridges  indicating  the 
situation  of  the  sublingual  glands,  and  close  to  the  frenum  at  the  inner  end  of  the 
ridge  the  papillae  at  the  opening  of  Wharton's  ducts,  into  which  a  fine  probe  may 
be  pawed  (Fig.  1352).  The  inelastic  character  of  the  walls  of  the  latter  should  be 
remembered  as  explaining  in  part  the  intense  pain  caused  by  an  impacted  submax- 
illary calculus.     This  is  also  in  part  due  to  the  close  relation  of  the  duct  to  the 


—Anterior  lingua; 
Klund 


—Cut  Hurlacc  ol 
mucuua  niembrwie 


■LfTiKual  vein 
i^l.injeual  aner>- 


Siibmaiillar)'  duct 
— Sublinxual  gland 


Disaectionof  under  surface  ol  tongue  and  aublinxtjal  >P*c*i 
mucout  membrane  removed  and  tongue  drawn  upvrard  and  for- 
ward Irom  mouth. 


1594 


HUMAN  ANATOMY. 


lintfual  nerve.  The  relation  of  that  nerve  to  the  floor  of  the  mouth  posteriorly 
has  already  been  described  ( page  1 249). 

The  fold  of  mucous  mtmbrane  constituting  the  frenum  may  be  abnormally 
short  and  prevent  the  free  movements  of  the  tongue,  interfering  with  sucking  during; 
infancy  and  with  articulation  later.  When  its  division  is  necessary,  it  should  be  ciit 
through  close  to  the  jaw,  and  with  blunt-pointed  scissors  directed  away  from  the 
tongue  so  as  to  avoid  the  ranine  veins  which  may  be  seen  close  to  it  on  the  under 
surface  of  the  tongue. 

The  ranine  arteries  lie  farther  out  and  are  more  deeply  situated,  being  placed 
beneath  two  converging  raised  fringed  lines  of  mucous  membrane,  the  plica 
fimbnattt.  ' 

A  sublingual  bursa  is  described  by  Tillaux  as  a  triangular  space  situated  lietween 
the  genio-hyo-glossus  and  the  mucous  membrane,  its  tip  being  at  the  frenum  its 
ba.se  at  the  sublingual  gland.  Its  existence,  by  no  means  constant,  is  said  by  Tillaux 
to  explain  the  occurrence  of  the  acute  cystic  tumor  (grenouillelte),  "acute  ranula  " 
which  IS  occasionally  met  with  in  this  region. 

Ilanulae— ordinary  retention  cysts— are  common  in  the  floor  of  the  mouth,  and 
branchiogemc  cysts,  due  to  the  incomplete  closure  of  the  first  branchial  cleft,  are 
sometimes  found  there. 

The  Cheeks — The  buccal  limits  of  the  cheeks  are  accurately  indicated  by  the 
reflections  of  mucous  membrane  lining  them.  By  making  outward  tr.iction  on  the 
angle  of  the  mouth  that  membrane  can  be  seen  and  palpated,  and  ulceration,  as 
from  a  jagged  tooth  or  beginning  epithelioma,  or  mucous  patches,  or  abscess,  or  new 
growths,  can  easily  be  detected. 

The  papilla  indicating  the  opening  of  the  parotid  duct  may  be  seen  or  felt 
opijosite  the  upper  second  molar  tooth.  A  fine  probe  may  be  made  to  enter 
the  duct  for  a  short  distance,  the  normal  curves  then  interfering  with  its  passaee 
(F«-  »343)-  ^^ 

Lipoma  originating  in  the  "boule  de  Bichat"  (page  493)  can  be  recognized. 

As  the  jaws  are  separated  and  closed  the  anterior  border  of  the  masseter  may 
be  seen  and  felt.  The  important  structures  of  the  cheek-  -the  facial  vein  and  artery 
and  the  parotid  duct— are  all  anterior  to  this  line  (Fig.  691). 

The  Tongue. — Congenital  deformity  of  the  tongue  is  rare.  Forked  tongue 
—normal  in  some  birds  and  reptiles  and  in  seals— is  rare  ;  it  is  usually  in  asso- 
ciation with  other  developmental  defects,  as  cleft  palate.  Congenital  absence  has 
been  noted  (de  Jussieu). 

Macroglossia  {lymphangioma  cavemosum,  Virchow)  is  a  congenital  affection 
in  which  the  lymph-channels  and  lymph-spaces  are  dilated  and  the  lymphoid  tissue 
throughout  the  tongue,  but  especially  at  the  base,  greatly  increased.  The  tongue 
may  attain  an  enormous  size,  and  has  even,  by  pressure,  caused  deformities  of  the 
teeth  and  alveolar  arches  and  luxation  of  the  mandible.  The  foramen  c.srum,  indi- 
cating the  junction  of  the  pharyngeal  and  buccal  parts  of  the  tongue,  is  the  superior 
termination  of  the  foetal  thyro-glossal  duct.  ' '  Ducts  lined  with  epithelium  have  been 
found  leading  from  the  foramen  cscum  to  accessory  glands  about  the  hyoid  bone 
It  IS  probably  from  these  glandular  and  epithelial  collections  about  the  hyoid  bone 
that  certain  deep-seated  forms  of  cancer  of  the  neck  are  developed.  Some  of  these 
take  the  form  of  malignant  cysts"  (Treves). 

The  upper  surface  of  the  tongue  has  for  centu.ies  '.,  en  the  objea  of  especial 
observation  in  disease.  The  practical  value  of  these  olwer rations  is  not  univer- 
sally conceded,  and  too  much  weight  has  been  placed  upon  tiiem  ;  but  there  can 
be  no  doubt  that  some  help  in  prognosis  and  even  in  diagnosis  in  digestive  de- 
rangements, in  fevers,  and  in  various  toxaemias  may  be  obfcilned  by  inspection  of 
the  tongue. 

The  "fur,"  so  carefully  studied,  consists  of  a  mixture  of  desquamated  nithelial 
cells  food  ^articles,  and  micro-organisms  of  various  kind  uvcrlying  living  epithelium 
which  may  be  abnormally  proliferating. 

The  surface  between  the  circumvallate  papilla  is  apt  to  be  the  most  heavily 
coated,  either  in  health  or  disease,  because  it  is  the  least  mobile  part  of  the  tongue 
and  IS  not  kept  clean  by  friction,  as  are  the  sides  and  tip.     The  appearance  of 


PRACTICAI-  CONSIDERATIONS:  THK  MOITH. 


ISMS 


the  coating  and  of  th«  tongue  its*"  va'ii-*  (jreatlV'  but  it  may  be  said  that  dry- 
HISS  not  due  to  niouth-brcathin^;,  hut  In.ui  deficient  setretion.  as  in  ievtrs  ;  Jari-- 
Hfss,  from  decomposition  and  desiccation  ol  the  coalill^^  or  from  iinj>erfect  oxy- 
genation of  the  blood  ;  roughnfss,  from  papillary  overgrowth  with  marked  epithelial 
proliferation  and  desquamaticm  ;  redness,  from  epithelud  denutlation  ;  and  stiff- 
ness, slowness,  ox  tremulousfsf  in  protrusi»)n,  from  either  thick,  inrtexilde  coating, 
muscular  weakness,  or  nieu;-'   hebetude,   are   uniformly  regarded  us  unfavorable 

conditions.  ,    .        i        •         i 

Unilateral  furring  of  the  tongue  has  been  observed  m  cases  of  dental  canes,  ol 
fractured  skull,  and  of  intracranial  disease,  in  all  three  instances  the  furring  Iwnig  on 
the  side  on  which  there  was  irritation  of  the  branches  of  the  tilth  pair  of  nerves.  In 
some  of  them  it  was  confined  to  the  anterior  two-thirds  ol  the  upper  surface,— /.<■. , 
to  the  distribution  of  the  lingual  branch  of  the  fifth  ( Hilton ). 

In  tonsillitis  the  tongue  will  often  be  furred  over  its  posterior  part  only  — 
i.e.,  the  portion  which,  like  the  tonsil,  receives  its  nerve-supply  from  the  glosso- 
pharyngeal (Jacobson).  Unilateral  furring  in  the  presence  of  t<H)thache  may  be  due 
partly  to  the  instinctive  immobilizing  of  that  side  of  the  tonguo  nearest  the  pamful 
tooth  (Hutchinson).  . 

In  chronic  superficial  glossitis  the  epithelium  thick -n'-  at  places  mto  rounded, 
whitish  patches,  which  are  difficult  to  heal  on  accou  i  it  ii  e  constant  exjK«ure 
to  warmth,  moisture,  infection,  and  minor  traumatism  w,  ■  '.  ..he  im|X)ssibility  of 
securing  rest.  This  condition  {leukoplakia)  may  pn.-cede  the  development  of 
epithelioma. 

In  rare  cases  the  epidermis  covering  the  filiform  papillx  undergoes  hypertrophy, 
producing  the  so-callecf  "  hairy  tongue." 

The  lymphoid  tissue  behind  the  circumvallate  papilla,  from  overgrowth,  forms 
an  irregular  rounded  mass  just  beneath  the  mucous  membrane, — the  lingual  tonsil, 
—which  Iron  its  proximity  to  and  interlerence  with  the  epiglottis  may  require 
removal. 

The  connective  tissue  ol  the  tongue  is  scanty,  but  is  abundant  enough  to  permit 
of  great  swelling  in  cases  of  acute  glossitis,  and  this  is  favored  by  the  vascularity  of 
the  organ.  The  cause  is  always  infection  through  a  surface  solution  ol  continuity 
either  traumatic  or  during  some  disease  attended  by  drying  and  Assuring  ol  the 
tongue.     On  account  ol  the  vascularity,  naevoid  growths  are  Irequent. 

Carcinoma  ol  the  tongue  is  exceedingly  common,  and  Treves  calls  attention  to 
the  lact  that  it  usually  aHects  the  anterior  two-thirds  or  that  portion  which  is  derived 
from  the  mandibular  arch,  as  is  the  lower  lip,  which  is  also  one  ol  the  commonest 
sites  of  epithelioma.  Cancer  of  the  fore  part  of  the  tongue  may  follow  the  lym- 
phatics of  that  region  into  the  submaxillary  glands,  or  pass  by  the  main  lymphatic 
channels  into  the  deep  cervical  glands.  Those  first  demon.strably  enlarged,  what- 
ever the  site  of  the  cancer,  are  apt  to  be  in  the  group  beneath  and  behind  the  angle 

of  the  jaw.  .       .     •  .      l 

The  pain  in  cancer  of  the  tongue  is  almost  always  associated  with  what  are 
described  as  "earache,"  "toothache."  "laceache,"  and  sometimes  with  spasm  ol 
the  muscles  ol  ms^tication.  These  symptoms  are  due  to  the  connection  of  the 
lingual  branch  ol  the  filth  pair  with  other  branches  ol  the  third  division  ol  the  filth, 
especially  the  auriculo-temporal  and  inlerior  dental,  with  the  tympanic  branch  ol  the 
glosso-pharyngeal,  and  with  the  chorda  tympani  Irom  the  lacial. 

Pressure  upon,  or  disease  ol,  the  hypoglossal  nerve  may  cause  unilateral  atrophy 
ol  the  tongue.  The  various  paralyses  should  be  studied  in  connection  with  the 
nervous  supply  ol  the  tongue. 

As  the  tongue  depends  upon  muscular  and  not  ligamentous  attachments  for  the 
preservation  of  its  position  in  the  mouth,  its  tendency  to  drop  backward  by  gravity 
during  complete  anaesthes'  or  some  other  forms  of  profound  unconsciousness  in 
which  muscular  rclaxatior.  uf  paru'ysis  occurs  shoH?--i  not  be  fr.r--r!tter.  If  it  is 
allowed  to  fall  back,  the  pressure  on  th6  epijtlottis  may  close  the  "ing  into  the 
larynx.  During  anaesthetization  it  is  well  press 'he  lower  jaw  wt  -ward,  carry- 
ing  the  tongue  with  it  throu! '  *«  of    r.-  genio-glossi,  ai..i  to  elevate  the 

chin,  which  still  farther  adv  lad  removes  it  Irom  close  proximity  to 


1596 


HUMAN  ANATOMY. 


the  epiglottis.     Often  this  does  not  sufl&ce,  and  direct  traction  on  the  toncnie  itself 
IS  required.  " 

Excision  of  the  entire  tongue  necessiutes  division  of  the  muscles  of  the  tongue 
Its  connections  by  mucous  membrane  with  the  soft  palate,  the  alveoli,  and  the 
epiglottis,  the  lingual  arteries  and  veins,  and  the  glosso-pharyngeal,  lineual,  and 
hypoglossal  nerves. 

In  opening  abscesses  of  the  tongue  the  position  of  the  lingual  arteries— much 
nearer  the  lower  than  the  upper  surface— should  be  remembered. 

Hemorrhage  from  wounds  or  during  operation  may  temporarily  be  controlled  by 
pressure  from  behind  forward  on  the  base  of  the  tongue  by  two  fingers  thrust  well 
below  and  behind  it  in  the  pharynx.  By  this  procedure,  or  by  forcing  up  the  soft 
tissues  between  the  inferior  maxilla  and  the  hyoid  bone  with  the  finger  or  thumb 
the  cut  surface  during  partial  excision  may  be  brought  well  into  view  and  the 
hemorrhage  controlled  while  the  vessels  are  sought  and  secured. 

THE  PHARYNX. 

The  pharynx  is  a  bag,  open  in  front,  with  musculo-membranous  walls,  lined  with 
mucous  membrane,  extending  from  the  base  of  the  skull  to  the  lower  border  of  the 
Urynx,  near  the  level  of  the  top  of  the  seventh  cervical  vertebra.  Thus  it  is  bounded 
behind  by  the  spine,  covered  by  the  prevertebral  muscles  and  kscia,  and  by  the  basilar 
process  of  the  occipital  bone,  which,  especially  in  the  median  line,  is  separated  by 
much  areolar  tissue,  as  well  as  by  muscles  from  the  posterior  wall.  The  steep  rise 
of  the  basilar  process,  together  with  the  downward  growth  of  the  face,  forms  the 
deep  recess  known  as  the  naso-pharynx.  The  roof  is  formed  by  a  little  of  the  front 
of  the  basilar  process  and  by  the  back  part  of  the  basi-sphenoid.  The  anterior  wall  is 
formed  by  the  back  of  the  framework  of  the  face,  the  soft  palate,  the  back  of  the 
tongue,  the  hyoid  bone,  and  the  larynx.  The  pharynx  communicates  in  front  with 
the  nasal  chambers  and  the  mouth  ;  the  Eustachian  tubes  open  into  it  on  either  side 
near  the  top  ;  and  below  it  contains  the  opening  of  the  larynx,  behind  which  it  passes 
into  the  oesophagus.  The  framework  consists  of  \\i^  pharyngeal  aponeurosis,  a  dis- 
tinct fibrous  membrane  above,  placed  betveen  the  mucous  membrane  and  the  mus- 
cular layer,  which  grows  weaker  below  and  is  continued  into  the  gullet  This  is 
attached  above  to  the  pharyngeal  tubercle  and  to  the  occipital  bone  on  either  side 
of  it,  to  the  ciutilage  between  the  petrous  portion  of  the  temporal  and  the  basilar 
process,  to  the  EusUchian  tube  which  passes  over  it,  and  to  the  base  of  the  internal 
pterygoid  plate.  This  fascia  is  wanting  in  front.  The  parts  forming  most  of  the 
anterior  wall — the  soft  palate  and  the  back  of  the  tongue — are  capable  of  changing 
their  relations.  The  pharynx  is  enclosed  by  a  layer  of  fascia,  the  bucco-pkaryngeal 
(not  to  be  confounded  with  the  pharyngeal  aponeurosis),  the  front  part  of  which  is 
connected  with  the  ptervgo-mandibular  ligament  and  covers  the  buccinator  muscle. 
This  fascia  lies  beneath  the  parotid  gland  and  mingles  with  the  cobweb-like  tissue  of 
the  carotid  sheath  to  make  a  large  amount  of  rather  dense  areolar  tissue  on  either  side. 
At  the  back  it  is  very  lax,  allowing  the  pharynx  to  move  on  the  smooth  prevertebral 
fascia.     The  condition  there  approaches  that  of  a  serous  bursa. 

The  pharynx  is  divided  into  the  naso-,  oro-,  and  laryngo-pharynx  by  folds  on 
the  anterior  and  lateral  walls.  The  uninterrupted  posterior  wall  is  covered  with 
smooth  mucous  membrane,  which,  behind  the  larynx,  tends  to  be  puckered  into 
longitudinal  folds.  The  naso-pkarynx  is  that  part  above  the  free  edge  of  the  soft 
palate.  The  oro-pkarynx  communicates  at  the  anterior  pillar  of  the  fauces  with  the 
mouth.  The  isthmus,  a  niche  between  the  faucial  pillars  containing  the  tonsils,  is  its 
anterior  part.  It  is  separated  from  the  laryngo-pharynx  by  the  pharyngo-epigloUic 
fold,  which  extends  from  the  epiglottis  to  the  side  of  the  pharynx,  as  more  particu- 
larly described  later.  The  length  of  the  male  pharynx  is  about  13  cm.  (about  5  in. ), 
which  is  rarely  much  exceeded.  The  greatest  breadth  (4-5  cm. )  is  near  the  top  of 
the  laryngo-pharynx,  rather  below  the  greater  horns  of  the  hyoid  bone.  The  greatest 
breadth  in  the  naso-pharynx,  between  the  deepest  points  of  the  fossa  of  Rosenmiiller, 
w  3-  5  cm. ,  or  perhaps  a  little  more.  Behind  the  upper  margin  of  the  cricoid  cartilage 
the  breadth  is  not  over  3  cm.,  below  which  it  abruptly  diminishes.     The  antero- 


THE  PHARYNX. 


1597 


posterior  diameter  in  the  median  line  is  greatest  in  the  naso-pharynx, — about  2  cm. 
The  back  of  the  lower  part  of  the  soft  palate  is  less  than  half  that  distance  from  the 

Fio.  1353. 


Frontal  ainus 


Sella  turcica 


If Sphenoidal 

ainua 


— Na>o-pharyng«*l 
fold 

Fosu  or  Kuuamiaiat 
LiMUcliian  tuljc 
ynicnltonbU 
Iplnco-imiallne  fold 

—SilpinRo- 

pharyagcal  ioU 


Gcnio.h>'oid 
Hyoid 


'osterior  wall  ol 
pharynx 

lato-pharyngcal 
fold 


iar\  ngo^eplglottic 

■  Id 


Cuneiform  tuberciv 
.Tubercle  of  Santoriai 


ricoid  cartilage 


Tracheal  cattilai 


Sagittal  Mclion  of  head,  slightly  In  right  of  median  phine ;  toiigiw  has  hren  pulled  down. 

posterior  pharj'njjeiil  wall.     The  jjreatest  depth  in  this  direction  (,V4  cm. )  is  st  the 
side,  from  the  anterior  pillar  to  the  posterior  waU.     Behind  the  cricoid  cartilage  the 


1598 


HUMAN   ANATOMY. 


front  and  back  walls  are  probably  in  contact    In  the  female  several  of  these  distances 
are  smaller.     Thus  the  pharynx  is  in  horizontal  sections  at  most  levels  a  transverse 

The  naso-pharynx,  broad  from  side  to  side  and  short  from  before  backward 
pMses  msensibly  mto  the  oro-pharynx  when  the  soft  palate  is  not  raised  so  as  to  cut 
oB  communication.     Anteriorly  are  the  nasal  openings,  described  with  the  nose 
Ihe  separation  of  the  two  regions  on  the  lateral  wall  is  determined  by  the  naso- 
pharyngeal  fold  ^\iiz\i  runs  from  the  base  of  the  skull  to  the  beginning  of  the  soft 
palate.       1  his  fold  is  very  irregular  in  course  and  development.     It  occasionally  is 
grooved  so  as  to  present  a  hirrow.     Sometimes  the  hirrow  takes  the  place  of  the  fold 
and  at  other  times  the  fold  joins  that  in  front  of  the  opening  of  the  Eustachian  tube 
This  onfice  is  on  a  level  with  the  end  of  the  inferior  turbinate  bone  and  less  than 
I  cm.  behind  it     It  is  usually  a  triangular  opening  without  a  distinct  border  below 
although  It  may  be  oval  or  even  round.     •^;  ;  longest  diameter  is  about  i  cm.     The 
end  of  the  cartilage  of  the  tube  curves  <  ver  the  top  of  the  opening  from  the  front 
and  descends  along  its  posterior  border,  producing  a  strong  fold  of  the  mucous  mem- 
brane, the  salpingopharyngeal,  which  descends  to  be  lost  in  the  lateral  wall  of  the 
oro-pharynx,  or  even  sooner.     The  salpingopalatine  fold  in  front  of  the  opening  of 
the  Eustachian  tube  is,  as  a  rule,  less  prominent  and  very  variable.     It  is  formed 
above  by  the  bent  end  of  the  cartilage,  and  below  by  a  small  band  of  fibrous  tissue 
the  saiptngo-palatine  ligament,  running  from  the  cartilage  into  the  soft  palate.     The 
fossa  of  Rosenmitller  is  a  deep  pocket  at  the  angle  of  the  pharynx  between  the 
posterior  wall  and  the  back  of  the  projection  of  the  cartilage  of  the  tube.    Its  anterior 
and  posterior  walk  are  almost  in  contact  and  are  often  connected    by  accidental 
adhesions.    This  is  the  broadest  part  of  the  naso-pharynx.    Adenoid  collections-the 


tubal  tonsils— ^^\oyxrA  in  varying  degree  about"  the' orifice'of' the 'tub^r«peci^'l'y 
The  bdly  of  the  levator  palati  muscle  makes  a  prominence 


over  the  fold  behind  it      ^  „.  „ 

in  the  lateral  wall  below  the  tubal  orifice. 

The  oro-phaiynx  opens  into  the  mouth  at  the  anterior  pUlar  of  the  fauces 
I  he  posterior  pillar,  covenng  the  palato-pharyngeus  muscle,  runs  down  the  side  of 
the  pharynx  as  the  palato-pharyngeal  fold.  It  may  be  traced  to  the  base  of  the 
superior  horn  of  the  thyroid  cartilage,  or,  as  is  most  common,  it  is  lost  on  the  lateral 
wall  a  little  higher.  The  pharyngo-epigloUic  fold  above  mentioned  arises  from  the 
front  of  the  epiglottis  ntar  the  lateral  edge  and  runs  upward  and  backward  across 
the  pharynx.  It  may  end  soon,  or  A  may  reach  the  palato-pharyngeal  fold  or 
crossing  this,  may  extend  eN-en  as  far  as  the  salpingo-pharyageal  one.  It  contains 
muscular  or  tendinous  fibr-s  from  the  stylo-pharyngeus.  If  well  marked,  it  may 
bound  below  the  niche  containing  the  tonsil.  The  anterior  wall  of  the  oro-pharynx 
IS  formed,  the  mouth  being  closed,  by  the  posterior  vertical  part  of  the  tongue  The 
respiratory  tract,  passing  through  the  nose,  and  the  digestive,  passing  through  the 
mouth,  cross  each  other  m  the  oro-pharynx.  so  that  the  former  is  the  anterior  below 
this  point 

th»  ^!!f  il!i'''"i°'?*"P'?*i  *'!*  '*?!"?*  P^^*  *^  ">*  pharynx,  is.  roughly  speaking, 
the  oart  below  the  level  of  the  hyoid  bone.     It  is  separated  fr«m  the  oro-pharynx 
by  the  pharyngo-epiglottic  fold.     In  the  middle  of  it  is  the  opening  of  the  larynx 
behind  the  epiglottis  and  enclosed  by  the  aryteno-epiglottic  and  interarytenoid  folds 
Ihe  sinus  pyrtformts  is  a  depression  on  either  side  of  the  entrance  of  the  larynx 
between  the  aryteno-epiglottic  fold  and  the  arytenoid  cartilage  internally  and  a  part 
of  the  great  wing  of  the  thyroid  cartilage  and  the  thyro-hyoid  membrane  externally 
It  IS  open  behind.     The  thin  mucous  membrane  lining  the  sinus  has  a  transverse 
fold,  formed  by  the  supenor  laryngeal  nerve,  in  front  between  the  hyoid  bone  and 
the  thyroid  cartilage.      The  lower  part  of  the  palato-pharyngeal  fold  is  seen  in  frozen 
sections  near  the  superior  horn  of  the  thyroid  cartilage  at  the  lateral  aspect  of  the 
cleft,  which  IS  all  that  appears  of  the  pharynx.     The  anterior  wall  behind  the  aryte- 
noid rartilages  and  the  structures  between  them  slants  backward  as  it  descends 
Behind^  the  cricoid  cartilage  it  is  vertical      Here  the  pharynx  narrows  to  join  the 

The  mucous  membrane  of  the  pharynx  is  smooth,  except  for  the  elevations 
caused  by  collections  of  lymphoid  follicles.     It  is  more  loosely  attached  and  more 


THE  PHARYNX. 


1599 


disposed  to  be  thrown  into  folds  in  the  lower  (lart.  Mucous  glands,  on  the  other 
hand,  are  numerous  in  the  upper  part,  scarce  below  ;  they  lie  partly  within  the 
mucosa  and  partly  in  the  submucous  tissue  and  between  the  muscular  bundles.  The 
character  of  the  pharyngeal  epithelium  varies  in  different  localities.  In  the  nasal 
pharynx  the  stratified  ciliated  columnar  cells  of  the  nasal  fossa  are  continued  as  the 
covering  of  the  pharyngeal  mucous  membrane,  while  the  oro-pharynx  is  clothed  with 
stratified  squamous  epithelium  continued  from  the  mouth.  The  last-named  ty[)e 
of  epithelium  likewise  covers  the  greater  part  of  the  laryngeal  portion.  The 
exact  distribution  of  the  two  varieties  of  cells*is  subject  to  considerable  individual 
variation.  The  ciliated  columnar  type  extends  laterally  to  include  the  openings 
of  the  Eustachian  tubes,  but  lower  down  gives  place  to  the  L.|Uamous.     By  no 


Fio. 


Bate  of  skull 


I3S4- 

Naial  Mptnm 


Naso-pharynxtal  fold 

Lymphoid  tiuue 

Posterior  pillar  of  fauces. 
Faucial  tonsil 

PharyfiKo.«ptglottic  fold 


Cut  edge  of  pharyns. 


Unia 

Dorsum  of  tonf  u* 

Gloaao-epijelottic  fossa 
Median  KloKso.epiKlo(tic  fold 

EpiKloltis.  tnnied  back 
linus  pyrifnrmia 

Posterior  surface  of  larynx 


Pharynx  opened  from  behind ;  epiKloltis  turned  back. 


means  the  entire  posterior  surface  of  the  soft  palate  is  clothed  with  ciliated  colum- 
nar cells,  since  the  entire  uvula  and  the  edges  of  the  palato-pharyngeal  folds  are 
invested  with  stratified  squamous  epithelium.  The  latter  also  covers  the  jM>sterior 
wall  of  the  pharynx  and  extends  above  as  far  as  the  vault.  When  covered  with 
ciliated  epithelium,  the  mucous  membrane  is  redder,  thicker,  and  contains  more 
glands,  but  fewer  papitlse,  than  in  those  parts  in  which  the  squamous  cells  prevail. 
While  containing  much  lymphoid  tissue,  fat  is  limited  to  a  few  deeply  seated  lobules 
of  adipose  tis.sue. 

Lymphoid  Structures. — The  upper  part  of  the  pharynx  contains  many 
lymphoid  collections  which  make  the  surface  uneven.  They  are  much  less  frequent 
below.  The  larger  and  more  o)nstant  masses  are  called  ' '  tonsils. ' '  These  include 
the  faucial  tontiU  in  the  oro-pharynx,  between  the  pillars  of  the  fauces,  the  pkaryn- 


i6oo 


HUMAN  ANATOMY. 


Pio.  1355. 


ules 


geal  tonsil  in  the  upper  part  of  the  pharynx,  the  tubal  tonsils  at  the  openings  of 
the  Eustachian  tubes,  especially  on  the  posterior  fold,  and  the  lingual  tonsil,  con- 
sisting of  the  scattered  adenoid  collections 
over  the  posterior  third  of  the  tongue.  Many 
additional  lymph-nodules  are  scattered  over 
the  sides  and  roof,  so  connected  as  to  form 
a  lymphoid  ring  at  the  upper  part  of  the 
pharynx. 

Thefaucial  tonsils  (Figs.  1326,  1353) 
are  theoretically  two  almond-shaped  masses 
of  adenoid  tissuo.  placed  one  on  each  side  of 
the  oro-pharjr  t,  between  the  pillars  of  the 
fauces.  The  linjf  diameter  is  vertical,  and 
they  have  un  outer  and  an  inner  surface  and 
an  anterior  and  a  posterior  border.  The 
length  is  conventionally  put  at  from  20-25 
mm.,  the  breadth  at  15  mm.,  and  the  thick- 
ness at  10  mm.  Practically,  however,  there 
is  no  definite  shape  nor  size.  In  childhood 
the  tonsil  generally  projects  as  a  globular 
mass.  If  it  extends  more  than  Mightiy  be- 
yond the  level  of  the  faucial  pillars,  it  is  said 
to  be  enlarged.  After  middle  life  it  rises  usu- 
ally but  little  froni  the  floor  of  the  niche. 
The  shape  of  the  free  surface  gives  no  clue 
to  the  size  of  the  deep  surface.  In  structure 
the  tonsil  is  a  mass  of  adenoid  tissue  en- 
closed in  a  fibrous  capsule  which  is  crossed 
on  both  the  deep  and  free  surfeices  by  a  thin 
layer  of  muscular  fibres.  The  superficial  layer 
belongs  to  the  [talato-glossus ;  the  deep  or 
external  layer  arises  from  the  superior  con- 
strictor and  passes  to  the  tongfue.  Beyond 
this  externally  are  fat  and  areolar  tissue.  The  closely  adherent  mucous  membrane 
covers  the  free  surface,  which  is  full  of  pits  from  i  or  2  mm.  to  i  cm.  in  depth. 

The  larger  ones  often  expand  be- 
low the  orifice,  so  that  they  may 
collect  and  retain  secretions.  A 
small  free  space,  the  supratonsillar 
fossa,  lies  above  the  tonsil  at  the 
apex  of  the  niche  containing  it ;  at 
the  front  of  this  there  is  very  often 
a  series  of  crypts  with  detached 
adenoid  tissue  about  them,  bur- 
rowing under  the  anterior  pillar 
from  behind  and  making  a  pouch 
beneath  a  fold,  the  plica  trian- 
gularis. The  adenoid  tissue  is 
continuous  below  with  that  of  the 
tongue.  The  mucous  membrane 
of  the  oro-pharynx  shows  many 
scattered  lymphoid  follicles  in  its 
walls,  especially  on  the  sides  at 
and  above  the  level  of  the  tonsils. 
Vessels. — The  arteries  sup- 
plying the  faucial  tonsil  are  de- 
rived from  .several  sources,  and  the  arrangement  of  the  vessels  is  extremely  irreguHr  ; 
the  branch  from  the  ascending  pharyngeal  and  that  from  the  facial  artery — one  or 
both — enter  its  base,  while  twigs  from  the  lingual  and  descending  palatine  arteries. 


Section  through  fiucial  tonsil,  showing  general  dis- 
position of  lymphoid  tissue.    X  30. 


Fig.    1356. 


L^pliocytes, 
in\'ading 

Epitheliiun 


Blood-vessel 


Ponion  of  ttncUl  tonsil,  showing  epithelial  lining  of  crypt  invaded 
by  escaping  lymphocytes.    X  325. 


THE  PHARYNX. 


1601 


and  perhaps  others,  reach  it  beneath  the  mucous  membrane.  Under  ordinary  cir- 
cumstances the  tonsil  a  not  very  vascular,  but  receives  a  large  quantity  of  blood 
when  inflamed.  There  is  a  venous  plexus  communicating  with  the  veins  of  the 
pharynx.  The  lymphatics  probably  communicate  both  with  those  of  the  dorsum 
of  the  tongue  and  with  the  glands  near  the  angle  of  the  jaw. 

Nerves.— Tm  nervous  supply  is  from  the  fifth  and  the  glosso-pharyngeal. 
(The  rela'ions  of  the  tonsils  are  given  with  those  of  the  pharynx,  page  1602.) 
The  pharyngeal  tonsil  (Fig.  1353),  sometimes  called  the  third  tonsil,  is  a 
median  mass  of  adenoid  tissue  m  the  postero-superior  wall  of  the  pharynx,  which 
reaches  its  greatest  development  in  early  childhood,  generally  dwindlmp;  after  the 
twelfth  year.  When  well  developed,  it  lies  below  the  occipital  and  the  basi-sphenoid, 
nearly  fUling  the  space  from  the  nasal  septum  to  the  back  of  the  pharynx  and  almost 
touching  on  either  side  the  folds  made  by  the  tubal  cartilages.  Its  thickness  in  the 
median  line  is  nearly  i  cm.  Thus  without  being  hypertrophied  it  nearly  fills  the  naso- 
pharynx.   The  pharyng«J  tonsil  is  a  lobuUted  organ,  the  swellings  bemg  often  regu- 


Fio.  1357. 

Foi«m«c«:am         cri«a«.lU 


Gcnio-hyoid 

Mylo^hyoid 


Hyoidbonc 
Thyroid  cartilage  [ 


Fttultuy  body 

Cnnlo-pharyngcal  canal 


Pharynccal  toasil 
Cccipiul  bone 
PhaO'OBOi  toiuU 
Anterior  arch  o(  attea 

Xdontold  proceia 
-Uvula 

Epiglottis 

Third  cervical  vettcbra 


Vantricle  o(  larynx 


-Cricoid  cartilage 


Anterior  portion  of  meaial  sagitui  lection  of  child'i  head,  pitifaably  of  about  three  yeare.    Reduced  one-fourth. 

larly  arranged  around  a  central  depression  ;  consequently  it  presents  many  pockets. 
The  central  one,  which  varies  widely,  is  often  improperly  called  the  bursa  pharyngea. 
It  has  absolutely  nothing  to  do  with  the  canal  from  the  mouth  to  the  sella  turcica, 
through  which  a  process  of  the  oral  tissue  passes  in  early  foetal  life  to  the  pituitary 
body  (Fig.  1357),  being  decidedly  behind  that  past.  ^.  Neither  is  it  the  true  bursa 
pharyngea,  since  this  term  is  more  properly  applied  to  a  structure  of  uncommon 
occurrence, — namely,  a  still  more  posterior  pocket  in  the  mucous  membrane  leading 
from  the  roof  of  the  pharynx,  just  behind  its  tonsil,  into  a  small  recess  not  over  1.5 
cm.  in  length,  on  the  under  side  of  the  basilar  pt^cess. 

Relations  of  the  Pharynx. — The  structures  behind  the  posterior  wall  have 
been  mentioned  (page  1596).  The  tip  of  the  normal  uvula  hangs  on  a  level  near  the 
lower  part  of  the  axis  or  the  top  of  the  third  cer%  ical  vertebra.  The  tip  of  the  epi- 
glottis is  usually  opposite  the  lower  part  of  the  third.  The  second  and  third  cervical 
vertebrae  are  those  behind  that  part  of  the  phar>-nx  seen  through  the  open  mouth. 
The  pharynx  ends  at  about  the  top  of  the  seventh  cer\'!cal  vertebra.  The  lateral  wall 
of  the  pharynx  is  very  narrow,  except  in  the  region  of  the  tonsils,  where  it  reaches  for- 
ward to  the  anterior  pillar  of  the  fauces.     From  the  top  of  the  thyroid  downward  it 


1 603 


HUMAN  ANATOMY. 


Fio.  1358. 


Pharyngeal  toasil  of  child  one  year 
old.    (Sckwaiac*.) 


Lymph-nodulc 


is  nothing  more  than  the  fold  around  the  end  of  a  transverse  linear  cleft.  The  whole 
lateral  aspect  is  covered  by  a  thick  layer  of  areolar  tissue,  continuous  with  that 
of  the  carotid  sheath.  It  is  most  convenient  to  give  the  relations  of  the  lateral  wall 
from  below  upward,  excepting  the  nerves.  The  upper 
part  of  the  lobes  of  the  thyroid  gland  comes  very  close 
to  the  lower  part  of  the  pharynx,  and  may  even  touch 
it  without  undue  enlargement.  They  separate  the 
common  carotid  from  the  pharynx.  A  little  higher 
this  vessel  is  on  the  outer  side  of  the  great  wing  of 
the  thyroid  cartilage,  but  if  the  h«id  be  turned  to 
one  side  the  vessel  of  the  other  side  will  rest  on  the 
pharynx.  The  common  carotid  artery  is  very  dose 
to  the  pharynx  just  before  its  division.  The  inter- 
nal carotid  lies  against  it  until  it  reaches  the  skull. 
The  beginning  of  the  external  carotid  with  its  lingual  and  facial  branches  is  also 
against  it.  The  ascending  pharyngeal  artery  runs  along  it,  the  middle  meningeal 
lying  agiinst  its  upper  part.  The  internal  jugular  vein  is,  probably,  nowhere  in 
direct  contact  with  the  pharynx  unless  just  below  the  skull.  The  submaxillary 
gland  touches  it  at  the  angle  of  the  jaw. 

The  sympathetic  nerve  comes  in  contact  with  the  back  or  side  of  the  pharynx. 
The  vagus  lies  against  the  pharynx  behind  the  internal  carotid  ;  on  reaching  the 

common     carotid,     however, 
Fic.  1359.  jj   jg  in    [ggg  direct    contact. 

Its  superior  laryngeal  branch 
crosses  the  pharynx  to  reach 
the  thyro-hyoid  membrane. 
The  spinal  accessory  and  the 
glosso-pharyngeal  nerves  lie 
against  the  upper  part  of  the 
pharynx. 

The  faucial  tonsil  lies 
about  2.5  cm.  above  the  angle 
and  opposite  a  vertical  line  di- 
viding the  ramus  of  the  jaw^ 
into  a  front  and  a  back  half.  It 
lies  between  the  pillars  of  the 
buces,  and  is  separated  from 
the  mucous  membrane  by  a 
thin  layer  of  muscular  fibres. 
The  lower  end  reaches  the 
tongue,  the  adenoid  tissue 
being  at  times  continuous 
between  them.  The  tonsil  is 
covered  by  the  sujserior  con- 
strictor. External  to  this  is  a 
yielding  mass  of  areolar  tis- 
sue, continuous  with  that  of 
the  carotid  sheath,  into  which 
the  tonsil  may  force  its  way 
if  enlarged.  This  areolar  tis- 
sue is  bounded  in  front  by 
the  internal  pterygoid  muscle, 
and  is  pierced  by  the  stylo- 
glossus and  the  stylo-pha- 
ryngeus,  which  subdivide  it, 
leaving  a  small  part  of  it  be- 
tween them  and  the  tonsil.  At  this  level  both  carotids  are  at  a  considerable  dis- 
tance from  the  tonsil.  The  internal  is  posterior  and  external,  about  2  cm.  distant. 
According  to  Zuckerkandl,  a  transverse  line  through  the  posterior  pillar  will  pass 


Bundles  of 
muscular  tis- 
aue  of  constric' 
torv 


Surface 
epithelium 


Sagittal  section  of  poaterior  wall  of  pharvnx  of  child,  showing  part  of 
pharyngeal  tonsil. 


THE  PHARYNX. 


1603 


2  cm.  in  front  of  the  vessel.  The  external  carotid  is  placed  more  d.rectly  outward  and 
is  rather  the  nearer  of  the  two.  The  parotid  gland,  according  to  Tillaux.  sends  a 
process  in  front  of  the  styloid  process,  which  reaches  the  lateral  wall.  This  extension, 
however,  does  not  seem  to  be  by  any  means  constant.  ,   .     t         ,■ 

Development  and  Growth  of  the  Pharynx.-An  account  of  the  formaUon 
of  the  primitive  pharynx  is  included  in  the  Development  of  the  Alimentory  Tract 
f  oaee  iW).  the  later  changes  being  here  noted.  In  the  section  on  the  bones  it  was 
shown  tlat  the  chief  peculiarities  of  the  infant  skeleton  in  this  region  are  due  to  the 
small  size  of  the  face  and  the  more  horizontal  base  of  the  skull  The  nasopharynx 
has  very  little  height,  while,  owing  to  the  peculiar  disposition  of  the  parts,  it  has  nearly 
the  same  anteroposterior  diameter  as  in  the  adult.  It  is  relatively  broad  and  long, 
but  very  shallow.  The  tongue,  in  proportion,  is  much  less  thick  at  the  base  than 
later.  The  larynx  is  small,  and,  moreover,  is  placed  higher  m  relation  to  the  vertebral 
column,  so  that  the  termination  of  t!>e  pharynx  is  also  higher.  The  position  of  the 
larynx  at  different  ages  is  considered  with  that  organ  (page  i8a8).  The  soft  palate  is 
in  the  main  horizontal  at  birth  and  about  on  a  level  with  the  top  ol  the  atlas.  The 
uvula  is  rudimentary.  In  a  child  of  probably  not  over  three  years  we  have  found 
the  tip  of  the  uvula  rather  below  the  middle  of  the  body  ol  the  axis.  In  Synwngton  s 
section  of  a  girl  of  thirteen  it  is  pretty  nearly  in  the  adult  i»siUon  In  mfancy  the 
soft  palate  probaWy  closes  the  passage  into  the  naso-pharynx  from  below  less  perfecUy 

than  later.  -,    •     %.  u 

The  oiieninz  of  the  Eustachian  tube,  although  neceanarily  m  the  nasopharynx, 
is  in  the  foTtus  below  the  level  of  the  hard  palate.  At  birth  it  is  at  about  that  level, 
but  rather  below  than  above  it  According  to  Disse,  there  is  but  litde  change  for 
nine  months,  after  which  the  opening  is  on  the  levd  of  the  inferior  meatus.  Proba- 
bly  the  adult  position  is  generally  reached  after  puberty.  The  ojwiing  is  smau 
in  the  infant  and  young  chQd,  and,  owing  to  want  of  development  of  the  cartifage, 

.  ...  ••    ,  .     \^"-^: .1 •.    :•   ._J  «^«_.ui,ur,»lu  halt  a  amall  ffVlsa  of    KOSen- 

there  is  but  a  ! 
miiller.  The 
before  birth 


ina  young  tiiuu,  aiiu,  v*w  11115   •"   "—•••■>"  — -• — 1 y  to 

slight  elevation  about  it  and  consequendy  but  a  small  fossa  ot  Kosen 
s  entire  adenoid  system  <rf  Uiis  region  •  has  made  but  litde  progres 


At  birth  the  pharyngeal  tonsil  is  a  very  small  collection  of  adenoid  tissue  at  the 
back  of  the  roof,  covered  by  more  or  less  converging  folds  of  the  mucous  membrane. 
It  is  not  necessarily  present  During  the  first  year  it  grows  rapidly,  and  particularly 
forward,  so  that  by  the  end  of  that  time  it  extends  to  die  back  of  die  upper  margin  ol 
the  choanae.  Under  nor.  d  conditions  the  pharyngeal  tonsil  retains  its  relative  size 
to  the  cavity  of  the  pharynx  up  to  twelve  years  ;  but  during  this  time  the  total  amount 
of  adenoid  tissue  has  decidedly  increased,  owing  to  the  development  of  the  tubal 

The  faucial  tonsils  are  developed  in  a  recess  of  the  primitive  pharynx  between 
the  second  and  third  visceral  arches.  By  the  fourth  foetal  month  the  tonsillar  anlage 
presents  a  number  of  slit-like  depressions,  lined  with  entoblastic  epithelium,  from 
which  secondary  epithelial  sprouts  invade  the  neighboring  mesoblast.  This  process 
continues  after  birth  during  the  first  year.  The  young  connective  tissue  surrounding 
the  epithelial  sprouts— the  latter  being  at  first  solid,  but  later  possessing  a  lumen- 
becomes  infiltrated  by  accumulating  leucocytes  and  gradually  assumes  the  character 
of  adenoid  tissue,  the  differentiation  into  distinct  lymph-nodes,  however,  being  delayed 
until  after  birth.  The  source  of  the  lymphoid  cells  is  a  matter  of  dispute.  Accord- 
ing to  some,  these  elements  are  leucocytes  from  the  circulation  caught  within  the 
young  connective  tissue  ;  others  maintain  that  they  are  derived  ft-om  the  transforma- 
tion of  the  epithelium,  the  lymphoid  tissue  resulting  from  the  mutual  invasion  and  in- 
tergrowth  between  the  ento-  and  mesoblastic  elements.  According  to  Hamm  ■  -ho 
has  carefully  studied  the  development  of  the  tonsils,  the  lymphoid  cells  are  .  /«! 
chiefly  from  the  fixed  connective-tissue  elements.  At  birth  the  tonsils  _.e  insignih- 
cant,  but  grow  rapidly  during  the  first  year.  At  from  the  twelfth  year  to  puberty 
the  entire  adenoid  system  of  the  pharynx  enters  upon  a  stage  of  retrogression.  In 
the  adult  the  pharyngeal  and  tubal  tonsils  are  much  smaller  ;  after  middle  age  they 
undei^o  at  ophy. 

>  Escat :  fevoltition  de  la  Cavit6  Naso-Pharynglenne,  1894. 

•  Archiv  f.  mikro.  Anat,  Bd.  xli.,  1902. 


II 


i6o4 


HUMAN   ANATOMY. 


THE  MUSCLES  OF  THE  PHARYNX. 

The  arnuigement  of  the  muscular  tissue  differs  from  the  ordinary  one  of  the 
digestive  tract,  inasmuch  as  the  outer  layer  is  approximately  circular  and  the  longi- 
tudinal fibres  are  largely  internal.  The  chief  elements  are  the  three  constndon, 
which  overlap  one  another  from  below  upward,  the  sMo-pkaryngeus,  the  palato- 
pkuryngeus,  and  certain  accessory  and  rather  irregular  bundles  of  muscular  fibres. 


tatmial  caiMM  » 
IntcniAl  jognlai 

V 


Fic.  1360. 

Coodykis 


,C«atral  Mtachmeiuol  pharynx 


Tip  oi  cnal  corna  c4 

hyoid  bone< 

Thyro-hyoid  liniiicnt 

Superior  coma  ol  tk|naid 

carUlacc 


Middle 

COUUtelOT 


Inferior  comtrtetor 


onitlludinal  muscle  of  mo^aetn 


Mwclea  of  pharynx  from  behind ;  portion  of  interior  constrictor  has  been  removed. 

The  superior  constrictor  (Figs.  1339,  1360)  arises  from  the  lower  part  of  the 
internal  pterygoid  plate,  from  the  hamular  process,  the  pterygo-mandibu!ar  Hjjament 
whi(;h  is  stretched  from  it  to  the  lingula  of  the  lower  jaw,  from  the  neighboring  end 
of  the  mylo-hyoid  ridge,  and  from  the  side  of  the  tongue.  From  this  origin  the  fibres 
pass  backward  to  meet:  their  fellows  in  a  median  raphe,  which  extends  almost  the 


THE  PHARYNX. 


1605 


entire  lenrth  of  the  posterior  wall  oJ  the  oharynx.  being  atuched  abov  to  the 
^hS^ngeil  tubercle  o^he  under  side  of  the  basUar  P/«=««:  J**^  JP^' ,  ^^j^^^ 
The  muscle  is  concave  on  either  side,  not  reachmg  the  bwe  of  the  skull  and  passing 
under  £  Eustachian  tube,  the  vacant  space  being  Wledby  the  P'^O'ngeal  aponeu- 
rosis The  lower  fibres  pass  somewhat  downward  as  well  as  backward.  Thepterjgo- 
Sibular  Hgament  s^rates  the  superior  constrictor  from  the  bV^"-'"-"'  *"f 
which  it  woulJ  otherwise  be  continuous,  forming  a  circle  around  the  almientar>-  canal. 


Fic    i3<ii 


Anwrlor  marKiii  ..I  1  .i-micii  maniium 


ll.   -fe 


r 


styloid  prmn 
Fharynccal  •poocumsiis 

8(yla.h]roid  liiianwnt 

8tylo.gfcMMH 
ylo-hyold 

__^  6br«  o«  lupcrior 
comtrictot 

PllMoiiharyiiKeiw 
.Grcftt  coma  <A  hyokl  bone 
Slylo.ptaryngcn« 

Tbyroki  caftiUxe 
Pharyngeal  aponeurosis 


SitnphaKua 


Pharyngeal  aponeurosis  and  longitudinal  musculature,  seen  (rem  behind. 

The  middle  constrictor  (Figs.  i339>  '36o)  arises  from  the  lower  end  of  the 
stvlo-hvoid  ligament,  from  the  lesser  horn  of  the  hyoid  bone,  and  from  the  upper 
border  of  the  greater  horn.  The  iibrcs  diverge  from  this  narrow  ongm.  the  upj^r 
reaching  the  pharyngeal  tubercle,  the  lower  going  to  neariy  the  lower  end  oJ  the 
pharynx,  and  all  meeting  their  fellows  in  the  median  raphe.  It  conceals  a  consider- 
able part  of  the  preceding  muscle. 


it*' 


i6o6 


HUMAN  ANATOMY. 


The  inferior  constrictor  (Figs.  1339,  1360),  the  thickest  of  the  three,  arises 
from  the  posterior  part  of  the  outer  aspect  of  the  cricoid  cartilage,  from  ihe  oblique 
line  and  the  triangiilar  surface  below  and  behind  it  on  the  thyroid  cartilage,  including 
the  inferior  horn.  It  overlaps  the  preceding  muscle,  its  upper  fibres  reaching  to  some 
3  cm.  below  the  base  of  the  skull  and  the  lower  ones  bemg  nearly  horizontal.  The 
median  raphe,  which  receives  almost  all  the  fibres,  is  wanting  bielow.  The  lowest 
fibres  are  circular  and  continuous  with  the  circular  fibres  of  the  gullet. 

The  atylo-pharyngeus  (Fig.  1361;  arises  from  the  inner  side  of  the  styloid 
process  near  its  root  and  descends  to  the  interval  between  the  superior  and  middle 
constrictors  near  the  hyoid  bone,  where  it  passes  under  the  latter  and  ends  by  expand- 
ing in  the  side  of  the  pharynx,  some  of  its  fibres  going  to  the  posterior  border  of  the 
thyroid  cartilage  and  others  joining  the  expansion  of  the  palato-pharyngeus.  A 
bundle  from  the  thyroid  division  passes  to  the  side  of  the  epiglottis,  forming  on  the 
wall  of  the  pharynx  the  fold  known  as  the  plica  pharyngo-epighttita.  The  fibres 
of  the  superior  constrictor  may  be  inseparable  from  the  upper  part  of  this  layer. 

The  salpingo-pharjmgeus  has  been  described  in  connection  with  the  levator 
palati  (page  157 1). 

VariuioM.— Additioaal  muscles  are  very  common,  beinc  chiefly  kxigitudinal  bundles  due 
to  splittiiiy  <A  one  oi  the  normal  muscles,  especially  the  stylo-pharyngeus,  or  to  new  bundles  r 
fibres  arisuiK  from  the  base  of  the  skull  in  tlie  vidnity  of  the  upper  insertion  of  tlie  pharyngro 
fascia.  Tliere  may  be  a  pair  of  acr^^(A>/Aao'«lf m^  "••u<'^',  araing  from  tlie  occipital  bone  .  . 
eitlier  side  of  the  median  Ifaie  and  descending  to  be  lost  in  the  posterior  pharyngeal  wall ; 
there  may  be  an  azygos  muscle  instead.  Bands  may  arise  at  the  side  from  the  peuous  portii  .1 
of  the  temporal  bone  or  tlie  spine  of  the  sphenoid. 

Actions. — ^The  general  action  of  the  pharyngeal  muscles  is  sufficiently  evident ; 
the  constrictors  decrease  the  siie  of  the  pharynx,  probably  drawing  the  larynx  upward 
and  backward  at  the  same  time.  The  longitudinal  muscles  raise  the  larynx  and 
pharynx,  acting  chiefly  on  the  latter. 

Vessels. — The  arteries  of  the  pharynx  are  from  many  sources  and  are  irregu- 
lar. The  chief  is  the  ascending  pharyng^,  which  runs  up  near  the  posterior  lateral 
angle.  Occasionally,  when  enlarged,  it  b  seen  pulsating  on  the  posterior  wall. 
Branches  from  the  facial  play  an  un  rtain  part  The  veins  form  the  pharyngeal 
plexus  situated  outside  of  the  constrit  :i  and  communicating  in  all  directions.  The 
chief  outlets  are  by  a  pair  of  veins  on  each  side,  one  going  up  to  the  internal  jugular 
near  the  base  of  the  skull  and  the  other  down  to  the  external  jugular  or  some  of  its 
tributaries  (Luschka).  A  submucous  plexus  is  particularly  developed  in  the  lower 
posterior  wall,  which  opens  into  the  pharyngeal  plexus  by  several  branches  piercing 
the  inferior  constrictor.  The  following  are  nearly  constant  :  a  superior  and  posterior 
one  near  the  middle  line,  one  running  outward  on  each  side  near  the  back  of 
the  thyroid  cartilage,  forming  a  part  of  the  origin  of  the  pharyngeal  vein,  and  one 
passing  forward  to  the  superior  thyroid  vein.'  The  lymphatics,  which  are  numerous, 
run  in  the  upper  part  to  the  prevertebral  nodes  and  to  the  deep  cerviral  system,  as 
do  the  lower  ones  at  another  level.  The  presence  of  lymphatic  nodes  behind  the 
naso-pharynx  is  of  practical  importance,  as  they  are  sometimes  inflamed  and  may 
suppurate.     They  lie  near  the  foss£E  of  Rosenmiiller. 

Nerves. — The  constrictors  are  supplied  by  the  pharyngeal  plexus,  the  lower 
receiving  fibres  also  from  the  recurrent  laryngeal.  The  stylo-pharyngeus  b  supplied 
by  the  glos.so-pharyngeal.  The  nerves  of  the  mucous  membrane  are  from  the  glosso- 
pharyngeal, the  pneumogastric,  and  the  sympathetic,  to  a  great  extent  in  a  plexiform 
arrangement. 

PRACTICAL  CONSIDERATIONS  :   THE   PHARYNX. 

The  pharynx  may  be  said  to  present  only  three  sides  for  consideration,  but  its 
continuity  above  with  the  nares,  anteriorly  wilh  the  mouth,  and  below  with  the  ori- 
fices of  the  larynx  and  oesophagus  associates  it  intimately  with  the  diseases  of  those 
regions.  The  naso-pharynx  and  the  lar\'ngeal  relations  will  be  considered  with  the 
Respiratory  Passages  (fiage  1829). 

•  Bimar  et  1-apeyre  :    Comptes  rendus  de  I'Acad.  des  Scienres.  Paris,  tome  cv.,  1887. 


PRACTICAL  CONSIDERATIONS:   THE   PHARYNX. 


|6(>7 


The  posUrior  wall  of  the  pharynx  »  separated  from  the  anterior  surfaces  of  the 
bodies  of  the  first  five  cervical  vertebr*  only  by  some  loose  connective  tissue  and  by 
the  prevertebral  fascia  and  muscles.  Through  it.  by  pushint;  the  finger  up  above 
the  soft  palate,  the  basilar  process  of  the  occipital  bone  may  be  felt,  and  below  the 
bodies  ofthe  upper  four  cervical  vertebr*— in  children  the  upper  six— may  be  pjil- 
pated.  The  hard  palate,  or  the  lower  margin  of  the  posterior  nares.  and  the  anterior 
arch  of  the  atlas  are  on  the  same  level.  ,    .     ^  .    u      i    h 

In  disease  of  the  body  of  the  sphenoid,  m  fracture  of  the  base  of  the  skull 
involving  the  basilar  process,  or  in  fracture  or  dislocation  of  the  cervical  vertebne 
the  information  gained  by  this  examination  will  often  be  of  great  value. 

The  retropharyngeal  alveolar  tissue— which  is  necess;irily  loose  to  permit  ot 
the  movements  of  the  pharynx  during  d^lutition  and  of  ite  disteiaibility— is  some- 
times the  seat  of  infection  which  may  have  gained  access  through  the  pharynx  itsell, 
or  through  the  lymphatics  which  spring  from  the  posterior  nares,  the  summit  ol  the 
pharynx  and  the  prevertebral  muscles,  and  which  empty  into  a  lymph-gland  situ- 
srted  between  the  prevertebral  fascia  and  the  pharyngeal  wall.  Abscess  in  this 
situation  may  by  gravity  descend  by  the  side  of  the  cesoph^us  into  the  mediasti- 
num and  has  been  known  to  reach  the  base  of  the  thorax  (page  553,  Fig.  54o)- 
During  its  descent  it  may  cause  much  dyspnoea  by  setting  up  adema  in  the  region 
of  the  glottis.  Usually  it  first  pushes  forward  the  posterior  wall  of  the  pharynx, 
and  can  be  recognized  as  a  fluctuating  swelling  and  opened  by  direct  inciMon. 

Collections  of  fluid  resulting  from  tuberculous  disease  of  the  cervical  vertebra 
may  occupy  the  same  space  after  perforating  the  thin  prevertebral  fascia  and  may 
take  the  same  course,  or  they  may  be  guided  by  the  lateral  expansions  of  that 
fascia  to  the  posterior  and  lateral  portions  of  the  root  of  the  neck  or  to  the  axilla 
(page  ssa  Fie  545)-  As  in  these  cases  the  avoidance  of  mixed  infection  »  very 
important,'  such  tuberculous  collections,  when  they  require  opening,  should  be 
approached  through  the  neck  by  an  incision  along  the  postenor  border  of  the 

stemo-mastoid.  ...  ^      «       j  » 

Retropharyngeal  abscess  of  any  type  should  never  be  allowed  to  open  spon- 
toneously  on  account  of  the  danger  of  immediate  suffocation  from  flooding  of  the 

larynx  with  pus.  ...  .    ,      ,    „      ... 

In  cases  of  fracture  of  the  posterior  fossa  of  the  base  of  the  skull,  with  hemor- 
rhage into  the  pharynx  (fracture  of  the  basilar  process),  or  of  the  middle  fossa, 
with  hemorrhage  reaching  the  pharynx  through  the  Eustachian  tube  (fracture  of 
the  petrous  portion  of  the  temporal),  the  need  for  frequent  and  persistent  attempts 
to  make  and  keep  the  pharynx  as  neariy  aseptic  as  possible  should  never  be 

forgotten.  ,         .,  j 

The  adenoid  tissue  .A  the  posterior  wall— the  pharyngeal  tonsil— may  undergo 
hypertrophy,  cause  deafness  or  respiratory  obstruction,  and  rec^uire  removal. 

The  iaieral  walls  of  the  pharynx  are  in  such  close  relation  with  the  internal 
carotid  artery  that  in  aneurism  of  that  vessel  the  pulsations  may  most  easily  be '«t 
and  seen  through  the  pharynx.  In  many  instances  the  vessel  has  twen  opened  in 
penetrating  wounds  of  the  pharyngeal  wall  by  foreign  bodies.  The  internal  jugular 
vein  is  not  so  exposed  to  injury  and  is  more  rarely  wounded.  In  one  instance  of 
pulsating  tumor  of  the  pharynx,  pressure  on  the  external  carotid  arrested  the  pulsa- 
tions (Barnes).  ,,.,,.  u    «  u 

The  styloid  process  and  a  rigid  or  ossified  stylo-hyoid  ligament  can  be  teit 
through  the  lateral  wall.  Attempts  have  been  made  (in  cases  of  hysterical  persist- 
ence of  pharyngeal  symptoms  after  the  supposed  swallowing  of  a  foreign  body)  to 
remove  these  stnictures  or  a  cornu  of  the  hyoid  bone,  under  the  impression  that 
they  were  the  offending  substances. 

The  pharynx  is  very  distensible,  and  foreign  bodies,  if  not  ol  great  size,  are 
apt  to  pass  through  it  as  far  as  the  level  of  the  cricoid  cartilage,  where  its  diameter 
is  only  18  mm.  (  Ji  in.).  In  an  adult  this  point  is  beyond  the  reach  of  an  average 
finger,  as  it  is  about  the  entrance  of  the  oesophagus,  which  is  about  six  iiv.nes  from 

the  incisor  teeth.  ^„A• 

For  the  removal  of  impacted  foreign  bodies,  or  for  operation  on  malignant  dis- 
ease, the  pharynx  may  be  reached,  after  a  preliminary  tracheotomy,  by  an  incision 


\ 


l6o8 


HUMAN    A\ATOM\. 


through  the  neck  from  a  point  midwa^  u.-tween  t!  e  symphysis  and  the  angle  of  the 
jaw  to  the  cricoid  cartilage,  dividing  die  platvs-i  ai  J  th<  -mio-hyoid  and  iwpa- 
rating  the  posterior  belly  of  the  diga^iri*  ii.d  lii  .;  vlo-hvoiu  from  the  hyoid  bone  • 
or  a  subhyoid  pharyngotomy  will  give  <  <  «w  tt.  :  ,  ■  lower  walls  of  the  pharynx  by 
division  of  the  superficial  fascia,  the  ster  la-hyoid  md  fhyroid  mu»cU-s,  the  thyro- 
hyoid ligament  and  membrane,  and  the  mucous  in.  mbraae  of  the  pharynx  at' the 
level  of  the  lower  margin  of  the  hyoid  Iwne.  These  oj-erations  are  more  interest- 
ing anatomically  than  surgically. 

The  tonsils,  as  seen  from  the  mnuth,  are  situated  Mween  the  arches  of  th«- 
palate  and  the  base  of  the  tongue.  Ihey  may  be  aim.,  t  concealed  in  these  re- 
cesses or  may  project  into  the  pharynx,  and  when  hypcrtrophied  may  actually  meet 
m  the  middle  line.  They  rest  on  the  superior  constri<  tor  muscles  and  move  with 
those  muscles  during  the  act  of  deglutition.  Thev  are  somewhat  elevated  and  with- 
drawn from  the  pharynx  by  the  coincident  contraction  of  the  stylo-pharyngei 
-Swallowing  is  therefore  apt  to  be  painful  in  all  forms  of  tonsillitis.  If  not  t  nlarged, 
they  are  often  almost  hidden  in  persons  who  have  large  palato-glossi  musrles,  and 
therefore  prominent  anterior  palatal  arches..  Externally  they  .re  separated  by  the 
pharyngeal  aponeurosis  and  the  superior  constrictor  muscle  (r  .m  the  pharyngo- 
maxillary  space.  This  space  is  bounded  bv  these  fibro-muscular  structures 
internally,  the  internal  pterygoid  muscle  extemaily,  and  the  antero  lateral  aspects  of 
the  bodies  of  the  second  and  third  cervical  vertebra.  It  is  occupied  by  some  con- 
nective tissue  and  fat.  According  to  Zuckerkandl,  the  stylo-pharyngeus  and  stylo- 
glossus muscles  divide  the  space  into  an  anterior  portion  in  relation  to  the  tonsil 
and  a  posterior  in  relation  to  the  internal  carotid  artery  and  internal  jugular  vein. 

Tonsillitis  in  the  lacunar  or  follicular  form  does  not  usually  mvoKe  the  stroma 
of  the  gland,  the  infection  and  the  exudate  being  limited  to  the  tonsillar  crypts  and 
to  the  surface.  In  the  suppurative  form  the  infection  is  deeper,  the  stroma  is 
afiected,  and  the  resulting  abscess  may  in  rare  cases  become  peritonsillar,  extend  to 
the  cellular  tissue  of  the  pharyngo-maxillary  space,  and  open  the  internal  carotid 
artery.  Usually,  as  the  infection  progresses,  even  if  this  space  is  invaded,  the  out- 
ward extension  is  limited  by  the  internal  pterygoid  muscle,  and  the  swelling  and  the 
ulceration  or  necrosis  take  the  line  of  least  resistance, — i.e.,  towards  the  pharynx, 
where  tonsillar  abscesses  often  open  spontaneously. 

During  an  acute  tonsillitis  the  palato-glossus  and  its  covering  of  mucous  mem- 
brane, with  the  soft  palate  on  the  afiected  side,  are  tense,  thinned,  and  spread  out 
over  the  surface  of  the  tonsil.  Abscesses  may  be  evacuated  by  im  ision  directly 
through  these  structures  and  from  above  downward  in  a  direction  p..  illel  with  the 
anterior  pillar. — that  is,  with  the  fibres  of  the  palato-glossus. 

Tlie  vascular  relations  of  the  tonsil  should  be  remembered  in  th  s  operation  or 
in  tonsillotomy  for  hypertrophy.  The  internal  carotid  is  nearly  i.-  rm.  (i  in.) 
behind  and  to  the  outer  side  of  the  tonsil.  The  external  carotid  is  snii  farther  re- 
moved, as  it  lies  outside  of  the  stylo-glos  n^  and  stylo-pharynjreut  mu^des.  Its 
ascending  pharyngeal  branch  is  nearer  the  t,,fi,.l  than  either  of  the  mam  trunks,  and 


in  a  case  of  accidental  wounding  by  a  foreign  body  has  been  the 
hemorrhage.  Wounding  of  the  tonsillar  branch  of  the  facia!  rtei 
proved  fatal  after  tonsillotomy,  and  either  this  \essel  or  the  fac  t- 
It  is  tortuous  where  it  passes  between  the  stylo  clossus  and  d^astru  n 
ably  involved  in  cases  of  grave  hemorrhage  after  this  operation 
lymphatics  surrounding  the  follicles  of  the  tonsils  communicates 
deep  cervical  lymph-glands  behind  and  beneath  the  angle  of  the  jaw 
are  therefore  commonly  enlarged  in  affections  of  the  tonsils,  and  w 
palpable  are  sometimes  mistaken  for  the  tonsils  themselves.  Th- 
however,  be  palpated  externally,  except  in  ca.ses  nf  new  growth,  as  .> 
offered  by  the  constrictor,  the  internal  pterygoid,  ■■•  nd  other  structur*^  ini 
between  the  tonsils  and  the  skin  causes  thcni  to  pro;-  ct  tcvrards  the  pharyn 
projection  may  be  a  cause  of  various  forms  of  ill  healt'  associated  with 
oxygenation,  of  chronic  phar>ngitis  from  mouth-breatt.  ng,  of  thickened 
tion,  and  even  of  alterations  in  the  fades  or  in  the  skeleton 
breast"  (page  167). 


>ui.e  of  fatal 
has  likewBf 
especial  !v  if 
scles,  is  y-^i-^ 
f'he  pU     s  t 
HTtly  "        the 
These  g.   nds 
1  tender     nr 
attpr  caiino! 
he   :    "^istrnr 


g.,  "pi J  eon- 


THE  (KSOPHAGl^ 


1609 


The<kaln««  oJien  asscKTiateo  with  h.  .ertr.>phi«l  'o*"^'*  «/»)!."*•»»  °!,»J"°i! 


jxrowth  in  and  about  the  Eustachian  tubt 

vents   Jirect  pressure    .y  the  enlarged   t 

cough  mav  follow  irrita  on  <A  the  glosso-, 

tion  within  the  follicle^     fetid  breath  ofte. 

secretion  :  epithtli  tl  nt-  rosis  and  denud.i 

entrance  of  various  int.    tions,  .»    he  tu> 

with  which  the    .-,    i.al       nds  jom     ient»n^  are  tl 

adenitis  of    the  ne  k-.      those  .tococ. 

ajute  arth     js  ( inciodinu   many     as.     ol  so- 

endocardt'is  may  follow  :   trWinp    'sore  thro; 


In    intervention  o(  the  soft  palate  pre- 

^  up<>n  ■'   «t  canal.      ReHcx  spasmodic 

laments  by  inspis-'^ited  secre- 

11  the  'li      iii|)0»iiion  of  -  "'h 


larvnjje.i 
r'  ->ult»  ' 
ren 
:ulou.-> 


uch  t<i 
mphaiii 
tirst  to 
or  staphylocot< 
lied  ' '  infliammai. 


5  a  common  scm 
I    by  the  frequi 
irj{e  in  tubrrtul.-  is 
varieties  in  whi<  h 
rheumatism")  o 


:  CESOPHAGUS. 


The  asoohaeus  or  L'uUel   s  a  n.usculo-membranous  tube,  about  25  cm.  (10  in  ) 
in  leiiSh.^n^^nK  the  phan  nx  and  the  stomach.     It  begins  «  the  lower  IxmL 
Ihe  mco.!     ,    tku-  near  t        iisk  between  the  sixth  and  seventh  i     vical  v. 
aLt  Tern       'm  the  incis...  teeth,  and  ends  below  the  diaphra«m.  «,hh«,,. 
JsZllii^-sth.neventhj    horaoc  vertebra.    The  entrance  mt.     he  stomach 


1)1  h 


I  ite< 
i  he 
inal 


.Ids 
r  <ha|« 

t!  vf 
oil.  tV 
uf  tl.  uirui 
ijin  of  the  U-ft 
''•  -re  may  be 
rie  li,  accord - 
ophiigus  is  much 
■d  in  life.     After 


bv  a  iTTO.  ^e  on  the  left  of    he  ifvillet.  best  seen  when  the  organ.,  mc  m 
is  no  line  of  separation  on  the  right  when  the  oarts  «;«  "««P«"^: 
calibre  of  the  cesopha    »  ^  very      nable  and  uncertain.      L^ng" 
som,  times  found,  espe  lally  in  t  le        nr  part,  which  give  the  cavit 
!^.arance        tr;nsv?e«c  s;=  tion.     <       „  the  front  wall  hes  in  conuct 
«.r     4t  the  lower  part,  nowever.  Ui>       may  be  a  permant.tt  ca\  1  v. 
have  been  des.  nbed    erv  variouiay.     1  robably  the  most  marked 
be«ir.r,insr,  wi"^      diam<  er  of  fjerhaps  only  14  mm.      There  is 
^^c   hrouK^    .he  diapunif:  n.  often  one  at  the  pomt  where  the 
crossed     le  guli  t,  and  another  where  the  latter  goes  beh    -1  tl 
bronchu.      \feh  er  '  has    ..-scribwl  thirteen  places,  at  any  >t 

ao    strution.     I        con -ipond  to  the  points  of  entrance  ot 
inc  ^o  him,  hav         meu.    'mic  significance.     Occasionally 
d,:,iied,    the  diam.     r  ex       ding  3  cm.     It  is  probably  coi, 
oaWine  throueh  th.         Aragm  it  presents  a  hinnel-like  expan^.-jn. 
pa,.Mng  tnrougn  t^.       ^^^^as^  _  P^^^^  ^^^^  its  course  the  gullet  is  surrounded  by 

much  3^  tissue  and  frequently  sends  fibres  from  ite  mus<  ilar  coat  to  ne.ghlw- 
Tp^  WhUe  following  the  general  direction  of  the  vert  ^  «^'''7"- "l^^" '"^^"^^ 
n.ft  ffiy.  below  the  bihircationof  the  t,^hea  the  gullet  •  or  2  c^  m  •  mnt 

f  the  spine.     Direcdy  after  its  beginning  it  inclines  to  i  >  that  Mwn  it  pr. 

ts  by  one-half  beyond  the  left  border  of  the  trachea.  ..•^'  seen,  in  a    hild 

.he  two  tub^  lie  side  by  side.    Just  above  the  bifurcation  ,.      e  j^^^^^ea  the  c^phagus 
m«te  the  arch  of  the  aorta,  which,  so  to  speak,  pushes  ,t  to  the  right  ;  it  I.e..  how- 
Tv^  alwai  beWnd  the  beg^miing  of  the  left  bronchus,  while  to  a  less  degree,  or  even 
nor;t  K  ?in  relationIS  the  Tight  one.     Owing  to  the  influence  .  f  the  aorta   the 
SC  let  ^  LSier  to  the  right;  l^t.  leaving  the  spine,  it  lies  behind  th.  "^^^;^-^ 
S^a  plS^mewhat  anterior  to  that  of  the  aorta,  and  "ear  the  duijjhm^^i    ^^^^u 
front  of  the  aorta  to  the  left  of  the  median  line,  passes  into  the  abitomer       -ar  the 
tower  border  of  the  tenth  thoracic  vertebra,  ami  ™"'^^'"^'V?>' "W''J"'^'>;  i  T£ 
end^  in  the  stomach.     Hardly  more  than  i  cm.    «hich  l«^  hehmd  the  left  U^*    .f  the 
HvS  and  in  Kt  of  the  left  pillar  of  the  dia,>hr^m.  c     l--  ^  to  he  subd«ph«g- 
matic   when  examined  from  {(ithout.    The  li^;  ^  s^      ^JTw^e  'o  Tsi^en 
and  the  stomach,  however.  i>  very  clear  on   ^  mm-r    -'*«^-  •;*";^  ,he  left  o    the 
chance  in  the  nature  of  the  epithelial  lining       llmv*- 1*  .*en  a  fold  on  the  left  o    the 
e^T  the  gullet,  usually  at  Ihe  upper       ^  b^  ^piirt,  01^2-5  mm    ■c<^d.    w^uch 
perhaps,  .acts  as  a  valve  against  reynirv  a,,,  .on       The  «**whragmatic  t>«n   ..about 
3  cm.  long.     Sometimes  the  longitudinal  lold     t  the  gwe  -een.  i-  p...,^i  .nto  the 
stomach,  but  usually  it  ends  in  a  gradui*!  e><iiiw»sion. 


•  Verhandlune.  der  Anat.  Cesellschaft,  iHg*- 

»  Berry  and  Crawford  :  Journal  of  AniMon»>  and  Physiolog>. 


vol.  xxxiv..  I9i»- 


i6io 


HUMAN  ANATOMY. 


At  &st  the  oesophagus  lies  behind  the  trachea  on  the  prevertebral  fascia,  the 
lobes  of  the  thyroid  gland  touching  it  on  either  side.  As  it  descends  to  the  left'  the 
trachea  is  pardy  on  the  right.  The  left  recurrent  laryngeal  nerve  runs  on  the  from. 
The  right  one  is  in  relation  with  only  the  very  beginning  of  the  gullet.  The  rikjht 
inferior  thyroid  artery  is  against  it.  On  the  right  also  a  chain  of  lymphatics  in  the 
areolar  tissue  lies  very  close  to  it.  The  left  carotid  and  subclavian  arteries  are  very 
near  it,  if  not  in  actual  contact.     As  may  be  inferred,  the  gullet  and  the  aorta  are 

Fio.  1363. 


Superior  cornu  of  thyroid  cartilage 


Thyroid  body 


Left  common  carotid- 
Left  subclavian  artery 

Arch  of  aorta- 
Left  pulmonary  artery 

Left  bronchuft^ 
Left  pulmonary  vein- 


Thyroid  body 
RiKht 


carotid 
Right  aabcbirian  artery 


— Innominate  artery 
—Trachea 
— Superior  vena  cava 


Right  bronchua 


Cardiac  end  of  stomach. 

Abdominal  aorta- 
Spleen. 


-Right  pulmonary  veins 
— -Aiygos  major  vein 


— .Diaphragm 

Inferior  vena  cava 


l*oftterior  surface  of 
liver 


Rifrht  luiirarcnal  body 

Si«ht  kidney 


CEaophagus  and  related  structures,  teen  from  behind.    Lungs  have  btvn  pulled  aside  and  posterior  part  of  dhiphraam 

removed.  * 


spirally  entwined.  The  thoracic  duct  and  the  vena  azygos  major  are  in  contact  with 
it  from  the  diaphragm  to  above  the  roots  of  the  lungs,  the  former  lying  between  it 
and  the  aorta  as  far  as  the  level  of  the  aortic  arch,  the  latter,  at  first  more  posterior 
than  the  duct,  passing  as  it  rises  behind  the  oesophagus  and  finally  arching  forward 
close  to  its  right  side.  The  left  vena  azygos,  such  left  intercostal  veins  as  open  into 
the  azygos  major,  and  the  right  intercostal  arteries  pass  behind  the  gullet.  The  pncti- 
mogastrics  reach  it  in  the  thorax  :  the  right  after  crossing  the  subclavian  artery  and 


THE  CESOPHAGUS. 


1611 


the  left  liter  crossinif  the  aorta.  The  nerves  then  break  up  into  plexuses,  from  which 
thev  ernerire  near  the  diaphragm,  the  left  in  front,  the  riKlit  behind  the  food-tube. 
On  en-erinic  the  thorax,  the  cESoph^?us  is  in  contact  with  the  left  pleura,  and  con- 
tinues to  be  untU  separated  from  it  by  the  aorta.  Behind  the  pericardium  it  is  in 
contact  with  the  right  pleura,  and  just  before  passing  through  the  diaphragm  it  is  in 

contact  with  both.  •  .i.    ■       »      .  a  .„i... 

Muscular  fibres  bind  the  oesophagus  to  various  neighboring  structures.  A  toler- 
ably constant  band  attaches  it  to  the  left  bronchus,  and  others  may  go  obliquely  to 
the  right  bronchus.  Several  irregular  bands,  mosUy  muscular,  pass  from  it  to  various 
parts  of  the  pleurae  and  pericardium.  •.      t  t  ,., 

Structure.— The  wall  of  the  oesophagus  (3.5-4  mm.  thick)  consists  of  four 


Fio.  1363. 


Epithelium 


Tunica  propria  of 
mucous  membrane 


Muacularis 
mucosa; 


,GUind.ducU, 
obliquely  cut 


Lonfcltudlnal 
bundles  of  non- 
striated  muscle 

Bundles  of  striated  fibres 
Tiansvene  section  of  cnophacus,  Junction  of  middle  with  upper  third.    X  as- 

layers,  which,  from  within  outward,  are  the  mucous,  the  submucous,  the  muscular, 

and  the  fibrous  coats.  ...,,,.'  _j    « -  ,..„;— 

The  mueous  ct>ai,  usually  thrown  into  longitudinal  folds,  is  composed  of  » j""l«^ 
propria  formed  of  fibrous  connective  tissue  and  delicate  elastica  and  covered  with 
stratified  squamous  epithelium.  Beneath  the  latter  the  surface  of  the  stronria-layer 
presents  longitudinal  ridges  and  papillae,  between  which  pass  the  ducts  of  the  glands  m 
their  course  to  the  free  surface.  The  deeper  part  of  this  layer  is  occupied  by  a  mus- 
culans  mueosie,  the  involuntary  muscle  of  which  begins  at  the  cricoid  cartilage,  hrst 


l6l2 


HUMAN  ANATOMY. 


appearing  in  the  continuation  of  the  elastic  lamina  of  the  pharynx.  At  the  upper  end 
only  slightly  developed,  the  muscularis  mucosa  becomes  more  robust  until  in  the 
lower  portion  of  the  oesophagus  it  is  conspicuous. 

The  submucous  coat,  between  the  mucous  and  muscular  layers,  although  consid 
erable,  is  not  dense,  and  therefore  allows  free  motion  of  the  former  upon  the  latter 
as  well  as  the  formation  and  efiacement  of  folds.  It  is  continuous  with  the  pharyn- 
geal fascia  above. 

The  asophttgeal  glands  are  of  two  kinds,— the  ordinary  mucous,  situated  within 
the  submucous  coat  and  scattered  throughout  the  length  of  the  tube,  and  special 
glands  withm  the  tunica  propria  limited  to  the  two  ends  of  the  oesophagus  The 
last  mentioned  correspond  in  structure  to  those  found  at  the  cardiac  orifice  of  the 
stomach  ;  they  are  therefore  known  as  the  upper  and  lower  cardiac  vesophageal glands 
(J.  Schaffer).  r    a      & 

The  usual  secretory  structures  are  small  tubo-alveolar  mucous  glands  in  which 
mucus-producing  cells  are  alone  present,  crescents  of  serous  elements  being  absent 
The  ducts  are  commonly  somewhat  tortuous,  and  often  present  dilatations  or  ampullae; 
p,_       5  the  smaller  tubes  are  clothed  with  simple 

^  *  columnar  epithelium.      In  the  larger  the 

epithelium  may  be  stratified,  and  near  the 
free  surface  assume  a  squamous  character. 
The  cardiac  glands  at  the  lower  end 
of  the  cesophagus  are  continuations  of 
those  situated  about  the  entrance  of  the 
gullet  into  the  stomach,  in  connection  with 
which  organ  they  are  more  fully  described 
(page  1624).  They  form  oval  or  pyrami- 
dal groups  of  branched  tubular  glands,  the 
bases  of  which  lie  against  the  muscularis 
mucosae,  the  narrow  parts  being  directed 
towards  the  free  surface  onto  which  their 
wavy  or  tortuous  ducts  open.  The  upper 
cardiac  glands  form,  according  to  Schaf- 
fer,' a  constant,  though  variable,  group 
around  the  superior  end  of  the  oesophagus. 
Lymphatic  tissue  occurs  within  the 
mucosa  01  the  oesophagus  as  more  or  less 
distinct  aggregations.  Sometimes  these 
.  .  are  in  the  fo.m  of  small  diffuse  areas  of 

mfiltration  around  the  ducts  of  the  mucous  glands  ;  in  other  places,  especially  towards 
the  lower  end,  distinct  lymph-nodules  are  present  (Fig.  1364). 

The  muscular  coat  consists  of  an  inner  circular  and  an  outer  longitudinal  layer, 
although  the  disposition  of  the  individual  bundles  is  often  irregular  and  oblique,  and 
above  somewhat  intermingled.  In  the  upper  third  of  the  tube  the  muscular  tissue 
consists  entirely  of  striped  fibres,  the  circular  ones  being  continuous  with  the  simi- 
lariy  disposed  fibres  of  the  inferior  constrictor  of  the  pharynx.  The  longitudinal 
fibres  arise  from  a  tendon  attached  to  the  median  ridge  of  the  cricoid  cartilage  and 
to  the  fajjcia  covering  the  posterior  crico-arytenoid  muscles,  whence  they  descend 
to  embrace  the  gullet.  They  are  few  at  the  top  behind,  but  lower  down  the  circular 
and  longitudinal  layers  are  distinct  and  symmetrically  disposed.  Towards  the  middle 
of  the  oesopl.agus  the  muscular  coat  includes  both  the  striated  and  non-striated  form 
of  tissue,  the  involuntary  variety  gradually  predominating  until  in  the  lower  third  it 
alone  is  present. 

The  fibrous  coat  is  pooriy  developed  above  the  diaphragm,  consisting  of  the 
areolar  tissue  which  connects  the  gullet  to  the  surrounding  structures.  After  piercing 
the  diaphragm,  the  peritoneal  investment  contributes  a  limited  serous  tunic  which  from 
this  point  on  is  well  represented. 

Vessels. — The  arteries  are  links  in  the  chain  running  the  whole  length  of  the 
alimentary  canal.     The  highest  are  from  the  inferior  thyroids,  succeeded  by  those 
'  Beitrage  «ir  Histologie  mensch.  Orjtane,  Bd.  vi. 


Muscular  , 

tissue 


Section  uf  niucoUN  membiaiic  uf  u»o|>h«pu,  showhir 
l>niph-liodc.    ,■  55. 


PRACTICAL  CONSIDERATIONS:  THE  (ESOPHAGI'S.  1613 

from  the  thoracic  aorta  and  the  gastric.  The  r««J  are  interesting  only  iM»«n«ch 
s^the^pper  ones  open  into  the  azygos  system  and  that  of  the  mfenor  thyroid  above 
and  theatric  system  below  ;  they  thus  form  a  communication  between  the  general 
and  the  portal  venous  systems.  The  lymphatics— noX.  numerous-go  to  the  nodes 
of  the  deeper  part  of  the  neck  and  of  the  postenor  mediastmum. 

Nerves  are  from  the  oesophageal  plexus.  . 

The  mechanism  of  the  closure  of  the  cardiac  end  of  the  stomach  is  most  properly 
considered  with  the  cEsophagus,  depending  as  it  does  partly  on  the  «hrection  of  that 
tX^Sy  on  the  relation^  the  d&phragm  to  it.  and  partfy  on  the  folds  of  mucous 
meSlHw  at  its  orifice.  Frozen  sections  (Fig.  1509).  both  horizontal  and  frontal 
(GuS')  show  that  the  termination  is  almost  horizontal.  Dissections  of  the  dia^ 
Dhrwn  from  above  demonstrate  that  the  anangement  of  the  muscular  hbres  is  that  of 
rSter  although  a  weak  one.  The  projection  of  the  folds  into  the  stomach  b  a 
hiSer  pro  S.*  It  has  been  shown  tkat  the  cardia  wiU  r««t  moderate  pressure 
SSnbJ^w  upward,  butwiU  yield  to  considerable  force  The  action  of  the  long^- 
SliSl  fiTresTom  both  the  cricoid  cartilage  and  the  diaphragm  is  to  ddate  the  tube. 

PRACTICAL  CONSIDERATIONS:  THE  (ESOPHAGUS. 
Cmgenital  mal/ormatums  are  rare,  as  yet  unexplained  «™bryologically.  and  usu- 
ally faud  The  esophagus  may  be  double,  deficient,  or  absent.  Most  commonly 
There  Se  an  upper  culTsac  and  a  lower  segment  opening  into  the  stomach,  some- 
tim«  communi^ting  with  the  respiratory  passage.  Cases  in  which  there  has  been 
rSi^Ko-pleurc^cuUneou,  fistula  are  possibly  associated  with  this  malformation 
mSdhkn.  Osier).  Congeniul  diverticula  are  found,  and  Francis  sugg«ts  Aree 
tC^fo  their  occurrence  :  first,  that  they  might  be  analogous  to  he  diverticula 
wl^h  were  found  in  some  of  the  Sauropsida  and  in  ruminant  animals,  orming  the 
fi«t  two  ^mpartments  of  the  stomach  ;  secondly,  that  they  were  foetal  vanelies 
StSs To  tKophageal  diverticulum  from  which  the  larynx,  trachea  and  lungs 
are  f^mXandSly.%hat  they  resulted  from  a  failure  in  the  mtenial  closure  of 

a  ''™^^^'*^^^^^^di*y  *,'ib:{ity,  and  constrictions  of  the  normal  oesophagus  and  ito 
relations  to  surrounding  structures  are  of  importance  with  reference  tp Jp^eg" 
todies  to  stricture,  to  disease  of  the  gullet  with  possible  extension  to  ne  ghboring 
oSS  0°  to  extrinsic  disease  involving  the  oesophagus  either  by  mechamcal  pressure 
or  traction  or  bv  extension  to  its  walk.  u  »-w4 

Foreign  bodies,  if  moderately  smooth  or  regular  in  shape,  are  apt  to  be  an-ested 
at  one  of  the  three  relatively  constricted  i    rtions.-i.r  (i),  and  ^0*^  ^o™™^';/: 
at  the  commencement.  15  cm.  (6  in.)  .'rotn  the  inc«or  teeth,  wh^h  (*th  the  head 
midway  between  flexion  and  extension)  is  opposite  the  lower  edge  of  the  cncoid 
cartilage  and  the  sixth  cervical  vertebra.    At  this  point  its  »>'«^"««l,  *^'.f'«f '*  '  "J 
mm.  (approximately  Ji  in.)  ;  foreign  bodies  arrested  here  are  ^«»y,'"/he  lower 
pharynx      (2)  At  the  point,  about  10  cm.  (4  in.    lower,  where  the  left  bronchus 
crosses  the  Esophagus  ^d  where  the  lumen  is  again  lessened  by  pre^ure  (the  dis- 
tance  occupied  by  the  left  bronchus  in  crossing  the  (Esophagus  is  about  25  cm. ). 
(»)  At  the  diaphragmatic  opening,  where  the  diameter  is  once  more  reduced  to 
U  mm.  by  the  constriction  of  the  muscular  and  tendinous  fibres  surrounding  the 
ojening-  Vis  point  is  about  12.5  cm   (5. '"•)  below  «he  level  of  the  left  brond^^^^^ 
aS  therefore,  approximately.  38  cm.  (15  -...)  from  the  >""«"■  t'«^'h.    The  majority 
of  foreign  bod i«  that  pass  completely  from  the  pharynx  and  are  arrested  in  the 
«sopha|us  are  stopped  at  or  about  the  level  of  the  left  bronchus.     Many  of  them 
can  be  extracted  through  the  mouth  by  suitable  instruments  ;  others  require  an 
oesophagotomy,  which  may  be  done  through  an  incision  along  the  antenor  lx,rder 
of  the  left  sterno-mastoid   muscle  from  the  cricoid  cartilage  to  the  sternum.     Ihe 
longitudinal  fibres  of  the  esophagus  will  be  recognized  a  little  to  the  left  of  the 
trachea,  at  the  bottom  of   the  space  between  the  sterno-thyroid  muscle  anc    the 
common  carotid  artery.     An  oesophageal  bougie  passed  through  the  mouth  will  aid 
in  the  recognition  <tf  the  tube. 

'  Arch,  fiir  Anat.  und  Phy».,  Anat.  Abtheil.,  1885. 


! 


'I! 


f6i4 


HUMAN   ANATOMY. 


The  recurrent  laryngeal  nerve  lying  in  the  groove  between  the  trachea  and 
oesophagus  should  be  avoided,  as  should  the  superior  and  inferior  thyroid  arteries 
which  run  across  the  deeper  part  of  the  wound. 

With  the  additional  help  of  a  gastrotomy,  digital  exploration  (with  perhaps  the 
disengagement  of  impacted  foreign  bodies)  is  possible  throughout  at  least  the  lower 
two-thirds  of  the  gullet.  If  the  impaction  is  near  the  cardiac  end,  gastrotomy  alone 
may  suffice. 

Mediastinal  or  posterior  oesophagotomy  has  been  done  on  both  the  left  and 
nght  sides  by  resection  of  three  or  four  rib:  '  third  to  eighth),  pushing  the  parietal 
pleura  to  one  side.  The  pleura  on  the  left  side  is  more  easily  displaced  than  that  on 
the  right,  which  extends  across  the  median  line  as  far  as  to  the  right  of  the  thoracic 
aorta. 

Strictures  from  escharotics  or  from  trauma  of  foreign  bodies  may  otcur  at  any 
point,  but  are.  for  obvious  reasons,  most  often  found  at  the  upper  end.  Compression 
of  the  oesophagus,  giving  rise  to  the  clinical  phenomena  of  stricture,  may  be  sec- 
ondary to  enlargement  of  the  thyroid  body  or  of  the  bronchial  lymph-glands,  to 
tumors  of  the  mediastinum,  to  disease  of  the  lower  cervical  or  upper  dorsal  verte- 
brae, or  to  aortic  aneurism.  The  measurement  from  the  incisor  teeth  to  the  seat  of 
the  n.ii  rowing,  and  comparison  with  the  oesophageal  relations  at  that  point,  may  be 
of  great  service  in  diagnosis. 

Carcinoma  is  the  chief  disease  by  which  the  gullet  is  attacked.  It  is  found 
most  often  at  either  the  upper  or  lower  end  of  the  tube  in  accordance  with  its  predi- 
lection for  sites  where  epithelium  changes  in  character,  as  at  the  various  muco- 
cutaneous outlets  of  the  body.  It  is  also  not  infrequent  at  the  region  where  the 
left  bronchus  crosses.  It  may  extend  by  continuity  to  the  pharynx  or  stomach  or 
to  any  of  the  structures  with  which  the  oesophagus  is  in  close  contact,  or  it  may 
spread  to  the  bronchial  or  mediastinal  lymph-glands. 

Extrinsic  disease  may  not  only  (as  in  the  case  of  tumors  or  of  aneurism)  affect 
the  oesophagus  by  causing  compression  of  its  walls  {vide  supra),  but  may  open  it  by 
pressure-necrosis  or  ulceration,  or  may  involve  it  in  the  extension  of  the  disease,  as 
in  cases  of  tracheal,  bronchial,  or  pulmonary  suppuration  or  gangrene,  or  of  vert<"- 
bral  caries. 

Disease  extending  from  the  left  lung  or  pleura  to  the  oesophagus,  or  in  the 
reverse  direction,  is  more  apt  to  affect  the  upper  portion  of  the  gullet  on  account  of 
its  closer  relation  to  the  pleural  sac  on  the  left  side.  Below  it  is  in  more  intimate 
relation  to  the  right  pleura. 

Diverticula  of  the  (Esophagus,  when  acquired,  may  be  due  to  (a)  pressure 
from  within,  as  in  the  region  just  above  a  stricture,  or  oftener  on  the  posterior  wall 
at  the  pharyngo-oesophageal  junction.  At  this  point  the  inferior  constrictor  and  the 
circular  fibres  of  the  oesophagus — both  horizontal  in  direction— fuse  ;  it  is  a  point  of 
marked  constriction  ;  the  cricoid  cartilage  in  front  is  movable  and  non-resistant. 
In  whatever  situation  found  they  are  apt  to  be  in  effect  a  hernia  of  the  mucous  and 
submucous  tissues  through  the  thinned  and  weakened  muscular  fibres  of  the  oesoph- 
agus or  of  the  inferior  constrictor  ;  or  they  may  be  due  to  {b)  traction  from  without, 
as  in  cases  of  bronchial  lymphadenitis,  in  which  adhesions  and  subsequent  cicatricial 
contraction  have  dragged  the  wall  out  into  a  pouch.  It  is  apparent  that  the  anterior 
wall  in  the  neighborhood  of  the  bifurcation  of  the  trachea  and  of  the  left  bronchus 
is  most  likely  to  be  thus  affected. 

The  recorded  cases  in  which  hemorrhage  into  the  oesophagus  has  taken  place 
from  the  ascending  portion  of  the  aorta,  the  innominate  arterv,  and  the  superior  vena 
cava  will  readily  be  understood.  The  relation  of  the  oesophagus  just  below  the 
aortic  arch  to  the  pericardium  and  left  auricle  e.\plains  the  dysphagia  sometimes 
seen  in  pericardial  dropsy  or  in  cardiac  enlargement  when  the  patient  is  supine,  as 
well  as  the  cases  in  which  foreign  bodies  impacted  in  the  oesophagus  have  wounded 
the  heart. 

In  a  general  way  it  may  be  said  that  the  upper  or  tracheal  curve  or  segment 
of  the  oesophagus  is  most  liable  to  invasion  by  diseased  conditions  from  without  and 
to  nlwtructinn  from  within,  and  the  lower  or  aortic  cur\'e  is  relatively  free  from 
liability  to  external  pressure  or  intrinsic  occlusion  (Allen). 


THE  ABDOMINAL  CAVITY. 


l6is 


In  the  use  of  oesophageal  instruments  the  nonnal  curves,  measurements,  and 
constrictions  should  be  remembered,  as  should  the  possible  relation  of  abnormal 
narrowing  to  abscess,  aneurism,  or  thoracic  disease.  The  curve  made  by  the  roof 
of  the  mouth,  the  pharynx,  and  the  beginning  of  the  <£Sophagus  should  be  some- 
what straightened  out  by  throwing  the  patient's  head  slightly  back  ;  the  tongue  and 
anterior  pharyngeal  wall  should  be  pulled  forward  or  pushed  m  that  direction  by  a 
finger  in  the  pharynx.  The  point  of  the  instrument  should  be  guided  past  the 
epiglottis  and  brought  in  contact  with  the  posterior  wall  of  the  pharynx  liefore  it  is 
pushed  downward.  This  wall— like  the  upper  wall  of  the  urethra— is  the  more 
fixed  and  should  guide  the  instrument  safely  into  the  gullet,  except  in  c;ises  of 
pressure  of  diverticula.  The  beginning  of  the  procedure  may  be  facilitated  by 
voluntary  deglutition  on  the  part  of  a  non-anaesthetized  patient. 

In  some  cases,  especially  in  children,  it  is  preferable  to  pass  the  mstrument 
through  the  nose  to  avoid  the  stniggle  to  keep  the  mouth  open. 

THE  ABDOMINAL  CAVITY. 

Th«  general  shape  of  the  abdominal  cavity  b  best  understood  by  dividing  it  into 
three  im^inary  zones,  one  above  the  lumbar  region  of  the  spine,  one  opposite  to  it, 
and  one  below  it.  The  anterior  wall  is  but  slighdy  convex.  The  upper  zone, 
excepting  a  small  part  in  front,  is  within  the  cage  of  the  thorax,  from  which  it  is 
separated  by  the  dome  of  the  diaphr^m,  the  lower  part  of  which  is  nearly  vertical 
and  posterior  to  the  abdominal  viscera.  This  zone  U  very  capacious.  The  second 
zone  bounded  behind  by  the  convexity  of  the  lumbar  spine,  which  is  broadened  on 
each'  side  by  the  psoas  muscle,  is  very  shallow  in  the  middle,  the  antero-postenor 
diameter  not  being  more  than  5  cm.  (2  in.).  At  the  sides  it  is  deep,  extending  into 
the  hollow  of  the  lower  ribs.  Thus  it  presents  two  deep  lateral  recesses  connected  by 
a  shallow  median  portion.  The  lowest  zone,  below  the  promontory  of  the  sacrum, 
consists  in  the  middle  of  both  abdominal  cavity  proper  and  of  the  cavity  of  the  true 
pelvis  •  for,  owing  to  the  inclination  of  the  pelvis,  the  promontory  is  near  the  level 
of  the  anterior  superior  spines  of  the  Uia.  On  each  side  of  this  deep  median  portion 
the  lower  zone  is  bounded  behind  by  the  shallow  iliac  fossje,  rendered  yet  more  so 
by  the  ilio-psoas  muscles.  The  deep  lateral  divisions  of  the  middle  zone  pass  with- 
out interruption  into  thrae  shallow  ones.  . 

It  has  been  so  long  the  custom  to  divide  the  abdomen  into  nine  regions  by 
drawing  two  vertical  and  two  transverse  lines  on  the  anterior  wall,  that  the  names 
applied  to  these  conventional  regions  must  be  retained  for  general  and  vague  use, 
although  the  method  is  worthless  for  accurate  description.'  Hardly  two  authorities 
agree  as  to  the  location  of  the  lines,  but  for  general  purposes  the  following  sufhces. 
Draw  a  vertical  line  upward  from  the  middle  of  Poupart's  ligament  on  each  side. 
Let  the  upper  transverse  line  cross  these  at  their  points  of  contact  with  the  lower 
borders  of  the  costal  cartilages  ;  let  the  lower  line  connect  the  anterior  superior  spines 
of  the  ilia.  The  three  middle  regions  thus  mapped  out  are  named,  from  above  down- 
ward, epigastric,  uinbiluat,  and  hypogastric;  the  lateral  ones,  the  right  and  left 
hypochondriac,  lumbar,  and  iliac.  The  advantage  of  this  method  is  that  the  vertical 
lines  approximai^lv  represent  the  borders  of  the  median  divisions  of  the  two  lower 
zones,  and  the  lower  cross-line  is  near  the  level  of  the  sacral  promontory. 

The  abdominal  cavity  is  lined  by  a  serous  membrane,  \.hc  pcriloneutn ,  which,  in 
addition  to  covering  the  walls  of  the  space,  forms  a  more  or  less  extensive  investment 
for  the  abdominal  organs.  The  latter,  however,  all  lie  really  without  the  cavity  of 
the  peritoneal  sac,  the  serous  membrane  being  pushed  in  by  the  viscera.  When  the 
latter  remain  attached  to  the  body-wall,  as  the  kidneys,  the  peritoneal  reflection  is 
limited  ;  if,  on  the  contrary,  the  organ  becomes  otherwise  free,  as  the  small  intestine, 
the  serous  covering  forms  practically  a  complete  investment.  The  latter  is,  however, 
never  absolutely  complete,  since  there  is  always  an  uncovered  area  through  which 
the  blood-vessels,  lymphatics,  and  nerves  reach  the  organs.  The  detailed  description 
i)f  the  complex  relations  of  the  peritoneum  will  he  given  later  (p.-.sre  1740'  :  suffice  it 

'  The  information  conveyed  by  this  method  is  of  the  same  natun-  as  that  given  by  saying 
that  Boston  is  north  of  Washington  anil  Chicago  west  of  it. 


I6t6 


HUMAN   ANATOMY. 


now,  in  anticipation  of  the  references  to  peritoneal  relations  which  necessarily  follow 
in  the  consideration  of  the  organs,  to  point  out  that  the  parieta/  and  viscera/  portions 
of  the  serous  membrane  are  continuous,  the  former  investing  the  abdominal  walls, 
the  latter  the  organs.  The  peritoneal  folds  passing  from  a  viscus  to  the  body-wall 
have  received  in  many  cases  the  name  ligaments,  although  often  such  bands  con- 
tribute little  support.  The  intestinal  canal  was  originally  attached  to  the  abdominal 
wall  by  a  fold  covering  vessels  and  nerves  named  the  mesentery,  parts  of  which  per- 

Fio.  1365. 


Infraclmvicular  U 
Cormcofd  process 


Suprmslcniil  notch 
CUvicle 


<>roove  between  deltoid 
and  (lectoralls  major 


temum 
Acromion 


Deltoid 
Leit  limR 


X-rib  cartilaj^ 


Mnea 
semilunaris 

cuUili 


Anterior  superior  iliac  spine 
Line  of  PouiKirt's  liifament 


\'t  imilorm 
apiwndix 


— Spermatic  cord  cmeri^ine 
at  external  abdtmiitial 


Anterior  surface  of  body,  drawn  from  photoicraph.    General  relations  of  thoracic  and  abdominal  organs  to  txidy-wall 

are  shown  by  colored  outline. 


sist  as  free  folds,  while  others  fuse  with  the  abdominal  walls.  The  term  mesctUery  is 
vaguely  applied  to  that  [lortion  going  to  the  jejunu-ileuni,  while  other  parts  arc  distin- 
guished by  the  name  of  thi;  part  of  the  intestine  to  which  they  are  attacheii,  as  nieso- 
colon.  The  term  omentum  is  applied  to  folds  attached  to  the  stom.Hch,  as  the  gastro- 
hepatic  omentum.  The  peritoneal  sac  is  entirely  closed,  except  in  the  temale  at  the 
upper  end  of  the  oviduct,  where  the  mucous  membrane  of  the  K\\\\c  an<l  the  serous 
lining  are  directly  continuous.     The  opposed  smooth  walls  of  the  peritoneal  sac  are 


THE  STOMACH. 


if>i7 


in  contact  and  lubricated  with  a  thin  layer  of  serous  fluid,  secreted  by  the  membrane, 
by  which  friction  between  the  organs  and  movable  surfaces  "reduced  to  a  minimum. 

The  serous  membrane,  consisting  of  the  cndothehum  and  the  hbro-elastic  tunica 
orooria.  is  attached  to  the  subjacent  fasciae  of  the  abdominal  wall  and  the  organs  by 
a  layer  of  subperitoneal  tissue,  an  areolar  stratum  forming  a  more  or  less  intimate 
connection  between  the  serous  coat  and  the  structures  which  it  covers 

The  relations  and  attachments  of  the  peritoneum  observed  in  the  adult  are  in 
some  places  entirely  different  from  those  existing  in  eariy  life  ;  hence  the  history  of 
th^hanges  occurring  during  development  is  essential  for  understanding  the  complex 
relations  found  at  later  periods. 

PLAN  OF  THE  DIGESTIVE  TRACT   BELOW  THE  DIAPHRAGM. 
The  subdUphragmatic  digestive  tube  is  divided  into  the  stomach  the  small  intes- 
tine and  the  large  intestine.     The  small  intestine  is  subdivided  into  the  duodenum  and 
the '/«•««*-./?««.     The  former  of  these  is  an  imperfect  ring  or  horseshoe-shaped 
portion  from  25-30  cm.  C.<^i2  in. )  long,  all  of  which,  except  the  first  inch  or  two. 
C  on  the  posterior  abdominal  wall  behind  the  peritoneum  in  the  adult ;   hen  comes 
seething  over  6  m.  (usually  about  21.5  ft.)  of  intestine  thrown  in  o  folds  by  ite 
aSment  to  the  free  Uge  of'the  mesentery.     The  upper  two-«ths  o    this  «  cabled 
the /«««««  and  the  rest  the  ileum;  but.  as  the  division  is  absurd.it  is  better  to 
speak  of  this  portion  of  the  small  intestine  as  the  jejuno-tleum,  sometimes  a"ud  ng 
toThe  upper  part  as  jejunum  and  to  the  lower  as  ileum      It  ends  at  the  right  iliac 
ossa  by  joining  the  large  intestine,  a  little  over  ..5  «•  (usually  about  55  .«t)  «onK. 
which  fa  subdivided  imo  the  cacum,  a  blind  pouch,  and  th^  colon,  which  is  ascend- 
inir  in  the  right  flank,  transverse  across  the  middle  of  the  abdomen   and  descending 
on  the  left.    This  is  followed  at  the  crest  of  the  ileum  by  the  sigmoid  flexure,  a  free 
fold  attached  to  the  left  of  the  pelvis,  usually  reckoned  as  a  part  of  the  colon,  which, 
after  crossing  the  left  sacro-iliac  joint,   descends  in  the  hollow  of   the  sacrum,  to 
become  the  rectum  at  the  third  sacral  vertebra.     The  termination  of  the  gut.  passing 
through  the  thickness  of  the  floor  of  the  pelvis,  is  the  anal  canal.    Two  large  glands 
—the  liver  and  the  pancreas— pour  their  secretions  into  the  second  part  of  the  duo- 
denum, from  which  they  originally  sprouted.  ,      „    .  •    .u    ^„,^- 
The  liver,  the  stomach,  and  the  spleen  occupy  neariy  all  the  space  in  the  dome- 
like upper  zone  of  the  abdomen  ;  the  right  kidney,  caecum,  and  ascending  colon 
on  the  Tight,  the  left  kidney  and  the  descending  colon  on  t'   •  left,  occupy  the  lower 
lateral  r^esses,  leaving  the  middle  space— shallow  in  the  umbilical  region  and  deep 
below  it— for  all  the  rest  of  the  intestines,  except  such  parts  as  can  be  squeezed  mto 
the  preceding  regions,  and  for  the  greater  part  of  the  pancreas. 

THE  STOMACH. 

The  stomach,  the  most  dilated  part  of  the  digestive  tube,  follows  the  oesopha- 
irus  Ivine  in  the  upper  part  of  the  abdomen  below  the  diaphragm  on  the  left,  and 
passing  downward  and  inward  across  the  median  line.  In  the  eariy  embryo  it  la  a 
tubular  dilatation,  but  it  becomes  flattened  from  side  to  side  and  the  posterior 
border  develops  excessively,  so  that  it  rises  above  the  upper  opening  and  descends 
below  the  lower  one.  The  stomach  also  swings  on  its  long  axis,  so  that  its  posterior 
border  is  carried  to  the  left  and  the  original  left  side  to  the  front.  The  lesser  curva- 
ture is  that  part  of  the  right  border  of  the  stomach  between  the  two  orifices.  It  is 
straight  or  neariy  so,  and  runs  downward  and  forward  to  near  its  end,  when  it  rises 
and  passes  to  the  right.  The  lessier  omentum,  originally  the  .interior  mesenterv-.is 
attached  to  it.  The  grecUer  curvature  is  more  difficult  to  define.  It  is  usually 
erroneously  described  as  identical  with  the  line  of  attachment  of  the  greater  omentum. 
It  is  more  accurate  to  define  it  as  the  line  from  one  orifice  to  the  other  which  passe? 
along  the  left  side  of  the  stomach  and  separates  the  anterior  from  the  postenor 
asp^t.  The  greater  omentum-the  original  posterior  mesentery— is  attached  to  the 
greater  curvature  all  along  except  at  the  upper  part,  where  it  passes  onto  the  pos- 
terior surface. 

13* 


I6i8 


HIMAN   ANATOMY. 


Gastro-phrcnic. 
ligament 

CKsophagus 


GKatrD>hcpaiic 
omentum 


Pandua 


Pylonu- 


Anterior  aspect  of  stomach,  moderately  distended. 


The  shape  of  the  stomach  may  be  compared  to  that  of  a  pear,  somewhat  flat- 
tened, with  the  large  end  up  and  the  point  bent  to  the  right.  The  fundus  is  the 
highest  part  of  the  stomach  which  projects  upward  above  the  level  of  the  end  of  the 
Obsophagus.  The  greatest  breadth  of  the  stomach  is  at  about  the  level  of  the  oeso- 
phageal or  cardiac  orifice,  and  exceeds  the  antero- posterior  diameter.  The  fundus 
generally  contains  air,  if  nothing 

else,  and  is  somewhat  distended,  '■3*^' 

although  thrown  into  uncertain 
contours  by  the  partial  contraction 
of  its  walls.  Towards  the  lower 
ox  pyloric  end  the  stomach  gradu- 
ally becomes  more  tubular,  but 
the  termination  is  often  dilated 
into  a  cavity  known  as  the  antrum 
Pylori.  The  constriction  on  its 
left  may  be  very  slight,  so  that 
the  antrum  is  hardly  to  be  seen, 
or  it  may  be  so  deep  as  to  be 
mistaken  for  the  pylorus.  The 
antrum  may  be  double  or  even 
triple.  Sometimes,  on  the  other 
hand,  the  terminal  part  of  the 
stomach  is  tubular  and  to  be  dis- 
tinguished from  the  intestine  only  by  its  thick  walls.  Fig.  1368  shows  such  a  .:ase 
which  seems  to  extend  beyond  the  usual  limits  of  the  stomach.  The  superior  or 
cardiac  orifice  faces  upward  and  to  the  right,  being  much  nearer  the  front  than  the 
back  of  the  stomach.  Its  diameter  is  at  least  2  cm.  and  may  be  much  more.  When 
the  stomach  is  distended  a  well-defined  groove  appears  between  the  fundus  and 
the  left  of  the  o-sophagus.  Further  details  have  been  given  with  the  gullet  (page 
1609).  The  position  ot  the  lower  orifice  or  pylorus  may  not  be  recognizable  on  the 
outer  surface,  or  it  may  be  marked  by  a  groove.  Internally,  it  presents  a  distinct 
ring  caused  by  the  thickening  of  the  layer  of  circular  muscular  fibres,  improperly 
called  the  valve  of  the  pylorus,  which  raises  the  mucous  membrane.  This  can 
always  be  felt  through  the  walls.     It  is  only  by  touch  that  the  position  of  the  pylorus 

can  be  certainly  recognized  when  the 
Fig.  1367.  parts  are  unojjened.    The  gastric  cavity 

gradually  narrows  towards  the  pylorus 
on  the  stomach  side,  but  from  the  duo- 
denum there  seerts  to  be  a  (terforated 
partition  across  the  tube  like  an  optical 
diaphragm.  The  opening,  although 
nearly  always  elliptical,  is  sometimes 
almost  circular.  Some  of  the  larger 
openings  in  a  series  of  thirty  casts' 
showa  long  diameter  of  from  17-18  mm. 
and  a  short  one  of  from  13-15  mm. 
Some  of  the  smaller  openings  measure 
6x7  mm.  and  8x8  mm.  We  have 
observed  more  extreme  figures  at  both 
ends  of  the  series  than  those  quoted. 
It  is  difficult  to  say  whether  some  of 
the  smaller  ones  would  admit  of  greater 
dilatation.  Probably  13x15  mm.  is 
not  far  from  the  average  size.  The 
position  of  the  longer  axis  of  the  orifice  is  uncertain,  although  it  usually  runs  down- 
ward and  bai-kward." 

Owing  to  the  difference  in  size  of  the  two  ends  of  the  organ,  the  axis  0/  the 

'  DwiRht ;  loumal  of  Anatomy  and  Physioloftj-,  vol.  xxxi.,  1897. 
'  Berry  and  Crawford  :  Ibid.,  vol.  .xxxvi.,  1902. 


Gastro-spletiic 
omentum. 


Gastro-plirenic 

liKameiit. 

I'ncovered 

area 

CEsophajcus 


Posterior, 
surface 

(sastro-hepatic 
nmentum 


jreater 
omentum  fcut) 


Fundus 


Right  aspect  of  stomach,  moderately  distended. 


THE  STOMACH. 


l6ly 


Fio.   1368. 


Pyloru 


Outline  of  sliimach  with 
conttricicd  and  greatly  eton- 
gatcd  pyloru*. 


iUmuuk  »  necessarUy  oWique.  although  the  kss^r  cunature  is  vertical  until  near  its 
end  The  axis  slants  downward  and  to  the  right  as  well  as  forwani,  the  pyloric 
portion  being  disregarded.  The  stomach  is  sometimes  c.>m,«ratively  tubular,  the 
Wdus  being  but  little  developed,  although  the  cardiac  opening  is  always  on  the 
riirht  side  This  is  a  continuation  of  the  loetal  form,  and  is  more  often  seen  in 
^  women.     There  is  often  (possibly  normally )  a  hint  of  a  con- 

striction about  the  middle. 

The  above  description,  which  is  essentially  the  conven- 
tional one,  is  that  of  a  distendetl  stomach.  The  constrictions 
marking  off  a  single,  double,  or  even  triple  antrum  pyU.ri 
are  due  to  the  contraction— which  generally  i)ersists  for  some 
hours  after  death— c.f  bundles  of  the  circular  tibrcs.  buch 
constrictions  sometimes  become  fixed.  The  trui-  shape  of 
the  stomach  in  life  when  non-distended  is  very  different,  but 
not  yet  thoroughly  known.  It  is  rather  tubular,  owing  to 
the  contraction  of  the  muscles  in  its  walls.  The  fundus  is 
puckered  and  more  or  less  constricted  off  from  the  rest,  as  is  shown  by  the  study 
of  hardened  bodies  (Fig.  1369).  ...  1  j       t       .„„,««   »k« 

Weight  and  Dimensions.— Not  only  is  the  normal  development  o!  the 
stomach  very  variable,  but  it  is  impossible  to  define  the  limits  between  the  normal 
and  the  pathological  ;  naturally,  therefore,  statements  differ  widely  and  are  of  little 
value  According  to  Glendinning,  the  weight  is  127  gm.  (4J4  of). 'or  man  and  a 
little  less  for  woman.  The  greatest  length,  directed  nearly  vertically,  is  some  25  cm. 
( ID  in  )  the  greatest  breadth  from  lo-i  2  cm.  (4-5  «"• ).  and  >ts  diameter  from  betore 
backward  from  7-5-'C  «"■  ( .W  '"•  )•  The  average  adult  capacity  is  said  to  range 
from  6OCV-2000  cc.  (1.25-4-25  pints),  with  an  averse  of  1200  cc   (2.50  pints). 

Peritoneal  Relations.— The  greater  omentum,  the  origin.d  posterior  mesen- 
tery passes  to  the  back  of  the  stomach  just  to  the  left  of  the  oesophagus,  where  its 
layers  diverge  so  as  lo  leave  a  small  triangular  part  behind  it  attached  to  the  dia- 
ohragm  without  peritoneal  covering.  The  lower  of  the  diverging  lines  runs  to  the 
lesser  omentum.  The  line  of  attachment  then  passes  across  the  posterior  surface  ol 
the  fundus  near  the  top,  but  posterior  to  ihe  greater  curvature.  At  the  left  of  the 
stomach  the  line  of  insertion  is  at  u  *„ 

the  greater  curvature,  and  continues  F'O-  >309- 

so  till  it  reaches  the  pylorus.      The  Caru«c  end 

fold  passing  to  the  diaphragm  at 
the  beginning  is  the  g astro-phrenic 
ligament.  This  is  joined  by  the 
gastro-pancreatic  fold  on  the  pos- 
terior abdominal  wall  which  con- 
veys the  coronary  artery  to  the 
right  of  the  cardiac  opening.  This 
last  fold  is  important  in  relation  to 
the  topography  of  the  peritoneum, 
but  not  to  the  stomach.  The  lesser 
omentum  is  attached  along  the 
whole  of  the  lesser  curvature,  ex- 
C(.j't  that  its  posterior  layer  may 
leave  it  below  the  cardia  to  join  on 
the  back  of  the  stomach  the  layer 
of  the  greater  omentum  which  forms 

the  itiferior  border  of  the  non-serous  j    ,    ,        .„.       .,        i  k  .     »„ 

trianele      With  the  exception  of  this  tnangle,  and  of  the  trifling  interval  between 
the  lines  of  attachment  of  the  omenta,  the  whole  organ  is  invested  by  peritoneum. 

Position  and  Relations.— The  cardie  opening  is  opposite  the  tenth  thoracic 
vertebra  and  not  far  from  the-  level  of.  hut  from  .^  -10  rm^  f  3-4  in.  ^  behind  the  sixth 
left  costal  cartilage,  about  12  mm.  (>.  in.)  to  the  left  of  the  median  hne  The 
lesser  curvature  descends  vertically  in  an  antero-posterior  plane,  parallel  to  the  left 
border  of  the  ensiform,  but  slanting  strongly  forward,  until  it  suddenly  turns  to  the 


Pylorua 


Stomach  with  purltrred  fundus,  seen  from  behind  and  soinewhal 
from  left ;  hardened  by  iormalin. 


l630 


HUMAN   ANATOMY. 


Non-peritonral  area 


ardiac  orifice 


right,  rises,  and  ends  opposite  the  space  between  the  ensiform  and  the  end  of  the 
eighth  or  ninth  right  cosul  cartil^e,  on  a  level  with  the  first  lumbar  vertebra  or  the 
disk  below  it,  about  1.3  cm.  (>^  in.)  from  the  median  line.  The  pyloric  orifice  is 
affected  to  such  an  extent  by  changes  incident  to  variations  in  distention  that  it 
is  manifesdy  impossible  definitely  to  fix  the  position  of  the  lower  end  of  the  stomach. 
The  pylorus  is  usually  separated  from  the  anterior  abdominal  wall  by  the  over- 
lapping liver,  when  the  stomach  is  empty  lying  near  the  mid-line.  According  to 
Addison,  a  point  1 2  mm.  (  Y,  inch )  to  the  right  of  the  median  plane  midway  between 
the  top  of  the  sternum  and  the  pubic  crest  will  ordinarily  correspond  to  the  position 
of  the  pylorus.  The  fundus  is  at  the  top  of  the  left  side  of  the  abdomen  under  the 
diaphragm,  reaching  the  level  of  the  sternal  end  of  the  fifth  costal  cartilage.  The 
anterior  surface,  looking  upward  as  well  as  forward,  b  covered  by  the  left  and  quad- 
rate lobes  of  the  liver.  A  varying  part  of  it  touches  the  diaphragm  in  front  of  the 
former.  The  extent  of  this  must  depend  on  the  size  of  both  organs.  The  liver  may 
separate  it  entirely  from  that  part  of  the  diaphragm  below  the  pericardium,  or  the 
stomach  may  be  gainst  the  diaphragm  in  the  anterior  part  of  this  region.  A  small 
triangular  part  of  the  stomach,  normally  in  contact  with  the  front  wall  of  the  abdo- 
men, bounded  below  by  the  greater  curvature,  is  seen,  on  opening  the  abdomen, 
between  the  liver  and  the  line  of  the  left  costal  cartilages.  This  appearance  ga\e 
rise  to  the  old  error  that  the  stomach  is  placed  transversely.     According  to  Tillaux, 

the  stomach   in   its   most  con- 
FiG.  1370.  tracted  state  always  descends  tu 

a  line  between  the  ends  of  the 
ninth  costal  cartilages.  The  pos- 
terior surface,  forming  a  part  of 
the  anterior  wall  of  the  lesser 
peritoneal  cavity,  rests  against 
the  transverse  mesocolon,  which 
lies  on  the  organs  at  the  back  of 
that  space,  so  as  to  make  a  part 
of  the  concavity  for  it  which  Bir- 
mingham' has  well  called  the 
stomach-bed  (Fig  1371).  This 
hollow  is  made  by  the  diaphragm 
on  the  left  of  the  aorta,  by  the 
left  suprarenal  cafMule,  the  gas- 
tric surface  of  the  spleen,  the 
antero-sujjerior  surface  of  .the 
pancreas,  and  U5u.illy  by  the  upper  part  of  the  left  kidney,  although  exceptionally 
this  may  be  shut  fiff  from  the  stomach  by  the  spleen  and  pancreas.  The  left  crus 
of  the  diaphragm  nakes  a  deep  indentaii  )ii  in  the  stomach  to  the  left  of  the  car- 
dia.  The  riliac  axis  and  the  semilunar  ganglia  are  rather  to  the  right  of  the  lesser 
cur\'ature.  Ihe  transverse  mesocolon  continues  the  lower  part  of  the  stomach-bed 
forward  to  the  transverse  colon,  which  lies  below  the  stomach,  following  its  curve 
when  the  stomach  is  distended.  The  splenic  flexure  of  the  colon  is  close  against 
it.  Whin  free  from  solid  contents,  the  stomach  is  usually  found  in  dissecting-room 
subjects  hanging  more  or  less  vertically  in  longitudinal  folds  containini;  more  or  less 
air  and  fluid  ;  but  during  life,  as  already  stated,  it  is  in  a  contracted  and  puckered 
condition,  the  long  axis  running  strongly  forward  as  well  as  downward.  With  dis- 
tention the  stomach  enlarges  at  first  upward,  backward,  and  to  the  left,  then  forward 
against  the  abdominal  walls.  The  upper  part  enlarges  chiefly  backward,  the  lower 
forward.  This  does  not  impl}'  a  forward  swing  of  the  greater  curvature  such  as 
has  been  described.  The  pyloric  end  is  moved  to  the  right,  it  may  be  as  far  as 
the  gall-bladdiT.  The  antrum  may  thus,  according  to  Birmingh.im,  be  carried  to 
the  right  of  the  pylorus.  The  lattrr  rarely  m- -ves  more  th.iii  5  em.  to  the  ri^l-.t  of 
the  median  line.  Except  in  its  last  part,  the  Ksser  curvature  continues  essentially 
vertical,  as  seen  from  before.  The  transverse  colon  is  driven  downward  unless  it  be 
so  much  distended  as  to  offer  effectual  resistance. 

'  Journal  of  Anatomy  and  Physiology,  vols,  xxxi.,  x\\\..  1897,  1901. 


Pylorul 


Pos'.erior  aspect  of  st<>     i<-h  at  I'H  tit,  sliuwing  perttoiieal  telatiotis. 


THK  STOMACH. 


1621 


Structure.— The  walls  of  the  stomach,  thickest  and  most  resistant  near  the 
pylorus,  consist  of  four  coate,— the  mucous,  the  submucous  or  areolar,  the  muscu- 

*The*  mucous  coat  or  mueosa  is  soft  and  velvety,  easily  movable  on  the  lax 
subjacent  areolar  tissue,  thickest  near  the  pylorus,  and  pre^nts  "l^*")' /'jY*  "' K^ 
which  during  distention  are  more  or  less  completely  effaced.     The  folds  are  m  the 

Fig.    I37>- 


FalcifomtliKan^cnt 


Ascending  colon 


llsum. 


Lcfl  V)br  01  livet 


Trantv«rM  mesocoloo 


DescendiMR  cc'oo 


SiKHioid 


main  longitudinal,  especially  at  the  pyloric  end.  but  many  smaller  ones  run  in  all 
'^'^%Z%/>itMium  covering  the  free  surface  of  the  mucous  membrane  consists  of  a 


I633 


MIMA.N   ANATOMY, 


transparent  columnar  cells  clothing  the  stomach.  The  line  o:  liansition  is  zigiajj 
and  well  defined,  the  oesophageal  suriace  being  paler  than  the  highly  vascular  red 
gastric  mucosa.     At  the  pylorus  the  mucous  membrane  is  raised  into  a  ring,  chicriy 


VIII  rilKanUajcc 
Truiivcrse  mestx-olun 


Kio.  1373 
VII  rilvcanilacc 


Emiform  cani'krr 

VII  riWaniUi*   / 


VI  rilM^rtilajir 

Kalcifurm  lixamcnt 


VI  rib-caniUtc 


Pylorir  antrum  ut 
»tfMitat-li 
r.iia[ihraKnt 


Jejunum 


Right  Hupra- 
renal  b'tdi 


XI  rib 


Xfl  rib         XII  vertebra    XII  rib 
Frozen  section  ac^o^s  body  at  level  of  twelfth  th«»rai-ic  vertebra. 


in  consequence  of  the  local  thickening  of  the  circular  fibres  of  the  muscular  coat,  but 
also  in  part  on  account  of  the  increased  thickness  of  the  mucosa  itself,  which  in  this 
part  of  the  stomach  may  measure  over  2  mm.  At  the  cardia  it  is  thinnest, — .5  mm. 
or  less, — while  in  the  intermediate  rejjion  it  is  about  i  mm.  The  increased  thick- 
ness at  the  pyloric  end   is  due  to  the  considerable  depth  of  the  depressions,   or 

Fig.   1374. 


Fig. 


1373- 


Surface  view  fil  mni-oim  membrane  frrtm  p\Ioricen»I 
of  stomarh.     N:itural  size. 


Surface  view  of  Kastri<  iiiucous  membrane,  show, 
ins  reticular  apiiearnnce  due  to  orifices  of  groups  of 
uasliicKlanils.      ■   jo. 


gastric  crypts,  into  which  open  the  gastric  ijlands.  Beyond  the  summit  of  the 
pyloric  ring  the  mucous  membrane  assumes  the  characteristics  of  the  intestine.  In 
addition  to  the  larger  ruga,  the  gastric  surface  exhibits  a  mammillattd  condition 


THK  STUM  At  M 


i6i,^ 


coittistinR  of  small  Hygonal  irca*  pitwd  by  tiw  -  r-pt«  *ft«rh  reanv*  the  .-n»c«  of 

the  K'*^"^'**-^^^^^  gland*  constitute  iw..  pnnc^wd  b»«i|»,  «»/»«*...  ami  tlw  #r/^V 
Wa*^*;  the  former  occupy  the  maj.^  i«.rt .-  th.-  .«wiad,,  iwUuliinf  the  '"«***  '^e 
interior  and  posterior  walls,  an.i  the  -  urv'atu«*  ibr  latter  »  .  ur  ,.  the  ,,vU.r.'  hfth 
of  the  organ  An  additional  fundus  va«ety-«k«  ^W/u,  .-'"A-  -  >  pr.se,,!^!  l.y 
a  narrow  zonular  uroup  in  the  immwliate  vicmm-  <«  the  u-s..,^^.i^(e..l    ^n>r.i;. 

Th^  fundus  eupeptic  glami*-tfae  ^-rtric  «l»ls  pr..,«-r--:o.>»««  ...  u^m.^.a« 
closely  srt  tubules,  uiimlly  somewha.  «  -y  ««J  fcm«^  ,4-'  mm  l.m.:  wh.d.  ext*n.l 
the  entire  thickness  of  th.  mucosa  and  abut  ;H£«..«t  the  „u.«:u*..ns  u.«c.««e  L.-  h 
MStric  cVypt.  corresponding  t.,  tte  ^^rrr/rn-V  *«r/  usualv  ,ec.-.v.-s  a  »:roup  of  s^ - 
S  of  th^smaller  ?ub„les*^  which  mdude  the  -W  and  /-«rf*.  of  i  .e  kU«I,  tl^ 
^nstricted  commencement  of  the  tubule  co«titu.  .,.g:  the  nea     At  the  l^ter  p««.t«.n 

Fic.  1375 


_(.a«rii  Klan't- 


»J 


i^^i^J^r^ 


M  iistriilanii 


Must  iilari'' 


Seros.'! 


4  jhli'iuflv  iut 
i-irculai 


Tnmsversf  stc 


lion  of  stoma.!,  ilelt  en.l  i.  5ho»i.iK  KM,.rjl  arranmiiKiU  o(  cmts. 


the  columnar  epithelium  prolonged  into  the  crypts  from  the  free  suriace  becomes 
lower  and  modified  into  the  secreting  elements. 

The  cells  lining  the  gastric  tul.ules  are  of  two  Icmds.  the  chief  and  the  parietal. 

The  chief,  central  or  adelomorphous  cells  correspond  I.,  ordinary  glandular  epi 
thelium.  being  low  columnar  or  pyramidal,  ..nd  surroumlin-  a  cir.nU.r  lumen  from 
!S  t™   .oo7^mm.   in  diameter.  '    During  certain  >.ages  of   digest,.,,,   they  -ontam 
numerous  granules,  which  are  probably  concerne.l  in  producing  P^I"*'". 

The  parietal  cells,  known  also  as  acid,  o.xynti.-,  ..r  delomorphous  although  rela- 
tivclv  few  u-  conspicil"U'=  eler-.e,,!-.  which  oc-u-.N-  the  periphery  of  the  gland  tul>es 
Their  position  is  indicated  by  protrusions  of  .he  profile  of  the  g.xstnc  tutn.les  caused 
by  the  cells  lying  immediately  l^neath  the  b;isement  membrane.  The  parietal  ce  Is 
although  arranged  with  little  regularity,  are  most  numerous  in  !he™tyof  he 
neck   where  they  may  equal  or  eyen  outnumber  the  central  cells  :  in  the  bod>  of  the 


1 634 


HUMAN  ANATOMY. 


gland  they  decrease  in  number  towards  the  fundus,  in  which  locality  they  may  be 
almost  absent.  Their  protoplasm  is  finely  granular  and  lighter  than  that  of  the  chief 
cells.  The  parietal  cells,  although  apparently  excluded  by  the  central  ones,  are  con- 
nected with  the  gland-lumen  by  means  of  lateral  intercellular  secretion-capillaries  ; 
the  iatter  extend  from  the  axial  space  to  the  peripherally  situated  elements,  over 
which  they  form  characteristic  basket-like  net-works. 

The  pyloric  glands,  branched  tubular  in  type,  differ  from  the  fundus  glands 
in  the  excessive  width  and  depth  of  their  excretory  ducts,  into  which  a  group  of 
relatively  short  but  very  tortuous  gland-tubules  opens,  and  in  the  simple  character  of 

their  lining.     The  latter  consists  of 


Fic.  1176. 


IVfper  portion  of  KitMrJc  glands  from  ftirhlus.  sno^inK  two 
varii'iit's  (if  ;initiK  iTlU  and  ftrcnrtion-capitlarirvt » unnt-.tHiK  [liirt- 
eta!  cclK  witli  lumen.      ■  41,1. 


a  single  layer  of  low  columnar  or 
pyramidal  elements,  which  corre- 
spond to  and  resemble  the  chief 
cells  of  the  fundus  glands.  Their 
secretion  often  reacts  as  mucus 
( Bensley).  Owing  to  the  tortuous 
course  of  the  pyloric  tubules,  the 
deeper  parts  of  the  glands  are  cut 
in  all  planes,  portions  of  the  same 
tubule  often  appearing  as  isolated 
transverse,  oblique,  or  longitudinal 
sections.  The  transitional  or  in- 
termediate zone  connecting  the  py- 
loric and  adjoining  portions  of  the 
stomach  contains  both  forms  of 
glands,  those  of  the  fundus  variety 
with  parietal  cells  being  intermin- 
gled with  the  pyloric  type.  Towards 
the  intestine  the  change  of  the  ,jy- 
loric  glands  into  those  of  the  duo- 
denum is  gradual,  the  gastric  tubules 
sinking  deeper  until,  as  the  glands 
of  Brunner,  they  occupy  the  sub- 
mucous coat  of  the  intestine. 

The  cardiac  glands  form  a 
narrow  annular  group,  some  5  mm 
broad,  surrounding  the  orifice  oi 
the  gullet,  into  which  ihey  are  con- 
tinued for  a  short  distance  (page 
161 2).  These  glands,  which  in  some 
animals  constitute  a  much  wider 
zone  ( in  the  hog  almost  a  third  of 
the  entire  stoniiich),  are  to  be  re- 
garded as  modified  fundus  glands 
(Oppel),  since  they  possess  similar 
epithelium,  including  usually  a  few 
parietal  cells.  Their  excretory  ilucts 
or  crypts,  lined  with  the  gastric 
epithelium,  often  exhibit  ampulln- 
like  dilatation.s.  Among  the  tvpi- 
ral  tubules  are  a  few  shorter  ones 
which  recall  the  gl.->nds  of  I.Ii-Iht- 
since  they  contain  1,'oblet- cells  and  exhibit  a  cuticular  border 


Ihicf  cell 


Parietal  cell 


kiihn  of  the  intestine 
(J.  SihiiffiT  ). 

The  s/roma  or  tunica  propria  of  the  gastric  mucous  membrane  consists  of  a 
loose  fibro-elastic  connective  tissue  containing  numerous  cells  anil  resembling  lym- 
phoid tissue,  which  fills  the  interstices  between  the  glands  and,  in  conjunction 
with  the  extensions  of  the  nmscularis  mucosa-,  forms  envelopi-s  and  partitions  for 
the  groups  of   tubules   constituting  the  deeper  parts  of   the  gastric  glands.      In 


THE  STOMACH. 


1625 


the  vicinity  "I  the  pylorus,  and  sometimes  also  at  the  cardia,  a  number  of  small 
lymphatic  nodes— the  so-called  lenticular  glands— normMy  occupy  the  deeper 
parts  of  the  mucosa ;  occasionally  they  are  of  sufficient  size  to  almost  reach  the 

tree  siirfcicc 

The  muscuiaHs  mucosa,  as  in  other  parts  of  the  intestinal  tube  consists  of  a 
wcU-marked  collection  of  involuntary  muscle,  deeply  situatecj  next  the  submucous 
coat     Two  layers  are  usually  distinguishable,  an  inner  circular  and  an  outer  longi- 


FiG.  1377- 


Mucous  coal 


Siibimicous  coal 


.Circular  miisi  le 


LonKitndinal  ni«*clc 


iStrnimcoat 


Transverse  section  o(  stomach,  pyloric  end 


rusa  is  rut  across,  showing  mucosa  sup|K>ried  by  core  ol  submucous 
tissue       ■    io. 


tudinal.  Towarils  the  mucosa  numerous  bundles  of  muscle-cells  extend  between  the 
Elands  and  in  places  penetrate  almost  as  far  as  the  epithelium. 

The  submucous  coat  consists  of  la.x  connective  tissue,  allowing  the  mucous 
membrane  to  move  freely  on  the  muscular  layer.  It  contains  blood-vesse!  of  con- 
8i<lerable  size,  a  mc-sh-work  of  Ivmphatics,  ami  the  nerve-plexus  of  Meissncr. 

The  muscular  coat  comprises  three  layers,— an  outer  lonR.tud.nal.  a  middle 
circular,    and  an   imneifect  inner   oblique,— of  which  the  middl-  one  is  the  most 


1 636 


HUMAN   ANATOMY. 


important.  This  layer  is  composed  of  circular  fibres,  which  are  thickest  and  most 
simply  arranged  near  the  pyloras.  Owing  to  the  enlargement  of  the  upper  end  of 
the  stomach,  and  the  fact  that  the  cardiac  opening  is  not  at  the  end  but  at  the  side, 
the  arrangement  becomes  complicated.  The  fibres  surround  the  cardia,  but  become 
oblique  at  a  short  distance  from  it.  At  the  top  of  the  fundus  they  are  arranged  in  a 
whorl  mingling  with  those  of  the  internal  layer.  Still  lower,  although  in  the  main 
circular,  their  course  is  uncertain.  Towards  the  pylorus  they  thicken  considerably, 
being  particularly  well  developed  in  stomachs  of  which  the  pyloric  part  is  tubular. 
At  the  opening  they  are  collected  into  a  ring — \)\e pyloric  sphincter — capable  of  closing 
the  oriiice.     The  longitudinal  layer  is  outside  of  the  circular  one  and  continuous 

Fig.  1378. 


Mouth  of  ji^land. 


Pyloric  Kl'^nd. 


Fundus  ul  trLiiid, 


Lvmph-lUiJt- 


Muscul.irisi  niuv'«»a* 


Scrti"iioi  i,\Ioru  end  of  Muniach.  ^huwiiiK  KlHud^  and  (kiit  of  I>mpti-iiudr.         kjo. 


with  the  lonjjitiidin.nl  fibres  of  the  (tsophagus.  Along  the  lesser  cijr\  ature,  and  to  a 
!<^->  extent  along  the  frreatcr,  these  fibres  are  collected  into  bantis  ;  over  the  front 
and  the  hack  of  thostoin.uh  they  are  oblique.  At  the  antrum  pylori,  although  the 
layer  is  rontinuiMis  all  around,  it  presents  an  anterior  and  a  posterior  hand, — the 
pyloric  ligaments. —\\\M  (lass  o\er  folds  of  all  the  layers  internal  to  them,  thus 
forming;  the  duplicature  .it  the  beginninu;  of  the  :i.H.um.  At  the  pylorus  itself  the 
loniijitudin.il  layer,  which  has  t)ecome  thicker,  sends  a  series  of  fibres  through  the 
circular  ti.ire-i.  sulKliviilin^;  them  into  n.any  groups,  CFig.  isgi").  The  innermost 
muscular  layer  ■> insists  i)\  fbliqiie  fibres  spreading  out  from  the  cardia  o\er  the 
front  ami  Ixick  of  the  stomach.      They  are  continuations  of  the  circular  fibres  of 


THE  STOMACH. 


1627 


ut  glands 


the  Bullet  and  diverge  to  either  side,  showing  a  well-marked  border  near  the  lesser 
curvature.  Their  p^terior  expansion  is  the  stronger.  The  diverging  hbres  are  lost 
near  the  pylorus,  while  in  the  vicinity  of  the  fundus  they  mingle  with  the  circular 
ones  that  form  the  whorl.     The  latter,  according  to  Birmingham,  is  formed  by  this 

'*y^''xhe"8erou8  coat  corresponds  in  structure  with  other  portions  of  the  perito- 
neum, consisting  of  the  endothelium  of  the  free  surface,  iKrnealh  which  lies  the 
fibro-elastic  stroma  attached  ^^^    ^^^^ 

to  the  muscular  tunic. 

Blood-Ve8»elB.—  The 
arteries  of  the  stomach,  de- 
rived from  the  cceliac  axis,  are 
arranged  in  two  arches  aloog 
the  lines  of  atuchment  of  the 
omenta  ;  hence  that  which  is 
attached  to  the  greatei  cur- 
vature below  passes  behind  it 
on  the  fundus.  The  arch 
along  the  lesser  curvature  is 
formed  by  the  coronary  ar- 
tery, which  sends  an  oesopha- 
geal branch  upward  tf)  meet 
the  lowest  of  the  oesophageal 
arteries,  and  joins  the  py- 
loric branch  of  the  hepatic 
artery  below.  The  arteries 
of  the  greater  omentiini  are 
the  right  and  left  ga.stro-epi- 
ploic,  reinforced  behind  the 

fundus   by    the   vasa   brevia 

of  the  splenic  artery.      The 

gastro-epiploicadextra  passes 

dow  n  on  the  right  of  the  first 

part  of  the  duodenum  close 

to    the    pylorus  ;     branches 

arising  on  the  front  at  that 

region   may  nearly  or  quite 

makt  an  arterial  ring  around 

the    organ.      The   coronary 

arterv    supplies    the    longer 

branches  to  the  walls,  there 

being  a  richer  arterial  distri- 
bution on  the  back  than  on 

the  front  and  at  the  cardiac 

than  at  the  pyloric  end.    The 

general  i)l;in  is  as  follows  :  on 

the  anterior   surface   seveml 

arteries,    of   which   some  four      ^^^  ^_^,  ___  ^^  ^^_^^;^,  „..n,hranr  fmn,  pvlork  «nd  of  M..n>a.  h.  ^ho« 

are  large  ones,   run  from  the  i,iK  Kinnils  i m  m  varimis  levtis.    ■  i<». 

S^ch"S:S.  ^r^iclSsive  lateral  branches  to  inosculate  with  those  from  their 
en"  s  finallv.'^he  main  vessel  breaks  up  into  branches  th.-it  meet  ^^-^ 
greater  curvature.  On  the  posterior  surface  the  chief  trunks  d.vule  witl  less  reg«- 
hritv.  At  first  the  artenes\,re  just  beneath  the  perit<,ne«m,  between  the  folds  .1 
which  they  gain  the  stomach  ;  presently  they  enter  and  pierce  the  muscular  coat,  the 
omer  p.,rtsof  which  are  supplied  during  their  passage.  On  reaching  the  ^^'-l^^'- 
coat  the  arteries,  now  reduced,  but  still  of  con .ider.nble  s,/e,  .livule  into  smaller 
branches  some  of  which  pa.ss  to  the  muscular  tunic,  while  the  ma).. rity  enter  the 
mucou    coat.     The  latter  soon  break  up  into  capillaries  which  surround  the  gland- 


1638 


HUMAN   ANATOMY. 


tubules  with  a  dose  mesh-work.  Somewhat  larger  capillaries  constitute  a  superficial 
plexus  beneath  the  epithelium  encircling  the  orifices  of  the  gastric  crypts.  The 
veins,  relatively  wide,  begin  in  the  subepithelial  capillary  net-work  and  traverse  the 
gland-layer,    between    which    and 

Fig.  1380. 


Pyloric  rinj 


Stomach  tanwd  inside  out,  •howinc  dincction  of  obliuur  ami 
circular  mnacular  coati. 


the  muscularis  mucosae  they  form 
a  plexus  ;  .'  om  the  latter  radicles 
pass  into  ;  t;  submucous  coat,  in 
which  the  venous  trunks  run  paral- 
lel with  the  arteries,  but  lie  nearer 
the  mucosa  (Mall).  The  emerging 
tributaries  are  often  provided  with 
valves  at  their  junction  with  the 
larger  gastric  veins. 

The  l)nnphatics  originate 
within  the  mucous  membrane,  be- 
neath the  epithelium,  as  wide,  ir- 
regular capillary  channels  which 
freely  communicate  with  one  an- 
other and  pass  between  the  glands 
as  far  as  the  muscularis  mucosa-  ;  at  this  level  they  form  a  plexus  from  which  vessels 
descend  mto  the  areolar  coat  to  join  the  wide-meshed  submucous  plexus.  Larger 
lymphatics  pierce  the  muscular  tunic  and  unite  to  form  the  chief  channels  which 
escape  from  the  walls  of  the  stomach  along  both  curvatures  to  empty  into  the  lymph- 
notles  which  occur  in  these  situations. 

The  nerves   supplying  the  stomach   are  from   the   pneumogastric  and   the 
sympathetic,   and   contain   both   medullated  and  nonmedullated   fibres,    the  latter 

predominating.         On 
Fic.  1381.  reaching  the  organ,  the 

stems  pierce  the  exter- 
nal longitudinal  muscu- 
lar layer,  between  which 
and  the  circular  layer 
they  form  \.\\cp/cxus  of 
Auerbach.  The  points 
of  juncture  in  this  net- 
work are  marked  by  mi- 
croscopic sympjithetic 
ganglia,  from  which 
non-meduUated  fibres 
supply  the  involuntary 
muscle.  Leaving  the 
intramuscular  plexus, 
twigs  pass  obliquely 
through  the  circular 
muscular  tunic,  ami  on 
gaining  the  submucous 
coat  form  a  second  net- 
work, the  picxtis  of 
Mf  issuer.  Numerous 
non-medullated  fibres 
leave  the  latter  to  enter 
the  mucous  coat,  in 
which  some  end  in  deli- 
CJite  ple.xuses  supplv- 
ing  the  gastric  glands 
<  Kytmannw  ),  as  well  as 
111  special  endings  in  the  muscularis  mucos«>  (Berkley ).  Large  medullate<l  fibres,  the 
dendrits  (if  sensory  neurones,  are  also  present  within  the  mucosa,  where  they  lorm 
a  suljcpitheliai  plexus  after  losing  their  medullary  substance.     The  ultimate'termi- 


Muciisji 


Submut  (isa  ^ 


Miis<  ulaii' 


Sfri.». 


■  ■    -     *  ^' 


I  ransverM;  Mrrlioii  01  iii)«:tli'd  Momach. 


PRACTICAL  CONSIDERATIONS:  THE  STOMACH. 


Ifi2i) 


Siirtac.  view  ol  (ragmenl  ol  muKUlar  c.«H  ol  Mom.ch.  .howini,  groups  o(  xa..- 
SurUit  V  '**  ,^;^^|,  a„d  ncrve-fibtc  ol  plexus  o(  Aurrtmch.     ■    ,o. 


nations  ol  the  nerve-fibres  within  the  mucosa,  especially  their  relations  with  the 

^'^^fet^r-SbSl^capacity  ol  the  stomach  is  .5  cc  The o^aj.  although 
sometimes  rather  tubular,  does  not  differ  very  much  m  shape  Irom  that  of  the  adult. 
ThTXphSus  enters  it  less  obliquely  than  later,  so  that  regurK.tat.on  occurs  more 
Teadir^  TrsphTncter  ol  the  pylorus  is  already  developed.  We  do  not  remem- 
l^Tever  to  have  seen  at  birth  a  well-marked  antrum  pylon.  An  ,m,M,rtant  pu- 
Srityol  theS^owtlfol  the  stomach  is  the  unequal  development  of  the  two  sules  at 
the  lund\«  At  an  early  period  the  top  ol  the  original  left  s.de.  which  becomes  the 
anterior    one.    grows 

upward,    so   that   the  F'"-  '3*»- 

line  of  attachment  of 
the  greater  omentum 
is  along  the  posterior 
surface.   This  unequal 

growth  is  quite  analo- 
gous   to   that  of    the 

csecum.    According  to 

Keith  and  Jones,  this 

asymmetry     is     most 

marked    in   the   thiid 

and  fourth  months  of 

foetal   life.     We   have 

examined  no  younger 

fiEtuses     than    these, 

and  cannot  st^'c  how 

early  the  process  be- 
gins.'    From  the  end 

foetal  form. 

wmAimes  caa4d  by  a  local  contraction  becominR  fix«l. 

PRACTICAL  CONSIDERATIONS  :    THE  STOMACH. 

Congenital  malforviations  are  rare.  Perhaps  the  most  common  is  a  constriction 
dividing^'  imo  two  unequal  compartments.  ■"  hour-glass  constnctu.n,  -a  conch- 
tion  somewhat  similar  to  that  found  normally  m  the  kangaroo 

Tre XL    o    the  stomach  varies  with  its  degree  of  distention.     When  .t  . 
emot    the  pSorc  end  descends  and  the  long  axis  of  the  stomach  ,s  obl.que  from 
fc7to  rSt    approximating  the  vertical  (/.r..  the  f<i-tal)  position  or  that  wh.ch  pre- 
ceded  f"mc  ion^ vHe      This  falling  of  the  pyloric-  end  is  due  to  gravity,  the  nearest 
fiilv  fiSpotnt  oTthe  alimentary  canal  U.w  being  the  lower  portion  of  the  duo- 

Journal  of  Anatomy  and  PhyMology,  vol.  xxxvi.,  I9«>»- 
»  Retch's  Pediatrics. 


1630 


HUMAN   ANATOMY. 


denuni  (the  fixation  being  du  to  the  relation  of  the  superior  mesenteric  arterv  and 
to  the  root  of  the  mesocolon  in  front),  while  above  the  cardiac  end  is  suspcndicl 
from  the^phagus  and  held  in  place  by  the  gastro-phrenic  and  gastro-splenic  iiira- 
nients  The  transverse  colon  may  then  lie  in  front  of  the  stomach  and  may,  if  djs- 
tended  be  uken  for  it.  The  empty  stomach  lies  upon  the  posterior  alxlominal 
wall  If  the  emptmess  is  habitual,  the  pylorus  will  resemble  the  first  portion  of 
the  tluodenum  and  regurgitation  of  duodenal  contents  is  exceptionally  easy  The 
•  gnawing  pains  of  hunger  or  starvation  (distinct  from  the  sensation  of' hunt'or 
itsel  )  are  at  leswt  partly  due  to  the  traction  on  the  nerve  plexuses  and  filaments 
resulting  from  this  altered  petition,  and  can,  therefore,  in  many  cases  be  relieved 
teniporanly  and  partially  by  tightening  th^  clothing  about  the  waist  and  abdomen 
giving  support  to  the  viscera. 

When  the  stomach  is  distended  the  enlargement,  which  occurs  at  first  upward 
and  backward  and  towards  the  left  side,  raises  the  arch  of  the  diaphragm  in  that 
region  and  with  it  the  heart  and  jiericardium.  The  gastric  plexuses  derived  from 
the  two  pneumogastrics  and  the  associated  sympathetic  fibres,  together  with  the 
coronary  plexus  from  the  sympathetic,  are  all  in  close  relation  with  the  lesser 
curvature,  especially  its  cardiac  end.  It  is  not,  therefore,  difficult  to  understand 
how  this  change  m  the  position  of  the  stomach  aids  in  producing  the  flushed 
face,  embarrassed  respiration,  and  irregular  heart  action  often  seen  in  various  forms 
ot  dyspepsia  or  after  overeating.  If  distention  continues,  the  right  lobe  of  the 
liver  IS  also  pushed  upward,  the  pylorus  moves  to  the  right,  and  the  transverse 
colon  downward  ;  the  stomach  comes  in  close  contact  with  the  anterior  wall  of  the 
abdomen,  the  " scrobiculus  cordis"  (page  171)  is  obliterated,  and  a  tympanitic 
note  replaces  the  norm  '  resonance.  ' 

Conversely,  cardiac  disease  may  cause  vascular  congestion  of  the  stomach 
catarrh,  dyspepsia,  or  even  hiematemesis.  The  "  black  vomit"  of  moribund  per- 
sons IS  due  to  a  similariy  produced  distention  and  rupture  of  the  stomach  capillaries 
1  he  |)osition  of  the  stomach  varies  with  the  respiratory  movements  In  forced 
inspiration  the  cardiac  opening  descends  about  one  inch  with  the  crura  of  the  dia- 
phragm ;  the  pylorus  reaches  about  the  level  of  the  umbilicus. 

Eructation  of  stomach  contents  in  its  typical  form  is  accomplished  by  con- 
traction of  the  muscular  walls  of  the  stomach  ;  vomiting  by  compression  of  the 
stomach  against  the  under  surfaces  of  the  liver  and  diaphragm  through  contrac- 
tion of  the  abdominal  muscles.  This  is  associated  with  contraction  of  the  circular 
pyloric  fibres  and  relaxation  of  the  oblique  fibres  at  the  cardia,  and  is  probably 
aided  l)y  contraction  of  the  stomach  walls  themselves. 

It  is  ob\  ious  that  a  full  stomach  is  more  easily  and  directly  compressed  in  this 
way,  and  therefore  the  ingestion  of  large  quantities  of  fluids  favors  emesis. 

Vomiting  IS  a  clinical  symptom  often  of  the  greati-st  significance,  and  should 
he  studied  in  relation  to  the  pneumogastric  and  sympathetic  distribution  to  the 
stomach,  lungs,  and  abdominal  viscera  ;  and  its  various  causes— central,  reflex  and 
direct— should  be  worked  out  systematic.-illy. 

Injuries  of  the  StomarA.— The  changes  in  pfwition  and  the  degree  of  distention 
are  of  the  utmost  importance  in  trauma  expended  upon  the  stomach,  which  if  quite 
empty,  almost  certainly  escapes  contusion  and  rupture.  It  is,  at  any  rate,  much  less 
trequintly  ruptured  than  the  intestines  on  account  of  its  thicker  walls  and  nf  the 
protection  afforded  it  by  the  overhanging  ribs  and  the  interposed  liver  The 
■  stomach-t)ed  (  page  1 620 )  supplies  an  elastic  and  movable  Iwse  of  support  which 
also  favors  its  escape  from  injury. 

In  penetrating  or  gunshot  wounds  its  condition  as  to  emptiness  or  the  reverse 
IS  even  more  important.  When  either  wall  is  opened  by  rupture  or  wound,  eversion 
of  the  mucous  membrane,  which  is  favored  l.v  its  thickness  and  by  the  laxity  of  the 
sulmiucous  connective  tissue,  may  temi>orarily  plug  the  opening;  and  through  the 
lormat.on  of  .i.lhesions  permit  of  spontaneous  cure.  The  diflerent  directions  of 
he  museul.T  fibres  m  the  three  layers  of  th.u  cat  ordinarily  prevent  wide  separa- 
M.n  of  the  margins  of  the  wound,  and  thus  also  favor  its  closure  by  natural  processes 
In  i-scape  of  stomach  contents  through  ulceration,  wound,  or  rupture  if  the  poste- 
rior wall  IS  involved,  the  le.sser  omental  cavity  is  infected,  and  a  localized— sub- 


PRACTICAL  CONSIDERATIONS:     THE  STOMACH. 


16.^1 


ohrenic— abscess  may  follow  ;  if  the  anterior  wall  is  opened,  infection  of  the  general 
oeritoneal  cavity  and  septic  peritonitis  are  more  likely  to  result.  On  account  of  the 
Murse  of  the  blood-vessels  (page  1627),  wounds  parallel  with  the  a.xw  of  the  curva- 
tures are  attended  by  free  bleeding,  especially  if  near  those  liorders  of  the  stomach. 
Wounds  running  more  or  less  at  right  angles  to  the  curvatures  and  removed  from 
them  are  much  Ic^s  likelv  to  open  large  vessels.  The  vessc- U  just  Ijeneath  the  sur- 
face of  the  mucous  membrane  are  numerous  but  smaller.  Bleeding  from  tlicm  may 
be  controlled  by  separate  suture  of  the  mucosa,  which  is  facilitated  by  it.s  thickness 
and  by  the  looseness  of  the  submucous  cellular  tissue.  „        .         ,     • 

Ulcers  of  the  stomach  are  found  most  often  on  the  posterior  wall  at  the  pyloric 
end  and  along  the  lesser  curvature.      It  has  lH.-en  suggested  that  they  originate  in  a 
bacterial  necrosis  of  the  epithelium,  which  is  favored  by  the  al)sence  of  the  fun.  us 
or  peptic  glands  (page  1623)  at  this  region,  and  is  followetl  by  -  digestu.n      of  the 
subkcent  tissues.     Allen  thinks  that  the  immense  preponderance  of  pyloric  ulcers  is 
an  illustration  of   the    Maw  of  localization  of   diseased  action,    -viz.,   that  parts 
enioving  the  most  rest  are  least  liable  to  involvement  by  structural  disease.     W  lu-n 
they  cause  hemorrhage,  it  is  apt  to  be  from  the  branches  of  the  coronary  artery.    1  or- 
foration  occurs  with  much  greater  frequency  in  ulcers  situated  on  the  anterior  wall, 
which  is  the  one  with  the  greatest  range  of  motion  in  van-ing  stages  of  digestion 
and  degrees  of  distention,  and  also  during  the  moveiner.ts  of  respiration.      I  ertora- 
tion  from  such  ulcers  with  spontaneous  cure  may  result  in  adhesions  between  the 
stomach  and  pancreas,  colon,  duodenum,  or  gall-bladder,  and  may  be  followed  bv 
fistula;  communicating  with  those  viscera.    They  may  perforate  the  diaphragm  and 
cause  empyema.     They  have  opened  into  the  pericardium  and  mto  a  ventricle  ot 
the"  heart      An  ulcer  may  be  so  surrounded  by  adhesions  that,  even  when  on  the 
anterior  wall,  perforation  does  not  cause  a  general  joeritonitis,  but  a  locali/.etl  atwcess. 
If  this  is,  for  example,  in  the  splenic  region,  it  will  be  obsenecl  that  there  is  i.nmo- 
bilitv  of  the  upper  left  quadrant  of  the  abtlomen  with  restriction  of  the  respiratory 
movements  of   the  left  thora.x,   both  occasioned  by  the  connection  between  the 
splanchnic  and  the  intercostal  nerves  through  the  sympathetic  ganglia.     The  local- 
isation of  such  collections  of  pus  after  perforation  of  the  anterior  wall  near    he 
cardia  is  favoretl  by  the  "  costo-colic' '  fold  of  peritoneum  extending  from  the  .  la- 
phragm  opposite  the  tenth  and  eleventh  ribs  to  the  splenic  flexure  of   the  colon 
and  forminri'art  of  the  left  portion  of  the  -stomach-bed.-    This  fold,  especially 
with  the  patient  supine,  forms  a  -  natural  well."  contaming  the  spleen  and  a  part 
of  the  stomach,  into  which  any  fluid  exudate  or  stomach  contents  may  gravitate 

^  ^Cancer  of  the  stomach  occupies  by  preference  the  pyloric  region.  When  the 
erowth  becomes  palpable,  but  before  it  is  ti'd  d'^n  by  adhesions  to  neighlx)ring 
organs,  it  often  illustrates  the  mobility  of  the  pyionc  end  of  the  stomach  (v,df 
supra),  as  it  can  be  pushed  even  ,across  the  mid- line  of  the  botly  into  the  splenic 

'^*^^'*Carcinoma,  according  to  its  situation,  may  extend  in  the  cours--  of  the  lym- 
phatic vessels  running  along  the  lesser  curvature  in  the  gastro-hepatic  omontuni  ami 
emptying  into  the  lymph-nodes  near  the  cieliac  axis  and  hepatic  l)lood-vv->stIs.  or 
along  the  greater  curvature  an.l  the  cardia  to  the  retro-.tsophageil  ir!an..s  f  tie 
retro-pvloric  lymph-nodes  mav  l)e  inv.ided  in  cancer  of  the  pylorus.  It»  .arly  r.  n;- 
nition  as  a  tumor  obviously  depends  upon  its  anatomical  site.  If  it  oc(  im>u-s  'he 
fundus  the  cardia,  the  lesser  curvature,  or  the  upper  and  ouu-.|ng  pon-ins  ■■(  .li.; 
anterior  wall,  the  ribs  and  the  liver  intervene  and  prevent  palpatioi"  of  tne  i;r<'\via  ; 
an.l  if  on  the  posterior  wall,  the  depth  at  which  the  tumor  lies  renders  its  palp  xvax 
difficult  and  unsatisfactory.  .      1    .        _       i       j 

Dilatation  of  the  stomach  { srastreclasis )  may  l>c  due  to  simiile  hypertropin  <.t 
the  pyloric  muscle,  may  follow  stricture  of  the  pylorus  or  duotlenum  .rom  cic.itriza- 
lion  of  an  ulcer,  or  may  result  from  pyloric  occlusion,  as  from  carcinomatous  growth 
invading  the  pylorus  itself,  or  from  pressure  of  an  extrinsic  tumor,  or  a  displ.ic.-.l 
liver  or  right  kidney.  The  distention  is  often  extreme,  and  in  some  instances  the 
outline  of  the  distended  stomach  can  plainly  be  seen,  the  lesser  curvature  a  couple 
o(  inches  below  the  ensiform  cartilaj;e  and  the  greater  curvature  passing  obliquely 


■SPHWHFiWB'^W^ 


16^2 


HUMAN  ANATOMY. 


from  the  tip  of  the  tenth  rib  on  the  left  side,  toward:!  the  pubea,  and  then  curving 
upward  to  tlie  right  costal  ;  margin  (Osier).  The  dilaution  may  l»e  of  any  degree, 
the  lower  border  of  the  stomach  sometimes  reaching  to  the  level  of  the  pubes. 

Displacement  of  the  stomach  (gastroptosis)  is  attended  by  (^re.it  stretching  of 
the  gastro-hepatic,  gastro-splenic,  and  gastro-phrenic  folds.  It  is  sometimes  a  dila- 
t.ition  with  the  stomach  vertical  instead  of  oblique  rather  than  a  true  descent  of  the 
whole  organ. 

Three  forms  are  described  :  (i )  a  slight  descent  of  the  pylorus,  and  with  it  of 
the  lesser  curvature,  so  that  the  latter  comes  from  l)eneath  the  liver  ;  (2)  "  vertical 
stomach,"  already  alluded  to;  (3)  a  descent  of  the  lesser  curvature,  the  pylorus 
remaining  fixed,  making  a  U-shaped  stomach  (Riegel).  The  last  is  very  rare.  All 
forrt  s  are  favored  by  the  use  of  corsets  or  dotl^ing  constricting  the  lower  thora.x. 
especially  in  women  with  flaccid  aNlominal  walls.  The  displ.icement  may  be  con- 
genital, or  may  be  due  to  primarv  elongation  or  rela.xation  of  the  pentoneal  folds 
which  act  as  ligaments,  or  to  malposition  or  displacement  of  other  abdominal 
visccr.i. 

Hernia  of  the  stomach  is  usually  diaphragmatic  and  often  congenital.  The 
viscus  may  enter  the  thorax  through  a  stab  wound  or  rupture,  or  through  weakened 
or  enlarged  spaces  at  («)  the  central  tentlon,  ( *)  the  posterior  inferior  muscular  area. 
(r)  the  interval  botwoen  the  sternal  and  costal  fibres,  (d)  the  (esophageal  foramen, 
( e )  the  fissure  between  the  lumbar  and  costal  portions,  or  ( / )  the  point  of  passage 
of  the  sympathetic  trunk  ( Sultan ).  These  possible  locations  have  been  mentioned 
in  the  order  of  frequency. 

The  hernia  may  carry  the  peritoneum  with  it  {true  hernia),  as  in  cases  c' 
partial  rupture  or  non-penetrating  wound  of  the  diaphragm,  or  may  avoid  or  pass 
tiirough  the  peritoneum  {false  hernia).  The  latter  are  more  common.  All  forms 
are  found  most  frequently  on  the  left  side  in  consequence  of  the  presence  of  the 
liver  on  the  right  side. 

Opf'itio'ts  on  the  Stomach. — The  stomach  is  most  accessible  for  operation 
through  a  triangular  space,  apex  upward,  bounded  on  the  left  by  the  eighth  and 
ninth  costal  cartilages,  on  the  right  by  the  free  edge  of  the  liver,  and  below  bv  a 
horizontal  line  joining  the  ti|)s  of  the  tenth  costal  cartilages  and  corresponding 
approximatf'I\  to  the  line  o'  the  transverse  colon.  The  tenth  cartilage  has  a  dis- 
tinct tip  and  plays  over  the  ninth  cartilage,  producing  a  peculiar  cre]>itus  (  LabW ). 

If  the  incision  is  median,  it  passes  between  the  recti  muscles;  if  lateral  and 
vertical,  it  is  made  through  the  rectus  or  along  its  outer  edge  ;  if  oblique,  through 
the  rectus  and  the  external  and  internal  oblique  and  transversalis.  The  terminal 
branches  of  either  the  superior  or  deep  epigastric  artery  may  be  divided,  or  the  latter 
vessel  itself  it  the  vertical  incision  is  prolonged  downward.  As  the  blood-supply 
of  the  stomal h  comj-s  from  three  distinct  sources — the  gastric,  hepatic,  and  splenic 
arteries — and  the  anastomoses  are  ver>'  numerous,  the  nutrition  of  the  flaps,  even 
after  extensive  resection,  is  usually  maintained,  in  the  al«ence  of  infection  or  of 
cardio-\asciilar  disease.  On  tiie  contrarj-,  in  operations  on  the  intestines  the  greatest 
care  must  !)e  exercised  in  tlealing  with  the  mcsenterv  to  preserve  the  vitality  of 
the  gut. 

I'pon  exposing  the  stomach,  it  is  well  to  bear  in  mind  its  obliciue  position  and 
the  facts  that  the  pylorus  is  the  only  part  that  is  really  transverse  that  thrce- 
fourtlis  of  the  stomach  ate  to  the  left  of  the  middle  line,  tli.it  the  upper  part  of  the 
cardia  is  an  inch  atxive  the  level  of  the  lowe:  end  of  the  tesophagus,  and  that  the 
l.irger  part  of  the  greater  cur^■ature  is  directed  to  the  kft  and  of  the  lesser  curvature 
to  the  right.  According  to  .Meinert,  the  pylorus  lies  Iwhind  the  intersection  of  a 
transverse  horizontal  line  draw  n  through  the  tip  of  the  xiphoid  cartilage  with  the 
riy;ht  costal  liorder  ;  while  the  lower  curvature,  fx-ginning  at  the  latter  point,  crosses 
the  mid-line  and  ascends,  describing  a  half-circle  around  an  antero-posterior  hori- 
zontal line  drawn  rhrough  the  xiphoid  tip. 

The  relations  of  the  stomach  in  general  have  been  described  Cpage  1619).  The 
transverse  colon — especfilly  in  cases  of  (esophageal  s'tricture  in  which  the  stomach  is 
contracted  and  rests  far  Kick  and  well  up  under  the  diaphragm — mav  pr(>sent  itself, 
and  has  lieen  mistaken  for  the  stoma-li.      The  gut.  however,  is  thinner,  not  so 


THE  SMALL  INTESTINK. 


'^^3 


Dinkiah  and  the  longitudinal  baml,  the  sacculations,  an.l  the  epiploic  appentlaRiii 
on  its  lower  aspect  may  ue  seen.  H  any  doubt  exists,  the  undir  siiilace  of  the  U  It 
lobe  of  the  liver  should  be  followed  up  by  the  fiiiRer  to  the  triiiHvcrs-  hssurc  ami 
then  down  on  the  gastro-hepatic  omentum  to  the  lessi-r  curvature  of  tlie  stomach. 
The  dependent  greater  omentum  and  the  gastro-epiploic  arury  «.n  the  nr-attr  cur- 
vature aid  in  the  recognition  of  the  stomach.  ,     , ,       • 

In  gaslroiomy—a^  for  foreign  body,  for  exploration,  or  for  retrograde  dilatation 
of  the  asophagus— the  incision  may  l.c  vertical  and  midway l).tweeii  the  two  curva- 
tures to  minimize  the  hemorrhage  (i/V^- f«/»-<i).  .  ,      ,.  ,        ,■      . 

In  gastrostomy— ttie  establishment,  for  purposes  of  feeding,  of  a  <iirect  com- 
munication between  the  surface  of  the  body  and  the  stomach  cavity— the  ulxlomma 
incision  may  be  oblique,  parallel  to  the  left  costal  cartilages,  and  2.5 -•i.  (>  m.) 
from  them,  or  vertical  down  to  the  left  rectus,  the  fibrc-s  of  which  may  be  separ.itcd 
without  division.  In  either  case  a  part  of  the  anterior  wall  of  the  stomach,  made 
conical  by  traction,  is  brought  out,  carried  upward  beneath  a  bridge  of  skiii.  and 
fixed  to  the  margins  of  a  second  opening  over  the  costal  cartilages.  V  ari.v.is  nioo- 
ifications  are  employed,  all  with  the  idea  of  securing  a  valvular  or  sphincteric  con- 
dition in  or  about  the  orifice  so  as  to  prevent  leakage  of  the  stomach  contents. 

In  Av/f^ro/^/aj/v— applicable  to  simple  hypertrophic  stenosis  or  cicatricial  stric- 
ture-an  incision  is^  made  from  the  stomach  to  •'e  duodenum  through  the  pylorus 
and  parallel  to  the  long  axis  of  the  tract  at  «t  point  Its  borders  arc  then 
separated  as  widely  as  possible  so  that  their  mid-points  becom.;  the  eiuls  of  the 
opening,  the  edges  of  which  are  then  sutured  together  m  this  position,  materially 
widening  the  lumeii  of  the  canal.  .t,      u  1      ,„,„ 

In  bylorectomy  or  ^astrectornvhr^v  portions  of  the  stomach,  or  the  whole  organ, 
are  e-xcised  for  malignant  disease  ;  in  the  former  the  omental  connections  of  the 
Dvlorus  must  be  severed  and  the  right  gastro-epiploic,  the  pyloric,  and  the  gastra- 
diiodenal  arteries  Jividetl  ;  in  the  latter,  in  addition,  the  pneumogastric  nerves 
below  the  diaphragm  and  many  more  vascular  trunits. 

Partial  gastrectomies,  as  for  the  excision  of  a  nodular  carcinoma  or  of  a  gastric 
ulcer,  are  much  less  serious.  Division  of  the  gastro-hepatic  omentum,  which  holds 
the  stomach  up  under  the  costal  margins,  will  facilitate  thefreei.ng  of  the  pylorus  and 
lesser  cur%ature  and  permit  of  ready  access  to  the  lesser  peritoneal  cavity.  The 
gastro-colic  omentum  attached  to  the  region  of  disease  can  then  he  made  tcnso  by 
The  tiiigers  passed  behind  and  beneath  the  pylorus  and  can  be  li>;..trd  and  divided 

(Mayo).  .  ,     .  •  (      .J. 

\n  zastro  enterostomy— xi  a  palliative  in  cancerous  pyloric  stenosis  or  tor  the 
treatment  of  gastric  ulcer-the  intestinal  canal  (usually  that  of  the  jcjui-.um,  as 
the  highest  movable  portion  of  the  small  intestine)  is  made  directly  continuous  with 
the  stomach  cavity  by  the  esUblishment  of  a  permanent  fistula  botween  the  two.  1  he 
posterior  wall  of  the  stomach  a  now  usually  selected  because  of  I's  nearness  to  the 
eiunuin  It  may  be  reached  through  the  transverse  mesocolon,  me  gre.it.  r  o",,  rx-MV 
with  the  transverse  colon  having  been  turned  upward  ;  or  the  gastro-colic  omentum 
may  be  torn  through  or  divided.  .  ,  .  1 

Gastroplasty  (analogous  to  pyloroplasty)  has  been  done  in  cases  of  hour-glass 
stomach  following  cicatricial  contraction  after  gastric  ulcer.  Occ.isionally  in  these 
cases  the  constricting  band  has  been  mistaken  for  a  thickened,  contracted  pylorus. 
Adhesions  sometimes  connect  the  constrictions  with  neighboring  parts,  as  with  the 
right  rectus  muscle  (Elder)  or  the  liver  (Childe). 

THE  SMALL   INTESTINE. 

The  stomach  is  followed  by  the  long  and  complicated  tube  of  the  small  intestine, 
divided  into  the  duodenum  and  the  jr/uno-i/eum.  According  to  Treves,  the  average 
length  in  the  male  is  6.8  m.  (22  ft.  6  in.)  and  in  the  female  neariy  15  cm.  (6  in.  ) 
more  This  excess,  however,  would  prol»bly  not  be  confirmed  by  a  larger  series. 
In  the  male  the  extremes  were  9.7  m.  (,ii  ft.  10  in.)  and  47  m-  ('S  ft.  ^'n)-  '" 
the  female  8.9  m.  (29  ft.  4  in. )  and  5-7  m.  ( 18  ft.  10  in.  ).  The  outer  waU  of  the 
tube  is  regular,  without  sharp  folds  or  sacculation, ,  beyond  the  duodenum.      Ihe 

»u3 


.*..'_     ■& 


I^M 


HIMAN  ANATOMY. 


circumference  is  greatest  in  the  durxlenum  (not  always  at  the  siune  point),  beyond 
whicli  it  gradually  decnases,  the  diameter  of  the  gut  at  its  lowt- r  f  nd  being  nearly 
one-third  smaller  than  at  the  beginning.  Since  certain  iitnictural  ftatures  are  com- 
mon to  the  entire  small  intestine,  it  will  be  convenient  to  consider  these  in  this  place, 
further  details  being  given  with  the  descriptions  of  the  special  parts. 

Fio.  1383. 


Traiisveiiic  tolut 


Pall  iiorm  liKamenl 


-Stumach 


Grratpr  omentum  (cut 
Hurfare  > 


Coils  of  jejunum 


Dc-scending  colon 


Sigmoid  ffexurr 


AlKloniiiial  nrKans  of  (nrmalin  suhjicl.     Stomach  was  unusually  large,  ffivinff  an  exaKKerate«l  impression  of  its 

transverse  iHtsition. 

Structure. — The  small  intestine,  as  <>t!u  r  parts  of  the  alimentary  tube  below 
the  diaphragm,  consists  of  fonr  coats,  the  mucous,  the  suSmucous,  the  muscuiar,  and 
the  serous. 

The  mucous  coat,  in  addition  to  the  j^landular  structures,  possesses  folds  and 
vilh  that  not  only  greatly  increase  its  surface,  hut  also  contribute  peculiarities  which 
aid   in   ditTcrcntiatinj^  between   typical  portions   taken  from   various   regions.      The 


THE  SMALL  INTESTLNK. 


ift-.'i 


fMMimm  covering  the  free  suriace  consists  of  a  sinnle  ay.  r  of  cylindrical  cells  uhu  h 
exhibit  a  striated  cuticular  border  next  the  intestinal  !.uncn.  1  us  U.rder  lacks 
stabUitv.  and  is  resolvable  into  minute  prisniatic  hkIs.  placctl  vcrt.ailly  and  j.roUil.ly 
continuous  with  the  spongioplastic  thre-.ids  within  the  U-dy  "  t'le  evil  In  nui.y 
XcL  especially  over  the  viUi.  m.uns-pr.KlucinK  Koblet-c. lis  share  the  frc-e  suriace 
with  the  onlinary  epithelial  elements.  Hetween  the  latter  ni.nratory  hucKrytes  are 
always  to  be  seen.  The  siratua  or  tunica  (jropria  of  the  mucous  cmt  re-scnihles 
lymphoid  tissue,  being  composed  of  a  connective-tissue  reticulum  cntanunu  numerous 
small  round  cells  similar  to  lymphocytes.  This  stroma  hUs  the  siM.es  iKtwt^n  tin- 
glands  and  forms  the  core  of  the  villi  over  which  the  .pithelunn  stretchc-s.    Ihe  deip- 

Fiii.   I384. 


Villu!! 


Puct  of  Brunner'j  ii'>"'la 


Muscularis  mucosic 


Brnnner  5  Klamls 


ilice  nl  kI*ih)  of  l.ichrrktihn 


_  Bnioner's  glandt 


Circulur  mincic 


-  LonKi.uflinal  tniiBcl« 
Tra.„verM  Mction  nl  small  .iHMline  (lower  p«rt  ol  diK«l«ii"m .   ,h..wi.iK  (eneral  arnnKemcui  of  c«i».     <  qo. 

est  part  of  the  mucous  coat  is  occupied  by    >    ■  ell-marke<l  musnilaris  miifosie,  in 
which  an  inner  circular  and  an  outer  longitu.iin.il  iiyer  are  distinguishable. 

The  villi  are  minute  pr.ijections  of  the  mucous  surface,  barely  visible  to  the  un- 
aided eye,  the  presence  of  which  imparts  the  characteristic  \el\ety  appearance  to  the 
inner  surface  of  the  sniill  intestine  Although  foun.i  thr.uighout  the  latter,  fnim  the 
pylorus  to  the  ileo-colic  valve,  thev  are  most  numer.uis  (from  20-40  to  the  s<i  mm  ) 
in  the  duodenum  and  jejunum  and  less  fre.iueiit  (from  i,s-.^o  to  the  sq.  mm. )  in  the 
ileum.  In  the  diiodeninn  thev  appear  immi-<liately  Ixyon.l  the  pylorus,  but  rea< ;h 
their  best  (iev.-lopnieiit  in  llie'  se.nn.l  part,  where  they  measure  from  .l-.s  mm,  ni 
height  ami  iri.m  ..^i  mm.  in  brea.lth  ;  th.v  are,  th.Tefore.  here  low  and  broail.  In 
the  jejumim  the  "villi  an-  .-..ni.Ml  an.!  somewhat  laterally  compressi-.!,  whiU-  in  the 
ileum  their  shape  is  rylin.lri.  ;il.  lililurm,  ..r  w.nige-like.jheir  length  an.l  br.a.lth 
l)cinj;  from  .  5-1  mm.  and  from    2-.  4  mm. 


,s!>'<iiv<lv       Tli<-  villi  are  projections 


1636 


HUMAN  ANATOMY. 


the  mucous  coat  alone,  and  consist  of  a  framework  of  the  lymphoid  stroma-tissue, 
covered  by  columnar  epithelium,  which  supports  the  absorbent  vessel  and  the  blood- 
vessels, together  with  involuntary  muscle.  The  reticular  tissue  constituting  the  villus 
is  condensed  at  the  periphery,  the  existence  of  a  definite  limiting  membrane  beinj; 
assumed  by  some  (J.  Schafler,  Spalteholz,  Ebner).  Each  villus  is  supplied  by  from 
one  to  three  small  arteries,  derived  from  the  vessels  of  the  submucosa,  which  break 
up  into  a  capillary  net-work  lying  beneath  the  peripheral  layer  of  ihe  stroma.  The 
blood  is  returned  usually  by  a  single  vein  which,  beginning  at  the  summit  by  the 
confluence  of  capillaries,  traverses  the  central  parts  of  the  villus  aiid  becomes  trib- 
utary to  the  larger  venous  stems  within  the  submucous  coat. 

The  absorbent,  chyle-vessel,  or  lacteal,  as  the  lymph-vessel  occupying  the  villus 
is  variously  termed,  lies  near  the  centre  of  the  projection,  surrounded  by  the  mus- 
cular tissue  and  the  blood-capillaries.  While  the  slender  cylindrical  villi  contain 
only  a  single  lymphatic,  from  .025-.035  mm.  in  diameter,  those  of  broader  form  r  ten 
contain  two,  three,  or  even  more  such  vessels,  which  may  communicate  by  cioss- 
channels.  Their  walk  consist  of  a  single  layer  of  endothelial  plates.  The  muscular 
tissue  within  the  villus,  prolonged  from  the  muscularis  mucosae,  forms  a  delicate 
layer  of  slender  fibre-cells,  longitudinally  disposed,  which  surround  the  central  chyle- 
vessel  Contractions  of  this  tissue 
'''"    '•'*5-  shorten  the  villus  and  aid  in  propel- 

ling the  emulsified  contents  of  the 
lymphatic. 

The  presence  of  numerous  oil- 
droplets  of  considerable  size  within 
the  epithelial  cells,  as  well  as  stroma, 
of  the  villi  during  certain  stages  of 
digestion  has  caused  much  specula- 
tion as  to  their  mode  of  entrance. 
On  histological  grounds  there  is 
good  reason  for  a.ssuming  that  a  large 
part  of  the  fat  particles  seen  within 
the  tissues  gains  access  in  a  condition 
either  of  solubility,  saponification, 
or  exceedingly  fine  molecular  sub- 
division, the  accumulations  observed 
within  the  tissues  being  due  to  sec- 
ondary change  (Ebner). 

The  valvulK  conniventes 
(plicae  circulares),  within  the  duo- 
denum and  the  jejuno-ileum,  model 
the  mucous  coat  and  greatly  increase  its  secreting  and  absorbant  surface;  they 
also  retard  the  passage  of  the  intestinal  contents,  thereby  facilitating  the  diges- 
tive processes.  These  transverse  folds  begin  in  the  second  part  of  the  duodenum 
and  consist  of  duplicatures  which  involve  not  only  the  entire  thickness  of  the 
mucosa,  but  contain  a  central  supporting  projection  of  the  submucous  coat; 
hence,  while  they  may  fall  on  their  sides,  they  cannot,  as  a  rule,  be  effaced  by  dis- 
tention. The  height  of  the  folds,  where  well  developed,  rarely  much  exceeds  I  cm. , 
and  towards  the  lo**  er  part  of  the  jejunum  is  much  less.  The  majority  of  the  valves 
do  not  extend  more  than  two-thirds  or  three-fourths  of  the  circumference  of  the 
gut ;  exceptionally,  however,  circular  and  spiral  ones  describe  two  or  three  com- 
plete turns.  Their  ends,  usually  simple,  may  be  bifurcated.  Smaller  folds,  more  or 
less  eflaceable,  run  obliquely  as  offshoots  from  the  larger  ones.  The  valves  are  much 
larger  on  the  attached  side  of  the  gut  than  on  the  free  one  ;  in  the  latter  position 
they  may  be  entirely  absent  in  localities  in  which  the  folds  are  feebly  developed. 
Succeeding  the  first  part  of  the  duodenum,  the  valvulae  conniventes  are  very  numer- 
ous and  large,  and  so  near  together  that  in  falling  over  any  fold  would  come  in  con- 
tact with  the  next  one.  Descending  the  small  intestine,  they  gradually  become 
smaller  and  farther  apart,  so  that  the  distance  between  them  considerably  exceeds 
their  height.     They  also  become  more  effaccable,  and  finally  ver)-  much  so.     In 


Gland 


Villus 


Surface  view  of  mucous  membrane  of  jejunum,  fthowing  villi 
and  orifices  of  glands.     /  35. 


THE  SMALL  INTESTINE. 


1637 


this  respect  much  variation  exists,  which  partially  accounts  or  the  differences  found 
at  the  lower  part  of  the  small  intestine,  where  often  the  valves  are  absent  while  at 
other  times  thley  are  well  marked.  Semoff '  found  in  subjects  treated  with  chromic 
acid  injections  that  the  valves  were  as  frequent  in  one  jxirt  of  the  small  intestine 
as  another,  but  less  regularly  transverse  in  the  lower  He  obser%-ed  places  without 
vllves  usually  at  the  convexity  of  folds,  in  all  parts  of  the  gut.  and  regards^them  as 
argeW  de'iendent  upon  the  condition  of  the  muscular  coat.  It  is  certain,  however, 
that  the  v^ves  of  the  upper  part  of  the  intestine  are  independent  of  this  influence  , 
those  in  the  lower  portion,  perhaps,  may  be  produced  in  such  manner. 

Glands.— The  >tructures  within  the  alimentary  tube  to  which  the  term     glands 
has  been  applied  include  two  entirely  different  groups,  the  true  and  tht  false  glands. 

Fig.  1386. 


Strom*  of  «nnic»  propria 


luriace  epithelium 


.Goblct-celt 


:iand  of  Lieberkiihn 


Muscularis  mucosc 


Circular  muscle- 
Tramverw  section  of  small  intestine  (jejunum),  showing  villi  cut  lengthwise.    X  150. 

The  former  are  really  secreting  ..rans,— the  glands  of  Lieberkiihn  and  of  Brvinner  ; 
the  latter  are  more  or  less  extensive  accumulations  of  adenoid  tissue,  and  are  appro- 
priately spoken  of  as  lymphatic  nodules  or  follicles. 

The  glands  of  Lieberkuhn  are  simple  tubular  depressions  which  are  found  not 
only  throughout  the  entire  small  intestine,  but  in  the  large  as  well.  They  are  very 
closely  set  narrow,  and  extend  the  thickness  of  the  mucous  coat  as  far  as  its  mus- 
cular layer.  In  length  they  vary  from  .  3-.  4  mm.  and  in  diameter  from  060-  o«o  nim. 
The  fundus  of  the  glands  is  slightly  expanded  and  in  exceptional  cases  divided.  The 
lining  of  the  crypts  rests  upon  a  delicate  basement  membrane,  and  consists  of  a  single 
'  Imemat.  Monatsschrift  f.  Awit.  u.  Ph\'sio!..  Bd.  xi..  1894. 


1638 


HUMAN  ANATOMY. 


layer  of  columnar  cells  directly  continuous  with  those  covering  the  villi.  They  differ 
from  the  latter  in  being  only  about  half  so  high  (.018  mm. )  and  in  not  presenting  the 
characteristic  cuticular  border.     This  last  gradually  disappears  as  the  cells  dip  into 


Fig.  1387 


.('.ohleicell 


.Capillao' 

Cuticular  hiirder 
cpithtrliuii) 


Fig.   1388. 


Transverse  section  of  sinKic  intestinal  villus,  showing  relation  ol 
epithelium,  stroma,  and  vessels,     x  350. 


Surface  view  of  mutous  membrane  from 
end  of  jejunum  showinK  valvulie  cotini- 
ventes.  Stippled  appearance  is  due  to  villi 
coverinK  folds.    Natural  size. 


the  follicles  to  become  the  lining  of  the  glands.  Under  low  magnification  the  sur- 
face of  the  small  intestine  presents  numerous  pits,  the  orifices  of  the  glands,  which 
almost  entirely  fil!  the  spaces  between  the  bases  of  the  villi ;  with  the  exception  of 


Fio.  1389. 

Submucous  coat  Villi 


Lonffiludiiial 
muscle 


Serous  coat 


Longitudinal  section  of  duodenum  ;  valvulie  coniiiventes  cut  across,  showinK  relation  t.f  these  folds  to  villi. 


the  areas  immediately  over  the  lymph-nodules,  where  they  are  partially  pushed  aside, 
these  glands  are  present  in  all  parts  of  the  intestine.  They,  howe\er,  take  no  part  iii 
absorption,  never  containing  fatty  particles  during  periods  in  which  such  substances 


THE  SMALL  INTESTINE. 


1639 


«re  seen  within  the  epithelium  of  the  villi.  It  is  worthy  of  note  that  even  in  the  adult 
mito^  figur^are  frequently  observed  within  the  cells  linnjR  L'^berkuhn  s  ^h»nds 
Sough  such  evidences  of  cell-division  are  rare  an.unK  the  elements  covering  the 


Fig.  1390. 

Uuct  oi  Bruiiner's  Klandt 
Villul 


Gland  of  Liebcrkubn 


LongUudinal  «c.io„  of  duodenum,  showing  Brunner',  and  Uebcrkuhn',  Kl.nd,.  vHII,  and  U-mph-node.    y  .00. 

villi  Bizzozero  therefore  regards  the  lining  of  these  glands  as  an  active  source  for 
he  regeneration  of  the  intestinal  epithelium  by  the  product.on  of  ".^/l-"«;^  ^s ^ m 
the  viUi,  so  also  in  these  glands  goblet-cells  he  among  the  usua  epithelial  elements  . 
likewise  migratory  leucocytes  are  present  between  the  gland-cells. 

Fio.  1 39 1. 

Pyloric  glands  • 


Mucous 
coat 


Stomach 


Duodenum 


Looiritudinal  section  through  junction  of  stomach  and  duo.lenun,,  showing  transition  of  pyloric  into  duodenal  glands ; 
Loogltuainai  section  >nro  g  ^  ,'hiekenii.g  of  circular  muscle  10  (orm  sphincter  pylori,     v  l). 

The  glands  of  3runner.  also  o'ten  appropriately  termed  the  duodena/ fr^ands, 
are  limited  to  the  first  division  of  the  small  intestine.  Beginning  at  the  PY^orua, 
where  they  are  most  numerous  and  extensive,  they  gradually  decrease  in  number  and 


1640 


HUMAN  ANATOMY. 


size,  being  sparingly  present  beyond  the  opening  of  the  bile-duct  and  entirely  want- 
ing at  the  lower  end  of  the  duodenum.  These  glands  are  direct  continuations  of 
the  pyloric  glands  of  the  stomach,  with  which  they  agree  in  all  essential  details. 
While,   however,   their  gastric  representatives  are  confined  to  the  mucous  coat, 

FiG.  1393. 


Surface  views  of  mucous  membrane  from  upper  (.4)  ar:d  lower  (ff)  pan  of  ileum.  showiiiK  folds  and  soliur^  IvmDh- 
nodules.    The  velvety  appearance  is  due  to  the  villi.    Natural  siie.         *  "  ~  "■'>  '>"'P" 

Brunner's  glands  chiefly  occupy  the  submucosa,  the  migration  taking  place  at  the 
pyloric  ring  ( Fig.  1 39 1 ) .  The  duodenum,  therefore,  possesses  a  double  layer  of  true 
glands,— those  of  Lieberkithn  within  the  mucous  coat,  beneath  which,  in  the  .submu- 
cosa, he  those  of  Brunner.  The  individual  glands,  tubo-alveolar  in  type,  form  some- 
what flattened  spherical  or  polygonal  masses,  measuring  from  .5-1  mm.,  which  con- 
sist of  richly  branched  tubules,  ending  in  dilatations.  Their  excretory  ducts  pierce 
the  mucous  coat  and  open  either  directly  on  the  free  surface  or  into  the  crj'pts  of 
Lieberkiihn.  While  narrower  than  the  flask-shaped  alveoli,  the  epithelium  of  the 
ducts  is  the  same  as  that  found  in 

the  deeper  parts  of   the  tubules.  Ptc.  1393. 

The  clear,  low  columnar  cells  lining 
the  duodenal  glands  are  proba- 
bly identical  in  nature  with  those 
of  the  pyloric  glands,  the  varia- 
tions in  size  and  granularity  some- 
times observed  depending  upon 
differences  in  hinctional  condition. 
Brunner's  glands  correspond  to 
the  pure  mucous  type  (Bensk  \  ). 

Lymph  -  Nodules.  —  the 
lymphatic  tissue  within  the  intesti- 
nal tube  occurs  in  the  form  of  cir- 
cumscribed nodules,  which  may 
remain  isolated,  as  the  solitary  nod- 
ules, or  be  collected  into  consider- 
able masses,  as  Peyer  s  patches. 

The  solitary  nodules  vary 
greatly  in  number  and  size,  some 


Surface  view  of  mucous  membrane  o(  ileum.    X  jo. 


times  being  present  in  profusion  in  all  parts  of  the  small  intestine,  at  other  times 
almost  wanting  ;  they  are  usually  scanty  in  the  upper  and  more  numerous  in  the 
middle  and  lower  parts.  They  appear  as  small  whitish  elevations,  spherical  or  pvri- 
forni  la  shape,  and  from  .  2-2  or  even  3  mm.  in  diameter,  at  the  bottom  of  small  pits. 


THE  SMALL  INTESTINE. 


1641 


The  walls  of  the  btter,  however,  are  so  closely  applied  to  the  nculules  that  the  exist- 
ence of  the  pit  is  not  at  first  evident.  Villi  are  wanting  over  the  prominence  of  the 
nodules  ;  likewise  the  glands  of  Lieberkuhn,  the  orifices  of  which  are  arrannetl  as  a 

wreath  aroiiiul  the  nmlules.      Ihe 
Fio.  T394.  latter  are  ftmnd  as  much  on  one 

side  of  the  intestinal  tube  as  on 
the  other. 

In  structure  the  solitary  no<l- 
ules  correspond  to  similar  lynii)h- 
nodes    in   other    localities,    con- 
sisting  of    a   capsule   of    denser 
tissue  enclosing  the  ilelicate  ade- 
noid  reticulum   which    supjxirts 
the    characteristic    lymphiK-ytes 
within  its  meshes.     Within   the 
larger     nodules      germ-centres, 
spherical  or  ellipsoidal   in  form, 
occupy  the  middle  of  the  notlules: 
the   germ-centres  are,   however, 
hot  constant,  being  present,  as  a 
rule,  in  young  subjects,  but  often 
absent    in   old   individuals.       A 
generous    blood-supply    is    pro- 
vided  by  the  rich    net-work  of 
small  vessels  which  surrounds  the  nodules  ;  fine  capillaries  penetrate  into  th'^i''  '"t);""';; 
but  usually  do  not  reach  the  centre  of  the  nodes.     Definite  lymph-paths  ha^e  n.  t 
bLen  demonstrated  within  the  nodules,  although  a  plexus  of  lymphatics  surrounds 

'''^'pf;ir^^''^^^:rino^nn  l>a.ph,Uci  .««re.ati)  are  collections  of  solitary 
lymph-nodules,  the  individual  follicles  being  blended  by  mterv'ening  ^'l;^"""'  'f  "•;• 
They  are  seen  in  the  lower  half  of  the  small  intestine,  especia  ly  near  the  h.wer  end 
(ileum)  ;  exceptionally  they  are  found  in  the  upper  part  of  the  jejunum  in  the 
vicinity  of  the  duodenum.     The  patches  appear  as  slighdy  raised,  elongated  ovals. 

Fig.  1395. 

Suhmncous  fold  supportinR  mucosa  with  villi 


Surface  view  of  portion  of  mucoun  mnnbnne  at  ileum,  ahowing 
Piyers  palcTand  solitary  lymph-nodutes.    Natural  ilze. 


Transverse  section  of  ileum,  showiiiK  Pcyer's  intch  cut  across.    X  10. 


always  on  the  side  of  the  intestine  opposite  to  the  attachment  of  the  mesentery. 
Their  „sua!  number  is  about  thirtv,  although  as  few  as  eighteen  and  as  many  as 
eighty-one  have  been  counted  (Sappey).     In  length  they  ordinarily  measure  from 


1643 


HUMAN  ANATOMY. 


Mucous  root 


Submucous 
coat 


1-4  cm.  and  in  breadth  from  6-16  mm. ;  exceptionally  their  length  may  reach  10  cm. 
or  mure.  In  general  the  size  of  the  patches  increases  as  the  termination  of  the  ileum 
is  approached.  Each  patch  contains  usually  from  twenty  to  thirty  Ivmph-nodulcs, 
although  as  many  as  sixty  or  less  than  ten  may  be  present.  The  individual  nodules 
are  commonly  somewhat  pear-shaped,  .iid  when  well  developed  occupy  both  the 
mucous  and  submucous  coats,  their  smaller  end  almost  reaching  the  epithelium  and 
their  base  the  muscular  tunic.  The  free  surface  of  the  patches  is  modelled  by  minute 
pits,  from  .4-2  mm.  in  diameter,  and  low  intervening  ridges  ;  the  former  mark  the 
positions  of  the  component  nodules,  the  latter  that  of  the  blending  internodular 
tissue.  The  villi  and  the  crypts  of  Lieherkiihn  are  present  over  the  areas  between 
the  pits,  although  less  developed  than  beyond  the  patch.  In  their  minute  structure 
the  lymph-nodes  composing  the  patch  closely  correspond  to  the  solitary  nodules,  the 

aggregated  nodules  Ik*- 
FiG.  1396.  ing  blended  into  a  con- 

tinuous mass  by  the  les.s 
dense  adenoid  tissue 
which  fills  the  sfiaces 
between  the  individual 
follicles.  The  entire 
patch  is  defined  from 
the  surrounding  struc- 
*'ires  by  an  imperfect 
apsule. 

The  submucous 
coat  is  lax,  but  not 
enough  so  to  allow  the 
gg  displacement  of  the  val- 
vulae  conniventes,  ex- 
cept at  the  lower  part. 
As  in  other  segments 
of  the  intestinal  tube, 
the  submucosa  contains 
blood-  and  lymph-ves- 
sels of  considerable  size 
and  the  nerve-plexus  of 
Meissner. 

The  muscular 
coat,  about  .4  mm. 
thick,  consists  of  an 
outer  longitudinal  and 
an  inner  circular  layer. 
The  latter  is  some  two 
or  three  times  as  thick  as 
the  former  and  is  pretty 
regularly  arranged.  The 

Transvcnescctionotinjectedsinallintestine.showingKcncraldistribulion.    XS5.     thin   longitudinal    layer, 

thickest  at  the  free  bor- 
der, is  often  imperfect,  especially  at  the  attachment  of  the  mesentery.  The  entire 
muscular  coat  diminishes  in  thickness  from  above  downward. 

The  serous  coat,  with  the  exception  of  that  of  the  duodenum,  completely  sur- 
rounds the  gut  except  at  the  line  of  attachment  of  the  mesentery,  where  the  two  layers 
of  peritoneum  diverge,  leaving  an  uncovered  space  between  their  jjst  large  enough 
for  the  pas.sage  of  the  vessels  and  nerves.  Its  structure  resembles  that  of  the  serous 
coat  of  the  stomach  (page  1627),  and  includes  the  fibro-elastic  stroma  covered  with 
the  endothelium. 

The  blood-vessels  supplying  the  small  intestine  are  distributed  to  the  walls  of 
the  tube  in  a  manner  closely  agreeing  with  the  arrangement  found  in  the  stomach 
(page  1627) ;  the  same  general  plan  applies  also  to  the  large  intestine.  The  arteries, 
which  pass  to  the  intestine  between  the  peritoneal  folds  constituting  the  mesentery, 


THE  SMALL  INTKSTINE. 


if•^^ 


aJter  supplying  the  serous  coat,  penetrate  the  muscular  tun.c  to  reach  the  submucos^ 
Within  the  latter  branches  arise  which,  in  conjunction  with  those  directly  ^o^^•>> «'» 
durine  the  passage  through  the  muscular  coat,  supply  the  muscular  tissue.  1  he  more 
Snportant  knd  larger  arterial  twigs  from  the  vessels  of  the  submucosa  enter  the 
murous  coat,  in  which  some  break  up  into  capillanes  forming  net-works  surrounding 
the  gland-tubules  and  supplying  the  muscular  and  stroma  tissue  ;  others  p;iss  directly 
towards  the  villi,  which  they  enter  and  supply  by  capillary  net-works  occupying  he 
^rioherv  of  the  projections.  The  veins  of  the  intestinal  walls  commence  within  the 
muc^  beneath  the  epithelium  and,  gradually  enlarging  :is  they  descend,  U-come 
Uibutary  to  the  larger  veins  within  the  submucosa.  The  l.-itter  follow  the  arteries  in 
their  pMsagc  through  the  muscular  tunic,  uniting  to  form  the  larger  emergent  venous 
channels  which  accompany  the  arterial  ti  unks  between  the  peritoneal  folds. 

The  lymphatics  of  the  small  intestine.  Umg  known  as  the  /acU-a/s  \um  their 
conspicuous  milky  appearance  when  filled  with  emulsifiecl  fat  dunng  certain  stage,  nf 
digestion,  begin  as  tlie  absorbent  or  chyle-vessels  within  the  villi,  l"  add.tu.n  to 
these  radicles  commence  within  the  stroma-tissue  of  the  mucosa,  in  which  the  lym- 


Bimnch  oJ  imsenteric  «nery. 
Mcsenterii-  vein 


LymphiKKlc 


Lymphatics 


Nerves 


Cut  edjfe  of  removed 
peritoneum  f 


Portion  of  sm  11  intestine  .nd  me«ntery.,howinK  .rterle.,  nerve,  .nd  lymphatic,:  latter  ta^^ 
quicksilver.     Anleriiir  layer  of  mesentery  has  been  remo\e<l. 


ohatics  form  a  plexus  in  the  plane  of  the  muscularis  mucosae.  Prom  the  latter  tribu- 
taries descend  to  the  larger  plexus  within  the  submucosa,  which  is  characterized  by 
channels  of  irregular  form  and  calibre  containing  numerous  valves.  The  emergent 
lymphatics  form  larger  vessels  within  the  serous  coat,  which  pa.ss  to  the  lymph- 
nod^  situated  between  the  peritoneal  layers  ;  from  these  smaller  lynnphatic  masses 
efferent  xessels  converge  to  the  larger  mesenteric  lymph-nodes  at  the  root  ot  the 

mesent    y.  ..,,,,        t  a 

The  nerves  supplying  the  small  intestine,  derived  from  the  solar  plexus  and 
consisting  of  both  medullated  and  non-medullated  fibres  from  the  cerebrospinal  and 
sympathetic  systems,  closely  follow  the  disposition  observed  in  the  stomach  (page 
1628)  After  piercing  the  other  longitudinal  layer  they  form  the  intramuscular  p/exus 
of  Auerlach,  consisting  of  both  varieties  of  fibres  and  microscopic  sympathetic  gan- 
•  glia  The  nerves  continue  obliquely  through  the  circular  muscular  layer  and  form 
within  the  submucous  coat  the  plexus  of  Meissner.  From  this  plexus  non-medullated 
fibres  enter  the  mucous  coat  and  are  distributed  as  periglandular  and  subepithelial 
net-works,  as  well  as  supplying  the  muscular  tissue,  in  which,  according  to  Berkley^ 
additional  special  end-organs  exist     Within  the  villi  a  rich  plexus  of  non-medullated 


1644 


HUMAN  ANATOMY. 


fibres  has  1  ccn  demonstrated  from  which  terminal  fibrillz  are  distributed  to  the  mus- 
cular tissue  and  vessels,  as  well  as  beneath  the  epithelium. 


THE   DUODENUM. 

The  duodenum  at  an  early  stage  is  a  loop  with  a  forward  convexity  passing  from 
the  pylorus  back  to  the  spine.  It  enlarges  into  nearly  a  circle  and  turns  onto  its 
right  side,  its  termination  remaining  attached  below  the  coeliac  axis  to  the  top  of  the 
second  lumbar  vertebra.  The  part  immediately  following  the  stomach  remains  free, 
but  a  little  farther  back  it  is  suspended  from  the  liver  by  the  duodena- hepatic  ligament, 

which  is  the  free  border  of  the  lesser 

Fio.  1398.  omentum,  containing   the  portal  vein, 

p>iorn»  the  hepatic  artery,    and   the  bile-duct 

'T^  <^~N     *'*'*  ^^^  connective  tissue  about  them. 

^~^T"      /^^  /wVV  i>     '^    This  structure  is  strong  enough  to  de- 

.f      ,,J^     i^*'^         k^W  *      '^    **'^*  '"   ^  *^'"^  ^   ligament.     The 

^' jl^ft^  I      \.  ^  j|         Cr>^^     d-     "^    duodenum  is  therefore  nearly  a  ring  sus- 

f^tj^'"      I    ^        fcy^lk  '       "m     P*"*^^  ^^  **"  points,    one   near  the 

^^P^/fWtnA      m  jitf^itL      "dr       ''^^'""'nK   and   tne   other    (to  be   de- 

^6fy«i(lv^r  ^5^^l^  J        scribed  later)  at  the  end.      In  the  adult 

*^^H^m|P^  T^JB^Jr  ^^  shape  is  more  or  le!»s  a  modification 

ijpiBBM'^  ^><wr  of  (hjg  imperfect  ring.     When  relaxed 

Cans  of  duodenum,  •howinKt-»ndVfonii».  and  empty  it  often  nearly  retains  this 

shape.  When  distended  by  inflation 
or  injection  it  usually  shows  four  parts.  The _/?«/,  some  5  cm.  (2  in.)  long,  runs 
backward  from  the  pylorus,  slighdy  upward  and  to  the  right.  The  beginning  of 
this  portion  is  movable  ;  later  the  part  is  fixed  by  the  structures  just  mentioned. 
The  other  divisions  of  the  duodenum  are  disposed  so  as  to  form  a  U.  The  second 
part  descends  along  the  right  of  the  spine  to  the  fourth  lumbar  vertebra.  The  third 
runs  forward  and  to  the  left,  with  a  slight  rise.  The  fourth  ascends  on  the  spine  to 
the  upper  part  of  the  second  lumbar  vertebra,  where,  after  a  sharp  bend, — the 
duodeno-jejunal  flexure, — it  becomes  the  jejunum. 

The  next  most  common  form  is  the  V-shaped,  of  which  there  are  two  varieties,  in  the 
more  usual  one  the  second  part  descends,  as  in  the  preceding  form,  and  the  third  and  fourth 
are  represented  by  one  which  ascends  obliquely  to  the  termination.  The  !ess  frequent  variety 
has  the  second  part  inclining  forward  and  to  the  left  as  it  descends,  so  that  the  V  is  more  sym- 
metrical. A  modification  ot  the  U-form,  which  we  have  called  the  C-shaped,  is  characterized  by 
a  very  short  second  part,  so  that  the  first  and  third  parts  are  almost  in  contact.  From  seventy 
observations'  on  adults  (including  one  girl  of  fourteen),  mostly  by  means  of  casts,  we  find  the 
following  forms : 

Male.        Female.    Sex  not  noted. 

U-shaped 10  3  9 

V-shaped 9  9  3 

Ring-sha^d j  2 

Indeterminate 7  3  i 

C-shaped 5 

Not  to  be  classified 5  .   .  2 

38  T7  IS 

By  "  indetenninate"  is  understood  those  that  might  be  placed  in  any  two  of  the  T,  V,  orC 
types,  according  to  the  classifier.  Those  marked  "  not  to  be  classified"  are  absolutely  irregular. 
The  \'-shape  is  particularly  common  in  women  and  the  irregular  forms  in  men.  It  should  be 
noted  that  a  very  large  part  of  the  duodenum  lies  in  an  essentially  antero-posterior  plane, — 
namely,  the  first,  second,  and  a  corMc'crpble  portion  of  the  third  part,  the  organ  being  moulded 
on  the  spinal  column.  The  length  of  the  whole  duodenum  and  of  its  parts  is  so  variable  that  a 
statement  can  be  only  general.  The  first  part  is,  according  to  Testut,  5  cm.,  the  second  8  cm.,  the 
third  6  cm.,  and  the  fourth  7  cm.,  the  total  length  of  the  duodenum  being  26  cm  ,  or  about 
U)  in.  The  circumference  varies  greatly  in  different  bodies.  The  fourth  part  is  the  smallest. 
The  second  increases  in  size  as  it  descends,  and  the  largest  point  is  in  either  the  seconder  third. 
The  two  largest  circamferences  that  we  have  measured  were  in  the  second  part.  We  are  sat- 
isfied that  the  size  oi  some  immense  duodena  is  in  no  way  due  to  artificial  distention  ;  to  what 
extent  it  is  pathological  is  uncertain. 

'  Journal  of  Anatomy  and  Physiology,  vol.  xxxi.,  1897. 


THE  DUODENUM. 


«<'45 


The  first  part  is  often  eKU-shaped,  narrowing  at  the  ends.  Its  main  directii .. 
i»  backward,  sl.ghtly  upward  and  to  the  riKht,  to  reach  the  first  lumbar  vertebra  ;  but. 
^U  is  movable  its  dlAnrtion  is  somewhat  variable.  The  ^ut  rests  aU.ve  ajj;  m.t  the 
S.^dratT"obe  «  the  liver  and  the  neck  ot  the  jrall-bladder.  beh.nd  which  .t  .s  fre... 
C£  the  lower  border  of  the  foramen  of  Winslow  The  left  side  l.H.ks  n«o  the 
Kr  Jerit..neal  cavity,  and  is  crossed  near  the  back  by  the  common  b.le-duct  1  he 
S  s^e  I,  chiefly  against  the  liver  and  Kail-bladder  :  otherwise  .t  is  m  contac  .  .us 
C  thebwer  side,  with  coils  of  the  small  intestine.     The  lower  s.de.  moreover.  r..>ts 

""  'Ve'iicond  ff  XK^ends  vertically.  forminK  an  acute  angle  with  the  firs. 
It  is  bent  so  sharply  that  a  fold  of  the  entire  thickness  often  projects  mto  the  gut  1 
fie^  .m  ?he  riKhtTicie  of  the  vertebral  bodies  beside  the  vena  cava,  and  IkIuiuI  res  son 
h^  right  suprarenal  capsule  and  kidney,  being  in  contact  also  *•'♦^'he  Ih^^'v;^  '•' J  - 
btter  the  renal  vein,  ^d  the  beginning  of  the  ureter  The  precise  relations  NMth 
The  right  kidney  are  Uncertain,  owing  to  the  variations  both  of  that  organ  and  of  the 
duodm  m  It  lies  on  the  right  against  the  ascending  colon  and  on  the  left  against 
fhe  hl^Z  the  pancreas,  which  may  overlap  it  in  front.  The  b.le-duct  runs  along  the 
left  SldTe  and  pt-^  obliqiiely  through  the  intestinal  wall,  to  empty,  m  conjunction  with 
the  pancreatic  duct,  some  lo  cm.  from  the  pylorus. 

S log ical.    The  mean  of  the  female  duodenun.,  m  whK:h  «x  the  \  -s 
U^attfe  lower  than  that  of  the  male,  but  not  stnkinRly  «>.    Th*-   uirU 
and  the  third^rts""  the  U-form  is  rather  Uss  sharp  than  that  betwe<.n  .be  , 


s  it  is  opposite 

,v«Ti-  jirohably 

.  mosl    rei^uent, 

leen  the  second 

and  the  second. 


Mill 


Its  front 

'hi'  Villa 

tv-nds  to 

lird  part 

.   .  jiiarter  i  >f 

^se  than  thf 

es]xi-ially 


li  a-,     nds 
is  tin  list' 

-h.     i 

Sitrfttr* 


The   bird  part  curls  around  the  spinal  column,  passing  U>rv. 
then  to  the  left  with  a  slight  ascent  till  it  reaches  the  aorta. 
cava  and  has  the  pancreas  above  it.  which,  with  the  first  and  sect, 
enclose.     The  head  of  the  pancreas  may.  howeve;,  more  or  less  o\ 
as  it  dfMis  the  second,  and  also  insinuate  itself  behind  it.      In  U  >s  Ui. 
the  cases  the  third  part  crosses  the  aorta,  its  course  being  more  trai 
one  iust  described.     It  may  be  connected  to  the  aorta  by  areolar  t.ss 
if  it  run  only  just  beyond  the  aorta,  a  fold  of  peritoneum  may  interv. 

The  fourth  part  usually  begins  at  an  obtuse  angle  with  the  thi. 
on  the  front  of  the  spine  to  the  top  of  the  second  lumbar  vertebra.      . 
it  overlaps  the  aorta  and  usually  ends  either  directly  over  it  or  just   at 
fifty-four  observations  the  duodenum  was  on  the  right  of  the  aorfci  unt; 
its  final  fle.xure  twenty-six  times.     It  was  wholly  on  the  right  of  the  aort.i 
The  fourth  part  lay  in  front  of  the  aorta  eleven  times  and  the  thrrt  p  u 
crossed  it  eleven  times.      It  Is  clear  from  the  above  that  it  is  exceptional  tor 
denum  to  reach  the  left  kidney  and  ureter,  but  it  may  do  so  when  it  real 
the  aorta      The  tail  of  the  pancreas  is  behind  it,  as  is  usually  a  part  of  the  U 
renal  capsule.     The  head  of  the  pancreas  may  be  so  develoi>ed  ;ls  to  overlaj. 
this  is  rare      The  mesentery  of  the  small  intestine  usually  rises  above  on  its  troni 
face  and  gradually  crosses  it  to  the  right.     It  may  be  very  neariy  siirround.. 
peritoneum,  or  the  posterior  surface  may  be  without  it.     Sometimes,  although  r^ 
ihe  last  part  stops  short  of  the  second  lumbar.     In  the  V  -shaped  duodenum  th.        . 
and  fourth  parts  are  in  one.     This  form  evidently  is  wholly  to  the  right  of  th-  . 

except,  perhaps,  the  very  end.     It  sometimes  ascends  along  the  right  side  of  tl  h. 

iliac  artery,  and  then  on  the  right  or  front  of  the  aorta.  The  duodenum  en. 
sharp  turn,  the  duodeno-jejunal  flexure.  The  very  top  of  the  gut  at  the  h 
suspended  from  the  left  cms  of  the  diaphragm  and  from  the  areolar  tis.sue  a^.  he 
coelmc  axis  by  the  duodenal  suspensory  musele  of  Treitz,  a  small  triangular  v,„,l  ot 
.nuscular  and  fibrous  tissue,  which  reaches  the  gut  where  it  «  ""covered  h>  (K-nto^ 
neum  and  is  sjiid  to  join  the  layer  of  longitudinal  muscular  fibres.  This  Land  and 
the  duodeno-hepatic  ligament  hold  all  the  duodenum  after  the  very  beginning  sus- 
pended and  fixed  so  that  only  the  beginning  is  movable.     It  is  further  secured  by 


t«4A 


HITMAN   ANATOMY. 


thf  retro-peritoneal  connective  tissue  and  by  the  peritoneal  reflections.  The  shape 
allows  the  food  from  the  stomach  as  well  as  the  fluid  j>oured  inii>  it  from  the  li\ir 
and  [Kincreas  to  accumulate  and  thus  to  act  as  an  S-lrap  to  prevt  iit  the  pa**sii^e  of 
ji;ises  from  the  intestine  into  the  stomach.  At  the  same  time  the  ^jreat  dcv.*  -  neiii 
of  the  valves  tends  to  retaril  the  |>assage  (»f  the  fixxi. 

Peritoneal  Relations. — The  peritoneum  of  the  front  and  l>ack  of  the  ston..tcii 
is  continued  alon^  the  ri^ht  and  left  sides  of  the  tirst  p;u-t  of  the  duodenum  respec- 

FlG.    Ijpq. 


RIkM  lung 


Cut  dia|>hniKni 


Hv;iatic  veins 


K  t^H  iu|>rarcnal  body. 

Caatro-hrpMtk  onicniufli 

Pr'i)«  In  fiir&ntcn  at 

Wln<.l<.w 

RiRht  kidney 

B«KinninKU[. 

(luiMlciium 

Bc'KitininK  of 

traiisvene  c<>i*>ii^ 

Head  of  pai)rreaa_ 


Lefi  luDfC 

Pericardium 

CavaloprnJii^'  iti 
diaphraKni 

CE!K>phaKU!i 

Spleen 

Left  ftupraretial 

body 

Left  kidney 

Sjilenic  flexure  , 
ail  ui  panirrt-as 


•eft  end  of  cut 
■ttaiisverM  colon 
.Jejunum 
SU|»erior  mesen- 
teric artery 


X.eft  mesocolon 


.Cut  r<M>t  of 
mesentery 


SiKinuid  flexure 


Abdomen  of  formalin  subject :  peritoneum  partially  dissected  off,  exposing  or^pans  $»  si/m  on  posterior  wall ;  transverse 
loloii.  mesocolon,  mesentery,  and  jejuno-ileum  removed. 


ti\ely.  These  layers  meet  above  alonjr  the  jjreater  portion  of  the  first  part  lo  form 
the  lesser  omentum,  which  ends  posteriorly,  as  already  stated,  by  forming  the  hepatico- 
duodenal  lijfament,  consisting?  of  the  vessels  enterinjr  the  portal  fissure  of  the  liver 
with  their  enveloping  connective  tissue.  The  free  ed^e  where  the  peritoneum  passes 
behind  the  lijjament  is  on  the  inner  side  rather  than  above  the  ^t.    Just  back  of  this 


<H   DLODEMM. 


.'fi47 


,. ,    part  ol  the  liuudcniim  is  coverLtl  bv  ix-ritoncuni 
and  lorim"  Ihe  fl.>or  <.f  tht  •         .en  ol  Winslow.     The  aitachnu-nt  ..I   the  urtaur 


fold  the  upper  surface  of 


omemum.  which  is  continuev.  irom  the  greater  curvature  of  the  stomach  on  o  the 
under  side  of  the  duodenum,  passes  alonK  its  mkM-ior  surface  to  the  second    wrt 
where  in  the  adult  it  has  .used  with  the  mesentery  cf  the  transverse,  colon.      The  jari- 
roneunloi  the  ri^ht  side  of  the  first  part  of  the  duodenum  l.K.ks  nuo  the  general 
neriton.al  cavity  and  that  of  th<-  left  side  into  the  lesser  cavity. 

•^  T  relations  of  the  rem;iinder  of  the  duodenum  necc-ss;inly  vary  with  the  dis- 
tcntion  of  the  intestine  ;  but  it  is  correct  to  say  that  it  las  iHh.nd  the  pntoneum 
oS  to  the  change  into  connective  tissue  subsequent  to  the  (usum  oi  the  s.r  us 
membrane  of  the  riRht  side  of  the  duodenum  .nd  that  of  the  p<«tenor  aUlonunal 
wST  Verv  o  ten  when  the  fourth  part  lies  in  front  of  the  aorta  a  '  .Id  of  jKrUon.um 
Ses  some  distance  in  between  them  from  the  lef.  :  hut  ns  l>'-^'^'/.»'*''»;»;;;';.;*'"^" 
SeRUt  is  distended.  The  pancreas,  when  it  overlaps  the  second,  th.r.l.  or  ,  n  en  the 
ourd^  part,  more  or  less  displaces  the  peritoneum.  Ihe  dumlenum  .s  c  ossed  by 
he  attachment  of  the  mesentery  of  the  jejuno-ileum  and  by  that  o  ^-^l^-^ 
rnesocolon.      The  series  of  changes  by  which  this  has  occurred  is  dealt  with  unth-r 

Fm.  1400. 

Transvcrae  oiooiuloii 
}tjanuin  Uuodctmm 


tltUXK-Ilill  ll'.--.1 

BmiKli..!  If  ft 
lolu  artiry 


inferior  Hutwlenal 

f(H,lUl 

Dencc  thug  culuh 


Mesemery  of  small 
inustiiiv 


Duodeno-Wan.1  junction,  showimt  duixlCTal  fo.s« ;  i«)ununi  turm^d  to  the  right. 

Peritoneum  (page  1742).  the  adult  condition  alone  being  hereconsidere.i  The  line 
oflttachment'of  the  transverse  mesocolon  crosses  the  second  part  of  he  duodenum 
a  litde  below  the  deep  flexure  which  on  the  front  separates  it  from  the  hrst.  1  he 
Dosition  of  the  line  of  attachment  of  the  mesentery  of  the  jeju.io-ileum  vanes  with 
S^  sha^  and  position  of  the  duodenum.  Should  the  latter  have  its  third  part 
crossing  the  aorta,  the  attachment  ol  the  mesentery  will  cross  the  third  part  only, 
pacing  somewhat  obliquely  downward  to  the  right.  In  the  more  usual  arrangement 
In  which  the  fourth  part  of  the  du.xlenum  either  ends  on  the  front  of  the  Mot 
crosses  it  only  just  before  its  termination,  the  lint  of  attachment  starts  on  the  Iront 
of  the  fourth  part  or  somewhat  on  the  right  of  it  and  descends  on  more  or  less 
sometimes  on  the  whole  length  of  this  portion,  or  else  lies  just  to  the  right  of  it  anti 
?h«i  crosses  the  third  part.  In  the  ca.se  of  the  V-shaped  duodenum  the  m.-sentery 
runs  down  on  or  along  the  right  of  the  oblique  portion.  •.  „    ,„ 

Duodeno-Jeiunal  Fossae.— Several  pockets  farmed  by  folds  of  peritoneum 
are  found  near  the  end  of  the  duodenum  in  the  greater  cavity  of  the  peritoneum 
Some  arc  vascular.-that  is.  containing  a  vessel  at  or  near  the  edge  of  the  foul,      while 
others  are  not.     We  have  adopted  the  classification  of  Jonnesco,  who  descrit>e>s  hve 
forms. 


1648 


HUMAN   ANATOMY. 


'l\\e  inferior  d  dettal fossa  (Fig.  1400)  is  the  most  common  form,  occurring, 
according  to  Jonnesco,  in  75  per  cent. ,  and  to  Treves  in  40  p>er  cent.  It  is  non- 
vascular, formed  by  a  fold  of  peritoneum  passing  from  the  left  of  the  fourth  part  of 
the  duodenum  to  the  |K)sterior  wall,  with  a  free  concave  edge  looking  upward.  The 
pocket  extends  down  behind  this  fold  for  a  variable  distance.  It  may  reach  the 
fourth  lumbar  vertebra. 

The  superior  duodenal  fossa  occurs  in  50  per  cent.  This  corresponds  to  the 
preceding,  only  it  runs  upward  behind  a  fold,  with  a  concave  free  edge  lookini; 
downward,  passing  from  the  duodeno-jejunal  flexure  to  the  posterior  wall  on  the 
left.  The  pocket  is  less  deep  than  the  preceding.  It  is  usually  vascular,  the  in- 
ferior mesenteric  vein  running  in  the  fold,  sometimes  near  its  edge.  These  two 
fossse  frequently  coexist,  and  the  left  ends  of  the  folds  may  be  continuous,  so  as  to 
form  a  large  C-shaped  fold,  oj.en  to  the  right,  with  a  pocket  under  both  the  upper 
and  the  lower  limbs.  In  this  case  the  vein  may  be  in  the  vertical  part  of  the  fold. 
An  arterial  arch,  formed  either  by  the  ascending  branch  of  the  left  colic  artery  or 
by  the  left  branch  of  the  middle  colic,  is  often  very  close  to  the  vein.  Such  a 
pouch  may  extend  deeply  under  the  fourth  part  of  the  duodenum. 

The  mesocolic  fossa,^  found  in  20  per  cent.,  and  always  alone,  is  a  little  pocket 
on  the  top  of  the  duodeno-jejunal  flexure  under  a  fold  from  the  posterior  layer  of  the 
transverse  mesocolon.     When  th  s  membrane  is  reflected  so  as  to  show  it,  the  fossa 

appears  to  run  upward.     The  in- 


Fio.  1401. 


ferior  mesenteric  vein  may  be  in 
the  fold. 

The  paraduodenal  fossa  is  in 
the  peritoneum  of  the  posterior 
abdominal  wall,  less  intimately 
connected  with  the  gut  than  the 
others.  It  is  a  pocket  formed  by 
the  superior  branch  of  the  left  colic 
artery  raising  a  fold  of  the  perito- 
neum. The  mouth  of  the  pouch 
is  to  the  right.  It  is  not  uncom- 
mon in  the  infant,  rare  in  the  adult. 
The  retroduodenal fossa  is  an 
uncommon  pouch  under  the  third 
and  fourth  parts  of  the  duodenum, 
extending  upward  with  the  mouth 
below. 

Interiorof  the  Duodenum. 
— The  mucous  coat  is  smooth  in 
the  first  part  and  overlies  the 
glands  of  Brunner  (page  «639), 
which  lie  chiefly  within  the  submucosa  and  form  a  continuous  layer  for  some  4  or 
5  cm. ;  beyond  they  are  scattered  for  some  distance  farther.  The  villi  are  small  at 
the  beginning,  but  soon  attain  their  complete  size.  The  valvulae  conniventes  are  at 
first  absent  for  about  4. 5  cm. ,  appearing  at  the  end  of  the  first  part,  and  are  almost 
at  once  large,  near  together,  and  non-effaceable.  A  very  large  one  is  formed  by  the 
folding  in  of  the  wall  at  the  junction  of  the  first  and  second  parts  ;  beyond  this  the 
valves  at  once  reach  their  greatest  development.  In  the  second  piart  the  bile-papilla 
is  seen  in  the  back  part  of  the  left  or  inner  wall,  from  8.5-10  cm.  (about  3>4-4  m-) 
beyond  the  pylorus,  or  rather  below  the  middle,  through  which  the  common  bile-duct 
and  the  duct  of  the  pancreas  pass  to  open  by  a  common  orifice.  The  papilla  is  almost 
always  overhung  by  a  valvular  fold  (Fig.  1401 ),  and  when  non-distended  is  only  some 
5  mm.  long.  The  accessory  duct  of  the  pancreas  often  opens  2  or  3  cm.  above 
the  main  one  through  a  much  smaller  and  inconstant  papilla.  The  submucous  coat 
holds  the  mucous  membrane  pretty  firmly  in  place,  so  that  the  folds  are  permanent. 

'  Jonnesco  calls  this  also  the  fossette  duodeno-jejunale ;  but,  althouKh  following  him  other- 
wise, we  have  retained  duodeno-jejuiiat  as  the  generic  name. 


Surface  view  ol  mucous  membrane  of  duodenum  ;  entrance  of 
bile  and  pancreatic  ducts  shown  by  probe,  which  lies  in  bile-duct. 
P.ipilia  is  surrounded  by  hood-like  fold.     .Natural  ai«. 


THE  JEJUNO-ILEUM. 


1649 


Fig.  1403. 


Abnormal  fitrm 
and  fourse  of  liuo- 
denum.  (Sckiejfff)  - 
deckrr.  I 


Blood-Vessels  — /^r/^r/W.-The  duodenum,  like  the  stomach,  is  attached  to 

m^S  %he  heX  artiy  gWes  oLhe  pyloric,  which  sends  some  ins.gn.hcant 

S  to   he  bepnning  of  the  duodenum,  and  the  gastro-duodenal. 

wW?h  runs  oTthe  left  of  the  first  part  ''"^  sends  off  the  supenor 

nancreatico-duodenal.  which  passes  downward  and  to  the  left  m   he 

concS  of   the  duodenum  between   it   and  the  pancreas,  lymg 

rathro^  the  front  of  the  duodenum,  of  which  t  is  the  ch.ef  artery. 

The   superior  is  met  by  the  inferior  pancreat.co-duodenal  artery 

whfch  a^  from  the  right  side  of   the  superior   mesenteric  and 

d^cends  along  the  right  of  the  fourth  part  of  the  duoden"™      The 

superior  mesenteric  distributes  one  or  two  small  twigs  to  the  very 

^"'  t£  ^^rSoric  vein.-larger  than  the  artery  of  the  same 

=u:gr:i?rp£^ft'e\i^e=^^^^^^ 

"'"?!;:  S^^^-^hKo^uZr^^^^^^^^^  other  parts  of  the  small 

intestine,  are  from  the  solar  plexus. 

higher,  described  a^loop  to  *« '«t  tehma  tnepemone  associated  with  other  errors 

there  was  a  mesenterium  commune. 

THE  JEJUNO-ILEUM. 
The  ieiuno-ileum  includes  the  remainder  of  the  small  intestine  which,  disposed 
in  folds  atfa'ched  on  one  side  to  the  mesentery,  "^ends  from  the  ducxlen^^^^^^^ 
tn  thp  ra-cum   its  leneth  be  ng.  therefore,  approximately  6.75  m.  ^nearly  22  u. ),  01 
wh  ch  the  fi«i  wo  fiffhs  are  conventionally  credit^  to  the  jejunum  and  the  remmn- 
W  three  fifths  to  the  ileum.     It  is  a  cylindrical  tube  contmually  decreasing  in  size. 
The  5  ameti«  Ire  variously  stated.  T«tut  giving  the  mean  diameter  f  the  upper 
part  as  fTom  25-30  mm.  and  that  of  the  lower  as  from  20-25  mm.    These  >=»ter  figures 
Cur  own  measurements  confirm,  since  on  thirty-seven  •"fl'"''^,-?-""^'"  °'  ''^^i";^ 
end  the  average  diameter  was  24  mm.,  the  extremes  being  17  and  37  mm      Chaput 
and  LenoHe'  assert  that  the  inferior  circumference  is  reduced  internally  to  32  mm 
f  on  inflated  specimens  to  50  mm.)  bv  a  valve  near  the  cacum      This  valve,  which 
te  have  found  Tabout  one-third  of  the  cases,  is  remarkable  in  being  always  s.u- 
Tted  on  the  posterior  aspect  of  the  gut.  generally  at  a  sharp  bend  ;  it  often  contains 
a  smal"  arterrand  is  probably  fon^ed  by  the  folding  in  of  the  muscular  coat.      Its 
J^sTtbn  S  JrVntly  neartheVint  at  which  the  ileum  »-^™J«J-j;K„»Sime: 
wall  of  the  cscum.  but  it  may  be  2.5  cm.  or  more  higher.     The  valve  is  sometimes 
douWe.  and  Ws'in  height  f'rom  2  ^m.  to  t  cm      We  have  not    o"nd.  however 
that  this  fold  is  necessarily  the  narrowest  point  of  this  part  of  the  gut.     A  p^ccc  o^ 
the  intestine  from  the  upper  part  of  the  ejunum  weighs  more  than  one  of  eq"*'  "ea 
rom  thTlowir  part  of  the  ilium,  owing  to  the  greater  thickness  of  the  wal  s  o^he 
former  and  to  the  greater  development  of  the  valves  •"  that  part.     The  structure 
of  this  part  of  the  small  intestine  has  already  been  descnbed  (page  1634). 
'  Arch,  fur  Anat.  iinfl  F.ntwicklng.,  1887. 
•  Bull.  See.  Anat.  de  Paris,  1894. 
104 


t650 


HUMAN  ANATOMY. 


The  Mesentery  and  Topography  of  the  Jejuno-Ileum. — Since  consid- 
eration of  the  mesentery  is  indispensable  for  the  study  of  the  disposition  of  the  folds 
and  relations  of  the  small  intestine,  this  structure  next  claims  attention.  The  serous 
covering  of  the  gut  itself  requires  no  further  description  than  to  note  that  it  com- 
pletely surrounds  the  bowel,  except  at  the  double  line  of  its  attachment,  where  there 
IS  left  space  just  large  enough  for  the  passage  of  the  vessels  and  nerves.  The  attached 
b«>rtler  of  the  mesentery  (Fig.  1399)  extends  from  the  left  of  the  tront  of  the  first 


Fio.  1403. 


Right  lungf. 


DiaphraK'n  (cut)- 


Hepatic  vein 

Behind  Spigeli 
lobe 

RiKht 
suprarenal  body. 
Probe  in  forann 
of  Winilow 

Right  kidney. 

Beginning. 

of  duodenum 

Left  end  nf, 
transverse  colon 
Duodeni 


Jejunum 


Ascending  colon. 


Ileum. 


Left  lung 


^sophagtts 


ipleen 
Left  suprarenal  body 
Lt^t  kidney 


Formalin  subject;  liver,  Momach,  transverrc  mefiorolnn.  and  colon  ha\'e  been  removed,  leaving  other  abdominal 
organs  ih  situ  ;  attachment  of  ^  iit  (teritoneum  tmlicated  by  white  linu. 


or  second  lumbar  vertebra,  immediately  below  the  end  of  the  duodenum,  where  the 
superior  mesenteric  artery  enters  it,  to  the  right  sacro- iliac  joint,  a  distance  of  about 
15  cm.  (6  in.  ).  The  relations  of  the  upper  part  of  the  fold  are  determined  by  the 
shape  and  position  of  the  duodenum.  Probably  the  usual  course  of  the  mesenteric 
attachment  is  from  the  front  of  the  aorta  downward  on  the  fourth  part  of  the  duo- 
denum, across  the  vena  cava  to  the  right  sacro-iliac  joint.     With  a  V-shaped  duo- 


THE  JEJUNO-ILEUM. 


l65» 


denum  the  line  of  the  mesentery  is  usually  on  the  right  of  the  gut ;  with  a  duodenum 
that  crosses  the  aorU  the  line  is  across  the  third  part.  The  lower  end  of  the  mesen- 
terv  is  determined  by  the  degree  of  adhesion  of  the  right  mesocolon  to  the  alxlomi- 
nal  wall.  It  rarely  stops  short  of  the  sacroiliac  joint,  but  it  may  be  continued 
farther  into  the  right  iliac  fossa. 

The  free  or  intestinal  border  of  the  mesentery  is  some  6  m.  or  about  20  ft.  long. 
In  the  middle  the  distance  between  the  borders  is  from  20-22.5  cm.  (»-9  in.). 
Near  its  origin,  in  the  first  si.x  inches  of  the  intestine,  the  mesentery  h;>s  reached  a 
breadth  of  from  12-15  cm.  (5-6  in. ).  At  the  lower  end  its  breadth  is  more  uncer- 
tain, being  usually  slight,  only  from  2.5-5  cm.  for  the  last  six  inches.  It  increases 
with  age,  presumably  concurrently  with  the  increase  of  girth.  The  mesentery  con- 
tains vessels  and  nerves  as  well  as  lymphatic  nodes  between  its  folds-  these  stnic- 
tun-s  may  lie  in  a  considerable  mass  of  fat,  adding  to  the  thickness,  which  is  much 
greater,  on  account  of  the  size  and  number  of  the  vessels,  m  the  upj)er  part  than  m 
the  lower.      The  larger  lymph-nodes 

and  .he  fat  accumulate  chiefly  near  the  Fio.  1404. 

spinal  border,  where  the  mesentery 
may  be  very  thick  and  heavy,  while 
the  part  near  the  intestine,  except  in 
the  case  of  excessive  fatty  accumula- 
tion, is  always  thin  and  yielding.  It 
is  evident  that  the  mesentery  with  an 
attached  border  of  only  15  cm.  (6  in.) 
and  a  free  one  of  6  m.  (20  ft.)  must  be 
very  much  folded  ;  and  further,  that 
while  the  intestinal  border  must  pre- 
sent a  vast  number  of  totally  irregular 
and  transitory  folds,  changing  with 
the  movements  of  the  gut,  the  heavier 
and  more  fixed  part  of  the  mesentery 
near  the  root  must  present  certain  chief 
folds  the  position  of  which  is  tolerably 
stable. 

Henke '  has  shown  that  if  the  hand 
be  introduced  among  the  coils  of  intes- 
tines in  the  line  of  the  left  psoas  muscle 
and  carried  upward,  it  enters  the  con- 
cavity of  a  horseshoe- shaped  fold  of  the 
mesentery,  and  that  the  intestines  easily 
fall  apart  to  either  side.  The  coils  on 
the  left  are  in  the  main  transverse  and 

those  to  the  right  chiefly  vertical.    This  .,  „      ,  •  11     ;„  ;„»,„». 

clan  although  sometimes  obscure,  is  often  beautifully  clear  especially  m  infants. 
Weinberg  '  from  studies  on  the  new-born  infant,  has  carried  the  plan  into  further 
details.  He  finds  that  the  upper  two-fifths  of  the  intestine  are  arranged  in  trans- 
verse folds  in  the  upper  left  part  of  the  abdomen  :  the  middle  fifth  lies  in  the  left 
iliac  region  without  definite  arrangement  ;  the  last  two-fifths  are  in  the  median 
part  and  in  the  right  iliac  region,  disposed  in  the  main  vertically  Still,  cases 
occur  at  all  ages  in  which  the  plan  is  obscure.  Mall*  has  traced  the  plan  of  the 
intestines  throughout  development,  and  incidentally  confirms  Weinberg  s  state- 
ments The  following  account  of  the  normal  arrangement  in  the  adult  is  essentially 
according  to  his  researches.  The  gut  is  to  be  conceived  as  arranged  in  spiral  coi  s 
travelling  from  the  left  hypochondriac  region  to  the  right  iliac  fossa,  successive  coils 
being  in  'le  main  parallel.  Starting  from  th.  iuodenum,  there  are  two  transverse 
folds  in  me  left  hypochondrium,  followed  by  long  fold  that  goes  across  the  body 
and  back.     Some  less  distinctly  transverse  fol.ls  occupy  the  left  iliac  fossa.      Ihe 

'  Arch,  fiir  Anat.  und  EntwicklnR.,  1801 

'  Internal.  Moiialssi-hrih  fiir  Anat.  und  Ph)-8.,  Bd.  xiii.,  i^. 

•  Arch,  fur  Anat.  und  Entwicklng.,  1897.    Supplement  Bd. 


Typical  ilisposilion  of  folds  of  m»entery  shown  after 
removal  of  jeiuiio-ileum.  i.  end  of  <liiodenum ;  2.  }.  4.  jeju- 
num ;  s,  ileum ;  6,  termination  of  ileum  into  large  nitestnie. 
IMaU.) 


m 


1652 


HUMAN  ANATOMY. 


remainder  is  disposed  vertically,  occupying  the  lower  part  of  the  umbilical  region 
and  the  pelvis,  and  extending  on  the  right  as  far  as  the  large  intestine  will  allow 
The  vertical  arrangement  of  this  portion  is  generally  less  striking  than  the  trans 
verse  disposition  of  the  preceding.  The  end  of  the  ileum  rises  from  the  pelvis  int<i 
the  right  iliac  fossa.  There  are,  of  course,  frequent  deviations  from  the  above  plan 
of  arrangement  of  the  folds.  It  is  easy  to  see  that  the  appearance  at  the  surface  of 
some  that  are  usually  deep  would  obscure  the  plan.  It  is  worth  noting  that  adjacent 
folds  should  never  be  assumed  to  be  continuous. 

Blood-Vessels — The  arteries  of  the  jejuno-ileum  are  branches  of  the 
superior  mesenteric,  which  enters  the  mesentery  below  the  pancreas.  The  vessels 
for  the  gut  are  straight  ones  arising  from  the  arterial  arches.  In  the  upper  part 
they  are  from  4-5  cm.  long,  3  cm.  in  the  middle,  and  very  small  at  the  end  of  the 
ileum.  They  run  without  anastomoses  to  the  edge  of  the  gut,  where  they  break  up 
mto  bunches  of  slighdy  diverging  branches.  All  of  these  usually  go  to  one  side  of 
the  gut,  each  alternate  vessel  taking  a  different  side,  although  sometimes  a  vessel 
may  send  branches  to  both  sides.  Anastomoses  in  the  walls  of  the  gut  between 
the  branches  of  neighboring  arteries  are  not  numerous,  and  occur  only  between 
very  fine  vesseb,  except  opposite  the  mesentery,  where  vessels  of  the  different  sides 
meet.     T  he  distribution  of  the  veins  is  essentially  the  same. 

The  lymphatics,  large  and  numerous,  empty  into  the  mesenteric  nodes, 
which  they  connect.  These  lymph-nodes  vary  in  number  from  one  to  two  hundred, 
the  largest  lying  near  the  root  of  the  mesentery,  from  which  position  they  grow 
smaller  as  they  approach  the  free  edge.  There  are  no  nodes,  however,  between  the  gut 
and  the  last  vascular  arch,  unless,  perhaps,  near  the  very  end  of  the  small  intestine. 

The  nerves  of  the  entire  small  intestine  are  from  the  solar  plexus.  They 
receive  many  cerebro-spinal  fibres  through  the  splanchnics. 

Meckel's  Diverticulum. — ^This  is  a  protrusion  from  the  ileum,  shaped  like 
the  finger  of  a  glove,  and  found  in  some  2  per  cent.  It  is  the  remnant  of  the  vitel- 
line duct,  which  at  an  early  stage  connects  the  gut  with  the  yolk-sac.  It  springs 
most  frequently  from  the  free  border  of  the  bowel,  sometimes,  however,  from  the 
side,  and,  as  a  rule,  but  not  invariably,  is  composed  of  all  the  intestinal  coats.  Its 
usual  position  is  within  i  m.  ( on  an  average,  82  cm. )  of  the  caecum.  Diverticula 
said  to  have  been  found  in  the  upper  part  of  the  small  intestine  are  regarded  with 
suspicion.  The  diameter  of  the  diverticulum  is  usually  that  of  the  gut,  but  it  may 
be  less  and  associated  with  a  conical  form.  The  length  varies  from  2.5  cm.  or  less 
to  17.5  cm.(7  in. ),  although  ordinarily  between  2.5  and  7.5  cm.  (i  and  3  in.). 
As  a  rule,  its  end  is  free,  but  often  a  delicate  band  extends  from  its  apex  to  the 
umbilicus  or  to  some  of  the  contents  of  the  abdomen,  generally  the  mesentery." 

PRACTICAL   CONSIDERATIONS  :   THE   SMALL  INTESTINE. 

1.  The  Peritoneal  Coat. — This  is  complete  below  the  duodenum  except  at  the 
mesenteric  aspect,  where  the  two  layers  of  peritoneum  diverge  for  about  8  mm.  {  Yi  in. ). 
The  jejuno-ileum  is  therefore  practically  an  intraperitoneal,  and  not  merely  an  intra-ab- 
dominal, viscus,  although,  of  course,  really  outside  the  peritoneal  sac.  Inflammatit.n 
of  this  portion  of  the  general  peritoneum  is  more  apt  to  be  acute,  to  spread  rapidly, 
and  to  be  attended  by  serious  or  fatal  results  than  is  that  of  any  other  portion.  Such 
infection  is  frequent  on  account  of  the  great  length  of  the  small  intestine,  its  exposure 
to  trauma,  the  thinness  of  its  muscular  walls,  the  variety  and  number  of  the  lesions 
of  its  mucosa,  its  close  relation  to  all  the  intra-abdominal  viscera,  and  its  consequent 
participation  in  their  injuries  and  diseases.  Direct  transmission  of  infection  from 
within  outward  is  favored  by  the  relatively  intimate  relation  between  the  peritoneal 
and  muscular  coats,  the  subserous  areolar  tissue  being  much  scan  r  and  containing 
much  less  fat  than  that  intervening  between  the  parietal  periloneuni  and  the  fascia- 
and  muscles  of  the  abdominal  wall.  The  extent  and  fataluy  ol  peritoneal  inflam- 
mation result  from  the  facility  with  which  it  spreads  by  both  continuity  and  contiguity, 
and  from  the  fact  that,  esteris  paribus,  its  to.xic  products  arc  proportionate  in  amount 
to  the  area  involved.  The  association  of  the  spinal  and  sympathetic  nerves  in  the 
'  Lamb  :  American  Journal  of  the  MedicJ  Sciences,  1893. 


PRACTICAL  CONSIDERATIONS  :  THE  SMALL  INTESTINE.     165.^ 

intramuscular  pkxus  0/ Aucrbaih  and  the  submucous  */r.rw  of  Mehstur,  and  their 
connrtion  with  the  lower  seven  intercostal  nerves  d.str.buted  to  the  sk.n  and  muscles 
of  the  abdomen,  explain  (a)  the  abdominal  rigidity  and  tenderness  which  often  pre- 
cede an  extension  of  disease  from  the  visceral  to  the  parietal  ,H;ntoneum  ;  (*)  he 
Sesis  or  paralysis  of  the  intestines  which  is  so  common  as  a  symptom  of  P«^"  om  «. 
S  which  favors  stasis  of  intestinal  contents,  putrefaction  and  distention  ;  (O  the 
imotor  disturbance  which  is  an  im,x>rtant.  if  not  the  chief,  factor  ,n  the  l>r<Kluct.on 
ofmeteorism  ;  (rf)  the  vomiting,  first  reflex  and  then  from  irregular  muscular  con- 
^L^Sn  (reversed  peristalsis)  :  and  (.)  the  reference  of  the  early  l'?''"^ "''  "^^r 
what  the  seat  of  the  peritonitis,  to  the  epigastnum  or  umbilicus.-/.*-.,  to  the  solar 

^"'  tT  u^uaT^ur  J  fnSis  of  the  small  intestine^  by  infection  from  within,  is 
penetration  of  its  walls  by  the  colon  bacillus,  following  epithelial  necrosis  or  "  cenU"'" 
due  to  catarrh  or  to  various  forms  of  infection,  or  secondary  to  diseases  which  pro- 
duce engorgement  of  the  terminal  vessels  of  the  portal  system.  It  is  sometimcjs.  in  a 
\L  acufe  form,  a  final  phenomenon  in  fatal  cases  of  renal  or  cardiac  disease.  It  ni.iy 
Xw  tuberculosis  or  tvphoid  ulceration  of  the  solitary  or  agminated  lymph-ncxluk-s. 
In  all  cases  of  ente^orrhaphy-^is  after  resection  or  anastomos.s-especal  atten- 
tion  should  be  paid  to  the  non-peritoneal  area  included  between  the  two  mesenteric 
ave.^  The  success  of  these  o^rations  depends  primarily  upon  the  rapid  union  of 
apW  peritoneal  surfaces  ;  hence  the  serous  coat,  including  the  two  layers  o  he 
m^Sry.  should  be  brought  together  through  the  complete  circumference  of  the 

bowel  and  accurately  sutured.  .      »•        t  ,u„  „,„^„inr  wall 

2.  The  Muscular  Coat.  -Irregular  or  spasmodic  contraction  of  the  muscular  wa^^ 
of  the  small  intestine  produces  typical  "colic.;'  the  pain  being  '»"^?K°"^ ^° ''^j^  'f^ 
in  a  "cramp"  of  one  of  the  voluntary  muscles.  Intestinal  colic  is  not  a^>t''».ted 
with  teXness  of  the  surface  of  the'abdomen,  or  with  ng.dity  of  the  abdominal 
muscles  and  is  usually  relieved  by  firm  pressure. -supporting  and  contr.  Uing  the 
Xtel'  s^nent  of  gut.  The  abdominal  wall  may  be  moved  freely  oyer  the  under- 
lying viscera.  It  mav  thus  be 'Vstinguished  from  the  early  pain  of  peritonitis. 
^  SL  greater  thickness  of  t  ner^ircular-coat  causes  longitudinal  wounds  to 
gape  more  than  transverse  01  The  latter  are  more  apt  to  gape  if  they  are  at   he 

frerborderof  the  gut.  where  ...  longitudinal  hbres  are  most  numerous.  As  the 
muscSr  coat  in  itf  entirety  lessens  in  thickness  from  above  downward,  wounds  of 
L  jejunum  gape  more  than  those  of  the  ileum  Intestinal  P»l«=tures  usually,  and 
very  small  wounds  not  infrequenriy.  are  closed  by  muscular  action,  so  that  healing 
SXe  without  extravaktion  of  intestinal  contents.  Sljghdy  larger  wounds 
ma^b^  stopped  bv  a  plug  of  mucous  membrane.  This  is  favored  in  the  u,^er 
3on  of  the  tube'bv  the  presen-e  <.f  the  vah'uhe  conniventes  and  in  the  lower  part 
W  the  bxity  of  the  submucosa.  This  eversion  of  the  mu.  ous  membrane,  caused  by 
muscular  contraction,  must  always  be  overcome  in  the  suture  of  intestinal  wounds, 
since  the  mucous  surfaces  will  not  unite  with  each  other.  . 

1  The  mucous  and  submucous  coals  and  their  contained  glandular  and  vascu- 
lar structures  are  subject  to  many  varieties  of  disease.  I  catarrhal  mflammaiwn 
affecTthe  mucosa  of  the  small  intestine,  it  is  apt,  if  locali^ed  in  the  duodenum,  to 
be  associated  with  gastritis  and  to  extend  into  the  bile-ducts  causing  jaundice  If 
fn  thele  uno-ileum,''it  may  be  mistaken  for  colitis  ;  usually,  if  in  the  s'-nall  intestiiie 
the  diarrh.^a  is  less  marked,  the  colicky  P='i"^='^«  R'-^=«»^'-;.»^,;.'^^y«"\'  I*  ,^ 'T,^!' 
less  mucus  is  found  in  the  stools,  and  tenesmus  is  absent  Neither  d''odemt.s  e,u- 
nitis,  nor  ileitis  can,  however,  positively  be  diagnosticated  from  one  another  or  from 
general  intestinal  catarrh  f  Osier).  .,  „i  ,a,  r^l 

Ulcers  of  the  duodenum  are  in  the  vast  majority  of  cases  (  242  oJt  of  262.  Lol- 
lin  quoted  by  Weir)  situated  within  5  cm.  (2  in.)  of  the  pylorus  (the  mcr.  movable 
portbn  of  the  duodenum)  and  are  most  often  on  the  =»nterior  wall,  especially  its 
n"  side.  The  peritoneum  of  the  right  side  of  the  f^rst  part  of  the  duodenum  looks 
,Uo  the  general  peritoneal  cavity,  and  of  the  left  side  into  the  lesser  cav.tv(  page 
■  647).  When  petlforation  follows,  the  general  peritoneal  cav.ty  is  therefore  .key  to 
be  in  ected.  and  the  death  of  one-half  of  the  subjects  of  perforating  dut.dcnal  ulcer 
K,m  general  peritonitis  is  thus  accounted  for.     The  second  part  of  the  duodenum  is 


i654 


HUMAN   .'NATOMY. 


in  close  relation  on  the  lower  part  of  the  right  aspect  with  the  liver  and  gall-bladder, 
on  the  upper  part  of  the  left  aspect  with  the  head  of  the  pancreas  and  foramen  of 
VVinslow,  and  posteriorly  is  pardy  uncovered  by  peritoneum  and  rests  on  areolar 
tissue  and  the  common  bile-duct. 

The  general  relations  of  the  duodenum  (page  1645)  explain  the  remaining 
lesions  following  duodenal  ulcer, — e.g.,  perforations  into  the  gall-bladder,  liver,  or 
colon  ;  opening  of  the  hepatic  artery  or  the  aorta,  or  of  the  superior  mesenteric  01 
f)ortal  vein  ;  or  the  development  of  subphrenic  abscess. 

As  compared  with  the  symptoms  of  gastric  ulcer,  pain  is  apt  to  be  lew  on 
account  of  the  relative  immobility  of  the  duodenum  ;  vomiting  after  feeding  is 
later  ;  hemorrhage  is  often  greater  on  account  of  the  larger  vessels  that  may  be 
involved  ;  bloody  stools  are  more  common,  as  is  jaundice  from  the  involvement  of 
the  bile-duct. 

In  exposure  of  this  part  of  the  duodenum  it  is  well  to  remember  the  suggestions 
of  Pagenstecher  (quoted  by  Weir),— viz.,  that  the  fundus  of  the  gall-bladder  when 
distended  lies  in  front  of  the  duodenum  ;  that  by  raising  and  drawing  forward  the 
transverse  colon,  which  lies  in  front  of  and  below  the  horizontal  portion  of  the  duo- 
denum, the  tirst  portion  is  revealed  ;  and  that  by  pushing  the  stomach  and  pylorus 
to  the  left  and  elevating  the  liver,  access  to  the  region  of  perforation  may  be  gained. 
In  emaciated  patients  with  contracted  stomachs  the  duodenum  may  be  found  lying 
above  the  level  of  the  transverse  colon. 

Infection  through  the  mucous  coat  has  already  been  spoken  of.  If  of  the  tuber- 
culous variety,  it  affects  chiefly  the  lower  part  of  the  ileum,  and  tends,  as  is  charac- 
teristic of  that  disease,  to  follow  the  course  of  the  vessels  which  run  from  their 
entrance  at  the  mesenteric  attachment  transversely  around  the  gut.  If  such  ulcers 
cicatrize,  they  are  therefore  especially  prone  to  lead  to  si  ricture  of  the  intestine,  a  very 
rare  sequel  of  typhoid  ulceration,  which,  affecting  the  same  portion  of  the  small 
intestine,  extends  in  the  line  of  the  agminated  lymph-nodules, — i.e.,  longitudinally. 
The  tuberculous  ulcer  sometimes  produces  a  slow  general  peritonitis,  rarely  a  local- 
ized abscess,  much  more  rarely  an  acute  perforation  with  general  septic  peritonitis, 
as  the  process  is  so  slow  that  protecti\e  adhesions  to  neighboring  coils  of  gut  or  to 
the  parietal  peritoneum  have  time  to  form. 

Typhoid  ulcers  cause  perforation  in  6. 58  per  cent.  ( Fitz )  of  all  cases.  The  large 
majority  of  perforations  occur  in  the  ileum,  most  of  them  within  60  cm.  (2  ft. )  of 
the  ileo-cacal  junction.  In  operation  this  should  therefore  be  sought  for  and  the 
ileum  followed  upward  from  that  point.  The  ulceration  may  so  thin  the  intestinal 
wall  as  to  permit  of  leakage  and  the  production  of  general  peritonitis  without  actual 
perforation  ;  or  it  may  be  accompanied  by  such  an  extensive  exudate  as  to  make  the 
ileum  palpable,  a  condition  which,  in  conjunction  with  localized  tenderness  and 
abdominal  rigidity  {vide  supra),  has  led  to  many  mistaken  diagnoses  of  appendicitis 
in  cases  of  typhoid  fever. 

Syphilitic  ulceration  of  the  small  intestine  is  rare,  but  is  said  to  be  most  frequent 
in  the  upper  portions  ( Rieder). 

The  lymphatics  of  the  mucous  and  submucous  coats  empty  into  the  mesenteric 
lymph-nodules  (page  1643)  and  convey  to  them  various  forms  of  infection  or  disease, 
— typhoid,  carcmomatous.  tuberculous,  etc. 

The  veins  emptying  into  the  vena  porta  through  the  superior  mesenteric  are 
likewise  channels  of  infection,  ulceration  of  the  biwel  sometimes  resulting  in  abscess 
of  the  liver. 

Contusion  and  rupture  of  the  small  intestine  are  favored  by  its  exposure  to 
trauma  through  its  close  apposition  to  the  abdominal  wall,  which,  if  relaxed, 
offers  but  little  protection.  The  interposition  of  the  greater  omentum  with  its  con- 
tained fat  is  a  slight  safeguard,  but  the  movement  of  the  coils  of  gut  upon  one 
another  and  their  elasticity  are  of  much  more  value. 

Contusion  here,  as  elsewhere,  may  be  followed  later  by  infection  and  ulceration. 
Traumatic  rupture  is  much  more  frequent  in  the  jejunum  and  ileum  than  in  any 
other  portions  the  alimentary  canal  (of  219  cases,  79  per  cent,  were  in  the  small 
intestine,  11. 5  lei  cent,  in  the  colon,  and  9.5  per  cent,  in  the  stomach,  Petrv). 
The  duodenum  suffers  very  infrequently  on  account  of  its  sheltered  position  ;  other- 


iitering  layer 


Intussusceptum 


PRACTICAL  CONSIDERATIONS:  THE  SMALL  INTESTINE.    1655 

wise  its  lower  portion-the  most  fixed  part  of  the  intestine-would  P^obabl>'  be  more 
^n  in  ur«l  The  upper  portion  of  the  e  unum,  which  partakes  somewhat  of  this 
Sffv  T^re  commoK  ruptured  than  any  other  part.  So,  too.  the  m,.st  fixed 
Srt^^f  the  «eum-Ta°  nLrest  the  ileo-c*cal  junction-is  most  often  the  site  of  rup- 
rS  An  inTcerlted  or  irreducible  hernia  may  constitute  a  fix«l  point  ..f  the  gut 
i„a  favor  iB^Sure  elsewhere  from  trauma  to  the  surface  of  the  abdomen. 

RuDtu^ero  the  imestin. ,  like  wounds  or  obstruction,  are  more  serious  he 
W  kS  tCv^re  si  uat^  The  nervous  disturbance  and  shcK:k  are  Krcater,  possibly 
•"If  Jcounr  of  the  moTe'  immediate  relation  of  the  lesion  and  of  the  rt;sult.n«  p^«tho- 
on  account  ot  the  "T^  L^p^'";  ,       ^^  ^r  to  the  pericardial  jjortion  o.  the  dia- 

'SLtcrU:)     vomitfnfbS  ns  eTrlier^nd  il  morJ^severe  for\he  s^me  reason  ; 

tract      Investigation  has  shown  (Cush- 

ine  and   Livingood.   and  later  Lorrain  Fto.  i4o<. 

Smith  and  Tennant)  that  the  bacteria 
flora  in  the  upper  portion  of  the  intestinal 
tract  is  moic  scanty  than  in  the  lo\yer 
portion  ;  and  it  is  true  that  peritonitis 
following  intestinal  wounds,  operative  or 
accidental,  is  dependent  for  its  charac- 
teristics upon  the  bacteria  at  the  site  ot 
lesion,  and  that  the  prognosis  should  be 
favorable  in  proportion  to  the  scarcity 
and  innocuousness  of  the  micro-organ- 
isms present.     But  the  anatomical  con- 
ditions,   by  adding  to  shock,   favoring 
intestinal  extravasation,  and  minimizing 
the  chance  of  a  reparative  peritonitis,  are 
more  than  sufficient  to  counterbalance 
the  relative  dearth  of  bacteria. 

It  should  be  remembered  that  the 
position  of  the  wound  or  contusion  on  the 
surface  of  the  abdomen  is  of  but  slight 
value  in  determining  the  area  of  gut  in- 
volved    Thus,  a  jejunal  fistula  following 

''''^^::S'oi  the  small  int^tinemav  be  due  to^r^/J;.^  Si^l^^ 
intestinal  concretions  and  gall-stones  ^h^t  ha^-e  vOccrated  in  o  the  ^»^^^      J;^     „, 

is  then  most  apt  to  occur  at  the  '1«"-'=*'^='V  ^nnLirtioT of  a  -oil  or  knu.kle 
the  canal  at  that  point :  (*)  ianJs  pr"duang  -"^^^l^'^^^  ,^  .,,i„„,  p,Hto- 
of  gut.  such  bands  arising  from  the  elongation  "«  ^^l^f J?"^. ^  ^verticulum  (page 
nitis.  from  inflammatory  attachment  of  the  '7^^^^"^,'^*  f^"„^^^^^^  through 

,652).  of  adventitious  diverticula  (from  P''^.^'''>'^.y^l"^^^Z  appendices 

the  muscular  coat),  or  of  the  appendix      Euher  the  p^^^^^^  pp^^^^^ 

epiploic^,  the  omentum,  or  the  mesentery  m^^^    uberculous  ulcer  in  the  ileum  or 


Intussuscipiens 


L»tiKil"<»i'>al  section  of  intussuscepted  K«t. 
**  layers. 


AhowitiK 


I6s« 


HUMAN  ANATOMY. 


ileum  when  its  mesentery  has  been  elongated  by  prolonged  stretching,  as  in  the 
presence  of  an  old  hernia  (Maylard);  (<•)  internal  hernia,  as  into  the  ducKleno- 
jejunal,  perioecal,  or  intersigmoid  fossa,  or  through  the  foramen  of  Winslow  .,r 
through  an  aperture  in  the  omentum  (page  1758),  which  may  be  traumatic  or  may 
be  one  of  the  rounded  openings  due  to  congenital  atrophy  of  a  comparatively  viis- 
cular  area  of  the  mesentery  of  the  terminal  portion  of  the  ileum  and  embraced 
w-ithm  the  ileocolic  artery  and  the  lowest  vasa  intestini  tenuis  ;  (/)  hemite  throiijfh 
the  usual  hernial  apertures  or  regions  of  the  parietes  (page  1762);  {g)  intussuscep- 
tion, one  form  of  which  is  due  to  irregular  contraction  of  the  circular  fibres  of  the 
muscular  coat,  so  that  as  the  peristaltic  wave  passes  downward  a  segment  of  gut, 
made  smaller  by  this  contraction,  is  forced  into  the  portion  immediately  beneath  it! 
which  IS  of  larger  calibre  as  a  result  of  having  failed  to  contract  at  the  proper  time  ; 
{h}  pressure  from  without,  as  from  tumors,  which,  as  they  must  meet  with  counter- 
resistance  and  relative  fixity  of  the  gut  to  produce  constriction,  most  often  affect  tl.- 
duodenal  (as  in  cancer  of  the  pancreas),  upper  jejunal,  or  ileo-cacal  segments- 
(t)  Pentonitis,  the  relation  of  which  to  intestinal  obstruction  will  be  subsequently 
explained  (jwge  1756);  'J)  tumors  of  the  intestines  themselves,  not  very  frequent  iii 
the  small  intestine,  but  most  often  found  at  its  two  extremities. 

The  position  of  the  different  portions  of  the  small  intestine  varies  greatly.  The 
lower  end  of  the  duodenum,  the  upper  end  of  the  jejunum,  and  the  lower  end  of 
the  Ileum  are  the  most  fixed  points.  A  description  of  the  normal  arrangement  of 
the  coils  of  the  jejuno-ileum  h;is  been  given  (page  1651). 

Of  the  duodenum  only  the  first  portion  has  lieen  found  involved  in  internal 
herniae.  The  more  or  less  vertical  coils  of  the  jejunum,  and  especially  those  of  the 
terminal  portion  of  the  ileum  which  occupy  the  pelvis  when  the  bladder,  rectum 
and  sigmoid  are  not  distended,  are  those  most  \ikc\y,  for  a  priori  reasons,  to  be 
found  m  inguinal  or  femoral  enteroceles,  but  clinical  evidence  in  support  of  this  is 
not  conclusive,  fn  umbilical  hernia  the  jejunum  is  apt  to  be  involved,  and  the 
gravity  of  this  form  of  hernia,  when  strangulated,  is  supposed  to  be  partly  due 
to  this  fact  as  well  as  to  the  effect  upon  the  circulation  of  the  constricted  coil 
produced  by  the  sharp  edge  of  the  cicatricial  tissue  which  surrounds  the  openine 
and  aggravated  by  the  downward  pull,  through  gravity,  of  the  remainder  of  the 
intestines. 

When  the  stomach  is  full  the  intestines  are  depressed  ;  when  it  is  empty  thev 
rise,  so  that  in  the  left  hypochondriac  region  they  may  be  in  contact  with  the  dia- 
phragm. If  the  colon  is  distended,  the  small  intestine  can  occupy  but  little  of  the 
lumbar,  epigastric,  or  hypochondriac  regions.  Conversely,  if  the  small  intestine  is 
distended  it  may  so  fill  the  pelvis  and  compress  the  rectum  as  to  prevent  the 
pas.sage  of  a  tube  or  bougie  into  the  sigmoid,  and  thus  give  rise  to  a  mistaken  diag- 
nosis of  obstruction  at  that  point.  If  the  spleen  is  enlarged,  they  are  carried  down- 
ward and  to  the  nght  ;  if  the  liver,  downward  and  to  the  left  ;  if  the  bladder  or 
uterus,  upward. 

In  ascites  they  are  above  the  fluid, -/.<f.,  in  the  umbilical  regfon  in  the  supine 
and  the  epigastric  region       the  erect  position. 

...  ^'ormally  the  coils  01  jie  small  intestine  are  closely  applied  to  one  another  and 
this  condition,  by  permitting  of  rapid  adhesion,  and  thus  of  isolatfon  of  an  infected 
focus,  has  saved  thousands  of  lives,  especially  in  cases  of  appendicitis  and  pyosal- 
pmx,  and  less  frequently  in  cholecy.stitis  and  other  forms  of  intra-abdominal  infection 

Opj-raf,ons.— The  principles  which  should  govern  in  opening  the  small  intestine, 
in  avoiding  or  comrolling  hemorrhage,  and  in  suturing  wounds  accidental  or  opera- 
tive tiave  been  sufficiently  explained  (page  1653). 

The  recognition  of  the  duodenum  is  not  difficult.  It  occupies  portions  of  the 
right  hypochondriac,  right  lumbar,  and  umbilical  regions.  The  spine  of  the  second 
lumbar  vertebra  is  just  above  it.  The  he,,atic  flexure  of  the  colon  is  anterior  to  it 
at  a  point  just  below  the  ninth  rib  on  the  right  side.  The  mesentery  commences  at 
the  duodeno-jejunal  junction.  A  notch  which  can  be  felt  in  the  peritoneum  serves 
as  a  guide  to  this  particular  part  ( Maylard). 

Diwdenotomy  m^y  be  required,  either  as  an  aid  or  as  the  main  avenue  of  ap- 
proach, m  cases  of  impacted  calcul-is  in  the  common  bile-duct  (page  1732)       It  is 


THE  LARGE  INTESTINE. 


1657 


rarely  needed  lor  the  removal  of  foreign  bodies,  as  those  small  enouRh  »«  P^^  |5« 
pylorus^ect.  08  a  rule,  only  temporary  lodgment  m  the  du.KUnum  and  usually 

'"^Vhe'JS^^t^^t:- distinguished  from  the  ileum  by  its  .-t.r  width  and 
thickness   its  deeper  color,  and  by  the  presence  of  the  many  large  folds  of  the  x.il- 
uSc^n^iv^ntw  which  can  In.  seen  in  the  collated  and  tense  gut  by  transnutted 
£      By  Rawing  a  lcK>p  of  intestine  out  of  the  abdomen  so  that    u.th  the  loop 
oLailel  wUh  the  long  axis  of  the  body,  its  mesentery  is  stretched  an.l  s  ra.ghtened 
Hs^y  to  determine  which  is  the  up,,er  end  of  the  loop,  and  so  to  follow  the  gu 
eitheMoVards   he  dumlenum  or  the  c^um.  as  may  Ik-  dc-s.red      The  fng-r  should 
L  p^  down  to  the  spine,  keeping  in  close  contact  with  the  mesentery  ;    f 
remat^n  one  side  until  the  posterior  attachment  is  reached,   .t  is  evident    hat 
hTret  no  twistof  the  loop  and  that  its  up,K.r  portion  .s  normally  the  portion 
nearest  the  Stomach.     As  Jp  after  Ux.p  is  examined,  .f  the  mtestn,e  ka.ls  m  an 
unwS  direction  the  color  becomes  pal.r.  and  the  walls  become  thicker  own  g  to  the 
vE.- con^iventes  and  to  the  increase  in  the  submucous  and  ■^•«^"J»^  ^^^'^^    ,.^„^ 
Oti,>  r  methods  of  locating  with  accur.icy  a  given  coil  of  lx>wel  are  ( i)  bv  m.  ans 
of  the  length  of  U^e  vasa  rect^  (3-5  cm.  in  the  upper  and  i  cm.  or  less  .n  the  lower 
«>iSonr  (2)  by  the  vascular  loo^  from  which  the  vasa  recta  originate,  which  are 
Sa^  in  the  first  four  feet  of  th^mesentery.     Secondary  U^ops  appear  as  we  g.> 
farther  down   until  in  the  lower  third  there  is  a  net-work  of    .>ops  ;  (3    by  the  loops 
or    ■  kinetre^"  rt  the  intestinal  attachment  of  the  mesentery.  »--t  v.s^le  by  trans- 
mitted liffht      Below  the  first  eight  feet  these  lunettes  disappear  (Monks) 

?SofoJr-ior  temporary  relief  of  obstruction  or  distention  or  for  the  removal 
of  a  fordgn  b^y-i«  done  at'as  Iowa  point  as  circumstances  permit,  through  a 
transverse  incision  at  the  part  opposite  the  mesenteric  attachment. 

F^rZoZ-L  establishment  of  a  permanent  fistu  a  f..r  the  purpose  if  it  is  a 
/«•««; /?mo7  feeding  the  patient  in  cases  of  obstruction  of  the  alimentary  tract 
^tovTi  openingTor  if  it  is  an  i/roslom;  of  relieving  fecal  accumulation  m  cases 
of  otetructZ  It  a  ower  point-is  done  by  suturing  the  selected  knuckle  o  gut  to 
i^S  peritoneum  by  a  double"  line  of  sutures  and  openmg  the  l«wel  between 

^^^"^En/er^rtomv  and  .ntrro-anastcmosis  (either  lateral  or  end-to-end)  require  for 
their  performance,  so  far  as  anatomy  goes,  application  of  the  facts  and  principles  to 
which  reference  has  already  been  made. 

THE  LARGE   INTESTINE. 

The  ireneral  plan  ut  the  large  intestine  has  already  been  given  (page  1617).     It 
is  easTlv  cuSirhed  from  thefmall  intestine,  not  so  much  by  its  greater  sue  as  b> 

'^'^heTSof'-'the^tS  i^ntirefr'o^XrroTrhrappendix  to  the  beginning 
of  thlrlctuS  is?  according  to  Treves,  about  ..4  -.  (4  ft  «  -  )  -  ^^  '-"  ^.^  " 
(^\n  \  less  in  woman.  The  extremes  were  2  m.  (6  ft.  6  m.  )  and  i  m  (t,  it.  3  m.  )• 
^xldinTthe  duld  part  of  the  rectum,  the  capacity  decr^ses  from  .d>ov.  Ow.rig 
both  to  variation  and  to  occasional  cases  of  «'''^-"'-,'^°"';«^;„'%=V"  in  to  .1  cm 
tention  the  diameter  is  very  uncertain.  It  may  vary  from  7  cm.  (  2^  in  )  to  3- 5  cm. 
(i*Tn)  without  the  more  extreme  figures  implying  a  pathological  condi  o„^ 

*  Structure.-The  mucous  coat  of  the  large  intestine  agrees  in  its  essential 
structure  with  that  of  the  small  gut,  consisting  of  a  stroma  resemb  mg  adenoid  t.ssi.e 
covered  by  as  ngle  laver  of  columnar  epithelium  exhibiting  a  cuticular  border.  The 
chef  difference  on  the  other  hand,  is  (he  absence  of  villi,  in  consequence  of  which 
Sr  velvety  appearance  imparted  by  the  latter  is  not  seen  in  the  large  intestine^ 
VrivuirconniVentes  are  also  wanting,  although  there  are  P';"J-.'^t>""5,.>";"  f^ '^^^f;^ 
ffu  involving  all  or  a  part  of  the  coats  internal  to  the  serous  tunic.  Tne  muscularis 
ScosL  IrKegular'^in  its  development,  being  feebly  represented  in  the  colon  and 

"^'^?KLS'^';iS;^"in  general  resemble  those  of  the  small   intestine, 
but  are  lal^ger  (about  .45  "im.  in  length),  and  form  a  more  regular  and  less  inter- 


1658 


HUMAN   ANATOMY. 


nipted  layer  of  parallel  tubules.  The  largest  ones  are  in  the  rectum,  where  they 
measure  7  mm.  (Verson).  The  lining  of  the  glands  is  conspicuous  on  account  of 
the  great  number  of  goblet-cells,  which  in  the  middle  and  upper  parts  of  the  tubules 


Fio.  1406. 


iig 

or  Liebtrrkiibirs  xtaridi. 

often  exist  in  such  profusion  that  the  ordinary  cells  are  almost  entirely  replaced  ; 
towards  the  deepest  part,  or  fundus,  of  the  glands  they  are  comparatively  infrequent. 
The  presence  of  goblet-cells  in  such  numbers  accounts  for  the  considerable  amount 
of  mucus  normally  poured  into  the  large  intestine. 


Fio.  2407. 


Litfberkufan's  j{!andS' 


Solitary  lymph-nodulc. 


Murr>u<t  coat 


Submucous 
coat 


.■wrous  coat 


LoriKitudinal  section  of  ascendinit  colon,  showing  fceneral  arranKcment  of  coats  and  solitary  lymph-nodule.     X  30. 

The  lymphatic  tissue  in  definite  collections  occurs  as  solitary  nodules  only, 
Peyer's  patches  being  absent  within  the  large  intestine.  The  lymph-nodules,  which 
occupy  a  portion  of  the  submucous  coat  as  well  as  the  mucosa,  are  largest  and  most 


THE  LARGE  INTESTINE. 


1659 


nodules  are  so  plenulul  that  they  form  .n  P^"^^    j^^^  ^^.^^^^  ,„,jieies  are  1«»  fre- 

.  <.ucnt  in  the  colon,  but  arc  again  numcr- 

Fio.  i40«.  _  ^^^  .^  j^^.  ^^,^,„       rhey  are  Renerally 

of  larger  size  than  in  the-  small  intestine, 
measuring  from  1.5-,^  mm.  in  diameur. 
and  are  situated  at  the  iHrtti.m  of  pit-ltke 
depressions  on  the  mucous  surface  mto 
which  the  nodules  project. 

The  •obmucou*  coat  closely  cor- 
responds with  the  similar  areolar  tunic  of 
the  small  intestine,  allowing  ot  lairly  free 

Fio.  1 400- 


Portion  of  mucota  of  lar^c  < 
berkiihns  K'anJ"  '■■'"  leiiKthwi« 
mcnts  conuin  mucus  and  are  '  gol. 


•le.  nhowine  Lie- 
iiy  enilhelial  ele- 
oelli.''     <  2J5. 


Fio.  i4>o. 


Muro«  ol  lar«  intmiline  sectioned  parallel  to  free 
.urfice^-vJini  Lieberkuhns  ulands  cut  croMWise; 
Xtd'^jTmtJyb,  intervening  .tromaof  mucous  mem- 
brane.   X  W5- 

Fio.   1411. 


Peritoneal  coat 


i_Adipose  limue 


Artery 


Portion  of  descendine  colon,  somewhat  'l]»«"f|^;?J"»' 
ing  sacculations.  lOTM,  and  epi^Io'i  appcntw 


Longitudinal  section  of  epiploic  appendage. 


fii';r=J:.ss^r.xr»^^^;£^^^^^^^^^^ 


i6te 


HUMAN  ANATOMY. 


Maroutcual 


The  mutCttUr  coat  consists  of  a  thicker  layer  of  interna]  circular  fibres  and  of 
an  pxternni  lonK:itu(linal  one,  the  fibres  of  which  are  in  nu>st  places  collectetl  inl.. 
three  bunds.  Although  lon^itudinul  fibres  exist  between  these,  they  are  few  iiixl 
apparently  not  quite  universal.  Beginning  in  the  c*cum,  :it  the  Ul^M.■  i.f  the  vcrnii 
form  appendix,  the  three  bands,  or  titHiu  coli,  continue  alonjj  the  large  intestine  as  far 
p,g  as  the  sigmoid  Hexure,  over  whiili 

and  the  rectum  the  hands  an- 
only  two,  and  no  longer  sharjiy 
defined.  In  the  rectum  ont-  is 
on  the  front  and  the  other — the 
stronger— behind.  The  circul.ir 
fibres  increase  very  much  tow  ards 
the  end  of  the  rectum,  the  muscu- 
lar apparatus  of  which  will  reci.i\  e 
special  description  (page  1675). 

The  aeroua  coat  which  once 
surrounded    the   gut,  in    certain 
places  disappears  during  de\el<>p- 
ment.  and  in  others  its  arrange- 
ment becomes  modified   by   now 
relations    with    other    peritoneal 
layers.       These   features  will   be 
described    with    the    parts    con- 
cerned.       In   structure   it  corre- 
sponds  with   the  serous   coat  of 
other  parts  of  the  intestinal  tube. 
The  appendicea  epiploicae 
are  little  fringes  or  bags  of  perito- 
neum containing  fit  hanging  from 
the  large  intestine.       They  may 
be  as  much  as  2. 5  cm.  ( i   in. )  in 
length,  and  are  very  prominent  in 
fat  subjects,  but  in  thin  ones  may 
be  overlooked.     They  are  found 
particularly  on  the  inner  aspects 
of  the  ascending  and  descending 
colon   and  on   the   lower  one  of 
the  transverse  colon.      It  is  often 
stated  that  they  occir  along  one 
of  the  bands,  but  this  relation  is 
at    least    not  constant,   although 
they  are  generally  arranged  in  a 
single  line.    They  are  found  al.so 
on  the  sigmoid  flexure.    It  is  usu- 
ally stated  that  they  are  not  pres- 
ent during  childhood.     Oddono.' 
,      ,, ,  ,      ,   ,  however,  has  shown  that  they  ap- 

pear m  the  fifth   month  of   fcetal   life,   first  on  the  descending  colon  and  sigmoid 
flexure.     We  have  seen  them  before  birth. 

The  blood-vessels,  lymphatics,  and  nerves  of  the  large  gut  in  general 
oilow  the  arrangement  already  described  in  connection  with  the  small  intestine 
(page  1642). 

THE   C^XfM. 

The  caecum,  or  blind  g.it,  the  first  p.irt  of  the  large  intestine,  is  a  pouch  haniMnu 
downward  at  the  junction  of  the  ileum  and  colon,  fro-.T>  which  the  vermiform  appendix 
arises.     The  ileum  opens  into  the  large  intestine  '     a  transverse  orifice  placed  in- 
'  Dal  Bollettino  della  Societe  Medico-Ch       ,.  a  di  Pavia,  1889. 


Serous  cctal 

Transverse  section  of  injected  larite  intestine,  showing  .listribution 
of  arteties  to  coats.     >  30, 


THE  C/ECIM. 


16'Si 


Anterior  band 


AKrixlitiK  loi.jti 


temally  and  somewhat  pmtcriorl> .  Fn.m  the  t..|.  <.l  th.-  ileum  ;.  deep  furr.«»  p.-;^ 
Seiorlv  |«rtly  ar..u.ul  the  RUt.  ami  a  U-hs  ...ark.,!  onv  h  louml  .n  l...„t. 
ffioZh  starting  a.  just  .tated.\he  furnm.  at  once  .'  a  lutle,  ...  a.  t..  rq.rc-- 

«nM  uly  the  mUUIle  l.f  the  orirtce.     Th.-,^-  .erve  a,   .  .nal  Unnulary  Utween 

t^e  c*cum  ami  the  colon.  « hk  h  are  much  alik,  r  .  naracter>      The  averaKC 

K Tthe  aecum  in  the  a<lult  is  U-tween  6  .  .m.  (aN.ut  2;.  .n.  ).  anU  «* 

br^dthab..ut  S  cm.  i^'i  in.).'  The  l«mls  o  .  •  colon  are  .ontimu-.l  onto  the 
r^um  of  the  adult,  and  terminate  at  the  orinin  ...  <he  append.x  One  hand  «  m 
[^nld  the  othe  two  externally  ami  intern..lly  at  the  back  The  ..arts  Utween 
thrb^n  b  are  irenerally  expande<l  p..uches.  which  may  U-  suWivide.1  by  honz.mt.d 
^nsSSon'  There  Ire  two  chief  forms  of  c.^cum  with  sever.d  mu.or  mod.tKa- 
tions:  the  first  is  a  persistence  of 

the  foetal  type,  in  which  the  c;i-cum  ^^'o-  '*'J 

has  the  »ha|)e  of  a  cornucopia  bent 
towards  the  left,  with  the  tapering 
end   continuetl   as   the   vermiform 
appendix  ;  the  other,  which  is  the 
usual,    and   occurs  in  from  9«-94 
per  c  t<t.  of  adults,  is  due  tc  the 
part  ••.-iween  the  external  and  the 
anterior  band  Rrowing  out  of  all 
proportion,  so  that  the  pouch  be- 
tween  them    becomes    the   lowest 
part,     pparently  the  apex,  the  ap- 
pendix  arising  from   the   internal 
posterior  side  near  the  ileum.     In 
extreme  cases  the  two  may  be  very 
close   together.      \'ery   rarely  the 
cacum  is  symmetrically  sacculated, 
with  the  appendix  at  the  lower  end. 
To   understand  the  interior 
of  the  caecum  it  must  be  remem- 
bered that  the  end  of  the  ileum  is 
thrust  in  at  the  angle  between  the 
colon  and  ctecum  in  such  a  way 
that  originally  in  fcetal  life  all  the 
coats  were  involved.     The  serous 
coaf  is  replaced  by  areolar  tissue 
where   two  layers   come  together 
and     new    longitudinal    muscular 
fibres  are  subsequently  developed 
which  do  not  enter  the  folds  ;  how- 
ever, the  original  longitudinal  mus- 
cular layer,  as  well  as  the  circular 
one,  does  so.     The  latter  is  thick- 

as  U  aSlch«  Stul'ii^  S^n  tT^e  surface  of  the  c^um  below  and  the  lower 
swe  Hn^of  the  colon  above  ;  thus  the  upper  of  the  two  lips  of  the  elhpt.cal  openm|,' 
is  composed  of  colon  an<l  ileum,  the  lower  of  ileum  and  caecum.  They  form  promi- 
nent shelf-like  projections  into  the  large  gut,  opposite  the  external  furrows  and 
constitute  the  Keo-c«cal  valve  (valvula  coliV  The  folds  meet  at  the  ends  of 
the  opening,  forming  single  continuations  or  rfUnacula.  of  which  the  postiri or  is 
much  the  larger.  It  often  extends  acr.«s  the  posterior  to  the  lateral  aspect  of  ;  e 
eut  The  two  segments  converge,  but  at  different  angles.  The  upper,  slan.  .^g 
^mewhat  downward,  is  apr-roximately  horizontal,  while  the  lower  is  n^"re  "early 
vertical  The  orifice  of  the  ileum  between  these  folds  is  elongated  wlieii  ll.e  gut 
s  distended  the  post^nor  end  being  sharper  th.,n  the  anterior.  The  <l,anie,^  o^ 
the  segments,  measui.d  from  the  origin  to  the  free  edge  on  35  inflated  and  cried 
>  Berry  :  The  Anatomy  of  the  Caecum,  Anat.  Anzeiger,  Bd.  x.,  1895. 


IWum 


R«Kinnir  ;   ■> 
terior  wall  rerii 
form  appendix. 


,,    aomewhat  inflatrd  ;  (mrt  nl  an- 
..^aecml  valve  ami  orifice  o(  vt-rmi- 


ififia 


HUMAN  ANATOMY. 


specimens,  is  as  follows:  average  of  upper  segment  25  mm.,  of  lower  33  mm. 
The  largest  pair  was  an  upper  of  37  mm.  and  a  lower  of  44  mm. :  the  smallest  ol 
12  mm.  and  3  mm.  respectively.  The  last,  perhaps,  was  pathological  ;  the  next 
smallest  was  14  mm.  and  19  mm.  We  have  seen  a  caecum  with  the  upper  seg- 
ment entirely  wanting.  The  absence  of  both  has  been  observed.  The  average 
length  of  the  ileo-c£ecaI  opening  on  30  similar  specimens  was  31  mm.,  the  e.\trenies 
being  46  mm.  and  21  mm.  It  is  probable  that,  o»  ing  to  the  shrinking  of  the  tissues, 
these  dimensions  of  the  opening  are  excessive.  Although  the  lower  fold  is  the 
larger,  the  upper  overlaps  it  almost  invariably,  so  that  when  the  valve  is  closed  the 
two  edges  do  not  come  in  contact,  the  orifice  being  closed  by  the  application  of  the 
lower  fold  to  the  under  surface  of  the  upper  one.  Inflated  specimens  show  that 
the  upper  fold  is  tense,  while  the  lower  remains  flaccid.  .Much  difference  of 
opinion  exists  as  to  the  completeness  of  the  closure  of  the  ileo-crecal  valve,  and 
experiments  do  not  agree.  If  the  experiment  of  injecting  water  or  air  from  the 
colon  be  performed  in  situ,  the  closure  is  more  likely  to  be  perfect  than  if  the  parts 
have  been  removed.     These  experiments,  however,  do  not  represent  the  true  con- 


FiG.  1414. 


AscemliiiK  colon 


Anteritir  hand 


lleoHTarcal  artery 
— ■  Superior  ileo-ca-cal  fossa 


Mesenlery 


Meso-appendix 
Vermiform  apjieiidix/ 
Ceecum  and  related  structures  seen  from  the  left. 


Ileum 


Appendicular  artery 


ditions  during  life,  since  the  tonicity  of  the  muscular  fibres  of  the  gut  is  lost,  and, 
ill  tlie  opened  abdomen,  the  pressure  of  the  viscera  on  the  end  of  the  ileum  is  less 
than  normal.      In  life  the  valve  probably  is  efficient. 

The  orifice  of  the  vermiform  appendix  is  very  variable.  In  some  cases 
the  cipciiiii  narrows  to  it  so  gradually  that  it  is  hard  to  say  where  it  begins  ;  in 
others  it  fjegins  suddenly  with  an  oval  or  round  opening  measuring  from  5  mm.  or 
less  to  I  cm.  or  more.  The  valvr  w  hich  often  is  found  at  the  orifice  is  not  usiially 
a  true  valve,  but  the  projection  made  by  the  wall  at  the  union  of  caciini  and  ajipen- 
dix  in  the  entering  angle  when  it  arises  obliciuely.  According  to  Struthers,  there  is 
nf)  valve  when  it  arises  at  right  angles.  Owing  to  its  usual  upward  course,  the  fold 
is  most  often  on  that  side  when  present.  We  ha\e  seen  a  true  valve  as  a  small 
independent  fold  ;  usually,  however,  there  is  no  effective  guard  to  the  entrance  of 
the  appendix. 

Position. —  The  ca-  .m  is  situated  in  the  right  iliac  fossa,  resting  on  the  iliac 
fascia  covering  the  ilio-p.,o;      muscle,  above  the  outer  part  of  Poupart's  ligament. 


m 


THE  C^XUM. 


1663 


about  half  below  and  half  above  the  level  of  the  anterior  superior  iliac  spine.  Sorne- 
S^infe  to  the  shortness  ..f  the  ascending  coon,  the  cu-cu.n  rc-mains  in  the 
S'isition  under  the  liver,  or  it  may  be  arrested  at  any  p;irt  of  its  descent.  It 
Sra?d  "hangs  down  into  the  pelvis,  and  when  the  lower  part  u  the  >"esemcry  is 
"onV  particulaVly  if  the  lower  part  of  the  ascending  colon  be  not  attached  to  the 
n^fmor  wall  it  may  be  very  freely  movable.  In  cases  of  „usenUr,nm  .ommune 
K  1ms  to  be  no  anatomical  reason  why  it  should  not  be  anywhere  I  he 
c^um^  sometimes  turned  up  over  the  lower  part  of  the  ascending  colon  but  ue 
c^not  aeree  with  Curschmanns '  statement  that  this  is  not  rare  In  these  cases  the 
aCndffriseT^^om  near  the  highest  point  of  the  c*cum.  VVe  have  seen  the  cecum 
fn  The  pmbtlTcal  region  with  two  vertical  coils  of  small  intestine  occupying  Mk-  right 

"^"''structure.-The  description  of  the  structure  of  the  large  intestine  already 
given  (page  1657J  applies  in  general  to  the  aecum.     Its  mucous  membrane,  like 


Fig.  I4I5- 


Lymph-nodules. 


Lieberkiilins  ttlands 
Groups  ol  tal<«ll8 


Mucous  coat 


Submucoua  tiuue 


LonKitudinal  section  throuRh  lunction  of  appendix  with  circuni.    V  n. 


that  of  the  rest  of  the  large  intestine,  has  no  villi.  This  change  occurs  near  the 
ma  gS  of  each  segment  of  the  ileo-ca-cal  valve,  the  villi  gradually  d.mm.sh.ng  and 
finally  disappearing  before  the  free  edge  of  the  folds  is  reached  (  La nger).  The 
KndLf  lo^n^ntudinal  muscular  fibres  always  en.l  at  ^h^"  ^ase  of  the  aprn-^^^^^ 
the  precise  manner  of  their  termination  is  uncertain.  According  to  .Struthcrs  eac^i 
band  bifurcates  as  it  approaches  the  appendix,  and  the  divisions,  meeting  hose  o 
the  others,  form  a  ring  around  a  weak  spot  close  about  it.  .\ccord.ng  to  Told  the 
ring  is  formed  by  the  circular  layer.  The  arrangement  is  not  always  ^''''^  «"  "^S 
incline  to  think  the  latter  the  more  common.  The  coats  of  the  ca-cum  ■''r-  «"  """^ 
in  the  appendi.x.  The  lumen  of  the  latter  is  small,  except  near  the  entranc.  ..nrt 
the  walir  may  be  in  contact.  The  lymph-no.lules  of  the  appendix  are  exce«l.ngly 
numerous  and  large,   in  places  fusing  into  masses  of  considerable  size,  which  en- 

>  Deutsches  Archiv  fur  Klin.  Med..  lUl.  liii.,  1894. 

'  EdinbufKli  Mediiat  Journal,  1S9.V 

•  SitzuHRsber.  Acad.  Wissen.,  Wien,  Bd.  ciii.,  1894. 


1664 


HUMAN  ANATOMY. 


croach  upon  the  mucosa  and  its  glands  to  reach  almost  the  free  surface.  The  la)-er 
of  circular  muscular  fibres  is  i  mm.  thick,  or  abom  twice  the  thickness' of  the  lon- 
gitudinal one.  Both  layers  have  interruptions,  so  that  the  submucous  and  subperi- 
toneal layers  are  in  places  continuous.  This  occurs  particularly  along  the  insertion 
of  the  fold  of  peritoneum  called  the  mesentery  of  the  appendi.x. 

The  vermiform  appendix  (processus  vermifornis)  is  a  long,  slender,  worm- 
like  diverticulum  from  the  ca^um,  formed  of  all  the  coats  of  the  intestine.  Its  length 
varies  from  i  cm.  (^3  in.)  to  24  cm.  (9^3  in. ;,  the  average  being  probably  about 
8.4  cm.' (3^  in.).  Monks  and  Blake,' Irom  the  records  of  641  autopsies  at  the 
Boston  City  Hospital,  give  the  average  length  as  7.9  cm.  (3  in.  »,  with  the  extremes 
as  above.     Berry  finds  that  the  appendix  is  on  the  average  about  i  cm.  longer  in 


Flo.  1416. 


Longitudinal  muscle 


.Circular  muscle 


OI>liquely 
cut  glands 


Submucous 
coat 


Transverse  section  of  vermiform  appendix,    x  12. 


the  male  ;  others  find  no  particular  difTerence.  The  diameter  at  the  base  is  6  mm. 
and  at  the  apex  5  mm.  Its  usual  origin  is  .i  .n  the  postero-median  aspect  of  the 
cecum.  According  to  Berry,  this  occurs  .11  more  than  90  per  cent.,  the  point  of 
origin  being  i .  7  cm.  distant  from  the  end  of  the  ileum.  This  is  very  important  as 
showing  a  relatively  fixed  point  of  origin,  as  the  general  direction  of  the  appendix  is 
very  uncertain.  That  of  the  distal  half  especially  is  largely  a  matter  of  chance. 
Moreover,  the  position  after  death  is,  except  in  certain  cases,  no  guide  to  that 
during  life.  The  appendix  is  attached  to  the  caecum  and  to  neighboring  structures 
by  a  |>eritoneal  fold  to  be  descrilied  later.  If  this  fold  be  long  and  narrow,  the 
movements  of  the  appendix  are  much  restricted  ;  if  the  base  of  the  fold  be  short 
and  its  attachment  to  the  a|)pendix  a  long  one,  the  appendix  is  thrown  into  coils. 

'  Fawcftt  and  Blatchford  (for  the  avt,  „v!  length)  :  Proceetlings  of  the  Anatomical  Society 
of  Great  Britain  and  Ireland,  Journal  of  Anatomy  and  PhysioloR)-,  vol.  xxxlv.,  1900. 
'  Boston  Medical  and  Surgical  Journal,  Noveinber  17,  1902. 


THE  CiCCUM. 


1665 


Thi,  to  a  ereater  or  less  extent,  is  the  normal  condition.  There  is  no  doubt  that  in 
7he  .^iSt  Srity  of  cases  the  appendix  is  wholly  behind  the  c«:um  meswl  to  it 
or^iTt  Monks  and  Blake  fiund  a  reference  to  this  point  in  the  records  o 
«2  autoi  It  was  'down  and  in"  179  times,  "behind  '  with  no  statement  o 
the  dSrio4  times,  "down"  79  times,  and  "in'    62  Umes.     Jhus  in  almost 

hree-qSers  of  the  cases  it  was  in  one  of  these  positions      It  ran  ".»P     5^  tirn". 

•uD  and  in"  M  times,  and  "up  and  out"  29  times.       n  (,  cases  it  was     out. 

Sly  in  18.  on  the  right  of  the  caecum  m  19.  and  behind  it  in  75-    ^oUl  absence 
ofihe  appendix  is  extr,^ely  rare,  but  has  been  observed  by  ourselves  and  others. 

ni.ii..,.ti«n  of  the  C«Tlty  of  the  Appendix.— The  adenoid  tissue  of  tiie  yermiform  ap- 
Coinadent  with  this  at^Wj^y '!.A,''D2'^i}"    Ribbert*  found  in  400  specimens  more  or 

f»iS„-i5.^'S2r^&      ^^:rIiBr^i^  cW^e 

After  fifty  it  occurred  in  more  than  »>r«r  cent     He  found^^ver^^^^^^  ^^i'^^^^ 

SrfT  2w'°™<R.SS»  S'.i^S'SSphi  <*  ft.  w^dix  to  <*i  w  « .to 

middle  life. 

Peritoneal  Relations.— The  caecum,  being  originally  an  outgrowth  from  the 
convfx"de  of    he  primitive  intestinal  loop,  is  completely  'hovered  by  peritoneum 
3  has  no  mesenter?,  since  the  mesentery  of  the  ileum  passes  direcriy  o  the  colon. 
The  aopendbT^inT  he  original  end  of  the  c«cal  pouch,  is  cci- f^iuenUy  also  com- 
Ilrterv  CS  with  peritoneum.     When  the  ascending  colon  has  c- me  to  lie  in  the 
SLnk  the  posterior  layer  of  its  mesentery  degenerates  in^^o  areolar  tissue,  fusing 
wfth  that  ri^uftin?  from  the  degeneration  of  the  parietal  pentoneum  behind  it  and 
bv  the  same  process  the  back  of  the  colon  is  attached  by  areolar  tissue  to  the 
abdominTwalfbehind.     This  condition  almost  always  ends  a  short  distance  above 
t^e  c^utn        t  b  far  more  common  to  find  the  lower  third  of  the  ascending  colon 
lith  Sneum  on  its  posterior  suriace  than  to  find  none  on  the  upper  posterior 
nit  d   he  ca^"m      Thi^condition,  indeed,  does  occur,  we  having  seen  it  at  birth  ; 
but  it  is  ve^  exceptional.     From  the  preceding  facts  it  follows  that  the  c^cum 
and  the   appendix   can   have  no   mesentery  in  the  strict  sense  ;    nevertheless,  the 
termt«KV  ^^  appe,ulix,  or  mescappendix  ( mesenteriolum  processus  vermi- 
oralsTTs  applied  to  an  almost  constant  fold  of   peritoneum,  presumably  caused 
Khe  arterv'^o    the  appendix,  which  usually  is  attached  to  neariy  the  entire  length 
ofthat  orgJn      Autli^rities  differ  widely  as  to  how  far  the  »!"^°«  «";^hment  ex- 
tends afi  the  appendix.      Beyond  question  it  is  very  variabe.      According  to 
Monks  and   Bla'.e   it  extends  nearly  o."  quite  to  the  end  in  fully  one-half  of  the 
Ss«   and  Tn  mosi  of  the  other  half  it  reaches  or  passes  the  middle  of  the  apj^ndix 
hsieneral  appearance  is  triangular,  but,  according  to  both  Jonnesco' and  Berry, 
with^whom  we^ree.  it  is  morlproperiy  described  as  quadrilateral.     One  side  runs 

'  American  Journal  of  the  Medical  Sciences,  1891. 
'  Virchow's  Archiv,  Bd.  cxxxii.,  1893. 

'pr"oceedinS^'^the  A^omical  Society  of  Great  Britain  and  Ireland,  Journal  of  Anat- 
omv  and  Physiolojfv,  vol.  xxxiy.,  igoo. 

■ :  ?hTS1^ll -^TiCS/Tol^K^^^^^  Anatomy  of  the  Vermiform  Appendix, 

Edinburgh,  1897. 

105 


1666 


HUMAN  ANATOMY. 


along  the  proximal  half  or  even  the  whole  length  of  the  appendix,  one  is  free,  and 
the  other  two  are  attached  to  the  left  side  of  the  mesentery  and  to  the  cacum 
respectively.  These  latter  are  not  readily  distinguished  from  each  other;  hence  the 
triangular  effect.  The  artery  of  the  appendix  enters  the  fold  on  the  back  of  the 
caecum,  and  runs  at  first  from  5  mm.  to  i  cm.  disUnt  from  its  free  edge,  which 
gradually  approaches  it.  Although  the  fold  may  terminate  before  reaching  the  end 
of  the  appendix,  it  does  not  follow  that  the  whole  of  the  latter  is  not  enclosed  in  peri- 
toneum, since  under  normal  circ  ^stances  it  always  must  be.  The  course,  shape, 
and  size  of  the  meso-appendix  aie  very  irregular.  It  is  almost  invariably  so  short 
that  the  proximal  half  of  the  appendix  is  thrown  into  coils.  We  have  seen  this  fold 
attached  to  the  right  side  of  the  mesentery,  as  well  as  not  attached  to  it  at  all. 
Sometimes  it  runs  upward  along  the  posterior  part  of  the  left  side  of  the  colon,  so 
that  the  appendix  is  vertical  ;  at  other  times  it  is  attached  to  the  floor  of  the  iliac 
fossa  ;  and  very  rarely  it  is  wanting.  In  the  female  adult  a  secondary  fold  can  very 
often,  but  by  no  means  always,  be  traced  from  the  meso  appendix  to  the  broad 
ligament.  This  fold  is  probably  due  to  the  persistence  of  one  which  in  the  fcetiis 
often  connects  the  appendix  or  caecum  with  the  early  ovary  and  the  oviduct.  The 
lymph-node  which  the  meso-appendix  is  said  to  contain  we  have  seldom  found. 

It  happens  frequendy  that,  from 
Fio.  1417.  pathological  causes  by  which  ad- 

r  nesions  have  changed  the  perito- 

neal relations,  the  appendix  lies 
behind  the  peritoneum.  Fergu- 
son found  it  so  77  times  in  200. 

Pericaecal  Fossae.  —  An 
indefinite  number  of  fosss  or 
pouches,  all  more  or  less  variable, 
are  to  be  found  about  the  caecum. 
The  two  following  are  usually 
demonstrable,  although  not  so 
constant  as  held  by  some  authors. 
The  superior  ileo-ceecal 
fossa'  (Fig.  1414)  is  roofed  in 
by  a  peritoneal  duplicature,  the 
superior  iUo-cttcal  fold,  which, 
starting  from  the  right  surface  of 
the  mesentery,  curves  over  th'; 
end  of  the  ileum  from  behind  forward.  The  attached  border,  in  which  the  ileo-colic 
artery  lies,  runs  along  the  colon  just  where  it  joins  the  ileum,  and  is  usually  con- 
tinued forward  down  onto  the  front  of  the  caecum  for  a  sho--*-  'listance.     The  pouch 

"  die 


Ileum,  turned  up 


Inferior  iIeo.c(ecal 


Meso-appendix 


CVrum  from  inner  side  and  below. 


0  the  left,  but  if 

1  to  it  that  the  »o^sa 
It  is  most  c  -     ct 

careful  examination  often 
Berry  found  this  fossa 


between  this  fold  above  and  the  end  of  the  ileum  below  - 
ileum  be  distended,  the  free  edge  of  the  fold  is  so  closely 
i.s  easily  overlooked.     The  depth  of  the  fossa  may  reach 
in  infants  and  frequently  obliterated  in  middle  life,  although 
reveals  a  small  fold  and  recess  that  may  be  overlooked, 
absent  in  12  of  100  cases,  all  of  the  12  bein^  over  forty  years. 

The  inferior  ileo-csecal  fossa'  (Fie'.  1417)  is  less  constant  and  much  mure 
complicated  than  the  preceding.  Its  practical  importance  is  greater,  since  it  may 
contain  the  appendix.  To  display  it  the  ileum  must  be  drawn  upward  and  the 
appendix  downward  and  to  the  right ;  the  caecum  may  or  may  not  require  to  be 
displaced  to  the  right  or  inverted.  This  fossa  is  situated  in  the  entering  angle 
formed  by  the  end  of  the  ileum  joining  the  caecum,  and  is  bounded  on  the  right  by 
the  first  part  of  the  appendix.  The  meso-appendix  shuts  it  in  behind,  and  in  front 
it  is  covered  by  the  inferior  i/eo-ctecal  fold.      The  latter,  which  usually  joins  the 


'  There  is  much  to  be  said  in  favor  of  the  term  ileo-colic,  since  the  pocket  lies  at  the  angle 
of  the  ileum  and  colon.  It,  houe^er,  so  frequently  extend.'^  dounw.ird  to  the  Iroulul  the  c<t:cuiii 
th.it  the  more  usual  nomenclature  is  here  adoptecf. 

'  Known  also  as  the  ileo-colic  fossa,  the  ileo-appendicular  fosta,  etc. 

'  This  is  the  "  bloodless"  fold  of  Treves  or  the  ileo-appendicular  fold  of  Jonnesco. 


THE  C^CUM. 


1667 


n  -so-appendix,  is  in  its  conventional  form  described  as  having  four  sides  :  a  superior 
ok  the  ileum,  a  right  one  on  the  caecum,  an  inferior  joining  the  appendix  or  the 
meso-append  X,  and  a  free  concave  one  looking  towards  the  let  and  "verhangmg 
Thf^ntra^ce  to  the  f,«sa,  which  may  be  nearly  4  cm  (i .4  in. ;  in  dqjtlK  The  fold 
usually  conuins  only  small  vessels,  and  has  been  described  as  "  bloodless  It 
sometimes  contains  muscle-fibres  passing  between  the  ileum  and  caecum.  The  sue 
^  well  as  the  formation  of  this  pocket  is  very  variable.  VVhen  we  consider  the 
extreme  variability  of  the  meso-appendix  which  is  concerned  in  its  typical  forma- 
tbn  it  is  manifest  that  such  must  be  the  case.  Sometimes  the  meso-ap,>endix  is  in 
no  way  connected  with  it.  only  a  small  fold  of  peritoneum  passing  from  the  ileum  o 
die  cJcum  at  the  side  most  removed  from  the  mesentery.    Berry  found  this  fossa  in 

74  P"^^"yj^j^Q.^.Qiig  Fossa.-In  the  great  majority  of  cases  the  fiosterior  sur- 
face of  the  c»:um  lies  free  in  the  abdominal  cavity,  covered  by  its  original  peri- 
toneum     At  a  variable  distance  from  it  the  back  of  the  colon  becomes  adherent  to 
he  ^terior  abdominal  wall  and  to  the  front  of  the  right  kidney  =  h«n;« /h^^.'*; 
or  may  be  especially  if  the  colon  be  drawn  away  from  the  wall,  a  fold  on  either  side 
stretching  fr^^he  gut  to  the  wall.    These  are  the  ligaments  of  the  colon,  the  exler- 
SSheintemJ    The  former  runs  outward  and  downward  from  the  side  of  the 
^ion  along  the  abdominal  wall,  or  perhaps  across  the  lower  end  of  J- J"d"^y ;  "•^'^ 
presents  a  free  concave  border  overhanging  a  pouch  running  upward  and  outward 
The  internal  or  mesian  fold  is  the  more  often  distinct,  and  is  formed  chiefly  by  he 
inser  ion  of  the  mesentery.     According  to  its  degree  of  development,  the  free  ale  - 
form  edge  overhangs  a  pouch,  looking  downward  and  ";'ore  or  Jess    o  the  right^ 
The  fold  may  be  continued  downward  either  to  the  right  or  to  the  left.     In  the 
former  case  it  may  form  a  pocket,  of  which  the  lower  end  opens  upward.     It  is 
cH  th^dore.^tet  with  boththese  folds  well  developed  a  retro-colu  fossa  exists 
wS  is  shown  when  the  caecum  is  turned  up.     Its  greatest  depth  «  in  the  middle 
be£d  the  colo*  and  it  is  continued  downward  on  either  side  under  the  folds 
caused  by  these  ligaments.     Should  either  ligament  be  wanting    there  can  be  no 
Lid  on  that  side.     Some  authors  have  thought  it  best  to  describe  an  external  and 
an  internal  fossa  under  each  of  the  ligaments,  of  which  the  internal  b  the  more  fre- 
quent ;  it  is  more  simple,  however,  to  dercribe  only  one.     The  f<«sa  may  be  sub- 
divided by  a  median  fold.     Very  often  there  is  1 ,0  definite  fossa  at  all.    The  internal 
part  is  more  commonly  well  developed  than  the  external.  „^  .„„„,;„,« 

The  subceecai  fossa  is  an  uncommon  pouch,  sometimes  small  and  sometimes 
large,  situated  above  the  middle  of  the  iliac  fossa.  It  seems  to  be  due  to  an  irregu- 
lar development  of  the  iliac  fascia,  which  forms  a  pocket  in  itself,  with  the  mouth 
above,  guarded  in  front  by  a  semilunar  fold.  The  fossa  is  ined  by  the  parietal  peri- 
toneum It  may  unite  with  the  inner  fold  of  the  retro-colic  fossa,  or  the  two  may 
exist  at  the  same  time.  It  may  contain  the  appendix,  even  a  part  of  the  c«:um. 
or.  according  to  Jonnesco,  coils  of  the  small  intestine.         .      ^     .,  ,.        l        t. 

Blood- Vessels.— The  artery  supplying  the  cscum  is  the  ileocolic  a  branch 
of  the  superior  mesenteric  artery,  which  sends  to  it  both  an  anterior  and  a  larger 
posterior  branch,  which  ramify  downward  over  the  front  and  t«ck  of  the  caecum 
A  large  branch  from  the  posterior  division  nins  between  the  folds  of  the  posterior 
retinaculum  ;  less  constantly  a  smaller  vessel  cours^  in  the  anterior  one.  The 
segments  of  the  ileo-cacal  valve  are  very  vascular  The  artery  of  '*' J""«?fr^ 
appendix  arises  from  the  posterior  division  of  the  ileo-colic,  crosses  the  back  of  the 
ileum,  and  runs  in  the  fold  of  peritoneum  to  the  end  of  the  appendix.  The  mw 
of  the  caecum  are  arranged  on  much  the  same  plan  as  tne  arteries.  That  oJ  the 
appendix  is  relatively  more  important,  receiving  tributaries  from  the  front  and  the 
back  of  the  caecum.     It  passes  behind  the  end  of  the  iK  uin  to  the  ileocolic  vein. 

The  lymphatics  are  divided  into  a  posterior  and  an  anterior  set.  1  he  lormer 
empty  into  small  nodes  on  the  back  of  the  caecum  beneath  its  peritoiveal  covenn^^ 
The  anterior  ones  are  in  or  near  the  fold  between  the  cjecum  and  colon.  The  appendix 
contains  a  1-rge  lymph-sinus  at  the  base  of  tho  fnllicW.  Lymphatics  pass  through 
the  interruptions  of  the  muscular  layer.  They  may  enter  a  node  in  the  peritoneal 
fold  iq  the  angle  between  the  c«cum  and  ileum.     There  are  several  possible  communi- 


i668 


HUMAN  ANATOMY. 


cations  :  one  with  nodes  in  the  mesentery  ;  one  with  nodes  on  the  left  of  the  as- 
cending colon  behind  the  peritoneum  ;  one  with  nodes  of  the  iliac  fossa  ;  and,  in 
the  female,  one  with  the  system  of  the  ovary.  There  is  a  constant  lymph-node  at 
the  angle  between  the  ileum  and  colon.' 

The  nerves  supplying  the  cxcum  and  appendi.x  are  derived  from  the  superior 
mesenteric  plexus.  Their  mode  of  distribution  within  the  gut  has  already  been 
given  (page  1643). 

Development  and  Growth. — At  birth  and  for  some  years  after  the  caecum 
is  very  small  and  the  foetal  or  cornucopia  shape  is  more  frequent  than  later.  The 
appendix  is  relatively  rather  long.  In  eleven  cases  below  ten  years  Berry '  found  the 
average  length  of  the  caecum  28  mm.  and  the  breadth  37  mm.  In  eighteen  cases 
he  found  the  average  length  of  the  appendix  74  mm.  (2  7/g  in. ).  Ribbert  gives  the 
following  lengths  of  the  appendix  :  at  birth,  34  mm. ;  up  to  five  years,  76  mm. 
(3  in. ) ;  from  five  to  ten  years,  90  mm.  (3}4  in. ). 

At  birth  the  caecum  is  usually  higher  than  in  the  adult,  since  it  has  not  de- 
scended to  its  permanent  position  and  the  adhesion  of  the  mesentery  of  the  ascend- 
ing colon  has  not  occurred  in  the  lower  part  of  the  flank.  It  is  often  rather  above 
the  anterior  superior  spine  of  the  ilium.  In  five  of  about  thirty-five  observations 
on  young  children,  mostly  newly-born,  it  was  so  free  from  fixed  attachment  that  it 
could  hardly  be  said  to  have  any  definite  position. 


THE  COLON. 

The  asce  ding  colon  extends  from  the  csecum  to  the  under  side  of  the  liver, 
where  it  ma.:es  a  sudden  bend — the  hepatic  flexure  (flexura  coll  deztra) — and  be- 
comes the  transverse  colon,  which  crosses  the  abdomen  to  the  splenic  flexure  (flexura 
coli  sinistra)  at  the  spleen,  whence,  as  the  descending  colon,  it  passes  to  the  crest  of 
the  ilium.  From  that  point  to  the  middle  of  the  third  sacral  vertebra  it  is  known  as 
the  sigmoid  flexure.  The  three  bands  of  the  colon  or  tanitt  coli,  formed  by  accu- 
mulations of  longitudinal  fibres,  are  each  about  i  cm.  broad.  Their  disposition  in 
the  walls  of  the  gut  is  difficult  to  follow  and  is  not  constant.  The  following  arrange- 
ment is  probably  the  most  usual.  In  the  ascending  colon  one  is  in  front  and  two 
behind,  one  of  the  latter  being  near  the  outer  and  the  other  near  the  inner  aspect. 
On  reaching  the  transverse  colon,  the  anterior  becomes  the  inferior,  while  the 
external  becomes  the  superior,  receiving  the  attachment  of  the  transverse  meso- 
colon. The  internal  also  lies  on  the  upper  surface,  but  behind  the  preceding.  On 
the  descending  colon  they  resume  their  original  positions,  but  tend  to  grow  indis- 
tinct. They  are  still  more  so  in  the  sigmoid  flexure,  and  before  the  rectum  is 
reached  there  are  but  two  bands,  an  anterior  and  a  posterior,  of  which  the  latter  is 
the  stronger.  The  interior  of  the  colon  shows  the  sacculated  condition,  but  there 
are  no  folds  or  valvulae  conniventes  like  those  of  the  small  intestine.  The  solitary 
lymph-nodules  continue,  much  like  those  of  the  jejuno-ileum. 

Relations. — The  ascending  colon  is  in  the  right  flank  against  the  psoas  and 
quadratus  lumborum,  but  does  not  overlap  the  latter  unless  greatly  distended.  It 
lies  in  front  of  the  lower  end  of  the  right  kidney,  projecting  but  little  beyond  its 
outer  border,  with  the  second  part  of  the  duodenum  on  its  inner  side.  It  ends  with 
the  hepatic  flexure,  which  makes  a  large  impression  on  the  under  side  of  the  right 
lobe  o{  the  liver  directly  anterior  to  the  kidney.  It  is  often  completely  covered  in 
front  by  the  small  intestine. 

The  transverse  colon  is  suspended  between  its  beginning,  the  hepatic 
flexure,  and  its  end,  the  splenic  flexure,  like  a  festoon,  forward  and  downward  ; 
for  the  ends  are  near  the  back  of  the  abdominal  cavity.  The  splenic  flexure,  in  front 
of  the  lower  part  of  the  spleen,  is  both  higher  and  more  posterior  than  the  hepatic 
one.  The  transverse  colon  is  covered  abo\'e  and  in  front  by  the  greater  omentum. 
It  runs  along  the  liver,  touching  the  gall-bladder  and  the  greater  curvature  of  the 
stomach,  amimd  which  it  ascends  to  the  spleen.     The  splenic  flexure  m;iy  or  may 

'  Lockwood  :  ProceedinKS  of  the  Anatomical  Society  of  Great  Britain  and  Ireland,  Journal 
of  Anatomy  and  Physiolog)-,  vol.  xxxiv.,  1900. 
'  Anat.  Anzeiger,  Bd.  x.,  1895. 


THE  COLON. 


t6«9 


not  rest  against  the  under  side  of  the  diaphragm,  according  to  its  distention  and 
that  of  the  stomach.  It  rests  behind  and  Jielow  on  the  small  intestine.  It  may  or 
may  not  be  in  immediate  relation  to  the  tail  of  the  pancreas. 

The  descending  colon  descends  partly  in  front,  but  still  more  external  to  the 
kidney,  and  after  passing  the  kidney  rests  wholly  on  the  quadratus  lumlxinim. 
Although  more  externally  placed  than  the  ascending  colon,  it  does  not  usually  j)roje. :t 
lieyond  that  muscle.      It' may  be  very  much  contracted  and  sacculated. 

The  sigmoid  flexure  (colon  siemoideuiii ),  the  continuation  of  the  large  intestuu-, 
begins  at  the  crest  of  the  ilium  as  a  loop  of  very  varying  length,  which  js  attached  by 


I  eft  side  ol  abdomen:  >m«ll  Intefitine  turned  to  risiht.  exposinR  mesentery,  mesocolon  of  desrending  colon,  ,.ii<l 
,  mesusiKmoid. 

a  mesentery,  and  ends  at  the  middle  of  the  third  sacral  vertebra.  Its  usual  length  is 
from  25-56  cm.  ( 10-18  in. ),  hut  is  occasionally  much  longer.  While  it  is  true  that  the 
gut  does  not  always  become  free  at  the  crest  of  the  ilium,  but  may  descend,  bound 
down  closely,  to  the  iliac  fossa  for  some  distance,  it  is  best  to  regard  tli<'  sigmoid 
flexure  as  beginning  at  a  definite  although  arbitrary  point  rather  than  at  the  less 
certain  one  at  which  the  gut  really  has  a  mesentery.  Moreover,  there  is  no  great 
inaccuracy  in  the  statement  that  this  generally  occurs  at  the  crest  of  the  ilium  or 
just  below  it.  The  simplest  form  of  the  sigmoid  flexure  is  a  loop.  If  it  be  a  small 
one,  it  usually  is  made  of  the  last  part  of  this  section  of  the  gut  ;  very  often  the  first 
part  is  but  slightly  free  while  the  last  part  is  very  much  so.    Short  sigmoid  flexures, 


1670 


HUMAN   ANATOMY. 


especially  with  short  mesenteries,  can  hardly  vary  much  from  a  simple  loop  ;  under 
opposite  conditions,  however,  they  may  present  the  most  diverse  forms,  so  that  a 
definite  shape  can  hardly  be  assumed.  The  M-form  is  common.  We  have  seen 
the  sigmoid  disposed  in  three  parallel  vertical  folds  occupying  all  of  the  left  iliac 
fossa  and  overhanging  the  true  pelvis.  As  the  sigmoid  flexure  descends  along  the 
sacrum  it  usually  curves  to  the  right  and  crosses  the  median  line. 

Peritoneal  Relations. — The  lower  part  of  the  ascending  colon  is  very 
often,  for  one  or  two  inches,  completely  surrounded  by  serous  membrane.  The 
ligaments  of  the  colon  (described  with  the  retro-colic  fossa,  page  1667)  occur  more  or 
less  well  marked  at  the  line  where  the  peritoneum  leaves  the  posterior  wall.  Above 
this  the  colon  is  connected  by  areolar  tissue  to  the  kidney.  Occasionally  the  colon 
is  adherent  as  far  as  the  ceecum.  The  non-peritoneal  {lortion  of  the  upper  part  of 
the  ascending  colon  equals  about  one-third  of  its  circumference. 

The  transverse  colon  is  attached  to  the  transverse  mesocolon  and  otherwise 
completely  surrounded  by  peritoneum.  The  transverse  mesocolon,  after  attaining 
its  permanent  condition,  arises  along  the  back  of  the  abdomen  from  one  kidney  to 


Flo.  1419. 


Anterior  band 


Bladder 


Anterior  abdominal  wall  turned 
forward 


'SiKntoid  flexure 
pulled  up 


Mcsenter%-  of 
sigmoid 


Anterior  superior 
spine  of  ilium 


r  supei 
of  iliu 

Recto-vesical  fold 


Sigmoid  flexure  and  rectum ;  sigmoid  has  been  displaced  upward  to  show  its  mesentery. 


the  Other.  It  crosses  the  front  of  the  right  kidney,  the  second  part  of  the  duo- 
denum, and  passes  along  the  lower  border  of  the  pancreas  above  the  duodeno-jejunal 
flexure,  to  end  on  the  left  kidney.  Sometimes  in  the  left  part  of  its  course  its 
origin  rises  onto  the  superior  anterior  surface  of  the  pancreas.  Its  greatest  breadth 
— i.e.,  the  distance  from  its  origin  to  insertion — is  at  the  middle,  and  varies  from 
10-15  cm.  The  posterior  layer  of  the  greater  omentum  fuses  with  it.  The  phreno- 
colic  ligament,  which  runs  inward,  shelf-like,  from  the  left  abdominal  wall  under  the 
spleen,  although  in  acquired  relation  with  the  mesentery  of  the  transverse  colon,  is 
really  a  part  of  the  greater  omentum.  The  latter  hangs  down  from  the  transverse 
colon  over  the  small  intestine,  but  its  relation  to  the  colon  is  not  the  same  through- 
out. On  the  right  it  is  fused  with  the  peritoneum  of  the  anterior  surface  of  the  gut 
and  leaves  it  at  the  lower  border.  On  the  left  it  leaves  the  upper  surface  of  the 
colon,  or  even  the  transverse  mesocolon,  before  the  latter  reaches  the  gut.  Thus 
the  line  at  which  it  leaves  the  intestine  rises  gradually  from  right  to  left. 

The  descending  colon  is  usually  uncovered  posteriorly  by  peritoneum. 
According  to  Lesshaft,'  whose  results  have  been  generally  accepted,  it  lias  more  or 
less  of  a   mesentery  once  in  six  times.     According  to  Symington,'  the  mesenteries 

'  Reichert  and  Du  Bois-Revmond's  Archiv,  1870. 

•  Journal  of  Anatomy  and  Physiology,  vol.  xxvi.,  1892. 


THE  COLON. 


X671 


thus  found  aredue  to  a  displacement  of  the  peritoneum,  which  is  but  loosely  atuched. 
Tn.e  mesenteries  are  pro^^^^^^^  ^^.^^^  ,„  surround  the  gut 

along  the  border  ot  me  uuc  y^  „,„  „(  course  be  an  ndehmle  number  of 

i,  descend,  ac«»»  the  '«"'"'n,J    The  «t'a?hm»no  the  »cr,nn  i.n.n.lly  ne» 

Sf=n'^™=^^*e=Sr.nJ|3^-^-^^^^^^ 

-l;'brea^rr;",«n»;}SSL:5^^^^^^^^^^ 

EVS  -ff?   noT  r^.Tr6're^oni*,rit°:,^:be  .,^;nch  a.  „  em. 

SfSa'Sgl^-p'lti.,^  S:.Ti."'."n7l"mrl"u7;  onea.  pooch,  p,«»nt 

peritoneum  of  the  posterior  wall,  and  ^"'Xfe  '^,^,™  ^e  co^^       iliac  artery. 

7^  erJdTirrnt.'tr.sx  .t^t^s.  a.  »„  .ch  „,  t... 

,h.  colon,  is'  according  to  Tr^"'  ""f""?""!';"'  tJ  ? 'id  that  o ItrUnje 

=io'Tr<f,;'ior;.7r^S£,h3-^^if^^^^^^^ 

the  small  intestine  grows  at  the  rate  of  abo.it  two  '^^^ /"""'i?;  / "^  ^^^^„  the  fact 

which  at  birth  forms  nearly  one-half  of  ^^^J^^^}^'JJ"^''  After  this  the  r  ^*th  of 
assumed  approximately  its  permanent  proportions  (Treves).  '>"*;™,,  ;  ^k  : 
toth  small  and  large  intestine  is  extremely  irregular,  as  shown  by  the  follov. .. 


Obterver. 
Dwight 
DwighL 
Treves. 
Dwight. 
Treves. 
Treves. 


Age. 
10  months. 
10  months. 
I  year. 
3  years. 
6  years. 
13  years. 


Small  Intntine. 

670  cm. 

435  cm. 

490  cm. 


l.mrgc  lnt»tiiK. 
78  cm. 
90  cm. 
76  cm. 
84  cm. 
91.5  cm. 
107  cm. 


As  the  sigmoid  flexure  is  relatively  lar^e  in  the  infant  and  the  pelvis  very  small, 
(he  convexity  of  the  loop  lies  in  the  right  side  of  the  abdomen. 

V«i..ion.._The  mesentery  of  the  -?" 'f-l'lJ-l^UlSen^rk  I^n'e?^^^^^^^ 
«,lon  may  remain  ^"-h/d -^^^  *;°"^^^^^^  ihe^i^Vr  hind   be  so 

dition  known  as  «"<'»''""'",;^??'^^'-  umann^  has  Seen  its  mwentery  long  enough  to  be 
long  as  to  make  secondary  folds.    Curechmann    nas  seen  flexures.     In  the  latter  case 

twisted.    The  nansverse  colon  may  V*„*^ort  *antme  one  or  dot^^  ^^  ^,     Probabtv 

the  ascending  and  the  descendmg  colon  are  .^ost  »^«  *^^J"^^^d  in  the  middle  like  an  V( 
much  more  often  the  transverse  If  «•""  "^V,  *^  *'^J°"|o"^morat  the  left  than  the  right.  A 
with  the  middle  point  at  the  pelvis  .^°„  J!n  This^rt  o"  the  gut,  when  over  large,  may 
double  fold  of  the  transverse  .  ^lon  has  Wn  seen_     ' '?^«  P2^^°^^5i„|"co,„n  may  also  present 

X  S-Eiir  irSSe.  £%&" £.:fre'X.S  o.  tio  .ncce^lve  loia.. 
>  Deutsches  Archiv  fiir  Klin.  Med.,  Bd.  lin..  1894. 


1673 


HUMAN  ANATOMY. 


Blood-Vessela.— The  arteries  of  the  colon  are  derived  from  the  superior  ami 
the  inferior  mesenteric.  The  former  supplies  the  citcum,  the  ascending  and  tlu' 
transverse  colon,  and  a  varying  amount  of  the  descending  colon.  The  supply  of  tin 
latter  is  completed  by  the  inferior  mesenteric,  which  is  iUao  distributed  to  the  sigmoid 
flexure.  The  general  plan  includes  a  series  of  anastomoses  between  neighbor  in(> 
branches,  by  which  long  arterial  arches  run  near  the  border  of  the  gut,  to  which 
they  give  off  irregular  twigs.  There  is  no  system  of  straight  vessels  as  in  the  greater 
|iart  of  the  small  intestine.  In  the  sigmoid  flexure  there  is  a  recurrence  of  the 
superimposed  arches,  which  may  be  three  in  number.  The  superior  hemorrhoidal 
branch  of  the  inferior  mesenteric  artery  runs  in  the  last  part  of  the  mesentery  of  the 
sigmoid,  and  often  divides  in  it  into  two  branches,  which  run  side  by  side  on  the 
hack  of  the  gut  towards  the  rectum.  The  veins  are  disposed  much  the  same  as 
the  arteries,  but  with  a  system  of  straight  vessels  from  the  intestine. 

The  lymphatica,  which  are  many,  empty  into  lymph-nodes  on  the  posterior 
wall  of  the  abdomen,  which  are  a  part  of  the  same  system  as  those  of  the  small 
intestine. 

The  nerves  are  from  the  i,>,peri  )r  and  inferior  mesenteric  plexuses,  which  are 
derived  chiefly  from  the  solar  and  the  aortic  plexus  respectively. 

THE  RECTUM,  ANAL  CANAL,  AND  ANUS. 

The  Rectum.— The  rectum  begins  at  the  middle  of  the  third  sacral  vertebra, 
the  point  at  which  usually  the  mesentery  that  restrains  the  sigmoid  flexure  termi- 
nates. It  was  formeriy  described  as  beginning  at  the  left  sacro-iliac  joint,  but 
this  division,  which  is  unwarranted,   is  falling  into  disuse.     The  rectum  descends 


Fio.  1420. 


RecUl  folds 


„  Bladder 

Seminal  veslite 
■Symphysis  pubis 


Hemorrhoidal  veitii 


Utelhra 

Bulb  of  penis 
Internal  sf>hincter 
LeTator  ani 


Internal  sphint-ter 


Veins  of  mucosa  of  anal  canal  i  * 

Fold  of  mucous  membrane  Kxternal  sphincter 

Sagitul  section  of  pelvis  passing  Ihrouxh  rectum,  anal  canal,  bladder,  and  urethra. 

alimj;  ihe  hollow  of  the  sacrum  and  coccyx,  passes  the  point  of  the  latter,  and  con- 
tinues until  it  reaches  the  lower  and  back  part  of  the  prostate  gland  in  the  male  or 
the  vagina  in  the  female. '  Its  length  is  about  12.5  cm.  (approximately  5  in.  ).  The 
gut  is  then  continued  by  the  anal  canal,  sometimes  called  the  sphincteric  portion  of 


THE  RECTUM,    ANAl.  CANAL,    AND  ANUS. 


1673 


the  rectum,  situated  in  the  thickneM  ol  the  pelvic  floor,  and  directed  downwanl 
and  backward,  makinif  a  sharp  angle  with  the  rectum  pro|K;r. 

¥he  r«i«  pro^r,  having  p^d  t!,e  lip  of  the  coccyx,  rests  on  ihe  leva  or  am 
mu«: le  ahhouKh'^se^rited  from  iTas  well  as  from  the  s;»crum  and  cncyx.  by  tl  e 
deiS  rectal  fLia.^The  rectum,   although  not  exh.b.tu.g  the  iH.ucung  seen  u 
fhe^olon     s  sacculated,  presenting,  when  distended,  usually  three  f -}-«;;'"•  " 
which  the  lowest  and  largci.t.  called  the  ampulla,  may  measure  25  cm.  (y-a  m.  ..  or 
Tven  more   in  circumference.      The  saccule,  are  separated  by  deep  cre.>scs.  pass  ng 
ItoutTo  thirds  around  the  gut.  caused  by  a  folding  m  of  all  the  c.«ts  uUernal  t-  the 
tw^  bands  of  longitudinal  muscular  fibres.     The  folds  form  the  valves  oj  /*'.""'"'■ 
to  be  described  with  its  interior.     In  the  male  the  ampulla  extends  agamst  th.  k,ck 
o^  the  prostate  and  the  lower  part  of  the  seminal  vc-s.cles  and  the  termmal  parts 
the  va-sa  deferentia.  to  all  of  which  it  b  connected  by  areolar  tissue.     A  picket  of 
iri^^um  intervenes  higher  up.  the  walls  of  which,  however,  come  m  cont..ct  wh.n 
^e  hollow  organs  are  distended.     In  the  female  the  end  of  the  ampulla  -  -ga"  st 
he  posterior  wall  of  the  vagina  from  about  opposite  the  level  of  the  ..s  uter  tu  the 
junc?U,n  of  the  middle  and  lower  thirds.     There  is  above  this  a  fold  of  ,H.ntoneu.u 
corresponding  to  that  of  the  male. 


Glands  uf  mucoM 


Levator  ani 


Intrnial  uphincttr 

Luiigitudiiial  muscle 

External  sphinctei 


Elternal  sphincter 


Skin       Anal  glands      Anal  K'aixiii 
Frontal  section  through  anal  canal 


The  Anal  Canal.— This  part  of  the  large  intestine  (pars  analis  recti)  is  situ- 
ated in  the  thickness  of  the  pelvic  floor  and  extends  downward  and  backward.  It 
differs  from  the  rest  of  the  intestinal  canal  in  having  no  lumen  under  ordinary  cir- 
cumstances, when  the  sphincters  surrounding  it  are  contracted.  The  anus  is  the 
very  vaguely  used  name  of  the  termination  of  the  anal  canal.  It  is  deeply  situate.l 
between  the  nates,  especially  in  the  female  :  its  distance  from  the  tip  of  the  coccyx, 
variously  stated  by  different  observers,  may  be  said  to  be  about  5  cm  (2  m.  ) 
Much  confusion  h^  arisen  from  the  difficulty  of  defining  the  Itiwer  end  o  t he  anal 
canal,  since  the  skin,  which  is  puckered  up  by  the  external  sphincter  and  the  cor- 
rugator  cutis  ani,  somewhat  resembles  mucous  membrane,  so  that  the  canal  appears 
longer  than  it  really  is.  The  anatomical  boundary,  the  ano-rcclal  groove,  the  so- 
called  while  lineoi  Hilton,  is  a  slight  zigzag  furrow,  usually  to  l)e  seen  on  the  living 
and  not  on  the  dead.  It  lies  a  little  above  the  lower  limit  of  the  internal  sphincter, 
which  covered  by  dilated  veins,  projects  towards  the  potential  lumen  alwve  the 
external  si.lilnctct,  and  is  I  cm.  or  more  within  what,  on  a  superficial  examination, 
would  be  called  the  anus.  When  the  dUsected  rectum  is  laid  open,  much  is  evidently 
a  part  of  the  skin  which  during  life  is  drawn  into  the  canal  by  the  contraction  of  the 
muscles  •  hence  the  length  of  the  canal  is  very  variously  stated.    .Seldom  does  it 


1 674 


HUMAN   ANATOMY. 


Fio.  141a. 


measure  as  much  as  15  mm.  from  its  upper  end  tn  the  ano-rectal  groove  ;  prubul>ly 
this  distance  is  usually  about  i  cm.,  while  what  may  practically  be  called  the  canal  is 
twice  as  mu^h,  or  even  more.  It  is  longer  in  men  than  in  women.  In  the  male  tho 
beginning  ol  the  anal  canal  is  near  the  lower  part  of  the  prostate  and  the  mem- 
branous urethra,  at  a  point  from  3. 5-4  cm.  in  front  of  and  somewhat  lower  than  tlit- 
tip  of  the  coccyx.  Lower  stil!,  the  bulb  oi  the  ur>.'hra  is  separated  from  the  anal 
canal  by  the  pyramidal  mass'  of  connective  tissue  constituting  the  perineal  My. 
The  latter  is  <if  greater  imporUnce  in  the  female,  and  separates  the  anal  canal  from 
tlif  lower  part  of  the  vagma  and  from  the  vulva.  The  moist  and  dark  skin  which 
is  puckered  up  to  form  the  continuation  of  the  anal  canal  is  at  first  very  thin,  hut 
gradually  assumes  the  appearance  of  ordinary  integument.  The  so-called  anal  glands 
surrounding  the  anus  are  of  two  kinds,  both  of  which  have  their  orifices  in  this  skin. 
Those  nearest  to  the  boundary  line  are  sebaceous  follicles,  and  external  to  them  is  a 
zone  of  large  sweat-glands.  Just  at  the  termination  ot  the  skin  apparently  forming  the 
end  of  the  canal  there  is,  especially  in  the  male,  a  considerable  development  of  hair. 
Structure  of  the  Rectum. — The  mucous  coat  is  thick  and  vascular,  and 
correspop<1s  in  its  ^CTicral  histj'ogical  details  with  the  mucosa  of  other  parts  of  the 
large  intestine.  The  glands  of  Litberkiihn,  however,  are  exceptionally  lai^e,  at- 
taining a  length  of  .  7  mm.  The  muscularls 
mucosa"  is  better  developed  than  in  the  colon. 
The  rec/al  valves  (plicx  transversales  recti) 
are  two  or  three  folds,  exceptionally  four  or 
five,  projecting  like  transverse  shelves  into 
the  cavity  when  it  is  distended,  and  hanging 
loose  when  it  is  not.  They  are  semilunar 
in  shape,  with  the  greatest  breadth  from  the 
attached  border  to  the  free  edge,  ranging 
from  I  cm.  to  more  than  3  cm.  They  cor- 
respond to,  or  rather  are  the  causes  of,  the 
constrictions  between  the  saccules.  They 
contain  all  the  coats  of  the  gut,  except  that, 
chiefly  on  the  posterior  wall,  some  of  the 
longitudinal  muscle-fibres  pass  outside  of 
them,  thus  securing  the  fold.  In  large  folds 
there  b  an  accumulation  of  the  circular 
fibres.  These  folds  tend  to  be  effaced  in 
the  isolated  and  opened  rectum,  but  they 
are  unquestionable,  being  shown  by  casts 
and  fro7en  sections,  and  in  both  the  living 
and  tiie  dead  body  when  placed  in  the 
knee-chest  position  with  the  rectum  cleared 
of  fseces  and  distended  with  air.  They  are  placed  laterally,  and  have  in  common 
that  their  points  cross  the  middle  line,  although  not  symmetrically,  extending  more 
onto  the  front  than  the  back.  According  to  the  usual  arrangement,  the  lov.est, 
which  is  also  the  smallest,  projects  from  the  left  ;  the  second,  the  largest,  from  the 
right  ;  and  the  third  from  the  left.  The  first  is  about  2. 5  cm.  ( i  in. )  above  the 
anal  canal  and  the  second  about  as  much  higher.  If  the  first — as  often  happens — 
be  wanting,  the  second  is  not  necessarily  any  lower.  The  third  is  usually  at  about 
the  same  distance  above  the  second,  but  is  subject  to  greater  variations,  since  the 
two  may  lie  very  near  together.'  The  columns  of  Morgagni  are  a  series  of  per- 
manent vertical  folds  of  mucous  membrane  passing  from  the  anal  canal  upward  into 
the  rectum.  The  number  of  these  folds  varies  from  five  to  considerably  more  than 
ten,  which  latter  number  is  perhaps  about  the  average.  The  length  of  the  folds  is 
in  most  cases  from  1-2  cm.,  but  some  are  considerably  longer.  They  are  broad 
and  highest  at  their  anal  end,  or  h.ise,  from  which  they  diminish  to  the  upper  end, 
a  transverse  cut  near  the  lower  end  showing  them  to  be  triangular  on  section.  The 
valves  of  Morgagni  are  semilunar  folds  of  the  mucous  membrane  connecting  the 
bases  of  the  columns  of  the  same  name,  and  forming  with  them  a  number  of 
'  Otis  :  Anatomische  Untersuchungen  am  menschlichen  Rectum,  Leipzig,  1887. 


Folds  of  rectum  seen  iftcr  riilautkm.    (Olii.'s 


THE  MUSCLES  AND  FASCIA.  OF  THE  RECTI  M  AND  ANUS.   ,675 

nourhai  ooeninir  upward.  They  are  situated  in  the  anal  canal  at  the  upper  part 
rclnte™  fpCer.  The  mucou.  memhrancuf  the  rectum  «  thrown  «u..  a 
«n'«  dStudinal  told*.  These  are  easily  efiaceable.  although  «.n,e  arc  cnt.nu- 
oua  with  the  columns  of  Mornagni.  1.1     ,.  wi;u.  ,li. 

The  .Ubmucou.  coat  is  lax,  allowinR  the  mucous  membrane  to  Ik-  rt.ul.  >  du^ 
placed   bl"at  the  lower  end  of  the  a^al  canal  the  latter  w  hrmly  attached  to  the 

'"'^The  mu.CuUr  coat  ol  the  rectum  is  thicker  than  that  of  ih,: .  olon  riachinR  to 
,  mni  The  thickeninK  is  greatest  in  the  layer  of  th.,-  circular  hbrc..  1  he  l..ng.tu. 
A^a7 ones  although  forming  a  continuous  layer,  are  for  the  n.ost  part  coll. .  ed 
t    I  ,„,!  Kark  into  the  two  tends  already  mentioned,  of  which  the  posterior  i!«  the 

Kr'nd'Th^rreconcemell^^^^  "^'l'^ 'rTlr^'nusde 

Kn  hypertrophy  of  the  circular  muscles,  while  the  external  sphiiuler  is  .y">'««j^^ 
o?  the  oenneum  It  has  been  thought  advisable  to  here  descr.U'  togetlu  r  the 
Iscles'^and  some  of  the  fasci*  of  the'rectum  and  anus,  including  some  that  are 
largely  extrinsic. 

THE  MUSCLES  AND  FASCIA  OF  THE  RECTUM  AND  ANUS. 
The  levator  ani(  Figs.  1423.  1424)  arises  from  thebackof  theNHly.f  th.iuil..s, 
.l^mtmidlav  between  the  upVr  and  lower  border,  very  close  to  the  middle  line, 
id  hTncrfromtre'' white  Une"  formed  by  the  splitting  of  the  ,m..1vic  fascia  as 
?.r  «  the  sdnTof  the  ischium.  The  anterior  fibres  from  the  pubic  bone  p:us9  Inflow 
lhe"r!^ur^me  goin^  to  i«  capsule,  as  a  strong  muscular  bundle  to  the  central 

Fm.  14*3. 


BalhocavenMMUi- 


I»chio-cavenio»u» — 


Trans,  perinei  - 
super! 


Obturator 
internus 

White  line  - 


Levator  ani  _ 
Coccygeus  . 


TrianKUlar  lig- 
^meiit.  itif   i.tyer 

Pcrint-al  i-cnlrc 

ruhen«ity  of 
isctiium 


\nus 

>  }bturator  fascia 

Kxternal 
sphincter 
-  levator  ani 


t  '.luteus 
maximus  (cut) 


.  Greater  sacro- 
Kiatic  ligament 


Coccyx. 


Muscli-s  of  pelvic  floor  and  perineum  from  below. 


point  of  the  perineum  and  he  front  and  sides  of  the  rectum,  in  which  some  of  them 
end  The  remainder  of  this  set  passes  with  the  fibres  from  the  white  line  to  the 
side  of  the  coccyx  and  to  a  fibrous  band  ( liuaineotuni  anococcjgcuin )  runi.ms  from  it 
to  the  anus.  This  latter  part  of  the  muscle  is  thinner  and  more  transversely  placed 
than  the  former.  In  the  female  the  pubic  portion  sends  some  fibres  to  the  vagina 
and  some  around  it  to  the  central  point  of  the  perineum.     The  fibres,  for  the  most 


1676 


HUMAN   ANATOMY. 


part  in  both  sexes,  pass  by  the  rectum  so  as  to  compress  it,  although  some  enter 
Its  walls  and  mingle  with  those  of  the  sphincters. 

Nen<e.—\  branch  from  the  sacral  plexus  (sometimes  there  are  more  than  one  i 
runs  to  the  levator  ani  on  its  upper  surface.  The  fibres  come  from  the  third  ami 
fourth  sacral  ne'-'/es.  According  to  some,  the  muscle  also  receives  fibres  from  the 
inferior  hemorrhoidal  branch  of  the  pudic  nerve. 

The  coccygeuB  (Fig.  1424),  a  triangular  muscle  arising  from  the  spine  of  tin- 
fcchium  and  inserted  into  the  border  of  the  coccyx,  is  in  the  same  plane  and  practi- 
cally continuous  with  the  levator  ani.  The  two  muscles  of  both  s.des  have  been  well 
called  the  diaphragm  0/ the  pelvis.  They  form  a  funnel-like  structure  with  the  walls 
converging  downward  to  the  anal  canal,  and  an  anterior  opening  for  the  prostate  in 
the  male  and  the  vagina  and  urethra  in  the  female. 

Fir.    t«»4. 


obturator  tntemus 


Ischial  spine 
Obturator  canal 


Cut  edge  of  pelvic 
fascia,  white  line 


Pubic  bone 


-Sacrum  (cut) 


Pyriformis 


..Coccygeus 


I.ewilor  ant 

~- Recto-coccyReal  fibres 

Levator  ani  fcul) 

— Rectum 


Triangular  ligament,  superior  layer 
Triangular  ligament,  inferior  layer  •' 

Urethra    Bulb  of  penis,  covered  by  muscle 
Muscles  of  pelvic  floor  from  within  ;  settion  |«sMd  to  left  of  mid-line. 

A^nr.— The  muscle  receives  branches  from  the  fourth  and  fifth  sacral  nerves 
and  perhaps  from  the  first  coccygeal. 

The  external  sphincter  kni  (Fig.  142.^),  situated  beneath  the  skin  and  car- 
ried up  into  the  puckenng  at  the  anus,  is  a  flat  oval  muscle  comtwsed  of  striated 
fibres  surroundmg  the  end  of  the  rectum.  It  arises  from  the  tip  of  the  coccyx 
from  the  skm  over  it,  and  from  a  raphe  extending  from  it  to  the  anus.  The  fibres 
diverge  on  either  side  to  enclose  the  anus,  meeting  in  front  of  it  at  the  central 
point  of  the  perineum  (page  191 7),  where  they  mingle  with  other  muscles  which 
meet  at  that  point.  Some  of  the  inner  fibres  completely  encircle  the  anus  In 
the  female  some  fibres  decussate  with  those  of  the  sphincter  vagin*  This  sphinc- 
ter is  "external"  in  two  senses:  it  is  nearer  the  outer  surface  than  the  internal 
sphincter  and  also  surrounds  it. 

AWre.—\t  is  supplied  by  branches  of  the  fourth  sacral  and  of  the  infcri(,r 
hemorrhoidal  nerve. 


THE  MUSCLES  AND  FASCIAE  OF  THE  RECTUM  AND  ANUS.     1677 

The  intern "1  sphincter  ani  (Fig.  142 «).  composed  of  involuntary  muscular 
fibres  is  a  thickening  of  the  circular  layer  of  the  rectum,  which  becomes  marked  at 
thf  beginning  of  the  anal  canal.  It  surrounds  the  latter  for  a  distance  of  from 
2  s-3  cm.,  and  is  about  4  mm.  thick. 

Nen'ts  reach  the  internal  sphincter  through  the  sympathetic  system.     Very 
nrobably  some  of  them  come  directly  from  spinal  nerves.  ,     .     ,       • 

Accessory  Muscular  Bundles.— As  they  reach  the  anal  canal,  the  longi- 
tudinal fibres  of  the  rectum  send  bundles  to  the  skin,  which  gain  their  destination  by 
coursing  through  those  of  the  external  sphincter  ;  the  longitudinal  muscle-hbres  o 
the  mucous  coat,  becoming  enlarged,  pass  in  the  same  way  between  the  bundles  of 
the  internal  sphincter.  No  important  accessions  are  received  from  the  levator  am. 
The  longitudinal  muscular  fibres  of  the  rectum,  moreover,  enter  into  connection  with 
the  areolar  tissue  of  the  pelvic  fascia  between  the  peritoneum  and  the  levator  am,  and 
perhaps  with  the  latter  also.     Various  bundles  of  muscle-fibres,  apparently  arising 

Fir.    I4>5' 


( tbturalor 
inteniiiH 

Ampulla 


Cowper'9 
Kland 


5cmln.il 

vrsici* 

.    Ant*Tior  »»ll 

of  rci  tiiiti 

l.pvilur  ani 

Prostate  xlaiid 


Obturator 
extcriius 


Puhir  ntniua 


Corpus  cavcniOBuni      / 
Ischio-cavemosua 
Triangular  ligament,  inferior  layer 
BulboK-aveniottUS 


I      Colles's  fawia 

Triangular  ligament,  superior  layer 
Trans,  perniei  su|Krrf. 
Bulb  of  penis 


Krontal  section  or  pelvis  passing  just  behind  the  bladder,  posterior  surface. 

from  the  pelvis,  mingle  with  those  of  the  rectum.  The  recto-coccyi^eus  of  Treitz 
arises  from  the  anterior  surface  of  the  coccyx  above  the  pelvic  floor  and  mingles  with 
both  the  longitudinal  and  circular  fibres  at  the  back  of  the  rectum.  It  is  said  to  con- 
sist of  striated  fibres  at  its  origin.  Bundles  of  fibres  are  described  as  arising  from 
the  fascia  on  the  deep  surface  of  the  transversus  perinei  profundus  muscle  and  pass- 
ing to  the  front  of  the  gut. 

The  corr'igalor  cutis  ani  is  a  small  system  of  muscular  fibres  radiating  from  the 
submucous  tissue  at  the  anus  to  the  deep  side  of  the  skin,  which  it  tends  to  pucker. 

Actions. — The  function  of  the  sphincters  is  to  keep  the  anal  canal  closed. 
They  differ,  inasmuch  as  the  external,  although  mostly  acting  automatically,  is 
under  the  control  of  the  will  and  he  internal  is  not.  The  levator  ani  has  a  more 
complicate*]  and  in  part  an  appa;cntl---  inconsistent  .irtinn,  since  it  may  pull  the  anus 
upward  and  probably  dilate  it,  a"  it  pulls  its  borders  apart  under  the  resistance  of 


1678 


hijman  anatomy. 


the  descending  faeces,  while  at  other  times,  by  its  antero-posterior  fibres,  it  may 
compress  the  sides  of  the  gut.  To  the  action  of  the  levator  is  probably  due  the 
control  of  the  fieces  which  sometimes  persists  after  division  of  the  sphincter,  unless, 
indeed,  the  upper  part  of  the  latter  has  escaped. 

The  Ischio-Rectal  Fossa. — This  space  is  a  deep,  roughly  pyramidal  hollow, 
filled  chiefly  with  fat,  on  either  side  of  the  rectum.  The  base  is  at  the  skin  between 
the  tuberosity  of  the  ischium  and  the  anus,  bounded  in  front  by  the  line  of  reflection 
of  the  deep  perineal  fascia  and  behind  by  the  great  sacro-sciatic  ligament  and  the 
edge  of  the  gluteus  maximus.  The  base  measures  some  5  cm.  (  2  in.  )  from  before 
backward  and  half  as  much  crosswise.  The  fossa  is  bounded  externally  by  the  tuber- 
osity of  the  ischium  and  above  the  latter  by  the  obturator  fascia,  internally  by  the 
external  sphincter  and  the  under  surface  of  the  levator  ani.  The  space  narrows 
above  to  a  line  at  the  splitting  of  the  pelvic  fascia ;  hence  it  can  only  vaguely  be 
called  pyramidal.     The  depth  of  the  fossa  is  about  5  cm.  (2  in. ). 


Fig.  1436. 


Venous  plexus 
Pelvic  fascia 


,  Anterior  wall  uf  bladder 
Superior  p 


Obturalor  inlernus 


Diaphnifnnatic 
fascia 


Obturalor  fascia 
Levator  ani 


CluteuK  maximus 
Ischiu-rectal  fossa 


Obturator  extenius 


External  sphincter       {    Anns 

Internal  sphincter 
Oblique  transverse  section  IhrouKh  pelvis  in  plane  shown  in  small  outline  fixure. 


The  diaphragmatic  fascia,  the  inward  continuation  of  the  pelvic  fascia  which 
covers  the  upper  surface  of  the  levator  ani,  reaches  the  side  of  the  rectum  as  a  bed 
of  areolar  tissue  beneath  the  peritoneum,  and  is  more  or  less  closely  attached  to  the 
gut,  sometimes  by  muscular  bands,  as  already  stated.  The  systematic  description 
of  this  fascia  is  given  elsewhere  (ftage  559). 

The  rectal  fascia  is  a  dense  layer  of  areolar  tissue  surrounding  the  rectum 
below  the  reflection  of  the  peritoneum,  being  continuous  below  with  the  preceding 
fascia.  It  is  particulariy  dense  behind  the  rectum,  which  it  separates  from  the 
sacrum  and  coccyx. 

The  anal  fascia  is  a  web-like  areolar  sheet  covering  the  -inder  side  of  the 
levator  ani. 

A  superficial  fascia  between  the  skin  and  the  base  of  the  ischio-rectal  fossa 
can  be  artificially  dissected,  but  is  of  litde  importance. 


THE  MUSCLES  AND  FASCIA  OF  THE  RKCTIM  AND  ANIS. 


1679 


Pio.  1437. 

Internal  hemorrhoidal  vein 
I 


Le\-ator  ani 


Peritoneal  Relation^  of  the  Rectum.-The  posterior  surface  of  the  highest 

of  the  posterior  wall  "'Jl^e  perns,  mc  Douglas,— known  from  its  anterior 

deep  pouch  in  front  °';'^7^^""^;;[;'^„^''^^rr^r/.-Ui«^/  in  the  female.  In  man 
wall  as  the  recto-vtsiral  in  the  male  anu  "  ^  /^  and  the  UDOer  part  of  the  seminal 
this  pouch  separates  the  rectum  ^■•"''"/^^"^fthe  vagina  ^T^he  distance  of  the  line 
vesicles  and  in  woinan  from  the  upper  part  ««  ^J^^^^"^^j  ^^^  .^juch-from  the  ano- 

of  reflection  oi  peritoneuin-that  is  to  say  '^^^^v  given -H  however,  by  the  word 
rectal  groove  may  be  as  little  asscm  (2  nO.asusuallyMven,  ^,  .  , 

. .  anus^  be  understood  what  is  P-jf  "^,f  ^  f/^"^^^  ^tended,  the  pouch 

LconiidelJbV^iJS^^HTthelL^u^.1;?^^^^^^^^^ 
testine  or  the  sigmoid  flexure.     The 
redo-veskal  folds  in  the  male,  although 
described  with  the  bladder  (page  1905) , 
should  be  mentioned  here.    They  are 
reckoned  among  the  false  ligaments 
of  the  bladder,  and  bound  laterally 
the  pouch  just  described  ;  extending 
backward  from  the  bladder  around 
the  rectum  to  the  sides  of  the  sacrum, 
they  tend  to  divide  the  cavity  of  the 
pelvis  into  an  upper  and  a  lower  com- 
partment.   Their  free  edges  are  semi- 
lunar and  sharp,   and  cur\e   around 
the  rectum  above  the  ampulla,  which 
they  partially  roof  in.      Thesfe  liga- 
ments  contain   more  or  less  fibrous 
tissue.     In  the  female   they  are  less 
developed,  although  important,  and, 
arising  from  the  uterus  instead  of  the 
bladder,  are  known  as  the  sacro-utertne 

JoWs.  _,         ^    . 

Blood-Vessels.— The  artenes 

supplying  the  rectum  are  derived 
chiefly  from  the  three  hemorrhoidals. 
The  superior  hemorrhoidal,  the  ter- 
mination  of   the   inferior   mesenteric 

WMm^mm. 

Zr^^^:L  .ucous  and  cutaneous  -^  =  "j^^^^^^^^^ 

the  ways  between  the  superior  and  external  hemorrhoidal  veins.      i  ne  lau 


Middle 

hemorrhoidal, 

vein 

Internal 
sphincter 


External, 

sphincter 


Iroove 

■External 

hemorrhoidal 
vein 


Frontal  leclion  of  wall  of  anal  canal,  showing  relations  of 
hemorrhoidal  veins.    (O/u.) 


i68o 


HUMAN  ANATOMY. 


a  circle  of  smaller  dilatations  just  l>elow  the  line  of  demarcation,  in  the  region  that 
is  reckoned  as  skin,  but  is  practically  puckered  into  the  anus.  There  are  communi- 
cations between  the  two  systems,  some  of  which  pierce  the  muscular  coat. 

Lymphatics — The  principal  lymphatics  of  the  rectum,  after  joining  the 
lymph-nodes  situated  along  the  superior  hemorrhoidal  veins,  pass  to  the  sacral 
glands  on  the  front  of  the  sacrum.  In  the  lower  part  of  the  bowel  a  ver>-  rich  plexus 
is  found  under  the  skin  around  the  anus,  which  drains  into  the  superior  internal 
inguinal  glands,  and  a  still  richer  one 'inside,  which  at  the  lower  part  is  concentrated 
on  the  columns  of  the  rectum,  but  few  vessels  lying  in  the  pouches.  A  considerable 
system  of  lymphatics  exists  also  in  the  muscular  layer.  Most  of  those  of  the  inside 
of  the  anus  run  to  a  few  small  lymph-nodules  discovered  bv  Gerota '  on  the  back 
of  the  muscular  coat  of  the  rectum,  distributed  with  the  branches  of  the  superior 
hemorrhoidal  artery. 

Nerves.— The  nerve-supply  of  the  rectum  includes  both  sympathetic  and 
cerebro-spmal  fibres.  The  former  are  derived  chiefly  from  the  inferior  mesenteric 
and  the  pelvic  plexuses,  accompanying  the  superior  and  middle  hemorrhoidal 
arteries  respectively.  The  cerebro-spinal  fibres  are  contributed  by  the  second, 
third,  and  fourth  sacral  nerves.  The  skin  around  the  anal  orifice  is  supplied  by  the 
inferior  hemorrhoidal  branch  from  the  pudic  nerve. 

Growth. — At  birth  the  rectum  is  tubular  and  generally  relatively  small.  We 
do  not  remember  to  have  seen  a  well-marked  ampulla  at  that  period.  At  least 
frequently  the  anal  canal  is  very  long,— about  I  cm.  The  transverse  folds  of  the 
rectum  are  apparent  in  the  latter  months  of  pregnancy.  We  have  found  an  ampulla 
with  a  circumference  of  13  cm.  (5  in. )  at  three  years.  In  the  same  specimen  the  valves 
were  well  developed,  and,  except  in  size,  it  resembled  the  rectum  of  the  adult. 
The  peculiarities  of  the  infantile  sacrum  have  their  effect  on  the  course  of  the  rec- 
tum, which  is  necessarily  straighter  than  in  the  adult  and  does  not  run  so  far  forward 
in  front  of  the  coccyx. 

PRACTICAL   CONSIDERATIONS:    THE   LARGE   INTESTINE. 

The  Caecum. — This  part  of  the  large  intestine  may  remain  undescended  in  its 
fujtal  position  in  the  left  hypochondrium,  at  a  point  above  and  to  the  left  of  the 
umbilicus,  the  ileum  opening  directly  into  it  in  this  locality  ;  or  it  may  be  found  in 
the  right  hypochondrium  just  below  the  liver,  or  at  any  level  between  that  and  its 
normal  situation.  The  csecum  is  rudimentary  in  man  and  other  meat-eating  animals, 
being  much  more  capacious  and  of  greater  functional  importance  in  the  herbivora. 

The  caecum  is  larger,  more  distensible,  and  more  superficial  than  any  other 
portion  of  the  large  intestine,  and  more  mobile  than  any  other  portion  except  the  sig- 
moid. On  account  of  its  mobility  it  is  selected  for  the  operation  of  iliac  colostomy 
when  that  operation  is  done  on  the  right  side. 

As  a  result  of  the  inspissation  of  the  intestinal  contents,  which  first  occurs  here, 
it  is  a  common  seat  of  fecal  impaction,  or  of  distention  by  gases  arising  from  fermen- 
tation. The  increase  in  numbers  of  the  intra-intestinal  pathogenic  bacteria  due  to 
imiiaired  inhibiting  power,  which,  as  we  descend  the  gut,  first  beconsis  marked  in 
the  lower  ileum,  continues  in  the  caecum.  As  in  the  former  situation  v.here  it  prob- 
ably aids  in  determining  the  localization  of  typhoid  and  tuberculous  le..ions,  so  in 
the  caecum,  in  conjunction  with  fecal  accumulation,  or  with  disturbance  of  circulation 
from  distention,  such  augmentation  adds  to  the  frequency  and  severity  of  catarrhal 
inflammations  and  of  stercoral  ulcers,  which  are  found  oftener  here  than  elsewhere. 

Fecal  concretions  (the  formation  of  which  is  favored  by  intestinal  catarrh  just 
as  is  that  of  renal  calculi  by  catarrhal  pyelitis)  are  often  found  in  the  c»cum,  and 
undoubtedly  by  mechanical  irritation  favor  here,  as  they  do  in  the  appendix,  epi- 
thelial necrosis  and  subsequent  infection. 

In  the  erect  position  gravity  aids  in  bringing  about  these  pathological  condi- 
tions, since  the  caecum,  having  no  mesentery  of  its  own,  and  yet  completely  covered 
by  peritoneum  (so  that  it  is  never  anchored  to  the  posterior  parietes  or  to  the  iliac 
fossa  by  areolar  tissue),  depends  upon  its  attachments  to  the  colon  and  ileum  to  hold 
'  Arch,  fur  Anat.  und  Entwicklng.,  1895. 


PRACTICAL  CONSIDERATIONS  :   THE  LARr.E  INTESTINE.     1681 

it  in  position.     It  has  often  been  part  of  the  contents  of  rJKht  inguinal  or  femoral 
t,„,nia   anfl  has  even  been  found  in  such  hernise  on  the  left  siUe. 
•^      The  hiflu^nce  of   gravity  in  retaining  '  .cal  masses  and  fav..rmg  concretu.n  « 
illnstmt^bv  the  Lt  that  foreign  bodies  small  enough  to  p^iss  through  the  ileo-c^eca. 
" Ive  aS  prone  to  remain  in  the  c^cum.  where  they  have  u,  many  casc-s  guen  nse 

Kieh  on  the^omen  will  empty  a  moderately  distended  caecum. 
"""^°;*""K3»/»  »  usually  competeu,  to  preveut  fc  r«urr.  of  !«»'"■«« 

to^    Wieffin),  and  occurs  most  commonly  (70  per  cent,  of  all  cases)  in  ""luri  • 
The  ileo-c^al  valve  forms  the  summit  or  apex  of  the  intussusceptum.  and  may  pass 
Sougl^thTentlrTcolon  (the  intussuscipiens).  aching  the  rectum  oi^an^^ 
colic  intussusception-in  which  the  ileum  passes    hrough  the  vaUc,  the  caecum 

-''l^:^^^^:^:^::^^^^  CltSlnrtrU  P-ureon  the  mesen. 

entering  and  returning  layers  of  gut  (Hg.  1405)-       '  "^^",  .^e  nassa^e  through  it  of 
narrows  the  lumen  of  the  intussusceptum  so  as  to  prevent  the  passage  tnroug 

spine  of  the  .hum  Appendix—On  account  of  the  frequency  with  which  it  i. 

I  to   5^'.\^"^'^^„f,^P,YdX  here  considered,  even  at  the  risk  of  repetition. 
'^''''^:;^^;'^n^'£^-    The  appendix  is  an  apparently  f-fjonl^s  orga 
found  oaty^n  manf  in  certain  of  the  anthropoid  apes,  and  m  the  wombat.     An  analo- 

106 


t683 


HUMAN  ANATOMY. 


gous  organ  exists  in  some  of  the  rodents  and  marsupials,  but  it  is  a  long,  taperiii; 
cecum  rather  than  an  appendix  strictly  compiarable  to  that  of  man.  The  app<jnili\ 
is  a  vestige  of  the  capacious  csecum  of  some  of  the  lower  animals,  or  may  be  regartleii 
as  a  rudimentary  Ciecum  just  as  the  human  caecum  is  a  rudiment  of  that  found  in  tin 
herbivora  or  the  rodents.  Like  other  vestigial  structures,  or  those  which  in  the  his- 
tory of  either  the  race  or  the  individual  have  outlived  their  usefulness,  it  appears  ti  i 
be  of  low  resistant  power.  This  doubtless  explains  in  part  the  special  susceptihilitv 
of  the  appendix  to  disease,  as  it  does  that  of  the  uterus  and  the  female  breast 
during  the  post-sexual  period  of  life. 

2.  Its  mesentery — a  fold  made  by  the  passage  of  the  appendicular  artery  from 
the  ileo-colic  at  the  back  of  the  ileum  to  the  appendix  (page  1665) — is  scanty;  its 
free  border  is  shorter  than  the  border  applied  to  the  appendix,  and  sometimes  dot-s 
not  extend  much  beyond  its  middle.  The  appendix,  like  the  small  intestine,  is 
therefore  thrown  into  irregular  curves  or  coils.  Another  jieritoneal  duplicature — tlic 
ileo-caecal  fold — runs  from  that  part  of  the  ileum  most  remote  from  its  mesenteric 
attachment  and  is  united  with  the  mesentery  of  the  appendix.  It  carries  no  bloixl- 
vessels  of  consequence,  and  is  regarded  by  Treves  as  the  remains  of  the  irue  mesen- 
tery of  the  appendix.  It  is  interesting  to  note  the  fact  that  in  the  different  types  »i 
the  human  caecum  those  which  involve  a  disproportionate  growth  of  the  c*cum  show 
that  it  derives  its  peritoneal  covering  partly  at  the  expense  of  the  mesentery  of  tin 
appendix,  which  becomes  more  scanty  and  more  vertical  in  direction  the  larger  the 
relative  size  of  the  caecum.  The  appendix  moves  directly  with  the  canrum,  but, 
through  the  attachments  of  the  meso-appendix  to  the  cecum  and  to  the  mesentery 
of  the  ileum,  distention  or  displacement  of  those  portions  of  the  intestine  makes  trac- 
tion upon  it  and  causes  increased  curving  or  angulation.  For  these  reasons,  and  on 
account  of  the  lessened  interference  with  the  blood-supply  {zi'Je  infra),  appendices 
with  exceptionally  ample  mesenteries  extending  to  the  tip  of  the  organ  are  less  fre- 
quently the  seat  of  disease  and,  when  diseased,  are  less  often  found  in  a  condition  of 
complete  gangrene. 

,•?.  The  single  artery  supplying  the  apprndix  and  running  in  the  folds  of  the  meso- 
appendix,  and  its  accompanying  veins,  are  subjected  to  pressure  by  such  traction, 
or  by  the  angulation  of  the  organ  itself,  and  various  degrees  of  vascular  obstruction  and 
congestion  may  result.  The  consequent  oedema  and  swelling  of  the  mucous  mem- 
brane aid  the  distortion  of  the  appendix  in  causing  interference  with  the  escape  of 
the  contents  of  the  appendix  into  the  c£ecum.  After  infection  has  started  the  vessels 
are  not  infrequently  occluded  by  septic  thrombi.  The  peritoneal  fold,  which  in  the 
female  is  often  found  running  from  the  appendrx  to  the  broad  ligament  (page  1666), 
may  contain  a  second  artery  the  presence  of  which  has  been  offered  ;is  an  explana- 
tion of  the  relative  infrequency  of  appendicitis  in  women. 

4.  The  disproportion  between  the  length  and  the  lumen  of  the  appendix  (16 
to  I,  Finkelstein),  the  similar  disproportion  between  the  lumen  and  the  area  of  the 
secreting  surface,  its  removal  from  the  direct  intestinal  current,  the  feebleness  of  its 
muscular  walls,  its  dependent  position,  the  absence  t..'  inefficiency  of  any  \alvular 
arrangement  at  the  appendiculo-oecal  orifice,  and  the  ease  with  which  that  orifice 
may  l)e  diminished  in  size  by  oedema  of  the  mucous  membrane  in  its  vicinity  readily 
explain  the  fact  that  under  most  circumstances  in  which  drainage  from  the  appendix 
into  the  intestine  would  be  desirable,  it  is  apt  to  be  lacking.  Even  a  hypera;mic 
catarrh  from  twists,  kinks,  or  traction  may  in  this  way  become  the  starting-point  of 
serious  trouble,  the  successive  steps  of  which  might  subsequently  be  retention  of 
mucus,  epithelium,  and  fecal  contents  (possibly  in  the  form  of  a  concretion), 
ulceration,  parietal  infection,  or  perforation  or  gangrene,  and  peritonitis,  localized 
or  general. 

5.  The  abundance  of  lymphoid  tissue  in  the  appendix,  as  in  the  tonsils,  favors 
rapid  swelling  and  infectious  inflammations  and  aids  in  obstructing  drainage.  It  may 
to  some  extent  accoimt  for  these  pathological  conditions  showing  themseh'es  during 
the  periods  of  growth  and  activity  of  the  svstem  much  more  frequently  th.in  in  old 
age,  when  the  lymph-nodules  in  the  walls  of  the  intestinal  canal  become  atrophied 
(Struthers).  In  this  connection  it  may  be  noted  th.it  other  causes  contributing  to  the 
relative  frequency  of  appendicitis  in  early  life  are  (a)  the  susceptibility  of  children 


PRACTICAL  CONSIDERATIONS  :  THE  LARGE  INTESTINE. 


if'83 


,n  catarrhal  enteritis,  favoring  the  formation  of  concretums  <>r  a  least  impairing 
L  SS  ve  Swer  of  the  intestinal  epithelium  ;  («)  the  relatively  greater  length 
o^  the  ISirryoung  ,>ersons  (in  infants  one-tenth  and  in  adults  one-nvenuth 
1  lenXof  the  large  intLtine,  according  to  RiblK-rt)  increasing  the  ^^*culty  of 
draiiag?  and  r^ssiWy  (r)  the  tendency  to  shrinkage  or  obliteration  after  middle 
lifp  _a  process  to  be  expected  in  a  rudimentary  organ.  •    1  <  ., .  w  t.. 

•  6    h^i^t  not  be  forgotten,  in  interpreting  the  foregoing  anatomical  f^cts  as  to 
(«)  the  mZentary  character  of  the  appendix,  (*)  the  --"'^-^^^.^^^^^^^^^ 

the  intestinal  tract  (p^ige  .'^^^^  „*"°  *;'7;'  ^^^^of  either  mechanical  or  chemical 
ready  to  take  on  pathogenic  action  m  t^^  1'  "f"^';  /  '  ^^^^^^  ^^ainago  of  the  eariy 

■'"t"S,^r5te  "tXtr,  ,h.  pain   i,  leU   in  ,he  ri„1„  ili»e  lc»«.. 

over  ihf  St  iliac  fossf^  is  often,  but  perhaps  not  necessarily,  diK- to  peritonitis, 
and  in  anv  event  arises  from  the  fact  that  those  muscles  receive  their  nene-supply 
mnianvfrom'he  six  lower  intercostals,  while  the  superior  mesenteric  plexus  gets 
fts  contribution  from  the  spinal  system  through  the  splanchnics,  derived  from  some 

«'  '':  XS^'^mmonlv  follows,  has  litde  ...ation  *"  gastric. conditi^sis^or^ 
narilyreflex  and  due  to  reversed  peristalsis,  and  is  apt  tu  be  assoc.atcu  with  moderate 
fever  and  slightlv  increased  pulse-rate  due  to  autotoxamia. 

Other  and  later  symptoms  are  mentioned  in  the  next  section. 


1684 


HUMAN   ANATOMY. 


Results  and  ComplicalioHs  0/ Appendicitis. — A  cursory  review  of  the  anatomicil 
relations  of  the  appendix,  considered  in  conjunction  with  the  [lathological  varietit  - 
of  appendicitis,  will  explain  the  varying  results  of  this  disease.  The  appendix  i> 
entirely  intraperitoneal  in  its  situation  and  becomes  primarily  the  focus  of  intrai>eritn 
neal  lesions,  although  in  certain  cases  {iHde  infra),  from  pathological  changes,  it  iiiid 
the  ;wsociated  exudate  or  abscess  may  be  either  practically  or  really  extraperitonejil 
That  focus  may  be  isolated  by  adhesions  between  the  peritoneal  coverings  of  thi 
neighboring  structures— the  coils  of  small  intestine,  the  ca-cum  or  colon,  the  jiarieto 
— or  may  become  the  starting-point  of  a  general  septic  peritonitis.  In  the  former  cast 
the  usual  local  symptoms  of  inflammation  or  of  abscess  will  follow  according  to  the  be- 
havior of  the  exudate,  which  may  remain  plastic  or  may  liquefy  and  become  purulent. 
In  the  latter  case,  to  the  above-mentioned  symptoms — which  are  much  intensified,  as 
a  rule--are  added  general  rigidity  from  involvement  of  larger  areas  of  the  abdominal 
wall,  distention  and  tympany  from  paresis  of  the  small  intestine  (page  1756),  and  from 
the  same  cause  obstinate  vomiting  and  more  or  less  complete  intestinal  obstruction. 

The  acuteness  of  the  attack,  the  presence  or  absence  of  gross  perforation  or 
gangrene,  and  the  anatomical  position  of  the  individual  appendix  will  often  determine 
the  localization  or  diffusion  of  the  septic  infection. 

The  usual  anatomical  situations  of  appendix  abscess  may  be  summarized  as  fol- 
lows, (i)  Anterior,  the  ciecum  forming  the  posterior  wall,  agglutinated  coils  of 
intestines  the  inner  wall,  and — after  the  abscess  has  attained  some  size — the  parietal 
peritoneum  the  anterior  wall.  (2)  Posterior,  the  hinder  surface  of  the  ca-cum 
forming  the  anterior  wall,  especially  if  the  appendix  is  post-c»cal  in  posi'on,  or  if  a 
septic  lymphangitis  has  extended  backward  between  the  layers  of  the  meso-appendix. 
Such  an  abscess  is  extraperitoneal,  and  may  originate  in  an  appendix  which,  it  is 
believed  by  some,  was  ab  initio  either  wholly  or  partly  extraperitoneal  (4  per  cent. , 
Bryant),  or,  as  seems  more  probable,  had  become  so  through  pathological  causes 
(38  per  cent.,  Ferguson,  page  1666).  The  abscess  b  limited  by  the  fascia  transver- 
salis  anteriorly  and  the  fascia  iliaca  posteriorly,  and  by  their  fusion  at  Poupart's  liga- 
ment inferiorly,  although  rarely  it  may  follow  the  femoral  vessels  downward  and 
appear  on  the  thigh,  or  may  perforate  the  parietes  above  the  outer  third  of  Poupart's 
ligament,  or  may  make  its  way  into  the  peritoneal  cavity,  or  into  the  pelvis,  escaping 
through  the  obturator  or  the  sacro-sciatic  foramen.  It  may  ascend  (following  some- 
times the  retro-colic  fossa,  page  1667)  to  the  perinephric  or  even  to  the  subphrenic 
region.  (3)  Inner,  the  inner  surface  of  the  colon  and  csecum  and  the  mesocolon 
bounding  it  postero-extemally  and  adherent  coils  of  small  intestine  antero-intemally. 
If  the  parietal  peritoneum  does  not  form  part  of  the  anteriv.'  wall  of  such  an  ab- 
scess, the  general  peritoneal  cavity  must  be  traversed  'n  reaching  and  evacuating 
it.  (4)  Inferior,  the  abscess  occupying  part  of  th'  pelvic  cavity  with  agglutinated 
intestinal  coils  bounding  it  superiorly. 

All  these  abscesses  may  perforate  into  the  cavity  of  the  peritoneum,  but  sponta- 
neous opening  into  the  cacum,  colon,  rectum,  small  intestine,  bladder,  or  on  the  sur- 
face of  the  body  has  frequently  (Kcurred  {  Finkelstein,  quoted  by  Mynter).  The  various 
symptoms  which  may  result  from  the  propinquity  of  the  abscess  to  other  structures 
should  be  worked  out  anatomically,— t-.;?^.,  ( i )  oedema  of  the  abdominal  wall  over  the 
abscess;  (2)  flexion  of  the  thigh,  extension  of  which  is  painful  from  involvement 
of  the  ilio-psoas  ;  or  marked  lumbar  tenderness  (perinephric)  ;  or  immobility  of  the 
right  lower  thorax  (subphrenic)  ;  (3)  tympany  over  an  ill-detined  swelling,  from  in- 
terposition of  coils  of  small  intestine  between  the  abscess  and  the  parietes  ( although 
this  may  be  simulated  by  the  escape  of  intestinal  g;»ses  through  a  gross  perforation 
into  the  cavity  of  an  aliscess  of  any  type)  :  or  (4)  vesical nr  rtrte/ irritation. 

Anatomical  Points  relating  to  the  Treatment  of  Appendicitis.— T)\e  medical 
treatment  of  this  disease  is  of  anatomical  interest  only  in  its  relation  to  the  possibility 
of  removing  the  mechanical  causes  and  favoring  either  resolution  or  localizing  adhe- 
sions. Opium  for  the  purpose  of  lessening  peristalsis  and  thus  permitting  omental 
;tnd  intestinal  adhesions  to  wall  of!  the  apjiendix  has  still  some  advocates,  especially 
when  combined  with  gastric  lavage  and  exclusive  rectal  alimentation  (Ochsner). 
But  the  received  views  as  to  etiology  {vide  supra)  and  clinical  experience  are  both 
overwhelmingly  in  favor  of  purgation  and  starvation  as  preventing  or  removing  the 


PRACTICAL  CONSIDERATIONS:   THE  LARGE  INTESTINE.    1685 

constipation  which,  when  involvinR  the  c-wrum.  may.  by  causing  irritetion  and  swell- 
[ne  of  mucous  membrane,  by  ena.uratjement  o.  bacteml  growth,  by  favonnR  the-  for- 
matinn  of  fecal  concretions,  by  producing  traction  on  the  meso-apijen.h.x.  <.r  by  direct 
Sure  upon  the  appendicular  vessels,  start  the  cham  of  ,«tholoK.cal  phenonuna 
E  begbning  with  hyperemia,  hypersecretion,  and  imperfect  drainage  pnK:ee< 
To  disiemVon,  ulceration. ^rforation,  or  gangrene,  with  their  assc^mted  degrees  ..f 

•^"^Sns^iStioTifprtSiTin  the  majority  of  cases  of  appendicitis  (  3H  out  of  69. 
McCosh).  ar^d  not  only  acts  as  a  causative  factor,  but  has  a  prejudicial  effect  on  he 
resVU  In  22  cases  ofVritonitis  from  appendix  disease  occurring  at  the  London 
Sital  there  were  9  c^es  of  constipation,  with  4  deaths  and  13  cases  in  which 
thrbowe  s  were  loose  or  e;isily  moved,  with  2  deaths.  In  another  series  of  cases 
r Richardson)  there  was  8  per  cent,  of  constipation  among  those  that  recovere.1  and 
is  Srce^ among  those  that  died  (White).  No  other  important  ,K>int  of  nK-dical 
treatment  is  in  dispute  and  none  has  any  anatomical  bearing  !,„..,,„,  „f 

operation  for  appendicitis  will,  of  course,  vary  with  the  scat  and  character  of 

the  d'se^e^  preferable  method  of  access  in  removal  of  an  appendix  very  early  in  an 
attack,  or  during  an  interval,  or  when  neither  abscess  nor  extensive  adhesions  .are 
present,  is  as  follows.  The  incision  begins  one  inch  above  a  line  drawn  rom  the 
anS  superior  spine  to  the  umbilicus,  and  crosses  that  line  one  and  a  half  inches 
interna  to^he  iliac  spine.  It  should  pass  downward  and  inward  and  be  »»-"  thr^ 
nches  long.  The  skin  and  aponeurosis  of  the  external  oblique  are  divided  in  that 
direction  ;  the  internal  oblique  and  transversalis  fibres  are  separated  in  a  direction 
aimSt  at  right  angles  to  the  first  incision  ;  the  transversalis  fascia  and  peritoneum 
are  divided  on  the  same  line  with  the  internal  obhc^ue.  ..vt.^„ 

The  advantages  of  this  incision  are  thus  described  by  its  originator.  Muscu- 
lar and  tendinous  fibres  are  separated,  but  not  divided,  so  that  muscular  action  can- 
not tend  to  draw  the  edges  of  the  wound  apart,  but  rather  to  actnely  approximate 
them  Excepting  during  the  incision  of  the  skin,  almost  no  bleeding  occurs  The 
ascia  transveVsalis  not  &ing  drawn  away  by  the  retraction  of  the  deepest  layer  o 
muscular  fibres,  this  fascia  is  easily  completely  sutured,  and  thus  greater  strength  of 
repair  is  assured"  (McBurney).  .„„„i..,  „, 

More  room  may  be  obtained  and  the  transverse  severance  of  niuscular  or 
fascial  fibres  still  minimized  by  stripping  the  external  oblique  aponeurosis  up  to  the 
mSbn  line,  dividing  the  anterior  sheath  of  the  rectus  in  the  line  of  the  separation 
of  the  internal  oblique  and  transversalis  fibres,  lifting  up  and  retracting  the  rectus 
towards  the  median  line,  ligating  the  epigastric  vessels  (which  will  be  seen  lying  on 
the  thin  transversalis  fascia  over  the  peritoneum),  and  then  extending  the  original 
peritoneal  incision  as  far  inward  as  may  be  necessary  (Weir).  ... 

2  In  later  operations  it  is  best  to  be  guided  by  the  situation  of  the  tumor  or 
the  area  of  tenderness  or  dulness.  inclining  to  approach  it  from  without  inward. 
An  oblique  incision  well  out  towards  the  upper  third  of  Poupart  s  ligament  will  l)e 
less  likelv  to  open  the  general  peritoneal  cavity  unneces.sarily  in  cases  of  abscess, 
and  less  lik.iy  to  be  followed  byventral  hernia.  In  retroperitoneal  abscess  an 
incision  so  placed  will  not  infrequently  open  the  abscess  without  going  through  the 

peritoneum  at  all.  ...  •!•••„  »!,« 

X    In  the  presence  of  general  purulent  peritonitis  a  vertical  incision  on  the 

outer  border  of  the  rectus  or  a  long  median  incision  will  best  enable  the  appendix  to 

be  dealt  with  and  at  the  same  time  permit  of  the  efficient  cleansing  and  irrigation  of 

the  peritoneal  cavity  and  the  introduction  of  drainage.  •,    u    .        1 

4.   After  the  peritoneal  opening  is  made  the  appendix  can  often  easily  be  found 

and  brought  out  of  the  wound.     If  this  is  not  done  readily,  the  colon  should  be 

identified— the  first  portion  of  intestine  found  att.iched  to  the  posterior  wall  as  the 

finger  is  passed  along  that  wall  inward  from  the  incision— and  the  anterior  muscular 

band  traced  downward  to  the  base  of  the  appendix.  ,  ,•  •  •  t 

The  Colon  and  Sigmoid  Flexure.— Like  the  other  main  sulxlivisions  ot 

the  intestinal  tract,  the  colon  is  larger  at  its  commencement  than  at  its  termination. 

measuring  on  the  average  8  cm.  (3>^  in.)  in  diameter  at  the  c^scwm  m^L^  c""- 


t«86 


HUMAN   ANATOMY. 


! 


(i^  in.)  at  thf  lower  end  of  the  sigmoid  flexure.  Its  average  capacity  in  iiif.iiu> 
of  »i.\  months  is  >^  litre  (i  pint);  in  children  two  years  old,  1.25  litres  (2.5  pints  i; 
and  in  adults,  4.5  litres  (9  pints). 

It  is  normally  ualpable  through  most  of  its  extent,  the  more  deeply  phu.d 
hejjatic  and  splenic  flexures  excepted,  the  former  Iwing  lieneath  the  liver,  the  latti  r 
l>ehind  the  cardiac  end  of  the  stomach.  The  ascending  and  descentling  portions  .ir«.- 
usually  overlapped  in  front  by  the  jiiore  mobile  small  intestine,  which,  if  not  dis 
tended,  can  Ik;  displaced  towards  the  median  line.  The  thickened  and  sometinio 
tender  edge  of  a  chronically  congested  or  inflamed  citcum  can  often  be  rolled  under 
the  finger  against  the  floor  of  the  iliac  fossa,  and  has  been  mistaken  for  the  appendix. 

The  colon  is  susceptible  of  great  distention,  and  in  cases  of  obstruction  in  tin 
sigmoid  flexure  or  rectum  it  may  occupy  most  of  the  abdomen,  push  up  the  dia 
phragni,  displace  the  heart,  and  occasion  dyspncia  and  palpitation. 

Distention  either  from  gas  or  fecal  accumulation  renders  the  colon  visible,  as 
well  as  palpable,  except  at  the  flexures.  In  chronic  obstruction  in  the  rectum  or 
sigmoid  its  peristaltic  movements  may  be  seen  through  the  thinned  abdominal  w  .ills. 
In  the  common  iIeo-ca?cal  variety  of  mtussusception  the  tumor  can  often  \yc  seen  as 
well  as  felt,  and  sometimes  the  progress  of  the  intussusceptum  along  the  colon  can 
be  traced  with  the  eye. 

Tumors  of  the  colon  or  upper  end  of  the  sigmoid  are  often  visible  in  thin  pa- 
tients, especially  when  they  have  contracted  anterior  parietal  attachments. 

Distention  of  the  colon  gives  rise  to  prominence  and  outward  curving  of  the 
flanks,  as  the  patient  lies  supine,  and  to  fulness  below  the  costal  arches  and  the 
margin  of  the  liver.  The  anterior  surface  of  the  belly— taking  the  umbilicus  as  a 
centre — is  relatively  flat.  In  distention  of  the  small  intestine  the  swelling  is  most 
marked  in  the  latter  region. 

Normally  the  colonic  percussion-note  is  of  somewhat  lower  pitch  than  that  of 
the  small  intestine,  but  of  higher  pitch  than  that  of  the  stomach,  the  variation  being 
due  to  the  difference  in  the  size  of  these  viscera  and  in  the  thickness  of  their  walls. 
In  general  gastro-intestinal  distention  the  same  variations  are  often  observable. 

A  large  quantity  of  fluid  faeces  in  the  colon  will  give  rise  to  f)ercussion  dulness 
in  the  flanks,  which  may  disappear  when  the  patient  is  turned  on  his  side.  That 
sign  is  therefore  not  conclusive  evidence  of  the  presence  of  free  fluid  in  the  peri- 
toneal cavity,  unless  the  condition  of  the  colon  is  known. 

Rupture  from  distention— a  rare  occurrence — will  usually  be  incomplete,  the 
mucous  membrane  remaining  unbroken. 

Idiopathic  dilatation  of  the  colon  has  been  seen  in  young  children,  chiefly  amon;- 
those  affected  with  rickets. 

Displacements. — The  caecum  and  ascending  colon  or  the  sigmoid  and  descend- 
ing colon  may  be  found  in  inguinal  or  femoral  herniae,  may  be  at  the  median  line  of 
the  body,  or  may  even  lie  in  the  iliac  fossa  of  the  opposite  side.  A  misplaced, 
movable,  or  enlarged  kidney  may  cause  variation  in  the  position  of  the  colon. 
"  When  the  left  kidney  occupies  the  iliac  fossa  or  is  situated  over  the  left  sacroiliac 
synchondrosis  there  is  generally  no  sigmoid  flexure  in  the  left  iliac  fossa  ;  but  the 
descending  colon  passes  across  the  middle  line,  and  the  rectum  commences  on  the 
right  side  of  the  sacrum"  (Morris).  Paranephric  tumors,  by  pressure  on  the  colon, 
have  produced  such  marked  symptoms  of  intestinal  obstruction  as  to  be  mistaken 
for  intussusception  ( Ibid.  ). 

The  transverse  colon,  as  the  most  movable  of  the  three  divisions  of  the  colon 
proper,  is  peculiarly  liable  to  assume  abnormal  positions,  usually  as  a  result  of 
habitual  constipation  or  secondary  to  obstruction  lower  in  the  gut.  It  can  readily 
be  understood  how  the  weight  of  fecal  masses  may  in  time  exaggerate  the  normal 
downward  curve  of  the  transverse  colon,  resting  only  on  the  easily  displaced  sni.ill 
intestine,  and  carry  it  towards  the  pubes.  which  it  sometimes  reaches.  The  normal 
level  of  the  middle  or  lower  portion  of  the  transverse  colon  is  at  the  upper  umbilical 
or  the  lower  epigastric  region,  or  on  the  line  separating  those  two  regions.  The 
[josition  of  the  transverse  colon  in  relation  to  the  stomach  varies  greatly  within 
normal  limits.  If  the  stomach  is  empty,  it  is  behind  the  colon;  if  full  or  distended, 
it  will  iflikkthe  latter  downward  and  overlap  it  from  in  front 


PRACTICAL  CONSIDBRATIOXS  :    THE  l.AROK  IXTh-iTIHE    .6., 

iJ^^T  C  iuU  tl»  in«.is«.tn.n  of  i..u-stin«l  c.nunls.  an,l  il..  .«.™ily  f" 
presence  ol  tnc  saccuii,  im.  iimi  ,  .     ,^  ,n^..  ^m-  iiUni,  unJ 

tuberculous  ulcerat.on  '« '^;^/f„^^^,;  ."^/.J    Z  iL  .ectum.  sigmoia.  clcscondinn 

account  for  its  -'-"-   sus^epUb^^^^^^^  (pa«e  .680) 

IpPnT/ht^'atlrnlrX^^^^^^  it  .nor.  frequenUy  the  ^t  of  car- 

'^n\£TanVJi:e^!tS£n\^  producing  stricture  and  obstruction,  .ay  ex- 
tend 'into  and  involve  any  of  the  "«>?J^"".f.^,f;'i;;rtio„  of  the  Ix^wel  upon  an  axis 

usual  cause  is  habitual  «^«"«t,paUon      The  gut.  l^commR  ,^^^^^^^^^  ^esc^iRmoid. 

tention    hangs  over  '"f  »J^^  P^'jf^,:,"^^^"  o    Thegut  in  thT  effort  to  rid  itself  of  the 
Irreeular  contraction  of  the  muscular  layer  01  mc  ^ 

-?.  sr  tvriKKi  tr^.n^o-1;. -^^^^^^^ 

,„d  only  indi,«lly  .ith  the  solar  ptos     Tte  r^SJon  o^^hj  ^"^  M     ,^.|^. 

order  to  understand  .-.'W  (a)  a  renal,  P*"" J      ••jj^either  the  ascending  or  de- 

.,  ,     ^^TsJp^uS  gS- £^c    -  r:ii:^l^^    liver  may  ^acuate 
scendingcolon;  (/>)asuppurat.n^^^^^^  gastro-colic  fistula  may  become  es- 


t688 


HUMAN   ANATOMY. 


of  the  abdominal  aorta  may  burst  into  the  g»t,  the  blood  paiMini;  between  the  l.i\  1 1 - 
of  the  transverse  mesocolon  ;  (*■)  an  iliac  aljsccss  may  dischar{{e  into  the  ca-iiuii  .  i 
sigmoid  flexure  ;  (/)  the  latter  may  by  ulceration  communicate  with  the  bladiKr  m 
vagina  ;  (jf)  or  may,  in  chronic  fecal  distention,  produce  left-sided  varicocele  (ili< 
more  frequent )  by  pressure  on  the  left  spermatic  vein. 

The  angulation  at  the  junction  of  the  lower  enti  of  the  sigmoid  flexure  with  tht 
first  part  of  the  rectum,  caused  by  the  greater  mobility  of  the  former  an'! !'«  descent  by 
gravitation  to  a  lower  level,  often  constitutes  an  olMUcle  to  the  pas.s.igc  .  i  bougie  or 
tube,  or  sometimes  even  of  liquids,  into  the  sigmoid.  In  various  examinations  anil  in 
washing  out  the  colon  it  is  therefore  frequently  desirable  to  put  the  patient  in  the  kiRc 
chest  posture,  which  ofti  ii,  by  gravity,  lessens  or  removes  this  cause  of  obstruction 

Usually  a  tube  cannot  be  passed  completely  through  the  sigmoid  flexure,  l)ui 
often  carries  the  latter  with  it  by  engaging  in  a  sacculu>  or  a  fold  of  mucous  nitm 
brane.  The  tip  of  the  instrument  may  Ijc  felt  through  the  abdominal  wall  at  a  iK)int 
at  or  beyond  the  mid-line,  which  ma>'  lead  to  the  mistaken  belief  that  it  has  entered 
the  colon.  Exceptionally  it  is  possible  to  make  it  do  so,  the  passage  of  the  tiil)c 
being  facilitated  by  the  injection  through  it,  as  it  advances,  of  an  oily  liquid  in  siif 
ficient  quantity  to  distend  as  well  as  lubricate  the  sigmoid  curve. 

Wounds  of  the  latge  intestine  are  less  dangerous  than  those  of  any  other  jMirtion 
of  the  intestinal  tract  becaus*?  (a)  the  lessened  fluidity  of  the  intestinal  contents  dimin- 
ishes the  risk  of  fecal  extravasation,  and  {b)  if  the  wound  passes  through  the  lumbar 
parietes  and  involves  only  the  fxjsterior  wall  of  the  gut,  the  opening  may  be  entirely 
extraiJeritoneal.  According  to  Treves,  a  mesocolon  is  found  in  connection  with 
the  ascending  colon  approximately  once  in  four  times,  and  with  the  descending  colon 
once  in  three  and  one-half  times.  In  75  cases  out  of  100,  therefore,  such  a  wound 
of  the  colon  would  be  attended  by  a  minimum  of  danger. 

In  operations  on  the  large  intestine  it  may  be  identified  by  (a)  the  longitudinal 
bands,  especially  the  anterior  and  inner,  the  posterior  being  uncovered  by  peritoneum 
and  therefore  less  conspicuous,  and  being  placed  alon^  the  attached  border  of  the 
ascending  and  the  dc-scending  colon  ;  {b)  the  epiploic  appendages  found  more  abun- 
dantly along  the  inner  ban  '  and  on  the  transverse  colon  ;  (c)  its  sacculi  which  may  be 
seen,  and  its  fecal  concretions  which  may  often  be  felt ;  and  in  addition,  as  compared 
with  the  small  intestine,  (d)  its  lesser  mobility,  greater  diameter,  and  the  absence 
of  the  palpal Je  transverse  ridges  of  the  vaU  uI.t  conniventes.  It  should  be  remem- 
bered that  when  it  is  greatly  distended  the  longitudinal  bands  and  sacculi  are  almost 
or  ciuite  obliterated,  and  that  the  epiploic  appendages — peritoneal  pouches  filled  with 
fat — ^are  absent  on  the  posterior  ai-pect  of  the  gut  and  in  the  rectum. 

Colostomy. — (a,  Lumbar. — If  the  descending  colon  is  opened  through  the  loin, 
it  should  be  through  an  incision  following  the  oblique  supra-iliac  crease.  The  course 
of  tht  gut  corresponds  to  a  verucal  line  1 2  mm.  ( J^  in. )  external  to  the  centre  of 
the  crest  of  the  ilium.  The  incision  crosses  this  at  its  middle,  therefore  a  little  below 
the  kid-  ey  or  on  a  level  with  its  lower  edge,  and  divides  the  posterior  fibres  of  the 
external  oblique,  the  anterior  ones  of  the  latissimtis  dorsi  and  those  of  the  internal 
oblique,  the  lumbar  fascia,  the  posterior  fibres  of  the  transversalis  muscle,  and  the 
transversalis  fa.scia.  At  this  lc\-el  the  descending  colon  lies  in  the  angle  Ijetween  the 
psoas  and  quadratus  lumborum  muscles.  In  the  absence  of  a  mesocolon  (64  per 
cent. )  the  operation  should  be  extraperitoneal. 

(^)  Inguinal. — An  incision  similar  to  that  often  employed  in  appendix  cases 
and  lartjely  interim  ular  may  be  made,  its  centre  being  4  cm.  (about  iJ4  in.  )  from 
the  left  anterior  su|h  lior  spine  on  a  line  from  that  point  to  the  umbilicus.  The  sig- 
nioid  flexure,  the  portion  of  gut  to  be  opened,  may  be  recognized  by  the  ta-nia-.  the 
sacculi,  the  appendages,  etc. 

The  various  operations  to  effect  anastomosis  between  portions  of  intestine  ahoxe 
and  below  ficcluded,  diseased,  or  gangrenous  areas  depend  for  their  success  in  many 
instances  upon  the  mobility  of  the  intestine  and  therefore  upon  the  exi~  cnce  and  the 
length  111  a  ni  -Mjcolon. 

In  colectomy,  or  complete  resection  of  a  portion  of  the  large  intestine,  the  usual 
cr.re  as  to  the  vascular  supply  of  the  retained  gut,  the  inversion  of  its  edges  w\(\  thr 
approximation  of  serous  surfaces  must  be  exercised. 


PRACTICAL  CONSIDERATIONS-    THE  l.ARC.K  INTESTINK.    I'-s., 

The  Rectum  and  Anu».— In  rcUiion  to  it»  discasts  and  injuries  th.-  rictuni 
«avI^t?onv"„?nriyt^Jivided  into  two  .x.rtion.  :  ( .  »  th.^vu,  fro.n  th.  ,.r- 

'''^  TnTaS  childtr  thiSwc'S^tL  of  the  rectum  is  strajghter.  more  vertical 
more  of  anVwomS  orga'^.  and  more  movable  than  later  m  life.     The  su,,,>ort 
Svln  hv  the  f™l  reflections  from  the  rectum  to  the  other  pelvic  organs  .s  less,  on 
f^oantVf  theTndeviSd  condition  of  the  pr.«tate  and  uterus.     The  sacral  curve 

r:  ':;;^'^e  ItrrZidcilrand  th^e  superior  hemorrhoidal  t^UnesCPj    7  7  .; 

and  of  the  terminal  branches  of  the  inferior  mesenteric  vems  to  the  feci  con- 
tents of  the  sigmoid  and  rectum,  exposing  them  to  frequent  pressure. 


1690 


HUMAN   ANATOMY. 


It  may  now-  readily  be  understood  how,  in  the  presence  of  the  above  pre- 
disposing conditions,  hemorrhoids  may  result  from  (a)  direct  pressure  upon  the 
veins,  as  in  constipation,  pregnancy,  ovarian  or  prostatic  enlargements  ;  (6)  indirect 
pressure  through  the  column  of  blood,  as  in  hepatic  or  splenic  disease,  or  from 
the  contraction  of  the  diaphragm  and  abdominal  muscles,  as  in  coughing  or  lifting 
heavy  weights,  or  as  in  straining  due  to  the  presence  of  stricture  or  vesical  cal- 
culus or  cystitis  ;  and  (c)  irriutiun  of  the  rectum  or  anus,  causing  congestion  of 
the  hemorrhoidal  veins. 

It  will  be  seen  that  chronic  constipation  is  a  possible  cause  of  hemorrhoids 
under  each  of  the  above  headings  :  the  fecal  masses  press  upon  the  veins,  irritate 
the  rectal  mucosa,  and  necessitate  straining  for  their  expulsion. 

Ulceration  of  the  rectum  and  anal  canal,  whether  from  inflammation  or  infec- 
tion following  trauma  (from  indurated  faeces  or  from  foreign  bodies),  or  caused  by 
dysentery,  tuberculosis,  syphilis,  or  cancer,  is  of  anatomical  interest  in  its  relation, 
first,  to  the  vascular  and  nervous  supply  of  the  parts,  and,  next,  to  the  surrounding 
regions. 

The  rectum  proper  is  characterized,  as  Hilton  long  ago  showed,  by  great 
distensibility  and  little  sensibility  ;  the  anal  canal  strongly  resists  distention  and  is 
extremely  sensitive. 

The  rectum  is  supplied  largely  from  the  sympathetic  system  through  the  infe- 
rior mesenteric  and  hypogastric  plexuses.  The  anal  ner\e-supply  is  chiefly  from 
the  sacral  plexus,  especially  the  fourth  sacral  and  the  pudic  nerves,  the  filaments  of 
which  enter  the  gut  at  about  the  level  of  the  "white  line"  which  marks  the  junc- 
tion of  skin  and  mucous  membrane  and  also  the  demarcation  between  the  internal 
and  external  sphincters.  The  motor  and  sensory  supply  to  the  anal  canal  is  far  in 
excess  of  that  to  the  rectum.  Corresponding  differences  are  observed  in  the  vascu- 
lar supply.  Although  the  inferior  mesenteric  artery  brings  through  the  superior 
hemorrhoidal  a  relatively  large  amount  of  Uood  to  the  rectum,  it  contributes  but 
little  to  the  anal  canal,  which  is  richly  vascularized  by  the  pudic  arteries. 

These  facts  explain  the  extraordinary  absence  of  subjective  symptoms  often 
observed  in  cases  of  large  fecal  accumulation,  malignant  growths,  or  extensive 
ulceration,  when  the  rectum  alone  is  involved.  They  likewise  explain  (through  the 
association  of  the  pudic,  the  fourth  sacral,  and  other  branches  of  the  sacral  plexus) 
the  great  pain  of  anal  ulceration  (fissure)  or  of  inflamed  and  protruding  hemor- 
rhoids and  the  associated  muscular  cramps  in  the  limbs,  the  vesical  irritation  or 
spasm  (often  causing  post-operative  retention  of  urine),  the  lumbar  !nd  iliac  pains, 
and  other  reflex  phenomena  so  common  in  anal  disease. 

The  great  power  conferred  upon  the  sphincters  by  their  unusually  rich  nerve- 
supply,  and  developed  by  the  resistance  they  must  frequently  and  necessarily  offer  to 
the  peristaltic  action  of  the  intestines  and  to  the  descent  by  gravity  of  feculent  matter, 
enables  these  muscles,  especially  the  external  sphincter,  through  their  obstinate  and 
almost  continuous  reflex  spasm,  to  become  not  only  a  cause  of  the  excessive  pain  of 
fissure,  but  also  an  obstacle  to  healing.  It  is  therefore  usually  requisite  in  the  treat- 
ment of  such  ulcers  to  paralyze  the  sphincters  by  overstretching,  often  supplemented 
by  either  partial  or  complete  section  of  the  external  sphincter.  The  higher  an  ulcer 
in  the  rectum  the  more  amenable  it  is  to  treatment  by  physiological  rest  (Hilton). 

Ulceration  in  the  rectum,  as  elsewhere  in  the  intestinal  tract,  may  result  in 
stricture,  or  in  fistulous  connection  with  neighboring  organs  or  tracts,  as  the  bladder 
or  vagina. 

Lymph  infection  proceeding  from  the  rectum  involves  the  pelvic  and  lumbar 
glands,  especially  those  lying  on  the  front  of  the  sacrum  ;  if  from  the  anal  canal,  the 
upper  and  inner  inguinal  glands  are  involved.  The  lymphatic  distribution,  like  that 
of  the  ner\'e8  and  blood-vessels,  is  thus  seen  to  be  quite  different  for  the  rectum 
and  for  the  anal  canal. 

If  infection  spreads  by  vascular  rather  than  lymphatic  channels,  it  usually  travels 
by  way  of  the  portal  vessels  and  affects  organs  connected  with  the  digestive  system, 
especially  the  liver.  Thus  a  not  uncommon  secjuel  of  dysentery  is  hepatic  abscess. 
On  the  other  Iiand,  emboli  from  external  hemorrhoids  have  been  known  to  enter  the 
general  venous  circulation  and  have  caused  death. 


I 


PRACTICAL  CONSIDERATIONS:   THE  LARGE  INTESTINE,    .r.,. 
Subcuuneous  or  submucous  infection  invoK^^^^^ 

tuberculous),  and  may  extend  f  °  ^fj'^t;;;" S^J^ther  of  the^b.,ve  varieties  of 
space,  and.  beginning  as  an  "'•'*'^-^«^«l^f*^„^"^  ?""  the  proximity  of  the  rec- 
fiWula.     Such  abscesses  are  very  frequent  because  om  a  j  v       character  of  the 

Turn,  the  frequency  of  rectal  ulceraUon  and  ^^e  'nva^ly  scpt.c 
rectal  contents  :  (*)  the  poorly  ^»^"'^„"f  ! J  ?"^  ^estL  ;  ^       the  aWnce  of 
ing  the  fossa  ;  (r)  the  effect  of  pvity  m  'nducing  ^^T^/t^e  slight  but  often 
iles  competent  to  faciliute  «he  -etum  of  venou    "ood     (^)/;^^^^       .^e  fossa 
repeated  trauma  caused  by  '^P^K'^'^K  . ^r J«^™"^'  \  ^     ^y^  ^he  expc«ure  of 

a  sufficient  barrier  to  the  progress  of  *^  ^t^;^„X^^'^^^and  the  tuberosity  of  the 
limited  by  the  obt"mtorfa^«.  the  obturator^  m^^^^  ^^.   ^^^^^^ 

ischium  (Fig  '426).     Internally  Mow  the  ^^^^  resistance,  and  accordingly, 

mm.  (H  «n. )  above  the  anus.  '»  ""f  J^  P°'  ;„  ^^^^y  be  found  about  on  the  hne 
when  it  results  in  fe'"la^  t»^f.'"^""*]°Cm^Zfo^  bring  prevented  by  the  blend- 
between  the  sphincters,  .ts  higher  ex«  from  the  (^  ^^"f  P^  ,^  ^.j.^^he  bowel- 
i„goftheanalandrecto-v«.calfa^a^  and  the  le^a^^^^^^^  .^  ^^^ 

wall.  If  it  reaches  the  surface  ?  '^J  .^ch  Jm  and  the  edge  of  the  gluteus  maxi- 
between  the  anus  and  the  tuberosity  «* '^^ '"^^'T  fro„t  (Fig.  H^J)-    This 

mus  behind  and  the  --efle^;""  "'/t! '^^P  ^utt  m^^^^  the  external  sphincter, 
external  opening  .s  apt  t^^Too^^  Irfy  on  acc3  of  the  suffering  caused  by 
Such  abscesses  should  be  «f  "^.fX  ^"  ^th  sacral  (on  its  way  to  supply  the 
pressure  on  the  twigs  of  ^he  «™^' ^^*'^v'^^i°"^^^  Tu^rficia!  perineal  nerves,  and 
external  sphincter),  the  '"««="««■  •^'='"°y^*'°''*,i^", ,  an^^^  extension  upward 
also  to  avoid  the  formation  o  fistula,  and  t°J°^f  jJ.  *"y„P^^^  tissue  between  the 
and  a  resulting ;^r/.,V  cellultUs  ^^l^.'''y^'^^l^l^''^§^Xn^^  They  should  be 
recto-vesical  and  pelvic  fasci*  ^"^ '.^^  .P!"f  "^7he  wal  s  ^nnot  definitely  be  ap- 
opened  widely  to  permit  of  Pfi^f^^^^'^X^^'  dialinVfro^  the  anus,  so  as  to  avoid 
proximated;  the  incision  *h«">^  »^ ,«"/J•"^'?S^&  such  an  abscess,  the 
5,e  hemorrhoidal  vessels.     In  ^^^f  P'.^f  "^/„°J,  *^^^^^^^^  usually  divide  the 

incision  should  ""ite  the  externa  and  internal  «P^^;"8f-  ^^  j^,^  j^  not  per- 

^-t:^:l^  aS.  f  f  ^itri;r^  jSs^k  r^K^s 
LrJ'sr;evTnrg^tt'=^^^^^^        ^^^^  -  -  '^  ---^ 

through  the  medium  of  t^etriangdar  ligament  ^^^  ^^^  .^^^^ 

Fistula  requires  ?P-"7"  ^f^^"^,^  ^^rX  mSar  coat  of  the  gut  itself,  and 

ir^l^^n^VS^^rLX^^^^:;:'^^^  -penally  irritate  and  sometimes 

''^'SS^  the  rectum  may  ^^^^^:,Xi^l^JS'^ 
two  or  three  inches  of  the  anus. , '"  »^'''°V^^^' and'^SrWoo^  which  may  streak  the 
from  contact  of  fsces  with  an  ">f^™*f„^""'^^^^^^^^  ^hi-^h  should  be  care- 

stools,  there  are  symptoms  due  '" ''*  ^"/'Xw  ^f  ^e  Lrum,  it  will  press  upon  the 
fully  studied.  If  it  extends  ^.^'^^^^ 'J'^,,;™  sdatica^umbago.  sacro-iliac  disease, 
sacral  plexus,  causing  pain  ^^^^^^^l^^  ^S^J'S  J  symptoms  in  the  male  may 

Sr^Ksi,^;SngY^  iirerSip.e'and  iniracuble  fistul.. 


m 


1693 


HUMAN  ANATOMY. 


The  relations  oi  the  rectum  a^e  of  much  practical  importance      Those  urith  ft,- 
pentoneum  have  been  described  (page  17s?)      Th*  fart  tfia^h?;  J™?^      1        * 

in   suprapubic  lithotoS^TpLVtectomyf^  In  tli'e  feUl^r^T^-   "'"•  °' 

pushes  the  hindus  uteri  Va?d  and  to3s  the  pubei  "*'  '"^  *''""'"'" 

Enlargement  of  the  prostate  may  so  dep' 
gready  to  diminish  its  lumen.     Occasio 
produced  thereby.     Acute  prostatic   inf 
recognized  by  rectal  touch,  as  may  similai 
are,  for  obvious  reasons,  apt  to  be  associ. 
painful  defecation. 

(n\  fio^T^^'^u"  ^^t  ''!■*"'"•  ?*  '°''  ^''"^'«"  «'  carcinoma,  it  may  be  approached 
(a    komMou,,  when  the  d.se^  is  near  the  anus,  by  isolating  the  lower  Kf  the 

Si      f      .^K""•'  '?  ■'"'''''^'^'  ^^^  '"^'^'°"  "«y  ''^  "nade  outside  the  extemTsnhinc 

tTe'ir,siLirr"re^t^""t°h:  ta;:;^!  t-^ch''  ?  fn  "«2:™tftde 

eased  segmen    of  ^t  invaginated   into  it  and  excised,  and  U^e  reSder  of  th,l 
rectum   and   sigmoid  united   (Maunsell).      U)   It  may  be    reach^  C,;  ^n   ^      , 

or  b/sriKrhcTi^r^  '^  '^^  «"«"•  ^^  ^-^'""^  ^i*. 


the  anterior  wall  of  the  rertum  as 

!■  ptoms  of  rectal  obstruction  are 

•   and  prostatic  abscess  may  be 

"ins  of  the  seminal  vesicles.     They 

'th  rectal  irritation,  tenesmus,  and 


PRACTICAL  CONSIDERATIONS:  THE  LARGE  INTESTINE.    Km 

«ve  a  sensation  of  a  broad  muscular  band  around  the  bowel"  (CripP*)-  T»^«  « 
S^^  dSt  Dosteriorly  and  represents  the  posterior  edge  of  the  levator  am.  It  is 
1^1  fSL  CTtf^  anus.  A  patulous  condition  of  tl..  anus  or  a  cavernous  or 
CuoSi*^''  condTtion  of  the  rectum  should  suggest  stricture,  the  muscles  below 
whtlT^ng  no  function  to  perform,  become  enlarged  t"'*  >'"'^'"«\  ,tnre  '^' 
rSv  tiX  eriD  of  the  finger,  with  marked  tenderness,  should  suggest  tissure. 
tionaly  tight  gnpotneng    ,  increased  area  of  bowel  wi.l  be  made 

vesicles  and  in  som^c^aporuon^^^^^^  ,he  rectum  explain 

tate  and  at  the  «*1"' ^^'^^'^^^jch  during  defecation,  their  contents  are 
*:reS  into^e'urlt^KrrScr^^^^        mises.  exciting  the  apprehension 

"*  *?„PSer  th^l^Sr'm™^^^^^^^^^  to  its  bas-fond.  and  evenif  not  dis- 

-4sSH^cifei^:sa^i^t^£^a..so 

'^  Tn  femST/l^o-vaginal  walls  and  the  os  uteri  '-X  .^j^J -^^Sll^^^ 

ss3-fs3ss:ss|»=gs 

under  normal  conditions,  and  tense,   tender,  and  bulging  if  an  abscess  occupies 

admission  ol  air.  and  inspection  is  thus  'acihtateri.  ^ 

(c)  By  iaugies  stricture  may  be  recognized  but  '^[^ JJ*,"**  '^^T'""  Lids-is 
action  dL  to^  contact  with  one  of  the  -fjf^b^S^^^ST  si'^^^^^^^  Ss 
not  mistaken  for  a  contracUon.     It  should  be  remembered  too  t^^^^  tne    ^ 

to  the  .traeture.  menSonc.  ,.  «)( . )  *«»f'"°  "  ^^f  3l'e«,  S^o-iKhiatic 


t694 


HUMAN  ANATOMY. 


arch  ;  (5)  the  internal  iliac  artery  through  most  of  its  course  ;  (C)  in  the  female  the 
uterus  and  the  ovaries.  If  the  hand  will  enter  the  sigmoid  flexure,  most  of  the  abdo- 
men may  be  explored. 

Examination  through  the  rectum  by  this  method  is  distinctly  dangerous  from 
the  risk  of  laceration  of  the  gut.     It  is  therefore  not  in  much  favor. 

DEVELOPMENT  OF   THE  ALIMENTARY   TRACT. 

Reference  to  the  cross-section  of  a  young  mammalian  embryo  (Fig.  1428)  shows 
the  early  relation  between  the  primitive  gut  and  the  yolk-sac,  of  which  latter  the 
former  is  evidently  a  part.  The  longitudinal  section  of  a  very  young  human  embryo 
(Fig.  46,  page  39)  emphasizes  the  wide  communication  between  the  two.  The 
differentiation  of  the  gut  from  the  yolk-sac  is  accomplished  by  the  approximation 
and  union  of  the  two  splanchnopleuric  folds  which  consist  of  the  entoblast  internallv 
continuous  with  that  of  the  yolk-sac,  and  the  visceral  layer  of  the  mesoblast  exte'r- 
nally.     As  the  union  of  the  splanchnopleurae  proceeds,  the  gut-tube  becomes  closed 


Fio    i4a8. 


Neural  tube 


Amniotic  lac. 


Amnion, 


Body-<»vity_/, 


Vitelline  vein. 


Open  K"t-tulw 
Transverse  section  of  esrly  rabbit  embryo.  %h< 


Myotome 

•Xotochord 
Primitive  aorta 

Body<avity 

.VitcMine  vein 


Visceral  mesoblast 


ii^  differentiating  gut-lube  still  communicating  with  vitelline 

throughout  its  cephalic  and  caudal  segments,  between  which,  however  it  remains 
open  and  connected  with  the  yolk-sac  by  a  communication  that  rapidly  narrows  and 
elongates  into  the  vitelline  or  umbilical  duct,  a  structure  that  for  a  considerable  time 
remains  as  a  can  il  bearing  the  diminishing  yolk-sac  or  umbilical  vesicle  at  its  outer 
end.  The  primitive  digestive  tract,  therefore,  is  closed  both  anteriorly  and  pos- 
teriorly, and  soon  may  be  divided  into  three  segments  ;  the/ore-,  mid-,  and  hind-gut 
Formation  of  the  Mouth.— The  cephalic  segment,  the  fore-gut,  is  somewhat 
dilated  at  its  anterior  extremity,  and  there  constitutes  the /Jr/iw/Zfrr //farj'// r  which  at 
hrst  IS  separated  from  a  bay-like  depression,  the  oral  recess  {stonwdteum)  which 
meanwhile  has  been  formed  by  the  downward  flexure  of  the  anterior  cerebral  vesicle 
and  the  development  of  the  visceral  arches.  The  septum  between  the  fore-eut  and 
the  oral  recess,  ih^  phanmgeal membrane (¥\k.  1429).  consists  of  the  directly  aniKJsed 
entoblast  lining  the  primitix-e  pharynx  and  the  ectoblast  continued  from  the  surface 
no  mesoblHst  mtervenm-.  The  ph.-,ryngea!  membrane  very  cariy  (probably  aln.ui 
th.^  thirteenth  or  fourteenth  day  in  man)  becomes  broken  up  by  the  formation  of 
holes  and  soon  disappears,  the  primitive  oral  and  pharyngeal  spaces  thereafter  freelv 
communicating.  ' 


DEVELOPMENT  OF  THE  ALIMENTARY  TRACT. 


1695 


The  entrance  into  the  primary  oral  cavity  is  a  pentagonal  opening  bounded  by 
five  proje^fo^s -superiorly  by  the  unpaired /r^«/«//r.r«.  extending  downward 
fromTi  region  of  thVanterior  cerebral  vesicle,  laterallv  by  the  n.ax,llary  proasscs, 
and  inferioriy  by  the  fusetl  mandibular  processes  of  the  hrst  visceral  arches  (F'K- 74)- 
The  Ser  changes  leading  to  the  formation  of  the  definitive  mouth  and  the  sepa- 
Sfon  Sf  the  oral^and  nasal  cavities  are  described  in  connection  with  the  development 

"'  "iL'pTTmSpL'inx  bear,  on  each  side  a  series  of  four  lateral  dilatations  the 
tharmilTpluches  (Fig.  73).  corresponding  to  the  inner  half  of  the  visceral  cle  s 
S^iTter  breathing  animtk.  In  t\ie  mammals  true  fissures  are  not  formed,  the 
^e^  dehs  be?ng  represented  by  the  external  and  interna  furrows  lying  be  ween 
The  vSceSl  archi  and  separated  by  a  delicate  ecto-entoblastic  partition.  The  details 
of  theTTelopment  and  meUmorphosis  of  the  viscera!  arches  and  furrows  have  been 
considered  (page  60). 


Fio.  14*9- 


Posterior  c«rebr»l  veiicle- 
Primitive  pharynx 


Ventral  aorta 


Gut-tube 


Neural  tube 


Caudal  pole  (obliquely  cut) 


Middle  cerebral  vesicle 


Anterior  cerebral  vesicle 


Pharyngeal  membrane 


Oral  recCTS  istomodBUm) 
.Truncus  arteriosus 
Pericardial  sac 
li Primitive  auricle 


Primitive  ventricle 


Vitelline  duct 


Sagittal  section  o.  early  rabbit  embryCrfiowinK  oral  reces.  and  primitive  pharynx  still  separated 


<  n. 


Formationofthe  Anus.— The  posterior  or  caudal  segment  of  the  primitive 
gut-t^'^thTseaTof  the  changes  leadll^g  to  the  formation  of  ^f  ^ --3,-'  - 
Formeriv  the  development  of  the  anus  wa.^  regarded  largely  as  »•«• /^P^*'*"  "  "'  ^ 
pr™  similar  to  that  leading  to  the  communication  between  the  "^a  /ev-ess  an  the 
Fr^^^t  an  external  depression  {proctodeum)  being  separated  from  the  hind-gut  by 
'Z"S:^o^STl:ZT:.l^c^\.l.r  was  broken  down  to  form  the  anus,  which  was 

!£t  the^rimary  podtbn  ol  the  anal  .ntage  »  on  the  dor-l  .urface  o(  the  ea,l,ryo. 


1696 


HUMAN   ANATOMY. 


Its  migrauon  to  the  ventral  surface  is  associated  with  the  growth  and  changes  affect- 
ing the  tract  situated  between  the  neurenteric  canal  and  the  anal  anlage  giving  rist 
to  the  /«//-3«rf  (Hertwig)  from  which  the  caudal  appendage  arisesT  In  conse- 
quence of  the  displacement  occasioned  by  these  changes,  the  anal  anlage  eradualh 
assumes  a  ventral  position  immediately  beneath  the  tail.  -»     s  ^ 

Coincident  with  this  migration  the  primitive  gui-tube  becomes  enlarged  in  the 
Zr^i^  n  ^'anto's  to/o™  a  common  space,  the  c/oaca,  into  which  open  the  hind 
gut,  the  allantois,  the  Wolffian. ducts,  and  the  caudal  or/V^rf-awa/p-w/,  a  temporary 
entension  of  the  gut-tract  toward  the  tail-bud.  The  ventral  wall  of  the  cloaca  shutting 
It  off  from  the  extenor  is  formed  by  a  delic;ite  partition,  the  anal  or  c/oaca/  mem- 
brant  (Fig  1644),  consisting  of  the  apposed  entoblast  and  ectoblast  A  slight  de- 
pression the />ni»»V»ir  anal  groove,  indicates  the  position  at  which  the  membrane 
breaks  through  to  establish  the  cloacal  orifice  in  those  forms,  as  birds  and  mono- 


FiG.  I4JO. 


Mid-brain 


Optic  vesicle. 
Fore-brain 


ind-brain 


I  pharyng.  pouch 

Ventral  aorta 


n  pharyiig.  pouch 

■III  phary-ng.  pouch 

.Gut-tube 

Duct  of  Cuvier 
Aorta 


Liver 


Vitelline 
duct 
Vitelline 
Neural  tube  artery 


Gut-lube, 
lower  part 


Belly-stalk 


Reconstruction  of  sagittally  sectioned  human  embr>o 
?^,v  '^■"■■'''  sJiowinK  relations  of  dixestive  tube,  x  26. 
{ji/ler  His  modrl.) 


I  pharyng.  pouch 

3  aortic  bow 

II  pharjng.  pouch 
3  aortic  bow 

III  pharyng.  pouch 
4  aortic  bow 

IV  pharyng. 
pouch 


Lung-anlage 


Allantoic  duci. 
L'n-.bilical  artery- 


Reconstruction  of  digestive  tube  of  preceding  em- 
bryo ;  aortic  bows  and  trunk  also  shown.  X  36.  (Aftrr 
His  model.)  ^ 


o,?lv7J^rM  cloaca  persists.  In  the  higher  mammals  the  cloacal  stage  is 
only  temporary,  the  cloaca  becoming  subdivided  into  two  compartments  by  the  for- 
mation of  a  septum,  which  grows  downward  to  meet  the  cloacal  membrane  The 
anterior   compartment  becomes    the   uro-genital   sinus,    the   posterior  the   rectum. 

wffh  th.';,'''"""'""-^  f  ,  <!  "^""f^  membrane  disappear,  and  these  spaces  are  provided 
with  the  uro-genital  cleft  and  the  definitive  anus  respectively 

Differentiation  of  the  simple  gut-tube  into  distinctive  segments  begins  with  the 
stomach,  which  appears  as  a  small  spindle-form  enlargement  at  some  little  distance 
below  the  pnmitive  pharynx,  the  portion  of  the  tube  between  the  two  correspond- 
mg  to  the  early  oesophagus.  The  gut-tube  lies  close  to  the  posterior  wall  of  the 
Dody-cayity,  .-.nd  at  this  stajje  (corresponding  to  about  the  fourth  week  in  the  human 
embryo)  presents  five  divisions,— the  primitive  ora  cavity,  the  primitive  pharynx, 
^L3  fr''  f^  ^'°'P'«=h,  and  the  intestinal  tube,  which  latter  freely  communil 
cates  with  the  yolk-sac  through  the  vitelline  duct. 


DEVELOPMENT  OF  THE   ALIMENTARY   TRACT.  1697 

The  digestive  tube  is  at  first  closely  bound  to  the  posterior  body^^;!  ^y  a  short 
K,™.rf  m«^tir  band.     This  attachment,  or  primtttve  mesentery,  itom  the  lower 

rinn  of  ite««  which  becomes  oblique,  the  lower  end  of  the  or^an  {msing  to  the 
SX  whu"te  up«er  end  is  displaced  towards  the  left  in  consequence  of  the  mcreasmg 
volume  ofthe  liver  Embryos  of  the  sixth  week  exhibit  marked  chaijge  m  the  fonn 
volume  01  ine  uver.      r.       y  neater  curvature,  has  bt-come  bulged 


Fio.  143I- 


Allantoic  duct 


Bzteinal  tuifac*' 


.IntotiM 


Cloaol  membniw 


-ail-bad 


P.«  o,  caada,  «.d  o,  «|.tul  ^X^.r^^^^V^tl^^^iJ^k"'^"''''  "*"  '"  "™"'"'"""' 

Stomach  consists  of  the  entoblastic  lining  surrounded  by  the  Manchnopleuric  meso- 
S^  The  differentiation  of  the  gastric  glands  begins  towards  the  close  of  the  th^^d 
month  as  minute  epithelial  outgrowths  from  the  entoblastic  layer.  A  few  weeks  ater 
J^rela^sWme  branched,  and  the  parietal  cells  appear  f  d.fferentjat.ons  from 
sinieepitheUd  elements  lining  the  pept'kfoUicles.  In  the  fifth  tnor^.  the  length  of 
Te  glandrhas  increased  to  about  %  mm.,  and  during  the  succeeding  monh  to 
fr^m^4^.7o  mm.  (KoUiker).  Differentiation  of  the  mesoblasUc  tissue  into  the  inner 
circular  and  outer  muscular  layers  occurs  during  the  fourth  month.  •  „„„:ki„ 

circular  ana  ^  j^  ,  ,^  .'  j^ric  end  of  the  stomach  at  first  pa.sses  msensibiv 
into  the  ro-  ..y  ^de  be^munR  of  the  characteristic  U-shaped  ntestinal  >ooP  -h.cK 
LxTe.  •  from  the  ston.ach  ventrally.  its  closed  end  or  arcf.  being  attached  o  he 
vUeline  ducT  and  then  returns  to  the  posterior  body-wall  to  be  continuous  with  the 
Sinai  Snent.  which  maintains  itrsagittal  relations  in  close  attachment  wUh 
th^o™^Snmd.;r^'  of  the  bodv-c.ivity.  The  inferior  limb  of  the  loop  early  shows 
WinnSdifferentStion  into  large  int^tine.  the  junction  of  the  latter  with  the  smdl 
Stbe  beingTndicated  by  the  flight  c<-ecal  expansion.  Even  at  this  period  a  defi- 
SrSular  relation  has  been  established  by  the  three  main  segments  of  the  gastro- 

107 


1698 


HUMAN   ANATOMY. 


intestinal  tube  and  its  mesentery.  Within  the  meaogastrium  course  the  three 
branches  oi  the  coeliac  axis  ;  the  superior  mesenteric  artery  passes  within  the  mesen- 
tery between  the  limbs  of  the  intestinal  loop,  while  the  inferior  mesenteric  artery  is 
distributed  to  the  last  part  of  the  intestinal  tube. 

The  subsequent  changes  which  the  intestinal  tube  exhibits  during  its  growth  have 
been  carefully  studied  in  reconstructions  by  Mall,'  whose  conclusions  differ  materially 
from  the  prevailing  views.  According  to  this  investigator,  the  rapidly  augmenting 
liver-mass  occupies  so  large  a  portion  of  the  still  small  abdominal  cavity  that  there  Ls 
no  space  left  for  the  expansion  of  the  intestinal  tube.  In  consequence  of  this  con- 
dition the  greater  part  of  the  gut  is  early  displaced  from  the  abdominal  cavity  into 
the  coelom  within  the  umbilical  cord,  the  upper  limb  of  the  U-loop  then  lying  to  the 
right  and  the  lower  to  the  left.  The  growth  of  the  small  intestine — more  rapid  than 
that  of  the  large — soon  results  in  the  production  of  six  primary  coils,  the  identity  of 
which  is  retained  not  only  throughout  development,  but  can  be  established  even  in 
the  adult  (Mall).  The  first  part  of  the  gut-tube,  continuous  with  the  stomach  and 
receiving  the  ducts  of  the  liver  and  the  pancreas,  increases  relatively  little  in  its 


Fio.  1 43 J. 


Future  diaphngm 


Anterior  mesentery 
(falcifurm  ligament) 


Anterior  menentery 
(gastr^hepatic  omentum) 


Umbilical  vein 
Body-cavity, 


Connection  of. 
vitelline  btallc 


jSujierior  menen- 
leric  artery 

Mesenterium 
commune 


Inferior  mesenteric  artery 

Allantoic  duct 

Cloaca 


deginninjc  of  large  Intestine 
Diagram  showing  early  relations  of  anterior  and  posterior  mesentery.    { Based  tm  JIgurta  of  Mall  and  Toldt.) 

length,  and  therefore  does  not  become  secondarily  convoluted,  as  do  the  remaining 
coils  of  the  small  intestine.  This  part  is  later  represented  by  the  duodenum.  The 
outer  primary  coils  undergo  great  elongation,  and  consequently  present  secondary 
convolutions  of  increasing  complexity,  all  of  which  for  a  considerable  time  (uniil  the 
embryo  has  attained  a  length  of  about  30  mm. )  are  retained  within  the  umbilical 
ccelom.  About  this  period  the  lower  part  of  the  body  grows  rapidly,  resulting  in 
increa.sed  space  within  the  peritoneal  cavity,  which  now  affords  room  for  the  tempo- 
rarily displaced  gut-coils.  In  consequence  of  these  changes  the  intestine  returns  to 
the  abdominal  cavity,  and  in  embryos  of  40  mm.  length  the  coils  no  longer  lie  within 
the  umbilical  cord.  Mall  has  shown  that  their  return  to  the  abdominal  cavity  occurs 
ill  a  definite  order,  the  upper  part  of  the  small  intestine  being  first  withdrawn,  the 
large  intestine  with  its  ciecal  dilatation  last.  On  re-entering  the  abdomen  the  upper 
part  of  the  smalt  gut  passes  to  the  left  hypochondriac  region,  while  the  lower  segment 
of  the  small  iiitestine  with  the  caecum  takes  up  a  position  towards  the  right  hypo- 
chondriac region.  Coincident  with  this  migration  the  large  intestine  is  differentiated 
'  Arch,  fur  An.it.  u.  Physiol.,  Supplement  Bd.,  1897. 


DEVELOPMENT  OF   THE  ALIMENTARY  TRACT. 


1699 


to  the  segment  in  front  of  the  bend.     Once  back  .m  »^^„l.^^;^^,y  ,^y  ;„  the  saR.ttal 

plane  of  the  cord,  are  arranpl  gen- 
erally at  right  angles  to  the  long  ax» 
of  the  bcKly.  and  the  antero-}x«tenor 
colon  becomes  transverse  (  Mall   ).      m 
consequence  of  these  changes  the  p«jr- 
tion  of  the  large  g..t  that  lay  w.thm  the 
cord  now  lies  obliquely  acr.«s  tht  ab- 
domen in  front  of  the  ducKlenu.n    the 
remaining  coib  of  the  small  mtestme 
Cg    placed   below.       The    oecum 
therefore,  occupies  a  position  beneath 
tSe  liver  on  the  right  side,  as  a  slight 

dilatation  at  the  beginning  of  the 
Tiinsverse  colon. .  The  ca<um  while 
gradually  increasing,  retains  this  gen 
Cl  posUion  until  ad  ustment  in  the 
teTgtrof  the  segments  of  the  large 
int^^tine  takes  place  shortly  ^^-'^^\ 
The  lower  part  of  the  large  gut  is 
,«i..»«,. "«"««• thrown  into  a  loop  extending  acroM 

the  abdominal  cavity,  which  becomes  the  sigmoid  fl^-J^u^m^n^h^'af;:^^^ 
nearly  one-half  of  the  enUre  length  of  tJ^«/^°";,,herpaS  of  the  colon  proport.on- 
the  sigmoid  flexure  becomes  shorter  and  theot^e^p  downward  towards  the 

ately  longer,  in  consequence  of  which  the  ^"J  the  ascending  colon.  These  por- 
right  iliac  fossa,  with  c«>-^«Po"<l>"K  1^^^  to  ^^  «or  s^^e  time  after  birth, 
tions  of  the  large  intestine,  however    con^«eto^  relations 

and  it  is  not  until  the  third  y-^'^^'^^^^^'^i    he  transverse  and  ascending  colon 
The  anomalous  anangement  ^^P^*  °"  ™  ^^^j^  ^^e  usually  dependent  upon 
""'^  *':^r"eroomenraSe'  imSffig  to  t^ke  up  a  transverse  and  superior 
Sot  a^d  hrcrlitJringTrelations  with  the  small  intestine. 


hain«ii  embryo  ot  17  mni.vert«-br.«Bl«pn      ^^^^     ^,^, 
umbilical  vein  ;   ft  .  I"™"  y"!" '     ;„  '(f,,  and  in  th»  Iw" 


Fio.  US*" 


Fio.  1435- 


Stion  of  (oramen  of  Wioslow.    X  8.    (.Vail.) 

»  ^Wrrht  literal  diverticulum  from  the  larger 

The  c«cum,  which  ^^J  «PP^^"f4^Su^  (fS.  1432T.  increases  in  size  until 
inferior  Umb  of  the  primary  Ujoop^f  the  gut^^^^^  ^    ^1  ; 

i^tinr   m"'^vJS"ofT^rl^  the  cLum.  however,  is  not  uniform,  since  its 

'Anatom.  Anzeiger.  Bd.  xvi.,  1899. 


1700 


HUMAN   ANATOMY. 


if 


dependent  terminal  portion  does  not  keep  pace  with  that  nearest  the  intestine.     I  li, 
ajjical  sefrment  of  the  aecum  remains  proportionately  small,  and  persisis  as  the  \«  i 
mifornr  appendix.     The  latter,  therefore,  corresponds  to  the  unexpandetl  morplio 
logical  termination  of  the  caKum.    This  relation  is  evident  at  birth,  when  the  apin  ndi  v 
forms  the  direct  ce)ntinuation  of  the  funnel-shaped  c*cum  ;  it  is  exceptionally  r. 
tainetl  in  the  adult  as  the  fcetal  type  of  caecum  occasi«)nally  observed.     Usually  tli. 
cacum  continues  to  expand  with  the  colon,  the  demarcation  of  the  apiiendix  1.. 
coming  progressively  more  emphiusized.  until  the  relative  size  of  the  two  tulx-s  cmn 
monly  seen  is  established.     The  usual  displacement  of  the  appendix,  so  that  it  aris.s 
from  the  left  and  posterior  wall  of  the  ciecum,  results  from  the  later  unequal  exp;insi..n 
of  the  right  side  of  the  latter,  whereby  the  origin  of  the  appendix  is  pushed  to  th. 
left. 

Differentiation  of  the  walls  of  the  intestinal  tube  begins  eariy  in  the  third  month 
by  the  formation  of  longitudinal  folds,  at  first  in  the  upper  part,  later  the  entin 
length  of  the  small  intestine.  These  folds  increase  in  number  and  size,  and  siil»it- 
quently  break  up  transversely  into  areas  from  which  the  villi  are  formed.  The  lattoi 
first  apjjear  in  the  upper  part  of  the  .mall  intestine  in  embryos  of  about  30  mm 
in  length  (Berry'),  and  gradually  .v^end  to  the  lower  segments,  the  villi  Ikmiil- 
present  throughout  the  small  intestine  in  embryos  of  about  10  cm.  in  length  \'illi 
also  exist  tempora-ly  in  the  large  intestine,  but  later  undergo  absorption,  so  th.it 
shortiy  after  birth  .  y  have  completely  disappeared,  while  those  within  the  small 
intestine  have  pr-  -j  increased  in  numbers  and  .size.  Early  in  the  fourth  month  tin 
intestinal  glands  ,  pear  in  the  upper  part  of  the  tube  as  minute  diverticula  clothed 
with  e.xtensions  the  entoblastic  lining  of  the  gut.  The  glands  of  Brunner  de\  elon 
somewhat  later  during  the  same  month  as  outgrowths  of  the  entoblast.  During  the 
fourth  month  the  mesoblastic  stratum,  from  which  arise  all  parts  of  the  intestinal  wall 
except  the  epithelial  elements  of  the  mucosa  and  the  glands,  undergoes  differentia- 
tion into  the  muscular  and  areolar  layers  ;  by  the  close  of  the  fifth  month  all  coat.s 
of  the  intestine  are  well  defined. 

Differentiation  of  the  Body-Cavity.— Owing  to  the  precocious  develop 
ment  of  the  mammalian  heart,  the  latter  organ  is  formed  by  the  approximation  and 
hision  of  two  lateral  aniages,  at  first  widely  separated,  in  consequence  of  which  union 
the  upper  part  of  the  ventral  body-wall  is  closed,  while  the  more  caudally  situated  is 
still  incomplete,  the  gut-tube  being  but  imperfectly  separated  from  the  yolk-sac. 
With  the  more  advanced  closure  of  the  ventral  body-wall  the  abdominal  canity  is  de 
fined.  The  primary  ccelom,  according  to  His,  may  be  divided,  therefore,  into  an 
upper  and  a  lower  portion,  the  parietal  and  the  trunk-cavity  respective!) .  These  spaces 
communicate  on  either  side  by  an  extension  of  the  parietal  cavity,  xh^i parietal  reass 
of  His.  The  ventral  portion  of  the  parietal  cavity,  which  from  its  e:!rliest  api>ear- 
ance  contains  the  heart,  becomes  the  pericardial  cavity,  and  is,  therefore,  appropri- 
ately named  Xhe pericardial  cvlom  (MalD.  The  upper  part  of  the  parietal  recess, 
since  It  later  contains  the  lung  and  forms  the  greater  portion  of  the  surrounding 
lung-sac,  may  similariy  be  designated  the  pleural  cielom.  For  a  time  the  separation 
between  the  pericardial  and  pleural  coeloms  is  imperfect,  owing  to  the  incompleteness 
of  the  postero-lateral  walls  of  the  heart-.sac.  This  deficiency  is  corrected  by  the 
growth  and  difTerentiation  of  \he pulmonarv  ridge  (Mall),  a  structure  that  extends 
from  the  liver  along  the  dorsal  wall  of  the  duct  of  Cuvier  to  the  dorsal  attachment  of 
the  early  fold  suspending  the  heart,  or  mesocardium.  Mall  has  shown  that  the  pul- 
monary ridge  grows  headward  as  the  pleuro-pencardial  membrane,  which  completes 
the  separation  between  the  heart  and  lung-sacs,  and  later  tailward  to  form  the  pleuro- 
Peritmeal  membrane,  which  sui  sequentiy  aids  in  closing  the  communication  between 
the  pleural  and  peritoneal  cavities. 

At  first,  immediately  below  the  young  heart  lies  the  wall  of  the  wide  yolk-stalk 
embedded  within  the  mesoblastic  tissue  of  which  the  two  large  vitelline  veins  passs  in 
their  course  towards  the  lower  end  of  the  heart.     With  the  formation  of  the  body- 
wall  and  the  narrowing  of  the  yolk-stalk,  the  enlarged  vitelline  veins,  in  their  journey 
towards  the  heart,  produce  a  broad  fold  which  projects  horizontally  into  the  body- 


'  Anatom.  Anzeiger,  Bd.  xvii.,  1900. 

'  Johns  Hopkins  Hospital  Bulletin,  vol.  xii.,  1901 


Journal  of  Morphology,  vol.  xii.,  1897. 


DEVELOPMENT  OF  THE  ALIMENTARY  TRACT. 


I7f>l 


cavity  and  extends  from  the  ventral  wall  to  the  sinu»  venosus,  its  medan  part  be- 
neath the  heart  beinj;  attached  dorsally  to  the  gut-tulx;,  while  its  lateral  expansions 
form  the  floor  of  the  pleural  ccelom.  This  imperfect  piirtition,  the  s,ftum  IraHS- 
■ersum  of  His,  also  affords  passage  for  the  two  ducts  of  Cuvier,  formed  on  each  side 
bv  the  union  of  the  primitive  jugular  and  cardinal  veins,  to  gain  the  sinus  venosus  ; 
the  septum  transversuin  receives  the  hejiatic  outgrowth  from  the  prinutive  ducxlenum, 
which  soon  develop  a  conspicuous  liver-mass  within  the  sul»stance  of  the  st-ptuin. 
The  rapid  increase  in  the  mass  of  the  developing  liver  is  attendevl  by  grent  thicken- 
ing of  the  septum  transversum.  |>articularly  towards  its  dorsal  etlge.  Ciicidently 
with  this  augmentation,  the  septum  differentiiites  into  a  thinner  up|>er  antl  a  thicker 
lower  stratum,  the  former  constituting  the  floor  of  the  pericardial  cavity  and  sur- 
rounding the  ducts  of  Cuvier,  the  latter  enclosing  the  liver. 


Fio.  143*- 


Tniihea, 


Pericardial  uc 


Septum  traiuvcrkum 


Lotip  of  small 
intoliiie  extend 
ifiK  into  cord 
Vitelline  vesseh' 


Caecui 


Reconitructlon  of  human  embr>o  of  17  mm.  vertex  hreech  lenKth.    X   14.     ^Mall.) 

The  subsequent  development  of  the  liver  is  attended  by  progressive,  although 
only  partial,  separation  of  the  inferior  layer  from  the  superior  stratum  of  the  septum 
transversum,  the  latter  layer  remaining  as  the  primitive,  but  still  imperfect,  dia- 
phragm between  the  pleuro-pericr  iial  and  peritoneal  divisions  of  the  body-cavity. 
The  dorsal  attachment  of  the  septum  transversum,  at  first  high  in  the  cer\'ical  region, 
gradually  recedes  tailward.  On  reaching  the  level  of  the  fourth  cervical  segment  the 
fourth  myotome  is  prolonged  into  the  upper  layer  of  the  septum  to  supply  muscular 
tissue  to  what  now  becomes  the  diaphragm.  The  latter,  however,  is  still  incomplete 
dorsally,  owing  to  the  existence  on  each  side  of  the  communication  between  the  pul- 
monary B  id  peritoneal  sacs.  This  opening  is  gradually  closed  by  the  backward 
growth  '>  Iha  diaphragm  and  the  forward  and  downward  extension  of  the  pleuro- 
peritoneal  membrane  until  the  aperture  between  the  thoracic  and  abdominal  cavities 
is  effaced  and  the  diaphragm  is  complete. 


1702 


Ht  MAN   ANATOVIV 


li 


i 


Development  of  the  Peritoneum. -Th.    attachmtnt  of  the    -rimitiv.   . , 
menury  tube.  fr™.>    tht  -csophaKUs  downward,  lu  the  ,H,Ht.  rior  wall  ,„  the  1„ 
cavuy  by  means.,,   ..  sauttaf  fold,  the  />hm^.o'  mrsenUrv.  lu.s  already   !.ee„    , 
'pasre  1697)     I-ikewtse  tht-  conventional  divi     m  of  this  dupli,  iture  into  a  iou,r 
attac  he<l  to  the  intfwtin«.  th.   ,„,s.^r,um  (o...mune,  and  an  u,    .r  portion  paJ,,,. 
the  dorsal  surface  of  the  .t..ma.l,,  the  m^rso^a.Mum.     The  i   :ter  difle^C" 
common  mesentery  m  not  .  ndinK  at  the  ventral  border  of  th,    diKestivetZ    1 
after  enclosmg  th.-  stomach  and  the  upper  part  of  the  du.^enur,,  fn  confj.    „„.,  ,,., 
ward    embracmg  the  hver,  to  lie  attached  to  the  ventral   U^ly-u     I       Th.        nkm 
hedupl,cat«reb.-,ueen  the  stomach  and  duoden.  m  and   Zi,"  .  is  kn-nv,    astl, 
Vftra/ mcso^ras  num.  or  anterior  mesmtery,  as  di      .guished  fr.v.,  the  d.>rs..    me", 
K»>tr,um  U  h.nd  the  stomach.      The  ventral  mes.  ntcry  is  a.  t,r.    attachluLve  ,  , 
theseplm,.   transversum  and  in  front  to  the   body     all' as  fa.    a>      ,.   en'.  :  ,ce  of  th.' 
umbilical  vem.  which  .^upies  its  Umrer  free   horde,  as  far  a.s  the  liver      /.s  already 

PlO.    1437. 


Vertebral  column. 


Spinal  con  I 


Lun«. 

Pleural  Mc- 


Communication 
between   pleu- 
ral and  perito- 
neal t  :.vitica       ,  ^.-5»«-    . 
Spleen   M^fi 

Se\uaiK>and4 
Kidney 


Alri-.i  '  r  Wolffian  body 


Stom.li  h 

Omenta'    u- 
Greater  unn ntum 


Pi-^,  i>(  MKitlal  'section       ingi 

incidentalb     the  lai 
he  diaphras:!!!  by  tin 


note 

rotr. 

ilea-     the  sept 
tainit^  the  i  v.      > 
of     4aminat  i 

tht     -des  ami     ij  of 
folc;    ^tached  a     >  • 
liver    .Teyond  s- 
e> ;.       '.  {'■  ,t  x\y 
siispt    sorj 
c!osiiij4   tin 
surface  of  1 
dij^estive  tuL.       i, 
bilt-duct,  pori.il  vei, 


II . ,  ahowinx  thoracic  and  abdominal  oritana.    x  15. 

ng  its  development  is  almost  entirely  free<l 
of  grooves  on  each  side  and  before  which 
lost  completely  separate  the  lower  layer  con- 
of  which  organ  materially  aids  in  this' pro, xss 
ever,  is  not  complete,  since  the  recesses  <  ,\  .r 
lite  meet  in  the  mid-line,  but  leave  a  saijittal 
1  and  below  to  the  stipero-ventral  surface  of  the 
ig  the  body-wall  as  far  as  the  umbilicus.      It  I- 
,  sickle-shaped  fold  foreshadows  the  persistent /a/r^or/;/  ,. 
le  adult  organ,  the  lower  free  border  of  the  diiplir:5ti!r=   <  - 
.11,  later  the  ligamentum  teres,  in  its  passage  to  the  iindt- 
he  portion  of  the  sagittal  fold  continued  from  the  liver  !•>  th. 
nstitutes  the  gastro-hepatic  or  lesser  omentum  and  contair»-  the 
and  hepatic  artery. 


■in^versi! 
'  later.1l  e.\ 
'■e  Mjiarati, 
>(■  !!\er  do  ] 
■-'  tliaphni 
ends  all 


F.VEI.OI'NfENT  OF   THE  AI.IMENTARN     IKAl  I 


>7r>.l 


in  general,  the  ser>.js  niembranes  lining  the  pleural  and  peritoneal  cidoms  rep- 
resent the  specialized  nie8obl.i>uc  laver  forming  the  immediate  l).)nn(lary  of  thest 
cavitie;.     The  peritonei  n,  therdore,  covering  the  lower  surfaci-  oi  the   uaphrav'm 
md  certaii  surfaces  of  ! he  liver  is  derived  from  those  |)ortions  ..(  tht   st|  ;mn  trai\!*- 
^umthit  con-itiif-   the  up|)er  and  lower  walls  of  the  hep  'ic  reccssts  which     rt- 
,trumeiual  in  ft.    n      the  liver  from  its  primary  position  wiili.u    he  st-ptum. 
iwration  of  the  i         trom  the  diiiphragm  is  incomplete  not  only  abovt .  .is  alru..    ^ 
•ted,  but  also  bi     ad  ;  consetpiently  the  greater  part    .f  the  |)<»ittri(tr  surface  of     lo 
.in  remains  atta  hed  to  the  (M)Sterior  body-wall  by   iiclar  tLs-       an.    h  non-p.  ,i- 
"eal,  the  remains    f  thi  periphi-r  .1  portion  of  the  I.       r  layer  ol  the  -ipiuin  traiis- 
suin,  which  beco  nes  tlie  f^ri      «um  of   the  liv        >ein^  reflecteti    i'   the  sules 
backward  as  the  .w    tarv  //.'an      /'.i.  ...,., 

Coincidrntly  with  the  dev  pment  of  the  liver  ami  its  hi— ration  fr.  n  the  sep- 
■um  transver^um,  hestoin.i  h  u>  rgoes  change  in  its  axi^.  which  ijecomes  less  >  ortical 
and  more  obliquely  traiisv.  -•  and  in  consequence  its  ;  uch-  't  to  th  hver. 
the  primitive  ga;*'      ht-padt      net   urn,  is  drawn  tow         the  tight  and  assumes  a 


Fio.  i4j8. 


-ural  cube 


Myotont. 


t'mbilical  v«inai 
Umbilical  artery 

Body-wall  conlinuous  with  amnion^ 
Transverse  !>t  >i«n  rff  rabbit  embryo  of  eleven  and  a  half  day»  ahowint  primitive  r: 


transverse  position  almost  at  right  angles  to  its  former  sagittal  , 
lions  in  the  position  of  the  stomach  and  its  anterior  mesentery 
triuni,  whifh  liecomes  elongated  and  twisted  towards  the  right  td 
lit  order  tn    iiairatain  its  attachments  to  the  greater  curvature.        ii 
changei  is  nt-     .roduction  of  a  p.  K-'ket  liehind  ih  ■  stomach,  the  floor 
which  are  the     lesogastrium,  the   roof  be'my:   -.he   iinder  surface  of  th 
|H>'-k»-t,  the  /f,r  ■  sac  of  the  peritoneum .  cor.iiiuiiiicatcs  with  the  rem. 


tlK  pt-ritoneal  cavtty  on  the  right  by  me;.'i^  o)  a  i>.issage  liehind  the  di-placc 
..r  ;ra.s^.>-hepatic  .nnentum,  the  free  bordi  r  oi  the  latter  bounding  the  open 


;ht     f.iiiach 

■U  of  th«^ 

left  wah  Ol 

\cr.     T  'tis 

ling  pai       f 

e>-cr 

lead 


iii!^  int-  the  passage  or  vcsiibuU  (page   1749)      The  opening,  at  first  la-  laf 

diminishes  in   size  and  becomes  the  foramen  of   Winslow,  which  leads  i  .   the 
ijreater  prritoneal  sac  into  the  vestibule  of  the  lesser. 

H^»iwCT«-h  tpe  stotnach   vet  v   -oon   appear-   an   extension   of   the  pock.  which 

ushes  ou'    tetween  the  stomach  above  and  the  transverse  colon  below.     This  ,  ntru- 

m,  the  omefft  ■! sac,  continues  t  '  sjrow  downward  and  forms  an  apron  whi-h      i-r, 

.11-  the  greate      mentum,  covers  th'-  loops  nf  the  small  intestine.     On  re  to 

Ftg.  1439,  it        vident  that  the  greater  -imenium  at  tirst  comprises  a  dupli.  the 


1704 


HUMAN   ANATOMY. 


^\,. 


>:....., 


anterior  and  the  posterior  fold  of  which  each  consists  of  two  serous  surfaces  enclosing; 
a  thin  stratum  of  intervening;  tissue  ;  there  are,  therefore,  four  serous  layers  inchiil.d 
within  the  original  omental  curtain.  Tracing  the  posterior  fold  of  the  latter  upward. 
it  is  seen  to  pass  over  the  transverse  colon  and  the  mesocolon,  without  attachmi'iii, 
to  reach  the  posterior  body-wall.  On  gaining  the  latter,  the  anterior  or  inner  ser<iii^ 
layer  may  be  followed  in  front  of  the  pancreas  as  the  posterior  wall  of  the  leshi  1 
peritoneal  sac,  being  continued  over  the  under  surface  of  the  liver.  The  outer  i.r 
posterior  serous  layer  pas:»es  behind  the  pancreas  to  reach  the  body-wall,  from  whirli 
It  is  reflected  to  become  continuous  with  the  upper  layer  of  the  transverse  mtsi. 
colon.  For  a  time  these  original  fcetal  relations  persist,  the  greater  omentum  lieini; 
unattached  to  and  removable  from  the  transverse  colon  and  its  mesentery.  Later  thi> 
separation  is  no  longer  possible,  since  the  posterior  layer  of  the  greater  omentum  ami 
the  transverse  mesocolon  and  colon  become  fused,  the  intervening  serous  suriaces  and 
space  bfing  obliterated  in  consequence.  Thereafter  the  periton.-i  layers  of  the 
greater  omentum  are  attached  to  and  apparendy  enclose  the  large  gut,  one  pa.ssini; 
as  the  upper,  the  other  as  the  lower  serous  layer  of  the  transverse  mesocolon.  I 
consequence  of  these  fusions  the  serous  surfaces  originally  behind  the  pancreas  als. . 
disappear,  and  the  gland  thenceforth  assumes  its  permanent,  although  secondary, 
retroperitoneal  relation.  Subsequendy  the  originally  distinct  folds  constituting  the 
greater  omentum  fuse,  and  after  birth  usually  appear  as  a  single  sheet  attached  abovi- 
to  the  greater  curvature  of  the  stomach  and  behind  and  below  to  the  transverse  colon. 

The  excessive  volume  of  the  right  half  of  the  liver  not  only  induces  the  o!) 
liquity  and  rotation  of  the  stomach,  but  likewise  influences  the  disposition  of  the  in- 
testinal coils  on  their  return  from  the  umbilical  coelom  into  the  peritoneal  ca\  ity. 
The  duodenal  s^ment  necessarily  follows  the  migration  of  the  pylorus  ;  its  begin 
ning,  therefore,  lies  to  the  right,  while  the  lower  end  passes  to  the  left  with  the 
jejunum.  Since  the  most  available  space  within  the  abdomen,  to  the  left  and  below, 
is  appropriated  by  the  coils  of  the  small  intestine  which  first  return  to  the  peritoneal 
cavity,  the  most  movable  portion  of  the  elongating  large  intestine,  the  trans\  ersc 
colon,  is  displaced  upward  and  assumes  an  obliquely  transverse  position  beneath  tin- 
stomach  and  liver,  above  the  rapidly  increasing  volume  of  the  coils  of  the  small  gut. 
The  latter  tend  to  displace  the  descending,  later  also  the  ascending,  colon  later- 
ally and  backward.  In  consequence  of  these  influences  and  changes  the  transverse 
colon  crosses  and  lies  in  front  of  the  duodenum,  which  is  thus  pushed  against  ihv 
abdominal  wall.  The  serous  investment  of  the  duodenum  undergoes  obliteration 
where  such  contact  is  maintained,  and  later  occurs  chiefly  on  the  anterior  surface  of 
this  part  of  the  gut  (Fig.  1403). 

Reference  to  the  original  relation  of  the  primitive  mesentery  (Fig.  1432)  in- 
cluded between  the  limits  of  the  U-loop  shows  the  principal  dorsal  attachment  of  the 
mesentery  to  be  the  comparatively  limited  area  along  the  body-wall  opposite  the  urn 
bilical  loop.  The  intestinal  margin  of  the  mesentery,  on  the  contrary,  rapidly  expands 
to  keep  pace  with  the  increasing  length  of  the  gut-coils,  the  result  being  that  thu 
mesentery  attached  to  the  upper — soon  right — limb  of  the  umbilical  loop  assumes 
more  and  more  the  form  of  a  rufHe,  towards  the  edge  of  which  ramify  the  branches 
of  the  superior  mesenteric  artery  supplying  the  small  intestine, — the  later  vasa  intes- 
tini  tenuis.  The  branches  distributed  to  the  left  or  colic  limb  of  the  U-loop  pass  to 
the  large  gut  through  a  mesentery  only  slighriy  wavy.  When  the  arrangement  of 
the  intestinal  coils  takes  place,  the  small  gut  occupying  the  left  and  lower  parts 
of  the  peritoneal  cavity  and  the  large  intestine  being  reflected  upward  and  a  ;ross  the 
duodenuin,  twisting  or  "rotation"  takes  place  around  a  fixed  point  marking  the 
duodeno-jejunal  junction.  This  location  also  corresponds  in  general  to  the  early 
position  of  the  superior  mesenteric  arter>',  the  relations  of  the  branches  of  which  are 
also  affected  by  the  rotation  of  the  mesentery,  since  thereafter  the  vessels  passing  to 
the  coils  of  the  small  intestine  lie  on  the  left  and  those  to  the  large  gut  on  the 
right  side, — the  opposite  of  their  original  situation. 

On  assuming  its  position  in  front  of  the  duodenum,  the  attachment  of  the  trans- 
verse colon  is  at  dr-'.t  a  limited  sagittal  one.  With  the  backward  displacement  of  the 
duodenum,  the  mesentery  of  the  transverse  colon  also  comes  into  relation  with  the 
posterior  parietal  peritoneum  and  acquires  a  secondary  attachment  extending  cross- 


THE  LIVER. 


170S 


wise,  thus  forming  the  dorsal  connections  of  the  transverse  mesocolon  which  exist 
until  hision  takes  place  between  this  duplicature  and  the  posterior  fold  of  the  omental 
sac.  Since  originally  all  parts  of  the  large  gut  possess  a  mesentery,  the  descending 
colon  and  sigmoid  are  for  a  time  provided  with  a  free  mesocolon.  In  consequence 
of  the  increasing  bulk  of  the  small  intestine  the  descending  colon  is  pushed  not 
only  to  the  left,  but  also  against  the  body-wall.  The  intervening  serous  surfaces 
usually  disappear  behind  the  gut,  which  later,  therefore,  ordinarily  possesses  a  peri- 
toneal coat  only  in  front  and  at  the  sides.  In  a  considerable  number  of  cases,  how- 
ever, this  fusion  and  obliteration  do  not  teke  place,  the  mesocolon,  although  displaced 
towards  the  left,  then  persisting  as  a  free  mesentery  for  this  segment  of  the  gut. 
The  fold  attached  to  the  sigmoid  for  a  time  allows  of  great  mobility  ;  subsequently 
this  is  reduced,  although  partly  retained  as  the  definite  mesosigmoid.  The  rectal 
segment  of  the  large  gut  retains  its  primary  sagittal  situation,  but  loses  the  greater 
part  of  its  peritoneal  coat,  becoming  attached  to  the  posterior  pelvic  wall  by  areolar 

tissue.  .  .    .■■ 

The  ascending  colon  and  caecum,  in  their  downward  growth  towards  the  right  iliac 
fossa  h-om  the  hepatic  flexure,  carry  with  them  a  peritoneal  covering.     This  remains 

Fio.  1439. 
A  /I  c 


ago. 


pgo. 


DiaKtsRii  illiutratinfr  fomulion  of  grater  omentum  and  omental  nac.  A  showa  duixlenum  and  inncrras  in 
mesoxastrium  unattached;  in  ^ these  organs  are  pertlv  against  posterior  abdominal  wall,  postertnr  wall  nf  IcAwer 
prriumeal  cavity  is  still  free;  in  Cduodenum  and  pancreas  lie  against  posterior  abdominal  wall,  posterior  wall  of 
omental  sac  has  fused  with  transverse  mesocolon,  a,  aorta  ;  rf.  diaphragm  ;  /,  li\*er;  //,  falciform  ligament ;  ni'.  um- 
bilical vein  ;  s,  stomach  ;  Ic,  transverse  colon  attached  by  transverse  mesocolon  {Imc) ;  Ji,  small  Inlcslinc  attached  by 
tne5enter>-  («);  p,  pancreas;  du,  duodenum;  Ifis,  lesser  peritoneal  sac:  os,  omental  sac;  /«,  lesser  omentum;  /^o, 
greate.  omentum ;  ajro  and  pgo^  its  anterior  and  posterior  layers ;  /,  fusion  between  posterior  wall  of  lesser  peri* 
toneal  sac  and  transverse  mesocolon.    {After  Kollmann  and  ftertwtf,) 

unattached  over  the  caecum  and  appendix,  but  forms  secondary  connections  where 
the  ascending  colon  comes  into  contact  with  the  abdominal  wall  ;  hence  this  part  of 
the  colon  usually  posses.ses  a  serous  coat  only  anteriorly  and  laterally.  Sometimes, 
however,  obliteration  of  the  serous  covering  does  not  take  place,  the  ascendinc  -olon 
being  attached  by  a  mesocolon. 

The  vermiform  appendix  being  primarily  an  outgrowth  from  the  large  g  ince 
it  represents  the  morphological  apex  of  the  caecum,  is  completely  investta  with 
jieritoneum  and  is  without  a  mesentery.  Later  the  appendicular  artery,  in  its  course 
from  the  ileo-colic  to  the  appendix,  produces  a  serous  fold  which  stretches  from  the 
left  layer  of  the  mesentery  of  the  ileum  to  the  caecum  and  appendix.  This  fold,  the 
meso-appendix,  is,  therefore,  functionally,  but  not  morphologically,  a  true  mesenterj'. 


THE  LIVER. 

The  liver  (hepar),  the  l.irgest  gland  in  the  body,  is  formed  of  very  delicate  tissue 
disposed  around  the  ramifications  of  the  portal  vein.  It  is  developed  in  the  anterior 
mesentery,  its  mesoblastic  elements  having  a  common  origin  with  the  diaphragm. 


1706 


HUMAN  ANATOMY. 


[ 


:    I 

:    i 


while  its  duct  and  glandular  elements  are  derived  from  a  sprout  from  the  duodenum  ; 
hence  the  liver,  as  are  other  j?;lands  connected  with  the  digestive  tract,  is  an  nut- 
growth  and  appendage  uf  the  Jimentary  tube.  Its  peculiar  shape  is  chiefly  duu  ti> 
the  pressure  of  surrounding  organs,  as  its  tissue  is  so  plastic  that  it  is  moulded  l)\ 
them.  In  the  adult  it  becomes  firmer  from  the  increase  of  connective  tissue,  Ixit 
under  normal  circumstances  >t  is  always  verv  soft,  and,  unless  hardening  agents  arc 
used  before  its  removal,  collapses  into  a  flattened  cake-like  mass  affording  littk- 
information  as  to  its  true  form.  Indeed,  it  is  only  in  the  present  generation,  since 
the  introduction  of  adcqi'.ate  methods  of  hardening  in  situ,  that  this  has  bt-tn 
learned.  The  'iver  in  general  may  be  described  as  an  ovoid  mass  which  in  the  yniiti^ 
fcetus  nearly  fills  the  abdomen,  but  in  the  adult  has  the  appearance  of  having  ha<i  at 
least  a  third  of  its  substance  scooped  out  from  below,  the  back  having  been  left  iniart 
nt  the  right  end  only.  The  organ  is  therefore  a  thick  mass  in  the  right  hypochon- 
drium,  growing  thinner  to  the  left.  The  greatest  diameter  is  transverse  and  the 
ne.xt  vertical.  The  liver  is  usually  described  as  composed  of  five  lobes, — namely, 
the  rij^Ai,  the  /f/l,  the  /odf  of  Spigelius,  the  quadrate,  and  the  caudate.  More 
properly  it  consists  of  a  right  and  a  left  lobe,  separated  on  the  superior  surface  by 
the  falciform  ligament.     The  other  lobes  are  subdivisions  of  the  right  lobe,  the  lulie 


Pio.  1440. 


Vcnacav* 


Left  layer  of  falciform 

Unmcnt  continuous 

...nith  lateral  ligament 


Left  lobe 


Oblltentcd  umbilical  vein  In  free  marsin  of  falciform 
ligament 
ll-bladder 


Antero-superlor  surface  of  liver  hardened  in  sUm. 


of  Spigelius  being  at  the  back  and  the  other  two  below.  They  are  described  with 
the  respective  surfaces.  The  size  varies  greatly  with  the  size  of  the  body  and  from 
many  other  causes.  The  transverse  diameter  usually  nearly  equals  that  of  the  cavity 
of  the  abdomen,  although  it  often  falls  an  inch  or  so  short  of  it.  It  may  be  given  at 
from  22-24  cm.  (Sj^-g^  in.).  The  greatest  vertical  dimension  or  depth  is  about 
16 cm.  (6;{  in.);  the  antero-posterior  diameter  12-18.5  cm.  (4^-7 >^  in.),  dne 
peculiar  form  of  liver  occasionally  met  with  shows  great  increase  of  the  right  lol>e, 
partictilarly  in  the  vertical  direction,  with  a  want  of  development  of  the  left  lobe, 
which  is  thin  and  short  (Fig.  1456).  The  weight  is,  with  considerable  variations 
generally  from  1450-1750  gm. ,  or  approximately  from  3-35^  lbs.,  and  in  the  aihilt 
is  about  one-fortieth  of  the  body  weight.  The  specific  gravity  is  given  at  from 
1005-1006.  The  color  is  a  reddish  brown.  The  naked  eye  can  recognize  that  tin 
surface  is  covered  with  the  outlines  of  polygons  from  1-2  mm.  in  diameter.  These 
are  the  lobnlfs,  each  of  which  is  surrounded  by  vessels  and  ducts  in  connective  tissue, 
and  contains  in  the  middle  a  vessel,  the  beginning  of  the  system  of  the  hepatic  \ein. 
Sometimes  the  centre  of  the  lobule  is  lighter  than  the  periphery,  sometimes  tin 
reverse,  depending  upon  whether  the  blood  has  stagnated  in  the  portal  or  hepatic 
system  resjiectively. 


THE  LIVER. 


1707 


Surfaces. — In  its  natural  form,  as  shown  in  specimens  hardened  before  removal 
from  the  body,  the  liver  presents  five  surfaces.  The  superior  surface  is  in  the 
main  convex,  looking  upward  beneath  the  diaphragm.  The  anterior  surface,  directed 
forward,  is  continuous  with  the  former,  on  the  hardened  liver  a  fairly  distinct  line 
marking  the  change  of  direction  that  separates  them.  The  right  surface  faces 
towards  the  right  and  is  separated  in  a  similar  way  from  the  superior.  It  passes 
insensiWy  into  the  anterior  surface.  In  a  flaccid  liver,  in  which  the  normal  form  has 
been  lost,  these  three  surfaces  are  indistinguishable,  constituting  the  old  superior 
surface.  In  the  hardened  organ  the  three  represent  a  dome,  of  which  the  flattened 
upper  surface  is  slighdy  separated  from  the  others.  The  posterior  surface  is  on  the 
back  of  the  right  lobe.  The  inferior  surface  is  moulded  over  the  organs  beneath  it. 
The  borders  are  best  described  from  the  'posterior  surface  as  a  starting-point. 
The  upper  border  of  the  latter  separates  it  from  the  superior  and  right  surfaces  ;  the 
lower  border  from  the  inferior.  On  the  right  these  i  ict  at  a  mor-  or  less  acute 
angle.  On  the  left  the  posterior  surface  narrows  to  a  border,  first  thick  and  then 
sharp,  which  runs  around  the  liver,  separating  first  the  upper  and  lower  surfaces  of  the 
left  lobe  and  later  the  lower  from  the  anterior  and  right  ones,  until  finally  it  reaches 
the  right  end  of  the  lower  border  of  the  posterior  surface.  Along  the  front  of  the 
liver  the  border  is  sharp  and  directed  downward,  overhanging  the  concave  lower 
surface.  A  conspicuous  incision,  the  umbilical  notch  (incisura  umbilicalLs),  in  the 
anterior  border  marks  the  place  at  which  a  sickle-like  fold  of  peritoneum,  the/a/«- 
form  ligament,  conveying  the  obliterated  umbilical  vein,  now  the  round  ligament 
(liKamentnm  teres  hepatis),  to  the  lower  surface,  reaches  the  liver.  The  falciform 
ligament  is  continued  back  between  the  top  of  the  liver  and  the  diaphragm,  and  marks 
of!  on  the  anterior  and  superior  surfaces  a  large  right  lobe  and  a  small  left  one. 

The  superior  surface  (Fig.  1440)  includes  the  upper  part  of  both  lobes  and  is 
moulded  to  the  opposed  surface  of  the  diaphrs^.  The  top  of  the  right  lobe  fills 
in  the  whole  of  the  space  below  the  correspondii^  half  of  the  diaphr^m,  but  the 
left  lobe  does  not  usually  reach  the  walls  of  the  abdomen,  unless  in  front.  It  may, 
however,  touch  the  left  wall.  Well-hardened  livers  show  a  sl«ht  cardiac  depression 
on  the  left  lobe  beneath  the  heart.  The  posterior  border  of  the  superior  surface  is 
marked  on  the  right  lobe  by  the  reflection  of  the  peritoneum  onto  the  diaphragm 
above  the  triangular  posterior  surface,  and  on  the  left  by  the  rounded  postenor 
border  of  the  liver 

The  right  and  anterior  surfaces  lie  against  the  diaphr^m,  except  where 
the  anterior  rests  against  the  abdominal  wall  between  the  costal  arches,  and  offer 
little  for  description.  .  .    ,  . 

The  posterior  surface  (Figs.  1441,  1456),  on  the  back  of  the  nght  lob.,  con- 
sists of  a  triangular  non-peritoneal  area  and  of  the  lobe  of  i^igelius.  The  former, 
adherent  to  the  diaphragm,  extends  from  the  inferior  vena  cava  to  the  right,  where 
it  ends  in  the  point  formed  by  the  meeting  of  the  upper  and  lower  borders.  The 
greatest  vertical  dimension  of  the  non-peritoneal  area  is  not  over  7.5  cm.  (3  in.),  and 
the  transverse  not  over  1 2. 5  cm.  (5  in. ).  A  triangular  hollow  at  the  lower  border  of 
this  space,  just  to  the  right  of  the  vena  cava,  receives  the  right  suprarenal  capsule, 
which  rests  also  on  the  lower  surface.  To  the  left  of  this  depression  is  a  deep  furrow 
for  the  inferior  vena  cava,  which  som<  times  at  the  top  is  converted  into  a  canal.  Still 
farther  to  the  left  is  the  lobe  of  Spigelius  (,l">w«»  caudatas), — a  four-sided  prism  placed 
vertically  on  the  back  of  the  liver,  bouiiding  a  part  of  the  lesser  cavity  of  the  perito- 
neum. The  lower  end,  which  hangs  iree,  is  continuous  on  the  right  with  the  caudate 
lobe  (processus  caadatua).  It  often  presents  on  the  left  of  the  lower  end  a  distinct 
tubercle,  the  tuber  papillare  (His),  which  is  by  no  means  constant.  The  Spigelian 
lobe  lies  between  the  fossa  of  the  vena  cava  on  the  right  and  t\iK  fissure  of  the  ductus 
-.enosus  on  the  left  The  latter  joins  the  former  in  front  of  this  lobt .  just  below  the 
dinphragm,  so  that  the  lobe  ends  in  a  point  above.  It  more  or  less  encircles  the  vena 
cava,  sometimes  meeting  the  right  lobe  behind  it.  The  vena  cava  is  frequently  over- 
lapped by  a  projection  from  the  right  lobe,  and  sometimes  the  overiappinrj  is  done 
both  by  this  and  by  the  lobe  of  Spigelius.  The  prismatic  slia^e  of  the  latter  is  well 
shown  by  transverse  sections.  The  amount  of  attachment  to  the  rest  of  the  liver 
varies,  and  the  shape  of  the  lobe  with  it.      Sometimes  the  figure  of  the  ductus 


1708 


HUMAN  ANATOMY. 


venosus  makes  but  a  small  angle  with  the  portal  fissure,  so  that  it  is  a  three-  instcui : 
of  a  four-sided  prism.  It  is  also  influenced  by  the  depth  of  the  fossa  for  the  vcii.i 
cava,  at  times  being  attached  merely  by  a  line  of  tissue.  To  the  left  of  the  tissin. 
of  the  ductus  venosus  the  posterior  surface  of  the  liver  is  continued  as  the  postiric .r 
border.  This  at  first  is  thick,  and  presents  a  rounded  wsopkagetU  impression  for 
the  end  of  the  gullet  to  the  left  of  which  it  becomes  sharp. 

The  inferior  surface  (Fig.  1442)  of  the  liver  is  subdivided  by  a  system  i.f 
fissures  formerly  described  as  resembling  an  H.  This  description  must  be  moditicd 
by  recognizing  that  the  posterior  limbs  of  the  H  are  not  horizontal,  but  run  vertically 
on  the  hind  surface  of  the  liver,  and  that  the  cross-piece — the  portal  fissure — is  not 
in  the  middle,  but  very  near  the  posterior  border  of  the  inferior  surface.  The  oltl 
error  came  from  studying  distorted  livers  in  which  the  posterior  surface  had  flattened 
out  so  as  to  be  reckoned  a  part  of  the  inferior.  The  portal  or  transverse  fissure 
(porta  hepatls)  is  of  an  entirely  dif!erent  nature  from  the  others.  It  is  the  hi/um  of 
the  organ  for  the  passage  of  the  vessels  and  ducts  ;  while  the  other  fissures  more 
properly  deserve  the  name,  being  due  to  the  pressure  of  the  g^U-bladcier  and  of 
vessels.  The  portal  fissure  is  from  4-5  cm.  ( i  yi-2  in. )  long.  It  transmits  the  por- 
tal vein,  the  hepatic  artery,  the  subdivisijns  oi  the  gall-duct,  the  lymphatics,  and 


SpigctiAn  lobe 


Fio.  1441- 

Falciform  ligament 


Fitsure  for. 
ductus  venosus 


Tuber  omental*- 


■Vena  cava 


.Non-peritotieal 
surface 

Suprarenal 
.vein 


OWKeretcd  nmbtltral  win 

Quadrate  lobe 

Caudate  lobe        Gall-bladder 
Posterior  surface  of  same  liver ;  peritoneal  reflection  indicated  by  white  line. 


Rijfht  lateral 
ligament 


I 


the  nerves,  all  enveloped  in  a  mass  of  areolar  tissue  known  as  G/isson's  capsule. 
The  large  portal  vein  is  posterior.  The  hepatic  artery  lies  before  it  on  the  left  ami 
the  hepatic  duct,  formed  by  two  chief  tributaries,  lies  before  it  on  the  right.  The 
lesser  omentum  is  attached  to  the  lips  of  the  fissure  outside  of  these  structures.  At 
its  left  end  the  portal  fissure  receives  the  umbilical  fissure,  which  runs  backward 
from  the  notch  in  the  anterior  border  and  contains  the  obliterated  umbilical  vein,  in 
the  adult  known  as  the  round  ligament.  This  fissure  is  very  often  bridged  over. 
Continuous  with  the  umbilical  fissure,  the  fissure  of  the  ductus  venosus  ascends  the 
posterior  surface,  only  a  small  part  of  it  being  on  the  inferior  aspect.  In  foetal  life  it 
contained  the  blood -channel  (ductus  venosus)  which  established  a  short  cut  between  the 
umbilical  vein  and  the  inferior  vena  cava  ;  after  birth  it  is  reduced  to  a  cord  of  fibrous 
tissue  (liKamentum  venosum).  At  the  left  end  of  the  portal  fissure  the  falciform  liga- 
ment joins  the  lesser  omentum,  the  latter  being  continued  backward  in  the  fissure  of 
the  ductus  venosus.  The  fossa  for  the  gall-bladder  (fossa  vesicae  felles)  is  a  depres- 
sion on  the  under  surface  of  the  right  lobe,  in  which  that  organ  rests.  It  may  or 
vn-As  nnt  indent  the  anterior  border.  Broad  in  front,  the  foH,sa  narrows  t"  a  fissure 
behind  that  joins  the  right  end  of  the  portal  fissure.  The  quadrilateral  region  on  the 
under  surface  of  the  right  lobe,  bounded  by  the  portal  fissure  behind,  the  border  of 
the  liver  in  front,  the  gall-bladder  on  the  right,  and  the  umbilical  fissure  on  the  left, 


THE  LIVER; 


1709 


is  the  quadrate  lobe  (lobes  qaadratus).  Behind  the  portal  fissure  the  lower  end  ol  the 
lobe  of  Spigelius  appears  on  the  inferior  surface,  with  the  groove  for  the  vena  cava 
on  its  rwht  and  the  fissure  of  the  ductus  venosus  on  its  le»  The  caudate  lobe 
(proctasos  candatns)  is  a  rounded  ridge,  particulariy  developed  in  eariy  life,  running 
from  the  under  side  of  the  right  lobe,  just  behind  the  right  part  of  the  portal  fissure 
and  in  front  of  the  vena  cava,  obliquely  backward  and  to  the  left  into  the  lower  end 
of  the  lobe  of  Spigelius.  A  groove  caused  by  the  hepatic  artery  separates  it  from  the 
tuber  papillare.  The  caudate  lobe  overhangs  the  foramen  of  Winslow.  In  the  adult 
it  is  sometimes  rounded,  sometimes  sharp,  and  not  always  to  be  distinguished.  The 
under  side  of  the  liver,  being  moulded  over  the  neighboring  organs,  presents  many 
irregularities  dependent  on  their  pressure.  The  posterior  part  of  the  under  side  of 
the  right  lobe  is  hollowed  into  the  renal  impression,  a  concavity  fitting  closely  over 
the  right  kidney.  The  suprarenal  capsule  rests  against  the  liver  to  the  left  of  this, 
at  the  beginning  of  the  caudate  lobe  on  the  under  surface  and  also  on  the  posterior 
surface.  The  first  part  of  the  duodenum  rests  against  and  moulds  the  under  side  of 
the  right  lobe  between  the  renal  impression  and  the  gall-bladder.    This  area  of  con- 


Fio.  144a. 


Spicdiui  lob* 
CRiophatcal  iMprawioa 


Vena  cava 

Richt  capniUur  vein 


Fiuure  fac| 
ductus  vcnoftua! 


Hepatic  atttry 
Portal  vein 
Common  bile-duct' 

Oblitciatcd  umlrfllcal  vein 

Quadrate  kibe  . 
Cyntic  dud 

Gail-Uadder 

Inferior  and  porterior  .urfacet  ol  lame  liv«.  _  It  rnu*. he  clearly  underrtood  that  »|»  Sfi*'";"^*"?  «"  "^ 
areon  tlie  poMerior  lurface,  Uie  limit  d  Uie  interior  surface  behind  being  the  traraverse  fiwure. 

tact  can  hardly  be  called  an  impression,  for  the  surface  here  is  slightly  convex.  In 
front  of  the  renal  impression  is  a  hollow  for  the  colon  of  very  varying  size.  It  may 
be  almost  wanting,  or  it  may  be  very  deep.  It  may  be  confined  to  the  right  part  of 
the  under  surface,  or  it  may  compress  the  front  of  the  gall-bladder  and  indent  the 
quadrate  lobe,  and  even  the  left  one.  The  under  side  of  the  right  lobe  presents 
also  one  or  more  occasional  fissures  which  seem  in  the  main  to  diverge  from  the 
right  end  of  the  portal  fissure  and  from  the  fossa  for  the  gall-bladder.  They  are 
more  common  in  the  foetus,  and  some  of  them  occur  more  or  less  frequently  in 
anthropoid  apes.'  The  under  side  of  the  left  lobe  is  in  general  concave,  resting 
against  the  fundus  and  anterior  wall  of  the  stomach.  Near  the  posterior  part  of 
the  umbilical  fissure  on  the  left  lobe  is  a  rounded  prominence,— /K*^r  omentale,—d\iii 
to  the  growth  of  the  liver  against  the  non-resisting  lesser  omentum. 

The  Blood- Veasele.— The  portal  vein,  some  15  mm.  or  more  in  diameter, 
dividw  into  a  right  and  a  left  branch,  10  mm.  or  over  in  diameter,  of  which  the  nRht 
is  a  little  the  larger  and  shorter.    From  the  right  end  of  the  transverse  fissure  it  runs 
•  Thombtm  :  Journal  of  Anatomy  and  Physiology,  vol.  xxxiii.,  1899. 


m. 


I7IO 


HUMAN  ANATOMY. 


backward  in  a  curve  to  the  right  of  the  vena  cava,  keeping  in  the  lower  part  of  the 
liver  and  giving  of!  successively  a  series  of  large  branches  to  the  front  and  ri^ht  of 
the  organ.  Smaller  branches  arise  from  the  sides  of  these.  The  r^ht  prmiary 
division  soon  gives  ofi  a  large  superior  branch  almost  equal  to  itself,  which  describes 
a  similar  but  smaller  curve  at  a  higher  level.  The  general  course  of  the  left  subdi- 
vision is  towards  the  posterior  angle  of  the  organ,  giving  branches  chiefly  from  its 
anterior  side,  and  also  one  that  supplies  the  greater  part  of  the  quadrate  lobe.  The 
lobe  of  Spigelius  generally  receives  a  chief  branch  near  its  lower  end,  which  run:- 
upward  within  it.  This  branch  is  most  often  from  the  left  subdivision,  but  it  may 
be  from  the  right,  or  from  the  vessel  directly  behind  the  end  of  the  portal  vein. 
There  are  several  systems  of  so-called  accessory  portal  veins  around  the  liver  in  the 
lesser  omentum  near  the  gall-bladder,  about  the  diaphr^m.  and,  most  important, 
in  the  falciform  ligament,  where  the  parumbilical  veins  communicate  with  veins  of 
the  integument  of  the  abdominal  walls.  These  accessory  vessels,  small  and  incon- 
spicuous under  normal  conditions,  may  become  enlarged  and  important  channels 

Fio.  1443. 


Portions  of  inferior  and  poMrrior  rartaces  <rf  Ilv»r  have  been  remnvcd  to  show  injected  blood-vntsels  and  bile- 
ducts.  \>[ia  lava  is  siimewnat  diitplaccd  forward,  its  course  beinz  more  vertical  when  supporteil  on  |H>steriiir  sur- 
face. Large  tipjier  branch  of  riRht  division  of  [lortal  vein  i«  hidden  by  liver-iubstance.  Portal  vein  ai>d  hruiiL-litr^ 
are  purple  \  hepatic  artery,  red  ;  ncpatic  veira  and  vcn*  cava,  blue ;  bile^ucta,  jrellow.  «t>,  oblitetated  umbilical  vein  , 
vc,  inferior  vena  cava. 

for  the  return  of  the  blood  conveyed  by  the  portal  vein  when  the  hepatic  circula- 
tion is  obstructed.  Inder  such  conditions  the  blood  finds  its  way  from  the  portal 
vein  into  the  accessory  veins  and  by  the  anastomoses  of  the  latter  into  the  general 
circulation. 

The  hepatic  veins  carrying  off  the  blood  from  the  liver  arise  as  the  intra- 
lobular veins,,  which  empty  into  the  sublobular,  which  join  larger  vessels  con\  ergiiig 
towards  the  vena  cava.  At  first  the  general  direction  of  the  small  branches  is  paral- 
lel fo  that  of  those  of  the  portal  system  of  the  same  size  ;  but  the  hepatic  branches 
always  travel  alone.  The  direction  of  the  large  branches  as  they  near  the  vena  cava 
is  at  right  angles  to  that  of  the  portal.  The  arrangement  of  the  hepatic  branchis  is 
in  the  main  like  that  of  the  portal,  but  near  the  edge  of  the  liver  we  find  more 
instances  of  the  union  of  two  rather  small  trunks  meeting  symmetrically  like  the 
arms  of  t  Y.  The  main  trunks  of  the  right  lobe  run  between  the  upper  and  lower 
br.incheh  of  the  portal.  The  upper  end  of  the  vena  cava  is  considerably  en!arj,rr<l, 
and  immediately  below  the  diaphraifni  receives  two  large  hepatic  veins,  a  right  and  a 
left  one,  from  1 5  to  20  mm.  in  diameter.  The  latter  is  formed  by  two  large  branches 
thfit  unite  just  before  its  end.     Many  small  veins  open  into  the  vena  cava  at  different 


THE  LIVER. 


1711 


points  along  its  course  in  l.-  groove  on  the  posterior  surface  of  the  liver,  several 
coming  from  the  Spigelian  lobe.  Sometimes  quite  a  large  branch  from  the  right 
lobe  opens  at  a  low  level.  There  is  no  such  thing  as  an  hepatic  vein  in  the  adult 
considered  as  an  isolated  structure.  The  ramifications  of  the  porul  and  hepatic 
veins  are  inextricably  mingled  throughout,  but  in  the  main  the  branches  of  the  latter 
lie  above  those  of  the  former  (Fig.  1443). 

The  hepatic  artery,  the  nutritive  vessel  of  the  liver,  divides  into  two 
branches  which,  together  with  the  bile-duct,  accompany  the  portal  vein,  the  two  arte- 
ries generally  being  on  the  same  side  of  the  vein.  The  hepatic  artery  gives  off  so 
many  branches  in  its  course  as  to  be  almost  or  quite  of  capillary  size  when  it  reaches 
the  twigs  of  the  portal  vein  that  break  up  into  the  interlobular  net-work.  The  blood 
conveyed  by  the  hepatic  artery  is  distributed  by  three  sets  of  branches,  the  capsular, 
the  vascular,  and  the  lobular.  The  first  ramify  within  the  connective-tissue  envelope 
of  the  organ  and  anastomose  with  branches  from  the  internal  mammary,  phrenic,  cystic, 
suprarenal,  and  sometimes  right  renal.  The  second  supply  the  structures  between 
the  lobules,  especially  the  walls  of  the  ramifications  of  the  portal  vein  and  the  bile- 
ducts.  The  third  are  small  in  size,  and  accompany  the  intralobular  branches  of  the 
porui  vein  for  a  short  distance  within  the  lobule.  There  is  no  special  system  of 
veins  to  return  the  blood  carried  by  the  hepatic  artery  to  the  venous  trunks  outside 
the  organ,  the  minute  veins  collecting  the  blood  from  the  capsular  and  vascular  sets 
being  tributaries  usually  of  the  smaller  branches  of  the  portal  vein.  The  blood 
passing  through  the  lobular  arterioles  is  emptied  into  tht  intralobular  capillary  net- 
work. 

The  lymphatics  of  the  liver  constitute  a  superficial  and  a  deep  set,  the  former 
lying  beneath  the  peritoneum,  the  latter  within  the  deeper  interiobular  connective 
tissue.  The  superficial  lymphatics  of  the  superior  surface  are  a.ranged  as  thr«;e 
groups,  posterior,  anterior,  and  superior.  The  posterior  group  forms  a  lieht  irunk 
which  passes  from  the  right  triangular  ligament  across  the  right  crus  of  the  dia- 
phragm to  the  coeliac  lymph-nodes.  Middle  trunks — from  five  to  seven  in  number- 
accompany  the  inferior  vena  cava  to  end  in  diaphragmatic  nodes  around  the  vein. 
Left  trunks  traverse  the  left  triangular  ligament  and  terminate  in  the  iRsophageal 
nodes  surrounding  the  lower  end  of  the  gullet.  The  anterior  group  passeti  in  the  op- 
posite direction  to  those  just  described  and,  crossing  the  anterior  border  .f  the  liver, 
empties  into  the  hepatic  lymph-nodes  within  the  lesser  omentum.  The  superior 
group,  the  most  important  of  those  of  the  upper  surface,  ascends  within  the  falciform 
ligament.  A  number  of  anastomosing  vessels  form  a  posterior  trunk  which  crosses 
•he  inferior  vena  cava  and  enters  the  thorax  with  the  latter,  to  end  in  the  lymph-nodes 
around  the  vena  cava.  An  anterior  trunk  accompanies  the  round  ligament  to  the  infe- 
rior surface  and  end«  in  the  hepatic  nodes  at  the  hilum.  Numerous  middle  tru  I'.s 
form  vessels  which  pierce  the  diaphragm,  to  end  in  the  anterior  mediastinal  nodes, 
becoming  tributaries  to  the  right  lymphatic  duct.  The  superficial  lymphatics  of  the 
inferior  surface  include,  on  the  right  lobe,  a  posterior  group,  accompanying  the  vena 
cava  into  the  thoracic  cavity,  to  end  in  nodes  around  that  vein,  a  middle  group  p.-issing 
to  the  hepatic  nodes  around  the  cystic  duct,  a.id  an  anterior  group  terminating  in  the 
same  nodes  as  the  preceding.  On  the  left  lobe  the  vessels  pass  to  the  nodes  of  the 
hilum  and  about  the  hepatic  artery.  The  lymphatics  of  the  Spigelian  lobe  pass  partly 
to  the  hilum  nodes  and  partly  to  those  surrounding  the  thoracic  sejjini  nt  of  the  infe- 
rior vena  cava.     Communications  exist  between  the  superficial  and  deep  lymphatics. 

The  deep  lymphatics  include  two  distinct  groups,  the  one  following  the  hraiiohes 
of  the  portal  vein,  the  other  accompanying  the  hepatic  veins.  The  first  descends 
within  the  capsule  of  Glisson  in  company  with  the  portal  vein  and  other  interlobular 
vessels.  On  emerging  at  the  hilum,  the  fifteen  to  eighteen  trunks,  arranged  as 
two  groups  at  the  ends  of  the  transverse  fissure,  join  the  hepatic  nodes.  The 
lymphatics  which  accompany  the  hepatic  veins  form  a  plexus  surrounding  the 
blood-ves.seIs  and  proceed  towards  the  vena  cava,  with  which  they  pass  through 
the  diaphragm  to  enter  the  nodes  lying  immediately  above  the  eaval  opening. 

The  nerves  are  chiefly  derived  from  the  solar  plexus  of  the  sympathetic  with 
some  fibres  from  the  left  pneumogastric  which  reach  the  liver  by  passing  from  the 
anterior  surface  of  the  stomach  between  the  layers  of  the  lesser  omentum.     The 


Ufa 


>*>. 


,7ia  HUMAN  ANATOMY. 

•ympathedc  fibre*  accompwy  the  hepatic  artery,  forming  the  hepatic  plexus,  to 
the  transverse  fissure,  where,  together  with  the  fibres  from  the  vagus,  they  pass  into 
the  liver  along  with  the  interlobular  vesseU,  to  the  walls  of  which  they  are  chiefly 
dutributed  According  to  Berkley,  the  interlobular  plexuses  give  oH  fine  intralob- 
ular twigs  which  terminate  between  the  liver-cells. 

STRUCTUP       OF   THE    LIVER. 

In  its  hindamental  arrangement  the  liver  corresponds  lo  a  modified  tubular 
gland,  the  system  of  excretory  ducts  of  which  is  an  outgrowth  from  the  pri-nary 
gut-tube.  Early  in  fastal  life,  however,  the  terminal  divisions  of  the  tubules  unite 
to  form  net-works,  after  which  the  tubular  character  of  the  liver  becomes  progressively 


Blood-cmpillarici 


Blood -capillaries 


Snbi'cbalar  bnuicb  of  hepatic  vdn 


DtaKram  of  hepatic  lobule ;  portions  of  (inure  reprwent  median  lonriludinal  •"J'""  "i '*<''^yP»"*  "f '""iJJ^i!! 
section!,  also  nhown  Branches  of  porul  vein  are  purple ;  of  hepatic  artery,  led ;  at  bUe^ducU,  yefiow.  Intralobular 
bile-capillaries  are  black. 

more  masked  by  the  intergrowth  of  the  cell-cords  and  the  la^e  veins.  Among 
some  of  the  lower  vertebrates,  as  in  certain  vermiform  fishes  or  cydostomes 
{Myxitu),  the  primary  tubular  arrangement  is  retained. 

"  The  glandular  tissue  composing  the  liver  is  subdivided  into  small  cylindrical 
masses,  the  lobules,  by  the  connective  tissue  which,  in  continuation  of  the  fibrous 


STRUCTURE  OF  THE  LIVER. 


«7»S 


...uelooe    or  (t^uU,  investing  the  exterior,  at  the  transverse  fiwure  enters  the 
or^-anind  accoiipanies  the  interlobular  vessels  in  their  ramifications  as  the  capsuie 
Z^GlissoH  (cpMla  fibroM).     The  distinctness  with  which  the  lobules  are  defined 
deJendi  upon  tiTe  amount  of  this  interlobular  tissue       In  ceru.n  animals,  notably 
M  ^e  hoTthis  is  great,  the  lobules  being  completely  surrounded  and  pUinly  dis- 
ShaWe  as  sharply  marked  polygonal  areas.     In  the  human  liver  on  the  con- 
r  ,rv  the  interlobular  connective  t»sue  is  present  m  small  amount,  the  lobules,  in 
conswuence,  being  poorly  defined  and  unceruin  in  outline.  ,    .     . ,      .  , 

^he  Lobular  ilood- Vessels.— Since  the  arrangement  of  the  blood-vessels 
is  the  salient  feature  in  the  architecture  of  the  fully  formed  lobule,  it  is  desirable  to 
Itudv  the  vascular  distribution  before  considering  the  disposition  of  the  hepatic  cells. 
As  already  described,  the  branches  of  the  portal  vein,  the  functional  blood-vessel 
of  the  organ,  ramify  within  the  capsule  of  Glisson  and  encircle  the  periphery  of  the 
obule  ;  inasmuch  L  these  vessels  supply  the  divisions  of  glandular  tissue  with 
bUiod  for  the  performance  of  their  secretory  rdle,  they  correspond  with  the  inter- 
lobular arterioles  of  ordinary  glands.  ,  .  .  .  ,  .:  .•  i 
Numorous  minute  branches  are  given  ofi  from  the  interlobular  ramifications  of 
the  portal  vein  which  enter  the  periphery  of  the  adjacent  lobules  antl  break  up  mto 


Central  vein 


Section  o»  liver  Injected  from  taepatk  vein,  «liowin«  intralobatar  capiltary  net-work 


Portal  vein 


X  100. 


the  intralobular  capillary  net-work.  The  disposition  of  the  latter  is  in  general 
radial,  the  capillaries  converging  towards  the  middle  of  the  lobule,  where  they  join 
to  form  the  central  or  intralobular  vein,  the  beginning  of  the  system  of  the  hepatic 
veins  by  which  the  blood  passing  into  the  lobules  is  eventually  carried  into  the 
inferior  vena  cava.  The  general  course  of  the  central  vein  corresponds  to  the  long 
axis  of  the  lobule  (Fig.  1444).  and  hence  in  cross-sections  of  the  latter  the  vein 
appears  as  a  transversely  cut  canal  towards  which  the  capillary  vessels  converge 
(Fig.  1445). 

The  capillary'  network  within  the  lobule  is  composed  of  channels  with  a 
diameter  usually  of  about  .010  mm.  ;  the  widest  capillaries — some  .020  mm.  in 
diameter — are  found  in  the  iminediate  vicinity  of  the  afferent  and  efferent  veins, 
the  narrowest  occupying  the  intermediate  area.  The  meshes  of  the  vascular  net- 
work vary  from  ,oi5-.040  mm.  in  their  greatest  dimension,  those  at  the  periph- 
ery being  broader  and  more  rounded,  while  those  near  the  centre  are  narrower 
and  more  elongated.  The  central  vein  occupies  the  long  axis  of  the  lobule  and 
increases  in  size  as  it  proceeds  towards  the  base  of  the  lobule,  as  the  side  of  the 
latter  through  which  the  vein  escapes  is  termed.     It  begins  usually  about  midway 

108 


I7»4 


HUMAN  ANATOMY. 


<■-■• 


between  the  base  and  the  opposite  tide  of  the  lobule,  by  the  confluence  of  the  capil- 
larica,  which,  after  the  central  vein  i«  formed,  open  directly  into  the  lattti  i, 
lower  planes.  in  those  lobuleti  which  form  part  of  the  exterior  of  the  liver  tii< 
central  vein  ascends  almost  to  the  free  surface  ;  otherwise  its  commcncemi-nt  is 
separated  from  the  periphery  by  about  one-half  the  thickness  of  the  lobule.  Im 
mediately  on  emerging  from  the  lobule  the  central  vessel  opens  into  the  sub/obulai 
vein,  which  runs  generally  at  right  angles  to  its  intralobular  tubularies  and  along  and 
beneath  the  bases  of  the  lobules,  the  outlines  of  which  are  often  seen  through  tlu' 
waHs  of  the  vein.  The  channels  for  the  sublobular  veins  are  thus  surrounded  by 
the  boMs  of  the  lobules,  a  single  central  vein  returning  the  blood  from  each.     The 

Fto.  1446. 


fitv 


HcfMtlc  ancry^ 

Purul  vein. 
Bile^dnct. 


{^,:r 


>.v  -■:.'-:-» 


.  Central  (intra 
lobular)  vein 


.Interlobular 
connective 
tiBsue 


•v^^^-: 


i'/V  ■.:■'<■  /.•'.. -v-vm--  >v.- 


Section  of  unbijt^  \<A  Hver,  ahowinn  Kcncral  ■mngemcnt  o<  lobnla,  inWrlobular  and  intnlobular  vessels.    X  i». 


sublobular  veins  join  to  form  larger  vessels,  which  in  turn  unite  and  constitute  the 
branches  of  the  hepatic  veins. 

The  Liver-Cells. — The  meshes  of  the  interlobular  capillary  net-work  are  oc- 
cupied by  the  hepatic  cells,  the  bile-capillaries,  and  a  meagre  amount  of  connective 
tissue.  The  cells  are  arranged  as  cords  or  trabeculce  which  conform  in  their  general 
disposition  to  the  tntcrcapiilarv  spaces,  which  they  completely  fill.  In  a  sense,  the 
entire  lobule  consists  of  a  solid  mass  of  hepatic  cells  elaborately  tunnelled  by  the 
radially  coursing  capillaries  and  their  short  anastomosing  branches,  the  proportion 
of  the  space  occupied  by  the  vascular  channels  to  that  filled  by  the  cells  being  ap- 
proximately as  one  to  three      When  isolated,  the  liver-cells  present  a  polygonal 


STRUCTURE  OF  THE   LIVER. 


>7>5 


outline  and  measure  usually  from  .015-.025  mm.  in  their  lonRest  dimension.  Each 
cell  comes  into  contact  with  from  six  to  nine  other  elements,  the  surfaces  of  con»»ct 
beinrf  plane  from  mutual  pressure.  Always  one  side,  often  more  than  one,  cxhibitt 
a  sliallow  depression  which  indicates  the  surface  of  former  contact  with  a  capillary 
ami  emphasizes  the  intimate  relation  existing  between  the  blootl-vesstis  and  the  cells. 
The  latter  Ue  against  at  least  one  capillary  and  sometimes  several,  this  relation  being 
dcDcndent  upon  the  size  of  the  blood-channeU.  The  larger  the  latter,  as  at  the 
Dcriphery  and  near  the  centre  of  the  lobule,  the  greater  the  nmnUr  of  cells  with 
wilv  one  or  two  capillary  facets  ;  conversely,  where  the  capillaries  are  of  smaU 
diameter,  the  cells  come  into  contact  with  three  or  four.  The  livcr-cell  consists  ot 
finely  granular  protoplasm  which  sometimes  exhibits  a  differentiation  into  an  outer 
and  an  inner  zone.  It  a  without  a  cell-membrane,  although  the  peripheral  zone 
of  its  cytoplasm  is  condensed,  especially  when  it  forms  part  of  the  wall  of  the  bile- 
canaliculi.  The  nucleus,  of  vesicular  form  and  from  .006-.008  mm.  in  diameter, 
contains  a  small  amount  of  chromatin  and  usually  a  nucleolus.  Occasional  cells 
are  conspicuous  on  account  of  their  large  size,  as  weU  as  the  unusual  diameter  of 

Fio.   1447- 


Section  ol  onin)ected  liver,  ihowdiK  cords  of  hepatic  cell*  between  cmpHUry  blood  veueh.    X  450. 


their  nucleus.  Such  cells,  according  to  Reinke,'  undergo  direct  division  and  pro- 
liuce  the  double  nucleated  elements  constantly  encountered  in  sections  of  normal 
liver.  Centrosomes  have  also  been  observed  in  resting  hepatic  cells.  Particles  of 
gtvcogen,  minute  oil  droplets,  and  granules  of  bile-pigment  are  more  or  less  constant 
constituents  of  these  elements.  The  fat-containing  cells  are  most  numerous  at  the 
periphery  of  the  lobule,  those  enclosing  pigment  particles  near  the  centre 

The  Bile-Capillaries.— These  minute  canals,  representing  the  lumma  of 
ordinary  tubular  glands,  form  a  net  work  cf  intercommunicating  chanmls  throughout 
the  lobule  closely  related  to  the  liver-cells.  Whereas  in  the  usual  atrangement  a 
single  surface  of  several  gland-cells  borders  the  lumen,  in  the  exceptional  case  of  the 
liver  the  excretory  channels  are  bounded  by  the  opposed  surfaces  of  only  two  cells, 
the  bile-capillary  occupying  but  a  small  part  of  the  surfaces,  on  each  of  which  it 
mr-4eh  a  narrow,  c^ntrallv  situated  groove.  Moreover,  not  only  a  single  surface 
of  the  hepatic  cell  takes  part  in  bounding  the  canaliculi,  but  the  latter  are  found 
between  all  surfaces  where  two  liver-cells  are  direcriy  in  contact,  so  that  each  hepatic 
element  comes  into  direct  relation  with  a  number  of  bile-capillaries.  The  latter, 
'  Vcrhandlung  d.  Anatom.  Gesellschaft,  1898. 


I7'6 


HUMAN   ANATOMY. 


however,   never  lie  on  the  narrow  sides  of  the  Hver-celb  ofiposed  to  the  blot 
vcsspU,  the  bile-canal  never  separating  the  blood-capillary  from  the  cell.     While  tl 
picuoRiinating  direction   of  the  bile-capillaries  is  radial  and  corresponds  to  il.- 


Fio.  144S. 


'  tin 


^T  •. 


-Blood-«|>iair>' 


.BII«-vmi>*Uanr 


.Uvcr-ccll 


FlO. 


>449- 


j}'  ^'z:': 


'-1^  ^  ^^  ':^. 


'^^ 


Section  of  liver  in  wliick  both  blood-  mA  bilc-capilkric*  tatv*  been  mJccMd :  the  latter  MimMnd  the  Individual  livrr 

ctlli.    X  3110. 

similar  general  disposition  of  the  cylinders  or  leaflets  of  hepatic  tissue,  the  ncii.il 
arrangement  is  converted  into  a  net-work  by  the  numerous  cross-branches.  Tlie 
rt-sulting  meshes  correspond  in  size  with  the  individual  liver-ct  'Is,  \}hich,  in  appio- 
priate  sections,  often  appear  almost  com- 
pletely surrounded  by  the  bile-capillaries. 
The  latter  possess  no  walls  other  than  the 
substance  of  the  liver-cells  between  which 
they  lie.  The  diameter  of  the  bile-capil- 
laries, from  .001-.002  mm.,  remains  prac- 
tically the  same  throughout  the  lobule  until 
the  canaliculi  reach  the  extreme  periphery. 
At  this  point  the  liver-cells  abruptly  dimin- 
ish in  height  and  are  transformed  into  the 
low  cuboidal  cells  lining  the  excretory  tubes 
that  pass  from  the  lobule  into  the  surround- 
ing connective  tissue  to  become  tributaries 
to  the  larger  interlobular  bile-ducts. 

The  ultimate  relations  between  the 
bile-capillaries  and  the  liver-cells  is  still  a 
subject  of  discussion.  Based  upon  the  evi- 
dence supplied  by  injections  and  silver 
impregnations,  it  is  believed  by  some 
(Kupffer,  R.  Krause,  and  others)  that  ex- 
tensionsof  the  bile- capillaries  normally  exist 
within  the  substance  of  the  cells,  thus  form- 
ing intracellular  secretion  canaliculi.  The  latter  are  sometimes  pictured  as  ending  in 
connection  with  minute  dilatations  or  secretion  varuoles.  It  is  by  no  means  certain 
that  such  appearances  are  not  artifacts,  or  at  least  due  to  changes  after  death  of 


Section  o^  liver  treated  by  Golci  ailver  methoH. 
frhowlug  pan  of  intralubuWi  (Mft-wurk  uf  bit«-i.-itiiii- 
lanes.     X  aoo. 


STRUCTURE  OF  T»    L1VP:R. 


I7«7 


^  c**      Tfce  •icretion  vsKucrte..   protwWy    im-  to  the  oorfesceoce  ol  mimite 
Llcrf  bfle  e««  only  as  trwMCTt  d*taita.  and  cannot  be  rrtrarded  as  constant 
^  of  the  h«iwbc  celta.     Holmgren  '  iiwert>  thr  existence  «t  • '  ,aK:e-cana  k  uli 
'"**•  °'  *"*  ^^  "  wMwn  the  liw-  <!!•  in  addition  to 


fnc.   1450. 


and  iMdependent  of  the  Mtrw-ellular 
gtccretMm  ctoaiwelH.  Sdwter'  ha» 
docrilwd  nMtritivc*  chanario  within 
tbr  liver-cetis  which  comaHinicate 
w«h  the  bJfl»»rt-capiUarie9. 

The    iHtralolMlar    canncc- 
tivr  ttMue.  <tr  rettenlum,  t-onsints 
of    iielicate    prolamKations    of    tb«- 
tibrnos  tiasur  of  Glisson'si    caj;  tite 
which  unite  the  Wood-capillaries  ...wl 
cords  of  liver-«ell».     This  tMSue,  bh 
general    meagw  in   anwunt,   form* 
a  delicate  reticulum  extending  be- 
tween the   Wood-channels  ana    the 
glandukir  elements  throughout  Ae 
lobule,  and  connects  the  peripheral 
nbrouH  tissue  with  the  perivascular 
tiMiue  that  exists  an    nd  the  centrrf 
vein  in  considerable  quantity       In 
addition  to  the  delicate  fibres  of  the 
intralobular  reticulum,  the  perivas 
cular  ttaaue  conuins  lymph-spaces 
anA  conaective-tissue  elem«Tts,  the 
cHh  of  kHfiffer.      The  latt.r  are 
aoell  spindle  or  stellate  and  lie  in 
daae  relation  with  the  bloi.d-vessels, 
their  processes  penetrating  for  a  limited  distance  between  the  adjacent  liver-'-ells. 

The  interlobular  bile-ducts,  which  iweive  the  biliary  canals  that  p.<;rce  ihe 
^*»iphery  of  the  lobule  as  the  outlets  of  th^  intralobular  net-work,  accompany  the 

Fir.     14"'. 


FUMon 


ArtifaiaHy  ■!'■»■»' i<  •Mtionol  Uv«r,  «howm«  anponmic  liner- 
lobular  fibffow  tiMiw  aa*  inlralobslar  reticulum         i.w. 


PtMtalvcin 


HcfiUic  Mtcry 


Intertobular  coiacctive- 
liHoe 


Htftx  cclli 


Scctioa  a(  liver.  ahowiuK  iitUfkbulat  tiuuc  and  vessels,    x  160. 

branches  of  the  portal  vein  and  the  hepatic  artery  within  the  c;^)sule  of  Glisson. 

These  ducts,  frr>m  .030-.050  mm.  in  diameter,  constitute  a  net-wors  over  the  exterior 

'  Anatomischer  Anzeiger,  Bd.  xxii.,  No.  1,  1902.  '  Ibid.,  Bd.  xxi.,  No.  i.  1901. 


I7I8 


HUMAN  ANATOMY. 


surface  of  the  lobule.  They  consist  of  a  dense  fibro-elastic  coat  lined  with  cylindri 
cal  epithelium,  some  .oao  mm.  thick,  which  latter  is  continued  into  the  low  cuboid. il 
or  flattened  cells  that  form  the  lining  of  the  excretory  channels  connecting  the  intra 
lobular  net-work  of  bile-capillaries  with  the  bile-ducts.  Beginning  as  the  small 
vessels  that  surround  the  lobules,  they  become  tributary  to  the  larger  bile-ducts, 
which  increase  in  diameter  as  they  approach  the  transverse  fissure.  In  the  vicinity 
of  the  latter  these  trunks  join  into  the  two  main  lobular  ducts  forming  the  hepatic 
duct.  The  largest  bile-vessels  possess  bundles  of  unstriped  muscle  which  in  tho 
hepatic  duct  are  arranged  principally  as  a  longitudinal  layer,  supplemented  by  cir 
cular  and  oblique  bundles  (Hendrickson). 


m 


Gall-bUdder 


Vena  cava 

Probe  tn  ror*iB«a 


THE  BILIARY  APPARATUS. 

In  addition  to  the  small  interlobular  bile-vessels  already  described,  the  systrni 
of  canab  receiving  and  conveying  the  secretion  of  the  liver  to  the  intestinal  tract 
consists  of  the  hepatic  duct,  the  excretory  tube  of  the  organ  ;  the  galt-bUulder,  a  ren 

ervoir  in  which  the  bile  ac 
Fio.  i4S»'  cumulates   during   intervals 

of  digestion;  the  cystic  duct, 
the  continuation  of  the  bile- 
sac  opening  into  the  side  ot 
the  hepatic  duct ;  and  the 
common  bile-duct,  which,  al- 
though formed  by  the  union 
of  the  other  two,  is  in  struc- 
ture and  direction  really  the 
continuation  of  the  hepatic 
duct. 

The  hepatic  duct  (duc- 
tus hepaticus)  is  formed  be- 
low the  hilum  by  the  unior 
of  its  two — a  right  and  a 
left — chief  tributaries.  The 
latter  issue  from  the  porta! 
fissure,  one  on  each  side, 
and  generally  unite  with  the 
hepatic  duct  nearly  in  the 
shape  of  a  T,  the  last-nainetl 
canal  forming  almost  a  rij,'ht 
angle  with  each  of  its  tribu- 
taries. Tracing  the  chief 
ducts  into  the  liver,  the  left 
branch  runs  at  first  in  front 
of  the  left  division  of  the 
portal  vein,  while  ihe  right 
one  usually  crosses  it.  \Ve 
have  seen  the  hepatic  duct 
issue  from  the  right  lobe 
and,  forming  a  loop  in  the 
fissure,  leave  it  with  the  left 
division  of  the  portal  vein, 
receiving  branches  alonjj  its 
convexity  from  the  various  parts  of  the  liver.  .Sometimes  the  chief  ducts  are  longer 
than  usual,  and  meet  to  form  the  hepatic  duct  at  an  acute  angle  farther  from  the 
liver.  The  length  of  the  hepatic  duct,  therefore,  varies  with  these  details,  prol)a- 
bly  l)eing  usually  from  20-40  mm.  (  %-\  4  in.),  with  a  tliameter  of  from  4-6  mm. 
It  lies  in  the  gastro-hepatic  omentum,  in  front  of  the  portal  vein  and  to  the  right 
of  the  hepatic  artery,  and  inclines  downward  to  the  inner  side  of  the  second  part 
of  the  duodenum,  resting  previously  on  the  top  of  the  first  part.     The  hepatic  duct 


Paiicmtic 
duct 


Superior 

mrwntcric 

vein 
Superior 

meaenleric 

artery 


Portions  trf  liver,  iiuodenuit.  nnd  pancreas,  <.howiiiK  biliary  and  pancreatic 
duLlk  ;  head  uf  pancffus  fumed  Daclt. 


THE  BILIARY  APPARATUS. 


1719 


ends  at  the  point  at  which  the  cystic  duct  opens  into  it  The  duct  a  lined  *tidi 
mucous  membrane,  covered  with  simple  columnar  epitheliuni,  and  presentt  many 
minute  pi's,  into  which  open  the  onfices  of  numerous  sm^  tubular  glands.  Its 
walls  consist  of  fibro-elastic  connective  tissue  and  unstnped  muscular  nbres.  Ihe 
1  itter  neither  numerous  nor  separated  into  a  dislmct  layer,  are  grouped  for  the 
most  'part  into  longitudinal  bundles,  but  there  are  also  circular  and  oWioue  ones. 

The  gtll-bUdder  (vesica  fellea)  is  a  pear-shaped  recepUde  for  the  bUe,  rest- 
ing in  its  fossa  on  the  under  side  of  the  liver,  with  the  large  end  forward.  The 
lone  axis  runs  also  somewhat  inward.  The  length  is  from  8-io  cm.  (3^-4  in.) 
and  the  capacity  some  50  c.c  (about  ij^  fl.  oz.).  It  narrows  to  a  point  where 
ir  usually  bends  to  the  left  and  ends  in  the  cystic  duct  without  definite  external 
demarcation.  The  bent  terminal  portion,  or  neck,  about  i  cm-  long.  »  •nof*  «' 
less  closely  bound  beneath  the  peritoneum  to  the  side  of  the  gall-bladder,  so  that 
before  this  is  separated  it  sometimes  looks  as  il  the  duct  arose  from  the  side  of 

'  *  The'fundua  of  the  gall-bladder  lies  near  the  end  of  the  ninth  right  costjd  carti- 
laee.  The  neck  is  at  the  right  end  of  the  porul  fissure.  Anteriorly  the  bladder 
rests  on  the  transverse  colon,  behind  which  it  lies  first  to  the  nght  of  and  then  above 
the  first  part  of  the  duodenum. 


Fio.  1453. 


Fio.  1454- 


ill-bUuUcr 


.Cymcdnct 


SuTtecc  view  o(  poniuo  ot  mucoui  membrane  at  gall- 
bladder,   xu. 


Hepatic 
duct 


Portion  of  (all-bladder  and  biliary 
pamagei  laid  open,  ahowing  surface  of 
mucous  membrane.    Natural  liie. 


The  wall  of  the  gail-bladder  is  very  resistant,  being  composed  of  a  mixture  of 
fibrous  tissue  and  of  unstriped  muscular  fibres.  Most  of  the  latter  are  disposed  circu- 
larly, but  oblique  and  longitudinal  ones  are  interwoven.  The  fibro-muscular  tunic  is 
lined  by  a  layer  of  mucous  membrane  which  is  very  adherent  to  it.  The  mucous 
membrane,  covered  with  simple  columnar  epithelium,  presents  slightly  raised  ndges 
marking  of!  a  net-WDrk  of  small  irregular  spaces  some  5  mm.  in  diameter.  The 
small  bifurcated  tubular  glands  are  few  and  may  be  wanting.  The  bent  portion,  or 
neck,  is  separated  from  the  bladder  by  a  strongly  raised  fold.  There  are,  or  may 
be,  one  or  two  smaller  folds  within  the  neck,  the  separation  of  which  from  the  duct 
is  usually  arbitrary.  .....  ,    , 

Vessels  of  the  GalUBUdder.— Wr/^n«.— The  chief  distribution  of  the 
cystic  artery,  a  branch  of  the  hepatic,  is  on  the  free  under  surface,  which  it  ap- 
proaches from  the  left,  running  on  the  cystic  duct.  There  is  a  smaller  branch 
which  lies  deeply  on  the  right  between  the  gall-bladder  and  the  liver-substanr^'. 
l/eins.— The  superficial  veins  join  the  cystic  artery  and  empty  into  the  nght 
division  of  the  portal  vein.  According  to  Sappey,  a  number  of  small  veins  run 
directly  into  the  li-er-tissue  joining  the  portal  system.     The  lymphatics,  for  the  most 

'  For  the  musculature  of  the  biliary  apparatus,  see  Hendrickson :  Johns  Hopkins  Hospital 

Bulletin,  Nos.  90,  91,  1898. 


I730 


HUMAN  ANATOMY. 


part,  empty  into  the  nodes  in  the  portal  fissure.     Some  open  into  a  node  said  u  ■ 
lie  in  the  angle  at  the  bend  of  the  nock. 

The  nerves  are  from  the  solar  plexus  through  the  hepatic  plexus. 
The  peritoneal  relations  of  the  bladder  and  ducts  are  considered  with  those  <>: 
the  liver  (p^e  1731). 

The  cystic  duct  (dsctm  cystkns),  3  or  4  cm.  in  length,  with  a  diameter  of 
from  2-5  mm.,  passes  in  a  fold  of  peritoneum  from  the  neck  of  the  gall-Uadder  to 
the  gastro-hepatic  omentum,  where  it  joins  the  hepatic  duct  at  an  acute  angle  or. 
rather,  opens  into  its  side.  It  is  said  sometimes  to  present  an  enlargement  at  its 
end.  In  its  natural  condition  it  looks  externally  like  the  other  ducts,  but  if  distended 
and  dried  it  presents  a  series  of  irregular  folds  ffiving  the  impression  of  a  spiral  fold 
which,  in  the  adult  at  least,  a  closer  inspection  does  not  confirm. 

Structure. — In  structure  the  cystic  duct  presents  much  more  of  a  muscul.ir 
layer  than  the  others.  This  is  thickest  at  the  upper  part,  and  consists  chiefly  of 
circular  fibres.  These  enter,  especially  near  the  beginning,  the  valvular  folds  of  the 
mucous  membrane,  which  is  clothed  with  simple  columnar  epithelium.  In  the  fu:tiis 
there  is  a  fairly  distinct  spiral  valve,  most  developed  In  the  upper  part,  and,  in  fact, 
starting  in  the  neck  of  the  gall-bladder.     later  the  continuous  spiral  ridge  {vtUvula 

spiralis  HetsUri)  usually  atro- 
Pio.  I4SS.  phies  and  is  broken  up  at  many 

places,  leaving  detached  fol<ls 
with  a  semilunar  outline  and 
no  longer  dii^nctly  spirally  ar- 
ranged. Little  pockets  also  de- 
velop between  them.  Small 
tubular  g^ds  are  few  in  the 
upper  part,  but  plentiful  in  the 
lower. 

The  comnoo  bile-duct 
(dnctos  chsMscksB)  is  about 
7  cm.  (3)^  in. )  long.  Its  diam- 
eter is  from  6-7  mm.  at  the 
commencement  and  rather  less 
at  the  end.  Beginning  imme- 
diately below  the  transverse 
fissure,  althoi^h  conventionally 
regarded  as  formed  by  the  union 
of  the  cystic  and  the  hepatic 
ducts,  being,  in  fact,  the  direct 
continuation  of  the  latter,  the 
common  bile-duct  passes  down- 
ward between  the  layers  of 
the  gastro-hepatic  omentum,  in 
front  of  the  foramen  of  Winslow,  with  the  hepatic  artery  to  its  left  and  the  portal 
vein  behind.  It  descends  alon^  the  postero-inner  aspect  of  the  bend  joining  the 
first  and  second  parts  of  the  duoctenum,  then  along  the  inner  side  of  the  second  part, 
where  it  is  more  or  less  surrounded  bv  the  head  of  the  pancreas.  Near  its  termina- 
tion it  meets  the  pancreatic  duct  ind,  in  company  with  the  latter,  pierces  the  duo- 
denal wall,  which  it  traverses  obliquely  for  the  distance  of  some  15  mm.,  to  empty 
into  the  duodenum  at  a  |)apilla  marking  the  -ommon  orifice  of  the  two  ducts.  This 
papilla  is  situated  near  the  posterior  border  of  the  internal  aspect  of  the  descending 
part  of  the  duodenum,  from  9—10  cm.  ("about  ^l4-4  in.)  from  the  pylorus.  In  the 
natural  condition  it  is  not  easy  to  find,  being  situated  lieneath  a  transverse  fold  and 
not  being  prominent  in  the  shaggy  mucous  membrane.  Its  length  undistended  is 
only  about  5  mm.  When  inflated  or  injected  it  is  a  prominent  object  more  than 
twice  as  large.  Moreover,  it  does  not  project  freely,  but  lies  on  its  side  pointing 
downward,  the  surface  next  to  the  wall  becoming  free  only  very  near  its  end.  The 
orifice  looks  downward.  It  may  be  oval  or  circular,  with  a  diameter  of  from  i-a  mm. 
A  slight  vertical  fold,  the  frenum,  often  runs  downward  from  the  oprning  tor  the 


A,  ponion  ol  dnodcnnm,  with  nmcrior  wall  mnovcd.  nhnwing 
vntrancc  n4  bile  ind  paiirmtic  dact>;  A,  papilla  laid  open,  thowioc 
floor  of  ampulla.    One-half  natural  aiie. 


■i-i 


THE  BILIARY   APPARATUS. 


i7ai 


lutanc*  of  I  cm.  The  structure  of  the  common  duct  is  much  the  same  as  rtiat 
r^^ewtic  ~nto  ning  but  little  muscular  tissue  and  that  not  well  defined^  The 
n?a  S'ns  a  fusifom  dilatation,  the  ampulla  (of  Vater),  which  may  be  i  cm. 
rt«C^Se^dS  ™toThis  the  bile-durt  and  the  duct  of  the  pancre=«  usually 
''I^^Timmon  orific^  Be  these  orifices  common  or  distinct,  each  «  sur- 
roCdS  irlT "Cumulation  of  the  circular  muscular  fibres  wh.ch  amounts  p  a 
X,Sr    Th^  gl^ds.  which  are  found  throughout  the  common  duct,  are  particu- 

,o  thefSS  of  serous  membrane,  is  entirely  inappropriate.     It  .s  «"  ?»"  reUmed 
^,t  the  wmrneration  of  five  ligaments  as  separate  enuues  is  antiquated.     The  round 
but  the  f*""^"""  hcMtte)  is  a  cord  of  fibrous  tissue,  the  remains  of  the 

''S?,'^edutMSve?n  mSfrom  the  umbUicus  to  the  left  end  of  the  portal 
fiSLTlt-^SaS  JHe  duLs  venosus.  is  represented  by  fibrous  t^ue(lljj.. 
^Z^  veaoMB)  in  the  fissure  of  that  name.  The  round  ligament  lies  against  the 
^SSfor  an  inchor  more  above  the  navel  and  then  Pa*«?,*«^''*^';;'l ."!»''« 
t^ZZo\x\l  falciform  ligament,  a  fold  of  peritoneum  presumably  detached  froni 
t^  interior  wkll  a/d  from  the  diaphragm  by  the  development  of  this  vein.     The 


Fio.  1456- 


(XtophagoU  Impi  •Mioa 


Left  coronary  ligaincnt 


RifM  coroiiar>  liKamciit 


Ridhl 
trmiiKuuir 
-linmnmil 
Saprarmal 
imiireMton 


PoMerior  turfacc  <A  liver,  showing  perUonnI  r«(l«ction«. 


front  part  of  the  falciform  ligament  is  appropnately  described  as  sickle-shaped.  The 
m.int  is  in  front,  and  it  grows  broader  as  it  passes  backward  until  it  •■;^<:|'f^'hehver 
where,  growing  narrower,  it  extemls  above  the  liver  to  the  spine  at  about  the  median 
line  It  contains  very  little  tissue  between  its  folds,  which  are  reflecteil  on  either 
side  over  the  superior  surface  of  the  liver.  At  the  notch  in  the  anterior  border  the 
round  ligament  i-asses  onto  the  inferior  suriace  of  the  liver  in  the  iimbilical  fissure. 
The  cor%tary  ligamfnh  are  differently  arranged  on  the  two  sides.  The  right  one  is 
made  by  the  two  reflections  onio  the  diaphragm  from  the  up|)er  and  lower  Iwrders 
„f  the  part  of  the  posterior  surface  adherent  to  it.  These  come  together  at  the 
right  of  that  surface  and  are  continued  as  a  fold,  the  right  triangular  ligammt  on 
the  right  surface,  connecting  it  to  the  diaphragm  in  the  flank  by  a  line  of  attach- 
.nent  J«me  5  cm.  long.  On  the  top  of  the  left  lobe,  but  not  on  the  P"''*^""^  »«;;• 
.ler.  there  is  a  small  area  without  peritoneal  covering,  enclosed  by  the  two  folds  ot 
the  left  coronary  ligament,  of  which  the  anterior  is  analogous  to  the  right  one,  luit 
the  posterior  b^ins  at  the  left  of  the  upper  end  of  the  fissure  o  the  ductus  venosus. 
TheVloon  unite  to  form  the  left  triangular  ligament  which  lies  between  the  d  a- 
phragm  and  the  top  of  the  left  lofje,  being  considerably  longer  than  the  right  one 


1732 


HUMAN  ANATOMY. 


On  the  under  side  of  the  liver  the  end  of  the  round  ligament  lies  in  its  fissure  cov- 
ered by  a  slight  fold  of  peritoneum.  Th"  same  is  true  of  the  gall-bladder.  Sonit- 
times  the  latter  is  more  or  less  surrounded,  and  it  may  be  almost  completely  so. 
hanging  from  the  fossa  by  a  fold.  The  lesser  or  gastro-hepatic  omentum  is  a  fold 
enclosing  the  vessels  in  the  portal  fissure  and  passing  to  the  lesser  curvature  of  the 
stomach  and  the  first  part  of  the  duodenum.  A  secondary  fold  containing  tin- 
cystic  duct,  the  duodeno-eyslic  fold,  joins  it  on  the  right.  Near  this  it  presents  a 
free  border  forming  the  edge  of  the  foramen  of  Winslow.  On  the  left  it  runs  alon^ 
the  fissure  of  the  ductus  venosus  to  the  notch  in  the  liver  made  by  the  passage  of 
the  o^phagus.  There  its  left  layer  is  reflected  as  the  under  one  of  the  left  coro- 
nary ligament,  while  the  right  layer  descends  along  the  left  of  the  vena  cava  to  join 
the  right  inferior  coronary  ligament.  The  posterior  surface  of  the  Spigelian  lobe  is 
covered  with  peritoneum  which  is  almost  surrounded  by  these  lines  of  attachment, 
but  is  continuous,  by  means  of  the  caudate  lobe,  with  the  serous  coat  of  the  undtr 
surface  of  the  right  lobe.     Thus  a  pocket  is  roofed  in  behind  the  lobe  of  Spigelius. 


Fio. 


Pericurdial 


«4S7- 


pcricard 


Inferior  vena 


IX  rib  ' 

Major  azypM  vein 


X  thoracic  vertebra 


Tranitverae  Mction  at  level  of  tenth  thoracic  vertebra,  upper  surface  of  diapfaraxm  expoaed,  showinK  relation  of 
viscera  ;  outline  of  liver, ;  of  stomach, ;  of  colon,  o  o  o  o  o ;  of  spleen,  x  x  x  a  a. 


The  hepatic  duct  lies  within  the  lesser  omentum  to  the  rijfht  and  in  front  of  the 
portal  vein.  It  is  joined  by  the  cystic  duct  in  its  fold,  already  mentioned.  As  it 
leaves  the  gall-bladder,  the  duodeno-cystic  fold  is  a  distinct  duplicature  which  joins 
the  lesser  omentum  at  an  angle  ;  but  at  the  lower  part,  where  the  cystic  duct  opens 
into  the  hepatic,  the  folds  become  one.  The  common  bile-duct  may  be  in  the  very 
lowest  part  of  the  lesser  omentum,  where  it  is  attached  to  the  postero-inner  surface 
of  the  duodenum  where  the  first  part  bends  down  to  fjecome  the  second  ;  but  the 
relations  are  variable,  and  the  common  duct  may  have  no  peritoneal  relation. 

Position  of  the  Liver. — The  relations  to  other  organs  have  been  treated  in 
the  account  of  the  surfaces.  The  relations  to  the  walls  of  the  alxlomen  can  be 
given  only  in  general,  owing  to  the  variations  of  both  the  organ  and  the  thora.x  in 
size  and  shape.  The  liver  lios  under  the  dome  of  the  diaphragm,  which  separates 
it  from  the  ribs.  Occasionally  it  extends  across  the  whole  breadth  of  the  alxlomen, 
but  the  left  lobe  may  end  at  the  left  mammary  line.     The  highest  point  is  on  the 


THE  BILIARY   APPARATUS. 


1723 


ri^ht  where,  after  death,  it  reaches  to  the  level  o   the  sternal  en^  ?'»*"=  ^''''.«*!S 
^rtuJe      It  b  doubtful  whether  in  life  the  liver  is  ever  quite  so  high.     On  the  le  t 
[f  b  Xut  I  cm   lower,  and  in  the  middle  it  is  not  more  than  2  cm.  lower  st.ll. 
The  rSon  of  Uie  left  lobe  to  the  floor  of  the  thorax  vanes  considerably.     "  1»  K*. 
Jie  oSS  Ly  extend  to  the  left  wall,  but  this  is  rather  uncommon      The  liv« 
m!v  S  the  front  waU  as  far  to  the  left  as  the  mammary  line,  in  which  case  it  wUl 
K^w  nearly  the  whole  of  the  floor  of  the  pericardium   although  it  may  not  lie 
^1      .r.  »^tILr  oarL     It  always  passes  just  in  front  of  the  oesophageal  openmg 
ThHneriorSder'^ts  agShe^^erior  wall  on  the  right,  the  diaphragm  o 
Sfr^  inttrvenhTe  afthe  right  bordeVof  the  right  kidney  near  the  end  of  ihe  last 
nb  Tn  S  thef^vd  of  thVsecond  lumbar  spine,  and  descends  to  the  ngh  along 
rib,  on  *7" '"!,'*;"  ^  rib.     At  the  mid-axUlary  1  ne  it  begins  to  rise,  foUowing 


Fio.  1458. 


VII  rilMWtilac* 
VI  rilxartiUcc 


Tfwuvenc  finara  „ 

FalcHonn  IlKimcnt 

Quadrate  lobe 


VI  rib 


VII  rib 


litelian  tobe 


RiKht  nipra- 
roialbody 


,  diaphragm 

XII  llioracic  vertebra 


XI  rib     Uiaphrapn 

FroMii  iwrtloo  Kmn  body  (t  level  of  twelfth  thoracic  veiUbra. 


after  which  it  crosses  the  epigastrium  to  strike  the  left  costal  arch  at  the  eighth  car- 
£e  The  no^hTo  the  round  ligament  is  a  little  to  the  right  ««  th<^  ™«^d.an  line 
aShe  fundus  of  the  gall-bladder%t  or  near  the  end  «'  '»?-  "'"^J^f^^''' ^^^^^^^^ 
It  in  usually  crossed  by  a  vert  ca    ine  from  the  middle  of  the  cHvicle.      in  ine  re 

umbe^t  po'^.idon  Se  Uver  gravitates  to  the  top  of  the  abdomen  so  that  normally 
inThe  male  no  portion  is  left  below  the  costal  arch  except  near  the  middle.     The 

nferior  vena  caCru^s  in  a  groove  on  the  back  of  the  organ,  but  the  aorta,  passing 

he  raphragm  at  a  lower  point,  has  the  latter  muscle  between  them.  The  vena  cava 
pierce  the  diaphragm  at  Ihe  level  of  the  body  of  the  ninth  thoracic  vertebra.  The 
Junes,  especially  the  right,  overiap  the  liver  very  considerably.  „,,.„„ 

%ev^elopr^ent  and  Growth—Very  eariy.  in  the  human  ^''ry'?  «' 3_  S  mm. 
in  length,  a  groove-like  evagination  appears  on  the>^^entral  wall  of  the  gut-tube 

n.nXtelv  above  the  widely  open  vitelline  duct.     This  evagination.  the  first  ind^ 

cronSlhc  hepatic  anlage.  extend,  into  the  primitive  ventral  or  anterior  mesentery 

'  Carmichael :  Journal  of  Anatomy  and  Physiology,  vol.  xxxvii..  190J. 


17*4 


HUMAN  ANATOMY. 


which  connects  the  stomach  and  the  duodenum  with  the  anterior  body-wall.  Th< 
hepatic  diverticulum  grows  forward  and  upward  into  the  anterior  mesentery  until  it 
comes  into  relation  with  the  imperfect  partition  which  partially  separates  the  thoracic 
and  abdominal  divisions  of  the  body-cavity.  This  partition,  the  septum  transversuni. 
primarily  consists  of  lateral  folds,  projectmg  at  right  angles  from  the  anterior  mesen- 
tery, caused  by  the  large  vitelline  veins  traversing  the  anterior  mesentery  on  their 
way  to  the  sinus  venosus  of  the  early  heart.  The  relation  of  these  structures  is 
more  fully  considered  in  connection  with  the  development  of  the  diaphragm  (pagt-' 
1 701);  for  the  present  purpose  it  is  sufficient  to  note  that  the  liver-anlage  early 
comes  into  relation  with  the  septum  transversum.  The  ventral  portion  of  the  pri- 
mary liver-evagination,  ctothed  with  the  entoblastic  lining  of  the  g^t-tube,  very  soon 
dilferentiates  into  two  diverticula  :  the  one  nearer  the  head,  or  hepatic  division,  pro- 
duces the  liver  proper ;  the  other,  or  cystic  division,  later  becomes  the  gall-bladder 
and  its  duct.  These  divisions  are  gradually  removed  from  the  primitive  duodenum 
by  the  growth  of  the  primary  diverticulum,  which  at  one  end  becomes  converted 
into  a  tube  connected  with  the  digestive  canal  and  at  the  other  bifurcates  into  the 
hepatic  and  cystic  channels.  This  tube,  evidendy  later  the  common  bile-duct,  is  at 
first  short  and  wide,  but  later  rapidly  lengthens. 


Uver-anta] 


CyMic  diverticulum. 


Cul-tubc. 


— -Hepatic  dlvrrticulum 


Dorsal  iiaiicrealic 
divertii-utuni 


portion  of  ugittal  kcction  oi  early  rabbii  rmbryo,  showing  Hver-anlase  and  duds,    v  95. 


The  cells  lining  the  longer  hepatic  diverticulum  undergo  marked  proliferation 
and  produce  the  liver-mass  which  invades  the  septum  transversum  almost  as  far  as 
the  sinus  venosus  and  surrounds  the  vitelline  veins.  The  formation  of  the  liver-mass 
follows  at  first  the  type  of  development  seen  in  tubular  glands,  outgrowths  of  the 
hepatic  tube  branching  and  subdividing  to  form  solid  sprouts  and  buds  cf.mposed  of 
epithelial  cells.  In  some  of  the  lower  animals,  as  the  amphibians,  the  tubular  type 
is  retained  in  the  adult  organ;  but  in  the  higher  forms,  including  man,  the  tubular 
character  of  the  young  liver  is  soon  lost  and  replaced  by  the  reticular  arrangernent 
produced  in  consequence  of  the  growing  together  and  union  of  the  terminal  divis- 
ions of  the  gland. 

Coincidently  with  the  formation  of  the  net-work  of  glandular  tissue  by  the 
junction  of  the  cylinders  of  hepatic  cells,  the  meshes  of  the  reticulum  become  occu- 
pied by  blood-vessels  derived  from  vitelline  veins.  These  arc  now  represented  at 
the  hepatic  anlage  by  vrnaus  stumps  from  which  numerous  afferent  branches  (vrtier 
hepatic^  adrrhrnles')  penetrate  the  liver-mass  to  become  the  portal  system.  The 
division,  subdivisitin,  and  union  of  these  blood-vessels  keep  pace  with  the  increasing 
complexity  of  the  net-work  of  hepatic  cords,  the  intergrowth  of  these  constituents 
eventually  leading;  to  the  intimate  relations  between  the  hepatic  secreting  tissue  and 
the  intralobular  capillaries  seen  in  the  fully  developed  organ.  The  cell-trabecula' 
composing  the  primary  hepatic  net-work  are  partly  solid  and  partly  hollow  ;   the 


THE  BILIARY   APPARATUS. 


17*5 


Cummuii  bile-duct 


,  »«.   «kh  a  DOrtion  of  those  without  a  lumen,  are  converted  into  the  system  of 

^  «  DTfferSbn  of  the  developing  liver  into  lobules  does  nut  oca.r  until  the 
u"^^'  n^nrfhrfoCrth  fatal  month,  by  which  time  the  larger  blood-vessels  and 
SK  elcome'  su^roJ^S  by  condeLtions  of  the  mesoderm  which  form  the 

"•""rndSS^of  the  formation  of  the  hepatic  blood-v|ssels  are  con.id^^^^^^ 

rS  :^  tSKrSar    ^  rLSn  We  iPve^r^incL'ngth'r  .S  ^Teiiv 

^r    Vie  re  a  OM  of  the  placental  circulation  to  the  liver  are  secondary      The 

amount  of  the  placental 

blood,    the  development  *'°-  '*''°- 

of    the    ductus    venosus 
brings  relief  by  establish- 
ing a  short  cut  by  which 
the   excess   of   placental 
blood  passes  directly  into  - 
the  ascending  vena  cava. 
The  development  of 
the  gall-bUdder  and   its 
duct  proceeds,  as  already 
indicated,  from  the  more 
caudallv  pi  ced  cystic  di- 
vision of  tht  primary  he- 
patic diverticulum.     The 
subsequent    changes    in- 
clude the  j^rowth  and  ex- 
pansion of   ^he  terminal 
portion  of  the  primitive 
cystic  canal  to  form  the 
bile-sac,     its     elongated 
stalk  becoming  the  cystic 
Juct,  while  differentiation 

Id'^L'^S^^n^^'^^hl^^  produces  the  distinguishing  details  of  the  fully  formed 

"''^"with  the  conversion  of  the  primary  liver-mass  into  the  more  definite  or^n,  the 
relations  of  the  ventral  mesentery,  into  which  the  early  liver-anlage  grows,  become 
hanr  d  For  a  ti,:;e  the  developing  liver  lies  within  the  septum  transversum.  but 
ater  wiih  the  fon.ution  of  the  diaphragm,  it  separates  from  the  latter  and  projects 
to  the  h  ...iv-cavav,  .his  projection  results  in  a  differentiation  of  the  ventral 
m^entery  into  threi  vv...ts  :  (a)  the  middle  portion,  the  ^V-'i^  ««  *»^!^»^ '^";;^,'= 
Zv^r'Jbv  the  urouinj.  'iver  to  form  its  serous  investment ;  d  the  anterior  portion, 
Xh  cxten  Is  P.m  n.e  ont  surface  of  the  liver  to  the  umbilicus  and  becomes  he 
falciform  lit  vn-nl  enciosimr  the  umbilical  vein,  later  the  ligamentum  ter.^s  ;  (f)  the 
posterior  iH>rtion,  which  stretches  between  the  digestive  tub.  and  the  nver  and  ns 
the  gastro-heiwtic,  ..r  lesser    omentum,  maintains  similar  relations  and  encloses  the 

"  '*Tn  the  f<Ktus  the  liver  is  relatively  immense,  especinlly  at  an  early  period.  Al 
the  fourth  foetal  month  it  practically  fills  the  u  hole  of  the  top  "  /^'^J''^'" 
Although  it  increases  abs.^l"tely  after  this,  it  nlatisely  diminishes,  but  't  birth  is  still 
considerably  above  the  relative  size  of  the  aduit  organ,  forming  approximately  one- 


Portion  ol  Hcitul  »«ction  of  rahbll  embryo,  nhow 
ducU.     K  <»5 


i(  de\elopiiw  liver  and 


lyafi 


HUMAN  ANATOMY. 


eighteenth  of  the  entire  body  weight.  The  left  lolje  reaches  across  the  bt  Jtnach  s.i 
as  to  be  in  contact  with  the  spleen.  The  tuberd'?  at  the  lower  extremity  o»  tlu 
Spigelian  lobe  and  the  caudate  lobe  are  relatively  large.  In  the  infant  th' -e  is  littl. 
connective  tissue  in  the  organ,  which  is  very  friable  and  also  easily  .noulaed  on  tlic 
surrounding  structures.     At  birth  the  weight  of  the  liver  is  about  150  gm.  (3  oz.  1. 

PRACTICAL  CONSIDERATIONS:    THE  LIVER,  GALL-BLADDER, 
AND  BILIARY  PASSAGES. 

The  Liver. — Anomalies  in  the  position  of  the  liver  occasionally  occur,  as  in 
•'  transposition,"  when  the  whole  organ  may  be  on  th  •  left  side  ;  in  such  cases  the 
spleen  and  other  asymmetrical  abdominal  viscera  (and  frequently,  but  not  nect-s- 
sarily,  the  thoracic  organs)  will  also  be  found  to  be  transposed.  "  Accessory"  lobes 
are  not  uncommon  and  have  been  mistaken  for  new  growths. 

The  shape  of  the  liver  may  obviously  be  affected  by  compression  exerted 
through  the  parietes.  The  chief  type  of  the  so-called  "lacing"  or  "corset"  liver 
is  m.-^rked  by  a  transverse  groove  separating  the  main  body  of  the  organ  from  a  pro- 
longation downward  of  the  anterior  portion,  especially  of  the  right  lobe,  which  may 
reach  to  below  the  umbilical  level.  This  portion  has  been  mistaken  for  a  movable 
right  kidney.  Knuckles  of  intestine  may  lie  between  it  and  the  anterior  abdominal 
parietes  a  d  prevent  the  recognition  of  its  continuity  with  the  liver  by  either  palpa- 
tion or  percussion. 

Movable  liver  {hepatoplosis)  is  a  condition  in  which,  through  stretching  of  the 
tissues  and  structures  which  normally  retain  it  in  place  beneath  the  arch  of  the  dia- 
phragm, it  sinks  by  gravity  to  a  lower  level.  It  has  then  been  mistaken  for  various 
forms  of  abdominal  or  rei.  il  tumor  and  for  movable  kidney.  Hepatoptosis  is  often 
associated  with  displacements  or  a'morm-il  mobility  of  other  abdominal  viscer.r 
Traction  of  the  liver  on  the  suspensory  ligament  is  said  to  produce  a  fold  of  sk'n 
which  hides  the  lower  part  of  the  un-i'ilicus  (Glenard). 

The  structure?  most  potent  in  holding  it  in  its  proper  position  are,  in  tl;e  '-rder 
of  their  importance:  (a)  '.he  attachment  of  the  hepatic  veins  to  the  inferior  vena 
cava,  (^^  the  coronarv  ligaments  and  the  celiulo-vascular  bands  in  and  between  its 
layers,  (c)  the  tibrofa  tissue  near  the  vena  cava  and  on  the  non-peritoneal  posterior 
surface  of  the  right  lobe,  (rf)  the  muscular  wall  of  the  abdomen  (keeping  the  in- 
testinal mass  pressed  upward  beneath  the  liver),  and  (e)  the  lateral  and  "suspen- 
sory"   'gaments. 

Loincidently  with  the  descent  of  the  viscis  it  undergoes  a  rotation  or  tiltmg 
forward  so  that  its  diaplirapmatic  surface  is  in  contact  with  the  abdominal  wall. 

Hepatopexv  consisU  in  suturing  such  a  movable  liver  in  its  normal  position  by 
stitches  which  may  be  variously  placed,  lut  the  most  useful  of  which  seem  to  bi- 
those  whicii  unite  the  round  ligament  and  'Ker-substance  with  the  anterior  abdominal 
wall  near  the  xiphoid  cartilage  (Francke,  Treves). 

The  normal  relations  of  the  liver  to  the  diaphragm  and  the  abdominal  parietes 
cause  it  to  be  much  influenced—  specially  as  to  its  circulation— by  the  respiratory 
and  other  movements  associated  with  enrrjjetic  exercise  ;  hence  the  cunnestion  of 
the  organ  resulting  in  'biliousness,'  or  .  n  in  iaundice,  seen  in  civses  in  hith, 
from  accident  or  disease,  persons  who  have  led  active  lives  are  confined  to  beo.  In 
walking,  and  more  markedly  in  horseback  riding,  the  compression  of  the  organ  l)e- 
tween  the  diaphragm  and  the  upper — or  respir;  *rry — segment  of  the  abdominal  wall 
which  takes  place  during  deep  inspir.it  >n  is  aided  by  its  downward  mcvement  from 
gravity.  It  has  been  suggested  (Jacobson)  that  such  movement  must  slightly  open 
the  inferior  vena  cava,  which  is  then  immetliately  compresse<l  by  the  following  up- 
ward movement, — during  expiration, — thus  directly  influencing  the  systemic  venous 
current  and  with  almost  equal  directness  that  in  the  hepatic  veins. 

In  deep  inspiration  the  anterior  edge  of  the  liver  descends  from  under  cover  of 
the  lower  rils,  and  in  very  thin  persons  may  be  palpated.  A  similar  descent  occlis 
when  a  reclining  is  exchanged  for  an  erect  position. 

The  direct  connection  between  the  gastrointestinal  and  the  portal  circulation 
causes  the  latter  to  be  markedly  affected  by  the  use  of  alcoholic  or  other  irritants  and 


H'  i. 


PRACTICAI.  CONSIDERATIONS:   THE  LIVER, 


I7»7 


bv  the  amount  and  character  of  food  taken.  DrinkinR  and  overeaunp;  thus  exaggerate 
tho  oeri  xlic  physiological  conjrestions  of  the  liver  and  often  result  ultimately  m  organic 
<  harwes.  Of  course,  passive  congestion  is  likely  to  follow  valvular  disease  of  the 
heart  emphysema,  pulmrnary  cirrhosis,  or  any  condition  in  which  the  right  heart  is 
or  'oreed  the  backward  pressure  through  the  vena  cava  reaching  the  hepatic  veins 
and  their 'subloDular  tribuuries.  The  thin  interlobular  and  perihepatic  connective 
tissue  known  as  C.lissons  capsule,  which  closely  invests  the  ducts  and  vessels,  is 
commonly  affected  in  chronic  irritation  of  the  liver,  especially  that  form  due  to  al- 
coholic excess,  and  in  some  infectious  diseusc!!,  notably  the  specific  fevers  and 
syphilis  Its  anatomical  relations  explain  the  usual  sequence  of  phenomena.  Pro- 
iiferation  of  the  portions  surrounding  the  terminal  branches  of  th'  ;-.'  t .!  "eip  causes 
obstruction  which,  either  alone  or  aided  by  the  concurrent  tox;vtni .  t-  .u  :  m  con- 
gestion and  catarrh  of  the  stomach  and  intestines,  in  enlargement  .1.  .ucen  ?nd 
pancreas,  and  later  n  ascitf^.  .  ,4.^,. 

As  the  obstruction  increases,  a  collateral  circulation  is  often  e.ti-o  -  ■<  <i  .o  a- 
lieve  the  portal  congestion  by  means  of  communication  betwcn  a-  >  ,iCi-rs.sory 
portal  veins  (particularly  those  in  the  falciform  ligament)  and  tt.-  unra -niatic, 
nara-umbilical.  and  epigastric  veins  ;  (6)  the  veins  of  Retznis  and  t.c  retjopc.  noneal 
veins  •  (c)  the  hemorrhoidal  and  the  inferior  mesenteric  veins  ;  (d )  the  gastric  and 
the  oesophageal  veins.  An  operation  has  been  employed  to  establish  a  better  and 
more  satisfactory  comj>ensatory  circulation  in  cases  of  cirrhosis  by  effecting  adhesions 
between  the  suriaces  of  the  liver  and  the  spleen  and  the  diaphragmatic  pentoneum, 
on  the  one  hand,  and  the  parietal  peritoneum  and  omentum,  on  the  other. 

When  compression  of  the  liver  is  carried  lieyond  physiological  limits,  as  from 
contusion  or  from  forced  flexion,  rupture  results.  This  is  more  frequent  in  the 
liver  than  in  the  i>ther  abdominal  viscera  on  account  of  its  size,  its  fnability,  ito 
fixity  its  close  diaphragmatic  a  id  jiarietal  relations,  and  its  great  vMCulanty.  A 
similar  dbjunction  of  liver-substance  may  occur  from  a  fall  on  the  feet  from  a  height. 
It  is  grave  in  proportion  to  the  extent  of  the  rupture  and  to  its  involvement  or  non- 
involVement  of  the  peritoneal  covering.  Ruptures  confined  to  the  liver-substance,  ~ 
i  f  not  reaching  the  surface,— and  moderate  in  extent,  are  not  infrequently  recovered 
from  The  commonest  seat  of  rupture  of  the  liver  is  near  the  falciform  and  coro- 
nary ligaments,  with  which  the  rupture  is  apt  to  be  parallel.  If  they  are  extensive 
enough  to  reach  the  surface  of  the  organ,  death  often  results  from  hemorrhage,  the 
intimate  association  of  the  hepatic  substance  with  the  thin-walled  vosseb  preventing 
their  retract!  .-»n  or  collapse.  Hemorrhage  is  also  favored  by  the  dirtct  connection 
of  the  valveltrs  hepatic  veins  with  the  vena  ca\  ;  and  by  the  absence  of  valves  in 
the  portal  veias.  According  to  the  situation  of  the  rupture,  the  blood  may  be  poured 
into  the  general  peritoneal  cavity  ;  into  that  portion  of  it  known  as  the  subheput.r 
space  and  bounded  below  by  the  transverse  mesocolon  ;  or  into  the  retropentnn.  «i 
space' behind  the  liver  and  ascending  colon.  The  local  symptoms  will  vary  with  rVt 
situation  of  the  collected  blood. 

Wmivd.  of  the  liver  should  be  considered  with  reference  to  its  relations  to  the 
parictes,  especially  on  t'.iL-  riylit  side,  where,  on  account  of  its  grer.tPi  bulk,  it  is 
more  often  injured.  Except  at  the  subcostal  angle,  where  a  small  part  of  the  interior 
surface  lies  against  the  abdominal  wall  (the  lower  edge  being  on  a  line  ft^twcen  the 
eighth  left  and  the  ninth  right  costal  cartilages),  the  lower  ribs  and  costal  cartilages 
surround  the  liver.  Thus  stab  wounds  must  pass  between  them,  while  fracture  of 
the  ribs  with  depression  may  penetrate  the  interposed  diaphragm  and  then  the  liver- 
substance.  Anterioriy,  a  little  internal  to  the  mammary  line,  the  liver  may  reach  to 
the  fourth  intercostal  space  or  even  quite  to  the  level  of  the  nipple,  and  niiiy  be 
directly  wounded  throughout  that  area.  Laterally  it  is  not  usually  found  a»x>ve  the 
bixth  interspace.  Posterioriy  a  stab  wound  through  tiie  sixth,  seventh,  or  eighth 
intercostal  space,  or  even  down  to  the  level  of  the  tenth  tlorsal  spine,  would  pene- 
trate four  layers  of  pleura,  the  thin  concave  base  of  the  right  lung,  and  the  <lia- 
phragm  before  reaching  the  liver.  Still  lower,  the  b.ise  of  the  lung  may  escape, 
but  a  wound  of  the  liwr  -nay  involve  the  two  layers  of  pleura  of  the  cf«to-phrenic 
sinus  and  the  diaphr.igin.  Of  course,  the  alterations  in  position  oi  the  liver  during 
inspiration  and  oxpiration,  and  according  to  the  position  of  the  body,   must  be 


lyaS 


HUMAN  ANATOMY. 


tl.. 


remembered   in  objure  caiea  before  baaing  a  diagnotis  upon  the  utuation  of 

external  wound.  .         j    • 

In  bk-vding  from  the  liver  after  either  rupture  or  »Ub  wound,  or  during  opera 
tiorai,  temp-irary  occlusion  of  the  (wrtal  vein  and  hepatic  artery  may  be  »ecure<l  !> 
preMing  them  between  the  finger  and  thumb,  the  former  being  placed  ju»t  withn, 
the  foramen  of  Winslow  and  the  latter  externally  on  the  gastro- hepatic  omentum. 

Eniargement  of  the  liver,  if  uniform  (congestion,  muldple  afaKew,  penhepatitis. 
fatty  ilegeneration,  hypertrophic  cirrhosis),  causes  a  bulging  of  the  right  lower  nl)s 
and  their  cartiWes  and  an  increa.se  of  the  area  of  absolute  ptrmssum  dulntss.  Tli. 
upper  limits  of  the  latter  should  normally  be  found  at  the  sterno- xiphoid  junction  ii> 
the  median  line,  the  sixth  intercostal  space  in  the  right  mammary  line,  the  seventli 
rib  in  the-  axillary  line,  and  the  lower  border  of  the  ninth  nb  in  the  scapular  Imt 
A  mo<lified  dulness  b  obuined  posteriorly  over  the  area  where  the  lung  overlaps  th. 
liver  down  to  the  level  of  the  ninth  rib.  The  lower  level  of  the  dulness— and  thus 
of  the  Uver  itself— is  in  the  mid-line,  half-way  between  the  stemo-xiphoid  juncti.  .n 
and  the  umbilicus,  at  or  a  little  below  the  costal  margin  in  the  mammary  line,  on  ;. 
level  with  the  tenth  and  eleventh  ribs  laterally  and  opposite  the  eleventh  dorsal  ver 
tebra  posteriorly.  At  this  point  it  is  continuous  with  the  lumbar  dulness  due  to  th. 
thickness  of  the  spinal  muscles,  the  quadratus  lumborum.  the  kidneys,  and  the 

perirenal  fat.  .  .     ■    -j  •       .u 

In  localized  enUrgements,  as  from  tumor,  abscess,  or  hydatids  occupying  the 
upper  surface  of  the  nght  lobe,  the  diaphragm  is  pushe<l  upward  and  the  upiK-r 
limit  of  the  percussion  dulness  raised,  the  lower  limit  remaining  temporarily  unaf 
fected,  the  area  of  dulness  being  thus  increased. 

In  emphysema  or  pneumothorax  both  limits  are  lowered  (as  they  are  also  in 
empyema,  althouijh  in  that  condition  the  liver-dulness  merges  into  that  of  the  pleural 
abscess),  and  in  phthisis,  collapse-  or  nlr.iction  of  the  lung,  or  abdominal  meteor- 
ism  both  limite  are  raisetl.  the  total  area  of  dulness  remaining  unchanged  m  thes. 
cases  Of  course,  in  atrophic  disease  the  area  is  diminished  and,  as  in  cases  in 
which  the  whole  liver  is  drawn  or  pushed  up,  or  there  is  free  gas  in  the  abdommal 
cavity,  there  may  be  tympany  over  the  right  lower  ribs. 

AbscMS  of  the  liver  may  be  due  to  infection  through  the  jwrtal  system,  as  from 
dysentery  or  hemorrhoids,  or  from  typhoid  fever,  colitis,  or  appendicitis  ;  or  through 
the  general  blood-supply,  as  from  osteomyelitis  or  cranial  trauma.  In  addition  to 
the  usual  symptoms  of  suppuration,  it,  like  many  other  liver  troubles,  is  sometimes 
characterized  bv  pain  in  or  above  the  right  shoulder.  This  is  thought  to  be 
explained  by  the  facts  that  («)  the  right  lobe  is  far  more  commonly  affected,  (*) 
the  phrenic  contributes  to  the  nerve-supply  to  the  liver  and  b  derived  partly  from 
the  fourth  cervical,  and  (f )  the  supra-acromial  nerve  is  a  branch  of  the  latter. 
Other  evidenn  bowing  relations  between  the  supra-acromial  and  phrenic  nerves, 
f  tr     hiccough  in  shoulder  arthritis,  makes  this  explanation  seem  reasonable. 

'  Hepatic  abscess  may  open  (a)  inferiorlv  into  the  stomach,  colon,  duodenum,  or 
rich'  kidney,  or  intc  ^omt  portion  of  the  peritoneal  cavity,— either  the  subhepatic 
siwce,  the  general  t.ivity.  or  the  lesser  cavity  via  the  foramen  of  Winslow  ;  (b\ 
sufofrior/v  into  the  pleura,  lung,  or  bronchi,  or  into  the  pericardium  ;  (r)  pos/eri- 
orlv  into'  the  retrofieritoneal  space  and  the  loin  ,  (rf)  anteriorly  on  the  surface  ol 
the  body   sometimes  following  the  remains  of  the  umbilical  vein  to  the  umbilicus. 

The  resistance  of  the  nbs,  intercostal  muscles,  and  diaphragm  makes  pointing 
in  other  directions  of  rare  occurrence.     Pus  may  invade  the  suprahepatic  (subdia 
phragmatic)  space  or  the  Hver  itself  from  above  the  diaphragm.     Many  empyemas 
have  taken  this  course.      Nephric  or  perinephric  abscess  on  the  right  side  may 

extend  to  the  liver.  ,         ,       .  ,  ,  t 

Hydatid  cysts  are  more  common  in  the  h\er  than  elsewhere,  as  the  enihrxo  ot 
the  egg  of  the  taenia  echinococcus,  freed  from  its  shell  by  digestion,  readily  pene 
trates  the  g.istric  and  intestinal  vessels,  and  is  very  likely  to  enter  a  tributary  ol  the 
portal  system  and  thus  lie  carried  direct  to  the  liver,  where  it  multiplies  and 
develops  into  the  mature  hydatid.  Spontaneous  evacuation  of  the  cysts  may  occur 
in  any  of  the  directions  already  mentioned. 

In  opening  an  hepatic  abscess  or  hydatid  cyst  the  liver  must  be  reached,  as  m 


PRACTICAL  CONSIDERATIONS:  THE  GALL-BLADDER.      1729 

u-  nn^frndom  bv  tmvming  either  the  peritonei  or  the  pleural  avjty-  J." 
^I'^^T^^r^  XnthwT  b  an  anterior  iWeUing.  m  vertical  incuwon  in  the  mid- 
doubthil  "f^'^JX"  "!!"  „,  „,  its  omer  edire.  beginning  at  the  cortal  margui 
'Z  'S^Sl^ni^JTSl  l^ii  Vex^^^^^  "l^liver^and  evacuation  of  the 
and  P^*''«^.'~r"r^' "  I'-.vitv  beinz  waU«l  ofl  by  gauxe  packing.  H  the 
hveraapproachul  above  th   ^P^^^  thT  diapliJapnatic  and   parieU    pJeune 

"  P^^or  to  S^  ttonTc  wound.  «d  then  inci«:  UveSaphragm     Jfthe  liver  »  to 
together  or  to  the  thoracc  T^^v  .         yj^  li„e -reaecUon  of  the  tenth  nb  wUl 

•^rll^yuli'um  is  u.,uaUy  secondary  (to  metastasis  through  the  portal 
Cameer  ol   *»*  "y*\.  "         J/y^     Drimary  and  consisting  of  a  single  nodule. 

E  5M^n«  was  perfonned  on  a  gall-bladder  lying  on  the  left  side. 

M^««iiA  of  the  call-bladder  are  rare.  ....    1 : 

!KS^  of  tl^'Su-Wadd^  "«y  <^'  <"""  tiaumatism  to  the  "bdominal  pan- 
etes  itVfavored  by^tention  of  the  viscus  and  by  enlargement  of  the  liver,  both 
«f"  hich  cTy  the  Ll-bladder  downward  to  a  less  protected  position  and  favor  the 
dirStraS^Uond  the  force.  Extravasation  of  Ue  into  t\,e  general  penton^ 
S  fXws  It  may  be  sterile,  and  may  then  act  merely  as  an  imtant.  causing  an 
TxreS  pU^tic  exudate,  but  is  apt  to  be  fatal  by  setting  up  ^Pt^^P^"'"""":  .  .^ 
If  operation  discloses  such  a  rupture,  it  may  be  '■«r«"^*^'^  ( '  >  ^'t*  |r 
extravaffibile  first  flows  into  the  targe  peritoneal  pouch  t>«"nded  aboveby  ** 
\^^^  nf  the  liver  below  by  the  ascending  fayer  of  the  transverse  mesocolon 
c^viiS^  dS  Jrum^t^ly.  externally  by  th'e  peritoneum  lining  the  panet« 
^r  to  Se  crest  of  the  Uium.  posteriorly  by  the  ascendmg  mesocolon  covenng 
the  kidnev  and  internally  by  the  peritoneum  covenng  the  spine  (2)  that  this 
tlTuch  «7'l^  «^ay  and  thoWir  thmugh  a  lumbar  mosion  ;  and  (3) 

fft  fa  caMble  of  holding  n4riy  a  pint  of  fluid  before  it  overflows  into  the 
gteii^S  cavity  through  the  fonunen  of  Winslow  or  over  the  pelvic  bnm 

^^""^iLion  of  the  gall-bfadder  is  ordinarily  due  to  ( .)  inflammatory  obstruction 
of  thecShirt  (chobmgitis) ;  (2)  mechanical  obstruction  of  the  cystic  duct  usu- 
aiXTrte  iSpaSion^  gall-stones;  (3)  acute  cholecystitis,  (a)  catarrhal  (*) 
suDtSive;  or  (4)  obstru^on  of  the  common  duct  from  »«"?«-;  "^- ™"'=^™»« 
3y  from  impaction  of  a  calailus  in  that  duct  before  the  gall-bladder  has  become 
Sed  «>nt.^ted.  and  formed  adhesions.  The  gall-bladder  'tseU  may  be  the 
pS^'s.^  of  a  malignant  growth.     It  is  impossible  to  feel  the  normal  gall-bladder 

^''Tnwt-nrdthet4-bladd«  from  any  cause  usually  takes  place  in  a  down- 
ward and  forward  directio'n  on  a  line  which,  beginning  a  little  b^io*  ^he  "inth  c^ta^ 
<artilaKe  crosses  the  linea  alba  ust  below  the  umbilicus.  If  the  iver  is  ot  normal 
sfze  the'nedTQfthe  gall-bfadder  is  about  opposite  the  ninth  costal  carti  age.  If  the 
HvCT  s  enlarged  the^llbfadder  will  be  so  much  depressed  that  its  neck  niay  be  on 
a  kvel  S  «;  even  lower  than,  the  umbUicus.  The  rounded,  pear-shaped^.r 
gou^i  likeTu'ndus  can  usually  be  felt.  mo>«ible  later.ally.  and  --«^'Xrdeie^ds 
pable  groove  between  it  and  the  lower  edge  of  the  liver.     The  swellmg  descends 

109 


I730 


HUMAN  ANATOMY. 


t  f  ■' 


I 


!. 


during  inspiration.  If  the  cause  of  the  enlargement  is  inflammatory  and  adhesiv  e 
peritonitis  has  resulted,  the  tumor  may  be  fixed  so  that  it  does  not  move  with  i  as- 
piration ;  but  there  is  then,  especially  in  acute  cases,  apt  to  be  pain  and  tender- 
ness over  the  swelling  or  at  a  point  between  the  ninth  costal  cartilage  and  the 
umbilicus. 

It  may  be  mentioned  here  that  the  diagnosis  between  the  chronic  form  of  gall- 
l:^dder  disease  and  movable  kidney  is  not  always  easy  ;  that  the  two  conditions  not 
infrequendy  coexist  in  the  same  person  ;  and  that  the  possibility  of  error  is  increa.st"d 
by  the  fact  that  they  are  each  met  with  much  oftener  in  women  than  in  men,  and 
that  the  right  kidney  is  far  more  frequendy  movable  than  the  left. 

The  anatomical  explanation  is  that  in  women  with  flabby  abdominal  walls 
either  tight  lacing  or  a  relatively  slight  jar  or  strain  tends  to  produce  displacement  of 
both  the  kidney  and  the  liver,  the  latter  resulting  in  tension  or  angulation  and  con- 
sequent obstruction  of  the  bile-ducts.  The  two  conditions  also  act  reciprocally, 
descent  of  the  liver  causing  displacement  of  the  kidney,  which,  through  its  traction 
upon  the  duodenum,  tends  to  obstruct  the  bile-ducts. 

A  movable  kidney,  as  compared  with  an  enlarged  gall-bladder,  is  less  influenced 
by  respiration  ;  has  a  wider  range  of  motion,  especially  in  the  long  axis  of  the  body  ; 
is  more  influenced  by  position  ;  slips  backward  towards  the  loin  instead  of  upward 
beneath  the  liver  ;  is  less  often  visible  and  less  frequendy  tender  on  pressure,  which 
b  apt  to  cause  a  sickening  sensation  analogous  to  testicular  nausea  (page  195 1). 

Acuie  cAaUcysiiiis  (phl^monous)  is  due  to  infection.  The  colon  or  typhoid 
bacillus,  or  the  pneumococcus,  streptococcus,  or  staphylococcus,  may  reach  the  gall- 
bladder either  through  the  blood,  as  during  a  pneumonia,  by  lymphatic  and  vascular 
channels,  as  after  an  appendicitis,  or  through  the  intestine  and  bile-ducts,  as  in  some 
of  the  post-typhoidal  cases. 

The  symptoms  are  (a)  generalized  abdominal  pain,  due  to  the  association  of 
the  cystic  plexus,  through  the  cceliac,  with  the  superior  mesenteric  ;  (6)  pain  below 
the  right  costal  margin  passing  towards  the  epigastrium,— 1>. ,  referred  to  the  cceliac 
and  solar  plexuses, — and  towards  the  right  scapular  region,  hrom  the  association  of 
the  phrenic  and  the  supra-acromial  nerves  through  the  fourth  cervical  (page  1758) ;  (f) 
rigidity  over  the  right  hypochondrium,  due  to  the  connection  between  the  splanch- 
nics  and  the  intercostals  ;  {d  )  nausea,  vomiting,  and  prostration,  due  at  first  to  the 
close  relation  of  the  cystic  plexus  with  the  coeliac  and  solar  plexuses,  later  to  toxxmia 
and  to  peritonitis  ;  («f )  localized  tenderness  at  the  junction  of  the  upper  and  middle 
thirds  of  a  line  drawn  from  the  ninth  rib  to  the  umbilicus, — i.e.,  over  the  fundus  of 
the  inflamed  gall-bladder;  (/)  distention  and  paresis  of  the  intestines,  due  sometimes 
to  a  localized  peritonitis  affecting  the  hepatic  flexure  of  the  colon  and  simulating 
an  acute  intestinal  obstruction. 

Gangrene  has  occurred,  emphasizing  the  clinical  and  pathological  resemblance 
of  this  condition  to  appendicitis,  but  is  very  rare,  illustrating  the  importance  of  one 
anatomical  factor— the  scanty  blood-supply— in  causing  the  gangrene  which  is  so 
exceedingly  common  in  that  disease  (page  1682).  Bacterial  infection  and  absence  of 
drainage  (and  therefore  tension)  are  two  conditions  predisposing  to  gangrene, 
present  in  both  cases  ;  but  the  third— thrombosis  of  the  nutrient  vessels— determines 
the  frequency  of  gangrene  in  the  appendix,  which  is  supplied  by  only  one  nutrient 
artery,  and  is  relatively  ineffective  in  the  case  of  the  gall-bladder,  uhich  has  a  rich 
blood-supply  through  the  large  cystic  artery  and  also  through  the  anastomoses  of  iis 
branches  with  the  hepatic  vessels  where  the  gall-bladder  is  fixed  to  the  liver  (Mayo 
Robson). 

.  -^"'/.Vwa  of  the  gall-bladder  (suppurative  cholecystitis),  due  usually  to  chole- 
lithiasis, obstructive  catarrh,  and  infection  through  the  ducts,  may  discharge  itself  in 
various  directions  determined  by  the  occurrence  of  inflammatory  adhesions.  The 
most  common  communication  is  with  the  cutaneous  surface,  the  pus  having  been 
evacuated  through  the  parietes  beneath  the  costal  margin  in  50  per  cent,  of  Cour- 
voisier's  184  cases,  and  in  the  umbilical  region,  where  it  was  conducted  by  the  sus- 
pensory ligament,  in  29  per  cent.  The  colon  or  duodenum  beneath,  the  subphrenic 
space  or  pleural  cavity  above,  and  the  right  prcncphric  periloneal  pouch— watieil 
off  by  adhesions — have  been  favorite  seats  for  the  spontaneous  evacuation  of  pus 


PRACTICAL   CONSIDERATIONS:    THE   BILE   PCCT.  17.^1 

and  gall-stones  in  old  cases  of  empyema  of  the  gall-bladder.  Its  anatomical  relations 
to  surrounding  structures  and  spaces  should  therefore  be  carefully  studied. 

Cholelithiasis.— hs  the  norma!  e.xpulsive  efforts  of  the  muscular  walls  of  the 
gall-bladder  are  usually  aided  by  the  contraction  of  the  abdominal  muscles  dunng 
exercise  gall-stones  are  more  commonly  found  in  persons  of  sedentary  habits,  in 
invalids,'  and  in  females,  especially  in  multipara.  Tight  lacing,  by  depressing  both 
liver  and  gall-bladder,  as  well  as  kidney  {vide  supra),  is  also  a  distinct  predisposing 
cause  Bacterial  infection  with  the  colon  or  typhoid  bacillus,  and  more  rarely  with 
other  organisms,  is,  however,  a  frequent  exciting  cause  of  the  hypersecretion  and 
epithelial  proliferation  which  lead  to  the  formation  of  gall-stones. 

The  presence  of  stones  in  the  gall-bladder  may  be  unaccompanied  by  symptoms, 
or  may  cause  the  development  of  such  phenomena  as  either  have  no  distinct  ana- 
tomical bearing  (biliary  fever  and  secondary  visceral  lesions)  or  as  have  already 
been  considered  (abscess  of  the  liver,  empyema  of  the  gall-bladder,  fistula,  etc.). 
There  are  mechanical  accidents,  however,  connected  with  the  emigration  of  the 
stones  which  will  be  considered  from  the  anatomical  stand-point  in  relation  to  the 

biliary  ducts.  ^,  .      j        •      . 

The  Cystic  and  Common  Bile-Ducts.— The  cystic  duct  is  the  narrowest 
portion  of  the  biliary  passages.  Its  calibre  would  permit  the  passage  of  a  probe 
through  it  into  the  hepatic  duct,  but  the  irregular  folds  of  its  mucous  membrane 
(sometimes  regarded  as  constituting  a  "spiral  valve,"— the  valve  of  Heister)  usu- 
ally effectually  prevent  satisfactory  probing.  Its  muscular  fibres  are  better  devel- 
oped than  are  those  of  the  other  biliary  ducts.  The  passage  of  a  stone  through  it 
is  attended  by  (i)  colicky  pains  of  the  sort  usually  associated  with  violent  mus- 
cular contraction  ;  (2)  continuous  paim  resembling  thai  due  to  an  acute  cholecystitis 
(the  two  conditions  being  often  mistaken  one  for  the  other),  and  due  (a)  to  the  slow 
prcMjressof  the  stone  in  the  cystic  duct,  in  which  it  takes  a  rotary  course  owing  to 
the  arrangement  of  the  mucous  folds  ;  (*)  to  the  acute  inflammation  which  usually 
accompanies  an  attack  ;  and  {c)  to  the  stretching  and  distention  of  the  gall-bladder  by 
retained  secretions  (Osier).  The  pain  may  be  even  more  intense,  and  is  apt  to  be 
accompanied  by  (3)  vomiting,  ^)  pro/use  sweating,  and  (5)  great  depression  of  the 
circulation,  all  due  to  reflex  irritation  of  the  sympathetic  plexuses  and  the  pneumo- 
gastric.  There  may  be  (6)  a  rigor,  either  purely  nervous  or  due  to  retained  secre- 
tions  and  a  concurrent  lithaemic  inflammation.  In  he  latter  case  there  will  he  (7) 
fever  from  the  accompanying  toxamia. 

If  the  stone  passes  into  the  intestine,  all  the  symptoms  usually  disappear.  It 
may  cause  (8)  intestinal  obstruction,  and  is  a  far  more  common  factor  in  the  pro. 
duction  of  this  condition  than  are  enteroliths.  Of  149  cases  of  this  type  of  obstruc- 
tion, 133  were  due  to  gall-stones  and  only  16  to  enteroliths,  and  10  of  these  had 
gall-stone  nuclei.  Although  a  stone  of  considerable  size  may  pass  through  the  duct, 
those  large  enough  to  bring  about  intestinal  obstruction  usually  enter  the  duodenum 
by  ulceration.  If  the  stone  becomes  impacted  in  the  cystic  duct,  (9)  dilatation  o{ 
the  gall-bladder  with  mucus  (hydrops)  occurs  ;  or  (10)  cholecystitis,  acute  or  chronic, 
may  follow  {vide  supra).  Calcification  and  atrophy  of  the  gall-bladder  are  not 
uncommon  sequelse.  ^.  ■     •      .  u 

The  stone  may  pass  into  and  obstruct  the  common  duct.  This  is  about  three 
times  the  diameter  of  the  cystic  duct,  and.  therefore,  many  stones  which  have  given 
rise  to  the  above  symptoms  pass  through  it  easily.  If  a  stone  permanently  occludes 
it,  there  will  usually  be  deep  and  persistent  jaundice,  clay-colored  stools,  vague  and 
dull  hepatic  and  shoulder  pain,  rarely  colicky  in  character,  and  absence  of  sejitic 
phenomena  and  of  enlarged  gall-bladder,  the  latter  symptom  occumng  m  not  more 
than  10  or  12  per  cent,  of  cases  of  calculous  common-duct  obstruction.  A  stone  may 
pass  as  far  as  the  ampulla  of  Vater  and  act  as  a  "  ball-valve."  in  which  case  there 
will  be  variable  jaundice  and  ague-like  paroxvsms  of  chills,  fever,  and  sweating, 
accompanied  by  hepatic  pains  and  gastric  disturbance  (Osier).  The  mechanical 
effect  of  a  stone  in  such  a  position,  plus  the  resulting  nerve  irritation  and  infective 
cholangitis,  sufficiently  explains  these  phenomena. 

Occlusion  of  the  cuinmon  ducts  may  occur  from  other  r.iu.ses,  a.s  stricture  follow- 
ing ulceration  due  to  stone,  the  presence  of  lumbricoid  worms,  echinococci,  etc.,  or 


173* 


HUMAN  ANATOMY. 


ii  i 


'■  . 


ii 


even  of  foreign  bodies  which  have  been  swallowed.     Pressure  from  extrinsic  causes  i- 
far  more  frequent,  however,  as  a  cause  of  occlusion.     It  may  be  due  to  carcinoma  of 
the  lymph-nodes  in  the  transverse  fissure,  secondary  to  rectal  or  to  gastric  cancer 
or  to  enlargement  of  the  head  of  the  pancreas  from  new  growth  or  from  inflammation 
or  to  aneurism  of  branches  of  the  coeliac  axis. 

In  these  cases,  contrary  to  what  is  found  in  occlusion  from  gall-stones,  the  gal! 
bladder  is  usually  enlarged. 

Congenital  obliteration  of  the  ducts  may  occur. 

Operations  on  the  Gail-Bladder  and  Biliary  Ducts. — A  vertical  incision,  at  leasi 
7.5-10  cm.  (3-4  in. )  in  length  from  the  costal  mar^n  downward,  made  over  tht 
middle  of  the  right  rectus  muscle,  the  fibres  of  which  are  separated,  will  usualK 
satisfactorily  expose  the  gall-bladder.  If  it  is  necessary  to  open  either  of  the  ducts, 
the  incision  may  be  prolonged  upward  in  the  interval  between  the  xiphoid  cartilage 
and  the  costal  cartilages.  If  the  liver  b  then  dra\'  1  downward  from  beneath  the  ribs 
and  rotated  upward  and  outward  and  the  trans'  rse  colon  fe  drawn  downward,  the 
subhepatic  space  will  be  well  exposed,  bounded  y  the  under  surfeice  of  the  liver  above 
and  externally,  the  colon  and  transverse  m-  ocolon  below,  and  the  duoderum  and 
pyloric  end  of  the  stomach  internally.  In  this  position,  especially  if  a  sand  ;  ig  has 
been  placed  beneath  the  back  opposite  the  liver,  so  as  to  push  the  spine  forward,  the 
cystic  and  common  ducts  are  brought  close  to  the  surface,  the  angle  between  them  is 
effaced,  the  region  of  entrance  into  the  duodenum  is  in  full  view,  and  ■ncisivyn  for  drain- 
age of  the  gall-bladder  (cholecystostomy),  or  for  the  extraction  of  a  calculus  either 
from  the  gall-bladder  (cholelithotomy)  or  a  duct  (choledocjiotomy),  or  for  the  re- 
moval of  the  gall-bladder  (cholecystectomy)  becomes  possible.  If  there  are  many  and 
troubl^me  adhesions,  the  fundus  and  body  of  the  gall-bladder  being  buried  and  not 
recognizable,  it  is  well  first  to  locate  the  hepatico-duodenal  fold  of  peritoneum, — the 
right  border  of  the  lesser  omentum, — in  which  the  common  duct  may  be  traced  from 
its  duodenal  termination  upward,  the  portal  vein  lying  behind  it  and  the  hepatic 
artery  to  the  left.  The  cystic  and  hepatic  ducts  may  then  be  identified.  The  ducts 
may  often  best  be  examined  by  passing  the  forefinger  of  the  left  hand  through  the 
foramen  of  Winslow,  the  back  of  the  surgeon  l^ing  turned  towards  the  patient. 
The  duct,  the  portal  vein,  and  the  hepatic  artery  may  thus  easily  be  grasped  between 
the  thumb  and  finger.  The  close  relation  of  the  lower  end  of  the  common  duct  to 
the  vena  cava  should  be  remembered  in  operations  upon  it.  This  portion  may  be 
reached,  if  necessary,  as  in  some  cases  of  stone  impacted  at  the  duodenal  papilla, 
by  opening  the  second  portion  of  the  duodenum  and  slitting  up  the  duct  as  it  lies  iii 
the  inner  and  posterior  wall  of  the  intestine,  where  it  may  be  felt  as  a  cord. 

The  duct  may  be  reached  at  a  higher  point  by  an  incision  through  the  perito- 
neum to  the  right  of  the  duodenum,  the  latter  being  freed  posteriorly  and  drawn 
towards  the  median  line. 

In  cases  in  which  the  common  duct  is  permanently  obstructed  a  portion  of  the 
duodenum  or  jejunum  may  be  anastomosed  with  the  gall-bladder  (cholecystenteros- 
tomy)  by  direct  suture. 

THE  PANCREAS. 

The  pancreas,  the  "  abdominal  salivary  gland,"  lies  moulded  across  the  spinal 
column  with  its  head  on  the  right,  enclosed  in  the  loop  of  the  duodenum,  and  its 
tail  on  the  left,  in  contact  with  the  spleen.  It  is  of  a  light  straw  color  running  into 
red,  according  to  the  amount  of  blood  within  the  organ.  The  weight  ranges  from 
30-150  gm.  ( 1-5  oz.)  or  even  more.  The  specific  gravity  is  about  1045.  The 
length  in  situ  is  approximately  15  cm.  (about  6  in.).  It  consists  of  an  enlarged 
descending  part  on  the  right,  the  head,  and  of  a  long  body  placed  transversely, 
which  is  needlessly  divided  into  nerk,  body,  and  tail.  When  the  organ  is  removed 
from  the  body  and  straightened  it  somewhat  resembles  a  revolver  in  shape,  the  head 
being  the  handle.  The  gland,  however,  is  so  modelled  by  the  surrounding  parts 
that  its  true  form  is  seen  only  in  its  undisturbed  position,  or  after  hardening  in  situ 
be*  .e  removal  from  the  body. 

The  head  (caput  pancrestin)  is  a  rotmded  hwx  irregular  disk  packed  into  the 
space  between  the  first  and  third  parts  of  the  duodenum,  and  lying  close  against  the 


V'' 


THE  PANCREAS. 


17.W 


1  (t  of  the  second  part.  It  overlaps  both  the  second  and  third  parts  antenorly,  and 
tnds  to  insinuate  itsel;  behind  them.  We  have  seen  it  overlapping  the  fourth  part 
ll«>  So  much  has  been  said  of  the  variations  of  the  duodenum  ( page  1644 )  that  it 
must  be  evident  that  the  head  of  the  pancreas  can  hardly  have  any  certain  size  or 
!;haoe  Its  diameter  from  above  downward  is  probably  rarely  less  than  7  cm.  and 
m  »rbe  ereater.  It  U  separated  from  the  neck  by  a  groove  on  the  front  of  the  gland 
r  the  MStro-duodenal  branch  of  the  hepatic  artery.  It  rests  behind  on  the  infenor 
vena  cava,  sometimes  on  the  right  renal  vein,  and  may  approach  the  right  suprarenal 
body.     It  is  opposite  the  first  and  second  lumbar  vertebrae  and  often  a  i>art  of  the 

third  lumbar  vertebra.  ....  .•     u     • 

The  body  (corpus  pancreatis).  including  the  neck  and  tail,  is  pnsmatic.  having 
a  />aslfrior,  an  antfro- superior,  and  a  narrow  in/frior  surface  It  is  so  tortuous  in 
Us  natural  Uition  as  to  seem  shorter  than  it  is.  Starting  on  the  right  of  the  spine 
at  the  levefof  the  first  lumbar  vertebra,  it  passes  around  it  to  the  left  and  backward 
and  again  forward  to  the  spleen,  which  it  may  or  may  not  cross.  Towards  its  end 
it  also  turns  downward. 


Fig.  1461. 

Ponal  vein      Hepatic  artery 


Left  >uprarenal  body 
--Left  Itldney 


RUht  Mprarenal. 
Vena  cava" 


First  part  of  ___. 
duodenum        f_ 
Right  kidney 


Spleen 


Tail  of 
paiKreas 


Splenic 
flexure  of 
colon 

Resinning 

of  je]unum 

Superior  mes- 
enteric artery 

Superior  mes- 
enteric vein 

Descending 
colon 


Vena  cava 


Anterior  aspect  of  pancreas  m  situ ;  the  organ  is  exceptionally  broad,  and  covers  more  of  left  kidney  than  usual ; 

peritoneum  has  been  removed. 

The  neck  is  the  part  (2-3  cm.  in  length)  which  crosses  the  portal  vein  with  a 
forward  convexity,  being  deeply  grooved  by  the  vein  on  its  posterior  surface.  The 
left  extremity  of  the  body  is  the  tail  (cauda  pancrcitis),  the  end  of  which  is  very 
variable  in  form.  If  it  lies  in  front  of  the  spleen  it  is  more  or  less  pointed,  but  if  it 
ends  against  the  gastric  surface  of  that  organ  it  may  have  a  true  terminal  concave 
surface,  fitting  it  accurately  (Fig.   146 1). 

The  posterior  surface  has  first  (from  the  neck  towards  the  left)  the  deep 
groove  for  the  portal  vein,  which  may  be  entirely  surrounded  by  glandular  tissue. 
Beyond  this  it  lies  on  the  vena  cava,  then  on  the  aorta  between  the  coeliac  axis  and 
the  superior  mesenteric  artery,  which  groove  it  above  and  below.  It  next  lies  on  the 
left  pillar  of  the  diaphragm,  the  left  suprarenal  capsule,  and  thi  left  kidney.  The 
left  end  may  have  a  concave  surface  resting  on  the  gastric  surface  of  the  spleen,  or 


mmmmn 


IPPHW 


17.^4 


HUMAN   ANATOMY. 


it  may  extend  across  this  surface,  or  rest  on  the  bas.il  one.  There  are  two  horizun 
tal  grooves  on  the  posterior  surface.  The  lower,  which  is  the  longer  and  deeper,  i^ 
caused  by  the  splenic  vein.  It  extends  from  the  left  end  to  the  groove  for  the  [hkuu 
vein,  inclining  to  the  lower  border  as  it  approaches  it  A  smaller  groove  for  tlir 
splenic  artery  lies  above  the  former  from  the  left  to  near  the  aorta. 

The  antero-supierior  surface,  the  largest  of  the  three,  slants  downward  and 
for  wd,  presenting  a  concavity  which  forms  a  part  of  the  stomach-bed.  It  is  (ui 
the  average  some  4  cm.  broad,  but  may  exceed  5  cm.  There  is  often  a  swelling— tlu 
omenta/  tuberosity  (tuber  omentale)— to  the  left  of  the  neck  opposite  the  aorta.  This 
is  behind  the  lower  end  of  the  vertical  part  of  the  lesser  curvature  of  the  stomach, 
and  is  in  contact  with  that  organ  rather  than  with  the  omentum. 

The  .nferior  surface,  the  smallest,  rarely  as  much  as  2  cm.  in  breadth, 
rests  on  the  lower  layer  of  the  transverse  mesocolon.  It  is  rounded  and  irregular! 
except  where  it  lies  above  the  duodeno-jejunal  fold,  where  •  is  smooth  and  concav  e. 
To  the  right  of  this  it  b  grooved  by  the  superior  mesenteric  artery. 

The  borders  at  which  the  surfaces  meet  call  for  no  special  description  beyond 
that  both  the  inferior  ones  are  grooved  by  the  superior  mesenteric  artery  and  the 
upper  by  the  cceliac  axis. 

Structure.— While  agreeing  in  its  general  structure  with  other  serous  salivary 
glands,  as  the  parotid,  the  pancreas  differs  in  certain  particulars.     The  most  im- 

Fig.  1463. 


S«lion  ol  pancm>  under  1'  w  magn ideation,  showing  (encrml  trrangnnent  of  lobul«.    x  30. 


portantof  these  are  the  tubular,  rather  than  saccular,  form  of  the  alveoli,  the  marked 
differentiation  of  a  granular  zone  in  the  protoplasm  of  the  secreting  cells,  the  absence 
of  specialized  intr  .lobular  ducts,  and  the  presence  of  the  islands  of  Langerhans. 

The  chief  pancreatic  duct  gives  off  numerous  lateral  interlobular  branches  which 
are  lined  with  a  single  layer  of  columnar  epithelium,  about  .006  mm.  in  height,  the 
direct  continuation  of  that  clothing  the  lai^e  ducts,  in  which  the  cells  are  from  two 
to  three  times  as  tall.  The  canals  springing  from  the  interlobular  ducts  after  enter- 
ing the  lobules  possess  a  layer  of  flattened  epithelial  plates  some  .012  mm.  long  by 
.003  mm.  high,  and  correspond  to  the  intercalated  or  intermediate  ducts.  The  in- 
tralobular canals  being  wanting,  the  relatively  long  intermediate  ducts  pass  directly 
into  the  tubular  alveoli,  within  which  their  attenuated  epithelium  protrudes  as  the 
centro-arinal  cells.  The  relation  of  the  latter  to  the  usual  glandular  elements  lining 
the  alveolus  is  pt^-uliar,  the  thinned-out  and  spindle  duct-cells  being  surrounded  ex- 
ternally by  the  si    rcting  cells. 

The  tubular  veoli  of  the  gland,  often  tortuous  and  sometimes  divided,  possess 
a  well-defined  membrana  propria  against  which  lie  the  secreting  ceils.     The  latter 


THE  PANCREAS. 


17.VS 


Alvcolu* 


are  usually  of  a  blunted  pyramidal  shape.  althouRh  many  aberrant  forms  are  seen. 
with  an  average  length  of  about  .010  mm.  During  functional  inactivity  their  cyto- 
plasm exhibits  two  well-differentiated  zones  :  an  inner  one,  ne.xt  the  lumen,  which  is 
hiirhly  granular,  and  an  outer  one.  next  the  basement  membrane,  which  is  free  from 
eranulM  and  at  times  almost  homogeneous.  The  round  or  oval  nucleus  occupies 
the  external  area.  The  relative  breadth  of  these  two  zones  varies  with  the  func- 
tional activity  of  the  cells.  During  fasting,  when  the  latter  are  stored  with  zymogen 
particles  the  granular  zone  is  very  broad  and  the  outer  homogeneous  one  corre- 
spondingly narrow.  With  beginning  discharge  of  the  pancreatic  secretion  during 
digestion  the  granular  zone  diminishes  and  reaches  its  minimum,  almost  dis- 
appearing when  the  gland  is  exhausted.  The  return  of  the  latter  to  a  condition  o 
rest  is  accompanied  by  the  formation  and  gradual  accumulation  of  a  new  store  ol 
zymogen  particles  until  the  granular  zone  is  again  restored  to  ;ts  maximum.  Occa- 
sionally in  fixed  tissue  the  parietal  cells  exhibit  within  their  cytoplasm  a  body 
termed  t\i<i  paranucleus  (Nebenkern).  The  latter  is  of  uncertain  form,  often  singu- 
larly round  and  indented,  and  ^^^  ^^^^ 
smaller  than  the  nucleus  in  the 
vicinity  of  which  it  usually  lies. 
The  nature  and  significance  of 
this  body '  are  still  undeter- 
mined, some  observers  regard- 
ing it  as  an  artifact  (Ebner), 
others  that  its  presence  is  in 
some  way  connected  with 
changes  affecting  the  nucleus 
( Henneguy).  Intercellular  se- 
cretion-capillaries have  been 
demonstrated  in  the  alveoli  of 
the  pancreas.  They  extend 
between  the  cells  for  some  dis- 
tance, but  do  not  reach  the 
basement  membrane  surround- 
ing the  acini.  Intracellular 
secretion-vacuoles  are  also  de- 
monstrable at  times  by  means 
of  Golgi  stains,  but  are  tem- 
porary and  cannot  be  regarded 
as  constant  details  of  the  cells 
(Ebner). 

The  interalveolar  cell- 
areas,  or  islands  of  Langer- 

hans,  appear  as  small  coUec-  . 

tions  of  cells,  some  .3  mm.  in  diameter,  lying  between  the  tubular  acini,  from  which 
they  are  separated  by  a  delicate  envelope  of  connective  tissue.  These  cell-areas  are 
constant  features  of  the  pancreas,  not  only  of  man,  but  likewise  of  a  wide  range  of 
animals  representing  mammals,  birds,  reptiles,  and  amphibians.  Their  distribution 
within  the  pancreas  is  by  no  means  uniform,  since,  as  has  been  shown  by  Opie,  while 
about  equally  numerous  in  the  head  and  adjacent  part  of  the  body  of  the  organ,  they 
may  be  almost  double  in  number  towards  the  tail.  The  cells  composing  these  masses, 
although  developed  from  the  same  tssue  which  gives  rise  to  the  usual  glandular 
elements  of  the  pancreas,  differ  from  the  latter  in  being  smaller,  polygonal  rather 
than  pyramidal  in  form,  less  granular,  and  undifferentiated  into  the  characteristic 
zones  usually  -een  in  the  pancreatic  cells.  They  are  arranged  as  a  net-work  con- 
sisting of  solid  cords  or  trabeculae,  the  meshes  of  which  are  occupied  by  blood- 
capillaries  of  large  size  ;  the  whole  recalling  the  arrangement  of  hepatic  tissue.  No 
extension  of  the  system  of  excretory  tubes  has  been  demonstrated  within  these 
cell-islands,  secretion-capillaries  being  therefore  wanting.  The  significance  of  the 
islands  of  Langerhans  has  long  been  a  subject  of  dispute,  but  in  view  of  their  isola- 
>  Johns  Hopkins  Hospital  Bulletin,  September,  1900. 


Section  of  pancreas.  thowinK  Interlobular  connective  tissue  with  vessels 
and  duct  surrounded  by  tubular  alveoli.     X  3oo. 


1736 


HUMAN  ANATOMY. 


tion  from  the  surrounding  glandular  tissue  and  their  close  relation  with  the  bloo,i 
vessels,  the  opinion  is  held  by  many  that  they  produce  some  substance  which  pasM 
directly  into  the  blood  and  may  be  regarded,  at  least  provisionally,  as  concerned  , 
internal  secretion.  '  •■■="  i.. 

The  Pancreatic  Ducts—The  gland  is  surrounded  by  a  fibrous  sheath  whicii 
sends  in  many  processes  dividing  it  into  small  lobules.  The  chief  excretory  canal  .■ 
the  adult  IS  therf«rf  of  IVirsung  (ductus  pancreaticus),  which,  beginning  near  the  ui,i 
of  the  tail,  runs  through  the  middle  of  the  pancreas  towards  the  right,  and  ben.l 
downward  as  it  passes  through  the  head.  Branches  sprout  from  the  main  d"  , 
at  nght  angles,  which  receive  bunches  of  smaller  ramifications.  The  diameter  ..i 
H„rt  t«  tK*""  ' n  ^f.u  *^"i  5  mm.  It  descends  just  in  front  of  the  common  bil. 
duct  to  the  wall  of  the  duodenum  and  empties  in  common  with  it  at  the  pai)ill  i 
a\S'  ^f\^''  u  ^1™'"*"?"  ^^""y  o'ten  '»  in  the  floor  of  the  ampulla  (diverUculum 
duodenale)  so  that  the  papilla  presents  but  one  opening.  The  tribuUry  ducts  of  th, 
head  are  larger  than  the  others.  A  particularly  lai^e  one-the  duct  of  Santorim 
p  (ductus  pancreaUcus  acces- 

*  *■  uorius)— is   in   the   early 

sUge  of  development  the 
chief  duct  of  the  head, 
and  consequently  of  the 
gland.  In  the  adult  it 
usually  descends  from  the 
right  to  empty  into  the 
duct  of  Wirsung  as  the 
latter  turns  downward. 
In  about  half  the  cases, 
according  to  Schirmer,'  it 
opens  independently  into 
the  duodenum,  some  ,i 
cm.  above  the  papilla  and 
more  anteriorly.  The  or- 
ifice is  usually  surrounded 
by  a  small  raised  ring. 
Even  when  so  terminating 
it  retains  its  connection 
with  the  duct  of  Wir- 
sung. Thus  fluid  in  the 
body  of  the  pancreas  may 
in  such  cases  pass  into 
the  duodenum  by  either 

duct  of  Santorini  may  pass  either  directly  into  the  gut  or  th^uSf  thTl^cfof '  Vfc 

StheT,':rTly'£^rc"hK  Sle",''ex"J%ro?yTct  •"^*"^'^^"  ^^'  '''"'''''' 

anH  th.''lnV°"'  *°  **"*  Peritoneum—Although  developed  in  both  the  posterior 

on  them„"H°^K'"!?^"*^'!f  •  '^^  P*"f 't'"'  °*'"^  *°  '^^  '^'"'S^^  ^y  which  the  spleen 
on  the  left  and  the  descending  part  of  the  duodenum  on  the  right  have  come  to  lie 

against  the  posterior  abdominal  wall,  is  entirely  retroperitoneal.  The  posterior  sur- 
face with  the  possible  exception  of  the  end  of  the  tail,  which  may  be  surrounded  bv 
peritoneum,  is  attached  to  the  parts  behind  it  by  connective  tissue.  The  layers  of 
peritoneum  co%'ering  the  antero-superior  and  the  inferior  surfaces  meet  to  form  the 
™Zfjr"°»K  "•'  Z^'""^  "  «t^<:hed  along  the  border  between  these  surfaces,  and 
L*Tlh  r  ^  "^•'"  '"'T^  *'''  ^^'"^'  ^"'^  """y  sometimes  rise  towards  the  left 
artlrv  rrn?ilT"P7'''..'  ""'^''''^.i  r  ^^^  gastro-pancreatic  fold,  made  by  the  gastric 
artery,  crosses  the  gland  upward  from  a  point  a  varying  distance  below  the  cceliac 

Vessels— The  ar/eries  are  many  small  branches  derived  from  th-  splenic 
hepatic,  and  superior  mesenteric.     As  the  splenic  runs  along  the  top  of  the  posterior 
'  Beitrage  zur  Geschichte  und  Anatomie  des  Pancreas,  Basel,  1893. 


.Conncctlve- 
liMuc  envelope 


.Capillary 
blood-ve* 


Modified 
epilhelial  cells 


.Alveotiu  wilh 
ordinary  cells 


Section  of  pancreas,  showinc  island  of  L4inferliana.    X  soo. 


THE  PANCREAS. 


17,^7 


surface  it  sends  a  series  of  branches  into  the  upper  part  of  the  body  and  tail  The 
hepatic  runs  along  the  top  of  the  front  of  the  head  and  n<ck,  doing  the  same.  In  the 
aroove  between  head  and  neck  the  gastro-duodenal  sends  the  superior  pancreatico- 
duodenal across  the  front  of  the  gland,  supplying  chiefly  the  head.  The  superior 
mesenteric  artery,  just  after  its  origin,  sends  from  its  right  the  inferior  pancreatico- 
duodenal. This  vessel  gives  off  a  larger  branch  running  to  the  right  to  meet  the 
superior  pancreatico-duodenal  on  the  front  of  the  head,  and  sends  a  smaller  branch 
to  the  left  ilong  the  lower  surface.  Sometimes  the  two  branches  which  meet  across 
the  head  enclose  it  by  a  similar  anastomosis  behind.  The  veifts  follow  in  the  main 
the  arteries.  They  are  all  tributaries  of  the  portal  system,  and  some  open  directly 
into  the  portal  vein.  The  lymphatics  are  many.  Most  of  them  run  to  the  coeliac 
and  splenic  plexuses.     A  small  group  of  lymph-nodes  is  situated  on  the  front  of  the 

The  nerves,  composed  chiefly  of  non-meduUated  fibres,  are  from  the  solar 
plexus,  by  way  of  the  cceliac,  splenic,  and  superior  mesenteric  plexuses. 

Fio.  1465. 


Section  of  injected  fiancreas,  showing  intralobular  capillary  nct-worka;  also  convolutions  of  islands  of 

Langerhans.    X  50. 

Development. — The  human  pancreas  develops  from  two  separate  anlages,  a 
dorsal  and  a  ventral  one.  The  former,  which  appears  by  the  fourth  foetal  week,  is 
a  direct  outgrowth  from  the  primitive  duodenum.  The  ventral  anlage,  slightly  later 
in  its  formation,  develops  as  two  outgrowths,  one  from  each  side  of  the  early  bile- 
duct,  and  is  therefore  not  strictly  a  direct  derivative  from  the  gut.  The  left  ventral 
outgrowth  soon  disappears,  leaving  the  right  one  connected  with  the  bile-canal. 
This  close  association  is  retained  throughout  life,  as  evidenced  by  the  intimate  rela- 
tions between  the  common  bile  and  pancreatic  ducts.  The  dorsal  paricreas  rapidly 
grows,  elongates,  and  soon  becomes  the  chief  part  of  the  organ,  opening  by  an  in- 
dependent canal — the  duct  of  San!  rini — into  the  duodenum.  The  repeated  division 
of  the  duct  and  the  proliferation  and  extension  of  the  terminal  compartments  pro- 
duce the  system  of  excretory  passages  and  glandular  tissue  of  the  organ.  The  ven- 
tral pancreas,  which  has  meanwhile  increased  more  slowly,  and  in  consequence  of  the 
changes  in  the  gut  has  suffered  displacement  to  the  left  and  behind,  grows  towards 
the  dorsal  gland,  with  which  it  soon  inseparably  hises.     The  head  of  the  fully  formed 


1738 


HUMAN   ANATOMY. 


organ  represents  the  primitive  ventral  pancreas,  the  body  and  tail  the  dorsal  sii;. 
ment.  The  duct  of  the  ventral  portion,  which  remains  as  the  duct  of  VVirsung,  furms 
a  communication  with  that  of  Santorini,  and  for  a  tune  the  pancreas  possesses  tu  i 
outlets  into  the  duodenum.  Usually  the  duct  of  Santorini  loses  its  intestinal  c> 
nection  and  becomes  tributary  to  the  duct  of  Wirsun^.  Variations  from  this  ar- 
rangement are  often  encountered,  the  different  combinations  being  due  to  deviatiuns 

Fio.  1466. 


Diagrunniatic  reconstructions,  showing  development  of  paiKreas  and  relations  to  liver-ducts,  a,  commnn  UW- 
duct;  A,  hepatic  and  c  c>-stic  ducts;  (/,  right  and  e  left  ventral  pancreatic  nti1aee«;  /,  dorsal  pancreas  aiui  irs 
duct  ( jr) ;  A,  junction  of  common  bite  (a)  and  ventral  pancrvatic  (1/  )  ducts.  Alter  fusion  of  ventral  and  dorsal  pan- 
creas, d  biecomes  duct  of  Wirsung,  g  duct  of  Santorini,  and  1  head  of  pancreas. 

from  the  ordinary  prc^ess  of  development  as  to  the  fusion  of  the  two  parts  and  per- 
sistence of  their  canals.  The  areas  of  Langerhans  are  developed  from  the  same 
entoblastic  outgrowths  as  give  rise  to  the  ordinary  glandular  tissue  (Laguesse, 
Pearce").     The  connective- tissue  septa  are  derived  from  the  ingrowing  mesoblast. 

Variations — The  pancreas  has  been  seen  to  surround  the  descending  part  of  the  duodenum. 
Small  accessory  pancreases  have  been  found  in  the  walls  of  the  intestine.  Although  usually  in 
the  duodenum,  they  may  be  in  the  stomach  or  at  the  bepnning  of  the  jejunum,  and  occasion.illy 
some  distance  from  it.  Presumably  they  are  parts  of  the  gUind  which  became  separated  at  .in 
early  stage  and  were  drawn  by  the  growth  of  the  intestine  away  from  their  original  position.' 


PRACTICAL   CONSIDERATION  , :   THE   PANCREAS. 

Certain  abnormalilies  that  may  affect  surgical  procedures  or  may  of  themselves 
produce  symptoms  of  disease  should  be  mentioned.  Accessory  pancreases  are 
found  in  various  localities  and  may  be  mistaken  for  new  growths.  The  anterior  wall 
and  the  two  curvatures  of  the  stomach  and  the  walls  of  the  small  intestine,  especially 
the  duodenum,  are  the  situations  in  which  such  glands  are  most  frequently  found. 
They  have  ducts  opening  into  the  intestine. 

An  accessory  gland  has  been  found  to  the  right  of  the  duodenum  entirely  dis- 
tinct from  the  main  gland.  Perhaps  the  most  important  anomaly  is  one  in  which 
the  gland  completely  .surrounds  the  .second  part  of  the  duodenum,  constricting  it  and 
causing  dilatation  of  the  first  jx)rtion  and  of  the  stomach.  Several  cases  have  been 
reported.  The  common  bile-duct  may  also  be  contained  within  the  head  of  the  pan- 
creas, as  may  the  superior  mesenteric  vessels  within  its  body.  The  accessory  pan- 
creatic duct  may  be  absent,  or  there  may  be  three  ducts,  all  opening  into  the 
duodenum. 

Movable  Pancreas. — The  gland  may  fall  forward  or  downward  (when  it  may 
sometimes  be  felt  below  the  stomach),  or  it  may  be  a  part  of  the  contents  of  a  dia- 
phragmatic hernia,  or  may  even — but  with  great  rarity— be  contained  within  the  sac 
of  an  umbilical  hernia. 

Injuries. — The  situation  of  the  pancreas  behind  the  lesser  jieritoneal  cavity  and 
the  stomach  and  between  the  spleen  and  the  duodenum,  the  partial  protection  it 
receives  from  the  costal  arch,  and  the  depth  at  which  it  lies  render  its  uncompli- 

•  American  Toiimal  of  Anatomy,  vol.  ii.,  1903. 
» Sinker  :  Virchow's  Archiv,  Bd.  xxi.,  1861. 


PRACTICAL  CONSIDERATIONS:   THK  I'ANCRKAS. 


1739 


cited  injury  of  very  rare  occurrence.     In  only  three  fatal  cases  in  which  all  other 
ilHlominal  viscera  escaped  has  it  been  found  to  be  ruptured. 

In  less  severe  cases  it  has  been  bruised  or  torn,  hemorrhage  has  occurred,  a 
1  ipidly  enlargiiHJ,  fluctuating  epigastric  tumor  has  formed,  and  the  patient  has  recov- 
ered ifter  a  Uparotomy,  evacuaUon  of  the  blood-cyst,  and  drainage.  In  such  cases 
it  is  probable  that  the  traumatism  has  caused  a  laceration  of  the  jKwterior  layer  of  the 
l.-sser  sac  of  the  peritoneum  ( with  which  the  pancreas  is  intimately  adherent )  and  of 
the  pancreas  itself.  Blood,  or  blood  with  pancreatic  secretion,  is  |M>ured  into  the 
lesser  sac,  causing  adhesive  peritonitis  and  sealing  the  foramen  of  Wmslow.  The 
lesser  cavity,  now  converted  into  a  closed  sac,  is  distended  with  serous  exudate, 
l)l.x)d  and  pancreatic  fluid.  After  evacuation  and  drainage,  the  pancreas  may  con- 
tinue to  pour  its  secretion  into  the  cyst-cavity  through  the  origmal  peritoneal  tear 
iRobsonand  Moynihan).  . .,     .   _      u-  u  •. 

Panerta/i/is.—The  close  relation  of  its  duct  to  the  co:.imon  bile-duct,  which  it 
often  joins  at  the  ampulla  and  before  reaching  the  duodenum,  explains  the  frequent 
issociation  c:  (pUl-stones  with  chronic  inflammation  of  the  pancreas.  A  small  ball- 
valve  calculus  in  the  ampulla  has  been  thought,  by  occluding  the  duodenal  onhce,  to 
convert  the  two  ducts  into  a  continuous  channel,  permitting,  if  the  gall-bladder  is 
functionally  active,  the  entrance  of  bile  into  the  pancreatic  duct  (duct  of  Wirsung) 
and  causing  pancreatitb.  A  larger  stone  might  occlude  alvo  the  orifices  of  both  the 
pancr  itic  duct  and  the  bile-duct  and  produce  in  both  glands  the  troubles  associated 
will  tained  secretions.  In  the  pancreas  these  troubles  are  lessened  by  the  fact  that 
occlus  ,1  of  the  main  pancre?.tic  duct  does  not  of  necessity  completely  obstruct  the 
egress  of  the  pancreatic  fluid  COpie).  In  about  50  per  cent,  of  bodies  the  acces- 
sory duct  (duct  of  Santorini)  communicates  within  the  gland  with  the  mam  duct 
and  opens  into  the  duodenum  by  a  separate  orifice  about  2.5-3-5  cm-  (\-^f^  •"• ) 
nearer  the  stomach  than  the  papilla  at  which  the  ampulla  of  Vater  opens  (Schirmer). 
Nevertheless,  just  as  jaundice  follows  occlusion  of  the  common  bile-duct  by  forcing 
the  secretion  of  the  li-er  back  upon  that  gland,  whence  it  finds  its  way  into  the  inter- 
stitial tissue,  the  lymphatics,  the  thoracic  duct,  the  blood,  and  the  tissues  at  large, 
so  the  fat-splitting  ferment  of  the  pancreatic  juice,  in  cases  of  occlusion  of  the  pan- 
creatic duct,  finds  its  way  beyond  the  parenchyma  of  the  gland  and  causes  fat- 
necrosis,  first  in  the  vicinity  of  the  pancreas,  later  over  widespread  areas  (Opie). 

There  can,  at  any  rate,  be  no  question  of  the  etiological  association  of  gall- 
stones with  many  cases  of  pancreatitis  ;  but  it  is  probable  that  in  a  large  proportion, 
in  addition  to  mechanical  pressure  or  inde  »ndently  of  it,  bacterial  invasion  follow- 
ing inflammation  of  the  ducts  or  of  the  duov.  wm  is  an  important  factor. 

The  anatomical  symptoms  of  acute  pancreatitU  depend  upon  the  close  associa- 
tion of  the  gland  (a)  with  the  solai  plexus  through  the  coeliac,  superior  mesenteric, 
and  splenic  plexuses  ;  (*)  with  the  duodenum  ;  (t)  with  the  bile-ducts  ;  (</  )  with 
the  great  blood-vessels  behind  it ;  and  (^)  upon  its  more  remote  relation  with  the 
epigastric  region,  direcdy  beneath  which,  but  at  a  considerable  depth,  it  lies.  These 
relations  explain  (a)  the  acute  and  agonizing  pain,  vomiting,  and  collapse;  (*) 
the  intestinal  paresis  and  distention,  often  simulating  intestinal  obstruction  ;  (f)  the 
slight  but  deepening  jaundice  sometimes  present;  (</)  the  cyanosis  of  the  face  and 
abdomen  so  commonly  seen,  and  probably  due  pardy  to  reflex  cardiac  disturbance  ; 
and  (e)  the  circumscribed,  tender  epigastric  swelling  which  follows  closely  on  the 
above  symptoms.  In  differentiating  the  condition  from  acute  intestinal  destruction, 
—for  which  it  is  most  likely  to  be  mistaken,— the  immediate  presence  of  localized 
epigastric  tenderness  and  the  usual  absence  of  both  conspicuous  general  tympany  and 
of  limited  distention  of  intestinal  coils  should  be  given  d  je  weight.  The  rarity  in 
the  epigastrium  of  an  obstructed  small  intestine  should  be  remembered,  and  the 
patency  and  capacity  of  the  large  intestine  should  be  determined  (Fitz). 

Chronic  obstruction  of  the  duct  may  cause  the  development  of  retention-cysts, 
of  chronic  interstitial  pancreatitis,  or  of  pancreatic  calculi.  The  latter  may  later 
Ijecome  themselves  the  chief  cause  of  continued  obstruction  and  of  further  cystic 
changes. 

In  chronic  pancreatitis,  especially  in  thin  patients  and  when  the  stomach  and 
colon  are  empty,  it  may  be  possible  to  feel  the  tender,  sw  >llen  gland  through  the 


1740 


HUMAN  ANATOMY. 


abdominal  wall.     In  gastroptoais  the  normal  pancreas  may  easily  be  felt  above  i: 
stomach  and  might  readily  be  mistaken  for  a  new  growth.     Usually  the  swell ini;  ,, 
behind  the  stomach  and  above  or  behind  the  colon.     In  suppurative  pancreatitis  ih 
collection  ol  pus  may  push  the  stomach  forward,  or  may  I    come  superficial,  titli.  i 
above  or  below  it ;  it  may,  starting  at  the  pillar  of  the  diaphragm,  and  guided  by  ih, 
pnoas-sheath  or  the  iliac  fascia,  reach  the  iliac  region  ;  it  may  occupy  the  ar'jf.l.,; 
tissue  of  the  loin,  becoming  a  perirenal  abscess  ;  it  may  open  into  either  the  stoma.  1 1 
or  duodenum.     When  confined  to  the  pancreas,  it  will  usually  be  recognized  diirii, 
an  exploratory  operation.     It  may  be  drained  posteriorly  by  an  incision  at  the  cost." 
vertebral  angle,  or  anteriorly  through  a  large  tube  surrounded  by  gauxe  packing. 

Cancer  of  the  pancreas  usually  affects  the  head  of  the  gland,  which  account.-)  f..r 
the  fretjuency  with  which  obstructiGn  of  the  common  bile-duct  and  of  the  duodenum 
occurs  m  such  cases. 

The  hirther  growth  of  the  tumor  may  cause  compression  of  the  pylorus,  of  tlu 
cardiac  end  of  the  stomach,  of  the  whole  stomach  by  forcing  it  against  the  anterii  n 
abdominal  wall,  of  the  colon,  the  ureter,  the  portal  vein,  the  vena  cava,  the  aort.i 
the  splenic  vessels,  and  the  superior  mesenteric  vein  (Robson  and  Moynihan). 

If  the  tumor  extends  to  the  right,  there  are  apt  to  be  jaundice  and  intestinil 
obstruction  ;  if  upward,  in  addition  to  these  symptoms,  pyloric  obstruction  ami 
pastric  dilatation  ;  if  backward,  ascites  and  cedema  of  the  lower  limbs. 

The  pancreas  may  be  approached  for  operation  through  a  median  incision,  and 
reached,  above  the  stomach,  through  the  gastro-hepatic  omentum  ;  below  the  stom 
ach,  through  the  gastro-epiploic  omentum  or  the  transverse  mesocolon,  the  omentum 
having  been  turned  upward.  It  has  been  exposed  (in  a  case  of  hydatid  cyst 
b^  an  incision  beginning  at  the  tip  of  the  twelfth  rib  and  passing  forward  in' tlu 
direction  of  the  umbilicus.  Indirect  drainage  in  chronic  pancreatitis  by  means  oi 
cholecystostomy  has  given  excellent  results  (Robson). 

In  cases  of  nephrectomy  the  relations,  of  its  tail  to  the  left  kidney  and  renal 
vein  should  be  remembered.  The  relations  of  the  vena  porta,  the  vena  cava,  tht 
aorta,  the  superior  mesenteric  artery,  and  the  cceliac  axis  are  so  close  that  wlun 
complicated  by  adhesions  or  infiltration,  as  in  chronii  inflammations  or  new 
growths,  operations  for  total  excision  of  the  pancreas  bc_  iie  formidable  and  ha\f 
rarely  been  undertaken.  The  close  relation  of  ?he  pylorus — especially  when  th.- 
Stomach  is  depressed  by  a  new  growth — to  the  neck  of  the  pancreas  should  W 
remembered  in  pyloroplasty  or  pylorectomy,  as  should  the  proximity  of  the  spleen 
to  the  other  extremity  of  the  pancreas  in  cases  of  splenectomy. 

THE   PERITONEUM. 

The  peritoneum  is  the  serous  membrane  lining  the  abdominal  cavity  and  reflected 
over  the  viscera.  Like  all  serous  membranes,  it  consists  of  a  free  mesothelial  sur- 
face and  a  deeper  layer  of  fibro-elastic  tissue,  the  tunica  propria.  Beneath  the  latter  a 
variable  amount  of  subperitoneal  tisstte  connects  the  peritoneum  with  the  structures 
which  it  covers.  The  quantity  of  this  areolar  layer  differs  in  various  localities,  and 
it  is  at  times  difficult  to  decide  just  what  is  really  a  part  of  the  serous  membrane 
proper.  It  is  convenient  to  look  upon  the  peritoneum  as  having  a  right  side  and  a 
wrong  side  ;  the  former  is  the  free  mesothelial  surface,  the  latter  the  areolar  which 
is  attached  to  other  structures.  Thus  it  may  be  compared  to  a  wall-paper  of  a 
room  without  door  or  window,  of  which  the  right  side  is  always  free  and  the  wrong 
side  adherent  to  walls  or  to  projections  from  them.  Should  a  flue  traverse  the 
room,  it  is  easy  to  imagine  it  invested  by  a  continuation  of  the  paper  on  the  walls. 
It  passes  through  the  room,  but  is  not  within  the  closed  sac  formed  by  the  right 
side  of  the  paper.  While  it  is  true  that  during  development  the  mesothelial  covering 
grows  pari  passu  with  the  tissue  beneath  it,  the  conception  that  projections  of  organs 
into  the  peritoneal  cavity  carry  the  serous  membrane  before  them  is  very  convenient 
and  justified.  The  peritoneum  of  the  f-  .  s  is  the  onlv  serous  membrane  that  is 
not  a  closed  sac,  on  account  of  the  op  gs  of  the  Fallopian  tubes.  The  blood- 
vessels for  the  viscera,  around  which  the  peritoneum  If  thrown,  must  pass  on  its 
wrong  side.     To  return  to  the  simile  of  the  flue  in  the  chamber  ;  if  this  should  need 


THE   PERITONEUM. 


«74i 


support,  we  can  imagine  it  susi)ended  in  the  middle  by  a  series  of  cords  wl  might 
be  all  enclosed  in  one  fold  of  paper  from  the  ceiling.  This  would  be  a  m«.  leryanA 
the  cords  would  be  blood-vessels  going  to  the  gut.  The  cords,  of  course,  would  be 
on  the  wrong  side  of  the  paper  and  the  vessels  on  the  areolar  side  of  the  mem- 
brane. A  fold  of  peritoneum  may  contain  lar^e  vessels  ;  nd  strong  bundles  of  fibres, 
arid  at  other  places  be  no  more  than  a  duplicature  of  r  ?mbrane.  The  former  are 
the  mesenUrus  and  certain  bands  caUed  "  lir .  ■ '.ents,  the  latter  piictt  or  folds. 
Tlie  complications  of  the 

F-..  1467. 


Diaphrafm 


[>«  ritoneum  are  reduced 
us  much  as  possible  by 
biudymg  it  in  the  light  of 
development,  the  account 
of  which  has  been  already 
j;iven(page  170J).  Here 
only  some  of  the  chief 
IKjints  and  general  prin- 
ciples are  recapitulated. 

In  the  early  foetus  the 
peritoneum  is  merely  the 
lining  of  the  abdomen, 
the  parietal  peritoneum, 
which  covers  the  Wolffian 
bo'iies  and  the  beginning 
of  the  abdominal  walls, 
and  certain  median  folds 
called  mesenteries,  con- 
veying blood-vessels  to 
the  gut,  within  which  cer- 
tain accessory  organs  are 
developed.  There  b  a 
posterior  mesentery  ex- 
tending from  the  spine  to 
the  whole  length  of  the 
alimentary  canal  below 
the  diaphragm,  to  which 
it  carries  vessels  from  the 
aorta,  and  an  anterior 
mesenterj-  running  to  the 
upper  part  of  this  canal 
from  the  anterior  abdom- 
inal wall  (Pig.  1433). 
The  original  posterior 
mesentery  is  divided  into 
three  regions,  each  of 
which  conveys  a  particu- 
lar arten,?.  I.  The  mesen- 
tery of  the  stomach  and 
of  the  duodenum,  con- 
taining the  coeliac  axis. 
It  is  to  be  noted  that  this 
region  mav  be  subdivided 

into  two  parts,  the  upper  formed  by  the  stomach  and  the  first  part  of  the  duodenum, 
the  lower  formed  by  the  remainder  of  the  duodenum.  The  latter  originally  arches 
forward,  both  ends  being  fixed  at  the  spine.  2.  The  mesentery  of  the  st  of  the 
small  intestine  and  of  the  ascending  and  the  transverse  colon,  containing  the  superior 
mesenteric  artery.  3.  The  mesentery  of  the  remainder  of  the  large  intestine,  con- 
taining the  inferior  mesenteric  artery. 

The  anterior  mesentery,  in  which  the  liver  is  developed,  reaches  the  stomach 
and  the  upper  part  of  the  duodenum,  extending  on  the  antetior  wall  as  low  as  the 


Diajrram  showing  general  arrangement  of  |>t^ritoneuin.  which  is  represented 
by  the  blaclc  line ;  arrow  passes  from  greater  into  lesser  sac  through  foramen 
01  Winslow.  A,  liver;  .V,  stomach;  /*,  pancreas;  /J.  duodenum;  TC,  trans- 
verse colon  ;  /,  small  intestine ;  R,  rectum  ;  B,  bladder ;  V,  utenia. 


1742 


HUMAN  ANATOMY. 


umbilicus  (Fig.  1432).  The  umbilical  vein  runs  in  its  iiee  lower  border  io  the  per 
ta'  fissure  of  the  liver,  whence  its  continuation,  the  ductus  venosus,  ,  .sses  to  the 
in  erior  vena  cava.  The  anterior  mesentery,  containing  the  liver,  is  opposite  to  ilif 
nusogoitrium,  or  mesentery  of  the  stomach,  which  contains  the  spleen.  The  |>;i]i- 
creas,  although  developed  in  both  the  anterior  and  the  posterior  mesenteries,  liis 
chiefly  in  the  latter.  As  the  jejuno-ileum  enlarges  it  hangs  in  loops  from  the  s|)iiu'. 
carrying  folds  of  mesentery  with  it  surrounding  the  vesseb.  The  multiplication  <<i' 
these  folds  gives  rise  to  the  complication  of  the  adult  arrangement. 

When  two  layers  of  a  serous  membrane  rome  to  lie  permanently  and  practicallv 
immovably  upon  each  other,  there  is  a  tendency  to  fusion  between  them,  the  meso 
thelium  covering  the  apposed  surfaces  disapptearing  and  its  place  being  taken  l)v 
connective  tissue  (Fig.  1473).  Thus,  when  a  mesentery  lies  against  the  abdominal 
wall,  the  mesothelium  of  the  parietal  peritoneum  and  of  the  mesentery  apposeil  t(^ 
it  degenerates  into  connective  tissue,  and  the  peritoneum  on  the  free  surface  of  tlit- 
mesentery  becomes  a  part  of  the  permanent  parietal  peritoneum.  Much  of  the 
originally  free  [>arietal  peritoneum  is  thus  replaced  by  fusion  with  what  once  belonged 
to  a  mesentery. 

The  stomach  undergoes  rotation,  so  that  the  original  left  side  becomes  the 
anterior  and  the  posterior  border  the  greater  curvature.  The  mesogastrium  grows 
out  of  all  proportion,  so  as  not  only  to  describe  a  curve  to  the  left,  but  to  han^; 
downward  in  a  free  fold.  The  loop  of  the  duodenum  turns  to  the  right,  so  that  all 
of  it,  except  the  first  part,  lies  against  the  posterior  abdominal  wall.  The  head  of  the 
pancreas  is  carried  with  it.  The  serous  covering  of  the  back  of  the  duodenum  ( in 
its  new  position),  that  of  its  mesentery,  and  that  of  the  back  of  the  head  of  the 
pancreas  disappear,  fusing  with  the  f)arietal  peritoneum  of  the  fjosterior  abdominal 
wall. 

The  mesentery  attached  to  the  jejuno-ileum  and  to  most  of  the  large  intestine 
becomes  twisted  as  the  gut  returns  into  the  abdomen  from  the  umbilical  cord,  so 
that  the  caecum  is  thrown  upward  and  to  the  right  to  lie  under  the  liver,  whence  it 
descends  to  its  permanent  place  ;  hence  the  original  right  and  left  sides  of  the 
mesentery  change  places.  The  mesentery  of  the  ascending  colon  fuses  with  the 
posterior  covering  of  the  right  side  of  the  abdomen  ;  that  of  the  descending  colon 
to  the  sigmoid  flexure  does  the  same  on  the  left. 

The  sub-  or  retroperitoneal  tissue  is  very  important.  As  above  stated,  there 
is  a  thin  fibro-elastic  layer  supporting  the  mesothelial  cells,  which  is  a  part  of  the 
serous  membrane,  although  it  is  not  present  in  the  earlier  stages.  Beneath  this 
tunica  propria  there  may  be  a  continuous  mass  of  connective  tissue,  to  be  compared 
to  dense,  sfKjnge-like  cobwebs,  which  serves  as  a  packing  between  different  organs 
and  around  vessels,  nerves,  and  ducts.  It  may  contain  a  large  amount  of  fat.  This 
is  particularly  developed  about  retroperitoneal  viscera  and  along  the  aorta.     The 

Carietal  peritoneum  is  usually  thin  where  no  fusion  with  another  layer  nor  with 
isciae  has  occurred. 

We  shall  describe  ( i )  the  peritoneum  of  the  anterior  and  lateral  abdominal 
walls,  with  its  prolongations  onto  the  diaphragm  and  into  the  pelvis  ;  (2)  the  folds 
denved  from  the  anterior  mesentery  ;  (3)  those  from  the  posterior  mesentery  from 
above  downward.  Most  matters  of  detail  are  discussed  with  the  various  organs 
having  peritoneal  relations. 

The  Anterior  Parietal  Peritoneum. — Four  folds  diverge  from  the  umbili- 
cus, three  running  downward,  symmetrically  disposed, — namely,  a  median  fold  (plica 
ufflbilicalis  media),  expanding  to  the  top  of  the  bladder  covering  the  urachus,  a 
fibrous  cord  representing  the  atrophied  intra-embryonic  segment  of  the  allantoic 
duct,  and  two  lateral  folds  (plies  umbilicales  taterales)  containing  fibrous  cords,  the 
obliterated  hypogastric  arteries,  continuous  with  the  permanent  superior  vesical  arte- 
ries. If  the  bladder  be  distended,  they  can  be  traced  to  its  upper  lateral  aspects  : 
otherwise  to  the  sides  of  the  pelvis.  The  fibrous  tissue  of  the  obliterated  arteries 
becomes  very  scanty  near  the  umbilicus.  The  supravesical  fossa  (fovea  supravcsi- 
calls)  or  depression  lies  on  each  side  above  the  piibes,  between  the  median  and 
lateral  folds.  On  the  outer  side  of  the  latter,  above  the  middle  of  Poupart's  ligament, 
is  the  internal  or  median  inguinal  fossa  (fovea  inguinalis  medialis),  which  is  very 


THE   PERITONEUM.  >743 

jctinrt  uid  often  extends  inward  under  the  obliterated  hypogastric  artery.  Farther 
'^  t  a  ve^  sSTfold  (plica  epigastrica).  caused  by  the  deep  epigastric  artery,  runs 
ulard  tnd  iWdirom  the  external  iliac  artery  just  as  '^e  latter  pa«es  under  Pou- 
^H^.  lirament  The  txtemal  or  lateral  inguinal  fossa  (fovea  inpiinalis  lateralis) 
rTh^eSv  just  external  to  thb  fold,  but  the  fold  is  barely  raised  and  a  fossa  not 
P^SrS  out  The  inUmal  abdominal  ring  (annulus  Inguinal.s  abdommal.s )  « 
^  hi,  f^  about  I  cm.  above  the  middle  of  Poupart's  ligament.  A  slight  fold 
cauS  S^'e  v^  de  erens  or  the  round  ligament,  is  described  as  running  downward 
causea  oyine  V  however,  that  the  structure  can  be  only 

lmrS.r^i^r  to  >h.n,  b  derived  In.™  the  mooiMne.  of  the  <»lo».  which 


Fig.  1468. 


Umbiliciu 


— Uiu...ic>lveiii 


Rectus  muKle 


External  inguinal 
fossa 

Anterior 
crural  nerve 
Ext.  iliac  artery 
External  iliac  vein 


Internal  inguinal 
fossa 

Supravesical  fossa  •• 


Anterior  superior 
Iliac  spine  (cut) 

Median  umbilical 
fold  (urachus) 
lateral 
umbilical  fold 
Epigastric  fold 

Internal 
abdominal  ring 

Vas  deferens 


_        _   __  Peritoneum 

Summit  of  bladder  ^  Bladder  (cut  I 

Pubic  bone  (cut) 
Frontal  section  o.  formalin  sub)ect.  showing  posterior  «^  o.  abdominal  wall,  covered  with  ,*rl.oneum. 

have  fallen  over  onto  the  posterior  abdominal  walls.  It  will  he  considered  later. 
Se  irieul  peritoneum  is^lso  to  be  traced  onto  the  under  suriace  of  the  da- 
phraS  untilfar  back  it  meets  the  folds  derived  from  the  mesenteries.  On  either 
siW  the  bundle  of  fibres  arising  from  the  ensiform  cartilage  there  is  an  mter- 
rliption  in  the  muscle  of  the  diaphragm,  where  only  areolar  tissue  separates  the 

^''''■^r^:iT;^Z^t^^^-^^^o  the  pelvis,  where  it  meets  the  mesen- 
tery of  th^Toon'^and  is  continued  over  the  bladder,. and  in  the  female  over  the 
uterus  and  Fallopian  tubes.  Nowhere  is  the  comparison  to  a  wall-paper  so  apt  M 
here  where  the  %ritoneum  can  be  traced  from  the  walls  "ver  the  .nequalit.es 
formed  bv  the  upper  surfaces  of  the  pelvic  organs.  The  depression  between  the 
wldder  and  the  r^e'ctum  in  the  male,  the  rccto-vesical pouch  (excavat  o  recto- ves  calls) 
n  the  female  is  subdivided  into  the  utero-vesical  pouch  (excavatio  utero-vesicalls)  and 
V^redTuicrinhonch  (excavatio  recto-uterina).  The  latter  and  deeper,  also  known 
l^Zl pouch  of  Douglas  (cavum  DouKlasi).  is  bounded  latera  ly  by  the  ^^ero-s^^^ 
folds  SL.  recto-uterin*).  which  pass  from  the  lower  part  of  the  uterus  backward 


1744 


HUMAN  ANATOMY. 


and  outward  to  the  side  of  the  rectum  and  the  pelvic  wall.  The  peritoneal  f  .ll 
investing  the  uterus  extends  laterally  on  either  side  as  the  broad  ligament  (liiianiiu- 
tum  latnm)  to  blend  with  the  parietal  peritoneum  covering  the  sides  of  the  peh  i^. 
Below,  the  broad  ligament  is  attached  to  the  pelvic  floor,  its  superior  margin  bciii<,r 
the  free  edge  of  the  fold.  On  either  side  of  the  rectum,  between  the  gut  and  tiiv 
wall  of  the  pelvis,  lies  the  pararectal  fossa,  the  size  of  which  varies  with  the  disti  ii 
tion  of  the  intestine.  The  special  features  of  the  peritoneum  are  described  with  the 
rectum  (page  1679)  and  with  the  uro-genital  system  (page  1905). 

The  arrangement  over  the  anterior  half  of  the  lateral  wall  of  the  true  pelvis  is 
different  according  to  sex,  since  in  the  female  there  is  the  line  of  attachment  of  tiie 
broad  ligament  of  the  uterus  and  the  fossa  for  the  ovary.  Otherwise  the  featurt^ 
are  about  the  same,  the  vas  deferens  of  the  male  and  the  round  ligament  of  tlit 
female  causing  similar  folds.  These  structures  run  backward  from  the  internal  riiii; 
along  the  wall  of  the  pelvis,  turn  down  to  the  side  of  the  bladder,  and  bound 
externally  and  posteriorly  X\ie  paravesical  fossa  bei  veen  the  pelvic  wall  and  the 

Fig    i46q. 


Bladdci 


I 
I 


Internal-^-, 
abdominal  ring 

Trans  verse -^ 
vrsical  fold 


External  iliac- 
vessels 


Left  ureter — 
Sigmoid  flexure' 


Urachus 


—Vas  deferens 
-_J5per Hiati c  \rsbcls 
— Sup.  vesical  utny 

~£xt.  iliac  arter> 
-Ureter 
-Vas  deferens 

Recto-vesical 

fold 
Ireter 
_  Peritoneum 
(cut) 

Internal  iliac 
arter>- 


Left  common  iliac  arter>- 


If'  * 


Pelvic  peritoneum  from  above  and  behind,  showing  folds  and  fosss. 

bladder  when  the  latter  is  not  distended.  A  transverse  fold  of  peritoneum,  plica 
vesiccUis  transversa,'^  passes  laterally  from  the  upper  suriace  of  the  empty  bladder 
and  subdivides  the  paravesical  fossa  into  an  anterior  and  a  posterior  compartment. 
The  vas  deferens,  or  round  ligament,  forms  (the  body  being  upright)  the  lower  side 
of  the  obturator  triangle,  which  is  completed  in  front  by  the  external  iliac  vein  and 
behind  by  the  ureter,  wtiich  crosses  the  external  iliac  vein  at  the  apex.  The  obtu- 
rator vessels  and  nerve  lie  in  the  floor  of  this  triangle.  In  the  female  it  is  crossed 
by  the  lateral  attachment  of  the  broad  ligament  of  the  uterus,  behind  which  is  the 
fossa  for  the  ovary  (fossa  ovarica). 

The  Anterior  Mesentery. — This  originally  extended  from  the  anterior  abdom- 
inal wall  to  the  lesser  curvature  of  the  stomach  and  to  the  beginning  of  the  duo- 
denum. It  is  subdivided  into  two  portions  by  the  liver,  which  develops  within  ii 
The  anterior  part  is  the  falciform  ligament,  between  the  abdominal  wall  and  the 
liver  ;  the  posterior  part  is  the  gastro-hepatic  omentum,  between  the  liver  and  the 
stomach. 

'  Waldeyer :  Journal  of  Anatomy  and  Physiology,  vol.  xxxii.,  1898. 


THE  PERITONEUM. 


1745 


The  falciform  ligament  (llRBmentam  falcifonne  hepatte)  makes  the  fourth  fold 
which  has  been  mentioned  as  leaving  the  umbilicus.  Seen  from  the  side,  .t  is  a 
Ikle-shaped  fold  attached  to  the  anterior  wall  above  the  umbilicus  and  later  to  the 
dtaDhraKiT as  far  back  as  the  top  of  the  fissure  of  the  ductus  venosus  on  the  pos- 
SHurface  of  the  liver  (Fig.  1441  )•  In  its  free  inferior  border  runs  the  round 
.Jament  once  the  umbilical  vein,  from  the  umbilicus  to  the  notch  in  the  liver,  and 
hence  in  its  own  fissure  on  the  under  surface  until  it  reaches  the  portal  figure, 
where  the  falciform  ligament  ends.  The  latter  divides  the  "PP^'^^P*';*  ^^  ),h^dome 
of  the  abdomen  into  two  chambers,  one  on  either  side  of  which  the  left  one  is  the 
kwer  There  is  but  little  areolar  tissue  in  the  folds  of  the  falciform  ligament. 
SnnU'veins  run  along  the  round  ligament,  connecting  the  hepatic  system  with  that 
of  "he  abdominal  walls.  AlthoMgh  in  the  embryo  the  fold  starts  from  the  navel,  in 
the  adult  it  does  not  leave  the  abdominal  wall  for  an  inch  or  more  above  it 

The  superior  surface  of  the  liver  is  covered  with  peritoneum  from  either  side  of 
the  falciform  ligament,  which  at  the  top  of  the  posterior  surface  is  reflected  onto 
the  under  side  of  the  dia-  ^^^ 

phragm.  At  the  edge  of 
the  right  lobe,  which  has  a 
considerable  posterior  sur- 
face uncovered  by  jjerito- 
neum  and  attached  to  the 
diaphragm,  the  layers  cov- 
ering the  upper  and  lower 
surfaces  meet  to  form  the 
right  triangular  ligament, 
which  is  attached  for  a 
short  distance  beyond  the 
liver  to  the  diaphragm  and 
has  a  sharp,  free  edge. 
There  is  a  similar  arrange- 
ment on  the  upper  surface 
of  the  left  lobe,  but  the 
left  triangular  ligament  is 
longer,  and  passes  to  the 
diaphragm  on  the  left  of  the 

rvfte  ?pl^"  Pl«"g  around  the  border  of  the  right  lobe  of  the  liver  the  peri- 
toneum  irSds  over  the  inferior  surface  of  that  lobe  as  well  as  of  the  quadrate  coy 
enW  the  gall-bladder  which  lies  in  a  hollow  between  them.  Exceptionallythe  gall- 
bkdder  is  entirely  surrounded,  and  is  attached  to  the  liver  merely  by  a  narrow  old. 
The  pJr^toneum  i  continued  over  the  cystic  duct  to  the  edge  of  thelesser  omentum 
to  be^pSTtW  described.  The  entire  under  surface  of  the  left  obe  is  also  covered 
Ly  perTtreum^  continuous  with  the  preceding.  The  parage  of  the  finger  o^^^^^^^^ 
surface  to  the  right  is  interrupted  at  the  front  by  the  end  of  the  falcifonn  hgamen* 
b^fw^n  it  and  ?he  quadrate  W.  At  the  back  farther  progress  to  the  nght  is 
stopped  by  the  lesser  omentum  in  the  fissure  of  the  due  us  venosus.  All  the  peri- 
toneal covering  of  the  liver  has  thus  been  accounted  for.  excepting  that  of  the 
caudate  lobe  and  of  the  lobe  of  Spigelius.  „„„„*„„ 

The  postro-hePatic  or  lesser  omentum  (liRamentum  hepatogastrium,  omentum 
minus)  is  that  part  of  the  original  anterior  mesentery  '^""''"ting  the  stomach  and 
the  beginning  of  the  duodenum  with  the  liver.  It  must,  theoretically,  have  been 
origin^y  a  median  antero-posterior  fold,  but  it  is  now  so  twisted  in  consequence  o 
thJ^change  in  position  of  the  stomach  as  to  be  chiefly  nearly  transverae  Its  line  of 
attachment  to  the  stomach  is  along  the  lesser  curvature  from  the  gullet  past  he 
pylorus,  continued  onto  the  first  part  of  the  duodenum,  where  it  crosses  from  the 
Top  to  the  left  of  the  gut,  until  it  passes  the  common  bile-duct  (by .^hicji  'he  duct, 
of  the  liver  originally  grew  out  of  the.gut)  with  its  companions,  the  hepatic  artery 
andThe  porul  vein  It  is  formed  by  the  union  of  the  peritoneal  layers  covering 
?«p«Sively  the  front  and  back  of  the  stomach  and  the  sides  of  the  duodenum  con- 

no 


icnm  showing  «»rly  «rtmnf«i»nt  ol  P«rl«««l  "ncl.  vi.ceril  pCTlto- 
_      ^ue  p«rietar;>-ellow,  right  side,  red, left  iideolvnceral.    /..liver; 
!5,  stomach '  5,  spleen ;  P.  pancreas  ;  *■.  kidney. 


Uia 
neom. 


1746 


HUMAN  ANATOMY. 


1  Ji 


\r 


Pio. 


tinuous  with  them.  The  two  layers  join  at  the  bundle  of  vessels  just  mentioned, 
thus  forming  a  fold  which  is  the  termination  of  the  lesser  omentum  on  the  right, 
known  as  the  duodtno-hepatic  omentum  (ligamentum  hepatodnodenale).  The  lesser 
omentum  is  sometimes  described  as  prolonged  across  the  first  part  of  the  duodenum 
to  the  transverse  colon,  fusing  with  the  greater  omentum.  This  is  only  an  acci- 
dental modification,  although  a  very  common  one.  An  accessory  fold,  the  duodeno- 
cystic  ligament,  is  prolonged  to  the  right  from  the  front  of  the  lesser  omentum, 
around  the  cystic  duct  from  the  gall-bladder.  The  hepatic  attachment  of  the  lesser 
omentum  is  to  the  transverse  fissure  of  the  liver  and  from  its  left  end  to  the  fissure 
fA  the  ductus  venosus.     From  the  point  at  which  the  latter  reaches  the  diaphragm 

the  two  layers  diverge,  the 
'*'*•  left  one  passing  to  the  lower 

side  of  the  left  lobe  and  the 
right  one  to  the  lobe  of 
Spigelius.  The  structure 
of  the  lesser  omentum  is 
dense  and  fibrous  at  the 
right.  It  is  very  delicate  in 
the  middle,  but  somewhat 
thicker  at  the  left  end.  The 
fold  siround  the  vessels  at 
the  free  edge  (Fig.  1473) 
forms  the  anterior  border 
of  xiat  foramen  of  Winslow 
(foramen  epiploicum),  a  nar- 
row part  of  the  peritoneal 
cavity  by  which  the  general 
cavity  communicates  with 
that  behind  the  stomach 
which  has  been  formed  by 
the  rotation  of  that  organ 
and  the  inordinate  growth 
of  the  mescw^trium.  The 
Of   the  three  vessels  in 


I>iagnin  showing  cbannd  relation  of  vifccral  peritoneum  in  consequence 
of  twisting,  so  that  oriKinal  right  and  left  sides  of  mesentery  of  small  intes- 
tine and  of  part  of  colon  have  exchanged  places.  The  detached  portion 
which  is  twisted  is  supposed  to  be  attached  :it  a  higher  level.  D,  duode- 
nunij  C,  C.  ascending  and  descending  colon  ;  y,  amallintestine  j  K,  kidney ; 
D,  C  t  are  being  displaced  towards  posterior  wall. 


foramen  is  circular,  with  a  diameter  of  from  2-3  cm. 
the  fold  forming  its  anterior  border,  the  portal  vein  is  the  posterior  at  the  point 
of  entrance  into  the  liver,  with  the  hepatic  artery  in  front  on  the  left  and  the 
hepatic  duct  in  front  on  the  right.  The  cystic  duct  is  really  in  an  accessory  fold. 
The  hepatic  artery,  which  passes  along  the  left  side  of  the  duodenum  and  turns 
upward,  is  the  vessel  that  most  definitely  bounds  the  foramen  in  front.  The  duo- 
denum lies  below  the  foramen,  but  its  loteer  border  is  often  formed,  not  by  the 
gut,  but  by  a  fold  of  serous  membrane  arising  from  it.  The  foramen  is  bounded 
behind  by  the  vena  cava  and  ahove  by  the  caudate  lobe  of  the  liver,  which  is  covered 
by  peritoneum. 

The  Posterior  Mesentery :  Part  I. — The  posterior  mesentery  arises  from  the 
spine,  with  the  aorta  between  its  folds.  The  first  part  is  the  mesogastrium,  in  which 
run  the  branches  of  the  coeliac  axis.  It  will  be  remembered  that,  except  at  the 
fundus,  this  is  attached  to  the  greater  curvature  of  the  stomach,  which  was  originally 
the  posterior  border,  but  which  has  turned  to  the  left.  The  spleen  and  most  of  the 
pancreas  are  developed  in  this  fold,  which  grows  inordinately.  We  must  trace  it  both 
m  a  horizontal  and  m  a  sagittal  plane.  To  understand  the  horizontal  arrangement, 
it  is  sufficient  to  remember  that  the  original  mesentery,  which  ran  straight  forward 
from  the  spine  to  the  stomach,  in  its  subsequent  excessive  growth  describes  a  loop 
to  the  left  (Fig.  1470),  so  that  the  original  left  side  of  the  mesentery  near  its  root  faces 
backward,  and  later,  after  the  bend  of  the  loop,  forward,  ultimately  covering  the  an- 
terior wall  of  the  stomach.  This  fold  forms  a  great  pouch  behind  and  below  the 
stomach  called  the  lesser  cavity  of  the  peritoneum  (bursa  omentalis),  which,  of  course, 
is  continuous  with  the  general  cavity.  The  mesothelium  of  the  left  side  of  the  mes- 
entery nearly  to  the  spleen  fuses  with  that  of  the  posterior  wall  o*  the  abdomen,  so 
that  the  splenic  vessels  and  the  pancreas  which  are  in  it  come  to  lie  behind  the  per- 


i. 


THE   PERITONEUM. 


1747 


manent  serous  covering  of  the  posterior  abdominal  wall,  which  here  is  that  o  the 
SS  right  side  of  the  mesogastrium.  The  spleen,  and  perhaps  he  tail  of  he 
S2rL.  Tie  free,  surrounded  by  peritoneum.  If  the  hand  be  introduced  into  he 
K^ondriuk,.  it  slides  along  the  wall  behind  the  sp^een^o  the  pomt  at^whjch 

F,o    147a.  posterior      ill  and  pass  in 

a  fold,  tht  .  If  no-renal  liga- 
ment, to  the  hilum  of  the 
spleen.    From  this  position 
tiie   hand   can    be   carried 
arounvl    the   spleen  to  the 
front  of  the  vessels  at  the 
hilum  and  thence  tf)  the 
right   along   the  continua- 
tion of  the  mesHgastrium  to 
the  greater  curvature  of  the 
stomach,  where   its  layers 
separate  to  coat  the  front 
and  back  of    that   organ. 
The  part  of  the  mesogas- 
trium between  the  stomach 
and  the  spleen  is  the^oi/ro- 
spUnic  omtntum.  The  right 
layer  of  peritoneum  of  the 
mesogastrium,   lining  first 
the  hind  wall  of  the  abdo- 


Diaimm  showinu  later  sUije  where  secondary  tneKntery  is  Ipmvrf  and 


men  and  then  the  back  of  the  stomach,  bounds  the  lesser  cavity  of  the  pentoneunL 
TZzastr^phr^nic  ligament  is  a  small  vertical  fold,  usuaUy  found  extending  fom 
the  Irfforthe  end  of  the  oesophagus  to  the  top  of  the  stomach.  Near  it  is  often 
'anoth  ,  the  ..S^li'  ligalJof  the  spleen,  "^enjng  from  the  diaph-gm  to 
the  too  of  that  onran,  of  which  it  may  enclose  a  small  part.  It  marks  the  upper 
oart  o?the  hne  ofTeflection  of  the  mesogastrium  from  the  posterior  abdominal  waU 
^C^phr^Tolicfold,  also  derived  from  the  mesogastrium,  is  a  horizontal  shell 
with  a  free   anterior  semi- 

lunar  edge  forming  the  floor  ""•  "♦"• 

of  a  niche  for  the  spleen. 
It  extends  from  about  the 
eleventh  rib  inward  onto  the 
upper  surface  of  the  trans- 
verse colon.  That  this  liga- 
ment is  really  a  part  of  the 
mesogastrFum,  and  not  a  lig- 
ament of  the  colon,  is  shown 
by  development,  as  well  by 
its  existence  (as  in  the  mon- 
key) when  the  descending 
colon   is  unattached  to  the 

wall. 

The  Greater  Omentum. 

We  are  now  to  trace  the 

mesogastrium    in  a   sagittal 

plane   downward   from   the 

greater    curvature    of     th" 

stomach.      On  opening  t 

abdomen  the  first  tb'ng  that  .        ,         ^  \    ™t,;^»,  u 

appears   below  the  stomach  b  the  greater  amentum  (omentum   "»>"^)-  ^'''^'J  « 

spread  like  an  apron  over  the  intestines.      It  is  that  part  of  the  mesogastrium 

:Ch    ITILJ  in   front.       The    terms  ^-'--'"-.^"^'^-'^Lt^he  '^^^^ 
are  but  names  for  different  parts  of  this  structure.     It  extends  from  the  greater 


Diagrammatic  action  pawinK  through  level  of  f"™"*"  »'  y^^}"^^ 
winB^elalions  of  parietal  an?!  visceral  perUnneum««^  mc 


USUiiH  CM  Rastrtihepalic  omentum,  contammK  I""^""  «'"  Z^^?" 
^Uc  knen^  ( //)^n.l  bile^uct  ( /?);«.  stomach  ;  6.S,  «lsln«.plenic  omen- 
tum ;  LK.  lieno-renal  omentum ;  f'C  A.  vena  cava  an.l  aorta. 


1748 


HUMAN  ANATOMY. 


curvature  of  the  stomach,  where  it  is  continuous  on  the  left  with  the  double  layer 
coming  from  the  spleen  and  on  the  right  with  that  coming  from  the  inferior  sur- 
face of  the  first  part  of  the  duodenum  ;  from  this  broad  origin  the  greater  omentum 
hangs  down  over  the  intestines  to  near  the  pubes,  where  it  turns  upon  itself  and 
ascends  posteriorly.  Often  it  does  not  descend  so  far,  but  may  be  folded  uf>on 
itself  to  almost  any  degree  and  in  almost  any  position.  F"or  purposes  of  description 
it  is  supposed  to  lie  spread  out  smoothly,  and  to  consist  of  an  anterior  and  a  jjos- 

Fio.  1474. 


Ensiionn  cartilage 


Liver- 


Uall4>laddcr. 


Ascendinjc  colon 


Carcuifi 


DescendJtiK  colon 


iginoid  tiL'Xurb 


l*rulisturht:d  abdominal  viscera  of 


t)  subject ;  liver  and  stomach  abnormally  large,  hence  the  exaggerated 
,  ip.ireiit  tniiiH\erse  iN>stti<>n  of  stomach. 


terior  fold  (  Fijj.  1467).  The  former  passes  down  over  the  transverse  colon,  but  with- 
out adhering  to  it.  The  peritoneum  on  its  anterior  surface  faces  forward  into  the 
greater  peritoneal  cavity,  while  that  on  its  posterior  surface  looks  into  the  lesser  one. 
On  turning  backward  upon  itself,  it  runs  up  to  the  transverse  colon.  If  this  were 
literally  tnic,  it  is  evident  th.it  the  lesser  cavity  would  extend  from  behind  the  stomach 
over  the  colon  down  into  this  fold  (recessus  inferior  omentalis)  of  the  greater  omen- 
tum, and  in  fact  this  is  actually  the  case  in  the  fuetus  (Fig.  1439)  and  exceptionally 


m 


THE  PERITONEUM. 


1749 


in  the  adult ;  but  generally,  except  iuj  J-'-^^'^-t'^^^^^^^^^^^ 
In  the  adult,  when  the  returning  «°W  f^.^^"?  J^^,^^  and  re"niti"K  ^^"^  "•  '"  ^ 
composing  it  seem  to  diverge  to  «"'^>°*1,'J^ '"'!^""^„^^"running  across  the  back  of 
cont&upw^d^  t^ej«n-«e  n--t"ai  ext';::iry'and  apparently  con- 
the  abdomen,  to  be  a»cnDea  ater.      i  m  ^ggogastrium,  or  mesentery  i>f  the 

tradictory  arrangement  by  which  a  Pf"  ot  the  mesoga^         ^  explanation 

stomach,  has  become  also  »»»^  "'"^"'/"^^y  •"i.^'^"  °'  em^^  is  very  different.  In 
is  furnished  by  embryology,  since  'f ^^/"«"!*  .^^^^ef  omentum  pSses  up  in  front 
the  foetus  (Fig.  1439)  «»>^'-^*"Tlnl  tt  lowe^r  Srder of  the  ,>a)^eas.  The  pos- 
of  the  colon  to  the  posterior  wal  f l°"g  t»^f J°*^;  ^,Xer  of  the  original  mesogas- 
terior  layer  of  the  greater  omentum  s  '"  *f »  f  ^  '^"  '^l^\  „„(  „i,h^,he  pancreas, 
trium,  which  we  should  be  ab  e  to  fdlow  to  die^orta.  ^^^^J^^  J  ^  -^j,  ,he 

Xl^llwC  tt^^Hg^t  l"nThig?:nXLt  "^^nSe^^^ear  thespleen  it  Joins. 

from  the  vessels  that  course  through  ,t.  f^^'l  ^  ^^^^^nJ^^Lt  is  found  al)out 
tissue  which  supports  the  m^'»;^''"'^,„;"^^!:  ^a^ed  wTth  it  The  two  lavers..f 
the  vessels,  and  in  some  cases  »he jmen  urn  is   oaded  w«n  n^  ^^  ^ 

serous  membrane  are  sometimes  »^|""*"yJ='"^2s'orthe  omentum  atrophy  and 
double  origin  can  be  recognized      Sometnnw  parts  01  t^  k      ^^^^ 

disappear,  leaving  ^^^"dows,  or /.«../r^^^^^^^^  .Series  at 

arteries  are  long  and  very  slender.     T^^«y*"!*'™7aiifht  downward  to  the  folded 

colon,  it.  continuation  from  bdow  the  !»»=«»»■  ,„  ,,,'  dZrio,i„„  of  the  fold, 
colon  «  the  posteriorUyer  ol  >Kf «""  ~'°'"  „„';cS.nr3^t£  aSUion.  to 
of  the  adnlt  in  a  aigitul  plane  it  wa.  "«^7;  ,?li'S,°into  the  stomach  tack 
,,,e™e,heno,Tn.lc™,»a^.of*Y^^™^^^^^^^^ 

the  median  vertical  \o\A—piica  gastro-pancremuu  ,.  '     ■    .    j^    card  a.     On 

and  extending  upward  behind  the  lobe  of  f  P'Kr:"\^;^\^o„fof  the  peritoneum  over 
pocket  behind  the  liver  (recessus  superior)  a.-^V*  /?hrE,rvenosus  which  meet 
is:  left  of  the  .inferior  vena  cava  and  th^^^^^^^^^^ 


I750 


HUMAN  ANATOMY. 


I    ' 


i 

4 

ri 


Ih 


over  onto  the  right  side  against  the  right  of  the  spinal  column,  to  the  peritoneal 
covering  of  which  it  has  grown  with  the  transformation  into  connective  tissue  of  the 
right  serous  covering  of  its  mesentery.  The  second  or  descending  portion  of  the 
duodenum  lies  against  the  right  of  the  column  under  the  permanent  parietal  peri- 
toneum, derived  from  the  mesocolon,  as  is  shown  later.  The  great  difficulty  of  un- 
derstanding the  lesser  cavity  is  that  in  man  the  duodenum  rises  to  so  near  the  liver 
that  the  entrance  to  the  vestibule  at  the  foramen  of  Winslow  is  very  small.  If,  as  in 
many  animals,  these  parts  were  more  distant,  it  would  be  evident  that  this  is  a  pouch- 


Fio.  1 475. 

Hepatic  artery 


Gaitro-hepatic  omentam 


Accidental  peritoneal  (old 

Pylonia 
Firvt  (tart  of 
duooeniun 


Foramen  of  Winslow 

Gaitro- pancreatic 
fold 


Stomach 


Peritoneum  lining  posterior 
wall  of  lesser  sac 


Transverse  coloa 


Greater  omentum,  cut 


Spleen 


Pancreas 
Folds  of  greater  omentum 

Gastro-splenic  omentum 


The  subject.  King  on  its  back,  is  seen  from  the  left  side ;  the  stomach,  except  fundus,  is  turned  over.  The  greater 
omentum  has  been  cut  below  the  greater  curvature  of  the  stomach  so  as  to  open  the  lesser  sac  to  show  the  foramen 
of  Winslow  from  the  left  side. 


I''  I 


III' 


■  S< 


like  formation,  the  mouth  of  which  is  behind  the  edge  of  the  lesser  omentum.  The 
relations  to  the  mesogastrium  of  three  branches  of  its  artery,  the  coeliac  axis,  are  as 
follows.  The  splenic  artery,  in  the  adult  condition,  lies  entirely  behind  the  perma- 
nent peritoneum  to  near  the  hilum  of  the  spleen,  where  the  mesogastrium  is  no 
longer  attached  to  the  wall.  It  then  sends  its  terminal  branches  to  the  spleen,  the 
gastro-epiploica  sinistr.i  to  the  gre.iter  curv.iture  of  the  stomach,  and  the  vasa  brevia 
to  the  fundus.  The  gastric  artery,  originally  in  the  mesentery  of  the  duodenum, 
reaches  the  cardiac  end  of  the  stomach  through  the  piica  gastro-pancreatica,  and 
then  runs  between  the  layers  of  the  lesser  omentum  along  the  lesser  curvature. 


H 


THE  PERITONEUM. 


1751 


Til.  henatie  Mterv  reaches  the  duodenum  through  its  mesentery,  and  crowesthe 
S  .iWthrS?  to^lS  it  gives  branches  f  hence  it  ru.«  in  or  near  the  edge 
d  ^leMer  omenium  at  the  foramen  of  VVinslow  to  the  portal  fissure. 


Fio.  I476- 


Ga!itri>-iiam'rcatic  fold 


Vettibulc  o(  Icuer  uc 


Lcsiser  or  (astro-bepaiic 
oiii«tituin. 


|.ieii<>-renal  fold 

J>  Lcswr  Site  uf 
|>cril»iiieum 


Cutro-iplcnk  omcntUBi 


Greater  omcntttm 


^Sf^^ 


denum  {D)  at  floor  of  toP'""""' Wm»^°S' 'f?^l,  ™»?'>I^^i^^^^^^  «l."  h  lies  to  left  of  .orta. 

The  Posterior  Mesentery:  Part  II.-This  is  that  part  of  the  peritoneum 
derivL  from  the%riginal  mesente^  of  the Jejuno-ileum.  t^e  -cum  pd  the  a^^^^^^^ 
in«r  and  transverse  colon.     Its  artery  is  the  supenor  mesenteric.     I    the  t"nsverse 
ciorwith  the  «^ter  omentum  be  turned  upward  and  the  sma  1  mtest.ne  to  he  r^ht 
the TefTside  of^e  mesentery  of  the  jejuno-ileum  is  seen  running  from  the  left  of  the 
too  o    the  body  of  the  second  lumbar  vertebra  to  the  nght  sacro-ihac  joint.     At 
the  beginninTthis  is  attached  to  the  lower  side  of  the  gut  where  it  -"akes  a  sharp 
flexure  at  the  origin  of  the  jejunum  from  the  end  of  the  duodenum.     This  flexure 
fiesTrectly  b  fX  of  the  iJrta.  which  usually  Ues  covered  w  th  P-ntoneum  at  the 
STck  of  the  abdomen,  with  the  fourth  part  of  the  duodenum  to  the  righ   of  «     (Tlus 
relation  is  more  fully  described  with  the  duodenum  (page  1647)-    The  line  ot  attach 
mlrof  rresentLy  (Fig    .477)  descends  over  »!- ^-^^^^^,^^1^,  J^^^^^ 
crossing  the  third  part  and  the  inferior  vena  cava.    The  greatest  breaatn  o!  ine  mes 
OTW  the  free  border  is  from  ^23  cm.  (8-^  in.).     It  reaches  its  full  breadth 
S  S  once  after  its  origin.    Usually  it  becomes  very  r^-"?;^-^^^''P'£y,l^^^^. 
—at  its  termination  ;  but  this  varies  much,  as  does  also  the  point  of  that  terniina 
;^n     ThJTonnectiv;  tissue  between  the  layers  is  thickest  and  the  lymph-nodes  mc«t 
numerLs  near  the  attached  part.    Except  in  very  fat  subjects,  \he«  «  »f  ^^'*^"e 
the  layers  of  peritoneum  besides  the  vessels,  within  an  inch  or  so  of  the  gut^    The 
surJrK)r  mesenteric  artery  can  be  felt  at  the  top,   entering  it  from  under  the  lower 
Kr  of  the  pLnTreS     The  peritoneum  can  bi^followed  at.  any  point  across  from 
the  left  to  the  ^ght  side  of  the  mesentery.     From  the  latter  it  is  fol  owed  along   he 
Ste   or  wall  tl  the  kidney  and  the  ascending  colon,  lying  on  the  front  of  the 
K   where  they  are  in  contact.      The  membrane  crosses  the  ascending  colon 
Sg  itsVsterbr  surface  without  covering  attached  to  the  parts  behind  it,  and 
Ste?  ^velops  the  caecum,  passing  on  the  left  into  the  mesenten^     Very 
S?he>ritoneum  is  carried  for  an  inch  or  two  behind  the  lower  pa^  of  the 
Mcending  ^lon.     It  then  passes  into  the  left  flank  and  the  pelvis  without  incident^ 
Developmen  shows  that  this  is  a  departure  from  the  original  condition,  in  which  the 


175* 


HUMAN  ANATOMY. 


liil 


nil 


attachment  of  this  mesentery  was  exceedingly  short,  merely  broad  enough  to  contain 
the  superior  mesenteric  artery.  The  so-called  ptrmantnl  mesentery  is  caused  by  the 
fallii;g  over  to  the  right  of  the  fold  of  mesentery  for  the  ascending  colon,  twisting  the 
membrane,  and  the  downward  growth  uf  that  part  of  the  gut  which  brings  the 
caK:um  down  from  under  the  liver  to  the  right  iliac  fussa.  The  twist  having  occurred, 
and  the  ascending  colon  having  fallen  against  the  abdominal  wall,  the  fold  ))caring 
the  ascending  and  transverse  colon  becomes  fused  with  the  peritoneum  of  the  pos- 
terior right  abdominal  wall  on  the  right  of  a  line  from  the  b^inning  of  the  jejunum 


Right  lupim- 
muu  body 

Venacavm 
Porul  vein 


FlO.    1477- 


Duodcni 


Splenic  flexure  ol 
colon 


Jejunum 


Showing  relations  and  attachments  of  mesentery  of  small  and  targe  intestines ;  greater  part  of  transverse  colon, 
of  sigmoid  flexure  and  of  jejuno-ileum  has  been  removed,  the  latter  by  cutting  through  the  mesentery  near  its 
posterior  attachment. 

to  the  end  of  the  ileum,  the  part  bearing  the  small  intestine  remaining  free.  This 
oblique  line  of  attachment  becomes  the  permanent  mesenter}*.  The  peritoneum  to 
the  right  of  it,  as  far  as  the  ascending  colon,  forms  the  permanent  parietal  perito- 
neum, having  fused  with  the  original  parietal  layer  behind  it.  When  the  colon 
under  the  liver  becomes  the  transverse,  the  fwrt  nearest  to  the  latter  continues  free 
and  hangs  down  as  a  transverse  fold,  on  which  the  >ifreater  omentum  lies,  and  sub- 
sequently fuses,  as  already  described.  The  transverse  colon  is  attached  by  the 
transverse  mesocolon  (also  a  secondary  adhesion)  to  the  front  of  the  right  kidney 
and  to  the  posterior  wall  across  the  second  part  of  the  duodenum  and  the  head  of 


THE  PERITONEUM. 


I75i 


,1...  nancreas  alone  the  lower  border  ol  that  gland  to  the  left  kidney  (  Fig.  I477>  !» 
ieaC  b^dthb  wme  five  or  .ix  inches.  (For  a  fuller  description,  «...  ,H.r.toneal 
greatest  »>'^«f5""  *!  """^  "J  .  .  jh^  breadth  oJ  the  transverse  mcsoc..l„n  is  from 
7inrm  (S^TnT.'  I^the  adit  ilu.  fu^  with  the  greater  omentum  as  already 
d^S.  The  superior  mesenteric  artery  enters  thin  mc.sentcry  u.uler  t ho  ,«ncre;« 
SgwSfromi.|t<.conj.x^ 

»'^Ke'.LirTnd\L^^^^  I"  «he  adult  the 

rChtcdic  artery  runs  behind  the  permanent  posterior  parietal  ,jeritoncuin. 

STnSrrS-un"?^^^^^^^^^^  abdominal  wall,  over 


Fio.  1478. 

CKvnm  S"«>"  Intntinc 

\    — ■ 


Treiitveric  cokm 


AtccndiriK  colon 

Lower  end  of  ileum 

Mnentery 


Duodrnum 

Dncniiliiix  lolon 
MesenUry 


Poaterior  wall  ol  abdomen  _i 


Bladder 


I      1.11.1  „i  ihrM.  von  •  the  usual  relations  would  be  restored  by  bringinis  upper  dotted  line 
Mesenterium  commune  in  child  ol  three  year. .  «J«^;^^  ^J^^  lower. 

the  lower  oart  of  the  left  kidney,  and  over  the  descending  colon  which,  although 
S^ching'th^t^o^'rglnriies  chiefly^  external  to  it      The  P-tX^:^s^^h' t'Jhe'^^r" 

freedom  of  the  fold,  from  that  point  to  the  middle  °' ''^I^Xl;  Wei  the  rectum  is 
chief  forms  are  described  on  page  167..)  Be>°"*L'»'^  '*'  ^'  ^Lmy  diverging 
parUy  uncovered  behind,  where  the  mesentery  ceases,  and  its  gradually  aivergmg 


«754 


HUMAN   ANATOMY. 


: 


l- 


h 


1ft 


m 


;i 


lines  uaa>  onto  its  sides,  leaving  the  termination  ol  the  gut  without  any  peritoneal 
covenng.  The  branches  of  the  inferior  mesenteric  artery  in  thit*  region  are  the  lift 
colica  sinistra,  which  runs  behind  the  |>ermanent  parietal  peritoneum  ;  the  sigmoid, 
which  does  the  same  until  it  reaches  the  part  of  the  mesentery  which  is  free  :  and  the 
superior  hemorrhoidals,  which  descend  m  the  lower  part  ol  the  original  mesentery 
until  they  reach  the  retroperitoneal  area  behind  the  rectum. 

PRACTICAL  CONSIDERATIONS  :    THE  PERITONEUM. 

The  development,  topography,  and  relations  of  the  i)eritoneum  have  already 
been  sufficiently  described  It  remains  to  consider  its  diseased  conditions  and  those 
in  which  it  is  an  important  or  controlling  factor  in  the  production  of  disease  in  so  far 
as  they  are  influenced  by  anatomical  circumstances. 

PerHonUis  is  the  most  common  and  the  most  serious  of  peritoneal  diseases.  The 
separate  consideration  of  wounds  of  the  peritoneum  is  not  necessary,  as  traumatism, 
unassociated  with  infection,  produces  merely  hyperemia  and  exudation.  The  pro- 
cess is  for  convenience  known  as  plastic  or  reparative  |)eritonitis,  a  term  also  applied 
to  those  forms  of  true  ( infective)  peritonitis  in  which  the  bactericidal  and  absor})tive 
powers  of  the  membrane  itself  and  of  its  serum  have  resulted  in  the  destruction  or 
thf  isolation  of  the  invading  oacteria. 

The  anatomical  routes  by  which  bacteria  may  reach  the  peritoneum  are  : 

1.  From  without,  as  through  an  accidental  or  operative  wound. 

2.  Prom  within,  as  from  an  escape  of  the  micro-or^nisms  through  intestinal  walls 
leaky  as  a  result  of  strangulation  (as  in  intestinal  hen.ias  or  volvulus  or  intussuscep- 
tion) or  of  inflammation  (as  in  appendicitis)  ;  or  through  an  actual  i)erforat'  .n,  as 
in  gastric  ulcer,  typhoid  fever,  or  intestinal  cancer. 

3.  Through  the  blood-  or  lymph-channels,  as  in  many  cases  of  tuberculous 
peritonitis  and  possibly  in  so-called  rheumatic,  nephritic,  and  other  clinical  forms  of 
peritonitis,  in  some  of  which  the  infecting  organism  is  still  unknown. 

4.  Through  the  Fallopian  tubes. 

The  peritoneum  is  not  equally  susceptible  to  traumatism  or  to  infection  on 
b...h  its  surfaces  or  in  all  its  parts.  The  exterr.al,  areolar,  or  "wrong"  side  (page 
1740 )  may  be  extensively  separated  from  the  subjacent  structures  (as  in  the  extraperi- 
toneal approach  to  the  ureter  or  to  the  common  iliac  artery),  or  may  be  in  contact 
for  a  long  time  with  an  inflamed  or  a  suppurating  surface  (as  in  perirenal  or  other 
retroperitoneal  abscess)  without  damage  to  the  mesothelisil  or  free  surface  of  the 
membrane,  and  with  but  littie  risk  of  the  supervention  of  peritonitis. 

On  the  other  hand,  a  small  penetrating  wound  made  with  a  dirty  instrument  will 
probably  set  up  a  diffuse  and  perhaps  a  fatal  inflammation. 

The  difference  in  results  is  due  to  the  delicacy  and  vulneribility  of  the  mesothe- 
lial  as  compared  with  the  fibrous  surfar  ,  to  the  great  absorbent  power  of  the  former 
(vide  infra),  the  area  of  which  is  about  equal  to  that  of  the  cutaneous  surface  of  the 
body,  favoring  toxemia  if  the  bacteria  and  their  toxins  are  not  destroyed  or  encap- 
sulated ;  to  the  excellent  culture  material  supplied  by  blood-dot  or  by  the  injured  or 
necrotic  epithelial  surface  ;  and  to  the  involvement  in  diffuse  or  spreading  cases  of  the 
peritoneal  covering  of  the  neighboring  viscera,  particularly  the  intestines. 

These  facts  determine  the  surgical  rule  that  in  doubtful  cases  of  bullet  and  stab 
wounds  of  the  abdominal  wall  it  is  well — under  aseptic  conditions — to  enlarge  the 
wound,  ascertain  the  presence  or  absence  of  penetration,  and  cleanse  or  drain  if 
necessary. 

Not  only  are  the  two  sides  of  the  peritoneum  thus  unlike  in  susceptibiliiy  to  m- 
fection,  but  a  similar  difference  exists  between  the  parietal  peritoneum  and  that  cover- 
ing the  viscera.  The  former,  applied  by  a  layer  of  fat-containing  connective  tissue  to 
the  relatively  immobile  muscular  layer  of  the  abdominal  wall,  is  less  easily  inflamed, 
or  if  inflamed  develops  a  less  diffused  and  less  quickly  spreading  form  of  peritonitis 
than  does  the  thinner,  more  sensitive,  and  more  vulnerable  visceral  peritoneum, 
especially  that  covering  the  most  mobile  of  the  abdominal  viscera,  the  small  intestine. 

So,  too,  peritonitis  originating  in  certain  regions  is,  by  reason  of  the  facility 
with  which  they  may  be  shut  off  by  adhesions,  less  threatening  in  its  course  and 


PRACTICAL  CONSIDERATIONS.  THK   I'F.RITONEUM. 


1755 


Pelvic  jierit"- 
aml   subhf|»atic 


more  amenable  to  .urgical  treatment  than  that  beRinninK  tlsewhere. 
nitis   uara-appcndioil  and  iMracolic  i.eritonitw.   »ubdiaphrajrmatic 
SoSitb,i^ peritonitis  limit«l  to  tL  l«»er.  fH.ritonc;al  «c  iv,d.-  '«/-)»"„;'' V'^^ 
S«  that  are  l«»  danRerous  than  i»  peritonitis  beRmnm^  am-.n^  the  »hiftmK  coil* 

"•""Se'Somical  «<.urc«  of  peritoneal  infection  may  therefore  be  arranged  ap- 
nroximLteirin The  order  uf  their  Rravity.  as  follows  :  ( «  )  ,H.rioratKms  or  wounds  of 
The  Sr  m  «  ineV(*)  ixrriorations  or  wounds  of  the  stomach  or  larjce  mtest.m.  : 
U)  Sor^S  or 'wounds  .>f  other  viscera,  including  kidneys,  »«t-^.  »'»^;^^'«^,^;  P;"', 
irias  and  bile-passanes  ;  {d)  entrance  of  l«cteria  by  contmuous  «row  h  throuKh 
a^g=«rlC^nal  walls;  (.)  bacterial  migrat on  through  stra.«uU^^ 
tineT(/)  infection  through  the  Fallopian  tubes  ;    (g)  wounds  of    the  aNlommal 

**"  ThriSnuement  is  based  upon  two  factors  :  the  number  and  virulence  of  the 
bacteria  wSare  likely  t..  gain  ^trance,  and  the  op,x,rtunity  wh.ch  w.ll  j.rolMbly 
SSdtXXe  form'Ltion  of  limiting  adhesions.  The  latter  factor  ^"uc  l|e  co  ; 
Sdered  from  the  anatomical  stand-point.  ;is  the  variations  in  the  intensity  of  tht  in 
flamimtion  due  to  varving  forms  and  doses  of  the  invading  bactena  arc  influenced  by 
fhe  sTe Ta  wLnd  or'other  traumatism,  or  of  an  ulcerative  or  "'^^'^if^-Vr.ti 
Y^„.».;nri  vi«^a  For  example  and  for  reasons  already  indicated,  pe  tratmg 
tS^boveXlevel  of^eTim^  less  likely  to  pr-xluce  fataT:   M.on.tis 

rCn  a?e  tK  n  the  low.r  half  of  the  abdomen.  The  differences  in  this  res,3ect  be- 
hT^^nwoun^  or  perforations  of  the  stomach,  of  the  different  portions  of  the  M.iall 
St^dne?  and  oTthTe  lar^e  intestine  have  been  described  in  relauon  to  the  an.Uomy  ..f 

'''^T^e^SltWe^irutTinfection  is  usually  in  direct  proportion  to 
the  nor^LTy^f  its  mesotiielial  coat,  which  is  les-     ed  by  all  forms  of  traumatism 
"eluding  handling  or  sponging,  or  irrigation  with  strong  antiseptics.     To  a  ceru  n 
exter'KnstKTeness  of    he^toneum  and  the  rapidity  with  which  it  responds  to 
Son  isTcon^^^ive  proc^.    The  prompt  exud      m  wh.ch  follows  either  injury 
rSon  ohen'Ses  t'he  affected  are'a  Uprevonts  a  fatal  'f-r--y^^;;^^Zl 
tion    The  ereat  absorptive  power  of  the  peritoneum— which  should  be  studied  als.>  n 
SnnecAionSthVly^pha^'  system-may  be  alluded  to  here  as  it  aids  materially 
^iSng  the  danger  from  infection.     It  has  been  demonstrated  expenmentolly 
that^m  V  to  8  per  cent,  of  the  body  weight  in  fluid  can  be  taken  up  by  the  pen- 
toneum  from  witWn  its  cavity  in  one  hour,  which  is  equ  valent  to  fe  total  body 
weiehTin TenTy-four  hours  ( Wegner ).     The  current  of  this  process  of  absorption  of 
Soneal  3  has  been  shown  to  set  normally  from  the  peritoneal  cavity  towards 
Ae  di^pS   and  to  be  much  hastened  by  elevation  of  the  pelvis  and  lower  abdo- 
men     SmTiUrticles  (carmine,  bacteria,  etc. )  are  carried  through  the  'ntercellular 
Ses  in  the^aphragmatic  peritoneum-"  the  openings  made  by  the  retracUon  o 
KdothelUim"  (Kdly)-iluo  the  lymph-spaces  beneath,  then  into  the  medmstinal 
ymph-Saces  and  glands,  and  then  into  the  blood-current  (Muscatello)^  This  pro- 
c^  go^  on  much  more  rapidly  in  this  direction-towards  the  diaphragm  and  m«l.- 
SrSand^than  does  the  similar  process  beginning  m  the  v>sceral    int^tina^ 
peritoneum  and  associated  with  the  mesenrenc  lymph-nodes,-an  additional  ana- 
lomical  explanation  of  the  greater  fatality  of  visceral  pentonitis 

The  dose  relation  of  the  nerves  of  the  peritoneum  and  of  the  abdomina^  viscera 
to  tho  nerves  supplying  the  abdominal  and  the  lower  intercostal  muscles  has  l^n 
mentioned  in  reir^on  to  appendicitis  and  other  intra-abdominal  lesions  (pag«.  V8. 
T683),  and  is  of  the  high^t  importance  in  connection  with  the  mimical  symptoms 
of  peritonitis.  Hilton  comparer  the  peritoneum  and  the  muscles  of  fje  aMomen  to 
the  synovial  membrane  and  the  muscles  moving  a  joint.  The  "P*  X '''«5 '°"' ^^ 
inflammation  in  either  case  is  due  to  the  reflex  muscular  spasm  resulting  from  the 
correlation  of  the  nerve-supply.  Thus  the  six  lower  intercostals  supplying  tje  com-- 
spondinK  intercostal  muse!.-,  and  pAssing  through  thed.aphragm,  to  which  they  send 
twigs,  are  I  tributed  to  the  skin  over  most  of  the  abdomen,  and  to  the  rectus  ex- 
erS  i.-^  eternal  oblique,  and  transversalis  muscles.  Through  the  splanchnics 
they  join      .  in  the  innervation  of  the  peritoneum  and  of  the  abdominal  viscera.     In 


1756 


HUMAN  ANATOMY. 


a  case  of  injury  to  the  abdominal  wall,  therefore,  the  impression  is  barely  made  upon 
the  skin  before  the  muscles  contract  and  an  attempt  at  protection  is  made.  In  a  case 
of  visceral  lesion  or  of  beginning  peritonitis  the  rigid  contraction  of  the  muscles  in 
closest  nerve  relation  to  the  area  involved  will  constitute  a  valuable  diagnostic  symp- 
tom. In  general  peritonitis  the  board-like,  tender  abdomen,  the  fi.xed  diaphragm, 
and  the  thoracic  breathing  (to  lessen  movement  of  the  abdominal  viscera)  are  all 
phenomena  to  be  understood  only  by  recalling  the  correlation  of  the  nerves  involved. 
The  flexion  of  the  thighs  (to  remove  pressure  from  the  tender  surface  and  to  relax 
the  muscles  as  much  as  possible)  is  a  secondary  symptom  due  to  the  same  cause. 
The  condition  is  in  strong  contrast  with  that  seen  in  intestinal  spasm  (co/ic),  in 
which,  although  the  patient  may  be  doubled  up  with  pain,  pressure  gives  relief  and 
the  loose,  relaxed  abdominal  muscles  may  be  moved  easily  and  freely  over  the  un- 
derlying viscera.  The  intestinal  distention  and  paresis  of  peritonitis  are  due  partly 
to  the  involvement  of  the  nerve-plexuses  of  the  gut  and  partly  to  the  extension  of  in- 
flammation to  its  muscular  walls.  They  are  increased  by  later  vasomotor  paralysis 
and  by  fermentative  decomposition  of  intestinal  contents. 

Other  phenomena  common  to  many  abdominal  lesions,  but  especially  to  those 
affecting  the  peritoneum,  are  due  to  the  relation  of  the  nerves  of  the  latter  to  the 
great  abdominal  nerve-plexuses.  They  have  been  grouped  by  Giibler  under  the 
term  peritonism,  are  indejjendent  of  toxaemia,  and  are  essentially  the  symptoms  of 
"  shock,  ' — subnormal  temperature,  a  running  pulse,  pallor  or  lividity,  quick,  shallow 
breathing,  and  great  mental  and  physical  depression.  The  more  distinctive  peritoneal 
symptoms  are  vomiting  (although  that  is  not  uncommon  in  many  forms  of  shock ) 
and  generalized  abdominal  pain  becoming  epigastric  or  umbilical,  and  later— if  peri- 
tonitis develops — associated  with  tenderness.  In  illustration  of  this  relation  of  nerves 
and  nerve-centres,  Treves  says,  very  truly,  that  almost  all  acute  troubles  within  the 
abdomen  begin  with  the  same  group  of  symptoms,  and  that  until  some  hours  ha\e 
elapsed  it  is  often  impossible  tc  say  whether  a  violent  abdominal  crisis  is  due  to  the 
perforation  of  an  appendix  or  other  portion  of  the  intestine,  the  bursting  of  a  pyo- 
salpinx,  the  strangulation  of  a  loop  of  gut,  the  passage  of  a  gall-stone,  the  rupture  of 
a  hydatid  cyst,  an  acute  infection  of  the  pancreas,  the  twisting  of  the  pedicle  of  an 
ovarian  tumor,  or  a  sudden  intraperitoneal  hemorrhage. 

The  later  symptoms  of  peritonitis — the  board-like  rigidity  of  the  abdominal  mus- 
cles, the  tenderness,  the  meteorism,  the  intestinal  paresis  or  paralysis,  and  the  ascitic 
dulness  in  the  flanks — require  no  further  anatomical  explanation.  The  factors  already 
described,  plus  the  existence  of  profound  tox£emia,  sufficiently  account  for  them. 

Chronic  peritonitis  oi  the  proliferative  type  (said  to  be  found  frequently  in  the 
subjects  of  chronic  alcoholism)  is  attended  by  great  thickening  followed  by  fibroid 
contraction,  which,  in  accordance  with  the  locality  chiefly  involved,  may  cause  (a) 
constriction  of  the  gastro-hepatic  omentum  with  pressure  on  the  portal  vein  and  re- 
sulting serous  effusion  ;  ib)  diminution  in  the  volume  of  the  liver  from  perihepatitis  ; 
(c)  thickening  of  the  omentum,  which  forms  a  hardened  roll  lying  transversely 
between  the  colon  and  the  stomach  :  (d )  shortening  of  the  mesentery  so  that  the 
intestines  are  drawn  into  a  rounded  mass,  situated  in  the  mid-line  and  feeling  like  a 
solid  tumor  ;  (e)  thickening  and  contraction  of  the  intestinal  walls,  the  mucous  mem- 
brane being  thrown  m*  'olds  like  the  valviilae  conniventes  ;  (/)  the  formation  of 
cicatricial  bands  attacht  :  their  ends  to  intestine  and  parietes  or  to  two  portions  of 
the  gut,  and  under  which  other  coils  of  intestine  may  jjass  and  become  strangulated. 

Tuberculous  peritonitis  is  the  most  common  chronic  form  of  the  disease.  The 
infection — especially  in  children  and  males — usually  proceeds  from  the  digestive  tract 
through  the  retroperitoneal  lymphatics  ;  or  from  the  lung  or  pleura  and  bronchial 
lymph-nodes  by  the  same  route  ;  or,  less  frequently,  directly  from  ulcers  within  the 
intestine  ;  in  women  it  often  enters  through  the  Fallopian  tubes.  It  may  be  con- 
veyed by  the  blood. 

Of  the  conditions  described  as  due  to  chronic  peritonitis,  the  omental  thickening 
and  the  retraction  and  thickening  of  intestinal  coils  are  frequently  present.  Agglu- 
tination of  these  coils  is  apt  to  occur  and  to  contribute  to  the  sense  of  resistance  which 
may  l>e  erroneously  interpreled  as  indicating  the  presence  of  a  tumor.  In  addition 
there  are  apt  to  be  (a)  a  sacculated  exudation  in  which  the  effusion  is  limited  and 


PRACTICAL   CONSIDERATIONS:   THE   PERITONEUM.         1757 

ronfined  by  adhesions  between  the  coils  of  gut.  the  parietal  peritoneum,  the  mesen- 
te,!y!  !nd  the  abdominal  or  pelvic  organs  (Osier)  ;  and   (*)   enlargement  at  the 

'"'^Th'TexSSe  of  a  superficial  periumbilical  area  of  redness  and  thickening  is  said 
.o  be  a  symptom  of  this  variety  of  peritonitis  (Fagge),  and  is  even  thought  to  Ik; 
^thn^nomonic  (  Henry ).  It  may  follow  adhesion  of  intestme  to  the  mner  ,«r.etes, 
^  X  protebly  Is  due  to  exten^sion  of  the  inflammation  of  the  partetal  per.toneum 
tilAno-  the  track  of  the  obliterated  umbilical  vessels.  /•    i     .  „.i 

^^^SJdperitonitis  should  be  briefly  considered  from  the  topographical  sund- 

^'"^'Peh'k  fienloniiis,  usually  due  to  infection  by  way  of  the  uterus  and  Fallopian 
tubes  is  ofV^CSy  essened  danger  <.n  account  of  (a.  'he  fact  that  the  so-irce  of 
ElSriLl  supply  is  not  large,  the  endometrium  possessing  a  high  degree  of  uul  e- 
Stance  and  its'^secretion  rendering  its  cavity  in  most  instances  sterile  ( ^V  a  basse) 
fl,  the  comparatively  low  virulence  of  the  bacteria  most  frequently  found  in  tuKil 
nfiction Te  Konococcus  and  bacillus  tuberculosis  ;  and  (O  the  opf>ortun.tv  usually 
S^  (by  the  thickness  and  immobility  of  the  subperitoneal  tissues  iny<.iv«l)  fur 
the£iKcompetent  adhesive  barriers,  including  those.wh.ch  seal  the  openn^g 
of  the  tX  and  conf^Ae  the  infection  to  the  latter  and  its  vicinity  (Fowler  . 

Pue^i^ral  peritonitis  is  much  more  serious,  owing  to  the  anatomical  contl  .  ms 
associaed  with  pregnancy-chiefly  the  vastly  greater  size  and  vascularity  of  the 
mer^fand  S  el^ement  of  its  ijmph-channels-and  to  the  minor  traumaUsms  to 
the  endometrium  which  occur  even  in  physiological  parturition.  These  oHtr  an 
OD  Jrturyforlncreased  dosage  of  bac-teria  and  of  their  toxins.  The  'linger  is 
TnSed  by  the  fact  that  the  invading  organism  is  apt  to  be  a  streptococcus  and  by 
the  usual  Dost-partum  diminution  of  vital  resistance.  .u         i,    i 

Subd^hmgmatic  peritonitis  may  be  confined  to  the  space  between  the  arch  of 
the  d^aoKm  and  the  upper  surface  of  the  liver  to  the  right  or  left  of  the  suspen- 
sory iSmen  It  is  apt  to  assume  a  suppurative  form.  It  may  follow  (or  prececk) 
rpleuralor  pulmonary^  infection.  It  is  commonly  mistaken  for  an  empyema.  1  he 
fnfectbn  is  of  course  at  its  onset  within  the  greater  cavity  of  the  peritoneum  but  is 
o"  en  ^n  shut  off  by  adhesions.  When  it  has  followed  a  perforation  of  the  stomach 
or  duXum  the  abscess  usually  contains  air  (pyo-pneumothorax  subphrenicus 
Ae  Sragm  may  be  pushed  up  to  the  level  of  the  second  or  third  nb.  the  liver  is 
feprSd    fh^rriJ  bul|ing  of  the  right  thorax,  and  the  physical  signs  are  those  of 

P"'Thf  SyTsibdiaphragmatic  peritonitis  which  involves  the  'esserJ>erito^ 
«r.//r  may  orfgLte  in  gastric,  duodenal,  or  colic  perforations,  in  pancreatic  dlseast^ 
or  in  Xer  ways  The  communication  with  the  greater  peritoneum  is  soon  cut  off 
by  Ldhiive  rnflammation  of  the  edges  of  the  gastro-hepatic  omentum  at  the  foramen 

***  ^^Sention  of  the  lesser  sac  with  serum  or  with  pus  follows  and  first  causes  an 
enieastric  swelling  extending  by  gravity  to  the  umbilical  region  ;  on  account  of  the 
E  re^istlnSer'ed  by  ifs  left  boundary-the  lieno-renal  ligament-as  compar^ 
whh  th^  of  the  gastro-hepatic  omentum,  and  because  the  lesser  sac  extends  farther 
Towards  that  side  the  swelling  may  appear  later  in  the  leh  hypochondriac  reg  on. 
As  The  flo^r  of  the  space  is  formed  by  the  upper  layer  of  the  transverse  mes,>cc^on, 
The  colon  UdepreLset  and  never  lies  in  front  of  or  above  the  enlargement,  as  it  A<^ 
nc^  of  renal  tumor.  As  the  space  lies  below  and  behind  the  stomach,  distention 
of  thTfatter  Tf  w  th  liquid,  will  render  the  swelling  less  palpable,  but  may  apparent  v 
increase  its  area  of  dulness  :  if  with  air,  will  convert  the  dulness  into  resonance  and 

^^^^'?L;;^Srev:;:;S:rS^X^  abs«^  n.y  -^e  place  into  any 

S  diaphragm  or,  more  circuitously,  through  the  weakened  intervals  between  the 

sternal   costal,  and  vertebral  portions  of  that  muscle. 

Ihl  appendicular  and  st'^hepatic  varieties  of  localized  penton.t.s  have  been  sufti- 
ciently  described  in  connection  with  the  organs  involved. 


1758 


HUMAN   ANATOMY. 


Cancer  of  the  peritoneum  is  occasionally  primary,  b«t  is  usually  due  to  exten- 
sion from  the  stomach,  uterus,  ovaries,  liver,  or  other  organs.  The  irregular  mass  of 
a  carcinomatous  omentum  cannot  be  distinguished  by  touch  from  the  similar  tumor 
due  to  chronic  peritonitis. 

lYve  peritoneal  cavity  as  a  whole — the  interval  betivi:»n  adjacent  visceral  surfaces 
or  between  such  surfaces  and  the  parietes — may  be  scarcely  more  than  a  pote.itial 
space,  containing  enough  serous  fluid  for  pur{>oses  of  lubrication,  or  may  be  more  or 
less  distended  by  an  eflusion  of  the  same  fluid, — ascites.  Such  eflusion  may  result 
from  (a)  infection  followed  by  chronic  inflammation  ;  {b)  abdominal  tumors,  causing 
irritation  and  pressure  ;  (f )  obstruction  of  the  portal  circulation,  either  terminal,  as 
in  hepatic  cirrhosis,  or  by  pressure  on  the  vein  itself  in  the  gastro-hepatic  omen- 
tum, as  from  certain  pancreatic  or  duodenal  growths,  aneurism,  or  the  exudate  of 
a  chronic  peritonitis  (^vide  supra);  or  {d)  from  conditions  producing  a  general 
dropsy  (of  which  the  ascites  is  but  a  part),  such  as  cardiac  or  renal  disease,  chronic 
empyema,  or  pulmonary  sclerosis.  Ascites  is  recognized  by  (a)  a  flat  abdomen 
bulging  at  the  flanks,  with  prominent  umbilicus  ;  {b)  dulness  in  the  flanks  varying 
with  change  of  posture  ;  (f)  resonance  over  the  uppermost  part  of  the  abdomen 
in  either  dorsal  or  lateral  decubitus  (from  floating  upward  of  the  intestine)  ;  {d)  flue 
tuation.  Sudden  withdrawal  of  ascitic  fluid  may  cause  syncope  in  persons  with 
pre-existing  cardiac  lesions  by  diminishing  intra-abdominal  pressure,  permitting  a 
dilatation  of  the  deep  circumflex  iliac,  the  deep  epigastric,  the  lumbar  and  other 
deep  abdominal  veins,  and  thus  suddenly  lessening  cardiac  blood-pressure. 

The  difference  between  the  peritoneal  cavity  and  the  abdominal  cavity  should 
not  be  overlooked  by  the  student.  A  number  of  the  abdominal  viscera  are  not  intra- 
peritoneal, but  lie  more  or  less  completely  behind  that  membrane.  Thus  the  kidney 
and  pancreas  and  certain  aspects  of  the  ascending  and  descending  colon  and  duode- 
num may  be  wounded,  or  may  be  the  subject  of  infectious  disease,  without  involve- 
ment of  the  peritoneum,  while  similar  wounds  or  infections  of  the  liver,  spleen,  stom- 
ach, or  small  intestine  would  necessarily  include  it  to  some  extent. 

The  parietal  peritoneum,  the  least  sensitive  portion  of  the  membrane  (vide 
supra),  is  thickest  below  and  posteriorly,  and  is  there  connected  loosely  with  the 
abdominal  wall  by  relatively  abundant  subperitoneal  cellular  tissue  containing  fat. 
This  loose  connection  permits  it  to  be  stripped  forward,  as  in  some  operations  on 
the  kidneys  or  ureters  or  on  the  iliac  vessels.  About  the  umbilicus  and  along 
the  mid-line  of  the  abdomen  it  adheres  much  more  closely.  It  is  strong,  bearing 
a  weight  of  fifty  pounds  (Huschke)  ;  distensible,  as  shown  by  the  gradual  stretch- 
ing it  undergoes  in  ascites,  during  pregnancy,  or  in  a  hernial  sac  ;  and  elastic,  as  in 
such  cases  it  returns  to  its  normal  dimensions  when  the  distending  cause  is  removed. 
It  may  be  ruptured  by  sudden  force  without  injury  being  done  to  the  underlying 
viscera. 

From  Its  superficial  position,  the  greater  omentum  is  often  involved  in  penetrating 
wounds  of  the  abdominal  wall.  Wounds  of  the  omentum  are  not  in  themselves  seri- 
ous, except  from  hemorrhage.  The  rapid  adhesive  inflammation  which  follows  injury 
to  the  omentum,  as  to  other  parts  of  the  peritoneum,  may  act  beneficially  by  leading 
to  the  closure  of  an  intestinal  wound  or  perforation  before  extravasation  occurs,  or  by 
favoring  the  localization  of  an  area  of  infection.  It  is  sometimes  utilized  by  the  sur- 
geon to  reinforce  an  intestinal  suture  or  to  cover  intestinal  defects,  especially  in  the 
cjecum  (E.  Senn)  ;  or  to  protect  the  general  peritoneal  cavity,  as  in  some  operations 
on  the  bile-diK  ts.  Through  inflammatory  adhesions,  portions  of  the  omentum  may 
act  as  bands  beneath  which  a  loop  of  gut  may  be  strangulated,  or  such  a  loop  may 
pass  through  an  aperture  in  the  omentum  itself  and  become  strangulated.  The 
omentum  is  constantly  found  in  sacs  of  ordinary  hernia  or  may  constitute  their  only 
contents  (epiplocele),  especially  in  umbilical  and  frequently  in  femoral  herniw.  It 
almost  always  contracts  adhesions  to  the  neck  or  other  portion  of  a  hernial  sac,  if  the 
hernia  is  not  kept  permanently  reduced.  It  then  prevents  reduction.  It  is  found 
oftener  in  left-sided  herniae,  because  it  was  developed  from  the  mesogastrium  and 
inclines  somewhat  towards  that  side.  It  is  very  vascular,  and  has — through  acci- 
dental adhesions — maintained  the  blood-supply  of  an  ovarian  tunwr  the  pedicle  of 
which  has  been  twisted  so  as  to  occlude  its  vessels.     Its  vascularity  and  rapid  adhe- 


PRACTICAL  CONSIDERATIONS:  ABDOMINAL  HERNIA.  .750 
sion  to  other  peritoneal  surfaces  have  been  utilized  in  an  operation  for  the  relief  of  the 
^^^T^^^£^  o!  ^^^^^^^  is  of  in,..ance 

-t^£B  ^si^iJ^  !=^lS:;r  1^'^n  r  i^LS 

hemorrhage  takes  P>^«=!,'°  V^ '^^^  ?  i^."^^^^         be  more  common  in  the  ri^ht 

than  m  the  left  liac  tossa.        '^\;"  '     ...  coneenital  defects  in  the  mesentery, 

holes  due  to  injury,  there  are  others  which  ^'^^°"f  "'^^j  .  ^^  {„  jhe  lower  ileum  ; 
and  has  called  attention  to  the  fact  that  ^"^^^^["^"Sic^Lch  of  the  su,K.rior 
are  surrounded  by  an  f "^»7°  \'=.  f^f'^.^Xrterie^  tha  t^  area  is  often  the  seat 
mesenteric  artery  and  the  l'^' °  j]'; 'f  ^S  and  glands  are  absent. 

?SeSrWnr£Tgi.rtJrS^^^^^^^^^^^  area  of  mJ^ntery  could  occur 

with  -7;-»-^,f  ^^„,ery  as  a  means  of  recognition  of  a  particular  portion  of  gut 

^"^^h^^SXeLlTofThe^A"^^^^^^  ^  -^'^-^  '"  ''^ 

section  on  hernia  (page  1765). 

PRACTICAL  CONSIDERATIONS:  ABDOMINAL  HERNIA, 
and  ileum)  and  of  the  o"l^"™™'  "  7"  however   in  which  a  portion  of  the  mtestin.- 

""'°°/r? wXS -tS"  gene^l  condition.  .I»t  prriispose  to  o,  actually  |.to.l..cj 
e,..,Sd.aS^io««so?i.ted»i.h  (■)  inctc^d  in,„-abdo,n»0  prc«,o,.-  and 

*"'  1'"Sl',t"o™e°'s?»rd"r;iiS    «)  oc„p.ti„„,  that  „cc.».itate  n,uch 

^'°^?  'S^&TeSS^ttSrabdominal  wall  may  be  due  to  (a)  debili- 
2.   Decreased  resisianc  j       gd  distention  (ascites,   abdominal  tumor, 

tatmg  f -^^'^ (*>^i°'^(f)"'e44irco.|ulence,  or  (.)  emaciation.     The  last  two 
repea'  ■'  i<regnancies,  (a)  "c^^^c     .  {^   .  f  .renera  emaciation,  the 

the  £l'";eS"c;;ir'=,t?M«"Lvlti,  pAbly  dae  ,0  ,.,-,he   c„„e„cc  „■ 


1760 


HUMAN  ANATOMY. 
Fig.  X479. 


SuperfkUl  iuda 
Uitenul  otiliiiuc  musck 

Anterior  wperior  «ptne  of  lUum 


Dmp  layer  of  tufwrfictal  fucia.  cut  Hue 

SuperlicUl  circuniAcx  iliac  artery. 

Outer  i<il1ar  of  evtenul  rinu 

Fascia  lata 

Part  of  deep  layer  of  »ui)ertid*I  btda 

Cribriform  btcia 

MlihUc  cutaoeous  nerve  -Jglt— - 


External  cutaoeout  nerve 

SoperticiAl  fascia 

Superficial  fascia,  cut  edkce. 


Aponeurosis  of  external  oUiqua 

LInea  alba 

/ 

Intcrcolunii:  ■  i.i->r« 

Intercolumnar  fascia.  anificUlly  distended 
Inner  pillar  of  external  rinjC 

Uutos,  cut  cdg« 


Branch  of  internal  cutaneous  Dcrvf 
Internal  saphenous  vein 


Superficial  dissection  of  inguinal  region;  spermatic  cord  is  seen  issuing  from  external 
abdomitia)  ring;  intercolumnar  fascia  has  been  artificially  distended  by  injection  ol  fluid; 
saphenous  opening  is  closed  by  cribriform  fascia. 


Fig.    1480. 


external  nMiquc.  cut  edge 


Internal  oblique  muscle 

Aponeurosis  of  external  obll.)ue. 

cut  edifc 


Anterior  superior  «r'n«  '>'  '''"' 

PoupartA  liKaitiefit 

AtUchtnent  irf deep  layer  »>f  su[ierfictal 

fascia  of  abdomen  to  fnscia  laU 

Transversalis  muscle 

Spermatic  cord 

Fascia  lata 

Eitrmal  pillar  <tf  external  rintf. 

turned  down 

Falriform  process  of  fascia  lata 

i-eniorat  sheath  seen  through 

saphenous  oiipnine 

Middle  intane-ms  nerve 

txlemal  iutaneoi«  nerve 


Internal  satihenniis  vein 


Branch  of  internal  cutaneous  nerve 


Conjoined  ^ 
Triangular  fascia 
•Sus)iensory  litfament  of  pcnli 
Insertion  of  crema&ter  muscle 
Pubic  portion  of  fiucia  laU 


CrcniaUer  niusclc 


Deeper  dissection  in  which  external  oblique  has  been  partially  removed,  exposing  spermatic 
cord  lyiiig  in  inguinal  canal :  cribriform  fascia  removed  to  show  saphenous  opening. 


PRACTICAL   CONSIDERATIONS : 

Fio.  14S1. 


ABIX)MINAL   HERNIA.       i7fc» 


iBimul  otUqUt ' 


TffUMvvtMlte  maKte- 

Aponruiml*  €j#  trwwvCTMlii 

Intmial  oWi.iue.  iliac  origin 

External  oMi^ue.  ilUc  Imrrtlon 

Braath  nfttecp  circuniflci 

iltar  artet>- 

Anlcritif  sui*rk>r  t\^w  of  lllutii 

Internal  <ibli<|ue.  cut  edg*-  ^ 

Poupwt'i  HtEament 
Spermatic  c<>fd 
TnnsveivaUi  £uKia 
Crrmasttoric  fiwcU,  cut  edije  ^ 
Conjoined  tendon  -^' 
Anterior  tniral  nerve—-" 

Falciform  procew  of  faicla  Ian 

L'rural  hranchof  ijenlto-crural  nerve — 
hrtnoral  art.  within  femoral  cheath 
Femoral  c*nal.*rtificially  distended — 

Femoral  vein  wMiln  fnnoral  sheath 

batcmal  pUUr  of  external  rtBt[,  turned  down 

ln»crtiou  of  crenuulcr 


A|<oneuruu.>>  *'f  ntemal  i>Ui«iue, 
t.ut  eilKC 


Inlemal  rftli-iue. .  "t  edtje 
Tmn-iversali*  mii*  Ir 


TrlaniEular  f^s.  la 


Spermatic  t>)u<Hl-te^.eU 


Crcmaiteric  fascia,  reflet  led  fnm 

«pennatH.  (.urd 


Fig.   I4*^» 


AiNKieuroKis  of  transversall* 

Internal  nlillkiiie.  cut  edge 

Traoivenalis  mi»<:le 

TnnfversaliK.  cut  edge 

Internal  oblique,  iliac  orltftn 

External  oblique,  iliac  insertion 

Transversalis  (ascla 

Bran'  h  of  dee(>  circumflex  iliac  ar^ 

|irp()ep*ip«tt  ■ 

Internal  aWion. 

Pmii«rt'<  li«a 
Infundibuliform  fascia,  artiflc 
distendedl  Anterior  crural  net  e 

Femoral  sheath' 
Saitorius 
Fascia  lata 
Femoral  artery 
Fascial  ^ej^um  between  artery  an.l  vein 
Feninml  vein 


Se|)titiii  l»el«  een  vein  and  femoral  <  anal 

l-'einoral  canal 
External  pillar  o(  external  rina,  tumcl  <Iown 

Cremasteric  fascia,  cut  edtft 


Deep  epf«af«rir  artery 
■rosteriur  wall  of  ihcath  of  rectus 
■Kertus  abdominis 
■  Anterior  wall  of  shcsth  of  rcitus 


—  I.ine«all)« 


•  A|A>neur(>«iH  «f  external  oUk)ue, 
cut  eittfc 


^Transversalis  frscia 
Conjoined  tendon 

TriannuUrfr'Scia 
S|iemtatie  run! 
.  XremasteriL  &scia  reflecWd  fro« 


si>erni4lic  rord 


uwTr  .irt  ol  mascl.  r.n.ov«l  .nd  posterior  wall  of  »h«lh  «p««l. 

Ill 


1762 


HUMAN  ANATOMY. 


.  r\ 


developmental  defects  ;  (6)  the  presence  in  the  abdomen  of  portions  of  the  pelvic 
organs  increiising  intra-abdominal  pressure  ;  ( c)  the  habitual  flexion  of  the  thighs  on 
the  abdomen  in  infants,  relaxing  the  tissues  about  the  hernial  orifices  ;  ( </ )  the  ex 
treme  shortness  of  the  inguinal  canal,  the  internal  ring  then  lying  almost  directly 
behind  the  external  ring,  so  that  the  canal  is  about  equal  in  length  merely  to  the 
thickness  of  the  abdominal  wall.  The  diminution  in  frequency  during  childhood  is 
due  to  the  improvement  in  posture,  to  the  lessening  in  size  of  the  abdominal  rings 
and  to  the  shortening  of  the  tissues  about  them,  and  to  the  lengthening  of  the  interval 
between  the  rings  as  the  ilia  grow  and  incline  outward  and  the  internal  ring  follows 
them, — i.e.,  to  the  formation  of  the  inguinal  canal  with  its  valve-like  resistance  to  the 
protrusion  of  viscerc.  The  increase  in  fretjuency  as  puberty  approaches  and  is 
passed  is  due  to  the  more  active  habits  of  life  and  the  assumption  of  occupations 
often  laborious.  It  may  also  be  due  to  a  slight  extent  to  the  fact  that  until  the  pel- 
vis has  fully  developed  the  femoral  ring  and  canal  scarcely  exist,  and  that  therefore 
the  femoral  variety  of  hernia  is  rarely  found  before  that  time  of  life.  Later  in 
life  hernia  is  still  more  frequent,  although  it,  like  aneurism,  lessens  in  numbers  as 
old  age  draws  on.  This  is  due  to  the  fact  that  although  in  both  instances  the  pre- 
disposing cause— the  weakness  of  vessels  or  of  the  abdominal  wall-^may  be  said 
usually  to  increase  when  the  active  period  of  life  is  passed,  the  exciting  causes  due 
to  occupation  and  muscular  effort  diminish  with  relatively  greater  rapidity. 

^u,— Hernia  is  more  frequent  in  males  because  (a)  the  structures  connected 
with  the  male  genitalia  are  more  often  the  subject  of  developmental  defects  (riiie 
infra),  and  (b)  the  inguinal  canal  in  the  female  is  narrower  (containing  only  the 
round  ligament)  and  longer  (the  distance  between  the  anterior  superior  iliac  and  t)  e 
pubic  spines  being  greater),  and  for  both  these  reasons  offers  less  opportunity  for  ne 
descent  of  viscera. 

The  descent  of  the  testicle  and  the  associated  changes,  which  are  often  imperfect, 
sufficiently  account  for  the  great  frequency  of  inguinal  ( 92-95  per  cent. )  as  compared 
with  all  other  forms  of  hernia  in  males. 

In  females  femoral  hernia  is  less  common  than  inguinal  hernia.  It,  is  however, 
relatively  more  common  than  in  males  because  (a)  in  females  Gimbernat|s  ligament 
{q.v.)  is  narrower,  thus  increasing  the  area  of  the  femoral  ring  ;  and  (b)  it  is  weaker 
and  less  firmly  attached,  and  accordingly  offers  less  resistance  to  visceral  protrusion. 
In  100  ruptured  persons  the  percentages  as  to  inguinal  and  femoral  hernia  in  the 
two  sexes  are  as  follows  :  male  inguinal,  83.5  ;  female  inguinal,  8.5  ;  female  femoral, 
5.9;  male  femoral,  2.1  (Macready). 

The  extent  of  the  influence  of  a  certain  shape  of  the  abdomen— with  lateral 
bulgings  parallel  with  and  just  above  Poupart's  ligament  and  extending  above  the 
level  of  the  crest  of  the  ilium— is  doubtful,  but  it  certainly  indicates  a  laxity  of  the 
abdominal  wall,  and  just  as  certainly  is  often,  as  a  precedent  condition,  associated 
with  hernia.  . 

The  almost  invariable  preponderance  of  right-sided  hernia  in  all  varieties,  at  all 
ages,  and  in  both  sexes  has  been  variously  attributed  to  ( a )  the  greater  bulk  and 
weight  of  the  liver  ;  (*)  to  right-sidedness  in  walking  and  lying,  and  to  the  greater 
strain  on  the  muscles  of  the  right  side  caused  by  "right-handedness  ;"  (c)  to  the 
inclination  from  left  to  right  of  the  mesentery  of  the  small  intestine  as  it  descends  ; 
( (/  )  to  the  greater  frequency  of  incomplete  descent  of  the  testis  and  of  a  patulous 
funicular  process  on  the  right  side  ;  and  (<•)  to  the  larger  capacity  and  circumference 
of  the  right  side  of  the  pelvis  (Knox,  Macready)  as  compared  with  the  left,  causing 
a  corresponding  increase  in  the  size  of  the  right  femoral  ring. 

Fixternal  herni;e  are  influenced  as  to  the  silc  of  their  protnision  by  anatomical 
conditions  c.iusing  a  diminution  over  certain  localize^  areas  in  the  resistance  of  the 
al)dominal  wall  to  intra-alxlominal  pressure.  These  conditions  depend  usually  upon 
the  necessity  for  the  passage  from  within  out  of  (a)  normal  stnictures  such  as  the 
spermatic  cord  (oblique  nx  external  inguinal  hernia)  i^r  the  round  ligament  (the 
/(?3/Vi/ varietv  of  oblique  hernia)  ;  or  (/5)  such  as  the  larger  vessels  or  nerves  {umbilieal. 
femoral,  obturator,  sciatic  hernia)  :  or  (c)  upon  the  weakness  or  absence  at  given 
points  of  some  of  the  components  of  the  alulominal  wall,  as  at  the  internal  inguinal 
fossa  or  the  supravesical  fossa  (direct  or  internal  inguinal  hernia),  along  the  linea 


Fig.   1483- 


PRACTICAL  CONSIDERATIONS:    ABDOMINAL   HERNIA.       1763 

alba  or  the  linea  semilunaris  ( ventral  hernia),  through  the  pelvic  'l'»P»""fK'"-;';^V'!^r' 
cveeus  and  levator  ani  (^perineal  hernia)  ;  or  throu  -h  I'et.t  s  tnan^le  ( pa^'e  530)    or 
thfsuSr  lumbar  trianSe of  Grvnfelt and  Lesshaft  ( paj;e  .777).  "r  ' " Braun  s sp.ce 
(mee^777)  U'^'nbar  hernia).     Other  varieties  de,H.nd  u,K,n  (rf    con^emtal  defects 
LTsome  forms  of  inguinal,  umbilical,  ventral,  Maphragmatu  (^-"'"^^  3"  J^ 

varieties  of  properitotual  or  inlerstitiai  ni  rnia 
that  acctjnijwny  misplaced  or  undeveloi)ed 
testes;  or  (<•)  patholojrjcal  changes,  as  m 
those  ventral  hernite  that  follow  abscesses  or 
wounds. 

This  classification,  although  not  e.xhaustive, 
will  serve  as  a  basis  for  the  later  and  more  de- 
tailed consideration  of  the  anatomical  factors 
concerned  in  the  production  of  special  e.vtemal 
herni.-e  and  of  their  symptoms. 

The  component  parts  of  an  external  ab- 
dominal hernia  (Fig.  I4«3)  ^^e  (  i  )  the  sac 
consisting  of  distended  and  protrudmg  parietiU 
peritoneum,  and  subdivided  into  ( a)  the  mouth, 
the  aperture  corresponding  to  the  internal  her- 
nial orifice  ;  (*)  the  body,  the  expantled  pro- 
truding portion,  the  lowest  portion  of  which  is 
called  the  fundus:  and  (f)  the  neck,  the  constricted  portfon  connecting  the  Ix.dy 
Sd  mouth  ;  and  (2)  th^  contents,  which  in  the  order  of  frequency  are  ileum,  omen- 
n  ieiunum,  sigmoid,  canrum,  and  transverse  colon.  More  rarely  the  ascending 
InddSdiigcSlon,  the  bladder,  the  ovary,  arid  the  various  abdominal  viscera,  with 

the  exception  of  the  liver,  have  been  found  among  tne  contents  of  herni*. 

except  ^^^  ^^^   ^^^   ^^  ^j  ^„  ^^  varieties  of  hernia, 

(954"  P^r  cent,  in  males,  55-60  per  cent,  in  females),  may  best  be  studied  anatom- 

Fin.  1484. 


VrrWantnm 

-SupertK^ial  &&Lia  and  skin 


\Body 


Fundus 

Diagram  showinR  Keneral  comp»>nenU  of  external 
abdominal  henita. 


»>4: 


Anterior  superior  iliac  spine 


Poupart's  lii{«nicni 

Falciform  process- 
Iliac  portion  of  fascia  lata^ ' 

Femoral  ring — 
Femoral  artery — 
Femoral  vtin 


Aponeurosis  o«  extenial  oblique 


— Intercolumnar  ,ibres 

External  aNIominal  ring 

— Kxternal  pillar 
Internal  pillar 

^Gimliemat's  ligament 


Internal  saplielious  vein 


I'liliii  poriioti  i>f  fascia  lata 
-^Spermatic  coril 


Scrotum 


Dissection  o.  ri«h.  inguinal  region,  showing  -xtern.-.l  ah.lominnl  ring  an.l  saphenous  opening  in  fascia  lata. 

ically  by  considering  its  mode  of  production  when  /«)  .-«;a'l'rect  ^«-':"'t  "' Z^;:;"^ 
dcvdutmiental  defcrt  it  is  pr.-sent  at  or  s..on  after  birth  ;  (b)  the  hernial  sac  being 
p™  congenSv,  the  hernia  follows  some  increase- ..f  intra-alxlomina  pressure; 
or    r")  as  a^onsec'iuence  of  a  less  mark«l-or  less  complete-original  defect  or  oJ 


1764 


HUMAN   ANATOMY. 


an  acquired  delect  (vide  supra),  the  hernia  develops  in  the  presence  of  causative 

factors  (page  1759)-  ......      n      j        •.  11 

Acquaintance  with  the  changes  in  the  abdominal  wail  and  peritoneum  involved 
in  the  descent  of  the  testis  is  necessary  to  an  understanding  of  the  anatomy  of  inguinal 
hernia.  Although  these  changes  are  described  with  the  development  of  the  testicle 
(page  2040),  the  chief  features  of  the  process  may  be  noted  here  with  advantage. 

By  the  end  of  the  second  fcetal  month  the  developing  testicle  lies  behind  the 
peritoneum  at  the  side  of  the  upper  lumbar  vertebrie,  the  epididymis  and  later  the 
testicle  being  attached  to  a  fibro- muscular  band,  the  frenito-inguinal  ligament,  which 
stretches  from  the  sexual  gland  to  the  lower  part  of  the  anterior  abdominal  wall. 
During  the  third  month,  guided  by  this  attachment,  the  testicle  migrates  from  its 
primary  location  to  a  position  which  later  corresponds  to  the  internal  abdominal  ring. 
About  this  time  the  muscular,  fascial,  and  peritoneal  layers  of  the  abdominal  wall 
show  a  protrusion  in  the  inguinal  region  which  results  in  the  production  of  a  sac, 
the  inguinal  bursa ;  this  deepens  and  extends  into  the  scrotal  fold,  which  meanwhile 
is  formed  independently  as  an  integumentary  fold.     The  genito-inguinal  ligament. 

Fio.  1485. 


•n: 


internal  ohiiqi 


rrenuster  mosilt 


Apniwurusia  of  extenuil_A 
oMiqur.  turned  outward 


SapheniHU  opening 


<°ut  edge  of  i(ianeuro>i>  of 
external  oblique 


.Sheath  uf  rectus 


Tranaver^alis  fascia 
Conjoined  tendon 
.Triangular  faM-ia 

Spermatic  cord 


l>i»!iection  of  right  inguinal  canal ;  aponeurosis  of  external  oblique  has  been  cut  and  tum«l  outward. 

being  attached  to  the  structures  undergoing  evagination,  extends  into  the  inguinal 
bursa.  The  muscular  tissue  within  the  wall  of  the  latter  is  derived  from  the  interna 
oblique  and  transversalis  and  constitutes  the  cremaster.  The  lining  of  the  inguinal 
bursa  is  obviously  the  direct  continuation  of  the  general  serous  membrane  of  the- 
abdominal  cavity  and  later  constitutes  the  processus  vagina/is  peritonei.  Thicken- 
ing of  the  lower  end  of  the  genito-inguinal  ligament  produces  an  elevation  of  the 
floor  of  the  bursa  known  as  the  inguinal  conus,  a  structure,  however,  that  in  man  is 
very  feebly  developed  as  compared  with  that  found  in  some  lower  animals.  Subse- 
quently, during  th-e  seventh  and  eighth  months,  the  inguinal  conus  and  tbe  attached 
testicle  are  drawn  downward  into  and  through  the  inguinal  canal  until,  shortly  before 
birth,  the  sexual  gland  gains  its  permanent  position  in  the  scrotum.  The  rudimentary 
conus  and  the  genito-inguinal  ligament,  which  together  correspond  to  the  structure 
usually  described  as  the  giibernaculum  testis,  Ijecome  progressively  shorter  and 
smaller  as  the  testicle  descends,  their  remains  constituting  the  scrotal  ligament,  the 
subserous  band  which  permanently  attiches  the  tunica  vaginalis  and  the  testicle  to 
the  surrounding  tissue  of  the  walls  of  the  scrotum. 

The  original  retroperitoneal  position  of  the  testicle  is  always  retained,  this  organ 
and  the  accompanying  constituents  of  the  spermatic  cord  descending  outside  the 


PRACTICAL  CONSIDERATIONS  :   ABDOMINAL   HERNIA.      i7r..S 

pr<K:ess  at  the  time  of  puberty  (  Merkel ).  connenital  h.rni;.!  sac 

If  obliteration  of  the  processus  vaginalis  <lt)es  "<« /"^""r,  •»        ^  ,jj     , 

results  cFiR.  .488..  -^ this  may  Ix-co^^^^^^^^ 

the  descent  of  some  of  the  abdomma  ^■'^*^"-'^^-  ,2'"""'^ ',,.  ^^^h  .arts  of  the  alxl..nu- 
spermatic  cord  obtain  more  or  less  extensive  '"^7»^^"*^'  ^J,"^,';^,  fn  '  ^  From 
n^  walls  as  have  taken  ,art  n,  tj^j"™''^   ''  'J^^^^^^^^^  of  the 

within  outward  these  would  iH^,  ''^'^'^f '^^^'  '  '  £''^ ^h  „nly  the  timica  vaginalis: 
^^^.S^T^r!::::^^^  co^inu.,.rom  the  trans- 


Fio.   i486. 


Interna)  oblitiue,  i  ut  and 
turned  ontwani 

TrausviTHalis  nuisilr 


A|»«ineHr«isis  of  external 
(^)t4|ue 


External  abtlomiiial  ritiK— 


Saphenous  opetiinit.^ 


AptiHeiirosia  ol  extcrnwl  i»*iliMue. 
I  uledK*-' 

-A|H>ntun>si>  ni  inttrnal 
<>lilU|UV,  i'ut  eflK«-* 

Inti-rnal  ulMlomimtl  riiiii; 
— loiil  ojvere*!  I»>  inluii'iih- 
ulittirm  laiK'ia 

— Traiit»rni.»lis  (•.•Mi.uvt'.tk  -^i-t) 
-t\>iiit>itittl  UMitlmi 

TriuHKiiIar  fa^t  ia 


DUs«.i.m  ..(  riKh.  h,,«in..  >»na.;  «..n,a.  .n.l  internal  obliqu.  c„,  an.,  r,flc...l.  e„K.i„K  .n.n,v,r«..,,  n.n^-l,. 

versalis  fascia  ■  1  %)  cremaster  fibns,  irom  the  transversalis  and  internal  oblique_mus- 
clTSend^  by  areolar  tissue  into  the  cremasteric  fascia  ;  (4)  intrrfolumnar  fasaa, 
f mm  the  a?o,  e,m«is  of  the  external  oblique.  In  a.ldition  to  thes.-  covennRS  from 
the  aSoiS  «'ill.  the  envelopes  forming  the  sorot.nn  proper  contribute  (5)  the 
mo.l£d  rU  W  fascia  or  tunica  darios  and  (  6 )  the  ski,,.  Unusual  attachments 
rfLniKa^lum  below  to  the  tulx-r  ischii  and  sphincter  an.  account  for  some  of 
"he  form^^  tt^ticular  ectopia  (q.v. ).  Attachments  above  to  the  peritoneum  of  Jf 
ci^nTr  ileum  or  of  the  siRmoid.  or  to  the  l.H.sely  attach«l  ,K.r.toneum  hnm^  the 
TxcZZ  account  in  part  f..rNhe  formation  of  the  s=»c  in  i„/antilc  hem.a  (  v,dc  ,„/ra  ». 

ThT^treuRth  of  the  attachments  of  the  ^.ubernacula  t<>  the  testes  and  to  the  dart.« 
is  shown  bv  the  fact  that  in  cases  of  elephantiasis  scroti.  althouKh  the  enormously 
thicken^  skin  and  dartos  may  form  a  tumor  reaching  to  the  knee,  the  testicles  w.ll 
iwnaltv  he  found  ne-ar  its  lower  extremitv.  .... 

The  nex  step  in  the  anatomical' study  of  inguinal  hem.a  should  oms.s.  .n  a 
survey  of  the  innir  surface  of  *e  alKlo.uinal  cavitv  in  the  ...gu.nal,  .l.ac  and  hyi^v 
cistric  regions  (Fie.  14«7  >•  This  will  show  that  the  space  bet^^en  the  lateral  wall 
o  Ihe  Smen  and  the  mid-line-marked  by  the  pentoneal  fold  over  the  urachu. 


IV 


HUMAN  ANATOMY. 


(plica  Mrachi)—i»  divided  on  each  side  into  two  shal'ow  depressions  by  a  slight  eleya- 
Uon  of  the  peritoneum  over  the  deep  tpiKastric  artery  (p/ica  epij^as/rua )  ninnmg 
from  a  little  internal  to  the  middle  of  Pcjupart's  liRament  to  a  i>omt  on  the  outer 
edge  of  the  rectus  muscle  abijut  one-third  the  distance  between  the  level  of  the 
symphysis  pubis  and  that  of  the  umbilicus.  The  outer  of  these  depressions  is  called 
the  exUrnai  inguinal  fossa  (hernial  fos-sa).  The  inner  contains  a  triangular  spiice 
known  as  Hesselbach's  triangle,  bounded  by  the  plica  epigasirica,  the  outer  edge 
of  the  rectus,  and  Poupart's  ligament.  The  whole  inner  region— extended  to  the 
mid-line — is  further  subdivided  by  a  line  corresponding  to  the  peritoneal  fold  over 
the  obliterated  hypogastric  artery  (plica  h^pogasUica)  into  two  other  fossa;,  the 
internal  inguinal  and  the  supravesical,  which  are  of  use  as  aids  to  the  descnption 
of  hernia,  but,  viewed  as  mechanical  factors,  have  little  bearing  on  its  production. 

The  external  inguinal  fossa  is  deepened  just  to  the  outer  side  of  the  epigastnc 
artery  into  a  slight  pouch  (Fig.  1487),  which  marks  the  point  of  exit  of  the  sper- 
matic cord  from  the  abdomen,  and  therefore  the  site  of  the  internal  abdominal  nng 
and  of  the  mouth  of  or.  .•  form  of  inguinal  hernia,— the  external,  oblique,  or  indirect. 
On  the  external  surface  of  the  abdomen  this  pouch  corresponds  to  an  area  about  three- 
quarters  of  an  inch  in  circumference,  situated  a  linger* s-breadth  above  the  middle  of 
Poupart's  ligament.     To  the  inner  side  of  the  epigastric  artery  are  two  other  and 

Fio.  1487. 


I"' 


Peritoneal  iiirfice 


Plica  epij(astnca_ 

Hesselbach's  triangle  - 

Vas  deferens. 

External  iliac  arter- 
External  iliac  vein 

Plica  hypogastrica. 


( )uter  edge  of  rectus 
nuacle 


Supiavesical  fossa 

'uter  inguinal  fossa 
Inner  inguinal  fossa 


Bladiler,  somewhat 
distended 


Median  umbilical  ligament 

Posterior  surface  of  anterior  abdominal  wall  of  fonnalin  subject. 

still  slighter  depres-sions  corresponding  approximately  in  position  to  the  outer  part 
of  the  posterior  wall  of  the  .-anal  and  to  the  external  abdominal  nng  (page  1771)  and 
the  lower  fifth  of  the  inguinal  canal.  When  viscera  make  their  way  outward 
from  either  of  these  depressions  as  the  point  of  departure,  the  resulting  hernia 
is  known  as  direct  because  it  does  not  pass  through  the  entire  length  of  the  inguinal 
canal  but  takes  a  shorter  route,  or  internal  because  it  hes  to  the  inner  side  ot  the 
epigastric  artery.  A  further  examination  of  the  structures  (already  described  on 
pages  52^  524)  which  are  related  to  the  production  of  inguinal  hernia  will  serve  to  ex- 
plain its  occurrence  in  certain  localities  and  in  certain  forms  that  may  now  be  considered 
separately  in  theif  simpler  varieties,  the  rarer  and  more  complicated  being  merely 
mentioned  or  altogether  omitted  as  unessential  to  the  anatomical  study  of  nemia 

Oblique,  external,  or  indirect  inguinal  hernia,  which  makes  its  exit  from  the  abdo- 
men at  the  internal  ring,  is  incomplete  if  it  remains  in  the  inguinal  canal,  complete  if  it 
emerges  at  the  external  ring,  and  scrotal  if  it  descends  into  the  scrotum.  In  frequency 
it  bears  about  the  same  relation  to  the  other  form  of  inguinal  hernia— the  direct— as 
inguinal  hernis  do  to  all  other  forms  of  hernia  in  males,— viz.,  from  95-97  per  cent. 
This  frequency  depends  upon  the  following  anatomical  conditions,  (a)  The  descent 
of  the  testicle  from  behind  the  peritoneum  (page  2040),  carrying  with  it  a  process 
(vaginal)  of  peritoneum,  a  portion  of  the  transversalis  fascia  (infundibuliform  fascia). 


r-1; 


PRACTICAL  CONSIOKRATIONS  :    ABIK1MINAI.    IIKRNIA.       I7f'7 

and  of  the  transversalis  and  internal  nbliciue  muscles  ( cremiister  muscle ) .  nialces  its 
rSon  oJ  exit  fr..m  the  aUlomen-/....  of  its  entrance  into  the  mKumal  can  I- he 
ir^a  in  he  abdo.ninal  wall  l^-st  a.lapte.1  l.y  reason  o  ,ts  weakness  and  ts  sha  k  t 
f  ,  ?K.V  ..vit  ..I  visceri  {b)  This  s|K)t  is  s  tuate.l  near  the  lowi'St  level  of  the 
So':.  :':;th:;^a;:;ty.^:<-.  at  a'level  at  which,  when  thesi.eof  .1,ecavr^« 
IXr  temi«jrarily  decreasetl  (as  during  cou^hin^;  or  stra.nin«i.  or  r.lam.y 
decrJased  US  when  the  upper  z..ne  is  compressctl  by  t.^ht  la.m^;..  or  actually 
tc^^  as  bv  intra-alxlominal  fat,  or  by  a  tu„,or  or  ascitc-s ,,  the  outward  thrust 
o^  the^bdominai  viscera  is  addeil  to  bv  their  suiK-nncunilK-nt  wei^h  (  r  i  I  he  per  - 
U  neum  ove^the  1  wer  ,«rt  ..f  the  anterior  alxlominal  wall  is  th.n  an.l  .«>sely  attached 
TtC  kis  unable  to  offer  much  effective  resistance  to  distention  by  pressure  fro, , 
wit£      Such  distention  is  favored  by  the  funnel-sha.jed  d^l.--'''"  ;'« '''^  l^t 

i^rii^r  fSa^iSr=eL;^ts  :.5r^f  ^^^ 

d^n  of  he  tendon  which  is  derived  from  the  internal  oblique  has  generally  a  less 

mViSef^acrKidy)  The  thinnest  and  least  protected  ,x,rtion  of  the  inner-posterior 
™w^U  of  the  3  s  therefore  that  adjacent  to  the  inner  edge  of  the  '^t-m^d  abclomina 
"iwhT  It  should  bv.'  noted  that  Treves  is  inclined  to  consider  the  resistant 
Zer  o  the  normtaMominal  ^^1  as  less  over  Hesselbtch' s  triangle  than  .wer  the 
^ternaVinBuinal  fossa  ;  but  even  if  this  is  true,  the  existence  of  the  internal  ring  and 
of  the  canal  more  than  compensates  for  it  in  favoring  hernia.  . 

TWfa^rsufficiently  explain  the  frequency  of  oblique  inguinal  hernia  of  the 
ocauirTio^iv^dein/ral-le.,  the  form  in  which  the  congenital  dehc.enc.es  or 
SeS  pat^logS  changes  next  to  be  mentioned  are  not  demonstrable,  although 
itt  not  Sikely  that  some  original  or  acquired  defect  of  the  abdominal  wall  in  the 
nerehtorhoK  the  hernial  orifices  is  present  in  the  great  majonty  of  cases  of  herma 
ofd^flsofaU  varieties.      (/)  The  not  infrequent  total  or  part.al  patency  of    he 
IdnaUroce^  givefri^  to  a  number  of  subvarieties  of  inguinal  hern.a  icon^en'lal 
LS/f/Sar).  all  of  which  are  oblique.-/....  enter  the  .ngu.nal  canal  at  t^ 
Sal  riir  nd  to   he  outer  side  of  the  epigastric  artery.     These  herniae,  depend- 
5  on  anoma.S  in  the  closure  of  the  proces.sus   vaginalis,  h- been  -r„^sly  s«h^ 
divided  and  defined,  often  w  th  unnecessary  complexity.      It  will  sutt.ce  ntre  to  s..y 
d^Itr7«r"i/a/ hernia  (Fig.  1488)  is  due  to  complete  patency  of  the  v^ag.nal  prcKess 
thfcavXofvhich  is  directly  continuous  with  the  cavity  of  the  abdomen,  the  sac 
of  the  £n°a  Jndosi..^      .th  its  visceral  contents  and  the  testicle,  which  lie  in  con- 
uct      Sough  the  ^..ndition  leading  to  the  formation  of  this  Jerma's  truly  con- 
genital  the  hernia  itself  is  very  rarely  in  existence  at  the   ime  of  birth   but  ''^  -ipt   " 
™  in  early  He  when  intri-abdominal  pressure  is  either  habitual  y  or  suddenly 
™ased      It  should  be  remembered  that,  although  a  true  congenital  herma  neces- 
S  depends  upon  a  patent  processus  vaginalis,  i>atency  of  the  P';??^'?  '"^'y  ,'^"'?* 
SoutTernia      A  foW  of  ^ritoneum  at  the  edge  of  the    '"'""'l*"''*"™  f*f '^ 
Sy  scrSg  the  abdominal  opening  of  such  a  process  has  been  descri^  and 
h^bLen  tl^ought  to  aid  in  nrevenling  hernia  (Macready)       In  wonjen   Potency  of 
fh^  S  of  Nuck  acts  similariy  as  a  predisposing  cause  of  congenita    herma.  wh.ch 
is  however   of  ereat  rarity,  on  account  of  the  narrowness  of  the  canal  .tself,  the  i.ict 

Thaf  it^b^l  frifice  is  s^ill  smaller.  - ^TXf i^Se  mTof  th'e^'SS 
larger  size  and  greater  distinctness  in  the  female  than  in  the  male  ot  tne  pcriionta. 
-_j  u^rvx\  fold  coverin"-  the  entrance  to  the  ran.il.  . 

MfnuThemlam^.  1489)  results  from  occlusion  of  the  processus  vaginalis  at 
the  internal  ring^ly  the  visceral  pressure,  aided  by  the  attachments  of  the  guber- 
nac^SmtesdL  above  described,  carrying  this  septum  and  the  ne.ghbonng  pento- 


1768 


HIMAN   ANATOMY. 


ncum  downward  tu  cunstitute  a  stac  that  d«»tcendii  behind  the  tunica  vaginalis, 
esiMx'ially  if  the  latter  is  capacious,  as  it  is  apt  to  be  when  its  upper  limit  is  at  the  in- 
ternal rinx.  A  hernia  of  this  variety  has,  therefore,  between  the  skin  and  the  con- 
tents three  layers  of  serous  membrane,  two  of  the  tunica  vajfinalis  and  one  of  peri- 
toneum ( its  own  sac)  connected  with  one  another  at  the  neck.  Not  uncommonly, 
however, — as  might  be  expected  from  the  tendency  of  serous  membranes  to  adhesive 


Fio.  1488. 


Fiii.  14S9. 


-lUllIaiiilb^U 


UlnudhxU 


Hernial  lac 


Tunica  vmginali* 


IHaKfam  of  crHti^nital  hernia,  ahowinn  relation  ot 
hrnilal  Mai-  to  (lerittmeuni. 


DiaKram  of  Infant  1e  hernia,  showing  relation  of 
hernial  aac  to  tunica  vaginalis. 


inflammation,— the  posterior  la  •r  of  the  tunica  vaginalis  is  intimately  blended  with 
the  front  wall  of  the  sac.  Infant-  •  ^'ernia,  while  due,  like  the  congenital  variety,  t<. 
anomaly  in  development,  is  even  ;  r  s  apt  to  e.xist  at  birth  and,  in  fact,  Ls  rarely  seen 
in  infancv.  A  variety  of  infantilt  hernia  known  as  the  encysted  (Fig.  1490)  is  de- 
scrilied.  in  which  the  intestine  depresses  the  septum  at  the  internal  ring,  making  a 
stc  which  |)asses  into  instead  of  behind  the  processus  vaginalis,  so  that  the  hernia 
has  in  frt)nt  of  it  a  layer  of  tunica  vaginalis  and  a  layer  of  septum  (sac).  This 
hernia  is  very  properly  described  (Lockwood,  Macready)  as  "a  figment  of  the- 
imagination."  When,  after  occlusion  of  the  process  at  the  internal  ring  only,  the 
septum  gives  way  suddenly  during  some  unusual  intra-abdominal  pressure,  the  intes- 
tine may  descend  at  once  into  instead  of  behind  the  tunica  vaginalis  and  lie  in  con- 
tact with  the  testicle,— a  form  of  "congenital"  hernia  that  appears  in  adult  life. 


Fig.  1490. 


Prritoneum 
Siienitatio  cotd 
Skin  and  IhKia 


IMaicmm  of  so-called  enc\-ste<i  hernia.  shnwinK  sui)- 
poseil  relation  of  hemi.il  sat   lo  iieritoneuin. 


Prritoneiini 
Sl-etniatu  lorii 
Bkip  ami  fas,  ia 


Hernial  sac 


Tunica  vaRinalis 


Diai^ram  nf  funicular  hernia,  showing  rcl 
hernial  snc  u>  tunica  vafcinalis 


elation  of 


Funicular  hernia  (  Fig.  1491  )  is  a  sequence  of  the  closure  of  the  vaginal  process 
at  the  iiitper  end  nf  the  epididymis  "nlv.  the  short  pouch  of  peritoneum  remaining 
in  communication  with  the  peritoneal  cavity.  The  contents  of  such  a  hernia  are 
separated  from  the  testicle  bv  the  septum  formed  at  the  point  of  closure. 

Interparietal  ( intraparictal.  interstitial)  hernia  is  so  usually  a  \ariety  of  oblique 
inguinal  hernia,  and  is  so  commonly  associated  in  the  male  with  anomalies  of  the 


|'--*t- ' 


PRACTICAL  CONSI DERATIONS:   ABDOMINAL  HKRNIA.       i7'-> 
dominal  */"•  ^  '  *  >  ^^t  Lcia  Z\  the  trunsvcrsiili.  musclf.  or  amonj;  tht-  hhrc-n 

'^"' While  the  exact  mechanism  of  the  formation  ..f  these  herniie  is  still  unknown 

and  .KarSts  Sclg  theoric.-althou«h  of  grjrat  i-^^r:^tT^ 

Tei  be  set  forth,  it  is  perhaps  ^-^^V^^^  ^X'  ^^E^r^^  n^h;Vl.r.!  tion 

It'rvT,;' p^^batll^^lrS^e'^m^^^^^         which  ft  ,«L.  and  with  which  it  is  so  .n- 

^^eT^s  found  in  the  extraperitoneal  connective  tissue  that  precedes  the  s.»c  and 
r      ^,;!  orthe  coverinirs  of  nearly  all  abdominal  hernije,  but  this  is  more  than 

the  scrotum^    ,hV  testicle   where  it  mav  be  ajjain  arrested-often  permanent  v—by 


I770 


HUMAN   ANATOMY. 


usefulness  as  denoting  the  route  of  the  hernU,  and  are  occasiondly  of  value  as  land- 
marks during  herniotomies  or  operations  for  the  radical  cure  of  hernia. 

The  sac  of  a  complete  oblique  inguinal  hernia  (Fig.  1492)  wo^'a  «rry  with  il 
(I)  a  layer  of  extraperitoneal  connective  tissue  ;  (2)  that  portion  of  the  transversalis 
fascia  known  as  the  infundibuli/orm  fascia  ;  (3)  the  muscular  fibres  derived  from  the 
transversalis  and  internal  oblique  muscles,  and  called  the  crcmaskr  muscle ;  (4)  the 
fibres  from  the  external  oblique  aponeurosis  that  aid  in  strengthening  the  external 
"ring,"  especially  the  upper  angle.— the  Mercolumnar  fascia ;  (5)  the  superjicial 
/'ai«(j,— in  the  scrotum  the  </tfr/<?f  layer  ;  (6)  the  skin.  ......         j 

The  coverings  of  an  incomplete  oblique  inguinal  hernia  will  obviously  depend 
upon  the  point  of  its  arrest,  but  such  a  hernia  cannot  be  covered  by  either  mter- 
columnar  fascia  or  dartos.  .  »       j 

The  sac  of  a  complete  oblique  inguinal  hernia,  if  followed  from  withm  outward 
would  show  first  a  puckered  or  pleated  appearance  at  the  mouth,  due  to  the  folds  of 

peritoneum     produced    by 

Fic.  1493. 


Deep  epigastric 
artery 


Prrltoneum  and  sut^Mnus  tissue 
'lafuDdihulifbnn  (traD^venalis  rascU) 
Internal  oMlqiie 

External  oblinue  (interrolumBM  fascist 
Supcrlicial  bscis  snd  skin 


Diagram  showing  coverings  of  complete  left  indirect  inguinal  hernia. 


constriction  ;  next  a  portion 
narrow  and  elongated  by 
the  pressure  of  the  walls 
of  the  canal, — the  neck,—- 
which  in  such  a  hernia 
would  extend  from  the  in- 
ternal to  the  external  ring  ; 
and  finally  a  portion — the 
fundus  or  body — which,  re- 
lieved from  pressure,  is  usu- 
ally irregularly  ovoidal  in 
shape. 

The  anatomical  points 
at  which  strangulation  is 
likely  to  occur  are,  in  the 
order  of  frequency,  ( i )  the 
edge  of  the  internal  ring, 
( 2 )  the  edge  of  the  exter- 
nal ring,  and  (3)  in  the 
canal  (from  fibres  of  the 
transversalis  or  internal  oblique),  but  the  constriction  of  the  contents  is  not  infre- 
quentiy  due  to  pathological  changes  in  the  neck  of  the  sac  itself.  In  operating  to 
relieve  constriction  at  the  internal  ring,  the  relation  of  the  epigastric  artery  should 
be  remembered.     The  in   sion  should  be  directly  upward. 

7kr«— In  reducing—/.^.,  returning  to  the  abdominal  cavity— an  oblique  in- 
guinal hernia,  the  shoulders  and  thorax  should  be  raised  to  relax  the  abdomina^ 
muscles  •  the  thigh  flexed  and  adducted  to  relax  the  fascia  lata  and  external  oblique 
aponeurosis,  and  thus  the  margins  of  the  external  ring  and  the  antenor  wall-the  most 
unvielding-Hjf  the  inguinal  canal  ;  and  the  pelvis  elevated  so  as  to  secure  by  the  aid 
of  gravity  a  backward  or  upward  pull  on  the  contents  of  the  hernia  After  genUe 
downward  traction  in  the  line  of  the  canal  so  as  to  remove  folds  and  lessen  lateral 
bulcing  of  the  sac  and  contents  over  the  pillars  of  the  external  nng,  and  while 
making  pressure  with  the  thumb  and  fingers  of  one  hand  at  that  point  to  prevent  its 
recurrence,  the  other  hand  encircles  the  fundus  of  the  sac  and  with  as  evenly  dis- 
tributed force  as  possible  makes  pressure  at  first  upward,  then  upward  and  outward,— 
in  the  line  of  the  canal,— and  finally  backward. 

Direct  or  interned  inguinal  hernia  occurs  in  only  3-5  per  cent,  of  cases.  1  ne 
r-asons  for  its  relative  infrequency  have  been  given.  To  understand  it,  the  region 
intenial  to  the  deep  epigastric  artery  should  be  examined  (  Pig.  1487  J.  It  has  been 
"lentioned  that  this  region  has  been  subdivided  by  a  fold  corresponding  to  the  plica 
hvwffastricrt  into  a  supravesical  and  an  internal  inguinal  fossa  (Fig.  1487 )■  At  the 
imle--  angle  of  the  former  we  find  the  abdominal  wall  strengthened  (a)  by  the 
Dresence  of  the  rectus  muscle,  which  extends  outward  as  far  us  the  pubic  crest  ;  (*) 
by  Colles's  ligament  {triangular  ligament,  ligamentum  inguinale  reflexum),  consist- 


PRACTICAL   CONSIDEK  ,T'..NS      ALOOMINAL   HERNIA. 


1771 


in,  of  the  inner  deeper  fi^^oJPoup^^H^^ 

from  the  crest  of  the  P"*^ '"J"^""*  ^'  ^^^nTto  be  inserted  into  the  anterior  sheath 

behind  the  internal  p.llar  o    the  X^;"^i.""f  J"  ^th"t^X-s  protect  the  inner  and 

oftherectusand.ntothemeaab^(^^^^^^^^^ 

posterior  wall  of  the  canal  in  the  '^"ff^J'^^Vy  j  ^  „^,  ,;„    ;„  ,„^ies  and  the 

ks  far  outward  as  corresponds  to  '''^'""V; '^  ™  '  ^^"':  ^.\,.  by  the  conjoined  tendon. 


versalis  muscle  running  from  the_«pper_suj;face  of^the^pubes  U^^  ^^^^^^^^  ^^^^^^.^^^  ^^^^^ 


these  two 


Fio.  1493- 


Rect' 


Deep  epigailrlc  «rtery 

Interfoveolar  or 
Hesselbach's  ligamen 
WeaV  area 
Conjoined  lendoir 
Muscular  fibres 

Lower  end  of  Poupwt"  1  ligaroent — 

Urachu 
Bladder 


•Poupart's  liitament 
.Transveraalis  muscle 
■Spermatic  vessels 
Ixtemal  iliac  artery 

l.Exlernal  iliac  vein 
■Deep  epigastric  artery  (cut) 

.^Vas  deferent 

Femoral  ring 
-Gimbemat's  ligament 


A  dfSt  inguinal  hernia  may  escape  through  (a)  the  inner  inguinal  fo^.  be- 

joined  tendon,  (4)  Colless  ligament.  (5)  intercolumnar  fascia,  ^ ^^JPf'^^'J  f^^^^' 

I7\lk\n      The  spermatic  cord  usually  lies  on  the  outer  side  of  the  s.ic.     As  many 

t  cVhemiJpi^ct^ally  issue  through  tL  lowest  part  oy^e  •"-  -m.unans^itj^ 

been  proposed  to  call  them  ventro-inguinai  benii^.     Thc-y  have  no  such  essentmi 


1772 


HUMAN  ANATOMY. 


Peritoneum 

Tnnsvenalis  fa^ci- 

ronjoloed  mdcHl  (ud  Colle.e  Uitaiiient 

Inten  oluiiinar  u<>k;ia' 

KascU  ami  bkin' 


.Deep 

t-pigmstric 

artery 


Diagram  showing  lovenngs  of  complete  direct  inKuiiial  hernia 


relation  to  the  inguinal  canal  as  have  oblique  herniae,  although  when  the  peritoneal 
pouch  first  forms,  and  before  the  resistance  of  the  aponeurosis  at  the  external  nnj- 
has  been  overcome,  they  usually  enter  the  lower  part  of  the  canal,  as  the  resistance 
in  that  direction  is  less  than  it  is  inward,  towards  the  rectus.     They  are  never  con- 
genital and  have  no  definite  pre- 
existing path.     They  are  there-  Fio.  1494- 
fore  hernije  of  slow  development, 
usuallyseen  in  adult  life.especially 
if  the  local  weakness  of  the  ab- 
dominal wall  is  emphasized  by 
its  laxity  from  general  muscular 
atrophy,  or  by  increased  intra- 
abdominal pressure  from   accu- 
mulation of  fat.    They  are  usually 
small,  globular  in  shape  (by  rea- 
son of  the  shortness  of  the  neck ),                                                   .  ..  .     j   .u 
do  not,  as  a  rule,  descend  into  the  scrotum,   but  remain  above  the  crest  of   the 
tjubes,  and  when  reduced  go  directly  backward  into  the  abdomen.     The  orihce  m 
the  abdominal  wall  is  easily  felt,  the  outer  edge  of  the  rectus  to  its  inner  side,  the 
crest  of  the  pubes  below.     The  epigastric  artery  is  to  the  outer  side  of  this  aperture, 
but  its  pulsation  can  rarely,   if  ever,  be  felt      Macready  says  •  the  opening  m  the 
posterior  wall  of  the  inguinal  canal  through  which  a  direct  hernia  comes  is  much  more 
accessible  to  examination  in  the  living  than  the  internal  abdominal  ring  so  that  it  is 
duite  possible,  in  the  majority  of  cases,  to  explore  the  conjoined  tendon  with  the 
finger  and  ascertain  the  shape  and  size  of  the  opening  as  well  as  the  extent  to  which 
the  posterior  wall  has  suffered.     When  a  hernia  is  oblique,  the  posterior  wall  of  the 
canal  is  felt  as  a  plane  surface  by  the  finger  passed  into  the  external  ring,  and  its 
attachment  along  the  pubes  can  be  traced.     The  finger  is  prevented  from  entering 
the  abdomen  till  it  reaches  the  internal  ring      But  in  direct  hernia,  when  fully  devel- 
oped  the  finger  at  once  passes  into  the  belly  over  the  bare  pubes,  and  can  feel  the 
hack  of  that  bone  and  of  the  rectus  muscle.     No  trace  of  the  posterior  wall  o    the 
canal  is  felt  nor  the  margin  of  an  opening  in  it.     All  that  remains  is  a  narrow  layer 
of  membrane  which  just  fills  the  angle  between  the  pubes  and  the  rectus  ;  it  seems 
as  if  the  triangular  ligament  had  alone  withstood  the  distending  force  of  the  hernia.    In 
*                                                          .               these  cases,  in  which  the  pro- 
trusion has  done  its  worst, 
all  the  posterior  wall  of  the 
canal  between  the  rectus  and 
epigastric  artery  has  gone, 
and  the  large  opening  has  a 
triangular  figure  coinciding 
with  the  triangle  of  Hessel- 
Imch. 

If  strangulation  occurs, 
it  is  apt  to  be  at  the  exter- 
nal ring,  and  the  incision 
for  relief  of  the  constriction 
should  be  upward  with  a 
slight  inclination  inward. 

Large   oblique    herniae 
(scrotal),  especially  when  of 
long    standing  and    in   old 
persons  with  relaxed  abdom- 
inal walls,  may  have  the  in- 
ternal ring  displaced  so  far  towards  the  median  line  by  the  weight  of  the  hernia  that 
it  occupies  almost  exactly  the  usual  site  of  exit  of  a  direct  hernia.     The  epigastric 
artery  will,  of  course,  -till  lie  to  its  inner  ■i\t\c,  hut  cannot  be  felt.     M  a  rule,  how- 
ever, a  sufficient  portion  of  the  jx)sterior  wall  of  the  inguinal  canal  will  be  left  to  pre- 
serve some  obliquity  of  the  neck  (  Macready ),  by  which  the  hernia  may  be  recognized. 


Fir.    1495. 


.Plica  hypoKastrica 

I'lica  epigastrtcH 

— Oblique  inguinal  hcinia 
(exlernalfoi-sai 
Direct  ingutiinl  hernia 

(internal  fofsa  J 
Femoral  hernia 


Obturator  hernia 


riica  urachi  Supravesical  fossa 


Semidiagrammatic  view  of  povn-rior  «urface  of  anterior  abdominal  wall. 
Nhowitig  relative  potiittonN  of  \arious  forms  of  hernias.     tAftrr  Sfftkft.  \ 


Fig.  1496. 


PRACTICAL   CONSIDERATIONS:    ABDOMINAL  HERNIA.      1773 
Femoral  hernia  is  more  common  in  females  than  in  males  for  reasons  already 

^«ition  in  the  abdomen  and  the  thigh.  .J^is  smcc     tnt  ^^  ^'j  ,^. 

h'*r='s:'*srLaz;iS;o,\L-;S»vS^^  ^^^^'y 

and  the  iliac  fascia  pos- 
teriorly.     This  sheath 
does  not  embrace  the 
vessels  closely  until  it 
descends  from  one-half 
to  three-quarters  of  an 
inch   below   the    rela- 
tively unyielding  Pou- 
part's  ligament,  about 
opposite     the      upper 
margin  of  the  saphe- 
nous    opening,  — /.  f. , 
to  a  point  at  which,  in 
the  movements  of  flex- 
ion and  extension  of  the 
thigh  on  the  abdomen, 
the  vessels  are  less  lia- 
ble to  injurious  traction 
or  compression.     It  is 
therefore    infundibuli- 
form,  and  at  its  begin- 


II -ac  (asc 


I'eclincal  fascia 


Vascular 
space 

External 
abdominal 
'rinK 
Outer  |)illar 
Pubic  spine 


i:imbemat's  lixament 
Deep  di^ction  of  right  half  of  ,«lvis.  showing  attachments  of  iliac  fa«i.. 


1774 


HUMAN  ANATOMY. 


Femoral  artery 
Femoral  vein 


Hernial  sac  pro- 
truding through 
saphenous  open- 
ing 


hood  is  relatively  undeveloped  ;  its  outer  edge  and  the  vein  may  then  almost  touch. 
It  is  strengthened  by  the  conjoined  tendon  and  Colles's  ligament,  while  some  hl)res 
of  the  iliac  portion  of  the  fascia  lata  and  of  the  deep  femoral  arch  {vide  injra) 
also  contribute  to  the  formation  of  the  inner  boundary.  On  the  outer  side  is  the 
femoral  vein.  Behind  lies  the  horizontal  ramus  of  the  pubes  covered  by  the  origin 
of  the  pectineus  muscle  and  its  fascia.  In  front  are  Poupart's  ligament  and  the 
strong  band  of  fibres  running  along  its  deep  surface  from  the  anterior  superior  iliac 
spine  to  the  pubic  spine,  and  known  as  the  deep  femoral  arch.  At  the  point  at  which 
the  sheath  of  the  vessels  closely  unbraces  them— the  lowest  limit  of  the  femoral  canal 
—the  saphenous  opening  in  the  fascia  lata  (described  on  page  635)  has  somewhat 
the  same  relation  to  a  femoral  hernia  that  the  external  abdominal  ring  has  to  an  in- 
guinal hernia.  After  emerging  from  these  openings  neither  hernia  is  further  arrested 
in  its  progress  bv  any  strong  aponeurotic  barrier,  and  they  are  both  therefore  more 
^  '  likely  to  increase  in  size ;  but  in  femoral  hernia 

the  change  in  direction  of  the  a.xis  of  the  fundus 
as  compared  with  that  of  the  neck  is  much 
more  marked. 

In  its  etiology  femoral  hernia  conforms 
to  the  general  laws  already  enumerated  ( page 
1 759  ).  As  the  knuckle  of  gut  involved  presses 
the  peritoneum  before  it  into  the  femoral  ring 
and  down  through  the  femoral  canal,  it  car- 
ries before  it  (  i )  the  extraperilotieal  tissue  ; 
(2)  the  septum  crurale,  when  that  constitutes 
a  distinct  layer  ;  (3)  ^^  femoral  sheath,  some- 
times described  as  transversalis  fascia  because 
the  anterior  layer  of  the  sheath  is  derived  from 
that  structure;  (4)  the  cribriform  fascia ; 
(s,)  ihc  superficial  fascia  ;  (6)  the  i*i«. 

As  the  transverse  axis  of  the  femoral  ring 
—parallel  with  that  of  Gimbernat's  ligament 
— is,  in  the  erect  posture,  neariy  horizontal,  a 
femoral  hernia  first  descends  aJmost  perpen- 
dicularly. After  it  reaches  the  point  of  close 
adhesion  of  the  sheath  to  the  femoral  vessels  it  takes  the  direction  of  least  resistance 
and  protrudes  through  the  saphenous  opening.  Its  neck  is,  of  course,  the  porUon  of 
the  sac  between  the  femoral  ring  and  the  bottom  of  the  femoral  canal.  The  body  is 
apt  to  be  small  and  globular  or  hemispherical  in  shape. 

The  following  anatomical  relations  of  the  latter  will  be  found  of  great  importance 
in  distinguishing  between  femoral  and  incomplete  inguinal  hernia.  («)  The  upper 
edge  of  a  femoral  hernia  does  not,  as  a  rule,  pass  above  the  inguinal  furrow  (page 
670),  although  it  may  reach  it,— «>.,  the  hernia  will  be  below  a  line  drawn  from  the 
anterior  superior  spine  of  the  ilium  to  the  spine  of  the  pubes.  This  may  usually  be 
determined  by  inspection.  Exceptionally,  on  account  of  the  stronger  attachment  of 
the  cribriform  fascia  to  the  lower  edge  of  the  saphenous  opening,  the  hernia  nnds  its 
direction  of  least  resistance  after  emergence  from  that  opening  to  be  upward,  when 
this  sign  will  be  fallacious,  {b ,  The  neck  of  a  femoral  hernia  is  external  to  the  pubic 
spine,  that  of  an  inguinal  hernia  internal  to  it.  The  already  described  methods  for 
locating  that  process  (page  349)  may  fail  in  very  fat  persons,  especially  m  females. 
In  that  ca.se  the  lower  crease  that  in  such  persons  crosses  the  abdomen  (page  530. 
and  which  in  the  mid-line  rests  upon  the  symphysis  pubis,  will  be  a  reliable  guide  to 
the  latter  point  ;  the  bone  may  thence  be  traced  outward  to  the  pubic  spine. 

In  the  reduction  of  a  femoral  hernia— apt  to  be  difficult  on  account  of  the  nar- 
rowness of  the  channel  of  exit— the  position  of  the  patient  should  be  that  already 
descrilied  as  appropriate  when  the  hernia  is  inguinal.  The  thigh  should  be  in  a  posi- 
tion of  inward  rotation,  flexion,  and  adduction,  to  relax  the  fascia  lata  and  relieve  ten- 
sion about  the  saphenous  opening.  After  the  hernia— the  axis  uf  the  body  of  which 
is  nearlv  at  right  angles  with  the  axis  of  the  neck— is  drawn  downward  so  that  the 
axes  correspond,  it  is  gradually  pushed  backward  and  then  upward. 


Superficial  dissection  of  left  femoral  hernia  pro- 
truding through  saphenous  upenmg. 


PRACTICAL  CONSIDERATIONS:   ABDOMINAL  HERNIA.      I775 
It  should  be  noted  that  in  this  form  of  hernia  the  density  of  the  ^ix^neuroses 

i^iliiSllgpii 


Fio.  1498. 


Anlerior  superior  iliac  spine  - 
Iliacus  muscle  - 
Deep  circumflex  iliac  arter>- 


^Artery 
External  iliac  <  > 

I    Vein^ 

Obturator  ner\' 

Rounil  lixament 

Obturator  canal '"^ 
Pubic  branch  of  obturator  artery- 


Pouitart's  ligament 
Transversalis  muscle 


Rectus  muscle 


epigastric  vessels 


emoral  ring 
imbemat's  ligament 

jurator  artery  from  deep 
epigastric 


lymphysis 


Bisection  of  ,«rt  of  left  half  of  pelvis  and  adiac.,,.  b.Mly-w.n.  showing  obturator  artery  arising  from  deep 
DIaicclion  01  iiaii  epigastric  and  crossmg  femoral  nng. 

Umbilical  hernia  is  most  conveniendy  divided  from  either  a  clinical  or  an 

the  antS abdominal  wall  fiilinR  to  close  in  the  region  of  the  "^vel      AnaloKOUS 

nmarkedcases  the  condition  resembles  an  eventration  (fissura  a^'d^mmahs)  rather 

S  p^enWum'^som'ttimS  present.     These  layers  are  rarely  separately  demon- 

^^t  thl^^trhiS.'riy'^a'^e^^rmrwUle  of  gut  or  a  d.vertict„u.n  i. 
involved  (he^at  the  r^t  of  t'he  corT)  there  may  be  merely  tbickenmg  ..r  enlarge- 


1776 


HUMAN  ANATOMY. 


ment  at  that  point.     If  this  is  overlooked  and  the  cord  is  tied  within  the  limits  of 
this  enlargement,  the  intestine,  if  not  previously  replaced,  may  be  included. 

Acquired  Umbilical  Hernia. — Usually,  although  the  cord  is  tied  at  a  short  dis- 
tance from  the  abdominal  wall,  the  stump  separates  on  a  level  with  Uie  latter  on 
account  of  the  contraction  of  the  elastic  fibrous  tissue  around  the  umbilicus.  This 
cuts  off  the  urachus  and  the  vessels  passing  through  the  ring, — ^the  two  allantoic 
or  hyiMjgastric  arteries  and  the  umbilical  vein.  Viewed  from  within,  the  fibrous 
cords  representing  these  obliterated  vessels  would  be  seen  converging  to  the  puckered 
umbilical  scar,  the  vein  from  above,  the  urachus  and  the  arteries  from  below.  As 
the  usu.il  contraction  of  fibrous  tissue  takes  place,  and  as  the  abdomen  grows,  the 
traction  of  these  cords  depresses  the  umbilicus  so  that  anteriorly  it  lies  a  litde  below 
the  surrounding  surface  of  the  abdomen.  The  larger  amount  of  tissue  represented 
by  the  urachus  and  the  two  arteries  and  their  close  attachment  to  the  lower  edge 
cause  that  portion  of  the  umbilicus  to  become  the  stronger,  the  umbilical  vein  being  less 
closely  connected  to  the  upper  edge  of  the  ring. 

In  infantile  umbilical  hernia  these  changes  are  not  complete,  but  when  a 
knuckle  of  gut  protrudes  through  the  umbilicus  during  infancy,  as  a  result  of 
increased  intra-abdominal  pressure,  it  usually  escapes  between  the  vein  and  the  upper 
margin  of  the  ring  on  account  of  their  loose  attachment.  The  coverings  are  peri- 
toneum, transversalis  fascia,  and  skin.  These  hemiae  are  usually  small,  and  are  often 
cured  spontaneously  by  the  contraction  of  the  umbilical  and  periumbilical  scar  tissue. 
Their  occurrence  is  favored  by  tight  phimosis  or  by  constipation,  causing  straining, 
or  by  improper  feeding,  causing  flatulence.  After  infancy  umbilical  hernia  is  rare 
until  adult  life. 

The  umbilical  hernia  of  adults  is  far  more  common  in  women  than  in  men  (73 
per  cent.),  and  is  especially  favored  by  obesity — with  accumulation  of  fat  in  the 
omentum  and  mesentery — and  by  repeated  pregnancies.  The  coverings  of  such  a 
hernia  are  peritoneum,  transversalis  fascia,  superficial  fascia,  the  fibrous  tissue  of  the 
umbilical  scar  and  the  linea  alba,  and  skin. 

For  the  reasons  above  given,  it  appears  usually  at  the  upper  semicircumference 
of  the  umbilical  ring  and  often  involves  the  linea  alba  immediately  above  it, — a  form 
of  ventral  hernia.  Such  hemise  are  very  apt  to  contain  omentum — the  growth  of 
fat  in  which  often  makes  them  irreducible — and  portions  of  the  colon,  and,  on 
account  of  the  readiness  with  which  fecal  obstruction  may  be  caused  in  the  large 
intestine,  they  are  prone  to  incarceration. 

Ventral  herniae  protrude  through  the  abdominal  parietes  at  other  points  than 
the  umbilicus  or  groin,  or  than  those  weakened  by  the  passage  of  vessels  and  nerves 
from  within  outward. 

The  most  common  are  in  the  linea  alba,  between  the  umbilicus  and  a  point 
midway  between  it  and  the  ensiform  cartils^e  {epigastric  hernia).  Above  that  they 
are  very  rare,  as  the  effect  of  gravity  is  lacking  and  the  contiguous  viscera  are  less 
mobile.  Immediately  below  the  umbilicus  they  are  not  uncommon,  as  the  linea  alba 
has  still  an  appreciable  width.  Lower,  where  it  has  become  a  mere  raphe,  they  are 
very  rare.  They  are  often  associated  with  subserous  lipomata,  and  may  be  caused 
by  them.  The  protrusion  of  fat  from  the  subserous  tissue  is  thought  to  draw  the 
peritoneum  out  into  a  diverticulum  which  readily  becomes  a  hernial  pouch  when 
intra-abdominal  pressure  is  great  enough. 

The  linea  semilunaris,  especially  below  the  level  of  the  umbilicus,  is  a  not 
uncommon  site  of  ventral  hemiae.  It  has  been  suggested  that  their  position  is  de- 
termined by  the  fold  of  Douglas  (page  522), —the  semilunar  lower  margin  of  the 
posterior  layer  of  the  internal  oblique  aponeurosis,  which  fuses  with  the  transversalis 
aponeurosis  to  form  the  posterior  sheath  of  the  rectus  muscle,  which  ends  about 
half-way  between  the  umbilicus  and  the  pubes.  Below  that  all  the  aponeuroses  pass 
in  front  of  the  rectus,  leaving  the  posterior  surface  of  the  inferior  portion  of  that 
muscle  separated  from  the  abdominal  contents  only  by  the  transversalis  fascia  and 
pcritnnc\im. 

Ventral  hernia  of  the  linea  semilunaris  near  its  lowest  portion  and  direct  hernia 
issuing  through  the  internal  inguinal  fossa  (page  1770)  are  indistinguishable,  if  not 
practically  identical. 


PRACTICAL  CONSIDERATIONS:    ABDOMINAL  HERNIA      .777 

has  not  been  demonstrated  by  "act  dissec  lo^  _Grynfelt  and  Lesshaffs 

Above  Petit's  triangle  is  another  triangular   space,     orynieii  *■ 


FlO.   I409. 


Latinimin  dor»i,  cot  edge- 
Xll  rib- 

Fanciallrianiile - 

Quadralus  lumborum— 

Intrnial  iibliuue- 
(PetilslrialiRfc) 
Vertebnl  aponeurosis. 


•Cut  digiution  ol  laliMimus  dorai 


External  oblique 


Iliac  crast 


Oi-ectlono.  pcter^late™.  ^^'^^^^5.^^^^!,'^^  po-erlor bou»U„ 


aponeurosis  of  the  latissimus  dorsi  lacking  on  both  sides  in  a  case  in  w 

hernia  existed  on  one  side.  „Kt„ratnr  r-inal   which  runs  downward, 

Obturator  hernia  escapes  through  the  obturator  canaO^  ^^^"^  internal  hernial 

•orward,  and  inward  below  the  horizontal  ramus  of  |he^  pubes-^  J^e  mte^^  ^^^^^^^^^ 


Fio.  1500- 


Entrance  ol  hernia 


orilice  IS  ai   iiic   iiaaui-    ."    — -  --- 

internus  muscle  which  permits  of  the  pas- 
sage of  the  vessels  and  nerve.  A  hernia 
starting  there  passes  through  the  opening 
between  the  upper  edge  of  the  obturator 
membrane  and  the  lower  surface  of  the 
pubic  ramus  (Fig.    1500),  and  usually 

descends  between  the  obturator  externus 

I^Wtfll^^^^^KJKI'  and  pectineus  muscles  to  lie  beneath  the 

\^M^^^^^^H|K  latter  muscle  and  the  adductor  loiigus. 

^IHP^^^^Bf  It  is  therefore  to  be  looked  or  felt  for 

\  *  "^IK  ^^^^HT:  ^,^^  j^p  pybes  and  the  inner  end  <>f 

Poupart's  ligament,  but  at  a  point  both 
low  1  and  more  internal  than  the  site  of 
femoral  hernia.  The  thigh  should  be 
flexed,  adducted,  and  rotated  outw.vd  to 
relax  the  pectineus,  adductor  longus,  and 
obturator  externus.     As  this  hernia  occurs  most  «requef  y  in  ^Weri^^  '^He 

well  to  note  that  the  inner  orifice  of  the  '^f  "?,»^  ^.^^ '^^^^  J^J^..^^^^^^^^ 

Z^resTaklt-^^-ir^^^^^^ 

112 


Hernia  seen  Ihrongh  obturator  membrane 

Right  obturator  hernia,  seen  from  within 


1778 


HUMAN  ANATOMY. 


value.  The  obturator  nerve,  which  is  in  close  relation  with  the  vessel  and  the  track 
of  the  hernia,  supplies  the  hip-  and  knee-joints  and  the  adductor  muscles  and  aids  in 
furnishing  sensation  to  the  inner  side  of  the  thigh  as  low  as  the  knee,  and  sometimes 
to  the  middle  of  the  leg.  Pain  in  these  joints  and  in  that  region  not  otherwise 
explicable,  and  especially  if  associated  with  mtestinal  symptoms,  should  therefore 
suggest  a  careful  examination  of  the  obturator  region. 

Sciatic  herniee  include  all  the  herniiu  that  emerge  from  the  pelvis  through  one 
or  other  of  the  sciatic  foramina, — that  is,  (I)  through  the  great  siicro-sciatic  foramen 
alongside  of  the  gluteal  artery  (above  the  pyr if ormis)  ;  (2)  through  the  same  fora- 
men alongside  of  the  sciatic  nerve  and  artery  (below  the  pyriforniis)  ;  (3;  thrt)ugh 
the  lesser  sacro-.sciatic  foramen  (Sultan).  They  are  all  very  rare.  The  peKic 
fascia  forms  one  of  the  coverings  of  the  sac.  Within  the  pelvis  the  hernia  is  anterior 
to  the  pyriformis  muscle  and  sciatic  nerve.  On  entering  the  thigh  the  sac  crosses 
over  the  nerve  to  its  posterior  surface,  and  is  covered  by  the  gluteus  maximus.  As 
the  rupture  enlarges,  it  emerges  from  beneath  the  lower  border  of  the  gluteus  and 
descends  the  thigh,  or  may  pass  forward  above  the  trochanter  towards  the  groin. 

When  the  hernia  is  small  and  makes  no  obvious  swelling  in  the  buttock,  it  is 
found  at  the  sjxjt  where  the  sciatic  artery  is  tied  just  outside  the  pelvis.  A  line  is 
drawn  from  the  posterior  superior  iliac  spine  to  the  trochanter  major  rotated  inward, 
and  about  half  an  inch  below  the  junction  of  the  upper  with  the  middle  third  of  this 
line  the  hernia  enters  the  buttock  (Macready). 

Perineal  herniae  include  those  which  pass  through  the  outlet  of  the  pelvis  and 
its  muscular  floor.  The  boundaries  of  the  former  are  the  glutei  maximi  and  coccyx 
posteriorly,  the  pubo-ischiatic  arch  anteriorly,  and  the  great  sacro-sciatic  ligaments  con- 
necting the  coccyx  and  the  tuberosities  of  the  ischium  (Fig.  1423).  The  coccygeus 
and  levator  ani  muscles  form  the  floor  of  this  space,  which  is  perforated  by  the  rectum 
and  urethra  and  vagina,  and  extends  from  the  outer  walls  of  these  structures  to  the 
inner  walls  of  the  pelvis  (Fig.  1424).  It  might  be  supposed  that  the  comparatively 
yielding  nature  of  the  parts  which  close  the  lower  opening  of  the  pelvis  would 
favor  the  production  of  herniae,  but,  as  Macready  has  shown,  hernia  through  muscular 
planes  is  everywhere  very  infrequent.  The  normal  oblique  inclination  of  the  pelvic  floor 
and  its  elasticity  are  doubtless  factors  in  preventing  the  occurrence  of  perineal 
herniae.  A  hernia  starting  at  the  upper  surface  of  the  pelvic  diaphragm  must  pass 
between  the  coccygeus  and  levator  ani  or  between  the  fibres  of  the  latter  muscle,  and 
will  descend  into  the  ischio-rectal  space  (Fig.  1423),  where  it  may  cause  a  protrusion 
of  the  skin  of  the  perineum,  or  may  advance  towards  the  rectum  {rectal  hernia), 
the  vagina  {vaginal  hernia),  or  the  posterior  portion  of  the  labium  majus  {pudendal 
hernia). 

The  development  of  perineal  hernia  is  believed  by  Ebner  to  depend  upon  an 
abnormally  low  descent  of  the  recto-uterine  peritoneal  fold  which  occupies  Douglas's 
pouch  in  the  female  or  of  the  recto-vesical  fold  in  the  male.  In  the  presence  of  such 
a  fold,  intra-abdominal  pressure  is  able  to  carry  a  peritoneal  pouch,  with  or  without 
included  intestinal  coils,  to  the  right  or  left  (its  progress  in  the  mid-line  being 
arrested  by  the  firm  septum  between  the  rectum  and  vagina  or  the  rectum  and 
urethra),  so  that  it  rests  on  the  levator  ani  muscle,  the  fibres  of  which  are  often 
separated  at  places  (Henle  descril)es  it  as  three  muscles).  Its  subsequent  downward 
progress  has  been  noted  (  vide  supra). 

A  form  of  perineal  hernia  known  as  inguino-perincal  has  been  described  (Coley) 
in  which  the  hernial  sac  accompanied — or  followed — the  misplaced  testicle  (ectopia 
perinwalis )  into  thft  perineum. 

Diaphragmatic  hernia  are  usually  congenital  and  <hie  to  defective  develop- 
ment of  the  diaphragm.  A  review  of  the  anatomy  of  that  muscle,  with  special  refer- 
ence to  its  various  openings  and  to  the  fissures  between  its  sternal  and  costal  and 
costal  and  lumbar  portions  (Fig.  549),  will  explain  the  occurrence  of  hernial  orifices 
in  certain  situations,  already  detailetl  in  connection  with  hernia  of  the  stomach 
(page  1632). 

The  symptoms  are  largely  those  due  to  gastric  disturbance  (when  the  stomach 
is  involved)  and  to  alteration  in  physical  signs  caused  by  compression  and  displace- 
ment of  the  heart  and  lungs. 


PRACTICAL  CONSlMhRATIONS  :   AUDOMINAl-  HKKMA. 


>779 


or  in  abnormal  pc-r.tonea  [;;'---4;^"*'"«„^  •  l,,^ ^'^^.n.fr.h.M^.iv  to  indu.le  all 
The  classification  ailoptcd  »  y  ^"'^*"  .';•.*,  V\"'\,,ri..tL  can  1^  clifferentiattd  : 
herniae  coming  under  ^he  aU'^^i^;;J,";"  'V,  hJ  „ia  rth'.lu-leno-K-junal  recess 
;;!  SoftllTrluiri/lJli:?:-^.!  -esses,  U)  hernia  o.  the  inters-K-noul 

cavity,  which  may  be  regarded  as  •■'  P;^^'-''.  ^"«, J^J^/X.-s  that  eit 
thenkrrownessof  the  o,,enmK(i.a!ie  1/46  .■md.^^^^^^^^^  ^^  ^^^.  ^,,,,,,^ 

:;;2Si?;:s.:;t^=;^^ar:'^^^  ^^^ 

Fio.  I5«>«- 

Jeiunom  ;  Ouodeoum 


Superior  dllod«ni>-Wun«l 
fasu 

.Branch  ol  l»'t 
colii-  an«ry 


Inferior  <luodcno- 

{ejuiial  (oaaa 
DcscvntiinK  colon 


MeMntery  ol  aniall 

inlesline 


^..«4-««l  f.^iuv  telunum  tuntcti  to  the  righl.. 
Duo<leiio.)e)uii«l  junction,  inowinu  ouodenal  i»«e.  jei"" 


Which  is  then  placed  behind  tKe  Po-^ior^rieUl  P^i-eun.     '^'^^^ 
be  seen  to  enter  the  sac  and  the  end  of  ^l^*; ''^"."\;" ''^^f  j^  (Treves).     The  inferior 

Thcv  confin  h.rnCT  will,  peat  r..nry  ,  tte  rcirocica    P  ^^^^  .^^^^^ 

behind  the  cii.M,„  anil  »!«"47«  """-^f  ^^^^^^       llic-  Ml.  the  i„li™„m..i.l 

,„^  in.y  l»  «»n  opemne  to..»r.l>  \\«. '^'  ;","",ie,iKm.«d  artery,  and  i.  ab»ul 
r^":e''Jt'"ur\rrrvir''TLVn  Jc^pied  „y  coil,  „i  »naU 


1780 


HUMAN  ANATOMY. 


jfravity,  or  by  their  own  vermicular  movement,  intestines  may  be  forced  into  a  cavity 
or  space  either  actually  or  potentially  pre-existing,  in  which,  under  lessened  pressure- 
as  compared  with  that  at  the  orifice,  the  bulk  of  the  hernia  may  increase,  with  the 


Fig.  1502. 


-^ 


Ileum 


l\ 


£ 

-J^ 

--/-  iieo-«ppcndicular 

^     fold 

Hairf 

W  / 

^1 

^i 

Inferior  ileo-i-iL-cal 

IP 

f  1 

fowu 

!i 

fold 

Ponterior  lavcr  of 

4.  /  vm 

meMtitery 
Retrociccal  foMta 

w 


V 


I 


■ 


Peritoneal  fosflv  of  Meo-csecal  rvKion,  necum  beitiK  drawn  fnrwiird  and  upward,    {/otineseo'i. 

constant  danger  of  incarceration  (stoppage  of  the  fecal  current)  or  strangulation 
(cutting  off  the  supply  of  blood).  The  symptoms  of  internal  hemise  are  therefore 
always  those  of  intestinal  disturbances  and  very  often  those  of  complete  intestinal 
obstruction. 


■  L 


i  * 


THK  SPLEEN. 


1781 


ACCESSORY  ORGANS  OF   NUTRITION. 

In  this  kjroup  .nav  Ik- indu.lcnl  the  ./>Av«.  ihv  thyroid  bodv.xh^- parathyroids,  the 
tainlv  n^Xncr  h"    amc  is  unfortunate.     To  certain  men,lH.Ts  o    the  above  «r..u,,. 

ing  according  to  the  organ  mvolvetl. 

THE   SPLEEN. 

The  spleen  i«  essentially  a  lymphatic  orpn.  It  is  of  a  l'"^P"'*|' ,^"'";,'*"f '*' 
verv  riable  structure,  and  is  situatc^l  in  the  left  hypo;  hon.lnum  U-hnul  the  -t.mia  h 
The  Sht  rexces;ively  variable,  changing  with  the  state  of  chgestmn.  ami  h.  lie 
to  imnS  increase  in  certain  diseases,  as  well  as  to  slighter  mod.ha.t.ons  .„  oth  rs. 
^«^v  Xes  the  average  weight  in  ten  men  as  195  gm-  (approximately  7  <>/  • 
S'^iclficgrav^ty  is  va'riously'stated  between  .037  and  1 060.  The  length  accord- 
ing to  Sapi>ey,  in  the  same  ten  men  was  12.3  cm.  (4?^  m.  >• 


Posterior  border 
loUnMdiate  bordi 


Kenal  (urface 

Splenic  artery 

Splenic  vein 


Internal  hiisal  angle. 


Gastric  !Hir(a<  e 
Anterior  bonier.  uo1i1k-<1 


t*nt  |ieritot.euni 
snrrounding  iiilum 


Anterior  basal  anxle 


Posterior  basal  angle 


Basal  surface 


Visceral  aspect  of  spleen  hardened  in  ttlu 


T,e  Shape  of  this  ^^at^;^  hasten  ^^..ntjy^-;^^ 

determined.      We  follow  Cunnmgham  .n  d^^"^"f  a^'3"'£^des  this  there  are 
lower  end.  although  it  is  by  no  means  =Jway^  o  be  recogn.z^^  Bes  _^^^ 

three  distinct  surfaces, -the /A^^/».,  the  rcna,,  and  the  gastnc, 
at  a  rounded  point  at  the  top  of  the  organ.  ^^^^^  ^„j 


The 


1783 


HUMAN   ANATOMY. 


outline  of  this  surface  is  that  of  a  Ioziiikc  ciKlosetl  by  an  anterior  and  a  pfwterior 
l)oriler,  one  jxiint  lK"injj  afxrte  and  iR-hind,  the  other  IkIow  and  in  front.  Thus  in 
the  main  the  l<m^;  axis  cdrres|x>nds  to  the  course  of  the  lower  rilw,  which  sometinus 
make  impressions  on  this  con\ex  surface.  The  anterior  border,  fortnerly  the  marj^o 
cnnatus,  separatin>j  this  surface  from  the  gastric,  is  sharp,  esi)ecially  Ih-Iow.  It 
shows  one  or  more  notches  in  9.^  (ht  cent.'  of  the  aiscs.  They  are  most  com 
nion  in  the  lower  jwrt  of  the  iM)rder,  which  is  st>metimc-s  (juite  scallo|)e<f.  The/Vu- 
terior  border,  formerly  the  mariio  obtusiis,  se|>aratin);  the  phrenic  surface  from  the 
renal,  is  nuich  k'ss  prominent.  Parsons  found  notches  in  it  in  ,^2  j)er  cent. ;  hut  the 
general  apjiearance  of  this  fxirder  is  very  different  from  the  preceding,  lx-in>j  in  the 
main  solid  and  uniform.  The  jjhrenic  surface  occ;i.sionally  (  20  per  cent. )  presents  a 
sharp  fissure,  rarely  more  than  one.  It  usually  starts  from  a  notch  in  the  posterior 
border  and  runs  some  distance  across  this  surface,  forward  and  upward.      I-ess  fre- 

qucndy  it  starts  from  the 
Fic.  1504.  anterior  border,  or  lies  en- 

tirely   in    the    convexity, 
reaching  neither  lx)rder. 

The  renal  surface, 
facing  inward,  does  not 
extend  so  high  as  the  pre- 
ceding. It  is  eiiclosetl  by 
the  |K)sterior  fjorder,  the 
internal  or  intermediate 
border,  which  separates  it 
from  the  gastric  surface, 
and  by  one  side  ct  the  ba- 
s.\l  surface.  In  the  upper 
third  this  surface  is  nearly 
plane,  resting  against  the 
suprarenal  capsule,  and  in 
the  lower  two-thirds  dis- 
tinctly concave,  where  it  is 
mouldeil  o\er  the  upper 
part  of  the  left  kidney. 
The  end  of  the  pancreas, 
if  that  organ  be  short,  may 
rest  against  the  anterior 
part  of  this  surface. 

The  gastric  surface, 
considerably  larger  than 
the  preceding,  -i  bounded 
by  the  intermediate  and 
anterior  borders  and,  be- 
low, by  another  side  of 
the  base.  It  is  concave, 
being  for  the  most  part  moulded  over  the  stomach.  It  contains  the  hihim.  a  fissure 
some  inch  and  a  half  long,  running  parallel  to  the  iiitirmediate  border  and  about 
one-half  inch  distant  from  it,  which  receives  the  \criHs.  The  part  of  this  surface 
which  is  not  against  the  stomach  is  at  the  lower  end,  and  r.  sts  against  the  splenic 
flexure  of  the  colon.  In  .some  ca.ses,  when  the  stomach  is  cvintr.icted  and  the  colon 
distended,  the  relative  areas  of  the  two  may  be  reversed  Moreover,  the  omenluni 
may  reach  the  spleen  between  them.  The  tail  of  the  panciea-  may  touch  the  right 
part  of  this  surface  or,  if  long,  lie  against  the  spleen  just  abo\  >•  the  colon. 

The  basal  surface  is  a  triangular  area,  much  smaller  than  the  other  surfaces. 
It  is  enclose  i  by  the  lower  part  of  the  posterior  border  of  Vic  spleen  and  !-.y  two  lines 
diverging  from  the  lower  end  of  the  intermediate  border.  One  of  these  separates 
the  basal  surface  from  the  gastric  and  the  other  from  the  renal  surface.  One  or  Ixjth 
of  these  lines  may  be  so  rudimentary  that  the  base  may  seem  a  part  of  either  the 
'  Parsons :  Journal  of  Anatomy  and  Physiolc^y,  vol.  xxxv.,  1901. 


Postero-Iateral  wall  of  fntmalin  siihjerl  ha-i  fc«ti  removed  to  show  relations  of 
spleen  hardeneti  in  situ. 


THi:  SPI.KKN. 


I7»3 


««tric  or  renal  surface,  n.on-  uftc-n  tlu-  w.rnu.  ..r  it  may  appir  simply  as  a  km.1.  at 
EuKr  siSf  the  lower  en.l.  This  k...l.  the  ,>0r,^.  /«^v</..  -  usually  more  or 
1  :  i....t  It  th.-  tcriniuiitioii  of  tli'-  iii'.iTiiu<hate  Uirtler. 

'"'  sSSie  1^    "i^i'-'  to  the  s^Tous  .overinu  contril.ut...l  by  .he  l-U'-'-^^i 

5'^£::'V^.x^!:f  tn:::i:sL!  nun.en.us  Xst.  .v;...,  a...^  in  us .  :n-  ;-^ 

lielHSributeci  bundles  of  involuntary  muscle.  At  the  '"  ""'  f*',,  ;  '^' "'■  ■  ^ 
stSand  brel  up  into  innu.nerable  delicate  pr.K.esses  wh.ch  un.te  to  lorn.  th.  sup- 


Ca|»*ule  — — 


_iitcrI<>l>tiliiT 
tralH-i  ulu  mill 
vein 


.Sfilcntc  |iulp 


Interlobular  vci 


MalpighianbiM 


Splenic  put] 


S«.io..  of  spl«,i  under  very  low  maKniftca.ion,  ,h„«mK  Kener..!  arrangement  of  splcnu  .is.ue. 


hut  freelv  communicate,  since  the  interveninR  trabeculae  form  only  inromjjlete  paiti- 
Snl      The  ~  wkhin  the  fibrous  framework  are  filled  with  the  highly  vascular 

lymphoid  tissue  constituting  the  splenic  pulp.  accordine  to 

The  relation  of  the  blood-vessels  to  the  lobules  of  the  spleen  is.  a«orciing  to 
Mall  very  definite.  The  branches  of  the  splenic  artery,  after  entering  at  the  hilum 
knd  mnning  f<-  ^^^  distance  within  the  trabecule  break  up  '"'<' 7=^"f  J.^'^' 
each  of  which  enters  the  pro.ximal  end  of  the  lobule,  through  the  middle  of  which  it 
Ssse^  giving  off  lateral  twigs,  one  for  each  pritnary  compartment  .,f  the  Jobu  c. 
Th^vmphoid  tissue  occupying  the  compartment  is  arranged  as  ?nf '""^"''/"K  ^y''"' 
drica^^^^^  the /*«//»  W..  Within  thVlatter  course  the  terminal  branch.^  of  the 
J  en  c  aTerie,.  w&^outside  and  between  the  cords  lies  the  plexus  of  venous  space, 
from  which  the  more  defini'.-  chann.ls.  the  intralobular  vetns  anse.  The  terminal 
tromwncntnL  mo  ^^  ^  g,„^,  branches  w'-.ch  terminate  in 

^:^^£^^mpu^of  Tkon,a      The  latter  communica,     -h  ^^^ -- 

spaces  surrounding  the  pulp-cords,  so  thn'     nely  dn  ,ded  substance^         ..  a^  metallic 

.  Johns  Hopkins  Hospital  BuH  aift  i    nurphol.  u.  Anthro,     ,  Bd.  ....  190a 


1784 


HUMAN  ANATOMY. 


pigments,  when  injected  into  the  arteries,  pass  into  tlie  veins.  The  walb  of  the 
ampulla:  are  very  thin  and,  towards  the  junction  with  the  venous  radicles,  imper- 
fect, being  here  composed  of  the  reticulum  of  the  surrounding  pulp-tissue.  The 
channels,  however,  are  sufficiendy  definite  to  prevent  the  escape  of  the  blood-cells 
under  normal  conditions,  although  the  plasma  constantly  passes  into  the  intercellular 
spaces  of  the  pulp  (Mai.,  The  walls  of  the  venous  spaces  are  even  more  pervious 
than  those  of  the  ampullse,  and,  like  the  latter,  possess  only  an  incomplete  endothelial 
lining,  supported  externally  by  a  mesh  of  circularly  disposed  elastic  fibres.  The  endo- 
theUum  consists  of  narrow,  elongated  spindle-cells  instead  of  the  usual  plate-like  ele- 
ments which  line  the  larger  splenic  blood-vessels.  The  round  or  oval  nuclei  project 
into  the  lumen  of  the  venous  s()ace  beyond  the  level  of  the  protoplasm  of  the  cell,  which 
often  presents  a  distinct  striation. 

The  venous  spaces  between  the  pulp-cords  are  the  beginnings  of  more  definite 
channels,  the  intralobular  veins,  which  pass  from  the  primary  compartments  towards 


Fio.  1 506. 


Capsule 


Primary  compartmcot 


Interlobular  trabecula 


Intralobular  trabecula 


Interlobular  vein 


Malpighian  body 


.Splenic  artery 


1; 


Diagram  showing  architecture  of  splenic  unit ;  splenic  pulp  is  rci>resenl«l  in  only  one  compartment.     t,^lfr  Mall.-, 


the  trabecula  between  the  lobules  to  become  tributaries  of  the  larger  interlobular 
veins  occupying  the  periphery  of  the  lobules  within  the  boundary  septa.  These  veins 
follow  the  larger  trabecule  until,  finally,  they  emerge  at  the  hilum  to  form  the  splenic 

vein.  ■        1  i_      1       1. 

In  their  journey  through  the  lobule,  shortly  after  leaving  the  trabecula,  the 
branches  of  the  splenic  artery  present  marked  local  accumulations  of  lymphoid  tissue 
within  their  adventitia.  These  aggregations  constitute  the  Malpighian  bodies,  or 
splenic  nodules.  When  seen  in  transverse  section,  they  appear  as  conspicuous  oval 
areas  of  dense  lymph-tissue  surrounding  the  artery,  which  usually  occupies  a  somewhat 
eccentric  position.  Longitudinally  sectioned,  the  splenic  nodules  appear  as  cylinders. 
They  correspond  in  structure  with  true  lymph-nodes,  possessing  germ-centres.  Sur- 
rounding the  Malpighian  bodies,  the  spleen-tissue  presents  the  usual  arrangement  of 
the  pulp-cords. 

The  splenic  pulp  consists  of  a  delicate  stipporting  reticulum,  continuous  with 
the  terminal  ramifications  of  the  intralobular  trabecule,  and  the  cells  contained  within 


THE   SPLEEN. 


1785 


and  supported  by  the  mesh-«ork.     Thepu/p-a/s  mclude  a  vanety  of  Jj^enU  *he 

mit  instant  of  which  are  :  (a  .  small  "mononuclear  lymphocyte    (*)leuc2«^ 

Se  mononuclear  and  polymorphonuclear  types  ;  (O  red  blood-cells  .  (d  )  nuclcatea 

red    blood-cells;     (e)    large 

phagocytic    cells    contammg  ""•     '  ' 

disintegrating  red  blood-cells, 

or  pigment  particles  derived 

from   the  destruction   of   the 

same;    (/)   giant  cells   with 

large  composite  nuclei,  chiefly 

in  young  animals.  In  addi- 
tion a  variable  amount  of  free 
pigment  is  present,  probably 
from  the  broken-down  red 
blood-cells.  During  embry- 
onic life  and  later,  in  response 
to  unusual  demands  for  addi- 
tional red  blood-cells,  as  after 
severe  hemorrhage,  the  spleen 
is  the  birthplace  of  new  red 
corpuscles  ;  these  are  at  first 
nucleated,  but  soon  lose  their 


Venous  space 


Arteriole' 


Reticulum. 


Pulp-cords 


.Venous  space 


Arteriole 


.Cell  cnntainiiiK 
pigment 


Section  of  spleen,  showhiK  details  ot  pulp-iissuc 


Hi/on/r  omfMhim  which  extends  forward  to  the  greater  curvature  and  above  to  the 
teck  ofThTSndurof  the  stomach.  These  two  folds,  stretching  respectively  tack- 
^rf  and  fori^ard  from  the  hilum,  bound  a  part  of  the  le«cr  cavity  of  the  pentonetim. 


1786 


HUMAN  ANATOMY. 


The  suspensory  ligament  of  the  spleen  is  an  inconstant  fold  belonging  to  the  lieno- 
phrenic  ligament,  extending  from  near  the  oesoph^eal  opening  in  the  diaphragm  to 
the  top  of  the  spleen.  It  contains  connective  tissue  between  its  layers,  which 
connects  a  triangular  retroperitoneal  area  of  the  spleen  with  the  diaphr^^m.  The 
phreno-colic  ligament  is  a  sheU-like  fold,  .lerived  from  the  greater  omentum,  stretched 
with  its  free  edge  forward  from  the  abdominal  wall  in  the  region  of  the  eleventh 
rib  to  the  transverse  colon  so  as  to  form  the  floor  of  a  niche  in  which  the  spleen 

rests.  .  , 

The  Vessels.— 7)1*  Arteries.— I^t  splenic  artery  is  a  large,  tortuous  vessel, 
a  branch  of  the  coeliac  axis.  It  is  remarkable  not  only  for  its  large  size  in  propor- 
tion to  the  organ,  but  for  the  thickness  of  its  walls.  About  an  inch  from  the  spleen 
it  breaks  up  into  six  or  more  branches  which  enter  the  hilum  one  above  another,  in 


Fio.  150.^. 

Eniifonn  cmrtilagc 


Diaphragm 


Left  li>be  oj  liver ^.     vV;      •.  ■. 


CEsophaciu 

(•astrfvhepatic  .^ 
omentum 

Lobe  o(  Spigelius 

Inferior  ^ 
vena  cava 
Vena 
azygoa  major 
Aorta 

Vena 
ai>'go5  minor 


Diaphragm 


Lung 


Lung 


GaMro-aplenIc  omcntam 
Left  half  of  froKB  Kction  acnw  body  at  level  of  eleventh  thoracic  intervertebral  disk ;  under  aide  of  section. 

the  main  anterior  to  the  veins,  with  which  they  travel  along  the  fibrous  walls  of  the 
interior.  No  arterial  branch  has  any  anastomosis  with  the  others.  Soon  after  its 
origin  the  splenic  artery  gives  off  a  branch  which  runs  above  the  main  trunk,  supplies 
some  twigs  to  the  stomach,  and,  breaking  up  into  smaller  branches,  enters  the  spleen 

near  the  top.'  ...  .1 

The  veins  ramify  in  the  spleen  in  company  with  the  arteries,  and  leave  it  in 
about  the  same  number  of  branches,  which  unite  to  form  the  splenic  vein  behind  and 

below  the  arterv.  ,  ,     ,  •.        u       1. 

The  lymphatics  are  chiefly  deep  ones  emerging  from  the  hilum,  but  there  are 

'  Haberer :  Archiv  fur  Anat.  und  Phys.,  Anat.  Abtheil.,  19M. 


PRACTICAL   CONSIDERATIONS:    THli   Sl'LEEN. 


1787 


They  empty  into  a  little  group  of  lymph-inxles  at  the 


also  a  few  superficial  ones. 

'""   m'll^^'eMrom  the  solar  plexus,  enter  the  hilum  with  the  vc^b. 

Develooment  and  Growth.-The  splenic  anlaue  appears  about  the  fifth 
,      I  fS  We  L  a  Siirht  condensation  of  the  mes».l.lastic  tissue  of  the  meso- 

SS^Th^SiSkn  bodies  %pear  relatively  late  as  accumulations  of  young 

?h7spi^v:£r  o-H7Xr  hand.^— ^^^    ^^::ii^:i  £ 

spleen  more  regular  t^anm  later  hfe      l-^^  Ji^ur  ^^^  ^^^^  ,„be 

Ircl^a^Vi^Tthr^ieeZ^^^^^^^^^  capsule  nearly  or  quite 

"•"  ArciUo;;'l;ie1n'»'^^^^^^^  common,  but  they  .-.  not  all  ofthe  same  signifi- 

mmtmm 

"""^     ■     MndonThe  spleen  near  the  hilu'm  are  due  to  the  fusion  c^such  accessory 
-  tto  has  seen  twenty-three  accessory  spleens  in  one  body.     They  are 

;ice  Anaiomy!-The  relations  of  the  spk.n  to  other  organs  have  been 
de  .but  itXuld'^  be  stated  that  the  phrenic  surface  1  es  beneath  the  ninth 

tenth  and  ereventh  ribe  (sometimes  the  eighth  also),  and  that  .to  long  '^''^  »  .'^f  «' 
!r.L^,nf  these  ribs      It  is  important  to  note  that  the  spleen  is  situated  behind  the 

A  line  from  the  top  of  the  sternum  to  the  tip  of  the  eleventh  rib  should  be  enureiy 
anterior  to  the  spleen. 

PRACTICAL   CONSIDERATIONS:    THE   SPLEEN. 

The  SDleen  may  be  congenitally  absent,  or  it  may  be  of  extremely  small  size  - 
no  Jeer  tC  wafnut ;  or  there  may  be  supernumerary  spleens  connected  with  he 
manfland  or  There  may  be  mu/iifi^e  spleens  entirely  separate  and  lying  m  the 
foWs  Tthe'^eaier  omentum,  the  gastro-splenic  omentum,  or  'J^^  t'-nsverse  m«o^ 
colon      It  is  conceivable  but  unlikely  that  these  anomalies  may  lead  to  mistaken 

diagnoses^  of  the  normal  spleen  is  difficult  of  accurate  determination  by  either 

pal  Jion  or  percuss  on  because  («)  it  is  covered  in  front  by  the  stomach  thecardjac 
33  whkh-if  the  stomach  is  distended-completely  overiaps  it ;  (*)  1>««  «i«;y 
ft  is  cov*r^  at  ts  lower  portion  by  the  diaphragm  and  by  the  tenth  «nd  eleventh 
Ste  and  ;?e  thick  musciroverlving  them,  and  »»»  '^.K'n^/.TintriorlyTtTs 
muscles  the  diaphragm,  the  ninth  rib,  the  pleura,  and  the  lung  ,  <  f ) '"'f  """X, "  '" 
r^nuct  intem^ally  with  the  upper  end  and  part  of  the  outer  edge  of  the  ^ft  W^-y^ 
and  externally  with  the  splenic  flexure  of  the  colon  ;  (d)  the  upper  part  01  ine 
Dhrenksurface  ^occasionally  in  contact  with  the  leh  lobe  of  the  hver  ( Quain )  ;(e) 
&he  r^S  viiable  in  both  shape  and  size  of  all  the  abdominal  viscera  ;  (/)  .t 

'  Archivf.  mikro.  Aiwt.,  IW.  Ivi.,  ig«J.  . 

•  Consult  articles  by  Parsons  and  by  Haberer.  just  noted. 


sio'- 

s-  ' 

U! 

de 


1788 


HUMAN  ANATOMY. 


changes  in  position  with  the  movements  of  the  stomach,  having  its  longest  diameter 
vertical  when  the  latter  is  contracted  and  horizontal  when  it  is  distended. 

These  relations  sufficiently  explain  the  difficulty  not  only  in  determining  the 
size  of  the  normal  spleen,  but  also  in  distinguishing  by  percussion  its  abnorma. 
enlargement  from  cases  of  colonic  fecal  impaction,  of  tumors  of  the  left  kidney, 
of  large  plastic  exudate  at  the  base  of  the  left  pleura  or  lung,  of  hypertrophic 
cirrhosis  mvolving  the  left  lobe  of  the  liver,  and  of  certain  growths  of  the  stomacli 
or  omentum. 

In  cases  of  hypertrophy  or  of  swelling  of  the  spleen,  as  in  malaria  ( ' '  ague-cake"  ), 
palpation  is  often  of  more  value  than  percussion,  the  sharp  creitated  anterior  border 
being  recognizable  below  the  tenth  costal  cartilage.  Physiological  increase  in  size 
occurs  during  d^^iution,  but  pathological  enlargement  may  follow  portal  congestion, 
leukaemia,  mala;i  i.  typhoid,  or  other  infectious  di.sease,  including  most  forms  of  general 
sepsis,  or  may  result  from  infection  of  the  splenic  substance.  It  may — as  in  some 
malarial  and  leuksemic  cases — so  enlarge  as  to  occupj^  most  of  the  abdominal  cavity. 
It  is  then  closely  applied  to  the  parietes,  and  is  not,  like  renal  tumors,  covered  ante- 
riorly by  the  intestines. 

Enlargement  of  the  spleen  in  infants  is  often  due  t  -.  inherited  syphilis,  and  if  it 
occurs  at  the  age  of  two  or  three  months  is  usually  of  that  character.  It  is  of  more 
diagnostic  value  than  enlargt.Tient  of  the  liver,  because  that  organ  is  normally  dispro- 
portionately large  in  infancy,  and  hecause  other  causes  than  congenital  syphilis  lead 
to  its  enlargement. 

In  all  forms  of  enlargement  of  the  spleen  in  children  there  is  said  to  be  more 
relative  encroachment  upon  the  thoracic  cavity  than  in  adults,  owing  to  the  firmer 
support  of  the  phreno-colic  ligament  in  young  persons  (Treves).  Whenever  it  is 
greatly  enlarged,  at  any  age,  it  is  apt  to  push  upward  the  diaphragm  and  compress 
injuriously  the  base  of  the  left  lung  and  the  heart.  In  splenic  tumors,  therefore, 
irregular  cardiac  action  and  dyspnoea  are  often  present  fc  mechanical  reasons  as  well 
as  on  account  of  the  associated  anaemia. 

The  normal  movements  of  the  spleen  are  not  so  much  affected  by  respiration  as 
are  those  of  the  liver,  which  is  more  closely  and  extensively  connected  with  the  dia- 
phragm. It  rises  slightly  in  expiration  and  descends  during  inspiration.  It  is 
pushed  down  in  emphysema  and  in  left-sided  empyema,  haemothorax,  or  pneumo- 
thorax.     It  is  pushed  up  by  ascites  or  by  intra-abdominal  new  growths. 

Its  relations  explain  why  abscesses  of  the  spleen  (usually  due  to  septic  emboli,  as 
in  pyamia  or  septicaemia,  typhoid  fever,  or  ulcerative  endocarditis)  open  spontaneously 
in  the  following  directions:  (i)  Into  the  general  peritoneal  cavity  (the  most  fre- 
quent). (2)  On  the  cutaneous  surface  below  the  costal  margin  anterioriy  or  poste- 
rioriy.  (3)  Into  the  large  intestine.  (4)  Into  the  left  pleural  cavity.  (5)  Into 
the  left  kidney. 

Afox'ablr  spleen  {dislocated ,  floating ,  wandering  spleen)  occurs  only  in  adult*, 
and  is  especially  found  associated  with  some  degree  of  splenic  enlargement — in- 
creasing its  weight — in  persons  with  relaxed  or  flabby  abdominal  walls.  It  is,  there- 
fore, often  found  in  anemic  multiparae,  as  it  is  held  in  position  normally  not  only  by 
the  phreno-splenic  and  phreno-colic  ligaments,  but  also  by  the  pressure  of  the  other 
abdominal  viscera  due  to  the  general  tonicity  of  the  abdominal  muscles. 

In  such  cases,  after  elongation  of  the  phreno-splenic  ligament,  the  spleen  falls 
forward,  lies  horizontally  with  the  hilum  directed  upward,  and  is  sustained  only  by  the 
gastro-splenic  attachments  and  the  vessels,  thus  drawing  the  stomach  downward  and 
causing  serious  gastro-intestinal  disturbance,  or  possibly,  if  the  vessels  are  twistetl 
and  obliterated,  a  fatal  peritonitis  (Shattuck). 

In  exceptional  cases  a  movable  spleen  may  reach  the  pelvis. 

From  a  movable  kidney  a  wandering  spleen  may  be  distinguished  by  the  super- 
ficial position  of  the  latter,  its  shape,  the  disappearance  of  the  spleen  from  its  normal 
position,  and  the  absence  of  urinary  symptoms. 

Wounds  of  the  spleen,  if  posterior,  usually  involve  the  diaphragm  and  the  base 
of  the  left  pleural  cavity,  or,  if  higher,  the  lung  itself ;  if  anterior,  the  stomach  may 
be  penetrated.  In  gunshot  wounds  the  kidney,  colon,  or  pancreas  may  likewise  he 
involved. 


THE  THYROID   BODY. 


1789 


In  fractures  of  the  ninth,  tenth,  or  eleventh  nb  the  fragments  may  lacerate  the 
1  Jn  OrTaccount  of  its  great  vascularity,  wounds  of  the  spleen  are  serious  and 
'&  necSitote  oJeStion,^but  occasionily,  after  small  stab  wounds  or  gu.«hot 
'*''^^^1M^llet^o?  small  calibre  spontaneous  recovery  ukes  place,  and  has  been 
Tllff^  /rr^vSto  r  contSity^of  the  muscular  tiLue  of  the  splenic  capsule. 
Sn1r^ow7  the\-ordrcKna^les  it  to  retain  the  blood-clot,  and  thus  stops 

'^"  '^TKte'i.v",  a  wound  of  the  spleen  is  usually  bright  red.     In  wounds  of 

ssjS-ssrss£:-r=sss 

'''  Tn"S^rr«.  on  the  spleen  it  may  be  approached. through  incision  either  at  the 
''"^'innS^^S:^^- ---  ^  t£  t'^t^l^'j^mature  tearing  or  di^^ion 
of   th^"  ^^"^{Y^^^^^ 

"^'''"^rltC'Sfberea  ftbylSbgth^^^  the  spleen,  and  some- 

Tes  twTen)^  P^lHnTthTspIeen  dfwn  from  beneath  the  diaphragm  and  turning 

'''Textio  hemorrhage,  the  chief  risk  is  that  arising  from  damage  to  acjoining 
viscera  during  trS^aradon  of  adhesions,  and  the  relations  of  the  stomach,  pan- 
crS  colon?  and  kidney  should  therefore  be  c.  -fully  borne  m  mmd. 

THE  THYROID   BODY. 


1790 


HUMAN  ANATOMY. 


antero-extemal  surfaces  of  the  lateral  lobes.  The  isthmus  varies  much  m  sizt . 
and  is  often  more  or  less  incorjwrated  in  one  of  the  lobes.  In  lo  |)er  cent,  it  i> 
absent  '  An  upward  projection,  the  pyramida/  process,  rising  from  either  the  isthniii> 
or  one  of  the  lateral  lobes,  and  usually  rejjarded  as  a  remnant  of  the  median  anlam 
ot  the  thyroid,  is  found  more  or  less  developed  in  probably  half  the  cases.  A  typical 
one  reaches  the  hyoid  bone,  to  the  body  of  which  the  process  is  generally  attachtil 
either  by  muscle  or  ligament.  It  is  rarely  quite  median,  being  more  frequently  found 
on  the  left.     Statements  as  to  its  frequency  vary  greatiy.     Streckeisen '  says  it  i> 

wholly  wanting  in  only  alxmi 
Fig.   isio- 


■EpiKlottis 


uperior  cornu  of 
ttiyroid  cartilage 


.Occasional  foramen 


■Thyroid  cartilage 


.Crico-thyroid 
membrane 

.frjco-thyroid 

muscle 
■Cricoid 

cartilage 
■Suspensory 

ligament 
-Pyramidal 

process 

■Isthmus 


■Lobule 


Thvn.iil  IhhIv  /»  siiu  ,  anterior  aspect. 


20  j)er  cent. ;  but,  since  goitre 
is  common  in  Switzerland,  his 
sources  of  information  are  not 
of  the  best.  Zuckerkandl, 
however,  puts  the  occurrence 
of  the  process  at  74  per  ctiit. 
timber,  in  Russia,  found  it  in 
only  40  per  cent.,  and  Mar- 
shall, in  England,  in  43  per 
cent.  We  incline  to  believe 
that  these  latter  figures  rep- 
resent the  more  common  pro- 
portion. 

The  thyroid  lies  beneath 
the  group  of  infrahyoid  mus- 
cles, from  which  it  is  separated 
by  the  middle  layer  of  the 
cervical  fascia.  The  sterno- 
mastoid  muscle  crosses  the 
lower  part  of  the  lateral  lobes. 
The  inner  surface  lies  against 
the  trachea,  the  cricoid  carti- 
lage, and  the  lower  posterior 
part  of  the  wings  of  the  thy- 
roid cartilage.  It  reaches  back 
to  the  oesophagus,  which  it 
touches  on  the  left,  and  some- 
times on  the  right  also.  It 
may  touch  the  lower  part  of 
the  pharyn.x  on  both  sides. 
The  sheath  of  the  carotid  lies 
against  the  posterior  surface  at 
its  outer  border  and  is  in  part 
external  to  the  organ.  The 
common  carotid  is  usually  be- 
hind the  thyroid  and  the  inter- 
nal jugular  vein  beyond  it. 
This  explains  how  an  enlarged 
gland  insinuates  itself  between 


these  vessels  Frozen  sections  show  that  often  the  carotid  is  external  rather  than 
posterior  to  tM  organ,  but  still  in  close  relation  to  it.  Internal  to  the  carotid 
sheath  it  rests  behind  against  the  prevertebral  fascia.  The  inferior  thyroid  arter-es 
enter  the  lateral  lobes  from  the  inner  side  and  the  superior  thyroid  arteries  from  the 
antero-cxternal.  The  middle  cer\  ical  sympathetic  ganglion  is  behind.  The  infenor 
lar\-ngeal  ner\es  lie  at  its  inner  surface,  the  left  one  being  in  actual  contact  with  the 
thyroid  and  the  right  one  at  least  very  close  to  it.  The  sheath  connects  the  thyroid 
body  verv  closely  to  ncighl«>ring  parts.  It  is  so  firmly  bound  to  the  trachea  as  to 
foUow  its' movements.     Median  bands  to  the  cricoid  and  thyroid  c.irtilages  have  been 

'  M.ir-hall :  Journal  of  Anatomy  and  Physiology,  vol.  xxix.,  1S95. 

'  Virchow's  Archiv,  lid.  ciii..  1886. 


THE  THYROID    BODY. 


1 79 1 


Histineuished  as  suspensory  ligaments.  A  lateral  ligament  from  the  'nner  side  of  the 
fateKbTis  tolerawTwdl  defined.  It  pas-Ses  backward  and  upward  to  the  first  nng 
of  the  tr^hea,  to  the  cricoid,  and  perhaps  to  the  inferu.r  horn  of  the  thyroid.  Ihe 
VTJ^andula:  thvroide^  is  a  small  muscle  often  fotnid  jxi^sinR  down  from  the  hyo.d 
toMtothe  capsule.     It  may  or  may  not  be  connected  with  the  pyramidal  process. 


Sterno-lhyroid  musi-Ie 


Fio.  1 51 1. 

Stermi-hyoid  muscle 


^  KiRht  internal 

Left  internal  JUKUlar  vein      /    ~'St^^'i.?r^.t^'^^'j^^^Bi^^\'^'/'i0pf^,\  \  juKuL-ir  \ tin 

Uft  pneumouBstric  nerve        /^^^ISSV^^^^SSSk^^LeSSX'^f^'^  PneumoRastric  nerve 

'        ijSjTCfl  -^MMMnBt  J  _C        r '  Richt  common  carotid  artery 

Left  common  carotid  artery       ^^^T^^^^^Sc!^^^ 

Inferior  larynKeal  nerve  /  •^'SJStBBF '^  1      „ 

Inferior  thyroid  arter^         TTT^*^         Inferior  laniig««>  "«""= 
Prevertebral  fascia       1  Trachea 

CEsophaKua 

Anterior  part  kA  froien  section  across  neck,  shawing  relation*  of  thyroid  body. 

Structure.— Although  in  principle  corresponding  in  its  development  with  other 
compound  alveolar  glands,  the  thyroid  body  pos-sesses  no  excretory  ducts  and  pre^ 
sentT  peculiarities  in  the  structure  of  its  terminal  compartments.  The  hbro-elastic 
f«/)*«/rinvesting  the  gland  gives  off  septa  which  subdivide  the  organ  into  the  chief 
lobules,  the  latter  being  composed  of  smaller  compartments  separated  by  thin  parti- 
tions of  connective  tissue.     These  subdivisions,  or  primary  lobules,  from  .5-1   mm. 

Fig.   1513. 


Interlobular, 
connective-tis- 
sue septum 


Colloid  mas! 
within  acinus 


Section  of  thyroid  body,  showiuK  acini  in  v.irious  degrees  of  distention. 


in  diameter,  contain  a  variable  and  usually  large  number  of  tenninal  vesicles  r  f  lli  _ 
cles  which  c-rrespond  to  the  alveoli  or  acini  of  ordinary  glands.  The  delu-.tt  and 
highly  vasci..ar  framework  supporting  the  follicles  consists  essentially  of  hbrot.s  r,m- 

nective  tissue,  elastic  fibres  being  few  or  entirely  absent.  

The  «r/»/ vary  greatly  in  size  (.050-.  200  mm.),  depending  upon  the  amount 


1792 


HUMAN  ANATOMY. 


of  secretion  and  the  distention  of  the  acini.  Their  hning  consists  of  a  single  layer  of 
fairly  regular  polygonal  cells,  about  .010  mm.  m  diameter,  the  height  of  the  cells 
varying  with  tlie  dotation  of  the  follicle.  In  young  subjects,  in  whom  the  acini  arc 
Kenerally  less  completely  filled  than  in  older  ones,  the  epithelium  of  the  follicles 
ipproaches  the  columnar  type.  A  similar  condition  is  often  to  be  noted  in  certain 
acmi  even  in  thyroids  in  which  the  usual  distention  affects  the  majonty  of  follicles. 
A  distinct  basement  membrane  is  wanting,  the  cells  resting  directly  upon  a  somewhat 
condensed  stratum  of  the  surrounding  connective  tissue.  Since  the  epithelia  lining 
is  the  source  of  the  peculiar  colloid  secretion  of  the  gland,  the  cells  ordinarily  con- 
tain a  variable  number  of  highly  refracting  granules,  particularly  m  the  «one  next 
the  sac  The  peculiar  substance  or  colloid  commonly  found  within  the  follicles  ot 
the  adult  organ  is  regarded  as  a  proteid,  although  its  exact  chemical  characteristics 
are  still  uncertain.  The  consistence  of  this  substancs  vanes  being  more  fluid  m 
young  than  in  old  glands.  Its  varying  appearance  within  the  follicles,  as  vacuo- 
lated reticular,  or  shrunken,  is  referable  to  the  action  of  reagents,  in  is  natural 
condition  the  secretion  being  homogeneous  and  entirely  filling  the  foUice.  the 
differentiation  of  the  epithelial  lining  of  the  acini  into  chief  and  colloid  cells  ^Lang- 
endorff).  as  represenUng  disUnct  elements,   is  doubdul.  since  specific  difference. 

probably  do  not  exist.  .  .       ,     , 

Vessels.— The  blood-supply  is  very  generous,  coming  from  two  pairs  ol  rela- 

tively  large  aHeries,  the  superior  thyroids  from  the  --'^^^^S^^^^i^X'^  I, 

_,  subclavians.    The  superior 

'■'°    '*'^"  descend  to  the  top  of  the 

lateral  lobes   and   ramify 
over  the  front  of  the  organ, 
sending  branches  to  the 
interior,    and    sometimes 
meeting  on  the  isthmus. 
The  inferior  arteries  pass 
upward  behind  and  enter 
the  organ  on  its  inner  sur- 
face.     Their  relations  to 
the  inferior  laryngeal  ner^'e 
are    of    practical    impor- 
tance.     In  437   observa- 
tions' the  artery  was  found 
in  front  of  the  nerve  on 
the  right  in  about  41  per 
cent,   and  on  the  left  in 
63  per  cent.     In  over  10 
per  cent,  of  the  cases  the 
branches  were  so    inter- 
laced that  the  relation  was 
uncertain.      It  is  evident 
that  in  enlargement  of  the 
thyroid  body,  with  conse- 
ouent  enlargement  of  the  arteries,  the  number  of  such  indefinite  relations  would  be 
verv  much  fncTLed,  as  very  minute  branches  would  then  spring  into  importance^ 
AnlnTrge^  tortiou;  artery  tends  to  curi  around  the  nerve.    There  was  no  artery  on 
£  rkht^in  one  case  and' none  on  the  left  in  five  cases  of  th«  series.     An  aW.;,^ 
ihvrofdea  ima  springing  from  the  arch  of  the  aorta  and  ascending  in  the  median  line  is 
Sonal  y  seen.     From  the  rich  superficial  arterial  plexus  numerous  branches  pass 
aS"he  interlobular  septa,  following  the  ramifications  of  ^he    atter    «  the^fo^^^^^^^^ 
where  the  arterioles  break  up  into  capillaries.     These  surround  the  fo"'^'^-_^^'  f, ^'^ 
meshetl   net-works,  which   are  often  common  to  the  adjacent  sacs,  rcscmbh.ig  the 
caoillarv  net-works  around  the  pulmonary  alveoli. 
•^  The  m«*  are  very  numerous.     Emerging  from  the  organ,  they  form  a  large 
'  Dwight:  Anatom.  AnzeiKer,  Bd.  x..  1895. 


'^Acinui 


Interlobular 
vewcis 


Acinus  con- 
taining col- 
loid 


Section  of  injected  thyroid  body.    X  4*. 


THE    THYROID   BODY. 


1/9.^ 


Irom  Ih.  d«per  part  of  .he '«."  »™  j''™  »  "'>■  t"n.«"V.n.  ,.«,.  .hi-  M.  in- 
ferior  thyroid  veins  can  be  injfcted  from  bcU.w.  .     ,      ly^ph-s.^ces  ;   from 

constitute  a  sunerhmlpexus  from  ^'l^f ,  .^^\  >  ^^'^fro^^  of  the  larynx,  some 

r:.  Edir ; :  :s  ^l-dral'^^h':^n^^^^      -d  .j.  .rom  the 

Sm^rand^U  parts  S.];n.a^^^^^^^^  ^^^,^_     ,, 

Sin::i%r/r;»l'£>i^^^^  end  around  the  foUid. 

median  and  two  lateral     The  -''''''?'' «'XJ^^«^^^^^^  pharynx 

3-4  mm.  as  an  ep.thelial  °"'Sr°«^VThmrtSoTen  close  relation  with  the 
fn  the  region  o    the  second  v'^-^arch^therefore  m  c^^^^   ^^^  evagination 

posterior  part  of  the  tongue.     At  hrst  P??*™  ?L  ^V         ^.hjch  for  a  short  time  is 
L>n  loses  its  cavity  and  becomes  a  -I'd  ^^^^^^  *^„d.     Usually  the  latter 

connected  with  the  pharyngeal  wall  by  a  dehca  e  ^^V^^^lia^^ra      j  J  increases 

soon  disappears  and  the  isolated  median  » Y'  /  tho  ttera^tnbees      The  position  ..f 
as  a  bilotid  mass,  pa^  to  the  lower  level  ««  ^J^  '^^^'„''J'X^  /.ra- 

the primary  -^'h^Xi^/rthe  V^-row  of  Ercumvallate  pa'pUte.     Occa- 
mrn  cacum,  just  behind  the  -^pex  oi  !"«  ^  .     (hvro-ghssal  duct,  a  narrow  tube 

sionally  the  evagination  persists,  and  thf";°""^^f  Sds  the  thyroid  body.  The 
extening  for  a  -^able  d.sunce  f^om  f„%  -^Tut^^^^^^  the  venLl  wall 

lateral  anlage  appears  on  each  side  a^"  an  epiineu  »  becoming  trans- 

of  the  fourth  pharyngeal  furrow  (F'K/S^O.the  «"'""»«  I^''"^^^  .^^    rudi- 

formed  into  a  sac.  ^^icW  ^  V '^f.XS  aLSm. .  join  to form^he  definitive 
mentsgrowventtBlly,  and  later.  '"^^.^'X^^/^r^X  medikn  anlage  contributes  the 
thyroid  -Ht^Sd  SvroidbLdy  tomparati"embryolo|y  emphasizes  the 
most  important  part  of  the  thyroia  '^5'y- .  J^  . . '^^  .  indeed,  all  participation  of 

significance  of  the  median  anlage  as  the  t'^^^^'V^Xanimairis  denWl  (Verdun). 

numerous  cyhndncal  epithelial  '^«™!,  •[°'"Jj/;'i^  ^^^^rds  into  a  net-work  the  meshes 
second  stage  witnesses  the  «"«'X,''**SblSt£ue  During  the  third  foetal  month 
of  which  are  occupied  by  vascular  mesoHast.ctis.u^^^  ^^^^.^j^  ^,  ^^^ 

the  epithelial  reticulum  breaks  up  into  masses  "^P^l^""'"*^    ,,    become  arranged 

and  behind  and  sometimes  below  it.      1  hey  are  remnam  thvro-glossal  duct. 

Uculum  from  the  pri|nit.ve  phaO^nx.  somet.^^^^^^ 

This  ,«^d  onginally  '"J™"*  "'   Those  behind  and  below  the  hyoid  are  probably 

SrSS'aru^a7d  »ownwar?g^wThU  the  primary  diverticulum. 

"3 


1794 


HUMAN  ANATOMY. 


PRACTICAL  CONSIDERATIONS:    THE  THYROID  BODY 

Congenital  absence  of  the  thyroid  body,  or  its  atrophy  with  loss  of  function, 
occurring  at  any  time  before  puberty,  is  apt  to  be  followed  by  the  interference  with  nii 
trition  and  with  normal  mental  and  physical  development  that  produces  the  condition 
known  as  cretinism.  Similar  atrophic  changes  occurring  later  in  life  cause  myxu- 
dema,  and  the  same  condition — also  known  as  cathexia  strumipriva — may  be  brought 
about  by  the  complete  excfaion  of  the  gland.  Calcification  of  the  gland  may  take 
place  in  old  age.  The  isthmus  may  be  congenitally  absent  and  two  separate  lobes  lie 
present,  representing  the  originally  distinct  embryonic  lateral  anlages  of  the  organ. 

Accessory  thyroids  may  undergo  hypertrophy  and  form  large  masses  occupying 
the  pleural  or  the  mediastinal  cavity  (Osier- Packard)  ;  or  they  may  develop  at  the 
base  of  the  tongue, — lingual  goitre  ;  or,  on  account  of  their  embryonic  relation  to 
the  thyro-glossal  duct  (which  passes  behind  the  hyoid  bone),  they  may  be  found  in 
the  median  line  of  the  neck  below  or  behind  the  hyoid,  and  may  be  mistaken  for 
growths  of  a  different  character  (page  554). 

The  thyroid  gland  may  be  temporarily  enlarged  in  women  during  menstruation. 

Hypertrophy  oi  the  thyroid  gland  (goitre)  may  be  (a)  parenchymatous  when 
it  results  from  a  general  hyperplasia  of  the  gland- tissue  ;  (*)  vascular,  due  to  a 
great  increase  in  the  size  and  number  of  the  blood-vessels  ;  {c)  cystic,  characterized  b^ 
the  formation  of  walled-off  cavities  within  the  already  enlarged  gland  ;  (rf )  fibrinov 
the  connective-tissue  elements  being  in  excess  ;  (^)  exophthalmic  (Graves's  disease 
in  which  the  thyroid  enlargement  is  associated  with  exophthalmos  and  function. . 
derangement  of  the  vascular  system  ;  (/)  adenomatous,  the  hypertrophy  affecting 
one  or  more  lobules  or  the  isthmus.  This  last  form  appears  as  a  one-sided  or  asym- 
metrical swelling,  is  common,  and  is  often  classified  with  tumors  of  the  thyroid, 
rarer  forms  of  which  are  the  cancerous  and  sarcomatous.  It  may  be  noted  that  the 
gland  is  relatively  larger  in  females,  and  that  the  right  lobe  is  larger  than  the  left. 
This  has  been  thought  to  explain  the  greater  frequency  of  goitre  on  the  right  side, 
and  in  women. 

Inflammation  of  the  thyroid  is  rare,  and  usually  occurs  dunng  typhoid  or  other 
infections,  although  it  is  favored  by  -'•evious  thyroid  disease  or  overgrowth.  The 
tumefaction  which  it  produces  may  cf  e  acutely  many  of  the  symptoms  brought  on 
more  slowly  by  the  chronic  forms  of  enlargement.  These  symptoms,  so  far  as  they 
have  any  anatomical  bearing,  are  :  (i)  The  swelling  rises  and  falls  with  the  latp^nx 
during  deglutition.  This  is  due  to  the  attachment  of  the  thyroid  gland  to  the  cricoid 
cartilage  by  the  upward  prolongations  of  its  capsule  known  as  the  suspensory  liga- 
ments and  to  the  subjacent  larynx  and  trachea  by  connective  tissue.  (2)  Dyspnaa. 
The  gland  is  covered  and  its  growth  anteriorly  resisted  by  the  sterno-hyoid  and 
stemo-thyroid  muscles  (Fig.  545),  and,  to  a  less  degree,  by  the  omo-hyoid  and  the 
anterior  border  of  the  stemo-mastoid.  Its  forward  progress  is  also  resisted  by  the 
pretracheal  layer  of  the  cervical  fascia.  Its  close  relation  to  the  trachea,  therefore, 
renders  the  latter  subject  to  direct  pressure,  especially  in  the  firmer  forms  of  bilateral 
enlargement,  or  in  those  adenomata  which  begin  in  the  isthmus  or  lie  between  the 
trachea  and  the  sternum.  In  the  unilateral  forms  the  trachea  may  be  displaced  to 
one  side.  (3)  Headache,  vertigo,  cyanosis,  and  epistaxis.  The  relation  of  the 
outer  border  of  the  thyroid  to  the  carotid  sheath  explains  the  disturbance  of  the  cir- 
culation in  the  carotid  and  internal  jugular  (either  through  direct  pressure  or  by 
deflection  of  the  vessels  outward)  and  accounts  for  these  phenomena.  (4)  Dys- 
phagia is  relatively  rare,  but  may  occur  as  the  result  of  pressure  upon  the  upper 
end  of  the  gullet  or  the  lower  portion  of  the  pharynx.  It  is  more  common  in  left- 
sided  goitres,  owing  to  the  curvation  of  the  oesophagus  towards  the  left.  As  a  great 
rarity  the  isthmus  of  the  gland  is  found  between  the  trachea  and  oesophagus  ( Burns). 

(5)  Dysphonia,  or  aphonia,  due  to  pressure  upon  the  recurrent  laryngeal  ner\es. 

( 6)  Pulsation  or  bruit.  These  may  be  apparent,  and  caused  by  the  close  relation  of 
the  enlargement  to  the  common  carotid  artery,  or — much  more  rarely — real,  and 
due  to  the  relatively  enormous  blood-supply  of  the  vascular  form  of  goitre,  the  thyroid 
with  its  four  constant  arteries  and  occasional  fifth  one  (the  thyroidea  ima, — 10  per 


THE  PARATHYROID  BODIES. 


"795 


.  ^  raaMt  beiiMT  normally  one  of  the  most  vascular  structures  ol  the  body. 
^Ir  ^  ^  cSon  in  th/  exophthalmic  form.  (7  )  The  trrmor,  lacky<ard,a 
A^^^^hoL  InZVvebalh  seen  Tn  Graves*  disease  in  association  with  thyroid 
^IjiCJ^tTave  no  Sactory  anatomical  explanation,  although  the  dose  relatwn 
^SSathrtic  n"  e  and  middle  cervical  sympathetic  ganglion  to  the  infenor 
S^vro'd  art^v  the  distribution  of  their  vasomotor  fibres  to  the  thyroid  vessels,  and 
o^  W  iSS^  ed  fibres  to  the  ocular  apparatus,  and  their  possible  ^ntpl  «>""«- 
°Ln-'' p^bly  in  the  medulla"  (Treves)-have  been  invoked  to  explain  the  phe- 

"'"'S^IS.  ^hyrolfen^^^^^^^^^        vary  with  the  character  of  the  latter. 

iTthe  adenomatous  and  cystic  varieties,  after  division  of  the  capsule  o    the 

'"  'Texdsi'oSr'the  skin  platysma  and  cervical  fascia  should  be  freely  divided  and 
the  ieSToids  and  th?roiL  retracted  or  divided  :  after  '".-'^  founrfix'd 
b^en  wdl  exposed  the  growth  is  first  loosened  externally. -:«  it  will  »*  «ound  hxeU 
o^vP  hv  fhi^rior  thyroid  vessels,  below  by  the  inferior  thyroids,  and  internally 
above  *'.y  ^''"'^"h/vS  setiaratcly  ligated.  great  care  being  taken  to  avoid  the 

structures,  and  the  growth  removed. 

THE   PARATHYROID  BODIES. 

Thi-^e  organs   the  ebilhelial  bodUi  of  many  authors,  are  small  elliptical  m.isses 

situaSTearThe  thjrdd^hich  formerly  were  Mistaken  either  for  accessory  thyroids 

or  for  lymphatic  nodules.     They  arise  from  the  posterior  wall 

of  the  third  and  fourth  pharvngeal  pouches,  and  thus  diHer 

from  the  thyroid  body  in  origin  as  wrll  as  in  stnicture.      1  hey 

are  6  or  7  mm.  long.  3  or  4  mm.  brrud.  and  1.50'  2  "^m-  'hick^ 

The  leneth  may  be  as  much  as  15  mm.     They  are  always 

separated  from  the  thyroid  '  y  the  ca,«ule.     Most  frequenriv 

theparathyroids  exist  as  two  p-iirs  on  each  side;  their  disposi- 
tion  however,  may  be  asy  nnietrical,  in  some  «^^  "J='"y 

as  four,  in  others  none,  lying  on  one  side.     The  position  of  the 

stiPerwr  pair  is  the  more  constant  and,  according  to  >\  elsh 

coVrespoAds  about  with  the  level  of  the  lower  edge  of   the 

cricoid  cartilage.     They  usually  lie  against  the  P<»'*^7«""r^^^^^^ 

of  the  lateral  thyroid  lobes,  between  the  middle  and  the  inner 

border  of  this  surface.      The  inferior  pair  is  lower  and  more 

anterior  than  the  superior,  their  position  being  less  constant. 

Sometimes  they  lie  against  the  side  of  the  t;^^»;«;»  "'^•'[.;^^;; 

ends  of  the  rings,  under  cov.r  of  the  lower  part  of  the  th>rod 

lobes;  sometimes  thev  are  found  in  a  corresfK.nding  relation  o 

the  windpipe,  but  much  lower,  so  as  to  have  "" /^'f ""  ^^."'^ 

the  thyroid ;  occasionally  they  lie  on  the  front  "t^e  trachea  ^__^ 

below  the  thyroid.     The  surest  means  «« '«^?,""K.  ^f^^'^     "f^  ^^:S^:^JS^^^^t 

bodies  are  the  minute  parathyroid  artenes,  small  tw  igs  chietiy     f^. ^r.    ".^^^  ,^,,, .  „,  ^^^. 

Tmlhe  inferior  thyroTds.  to  each  one  of  which  a  parathyroid     r.o^.Hv™--V,,i---, 

body  is  attached      It  is  evident,  therefore,  that  these  organs     „„„    (c.«»».<r ) 

into  »1-S nrf  lolS„  by^a  Ie«  detae  ip.a  .hich  .u,.p«rt  .he  Wo,-l.v»»,r. 
■Journal  of  Anatomy  and  PhysioloKy,  vol.  xxxii..  1898. 


Fig.  1514- 


1796 


HUMAN    .   NAiONW. 


The  Kland-tiasue  consists  of  closely  pt  -  i-l  i^'ly^-f  >al  epithelial  celU,  aUiut  .010  mm 
in  diiimeter,  varyin>{ly  disjxRied  as  c<  u.i'Uinis  my,  is  c;  im|M  '-ctly  separatwl  <«.riN 
ami  alveoli.  The  cells  ptjssess  rouno  nu.  !<  i  *|ii.  v.iitain  chromalin  r«licula.  Ihi 
cells  are  surroundiil  bv  a  honey -comb  «.  'lelioiU'  n  •  mbrafie».  rttirous  tissue  ap|)ear 
in>{  only  in  the  immediate  vidnity  of  th'  larger  i  l....<i-\e«iels  ami  not  lietwei-n  the 
epithtlii'il  tl.inents.  The  latter  lie  aK-iinst  tlit-  < ,,  lotli. 'lal  hni- hj  ot  the  relativelv 
wide  and  numerous  capillaries,  the  attenuated  membraiu  of  tht'  inttrcellular  h<ine\ 
comb  alone  intervening.      While  admitting  the  independence  < »!  the  parathyroids  as 


m 


Sections  of  human  ^^-. 
uniform  contitmuUA  masttes 
contain  lollojil  (rt.     v  joo 


parathyroid  bodi*^,  showinu  different  tjpes  ol  structure 
Sites;  A.  broken  nn  mto  lobiiln  by  vuKUttr  wpU  {v);  L. 


.1.  prmcipat  tttls  arranict^l  as 
->puM-d  ai  acini,  &onic  oi  which 


^ 


distinct  organs,  as  now  established  by  both  anatomical  and  physiolo>,'ical  investiga- 
tions,' opinions  differ  as  to  their  histological  relations.  Schaper'  and  others  incline 
to  the  view  ad\anced  by  Sandstroem,  that  the  parathyroids  corresjmnd  in  structure 
to  the  immature  and  undeveloped  thyroid.  Welsh,  on  the  contrary,  denies  this 
resemblance  and  points  out  the  close  similarity  to  th<  anterior  lobe  of  the  pituitary 
body,  in  both  organs  colloid-containing  alveoli  being  occasionally  present. 

'  The  arteries  distributed  to  the  parathyroids  are  deri\  ed  from  the  branches  sup- 
plying the  thyroid  body.  Regarding  the  lymphatics  and  the  nerves  little  is  known  ; 
the  latter  are  chiefly  sympathetic  fibres  destined  for  the  walls  of  the  hh  .od-vessels. 

THE  THYMUS   BODY. 

The  thymus  is  apparendy  an  organ  of  ser^ice  to  the  nutrition — -  >ssibly  blood- 
formation— of  the  foetus  and'infant,  since  it  usually  reaches  its  grea  >t  size  a  about 
the  end  of  the  second  year,  having  grown  since  birth  fairiy  in  pr  fx>rtion  to  the 
body.  It  continues  for  some  years  to  enl.irye  in  certain  directions  at -1  t=^  dwindle  in 
others;  coincidendy  deposits  of  fat  appeal  <1  it  gradually  degenerates  When  m 
its  prime  it  is  moderately  firm  and  of  a  pmki.sh  color  ;  later  it  1j.  .  -  nes  very  friable 
and  resembles  fat  and  areolar  tissue. 

Shape  and  Relations. — The  api'^arame  of  the  thymu     -  tl 
organ.     It  is  surrounded  by  a  fibrous  capsul    which  svnds  pro,    sya 
lobules.     It  is  situited  beneath  the  upper  pan  of  the  sternum,  n  11 
periiaps  2  cm.  into  the  neck,  descending  to  alniit  'he  fourth  cost, 
tionally  as  far  as  the  diaphragm.     The  organ  is  thickest  above,  w 
pericardium,  and  descends  in  front  of  the  latter  in  two  flattened  K 
distinct,  which  grow  thinner  and  sometimes  diverge  lielow.     Thes. 
a  layer  of  fibrous  tis-sue  which  enters  oblitjuely  from  the  front  i' 
above  the  left  lobe  overlaps  the  other.     The  lobes  are  generally  01  u  leqi       •^^ 
left  one  being  more  often  the  larger.     Sometimes   '-■  lobes  are  fused,  and 
be  a  thinl  one  between  then:,  such  vari-itions  merely  -imiilying  irregul-ir; 
fibrous  septa.     The  thymus  lies  in  front  of  and  above    he  pericardium,  ai 

'  A  critical  review  of  the  relations  of  the  tpithelial  onf:   is  derived  from  the  pbar)-ngi.il 
pouches  is  given  by  Kohii  in  Merkel  and  Bonnets  ErRebnissc,  Btl.  i.x.,  1899. 
'  Archiv  f.  mikru.  Anat.  u.  Entwick.,  Bd.  xlvi.,  1895. 


of  a  glandii.ar 

•i,.. 


■  ns  amor 
.  wher    ' 

irtilapt 

e  it  p  - 
s,  morr 
:e  separa 

!(■'        •     Wil 


.nth 
■-  le 


THK   Tl   VMIS   BODY 


>797 


I-*  in 

Mirfa'     ■'/  —  —  ,  , 

its  hi    Uest  jmrt  luav  r<    t  on  tht-  ir.ictiia 
ippeiir«  ■>«  thf  Ult  of  t    "  former.      It  txi, 
iwtwifn  tho  ptri.anJiu      and  the  i>lvura 
w.ntal  scxtion  in  thw  r. .  cm  Hhows  the  th> 
becomes  thinntr  a-  the  .  xan  atn.i    it-s. 

Fio. 


i>  latt-r.i 
-   thi- 
.  .IS  .1 
•hiiMl  til 


(»n  eatli  -iMlf  into  th»'  intt  rval 

•  of  it*  liitwt  -i/x',  a  !   >ri 

.^  cresc-  (Fix.  i.siH),  «'"*' 

ery  toj  i  the  sternum  its 


Common  carotid  arli 
Pneiimn||Kf(tTtc  nrr\ 

nit-rnal  V  filial- — 
-cm 


tl..;:.!:     


Rlf       lobr 


Luii( 


eni'ar- 
iliutn 


Dissection  of  new-born  child,  sliowing  th 


ind  II.  ■»«» bodies  IH  s^m. 


line  on  section  is  roughly  quadrilateral     ^^-;^^'^':^;:;:^f  ^S! 

botly  to  the  capsule  of  the  thymus  ar-    ■-.wmmt  as  t«-  suxpeniurj,     >, 

internal  mammary  vessels  run  in  front       rt.        ^^,^^   ,      jj^frag"   w-^itlit  of  the 

Weight  and  Change8.-Accor<l^j_    rne«fle&^    ^.'^l^!;-!^ .>  s^,,,,ev 

thvmusatbirthis  13.75  gjn- :  the  ^"^<='"'"'^^;^™^^„  '  ;^,^.,f'    .^^^^  "  VVi^n  hcavi- 
tri;rinK  ?  em.  and Testut.  from  twentv  o.^rr-  al^ms.  an  ^''^^'^f  5  J.m^  Xtrophv 

S^  aL'u^  puberty  according  to  Hamm.r,  ..  '--^^J^'^^^^;-  ^^,%     X-' 
and  the  replacement  of  thymus  tissue  bv  fat  -    m  while  gr.mtn  m  iLngxi  h 


1798 


HUMAN  ANATOMY. 


Groove  for 
left  innominate  vein 


Kressing ;  this  increase  is  said  to  continue  even  after  puberty,  the  organ,  how- 
fv^  bicoming  thinner  and  softer.  Although  later  almost  completely  replaced  by 
adip^  and  connective  tissue,  the  thymus  never  entire  y  disappears,  remains  of  it. 
autpv/<».  tissue  being  present  even  in  extremr 

Fjo.  1 517.  old  age  (Waldeyer).       Until  ab<iut 

twenty  years  the  organ  is  usually 
readily  found.  In  ordinary  dissec- 
tions It  is  not  easily  recognized  in  mid- 
dle age,  although  still  clearly  shown 
in  frozen  sections.  Occasionally  a 
well-preserved  thymus  persists  in  the 
adult ;  on  the  other  hand,  it  may 
suffer  atrophy  very  early  in  child- 
hood. 

Structure.  —  The  histological 
character  of  the  thymus  completely 
changes  during  its  development,  since 
it  begins  as  an  epithelial  outgrowth 
from  the  third  pharyngeal  pouch,  for 
a  time  attains  the  nature  of  a  tubo- 
alveolar  gland,  and  later  permanently 
assumes  the  type  of  a  lymphoid  organ. 
Externally  the  thymus  is  invested 
by  a  loose  fibro-elastic  capsule,  from 
which  sepu.  rich  in  blood-vesseb,  pass  towards  the  interior  and  subdivide  the  organ 
Tnto  a  number  of  indefinite  lobes.  iWlatter  are  broken  up  into  sma^l,  almost  spheri- 
cal lobules,  which  correspond  to  lymph-nodules,  and  consist,  therdore,  of  a  denser 
^rtical  and  looser  medullary  zone,  although  these  are  not  sharply  defined  from  each 

°*^The  cortical  substance  presents  histological  characteristics  resembling  those  of 
dense  lymphoid  tissue,— clo^ly  ^cked  lymphocytes  lying  within  the  narrow  meshes 
ofthe  supporting   reticulum.  "^  ¥he  latter  cons^ts  of  stellate  anastomosing  cells. 


PoMcrior  Mpect  jJ  thymu*  body  tardcncd  m  tilu. 


II  ribortllage 


Fio.  1518. 

sternum 


n  rib-cartltafc 


Left  luiiK, 


III  rib. 


IV  rib        HtM.i  of  IV  rib  lle«d  of  IV  rib  IV  rib 

Tramvetw  iertion  o(  body  >t  le%el  o(  fourth  thor«clc  vertebra ;  from  child  of  about  one  year 

In  ..ddition  to  the  usual  elements,  eosinophilic  cells  .»[^f«""'*.';!;;°"£*'"'  '^,^ 
cortex  Jarticularly  in  the  neighborhofKi  of  the  capillaries.  Accoiding  to  J. 
Saffer    the   cortex   of  the  thymus  contains  nucleated  and  other  developmental 


THE  THYMUS  BODY. 


I7» 


Fio.  isip- 


Lobalr, 


Blood- 
vesMls, 
inlccted 


CorpuMlC' 
of  itauaU 


Corte: 


Medulla 


Tr.n.«r«  ««ion  o.  Ihymu.  body  of  child,  .hewing  g«,e«l  .rr.n,«n«.i  o.  lobol».    X  aj. 


,„„^,_.jj**,n.  -  cj«^yJ^o™  .h^o;j^ -Sfl- r  '^'i 

tion  of  tie  cortical  and  medullary  zonM  T^^.y^^^JJ^  The  rrm  between  the 
lary  net-work,  the  medulla  being  relatively  P°"7^"PP^^he  larger  trunks  carrying 
lobules,  which  chiefly  dram  the  *=='P'"^':f-""''^fectb^,  the  most  important  being 
the  blood  from  the  organ.  These  run  l""^^.  «'^^\'°"';  '^i  numerous,  and  empty 
tribuury  to  the  left  innominate.     The  Wf^'^^^^"  n  erior  of  the  organ,  the  lym- 

sinuses,  has  not  been  established. 


i8oo 


HUMAN  ANATOMY. 


Cortex 


The  nerves  are  small  and  come  from  the  sympathetic  and  the  vagus.  They 
are  traceable  along  the  arteries  and  connective-tissue  septa,  and  end  chiefly  in  the 
walls  of  the  blood-vessels.     Bovero  has  described  terminal  filaments  which  pass  from 

the  interlobular  plexuses  into 
Fjo-  ^S'o.  the  medulla. 

Development.  —  The 
thymus  proper  originates  from 
a  jjaired  anlage  (Fig.  1521) 
which  appears  as  an  epithelial 
outgrowth  from  the  ventral 
wall  of  the  third  pharyngeal 
pouch.  From  this  results  a 
long  cylindrical  mass  of  closely 
packed  epithelial  cells  which 
grows  downward  and  en- 
closes a  narrow  lumen.  The 
lower  end  of  this  mass  in- 
creases in  size  by  the  formation 
of  solid  acinous  outgrowths 
resembling  those  of  an  im- 
mature tubo-alveolar  gland. 
Coincident  with  the  downward 
extension  of  the  organ,  the 
upper  cylindrical  portion  grad- 
ually assumes  the  alveolar  con- 
dition until  the  entire  thymus 
acquires  a  lobulated  character. 
During  these  changes  histo- 
logical .tltcrations  take  place, 
the  epithelial  masses  becoming 
invaded  by  ingrowing  lym- 
phoid tissue  and  blood-vessels 
and  broken  up  into  irregular  islands.  The  latter  become  smaller  and  less  conspicu- 
ous as  the  lymphoid  character  of  the  thymus  becomes  more  predominant.  The  cor- 
puscles of  Hassall  represent  derivatives  of  the  primary  epithelial  elements.  For  a 
time  the  two  originally  distinct  anlages  develop  independendy  ;  later  they  come  into 
close  contact  in   the  mid-line,   and  form  the  single  irregular  organ  the  bilateral 


Section  of  thymm  body 


Corpuscles  of  Hauall 
within  medulla 


•howine  details  o(  cortical  and  mdullary 
subfttanre.     .«  300. 


Fio.  ts>t. 


ReconHtrurtinna  of  ilevelopjnK  thvrnid.  thvmuit,  and  |>arathyroi(l  hodien  in  embryt«  of  14  mm.  ( .-f  t  und  of  26  mm. 
tfti.  mt.  mefljan  thyroid;  //,  lateral  thyroid:  /v,  thvmua;  /,  tliyroid;  ^1,/^,  superior  and  inferior  parathyroids; 
i-f.  \ftia  cava  su^wrior  ;  a,  aorta.    (  Toumritx  and  I 'frdnn. ) 


derivation  of  which  is  indicated  by  the  connective  tis.sue  separating  the  right  and  left 
divisions.  The  upper  ends  of  the  latter  are  often  continued  as  far  as  the  thyroid 
as  lateral  processes.     Subsequent  to  the  second  year  regression  sets  in,  and  the 


THE    SUPRARENAL   BODIES. 


1801 


.Thymus 


thymus  structure  is  largely  replaced  by  fibrous  and  adipose  tissue,  vestiges  «{  the 
'^•^^iS^^'tSSaS'Sl^i.-Hi^dVyngeal  pouch,  a  rudimenury 

^h-ere^iarwTo/Te 
fourth  one,  external  to 
the  origin  of  the  lateral 
thyroid.    According  to 
Groschufl,'  this  anlage 
may  persist  in  man  as 
iheparaihymus,  a  small 
body  which  occurs  in 
close    association,     or 
even  encloses,  the  para- 
thyroid   derived   from 
the  dorsal  wall  of  the 
fourth  pouch.    The  lat- 
ter,   therefo-',    corre- 
sponds   to    the    third 
pharyngeal    pouch    in 
giving  rise  to  both  a 
parathyroid  and  a  thy- 
mus ;  in  addition  it  pro- 
duces the  lateral  thy- 
roid anlage. 

According  to  Beard, 
Prenaut,  Bell  and 
others,     the    transfor- 


Thymus  tissue 


Section  of  thvmas  body  of  man  of  Iwenty-eiRht.  showlnj  invasion  nn.l  rrplace- 
meiu  of  thymus  liasiic  by  fat.     >  ». 


mSon  of  the  tWmus  into  a  lymphoid  organ  occurs  as  the  direct  conversion  ..fits 
nrSi  c-i'V'-lial  elements  into  lymphocytes  and  not  by  invasion  of  pre-exisling 
wTphoid'dis.  While  accepting  such  origi.i  for  the  reticulum,  Hammar'  regards 
the  lymphocytes  as  entering  from  without. 

THE    SUPRARENAL    BODIES. 

These  are  a  pair  of  cocked-hat-shaped  bcKlies  situated  at  the  back  of  the  alxlo- 
Tfht  inn^  asuect  of  the  upper  ends  of  the  kidneys.      F^nch  has  a  f>ase,  or 
S  surface  Tr^L^Sg  to  theT^tom...  the  hat.  and  a'n  anfenor  .ud ^  postrnor 
^.r^fhl^^dersof  which  are  concave  and  look  outward  and  downward. 
Thte  kre  an^?i?^nd  "  loweV  angle  at  either  end  of  the  base.     The  inner  convex 
Srder    :nds,"^^cially  in  the  right^  capsule,  to  present  ^ ^^ermor"  c^Jsc'^^  c^ 
the  middle      Thus  the  right  one  is  more  triangular  and  the  left  more  crescentic 
Thev  mavbe  6or  7  cm.  long  and  about  half  as  broad.     The  thickness  doe.  not 
orotabTv  often  exce^  2  cm.     The  base  is  concave,  adapted  to  the  kidney   of  which 
ft  ov^rhani  "he  a^rior  surface.     The  lower  end  is  much  thicker  than  the  upper. 
The  conca^tv  deeiLns  above  into  almost  a  hirrow  filled  by  areolar  tissue.     The  an- 
J^'L^rPlirrs^a  deep  fissure,  the  „i/un,,  in  the  "^^-J>l"^^,^'^J^^^,'  ^1 
dividing  it  into  two  approximately  equal  regions.     T'^^.  ^'^'^T  ^^r  „ve^ 
siderably  smaller  than  the  anterior,  owing  to  the  orojecton  "^^  J^^  »»""  ^ff  J^^, 
front  of  the  kidney.     It  also  presents  a  f^NSure  nearly  parallel  with  the  base-line.  Dut 
ndther  extending  the  whole  length  of  the  organ  nor  so  deep  as  the  front  one. 

I^cdor  he  suprarenalsa?eof  a  dirty  yelluwish  brown  and  more  or  less  p.g- 
mpntMl      Thev  weieh  6  or  7  gm.     The  left  one  is  usually  the  larger. 

ReUtioM.-The  W  W«r«  are  on  the  kidneys.  The  post.nor  surfaces 
are  as^iS  "he  diaphragm.  The  anUnor  surface  of  the  right  capsule  has  its  l<.«.r 
Tne^^^rtUtlnffe  inferior  vena  cava.  The  part  of  t^eow^r  end  near,  his  mav  he 
behind  the  duodenum.     The  remainder  is  in  contact  with  the  liver.      Ihe  hii,nest 


'  Anatom.  AnzeiRer,  Btl.  xvii., 
•  Ibid.,  Bd.  xxvii.,  1905. 


ll^UU. 


:i:M: 


i8oa 


HUMAN  ANATOMY. 


part  is  between  the  non-peritoneal  posterior  surface  of  the  liver  and  the  abdominal 
.vail.  This,  of  course,  like  the  two  preceding  areas,  has  no  peritoneum.  The  rest 
lies  in  contact  with  the  lower  surface  of  the  liver,  and  is  coated  by  the  peritoneum  ol 
the  posterior  abdominal  wall.  The  anterior  surface  of  the  left  capsule  is  neariy  or 
quite  peritoneal,  resting  against  the  stomach,  the  spleen,  and  the  tail  of  the  pancreas. 
Structure. — The  suprarenal  body  is  invested  by  a  thin,  but  fairly  strong, 
fibrous  capsule.  Section  across  the  thicker  parts  of  the  organ  displays  an  outer  zonf, 
or  cortex  (. 25-1. 20  mm.  in  thickness ),  which  surrounds  the  central  medulla.  Where 
thinnest,  as  towards  the  borders,  the  medulla  !;<  reduced  to  a  narrow  zone  and  may  he 
entirely  wanting  ;  where  best  developed,  as  in  the  middle  of  the  organ,  it  may  attain 
a  thickness  of  over  3  mm.     The  cortex  is  usually  of  a  dirty  yellow  color,  presenting 


Fio.  1513. 


Crura  of  dtephragm 


Captular  vein  in  groove, 
for  vena  cava 


Hepatic  surface' 

Peritoneal  surface- 
Inferior  vena  cavn. 

Riglit  liidiiey 


Ctzliac  artery 

Superior  mesenteric  artery 


.Capsular  vein 
cmerginK  from  hilum 


Lett  kidney 


Anterior  aspect  of  suprarenal  bodies  liardened  in  situ. 

Fio.  1534 


Diaphragmatic  surface -^H|.  ^^^^^Diaphragmatic  suHace 

Renal  surface        ^H  V^^^^^r„»i  surface 


I.eft 


RiKht 


Posterior  aspect  of  suprarenal  bodies  siiown  in  preceding  figure. 

ne.xt  the  medulla  a  narrow  darker  zone  of  varying  shades  of  brown.  The  medulla  is 
of  a  grayish  tint  and  generally  lighter  in  color  than  the  cortex.  Its  exact  tint,  how- 
ever, varies  with'  the  amount  and  condition  of  the  containe<l  blood,  when  engorged 
with  \enous  blood  appearing  dark.  In  consistence  the  medulla  is  less  resistant  and 
more  friable  than  the  cortex. 

The  cortical  substance  consists  of  a  delicate  framework  of  connective  tissue,  con- 
tinuous with  and  prolonged  inward  from  the  capsule,  in  the  meshes  of  which  lies  the 
glandular  epithelium.  The  arrangement  of  the  latter,  although  generally  columnar, 
varies  at  different  levels,  three  zones  being  distinguished  within  the  cortex.  The 
zona  glomeruhsa  lies  next  the  capsule,  and  consists  of  the  somewhat  tortuous  or 
coiled  groups  i>f  cells.  The  zona  fasciculata  forms  the  chief  part  of  the  cortex,  and 
maintains  the  radial  dispositic  n  of  the  cell-columns.     The  zona  reticularis,  next  the 


THE  SUPRARENAL   BODIES. 


1803 


Capiale 


rdJi  eSelS  «Us  from  O20-.o,6  mm.  in  diameter;  in  addition  there  are  numer- 

spaces.    The  cells  of  the  medulla  are  ^^^ 

more  prone  to  undergo  post-mortem 

change  than  those  of  the  corte-x. 
Veisels.— The   chief    artfru. 

supplying  the  organ  are  the  three 

sui^rarenal  or  capsular  arteries,— the 

middle  from  the  aorta  and  the  su- 
perior and  inferior  from  the  phrenic 

and  renal  aiteries  respectively.    They 

break  up  into  a  dozen  or  more  fine 

branches  before  reaching  the  organ, 

which  they  enter  at  various  points, 

some   penetrating  direcdy  into  the 

medulla,  others  terminating  m  the 

cortex.    The  latter  form  a  superficial 
capillary  net-work  within  the  cap- 
sule, from  which  continuations  pass 
between   the    cortical  cell-columns, 
around  which  they  constitute  capil- 
lary net-works.     The  medulla  is  di- 
rectly supplied  by  arteries  destined 
for  the  interior  of  the  organ.     These 
soon  break  up  into  capillaries  which 
surround  the  medullary  cords  and 
pass   over   into   an    unusually   rich 
plMUS  of  veins.     The  latter  claim  as 
tributaries  the  venous  radicles  of  the 
zona  reticularis  and   impart  to  the 
medulla  in  general  a  spongy  charac- 
ter.    The  veins  form  a  rich  plexus 
about    the    organ,    communicating 
freely  with  those  of  the  kidney.    The 

deeper  lyn^ajsmthe^^^^  «-m  the  solar  and  renal 

Dlexu^      The  num^7of  meduMed  fibres  would  imply  that  many  come  throu^i, 

mwimmmm 


Section  ot  ,upram«l  body  •"'''"»'■'«  «?J"3^S^°'  "a""' 


i8o4 


HUMAN  ANATOMY. 


ments  ;  but  in  all  cases  they  exhibit  the  characteristics  of  sympathetic  cells.  Indeed 
so  numerous  are  the  latter  that  the  suprarenal  is  regarded  by  some  anatomists  as  ai 
organ  accessory  to  the  sympathetic  nervous  system. 

Development  and  Growth. — ^The  genesis  of  the  suprarenal  body  has  been 
the  subject  of  much  discussion  and  uncertainty,  especially  as  to  the  origin  of  tht 
medulla.  Comparative  and  embryological  studies  clearly  indicate  that  the  mam 
malian  suprarenal  body  consists  of  two  separate  and  distinct  organs,  which,  although 
intimately  united  as  cortex  and  medulla,  possess  a  different  origin  and  function.' 

According    to    the    investigations  oi 


Pio.  1536. 


'^  Capiule 


Aichel,'  the  suprarenal  in  the  highei- 
mammals  first  appears  in  close  rela 
tion  to  the  Wolffian  body,  the  anla^i 
arising  from  the  proliferation  of  meso- 
blastic  cells  at  the  ends  of  invaginations 
of  the  mesothelium  lining  the  body- 
cavity.  The  individual  cell-groups 
thus  arising  with  the  several  invagina- 
tions fuse  into  the  general  anlage  of  the 
suprarenal.  The  primary  close  asso- 
ciation of.  the  latter  with  the  Wolffian 
body  is  later  lost,  the  subsequent  mi- 
gration of  the  organ  bringing  it  into 
secondary  relation  with  the  j>ermanent 
kidney. 

Regarding  the  origin  of  the  me- 
dulla two  views  obtain.  According 
to  the  one  now  widely  accepted,  the 
medullary  portions  are  developed  from 
cells  which  are  derived  from  the  ad- 
jacent embryonic  sympathetic  gan- 
glia, the  chief  support  of  this  opinion 
Ix'ing  found  in  the  close  correspond- 
ence of  the  medullary  cells  with  the 
chromaffin  elements  of  sympathetic  ori- 
gin occurring  in  other  localities,  such 
cells  wherever  found  exhibiting  an 
especial  affinity  for  chromium  salts. 
When  fully  developed,  the  medullary- 
cells  may  be  regarded  as  highly  special- 
ized cells  which  elaborate  a  powerful 
stimulant  that  passes  into  the  l)lf)od 
(Vincent).  The  other  view,  supported 
by  Janosik,  V'alenti,  and  Aichel,  attri- 
butes the  origin  of  the  medullary  cells 
to  the  same  mesoblastic  anlage  that 
produces  the  cortical  cords  of  which 
those  of  the  medulla  are  only  speciali- 
zations. The  differentiation  of  the  su- 
prarenal into  cortex  and  medulla  occurs 
comparatively  late  and  long  after  the 
primitive  oi^n  has  become  sharply  de- 
fined from  the  surrounding  tis.sue.  For  a  time  the  entire  organ  consists  of  cells  which 
are  identical  in  appearance.  During  the  third  month  this  common  tissue  differenti- 
ates into  cortex  and  medulla,  in  consequence  of  the  breaking  up  of  the  enter  zone  into 
columnar  ma-sses  by  the  ad\ent  t'f  connective-tissue  trabeculae  from  which  delicate 
lil)iillie  arise,  ioiiiiiiig  the  inner  boundary  of  the  corte.\.  Within  the  central  part  of 
the  organ  thus  defined  numerous  venous  capillaries  appear  and  break  up  the  tissue 


Capillar)- 

Znnn 
nrticularis 


Medulla 


iif  suprarenal  IxkIv.  shiiwiiiK  details  of  superficial 
and  deep  portions  of  cortex.    X  225. 


'  X'incent : 
•  Archiv  f. 


Joiimal  of  Anatomy  anrl  PhysioloRy,  vol.  xxxviii.,  1903. 
mikro.  Anat.,  Bd.  Ivi.,  1900. 


THE  SUPRARENAL  BODIES. 


1805 


rich  supply  o{  ner^•e-fibres  and  KanR)'''^  F,o.  .5,8. 

cells  distinRUisKing  the   medulla.       Ihese 

orirans  are   proportionally   very   large    in 

the   foetus   (Fig.    1529)-        At    birth    the 

intero-posterior  diameter  is  i  cm.  and  the 

greatest  transverse  diameter  at  the  base  is 

Fio    i5»7- 


Ceninil 
vein 


SKlioii  oi  suprarenal  body.  showinK  portions  of  cortex 
and  medulla.     X  225. 


•wiinn  of  injected  suprarwial  IkxIv;  the 
ve«^V.??o«er  th'ud  of  6^5..  are  chi.fl>  tr.bu- 
Uries  to  the  centml  vein-     v  'S- 


Fig.  i5»9- 


Suprarenal 
Kidney 


Suprarenal 


..5  cm.;  the  length  '- the  apex  to  the  ~^^^^^^^ 

srs;^"Mr:ar,ie?;.:ri:^x^^^^^^ 

to  resemble  the  kidneys  ;  at  term,  however, 
the  lobulation  has  nearly  disappeared. 

Accessory  Suprarenals.— These  are 
mostlv  very  small,  rarely  surpassing  a  pea 
in  size,     they  mav  be  found  near  the  su- 
prarenal lx)dy.  in  the  kidney,  in  the  liveT, 
in  the  solar  and  renal  ple.vuses,  or  beside 
the  testis  or  the  ovary.     The  accessory  su- 
prarenal situated  within  the  broad  ligament 
m  the  vicinity  of  the  ovary  is  regarded  by 
Marchand   and   others   as    a    normal   ami 
almost  constant  organ.     The  latter  under- 
goes  compensatory  hypertrophy  after  re- 
moval of    the  chief   suprarenal.      The  in- 
vestigations of   Aichel  empha-size  that  the 
organs    included    under    the    designation 
"accessory     suprarenals"     comprise    two 
groups  of  structures  of  different  origin  and 
morphological  significance.      Those  asso-  uidnev  or  liver,  are  derived 

sr^-pTJ?:;  ««-*p:?"=™-  r^-rnr^ftsri  *»  »p„™..  .^. 


rreier 
.  allopian  tube 
Round  liKament 
Bladder 


Fi 


Dissection  of  three  months  female  (.rtus.  show- 
ing h^^  suprareiuite.  lobed  kidneys,  and  «.x..:.l 


i8o6 


HUMAN  ANATOMY. 


therefore,  are  supernumerary.  The  bodies,  on  the  contrary,  situated  within  thf 
broad  ligament,  or  in  intimate  relations  with  the  epididymis,  are  probably  developed 
from  the  atrophic  tubules  of  the  Wolffian  body,  and  hence  must  be  regarded  as  inde- 
pendent structures.     It  is  said  that  the  suprarenal  bodies  are  sometimes  wanting. 

PRACTICAL  CONSIDERATIONS :  THE  SUPRARENAL  BODY. 

Hemorrhage  into  the  suprarenal  body  in  new-born  infants  has  been  obser\'ed 
(post  mortem)  in  a  number  of  cases.  Various  opinions  as  to  its  cause  have  been 
expressed.  They  have  been  summed  up  (Hamill)  as  follows  :  (i)  weakness  of  the 
vessel-walls,  normal  or  abnormal;  (2)  traumatism,  especially  during  labor,  from 
pressure  of  the  hands  in  making  traction  in  delivery  by  the  lower  pole,  and  from 
the  frictions  and  flagellations  used  to  resuscitate  the  apparently  dead-bom  ;  ( 3 ) 
asphyxia  from  delay  in  the  establishment  of  respiration  at  birth  ;  (4)  acute  fatty 
degeneration  of  the  vessel-walls  ;  (5)  fatty  degeneration  of  the  tissues  of  the  organ  : 
(6)  firm  contraction  of  the  uterine  muscles,  the  resistance  of  the  parts  traversed, 
and  consequent  compression  of  the  inferior  vena  cava  between  the  liver  and  the 
vertebral  column,  thereby  producing  congestion  and  hemorrhage  into  the  non- 
resistant  tissues  of  the  suprarenal  gland;  (7)  convulsions;  (8)  syphilis;  (9)  cen- 
tral vasomotor  influence  from  cerebral  lesions  ;  ( 10)  mechanical  squeezing  of  blood 
into  the  part  during  the  process  of  labor  ;  ( 1 1 )  too  early  ligation  of  the  cord  ;  (12) 
arrest  of  the  circulation  through  the  umbilical  artery  from  compression  of  the  cord 
or  separation  of  the  placenta;  (13)  thrombosis  of  the  renal  vein  or  inferior  vena 
cava ;  ( 14)  infection.  ,      .     ,      , 

Hamill  concludes  that  the  first  of  these  seems  to  be  the  fundamental  anatomical 
element  favoring  the  occurrence  of  hemorrhage,  that  in  still-born  children  prolonged 
and  difficult  labor  is  the  exciting  cause,  and  that  in  those  dying  later  some  form  of 
infection  is  responsible.  ,  ..      .  .         . 

In  cases  of  tumor  of  the  suprarenal  body  the  foUowmg  sj  mptoms  have  been 
noted  (Mayo  Robson)  :  («)  shoulder-tip  pain,  probably  explained  by  the  fact  that 
a  small  branch  of  the  phrenic  nerve  passes  to  the  semilunar  ganglia  ;  (*)  pain  radi- 
ating from  the  tumor  across  the  abdomen  and  to  the  back,  not  along  the  genito-crural 
nerve  ;  ic)  marked  loss  of  flesh  ;  (rf)  nervous  depression  with  loss  of  strength  ; 
(f)  digestive  disturbance,  flatulence  and  vomiting  ;  (/)  presence  of  a  tumor  beneath 
the  costal  margin,  right  or  left,  at  first  movable  with  respiration,  but  soon  becommg 
fixed  ;  it  can  be  carried  into  the  costo- vertebral  angle  posteriorly,  and  can  be  pushed 
forward  into  the  hollow  of  the  palpating  hand  in  front  of  the  abdomen. 

Bronzing  of  the  skin  is  not  usual  unless  both  suprarenals  are  affected. 

THE  ANTERIOR    LOBE  OF  THE  PITUITARY   BODY. 

The  pituitary  body  (hypophysis),  although  usually  described  in  connection  with 
the  brain,  to  the  base  of  which  it  is  attached  by  a  stalk  continued  from  the  infun- 
dibiilum  (Fig.  976),  consists  of  two  entirely  distinct  parts  which  differ  both  in  their 
genesis  and  structure.  These  a,e  the  so-called  anterior  and  posterior  lobes.  The 
latter,  being  derived  from  the  diencephalon,  is  appropriately  described  with  the  brain 
(page  1 130)  ;  the  former,  derived  as  an  outgrowth  from  the  roof  of  the  primitive  oral 
cavity,  in  view  of  its  probable  function  as  an  organ  of  intertial  secretion,  may  be 
here  considered,  since  in  certain  respects  it  resembles  the  thyroid  body. 

The  anterioi*  lobe,  which  constitutes  the  major  part  of  the  entire  hypophysis,  is 
kidney-shaped  and  receives  the  infundibular  process  in  a  hilum-like  depression  on  its 
(XJSterior  surface.  It  increases  in  size  until  about  the  thirtieth  year,  when  it  meas- 
ures in  the  transverse  direction  about  1 2  mm. ,  in  the  sagittal  about  7  mm. ,  and  in 
the  vertical  5  mm.  The  anterior  lobe  of  the  hypophysis  is  light  grayish  red  in 
color,  the  posterior  appearing  grayish  white.  It  is  surrounded  by  a  well-marked 
fibrous  capsule  which  forms,  even  where  the  two  lobes  are  in  contact,  a  distinct 
investment.  In  the  anterior  part  of  the  lobe,  on  either  side  of  the  mid-line,  a  con- 
densation of  the  connective  tissue  marks  the  position  of  large  blood-vessels.  Fine 
processes  extend  from  the  capsule  inward  and  form  a  delicate  net-work,  rich  in  capil- 


THE  ANTERIOR  LOBE  OF  THE  PITUITARY   BODY.         i«o7 

lori«L  the  meshes  of  which  arc  occupied  by  spherical  or  cord-like  masses  of  cuboidid 
ir^veonTShhelial  cells.     The  latter  are  apparently  of  two  k.n< Is.-the  smalle 
^rt?hUy  sSing  ckUf  ceUs,  from  .003-004  mm.  in  diameter,  and  the  larger  and 

FlO.  IS3°- 


Iiitttlotarxploni 


Conn«ctive4iM« 
tnbecula 

_Cap»ulr 
Tnin.«™e  action  o(  pituitary  bod,,  .howing  retatioo  o(  .nt«lor  (oral,  and  po.lcrtor  (crcbral*  lob«.    x  ^. 

def-ply  staining  chromophile  cells  (.005-008  mm. ),  so  called  because  of  their  mark«l 
Sty  for  certain  dyes  The  two  varieties  of  cells  seem  to  be  mtermmRlwl  w.thout 
S  tVa^ngement'  .ud  are  regarded  by  some  as  the  "P-'f-'T "L^^^mim; 
pending  upon  merely  functional  changes,  the  two  kmds  of    cells  bemg  e^ntuilly 

"^^"tS  .i^grt^ations  of  the  cells,  cord-like  or  spherical  in  form  and  usually  without 
distinct  luS^.r  lie  in  very  close  relation  to  the  wide  capillary  blood-vessels  that 

Fio.  153'- 


Chief  cells.. 


Chiet  cella 


Capillar)' 


Colloid 


Capillary 


Cbromoptaile  cella 


Section  of  anterior  lobe  of  pituitary  body ;  th-ee  acini  contain  colloid  material 


ramify  bet^vee^  th...n,  supported  by  the  delicate  connective-tissue  'l^jf-  "^J^  ;\"'' 
there  however,  the  glandular  epithelium  surrounds  a  lumen  which  ma>  contain 
Soid  material:  thus  riembling  the  acini  of  the  thyroid  body.     The  colloid-contain- 


l8o8 


HUMAN   ANATOMY. 


ing  acini  lie  chiefly  against  the  posterior  lobe,  in  which  location  a  number  of  siicli 
spaces  (Fig.  1531),  of  moderate  si«e  and  lined  with  cuboidal  epithelium,  are  usually 
normally  present,  although  colloid  vesicles  may  be  absent  in  other  parts  of  the  antf 
rior  lobe  ( Schocnemann  ). 

The  absence  of  excretory  ducts,  the  activity  of  the  epithelial  cells  as  excretory 
elements,  and  their  intimate  relation  to  the  blood-vessels  all  support  the  view  that 


Fig 


Wall  ct  rhombencephalon. 


Pituitary  cvaKinalion  from  diciicev»al<><> 


Pituitary  evaKination from  Dial  cavitv 


.Communication  with  oral 
cavity 


Wall  oi  oral  cavity 


Portion  of  sagittal  section  oJ  rabbit  embryo,  ihowinK  early  aUge  ol  development  ot  pituitary  body.    X  80. 


the  anterior  pituitary  lobe  is  to  be  regarded  as  an  organ  engaged  in  internal  secre- 
tion. Its  assumed  function  as  direcriy  concerned  with  somatic  growth,  suggested  by 
the  enlargement  of  the  pituiury  body  observed  in  giants  and  in  cases  of  acromegaly, 
needs  further  confirmation,  since,  as  pointed  out  by  Thom,'  such  changes  are  by  no 
means  con.-^ant.  .    . 

Development.— ,As  above  stated,  the  two  lobes  of  the  pituitary  t)ody  are  de- 
veloped from  entirely  different  sources.     While   the  posterior  lobe  originates  as  a 

tubular  e.xtension  of  the 


Fig.  isii 


diencephalo 


cavity  of  the  interbrain 
(diencephalon),  the  an- 
terior lobe  is  derivetl 
from  an  ectoblastic 
outgrowth  from  the  pri- 
mary oral  cavity  which 
appears  during  the 
fourth  week.  The  cere- 
bral end  of  this  evagina- 
tion  {Ralhke's  pouch) 
soon  expands  into  the 
hypophysial  pouch, 
which  remains  con- 
nected with  the  mouth 
for  a  considerable  time, 
until  the  formation  of 
the  base  of  the  primi- 
tive skull  leads  to  sev- 
erance of  the  tubular 
communication,  the  hy- 
pophysial anlage  then  lying  within  the  cranium  against  the  lower  surface  of  the 
interbrain.  In  very  exceptional  ca-ses  a  canal  in  the  sphenoid  bone,  leading  from 
the  sella  turcica  to  the  ba.se  of  the  skull,  contains  a  prolongation  of  the  hypophysis,  and 
'  Archiv  f.  mikro.  Anat.,  B<1.  Ivii.,  iqi.i 


Wall  III. 
rhombcncephalun 


agination 


Piirii.iii  lit  MKlttal  section  of  rabbit  embryo,  showinit  development  of 
pituitary  body.     >'  Ho. 


THE  ANTERIOR   I.OBF.  OF   THE   PITUITARY    BODY.         1809 

thus  represents  the  condition  existinR  in  s.)mc  animals,  in  which  the  pituitary  stalk 
persists  during  We.  passing  through  a  .anal  in  the  l«se  of  the  skull  and  connecting 
Uh  the  oral  epithelium.  During  the  latter  half  of  the  second  month  the  hypo- 
physial   sac    sends  jubular    out-  ^.^  _   ^^^ 


growths  into  the  surrounding  vas- 
cular mesoblastic  tissue.  l^ter 
these  tubules  become  separated 
from  the  main  pouch,  until  the 
Utter  finally  becomes  entirely  con- 
verted into  a  mass  of  small,  tor- 
tuous tubules  or  acini  which  in 
large  part  lose  their  narrow  lumen 
and  become  solid  masses  sejxuated 
by  septa  of  vascular  connective 
tissue.  The  anterior  lolx-  thus 
formed  becomes  pressed  .»,'ain!.t 
the  under  surface  of  the  brain-lolx' 
with  which  it  is  closely  bound. 

The  posterior  pituitary  lobe 
is  developed  from  the  tubular 
outgrowth  from  the  diencephalon 
and  retains  its  connection  with  the 
brain  through  the  infundibulum. 
The  primary  lumen,  however,  be- 
comes obliterated  and  the  organ 
converted  into  a  solid  mass  com- 
posed of  tissue  which  resembles 
neuroglia  and  contains  few  or  no 

rouVe'j:™^.''  irlrX'rluiirconcerning  the  posterior  lobe  are  given  in  connection 
with  the  brain  (page  1130). 


.W>ll  III  <licni:cphal<« 


Pcxlrrlot  (i-rrcbral)  Mw 


Anlrrior  (urmKlobr 


Dn'rlopiiiK 

ai  Mii 


■Canilaie  o{ 
ttaae  (M  ftkuU 


.Wllll  at  oral  cavity 


Pottio..  ol  «KitUI  wilion  ol  ™l*tt«mbpo.  showing  ^Ur 
rt««ol  iJ«veta|Mti«  piliiiury  body.  Antenor  lobt  now  im, 
!iUUi  of  ni-.ineroMi  lubutor  «cini.     X  3»- 


THE  CAROTID  BODY. 

nni^ard      When  freed  from  the  surrounding  fat  and  connective  tissue,  the  carotid 
S  aLar^  of "  Sh  or  brownish  red,  according  to  the  condition  of  the  capillary 

114 


,8io  HUMAN   ANATOMY. 

plcx  ol  Wood-veMeli,  nerve-fibres  and  peculiar  cells.  The  ki.vr  are  irregularly, 
disposed  as  dumps  or  cell-balls  (Schaper')  and  occupy  the  interspaces  within  th. 
cl«ie  net-work  ol  large  capillaries  which  ramify  among  the  cells.  The  charactensti. 
elements  of  the  carotid  body  are  the  polygonal  cells,  about  .01  mm.  m  diameter, 
with  large  round  nuclei.  Their  protoplasm  is  fintly  (jranular  and  is  especially  prom 
to  change  being  best  i)reser\fd  in  solutions  of  chromic  acid  salts.  When  so  treateil, 
thty  take'on  the  peculiar  yellow  color  entitling  them  to  be  cla-ssed  as  fAnwwa^"//* 
celh  The  large  number  ol  ner^•e-(ibres  within  the  carotid  body  is  remarkable.  They 
are  mostly  nonmedullated  and  are  derived  chiefly  from  the  neighboring  sympathetic 
plexus  surrounding  the  carotid  artery  and,  after  ent«rmg  at  different  places,  ramify 
within  the  organ  in  all  directions,  the  finest  filaments  l^inglost  among  the  groups  of 
cells.  The  penetrating  nerve-tninks  usually  enclose  typical  ganglion-cells  and,  in  a 
sense,  the  chromaffine  cells  likewise,  since  the  nerve-fibres  surround  the  groups  of 

these  elements. 

Fio.  1535 

CuotU  Body 


t'apilUricfl 


Capsule 


Section  ol  adult  hunun  carotid  bodv ;  one  entire  lobule  i*  ibown.    X  170. 

In  view  of  ( i )  the  identity  of  its  elements  with  other  chromaffine  cells,  which 
are  now  recognized  as  closely  associated  with  the  sympathetic  system  in  other  locali- 
ties, as  in  the  medulla  of  the  suprarenal  body,  (2)  its  extraordinary  nchness  in  nerve- 
libres,  (3)  its  general  resemblance  to  a  sympathetic  ganglion,  and  (4)  its  direct 
development  from  embryonal  sympathetic  ganglion  cells,  Kohn'  concludes  that  since 
the  carotid  boay  is  neither  a  gland  nor  a  typical  ganglion  it  must  be  regarded  as  acces- 
sory to  the  sympathetic  system  and,  in  recognition  of  this  relation,  proposes  the 
name  paraganglion  caroticum  for  the  organ.  Concerning  its  function  nothing  is 
definitely  known.  j-       1 

The  blood-vessels  supplying  the  carotid  body  are  branches  which  pass  directly 
from  either  the  common  carotid  artery  or  its  t<^rminal  branches. 

THE  COCCYGEAL  BODY. 
This  organ  (glomus  coccvReum),  also  often  called  the  coccygeal  gland,  or 
/  uschkas  gland  (in  honor  of  the  anatomist  who  described  it  half  a  century  ago"),  is 
a  small  reddish  yellow  ovoid  body  which  lies  embedded  in  fatty  areolar  tissue  usually 
ininietliately  in  front  of  the  tip  of  the  cocey.t,  but  sometime,  ju^t  below.  .Recording 
to  Walker,*  the  surest  guide  to  the  body  is  the  middle  sacral  arterj- ,  to  whose  ante- 

'  Archiv  f.  mikros.  Anatomie,  Bd.  40,  189J. 
» Archiv  f.  mikros.  Anatomie,  Bd.  56,  looo.  o    i-       o^ 

» Die  Himanhang  und  die  Steissdriise  ties  Menscnen.  Berlin,  istio. 
•Archiv  f.  mikros.  Anatcwnie,  Bd.  64,  1904. 


"■-^■■ 


THK  axrCYiiEAl    tf««w 


iHll 


nor  surface  the  littk-  orwan  is  uttacheti  its  i.«»«  ^  'r*  7 !!  ^  J'|v^^tl!^h 
ui \J\,-«..l  Annrkicheil  from  the  p.»«ierk*r  sawtic-  titr  i«^»fcH»o  l**^  i-»e|"" 
blood-vessel.     Appr  kicn«i  inmi  '      H'        i»-rnm      •=  thr  lr^.*tor  -wi  muscU-  wim.  the 

duimeter  beinj?  iroin  j-s  3"""'  j     ^^    drscnl-^  »,  how«-%«r. 

''f  ^e  Celu/:  ^^  TZ£  i  -h  i-U,  a'Lr^hU.  «u.„.^  <-  s.n.c.u.-. 
onlythelarK«tol.iseriwo   n    i  ^^  ,„i„„      ,^,.u,«^l    .rWHiri     *«•   ch-"t    -u«« 

or  the   most    part   of    inmiitc    «/<  ^  „'      ,2^\,,,n,™-„i  w  i?*  the  (.rirniH 

(Walker).     The  »*^ition.U  n.^du^^^^^^^  L, 

b«ly  by  means  of  ^^^''^^i",^,!^''!^,' .  "  ij;  ^^  Us^^-h.-s.  In  ..T«,.«iti. -n  to  tin-  pr^- 
St^SV^^TZr:^"^^^^^  ,.jnerve-U.y  aor  ..,..^t. 
^nll^v,.  b,:.      .n  the  coccygeal  UkK  and  the  ,v-n,p«thet,c, 


CuBiwctivr  tlMue 
fttronu 


rapitlaricii 


CelU 

Blood- VCMClk 


Si  iior  .^  human  a'oH  coccygwi  tM^T-     ^  »»• 


The  Structure  of  the  body,  as  ^n  in  ^--- -»„"-  StK';r;u£.^ 

an  irregularly  oval  field  "«  ™""--''- ^^\'^;,tlus  Lg^^^  of  epithelial  cells 
fatvy  areolar  t-ue   'n  .h.ch^.re^^^^^^^^^^  ^  ,„  ,^^ 

and,  sometimes,  a  ^^'ck-^*"^  »^^^^  '  ^^.^^^^^,  constituents  predominating,  but 
live  tissue  sirotna  vanes  m  '^"^  J^*^  more  NtlWy.  The  individual  cell-groupt,  are 
commonly  the  fibrous  stroma  '^"'^^''^  "^"'t,'?  „y,  ^hc  suiTour.ding  fibrous  stronw. 
uncertainly  circumscrilK^  by  a  slight  ^°"^;"^-\^V:^j;^^^^  by  an  endothelial 

Each  aggregation  of  cells  contuns  ^'^^"^ral  "oci  spac.,  ^r"^^^-^^,^  ^^  ^.jthout 
wall  similar  to  that  of  a  capillary.  Against  th^  uaU^  theS"^  are  cl.«ely  packed 
the  rtervention  of  connective  tissue;  I...  ^sc  J;^f^^'„7^^^^^^^  a  polygonld  con- 
in  direct  apposition  with  one  another  ^"'i '"  ^""^  "i^"^^,^'"^"  to  fiv/layers,  th- 
tour.  They  are  disposed  around  the  '^'^'[fj'^^"^^Z  ^L-  protoplasm  con- 
individual  4l!s  being  i"rf«t!"^tly  outlined  and  cx^rnpogo.^^   ^^  ^T^  ^  ^ 

Uining  a  relatively  large  and  deeply-  «t«"^"P  .""^;\"^";^  coccyS  b^v.  the  testimony 
tion  al  to  the  presence  of  ^Ij^^^^^^;^"^  *^.J^-  l^toTni^cnce  seems  convin- 
of  Walker,  Schumacher  and  especially  o*  Stm  rk    as  to  tne  ^^^.^.^  ^^^ 

cing.     The  last-named  investigator  concludes  that  tht^eceUs^  t^^pe^^  ^^^  ^^^  ^^ 

chrome-reaction,  and,  »"'^''-'' ^"^: '"  ."^^'C";;"  On  thTother  hand,'tnc  epithelial 
togenetic  relation  to  the  sympathetic  s  stun.     On  ^o^r  ^b^nce  cf 

clwracter  of  the  cells,  their  intimate  relation  to  the  blood  vessels. 
'  Archiv  f.  mikros.  Anatomie,  Bd.  69,  1906. 


LAB 


,8,2  HUMAN  ANATOMY. 

excretory  ducts,  seem  to  justify  the  inclusion  of  the  coccygeal  body  at  least,  pro- 
visionally, among  the  organs  of  internal  secretion,  as  suggested  by  Walker. 

THE  AORTIC   BODIES. 

These  temporary  organs  were  described  by  Zuckerkandl'  a  few  years  ^o  and 

are  also  known  as  the  Mifs  of  Zuckerkandl.     According  to  the.r  discoverer  as 

found  in  the  new-born  chUd,  they  are  a  pair  of  small  narrow  bodies  that  he  upon  the 

anterior  surface  of  the  abdominal  aorta,  opposite  the  origin  of  the  inferior  mesenteric 

arte  V  (Fig.  1537),  in  close  relation  with  the  aortic  plexus  of  the  sympathetic  nerves. 

Althoujrh  usually  separated,  in  about  15  percent,  of  the  bodies  examined   in  whirl. 

they  were  invariably  present,  the  bodies  were  joined  by  an  isthmus  into  a  horseshoe 

'  shaped  organ  of  varying  dimensions. 

Fio.  1537.  The  right  body  is  usually  the  larger, 

with  an  average  vertical  length  of  1 1 . 6 
mm.  the  corresponding  dimension  of 
the  left  body  being  8.8  mm.  .  The  ex- 
tremes of  length  for  the  right  body 
are  from  8-20  mm.,  and  of  the  left 
one  from  3-15  mm.  The  width  is 
about  one-fifth  of  the  length,  and  the 
thickness  something  less.  The  sur- 
face of  the  little  organ  is  smooth  and 
its  color  light  brown.  Whilst  its 
consistency  is  about  the  same  as  that 
of  the  neighboring  lymph-nodes,  the 
body  is  softer  than  the  adjacent  sym- 
pathetic ganglia.  The  aortic  ijdies 
are  essentially  oqpins  of  foetp'.  life  or 
at  most  of  early  childhood,  and  in 
the  adult  they  are  represented  by 
mere  atrophic  remains  (Zucker- 
kandl). 

The    structure  of    the  aortic 
body  includes  a  fibrous  capsule,  which 
is  prolonged  into  the  interior  as  con- 
nective tissue  strands  that  accompany 
the  numerous  blood-vessels  entering 
the    organ.      The    arteries,    minute 
twigs  from    the  aorta,    the  inferior 
mesenteric  and  sometimes  the  sper- 
matic, break  up  into  a  rich  capillary 
net-work    whose   wide   meshes    are 
filled  with  closely   packed   cells  of 
varying  size.     These  are  polygonal, 
spherical    or   cuboidal    in   form    and   distinguished    in    many  cases   by    exhibiting 
S  I^uliar  color  reaction,  after  treatment  with  the   chronr^-salts,  entit  ing  them 
hTcWd  as   chromaffine   cells.     According  to   the  observations  of   Zucker- 
kanS  the  genetic  relations  of  the  sympathetic  ganglia,  the  medulla  of  the  supra- 
renal s   and^he  aortic  bodies  are  m^t  Intimate,  since  these  vanous  structures  are 
Satives  of  a  cntinuous  primar>-  cell-mass.     In  ^nsiderat.on  of  this  association 
a.u  the  constant  presence  of  the  distinctive  chromaffine  cells   it  is  highly  probable 
tl^  the  aortic  b.^ies  .ire  to  l,e  regarded,  along  with  the  medullary  portion  of    he 
suprarenal  and  the  carotid  Ixnlies,  as  appendages  or  paraganglia  of  the  sympathetic. 
'  Verhaiidluniten  der  Anatom.  Hesellschaft,  1901. 


RAR- 


Aortic  IwdlM  of  new-born  child  :  KAB  LAB.  right 
>nd  Icfl  aortic  bodlcn  ;  a.  aorta  .  im.  inferior  "!'"«"- 
liric  artery :  hi.  left  common  iliac ;  ir.  inferior  cava  ; 
/,T,  left  renal  vein  ;  a(.  aortic  nympatheUc  pleius ; 
n,  ureter.      ■  l.    (^«r><-i*.i»rf/.l 


THE  ORGANS  OF  RESPIRATION. 

This  tract  includes  the  organs  by  which  an  interchange  of  gases  ^kcs  pla^ 
between  the  blood  and  the  air.  It  consists  of  ihUarynx,  the  Ir^ira  «r  *;ndp'^. 
^d  it*  subdivisions,  the  Sronchi,  the  /««^*  and  the  serov*  ^•^•"branes  the/^r«r^. 
which  surround  them.  Morphologically  thb  tract  is  an  outgrowth  from  the  fore- 
L  4he  l^nx  is  a  specialized  apparatus  for  the  production  of  the  vo.ce  situated 
S^tiie  beginning  of  the  windpipe,  of  sufficient  importance  to  be  consulered  by  itself. 

THE  LARYNX. 
The  larynx  consists  of  a  number  of  cartiUges  which,  by  their  relative  changes 
of  ix«"tion  modify  the  approximation  and  tension  of  two  folds  of  "lucous  mem- 
biJSrrer'fiKs  tissue,  known  as  the  vocal  cords,  on  either  side  of  the  cleft  through 
S  ^he  air  enters  the  windpipe.  The  larynx  is  in  the  neck,  being  suspended  from 
The  toid  tone  an^l^ding  to  the  trachea.  It  is  practically  subcutaneous  in  front.  Its 
upe^or  orifice  fs  tehind  the  base  of  the  tongue,  and  can  be  seen  in  life  only  by  a  m.iror 
The  artilatres  are  connected  by  joints  and  ligaments,  moved  by  muscles  and  covered 
Jy  mSS^membrane,  the  foldVof  which  iorm  important  morphological  parts  ..f  the 

'*^"'''  THE  CARTILAGES.  JOINTS.  AND  LIGAMENTS. 

The  cartilages  which  form  the  framework  of  the  h^nx  are  three  single  ones  :  the 
cricoid  \Sy^id.  ^nd  the. pigMiis;  and  three  pairs:  tht  apifn<»dcarMa,res,thecor. 
ZtX/a^^is  or  cartilages  0/  Santorim,  and  the  cunfi/cm,  cartilages  or  those  of 
W^J^rrL^^V^^^'"^^^^  determining  well-defined  swellings  of  the  mucous 
S^ne  are  very  small :  indeed,  the  cartilage  is  not  always  to  be  found     There  are 
othTr  Sr^^te  of  cartilage  to  be  mentioned  with  the  structures  m  which  they  ocaar 
The  StiS  the  upper  part  of  the  cartilages  of  Santonni,  those  of  Wnsherg,  and 
the  endLonh?  vS  and  apical^proces-ses  of  the  arytenoids  consist  of  elastic  cartilage  the 
^th^«  h^ni^of  h^ine  cartilage.    The  cricoid  and  arytenoid  cartilages  are  derivations 
Sht^rachea  a'S  reprSnnhe  more  primitive  form  of  larynx.    The  thyroid  and  the 
cp£ott1s"pp^ar  in  mammals.      In  monotremes  the  epiglottis  is  of  hyaUne  cartilage. 
P*  The  Cricoid  Cartilage—This  is  the  foundation  of  the  larynx,  being  a  nng 
on  tl«  top  o    the  trachea.     It  is  nearly  circular,  the  diameter  m  the  male  being  .9 
mm   (Lu^hka).     It  is  narrow  in  front,  being  from  J-H  mm.,  usually  alx.at  .s  mm. 
broad,  and  some  four  or  five  times  as  much 
behind.     The  height  at  the  back  is  approxi- 
mately 25  mm.  in  the  ni  >!••  and  from  16-23 
mm   in  the  female.    The  cricoid  is  3  or  4  mm. 
thick  in  the  lower  part  and  in  the  upper  as 
much  as  5  or  6  mm.     The  posterior  aspect  is 
somewhat  quaJrilateral,  the  upper  lx>rder  de- 
scending very  steeply  at  the  sides.     Internally 
the  cricoid  is  perfectlv  smooth.     The  lower 
border  presents  a  slight  median  descent  in  front 


Fio.  15.18. 


Articular  face* 
(or  nrylelioid 
cartilaiT 


Atticxlar  fai-rt 
for  thyroid 
cirtilaRt 


fricoid  cartilanc,  i^lhl  lateral  a«p«' t 


t8i4 


HUMAN  ANATOMY. 


Fio. 


■S39. 


Cartilage  of  Santori 


PoAterior  surface  for 
arytclioideus 
Potterior  crico- 
arytenoid ligament 
Muscular  proc 


Posterior  ridge  oa 

cricoid  cartilage 

Depression  for 

crico-arytcnoideua 

posticus 


Cricoid  and  ar>'tenoid  cartilaees  from  behind. 


extremely  variable  in  all  its  details.     A  median  ridge  divides  the  posterior  surface  u\ 
the  cricoid  cartilage  into  two  symmetrical  depressions  for  the  origin  of  the  jX)sterior 
crico-arytenoid  muscles.     Each  loUercl  surface  of  the  cricoid,  below  the  middle,  and 
nearer  the  back  than  the  front,  bears  an  oval  articular  facet  for  the  crico-thyroid 
joint,  its  long  diameter  extending  upward,  backward,  and  inward.     The  facet,  which 
is  nearly  plane,  faces  chiefly  outward,  but  also 
somewhat  upward  and  a  littie  backward.     The 
long  diameter  b  about  5  mm.  and  the  cress  one 
nearly  as  great.    A  ridge  connecting  it  with  the 
superior  articular  facet  bounds  the  posterior  sur- 
face of  the  cartilage.     The  anterior  surface  of 
the  cricoid  b  somewhat  convex  vertically,  si' 
as  to  resemble  an  over-large  tracheal  ring. 

The   Thyroid   Cartilage.  —  Thb,   tht 
shield-shaped  cartilage,  consbts  of  two  quadri- 
lateral plates,  the  alie,  broader  than  high,  which 
meet  in  front  and  are  widely  apart  behind.    The 
posterior  border  of  each  is  prolonged  upward 
and  downward  into  two  horns,  or  comua,  some- 
what flattened  from  side  to  side.    The  lower  pair 
rest  on  the  inferior  articular  facets  of  the  cricoid 
and  the  upper  are  attached  by  ligaments  to  the  .......  • 

ends  of  the  greater  horns  of  the  hyoid  bone.  Being  thus  open  behind,  the  thyroid 
cartilage  b  complementary  to  the  cricoid  upon  which  it  rests.  The  thyroid  notch 
(indsura  thyroldea)  b  a  deep  median  depression  of  the  upper  border  in  front,  extend- 
ing nearly  or  quite  half-way  down.  The  plates  are  strongly  everted  (especially  m 
the  male)  at  the  sides  of  the  notch,  thus  causing  most  of  the  prominence  known  as 
Adam's  apple  (protuberanUa  laryngea).  The  resulting  median  ridge  ends  shortly 
below  the  notch,  and  at  the  lower  border  the  front  of  the  thyroid  is  smooth  and 
convex.  The  upper  border  b  slightly  convex  on  either  side,  and  usually  presents  a 
small  notch  just  in  front  of  the  root  of  each  superior  horn.  The  superior  tubercle  is 
a  little  prominence  on  the  outer  surface,  just  below  and  anterior  to  this  notch.  The 
lower  border  b  alternately  convex  and  concave.  There  is  a  moderate  median  con- 
vexity followed  by  a  hollow,  external  to  which  b  a  marked  prominence,  the  inferior 
tubercle,  between  which  and  the  inferior  horn  is  a  deep  notch.     The  posterior  border 

is  dightly  concave  in  the  middle. 
The  oblique  line  is  a  ridge  running 
downward  and   forward   from  the 
upper   tubercle   to   the  lower.     It 
marks  the  intemiption  of  the  mus- 
cular layer  out  «)f  which  the  sterno- 
thyroid and  the  thyro-hyoid  mus- 
cles ari.se.     The  inferior  constrictor 
of  the  pharynx  is  inserted  behind  it. 
The  superior  horns,  usually  longer 
and  more  flexible  than  the  inferior, 
run  upward,  backward,  and  inward. 
They  become  more  cylindrical  and 
have  blunt  rounded  ends.    The  in- 
ferior horns,  liroader  than  thick, 
run  downwarii  and  slightly  inward, 
with  a  turn  forward  at  the  ends.    In- 
ternally each  presents  near  the  tip 
a  round  articular  surface  of  indefi- 
nite .shajK-  for  lh«-  inferior  articular  surface  of  i.ie  cricoid.    The  dimensions  of  the  alae 
vary  w  ith  the  sex  :  in  man  the  height  is  >,o  mm.  and  the  breadth  38  mm. ;  in  woman, 
2^  and  28  mm    respectively       The  prominence  and  sharpness  of  the  angle  are  male 
characteristics,   in  man  the  avcrt^n-  lH.ing  i)o°  and  in  woman  120°.      It  b  chiefly 
through  the  thyroid  cartil  ige  that  the  male  larynx  acquires  its  relatively  large  size. 


-Epiglottis 


Ohlique  line,  end- 
ing in  tHl»erclei* 
;ilM)ve  and  below 


Infvrior  coniu  - 
Thyroid  cartilagi'  with  ipiKloitis.  riKhi  aiilero-Uteral  aspeit 


THE    LARYNX. 


iftiS 


C  Wirchildhood  ;  subsequently  it  becomes  less  and  less  du^tmct. 

V.rUtl««..-U  is  not  rare  to  find  a  foramen  "-/ »he  .jpper  outer  an^^^^^^^^^^^^ 
superior  tubercle,  which  transmits  fh^.'J^P^^VneTve^  A^^mTnrtharth^^  developed 

of  the  external  branch  of  the  superior  '-'Onueal  n"^.  ^^^^^'^^"h^and  fifth  branchial  bars,  ft  is 
as  above  stated,  the  foramen  represents  a  ^«"  ^'r, Th  ,n  tte  Xr  and  not  verv  rare  for  one  to 
ra^n^S;:?  e1^^e:;'n^r:!tL%L^ror ?sTnt^^^^^^  the  absence  more  common  on 
the  left  side. 

and  is  nearly  plane,  but  either  par- 


ticipant of  the  joint  may  be  the 
contained  one.  The  capsule  is 
lax,  although  somewhat  strength- 
ened by  two  by  no  means  con- 
stant ligamentous  bands.  An  an- 
terior one  extends  downward  and 
forward  from  the  front  of  the 
lower  horn  ;  a  posterior  one  ex- 
tends upward  and  hac'-.ward  from 
the  back  of  the  same.  The  motion 
fa  usually  described  as  rotation  on 
a  transverse  axis  passing  through 
both  joints,  but  in  fact  a  great  deal 
of  irregular  sliding  is  possible. 

The  crico-thyroid  mem- 
brane, although  connecting  the 
cartil^es  in  front,  has  no  direct 
attachment  to  the  thyroid  at  the 
sides,  and  consists  of  a  central 
anterior  and  a  lateral  part.  The 
anterior  part,  a\so  known  as  the 
conoid  ligament,  is  triangular  in 
shape,  with  its  base  attached  to 
the  upper  edge  of  the  cricoid  car- 
tilage and  its  tnincatetl  aijc.x  to 
the  lower  border  of  the  thyroid. 


Fig.   I54'- 


EpiRMti* 


Ar>t<*>o><l 


Cartil»fotrttlc€«. 


Thyro-hyoJd 
menibfaiK,  left 
half 


uf  Santurin 


Pinterior 
crico-arytenoid 
ligametil 

Cricoid 
cartilage 


Ponlrrlor 
crit-^»-llryroid 
liKanwitt 


-"^^^^t^:^:^^:^^^^^ 


the-lower  border  of  the  thyroKl.    ^'^liU^V^riEftrs^^^^^^^  breeTdiVr^ 
taining  considerable  clastic  tissu^an^lc^^^the^^^'^^^^  ^^^   .^  , 

cartilages.      It  is  piercetl  by  .*f ^ '^^^J'"'*^'^ ", '/ .^./ ^„^/  (  Fig.  1544),  while  directly 

superficially  by  the  "•^-t^V'-"'^ ,''•"  fl^^,   J^^t  ^fthe  up.U  border'  .1  the  anterior 
continuous  with  the  anterior  and  attache^^^^  ^^  ^.^^^  ^i^,^  ^.,^,„„,, 

arch  of  the  cncoicl  cartilage  is  J'"  /"'  J^^'^^'^X  thyroid  ala-  without  l^^ing  at- 
upward  and  inward  l^neath  '^^,'f"?^'r\he  membrane  l>eco.nc-s  directly  blende.l 
tached.  The  upper  l«.rder  of  this  V'^^^f.^^^J^^Z^^^^^  „,^.  Uuter  being  practically 
and  continuous  with  tlic  inferior  \»^y;°;!^y  X  iri^  h^^  *»"'^''  '"  '^'^ 

the  thickened  and  free  superior  '^^'l^'^ '"' '^'^..^^'^.^^J^.S  cord.  The  lateral  crico- 
sense,  becomes  the  sup,M.rting  framework  or  the  t^^  ^^   ^^_^_,  ^^^ 

Slir^;:f';;^S-r'^r^:^cSthe  l^ter^,  covered  by  the 

laryngeal  mucous  mcinbrane.  „,mhrane  is  one  continuous  sheet  of  fibrous 


I8i6 


HUMAN  ANATOMY. 


Criitt  arcoat*. 


Aitkabir  ikcci 


Articular  facci 


A,  antero- 


rior  horns  of  the  thyroid  and  the  tips  of  the  greater  horns  of  the  hyoid.  They 
may  be  artificially  dissected  to  resemble  cords  (ligamcnta  thyreohyoldea  lateralta), 
although  in  faa  they  are  continuous,  not  only  with  the  rest  of  the  membrane,  but 
with  its  expansion  which  mingles  with  the  fascise  of  the  neck.  As  a  rule,  a  little 
nodule  {eoriilago  triticea)  is  tound  in  the  middle  of  this  lateral  thickening  (Fig. 
1 541).  .^  cording  to  Gegenbeur,  it  is  the  remnant  of  a  closer  connection  between 
the  third  md  fourth  branchial  bars.  The  more  membranous  part  of  the  ligament 
extends  from  the  superior  border  and  the  inner  side  of  the  superior  horns  of  the 
thyroid  to  the  upper  border  of  the  body  of  the  hyoid  and  its  greater  horn.  A  bursa, 
extending  under  the  body  of  the  hyoid,  lies  on  the  anterior  surface  of  this  membrane, 
which  is  denser  beneath  it  ,      ,         ..   . 

The  Arytenoid  CartiUge*.— These  are  a  pair  of  very  irregular  four-sided 
pyramids  (one  side  being  the  base)  perched  on  the  superior  articular  facets  of  the 
cricoid.  The  vocal  cords  extend  between  them  and  the  entering  angle  of  the  thyroid. 
Besides  the  base,  there  is  ?i  posterior,  an  internal,  and  an  antero-extemal  surface,  sep- 
arated by  tolerably  distinct  borders.  A  section  near  the  base  is  semilunar,  the  bound- 
ary between  the  posterior  and  internal  surfaces  being  effaced.  The  two  remaining 
angles  are  each  prolonged  (F«.  1542).    The  anterior,  extending  forward  as  the  vocal 

process  for  the  attachment 
Fio.  1543.  of  the  true   vocal  cord,  is 

•^  *  long  and  slender ;   the  ex- 

ternal or  muscular  process, 
short  and  thick,  projects  out- 
ward and  backward.  The 
base  is  chiefly  occupied  by 
an  oval  articular  cavity  rest- 
ing on  that  of  the  cricoid. 
The  long  axis  of  this  articu- 
lar facet,  which  does  not 
much  surpass  its  transverse 
one,  extends  in  the  main  for- 
ward, crossing  that  of  the  opposed  facet.  The  concavity  is  nearly  at  right  angles  to 
the  long  axis.  The  posterior  surface  is  well  defined  and  deeply  concave,  bein^  filled 
by  the  arytenoid  muscle.  The  internal  surface  is  nearly  plane,  offering  nothing  for 
description.  The  antero-extemal  surface  is  triangular.  A  ridge,  the  crista  arcuata, 
sUrts  from  the  vocal  process  and  runs  backward  and  upward,  ultimately  describing 
nearly  a  circle  around  a  hollow,  the  foi'ea  triangularis,  which  is  quite  as  often  oval. 
This  litde  hollow  is  filled  by  a  mass  of  glands,  and  is  overlooked  unless  the  cartilage 
be  cleaned  very  carehilly.  The  false  vocal  cord  is  attached  to  a  little  tubercle  on  this 
ridge  either  above  or  behind  the  fovea.     The  borders  meet  above  at  a  blunt  apex. 

The  Crico-Arytenoid  Joint. — From  the  foregoing  description  of  the  two 
opposed  articular  surfaces  it  is  evident  that  in  consequ»?nce  of  the  crossing  of  their 
long  axes  the  whole  of  one  is  not  in  contact  with  the  whole  of  the  other.  The  joint 
is  surrounded  by  a  lax  capsule,  strengthened  behind  by  straight  vertical  fibres,  which 
have  been  calle<i  the  posterior  crico-arytenoid  ligament  (Fig.  154'  )■  The  motions 
are  very  difficult  to  analyze.  The  arytenoid  may  tip  on  the  elongated  elevation  of 
the  cricoid  or  slide  along  it ;  moreover,  it  may  rotate  upon  it  at  any  point  occupied. 
This  movement,  from  the  nature  of  the  surfaces,  is  a  screw  motion  rather  than  a  true 
rotation,  but  the  term  is  sulficiendy  accurate. 

The  Epiglottis. — This  is  a  leaf-sha|>ed  plate  of  ela.stic  cartilage  which,  inserted 
by  its  stalk  into  the  angle  of  the  thyroid,  rises  above  the  hyoid  bone  and  guards  the 
entranre  into  the  larynx.  The  length  is  some  3. 5  cm.  The  epiglottis  expands  trans- 
versely and  uiiris  forward  over  the  root  of  the  tongue.  Its  posterior  surface  is 
entirely  free,  but  less  th;m  the  upper  half  of  the  anterior  surface  is  exiiosed.  Begin- 
ning at  the  free  border,  which  is  bent  forward  towards  the  tongue,  the  posterior 
surface  is  convex,  slightly  concave,  and  finally  convex  again,  owing  to  a  prominence, 
calletl  the  tubercle,  which  its  root  forms  in  the  larynx.  The  free  edge  is  rounded 
transversely  and  the  jxwterior  surface  in  the  main  concave  across.  The  st.nlk,  when 
well  develcipetl,  is  triangtilar  on  section,  fitting  into  the  angle  of  the  thyroid.     The 


Richt  ar>'tenaid  cactllaiK.  capped  by  caftila|c  of  Santorini. 
lateral  aapcct ;  B,  paatefo-aiadlal  aapcct.    x  |. 


THE  LARYNX. 


1817 


DeprtMioitK 
lor  glumls 


-a.«n™.«  stroma  is  lull  of  pits,  or  even  perforations,  conuining  glands.     The 
2Sn^Sr«  atSed  t^  it  very  closeir-  that  in  dissecting  the  cartilage  .t 

in  that  direction.     It  is  continuous  with  the  septum  of  tne 

'**"^7»<r  Movements  of  the  £/,igMtis.-Theo\6  idea  that 
the  epiglottis  turns  over  backward  like  a  l.d  to  close  the 
SArnx  in  swallowing  is  disproved.  That  .t  couW  ever  be 
^  bent  is  unlikely  In  swallowing  it  is  earned  bod  y 
teckward.  probably  receiving  the  bolus  on  its  laterally 
SSe  ^terior  surface  and  translerring  "to  the  grasp 
of  r*  ph^nx.  While  there  are  muscular  fibr«  m  the 
an^epiglottic  fold,  they  are  scanty  and  ^rrepA»T^'^^'^y 
^ke  of  exercising  any  great  influence  on  the  shape  of 

''''Th^cornicul.  l.ryngi..  or  cartiiages  of  Santo- 
rini  are  a  pair  of  small  horn-like  structures  of  elastic  car- 

"^B^^  «S™  t^sn?!:.:^ .- s 

/?:„   .c^c^       Thev  are  some  ?  mm.  or  more  long  and   i   mm.  thick,      wniie  ine 
wln^'wfiich^S^mrVLluce  in  the  folds  Ire  constant,  the  same  cannot  be 
!r:^^f  .h-  rartilapes      They  are  ohen  difficult  to  isolate. 

^'  «riTof  elJc  cartilage  are  occasionally  found  mcem^^^  tl,e 

larynx      The  posterior  sesamoid  cartilages  are  on  the  latent    sides  of    he  )"'"t^  ^^ 
SthearytLidsandthec™^^^^^^^ 

L"  '^^S:.^^Zt^^Z:r^.T:^l^  ptrynx  between  those  cartilages. 
'*%reU.«c7hS'"o??hrCn1c^^^^^^  areolar  tissue,  rich  in  Ca^c 
fibreZ^Sr^Il^^^gec^- ^^  'X'^u^;!^ -L'VS^te 

"[yrn^TllJatS  in'the'^f^rrnl^^^^^^^^^^     cords  respLctively  are  thickenings  ... 

.  DieulafC- :  U  membrane  Klosso-hyoidienne,  BiblioRraphie  Anatomi.iue.  tome  x,.,  .90.. 


EpiKlmlic  cartilaKi-  lron>  hrh""' 


I8l8 


HUMAN   ANATOMY. 


The  inferior  thyro-arytenoid  ligaments  (liKamenta  vocalla)  are  a  pair  of 
bands  of  tibrous  tissue,  chiefly  elastic,  supporting  the  free  edges  of  the  true  votal 
cords,  extending  from  the  angle  of  the  thyroid  a  little  below  the  false  ones  to  tho 
vocal  processes  of  the  arytenoids.  These  ligaments  are  continuous  with  the  lateral 
parts  of  the  crico-thyroid  membrane,  as  the  thickened  and  modified  upper  Ixirdirs 
of  which  they  may  be  regarded  (Fig.  1544).      Each  band  is  triangular  on  section. 

having  the  free  edge  at  that  of  the 
Fio.  1544.  .       -. 

Kpiglottis,  bent  forward 
Thyroid  cartilajec  left  ala 


Superior  coniu. 
01  thyroid  car* 
tilagc 


cord.  There  may  be  a  mmi'tc 
nodule  of  cartilage  in  the  ligament 
just  in  front  of  its  {wsterior  attach- 
ment. 


Anicu'ar  facet 
fur  inferior  thyroid 
coniu 


Riirht  thyroid 
ala  (cut) 
Lateral    |iart    of 
crico-lh>rold  mem- 
rane   attached    to 
vucal  process 
Afedian  mrt  of  crico- 
thyroid membrane 
.Cricoid  cartilage 


Trachea 


Ouification  of  the  L4U]mx. — The 
proces.s,  befnnninK  as  it  does  at  ab«>ut 
twenty,  is  a  normal  change.  Chievitz ' 
found  some  iissiticatiun  m  every  male 
larynx  of  over  twenty  and  in  every  fe- 
maJe  one  of  over  twenty-two.  it  ap- 
pears at  about  the  same  time  in  tine 
cricoid  and  thyroid, — namely,  at  alxiut 
the  bef^nniuK  of  the  twentieth  vear. — 
and  in  the  arytenoid  at  about  tfie  mid- 
dle of  the  twenties  in  man  and  nearer 
the  thirtitM  in  woman. 

r/ie  Cricoid.  -  The  first  nucleus 
appears  on  each  side  at  the  l)ack  of 
the  facet  for  the  arytenoid,  and  almost 
at  the  same  time  another  appears  at 
its  front.  These  are  shortly  lollowed 
b^-  one  at  the  joint  for  the  thyroid. 
These  three  unite,  forming  a  lateral 
ossification  which  spreads  across  the 
back.  One  or  more  ixjints  apfiear  in 
front  near  the  iipix-r  border  of  the  arch,  which  is  thus  ossified  and  joins  with  the  sides.  After 
these  various  unions  the  entire  lower  liorder  of  the  cricoid  is  still  cartilaKimitis.  The  younjtest 
man  otiserved  by  Chievitz  with  complete  ossification  was  forty-four  and  the  vouuRest  woman 
seventv-six. 

'thf  Thyroid.— The  prix-ess  l)eKins  near  the  posterior  inferior  an^le  and  invades  the  in- 
ferior honi.  It  appears  next  near  the  lower  part  of  the  anterior  aiijtle,  and  these  two  centres 
on  e.ich  side  join  by  spreading  alon^  the  inferior  border.  The  sti|>«-rior  horn  then  ossifies  either 
by  a  sejKtrate  centre  or  by  extension  along  the  hind  Ixjrder.  Kinallv  a  tongue-like  process, 
starting  near  the  inferior  tut)ercle.  extends  upward  and  forward  across  the  ala  to  meet  the  ossi- 
fication which  has  spread  along  the  su|)erior  Ixirder,  leaving  More  and  behind  it  places  which 
are  the  last  to  ossifv.  This  tongue-like  process  is  i>eculiar  to  the  male  ;  in  the  female  ossifica- 
tion advances  chiefly  from  the  [josterior  f)order.  The  youngest  man  with  complete  ossification 
of  the  thyroid  w.is  fifty  and  the  youngest  woman  seventy-six. 

The  .IrylfNoids.   -The  pnK-ess  tiegins  in  the  b.xse.'   In  man  the  starting-|Miint  is  the  mus- 
cular nrocess,  but  in  woman  it  is  less  certain.     The  youngest  man  in  whom  the  process  was 
complete  was  Sfventy-live  ami  the  vmingt^t  woman  efghty-five. 
The  larti/ago  triUtra.  when  present,  also  tends  to  ossify. 


Lateral  view  of  larynx  after  removal  of  greater  part  of  right 
thyroid  ala.  Hhowing  attachment  of  crico-thyruid  membrane  to 
ar\teiioid  cartilage.  The  free  bt>nicr  of  the  mcmhraue  constitutes 
the  tliyrit-arytenoiil  ligament  and  the  framework  of  the  vocal  cord. 


Tin:  FORM   OF  TlIK   L.'VKYNX   AND  IT.S  MiaH'.S  MEMBRANE. 

The  shajie  of  the  laryn.x  depends  not  only  on  the  cartilajjis.  but  also  on  folds  of 
miKous  membrane  stretched  over  bands  of  connective  tissue  .md  over  muscles. 

The  cavity  of  the  larynx  is  subdivided  into  three  parts  :  the  SHpragloHic,  the 
glottif.  and  the  infragloitic. 

The  supragiottic  region  ( vestibulum  larynsis)  Ix-gins  with  the  entrance  to  the 
larynx,  an  oval  (or  rather  a  he.irt -shaped )  plane,  which,  owing  to  the  height  and 
the  iMisition  of  the  larynx,  faces  nearly  backward.  It  is  Ixmnded  bv  the  free  Ixirder 
of  the  epiglottis  in  front  and  by  the  aryrpif^loltic  fold  which  pa.sses  from  this  on 
either  side  hick  over  the  top  of  the  arytenoid  cartil.iges,  Ft  is  interniptetl  in  the 
meilian  line  in-hind  by  a  notch.  On  either  side  of  this  the  fold  presents  a  sm.ill 
swelling  ( tulK'tddnni  corniculatum),  caused  by  the  cartilage  <if  Santorini,  anterior  to 
which  is  a  larger  one  (tuberculum  cunciforme)  containing  that  of  Wrisfwrg.  Hetween 
'  Archiv  f.  Anat.  und  Phys..  Anat.  Abth..  18.82. 


THE    LARYNX. 


1819 


^A  tU^  .idea  of  the  epielottis  the  told  contains  only  the  general  fibrous  envel- 
these  and  '•»*  »^"  ™  '^„Kbres  Helow  the  entrance  in  front  lies  the  pc«tenor 
"P^  L"1.fThTep1Str™^^^^^^^  side  to  side,  and  prc^nting  in  the  mclian  hnc-^ 
surface  ot  the  epigwius,  «-om^iv  ..vt^mliiur  <,.  f  .r  back  as  to  overhane  much 

1  n  rr^  tods  n  each  side.  Ix.unding  the  lower  part  of  the  ep>>;lott.s.  and 
,lecp  "^,'^[^^r'7J'  he  tubercle.  The  mucous  tnembrane  is  very  closclv  attached 
meeting  l^V.tr.nu  Im.  tlfin  k,t  he  straw  coL.r  of  the  cartilage  is  seen  through  it. 
to  the  epiglottis  •'"';*;.'"  \'^;';,"'Vhe  pits  lor  the  glands  in  its  substance  can  also 
TrnKr^  Thetterr:X"  thl  re^^ion.  which^s  separate.1  fron.  the  front  by 


Fio.  I54S' 


ronKUC 


Cushiiin  of  cplKli'llis 

Cuiu'ifinin  lutn-Klt 
TulK-ri  li;  i>l  Saliuiri.ii. 


HtHrterior  .;rii<>-*rslfiH>iil_ 
miucW 

I'riiiiiil  lartilaRi- 


Furamcn  arcum 


RiKht  fauiial  tonsil 


Mclia«  I  ,;,,„^„.,„^u,„|,  ,,,1,1 
l..-iti'ral   I 


Superior  !i>oiil  lormi 
Superior  thvroiil  cormi 


.SiiiUR  pyi>    <rmii> 
(iloUi* 


Ph«r>ine»l  wall 


(EM>phaKus 


mix ous  pourhCT  rnihratiH'  t  \ 


111  m»KOlt>  R-..  itif'talit 


,!a.  creiso  inclines  inward,  and  iK^-conies  llu  fold  of  nui.ous  tncnbrane  k.ioun  ^  the 
Wse^^TuS  Farther  luck  a  shallow  gr.H.vc,  the/*,//r««.,  nu.s  u.n.  in.  .  .r- 
tJn.:;:!.  the  tuberdes  .;<^-tonni  and  ..  WnsU^g^  |^^;- ^  ^,,,,  ,,..  „j 

.    f  .1,     .i.  ..f  tin  thvroid    and  the  t  ivr.)-livoid  nunibrane  l)etween  them.      It  is 

llilenul'b^aliro/t^ier' "l^o'g'l'^  passing  fron,  the  thyro-hyoid  mem- 

brane,  which  it  i)eii..rates.  to  the  l;nynx  pro|)er. 


ifiiitJii;  .;Jt,\ 


l820 


HUMAN  ANATOMY. 


The  glottic  region  extends  from  the  free  edges  of  the  false  cords  above  u< 
those  of  the  true  ones  belov  The  narrowest  part  of  the  larynx,  the  rima  glottidis  or 
eki*k  of  the  larynx,  is  the  interval  between  the  true  cords  in  front  and  the  arytenoid 


Fio.  154& 


Areolar 
Macoui  mrmbiane  covcriiiK  cpi(liAtii 
FiMore  bctwetn  cmnifaigca 
of  Santorinl 


Canilan  o(  epiglotU* 
tusiw 


Cattlluc  o(  Santorini  tubtn-le 
Slenio-hyoid 

Ttayro-h>oid 

Sinui  pvrlfonnii 


Suprrior 
conitt  a<  hyoid  (cnli 


Siemo-mastoid 


Prevcitcbnl  muscles 

Founli  cervical  veitebfB 


ArytaMMpiclottk  ioM  (cut) 
Poatarior  wall  of  pharynx 


Anterior  part  of  Mctioa  acroaa  neck  at  Icrcl  of  fourth  cervical  vertebra,  pawinc  through  upper  part  of  (uperior 

aperture  of  laryax. 

cartilages  behind.  The  false  vocal  cords  (plicae  ventriculares)  are  folds  of  mucous 
memb-ane  continuous  with  the  sides  of  the  supraglottic  space.  They  are  attached  in 
front  to  the  inner  side  of  the  angle  of  the  thyroid,  above  its  middle,  and  behind  to 
the  antero-e.\temal  surface  of  the  arytenoids.  They  are  soft  folds  of  mucous  mem- 
brane containing  connective  tissue  (out  di  which  a  skilful  dissector  can  manufacture 


Fio.  IS47- 


Body  of  hyoid 
Imnic 


Crico-lhvroid. 
membrane 
Cricoid  cartilage,, 
anterior  arch 


Traihi 


Superior  hyoid  ro<nn 
Thyro'hyoid  ligament 


Superior  thyroid 
comu 


Cuneltomi  tubercle 

Tubercle  of 
Santorini 

Falflc-  vocal  cord 
Vocal  cord 

Thyroid  cartilage 


Cricoid  car-  Ar\tenoid 
tilaxr,  Pol-  ca'rtilc.^ 
terior  arch 

Venlrida 


Fio.    If48. 


Appendix  ol 
ventricle 


Ar>tenoidi^u5 


Glottil 
Vocal  cord 


Median  ugiltal  wction  ol  larvin;  riifhl  side  seen  from 
withiii. 


I.ar^■nx  ha»  tv«n  partly  rut  acrrws  at  1«t1  Iviween 
false  and  true  vikhI  iur<l» ;  iipper  half  of  figure  represi'iiU 
under  Riirfai-e  ol  upper  piece,  which  \*  turned  backward. 


a  superior  thyro-arj-t(»noid  ligament"),  many  glands,  and  some  fibres  from  the  thvro- 
arj'tenoid  muscle.  The  true  vofal  rords  (plicae  vocalcs)  arise  a  little  belnw  the  f.ilse 
ones,  and  run  to  the  v»»cal  processes  of  the  arytenoid  cartilages.     They  arise  in  both 


THE    LARYNX. 


l83I 


^-,  a  litde  above  the  middle  of  a  line  from  the  bottom  of  the  thyroid  notch  to  the 
wfr  boSer T the  thy.-  id.  Taguchi '  gives  the  average  distonce  m  men  from  the 
nn^S^  M  the  voSTco^  as  8.5  mm.,  and  from  below  a.s  .0.5  m-"  «"  *«'«*^"  \^ 
?nS^,^dis^es  6  5  mm.  and  8  mm.  respectively.  The  cords  anso  either  d.- 
Sy^^r,S,Troid,  just  on  each  side  oTThe  depth  of  the  angle,   or  from  a 


F>lw  vocal  cord 
Vocal  cord 
Vtntricic  oi  tarynz 

Arytenoid  cartilacc 

Thyroid  cartilage 


PlO.   1549 
ocd 

u 


Sterno-hyoi«i 

Ventricle  o(  lanT« 
Buna 


Thyro-hyoiJ 
Phar>ns 
,Onio-hvoid 


Stcmcniaatoid 


Internal' 
Jupilar  vein 


,Stcm<f-nta*tt>td 


Paettmognitric  nerve  , 
Carotid  artery 

ralatu-pliarynsena    ^    , .      , 
Prevertehial  faicia 


i  \  ThynxrytenoideiM 

I  Inferior  pharyn(ea>  conilrictor 

ArytemMdeiu 


Anterior  part  o(  ^ucn  across  neck  at  level  o.  ..l.e  vocal  cord. ;  on  I, ft  .Me  ventrtel.  o.  larynx  i»  ..,«-«•. 

median  cartilaeinou    nodule,  o.  from  one  for  each  cord,  the  disunce  between  them 

membrane     The^ubstancc-  is  chiefly  muscular  tissue  from  the  thyro-^rytenoid.  which 

Fia.  1550. 


«  CH  tvn^\M 


Epiglottlt- 


Voc»l  cord- 


ArytMH>-«p(clottic  Mrf— ' 

Cunrifbrtn  tuhcrilc 
TulXTtU  of  Sutorini'— 


— I  »leral  yjloiso 


—  Mnlian  i{b>-.»i) 
•l>i|[lu«1tt  6>I>1 


l'3l««  voial  lortt 

Vcxal  lord 

Riina  ittottiili* 
X■un«^^«'"■  tul>rrvl« 
.\ixal  [tT'Ktts 

of  SAIlloTtat 


Interior  of  Unnx  ...  »ec„  «i.h  larvn^-^ope.    A.  rim.  ,.ottidi,  .ideh  opr„  :  «.  rim.  .Icttidi,  clo«d. 

J     .  .u      ^,1  r.rn/-.««Ps   a  Considerable  part  of  the  chink  of  the  glottis  is 

Selengrhof  £  chink  in  the  male  is  23  mm.,  of  which  the  vocal  part  is  .5.5  .nm. 
>  Archiv  f.  Anat.  u.  Phys    Anat  Abth.,  1889. 
•  Uull.  de  I'Acatl.  tie  >Kdecir,r.  ^ans,  1879. 


l822 


Hl'MAN   ANATOMY. 


and  the  respiratory  7.5  mm.  In  the  female  the  lenjith  is  17  mm. ,  and  the  respectn. 
parts  measure  11.5  mm.  and  5.5  mm.  The  elasticity  oJ  the  voc.il  part,  however 
sJlows  it  to  stretch.  The  shape  of  the  rima  Klo«'d«»  vanes  with  the  position  of  tlu 
arytenoids,  and  the  theoretically  straight  lines  of  its  borders  may  both  be  approxi 
mated  and  drawn  asunder,  and,  moreover,  may  be  bent  at  the  juncUon  of  the  tw.. 

The  ventride  or  laryngeal  sinus  ( ventriculus  lar)n)il»)  is  a  pouch,  lined  with 
mucous  membrane,  opening  into  the  laryn.x  between  the  true  and  false  cords  of  eaili 
side  The  horizontal  elliptical  opening  has  a  breadth  (vertically)  of  from  3-6  mm 
As  has  been  stoted,  the  upper  surface  of  the  true  cord  slants  downward  and  outwar.l 
but  the  ventricle  is  partly  under  cover  of  the  false  cord,  around  which  it  ascends. 
The  ascent  may  be  due  to  an  appendix  of  the  ventricle  (Fig.  1551).  which  may  be  an 
almost  separate  cavity  connected  with  the  front  of  the  ventride  by  a  slit  or  an  irregular 

Pio.  1551. 


Glandl 


FmIrc  \  iKal  cord 


Lymph(>i(l  tissue 
Vtxiil  cord 


Thyro-arNlenoiil 
miuclc 


Thyroid  cartilagr 


EpIclMtii 


.jL>inphaid  tiasiK 


Fat 


,Glands 


.Ventricle 


Point  at  whicli 
s<|uaim>us  epitlie- 
liuin  ends 


,l.ater  ;t    1  ICO 
ar>i  -ty.id  ni  iscle 


CMcoid  cani'an*  . 

Fronul  section  ol  lar>-nx.  abont  middle  ol  vocal  cords. 


X3. 


opening.  Not  rarely,  however,  it  is  ■  ithout  separation  from  the  rest  of  the  ventricle. 
It  may  a.scend  to  a  height  of  15  mm.  irom  the  bottom  of  the  ventricle.  These  cavi- 
ties are  compressed  laterally,  and  situated  in  the  thickness  of  the  wall  of  the  arynx 
proper,  internal  to  the  fossa  pyriformis.  According  to  Rudinger,  the  ventricle?  arc 
relatively  much  larger  in  the  male.  Occasionally  cases  of  great  over-development  ot 
the  ventricles  are  met  with.  They  may  even  periorate  the  thyro-hyoid  membr.we. 
This  is  analogous  to  the  sacs  of  the  anthropoid  apes.  Brosike'  has  seen  a  median 
pouch  perforating  the  thyroid  in  the  region  of  the  vocal  cords.  A  similar  structure 
occurs  in  the  horse,  ass,  and  mule.  The  function  of  the  true  cords  is  to  change  the 
size  and  shape  of  the  glottis  both  during  respiration  and  phonation,  and  to  cause 
sound  by  their  vibrations,  which  depend  in  part  on  their  tension.  When  drawn  into 
'  Virchow's  Archiv,  Bd.  xcviii.,  1884. 


THE    LARYNX. 


i>>^ 


region,  which  is  broadest  between  them.  .  j^ ,    ,^,^„„, 

Fio.  i55»- 


Glands 


Vortl  corJs 

Thyro-arytenoid 

Ventricle 


Fibres  o{  Ihvro- 
:ir\'tenoid  perhal*      ;^. 
ins»-rt«nl  liilo  votal     '  Tj. 
proccMi 


1  jiteral  crico- 


arytciiui«l  carlilage 


.CricoW  cartila«« 


Fronul  »«llon  of  lar>-nx  IhrouRh  vocal  proc«««  of  arytenoid  crtll.f«. 


X  3. 


grrniins  of  serous  elements.  ...  .    ,  11.,  „Uc--,.«r)  ,,n  the  D" >•*'»'<■''>'■ 

^'\ymphmd  tissue,  as  distinct  .u.Uul«    is  occasiomdly  observed  .m  tne  p-^_. 


1834 


HUMAN  ANATOMY. 


surface  of  the  epiglottis  and  the  side  and  back  walls  of  the  larynx,  its  most  usual 
position  being  the  ventricle  (Fig.  1551).  Within  the  laryngeal  pouch  the  lymphoid 
tissue  is  so  constant  and  plentiful  that  laryngeal  tonsil  has  been  suggested  (Fraenkel) 
as  an  appropriate  name  for  these  collections. 


THE  MUSCLES  OF  THE  LARYNX. 

The  extrinsic  muscles  of  the  larynx  should  include  those  going  to  the  hyoid  bone, 
which  is  physiologically  a  part  of  this  apparatus.  These  have  been  described  in  the 
systematic  consideration  of  the  Muscular  System  (page  543).  The  intrinsic  muscles 
are  the  crico-thyroid,  t\ie posterior  crico-arytenoid,  the  lateral  crico-arytenoid,  the  thyro- 
arytenoid, and  the  arytenoid.  All  of  these,  except  the  last,  are  in  pairs.  From  a 
physiological  stand-point  these  muscles  may  be  divided  into  three  groups  :  the  con- 
strictors, including  both  the  adductors  of  the  cords  and  those  which  draw  together  the 
supraglottic  portion  of  the  larynx  ;  the  dilators,  which  abduct  the  cords  ;  and  those 
which  modify  the  tension  of  the  cords  without  necessarily  approaching  or  separating 
them.  The  constrictors  are  the  lateral  crico-arytenoids,  the  thyro-arytenoids,  and 
the  arytenoid.  The  dilators  are  the  posterior  crico-arytenoids.  Those  modifying 
the  tension  of  the  cords  are  the  i:rico-thyroids,  which  stretch  them,  and  a  part  o' 

the  thyro-arytenoids,  which  relax 
Fio.  1553.  them.     Moreover,  many  of  these 

muscles,  even  antagonistic  ones, 
when  acting  together  may  be  con- 
sidered as  parts  of  a  sphincter. 
The  laryngeal  muscles  are  ex- 
tremely variable,  especially  the 
thyro-arytenoid,  detached  fibres 
of  which  have  been  described  as 
the  thyro-epiglottideus. 

The  cnco-thyroid  muscle 
(Fig.  1 5 10)  is  well  defined,  pass- 
ing upward  and  outward  from  the 
anterior  ring  of  the  cricoid  to 
the  under  border  and  the  inferior 
horns  of  the  thyroid.  The  origin 
is  from  the  whole  of  the  anterior 
surface  of  the  arch,  except  for  a 
slight  interval  between  the  mus- 
cles. The  internal  fibres  are  nearly 
vertical  and  the  lateral  ones  nearly 
horizontal.  The  insertion  is  into 
the  lower  border  of  the  thyroid 
cartilage  from  a  point  a  few  milli- 
metres in  front  of  the  inferior  tubercle  to  all  the  rest  of  the  lower  border  and  the  front 
of  the  inferior  horn.  It  often  extends  a  little  onto  the  posterior  surface  of  the  ala. 
The  muscle  is  frequently  divided  into  a  superficial  and  a  deep  part.  The  distinction 
may  be  very  striking,  and  also  not  to  be  seen.  The  superficial  is  the  more  internal 
vertical  f)art,  which  conceals  a  little  of  the  origin  of  the  deeper.  The  crico-thyroid 
may  be  continuous  by  some  fibres  with  the  inferior  constrictor  of  the  pharynx.  It 
may  descend  to  the  first  ring  of  the  trachea,  and  it  may  give  off  fibres  to  the  capsule 
of  the  thyroid  body.  Occasionally  the  muscles  of  the  two  sides  are  connected  at  the 
lower  border  of  the  cricoid.      In  extre.  ;e  cases  each  may  cross  the  median  line. 

Action. — This  muscle  is  a  tensor  of  the  vocal  cords  by.  separating  their  points 
of  attachment  on  the  thyroid  cartilage  from  those  on  the  arytenoids.  Although  the 
conventional  names  of  origin  and  insertion  have  been  used,  the  more  movable  of  the 
two  cartilages  is  the  cricoid,  and  the  action  of  the  muscles  is  to  raise  its  anterior  arch, 
thereby  tipping  the  posterior  plate  with  the  arytenoids  backward,  and  so  stretching 
the  cords.  While  the  thyroid  can  he  held  fixed  by  manv  muscles,  tht  only  extrinsic 
one  .attached  to  the  cricoid  is  a  part  of  the  inferior  constrictor  of  the  pharynx,  so  that 


CartilaKotriticca- 


Thyro-hyoid- 
membrane 


Ar>  t-pislotticus 

Arytetioideus, 
oblique  portion 

ArytenoideUB,- 
transverse  por- 
tion 

Crico-' 
arytenoideus 
posticus 


Epiglottis,  dorsal  surface 


Superior  comu 
of  llyoid  bone 

Superior  thyroid 
cornu 


'uneifurm 
tubercle 

'artilaffe  of 
Santurini 

Posterior  marjciii 
of  thyroid  car- 
tilage 


Inferior  thyroid 
comu 

ricojd  cartilage 
.Trachea 


Muscles  of  larynx  from  behind. 


m 


THE    LARYNX. 


1835 


upon  the  cricoid  cartilage  devolves  the  whole,  or  nearly  the  whole  of  the  movement. 
Although  the  movement  is  generally  described  as  rotation  on  a  transverse  axis  pass- 
ing through  the  two  cricothyroid  joints,  the  articulation  is  of  so  vague  a  character 
that  a  great  deal  of  sliding  occurs. 

The  posterior  crico-arytenoid  muscle  (Fig.  1554)  »*  very  distmct  and 
occupies  the  hollow  on  either  side  of  the  median  ridge  on  the  back  of  the  cricoid 
cartil^e  It  is  triangular,  with  rounded  angles  at  the  base,  which  is  at  the  ridge, 
and  the  third  sh^p  angle  at  the  posterior  border  and  upper  aspect  of  the  muscular 
process  of  the  arytenoid.  The  origin  is  not  from  the  whole  of  the  fossa  on  the  cri- 
coid, but  chiefly  from  the  region  of  the  ridge  whence  it  springs  by  tendinous  fibres. 
It  arises  also  from  the  lower  part  of  the  cricoid,  but  not  from  the  part  near  the 
arytenoid.  It  passes  over  the  capsule  of  the  joint,  with  which  it  is  intimately  fused, 
and  is  inserted  as  above  stated,  some  of  its  fibres  becoming  tendinous. 

Action.— It  pulls  the  muscular  process  downward  and  inward,  thus  raising  and 
everting  the  vocal  process  and  conseqn  .lUy  enlarging  the  cleft  of  the  glottis. 

Two  occasional  small  muscles  in  the  neighborhood  of  the  inferior  horn  of  the  thyroid  are 
orobabtv  aberrant  bundles  of  the  posterior  crico-arytenoid.  One,  the  poslertorcrtco-Myroia, 
SSKiverSr^  from  the  lower  eitemal  fibres,  runs  from  the  back  of  the  cncoid  upward  and 
oitwafd  to^  interna!  aspect  of  the  inferior  horn  of  the  thyroid.  The  other,  the  postertor  th}fro- 
fl^/^W.  runs  from  the  liwer  horn  upward  to  be  inserted  with  the  posterior  cnco-arytenoid  mto 
the  muscular  process. 

The  lateral  crico-arytenoid  muscle  (Fig.  1554),  of  an  elongated  triangular 
form,  arises  from  the  upper  border  of  the  lateral  part  of  the  cricoid  and  froni  the 
ascending  edge  of  the  plate  as  tar  as  the  arytenoid  joint.  It  also  may  have  fibres 
springing  from    the  cnco-thyroid 

membrane.     \x 'ts,  inserted  xtAq  i>c\t  Fio.  1554. 

front  of  the  muscular  process.  This 
muscle  is  less  well  defined  than  the 
posterior  crico-thyroid,  and  may 
be  more  or  less  fused  with  the 
thyro-arytenoid,  on  the  one  hand, 
and  the  crico-thyroid,  on  the  other. 

Action. — It  pulls  the  muscular 
process  forward,  thereby  bringing 
the  vocal  cord  nearer  to  its  fellow. 

The  thyro-arytenoid  mus- 
cle (Fig.  1554)  arises  from  the 
inner  suriace  of  the  thyroid,  just 
outside  the  entering  angle,  from 
the  level  of  the  true  cord  to  the 
lower  border.  At  the  side  it  arises 
from  a  part  of  the  crico-thyroid 
membrane,  and  may  there  be  con- 
tinuous with  the  lateral  crico-ary- 
tenoid. It  runs  backward  and  is 
inserted  into  the  upper  surface  of 
the  vocal  process  of  the  arytenoid 

and  into  the  antero-external  sur-  .      ,        .  ,       ,  .        1       ... 

face  of  that  cartilage.  It  is  convenient  to  speak  of  an  internal  and  an  external  p;irt. 
but  there  is  no  separation  between  them.  The  internal  portion  (m.  tbyreoarjtae- 
noideus  vocalis)  is  a  prismatic  ma.ss,  triangular  on  sect  .on  (Fig.  1551).  forming  the 
bulk  of  the  true  cord,  with  one  of  its  angles  against  the  ligament  m  the  free  edge. 
I.udwig  taught  that  fibres  diverged  from  the  body  of  this  muscle  to  be  inserted  suc- 
cessively into  the  ligamentous  band  of  the  vocd  cord,  which  thus  resembled  the 
tendon  of  a  muscle  receiving  oblique  fibres  along  its  side.  These  were  supposed  to 
modify  its  tension  indefinitely  by  pulling  upon  it  at  various  points.  This  view'  has 
been  denied  by  Luschka.  and  the  point  remains  undecided.  Jacobson  found  on 
'Archivf,  mikro.  Anat.,  Bd.  xxix.,  1887. 
ii5 


Suiierior  thyroid 
comu 

Aoepiglouicus  _ 


An-tenoideus 

Criro-arj1enoideiis 
lateralis 

Crico.ar>1enoid»ii» 
posticus 

Cricoid  carlilagv 


.L.ar>-nKcal  t>ou€-h 

RiRht  thyroid  ala 
(cut) 


Thyro-arytciioidcus 
extern  lis 


.Crico-lhyroideua 

(cnti 


Tr«ch«a 


Muscles  of  larynx 


lateral  view  alter  |iartial  removal  of  right 
thyroid  ala. 


1826 


HUMAN   ANATOMY. 


Body  of  hyoid 
bone  (cut) 


Epif;loltis 


Mass  of  fat 


microscopic  sections  that  fibres  were  often  inserted  obliquely  into  the  cord  and  into 
the  end  of  the  vocal  process.  There  was,  however,  much  variation,  and  in  some 
cases  no  such  fibres  were  found.  Our  own  observations  incline  us  to  look  upon  such 
fibres  as  possible,  but  probably  in  the  ordinary  larynx  they  are  few  and  far  between. 
The  external  portion  (Fig.  1554)  is  a  thin  membrane  on  the  outer  side  of  the  ven- 
tricle, with  its  fibres  spreading  upward  and  backward  towards  the  aryepiglottic  fold. 
Some  few  fibres  are,  or  may  be,  found  in  the  false  cord,  and  some  occasionally  arch 
over  the  ventricle.  The  external  portion  is  very  irregular  and  inclined  to  give  off 
aberrant  bundles.  The  superior  thyro-arytenoid  is  a  common  one.  It  arises  from 
the  inner  side  of  the  ala  of  the  thyroid,  near  the  top,  a  little  outside  of  the  notch,  and 
runs  downward  and  backward  to  the  top  and  .t  terior  aspect  of  the  vocal  process, 
resting  on  the  outer  side  of  the  external  part  >  the  thyro-arytenoid  and  crossing  it 
at  right  angles.  It  consists  of  long  parallel  .bres  and  varies  much  in  size.  Tht 
thyro-epiglottic  muscle  is  simply  fibres  of  th<  -.ystem  of  the  thyro-arytenoid  that  pass 
upward  to  the  side  of  the  epiglottis.     We  incline  to  consider  the  aryepiglol'-'    muscle 

(Pig.  1554) — a  little  L^ndle ex- 
tending from  the  side  of  the 
arytenoid  to  thf  epiglottis  in 
the  edge  of  the  fold — a  part 
of  this  same  system. 

Action. — That  of  the  in- 
ternal part  of  the  thyro-aryte- 
noid is  to  relax  the  vocal  cords 
by  approximating  their  ends  ; 
if,  however,  the  fibres  inserted 
into  the  cords  be  worth  consid- 
ering, this  action  must  be  modi- 
fied by  the  stretching  of  parts 
of  the  cords  while  others  are 
relaxed.  The  irregularity  of 
this  arrangement  is  quite  in  har- 
mony with  the  endless  variations 
of  the  human  voice.  The  shape 
of  the  walls  below  the  true  cords 
must  also  be  modified  by  the 
swelling  of  the  contracting  mus- 
cle. The  action  of  the  outer 
portion  of  this  muscle  must  be 
in  the  main  that  of  a  constrictor 
of  the  supraglottic  region.  It  is  possible  that  when  the  cords  are  abducted  some  of 
the  fibres  inserted  into  the  muscular  processes  may  act  as  adductors. 

The  arytenoid  muscle  (m.  interarjtaenoideus)  is  a  mass  of  fibres  running  trans- 
versely between  the  hollows  on  the  posterior  surfaces  of  the  arytenoid  cartilages,  which 
it  fills  (Fig.  1553).  There  is  usually  a  superficial  oblique  part  of  this  muscle  which, 
when  well  developed,  is  formed  by  two  bands  crossing  each  other  like  the  arms  of  an 
X  placed  on  its  side.  Each  arm  starts  from  the  muscular  process  of  the  arytenoid  and 
crosses  to  the  summit  of  the  arytenoid  of  the  opposite  side.  Here  it  may  end  or  be 
continuous  with  the  fibres  of  the  aryepiglottic  muscle,  which  ascend  to  the  epiglottis. 
One  or  both  arms  may  be  wanting,  and  this  part  may  be  more  or  less  fused  with  the 
deeper  transverse  fibres. 

Action. — It  draws  the  arytenoid  cartilages  together,  and  is,  moreover,  an  im- 
portant part  of   the  sphincter-like  arrangement. 

Vessels. — The  arteries  are  the  superior  laryngeal  and  the  crico-thyroid  from 
the  superior  thyroid  artery  and  the  inferior  laryngeal  from  the  inferior  thyroid  artery, 
he  superior  laryngeal  pierces  the  thyro-hyoid  membrane  some  5  mm.  from  the 
superior  horn  of  the  thyroid  and  about  midway  lx;tween  the  top  and  the  bottom. 
After  givir-  of!  an  epiglottic  branch,  which  on  its  way  supplies  the  areolar  tissue 
anterior  to  the  epiglottis,  the  vessel  runs  downward  and  backward  under  cover  of  the 
ala  of  the  thyroid  to  its  distril^ution  in  the  upper  part  of  the  larynx.    The  crico- 


False  vocal  cord 

Thyroid  cartilage. 

True  vocal  cord 

Thyro-arytenoideus. 

intemus 

Crtco-thyroidens 

Anterior  arch  of  cricoid 
cartilage 


Tracheal 

cartilages 


Greater  hyotd 
coniu 


Superior  thyroid 
cornu 


Ventricle  of  larynx 
Arytenoid  cartilage 

Crico-arytenoideus 

lateralis 
■Posterior  arch  of 

cricoid  cartilage 
Line  of  cut  mucosa 


Sagittal  section  of  larynx  from  within ;  mucous  membrane  has  been 
removed  from  vocal  cord  to  lower  level  of  cricoid  cartilage. 


THK  LARYNX. 


1827 


Fio.  1556. 


thyroid  branch  meets  its  fellow  so  xs  to  form  an  arch  across  the  median  line  and 
sends  (leriorating  branches  into  the  larynx  through  the  crico-thyroid  membrane. 
The  inferior  laryngeal  from  the  inferior  thyroid  reaches  the  region  of  the  Iwck  of  the 
larynx  from  the  side.  It  anastomoses  with  the  su|H?rior  laryngeal  and  sometimes 
sends  branches  through  or  into  the  arytenoid  muscle.  The  vocal  cords  |x)sse89 
relatively  few  blood-vessels. 

The  veins  correspond  in  the  main  to  the  arteries,  but,  owing  to  their  greater 
size  and  freer  anastomoses,  they  seem  in  more  immediate  relation  with  thosi-  <  if  the 
thyroid  body.  Moreover,  they  tend  to  form  a  median  descending  vessel  in  the  front 
of  the  neck.  There  is  a  plexus  on  the  pharyngeal  side  of  the  biick  of  the  larynx 
which  communicates  through  the  folds  at  the  sides  of  the  entrance  with  the  veins  of 
the  dorsum  of  the  tongue.  The  inferior  laryngeal  vein  empties  into  the  inferior 
thyroid  through  a  circular  plexus  around  the  entrance  of  the  trachea. 

The  lymphatics  of  each  side  empty  into  two  chief  ves.sels,  of  which  the  superior 
pierces  the  thyro  hyoid  membrane,  carrying  the  lymph  from  the  supraglottic  region 
to  the  nodes  under  or  near  the  stemo-mastoid.  The  inferior  vessel  descends  under 
the  mucous  membrane  outward  and  backward  to  the  ntKles  along  the  posterior  sur- 
face of  the  trachea.  It  may,  however,  open  into  an  inconstant  node  in  front  of  the 
crico-thyroid  membrane.  This  node  occurs  in  44  per  cent, 
of  adults  and  in  57  per  cent,  of  children.  It  may  be 
double.' 

Nerves. — ^These  are  the  superior  and  the  inferior 
laryngeal  nerves,  both  from  the  vagus.  The  sujiericr,  on 
reaching  the  thyro-hyoid  membrane,  divides  into  an  exter- 
nal and  an  internal  branch.  The  external  continues  down- 
ward and  forward  to  the  crico-thyroid  muscle,  which  it 
supplies.  It  is  in  relation  with  the  pharyngeal  plexus  and 
the  superior  sympiathetic  ganglion.  The  internal  branch 
pierces  the  membrane  together  with  the  superior  laryngeal 
artery,  and  supplies  the  greater  part  of  the  mucous  mem- 
brane. Its  ramifications  are  in  two  groups  :  ascending 
ones  to  the  epiglottis,  the  region  just  before  it,  and  to  the 
aryepiglottic  folds ;  others  passing  to  the  mucous  mem- 
brane within  the  larynx  and  to  that  of  the  posterior  surface 
looking  towards  the  pharynx.  The  inferior  laryngeal,  as- 
cending by  the  side  of  the  back  of  the  trachea,  divides  into 
two  branches.  The  branch  nearer  the  median  line  inner- 
vates the  posterior  crico-arytenoid  and  the  arytenoid  mus- 
cles. Its  fibres,  in  j)art  sensory,  enter  into  communication 
with  those  of  the  superior  laryngeal.  The  other  branch 
of  the  inferior  laryngeal  goes  to  the  other  intrinsic  muscles 
of  the  pharynx.  Thus  the  superior  laryngeal  divides  into 
a  motor  branch  that  ends  in  one  muscle,  and  a  sensory  division  which  plays  the 
greater  part  in  supplying  the  mucous  membrane.  The  inferior  laryngeal  is  also  a 
mixed  nerve,  but  chiefly  motor.  It  supplies  all  the  other  muscles  and  helps  to  sup- 
ply the  mucous  membrane.  A  remarkable  peculiarity  of  the  sensory  nerves  is  a 
tendency  to  cross  the  median  line,  so  that  certain  regions  are  reached  from  both 
sides. 

The  general  teaching  by  English  anatomists  has  been  that  the  superior  laryngeal 
is  as  above  stated  and  that  the  inferior  is  purely  motor.  Exner '  made  obser\ations, 
in  jjart  confirmed  and  in  part  disputed,  to  the  effect  th?i  both  nerves  are  mixed, 
supplying  both  muscles  and  mucous  membrane  (the  superior  supplying,  in  part  at 
least,  certain  muscles  within  the  larv-nx),  and  that  both  motor  and  sensory  fibres 
cross  the  median  line,  so  that  some  muscles  receive  the  corresjjonding  nerve  of  l)oth 
sides.  Moreover,  he  found  in  some  animals  a  middle  laryngeal  nerve  from  the 
pharyngeal  branch  of  the  vagus,  of  which  the  analogue  exists  in  man,  in  whom  it 
goes,  together  with  the  superior  laryngeal,  to  the  cricothyroid  muscle  of  both  side's. 

'  Nicolas  in  Poirier's  Trait<5  d'Anatomie  Humaine. 

'  Vienna  AkRd.  SitrtmRxN-richf,  iS-S.}. 


VrsUbule 


!'alse  vcxral 
cord 


Ventricle 
.Vocal  cord 


Trachea 


Cast  c»(  cavity  of  larynx  and 
•d)acenl  part  of  trachea  ;  anterior 
aspect. 


mm 


1828 


HUMAN  ANATOMY. 


In  the  above  description  we  coincide  with  Onodi,'  who  denies  entirely  the  existence 
of  the  middle  laryngeal  in  man. 

The  endings  of  the  numerous  sensory  nerves  in  the  mucous  membrane,  as 
def  "ribed  by  Retzius,  Fusari,  Ploschko,  and  others,  include  free  terminations  between 
th'  epithelial  cells  and  subepithelial  end-arborizations.  According  to  Ploschko, 
special  end-organs,  composed  of  columnar  cells  surrounded  by  delicate  nerve-fibrilla;, 
exist  within  the  true  vocal  cords.  Taste-buds  occur  not  only  on  the  posterior  sur- 
face of  the  epiglottis,  but  also  within  the  laryngeal  mucous  membrane  in  the  vicinity 
of  the  ary^moid  cartilages. 

Position  and  Relations  of  the  Larynx. — ^The  larynx  forms  a  part  of  the 
anterior  wall  of  the  pharynx  and  rests,  therefore,  against  its  posterior  widl.  In  the 
adult  male  the  tip  of  the  epiglottis  is  opposite  the  lower  border  of  the  third  cervical 
vertebra  and  the  lower  end  of  the  cricoid  opposite  some  part  of  the  seventh  vertebra. 
Thus  in  man  it  covers  about  four  vertebral  bodies,  with  the  intervening  disks.  It  is 
small  in  the  female  and  rather  higher.  Mehriert '  believes  that  in  the  living  body  in 
the  upright  position  the  cricoid  is  about  one  vertebra  lower  than  it  is  after  death  in 
the  recumbent  position.  Individual  variation  is  marked,  as  is  shown  by  the  results 
compiled  from  the  researches  of  Taguki.'  Thus  in  thirty-five  men  the  lower  border 
of  the  cricoid  was  opposite  or  below  the  seventh  vertebra  twenty-nine  times,  but  in 
thirty-three  women  only  twenty-one  times.  It  was  above  it  six  times  in  men  and 
twelve  times  in  women  ;  in  one  case  (male)  it  was  as  high  as  the  fifth  vertebra. 

Anteriorly  the  larynx  lies  beneath  the  middle  layer  of  the  cervical  fascia.  The 
lobes  of  the  thyroid  rest  on  either  side  against  the  cricoid  and  thyroid.  The  larynx 
as  a  whole  can  be  raised  and  depressed  by  muscles,  and  changes  its  position  with  the 
movements  of  the  spine.  Thus,  when  the  neck  is  bent,  it  falls  i  cm, ,  and  rises  3  cm. 
when  the  neck  is  extended.  When  the  head  is  turned  to  one  side,  the  hyoid  is  twisted 
less  than  the  head,  but  more  than  the  larynx,  although  the  latter  and  the  trachea  may 
share  in  the  movement.    The  larynx  may  be  displaced  sideways  by  external  pressure. 

Changes  with  Age  and  Sexual  Differences. — At  birth  the  larynx  is  very 
small,  but  may  be  said  to  be  relatively  larger  than  later.  The  sharp  angle  of  the  thy- 
roid cartilage  is  entirely  wanting.  The  larynx  grows  gradually  up  to  puberty,  when  it 
takes  on  a  sudden  expansion,  which  occurs  in  both  sexes,  but  is  much  more  marked 
in  the  male.  According  to  Luschka,  it  doubles  in  man  and  increases  by  less  than 
half  in  woman.  The  most  marked  sexual  difference  is  the  size  and  prominence  of 
the  thyroid  cartilage  in  the  male.  The  duration  of  the  process  by  which  the  larynx 
of  a  child  changes  into  that  of  an  adult  may,  according  to  F.  Merkel,  be  as  much  as 
two  years,  and,  in  fact,  changes  may  occur  throughout  growth.  In  the  foetus  the 
position  of  the  larynx  is  very  high.  At  birth  the  lower  border  of  the  cricoid  is  oppo- 
site the  lower  border  of  the  fourth  vertebra.  Symington  found  it  at  six  years  at  the 
lower  border  of  the  fifth  and  a*  thirteen  at  the  top  of  the  seventh.  Probably  it  reaches 
what  may  be  called  its  permanent  position  at  about  puberty.  Mehnert,  however,  finds 
from  his  observations  on  the  living  that  the  descent  continues  till  about  thirty,  when 
there  is  a  great  retardation,  or  even  a  suspension,  of  the  process  till  about  sixty,  when 
it  goes  on  again  with  renewed  activity.  According  to  him,  the  cricoid  n>ay  ultimately 
reach  the  second  or  even  the  third  thoracic  vertebra.  It  is  to  be  noted  that,  while 
the  earlier  descent  is  a  physiological  process,  that  of  old  age  is  a  degenerative  one, 
depending  in  part  on  changes  in  the  spine  and  on  the  loss  of  elasticity  of  the  tissues. 


PRACTICAL   CONSIDER.\TIONS :    THE   LARYNX. 

The  Air-Passages. — The  Avoid  done  is  closely  contiguous  to  the  opening  of 
the  larynx,  and  as  its  injuries  derive  their  chief  surgical  importance  from  that  rela- 
tion, they  are  considered  here. 

Fracture  of  'he  hyoid  results  from  compression  by  the  gr.isp  of  a  hand,  by  the 
rope  in  cases  of  inging,  or  from  a  direct  blow.  It  usually  occurs  near  the  junction 
of  the  greater  C'  rnu  with  the  body  of  the  bone.     Displacement  is  not  apt  to  be 

'  Die  Anatomie  und  Physiolojtie  der  Kehlkopfnerven,  Berlin,  1902. 

'  Ueber  topograpliLsche  Altersvcraiiderungeii  des  Atniungsapparates,  1901. 

•  Arcliiv  f.  Anat.  u.  Phys.,  Anat.  Abth.,  1889. 


PRACTICA!-   CONSIDERATIONS.   THK    LARYNX. 


I8i9 


marked,  because  the  great  horn  is  held  above  by  the  digastric  aponeurosis  and  thi- 
hyo-glossus  muscle  and  below  by  the  thyro-hyoid  ligament  and  muscle.  Kxcep- 
tionally  the  middle  constrictor  of  the  pharynx  may  draw  it  somewhat  backward  and 
inward.  The  attachments  to  the  hyoid  of  the  constrictor  and  of  the  hyo-glossus  and 
genio-hyo-glossus  invariably  make  deglutition  and  speech  jjainful  after  this  fracture, 
while  the  genio-hyoid  and  digastric,  by  their  contraction,  cause  pain  on  opening  the 
mouth,  the  associated  swelling  may  involve  the  epiglottic  mucous  membrane  and. 
spreading  thence,  give  rise  to  serious  dyspnoea. 

The  thyro-hyoid  tnembrane,  springing  from  the  posterior  upper  margm  of  the 
hyoid  bone  and  attached  to  the  upper  border  of  the  thyroid  cartilage,  has  inter|K>sed 
between  its  anterior  surface  and  the  posterior  face  of  the  body  of  the  hyoul  a  bursa 
which  descends  below  the  lower  border  of  that  bone,  and  when  enlarged  forms  a 
cystic  swelling  situated  in  the  median  line  of  the  neck,  just  beneath  the  hyoid. 
Thyro-lingual  cysts  are  sometimes  found  in  the  same  situation. 

A  similar  cystic  swelling,  lined  with  columnar  epithelium  and  occupying  the 
same  region,  is  referable  to  the  persistence  of  the  foeUl  thyro-lingual  duct.  At  the 
upper  end  of  that  duct  such  a  cyst  would  lie  in  the  mid-line  of  the  tongue  between 
the  two  genio-hyo-glossi  muscles.  At  the  lower  end  it  would  lie  over  the  thyroid  or 
the  cricoid  cartilage.  The  sinuses  formed  by  the  bursting  of  such  cysts,  or  ongmally 
by  the  persistence  of  jwrtions  of  the  thyro-lingual  duct,  are  obstinate,  and,  on  account 
of  their  epithelial  lining,  must  be  dissected  out  completely  to  secure  healing. 

The  lower  portion  of  the  thyro-hyoid  membrane  is  covered  in  the  mid-hne  by 
cervical  fascia  and  skin,  laterally  by  the  sterno-hyoid  and  thyro-hyoid  muscles. 

Cut-throat  wounds  of  the  neck,  especially  if  suicidal,  are  apt  to  pass  through 
this  membrane,  which  is  made  tense  when  the  head  is  thrown  l>ackward,  and,  if  they 
are  deep,  will  divide  the  inferior  constrictor,  open  the  pharynx,  and  possibly  wound 
or  sever  the  epiglottis  near  its  base,  first  passing  through  the  cellulo-adipose  tissue 
that  inter\'enes.  If  the  wound  is  not  immediately  beneath  the  lower  border  of  the 
hyoid,  it  may  divide  the  internal  branches  of  the  superior  laryngeal  nerve,  leading 
ultimately  to  a  pneumonia  from  the  inspiration  of  foreign  matter.  In  infrahyoid 
pharyngotomv  such  a  transverse  wound,  hugging  the  lower  edge  of  the  hyoid,  gives 
access  to  the  base  of  the  pharynx  and  the  supraglottideal  region. 

Above  the  hyoid  a  cut-throat  wound  would  divide  the  tongue  muscles  and  enter 
the  mouth.  Below  the  thyroid  it  would  pass  through  the  crico-thyroid  membrane 
and  open  the  larynx.     Still  lower  the  trachea  would  be  incised  or  severed. 

The  great  vessels  often  escape  in  suicidal  wounds,  as  the  usual  position  of  the 
head  in  extreme  extension  increases  the  projection  of  the  laryngeal  apparatus  and 
therefore  the  depth  of  the  vessels  from  the  surface.  One  reason  for  their  escape 
when  the  air-passages  below  the  glottis  are  opened  may  be  that  the  sudden  rush 
of  air  from  the  lungs  and  consequent  collapse  of  the  chest-walls  deprive  the  muscles 
running  from  the  thorax  to  the  humerus  of  their  fixed  point  of  support,  and  that 
the  arm  necessarily  drops  (Hilton).  Death  may  be  caused,  however,  by  hemor- 
rhage from  the  superior  thvroid  or  the  lingual  artery,  or  even  from  the  crico-thyroid 
if  the  blood  enters  the  larynx  or  trachea  ;  or  may  result  from  suffocation  produced 
by  the  dropping  backward  of  the  tongue  after  division  of  the  genio-hyoid,  hyo- 
glossus,  and  genio-hyo-glossus  muscles,  or  by  the  occlusion  of  the  glottis  by  a  partly 
divided  epiglottis  or  arytenoid. 

Fracture  of  the  thvroid  or  cricoid  cartilage  may  occur  from  the  same  causes  that 
produce  fracture  of  the  hyoid  bone.  The  thyroid,  on  account  of  its  greater  prom- 
inence, suffers  more  frequently.  Fractures  of  the  thyroid  are  seen  oftener  in  males 
tha  in  females,  because  (a)  in  the  former  it  is  relatively  more  prominent  ;  (b)  the 
process  of  ossification — ^which,  in  common  with  other  hyaline  cartilages,  it  undergoes 
after  adult  life  has  been  reached — is  more  complete  in  them  ;  and  (f )  males  are 
oftener  exposed  to  violence. 

The  symptoms  depend  for  their  gravity  chiefly  upon  the  degree  of  invoh  ement  of 
the  laryngeal  mucous  membrane.  If  that  is  wounded,  bloody  expectoration,  aphonia, 
and  dyspnoea  arc  present,  and  tracheotomy  may  be  urgently  indicated.  In  any  event, 
deglutition  is  painful.  The  voice  is  usually  altered,  and  there  is  apt  to  be  some  ex- 
ternal deformity.     Crepitus  may  be  present,  but  should  be  distinguished  from  the 


1830 


HUMAN   ANATOMY. 


sound  produced  by  moving  the  normal  larynx  laterally,  and  caused  by  the  friction  be- 
tween the  somewhat  irregular  anterior  surface  of  the  vertebral  column  and  the  posterior 
border  of  the  thyroid,  the  corresponding  surface  of  the  cricoid,  and  the  lower  part  of 
the  pharynx,  which  move  together.  This  normal  crepitus  disappears  in  retropharyn- 
geal abscess,  but  persists  in  retrolaryngeal  abscess  (Allen  ).  It  should  be  remembered 
that  the  superior  cornua  of  the  thyroid  are  sometimes  found  separate  from  the  body. 

The  cricoid  and,  much  more  rarely,  the  thyroid  and  arytenoid  cartilages  may 
be  the  subject  of  perichondritis  secondary  to  ulceration  (typhoidal,  cancerous,  syphi- 
litic, or  tuberculous)  of  the  interior  of  the  larynx.  In  the  case  of  the  cricoid  it  is 
asserted  that  the  condition  may  result  from  the  pressure  of  the  posterior  aspect  of 
the  cartilage  against  the  spine  in  very  debilitated  subjects,  or  from  the  traumatism 
caused  by  the  frequent  passage  of  an  (Esophageal  bougie  (Pearce  Gould).  The 
origin  of  the  inferior  constrictor  from  the  cricoid  accounts  for  the  pharyngeal  s[>asm 
and  dysphagia  said  to  accompany  disease  of  this  cartilage  (Gibbs). 

Allen  says  that  the  cricoid  is  elatively  more  prominent  in  women  than  in  men, 
and  that  it  is  often  the  site  to  which  abnormal  sensations  originating  in  the  pharynx 
are  referred,  because  in  such  conditions  deglutition  is  [jainful,  and  since  the  cricoid  lies 
at  the  lower  part  of  the  pharynx,  its  motions  determine  a  greater  amount  of  dbtress 
than  do  the  corresponding  motions  at  any  other  p.>rt  of  the  throat. 

The  epiglottis  is  not  infrequently  affected  by  syphilis,  and  is  also,  although  more 
rarely,  the  seat  of  tuberculous  lesions,  and  may  be  extensively  ulcerated  or  may  become 
necrotic.  The  danger  of  such  cases  results  usually  from  the  accompanying  oedema 
{vide  infra),  but  in  rare  instances  a  sloughing  and  wholly  or  partially  separated  epi- 
glottis may  directly  occlude  the  laryngeal  aperture. 

Infection  originating  in  disease  of  the  epiglottis  may  involve  the  cellulo-adipose 
tissue  between  its  base  and  the  thyro-hyoid  membrane,  giving  rise  to  a  thyro-hyoid 
abscess  which  may  extend  towards  the  mouth  and  project  in  the  groove  between  the 
root  of  the  tongue  and  the  epiglottis.  Such  an  atscess  may  also  follow  primary 
infection  of  either  the  tongue  or  the  thyroid.  It  is  very  apt  to  cause  adema  of  the 
glottis.  The  condition  known  by  this  name  may  occur  in  any  form  of  laryngitis,  or 
by  extension  of  inflammation  from  the  mouth,  tongue,  or  pharynx,  or  as  a  result 
of  trauma  or  of  wound,  scald,  or  the  application  of  local  irritants.  It  involves  the 
glottis  only  secondarily.  The  thin  mucous  membrane  covering  the  true  vocal  cords 
and  the  arytenoids  is  so  closely  applied  to  them,  and  the  subcutaneous  connective 
tissue  is  so  scanty,  that  there  is  no  opportunity  for  much  exudation.  But  in  the 
supraglottidean  region  the  mucosa  is  thick  and  the  submucosa  plentiful,  especially 
over  the  aryteno-epiglottidean  folds,  and  almost  equally  so  in  the  ventricles  and  over 
the  false  cords  and  the  posterior  surface  of  the  epiglottis.  Effusion  of  serum  and 
swelling  are  thus  favored  and,  according  to  their  degree,  will  produce  hoarseness, 
aphonia,  dyspnoea,  cyanosis,  or  positive  suffocation.  In  some  cases  of  oedematous 
laryngitis  the  swelling  affects  chiefly  the  region  below  the  glottis  {subglottic  oedema) 
and  causes  the  same  symptoms.  This  is  rarer  and  is  attended  by  less  effusion  on 
account  of  the  relatively  closer  association  of  the  mucosa  and  the  cricoid  cartil^e. 

The  mucous  glands  of  the  laryn.x  which  supply  the  moisture  needed  in  normal 
phonation  are  sometimes  inflamed  as  an  indirect  result  of  the  over-use  of  the  voice, 
— as  in  clergymen,  costermongers,  public  speakers,  etc.  The  increased  volume  of 
air  taken  in  through  the  mouth  dries  up  the  mucous  surface  of  the  larynx,  and  the 
effort  to  compensate  for  this  may  result  in  such  irritation  of  the  glands  and  mucosa 
as  to  cause  a  form  of  chronic  laryngitis, — "  clergyman's  sore  throat." 

The  rima  glottidis, — the  aperture  of  the  glottis, — the  narrowest  portion  of  the 
air-passages,  measures  a  little  less  than  one  inch  antero-posteriorly  in  the  adult  male. 
Its  transverse  diameter  at  its  widest  portion  is  about  one-third  of  an  inch.  In  the 
male  before  puberty,  and  in  the  female,  these  measurements  are  about  one-fourth 
less.  They  are  important  in  reference  to  the  introduction  of  instruments  and  the 
arrest  of  foreign  bodies  (vide  infra). 

The  level  of  the  glottis — i.e.,  of  the  true  vocal  cords — is  a  little  above  the 
middle  of  the  anterior  margin  of  the  thyroid  cartilage. 

The  shape  vA  the  aperture  varies.  It  is  linear  when  a  high  note  is  produced  in 
speaking  or  singing,  triangular  (with  the  apex  forward,  equal  sides  and  a  narrow 


mmmmm 


PRACTICAL   CONSIDERATIONS:   THE    LARYNX. 


IS.^I 


base)  during  quiet  respiration,  and  diamond- shaped  (with  the  posterior  angle  cut 
of!)  in  forced  breathing.  As  various  forms  of  ulceration  (.tuberculous,  syphilitic, 
diphtheritic)  may  affect  the  mucous  membrane  covering  the  true  vocal  corik,  or  the 
cords  themselves,  or  the  structures  in  their  immediate  vicinity  (( r^pecially  the  aryteno- 
epiglottidean  and  interarytenoid  folds  and  the  ventricular  bands),  and  as  cicatrization 
with  subsequent  contraction  of  scar  tissue  may  follow,  diminution  of  the  calibre  of 
the  rima  ghttidis  (stricture)  is  not  uncommon. 

Polyps,  warty  growths,  and  other  benign  tumors  are  found  in  the  vicinity  of  the 
vocal  cords,  and  if  they  cannot  be  removed  by  intralaryngeal  operation,  may  neces- 
sitate thyrotomy.  Subglottic  tumors  are  relatively  infretjuent.  They  often  spring 
from  the  inferior  surface  of  the  vocal  cords,  intraglottic  growths  from  thi  free 
border  of  the  anterior  part  of  the  vocal  cords,  and  supraglottic  growths  from  the 
epiglottis  and  the  aryteno-epiglottic  folds  (Dclavan). 

Spasm  of  the  glottis  (laryngismus  stridulus)  may  occur,  especially  in  infancy, 
from  reflex  irritation,  and  may  cause  great  dyspncea  or  may  even  result  fatally.  The 
irritation  is  conveyed  chiefly  to  the  inferior  laryngeal  nerves  through  the  pneumo- 
gastrics,  if  the  cause  is  undigested  food  ;  through  the  trifacial,  if  the  irritation  is  asso- 
ciated with  dentition  ;  or  through  the  spinal  accessory,  if  vertebral  disease  is  present. 

The  different  forms  of  laryngeal  paralysis  should  be  studied  in  connection  with 
the  p^  ''">"  of  phonation.  Some  of  the  chief  anatomical  considerations  may  lie 
indie  'oUowing  classification,  which  is,  however,  necessarily  incomplete, 

as  f.".'  .'ds  the  central  causes  of  paralysis — as  in  bulbar  palsy — and  those 

due         '  the  post-diphtheritic. 

^    to  direct  or  indirect  involvement  of  the  superior  laryngeal  nerves. 

(<.  ^  'ry  and  thyro-epiglottic — or  aryepiglottic— paralysis,  characterized  by  a 

tendency  of  food  or  liquids  to  enter  the  larynx,  by  dysphagia,  by  immobility  of  the 
epiglottis,  and  by  diminished  sensation  in  both  the  pharyngeal  and  laryngeal  mucous 
membranes,  would  suggest  especial  implication  of  the  internal  branch. 

(*)  Crico-thyroid  and  thyro-arytenoid  paralysis,  causing  loss  of  tension  in  the 
vocal  cords,  inability  to  regulate  and  control  the  voice,  and  with  evidence  of  the 
want  of  action  of  the  crico-thyroids  detected  by  the  finger  placed  on  either  side  of 
the  crico-thyroid  interval  externally  during  phonation  ( Agnew),  may,  in  some  cases, 
be  referred  anatomically  to  the  external  branch. 

2.    Those  dite  to  involvement  of  the  inferior  laryngeal  nerves. 

(a)  Lateral  crico-arytenoid  paralysis,  causing  separation  of  the  vocal  cords, 
with  more  or  less  complete  aphonia,  may  be  due  to  implication  of  the  external 
branch.  In  many  cases  there  will  be  evidence  of  the  existence  of  innominate  or 
aortic  aneurism,  thyroid  or  bronchial  glandular  enlargement,  carcinoma  of  the  oesoph- 
agus, or  some  other  condition  competent  to  produce  pressure  on  the  nerve.  The 
paralysis  may  be  unilateral  and  attended  only  by  hoarseness  and  partial  loss  of  voice. 

(3)  In  posterior  crico-arytenoid  paralysis  (abductor  paralysis)  the  loss  oi  power 
in  the  abductors  permits  the  lateral  crico-arytenoid  muscles  to  narrow  the  glottis 
into  a  mere  fissure,  so  that  inspiration  becomes  stridulous  and  dyspnoea  is  marked  ; 
the  voice  is  not  materially  interfered  with.  The  condition  may  be  due  to  intra- 
or  extralaryngeal  growths,  or  to  inflammatory  conditions,  possibly  causing  pressure 
on  the  inner  branch.     It  may  be  unilateral  and  due  to  aneurism. 

It  should  be  understood  that  the  relation  of  these  paralyses  to  the  external  and 
internal  branches  of  the  superior  and  inferior  laryngeal  nerves  cannot  be  demonstrated 
clinically  with  definiteness.  Pressure  on  the  main  trunk  of  either  nc;  e,  tabes, 
hysteria,  toxsemia,  and  other  central  or  general  causes  may  produce  any  of  these 
forms  of  paralysis. 

In  intubation  of  t'  larynx  (employed  in  some  forms  of  acute  stenosis,  as  in 
diphtheria  or  oedematous  laryngitis)  an  irregular  cylindrical  tube  with  a  fusiform 
enlargement  and  an  expanded  upper  extremity — so  that  it  may  rest  on  the  ven- 
tricular bands — is  carried  into  place  by  an  "  introducer' '  and  is  guided  by  the  left 
forefinger  of  the  surgeon,  which  is  passed  over  the  dorsum  of  the  tongue  to  the 
epiglottis  and  made  to  recognize  the  laryngeal  opening. 

Thyrotomy  is  sometimes  done  for  the  removal  of  intralaryngeal  tumors.  The 
incision  extends  from  the  thyro-hyoid  space  to  the  top  of  the  cricoid  cartilage,  is 


mm 


1832 


HUMAN   ANATOMY. 


directly  in  the  median  line,  and  divides  skin,  superficial  and  deep  fascia,  the  iuncli^n 
of  the  alse  of  the  thyroid,  and  the  mucous  membrane  of  the  larynx. 

Laryngotomy  (through  the  crico  thyroid  membrane)  may  be  indicated  in  adults 
for  impemUng  suffocation  from  any  form  of  obstruction  of  the  glottis.  In  children 
the  space  is  too  small.  A  median  incision  beginning  over  the  thyroid  cartilage  is 
r;>Tied  to  half  an  inch  below  the  cricoid  cartilage.  The  skin  and  fascia?  having  been 
uivided,  the  crico-thyroid  membrane  is  exposed  between  the  two  cri<  o-thy  roid  muscles, 
which  sometimes  require  separation.  1  he  crico-thyroid  arteries  ma\  be  exception- 
ally large,  and  in  any  event  should  usually  be  ligated,  although  in  cases  of  great 
emergency  that  step  may  be  postponed  until  the  membrane  has  been  divitled.  This 
may  be  done  by  a  transverse  incision  to  minimize  the  risk  of  hemorrhage.  The 
nearness  of  the  vocal  cords  to  the  opening  renders  this  operation  unsuitable  to  cases 
in  which  a  tracheotomy  tube  must  be  worn  for  some  time. 

Excision  of  the  larynx,  occasionally  done  for  malignant  disease,  necessitates  the 
separation  of  the  larynx  from  the  sterno-thyroid  and  thyro-hyoid  muscles  latemll) , 
from  the  inferior  constrictor  and  the  hyoid  bone  above,  from  the  trachea  below,  and 
from  the  pharynx  and  cesophagus  posteriorly.  The  superior  and  inferior  thyroid  arte- 
ries, or  their  branches,  and  the  superior  and  inferior  laryngeal  nerves  will  be  divided. 

For  landmarks  of  the  neck,  see  page  554. 

THE  SUBDIVISIONS  OF  THE  THORAX. 

As  the  entire  respiratory  apparatus,  with  the  excepdon  of  the  larynx  and  a  \yaxx 
of  the  trachea,  is  within  the  thorax,  it  is  advisable  to  describe  the  subdivisions  of  that 

Fio.  ISS7. 


(EsophaKii^ 


Innominate  arter\ 
Left  iiinominale  vein 
Arch  of  aorta — 


Traclie* 


IV  thoracic  vertebra 


.Right  pulmonary 
artery 


■ft  auricle 


thagus 


.Inferior  vena  cava 


Sternum 
Ascendin];  aorta 

RiKht  ventricle 

Right  auricle- 

t>iaphniKni  \ 


SpiKelian  lube 
Median  sagittal  smtion  of  formalin  subject ;  relative  position  of  mediastinal  spaces  outlined  in  red. 

cavity.     The  lungs,  enveloped  in  their  serous  coverings,  the  pleurae,  fill  the  greater 
part  of  the  sides  of  the  chest  external  to  planes  passing  forward  from  the  sides  of  the 


^ep 


^HHPVH 


mmm^F 


^^^m^m^ 


FRACTICAI.   CONSIDKRATIONS  :   THK   MKDIASI INIM. 


««.v; 


bodies  of  the  vertebrx  to  the  sides  of  the  stterniiin.  The  median  space  iMftweeii  tlu- 
pleurx  is  called  the  pmediastinal  state,  and  is  subdivided  into  four  |Kirts  called  medi- 
astina.  The  aliove  statement  of  the  lateral  boundaries  of  the  mediastinal  s|>ace  is 
only  a  general  one,  for  in  the  middle  the  mediastinal  space  expands  lieytmd  them 
and  in  front  is  ri-stricted  by  the  advance  of  the  pleura-  beneath  the  sternum.  The 
superior  mediastinum  is  that  part  of  the  space  above  a  plane  passing  from  the  disk 
lielow  the  fourth  thoracic  veaebra  to  the  junction  of  the  first  and  secontl  pieces  t>f  the 
sternum.  This  is  occupied  by  the  upper  part  of  the  thymus,  the  arch  of  the  aorta 
and  the  vessels  rising  from  it,  the  innominate  veins,  and  the  sujierior  vena  cava.  It 
is  traversed  by  the  trachea  and  uesophagus,  the  thoracic  duct,  the  pneumogastric, 
the  phrenic,  and  the  sympathetic  ner>'es.  Th  ■  region  below  the  ab<ive-m«-ntione«l 
plane  is  subdivided  by  the  pericardial  sac  into  an  anterior,  middle,  and  |M>sterior 
compartment.  The  middle  mediastinum  is  occupied  by  the  heart  within  the  peri- 
cardium. The  roots  of  the  lungs  are  partly  in  this  and  in  the  »u|)eric>r  mediastinum. 
The  shallow  anterior  mediastinum  is  between  the  middle  one  anti  the  sternum.  It 
contains  the  lower  part  of  the  thymus,  a  few  lymph-nodes,  fat,  ami  areolar  tisstue. 
The  posterior  mediastinum,  between  the  spine  ynd  the  middle  mediiistinum,  contains 
the  oesophagus,  the  aorta,  the  thoracic  duct,  the  ozygos  veins,  the  pneumogastric  and 
sympathetic  nerves 


PRACTICAL  CONSIDERATIONS;    THE   MEDIASTINIM. 

Wounds  {lenetrating  the  mediastinum,  even  when  they  do  not  involve  the  air- 
passages,  may,  in  consequence  of  air  being  drawn  into  the  space  by  respiratory 
movements,  be  followed  by  general  emphysema  or  by  mediastinal  emphysema.  This 
condition  is  not  infrequent  sdter  tracheotomy,  the  conditions  favoring  its  production 
being  free  division  of  the  deep  fascia,  continued  obstruction  of  the  air-passages,  and 
labored  inspiration. 

If  there  is  hemorrhage  into  the  mediastinal  space,  or  if  abscess  results  from  infec- 
tion of  a  clot,  or  from  extension  of  tuberculous  disea.se  of  the  bronchial  glands,  or  as 
a  sequel  of  typhoid  fever,  the  anatomical  symptoms  will  be  those  of  pressure  ( vide 
infra).  In  the  presence  of  a  large  abscess,  pus  may  perforate  the  sternum  by  ero- 
sion or  may  find  its  way  out  through  the  little  circular  openings  sometimes  found  as  a 
result  of  developmental  failuri  ixtge  i68).  It  may  also  be  evacuated  through  an 
intercostal  space  or  into  the  trachea  or  oesophagus. 

Tumors  may  be  malignant  or  benign  (lymphomata,  dermoids,  hydatids,  fibro- 
mata), the  order  of  mention  being  that  of  their  relative  frequency.  The  chief  symp- 
toms are  those  due  to  intrathoracic  pressure,  which  is,  of  course,  not  uniform,  and 
varies  with  the  origin,  extent,  and  density  of  the  tumor,  but  in  its  effects  upon  the 
separate  structures  contained  within  the  mediastinum  affords  a  reasonably  accurate 
basis  for  an  anatomical  classification  of  the  clinical  phenomena  of  these  growths. 

1.  Compression  of  veins,  (a;  The  suf)erior  vena  cava  :  cyanosis  or  lividity  of 
the  face  ;  dilatation  of  the  superficial  veins  of  the  neck,  face,  and  head  ;  oedema  of 
the  same  region  ;  epistaxis  ;  disturbances  of  vision  or  amaurosis  ;  tinnitus  aurium  or 
total  deafness  ;  cerebral  effusion  or  hemorrhage  ;  oedema  of  one  or  both  arms,  {b) 
The  greater  azygos  vein  :  dilatation  first  of  the  right  and  later  of  the  left  intercostal 
veins  ;  oedema  of  the  upper  part  of  the  chest-wall  ;  right-sided  hydrothorax  with 
secondary  or  later  effusion  into  the  left  pleura  (Stengel);  pericardial  effusion  ;  medi- 
astinal effusion,      (f)  The  pulmonary  vein  :  oedema  of  the  lung  ;  hiemoptysis. 

2.  Compression  of  arteries  (much  rarer  than  of  venous  channels),  (a)  The 
aorta  :  inequality  in  the  radial  pulses  ;  engorgement  of  the  left  side  of  the  heart ; 
pulsation  of  the  growth,  if  it  is  visible  or  palpable  (as  the  suprasternal  notch  or 
over  the  sternal  ends  of  the  clavicles);  pallor  ;  giddiness  ;  anginose  pains,  (b)  The 
pulmonary  arter)- :  distention  of  the  right  heart  ;  dyspnoea  ;  ultimately — as  a  sec- 
ondary result  of  the  cardiac  condition — ascites  ;  oedema  of  the  lower  extremities  ; 
general  anasarca. 

3.  Compression  of  nerves,  (a )  The  psieumogastric  :  irregular  heart  action 
with  marked  rapidity  or  slowness  ;  syncofie  ;  vomiting  ;  hiccough  ;  pharyngeal  or 
laryngeal  spasm  or  paralysis  ;  dysphagia  ;  spasmodic  cough.     (*)  The  inferior  laryn- 


l834 


HUMAN  ANATOMY. 


eeal  nerve  ;  posterior  crico-arytenoid  paralysis  with  rtridoi  and  inspiratory  dytpnoa 
( pajre  1 273).     (r)  The  sympathetic  :  various  disturbances  of  vision  ;  irregular  pupUs. 

4.  Compression  of  the  thoracic  duct  Emaciation  ;  chylo-thorax ;  chylous 
ascites  ;  mediastinal  effusion  of  chyle.  . .         j 

5.  Compression  of  the  air-passajfes.  (a)  The  trachea:  stridor;  dyspnaa. 
(d)  The  bronchi:  feeble  breath-sounds;  dyspnoea;  recess'on  of  ihc  suprasternal 
and  supraclavicular  fowa  and  base  of  chest ;  cough.  ( e)  The  lungs  and  pleura  : 
dyspncea  ;  collapse  of  the  lungs  ;  pleural  eflusion.  ,  .     u 

6.  Compression  of  the  heart  and  pericardium.  Displacement  of  the  heart ;  peri- 
cardial effusion  ;  irregular  heart  action. 

7.  Compression  of  the  oesophagus.     Dysphagia.  _  . 

8.  Outward  pressure  upon  the  walls  of  the  mediastinal  space.  Widening  ot  inter- 
costal spaces  ;  bulging  of  the  sternum  ;  increase  of  the  circumference  of  the  chest  on 

•^  "*  one  side ;   weakness  or 

Fio.  153*' 


Thyroid  cmrtilafc 


absence  of  vocal  fremi- 
tus ;  increased  area  of 
transmission  of  heart- 
■ounds. 

Of  course,  all  of 
these  symptoms  are  not 
present  in  any  given  case 
of  mediastinal  growth, 
but  some  of  them  are 
sure  to  be  and  can  be 
more  readily  understood 
if  referred  to  their  ana- 
tomical causes. 

The  phenomena  ref- 
erable to  the  separate 
subdivisions  of  the  me- 
diastinum can  be  classi- 
fied only  in  a  very  gen- 
eral way.      It  may  be 
said,  however,  that:  ( i ) 
The  anterior  mediasti- 
num   is  the  most  fre- 
quent seat  of  abscess ; 
that  its  growths  usually 
begin   in   the  thymus  ; 
and  that  the  chief  symp- 
toms are  apt  to  be  those 
of  pressure  upon  the  .su- 
perior vena  cava,  inva- 
sion of  the  suprasternal 
fossa,  involvement  of  the 
cervical  glands,  bulging 
or  erosion  of  the  ster- 
num, and  dyspnoea.  (2) 
Growths  of  the  poste- 
rior and  middle  mediastinum  are  apt  to  originate  in  the  lymph-nodes,  and  the  chief 
symptoms  are  those  of  pressure  upon  the  pneumogastric,  recurrent  laryngeal  or  sym- 
pathetic nerves,  the  greater  azygos  vein,  the  oesophagus,  and  the  air-passages.     The 
urgent  dyspnoea  and  troublesome  r'^       .  are  out  of  all  proportion  to  the  physical 
signs  (Osier). 

THE  TRACHEA. 

The  trachea  or  windpipe  (Fig.  1558)  is  a  tube,  composed  of  cartilage  and  mem- 
brane, extending  from  the  cricoid  cartil^e  to  a  point  opposite  the  disk  below  the 
fourth  thoracic  vertebra,  corresponding  to  the  level  of  the  junction  of  the  first  and 


Trachea  «nd  bronchW  Inw,  »nlerlor  upKt. 

com 

bronchus 


Icft'ipkarbronchuV'di'vidlnlTi'nto'ventrai  (o)  and  doreal  (o')  branch« 
itinuatlon  of  main  bronchus ;  *,  *'.  ventral  and  dorial  branch: 


K,  I.,  rJKht  and  left  bronchus; 


c,  cardiac 


■nSHIMi 


mmm 


im 


mmmfi 


mm 


mm 


THK  TRACHEA. 


iHm 


Tunica  pruprU 


a«».-und  pieces  ol  the  sternum,  where  it  divides  into  the  twi>  bronchi.  The  jxjint  ol 
division  is  usually  on  the  rijjht  ol  the  median  line  :  sonutinies  s«j  far  as  to  lie  behind 
the  ri^ht  edj{e  of  the  sternum.  The  trache;  is  a  cylindrical  tube,  flattened  behind. 
The  convexity  is  <.ue  to  the  so-calle<'  'ings,  '  iiich  represent  only  alH)Ut  three-i)iwrter» 
ol  a  circle.  The  lonKth  is  difficult  (•>  .cterr  ne  with  accuracy  on  acctmnt  of  the  eUis- 
ticity  ol  the  or^an  as  well  a.s  of  its  variaf-  ..  It  nwy  be  said  to  be,  on  the  average, 
Irorn  10.5-12  cm.  (4-4^4  i". )  in  man  and  Irom  9-11  cm.  (3^j-4'j  in.  1  in  woman. 
The  isolated  trachea  can  lje  stretched  and  comprcsscil  to  a  surprisim  xtent,  and 
even  in  life  the  changes  are  considerable.  The  aiu«ro-postirior  and  .u-  transverse 
diameters  are  not  very  different,  e.xcept  iii-.t  at  the  lower  end.  where  the  trachea 
enlarges  transversely.  It  is  very  plausibly  stated  by  I.ejars'  that  in  life  the  windpi|ie 
is  more  or  less  constricted  by  the 
tonic  ctmtraction  of  its  muscles.  J'"^-  '559- 

According  to  him,  it  grows  con-  -« Epithelium 

tinually  smaller  from  alxjvc  down- 
ward. Braune  and  Stahel'  be- 
lieved that  after  death  it  w  largest 
in  the  middle.  We  have  no  doubt 
whatever  that,  as  a  rule,  the  dead 
trachea  is  enlarged  transversely 
at  ti.e  lower  end.  Abey*  gives 
the  following  measurements  for 
the  upjier  and  lower  ends  :  upjier 
transverse  diameter  1 3. 1  mm. , 
sagittal  16  mm. ;  lower  transverse 
diameter  20.7  mm.,  sagi"^l  19.  i 
mm.  The  frameworU  jI  the 
trachea  is  so  light  that  its  shape 
may  be  influencerl  by  neighbor- 
ing organs,  such  as  the  thyroid 
body  and  the  arch  of  the  aorta. 
Structure.  —  The  frame- 
work of  the  anterior  and  lateral 
walls  of  the  trachea  consists  of 
the  so-called  rings  of  hyaline  car- 
tilage, which  form  some  three- 
quarters  of  a  circle.  In  the  great 
majority  of  cases  there  are  from 
sixteen  to  nineteen  rings.  It  is 
not  rare  to  find  twenty,  but  very 
rare  to  find  more.  The  rings  are 
from  2-5  mm.  broad,  usually 
measuring  3  or  4  mm.  They  are 
plane  externally  and  convex  in- 
ternally, becoming  pointed  at  the 

ends.  They  are  very  irregular  in  many  respects.  Sometimes  one  end  bifurcates, 
the  rings  above  and  below  ending  prematurely.  Occasionally  bifurcation  of  the  oppo- 
site ends  of  alternate  rings  is  observed.  Rarely  both  ends  of  the  same  ring  may 
divide.  The  first  ring,  which  is  broader  than  the  others,  is  occasionally  fused  with 
the  cricoid  cartilage.  A  highly  elastic  fibrous  sheath,  continuous  with  the  peri- 
chondrium of  the  rings,  envelops  them,  connects  their  posterior  ends,  and  completes 
the  tube.  The  distance  between  the  rings  is  less  than  their  eadth,  at  times  only 
half  as  much.  Involuntary  muscular  fibres  of  the  treuhtalis  muscle  lie  between  the 
fibrous  sheath  and  the  lining  mucous  membrane.  They  are  in  the  main  disposed 
transversely,  some  of  them  connecting  the  ends  of  the  rings  ;  some  bundles,  however, 
run  longitudinally. 

'  kevue  de  Chirurgie.  iSgi. 

'  Archiv  f.  Anat.  u.  Phys..  An.it.  Abth.,  1886. 

*Der  Bronchialbaum  der  Menschen,  u.  s.  w.,  i88a 


Canilaic 


Perichondrium 


Fibnnu  lunlc 


' V— 


Transverse  section  o(  trachea,  ihowinx  general  arrannement 
of  its  wall.     X  Ho. 


1836 


HUMAN   ANATOMY. 


muscle 


A  layer  of  connective  tissue,  representing  a  submucosa,  separates  the  cartilage 
and  muscle  from  the  mucous  lining  of  the  trachea.  The  submucosa  contains  small 
^gregations  of  fat-cells  and  the  tracheal  glands.  The  latter,  tubulo-alveolar 
mucous  in  type,  are  most  numerous  and  largest  between  the  rings  of  cartilage, 
especially  towards  the  lower  end  of  the  trachea.  Over  the  cartilages  they  are  small 
and  often  wanting.  Their  ducts  pierce  the  mucosa  to  gain  the  free  suiiEace  of  the 
latter. 

The  mucous  membrane,  smooth  and  atUched  with  considerable  firmness  to  the 
underlying  tissues,  is  clothed  with  stratified  ciliated  columnar  epithelium.  Many  of 
the  surface  cells  contain  mucus  and  are  of  the  goblet  variety.  The  stroma  of  the 
mucosa  is  rich  in  fine  elastic  fibres,  which,  in  the  lower  part  of  the  trachea,  are  con- 
densed into  a  distinct  elastic  lamella  separating  the  mucous  membrane  from  the  sub- 
mucosa. Lymphoid  cells  are  constantly  found  in  the  mucosa,  in  places,  particularly 
around  the  openings  of  the  ducts  of  the  tracheal  glands,  being  aggregated  into  small 
collections  which  suggest  lymph-nodules. 

Vessels. — ^The  arteries,  which  .ire  insiirnificant,  are  branches  of  the  inferior 
laryngeal  from  the  inferior  thyroid,  and  tend  to  form  a  series  of  horizontal  arches 
between  the  rings.     They  anastomose  below  with  the  bronchial  arteries  and  with 

the  internal  mammaries 
Fig.  1560.  through    the    anterior 

mediastinal  twigs.  The 
veins,  arranged  like  the 
arteries,  belong  to  the 
system  of  the  inferior 
laryngeals.  They  com- 
municate with  those  of 
the  oesophagus,  with 
the  thyroid  ple.\us,  and, 
according  to  Luschka. 
with  the  azygos.  The 
lymphatics,  which  are 
very  numerous,  are  also 
disposed  in  horizontal 
curves.  Leaving  the 
windpifie  at  the  sides 
of  the  membranous 
portion,  they  open  into 
small  tracheal  lymph- 
nodes  and  communi- 
cate with  the  bronchial 
nodes  also. 

The  nerves  are 
from  the  pneumogas- 
tric  and  sympathetic 
nerves.  Their  ultimate 
distribution,  in  addition  to  the  supply  for  the  muscular  tissue  and  the  walls  of  the 
blood-vessels,  includes  sensory  endings  within  the  mucous  membrane  which,  accord- 
ing to  Ploschko,  are  similar  to  those  of  the  larynx. 

The  Relations  of  the  Trachea.— The  oesophagus,  beginning  at  the  lower 
border  of  the  cricoid  cartilage,  lies  at  first  behind  the  trachea,  to  which  it  is  con- 
nected by  areolar  tissue ;  but  almost  at  once  it  is,  relatively  to  the  trachea,  displaced 
to  the  left,  to  be  pushed  over  again  by  the  arch  of  the  aorta,  where  this  vessel  lies 
on  the  left  of  the  trachea.  The  gullet  always  lies  behind  the  origin  of  the  left  bron- 
chus. Behind  the  first  piece  of  t'.ie  sternum  the  arch  of  the  aorta  passes  in  front  of 
the  trachea,  which  is  placed  almost  symmetrically  in  the  fork  made  by  the  innomi- 
nate and  left  carotid  arteries.  The  isthmus  of  the  thyroid  crosses  usually  the  second 
and  third  rings,  its  lobes  resting  on  tht  sides  of  the  trachea.  The  inferior  thyroid 
veins  constitute  a  vascular  layer  before  the  lower  part  of  the  cervical  portion  of  the 
trachea.     The  recurrent  laryngeal  nerves  run  up  at  the  back  of  either  side  of  the 


Cart  Ha  ice 


Traniverae  section  of  trachra  and  tesophaKUS  of  child,  seen  from  below. 


THE  TRACHEA. 


1837 


trachea,  the  left  one  being  the  first  to  reach  this  position.  The  inferior  laryngeal 
artery  and  veins  are  near  them.  The  relations  of  the  artery  and  nerve  are  given 
with  the  relations  of  the  thyroid.  The  remains  of  the  thymus  lie  in  front  of  the 
trachea  within  the  thorax.  Owing  to  the  forward  inclination  of  the  sternum,  the 
trachea  is  more  deeply  placed  as  it  descends.  A  lymph-node  or,  more  frequently,  a 
group  of  them  is  constandy  found  under  the  bifurcation.  Tillaux '  found  the  dis- 
tance of  the  cricoid  cartilage  above  the  sternum  (in  a  small  series)  to  range  in  the 
male  from  4.5-8.5  cm.,  with  an  average  of  6.5  cm.;  and  in  the  female  from  5-7.5 
cm.,  with  an  average  of  6.4  cm.  This  distance,  however,  may  be  modified  by  other 
factors  than  the  length  of  the  trachea. 

Growth  and  Subsequent  Changes. — In  the  infant  the  trachea  measures 
from  4-5  cm.  in  length,  b^ns  at  a  higher  point  in  the  neck,  as  has  been  shown  for 
the  larynx,  and  divides  at  a  higher  point  in  the  thorax.  The  level  of  this  division 
\aries  very  much  in  the  foetus,  but  at  birth  is  generally  opposite  the  third  thoracic 
vertebra.  The  lowest  position  is  opposite  the  fourth  and  the  range  extends  over 
two  vertebra. 

There  are  comparatively  few  records  of  the  changes  durine  childhood.'  We  have  found 
it  opposite  the  lower  part  of  the  fourth  thoracic  vertebra  in  a  child  whose  age  was  estimated  at 
about  three.  Symington*  has  found  it  at  the  top  of  the  fifth  in  two  children  of  six  and  oppo- 
site the  fourth  in  one  of  thirteen.  In  the  young  adult  it  is  opposite  the  disk  between  the 
fourth  and  fifth  thoracic  vertebrjE,  which  is  its  normal  position,  although  it  is  not  abnormal  for 
it  to  be  opposite  the  fifth.  I^te  in  life  it  descends  to  the  lower  border  of  the  fifth  and  even  to 
the  seventh  vertebra.'  The  trachea  of  the  infant  appears  almost  round,  the  rings  forming  a 
relatively  larger  part,  perhaps  five-sixths  of  the  periphery.  According  to  several  authorities, 
the  transverse  diameter  much  exceeds  the  sagittal ;  but,  although  we  have  seen  this  condition, 
we  are  not  inclined  to  agree  that  it  is  normal  in  the  infant,  unless,  perhaps,  at  the  lower  end. 
The  size  of  the  transverse  section  of  the  trachea  is,  for  many  reasons,  hard  to  determine. 
Merkel '  thinks  we  may  accept  the  following  statement  of  the  diameter  of  the  upper  part  of  the 
trachea  without  fear  of  being  much  out  of  the  way  in  particular  instances :  from  six  to  eighteen 
months,  5  mm.;  from  two  to  three  years,  6  mm.  ;  from  four  to  five,  7  mm.;  from  five  to  ten, 
8  mm.;  from  ten  to  fifteen,  lo-u  mm.  Ossification  of  the  rings  begins  deadedly  later  than  in 
the  larynx.  The  earliest  appearances  of  it  obser^•ed  bv  Chievitz  were  at  about  forty  in  man  and 
about  sixtj-  in  woman.  His  youngest  case  of  complete  ossification  was  at  fifty  in  man  and 
seventy-eight  in  woman.  The  deposit  is  first  seen  in  the  upper  rings,  but  not  in  the  first  one, 
the  points  being  irregularly  distributed  along  the  borders.  They  come  next  in  the  lower  rings, 
and  here  at  the  posterior  ends.  As  the  process  spreads,  there  is  left  a  median  unossified  tract 
along  the  trachea,  which  probably  is  usually  invaded  from  below. 


THE  BIFURCATION  OF  THE  TRACHEA  AND  THE  ROOTS  OF 

THE  LUNGS. 

The  carina  trachea  (Fig.  1561)  is  a  prominent  semilunar  ridge  running  antero- 
postetiorly  across  the  bottom  of  the  trachea  between  the  origin  of  the  two  bronchi.  It 
usually  starts  from  a  larger  anterior  triangular  space  and  ends  at  a  smaller  pos- 
terior one.  Heller  and  v.  Schrotter'  found  the  framework  of  the  spur  cartilaginous 
in  56  per  cent. ,  membranous  in  33  per  cent. ,  and  mixed  in  1 1  per  cent.  The 
spur,  when  cartilaginous,  is  derived  in  various  wajrs  :  from  a  tracheal  ring,  from  the 
first  ring  of  either  bronchus,  or  from  a  combination  of  these  sources.  The  height 
of  this  ridge,  especially  when  membranous,  is  difficult  to  measure,  but  these  authors 
believe  that  it  may  reach  6  mm.  According  to  Luschka,  the  free  edge  of  the  spur 
is  15  mm.  from  the  apprent  lowest  point  of  the  windpipe,  seen  from  without.  This 
great  distance  should  m  part  be  accounted  for  by  the  interbrmichial  ligament,  a  col- 
lection of  fibres  running  transversely  in  the  angle  between  the  bronchi.  This  band  is, 
however,  very  variable  in  development  and  nut  constant,  so  that  Luschka' s  estimate 
of  the  distance  is  probably  excessive  for  most  cases.     Heller  and  v.  Schrotter  found 

'  Anatomic  Topographique,  tme  Wit.,  i88j. 

•  Dwight :  Frozen  Sections  of  a  Child,  1881. 

*  Anatomy  of  the  Child,  1887. 

♦  Mehnert :  Ueber  topographische  Altersveranderungen  des  Atmungsapparates,  1901. 
»  Handburh  der  Topograph.  Anat..  Bd.  ii..  1899. 

•  Denkschrift  der  Acad.  Vienna,  1897. 


1838 


HTTMAN   ANATOMY. 


Fio.  1561. 

Anterior  surface    Carina,  anterior  triangle 


CartilaRe 


the  spur  on  the  left  of  the  middle  of  the  trachea  in  57  per  cent. ,  in  the  middle  in  42 
per  cent.,  and  on  the  right  of  it  in  the  remainder."  Semon,  in  100  tjxaminations  of 
the  living,  found  it  on  the  left  in  59,  at  the  middle  in  35,  and  on  the  right  in  6. 

The  roots  of  the  lungs  consist  of  the  bronchi  (the  right  one  giving  off  a  branch 
before  entering  the  lung),  the  pulmonary  artery  and  vein,  the  bronchial  arteries  and 
veins,  the  lymphatic  vessels  and  nodes, 
and  the  nerves. 

The  bronchi  (Fig  1562)  are  the 
two  tubes  into  which  the  windpipe  divides, 
one  running  downward  and  outward  to 
each  lung.  Until  they  enter  the  lungs, 
their  shape  and  structure  are  precisely 
those  of  the  trachea,  the  membranous  por- 
tion being  still  posterior.  This  applies  also 
to  the  branch  that  springs  from  the  right 
bronchus  before  it  enters  the  lung.  While 
treating  of  the  root  of  the  lung  we  shall 
consider  only  the  extrapulmonary  part  of 
the  bronchi.  According  to  modern  usage, 
the   term   "bronchus"   is  applied  to   the 

whole  of  the  chief  tube  that  runs  through  each  lung  ;  formerly  it  was  restricted  to 
the  part  from  the  trachea  to  the  first  branch.  As  the  left  bronchus  gives  off  no 
branch  before  entering  the  lung,  it  was  described  as  much  longer  than  the  right  one. 
The  length  of  the  left  bronchus  to  its  first  branch  is  about  5  cm.  (2  in.),  that  of  the 
right  is  rarely  more,  and  often  less,  than  2  cm.  (^4  in.).  There  are  some  eight  or 
ten  rings  in  the  left  bronchus  before  the  branch,  while  in  the  right  one  there  are  three, 
often  two,  and  sometimes  four.  The  right  bronchus,  which  is  the  more  direct  con- 
tinuation of  the  trachea,  is  the  larger.  The  diameter  of  the  bronchi  at  their  origin  is 
greater  from  above  downward  than  from  before  backward.  The  dimensions  are  very 
differentiy  given.     According  to  Aeby,  the  transverse  diameter  of  the  right  bronchus 

is  from  13. 5-21  mm.  and  that  of  the  left 


Left  bronctiiu 
Carina  tracheae  Origin  of  apical  bronchus 

Continuation  of  right  main  bronchus 

Bifurcation  of  trachea,  seen  from  above  after  section  of 
windpipe  just  above  carina. 


Flc.    I  563. 


Membranous 
part  of  tra- 
cheal wall 


from  1 2. 5-1 7  mm.  Braune  and  Stahel 
found  that  the  calibre  of  the  right  one  is 
to  that  of  the  left  as  100:77.9.  The 
extreme  ratios  of  the  series  were  100  :  71.6 
and  100  :  83.3.  We  have  deduced  from 
Heller  and  v.  Schrotter's  tables  that  in 
some  10  per  cent,  the  calibres  are  equal. 
It  was  formerly  taught  that  the  larger 
right  bronchus  is  more  nearly  horizontal 
than  the  left,  but  that  the  contrary  is  true 
is  easily  proved  by  a  glance  down  the 
trachea  in  a  frozen  section  (Frg.  1561). 
The  cause  of  the  error  is  that,  if  it  be  not 
recognized  that  after  the  apparent  splitting 
of  the  right  bronchus  the  lower  division  is 
the  main  trunk,  the  eye  is  apt  to  follow 
the  upper  border  of  the  primitive  bron- 
chus, which  carries  it  along  the  upper 
branch.  It  is  very  difficult  to  determine 
the  angles  at  the  origin  of  the  bronchi, 
for  the  parts  are  so  flexible  that  obsea-a- 
tions  on  non-hardened  subjects  are  of  little 
value,  and  it  is  not  easv  accurately  to  measure  even  good  preparations,  on  account  of 
the  irregularity  of  the  outline.  One  fact  which  adds  to  the  difficultv  of  taking  satisfac- 
tory measurements,  and  which  also  tends  to  make  the  right  bronchus  the  more  direct 
continuation  of  the  trachea,  is  the  inclination  of  the  latter  to  the  right  as  it  descends. 

'  They  st.itc  th.it  this  rcm.iindur  consists  of  3  cnscs,  but  as  their  series  comprised  125,  it 
would  seem  that  there  must  he  a  misprint. 


l.eft  bronchus 

Hifutc.-ition  i>f  trachea  Inid  open  after  incision  along  an 
teriur  wall  of  trachea  and  bronchi. 


THE  TRACHEA. 


1839 


We  have  made  measurements  on  two  casts  from  frozen  sections  of  the  adult,  and  one  from 
a  section  of  a  child  thought  to  be  of  about  three  years,  and  have  calculated  the  angles  between  the 
prolongation  of  the  axis  of  the  terminal  part  of  the  windpipe  and  that  of  each  bronchus.  An 
attempt  was  also  made  to  measure  the  angles  from  a  skiagraph  made  by  HIake '  aftiT  injecting 
fusible  metal  into  the  trachea  of  a  hardened  body.  Two  observations  on  adults  by  Kobler  and 
V.  Hovorka '  are  included  for  comparison. 

It  seems  that  ^Jnesubtracheal  angle,  that  of  divergence  of  the  bronchi,  is  about  70°.  We  have 
found  it  precisely  that  in  another  specimen.  Kobler  and  v.  Hovorka  measured  the  lateral 
angles  in  the  hardened  bodies  of  sixteen  new-bom  infants.  The  average  was  right  25.6,  |r.it 
48.9.  The  variations  ranged  on  the  right  from  10  to  35  and  on  the  left  from  30  to  65.  A'e 
found  their  average  angle  of  divergence  74.5.  This  shows  that,  contrary  to  the  general  im- 
pression, the  bronchi  are  not  more  nearly  vertical  in  the  infant  than  subsetjuently.  Aeby  gives 
the  angles  of  divergence  of  two  new-bom  children  as  33  and  61  ;  Mettenheimer "  as  50  and  63. 

Vessels. — The  pulmonary  artery  at  its  bifurcation  is  anterior  to  the  bronchi 
and  at  a  lower  plane.  Each  branch  of  the  artery  rises  over  the  bronchus  and  comes 
to  lie  more  or  less  external  to  it.  This  ap}Kirent  crossing  of  the  bronchus  by  the 
artery  occurs  on  the  right  just  after  the  origin  of  the  first  secondary  bronchus.  The 
usual  teaching,  following  Aeby,  that  the  artery  actually  arches  over  the  cxtrapul- 

Fio.  1563. 

Stenium 


Pulmonary  laniluiiar  valve 


L.eft  lun^ 


Leh  pulmonary  -1 
veini> 


Left  bronchua 


Aorta 


Superior  vena  cava 
/ 

Parietal  pleura 
Visceral  pleura 

Reflection  of  viscernl 
onto  mediastinal  pleura 


III  rib 


RiEbt  bronchus 


^    Rigbt  lunK 


Fimnre  / 

Thoracic  aorta      /      ""^V »'  vertebra    (EsopbaKua 
Kiltiit  pulmonary  artery 
Transverse  section  of  thorax  at  level  of  fifth  thoracic  vertebra. 


Spine  of  scapula 
Superior  fissure 


tnonary  bronchus  and  lies  behind  it,  is  incorrect.  The  artery  divides  before  enter- 
ing the  lung,  one  branch  entering  through  the  upper  and  the  other  through  the 
lower  part  of  the  hilum. 

The  pulmonary  veins  are  usually  two  on  each  side.  The  superior  lie  in  front  of 
and  below  the  artery.  The  inferior  are  the  lowest  of  the  large  vessels  of  the  lung- 
root,  passing  from  behind  under  the  bronchus  into  the  heart. 

The  bronchial  arteries  follow  the  bronchi  along  their  posterior  surfaces.  The 
bronchial  veins  Mc  hoth  anterior  and  posterior.  On  the  right  side  lK)th  open  into 
the  larger  azygos  vein.  The  left  posterior  ones  often  receive  the  anterior  and  open 
into  the  superior  hemiazygos.  There  may  be  various  anastomoses  with  mediastinal, 
pericardial,  and  tracheal  veins. 

The  lymphatics  run  f<ir  the  most  part  Ixjhind  the  bronchi.  The  lynij)h-nodes 
are  for  the  most  part  on  the  posterior  and  inferior  aspects  of  the  tul)es,  th<-  group 
under  the  bifurcation  joining  others  at  the  sides.     Some  nodes  occur  on  the      mt. 

The  nerves  from  the  sympathetic  and  vagus  form  plexuses  both  txiore  and 

behind. 

'  American  Journal  of  the  Medical  Sciences,  1899. 
»  Silzbericht.  Acad.,  Vienna.  1893. 
•  Morpholog.  Arbeit.  Schwalbe,  1894. 


1840 


HUMAN  ANATOMY. 


The  dimensions  of  the  lung-roots  are  difficult  to  determine.  They  are  nar- 
rower below  than  above  and  shorter  behind  than  in  front.  The  lower  posterior  bor- 
ders, which  are  formed  by  the  inferior  pulmonary  veins,  are  of  about  the  same  length 
(2  cm. )  on  each  side  and  very  symmetrical.  We  may  put  the  right  root  in  front  and 
above  at  from  4-4.5  cm.  and  the  left  at  about  i  cm.  longer.  They  are  thickest 
above,  and  expand  as  they  approach  the  hilum  of  the  lung,  where  the  diameter  is 
approximately  3.5  cm.,  the  left  one  being  rather  the  thicker.  The  height  at  the 
hilum  is  from  5-6  cm. ,  probably  sometimes  rather  more. 

The  Relations  of  the  Roots. — Below  lies  the  pericardium  covering  the  heart, 
chiefly  the  left  auricle.  The  great  azygos  vein  arches  over  the  right  root  from  be- 
hind, to  join  the  superior  vena  cava,  which  is  against  the  root  in  front.  The  arch  of 
the  aorta  crosses  the  left  root  from  before  bvrkward,  being  less  closely  applied  to  it 
behind  than  elsewhere.  The  oesophagus  is  behind  the  very  beginning  of  the  left 
root.  The  pleura  is  reflected  over  each  root,  which  it  completely  envelops  as  it 
passes  from  the  parietal  into  the  visceral  layer.  The  broad  ligament  of  the  lungs  is  a 
fold  of  pleura  extending  downward  from  the  end  of  the  root.  The  phrenic  nerve 
of  each  side  passes  in  front  of  the  root,  between  the  pericardium  and  the  pleura. 

PRACTICAL  CONSIDERATIONS  :  THE  AIR-PASSAGES. 

The  Trachea  and  Bronchi. — The  elasticity  and  mobility  of  the  trachea,  the 
compressible  character  of  its  walls,  the  loose  cellular  tissue  in  which  it  lies,  and  the 
variety  of  the  structures  with  which  it  is  in  close  relation  should  all  be  remembered 
in  considering  its  injuries  and  diseases. 

IVounds  of  the  cervical  portion  of  the  trachea — as  in  cut  throat  below  the  cricoid 
— are  not  rare.  The  trachea  is  rendered  more  superficial  by  extreme  extension  of 
the  neck,  and  is  also  elongated.  A  deep  wound  may  therefore  sever  it  completely, 
in  which  case  the  lower  end  may  retract  below  the  level  of  the  superficial  wound, 
making  the  hurried  introduction  of  a  tracheotomy  tube  difficult. 

Rupture — "fracture" — of  the  cervical  trachea  has  resulted  from  contusion,  and 
in  the  presence  of  pre-existing  disease  has  followed  coughing.  The  depth  of  the 
thoracic  trachea  protects  it  from  all  but  penetrating  wounds,  and  these,  on  account 
of  the  important  structures  also  implicated,  are  usually  fatal. 

Disease  beginning  in  or  confined  to  the  trachea  is  rare,  but  it  may  be  involved 
in  the  extension  of  either  bronchial  or  laryngeal  morbid  processes.  The  normal 
tracheal  mucous  membrane  is  said  to  resist  cadaveric  disintegration  longer  than  any 
other  mucous  membrane  of  the  body  (Elsberg). 

Stenosis  of  the  trachea,  if  from  intrinsic  change,  is  usually  due  to  ulceration, 
either  syphilitic  or  tuberculous,  followed  by  cicatrization.  It  is,  however,  far  more 
commonly  due  to  extrinsic  causes,  the  mechanism  of  which  will  be  readily  under- 
stood if  the  relations  of  the  trachea  are  recalled  (page  1836).  From  above  down- 
ward it  is  evident  .that  the  trachea  may  be  compressed  by  enlargements  of  the  thyroid 
gland,  by  retro-celophageal  tumors  or  abscesses,  by  carotid,  innominate,  or  aortic 
aneurism,  or  by  lymphatic  swellings  in  the  neck  or  near  the  bifurcation.  As  the 
posterior  part  of  the  tracheal  wall  is  musculo-membranous  (partly  in  order  to  a\oid 
undue  pressure  of  the  trachea  on  the  oesophagus),  the  impaction  of  a  foreign  body  in 
the  latter  tube  may  cause  tracheal  narrowing.  The  trachea  may  be  involved  in  dis- 
ease originating  elsewhere,  as  in  tuberculous  infection  of  the  thoracic  lymphatic 
glands,  or  in  carcinomk  of  the  same  glands,  or  of  the  cervical  chain,  or  of  the  oesoph- 
agus. Abscesses  or  aneurisms  may  ulcerate  through  its  walls  and  empty  into  its 
lumen,  suffocating  the  patient.  The  close  relation  of  the  trachea  to  the  aorta  makes 
it  possible  in  some  cases  of  aortic  aneurism  to  hear  a  systolic  bruit  either  in  the 
trachea  f)r  at  the  patient's  mouth  when  opened.  This  is  either  the  sound  conveyed 
from  the  sac  or  is  produced  by  the  air  as  it  is  driven  out  of  the  trachea  during  the 
systole  (Osier).  The  sign  known  as  "tracheal  tugging"  also  depends  upon  the 
same  close  relation.  With  the  patient  erect,  his  mouth  closed  and  his  chin  elevated, 
when  the  cricoid  is  grasped  between  the  finger  and  thumb  and  pressed  gently  and 
steadily  upward,  ii  aortic  aneurism  or  dilatation  e.xists,  the  pulsation  of  the  aorta 
will  be  jlistinctly  transmitted  through  the  trachea  to  the  hand  (Oliver). 


■litfli 


mm 


md  a  short  distance 
1  increase  with  the 
irom  the  surface  in- 
(.<•)  it  is  more  com- 


PRACTICAL   CONSIDERATIONS:   THE   AIR- PASSAGES.       1841 

Tracheotomy  may  be  required  for  obstruction  in  the  larynx  or  above  it,  for  the 
removal  of  foreign  bodies,  or  as  a  preliminary  step  in  other  operations,  as  excision 
of  the  tongue. 

It  may  be  done  at  any  point  between  the  cricoid  cartilage 
above  the  suprasternal  notch.  The  difiicuities  of  the  operai 
distance  from  the  cricoid  because  (a)  the  depth  of  the  tracht. 
creases  as  it  approaches  the  thorax  ;  (*)  it  is  more  movable  ;  k.^  ,  m  is  more  com- 
pletely covered  m  by  the  sterno-hyoid  and  stemo-thyroid  muscles  ;  (rf )  it  is  more 
apt  to  be  overlapped  by  the  common  carotids  ;  or  (.-)  crossed  by  the  left  common 
carotid  when  it  arises  from  the  innominate  artery  ;  or  by  (/ )  various  venous  trunks, 
as  the  transverse  branches  between  the  anterior  jugulars,  or  the  inferior  thyroids  or 
even  by  the  left  innominate  vein,  which,— lying  as  it  does  in  front  of  the  trachea,— in 
the  presence  of  venous  congestion,  may  extend  above  the  level  of  the  top  of  the 
sternum.  Moreover,  in  children  under  two  years  of  age  the  upper  edge  of  the  vas- 
cular thymus  gland  may  lie  in  fiont  of  the  trachea  at  the  root  of  the  neck.  The  in- 
nominate artery  itself  or  the  thyroidea  ima  may  occupy  the  same  position. 

For  these  reasons  tracheotomy  is  done  with  comparative  rarity  below  the  level 
of  the  isthmus,  which  lies  in  front  of  the  second,  third,  and  fourth  tracheal  cartilages. 
The  incision  is  made  with  the  head  in  full  extension  so  as  to  lengthen  the  trachea, 
steady  it  by  increasmg  its  tension,  and  bring  it  nearer  the  surface.  The  chin,  thyroid 
angle,  and  suprasternal  notch  should  be  in  the  same  line.  The  incision  should  be 
exactly  in  this  line,  extend  about  two  inches  downward  from  the  cricoid,  and  divide 
the  skin,  platysma,  and  fascia  and  expose  the  interval  between  the  siemo-hyoid  and 
sternothyroid  muscles,  which  may  be  separated  by  blunt  dissection.  The  pretracheal 
fascia  is  then  divided,  exposing  the  upper  ring  of  the  trachea  and  the  thyroid  isthmus. 
The  isthmus  may  be  depressed  to  give  more  room  for  the  tracheal  opening,  or  may, 
after  ligation  on  both  sides,  be  divided  in  the  mid-line,  where,  as  Treves  says,  it, 
like  other  median  raphes,  has  but  slight  vascularity.  A  large  communicating  branch 
between  the  superior  thyroid  veins  often  runs  along  the  upper  border  of  the  isthmus, 
and  oyer  its  anterior  surface  there  may  be  a  plexus  made  up  by  the  branches  of  the 
thyroid  veins  of  the  two  sides.  These  vessels,  if  present,  may  be  dealt  with  sepa- 
rately or  may  be  picked  up  with  the  two  sides  of  the  divided  isthmus  in  the  grasp 
of  heavy  haemostatic  forceps,  which  by  dropping  over  the  neck  raise  the  trachea 
into  the  wound  (Pearce  Gould). 

The  trachea  is  then  seen  and  felt,  steadied  and  made  still  more  superficial  by 
upward  traction  by  a  small,  sharp  hook  thrust  into  the  lower  edge  of  the  cricoid,  and 
opened  exactly  in  the  middle  line  by  a  bistoury  thrust  in  at  about  the  level  of  the 
third  or  fourth  ring  and  made  to  cut  upward  to'alwut  the  first. 

In  very  fat  or  very  muscular  persons  the  depth  of  the  trachea  is  increased, 
uu  t"^^'''*'^^"  '**  *'"*''  ''^^'  "^  shortness  (one  and  a  half  inches  in  the  neck  in  a 
child  of  from  three  to  four  years  of  age),  its  mobility,  its  depth  (on  account  of  the 
considerable  quantity  of  subcutaneous  fat  usually  present),  the  compressibility  of  its 
thin  cartilaginous  rings,  the  height  to  which  the  great  vessels  may  nse  in  front  of  it, 
the  venous  engorgement  usually  present,  and  the  occasional  interposition  of  the 
thymus  (^vide  supra),  all  increase  the  difficulties  of  the  operation. 

Foreign  bodie'  in  the  air-passages  are  most  likely  to  be  arrested  at  the  upper 
laryngeal  opening,  at  the  ventricle  or  the  glottis,  at  the  bifurcation  of  the  trachea, 
or  m  the  right  bronchus.  They  are  apt  to  enter  that  bronchus  instead  of  the  left 
because  (a)  the  right  lung  is  larger  (the  left  being  encroached  upon  by  the  heart) 
and  there  is  a  greater  intake  of  air  and  a  stronger  current ;  (<J)  the  right  bronchus 
has  the  larger  transverse  diameter  ;  {c)  it  is  less  horizontal  and  therefore  more 
directly  a  continuation  of  the  trachea  than  the  left  bronchus  (page  18,^8);  and  (</) 
the  carina  tracheae  is  siti-  'ed  to  the  left  of  the  middle  line  in  the  majority  of  cases 
(page  1837).  If  small  «....  ugh,  they  may  be  drawn  into  some  of  the  lesser  bron- 
chioles by  the  mspi.  .tion— usually  sudden— which  has  caused  their  entrance  into  the 
air-passages.  The  immediate  symptoms  are  always  those  due  to  obstruction  of  the 
air-current,  either  mechanical— from  the  size  of  the  foreign  body— or  refle.x,  as  when 
spasm  of  the  glottis  is  excited  by  the  irritation  of  the  superior  laryngeal  or  tracheal 
nerves. 


mC 


t843 


HUMAN   ANATOMY. 


The  symptoms  that  would  suggest  arrest  in  the  larynx  are  violent  cough,  alter- 
ation or  loss  of  voice,  frequent  spasm,  stridor,  and  rapidly  increasing  dyspncea  (from 
swelling  and  cedema  of  the  mucosa).  In  the  trachea  a  foreign  body  is  apt  to  cause 
moderate  but  persistent  cough,  hurried  respiration,  occasional  reflex  s^m  of  the 
glottis,  and  slight  dyspntea.  Arrest  in  a  division  or  subdivision  of  a  bronchus,  if 
the  body  is  large  enough  to  plug  it,  will  cause  absence  of  vocal  and  respiratory 
sounds  over  the  area  involved,  collapse  of  the  lung,  and  flattening  of  the  side  of  the 
thorax.  Later  symptoms  will  be  due  to  irriution  (hypersemia  and  caurrh),  fol- 
lowed by  infection  (inflammation  and  ulceration)  and,  in  cases  of  long  standing, 
possibly  by  the  involvement  of  neighboring  structures  or  organs  (the  lungs  or 
pleura,  the  aorta  or  vena  cava,  the  pericardium,  or  the  oesophagus).  The  relatively 
unyielding  walls  of  the  air-passages  render  this  termination  less  common  than  in 
cases  of  oesophageal  impaction  of  foreign  bodies.  Sponuneous  expulsion  during  a 
coughing  spell  may  take  place,  or  operation  may  be  needed.  (See  thyrotomy, 
laryngotomy,  tracheotomy,  bronchotomy. ) 

The  bronchi  begin  at  the  bifurcation  of  the  trachea,  about  opposite  the  space 
between  the  fourth  and  fifth  thoracic  vertebrae.  This  is  behind  the  lower  part  of  the 
arch  of  the  aorta  and  on  a  horizontal  line  passing  through  the  sternal  angle  (angu- 
lus  Ludovici)  and  the  root  of  the  spine  of  the  scapula.  As  at  their  origin  they  are 
nearer  the  posterior  than  the  anterior  wall  of  the  thorax,  ausculutory  sounds  in  the 
primary  bronchi  can  best  be  heard  between  the  scapula  and  about  the  level  of  the 
inner  ends  of  their  spines. 

The  most  frequent  as  well  as  the  most  serious  forms  of  compression  of  the  air- 
passages  are  found  within  the  thorax.  In  the  neck,  even  in  the  presence  of  large 
tumors  or  swellings,  the  feeble  resistance  of  the  skin  and  other  tissues  may  permit 
the  trachea  to  escape  ;  but  within  the  thorax,  between  the  spine  and  the  unyielding 
sternum,  even  small  growths  may  cause  striors  symptoms  of  obstruction. 

Thus  the  group  of  lymph-nodules  surroundmg  the  bifurcation  may,  when  dis- 
eased, make  pressure  upon  either  the  trachea  or  bronchi,  as  may  aneurisms  of  the 
aorta  or  innominate,  or  tumors  of  the  posterior  mediastinum,  or  even  a  dilated  left 
auricle. 

In  chronic  interstitial  pneumonia  attended  by  great  increase  in  the  connective- 
tissue  elements  of  the  lung,  followed,  as  is  invariably  the  case,  by  contraction  of 
such  tissue,  the  atmospheric  pressure  retains  the  lung  in  contact  with  the  inner  sur- 
face of  the  chest  in  spite  of  the  pull  of  the  atrophying  fibrous  tissue.  The  force  is, 
therefore,  exerted  on  the  bronchi,  the  walls  of  which  are  dragged  apart,  forming 
great  cavities  (^bronchieclasis).  Such  cavities  may  also  be  due  to  dilatation  under 
increased  pressure  from  within,  as  when  a  foreign  body  or  an  aneurism  occludes  one 
bronchus  ;  or  to  chronic  disease  and  weakening  of  the  bronchial  walls. 

Asthma  of  the  spasmodic  type  may  be  due  to  reflex  pneumogastric  irritation 
causing  contraction  of  the  muscular  tissue  in  the  walls  of  the  smaller  bronchi.  It 
should  be  noted  that  the  transverse  muscular  fibres  (trachealis  muscle)  connecting 
the  ends  of  the  tracheal  cartilages  have  in  the  bronchioles  become  converted  into  a 
complete  circular  muscular  coat,  and  are  found  even  in  divisions  so  small  that  the 
cartilage  has  disappeared. 

Bronchotomy. — The  relations  of  the  bronchi  (page  1857)  show  that  in  case  of 
impaction  of  a  foreign  body  in  or  just  below  a  primary  bronchus  it  might  be  reached 
by  a  posterior  thoracotomy  done  at  the  level  of  the  fourth  to  the  sixth  or  seventh 
rib.  The  flap  of  soft  par'  is  three  inches  square,  its  base  being  about  over  the 
costo-vertebral  gutter  on  Mde  to  be  operated  upon.  The  underlying  ribs  are  sepa- 
rated from  the  pleura  ant  >ii\ided.  The  proximity  of  the  great  azygos  vein  on  the 
right  side,  and  of  the  arch  of  the  aorta,  the  descending  aorta,  the  oesophagus,  and 
the  left  auricle  on  the  left,  must  be  remembered.  It  is  more  difficult  to  retract  the 
pleura  on  the  right  side  so  as  to  expose  the  bronchus.  Bryant  has  called  attention 
to  the  following  anatomical  points  bearing  upon  this  operation,  whether  it  is  under- 
taken for  the  removal  of  a  foreign  body  from  a  bronchus  or  the  oesophagus,  or  for 
posterior  mediastinal  tumors  or  abscess,  or  for  the  relief  of  pressure  from  enlarged 
bronchial  glands  :  the  lower  portion  of  the  fourth  dorsal  vertebra  is  the  boundary 
line  between  the  posterior  mediastinum  and  the  lower  part  of  the  superior  medias- 


THE  LUNGS. 


i»43 


tinum  ;  the  spinous  process  of  any  dorsal  vertebra,  with  the  exception  of  the  first, 
eleventh,  and  twelfth,  denotes  the  situation  o  the  posterior  extremity  of  the  rib 
articulating  with  the  transverse  process  of  the  vertebra  immediately  below  ;  the  tips 
of  the  spinous  processes  of  the  tirst,  eleventh,  and  twelfth  dorsal  vertebra?  are  above 
rather  than  opposite  the  transverse  processes  of  the  vertebr*  immediately  below  ; 
the  space  between  the  ends  of  the  transverse  processes  and  the  angles  of  the  rilw 
varies  from  one  to  two  and  a  half  inches,  according  to  the  numerical  position  of  the 
rib ;  the  incomplete  rings  of  the  bronchi  render  those  tubes  easily  recognizable  by 
touch  ;  they  are  found  about  an  inch  and  a  hall  anterior  to  the  opening  in  the 
thoracic  wall. 

THE    LUNGS. 

The  lungs  are  a  pair  of  conical  organs,  each  envelofied  in  a  serous  nembrane, — 
the  pleura, — occupying  the  greater  part  of  the  cavity  of  the  thorax,  and  >oparated  from 
each  other  by  the  contents  of  the  mediastina.  Although  in  general  conical,  the  lung 
diflers  in  many  respects  from  a  true  cone.  The  base  is  concave,  moulded  over  the  con- 
vexity of  the  diaphragm,  and  descending  farther  at  the  back  and  side  than  at  the  front 
and  internally.  The  apex  is  not  over  the  middle  of  the  base,  but  much  to  the  inner 
and  p<»terior  side  of  it,  so  that  the  back  and  inner  side  of  the  lung  descend  much 
more  directly  than  the  rest.  The  right  lung  is  the  larger  on  account  of  the  greater 
encroachment  of  the  heart  on  the  left. 

The  surfaces  of  the  lungs  are  the  base,  the  external  surface  (which  is  the 
mantle  of  the  cone  from  apex  to  base,  and  embraces  all  the  periphery  from  tht-  front  of 
the  mediastinal  space  around  the  wall  of  the  thorax  to  nearly  opposite  the  front  of  the 
vertebral  column),  and  the  interna!  or  mediastinal  surface. 

The  borders  are  the  inferior,  which  surrounds  the  base,  and  the  anterior  and 
posterior,  which  bound  respectively  the  back  and  front  of  the  internal  surface. 

The  external  surface  (facies  costalis),  much  the  largest,  is  closely  applied  to 
the  portion  of  the  wall  of  the  pleural  cavity  formed  by  the  ribs  and  the  intercostal 
muscles.  The  region  of  the  apex  is  a  part  of  this  surface.  It  rises  slightly — possibly 
I  cm. — above  the  oblique  plajie  of  the  first  rib,  which  indents  it  towards  the  front. 
The  apex  itself  is  in  the  internal  and  posterior  part  of  this  region.  It  rests  closely 
against  the  firm  fibrous  structures  that  roof  in  this  region,  and  is  grooved  trans- 
versely by  the  subclavian  artery,  more  anteriorly  on  the  right  lung  than  on  the  left. 
A  slight  groove  made  by  the  subclavian  vein  may  be  found  in  front  of  the  arterial 
one.  The  rest  of  the  external  surface  is  smooth,  except  where  it  may  be  slightly 
depressed  beneath  the  individual  ribs.  It  should  be  noted  that  a  part  of  what  is 
termed  the  external  surface  faces  inward  against  the  vertebral  column  and  the  first 
part  of  the  ribs  as  they  pass  backward.  The  external  surface  descends  lowest  at  the 
back  and  at  the  side. 

The  internal  surface  (facies  mediastinalis)  is  approximately  plane,  except  for 
the  cardiac  fossa,  which  is  much  deeper  on  the  left  than  on  the  right,  and  extends  as 
far  as  the  lower  surface.  The  left  lung  presents  a  shelf-like  projection  from  behind 
under  this  fossa.  The  other  chief  feature  of  the  internal  surface  is  the  hilum  for  the 
entrance  of  the  structures  composing  the  root  of  the  lung.  It  is  situated  nearer  the 
back  than  the  front  and  below  the  middle,  being  behind  and  above  the  cardiac  fossa. 
The  outline  of  the  hilum  in  the  left  lung  is  approximately  oval,  with  the  lower  end 
sharpened  and  the  long  diameter  vertical.  It  is  more  triangular  in  the  left  lung,  as 
the  root  expands  forward  near  the  top.  The  position  of  the  bronchi  and  the  chief 
vessels  as  they  enter  the  lungs  differs  on  the  two  sides.  Right  lung :  the  chief  bron- 
chus enters  at  the  middle  or  lower  part  and  its  first  branch  near  the  top,  both  being 
at  the  back  of  the  hilum  ;  the  pulmonary  artery,  generally  in  two  branches,  enters  one 
branch  in  front  of  the  main  bronchus  and  the  other  in  front  of  the  secondary  bronchus, 
but  at  a  higher  level ;  the  superior  pulmonary  vein  is  high  and  in  front  of  the  higher 
arterial  branch  ;  the  inferior,  often  subdivided,  is  near  the  lower  end  of  the  hilum  ;  one 
branch  may  be  in  front  of  the  bronchus  and  one  below  it.  Left  lung :  the  bronchus 
enters  the  back  of  the  hilum  rather  above  the  middle  ;  the  pulmonary  artery  is  at  the 
top,  sometimes  in  two  divisions  ;  the  superior  pulmonary  vein  is  high  up  in  front, 


. 


J844 


HUMAN  ANATOMY. 


Groove  lor  •ubclaviau 
artery 


Groove  lur 
Innominate  vein 


Right  lung,  hardened  m  tUu 


iddic 
lobe 


Inferior  lobe 

antero-lateral  aipect. 


causing  the  expansion  which  makes  the  outline  triangular,  the  inferior  vein  being  •" jhe 

lower  angle.     The  inner  surfaces  are  also  marked  by  certain  adjacent  structures  which 

require  a  separate  account  for  each  lung. 

The  right  lung  presents  a  vertical  groove 

above  and  in  front  for  the  superior  vena 

cava,  and  one  for  the  vena  azygos  major, 

which  is  distinct  behind  the  upper  part 

of  the  hilum   and  above  it  where  this 

vein  runs  forward  to  the  cava.    The  r^ht 

subclavian  artery,  owing  to  its  high  origin 

from  the  innominate,  indents  but  little  of 

the   internal   surface.      A  more  or  less 

marked  vertical  groove  for  the  oesophagus 

is  seen  behind  the  hilum  and  below  that 

for  the  azygos.     There  is  aiso  a  groove 

below  on  the  inner  surface  where  the  in- 
ferior vena  cava  turns  forward  to  enter  the 

heart     A  slight  impression  made  by  the 

trachea  may  also  be  present  near  the 

apex.     The  inner  surface  of  the  left  lung 

is  deeply  grooved  by  the  aorta  arching 

over  the  root  and  descending  behind  it, 

the  imprint  growing  faint  and  disappear- 
ing at  the  lower  end.    The  left  carotid 

and    subclavian    arteries   make  distinct 

impressions  at  the  upper  part  divei^ng 

h-om  the  aortic  groove. 

The  baae  (fadfs  diaphragmatica)  is 

concave,    that  of   the  right  one  being  ...  .  ..       » 

rather  the  more  so.      Both  are  semilunar  in  outlme,  owmg  to  the  part  cut  out 

of  them  by  the  heart ;  since  this  encroachment  is  greater  on  the  left,  the  base 

of  that  lung  is  a  narrower 
Fio.  1165.  crescent. 

The  inferior  border 
surrounds  the  base.  The 
latter  forms  about  a  right 
angle  with  the  internal  sur- 
face, but  at  the  periphery, 
especially  at  the  back  and 
at  the  side,  a  sharp  edge 
of  lung  is  prolongred  down 
into  the  narrow  space  be- 
tween the  diaphr^;m  and 
the  thoracic  walls.  The 
anterior  border  is  sharp 
and  somewhat  irregular, 
often  presenting  a  series  of 
convexities.  Starting  near 
the  apex,  it  descends  on 
both  lungs  with  a  forward 
curve,  which  is  most  promi- 
nent in  the  upper  part,  so 
that  the  lungs  nearly  or 
quite  meet  behind  the  ma- 
nubrium. The  anterior  bor- 
der of  the  right  lung  then 
inclines  downward  and  out- 
ward so  as  to  meet  the  inferior  border  in  a  gradual  curve.  On  the  left  this  convex- 
ity is  changed  into  a  sharp  concavity  where  the  border  curves  outward  around  the 


Groove  fur 
innominate  artery 


Groove  for  riftht' 
innominate  vein 

Groove  for 
vena  cava 

superior- 
Secondary, 
bronchus 

Blanches  of. 

pulmonary 
artery 

Cardiac 
impression 

Infrrior  pul- 
muiiary  vein 


Groove  for 
•ena  azygoa  major 


lain  bronchus 


Diaphragmatic  surface 

Preceding  lung ;  median  asfwft 


THE  LUNGS. 


»845 


Fio 


Groove  lor -~ 
■ubdtvisn  anery 

Groove  for 
hmumUiate  vein 


Inferior 


Bom 


Left  liini,  hardened  m  tilm  ;  antero-lateral  aspect. 


heart.  As  this  concavity  ends  in  front,  the  anterior  and  inferior  borders  enclose  a 
prolongation  of  the  lung  towards  the  median  line,  known  as  the  linguia.  The  pos- 
terior border  is  vanously  described. 
Often  the  term  is  applied  to  the  thick 
mass  of  lung  that  fills  the  region  of  the 
thorax  along  the  sides  of  the  vertebrse 
and  the  part  of  the  ribs  running  back- 
ward. Properlv,  it  is  a  ridge  starting  on 
the  inner  side  of  the  apex,  growing  sharp 
as  it  descends,  but  becoming  vague  and 
effaced  at  the  lower  end.  The  position 
of  this  line  is  not  the  same  on  both  sides, 
nor  is  it  probably  always  dependent  on 
the  same  causes.  On  the  le/l  it  is  more 
regular,  beginning  as  the  posterior  bor- 
der of  the  groove  for  the  siibi'lavian  ar- 
tery, and  continuing  as  that  oi  iIh  aortic 
impression  until  it  is  lost  near  the  lower 
border  of  the  lung.  Sometimes  the  be- 
ginning has  no  relation  to  the  subclavian 
groove,  but  appears  posterior  to  it,  the 
lung-tissue  forming^  a  ridge  which  enters 
a  little  into  the  space  between  the  front 
of  the  spine  and  the  cesopliagus,  which 
is  here  deflected  to  the  left  The  line 
behind  the  aortic  groove  lies  on  the  side 
of  the  vertebrie,  and  consequently  is  the 
farther  back  the  more  the  aorta  is  on  the 
side  of  the  column.  On  the  right  the  posterior  border  is  farther  forward,  being 
about  opposite  the  anterior  surface  of  the  spine.  It  may  begin  as  the  posterior  bor- 
der of  the  subclavian  groove,  or  more  posteriorly,  and  continues  as  a  ridge  tending 
to  insinuate  itself  between  the  spine  and  the  contents  of  the  posterior  mediastinum. 
From  just  above  the  root  of  the  lung  it  is  for  a  short  distance  continued  as  the  t>ack 
of  the  groove  for  the  major 
azygos  vein,  below  which 
it  tends  to  pass  between  the 
cesophag^s  and  the  pericar- 
dium, and  finally  disappears 
a  little  above  the  lower 
border. 

The  Lobes  and  Fis- 
sures.— The  lungs  are  di- 
vided into  lobes  by  deep 
fissures.  The  chief  fissure 
starts  on  the  inner  aspect  of 
the  lung,  behind  the  upper 
part  of  the  hilum,  and  as- 
cends to  the  posterior  sur- 
face, which  it  may  reach 
at  the  same  level  on  both 
sides,  or,  as  is  perhaps  more 
frequent,  the  right  fissure 
may  be  one  intercostal 
space  lower.  The  fissure 
then  descends  obliquely 
along  the  otitcr  aspect  of 
the  lung,  and  reaches  the 

inferior  border,  where  it  ends  somewhat  sooner  on  the  right  side  than  on  the  left. 
In  the  right  lung  this  occurs  at  the  front  of  the  lateral  a.spect,  while  it  is  likely  to 


Pio.  1567. 


Iroove  (or  left  rabclavten 
artery 


Groove  (or  left 
'common  carotid 
artery 


Superior  pulmo- 
nary vein 


Subcardiac 
shelf 


,LinKula 


Diaphraitmatlc 
surface 


PrecedinK  Inne ;  median  a«i<ecl, 


1846 


HUMAN   ANATOMY. 


gi 


encroach  somewhat  anteriorly  in  the  left,  terminating  below  the  lingula.  The  left 
lun<>  is  thus  divided  into  a  superior  and  an  inferior  lobe.  In  the  right  lung  a  middle 
lob7\a  cut  off  from  the  superior  by  a  secondary  Jissure,  which  starts  from  the  main 
fissure  far  back  on  the  lateral  aspect  and  runs  forward,  either  straight  or  with  an 
upward  or  a  downward  inclination.  The  foregoing  description  applies  to  the  course 
ofthese  fissures  as  seen  on  the  suriace  ;  but  the  chief  fissure  is.  moreover,  very  deep, 
penetrating  to  the  main  bronchus,  and  completely  dividing  the  lung  into  a  part  above 
iTand  one  below  it.  The  depth  from  the  suriace  of  an  inflated  lung  to  the  bronchus 
at  the  bottom  of  the  fissure  (uken  at  the  point  of  origin  of  the  secondary  hssure  on 
the  right  and  at  a  corresp«.nding  point  on  the  left)  is  from  7-8  cm  on  the  right  and 
about  I  cm.  less  on  the  left.  The  secondary  fissure  is  much  less  deep  and  may  end 
prematurely,  or  even  be  wanting,  so  that  the  middle  lobe  Is  a  very  irreguUu-  structure. 
The  left  superior  lobe  comprises  the  apex  and  the  entire  front  of  the  lung,  while 
the  inferior  takes  in  most  of  the  l>ack  and  all  of  the  base,  unl«s  the  lingula  be  re- 
garded as  constituting  its  anterior  border.  In  the  right  lung  the  middle  lobe  forms 
a  varying  part  of  the  front  and  one-fourth  or  one-third  of  the  base.  The  volume  o 
the  upper  and  lower  lobes  of  the  left  lung  is  about  equal.  In  the  right  l«."«/''f  "' 
the  inferior  is  about  equal  to  that  of  the  other  two.  We  consider  the  middle  lobe 
simply  as  a  piece  cut  off  from  the  upper,  so  that  the  right  upper  and  middle  lobes 
correspond  to  the  left  uppei  one. 

Variation*  of  the  Lobaa  and  Fiaaurea.— Were  it  not  for  the  ereat  difficulty  m  properly 
examining  the  lunes,  their  marked  tendency  to  variation  would  doubtless  be  more  fuIW  appre- 
ciated. Schaffner"  has  shown  that  an  accessory  in/enor  lode  is  very  freauently  found  on  the 
under  surface,  extending  up  onto  the  inner  surface  In  front  of  the  broad  ligament.  Ihis  lone 
may  be  merely  indicated  by  shallow  fissures  or  sharply  cut  off  from  the  rest.  It  may  present 
a  toninie-like  projection  inward  or  may  comprise  the  entire  mner  portion  of  the  liase.  It  usu- 
ally represents,  when  present,  from  one-fifth  to  one-third  of  the  base.  It  may  occur  on  either 
sitfe  or  on  both,  but  is  larger  and  more  frequently  well  defined  on  the  nght.  On  the  other  hand, 
it  is  present,  or  at  least  indicated,  rather  more  often  on  the  left.  Schaffner  found  it  in  47.  i  |)er 
cent  of  210  lungs.  The  lobe  of  the  right  lung  represents  the  siihcardtac  lobe  of  many  mam- 
mals, that  of  the  left  being  evidently  its  fellow.  The  irregularity  and  occasional  absence  of  the 
fissure  marking  off  the  middle  lobe  have  been  mentioned.  An  irregular  fissure  may  subdivide 
the  left  lung  into  three  lobes,  and  both  lungs  may  exceptionally  bestil  further  subdiv-ided,  espe- 
cially the  right  one.  A  little  process  of  the  right  lung  just  above  the  base,  behind  the  termina- 
tion of  the  inferior  vena  cava,  may  very  rarely  become  more  or  less  isolated  as  the  lobus  cava. 
The  azygos  major  vein  may  be  displaced  outward,  so  that,  instead  of  curving  over  the  root 
of  the  lung,  it  may  make  a  deep  fissure  in  the  upper  |>art  of  the  right  lung,  marking  off  an 
extra  lobe. 

External  Appearance  and  Physical  Characteristics.— The  adult  lung 
is  bluish  gray,  more  or  less  molded  with  black.  At  birth  the  lung-tissue  proper  is 
nearly  white,  but  the  blood  gives  it  a  pinkish  or  even  a  red  color.  It  grows  darker 
with  age,  jiartiy,  perhaps  chiefly,  by  the  absorption  of  dirt,  but  also  by  the  greater 
quantity  of  pigment.  Before  middle  age  the  lungs  become  decidedly  dark  by  the 
presence  of  black  substance  (be  it  dirt  or  pigment),  arranged  so  as  to  bound 
irregular  polygons  from  1-2.5  cm.  in  diameter,  which  are  the  lobules.  At  first, 
while  the  black  is  scanty,  the  lines  seem  to  enclose  considerably  larger  spaces,  but 
when  more  of  the  lobules  appear,  owing  to  a  greater  deposit  of  the  pigment  in  the 
areolar  tissue  and  lymphatics  marking  them  off,  it  is  clear  that  their  diameter  rarely 
much  e.xceeds  1.5  cm.  Some,  however,  are  relatively  long  and  narrow.  It  is  re- 
markable that  the  deposit  of  pigment  is  much  greater  in  certain  places  than  in  others. 
Thus  the  rounded  posterior  parts  of  the  lungs  are  darker  than  the  anterior  portions. 
In  general  the  external  surface  is  much  darker  than  the  mediastinal  or  the  base,  while 
the  surface  within  the  fissures  is  the. lightest  of  all.  Moreover,  the  pigment  on  the 
external  surface,  before  the  coloration  has  become  general,  is  often  m  stripes  corre- 
sponding to  the  intercostal  spaces,  as  if  there  were  more  pigment  in  the  places  most 
accessible  to  light. 

The  lungs  being  filled  with  air,  after  respiration  has  begun,  are  soft  and  crack- 
ling on  pressure.  They  are  extremely  elastic,  so  as  to  collapse  to  perhaps  a  third 
of  their  size  when  the  chest  is  op>ened. 

'  Yirchow's  Archiv,  Bd.  clii.,  1898. 


THE   LUNGS. 


1847 


Fio.  1 56*. 


Extcrmil  turiace  of  tuiiK,  thowlng  polyimnal  areas 
corresponding  to  lobuks  ma|>prtl  out  by  deposits  d 
pigmented  particles  within  cuiiuec-tivc  tissue. 


The  weight  (A  the  Iudk  is  difficult  to  determine,  owin^  to  the  imiMMtsibility  of 
quite  excluding  fluids.  Sappey  puts  it  at  60  or  65  urn.  lor  the  (ti'tus  at  term,  and  at 
94  gm.  on  the  average  for  the  new-bom  infant  that  has  breathetl  (thii.s  show- 
ing cunvinciiiKly  the  worthlessness  of  the 
method ).  Kniuse  gives  the  athilt  weight 
as  1.^00  gm.  in  the  male  and  loa;^  gm.  in 
the  female.  According  to  Rraune  and 
Stahcl,  the  weight  of  the  right  lung  is  to 
that  of  the  left  as  100 :  85. 

The  specific  gravity  of  the  lung  be- 
fore breathing  is  greater  than  that  of  water, 
so  that  the  lung  sinks  in  it.  VVilmiirt '  has 
recently  stated  it  as  1068,  which  i.«  the 
same  as  Sappey' s  statement  and  grc.iter 
than  that  of  Krause  (1045-1056).  After 
breathing  it  may  be  as  little  as  ,^42,  but 
may  go  as  high  as  746.  Probably  figures 
like  the  latter  represent  either  diseawd  or 
congested  lungs. 

The  dimensions  are  necessarily  nf  lit- 
tle value.  According  to  Krause,  the  length 
in  man  is  37.1  cm.  on  the  right  and  39.8 
cm.  on  the  left.  In  woman  these  dimen- 
sions are  31.6  cm.  and  23  cm.  resp-.ctively. 
There  is  little  difference  in  length  between 
the  lungs,  but  such  as  there  may  b«  is  in  favor  of  the  left.  The  other  dimensions 
are  probably  more  variable.  According  to  Sappey,  the  antero-posterior  diameter, 
which  increases  from  above  downward,  finally  reaches  16  or  17  cm.  Krause  gives 
the  transverse  diameter  at  the  base  in  man  as  13.5  cm.  on  tlie  right  and  13.9  cm.  on 
the  left,  and  in  woman  as  1 3. 3  cm. 
and  10.8  cm.  respectively.  Fio. 

The  average  capacity  of  the 
lungs  of  a  powerful  man,  after  an 
ordinary  inspiration,  is  stated  at  from 
3400-3700  cc.  The  vital  capacity, 
which  is  the  greatest  amount  of  air 
that  can  be  expelled  in  life  after  a 
forced  inspiration,  is  from  3300-3700 
cc.  for  men  and  2500  cc.  for  women. 
The  Bronchial  Tree.— The 
plan  of  the  bronchi  of  the  human  lung 
(Fig^  1558)  is  as  follows.  The  two 
primary  bronchi,  resulting  from  the 
bifurcation  of  the  trachea,  run  down- 
ward and  outward  into  the  lowest 
lateral  part  of  the  lungs,  the  right 
one  descending  more  steeply.  Their 
course  has  been  variously  described. 
That  of  the  right  one  has  been  said 
to  resemble  a  C  with  the  concavity 
inward,  and  that  of  the  left  an  S; 
but  both  comparisons  are  very  forced. 
On  their  way  they  give  off  secondary 
bronchi,  which  are  divided  into  ven- 
tral and  dorsal  branches.  The  ven- 
tral might  more  properly  be  called  lateral,  since  they  spring  from  the  outer  aspect  of 
the  primary  bronchus.  They  are  much  the  larger,  and  supply  all  the  lung,  e.\cept  the 
apex  and  the  posterior  portion  lying  along  the  spine  ;  the  latter  is  supplied  by  the 

*  La  Clinique,  1897. 


Relations  of  bronchial  tree  to  anterior  thoracic  wall,  as  shown 
by  X-rays.     K^lrr  Blakr.) 


m 


iM 


HUMAN  ANATOMY. 


donal  branches,  which  are  tnull  and  inwular.  There  are  usually  four  large  and  weli- 
nurked  ventral  secondary  bronchi,  besi<k8  one  or  two  insi^iAoint  ones  the  nature 
of  which  is  not  easily  determined.  The  ventral  bionchi  describe  a  spiral  course 
through  the  lung,  curving  forward  and  inward  as  they  descend,  so  as  to  be  in  the 
main  parallel  with  the  chief  fissure.  The  dorsa/  branches,  running  backward,  inward, 
and  downward,  are  not  more  than  four  in  number,  and  may  be  reduced  to  two.  There 
are  two  bronchial  tubes  besides  those  mentioned  above  :  one,  the  afica/  hrtmchus, 
supplies  the  upper  part  of  the  lung,  on  the  right  springing  from  the  primary  bronchus 
2  cm.  or  less  from  its  origin.  It  is  a  large  branch,  abmit  lo  mm.  in  diameter,  running 
upward  and  outward,  and  divides  into  three  branches,  one  of  which  ascends  and  two 
of  which  run  downward  and  outward  on  the  front  and  back  respectively.  It  is  really 
the  first  dorsal  branch  of  the  right  primary  bronchus,  but  we  have  not  included  it  in 
the  dorsal  branches.  On  the  left  the  apical  bronchus,  which  closely  resembln  the 
right  one,  but  is  rather  smaller,  rises  from  the  first  ventral  bronchus,  of  which  it 
may  be  called  a  dor«al  branch.  The  other  secondary  bronchus,  not  included  in  the 
foregoing  scheme,  is  the  subcardiat  bronthui,  which  on  the  right  arises  usually  from 
the  main  trunk  between  the  first  and  second  ventral  bronchi,  or  from  the  second 

ventral  bronchus.    It 
Fio.  1570.  ruiiji  downward  and 

»<rMi«-  inward  to  the  region 

^■^  ■*^WE  --f-ffSvi^lR  ^tA      in  front  of   the   hi- 

lum  and  above  the 
lower  border  of  the 
lung,  which  may  be 
marked  off  as  a  sep- 
arate lobe,  h  Id  to 
represent  the  cardiac 
lobe  of  mammab. 
On  the  left  the  cor- 
responding bronchus 
arises  always  from 
the  second  ventral 
branch. 

Homoloftes  of  tha 
Bionchi. — We  are  in- 
debted to  Aeby '  for  the 
idea,  now  practiciilly 
universally  accepted, 
that  there  is  a  main  or 
primary  bronchus  ex- 
tending   throuKh     the 

lune  and  giving  off  both  ventral  and  dorsal  branches.  After  the  bifurcation  of  the  pulmonary 
arter\-  each  of  its  subdivisions  reaches  thf  r.ont  of  the  primarj'  bronchus  of  each  lung,  and 
(according  to  Aeby)  crosses  over  it  so  as  to  lie  behind  it.  This  allied  crossing  occure  on  the 
right  just  after  the  origin  of  the  apical  bronchus,  which  is  said,  therefore,  to  be  above  the  cross- 
ing and  is  called  by  Aeby  the  eparierial  bronchus.  Thus  on  the  right  all  but  one  of  the  branches 
and  on  the  left  all,  without  exception,  are  given  off  below  the  crossing,  and  are  called  tiypartena/ 
bronchi  Aeby  attached  so  much  importance  to  this  relation  that  he  considered  the  little  irregu- 
lar middle  lobe  of  the  right  lung,  because  it  is  supplie<i  by  the  first  hyparterial  bronchus,  the 
representative  of  the  left  upper  lobe,  the  right  upper  lobe  being  without  a  mate  and  the  two 
.ower  lobes  homologous.  It  is  difficult  to  understand  why  such  a  relation  should  be  of  so  great 
import.  Narath,'  in  refut.ntion  of  Aeby,  pointed  out  that  during  fecial  life  the  pulmonary  artery  is 
a  very  insignificant,  and  withal  variable  structure,  and,  moreover,  that  it  does  not  cross  fairly 
over  the  main  bronchus,  but  runs  on  its  outer  side,  the  crossing  occurring,  if  at  all,  deep  in  the 
lung.  Narath  showed  also  that  the  so-called  eparterial  apical  bronchus  of  the  ngh*  lung  is 
present  in  the  left,  .vising  from  the  first  ventral  instead  of  the  primanr  bronchus.  It  is  a  ter- 
ti.iry  bronchus  from  the  first  ventral  which,  especially  on  the  right,  is  (among  mammals)  given 
to  wandering,  so  that  it  mav  spring  from  the  main  bronchus  or  even  from  the  trachea.  The 
arterial  relation  he  considers  of  no  importance.  Huntington,*  after  much  work  on  human 
and  mammalian  lungs,  came  to  somewhat  similar  mnrliisions.  He  believes  that  the  primary 
type  among  mammals  is  one  with  a  hyparterial  bronchus  on  both  sides,  and  the  furthest 

'  I>r  Bronchialbaum  der  SSugethiere  und  des  Menschen,  i88a 

»  Verhandl.  d.  Anat.  Gesellschaft,  189a. 

'  Annals  of  the  New  York  Acidemy  of  Sciences,  1898. 


Rctatloiu  of  bronchiil  trw  to  pouerlor  thoracic  wall,  m  ahown  by  X-ny*. 
(A/trr  Blakr.) 


iiM 


THE  Ll'NGS  1849 

depwturc  from  it  one  with  tymmetrical  eparterial  bronchi.    The  type  found  in  man  ii»  the  mutt 
cummun  among  nMmnwIs.     Huntington  would  do  away  entirely  with  the  ttrm-*     enaiterial 
and  ••hyparterid,"  except  «or  purposes  a<  topography.    Cetiainly  there  is  n<>  need  «,<  them  m 
human  anatomy  ax  a  special  study  ;  whether  or  not  the  arterial  relation!*  should,  an  Narath  main- 
Uins.  be  absolutely  di-scarded  in  comparative  anatomy,  we  must  leave  undetermined.' 

It  must  be  admitted  that  were  our  knowledge  derived  solely  <r«>m  the  human  lung  it  would 
be  impossible  to  make  out  this  plan.    We  shall  now  describe  what  is  actually  to  be  seen. 

EHMribution  of  tlM  BroncU.— In  the  rigki  Immg  the  apical  brunthus,  with  a  diameter  of 
about  10  mm.,  arises  about  a  cm.  from  the  trachea  (often  nearer  and  rarely  farther),  and, 
entering  the  top  of  the  hilum,  divides  as  described  above.  The  diameter  of  the  mam  trunk,  after 
giving  off  the  apical  branch.  Is  12  mm.  The  first  right  ventral  branch  arises  irom  its  outer  side, 
about  5  or  6  cm.  from  the  bifurcation  of  the  Uachea,  and  runs  downward,  outward,  and  for- 
ward. It  is  about  8  mm.  in  diameter.  The  apical  branch  and  the  first  ventral  supply  the  supe- 
rior lobe,  of  which  the  middle  lobe  is  really  a  part  Shortly  after  the  origin  of  the  first  ventral 
branch  the  chief  bronchus  seems  to  break  up  into  a  bundle  of  branches  runnmg  m«»tly  in  the 
same  general  direction,  but  diverging.  It  is  usually  not  prawible  to  determine  which  is  the 
main  trunk,  but  the  subcardiac  branch  may  sometimes  be  distinguished.  In  the  le/l  lung  the 
first  branch  is  the  first  ventral,  with  a  diameter  of  la  mm.,  arising  some  40  mm.  from  the  bihirca- 
tion  It  lives  off  the  apical,  7  or  8  mm.  in  diameter,  after  which  the  diameter  of  the  mam 
branch  J»  la  mm.  It  presently  breaks  up  like  the  right  one.  <)n  this  side  the  first  ventral  sup- 
plies the  upper  lobe.  A  branch  from  the  second  ventral  goes  tc  the  accessoiy  kibe,  ■{.  there 
be  one.  The  branches  of  the  left  bronchus  are  very  apt  to  rive  the  appeararice  of  being  divided 
into  an  upper  and  a  fower  set,  the  former,  consisting  of  the  first  ventral  branch,  bearing  the 
apical  and  supplying  the  superior  lobe,  while  the  lower  sheaf  of  branches  supplies  the  inferior. 

The  secondary  bronchi  give  off  branches  oi  4  or  s  mm.  in  diameter,  whic  iverge  at  acute 
angles  from  the  parent  trunk,  and  in  turn  give  off  smaller  branches  at  continu  '.>  greater  angles. 
THe  branches  'o  the  lobules  are  probably  the  fourth  or  fifth  branches  They  are  about  i  mm. 
in  diameter  and  arise  by  the  subdivision  of  the  preceding  branch.  In  the  larger  lubts  the 
ramification  is  clearly  from  the  side,  but  in  the  smaller  ones  it  is  more  sui^gestive  of  a  splitting. 
His  •  Minot,'  and  more  recently  Justesen*  defend  the  theory  that  the  onpfin  of  the  bronchi  is 
throughout  by  bifurcation,  with  subsequent  unequal  growth  of  the  subdtvisioii  until  we  come  to 
the  smallest.  Aeby  gives  the  following  table  of  diameters  of  the  mam  bronchus  above  the  ongin 
of  the  chief  branches,  the  nomeiKlature  being  his. 

Right.  tcft. 

Above  the  epartetial  branch »a.8  mm.  .   • 

Above  the  fit  &i  hyparterial  branch 9.6  mm.  10.1mm. 

Above  the  second  hyparterial  branch   ...             7.2  mm.  7.7  mm. 

Above  the  third  hyportcrial  branch 5-8  mm.  6.4  mm. 

Above  the  fourth  hyparterial  branch 4-6  mm.  5.3  mm. 

The  varUtioBS  of  the  bronchial  tree  are  very  numerous.  Very  rarely  indeed  the  right 
aoical  branch  does  not  spring  from  the  primary  bronchus,  so  that  the  disposition  of  the  two 
sides  is  symmetrical.  The  origin  of  the  left  apical  from  the  pnmary  bronchus  has  been 
observed  in  two  or  three  cases  of  infants,  which  also  makes  the  arrangement  symmetncar 
Chiari' has  seen  several  cases  in  which  the  right  apical  bronchus  is  double,  the  duplication 
being  apparently  due  to  the  springing  of  one  of  its  branches  from  the  mam  bronchus.  The 
right  apiS  bronchus  may  spnng  from  the  trachea,  as  in  *«  »heep  and  other  mamrnaK  U  e 
hlvesichan  instance  in  wfiich  it  is  separated  rom  the  chief  bronchus  by  ttie  ^SK^^J": 
The  dorsal  secondary  bronchi  are  particularly  likely  to  be  reduced  in  number.  The  ventral 
ones  may  also  be  reduced  by  two  having  a  common  origin  or  by  one  becoming  merely  tne 
branch  of  another.  The  number  may  be  apparently  increased  by  the  separate  origin  from  the 
parent  stem  of  what  are  normally  branches  of  branches. 

The  Lung  Lobule.— The  surface  of  the  lung  is  covered  with  lines  of  con- 
nective tissue  containing  blood-vessels  and  lymphatics,  with  pigment  either  within  the 
latter  or  free,  the  lines  marking  of!  little  polygons  (Fig.  1568),  which  are  the  bases  of 
pyramidal  masses  of  pulmonary  tissue  known  as  the  /o6u/es.  The  shape  of  the  latter 
within  the  depths  of  the  lungs  is  not  accurately  known  ;  those  at  the  sharp  borders 
are  modifications  of  the  typical  ones  at  the  surface.  The  bases  of  the  pyiamids  at 
the  surface  are  bounded  by  four,  five,  or  si.x  sides,  the  laiger  diameter  varying  from 
10-25  mm-  and  the  smaller  from  7-12  mm.  If  the  base  be  assumed  to  be  square, 
the  average  breadth  would  be  12.57  mm.*  The  average  height  is  13  mm.  The 
lobules  are  separated  from  one  another  by  a  layer  of  connective  tissue  containing 

*  The  latest  and  most  elaborate  work  on  this  subject  is  Narath'S  Der  Bronchialbaum  der 
Saugethiere  und  de«:  Menschen,  Stuttgart.  1901. 

»  Archiv  f.  Anat.  u.  Phys.,  Anat.  Abth  ,  1887- 

*  !  ''iman  EmbrN'olofO',  189a. 

*  K:-hivf.  mikro.  Anat.,  Bd.  Ivi.,  1900. 

'  .>  'schrift  fiir  Heilkiinde,  Prag.,  Bd.  x.,  1890. 
■  luiiographie  Anatomique.  1898. 


1850 


HUMAN   ANATOMY. 


1 1 


Diagram  showiiif;  relations  of  terminal  suh- 
diviHiuns  of  air-tuhes.  B,  bronchiole  eiidinK  in 
terminal  bronchi  iTB);  latter  divide  into  atria 
M).  each  of  which  communicates  with  several 
air-sacs  {s)  into  which  open  the  alveoli  (a); 
PA,  branch  of  pulmonar)'  arteo'  follows  bron- 
chiole; PK  pulmonary  vein  at  periphery  of 
lung-unit      ( /V'"'  Miller. ) 


vessels.  Each  lobule  is  entered  by  an  intralobular  bronchus  (.5-1  mm.  in  diam- 
eter), accompanied  by  its  artery, — not  quite  at  the  apex  of  the  pyramid,  but  slightly 
to  one  side  of  it.  The  bronchus  divides  into  two,  at  an  angle  of  from  go'-ioo",  a 
little  above  the  middle  of  the  lobule,  having  previously  given  of!  two  or  three  col- 
lateral branches  to  its  upper  part.     In  the  third 

quarter  of  the  lobule  the  two  subdivisions  (2-3  Fio.  1571. 

mm.  in  length)  again  split,  with  about  the  same 
degree  of  divergence  as  the  parent  stems,  but  in 
a  plane  at  right  angles  to  that  of  the  previous 
splitting.  This  is  repeated  in  three  or  four  suc- 
cessive bifurcations,  a  varying  number  of  col- 
lateral branches  being  given  off.  Thus  the  num- 
ber of  branches  in  the  third  quarter  is  much  in- 
creased ;  but  it  is  in  the  last  quarter  and  towards 
the  periphery  of  the  lobule  throughout  that  the 
tubes  break  up  into  the  great  number  of  truly 
ultimate  bronchi.  The  various  collaterals,  spread- 
ing and  even  reascending,  undergo  subdivision 
also.  Laguesse  and  d'  Hardiviller '  estimate  the 
number  of  terminal  bronchi  (ductuli  alveolares) 
within  a  single  lobule  at  from  fifty  to  one  hun- 
dred or  e  >  en  more.  The  slightiy  dilated  distal  ex- 
tremity of  the  terminal  bronchus  communicates 
with  from  three  to  six  spherical  cavities,  the  atria 
of  Miller'  (so  named  by  him  from  the  resemblance 
to  the  arrangement  of  an  ancient  Roman  house). 
The  atria,  in  turn,  communicate  with  a  group  of 
larger  and  irregular  cavities  or  air-sacs  ( sacculi 
alveolares),  into  which  directly  vyen  the  ultimate  air-spaces,  the  alveoli  or  air-cells 
( alveoli  pulmonis) .  The  latter  open  not  only  into  the  air-sacs,  but  also  into  the  atria,  the 
dilated  distal  part  of  the  terminal  bronchus  being  likewise  beset  with  scattered  alveoli. 
Miller  holds  that  the  terminal  bronchus,  the  air-chambers  connected  with  it, 

together  with  the  vessels  and 
Fig.  157a.  nerves,  is  the  true  lung-unit, 

and  calls  it  the  lobule.     We 
cordially  agree   that   this   is 
the  true  lung-unit,  and  pro- 
pose that  name  for  it,  retain- 
mg  the  term  "lobule"    for 
the  above-described  more  or 
less  isolated  pwrtion   of   the 
lung  which  is  surrounded  by 
connective  tissue  and  vessels 
and    receives  a  single   intra- 
lobular bronchus  and  artery. 
In  some  animals  the  lobules 
are  perfectly   distinct ;    they 
may  be  isolated  in  the  infant, 
and  can  be  in  the  main  easily 
made  out  in  the  adult.     The 
lung-unit,  on  the  other  hand, 
.  minute  bronchus    »  not  surroundcd  by  areolar 
e,  alveoli.    ■  8.       tissue,  and  its  limits  can  be 
determined  only  by   recon- 
struction from  microscopical  sections  ;  hence,  apart  from  its  minuteness,  it  is  practi- 
cally too  much  of  an  abstraction  to  deserve  the  name  almost  universally  applied  to 
something  tangible. 

>  BibliuKraphicf  Analomique,  1S9& 

•Journal  of  Morphology,  1893.    Archiv  f.  Anat.  u.  Phys.,  Anat.  Abth.,  1900. 


Corrosion-preparation  of  lung,  showing  lung-units.    1 
ending  in  terminal  bronchi  ib,f>)\  r, atria;  </,  air-sac 


i. 


THE  LUNGS. 


1851 


Fio.  IS73- 


Bronchiole 


Bronchiole 


Cartilage 


Pulmonary 
artery 


Section  of  lung,  showing  small  air-tube«  and  branch  of  pulmonar>-  arter>'.    X  35- 


The  intralobular  bronchus  is  accompanied  by  some  areolar  tissue,  and  certain 
fibrous  prolongations  extend  into  the  lobule  from  the  connective  tissue  disixiseil 
about  its- surface.     Although  superficially  these  appear  to  divide  the  lobule  into  from 

four  to  twelve  parts,  they 
penetrate  but  a  short  dis- 
tance. They  are  not  real 
partitions,  and  the  sub- 
divisions they  suggest 
have  no  morphological 
significance. 

Structure. — As  far 
as  their  entrance  into  the 
lungs,  the  bronchi  pos- 
sess essentially  the  same 
structure  as  the  trachea. 
After    the    division    of 
the  bronchus  within  the 
lung,  the  cartilage-rings 
are  replaced  by  irregu- 
lar angular  plates,  which 
appear    at    longer   and 
longer  .  intervals     until 
they  finally  cease,  the  last 
nodules  usually  marking 
the  points  of  bifurcation 
of  the  bronchi.     Within 
the  walls  of  bronchioles 
of  a  diameter  of  i  mm. 
or  less  cartilage  is  seldom  present.     As  the  cartilage  disappears  the  unstriped  muscle 
broadens  into  a  continuous  layer,  which,  however,  gradually  becomes  thinner  as  the 
air-tube  diminishes,  and  extends  only  as  far  as  the  terminal  bronchi.     Around  the 
circular  openings,  by  which  the  latter  communicate  with  the  atna,   the  muscle  is 
arranged  as  a  sphincter-like  band  _ 

(Miller).  "*■ 

The  walls  of  bronchi  of  medium 
size  consist  of  three  coats,  which 
from  without  in  are  :  (  i )  an  exter- 
nal fibro-elastic  tunic  which  encloses 
the  cartilage  and  blends  with  the 
surrounding  lung-tissue  ;  (2)  a  usu- 
ally incomplete  layer  of  involuntary 
muscle  composed  of  circularly  dis- 
posed elements  ;  (3)  the  mucosa, 
consisting  of  a  stratum  of  compact 
elastic  fibres  next  the  muscle,  the 
fibro-elastic  stroma  and  the  cili- 
ated columnar  epithelium.  Mucous 
glands,  similar  to  those  of  the 
trachea,  are  present,  decreasing  in 
number  and  size  until  the  bronchus 
approaches  i  mm.  in  diameter, 
when  they  disappear.  Their  chief 
location  is  outside  the  muscular 
layer,  which  is  pierced  by  the  ducts. 
In  addition  to  diffused  cells  within 
the  mucosa,  more  definite  aggre- 

gations  of  lymphoid  tissue  occur  as  minute  lymph-nodules  along  the  bronchi,  tfie 
points  of  bifurcation  of  the  latter  being  their  favorite  »e.its. 

The  epithelium  lining  the  air-tubes  retains  the  ciliated  columnar  type,  with  many 


Epithelium 
K>blctM:ell 


KihroHs  ttssuf 
*  Alvet>lar  wall 


Cartilage 


Portion  of  wall  of  small  bronchus.    X  iSo. 


1852 


HUMAN  ANATOMY. 


goblet-cells,  as  far  as  the  smaller  bronchi.  Within  these  the  riliated  cells  are  replaced 
by  simple  columnar  elements  which,  in  turn,  give  place  to  Vv  cuboidal  cells  within 
the  proximal  part  of  the  terminal  bronchi.  Towards  the  termination  of  the  latter, 
transition  into  a  simple  squamous  epithelium  takes  place. 

The  walls  of  the  air-spaces — the  atria,  the  air-sacs,  and  the  alveoli — have  es- 
sentially the  same  structuri-,  consisting  of  a  delicate  ■hro-elastic  framework  wh'ch 
supports  the  blood-vessels  and  the  epithelium.  Within  the  adult  lung  the  latter  is 
simple  and  is  represented  by  two  varieties  of  cells,  the  large,  flat,  plate-like  elements 
(.020-.045  mm. )  and  the  small  nucleated  polygonal  cells  (.007-.015  mm.)  occurring 
singly  or  in  limited  groups  between  the  plates.  Before  respiration  and  the  conse- 
quent expansion  of  the  air-spaces  take  place,  the  cells  lining  these  cavities  are  small 
and  probably  of  one  kind.  The  groups  of  the  smaller  cells  are  larger,  more  numer- 
ous, and  more  uniformly  distributed  in  young  animals  than  in  old  ones,  in  which 
they  are  often  represented  by  single  cells  irregularly  disposed. 

The  adjacent  alveoli  share  in  common  the  interposed  wall,  which  consists  of  the 
two  layers  of  delicate  elastic  membrane  beneath  the  epithelium  lining  the  alveoli  and 


Pio.  157S- 


Air^nc 


Passage  from 
atrium  into  air-sa* 


Alvcolui 

Trnninal  bronchus 

Pulmonary  aitcry. 
Bronchiole- 


-Atrium 


-Alveolus 


Air-sact 


Section  of  lung,  showing  general  relations  of  divisions  of  air-tubes.    X  so. 

the  intervening  capillary  net-work,  supported  by  a  delicate  framework  of  elastic  fibres. 
The  capillary  net-work  is  noteworthy  on  account  of  the  closeness  of  its  meshes,  which 
are  often  of  less  width  than  the  diameter  of  the  component  capillaries.  The  latter  are 
not  confined  to  a  single  plane,  but  pursue  a  sinuojis  course,  projecting  first  into  one 
alveolus  and  then  into  the  one  on  the  opposite  side  of  the  interalveolar  septum.  The 
capill.nries  are,  therefore,  excluded  from  the  interior  of  the  air-cells  by  practically 
only  the  attenuated  respiratory  epithelium,  the  large  plate-like  cells  lying  over  the 
blood-vessels  wliile  the  small  cells  cover  the  intercapillary  areas.  Distinct  intercellu- 
lar apertures  or  stomata,  formerly  described  as  affording  direct  entrance  from  the 
alveoli  into  definite  lymphatics,  probably  do  not  exist.  That,  however,  inspired 
foreign  particles  may  pass  between  the  epithelial  cells  into  lymph-spaces  within  the 
alveolar  wall  and  thence  into  lymphatics,  to  be  transported  to  more  or  less  dis- 
tant points,  is  shown  by  the  gradual  accumulation  of  carbonaceous  and  other  parti- 
cles within  the  interlobular  tissue  and  the  lymph-nodules  along  the  course  of  the 
lymphatic  vessels.  .Such  accumulations  may  acquire  conspicuous  proportions,  the 
entire  interlobular  septum  appearing  almost  black.  In  view  of  the  very  frequent 
presence  of  pigment-loaded  leucocytes  within  the  alveoli,  as  well  as  outside  the  alve- 


THE  LUNGS. 


1853 


CapllUiry. 
net'Work 


Branch  of  pulmonar)'  vein 


Portion  of  injected  *nd  inflated  lung.    X  80. 


olar  walls,  it  is  highly  probable  that  such  cells  are  important  agents  in  transporting 
the  particles  of  inspired  carbon  through  the  walls  of  the  air-cells.  Additional  par- 
ticles, however,  usually  occupy  the  cement-substance  between  the  alveolar  epithelial 

cells,    sometimes   lying   appar- 
Pio.  1576.  ently   within  the  cytoplasm  of 

the  latti  r. 

Blood-Vessels  of  the 
Lung. — The  pulmonary  artery, 
serving  not  for  the  nutrition  of 
the  lung  but  for  the  aeration  of 
the  blood,  is  very  large, — at 
first  larger  than  the  bronchus, 
which  it  follows  very  closely 
throughout  its  ramifications  to 
the  terminal  bronchi.  Situated 
at  first  anterior  to  the  bronchus, 
it  passes  onto  its  superior  and 
then  onto  its  outer  side,  and  in 
most  cases  twists  aroimd  the 
bronchus,  so  as  finally,  when 
deep  in  the  lung,  to  reach  its 
dorsal  aspect.  This  is  very  dif- 
ferent from  .At '.  y's  alleged  cross- 
ing of  the  main  bronchus.  The 
arterial  branches  accompanying 
the  apical  bronchus  are  in  the 
main  anterior  to  the  tubes  in  the 
right  lung  and  behind  them  in  the  left.  According  to  Narath,  the  genera'  course 
of  the  artery  along  the  main  bronchus  is  between  the  ventral  and  dorsal  branches  ; 
but,  as  he  states,  this 

is  not  constant.     We  Fig.  1577. 

have  found  certain 
ventral  bronchi  in 
the  lower  part  of  the 
lung  with  the  artery 
before  them.  An  in- 
tralobular branch  en- 
ters each  lobule  near 
the  apex  with  the 
bronchus,  and  follows 
its  ramifications  until 
the  ultimate  bronchi 
have  ended  in  the  air- 
chambers  of  the  lung- 
unit.  The  terminal 
arterioles  are  in  its 
in*"  'or  until  they 
^k  up  into  capil- 
laries in  the  walls  of 
the  alveoli.  Side 
branches,  interlobu- 
lar arteries,  run  in 
the  connective  tissue 
between  the  lobules. 
It  is  from  these,  ac- 
cording to  Miller,  that  the  subpleural  net-work  is  filled  ; 
held  to  be  supplied  by  the  bronchial  arteries. 

The  pulmonary  veins,  which  return  the  aerated  blood  to  the  left  auricle,  are  als.^ 
large  when  they  leave  the  hilum, — two  on  each  side,  one  near  the  top  and  the  other 


Smaller  cell! 
Larger  cella 


Epithelium 
lining  al- 
veoli 


Section  o(  lung,  showing  collections n(  particles  »■( 
tissue.    X  140. 


i-.irimn  in  |terivascular  connective 


formerly  the  latter  was 


1 854 


HUMAN   ANATOMY. 


I  i 


Portion  of  in] 


vessels  to  bronchi 
inK  bronchi  (white) 
of  lobule.  X  a 


ilccted  lung,  showing  relation  of  bloo»' 
l;  pulmonao'  arteries  (blue)  accomfiany- 


pulmonary  veins  (red)  at  periphery 


near  the  bottom.     They  arise  from  the  capillaries  in  the  walls  of  the  air-chambers, 

running  first  on  the  outside  of  the  lung-units,  unite  with  others,  and  ramify  in  the 

connective  tissue  about  the  lobules,  so  that,  first  in  the  lung-units  and  then  in  the 

lobules,  the  circulation  is  from  the  centre  towards  the  periphery.     As  they  ascend  to 

the  hilum  they  unite  with  others  and  form 

trunks  that  accompany  the  bronchi,  lying  Fio.  1578. 

in  the  main  lower  and  to  the  inner  side 

of  the  latter.       Corrosion    preparations 

(Fig.  1578)  show  very  clearly  that  the 

small  arteries  travel  in  close  comjiany 

with  the  bronchi,  while  the  veins  course 

by  themselves. 

The  bronchial  arteries  carry  the 
blood  for  the  nutrition  of  the  lungs,  es- 
pecially that  of  the  air-tubes,  the  lymph- 
nodes,  the  walls  of  the  blood-vessels, 
and  the  areolar  tissue  about  them  ;  hence 
they  follow  the  course  of  the  bronchi. 
They  are  in  communication  with  the 
interlobular  system  of  the  pulmonary 
arteries. 

The  bronchial  veins  are  very  irreg- 
ular. Both  anterior  and  jxjsterior  are 
described.  The  former  carry  the  blood 
back  from  the  bronchi  and  the  tissues 
about  them,  becoming  perceptible  at  the 

bronchi  of  the  third  order  {ie.,  the  branches  of  the  first  branches)  and  running 
to  the  hilum  anterior  to  the  bronchi,  two  with  each.  The  posterior  bronchial  veins 
appear  at  the  back  of  the  hilum  and,  without  any  close  connection  with  the  bronchi, 
anastomose  with  other  veins  at  the  back  of  the  roots  of  the  lungs. 

Anastomoses  between  the 
Fio.  1579.  Pulmonary  and  the   Bron- 

Pleura  chial  Systems. — Not  only  do 

■^.'■'-'-'^ — . —  the  capillaries  at  some  places 

drain  into  either  system  of 
veins,  but  important  com- 
munications occur  between 
both  the  arteries  and  the 
veins.  (a)  The  bronchial 
arteries  as  they  enter  the 
lungs  give  off  occasional 
branches  which,  running  for 
some  distance  beneath  the 
pleura,  suddenly  plunge  into 
the  lung  to  anastomose  with 
an  interlobular  artery.  Such 
a  branch  may  arise  from  an 
oesophageal  artery.  There 
are  also  deep  connections 
between  the  arteries  of  the 
two  systems  on  or  near  the 
secondary  bronchi  and  their 
br.inches.  (^)  The  com- 
munications between  the  two 
systems  of  veins  are  very 
extensive.  Apparently  all 
the  blotxl  from  the  smallest  branches  of  the  bronchial  arteries  returns  by  the  pul- 
monary veins  ;  and,  moreover,  the  bronchial  veins  about  the  larger  bronchi  have 
free  communication  with  those  of  the  pulmonary  system.      According  to  Zucker- 


Pulmonary  vein 
Lymph-vessel 

jnierted   lun>c-    showing  lymphatit^  accompanying  peripheral 
branch  of  pulmonary  vein,     v  60.     {MiUrr.) 


■I  * 


THE  LUNGS. 


1S55 


kandl, '  the  pulmonary  veins  anastomose  freely  with  those  of  the  orgjan'*  of  the  pos- 
terior mediastinum,  and  even  of  the  portal  system. 

The  lymphatics  of  the  lung  are  very  numerous.  The  deejier  ones  probably 
begin  as  lymph-spaces  within  the  interalveolar  septa,  distal  to  the  terminal  bronchi, 
distinct  lymphatics  being  found  only  along  the  arteries  and  veins.  These  commu- 
nicate with  the  subpteural  lymphatic  plexus.  Surrounding  the  walls  of  the  terminal 
bronchi  Miller  found  usually  three  lymph-vessels.  The  latter  increase  in  size  and 
number  as  the  calibre  of  the  air-tubes  enlarges.  On  reaching  the  bronchi  the  lym- 
phatics form  plexuses  along  them  which  ultimately  open  into  the  lymphatic  nodes, 
which  are  numerous  in  the  hilum  and  in  the  roots  of  the  lungs.  According  to  Miller, 
where  cartilage-rings  are  present  a  double  net-work  exists,  one  on  each  side  of  the 
cartilage,  the  inner  lying  within  the  submucosa.  The  lymph-nodes  of  the  lungs  are 
deeply  pigmented,  owing  to  the  colored  particles  of  foreign  substances  inspired. 

Nerves. — The  nerves  of  the  lungs,  from  the  pneumogastrics  and  sympathetics, 
form  the  very  rich  anterior  and  posterior  pulmonary  plexuses  about  the  roots,  whence 
they  enter  the  iungs,  running  adong  the  branches  of  the  bronchial  arteries  and  the 
bronchi  to  their  ultimate  distribution  in  the  septa  between  the  alveoli  ( Retzius,  Berk- 
ley). The  nerves  are  destined  chiefly  for  the  walls  of  the  blood-vessels  and  of  the  air- 
tubes.    Berkley  describes  interepithelial  end-arborizations  within  the  smaller  bronchi. 


THE   RELATIONS   OF   THE   LUNGS  TO  THE  THORACIC   WALLS. 

The  relations  of  the  median  and  diaphragmatic  surfaces  of  the  lungs  have  been 
given  (page  1844).  The  apex  rises  vertically  about  3  cm.  above  the  level  of  the  upper 
border  of  the  first  costal  cartilage  and  about  i  cm.  above  the  level  of  the  cla\icle. 
These  ul:;iances  are  to  be  reckoned  on  a  vertical  plane,  not  on  the  slanting  surface  of 
the  root  of  the  neck.  They  vary  extremely,  depending,  as  they  do,  on  the  formation 
of  the  body.  Thus  a  sunken  chest,  which  means  a  very  oblique  first  rib,  would  have 
more  lung  above  the  cartilage  than  a  full  chest  with  a  more  nearly  horizontal  first  rib. 
In  extreme  cases  the  lung  may  rise  as  much  as  5  cm.,  or  as  little  as  i  cm.,  above  the 
first  cartilage.  The  plane  of  the  inlet  of  the  chest  is  made  by  the  oblique  first  ribs. 
The  fibrous  parts  enclosing  it  are  dome-like,  the  roof  of  the  cavity,  to  which  the  lung 
is  closely  applied,  swelling  upward  perhaps  i  cm.  above  this  oblique  plane  ;  the 
top  of  the  lung,  however,  is  never  above  the  level  of  the  neck  of  the  first  rib.  It 
was  formerly  taught  that  the  right  lung  rises  higher  than  the  left.  As  a  rule,  there  is 
no  appreciable  difference  between  the  two  sides.  The  most  that  can  be  said  for  the 
old  view  is  that,  if  there  be  some  trifling  difference,  it  is  probably  rather  more  often 
in  favor  of  the  right.  The  anterior  borders  of  the  lungs  descend  obliquely  behind 
the  stemo-clavicular  joints,  knd  cur\'e  forward  so  as  to  nearly,  or  quite,  meet  in  the 
median  line  on  the  level  of  the  junction  of  the  manubrium  and  body  of  the  sternum. 
Below  this  the  '  "u  lung  extends  a  little  across  the  median  line  and  the  left  recedes 
slightly  fron  he  right  border  leaves  the  ste.num  at  the  sixth  right  costal  carti- 

lage, to  whit  i  gradually  cur-,  .'d,  runs  along  that  same  cartilage,  or  a  little  above 

it,  to  its  June.  vith  the  sixth  n'  hen  crosses  the  ribs,  passsing  the  eighth  at  about 
the  axillary  line,  and  reaches  the  spine  at  the  eleventh  rib  or  a  little  higher,  the 
guide  being  the  spine  of  the  tenth  thoracic  vertebra.  The  lowest  part  of  the  lung  is 
on  the  side  at  the  axillary  line  or  behind  it,  but  the  line  thence  along  the  back, 
although  rising  a  litde,  is  very  nearly  horizontal.  The  course  of  the  border  of  the  left 
lung  is  essentially  the  same,  except  that,  leaving  the  sternum  at  the  fourth  cartilage, 
or  at  the  space  above  it,  the  border  describes  a  curve  with  an  outward  convexity, 
exposing  a  large  piece  of  the  pericardium,  and  turns  forward  to  end  as  the  lingula 
opposite  the  sixth  cartilage,  some  distance  to  the  left  of  the  sternum.  As  this  point 
depends  on  the  development  of  the  lingula.  it  cannot  be  stated  accurately.  It  may 
be  said  in  general  to  be  3  or  4  cm.  to  the  left  of  the  median  line.  The  greatest  depth 
of  this  curve  is  in  the  fourth  intercostal  space,  about  5  cm.  from  the  median  line.  The 
course  of  the  inferior  border  along  the  side  and  back  is  practically  that  of  the  right 
one.  although,  perhaps,  the  left  lung  may  descend  a  trifle  lower  at  the  si<le.  At  the 
back  the  lower  borders  are  very  symmetrical. 

'  Sitzungsberichte  d.  Wiener  Akad.,  Bd.  Ixxxiv.,  1881. 


1856 


HUMAN  ANATOMY. 


Apiut  from  variations  in  the  lungs  themselves,  the  different  shapes  and  sizes  of 
the  chest,  with  the  consequent  differences  in  the  inclination  of  the  ribs,  make  these 
relations  very  uncertain,  especially  at.  the  side.  In  forced  respiration  there  is  no 
change  in  the  relations  of  the  top  of  the  lungs  and  the  dome  of  the  pleura,  as  they 
are  always  in  close  apposition,  and  but  litde  change  in  the  first  part  of  the  anterior 
borders.  The  latter,  however,  approach  one  another  behind  the  sternum  in  forced 
inspiration,  a  considerable  advance  oi  the  left  lung  taking  place  at  the  cardiac  notch. 
We  agree  with  Hasse  that  during  inspiration  the  antenor  parts  of  the  lungs  rise 
just  about  as  much  as  the  thoracic  walls.  The  greatest  changes  of  relations  are  below 
and  at  the  side.  It  is  said  that  in  the  axillary  line  the  border  may  descend  as  much 
as  from  3-4  cm.,  and  at  the  back  as  much  as  3  cm.  According  to  Hasse,'  the 
lower  border  of  the  lung  in  the  axillary  line  never  descends  nearer  to  the  lower  edge 
of  the  thoracic  wall  than  7  cm.  on  the  right  and  5  cm.  on  the  left.     He  finds  that  in 

Fio.  1580. 


/ 


SemidiaKrammatic  reconstruction,  showing  remiions  of  pleural  saca  (blue)  and  \nngs  (red>  to  thoracic  wall; 

anterior  aspect. 


extreme  expiration  the  lower  borders  of  the  lungs  rise  in  the  axillary  lines  to  13  cm. 
on  the  right  and  14  cm.  on  the  left  above  the  lower  border  of  the  chest.  He  states 
also  that  the  anterior  borders  may  withdraw  to  the  parasternal  lines  (vertical  lines 
dropjjed  from  the  inner  third  of  the  clavicles),  which  to  us  appears  excessive.  In 
our  opinion,  the  great  factor  in  the  expansion  of  the  li'n^  is  the  increase  in  the  vari- 
ous diameters  of  the  chest  rather  than  the  changes  of  relation  of  the  borders  of  the 
lungs  to  the  walls. 

The  re/a/ions  of  the  fissures  to  the  surface  are  rather  variable.  The  chief  ones 
ascend  from  the  hila  and  reach  the  posterior  surface  at  the  sides  of  the  vertebral  col- 
umn, generally  at  different  levels,  the  right  being  the  lower.     We  must,  therefore, 

'Die  Formen  des  inenschlichen   Korpers  und  die   Formanderungen  bei  der  Athmung, 
jena,  1888  and  1890. 


THE  LUNGS, 


1857 


trace  the  course  of  each  fissure  separately.  The  fissure  of  the  right  luns  leaves  the 
vertebral  column  either  at  the  fifth  rib  or  at  the  interspace  above  or  below  it  The 
fissure  tends  to  follow  the  fifth  rib,  being  in  the  axillary  line  still,  either  beneath  it  or 
beneath  an  adjacent  intercostal  space.  Towards  the  front  the  fissure  gets  relatively 
lower,  ending  in  most  cases  either  at  the  fifth  space  or  beneath  the  sixth  rib,  near 
the  junction  of  the  bone  and  cartilage,  from  5-10  cm.  from  the  median  line.  The 
secondary  fissure  of  the  right  lung  leaves  the  chief  one  somewhat  behind  the  axillary 
line,  and,  running  about  horizontally  forward,  ends  at  a  very  uncertain  point 
Rochard,  in  his  small  series  of  twelve  observations,  found  it  at  the  third  intercostal 
space  seven  times.  Once  it  was  higher  and  four  times  lower.  The  fissure  of  the  left 
lung  leaves  the  side  of  the  spine  at  a  less  definite  point,  ranging  in  most  cases 
from  beneath  the  third  rib  to  the  upper  border  of  the  fifth,  and  being  sometimes  even 

Fio.  1 581. 


N 


SetnlHiflffntmmfttic  reconslriution.  showinfc  relations  <»f  pleural  sacs  (bluel  and  lungs  (red)  to  body-w-all; 

ptMterior  as|>et't. 


lower.  At  the  axillary  line  it  is  at  the  fifth  rib  a  little  more  often  than  at  any  other 
particular  point,  but  it  is  almost  as  often  at  the  fourth  and  more  often  somewhere 
below  the  fifth.  Its  termination  is  more  constant  than  its  course,  being  beneath  the 
sixth  rib,  or  the  space  above  or  below  it,  usually  from  6-1 1  cm.  from  the  median 
line.' 

The  relations  of  the  bronchi  to  the  chest-wall  have  not  been  studied  on  a  suffi- 
cient number  of  bodies  for  satisfactory  conclusions.  Blake'  has  had  X-ray  photo- 
graphs taken  of  an  adult  body  hardened  with  formalin,  the  bronchi  being  injected 
with  an  opaque  substance.     The  bifurcation  was  normally  placed.     We  attach  the 

■Gazette  des  HApitaux,  1892.    Our  description  is  almost  wholly  a  synopsis  of  Rochard's 
work. 

•  American  Journal  of  the  Medical  Sciences,  1899. 

>i7 


,  i  ; 


1858 


HUMAN  ANATOMY. 


most  importance  to  the  course  of  the  main  bronchus  :  "On  the  posterior  w^l  the 
course  of  the  left  bronchus  is  from  a  point  to  the  right  of  the  fourth  thoracic  spine  to 
a  point  on  the  eighth  rib  three  inches  to  the  left  of  the  spine.  The  course  of  the 
right  bronchus  is  from  the  same  point  above  to  a  point  on  the  eighth  rib  two  inches 
to  the  right  of  the  spine.  On  the  anterior  wall  the  course  of  the  left  bronchus  is  from 
the  lower  part  of  the  second  right  sterno-chondral  articulation  to  a  point  on  the  fifth 
rib  just  internal  to  the  mammiilary,  and  of  the  right  bronchus  from  the  same  point 
above  to  the  intersection  of  the  fifth  rib  with  the  parasternal  line."  The  hilum  is 
opposite  the  bodies  d  the  sixth  and  seventh  thoracic  vertebrx  and  a  part  of  the 
adjacent  ones.     (Figs.  1569  and  1570.) 

(The  changes  of  the  relations  of  the  lungs  during  growth  and  in  old  age  are 
considered  with  those  of  the  pleurae. ) 


:' 


!!! 

in 

!i  i 


It 

'I  i 

iif 


Fio.  t58a. 


THE   PLEURA. 

The  pleurse  are  a  pair  of  serous  membranes  disposed  one  over  each  lung  and  then 
reflected  so  as  to  line  the  walls  of  the  cavity  containing  it,  thus  forming  a  distinct 
clewed  sac  about  each  lung  ;  hence  the  pleura  is  divided  into  a  viscera/ and  a  parietal 
layer.     The  latter  is  subdivided  according  to  its  situation  into  a  mediastinal,  a  costal, 

a  cervical,  and  a  diaphragmatic  part. 
The  visceral  layer  closely  invests  the 
lung,  following  the  surface  into  the 
depth  of  the  fissures.  It  leaves  the 
lung  at  the  borders  of  the  hilum  and 
invests  the  root  for  a  short  distance 
(1-2  cm.),  when  it  leaves  the  latter 
and  spreads  out  as  the  mediastinal 
pleura,  which  is  applied,  back  to 
back,  to  the  pericardium,  thus  form- 
ing on  each  side  a  vertical  antero- 
posterior septum  between  the  lungs 
and  the  contents  of  the  mediastina. 
The  prolongation  over  the  root  is  not 
quite  tubular,  since  a  triangular  fron- 
tal fold  extends  from  beneath  the  root 
to  the  inner  side  of  the  lung,  growing 
narrower  as  it  descends,  to  end  at  or 
near  the  lower  borders.  This  is  the 
broad  ligament  of  the  lung  ( ligamen- 
tam  latum  pulmonis ).  Its  line  of  at- 
tachment to  the  lung  often  slants 
backward.  The  mediastinal  pleura, 
besides  being  applied  to  the  side  of 
the  pericardium,  lies  also  against  some 
of  the  structures  of  the  other  medi- 
astina. Above  it  is  in  contact  with  the 
thymus  on  both  sides,  the  superior 
vena  cava  on  the  right  and  the  arch 
of  the  aorta  on  the  left.  The  phrenic 
nerve  descends  on  each  side  between 
it  and  the  pericardium  in  front  of  the 
root  of  the  lung.  In  the  posterior 
mediastinum  it  lies  against  the  left  side  of  the  descending  aorta  and  the  right  of  the 
upper  part  of  the  greater  azygos  vein.  It  is  in  contact  with  nearly  the  whole  of  the 
oesophagus  on  the  right,  and  just  before  the  latter  pas.ses  through  the  diaphragm  on 
the  left  also.  It  covers  the  gangliated  cord  of  the  sympathetic  on  both  sides  as  it 
passes  into  the  costal  pleura,  and  is  here  stretched  so  tightly  across  the  terminations 
of  the  intercostal  veins  as  to  keep  their  walls  distended.  Anteriorly  it  crosses  the 
areolar  tissue  of  the  anterior  mediastinum  below  the  remnants  of  the  thymus.     It 


Semidiarrammalic  recoiistruition.  showinif  relations  of 
right  pleurafsac  (blue)  and  lung  (red)  to  thoracic  wall ;  lateral 
aspect. 


THE    PLKURiC. 


»«59 


is  continued  outward,  both  before  and  behind,  to  become  the  costal  pleura,  and  is 
continuous  above  with  the  cervical  pleura  which  lines  the  dome  in  the  concavity  of 
the  first  rib.  It  |>asses  lielow  into  the  diaphragmatic  pleura  which  invests  the  upper 
surface  of  the  diaphrat^m.  Laterally,  and  still  more  behind,  it  follows  for  a  certain 
distance  the  vertical  fibres  of  the  diaphragm,  and  then  is  reflected  onto  the  thoracic 
wall  so  as  to  line  a  ]x>tential  cavity  between  the  two  layers  which,  except  (or  some 
litde  serous  fluid,  are  here  in  apposition.  Villous  projections  occur  alont;  the  borders 
of  the  lun^,  especially  at  the  inferior  border,  where  they  form  a  dense,  but  very 
minute  fringe,  not  over  i  mm.  broad. 

Relations  of  the  Pleurc  to  the  Surface.— In  some  places  the  lun^s  and 
the  pleura;  are  always  in  the  same  relation  ;  in  others  the  |)leuru;  extend  a  certain 
distance  beyond  the  lungs,  which  fill  them  in  complete  inspiration  so  that  their  out- 
lines correspond ;  in  other  places  the 

pleurae  extend  so  much  beyond  the  lungs  ''°-  '5*3- 

that  even  in  the  most  extreme  inspira- 
tion the  latter  do  not  reach  the  limits  of 
the  former.  At  the  apices  the  relations 
of  the  lungs  and  pleurie  are  constantly 
the  same,  both  being  in  contact.  All 
that  has  been  said  of  the  relation  of  one 
to  the  body-walls  is  true  of  the  other. 
Behind  the  first  piece  of  the  sternum  the 
relations  are  nearly  the  .>.ime,  but  below 
this  level  a  space  exists  in  the  pleiir»- 
into  which  the  lungs  enter  during  deep 
inspiration.  This  is  notably  the  case  at 
the  left  halt  of  the  body  of  the  sternum. 
The  pleurae  present  inferiorly  at  the  sides 
and  behind  a  merely  potential  cavity 
between  the  diaphragm  and  the  chest- 
wells,  to  the  bottom  of  which  ( probably 
at  the  sides  and  certainly  behind)  the 
lungs  can  never  descend.  The  pleurae, 
however,  never  approach  closely  the 
lower  border  of  the  chest  at  the  sides, 
for  the  diaphragm  arising  from  the  inner 
surface  of  the  frame  of  the  thorax  takes 
up  a  certain  amount  of  space,  and  above 
it  the  connective  tissue  fills  the  cleft  so 
that  the  pleura*  do  not  descend  to  within 
3  cm.  of  the  lower  border.  In  the  sub- 
ject used  by  Ha?se  the  space  in  the  ax- 
illary line  below  the  reflection  of  the 
pleurae  to  the  origin  of  the  diaphragm 
(the  lower  border  of  the  chest)  was  5.5  cm.  on  the  right  and  4  cm.  on  the  left. 

The  outlines  of  the  pleura  are  as  follows.  Beginning  at  the  apex,  about  3 
cm.  vertically  above  the  cartilage  of  the  first  ribs,  the  anterior  borders  descend 
behind  the  stemo-clavicular  joints  to  meet  at  the  median  line  at  the  level  of  the 
second  cartilage.  They  then  descend  together,  or  nearly  so,  behind  the  left  half  of  the 
body  of  the  sternum.  Half-way  down  the  body  of  the  sternum  the  left  pleura  tends 
to  diverge  to  the  left,  pa.ssing  from  behind  the  sternum  usually  at  about  the  junction 
*ith  the  sixth  cartilage.  The  right  pleura  descends  more  nearly  in  a  straight  line  and 
turns  suddenly  outward  at  the  level  of  the  seventh  cartilage.  Laterally  the  pleurae  run 
pretty  close  to  the  cartilages  of  the  sixth  rib  on  the  left  and  the  seventh  on  the  right, 
but  both  cross  the  eighth  rib  at  or  near  the  junction  of  bone  and  cartilage.  In  the  axillary 
line,  or  a  little  behind  it,  the  pleura  crosses  the  tenth  rib  at  about  the  same  place  on 
both  sides,  and  usually  endr,  posteriorly  opposite  the  lower  part  of  the  twelfth  thoracic 
vertebra,  the  right  one  being  often  the  lower  (Tanja).  While  such  is  the  general 
outline,  there  are  considerable  and  important  variations  both  anteriorly  and  pos- 


SemidlatframmaUc  rtrcun»tructiun,  showing  relatione  of 
left  pleural  sac  (blue)  and  lung  (red)  to  thoracic  wall; 
lateral  aspect. 


I 


l^f 


i860 


HUMAN  ANATOMY. 


Fio.  1584. 


tertoriy.  The  former  teaching,  according  to  which  the  left  (deuia  describes  at  the 
front  a  curve  somewhat  similar  to  that  of  the  left  lung,  is  auite  wrong.  However,  the 
point  at  which  it  leaves  the  sternum,  the  extent  to  which  it  is  in  contact  with  the 
right  pleura,  and  the  distance  the  latter  advances  under  the  sternum  are  all  very 
uncertain.  The  roost  important  point  is  the  extent  to  which  the  pleura  covers  the 
peticardium.  According  to  Side's'  observations  on  twenty-three  bodies  of  adults, 
the  reflection  of  the  left  pleura  at  the  fifth  cartilage  was  in  seventeen  either  behind 
the  sternum  or  just  at  its  border  ;  thus  it  left  the  sternum  at  a  higher  point  only  six 
times.  At  the  sixth  cartilage  the  pleura  was  ten  times  behind  the  sternum  and  less 
than  I  cm.  from  it  in  six.  At  the  seventh  cartilage  it  was  five  times  at  the  border  of 
the  sternum  or  behind  it  and  Ave  times  not  over  t  cm.  external  to  it.  It  left  the 
sternum  close  to  the  seventh  cartilage  five  times.  Tanja,*  however,  found  the  left 
pleura  leaving  the  sternum  at  the  fourth  cartilage  in  four  of  fourteen  bodies  ranging 

from  eight  years  upward.  The  left  pleura  may  ex- 
ceptionally cross  the  median  line,  and,  it  is  said,  mav 
not  extend  forward  as  far  as  the  sternum  ;  but  such 
a  condition  must  be  very  exceptional.  There  is  con- 
siderable variation  as  to  the  depth  of  the  descent 
posteriorly.  Tanja  never  found  the  lower  fold  at 
the  back  in  the  adult  higher  than  the  middle  of  the 
last  thoracic  vertebra.  It  may  descend  to  the  first 
lumbar  and  even  to  the  second. 

Structure. — The  pleura,  like  other  serous  mem- 
branes, consists  of  a  stroma-layer  composed  of  bun- 
dles of  fibrous  tissue  intermingled  with  numerous 
elastic  fibres.  The  general  disposition  of  the  con- 
nective-tissue bundles  is  parallel  to  the  free  surface, 
although  the  bundles  cross  one  another  in  various 
directions.  The  free  surface  of  the  pleura  is  covered 
with  a  single  layer  of  nucleated  endothelial  cells 
(from  .020-.045  mm.  in  diameter),  which  rest  upon 
a  delicate  elastic  limiting  membrane  differentiated 
from  the  stroma-layer.  The  existence  of  definite 
openings,  or  stomata,  between  the  endothelial  plates, 
leading  into  the  numerous  lymphatics  of  the  pleura, 
is  doubtful. 

The  subserous  layer  is  very  thin  over  the  lung 
where  it  is  continuous  with  the  elastic  interlobular 
tissue.  In  the  mediastinum  it  has  a  firm  fibrous 
backing  so  as  to  make  a  strong  and  dense  membrane. 
The  cervical  pleura  is  extremely  thick  and  resistant,  being  strengthened  by  fibrous 
or  muscular  bands  from  the  system  of  the  scaleni  muscles  spreading  into  it  from 
behind,  as  well  as  by  expmsions  from  the  areolar  tissue  about  the  trachea,  oesopha- 
gus, and  subclavian  vessels.  The  costal  pleura  has  a  subserous  layer,  known  as  the 
fascia  endothoracica,  through  which  it  is  attached  to  the  thoracic  walls  less  closely 
than  elsewhere.  This  fascia  is  thickest  near  the  top.  The  ribs  show  clearly  through 
the  pleura  of  the  opened  thorax,  appearing  light  in  contrast  to  the  congested  inter- 
costal spaces.  The  subserous  layer  is  hardly  existent  beneath  the  diaphragmatic 
pleura,  but  at  the  sides  of  the  thorax  there  is  a  considerable  space  below  the  reflection 
of  the  pleura  from  the  diaphragm,  occupied  by  areolar  tissue  connecting  the  dia- 
phragm and  walls. 

Blood-Vessels. — The  arteries  of  the  visceral  pleurae  have  been  shown  by 
Miller  to  come  from  the  system  of  the  pulmonary  arteries  instead  of  from  that  of 
the  bronchial,  as  previously  believed.  They  form  a  tine  net-work  over  the  lung. 
Those  of  the  parietal  pleurae  come  from  the  aortic  and  superior  intercostals.  the  in- 
ternal mammaries,  the  mediastinal,  the  oesophageal,  the  bronchial,  and  the  phrenic 
arteries. 

'  Archiv  f.  .Anat.  n.  Phys.,  Anat.  Abth.,  1885. 
•  Morphol.  Jahrhiich,  1891. 


Endothelium 
or  free  siirfat-e 


iiiiective-UMUe 
stroma  of  pleura 


Strrtiun  throujtih  free  cdfte  of  Iuiik.  show- 
ing visi-er«l  pleura,    v  ly). 


THE   PI,EUR/F.. 


1H61 


Injrctcfl  IvmphiilU-ii  nl  plcun,  acm  from  turticc. 

.  7,1.     iMillrr.) 


The  veiMt  of  the  visceral  pleurx  are  tribuUry  to  the  pulmonary  system  ;  those 
of  the  parietal  pleurae  open  into  the  veins  correspondinK  to  the  arteries.  It  » 
important  to  note  that  the  intercostal  spaces  have  many  veins  and  that  the  pleura 
over  the  libs  lias  but  lew,  these  chiefly  communicating  with  the  veins  above  and 

below  them.  Owin^;  to  the  arrangement  by 
which  the  intercostal  veins  are  kept  open,  the 
venous  circulation  of  the  |)arietsd  pleurae  is 
under  the  influence  of  the  suction  power  both 
of  respiration  and  of  the  heart. 

The  lymphatics  are  numerous  over  the 
lungs  and  also  in  the  intercostal  spaces. 
Those  of  the  parietes  open  into  both  inter- 
costal and  substernal  lymph-nodes. 

Nervet. — The  nerves  of  the  visceral 
picurx  are  from  the  pulmonary  plexuses,  con- 
taining both  pneumogastric  and  sympathetic 
fibres  ;  those  of  the  parietal  pleura  are  from 
the  intercostal,  the  phrenic,  the  sympathetic, 
and  the  pneumogastric  nerves. 

Development  of  the  Respiratory 
Tract. — The  respiratory  tract  develops  as 
an  outgrowth  from  the  primitive  digestive 
tube.  Early  in  the  third  week,  in  embryos 
of  little  over  j,  mm.  in  length,  a  longitudinal 
groove  appears  on  the  ventral  wall  of  the  fore-gut,  extending  from  the  primitive 
pharynx  above  well  towards  the  stomach  below.  This  groove  becomes  deeper, 
constricted,  and  finally  separated  from  the  fore-gut  as  a  distinct  tube,  the  differen- 
tiation resulting  in  the  production  of  two  canals, — the  respiratory  tube  in  front  an<l 
the  oesophagus  behind.  Separation  and  completion  of  the  former  proceeds  from 
the  lower  end  of  the  groove  upward  as  far  as  the  pharynx,  into  which  both  ceso|>ha- 
gus  and  air-tube  open.  The  cephalic  end  of  the  latter  becomes  enlarged  and  forms 
the  larynx,  the  adjoining  portion  correspond- 
ing to  the  trachea. 

The  Lungs. — The  distal  extremity  of 
the  primary  respiratory  tube  soon  enlarges 
and  becomes  bilobed,  pouching  out  on  each 
side  into  a  lateral  diverticulum  which  rep- 
resent- the  primitive  bronchus  and  lung. 
These  .  ulmonary  diverticula  elongate  and 
subdivide,  the  right  one,  which  is  somewhat 
the  larger,  breaking  up  into  three  secondary 
divisions  and  the  left  into  two,  thus  early 
foreshauowing  tK  liter  asymmetry  of  the 
lung-lobes.  Sii.  j  the  primary  air-tube  lies 
medially  in  the  dorsal  attachment  of  the  sep- 
tum transversum,  the  pulmonary  buds  extend 
laterally  and  backward  into  the  dorsal  parie- 
tal recesses  (later  the  pleural  cavities),  carry- 
ing before  them  a  covering  of  mesoblast. 

The  primary  lobes  increase  in  size  and 
complexity  as  additional  outgrowths  arise  by 
the  division  of  the  enlarged  terminal  part  of 
each  diverticulum.  The  resulting  divisions, 
or  new  bronchi,  are  at  first  equal,  but  soon 
grow  at  an  unequal  rate,  the  one  elongating 
most  rapidly  becoming  so  placed  as  to  continue  the  main  air-tube,  while  the  less 
rapidly  elongating  division  becomes  a  lateral  branch.  The  repeated  bifurcation  in 
this  manner  results  in  the  production  of  a  chief  bronchus,  traversing  the  entire 
length  of  the  lung,  into  which  open  numerous  lateral  tubes  or  secondary  bronchi. 


Fio. 


Prinilive 
oropharynx 


M»lian  th>r(iii(' 
aiilagc 


CEsophag^!'. 


Lung-tutx' 


Part  of  sagittal  Mction  o(  rabbit  einbr>  o.  »h<i»  - 
inc  lunK-tubc  growiflffdownwaftl  and  forward  frcHii 
primitive  larynKo-pharynx.    X  40. 


1863 


HUMAN  ANATOMY. 


: 


Fio.  1587. 


The  latter,  from  their  relation  to  the  principal  stem  of  the  pulmonary  artery  which 
i«ccom|«anie9  the  chief  air-tube,  are  regarded  as  dorsal  and  ventral.  They  alternate 
with  one  another,  and  usually  number  four  in  each  series  ;  not  infrequently,  how- 
ever, the  third  dorsal  bronchus  fails  to  develop,  thereby  leading  to  a  corresponding 
reduction  and  asymmetry  in  the  scries.  In  the  left  lung  the  lirst  dorsal  bronchus 
springs  from  the  corresponding  ventral  bronchus  inittead  of  the  chief  tube,  as  on 
the  right  side.  This  arrangement  is  probably  associated  with  the  fusion  of  the 
upper  and  middle  lobes  in  the  left  lung. 

The  secondary  bronchi  elongate  and  give  origin  to  tertiary  bronchi,  and  these, 
in  turn,  to  air-tubes  of  lesser  calibre,  until  the  ramifications  end  as  terminal  bronchi 
and  the  associated  divisions — atria,  air-sacs,  and  alveoli— of  the  lung-unit.  Since 
the  fore-gut  is  clothed  with  entoblast,  it  is  evident  that  the  lining  of  the  respiratory 
tract  is  derived  from  the  same  germ-layer.  At  first  the  outpouchings  of  the  respira- 
tory tube  are  surrounded  by  relatively  thick  masses  of 
mesoblastic  tissue.  Since  tfie  growth  of  the  latter  fails 
to  keep  pace  with  the  increasing  mass  and  complexity 
of  the  bronchial  tree,  the  intervening  mesoblast  bi.'C')iii»s 
greatly  reduced.  Coincidently  the  mesoblast  becomes 
vascular  and  rich  net-works  of  blood-vessels  appear 
between  the  terminal  divisions  of  the  epithelial  tubes, 
later  forming  the  chief  constituents  of  the  alveolar  walls. 
The  mesoblastic  tissue  remains  between  the  lobules  as 
the  interlobular  septa,  as  well  as  contributing  all  con- 
stituents of  the  walla  of  the  air-tubes  except  the  lining 
e  ithelial  and  its  glandular  derivatives,  which  are  ento- 
bl.  ••'-  By  the  close  of  the  fourth  month  of  foetal  life 
the  Um  columnar  cells  lining  the  trachea  and  bronchi 
acquire  cilia.  The  peripheral  layer  of  the  mesoblast 
invaded  by  the  lungs  eventually  becomes  the  investing 
serous  membrane,  or  pulmonary  pleura,  all  parts  of 
which  are  of  mesoblastic  origin.  Before  inflation  occurs 
at  birth,  the  lung-tissue  is  com[>aratively  solid  and  re- 
sembles in  many  ways  a  racemose  gland.  With  the 
expansion  following  the  establishment  of  respiration,  the 
epithelial  celb  lining  the  ultimate  air-spaces  undergo 
stretching,  a  majority  of  the  small  polygonal  elements 
becoming  converted  into  the  flat  plate-like  cells  seen 
in  the  functionating  lung. 

The  Larynx. — The  pharyngeal  end  of  the  pri- 
mary respiratory  tract  is  surrounded  in  front  and  later- 
ally by  a  U-shaped  ridge,  known  as  the/urcu/a,  anterior 
to  which  lies  the  paired  posterior  aniage  of  the  tongue. 
The  anterior  portion  of  this  ridge  forms  a  median  ele- 
vation from  which  is  formed  the  epiglottis  ;  the  lateral 
portions  cotistitute  the  arytenoid  ridges  which  bound  the  laryngeal  aperture  at  the 
sides.  During  the  fourth  month  a  furrow  on  the  median  side  of  the  arytenoid  ridges 
marks  the  first  appearance  of  the  ventricle  of  the  larynx,  the  margins  o!  the  groove 
later  becoming  the  vocal  cords.  About  the  eighth  week  the  cartilaginous  framework 
is  indicated  by  mesoblastic  condensations.  The  thyroid  cartilage  consists  for  a  time  of 
two  separate  lateral  mesoblastic  plates,  in  each  of  which  cartilage  is  formed  from  two 
centres.  These  are  regarded  as  representing  the  cartilages  of  the  fourth  and  fifth 
branchial  arches.  As  development  proceeds  the  cartilages  formed  at  these  centres 
fuse  and  extend  vcntrally  until  they  unite  anterioriy  in  the  mid-line.  Chondrification 
is  completed  comparatively  late,  and  when  incomplete  or  faulty  may  result  in  the 
production  of  an  aperture,— the  thyroid  foramen.  The  aiilages  of  the  cricoid  .ind 
arytenoid  cartilages  are  at  first  continuous,  but  later  become  differentiated  bv  the 
appearance  of  a  centre  of  chondrification  for  each  arytenoid  and  an  incomplete  ring, 
for  a  time  open  behind,  for  the  cricoid.  The  latter  thus  resembles  in  development 
a  tracheal  ring,  with  which  it  probably  morphologically  corresponds.     The  cartilages 


Reconstructions  of  developing 
bronchial  tree.  A,  fourth  week  ;  K, 
heKinninf(  of  6fth  week ;  C.  close  ol 
fiftliweek.    (His-Mtrktl.) 


THE   PLF.UR.f:. 


i86.^ 


of  WrisherK  (cuneiform)  and  o(  Santorini  (curnicula  laryngw)  are  formed  from 
•mall  portions  sc(>arated  from  the  epi|{lottiit  and  the  arytenoids  respectively.     The 


Nt«ral  canal 
ll|4ral  raril 
SpiiMl  nnrilion 


Pio.  ISS& 


*,-V«t«bf» 


Cardhal  vdi 


Rifht  lun(«> 


Right  bronchus 

Diaphrmitm 
luiehur  vena  cava 


Left  bronchua 


Lhrer 


Poitinn  o(  tranavcnc  aertion  of  rabbit  enibr>o.  showinf  drvelopinR  lunip.    v  js. 

ep^lottis  and  the  cricoid  possibly  represent  rudiments  of  the  cirtilages  of  the  sixth 

and  seventh  branchial  arches. 
Fio.  1589.  Changes  in  the  Relations  of 

the  Lungs  and  Pleura  to  the 
Chest-Walls. — At  birth  the  thorax 
is  small,  relatively  very  narrow,  with 
the  lower  part  undeveloped  and  with 
more  horizontal  ribs.  The  costal  car- 
tila(;es  are  relatively  lonjj  to  the  ribs 
proper.  Nevertheless,  at  birth  and  in 
childhood  the  borders  of  the  lungs  have 
very  nearly  the  same  relations  to  the 
chest-walls  that  they  have  in  the  adult, 
excepting  in  front.  Here  they  do 
not  extend  so  far  forward,  and  conse- 
quently the  pericardium  is  at  first  less 
covered  by  the  left  lung.  The  course 
of  the  pleur*  is  much  less  certain. 
Tanja  found  much  variation  in  that  of 
the  lower  borders  of  the  pleurae,  the 
latter  crossing  all  the  costal  cartilages 
fourteen  times  in  twenty-four  bodies 
of  children  under  two  years  and  not 
a  single  time  in  the  adult.  In  eleven 
of  the  same  series  the  pleurae  did  not 
meet  behind  the  sternum,  and  in  nine 
the  left  pleura  did  not  reach  it.  He  found  neither  of  these  conditions  even  once 
in  the  adult.     According  to  Mehnert,  there  is  a  very  slight  progressive  sinking  of 


Secliuii  of  fuKal  Iuhk.  sIu'winK  t«i"iiavl  ct.anii:tcr  oi  unin- 
flated  pulni<>nar>'  liasiw.     X  Joo. 


1864 


HUMAN  ANATOMY. 


the  lower  border  of  the  lung  during  the  period  preceding  old  age,  which  is  more 
rapid  than  the  senile  increase  of  the  declination  of  the  ribs. 


-r 


'' 


PRACTICAL  CONSIDERATIONS:   THE  LUNGS  AND  PLEURA. 

The  Lungs  and  Pleurc — Many  of  the  most  important  practical  questions 
arising  in  cases  of  injury  or  disease  of  the  lungs  and  pleurae  can  be  answered  only 
after  a  physical  examination,  the  value  of  which  will  depend  primarily  upon  com- 
plete knowledge  of  the  normal  phenomena  associated  with  respiration.  Such 
knowledge  must  be  based  upon  acquaintance  with  the  structural  conditions  that 
influence  the  sounds  caused  by  a  current  of  air  entering  and  leaving  the  normal  air- 
passages  and  with  the  chief  modifications  caused  by  disease. 

Only  a  few  of  even  the  most  elementary  facts  bearing  upon  this  subject  can  here 
be  mentioned,  but  their  consideration  at  a  time  when  the  pulmonary  system  is  being 
studied  can  scarcely  fail  to  be  of  practical  value,  and  is  necessary  to  an  understanding 
of  those  symptoms  of  pulmonary  or  pleural  injury  or  disease  which  have  the  most 
obvious  anatomical  bearing. 

Anatomical  Basis  for  Varied  Character  of  Breath-Sounds. — The  normal  sounds 
of  respiration  vary  with  the  situation  of  the  air-passages  examined.  Their  loudness 
is  in  direct  proportion  to  their  nearness  to  the  larynx,  so  that  laryngeal,  tracheal, 
bronchial,  and  vesicular  breathing  sounds  are  here  mentioned  in  the  order  that  indi- 
cates progressively  increasing  softness. 

Those  terms  acquire  pathological  significance  when  breathing  of  one  type  is 
heard  in  a  portion  of  the  chest  where  it  should  not  be  heard.  The  nearness  of  the 
larynx  to  the  surface  and  its  inclusion  of  air,  as  if  within  a  hollow  box  (West;, 
make  laryngeal  sounds  loud  and  noisy  on  both  expiration  and  inspiration.  In  the 
trachea,  part  of  which  is  deeper,  and  a  portion  of  the  walls  of  which  is  of  soft 
muscular  and  fibrous  tissue,  both  these  sounds,  as  heard  over  the  suprasternal  notch, 
or  over  the  lower  cervical  or  upper  dorsal  vertebrae,  while  still  loud,  are  softer  and 
are  raised  in  tone.  Over  the  bronchi,  heard  best  between  the  scapulae  (page  1842), 
they  are  both  audible  and  are  harsh,  but  have  still  further  diminished  in  loudness. 
Over  the  pulmonary  tissue  inspiration  has  become  soft  and  blowing  and  expinition 
can  scarcely  be  heard.  The  reasons  for  these  differences  are  as  follows.  The  sounds 
of  breathing  are  produced  chiefly  at  or  about  the  glottis,  therefore  distance  from  the 
larynx  accounts  for  the  diminution  in  loudness.  The  decrease  in  the  diameter  of 
the  air-tubes  accounts  for  the  rise  in  pitch  of  the  respiratory  note.  The  entrance  of 
the  air  into  compartments  of  various  sizes  within  the  pulmonary  tissue  breaks  up  the 
air-column  which  carries  the  sound  and  distributes  the  vibrations,  so  that  the  sounds 
are  mufiied  and  soft  (West). 

If  the  bronchial  tubes  or  tubules  are  obstructed,  as  from  hyperaemia  of  the 
mucosa,  or  the  presence  of  viscid  secretion,  the  exit  of  air  will  be  interfered  with, 
and  there  will  be  "  prolonged  expiration." 

In  a  broad  way,  it  may  be  said  that  in  cases  in  which  vesicular  breathing  is  dimin- 
ished or  absent  the  cause  should  be  sought :  (i)  In  obstruction  (pseudo-membrane 
or  fibrinous  exudate).  (2)  In  compression  (aneurism,  glandular  swellings,  medias- 
tinal tumors).  (3)  In  immobilization  of  the  chest-wall  on  the  affected  side  (fracture 
of  rib,  intercostal  neuralgia,  pleurisy  or  pleuritic  adhesions).  (4)  In  distention  of 
the  pleura  by  liquids  or  air  (pneumothorax,  empyema).  If  as  a  result  of  disease 
the  vesicular  structure  is  occupied  by  an  exudate  (as  in  pneumonia),  the  vibrations  are 
conveyed  more  directly  to  the  ear,  expiration  becomes  audible,  and,  as  consolidation 
increases,  the  sounds,  first  of  the  smaller  bronchioles  and  then  of  the  larger  bronchi, 
replace  the  normal  blowing  sound,  and  "bronchial  breathing"  Is  established.  If  the 
cavity  of  the  pleura  is  distended  with  air  {pneumothorax),  which  separates  the  lung- 
tissue  from  the  thoracic  wall  and  conducts  sound  vibrations  much  less  effectively 
than  do  solids,  the  breath-sounds  will  be  feeble  and  disUnt  or  absent.  If  the 
pleural  cttvi;.y  is  so  filled  with  either  air  or  fluid  {empyema)  that  the  lung  is  collapsed 
or  compressed  against  the  spine,  the  breath-sounds  may  be  feebh  or  distant  or  entirely 
wa^Iing  over  the  front  and  sides  of  the  chest,  but  bronchial  breathing  can  be  heard 
o\'e)  the  back.     In  exceptional  cases  of  pleural  effusion  such  breathing  is  also  heard 


PRACTICAL  CONSIP-V  /  TIONS  :   THE  LUNGS  AND  PLEUR/E.    1865 


over  the  sides  and  front,  and  it  has  been  suggested  that  this  is  due  to  contact  hetwi-en 
a  bronchus  and  a  rib,  the  latter  conveying  the  breath-sounds  directly  to  the  . 

If  the  larynx  or  trachea  is  narrowed,  the  air  has  to  pass  through  a  constricted 
aperture,  must  do  so  at  a  greater  rate,  and  will  make  a  louder  noise, — stridor. 

R&les  are  caused  by  changes  in  the  mucous  and  epithelial  lining  and  contents 
of  the  air-passages.  Like  the  normal  breath-sounds,  they  are  louder  and  noisier  the 
nearer  they  are  to  the  larynx  or  the  larger  the  tubes  in  which  they  are  produced. 

Mucous  r&les  are  moist,  are  thought  to  be  produced  by  the  bursting  of  air- 
bubbles  in  viscid  c-  watery  mucus  occupying  the  larger  air-passages,  as  in  bronchitis, 
and  vary  in  character  (i.e.,  in  fineness  or  coarseness,  or  in  loudness)  in  accordance 
with  the  size  of  the  tube  that  they  occupy.  The  bubbling  of  air  through  the  ac- 
cumulating mucus  in  the  larynx,  trachea,  and  bronchi  of  a  moribund  person — the 
"  death-rattle" — is  an  example  of  the  larger  kind  of  mucous  riles. 

Crepitant  r&les  arc  dry  r&les,  due,  it  is  thought,  to  the  gluing  together  of  the 
opposing  surfaces  of  a  number  of  air-vesicles  by  an  exudate,  the  entrance  of  air  on 
inspiration  then  causing  a  fine  crackling  sound,  ' '  like  that  which  is  heard  when  a 
small  bunch  of  hair  near  the  ear  is  rolled  backward  and  forward  between  the  tips  of 
the  finger  and  thumb"  (Owen).  If  a  similar  condition  affects  the  lumen  of  a  tube, 
\*  may  produce  larger  riles,  still  dry,  known  as  rhonchi  (%nox'm^~)  ox  sibili  (hissing). 
Other  factors  enter  into  the  production  of  riles,  but  the  chief  underlying  anatom- 
ical conditions  have  been  mentioned. 

Air  entering  a  cavity  (pulmonary  vomicig,  bronchiectasis)  causes  a  sound  re- 
sembling that  produced  by  blowing  into  an  empty  bottle, — amphoric.  A  peculiar 
sound  heard  often  in  pneumothorax,  and  caused  by  the  air  from  the  fistulous  com- 
munication with  the  lung  entering  the  pleural  cavity  and  producing  a  bubbling 
sound  at  the  orifice,  is  described  as  metallic  tinkling.  It  is  also  thought  to  be  due  to 
the  dropping  of  liquid  into  an  accumulation  of  fluid  at  the  base  of  the  pneumo- 
thorax. 

Voice-sounds,  like  breath-sounds,  are  louder  over  the  laryngeal,  tracheal,  antl 
bronchial  regions.  When  the  voice  seems  very  close  and  loud  to  the  ear  placed 
over  other  regions  (^pectoriloquy,  bronchophony),  it  indicates  increased  power  of 
conduction, — i.e.,  consolidation  of  lung- tissue. 

If  the  tremor  from  the  vibration  of  the  vocal  cords  in  speaking  (vocal fremitus) 
is  transmitted  with  increased  distinctness  to  the  hands  placed  on  the  surface  of  the 
thorax,  it  has  the  same  significance.     If  it  is  absent,  it  usually  indicates  the  interpo- 
sition of  some  relatively  non-conducting  substance,  as  air  (pneumothorax),  or  pus 
'  (empyetna),  or  blood  (hamothorax). 

Percussion-sounds  vary  with  the  region  and  the  condition  of  the  lungs  and 
pleurae.  Normally,  during  quiet  breathing,  the  resonance  is  increasingly  clear  from 
the  supraclavicular  region  downward  over  the  front  of  the  chest  to  about  the  fifth 
rib  on  the  right  side — where  the  pulmonary  tissue  begins  to  decrease  in  thickness  on 
account  of  the  presence  of  the  liver — and  to  the  sixth  rib  on  the  left  side.  It  is  less 
above  the  clavicle  and  over  it,  on  account  of  the  comparatively  small  amount  of  lung- 
tissue  in  the  apices  ;  and  over  the  upper  part  of  the  back,  on  account  of  the  interpo- 
sition ol  the  scapulae  and  of  thick  muscular  masses.  It  becomes  diminished  in  the 
presence  of  moderate  effusion,  as  in  oedema  ;  dull  if  there  is  consolidation  of  lung- 
tissue  ;  and  is  absent  (flat)  if  there  is  either  plastic  exudate  or  fluid  effusion  in  the 
pleural  cavity.  In  pneumothorax,  or  over  a  cavity  in  the  pulmonary  tissue,  especially 
if  it  is  superficial,  the  percussion-note  is  tympanitic. 

Injuries. — Contusions  of  the  lung  may  occur  without  fracture  of  the  bones  of 
the  thorax  or  obvious  lesion  of  the  parietes.  They  are  thought  to  be  due  to 
suddenly  applied  elastic  compression  when — the  glottis  being  closed — the  lung  or 
the  lung  and  pleura  are  ruptured  as  one  may  burst  an  inflated  paper  bag  between  the 
hands. 

The  consequences  are  interlobular  emphysema,  the  air  having  escaped  from 
the  ruptured  air-cells  into  the  connective-tissue  spaces  of  the  lung  (vide  infra); 
gerurcU  emphysema,  the  air  reaching  the  subcutaneous  cellular  tissue  of  the  neck  and 
trunk  through  a  ruptured  pleura,  or,  the  pleura  being  unbroken,  passing  from  the 
root  of  the  lung  into  the  mediastinum  and  thence  to  the  base  of  the  neck ;  pneumo- 


t866 


HUMAN   ANATOMY. 


;i^ 


il 


thorax,  the  air  entering  the  pleural  cavity  ;  in  traumatic  interlobular  emphysema,  or 
pneumothorax,  the  chest  on  the  affected  side  will  be  hyper-resonant,  the  vesicular 
murmur  will  be  feeble  or  absent,  and  in  the  latter  there  may  be  amphoric  breathing 
and — if  there  is  a  coincident  effusion — metallic  tinkling  ;  hetmoptysis,  not  an  invaria- 
ble symptom  in  either  these  injuries  or  lacerations  by  fractured  ribs,  probably  because 
they  are  usually  on  the  external  lung  surface  and  remote  from  the  larger  bronchi 
(  Bennett) ;  htemoihorax,  indicated  by  percussion  dulness  gradually  extending  upward, 
by  weakness  or  absence  of  respiratory  murmur,  by  bronchial  breathing  over  the 
compressed  lung,  and  by  absence  of  vocal  fremitus. 

Penetrating  wounds  of  the  lung  will  have  many  of  these  signs  plus  the  escape 
of  blood  from  the  external  wound.  In  the  absence  of  haemoptysis,  the  possibility  of  a 
wound  of  the  costal  pleura  and  of  an  intercostal  or  internal  mammary  artery 
causing  hsemothorax,  dyspnoea  (from  pressure),  and  hemorrhage,  apparently  in- 
fluenced by  respiration,  should  be  borne  in  mind.  Wounds  of  the  pleura  without 
involvement  of  the  lungs  are  rare,  the  visceral  pleura  being  closely  adherent  to  the 
lung  suriace  and  the  two  pleural  layers  in  close  contact  with  each  other.  At  the  base 
of  the  pleura,  where  a  potential  cavity  (page  iS.sq) — costo-phrenic  sinus — exists 
between  the  costal  and  diaphrs^^matic  layers,  a  wound  could  penetrate  both  layers 
and  the  diaphragm  and  open  the  abdominal  cavity  and  involve  the  liver  or  spleen 
(page  1788)  without  implicating  the  lung,  which  even  in  forced  inspiration  does  not 
descend  to  the  bottom  of  this  sinus.  Wounds  of  the  pleura  are  apt  to  be  followed 
by  pneumothorax  and  by  collapse  of  the  lung,  which  is  partly  driven  back  towards 
its  root  and  the  vertebral  column  by  the  atmospheric  pressure  from  without,  and 
partly  drawr  there  by  its  own  elasticity  even  when  the  pressure  within  and  without 
IS  equal.  In  operations  for  empyema  this  collapse  of  the  lung  i.iay  take  place,  but 
is  infrequent  because  the  pulmonary  tissue  has  often  already  undei^one  considerable 
compression,  and  because  the  atmospheric  pressure  is  resisted  by  preformed  pleural 
adhesions. 

General  emphysema  is  often  associated  with  wounds  of  the  lu.igs  and  pleura.  It 
may  be  due  to  (a)  escape  of  air  from  a  pneumothorax  into  the  subcutaneous  tissue 
during  respiratory  movements,  or  (^)  escape  of  air  direct  from  injured  lung-tissue 
when  pleural  adhesions  about  the  wound  prevent  the  formation  of  a  pneumothorax. 
Its  occasional  occurrence  in  laceration  of  the  lung  without  external  wound  and 
without  involvement  of  the  pleura  has  been  explained  (vide  supra).  It  may  follow 
a  non-penetrating  wound  of  the  chest  if  the  opening  happens  to  be  valvular,  so  that 
the  air  drawn  in  during  respiratory  movements  cannot  make  its  exit  by  the  same 
channel. 

Pneumocele — hernia  of  the  lung — is  rare  as  a  result  of  thoracic  wounds  because 
the  elasticity  of  the  lung-tissue  and  atmospheric  pressure  tend  to  cause  collapse  and 
retraction  of  the  lung  rather  than  protrusion.  When  it  is  primary  it  therefore  follows 
(a)  a  limited  and  oblique  wound  through  which  air  cannot  freely  enter  the  pleural 
cavity,  although  the  egress  of  the  lung  under  the  pressure  of  muscular  effort  or  the 
strain  of  coughing  is  unopposed  ;  or  (b~)  a  very  large  wound  when  the  lung  escapes 
at  the  moment  of  injury  (Bennett).  Treves  says  that  these  recent  hemiae  are  most 
common  at  the  anterior  part  of  the  chest  where  the  lungs  are  most  movable,  and  that 
the  injuries  that  cause  them  are  often  associated  at  the  time  with  violent  respiratory 
efforts. 

Pneumocele  is  more  apt  to  follow  the  rare  wounds  that  divide  only  the  costal  pleura, 
as  a  wound  of  the  lung  itself  tends  to  the  production  of  a  pneumothorax — which 
would  lead  to  collapse  of  the  lung — and  instantly  lessens  the  pressure  of  air  con- 
tained in  the  lungs  and  trachea,  one  of  the  forces  favoring  protrusion. 

Diseases  of  the  pleurse  and  lungs  can  here  be  very  briefly  summarized  only  with 
reference  to  the  anatomical  factors. 

Pleurisy  is  at  first  attended  by  a  "friction-sound"  due  to  the  roughening  of  the 
opposed  surfaces  of  the  visceral  and  parietal  pleurae  by  fibrinous  exudate.  Later  it 
may  be  lost  by  rea.son  of  (a)  the  temporary  disappearance  of  the  roughness,  (^) 
the  formation  of  adhesions  between  the  surfaces,  or  (f )  their  separation  by  effusion. 
It  is  tost  njomentarily  when  the  patient  holds  his  breath,  which  will  serve  to  differ- 
entiate it  from  a  pericardial  friction-sound.     As  the  costal  pleura,  the  intercostal 


PRACTICAL  CONSIDERATIONS  :  THE  LUNGS  AND  PLEURA.    1867 


muscles,  and  the  abdominal  muscles  are  all  supplied  by  the  lower  intercostal  ner\-fs, 
the  respiratory  movements  on  the  affected  side  are  painful  and  are  therefore  greatly 
limited.  Accordingly  there  will  be  hurried,  shallow  breathing  with  a  weak  vesicular 
murmur  on  the  affected  side  and  exaggerated  respiratory  sound;-  on  the  opposite 
side.  Pain  and  tenderness  in  the  epigastrium  may  result  from  implication  of  the 
trunks  of  the  lower  intercostal  nerves  when  the  pleurisy  is  near  the  Ixise  of  the  chest. 
When  it  is  higher  the  pain  may  be  felt  in  the  a.xilla  and  down  the  iniK-r  side  of  the 
arm  from  involvement  of  the  intercosto-humeral  nerve,  or  in  the  skin  over  the  seat 
of  disease  through  the  lateral  cutaneous  branches  of  the  upper  intercostals  (  Hilton). 
In  diaphragmatic  pleurisy  the  pain  may  be  intensified  by  pressure  over  the  point  of 
insertion  of  the  diaphragm  into  the  tenth  rib  (Osier). 

Pleural  effusion  (hydrothorax ,  empyema),  in  addition  to  the  sif'ns  already 
described  {vide  supra),  causes,  when  it  is  of  sufficient  amount,  additional  symptoms, 
as  bulging  of  the  side  of  the  chest  with  obliteration  of  the  intercostal  spact-s,  disten- 
tion of  the  net- work  of  superficial  veins  (from  pressure  on  the  vena  cava  or  greater 
azygos  vein),  and  displacement  of  other  viscera.  If  the  fluid  occupies  the  left 
pleura,  as  its  weight  depresses  the  diaphragm,  the  pericardium,  which  is  attached  to 
the  central  tendon,  d<  's  also,  and  with  it  the  apex  of  the  heart.     At  the  same 

time  the  heart  is  pusi  -^rds  the  right  so  that  the  ape.x  beat  may  be  felt  in  the 

epigastrium  (Owen). 

An  empyema  m.  v  /  .  and  discharge  itself  spontaneously,  in  which  case  it 
often  does  so  at  about  itte  fifth  intersjjace  just  beneath  and  external  to  the  chondro- 
costal  junction  (Marshall).  At  this  place  the  chest- wall  is  exceptionally  thin,  as  the 
region  is  internal  to  the  origin  of  the  serratus  magnus,  external  to  the  insertion  of 
the  rectus,  and  above  the  origin  of  the  external  oblique  (McLachlan). 

Evacuation  of  the  fluid  may  be  effected  by  paracenteses — in  pleurisy  with  serous 
effusion — through  the  sixth  or  seventh  intercostal  space  in  the  mid-axillary  line,  or 
through  the  eighth  or  ninth  space  just  anterior  to  the  angle  of  the  scapula.  The 
same  regions  are  selected  for  thoracotomy — incision  and  drainage — in  empyema.  The 
former  site  is  usually  preferred  for  anatomical  reasons  already  given  (page  170). 

Pneumonia  is  often  limited  to  one  lobe  of  a  lung,  usually  the  lower.  The  fis- 
sure between  the  two  lobes  of  the  narrower  left  lung  runs  from  the  third  rib  behind, 
or  from  about  the  third  dorsal  spinous  process  or  the  inner  end  of  the  spine  of  the 
scapula,  to  the  base  in  front.  The  fissure  between  the  two  lobes  of  the  right  lung 
begins  at  about  the  same  level  behind  and  extends  to  the  base  of  the  lung  anteriorly. 
Where  it  crosses  the  posterior  axillary  line  a  second  fissure  springs  from  it  which 
passes  horizontally  forward  to  the  fourth  chondro-costal  junction  making  the  middle 
lobe.  Both  lower  lobes  are  posterior  to  the  anterior  lobes,  and  on  both  sides  the 
fissures  run  from  the  level  of  the  inner  end  of  the  spine  of  the  scapula  behind  to  the 
base  in  front.  Therefore  the  dulness,  crepitant  rales,  bronchial  breathing,  and 
increased  vocal  fremitus  of  a  lobar  pneumonia  affecting  the  base  would  often  be  below 
that  line  posteriorly  and  would  be  less  marked  in  front ;  while  the  flatness,  prolonged 
expiration,  and  other  physical  signs  of  a  tuberculous  infection  (which  affects  by 
preference  the  upper  lobe)  would  be  above  the  spine  of  the  scapula  posteriorly,  and 
lower  would  be  more  marked  anteriorly. 

The  relations  of  the  lungs  to  the  thoracic  walls  have  been  described  in  detail 
(page  1855). 

The  congestion  and  oedema  which  precede  the  so-called  ' '  hypostatic  pneumonia' ' 
are  very  apt  to  begin  in  the  thick  lower  and  posterior  jiortions  of  the  lower  lobes  in 
weak  or  aged  persons  kept  long  in  the  supine  position. 

Tuberculous  infection  of  the  lungs  is  found  oftenest  in  the  apices,  probably 
because  of  the  relatively  defective  expansion  in  that  region  which  exists  in  all  persons, 
and  particularly  in  those  of  the  so-called  phthisical  type,  with  round  shoulders,  long 
necks  (page  143),  and  flat  chests  ;  possibly  also  because  of  the  greater  exposure  to 
changes  of  external  temperature  ;  and  perhaps  somewhat  owing  to  the  short  distance 
intervening  between  the  outside  atmosphere  and  the  ultimate  bronchioles  where 
tuberculous  pulmonary  disease  usually  has  its  inception. 

The  physical  signs  are  those  indicating  consolidation  followed  by  softening  or 
the  formation  of  a  cavity  {vide  supra). 


■i 


iM8 


HUMAN   ANATOMY. 


II 


b 


Surface  Landmarks  of  Thorax. — The  most  important  of  the  bony  points 
have  already  been  described  in  connection  with  the  spine,  thorax,  clavicle,  and 
scapula.  The  relations  of  the  thoracic  viscera  to  the  surface  have  likewise  been  given 
(page  1855). 

Inspection  or  palftation  of  the  front  of  the  chest  will  show  (a)  the  oblique  eleva- 
tions of  the  ribs  and  the  intercostal  depressions  ;  (^)  the  curved  arch  of  the  costal 
cartilages  ;  (/r)  the  sternal  groove  ;  (</  )  the  angulus  Ludovici  ;  (e)  the  infrastemal 
depression  ;  (/)  the  lower  border  of  the  great  pectoral  muscle  ;  (jf)  the  digitations 
of  the  serratus  magnus  from  the  fifth  to  the  eighth  rib  ;  (A)  the  nipple  (jiages  168, 
170,   171). 

The  infraclavicular  fossa,  the  coracoid  process,  and  the  pectoral  deltoid  groove 
have  been  described  in  connection  with  the  muscles  and  fasci;e  of  the  shoulder 
r|>age  579). 


KlG. 


1590. 


Infraclavicular  (ofwa    ^^  A£|K' 

Coracoid  |»rocMs^^r-A'^- ^5%^     '^  W^' 


(Groove  between  deltott) 
and  {lectoraliH  nia>>r 


SuprR!«lemal  notch 

.Clavkle 
criiuiii 
-ALTumion 


Deltoid 


KiiHifurm  cartilaK« 


Surface  Uindinark<t  of  the  anterfor  wall  of  the  thorax. 

On  the  jKJsterior  surface  of  the  thorax  the  most  useful  landmarks  that  may  Ik- 
seen  or  felt  are  («)  the  spine,  acromion,  vertebral  edge  and  inferior  angle  of  the 
scapula  (pages  255,  256)  ;  (b)  the  spines  of  the  dorsal  vertebra  (page  148)  ;  (r )  the 
median  spinal  or  dorso-lumbar  furrow,  the  groove  between  the  erector  spins  masses 
overlaid  by  the  trapezius  above  and  by  the  latissimus  dorsi  below  ;  {d  )  the  depres- 
sion at  the  inner  end  of  the  scapular  spine  indicating  the  tendinous  insertion  of  the 
lower  fibres  of  the  trapezius,  the  level  of  the  third  intercostal  space,  and  a  portion  of 
the  right  bronchus  ;  ( <*)  a  slight  groove  passing  upward  and  outward  over  the  erector 
spinae  elevation  from  one  of  the  lowest  dorsal  spines  to  this  depression  and  marking 
the  lower  edge  of  the  trapezius  (Quain). 

The  landmarks  of  the  il'  -costal  si)ace  and  lumbo-sacral  region  are  sufficiently 
<lescribed  on  pages  148,  349. 


THE  URO-GENITAL  SYSTEM. 

The  uro-genital  system  comprises  two  groups  of  organs,  the  urinary  and  the 
generative  ;  the  former  serves  for  the  elaboration  and  removal  of  the  chief  excretory 
fluid,  the  urine,  and  the  latter  provides  for  the  formation  and  liberation  of  the  prod- 
ucts of  the  sexual  glands.  The  primary  relations  between  these  sets  of  organs,  as 
seen  in  the  lowest  vertebrates,  are  so  intimate  that  the  excretory  duct  of  the  primitive 
kidney  may  also  transmit  the  sexual  cells,  both  groups  of  organs  being  inseparably 
united.  In  the  higher  vertebrates  the  primary  relations  are  suggested  by  only  tem- 
porary conditions  m  the  embryo,  since  with  the  development  of  a  definite  kidney 
differentiation  and  separation  take  place  until  the  urinary  and  generative  organs  con- 
.stitute  independent  apparatuses  except  at  their  terminal  segment,  where  they  are 
more  or  less  blended  in  the  external  organs  of  generation.  After  serving  for  a  time 
as  the  functionating  excretory  organ  of  the  foetus,  parts  of  the  Wolffian  body  and  its 
duct  become  transformed  into  the  ducts  of  the  male  sexual  gland.  In  the  female 
analogous  canals,  represented  by  the  oviducts,  uterus,  and  va^na,  are  not  derived 
from  the  Wolffian  duct,  but  from  an  additional  tube,  the  Miillenan  duct,  which,  how- 
ever, is  closely  related  to  the  primary  canal  of  the  ftetal  excretory  organ. 


THE  URINARY  ORGANS. 

These  include  the  kidneys,  the  glands  which  secrete  the  urine,  the  ureters,  the 
canals  which  receive  the  urine  and  convey  it  from  the  kidneys  to  the  bladder,  the 
receptacle  in  which  the  urine  is  temporarily  stored,  and  the  urethra,  the  passage 
through  which  the  urine  is  discharged. 

THE  KIDNEYS. 

The  kidneys  (renes)  are  two  flattened  ovoid  glands  of  peculiar  form,  described 
as  bean-shaped,  deeply  placed  within  the  abdominal  cavity  against  its  posterior  wall 
and  the  diaphragm,  one  on  either  side  of  the  lumbar  spine.  They  are  invested  in  a 
distinct,  although  thin,  smooth,  fibrous  capsule  (tunica  fibrosa)  and  lie  behind  the 
peritoneum,  surrounded  by  loose  areolar  tissue,  which  usually  contains  considerable 
fat  (tunica  adiposa).  This  fat  is  particularly  conspicuous  along  the  convex  lateral 
margin  and  about  the  lower  pole  of  the  kidney  and  is  least  abundant  around  the 
upper  end  and  over  the  anterior  surface.  The  fresh  adult  organ,  of  a  brownish-red 
color,  weighs  about  130  gm.  (4>^  oz. )  in  the  male,  slightly  less  in  the  female,  and 
measures  about  11.5  cm.  (4>4  in.)  in  length,  6  cm.  (aj^  in.)  in  width,  and  3.5  cm. 
( I J4  in. )  in  thicknes-s.  The  left  kidney  is  usually  somewhat  longer,  narrower,  and 
thicker,  and  slightly  uavier  than  the  right.  Individual  variations,  especially  as  to 
length,  are  responsible  in  some  cases  for  organs  unusually  long  (15  cm.),  in  others 
for  those  relatively  short. 

Each  kidney  presents  two  surfaces,  a  convex  anterior  or  visceral,  when  the 
organ  is  in  place  directed  forward  and  outward,  and  a  posterior  or  parietal,  some- 
what flattened  and  looking  backward  and  inward  ;  two  rounded  ends,  or  poles,  of 
which  the  upper  is  usually  the  blunter  and  bulkier  ;  and  two  margins,  the  external, 
marking  the  convex  lateral  outline  of  the  organ,  and  the  straighter  internal.  The 
latter  is  interrupted  by  a  slit-like  opening,  the  hilum  (hilus  renalis),  bounded  by 
rounded  edges,  which  leads  into  a  more  extended  but  narrow  space,  the  sinus  (sinus 
renalis),  enclosed  by  the  surrounding  renal  tissue.  The  capsule  is  continued  from 
the  exterior  of  the  kidney  through  the  hilum  into  the  sinui.,  wMeh  it  partly  lines. 
In  addition  to  the  blood-vessels,  lymphatics,  and  nerves  passing  to  rnd  from  the  kid- 
ney through  the  hilum,  the  sinus  contains  the  expanded  upper  cud  of  the  renal  duct 

1X69 


1  1 


iSro 


HUMAN  ANATOMY. 


or  ureter,  which  also  emerges  at  the  hilum.  The  interspaces  between  these  structures 
are  filled  with  loose  areolar  tissue,  in  which  lie  accumulations  of  fat  continuous  with 
the  perirenal  tunica  adiposa. 

Position. — The  kidneys  lie  behind  the  peritoneum,  embedded  within  the  sub- 
peritoneal tissue,  so  placed  against  the  side  of  the  vertebral  column  and  the  posterior 
abdominal  wall  that  they  occupy  an  oblique  plane,  their  anterior  surfaces  looking 
forward  and  outward.  The  long  axes  of  the  organs  are  not  parallel,  but  oblique  to 
the  spine,  in  consequence  of  which  disposition  the  upper  ends  of  the  two  organs  are 
closer  (8.5  cm. ;  than  the  lower  extremities  ( 1 1  cm. ),  the  planes  of  the  inner  margins 


Hepatic  veiiu 


Fig.  1 59 1. 


M' 


RiKht  supnireMal^'^-\ 
body 


Vctia  cava  -\ 
Right  renal  vein 

Riirht  kidney 1,' 

Right  ureter 


Right  spermatic- 
vein 

Right  s|K.'rniatic 
artery 


Externa)  iliac 
artery 


Vas  deferens 
Spermatic  cord 


Cteliai-  axis 
Oesophagus     y^         Superior  mesenteric  artery 

X y^       y^  ^^  Left  suprarenal 

^'     •       body 


Left  renal  vein 


Left  kidney 
Left  renal  artery 


Rectum  (cut) 

Vas  deferens 
Kladder 


Dissection  of  abdomen,  showing  kidneys  tn  position  and  course  and  relations  of  ureters. 

being  anterior  to  those  of  the  external.  The  greater  part  of  lx)th  kidneys  lies  within 
the  epigastric  region,  but  their  outer  margins  reach  within  the  hypochondriac  areas 
and  their  lower  ends  ordinarily  encroach  to  a  limited  and  varial^Ie  extent  upon  the 
umbilical  and  lumbar  regions.  The  intersection  of  the  plane  of  the  transverse  infra- 
costal line  and  that  of  the  vertical  Poupart  line  usually  passes  through  the  lower  pole 
of  the  kidney,  falling,  as  a  rule,  somewhat  higher  in  the  right  than  in  the  left  organ. 
Approximately  the  kidneys  may  be  said  to  lie  opposite  the  last  thoracic  and  the 
upper  two  lumbar  vertebrae,  reaching  to  within  from  2.5-3.5  cm.  (i-ij4  in.)  of  the 
highest  part  of  the  iliac  crest.     The  exact  level  of  the  kidneys,  however,  is  subject 


i 


THE     KIDNEYS. 


1871 


to  considerable  individual  variation,  as  v-oii  as  usually  differing  on  the  two  sides  in 
the  same  subject.  The  right  organ  corimunly  lies  somewhat  lower  than  the  left,  in 
consequence  chiefly  of  the  greater  permanent  volume  of  the  right  lobe  of  the  liver. 
Not  infrequently  the  kidneys  occupy  the  same  level,  and  in  exceptional  cases  the 
ordinary  relations  may  be  reversed,  the  right  lying  a  trifle  higher  than  the  left. 

Addison '  found  that  in  30  per  cent,  of  the  subjects  examined  by  him  the  right 
kidney  lay  as  high  or  higher  than  the  left.  According  to  Helm,'  in  women  the  kid- 
neys lie,  as  a  rule,  about  one-half  of  a  lumbar  vertebra  lower  than  in  men,  this  differ- 
ence depending  upon  the  smaller  size  of  the  vertebra  and  the  greater  curvature  of 
the  lumbar  spine  in  the  female  subject. 

As  a  rule,  the  right  kidney  extends  from  the  upper  border  of  the  last  thoracic 
to  the  middle  of  the  third  lumbar  vertebra,  or  somewhat  lx;low  the  lower  border  of 
the  third  lumbar  transverse  process.  While  always  obliquely  cros.sed  by  the  twelfth 
rib,  the  outer  margin  of  the  right  kidney  usually  falls  short  of  the  eleventh  rib. 


Fig.  1593. 

Aorta 


Pancroi! 


ro-hrpatic  omentum 

Superior  meiieiiterit:  artery 


Hepatic  arter> 


Portal  vein 


Left  Icidney 

Perirenal  Ut.'  ^-~-^<L'^^^M^ai|P.  .^^ ^Right  kidney 

Cross-r«ction  of  formalin-hardened  body  at  le\el  ol  first  lumbar  vertebra. 

Since  the  left  kidney  usually  lies  from  1.5-2  cm.  higher  than  the  right,  its 
upper  pole  is  opposite  the  lower  half  of  the  eleventh  thoracic  vertebra,  its  lower  lc\el 
being  opposite  the  lower  border  of  the  second  lumbar  vertebra  and  the  third  transverse 
process.  Its  outer  margin  may  reach,  or  be  crossed  by,  the  eleventh  rib  ;  the 
costal  r^'ations  are,  however,  variable  and  influenced  by  the  obliquity  of  the  ribs, 
which  is  greater  when  the  ribs  are  well  developed  than  when  they  are  rudimentary. 
The  kidneys  in  young  children  in  general  lie  somewhat  lower  than  in  later  life. 

Fixation.-— Although  possessed  of  mobility  to  ,i  limited  degree, — slight  depres- 
sion and  elevation  probably  normally  accompanying  respiratory  movements, — the 
kidneys  have  a  fairly  fixed  position.  The  maintenance  of  the  latter  has  been 
variously  ascribed  to  the  support  afforded  by  the  peritoneum,  the  perirenal  con- 
nective tissue  and  fat,  the  blood-vessels,  and  the  surrounding  organs,  all  of  which 
during  life  may  contribute  to  this  end.  Gerota,  however,'  has  shown  that,  apart 
from  the  blood-vessels  and,  especially  in  children,  the  suprarenal  bodies,  the  peri- 
toneum and  adjacent  organs  may  be  removed  without  materially  lessening  the  fixation 
of  the  kidneys,  the  latter  receiving  support  particularly  from  their  peculiar  and  inti- 
mate relations  with  the  subperitoneal  tissue.     This,  in  the  vicinity  of  the  kidney, 

'  Journal  of  Anatomy  and  PhysioloRy,  vol.  xxxv.,  1901. 
'  Anatom.  Anzei^er,  Bd.  xi.,  1896. 
•  Archiv  f.  Anat.  und  Entwick.,  1895. 


•i  ■ 


r 


1872 


HUMAN   ANATOMY. 


iugumes  the  character  of  a  distinct  fascia  (fascia  renalis),  which  at  the  outer  border 
of  the  organ  splits  into  an  anterior  and  a  posterior  layer.  The  former  passes  in 
front  of  the  kidney,  renal  vessels,  and  ureter,  and,  crossing  the  great  prevertebral 
vascular  trunks,  joins  the  corresponding  layer  of  the  opposite  side.  Traced  upward, 
the  anterior  layer  covers  the  suprarenal  body,  above  this  organ  fusing  with  the  pos- 
terior layer  of  the  renal  fascia.  The  latter  passes  behind  the  kidney,  over  the  fascia 
covering  the  transversalis,  quadratus,  and  psoas,  as  far  as  the  inner  border  of  the  last 
muscle,  along  which  it  becomes  attached  to  the  spine.  The  posterior  layer  extends 
upward  behind  the  suprarenal  body,  which,  in  conjunction  with  the  anterior  layer, 
is  completely  invested  un  all  sides  except  below,  where  it  lies  against  the  kidney,  to 


Fio.  1593. 


1 


Diaphragm 


>iaphraxni 


Kight  Miprarviial  bocly 


'Right  kuliivy 

AHceiKling  colon 
Psoas  muiale 


:    ^ 


I 


Posuri.ir  a»|>e<t  of  kldnevs  in  silu  in  formalin  subject;  portion  of  posterior  bo<1>-»all  has 
bet'ti  also  |iarts  of  pleural  sacs  and  diaphragni. 


been  removed,  as  have 


the  support  of  which  organ  it  materially  contributes.  Although  everywhere  sepa- 
rated from  the  fibrous  tunic  of  the  kidney  by  the  intervening  layer  of  fat  (tunica 
adiposa),  the  renal  fa.scia  is  attached  to  the  renal  capsule  proper  by  bands  of  con- 
nective tissue,  which  are  especially  strong  at  the  lower  pole,  thus  directly  affording 
support  to  the  organ.  Ikhind,  the  posterior  layer  of  the  renal  fascia  is  likew|ise 
attached  to  the  transA'ersalis  fascia  by  means  of  areolar  tissue,  between  the  connecting 
bands  of  which  a  \'ariable  amount  of  fat  is  usually  present.  Above,  beyond  the 
suprarenal  body,  the  renal  fascia  fades  away  over  the  diaphragm  ;  below,  it  passes 
into  and  is  lost  within  the  fatty  subperitoneal  tissue  of  the  iliac  fossa. 

The  fixation  of  the  left  kidney  is  firmer  than  that  of  the  right,  greater  security 
being  gained  for  the  left  organ  in  consequence  of  its  more  extensive  relations  to  the 


THE  KIDNEYS. 


1873 


Xll  rib- 


Dill  phraKm 


I.IVCT 

RiKht 

Hupraretial 

bu<l> 


fusion  which  takes  place  during  the  development  (page  1704)  of  the  large  intestine 
between  the  original  parietal  peritoneum  and  that  covering  the  applied  surface  of  the 
primary  mesentery  of  the  descending  colon  ;  in  consequence,  the  left  kidney  is 
mveated  anteriorly  with  a  subperitoneal  layer  of  exceptional  strength,  \yhen,  for 
various  reasons,  the  tonicity  of  the  tissues  supporting  the  kidney  becomes  impaired 
and  these  structures  become  abnormally  lengthened,  the  organ  may  acquire  undue 
mobility  and  suffer  displacement. 

Relations. — The  position  of  the  kidneys  being  wholly  retroperitoneal,  the 
posterior  relations  of  both  organs  are  chiefly  muscular,  since  they  lie  closely 
applied  to  the  diaphragm,  psoas  magnus,  quadratus  lumborum,  and  the  posterior 
aponeurosis  of  the  transversalis,  the  jiarietal  fascia  and  iK-rirenal  areolar  tissue  alone 
intervening.  The  inequalities  in  the  supporting  structures  produce  corresponding 
modelling  of  the  opposed  renal  surfaces,  which  is  clearly  distinguishable  on  organs 
hardened  in  situ.  In  specimens  hardened  in  formalin,  the  psoas  area  appears  as  a  nar- 
row, slightly  di'prcsse<l  tract  along  the  inner  border  ;  an  adjoining  broader  Ijand  marks 
the  area  for  the  quadratus  lumborum,  beyond  which  the  outer  part  of  the  posterior  sur- 
face rests  upon  the  transversalis  apo- 
neurosis. The  crescentic  diaphr^matic  Fio.  i$94. 
area  crosses  the  upper  pole,  the  inner 
limb  of  the  crescent  marking  the  con- 
tact with  the  crus.  In  organs  hardened 
in  the  recumbent  posture,  conspicuous 
and  probably  exaggerated  indentations 
show  the  former  positior^  f  the  trans- 
verse processes  of  the  second  and  third 
lumbar  vertebrae.  An  oblique,  shallow 
furrow  crossing  the  kidney  from  the 
upper  pole  outward,  usually  locates  the 
course  of  the  twelfth  rib.  In  connec- 
tion with  the  posterior  relations  of  the 
kidneys,  it  is  important  to  recall  the 
inferior  limits  of  the  pleural  sacs  (ps^e 
1859),  which,  where  they  cross  the 
twelfth  rib,  may  descend  as  low  as  the 
level  of  the  first  lumbar  transverse  pro- 
cess and  therefore  cover  the  upper  part 
of  the  kidneys. 

The  anterior  relations  of  the 
kidneys  uifler  on  the  two  sides,  not 
only  to  the  viscera  concerned,  but 
also  in  the  manner  of  their  contact  and 
the  consequent  extent  of  the  renal  peri- 
toneal investment    Primarily  the  entire 

visceral  surfaces  of  the  kidneys  are  covered  by  serous  membrane  ;  later  this  invest- 
ment becomes  only  partial,  in  consequence  of  the  permanent  attachment  wSich  certain 
organs,  as  the  pancreas,  duodenum,  and  colon,  obtain.  When  these  viscera  undergo 
the  backward  displacement  incident  to  acquiring  their  final  location,  they  are  pressed 
against  the  abdominal  wall  and  the  kidneys,  to  which  they  become  attached  by 
areolar  tissue,  since  the  intervening  opposed  peritoneal  surfaces  \ase  their  serous 
character.  Where  the  organs  touching  the  kidneys  remain  covered  with  peritoneum, 
the  renal  areas  of  contact  retain  the  original  serous  investment. 

The  right  kidney  is  in  relation  with  the  corresponding  suprarenal  body,  the  liver, 
the  duodenum,  the  hepatic  flexure  of  the  colon,  and,  to  a  limited  extent,  usually  the 
small  intestine.  The  right  suprarenal  body  covers  the  upper  pole  and  adjacent  part 
of  the  inner  border  of  the  kidney,  the  surface  of  contact  being  devoid  of  peritoneum, 
since  the  organs  are  closely  connected  by  areolar  tissue.  The  liver  covers  the  larger 
part  of  the  anterior  surface  and  outer  border  of  the  kidney,  which  models  the  hepatic 
tissue  as  the  conspicuous  renal  impression  seen  on  the  inferior  surface  of  the  organ. 
Both  the  liver  and  the  kidney  are  mvestcd  by  serous  membrane,  and  are,  therefore, 

liS 


Iliac  hone, 
■ectioncd 


niac  faucia 


lltacuH 
mttaclc 


DUgrunmatic  kMigitudinal  Mctlon,  showlna  relaUo 
•upporting  tluuc  to  right  kidney.    (Getola.) 


1874 


HUMAN   ANATOMY. 


1 
1 


separated  by  an  extension  of  the  greater  sac  of  the  peritoneum.  The  second  part  ol 
the  duodenum  overlies  the  hilum  and  the  inner  renal  border,  the  non-peritoneal  area 
being  of  uncertain  extent  in  consequence  of  the  variations  in  the  position  o.  this  part  of 
the  intestinal  tube.  Although  covering  usually  about  the  middle  two-fourths  of  the 
median  border,  the  duodenal  area  may  embrace  the  entire  inner  third  or  more  <rf  the 
anterior  surface  of  the  kidney,  extending  from  the  extreme  upper  to  the  lower  pole  ; 
or,  on  the  contrary,  the  duodenum  may  touch  the  kidney  only  near  its  lower  pole. 
The  hepatic  flexure  occupies  a  triangular  area,  external  to  the  adjoining  duodenal 
one  and  also  non-peritoneal,  which  includes  the  outer  and  lower  third,  more  or  less, 
of  the  anterior  surface  of  the  kidney.  The  extent  and  form  of  the  surkces  of  con- 
tact between  the  kidney,  colon,  and  du'jdenum  are  very  variable  ;  when  large  they 
may  cover  the  entire  lower  half  n'  'he  kidney,  or  when  less  extensive  they  may 
leave  uncovered  the  lower  pole.     1:  latter  case  coils  of  the  small  intestine  often 

occupy  this  area,  which  is  covered  .     .  peritoneum. 

The  left  kidney  is  in  relation  with  the  corresponding  suprarenal  body,  the 
spleen,  the  stomach,  the  pancreas,  the  splenic  flexure  of  the  colon,  and  the  small  in- 
testine.    The  suprarenal  body  lies  upon  the  median  side  of  the  upper  pole,  attached 


Fio    1595- 

Suprarenal  area  (non-pv>ritonral) 


Suprarenal  area  (non-periloneal) 


tIepaUc  area 

'peritoneal) 


Colic  area 
(non-peritoneal) 

Jejunal  area 
ijieritoneal) 


Pancreatic  area 
(non-peritoneal) 


Duodenal  area  (non-peritoneal) 

Ri(hl  renal  dud 


Colic  area 
(non-peritoneal) 

Jejunal  area 
(peritoneal) 


Left  renal  duct  (ureter) 


Inferior  vena  ca\-a 
Anterior  auriace  of  kidneys  ol  formalin-hardened  suD)eci,  snowint  viacerai  areaa,  blood-vessels,  and  renal  ducts. 

by  areolar  tissue  ;  its  area  is  therefore  non-serous.  The  upper  two-thirds  of  the 
outer  border  and  the  adjacent  part  of  the  anterior  surface  of  the  kidney  are  covered 
by  the  spleen,  the  peritoneum  intervening,  except  within  the  narrow  attachment  of 
the  layei^  of  the  lieno-renal  ligament.  Below  the  splenic  area  the  kidney  is  covered 
to  a  variable  extent  by  the  splenic  flexure  of  the  colon,  this  non-peritoneal  area 
usually  including  the  outer  half  of  the  lower  pole.  The  pancreas  lies  in  front  of  the 
hilum  and  approximately  the  middle  third  of  the  kidney,  frequently  reaching  as  far 
as  the  outer  border.  Above  this  non-peritoneal  area,  between  the  latter  and  the 
suprarenal  and  splenic  surfaces,  lies  the  small  triangular  serous  area  which  the  stomach 
touches,  while  below  the  pancreatic  zone,  internal  to  that  for  the  splenic  flexure,  the 
kidney  presents  a  triangular  peritoneal  area  over  which  the  coils  of  the  jejunum  glide. 

From  the  foregoing  it  is  evident  that  each  kidney  rests  within  a  depression,  the 
"renal  fcssa,"  formed  by  the  structures  with  which  it  comes  into  contact  above, 
behind,  at  the  sides,  and  below.  The  fossae  are  deeper  and  narrower  in  the  male 
than  in  the  female,  owing  chiefly  to  the  greater  development  of  the  muscles  against 
which  the  kidneys  lie. 

The  Renal  Sinus. — ^The  longitudinal,  slit-like  hilum,  occupying  somewhat  less 
than  the  middle  third  of  the  inner  border  of  the  kidney,  opens  into  a  more  extensive 
but  shallow  C-shaped  space,  the  renal  sinus,  which,  surrounded  by  the  kidney-dssue, 


THE  KIDNEYS. 


1875 


takes  in  approximately  the  median  half  of  the  interior  of  the  organ.  The  ifreatest 
dimension  of  the  sinus  corresponds  with  the  long  axis  of  the  kidney,  the  shortest  with 
the  distance  between  the  anttrior  and  posterior  walls.  The  space — most  extended 
vertically — is  compressed  from  before  backward,  while  its  greatest  depth  (  2. 5-3. 5  cm. ) 
is  just  above  the  upper  border  of  the  hilum.  The  sinus  is  occupied  in  large  measure 
by  the  dilated  upper  end  of  the  ureter,  the  rcna/  pelvis,  and  its  subdivisions,  the 
calyces;  the  remaming  space  accommodates  the  blood-vessels,  lymphatics,  and  nerves 
that  pass  through  the  hilum  and  the  intervening  cushion  of  areolar  and  adipose  tissue 
tx>ntinuous  with  the  perirenal  fatty  capsule.  The  fibrous  cipsule  of  the  kidney  covers 
the  rounded  lips  of  the  hilum  and  is  continued  into  the  sinus,  to  which  it  furnishes 
a  partial  lining. 

In  contrast  to  the  even  external  surface  of  the  ki'iiiey,  the  walls  of  the  sinus  are 
beset  with  conical  elevations,  the  renal  papilla,  which  are  well  seen,  however,  only 
after  removal  of  the  contents  and  the  fibrous  lining  of  the  sinus.  The  i)apill.-e  mark 
the  apices  of  the  pyramidal  masses  of  kidney-tissue  of  which  the  organ  i.s  composed. 
The  individual  cones,  from  7  to  10  mm.  in 
height,  are  in  many  instances  somewhat  com- 
pressed, so  that  their  bases  are  elliptical  in 
section  instead  of  circular.  Adjacent  ones 
may  undergo  more  or  less  complete  fusion, 
the  resulting  compound  papillae  being  often 
grooved  and  irregular  in  form.  Usually  from 
eight  to  ten  papilla;  are  present  in  each  kid- 
ney, but  their  number  varies  greatly,  as  few 
as  four  and  as  many  as  eighteen  having  been 
observed  (Henle).  The  walls  of  the  sinus 
between  the  bases  of  the  papillcC  are  broken 
up  into  elevations  and  depressed  areas,  the 
latter  marking  the  localities  at  which  the 
blood-vessels  and  nerves  enter  and  leave  the 
renal  substance.  The  apex  of  each  papilla 
is  pierced  by  a  number  of  minute  openings, 
barely  recognizable  with  the  unaided  eye, 
which  mark  the  terminal  orifices  (foramina 
papiliaria)  of  the  uriniferous  tubules  from 
which  the  urine  escapes  from  the  renal  tissue 
into  the  receptacles  formed  by  the  '"alyces 
which  surround  the  papillae  and  are  attached 
to  their  bases.  The  number  of  uriniferous  tu- 
bules opening  at  the  apex  of  a  single  papilla — 
the  field  in  which  the  pores  open  being  the 
area  cribrosa — varies  with  the  size  of  the  cone,  from  eighteen  to  twenty-four  being 
the  usual  complement  for  a  simple  papilla.  When  the  latter  is  compound  and  of 
large  size,  more  than  twice  as  many  orifices  may  be  present. 

Architecture  of  the  Kidney — The  entire  organ — a  conspicuous  example  of 
a  compound  tubular  gland— is  made  up  of  a  number  of  divisions  which  in  the  mature 
condition  are  so  closely  blended  as  to  giv?  little  evidence  of  the  striking  lobulation 
marking  the  foetal  kidney.  The  external  surface  of  the  latter  (Fig.  1597)  is  broken 
up  by  furrows  into  a  number  of  irregular  polygonal  areas,  each  representing  the 
base  of  a  pyramidal  mass  of  renal  tissue,  the  kidney  lobe  or  renculus,  which,  sep- 
arated from  its  neighbors  by  an  envelope  of  connective  tissue  includes  the  entire 
tiiickness  of  the  organ  between  its  exterior  and  the  sinus,  a  renal  papilla  being  the 
apex.  For  a  short  time  after  birth  the  lobulation  is  evident,  but  later  the  de- 
marcations gradually  disappear  from  the  surface,  which  becomes  smooth,  and  ti\c 
interlobular  connective-tissue  septa  within  the  organ  disap{>ear,  the  pyramids  alone 
indicating  the  original  lobulation. 


Rnul 
vein 
Renal  pel- 
vis, luwcr 
part 


Anterior  turface  o(  ilsht  kidney  from  which 
fibrous  capsule  has  been  partly  rctnnv<fd;  blood- 
vesaels  and  renalduct  aie  teen  entering  and  enicrKiiis 
through  hilum. 


AlthouKh  evidences  of  the  latter  occasionally  persist  in  the  adult  human  orgfan,  the  kidno.ys 
of  many  of  the  lower  animals  (reptiles,  birds,  ruminants,  cetaceans,  and  certain  camivora)  retam 


1 

1: 


1876 


HUMAN   ANATOMY. 


Fio.  1597. 


RivM  kidner 
hom  tTiiM,  •howlnn  lobula- 
tion ui  •uitacc. 


the  divisUms  in  a  more  «>r  less  marked  decree,  tht  reiwl  lobules  o<  the  aquatic  mammals  bein|f 
unuNually  distiiKt.  In  some  mammals  ( rodents,  insectivora )  the  entire  kidney  correspunds  to  a 
Hinxle  papilla,  while  in  others  lelephant,  horsej  no  distinct  papilla:  exist. 

On  making  a  lunKitudinal  section  of  the  fresh  kidney,  from  its  convex  border 
throu^rh  the  sinus,  the  papillae  will  l>e  seen  to  form  the  free  apices  of  conical  masses, 
the  renal  pyramidi,  the  b<ises  of  which  lie  embe<lcle(t  within 
the  darker  surroundinjf  kidney-substance  composing  the  outer 
third  of  the  organ.  This  peripheral  zone,  which  apj)ears  darker 
and  granular  in  contrast  to  the  lighter  and  striated  renal  pyra- 
mids, constitutes  the  cortex;  the  medulla  includes  the  conical 
areas  formed  by  the  pyramids  and  partially  occupies  the  inner 
two-thirds  of  the  thickness  of  the  organ.  The  cortex  contrib- 
utes the  bulk  of  the  kidney,  alone  forminjj  the  entire  surface, 
including  the  lips  of  the  hilum.  and  receiving  and  surrounding 
the  bases  of  the  pyramids.  The  cortical  tissue  further  pene- 
trates for  a  variable  distance  between  the  pyramids,  separating 
the  latter  and  in  places  gaining  the  sinus.  These  interpy- 
ramidal  extensions  are  the  renaUolumns,  or  columns  of  Berlin, 
and  consbt  of  typical  cortical  substance.  Since  the  branches 
of  the  renal  blood-vesseb  lie  within  the  interlobular  connective 
tissue  separating  the  pritnary  divisions  of  the  fcetal  organ,  these  vessels  never  enter 
the  kidney  by  passing  into  the  papillte,  but  always  enter  at  the  side  of  these.  They 
therefore  sink  into  the  renal  substance  within  the  areas  occupied  by  the  renal  columns, 
the  surfaces  of  which  directed  towards  the  sinus  are  pitted  by  the  vascular  foramina. 
Within  the  sinus  the  blood-vessels  surround  the  calyces  with  coarse  net-works,  enter- 
ing and  emerging  from  the  renal  substance  through  the  orifices  encircling  the  papillae. 
On  close  inspection,  preferably  with  the  aid  of  a  hand-glass,  it  will  be  seen  that 
the  cortex,  including  that  within  the  renal  columns,  is  not  uniform,  but  is  subdivided 
by  narrow  striated  bands,  wedge-shaped 

in  outline  and  lighter  in  color,    into  rio.  159*. 

radially  disposed  darker  and  lighter 
areas.  The  latter,  consisting  of  groups 
of  parallel  tubules,  are  known  as  the 
medullary  rays  (pare  radiata),  since 
they  are  apparently  due  to  prolonga- 
tions of  the  medullaiy  tissue.  The 
darker  tracts  intervening  between  the 
medullary  rays  form  the  labyrinth  (pars 
convoluta),  and  appear  granular,  owing 
to  the  tortuous  character  of  the  com- 
ponent tubules.  The  labyrinth  is 
studded  with  bright  red  points  mark- 
ing the  position  of  the  vascular  tufts 
or  glomeruli,  which  are  never  present 
within  the  medullary  rays  or  the  renal 
pyramids,  although  found  within  the 
columns  of  Berlin. 

On  sectioning  minutely  injected 
organs,  it  will  be  observed  that  the 
larger  radially  coursing  interlobular  ar- 
teries, on  gaining  the  boundary  zone 
between  the  cortex  and  medulla,  break 
up  into  smaller  branches,  some  of  which 
pa.ss  direc.'y  towards  the  surface,  while  others  change  t^Hr  direction  and  asiume  an 
arched  horizontal  course,  thus  producing  the  impression  of  "  arcades"  at  the  bast-  of 
the  pyramids.  The  terminal  twigs — "  end-arteries,"  sine?  anastomoses  are  wanting 
—run  generally  perpendicular  to  the  exterior  of  the  kidney  and  occupy  the  centre 
of  the  tracts  separating  the  medullary  rays.     The  latter,  therefore,  are  the  axes  of 


L.on{ 


-Portion  o( 

sinus 
-Renal 
p«t*tlla 

-Ureter 


JKttadinal  sectk  i  ol  rijiht  kMney.  ahowInK  r<-latlon»  of 
pelvis  and  its  divisions  to  renal  aubsunce  and  to  snius. 


THE   KIDNEYS. 


I877 


Prnsimal  iciit- 
Mtlittt'il  tiihulf^ 

Intffint^liatf 
luhiiU'  ulinlal 
ioii\olu(i-d) 

ItilrrnuMliatc 

tuhitlr 
Kffrrntl  \ff*vrl 

ArttTcnt  \ issel 
Caps  Ilk' 
liilfrlobiilar 
artery 


minute  conical  masMCii  ol  renal  sulnt.'.nce,  the  corliral  lobulfS,  the  basen  of  which  lie 
iit  the  surface  and  the  apiris  within  the  pyramids  of  the  nu-dulla.  From  the  forc- 
^oinK  it  is  evident  that  each  renal  pyramiti  corres|)onds  to  a  nf^'"!'  "'  cortical  lobules, 
the  tubules  of  which,  on  entering  thv'  medulla.  l)ccomc  i>roKres!tively  less  numerous 
but  larger,  in  consequence  of  repeated  juncture,  until,  as  the  wide  excretory  duets, 
they  end  at  the  summit  of  the  papilla.  The  relations  of  the  pyramids  to  the  papilhir 
are  less  simple  than  foni  ;  recognized,  since,  instead  of  each  of  the  latter  embracing 
Ixit  one  of  the  former,  Maresch '  hiut  shown  tlutt  a  single  p<tpiila,  as  a  rule,  incluiles 
from  two  to  four  pyramitis, 

which  are  blended  into  one  Fio.  1599. 

conical  mass  culminating  in  ijb\rinih      m^.i  rav  ijib>rinih 

the  papillary  apex. 

Structure  of  the  Kid- 
ney. —  The  fundamental 
coni|X)nents  of  the  verte- 
brate excretory  organ,  both 
in  the  fcctal  and  mature  con- 
dition, include  (i)  a  tuft  of 
arterial  vessels  derive*!  more 
or  less  directly  from  the 
aorta,  (  2 )  tubules  lined  with 
secretory  epithelium,  and 
( .•? )  a  duct  for  the  convey- 
ance of  the  excretory  pro- 
ducts. These  constituents 
are  represented  in  the  kid- 
ney of  man  and  the  higher 
animals  by  ( i )  the  glomeru- 
lus, (  2  )  the  convoluted  uri- 
niferous  tubules,  and  ( y, )  the 
collecting  tulies,  pelvis,  and 
ureter.  Since,  in  a  general 
way,  to  the  epithelium  lining 
the  tubules  may  be  ascribed 
the  function  of  taking  from 
the  circulation  the  more  solid 
constituents  of  the  urine, 
and  to  the  glomerulus  the 
secretion  of  its  watery  parts, 
obviously  the  most  favora- 
ble arrangement  to  secure 
the  removal  of  the  excretory 
products  is  one  insuring 
flushing  of  the  entire  tubule 
with  the  fluid  secreted  by 
the  glomerulus.  Such  ar- 
rangement implies  the  loca- 
tion of  the  vascular  tuft  at  the  very  beginning  of  the  tubule, — a  disposition  which 
in  fact  is  found  in  the  kidneys  of  all  higher  animals.  The  numt«r  of  the  glomeruli, 
therefore,  corresponds  with  that  of  the  uriniferous  tubules,  each  of  which  begins  in 
close  relation  with  the  vascular  tuft.  The  kidney-substance  consists  of  an  intricate 
but  definitely  arranged  complex  of  uriniferous  tubules,  supported  by  the  interstitial 
connective-tissue  stroma,  which  ha\e  their  commencement  in  the  cortex  and  their 
termination  at  the  apict  -  of  the  papillae,  their  intervening  course  l)eing  marked  by 
many  and  conspicuous  >  .liiatioiis  in  the  character,  ^i/ie,  and  din    iion  oi  the  tubules. 

The  uriniferous  tubule  begins  as  a  greatly  expanded  •'  extremity,  the 
capsule  (i),  which  surrounds  the  vase  r  ttift  >r  glomerulus,  x  vo  together  con- 
stituting the  Ji!i^»^A/a«  *  vith       hp  labyrinth.     *',.  leaving  the  Mal- 

;er,  Bd.  xii.,  i8q6. 


I-cHipof  Heiile 


PapnUir>  tlurt^ 


Papilla 
Diagram  showiiiK  course 


>f  uriniferous  tubule. 


i87« 


HUMAN  ANATOMY. 


pighian  body  the  tubule  becomes  very  tortuous  and  a»ches  towards  the  free  surfoce 
as  the  proximal  convoluted  tubuU  (2)  ;  this,  after  a  course  of  considerable  length, 

usually    leaves  the   labyrinth   and 
Fig.  1600.  enters  the  medullary  ray,  which  it 

'Capiuie  traverses,    somewhat    reduced    in 

diameter  and  slighdy  winding  in 
course,  as  the  spiral  tubule  (3)  and 
piasses  into  the  medulla.  Immedi- 
ately upon  gaining  the  latter,  the 
tubule  suffers  marked  decrease  in 
size,  penetrates  the  renal  pyramid 
for  a  variable  distance  towards  the 
papilla,  then  bends  sharply  upon 
Itself  and  retraces  its  course  to  once 
more  enter  the  labyrinth.  Its  ex- 
cursion into  the  medulla  includes 
the  descending  limb  (4)  and  as- 
cending limb  (5)  of  the  loop  of 
Henle.  The  ascending  limb— the 
longer  and  wider  of  the  parallel 
limbs  of  the  loop— rises  within  the 
labyrinth  to  the  immediate  vicinity 
of  the  corresponding  Malpighian 
body,  the  neck  of  which  it  crosses, 
and  then,  after  arching  over  the  cor- 
puscle, gives  place  to  the  distal 
convoluted  or  intermediate  tubule 
(6),  a  segment  which,  marked  by 
increased  diameter  and  tortuosity, 
crosses  the  general  course  of  the 
convoluted  tubule  and  is  succeeded 
by  the  narrower  and  arching  con- 
necting tubule  (7).  The  latter 
enters  the  medullary  ray  and,  join- 
ing with  similar  canals,  forms  the 
^XiMghX.  collecting  tubule  (%),  which, 
progressively  increasing  in  size  by 
junction  with  others,  traverses  the 
remaining  length  of  the  medullary 
ray  and  enters  the  renal  pyramid. 
Within  the  deeper  part  of  the  latter 
the  collecting  tubules  fuse  into  larger  and  larger  canals  until,  as  the  relatively  wide 
papillary  ducts  (9),  they  terminate  on  the  apex  of  the  papilla  at  the  orifices  {fora- 
mina papillaria)  which  open  into  the  calyces. 

The  relations  between  the  various  segments  of  the  uriniferous  tubules  and  the 
subdivisions  of  the  kidney  are,  therefore,  as  follows  : 


Blood, 
vessels 


■Ht  f%^  ^}1%JV 


Section  of  cortex,  showing  relation  ol  labyrinth 
and  medullary  rays.    X  Jo. 


Cortex 


Labyrinth 


Medullary  ray 


Medulla 


Malpighian  body, — capsule  and  glomerulus 

Proximal  convoluted  tubule 

Ascending  limb  of  Henle' s  loop 

Distal  convoluted  or  intermediate  tubule 

Connecting  tubule  (beginning) 

Connecting  tubule  (termination) 

Spiral  tubule 

Collecting  tubule 

I  Descending  limb  and 
Ascending  limb  of  Henle's  loop 
Collecting  tubule 
Papillary  ducts 


THE  KIDNEYS. 


»«79 


.Caiwule 


Injected  (loinerulas,  «ho«  ng  tffercnt  mm)  eflerem  vesnels  «nd 
continuation  into  intertubular  capilUrie*.    X  J50. 


Althoup^h  as  a  matter  of  convenienre  the  entire  canal,  from  its  commencement 
in  tlie  Malpigiiian  body  to  its  termination  on  the  papilla,  has  been  described  as  the 
uriniferous  tubule,  both  geneti- 
cally and  functionally  two  dis-  P««*-  '*«'• 
tinct  parts  must  be  recognized. 
These  are  the  unbranched  uri- 
niferous  tubule  proper,  which 
includes  all  divisions  from  the 
Malpighian  body  to  the  termi- 
nation of  the  intermediate  tu- 
bule, and  the  duct-tube,  which, 
when  traced  from  the  papilla 
towards  the  cortex,  undergoes 
refieated  division  until  from  a 
single  stem  the  number  of  con- 
necting tubules  is  sufficient  to 
provide  each  uriniferous  tubule 
proper  with  its  own  excretory 

canal.  ^'-^t^lKF"     ~^V&'.irlflH^IKiBBI^^~ — -■ latenubular 

^^■&  '^K^fr^l^^BHl^V!Qft  capillaries 

I.  The  Malpighian  Body.— This 
structure,  spherical  in  form  and  from 
.OI2-.030  mm.  in  diameter,  consists 
of  two  parts,  the  glomeruius  and  the 
capsule.  The  former  is  an  ajisi'ega- 
ion  of  tortuous  capillary  blood-ves- 
sels into  which  break  up  the  lateral 
terminal  twig;s  given  of!  from  the 

arteries  as  these  pass  between  the  cortical  lobules  towards  the  free  surface  of  the  kidney.  The 
lateral  branches— very  short,  often  arched,  and  only  .002-.004  mm.  in  diameter— spring  at  vary- 
ing angles  from  all  sides  of  the  interlobular  arteriole  and  enter  the  Malpighian  body  as  the  yas 
afferens.  On  entering  the  glomerulus,  the  afferent  vessel  divides  into  from  four  to  six  twigs, 
each  of  which  breaks  up  into  capillaries.  These  may  anastomose  and  form  a  vascular  complex 
that  may  be  filled  from  any  branch  ;  not  infrequently,  however,  such  communication  does  not 

exist,  each  terminal  twig 
Fio.  i6ot.  then  giving  rise  to  an  iso- 

lated capillary  territory, 
the  entire  glomerulus  con- 
sisting of  vascular  lobules, 
each  drained  by  its  own 
radicle.  Sooner  or  later 
all  the  channels  of  exit 
unite  to  form  the  single  ifos 
efferens,  through  which 
the  blood  from  the  en- 
tire glomerulus  escapes. 
The  efferent  ves.sel  as  it 
emerges  from  the  Mal- 
pighian body  is  close  to 
the  vas  afferens,  both  usu- 
ally lying  on  the  side  op- 
posite to  that  occupied  by 
the  neck  of  the  capsule 
from  which  the  uriniferous 
tubule  Is  continued.  In 
consequence  of  the  short 
course  and  manner  of  ori- 
gin of  the  twigs  from  the 
interlobular  arteries,  the 
glomeruli  are  disposed  in 
rows,  somewhat  like  berries  attached  to  a  straight  common  stalk. 

The  capsule  of  Bowman,  the  dilated  beginning  of  the  uriniferous  tubule,  almost  com- 
pletely iriVests  the  glomerulus  uith  a  double  layer  derived  from  the  wall  of  the  tubule,  which 
seemingly  has  suffered  invagination  by  the  vascular  tuft.    Such  pushing  in,  however,  is  only 


Capule 


Section  of  renal  cortex,  ihowinc  details  of  Malpighian  body . 
surrounded  by  capaule  whicn  {xuaes  into  obliquely  cut  neck. 


glomerulus  is 

X  joo. 


i88o 


HUMAN   ANATOMY. 


Fi8.  i6oj. 


i    ' 


BInocl-VCSKi 


Convoluted  tabuln.  cut  transveriely  and  ob- 
liquclv,  showing  character  of  epithelial  lining. 
X  400. 


apparent,  since  the  close  relations  oJ  glomerulus  and  capsule  result  from  the  (jrowth  of  the  latter 
around  the  vascular  tuft  and  not  from  invagination  of  the  dilated  tubule.    The  capsule  consists 

of  a  distinct  membrana  propria  and  a  liniiig;  composed 
of  a  single  layer  of  flat,  plate-like  cells,  the  modified 
epithelium  of  the  uriniferous  tubule.  In  sections  pa.ss- 
ing  through  the  afferent  vessel  and  the  neck  the  lumen 
of  the  capsule  appears  crescentic  in  outline,  since  the 
space  between  its  otfter  and  inner  walls  is  widest  at 
the  neck  and  reduced  to  a  mere  slit  where  the  two 
layers  are  continuous  around  the  narrow  stalk  tra- 
versed by  the  afferent  and  efferent  ves-sels.  The  inner 
or  "  visceral"  layer  of  the  capsule,  the  thicker  of  the 
two,  is  firmly  attached  to  the  glomerulus  by  the  deli- 
cate intervening  connective  tissue,  the  entire  complex 
appearing  rich  in  nuclei  which  belong  to  the  epithe- 
lium of  the  capsule,  the  endothelium  of  the  capillaries, 
and  the  ronnective-tissue  cells. 

i.  The  Proximal  Convoluted  Tubule. — After  un- 
dergoing !he  conspicuous  constriction  marking  the 
neck  of  the  capsule,  the  uriniferous  tubule  abruptly 
enlarges  into  the  convoluted  segment  which  forms  ap- 
proximately one-fifth  of  the  length  of  the  entire  canal 
and  has  a  diameter  of  from  .040-.060  mm.  In  com- 
mon with  other  parts  of  the  tubale,  its  wall  consists  of  a 
membrana  propria,  apparently  structureless,  but  com- 
posed of  a  delicate  reticulum  and  intervening  homoge- 
neous substance  and  a  single  layer  of  epithelial  cells. 
Although  the  histological  details  of  the  latter 
vary  in  different,  but  not  constant,  parts  of  the  convo- 
luted segment,  the  lining  cells  present  certain  charac- 
teristics, chief  among  which  is  the  differentiation  of 
the  cytopla.sm  of  the  cells  into  a  broader  outer  and 
a  narrow  inner  zone.  The  former  exhibits  coarse  radial  striations,  the  so-called  "  rods,"  pro- 
duced by  rows  of  granules  within  the  vertically  di.sposed  threads  of  spongioplasm  (Rothstein) 
which  occupy  approximately  the  pe- 
ripheral half  of  the  cell  extending  Fio.  1604. 
from  the  membrana  propria  towards 
the  inner  zone.  The  latter,  next  the 
lumen,  usually  appears  as  a  well- 
defined  narrow  border  whkh,  when 
successfully  preserved,  presents  a 
fine  vertical  striation  ("bristle  bor- 
der") that  depends  not  upon  rows 
of  ;/ranules,  as  do  the  rods  of  the  outer 
zone,  but  upon  the  disposition  of 
the  threads  of  the  spongioplasm.  In 
consequence  of  maceration  and  other 
post-mortem  changes,  the  inner  zone 
may  undergo  partial  disintegration 
and  break  up  into  short  hair-like  rods 
which  have  been  mistaken  for  cilia. 
Although  the  spherical  nuclei  (.005- 
.007  mm.)  of  the  epithelium  of  the 
convoluted  tubule  are  sharply  de- 
fined, the  demarcations  between  the 
individual  cells  are  obscure  and  often 
wanting,  the  tubule  being  lined  by  a 
seemingly  continuous  nucleated  layer 
or  syncytium.  The  lumen  is  not 
uniform  throughout  the  convoluted 
tubule,  in  some  places  being  wide  and 
In  others  reduced  to  mere  clefts ;  these 
differences  depend  chiefly  upon  the 
varying  height  of  the  epithelial  Ittlins. 

3.  The  Spiral  Tubule.— Following  the  tortuous  path  of  the  convoluted  tubule,  the  canal  is 
usually  continued  into  the  medullary  ray  by  a  segment  whkrh,  while  comparatively  straight,  de- 


flecting 


tubule 


Blood-vessel 
Portion  t  f  medullan'  rmy.  showing  spiral  and  collectinit  tubules.  Y  400. 


. 


THE  KIDNEYS. 


1881 


scribes  a  wavy  or  spiral  course  in  its  descent  to  the  pyramid.  This,  the  spiral  nibule  of  Schachowa, 
differs  from  the  preceding  in  the  graduat  reduction  of  its  diameter  (.35-.040  nmi. )  and  in  the 
thiclcness  of  the  epithelial  lining,  the  cells  of  which,  although  retaining  the  general  character  of 
those  of  the  convoluted  tubule,  exhibit  a  distinct  demarcation  from  one  another  and  a  narrow 
homogeneous  inner  zone.  The  spiral  tubules  are  distinguishable  from  the  surrounding  collecting 
tubules  by  the  lighter  sharply  defined  cuboidal  lining  cells  of  the  latter.  Just  before  pa.ssing  into 
the  medulla  to  become  the  descending  limb  of  Henle's  loop,  the  spiral  tubule  diminishes  in  width 
and  in  consequence  ends  as  a  canal  of  conical  form. 

4.  The  Loop  of  Henle.— The  descending  limb  of  this  I  -like  segnient  is  distinguishetl  not 
only  by  the  coaspicuous  reduction  in  its  diameter  (.012-015  mm.),  being  the  narrowest  iNirt  of 
the  entire  uriniferous  tubule,  but  also  by  the  altered  character  of  its  epithelium.  The  latter 
consists  of  low  elements,  so  thin  that  the  oval  nuclei  cause  distinct  elev-itions  in  the  cells  which 
project  beyond  the  general  level  of  the  epithelium.    Since  the  nuci . .  usually  do  not  lie  exactly 


Fio.  1605. 


Fio.  1606. 


Henle's  loop" 

Collectiin  tutnile  ' 

L.ongitudina1  section  of  medulla  passing  throuKh 
Henle's  loop.     ^  400. 


Ascending  liml 


Longitudinal  section  o(  medulla,  showing  pans 
of  limbs  of  Henle's  loop.     X  40a. 

opposite  each  other,  the  projections  on 
one  wall  alternate  with  those  of  the 
other,  in  consequence  of  which  dispo- 
sition the  lumen  appears  wavy  and 
irregular,  although  not  much  reduced 
below  the  diameter  of  that  of  the  pre- 
ceding spiral  segment  and  generous  in 
proportion  to  the  entire  width  of  the 

tubule.     The  flattened  cells  consist  of  clear,  slightly  granular  cytopla.sm,  in  which  is  embedded 
a  distinct  elliptical  nucleus  of  relatively  large  size. 

The  ascending  limb  differs  from  the  descending  in  its  increased  diameter  (.024-.038  mm. ), 
which  depends  upon  sudden  augmented  thickness  of  the  walls  and  not  upon  the  width  of  the 
lumen,  the  darker  and  striated  appearance  of  its  epithelium,  and  its  extension  from  the  medulla 
into  the  cortex.  The  outlines  of  the  individual  lining  cells  are  not  sharply  defined  in  well-pre- 
served organs,  although  the  readiness  with  which  these  elements  undergo  post-mortem  change 
often  results  in  their  artificial  separation.  The  cells  are  often  irregular  in  height,  the  lumen,  in 
consequence,  varying  and  in  places,  especially  within  the  cortex,  being  almost  obliterated.  The 
nuclei  often  occupy  a  clear  area,  and  are  separated  by  striations  of  unusual  length.  Although 
the  cells  exhibit  a  differentiation  into  an  outer  rodded  zone,  a  finely  striated  inner  border,  as  seen 
in  the  epithelium  of  the  convoluted  tubules,  is  wanting  ;  where  an  inner  zone  is  represented,  it 
as.sumes  a  variable  vesicular  rather  than  a  striated  character.  The  length  of  the  loop  of  Henle 
is  influenced  by  the  level  of  the  corresponding  Malpighian  body  within  the  cortex— the  nearer 
the  latter  lies  to  the  medulla  the  greater  the  descent  of  the  loop  towards  the  papilla,  and  vice 
versa,  this  relation  probablv  depending  upon  the  intimate  association  between  the  termination 
of  the  ascending  limb  and  the  Malpighian  body.  According  to  the  reconstructions  of  Huber,' 
>  Amer.  Joum.  of  Anatomy,  vol.  iv.,  Supplement,  1905, 


1 883 


HUMAN   ANATOMY. 


%K^: 


Fio.  1607. 


on  gaining  the  Malpighian  corpuscle  the  ascending  limb  crosses  the  neck  in  close  proximity  to 
the  glomerulus,  with  which  it  is  connected  by  twigs  from  the  vas  efferens  (Hamburger'),  and 
then  arches  over  the  corpuscle  to  end  in  the  succeeding  connecting  tubule.  The  position  of 
the  sudden  transition  from  the  narrow  into  the  wider  tube  of  Henle's  loop  varies,  the  change 
exceptionally  occurring  after  the  turn  is  reached,  sometimes  within  the  loop  itself,  but  most  fre- 
quently within  the  descending  limb  a  short  distance  above  the  loop. 

5.  The  Distal  Convoluted  Tubule— On  gaining  the  level  of  the  corresponding  Malpighian 
body,  the  ascending  limb  gradually  widens  into  the  distal  convoluted  or  intermediate  tubule,  a 
canal  approximating  the  diameter  (.o4o-.a45  mm.)  of  the  surrounding  convoluted  tubules,  but 
differing  from  the  latter  in  its  wider  lumen  and  in  the  character  of  its  epithelium.  This  consists 
of  well-defined  cuboidcl  cells,  with  spherical  nuclei,  the  cytopla.sm  oi  which,  while  granular,  is 

comparatively  clear  and  devoid  of  stria- 
tions.  The  moderately  tortuous  path  of 
the  intermediate  tubule  is  marked  by  a 
number  of  abrupt  changes  in  direction, 
but  in  general  lies  for  a  time  enclosed  by 
the  arch  described  by  the  corresponding 
convoluted  segment  (Schweiger-Seidel), 
which  it  finally  crosses  (Huber). 

6.  The  Connecting  Tubule. — This 
portioi  of  the  tubule  ( .023-.0J5  mm.  in 
diameter)  resembles  the  preceding  seg- 
ment in  its  clear  epithelium,  the  lining 
cells,  however,  being  lower,  with  a  cor- 
responding increased  lumen.  After  a 
short  and  usually  arched  course,  the  con- 
necting tubule  enters  the  medullary  ray 
and,  uniting  with  similar  canals,  joins  in 
forming  the  collecting  tubule. 

7.  The  CoUecting  Tubule.— This 
first  lies  within  the  medullary  ray,  where 
it  form:  .he  beginning  of  the  system  of 
straight  duct-tubes  that  culminates  in 
the  canals  opening  upon  the  papilla, 
and  then  passes  into  the  renal  pyramid. 
During  their  course  through  the  medul- 
lar}' ray  the  collecting  tubules  repeatedly 
unite  to  produce  stems,  which,  while  in- 
creasing four-  or  fivefold  in  diameter,  are 
diminishing  in  number.  In  consequence 
of  this  fusion  within  the  pyramid,  the  col- 
lecting tubules  are  disposed  in  groups 
(Fig.  1609),  each  of  which  corresponds 
to  the  tubules  prolonged  from  a  single 
medullar}'  ray  and  is  surrounded  by  the 
limbs  of  the  loops  of  Henle.  On  enter- 
ing the  renal  pyramid,  the  groups  of  col- 
lecting tubules  at  first  are  separated  by 
the  intervening  bundles  of  straight  blood- 
ves.sels  {vasa  recta)  that  are  given  off 
from  the  larger  twigs  within  the  boun- 
dary zone  for  the  supply  of  the  medulla. 

After  pas.sing  to  within  about  5  mm.  of  the  apex  of  the  papilla,  towards  which  they  converge, 
the  large  collecting  canals  undergo  repeated  junction,  increa.sing  in  diameter  but  rapidly  dimin- 
ishing in  number,  to  form  the  wide  papillary  ducts.  The  epithelium  lining  the  collecting  tubules 
— the  larger  as  well  as  the  smaller — consists  of  c'«;ar  cuboidal  or  low  columnar  cells,  sharply 
defined  from  one  another  and  provided  with  spherical  nuclei.  The  light-colored  cytoplasm 
and  distinct  demarcation  of  these  elements  render  the  collecting  tubules  conspicuous  and  their 
recognition  easy. 

8.  The  Papillary  Ducts.- These,  the  final  segments  of  the  kidney  tubules,  number  from 
ten  to  eighteen  for  each  sinj,-le  papilla,  at  the  apex  of  which  they  end.  Each  is  formed  by  the 
junction  of  from  ten  to  thirty  of  the  larger  collecting  tubules  (.050-.060  mm.)  and  attains  a 
diameter  of  from  .2-.  5  mm.  The  lining  epithelium  is  composed  rif  mnspimous,  clear  columnar 
cells,  about  .oao  mm.  in  height  and  one-third  as  much  in  width,  which  rest  upon  a  distinct 

>  Archiv  /.  .'Vnat.  u.  Entwick.,  Suppl.  Bd.,  1890. 


I.onptudinal  ocction  of  renal  medulla,  showing  Henle'i 
loops  and  collectinjc  tubules.     X  45. 


THE  KIDNEYS. 


1883 


Blood-vrad 


I  >encendinx 
limb  ul  loop 


membrana  propria  almost  as  far  as  the  termination  of  the  canal.    At  this  point  the  membrane 
fades  away  and  the  epithelium  of  the  duct  becomes  continuous  with  that  clothing  the  surface  of 
the  papilla  and  lining  the  pelvis  of 
the  kidney.  ^"»-  '*»*• 

It  is  evident  that  the  num- 
ber of  Malpighian  bodies  and  uri- 
niferous  tubu'es  proper  is  greatly 
in  excess  o*  the  larger  collecting 
tubes,  ead)  papillary  duct  repre- 
senting the  termination  of  an  elab- 
orate system  of  dividing  canals  as 
far  as  the  connecting  tubules,  from 
which  point  the  true  uriniferous  tu- 
bules complete  their  tortuous  path 
without  further  subdivision. 

The  Supporting  Tiiaue. — 
The  interstitial  stroma  holding  in 
place  the  tubules  and  the  blood- 
vessels consists  of  a  net-work  of 
modified  connective  tissue,  or  re- 
ticulum, which  has  been  shown 
by  Mall  to  withstand  pancreatic 
digestion  and  to  form  a  continu- 
ous framework  throughout  the 
kidney.  The  stroma  is  most  abun- 
dant along  the  paths  of  the  in- 
terlobular and  the  larger  blood- 
vessels, from  the  adventitia  of 
which  delicate  trabecule  extend 
in  all  directions  to  form  the  meshes 
lodging  the  tubules,  smaller  ves- 
sels, and  capillaries.  Within  the 
cortex  the  supporting  tissue  is  meagre,  being  best  developed  akMig  the  interlobular  ves.sel'  and 
around  the  Malpighian  bodies.  According  to  Mall,  the  membrana  propria  of  the  tub  ilts  is 
resolvable  into  delicate  net-works  of  reticulum  directly  continuous  with  the  surrounding  ■  .>ma, 
the  general  arrangement  of  which  corresponds  to  the  disposition  of  the  tubules.  Within  the 
medulla  the  interstitial  tissue  is  much  more  abundant  than  in  the  cortex,  its  amount  increasing 
towards  the  apex  of  the  papilla,  in  which  location  considerable  tracts  of  comparatively  coarse 
stroma-fibres  separate  the  papillary  ducts.    At  the  surfaces  of  the  divisions  of  the  renal  substance 


AscetutiriK 
limb  of  loop 


Section  of  medulla  acrou  renal  pvramld.  •howinK  large  collecting  tubules, 
limbs  d  Henle's  loops,  blood-vessels,  and  stroma.    X  130. 


Fio.  1 610. 

Space  for  blood-vesael 


Fig.  1609. 


Blood -- 

vessels 


Uriniferous. 
tubules 


.*.    »•-  a 

•  •  -^^  ,•    V  SP 


^^^%v 


Section  across  upper  part  of  renal  p>Tii- 
mid,  showing  Rroujis  of  blood-vessels  sur- 
rounded by  uriniferous  tubules.    X  so. 


SupportiiiK  ntroma-timue  of  kidney  after 
pancreatic  dijceAtlon ;  spaces  lodged  tubules 
and  blood-vessels.     X  no. 


the  interstitial  tissue  is  continuous  with  the  investing  fibrous  capsule,  the  interlobar  septa,  or  the 
lining  of  the  pelvis,  as  the  case  may  be.  Not  only  the  blood-vessels,  but  likewise  the  nerve- 
trunks  and  the  lymphatics  are  provided  with  sheaths  of  the  renal  stroma. 


1 884 


HUMAN  ANATOMY. 


Fio.  1611. 

Two  calyces 


Blood-Vt»ne\9.—^rierifs. — ^The  renal  arteries— usually  one  to  each  kidney, 
but  not  infrequently  two,  and  in  exceptional  cases  three  or  even  four — are  of  unequal 
length,  the  right  one  being  the  longer  in  consequence  of  the  parent  stem,  the  aorta, 
lying  to  the  left  of  the  mid-line.  Embedded  within  the  subperitoneal  tissue  and 
covered  by  the  renal  fascia  (ps^e  1872),  they  pass  laterally,  accompnied  and  more 
or  less  masked  by  the  renal  veins,  to  the  hilum  of  the  kidney,  dunng  their  course 
giving  of!  small  twigs  to  the  capsula  adiposa  as  well  as  to  the  suprarenal  bodies. 
Just  before  entering  the  kidney,  or  within  the  hilum,  the  renal  artery  divides  into  an 
anterior  (ventral)  and  a  posterior  (dorsal)  branch,  each  of  which  embraces  the  pel- 
vis and  divides  into  four  or  five  twigs  that  hug  their  respective  wall  of  the  sinus. 
Preparatory  to  entering  the  kidney,  each  twig  breaks  up  into  from  three  to  five 

smaller  divisions  which  enter  the 
renal  substance  through  the  vascu- 
lar foramina  surrounding  the  pa- 
pilla:. On  entering,  they  piss 
along  the  sides  of  the  papillae,  their 
course  corresponding  in  position  to 
the  original  tracts  of  connective  tis- 
sue that  separate  the  primary  di- 
visions of  the  foetal  kidney  (page 
1876)  ;  they  are  therefore  appro- 
priately designated  interlobar  ar- 
teries. The  general  expansion  of 
the  branches  derived  from  the  an- 
terior and  posterior  arteries  is  par- 
allel to  the  corresponding  ventral 
and  dorsal  surfaces  of  the  kidney  ; 
the  intervening  zone  along  the 
convex  border  of  the  organ  con- 
tains few,  if  any,  of  the  larger  ves- 
sels and,  in  consequence,  ap[>ears 
lighter  in  color,  constituting  the 
white  line  of  Brodel.  The  vessels 
supplying  the  kidney  do  not  anas- 
tomose, each  such  "end"  artery 
providing  for  a  particular  area  of 
renal  substance.  On  reaching  the 
level  of  the  bases  of  the  renal 
pyramids,  each  interlobar  artery 
breaks  up  into  a  tree-like  bundle 
of  twigs,  some  of  which  pursue  an 
arched  course  across  the  bases  of 
the  pyramids,  thereby  producing 
the  impression  of  a  series  of  arcades 
at  the  junction  of  the  medulla  and  cortex.  From  these  vessels  two  series  of  terminal 
branches  arise,  one  for  the  supply  of  the  cortex,  the  other  for  that  of  the  medulla. 


Inferior  divialon  of  pelvis 


preparation  of  injected  rirht  kidney, 
from  beliind,  sliowinff  relations  of  oranchen  of 
renal  arter>-  to  divisions  of  renal  pelvis. 


The  cortical  arterioles  pursue  a  course  Renerally  perpendicular  to  the  free  surface,  towards 
which  they  run  between  the  cortical  lobules,  ftiving  off  short  lateral  twigs  that  end  as  the  vasa 
afferentia  in  the  glomeruli  of  the  .Malpighian  bodies.  The  latter  are  arranged  in  columns  in 
correspondence  with  the  path  of  the  interlobular  cortical  arterioles.  Some  of  these,  however, 
do  not  give  off  vasa  afferentia,  but  ascend  to  the  kidney  capsule,  for  the  supply  of  which  they 
provide  in  conjunction  with  the  direct  branches  from  the  renal  artery. 

After  traversing  the  capillary  complex,  the  blood  is  carried  from  the  glomerulus  by  the 
vas  efferens,  which,  smaller  than  the  vas  afferens,  on  its  exit  immediately  breaks  up  into  the 
cortical  capillaries  that  form  net-works  enclosing  the  tubules  within  the  labyrinth,  and,  continuing, 
surround  those  within  the  medullary  ray,  in  the  latter  situation  the  meshes  being  relatively  longer 
and  more  open  and  containing  blood  that  has  already  supplied  the  proper  urniferous  tubules. 

The  medullary  arterioles,  derived  from  the  arching  terminal  branches  of  the  interlobar 
stems  at  the  ba.ses  of  the  pyramids,  descend  within  the  latter  as  bundles  of  .adially  disposed 


THE   KIDNEYS. 


1885 


straight  twigs  (arleriola  recta)  that  at  first  surround  the  groups  of  collecting  tubules  and  then 
break  up  to  take  part  in  forming  the  capillar>'  net-work  of  the  medulla.  From  these  meshes  the 
blood  Is  collected  by  the  straight  venous  radicles  that  accompany  the  arterioles  and,  with  the 
latter,  constitute  the  vasa  recttr,  owing  to  whose  presence  the  darker  stris  of  the  medulla  are  due. 
In  consequence  of  numerous  anastomoses  the  va.scular  supply  of  the  medulla  is  less  independ- 
ent of  that  of  the  cortex,  than  was  formerly  supposed  (Huber). 

Veins. — The  veins  of  the  kidney  are  also  disposed  as  cortical  and  medullary 
branches  which  empty  into  larger  stems  {vena  arci/ormes)  that  cross  the  ba.ses  of 
the  pyramids  as  a  senes  of  communicating  venous  arcades. 

The  blood  within  the  cortkal  capillaries  escapes  by  three  paths  :  ( i )  through  numerous 
small  veins  that  traverse  the  outer  third  of  the  cortex  towards  the  capsule,  beneath  which  they 
empty  into  larger  stems  running  parallel  to  the  free  surface  of  the  kidney.  From  three  to 
five  of  these  horizontal  ves- 

Fin    i6i*. 


sels  converge  towards  a  com- 
nion  point  and  thereby  pro- 
duce a  star-like  figure  (vena 
stellala),  which  is  the  begin- 
ning of  the  inlerlobular  vein 
that,  in  company  with  the  cor- 
responding arteriole,  passes 
through  the  cortex  to  become 
tributary  to  the  venous  arcade 
at  the  base  of  the  pyramid  ; 
(3)  through  small  venous 
branches  that  empty  directly 
into  the  interlobular  veins  at 
various  levels ;  (3)  through 
the  deep  cortical  veins  that 
traverse  the  inner  third  of  the 
cortex  and  are  tributaries  of 
the  venae  ardformes.  The 
medulla  is  drained  by  the  ven- 
ula  recta,  straight  vessels 
•hat  begin  in  the  medullary 
capillary  net-work  and  empty 
into  the  arciform  veins.  The 
latter  terminate  in  the  larger 
interlobar  veins  that  accom- 
pany the  arteries  along  the 
sides  of  the  pyramids  and 
emerge  into  the  sinus  around 
the  papills.  The  further 
course  of  the  relatively  large 
and  valveless  venous  trunks 
corresponds  with  that  of  the 
arteries ;  the  veins  draining 
each  half  of  the  kidney  unite 
into  a  single  stem,  the  two 


stellate 
vein 

Connecting 
vein 


EnBient 
vessel 


Medullary 


Capillar)-  net -work- 


Papilla 
Diagram  allowing  arrangement  of  blood-vcsielt  of  kidney. 


(After  Ditsr.) 


thus  derived  joining  to  form  the  renal  vein.  The  latter  usually  lies  anterior  to  the  renal  artery  in 
its  path  to  the  vena  cava,  the  left  vein  being  longer  than  the  right  in  consequence  of  the  position 
of  the  cava  on  the  right  of  the  spine. 

The  lymphatics  of  the  kidney  occur  as  a  superficial  and  a  deeper  net-work. 
According  to  the  investigations  of  Stahr'  and  of  Cunfe,'  the  superfia  'iphatics 
comprise  a  delicate  subcapsular  mesh-work  from  which  two  systems  jilecting 

trunks  arise  ;  the  one  passes  into  the  kidney  to  join  the  deeper  lyn.,  'atics  within  the 
renal  substance,  the  other  pierces  the  capsule  to  unite  with  the  perirenal  lymphatics 
within  the  capsula  adiposa.  The  deep  lymphatics  arise  within  the  cortex  from  deli- 
cate interlobular  net-works,  the  general  path  of  the  more  definite  stems  being  that  of 
the  blc  d- vessels.     On  leaving  the  hilum,  the  larger  collecting  trunks — from  four  to 

'  Archiv  f.  Anat.  u.  Entwick.,  1900. 
»  Bull.  d.  Soc.  Anat.,  F6v.    1902. 


1886 


HUMAN  ANATOMY. 


seven  in  number — follow  the  renal  artery  and  vein,  especially  the  latter,  which  they 
surround.  The  lymphatics  of  the  kidney  end  chiefly  in  the  nodes  lying  at  the  sides 
or  in  front  of  the  aorta  ;  small  lymph-nodes  frequently  occur  in  the  vicinity  of  the 
hilum. 

The  nerves  of  the  kidney  are  derived  from  the  renal  plexus  formed  by  contri- 
butions from  the  solar  and  aortic  plexuses  and  the  least  splanchnic  nerve.     The 


Pio.  1 613. 


StaUatevcia 


Glomenilui  ol 
Malpixhian  body 


Interlobular  aitcrjr 


Interlobular  vein 


O^tUlary  net-work  in 
labyrintli 


Capillary  nc 
mcduuar)' 


net-work  in 
rray 


Large  blood-vcaaels  at 
Junction  o(  cortex  and 
medulla 


Longitudinal  lectlon  ol  Injected  kidney  of  dog,  •howinK  xenenl  arrangement 
o<  blood-veuels  of  cortex  and  adjacent  mcdulu.    X  40. 


plexus  accompanies  the  renal  artery,  which  it  surrounds  with  its  mesh-work,  into  the 
sinus  ;  within  the  latter  is  formed  a  well-marked  perivascular  net-work  from  which  a 
number  of  twigs  are  given  off  to  supply  the  walls  of  the  pelvis  and  ureter,  while  the 
majority  accompany  the  vessels  into  the  kidney.  The  investigations  of  Retzius, 
Kolliker,  Disse,  Berkley,  and  especially  of  Smimow,'  have  shown  that  all  the  renal 
blood-vessels  are  generously  provided  with  fibres  for  the  supply  of  the  muscular 

>  Anatom.  Anzeiger,  Rd.  xix.,  1901 


PRACTICAL  CONSIDERATIONS:    THE  KIDNEYS  1887 

tissue  of  their  walls.  In  continuation  the  nerve-fibres  pass  between  •'  e  urinife/ous 
tubules  and  form  plexuses  surrounding  the  membrana  propria.  S.jirnow  traced 
the  ultimate  fibrillae  within  the  tubules,  their  free  endings  lying  between  the  epithelial 
cells.  The  vessels  and  tubules  of  the  medulla  are  provided  with  similar  but  less 
closely  disposed  nervous  filaments  which  are  destined  chiefly  for  the  muscular  tissue. 
According  to  the  last-named  investigator,  the  nerves  of  the  kidney  include  some 
sensory  and  both  meduUated  and  non-medullated  fibres.  The  fibrous  capsule  also 
possesses  a  rich  nervous  supply. 

Variations. — More  or  less  conspicuous  furrows  are  frequently  seen  on  the  surface  of  the 
adult  kidney  j  these  represent  a  persistence  of  the  lobulation  normally  present  in  the  hcUis  and 
the  young  child. 

In  addition  to  variations  in  size,  a  marked  deficiency  on  one  side  t>eing  usually  compensated 
by  a  large  organ  on  the  other,  the  Icidneys  often  present  difTerent  degrees  of  union  depending 
upon  abnormal  approximation  or  fusion  of  the  primary  renal  aniages.  The  connection  may 
consist  of  a  band,  chiefly  of  fibrous  tissue,  that  unites  otherwise  normal  organs  ;  or  it  may  tie 
formed  by  an  istnmwt  of  renal  tissue  that  extends  between  the  approximated  lower  |M>les ;  or 
the  two  organs  may  form  one  continuous  (J-shaped  mass  across  the  spine,  then  constituting  a 
"  horseshoe  "  kidney.  Extreme  displacement  .ind  fusion  may  produce  a  single  irregular  orvan 
whose  primary  double  anlage  is  indicated  by  the  presence  of  two  renal  ducts  that  descencTon 
different  sides  of  the  pelvis  to  terminate  normally  in  the  bladder.  Absence  of  one  kidney 
occasionally  occurs,  the  organ  present  usual  I  y  being  correspondingly  enlarged.  Complete  absence 
of  both  kidneys  has  been  observed  as  a  rare  congenital  malformation. 

PRACTICAL  CONSIDERATIONS  :   THE  KIDNEYS. 

Congenital  abnormalities  of  the  kidneys  may  affect  (a)  their  shapie,  size,  and 
numlier  ;  (6)  their  position  ;  and  kidneys  that  are  abnormal  in  one  of  these  respects 
are  apt  to  be  so  in  others.  The  matter  is  of  practical  importance  in  relation  to  the 
diagnosis  of  intra-abdominal  swellings  and  to  the  many  operations  now  undertaken 
for  the  relief  of  various  renal  conditions. 

(a)  Anomalies  as  to  Shape,  Size,  or  Number. — One  kidney  may  be  congenitally 
absent  or  gready  atrophied ;  may  be  constricted  so  as  to  a.ssume  an  hour-glass 
shape  ;  or  lobulated,  as  in  the  foetal  condition  ;  or  the  two  kidneys  may  be  fused  so 
that  ( I )  their  inferior  portions  are  united  by  a  band  of  tissue — glandular  or  fibrous — 
that  crosses  the  vertebral  column,  usually  in  the  lumbar  region  ("horseshoe 
kidney")  ;  or  (2)  they  may  form  an  irregularly  bilobed  mass,  one  side  of  which  is 
much  larger  than  the  other,  or  become  one  single  "disk-like"  kidney  lying  in  the 
mid-line  on  the  lumbar  spine,  on  the  sacral  promontory,  or  in  the  hollow  of  the  sacrum 
(Rokitansky,  Morris). 

Of  these  conditions  the  rarest  is  the  true  congenital  absence,  or  extreme  atrophy 
of  a  kidney  ( i  in  2650)  ;  horseshoe  kidneys  are  more  than  twice  as  common  ( i  in 
1000)  ;  while  one-sided  renal  atrophy  associated  with  post-natal  disease  is  relatively 
frequent  (i  in  138)  (Morris). 

Both  kidneys  have  been  absent  in  many  still-bom  children  and  acephalous 
monsters.     In  a  very  few  cases  a  sufiemumerary  kidney  has  been  found. 

Anomalies  affecting  the  blood-supply  to  the  kidney  occur  in  nearly  50  pier  cent, 
of  cases.  The  renal  arteries  are  usually  increased  in  number,  or  divide  at  once — 
before  reaching  the  hilum — into  several  branches,  foetal  conditions  in  the  human 
species  that  are  permanent  in  many  birds  and  reptiles.  Accessory  or  supernumerary 
veins  are  much  more  rarely  found. 

{b)  Anomalies  of  Position. — Congenital  displacement — apart  from  the  horseshoe 
kidney — usually  affects  one  kidney,  which  is  apt  to  be  found  in  the  vicinity  of  the 
sacral  promontory  or  the  sacro-iliac  joint,  but  may  be  either  higher  or  lower,  and 
may,  by  its  malposition,  pve  rise  to  serious  or  even  fatal  error  in  diagnosis  or  treat- 
ment 

It  would  seem  proper  to  include  here  those  rare  temporary  displacements  that 
are  due  to  the  congenital  presence  of  a  mesonephron,  which — as  the  usual  support 
given  by  the  peritoneum  is  lacking,  and  as  the  contained  blood-vessels  are  in  such 
cases  of  abnormal  length — permits  mobility  of  the  kidney  beyond  the  physiological 
limits  (floating  kidney). 


1888 


HUMAN  ANATOMY. 


Movable  Kidney. — The  extent  vk  the  normal  kidney  movement— of  ascent  during 
expiration  or  while  Tying  supine,  and  of  descent  during  inspiration  or  while  standing 
erect — does  not,  on  an  avenge,  much  exceed  an  inch  in  the  vertical  direction.  There 
may  also  be  a  slight  lateral  movement.  When  this  limit  is  distinctly  and  greatly 
overpassed  the  condition  known  as  ' '  movable  kidney' '  results.  The  normal  kidney 
is  usually  not  palpable  below  the  costal  arch.  Occasionally  the  lower  end  of  the 
right  kidney  may  be  felt  there  just  external  to  the  rectus  muscle.  In  emaciation  the 
lower  ends  of  both  kidneys  may  be  palpable. 

Three  degrees  of  abnormal  mobility  have  been  arbitrarily  but  usefully  agreed 
upon  fur  purposes  of  description  :  ( i )  The  lower  half  may  be  felt  by  bimanual  pal- 
pation— the  fingers  of  one  hand  being  pressed  into  the  ilio-costal  sf>ace  posteriorly, 
and  of  the  other,  into  the  subcostal  region  anteriorly— during  deep  mspiration. 
(3)  The  greater  part  of  the  kidney  or  the  whole  organ  may  be  felt  during  deep 
inspiration,  but  ascends  under  cover  of  the  ribs  and  liver  during  expiration.  (3)  The 
whole  kidney  descends  and  can  be  retained  between  or  below  the  examiner's  fingers 
during  the  respiratory  movements  (Morris). 

The  most  important  factors  in  holding  the  kidney  in  its  normal  position  in  the 
renal  fossa  ((Kige  1874)  are  :  (a)  the  perirenal  fascia,  which  through  its  attachment  to 
the  transversalis  fascia  and  to  the  perinephric  fat,  in  conjunction  with  (^)  the  peri- 
toneum, where  that  covering  exists,  prevents  any  undue  mobility;  (c)  the  renal  vesse'  . 
which  must  correspond  in  length  to  the  radius  of  the  circle  of  movement  of  the  kidn  - 
and,  to  an  extent,  resist  elongation  ;  (</)  intra-abdominal  pressure,  which,  thrc.a  .;. 
the  upward  thrust  of  the  more  mobile  viscera,  adds  to  the  support  that  (^)  thev  -d 
their  attachments  give  to  the  viscera  in  the  upper  zone  of  the  abdomen  ;  (/ )  ihe 
shape  of  the  renal  fossx,  which,  like  the  kidneys  themselves,  are  somewhat  narrower 
at  their  lower  extremities. 

Undue  mobility  of  the  kidney  b  thus  favored  by  (a)  congenital  absence  of  the 
peritoneal  support  (floating  kidney, — vide  supra)  ;  (^)  diminution  of  the  tension  of 
the  peritoneum  and  perirenal  kiscia  from  absorption  of  perinephric  fat ;  (<-)  repeated 
jars  and  jolts,  as  from  jumping  or  falling,  or  from  coughing  or  straining,  that  tend 
to  elongate  the  renal  vessels  as  well  as  to  stretch  the  peritoneum  and  its  attachments 
and  thus  increase  both  the  retroperitoneal  space  in  which  the  kidney  moves  and  the 
radius  of  the  arc  of  its  movement ;  '4)  pregnancy,  the  removal  of  intra-abdominal 
tumors  or  of  accumulations  of  flui  or  other  conditions  that  produce  laxity  and 
weakness  of  the  abdominal  walls  ;  (e)  ptosis  of  other  viscera,  acting  either  by  their 
push  from  above  (liver,  spleen)  or  their  drag  from  below  (colon)  ;  or  (/")  general 
muscular  weakness,  acting  not  only  by  reason  of  the  associated  lack  of  tonicity  of 
the  abdominal  wall,  but  also  through  the  modification  in  shape  of  the  renal  fossae, 
the  depth  of  which  depends,  cateris  paribus,  on  the  development  of  the  loin  muscles, 
and  especially  of  the  {>soas  and  quadratus  lumborum. 

A  careful  study  of  the  body-form  in  its  relation  to  movable  kidney  seemed  to 
show  ( Harris)  that  a  relative  diminution  in  the  capacity  of  the  middle  zone  or  area 
of  the  body-cavity  (containing  the  liver,  stomach,  spleen,  pancreas,  and  larger  por- 
tion ot  each  kidney),  either  original  or  acquired  (as  from  tight  lacing),  acts  by  forcing 
the  liver  and  spleen  downward  upon  the  kidneys,  and  at  the  same  time  depriving 
them  of  the  support  afforded  by  the  narrowest  or  most  constricted  portion  of  the 
parietes  of  this  zone,  which  narrow  portion  is  then  above  the  centre  of  the  kidney 
instead  of  below  it,  as  it  should  be  normally. 

Consideration  of  the  above-mentioned  anatomical  factors  makes  clear  the  greater 
frequency  (80  per  cent.)  of  movable  kidney  in  women  than  in  men.  It  should  be 
added  that  in  women  the  renal  fossae  are  normally  shallower  and  less  narrowed  at  the 
lower  ends  than  in  men,  the  depth  and  the  narrowing  def)ending,  as  has  been  said, 
upon  muscular  development.  It  will  be  understood,  too,  why  among  the  women 
who  suffer  from  this  condition  is  found  a  so  considerable  proportion  who  are  thin  and 
round-shouldered,  with  long,  curved  spines  and  flattening  and  adduction  of  the  lower 
ribs,  or  who  have  had  several  children,  or  one  difficult  labor,  or  an  exhausting  illness 
attended  by  emaciation,  or  have  been  addicted  to  tight  lacing.  In  both  sexes  the 
history  of  a  violent  fall  or  of  a  chronic  cough  is  not  infrequent. 

Movable  kidney  is  thirteen  times  more  frequent  on  the  right  side  than  on  the 


PRACTICAL   CONSIDERATIONS:    THE   KIDNEYS. 


1H89 


left,  because  of  the  foUuwing  conditions,  which  are  ol  varying  relative  importance  in 
different  cajes  :  (a)  the  left  perirenal  fascia  is  sUengthened  by  some  fibrous  bandh, 
remnants  of  the  fusion  of  the  descending  mesocoU)i»  with  the  primitive  |)arietal  jK-ri- 
toneum  (MoiUlin),  the  Idt  kidney  being  thus  more  firmly  bound  to  the  descending 
colon  than  is  the  right  to  the  ascending  colon  ;  (d)  the  greater  size,  weight,  and 
density  of  the  liver  as  compared  with  the  spleen,  and  its  more  intimate  association 
with  respiratory  movements,  making  the  impact  of  the  former  on  the  upper  surface  of 
the  right  kidney  both  more  frequent  and  more  potent  than  the  similar  conuct  of  the 
spleen  with  the  left  kidney  ;  (c)  the  greater  length  of  the  right  renal  artery,  which  has 
to  cross  the  mid-line  to  reach  the  kidney  ;  although  the  right  vein  issimilariy  shorter 
than  the  left  vein,  it  offers  less  resistance  to  elongation  than  does  the  left  renal  artery  ; 
(rf)  the  right  kidney  is  usually  lower  than  the  left  kidney  (page  1871),  and  therefore 
more  easily  loses  the  support  of  the  parietes  at  the  region  where  that  support  is  most 
effective  (vuU  supra)  ;  {e)  the  connection  of  the  left  suprarenal  capsular  vein 
with  the  left  renal  vein  gives  some  fixation  to  the  left  kidney,  as  the  capsule  remains 
in  position  and  does  not  follow  the  kidney  in  its  abnormal  movements  (Morris,  Cru- 
veiUiier)  ;  (/  )  the  right  renal  fossa  is  more  cylindrical — i.e.,  less  narrowed  at  its 
lower  end — than  the  left,  especially  in  women,  owing  to  a  slight  torsion  of  the  lumbar 
spine  (Moullin),  or  perhaps  to  the  greater  width  and  development  of  the  right  side 
of  the  pelvis. 

From  an  anatomical  stand-point,  the  symptoms  caused  by  excessive  mobility  are  : 

1.  Those  due  to  traction  upon  and  irritation  of  the  nerves ;  as,  for  example, 
pain,  felt  in  the  loins  and  often  referred  to  the  lower  abdomen  or  genitalia,  owing  to 
the  association  of  the  renal  plexus  with  the  spermatic  or  ovarian  plexus  ;  the  same 
association  gives  to  the  pain  produced  by  pressure  upon  a  movable  kidney  the  sick- 
ening quality  peculiar  to  testicular  nausea  (page  1951);  nausea  and  vomiting,  due  to 
a  similar  connection  with  the  solar  plexus  and  pneumogastrics  ;  neurasthenia,  which 
may  be  either  a  result  of  movable  kidney — through  nerve  irritation — or  a  c^use, 
when  it  has  produced  emaciation  and  muscular  weakness. 

2.  Those  due  to  traction  upon  the  gastro- intestinal  tract,  especially  upon  the 
duodenum  and  bile-ducts,  as  digestive  disturbance,  flatulence,  constipation,  and  even 
jaundice.  As  the  second  portion  of  the  duodenum  is  dragged  upon  throiigh  its 
areolar-tissue  connection  with  the  right  kidney,  its  lack  of  mesentery  prevents  it  from 
moving  downward,  it  is  stretched  so  that  its  lumen  is  diminished,  and  interference 
with  the  digestive  current  and  secondary  dilatation  of  the  stomach  follow  (Bartels)  ; 
at  the  same  time  the  bile-ducts  are  elongated  and  narrowed  and  the  passage  of  bile 
through  them  is  interfered  with  (page  1731).  On  the  left  side  similar  disturbance  of 
digestion  may  follow  the  pull  of  the  kidney  on  the  stomach  and  colon. 

3.  Those  due  t  traction  upon  the  vessels,  resulting — as  the  compressible  vein  is 
more  readily  affected — in  congestion  of  the  kidney,  sometimes  so  marked  as  to  give 
rise  to  a  temporary  haematuria. 

4.  Those  due  to  traction  upon  or  angulation  or  twisting  of  the  ureter,  causing  an 
acute  hydronephrosis,  at  first  intermittent.  Tuffier  has  shown  that  the  bending  or 
kinking  of  the  ureter  when  a  kidney  is  displaced  occurs  in  more  than  50  p^r  cent, 
of  cases  at  a  jxjint  a  few  centimetres  below  the  pelvis,  where  it  is  held  again.st  the 
abdominal  wall  by  strong  connective  tissue  and  cannot  follow  the  moving  kidney 
(Landau).  In  some  cases,  as  a  result  of  ureteral  stenosis  at  the  point  of  obstruc- 
tion, secondary  changes  occur  in  the  kidney  which  consist  essentially  in  (a)  an 
atrophy  of  the  renal  structure  most  directly  exposed  to  pressure  from  the  retained 
urine  (Virchow)  ;  and  (*)  interstitial  degeneration  resulting  from  interference  with 
nutrition,  due  to  the  facts  that  distention  of  the  pelvis  of  the  kidney  takes  the  direc- 
tion of  least  resistance,  which  is  forward,  and  that  the  pelvis  b  placed  behind  the 
vessels  where  they  enter  the  hilum,  so  that  as  it  distends  it  stretches,  flattens,  and 
obstructs  them  (Griffiths). 

As  Morris  has  pointed  out.  the  increased  resonance  and  diminished  resistance  in 
the  loin,  described  as  indicating  the  absence  of  the  kidney  from  its  nn  in.J  position,  are 
of  little  value  because  (a)  the  ilio-costal  space  in  some  positions  ^\  the  trunk  and 
thigh  is  somewhat  hollow  ;  (Jb)  the  thickness  of  the  loin  muscles  and  of  the  fat  makes 
the  percussion-note  dull  even  when  the  kidney  is  displaced  ;  and  (r)  in  its  normal 

119 


1890 


HUMAN    ANAiC'MY. 


position  the  kidney  is  so  overlappe<-  '<y  the  lo\  er  chnracic  wall  that  the  resonanct- 
and  resistance  of  the  loin  have  at  tx   '  Imt  little  idatii  1  to  it    page  1873)- 

Of  course,  obstruction  of  the  ui  'er  fri m  f  ^-r  causes — m  valvular  folds  at  the 
ureteral  orifice,  thought  to  follow  a  lu  ');t;nitai  c^  >  ptionally-  oblique  insertion  of  the 
ureter  into  the  pelvis  (Virchow),  or  i)rought  ,1  ^ut  by  distention  of  the  pelvis 
(Simon  >,  or  aggravated  by  liwelling  oi  the  peUu  .auc<>»a  (Kiister,  Cabot; — or  ob- 
structive disease  of  any  part  of  the  louer  urinary  tr.n.'  ojay  al»i  result  in  a  hydrone- 
phrosis which,  if  infection  occurs, — as  it  often  does, — becomes  a  pyonephrosis.  Either 
a  purulent  collection  thus  formed  or  an  abscess  originatHi^  in  the  renal  structure 
(pyogenic  or  tuberculous  infection)  may  find  its  way  iiii^  the  fatt  and  connective 
tissue  of  the  loin, — perinephric  tissue,— or  suppuration  may  reach  that  rejjiun  from 
other  sources  or  may  occur  there  primarily. 

Perinephric  abscess  is  characterized  by  certain  symptoms  which  should  be  studied 
in  connection  with  the  anatomy  of  the  region,  as  (^a)  pain,  radiating  to  the  lower  ab- 
domen, genitalia,  or  thigh, — i.e.,  in  the  distribution  of  the  iliu-hypogastrir  ilit)  ingui- 
nal, anterior  crural,  obturator,  and  othfcr  branches  of  the  lumbar  plexus  ;  bj  flexion 
and  adduction  of  the  thi^h,  from  irritation  of  the  motor  filami  nts  of  the  same  nerves, 
especially  if  the  abscess  is  about  the  lower  pol*-  of  the  kidney,  -md  therefore  in  inti- 
mate relation  with  the  third  and  fourth  lumbar  nerves,  from  which  the  supply  of  the 
flexors  and  adductors  is  chiefly '  derived  ;  (r )  bending  of  the  body  towards  the 
afiected  side,  towards  which  the  concavity  of  a  lateral  lumbar  curve  in  the  spine  is 
directed, — a  symptom  which,  like  6,  may  be  due  either  to  muscular  spasm  or  to  an 
instinctive  effort  to  increase  the  loin  space;  (d)  intestinal  disturbance  from  the 
proximity  of  the  abscess  to  the  colon,  into  which  it  may  ■  ;>en.  Such  abscess  may 
also  penetrate  the  lumbar  aponeurosis  and  the  quadratus  lumb«  rum  muscle  and  ap- 
pear in  the  loin  at  the  outer  border  of  the  erector  spinae  between  the  latissimus  dorsi 
and  external  oblique  (the  lower  part  of  which  interval  is  Petit's  triangle,  q.  v. ),  or  mav 
descend  by  gravity  into  the  pelvis,  or  may — very  exceptionally— open  into  the  peri- 
toneal cavity. 

Abscess  of  the  kidney  which  penetrates  the  renal  capsule  to  reach  the  perirenal 
region  usually  docs  so  at  a  non-peritoneal  area  of  the  kidney  surface,  but  does  not 
necessarily  reach  the  loin.  As  reference  to  the  relations  of  the  kidney  (page  1873) 
will  show,  the  pus  may  be  evacuated  directly  into  the  colon  or  duodenum,  or  more 
fre<juently — because  the  apposed  areas  are  covered  with  peritoneum  which  favors 
limiting  adhesions — into  the  stomach  or  liver,  or  through  the  diaphragm  into  the 
base  of  the  chest. 

Renal  calculus  produces  symptoms  which  are  analogous  to 
above  as  associated  with  suppurative  disease  in  or  about  the  kidnt 
apart  from  hsematuria  and  pyuria  and  the  physical  evidence  of  the  pr>^ 
such  as  is  afforded  by  the  X-rays — depend  for  their  interpretation  11  j  - 
of  the  renal  reflexes, — i.e.,  of  the  association  of  the  small  and  lesser 
the  tenth  to  twelhh  dorsal  and  first  Uimhar  spinal  segments  with  the  .enso^^'  and 
motor  nerves  derived  from  the  same  segmeri's.  These  sympton;--  are,  111  part,  pain 
radiating  to  the  genitalia,  vesical  irritability,  nausea  and  vomiting,  -rtil  tenesmus. 
and  retraction  of  the  testicle.  The  last-named  symptom  is  m- '■■  mi- 
and  young  jiersons,  in  whom  the  gland  is  "ften  drawn  up  '.\y 
even  into  the  inguinal  canal.  After  pubertj'  is  the  testis  increases 
cremaster  grows  feebler  with  age.  the  retraction  becomes  less  obvi  ^i 

It  has  been  suggested  that  occasionally  the  sudden  exacerbw 
ring  at  night  when  the  patient  is  at  rest  may  be  due  to  the  passa 
the  colon  that  presses  against  the  kidney  (Jacobson  . 

The  aching  pain  beginning  at  the  lower  edge  of  the  last  rib,  in 
it  and  the  spine,  and  extending  along  the  edge  of  the  rectus  mus.  i. 
of  the  umbilicus,   is  probably  reflected  along  tht   last  dorsal  nerve, 
certainly  relieved  by  uperatioiis  in  which  that  ner\  e  is  divided,  but  the  st     -  is 
found  (Lucas). 

Disease  of  the  kidney,  when  non-suppurative,  has   >ut  little  obvious  an;-    m: 
bearing.     It  may  be  noted,   however,  that  the  time-h  mored  practice  of  aDplying 
counter-irritants  and  heat  to  the  loin  in  renal  congestions  has  a  scientific  bas-    in  the 


'hose  described 

and  which — 

>  nee  of  i'  stone, 

rn  a  knowledge 

:  'anchnics  and 


Ked  in  cbikiv^Ti 
'  xtemal  t     _  'ft 
weight  a        ht 
-  (Lucc 
n  of  p.-i 
of  flatu 


•ccui 
rlon= 


ang-le  l)et»et 

>tki«i  the  \fv*- 


I 


PRACTICAL   CONSIDERATIONS:    THl     KIDNK    S. 


1891 


free  ^nastonn>-.i»  between  the  low  ■ 
the  par><-tt3>  oi  the  loin,  aiut  i«i>nv 
part  of  the  "  suhperitontal  arteri;' 
by  a  tiinilar  v(  '>ua  anaMlotnattis. 
or  countcr-irrit;!  ts  to  the  loin  may 
v«9!iels  an<)  with=  rawing  blood  fron' 
In  son. -whai  the  «ime  line  of  i, 


intercottal  and  upper  lumbar  arteries,  supplying 
tr.    nal  branrheaol  the  renal  artery.     Tni! 


iiJlexir*"   • 
ihus  the 
u-t    at  If 

u^ht, 


to  the  bi  ts  ?hat  1   •■  capsuU     nd  pelv  is  o«  tht 
reni»i  pain,    u,{  1- :>endent         iitfectioii,  or  on  the  Irrit. 
pla<    nent,  .suall    means  im  caaed  t     sion  ;  that  great 
gesuufl  is  theteforr  dten  e\ptnenced  a  tcr  nephrotomies 


Turner) — is  accompanied,  of  murse, 
,f>lication  of  cups  1  'r  hot  fomentation!! 
tempffrar  !v    by  cnlarginv   -iU'    rficial 
ixl  kidney. 

>n,  attention  mil  called 

he  seniutive  |)ort,   ns  ;  that 

11  of  a  calculus,  <  r  on   lis- 

liel  of  both  jwin  .,  ud  c<.n- 

at  are  merely  expl-  iratorv. 


or  infl 
(.onR. 
idney  1 


.if  ..,  the 

to  chronic 

n-A  ) ,  and 

<i)Miila- 

rated 


th. 


imp!' 
\i!a: 


althonjfh,  if  the  teiion  is   !ue  to  accunailation  of  fluid  wUhin  the  renal  \>e\\       i£rav 
rena,  congestion    ,iay  d  ito  evacuation  and  the  accompanying  siwlden  relief  from 

habitual  pressure  just  as  .  ((.'.lows  some  cases  of  catheterization  of  habituall ,  distewle.' 
iiladders  i  Belheld  :  ar.  1  th.it  occasional  cures  of  various  forms  of  acute  or  siib:uut. 
nephritis,  of  of  "albuminuria  associated  with  kidney  tension  '  1  Harrison  i-.  be«>n 
obtauivf?  m  rely  by  itiiitg  the  kidney  capsule  with  or  w  hout  pii 
kidney  r"«lf.  The  i.iore  rece  it  attempt  (Israel)  to  :inply  tl'..  m<  ' 
nttihriti  vith  sevt  or  .iangcrous  symptoms  (especial  colic  and  j 
th«  still  more  r.  I  ent  ntrmiuction  (  Edebohls)  of  bilateral  deco-  ali' 
tion — in  chronu  nephniis  without  such  symptoms,  have  not  at  is  tii 
their  value.  T  v  a  ;>  of  mii  <  interest,  however,  in  relation 
ject  of  tension  i  the  nidi  y  '  '>f  the  effects  of  nvxlification 
The  l-^  nclicial  resnitr  of  relie  tension  in  swellings  of  thf-  tes: 
)r  o!  the  eye  (acute  glaucoii  .ue  pointed  out  as  illusti  itio 
which  splitting  the  --apsule  benents  some  forms  of  nephritis 
rortiCBtf  Ml  is  sup;  >sed  to  act  by  removing  a  barrier — th 
aitaWkhp  '  nt  of  coilati  li  circulation,  promoting  a  fref-  sup] 
p  viousi'  impoverished  by  reason  of  the  inadetjuar'  >f  it 
ab- Hjftioi  exce*  tvt  interstitial  connecti\e  tissu        he 

thf-lium.  an        e  removal  ot  injurious  pressure  ujx)n  the 
The  probl.  1.:     pres-  "ted  have  so  distinct  an  anatonn 
here  does  M'      «?m       ppropriate. 

The  rici.  nl-supply  of  the  kidney, — an  amount  of  tJood  equal  in  weight  to 

that  of  the  or^ '  1  itsdf  flowing  through  it  each  minute  during  full  functional  activity 
(Tilden  Brown),    -while  it  favors  congestive  conditions     nakes  total  embolic  necrosis 
— such  as  occurs  in  other  glands  confined  within  dense  < 
salivary  gland  as  a  secondary  result  in  angina  Ludwig^ii 
cle  in  some  cases  of  torsion  with  complete  venoe 
(Gerster) — very  rare,  only  one  case  (Friedlander  i 

Subparietal  injuries  to  the  kidney  are  conm  .1. 
visceral  lesions  resulting  from  contusions  of  the  abdomen  or  loin.  Rupture  of  the 
kidney  by  abdominal  or  lumbar  contusion  has  been  experimentally  shown  (Kiister) 
to  depend  upon  the  effect  of  a  force  (hydraulic)  acting:  through  the  full  vessels  and 
the  pelvis  and  causing  the  kidney  to  burst,  usually  along  the  lines  radiating  from  the 
hilum  in  the  direction  of  the  tubules, — i.f.,  transverse  to  the  lonv  -  of  the  kid- 
ney, towards  the  point  of  maximum  impact  of  the  lowpr  ribs,  the  opp«>-  <t<.  resisUince 
being  supplied  by  the  spine  (Morris).  There  1  reamn  to  believe  v...<r  the  direc- 
tion of  ruptures — radiating  from  the  hilum  to  th^  ijtriph-  ry — is  influenced  by  the 
lines  of  least  resistance  indicating  the  orisuwi  at-  fm-  oi  vast^ilar  lo<tps  and  of  their 
accompanying  connective  tissue  betw<-  !he  ^.  -m«  \i,b\\i>^  of  which  the  tatal 
kidney  is  composed. 

As  the  ribs  in  immediate  rel.  •-'■■  n  -  l  •  k»*«»ey  ..re  the  eleventh  and  twelfth, 
which  are  rarely  fractured,  lacer<«s«'«  br  *rect  mepae*  of  brokes  n\x  is  relatively 
uncommon,  although  it  does  ewxm 

Ruptures  may  much  more  raretv  l»r  jwrxiiice^  «  muscular  action  alone,  but  in 
such  cases  the  violent  muscuiar  effort  tha'  usually  at«»«ct»  the  ribs  .<  forces  them 
against  the  kidney  and  towanis  the  spite  is  almost  .dways  associat.  with  forward 
or  lateral  bending  of  the  vertebral  column       Forcible  anterior  tiexion  >:  the  spine,  as 


sub- 
pjy. 
s) 
in 
le- 
ts Cii       lie  the 
>lood  ;     th--  kidney 
■els,  and  favoring  the 
tion  of  renal  epi- 
ou,s       -iiles  (  Exlebohls ) . 
iring  that  their  mention 


tiles,  .«s  in  the  si  hmaxillary 

'c  553)  and  in  the  testi- 

rtial  arterial  obstruction 

g  t.>een  reported 

constituting  34  per  cent,  of 


1892 


HUMAN  ANATOMY. 


from  a  wei^jht  falling  on  the  shoulders,  may  cause  compression  of  the  kidney  between 
the  lower  ribs  and  the  ilium,  and  is,  therefore,  not  infrequently  followed  by  hsema- 
turia,  indicating  some  degree  of  rupture  of  kidney-substance. 

The  rupture  may  be  (a)  incomplete, — i.e.,  may  involve  the  parenchyma  alone, 
the  symptoms  in  these  relatively  rare  cases  being  those  of  excessive  renal  tension 
{vide  supra),  the  constitutional  signs  of  hcmorrh^e  and  of  toxaemia  (usually  due  to 
urinary  extravasation  or  to  perinephric  cellulitis)  being  moderate  or  lacking  :  {b) 
complete  internally, — into  the  pelvis  of  the  kidney, — a  more  common  condition,  in 
which  haematuria,  acute  hydronephrosis,  from  blocking  of  the  ureter  with  blood- 
dot,  and  vesical  irritability  are  prominent  symptoms,  and  the  constitutional  signs 
of  hemorrhage  and  toxaemia  are  more  marked  ;  (f)  complete  externally, ^-exltadmfi, 
through  the  fibrous  capsule, — in  which,  in  addition  to  the  immediate  indications  of 
hemorrhage  and  the  later  symptoms  of  sepsis,  the  usually  free  urino-sanguineous 
effusion  into  the  loin  produces  marked  lumbar  swelling  and  tenderness  ;  or  (d)  com- 
plete,— running  from  the  pelvis  to  and  through  the  capsule, — in  which,  with  a  com- 
mingling of  the  above  symptoms,  there  is  often  profound  shock  which  may  terminate 
fatally. 

Rupture  of  the  kidney  extending  through  its  outer  surface  may  be  (^)  transperi- 
toneal, in  which  case  hemorrhage  is  apt  to  be  very  free,  as  there  is  no  surrounding 
pressure  to  resist  and  limit  the  extravasation,  and  fatal  peritonitis  will  almost  surely 
follow  unless  the  escaped  urine  is  normal,  acid,  and  sterile,  and  unless  both  it  and 
the  blood-clots  are  speedily  evacuated. 

When,  in  addition  to  the  laceration  of  the  kidney,  a  single  intraperitoneal  organ 
is  also  injured,  it  is  always  on  the  same  side  as  the  injured  kidney  (Watson).  The 
liver,  for  example,  or  the  ascending  colon,  may  be  involved  in  a  case  of  sutoarietal 
rupture  of  the  right  kidney,  but  never  the  spleen  or  the  descending  colon.  Inis  will 
readily  be  understood  from  a  consideration  of  the  frequency  with  which  the  cause  of 
rupture  is  a  forcible  forward  bending  of  the  vertebral  column,  the  kidney  being  caught 
in  the  angle  of  the  bend,  any  lateral  deviation  of  which  may  determine  the  side  on 
which  the  injury  occurs  and  the  involvement  of  liver  or  spleen  respectively. 

Transperitoneal  rupture  of  the  kidney  is  relatively  far  more  common  in  children 
than  in  adults.  Until  the  age  of  eight  or  ten  years  is  reached  the  kidney  lacks  its 
covering  of  perinephric  fat,  and  its  anterior  suriace  lies  in  contact  with,  and  is  closely 
connected  to,  the  ]>eritoneum.  A  rupture  involving  that  surface  is  therefore  practi- 
cally certain  to  open  the  peritoneal  cavity  and  is  likely  to  be  followed  by  excessive 
hemorrhage  and  septic  infection.  In  children  under  ten  years  of  age  85  per  cent, 
of  subparietal  ruptures  of  the  kidney  have  proved  fatal  (Maas). 

Wounds  of  the  kidney  must,  of  course,  involve  the  capsule  and  external  surface, 
so  that  hemorrhage  into  the  perinephric  tissues  is  an  almost  constant  symptom.  If 
the  wound  has  reached  the  calyces  or  the  pelvis,  urine  will  be  commingled  with  the 
blood.  Vesical  haematuria  may  be  prevented  by  the  presence  of  a  clot  in  the  ureter, 
or  by  the  actual  severance  of  that  tube.  If  large  vessels  have  been  opened,  the  blood, 
in  addition  to  reaching  the  bladder  or  the  perinephric  space  or  the  peritoneal  cavity, 
may  pass  upward  to  the  diaphragm,  downward  to  the  iliac  fossa,  or  along  the  spermatic 
vessels  to  the  external  abdominal  ring,  or  outside  of  the  ureter  to  the  perivesical  space, 
or  forward  between  the  two  layers  of  the  mesocolon.  In  a  reported  case  of  gunshot 
wound  in  which  the  missile  reached  the  kidney  from  above  downward,  injuring 
pleura  and  diaphragm  en  route,  the  concomitant  injury  to  the  lower  intercostal  nerves 
caused  rigidity  and  tenderness  of  the  anterior  abdominal  wall  and  gave  rise  to  the 
unfounded  suspicion  that  the  wound  was  transpteritoneal. 

Anuria  due  to'  reflex  effect  upon  the  normal  kidney  may  follow  a  rupture  or 
wound  or  even  calculous  irritation  of  the  other  kidney,  although,  as  a  rule,  calculous 
anuria  indicates  a  bilateral  lesion.  Both  kidneys  are,  of  course,  supplied  from  the 
same  segments — the  tenth,  eleventh,  and  twelfth  dorsal  and  first  lumbar — of  the 
spinal  cord.  Excessive  tension  from  compensatory  hyperaemia  has  been  thought  to 
explain  this  form  of  anuria,  and  the  theory  is  supported  by  the  facts  that  the  condi- 
tion sometimes  follows  a  nephrectomy,  the  remaming  kidney  being  normal,  and  that, 
whatever  its  cause,  it  is  often  relieved  by  nephrotomy  of  the  hitherto  sound  kidney. 
The  susreptibility  of  the  kidney  to  reflex  stimulation  or  inhibition  must  be  admitted, 


PRACTICAL  CONSIDERATIONS:    THE   KIDNEYS. 


«893 


however,  as  cases  of  both  polyuria  and  threatened  suppression  have  followed  the 
f/entle  and  partial  insertion  of  the  ureteral  catheter  (Tilden  Brown). 

Tumors  of  the  kidney  have,  as  a  class,  die  following  disUncUve  anatonucal 
characters,  which  have  been  well  summarized  by  Morris  :  ..... 

(a)  The  large  intestine  is  in  front  of  the  tumor.  NormaUy  the  right  kidney, 
unless  enlarged,  lies  a  little  way  from  the  lateral  wall  of  the  abdomen,  behind  and  to 
the  inner  side  of  the  ascending  colon  ;  not  in  close  contact  with  the  abdominal  wall 
and  outside  the  ascending  colon,  as  the  liver  does.  When  the  kidney  is  enlanjed, 
the  ascending  colon  is  usually  placed  in  front  of  and  towards  the  inner  side  of  the 
tumor.  On  the  left  side  the  descending  colon  is  in  front  of,  and  inclines  towards  the 
outer  side  of,  the  kidney  below  ;  in  some  cases  coib  of  small  intestine  may  overlie  either 
right  or  left  tumor  if  the  enlargement  is  not  sufficient  to  bring  the  kidney  into  direct 
contact  with  the  fro  it  abdominal  wall.  When  the  colon  is  empty  or  non-resonant, 
it  can  be  felt  as  a  roil  on  the  front  surface  of  the  tumor.  Bowel  is  not  thus  found  in 
front  of  splenic  tumors  and  very  rarely  in  front  of  a  tumor  of  the  liver. 

(*)  There  b  no  line  of  reson^mce  between  the  kidney  dulness  and  the  vertebral 
spine,  and  no  space  between  the  kidney  and  the  spinal  groove  into  which  the  fingere 
can  be  dipped  with  but  little  relative  resbtance,  as  there  is  between  the  spleen  and 

the  spine.  ,..,,,  i.       •   j 

(r)  While  a  renal  tumor  fills  up  the  "hollow  of  the  back  somewhat,  it  does 
not  often  protrude  or  project  backward.  Marked  posterior  projection  usually  indi- 
cates perinephric  swelling,  as  from  an  abscess  or  a  urino-sanguineous  effusion. 

(rf)  A  kidney  tumor  can  sometimes  be  recognized  by  its  proneness  to  maintain 
an  oudine  resembling  that  of  the  normal  kidney.  .... 

{e)  A  kidney  swelling,  if  inflammatory  in  origin,  descends  less  m  inspiration 
than  does  a  splenic,  hepatic,  or  adrenal  swelling;  this  symptom  in  a  case  of  new 
growth  is  not  very  valuable,  as  the  renal  Mmor  may  have  a  considerable  degree  of 

movement.  ... 

(/)  As  a  rule,  kidney  tumors  do  not  reach  the  mid-line,  do  not  invade  the 
bony  pelvis,  and  are  separated  from  the  hepatic  dulness  by  a  line  of  resonance.  If 
large  enough,  the  tumor  may  reach  the  anterior  abdominal  parietes  about  the  level 
of  the  umbilicus,  but  external  to  it  .....  .- 

{g)  In  large  renal  tumors  varicocele,  from  compression  or  distortion  and  dis- 
tention of  the  spermatic  vein,  has  been  noticed  in  a  number  of  instances. 

Optraiwns  upon  the  kidney  for  its  xation  (nephrorrhaphy,  nephropexy),  for 
drainage  or  relief  of  tension  (nephrotomy),  for  the  extraction  of  a  calculus  (nephro- 
lithotomy), or  for  the  establishment  of  collateral  circulation  (decortication),  are  almost 
invariably  done  through  the  loin. 

The  vertical  inasion— on  a  line  about  an  inch  posterior  to  the  middle  of  the 
crest  of  the  ilium  and  running  from  that  level  to  the  twelfth  rib — does  not,  as  a  rule, 
give  sufficient  room,  divides  the  last  dorsal  and  the  lumbar  vessels  and  nerves,  and 
hence  jeofwundizes  the  subsequent  integrity  of  the  ilio-costal  wall. 

The  oblique  incision  begins  about  a  half  inch  below  the  twelfth  rib  and  at  the 
outer  border  of  the  erector  spinse.  It  is  well  to  count  the  ribs  from  above  downward, 
as  when  the  twelfth  rib  is  rudimentary  it  may  not  project  beyond  the  edge  of  the 
erector  spinse  and  may  be  mistaken  for  the  transverse  process  of  the  first  lumbar 
vertebra.  In  such  circumstances  the  incision,  having  by  error  been  made  close  to 
the  edge  of  the  eleventh  rib,  has,  in  reported  cases,  opened  the  pleura. 

The  oblique  incision  ii  extended  forward  for  three  or  four  inches  parallel  with 
the  twelfth  rib, — i.e.,  with  the  vessels  and  nerves  of  the  region.  The  skin  and  super- 
ficial fascia,  the  latissimus  dorsi,  and  the  external  and  internal  oblique  muscles  having 
been  divided  and  the  lumbar  aponeurosis  and  the  transversalis  fascia  severed,  a 
layer  of  fat  will  then  appear  or  will  bulge  into  the  incision  (perirenal  or  transversalis 
fat).  As  this  is  cut  through  or  separated  with  fingers  or  forceps,  a  layer  of  con- 
nective tissue  may  be  recognized — the  posterior  layer  of  the  perirenal  fascia — and 
then  a  second  layer  of  fat  ({>erinephric  fat,  capsula  adiposa),  which  is  sometimes  finer 
in  texture  and  more  distinctly  yellowish  (Morris),  and  which,  if  it  is  incised  or  torn 
through  and  drawn  into  the  wound,  will  present  a  funnel-sh.-iped  opening  leading 
down  directly  to  the  kidney  (Gerota),  which  can  then  often  be  isolated  by  blunt 


Li 


1894 


HUMAN  ANATOMY. 


dissection  with  the  finger,  and  either  stitched  in  place,  decapsulated,  or  opened,  in 
accordance  with  the  indications. 

It  may  be  noted  that  bleeding  from  the  separation  of  the  capsule  is  comparatively 
trifling;  and  that  if  the  kidney  itself  is  to  be  incised,  the  fact  that  its  blood-supply  is 
naturally  divisible  into  two  independent  segments — anterior  and  posterior — which 
are  completely  separated  by  the  renal  pelvis,  and  the  vessels  of  which  are  given  ofi 
from  the  main  trunk  of  the  renal  artery  (Hyrtl),  indicates,  as  the  line  of  safety,  the 
convex  posterior  or  outer  border.  When  the  pelvis  of  the  kidney  is  distended  wiUj 
fluid,  a  white  line  on  that  border  (Brodel's  line)  is  said  to  indicate  the  relatively  avas- 
cular area.  The  anterior  vascular  division  is  said  to  carry  three-fourths  of  the  arterial 
blood-supply  and  the  posterior  divii.ion  the  remaining  fourth  (Brodel),  so  that  in  the 
majority  of  cases  the  posterior  surface  of  the  kidney  would  furnish  the  lesser  quantity 
of  blood. 

For  removal  of  the  kidney  (nephrectomy)  the  oblique  incision  may  be  prolonged 
forward,  the  peritoneum  being  detached  and  pushed  in  that  direction  ;  or  a  vertical 
incision  running  downward  from  it  may  be  added  ;  or,  if  the  nephrectomy  is  to  be 
done  for  the  removal  of  an  exceptionally  large  tumor,  the  anterior  or  transperitoneal 
route  may  be  adopted  and  the  incision  made  in  either  the  linea  semilunaris  or  the 
linea  alba,  the  outer  layer  of  the  mesocolon  being  opened  to  gain  access  to  the  retro- 
peritoneal space.  The  nerves  and  vessels,  as  they  enter  the  hilum  of  the  kidney,  the 
vein  lying  in  front,  constitute  the  "  pedicle."  The  ureter  lies  more  posteriorly  and 
on  a  slighdy  lower  plane.  The  irregularities  in  the  division,  distribution,  and  points 
of  entrance  of  the  renal  artery  should  be  remembered,  as  should  also — on  the  right 
side — the  proximity  of  the  vena  cava  during  the  separation  of  close  adhesions. 

In  all  the  lumbar  operations  ufton  the  kidney  the  colon  may  present  in  the 
wound  after  the  transversalis  fascia  has  been  opened,  and  should  be  looked  for  and 
displaced  antero-extemally  to  avoid  danger  rA  wounding  it. 


THE  RENAL  DUCTS. 

The  duct  of  the  kidney — the  canal  which  receives  the  urine  as  it  escapes  from 
the  kidney  and  conveys  it  to  the  bladder — consists  of  a  short  dilated  and  sub- 
divided upper  segment,  the  rentU pelvis,  and  a  long,  narrow,  tubular  lower  segment, 

the  ureter.     Since  not  only 
Fio.  1614.  these  but  also  the  papillary 

ducts  of  the  kidney  are  de- 
veloped from  a  common  out- 
growth from  the  Wolffian 
duct,  the  renal  duct  stands 
in  most  intimate  relations 
with  the  renal  substance. 

The  pelvis  of  the 
kidney  (pelTis  renalls),  al- 
though bq^inning  and  lying 
chiefly  within  the  sinus,  ex- 
tends beyond  the  latter, 
passing  downward  to  be- 
come continuous  with  the 
ureter.  Its  widest  part,  just 
within  the  hilum,  presents  an 
unbroken  convex  postero- 
mesial  surface,  its  opposite 
side,  directed  towards  the 
renal  substance,  being  inter- 
rupted by  the  subdivisions 
of  the  pelvis.  These  include 
the  divisions  of  the  pelvis  into  an  upper  and  a  Itmer  segment  (calyces  majeres), 
extending  towards  .the  respective  poles  of  the  kidney.  Each  of  these  segments 
rev.eive8  a  group  of  from  four  to  six  smaller  conical  passages,  the  calyces  or  infun- 


Casts  obtain^  by  corrosion,  showing  two  forms  <A  renal  pelvis: 
A,  usual  type ;  B.  variation. 


THE  RENAL  DUCTS. 


1895 


dibula  (calyces  minores),  that  proceed  from  the  renal  substance,  where  they  surround 
the  papillse. 

The  latter  are  embraced  by  the  expanded  bases  of  the  conical  calyces,  the  walls 
of  which  are  intimately  blended  with  the  kidney-substance  around  the  sides  of  the 
free  part  of  the  papillse,  a  narrow  cleft  separating  the  latter  from  the  enclosing  calyx. 
The  epithelium  of  the  papillary  ducts  is  directly  continuous  with  that  lining  the 
calyx,  while  the  subepithelial  tissue  of  the  latter  blends  with  the  intertubular  renal 
stroma.  On  laying  open  the  calyx,  the  papilla  is  seen  as  a  conical  elevation  project- 
ing into  the  hinnel-shaped  envelope  (Fig.  159S);  although  usually  enclosing  a  single 
papilla,  the  calyx  may  receive  two  or  even  more  such  projections. 

The  two  general  groups  of  calyces — an  upper  and  a  lower— open  into  the  two 
large  primary  subdivisions  (^superior  and  inferior  pelvis)  that  join  to  produce  the 
mwn  compartment  of  the  pelvis.  The  lower  end  of  the  latter  emerges  through  the 
hilum  and  arches  downward  to  pass — about  midway  between  the  hilum  and  the 
inferior  pole  of  the  kidney— insensibly  into  the  ureter;  exceptionally  this  junction 
is  marked  by  a  constriction  in  the  lumen  of  the  canal.  Although  surrounded  in  its 
upper  part  and  smaller  divisions  by  the  branches  of  the  renal  blood-vessels,  the  general 
position  of  the  pelvis  within  the  sinus  and  as  it  emerges  through  the  hilum  is  behind 
the  blood-vessels,  the  intervab  between  the  renal  duct  and  the  other  occupants  of 
t!ie  sinus  being  filled  with  adipose  tissue.  On  the  right  side  the  lower  part  of  the 
pelvis  is  covered  in  front  by  the  second  part  of  the  duodenum  ;  on  the  left  by  the 
pancreas. 

The  Ureter. — This  part  of  the  renal  duct  is  a  flattened  tube  which  connects  the 
renal  pelvis  with  the  bladder.  It  lies  beneath  the  parietal  peritoneum,  embedded 
within  the  subserous  tissue  and  surrounded  by  fat,  and  descends  akng  ihe  posterior 
abdominal  wall  to  the  pelvic  brim  ;  crossing  the  latter,  it  follows  the  lateral  wall  of 
the  pelvis,  curving  downward,  forward  and  finally  inward  along  the  pelvic  floor, 
to  reach  the  bladder.  The  general  direction  of  its  course  is  indicated  by  a  vertical 
line  on  the  surface  of  the  abdomen  drawn  from  the  junction  of  the  inner  and  middle 
thirds  of  Poupart's  ligament  (Tourneux).  The  average  length  of  the  undisturbed 
ureter  is  approximately  27  cm.  (lo.j  in.),  the  left  duct  being  usually  about  one 
centimetre  longer  than  the  right  in  consequence  of  the  higher  position  of  the  corre- 
sponding kidney.  ,  Apart  from  the  uncertainty  of  determining  just  where  the  pelvis 
ends  and  the  ureter  begins,  its  length  is  influenced  by  several  factors,  such  as  the 
level  of  the  kidneys  and  of  the  bladder,  the  descent  of  the  renal  pelvis,  body  height, 
and  sex,  so  that  considerable  variation  is  encountered  ;  the  excessive  figures  some- 
times given  are  probaMy  based  upon  measurements  of  the  ducts  after  removal  and 
abnormal  relaxaUon.  The  diamete:  of  the  ureter — from  4-5  mm. — is  not  uniform, 
since  at  certain  points,  corresponding  to  changes  in  the  direction  or  relations  of  the 
canal  (Solger),  constrictions  regularly  occur,  above  which  the  tube  exhibits  fusiform 
dilatations  or  spindles  (Schwsdbe).  The  most  constant  narrowings  are  situated 
(i)  from  4-9  cm.  (iyi-i%  in.)  below  the  hilum,  at  which  point — the  upper  isthmus 
of  Schwalbe— the  diameter  of  the  canal  is  reduced  to  almost  3  mm.:  (2)  near  the 
pelvic  brim  as  the  duct  crosses  the  iliac  vessels  {lower  isthmus'),  preceded  by  a  fusi- 
form enlargement  (chief  spindle)  ;  and  (3)  at  the  lower  end  of  the  ureter  as  the 
canal  penetrates  the  wall  of  the  bladder.  Since  its  course  and  relations  vary  in 
different  parts  of  its  path,  the  ureter  is  divided  for  description  into  an  abdominal  and 
a  pdvic  portion. 

The  abdominal  portion  (pant  abdominalis) — from  13-14 cm.  (about  5-5 J<  in.) 
in  length — begins  a  short  distance  below  the  hilum  and  descends  upon  the  anterior 
surface  of  the  psoas  magnus  muscle  and  its  fascia  towards  the  sacro-iliac  articulation, 
with  a  slight  inclination  towards  the  mid-li.ie  (Fig.  1591 ).  The  distance  between  the 
two  ureters  at  their  upper  ends  is  about  9  cm.  (3J^  in.)  and  at  the  pelvic  brim  about 
6  cm.  (2j4  in.).  Just  before  reaching  the  latter  level  the  ureters  obliquely  cross 
the  common  iliac  vessels,  approximately  the  point  at  which  the  artery  divides  mto  its 
external  and  internal  divisions,  or,  especially  on  the  right  side,  they  may  pa.ss  over 
the  external  Hiac  vessels  instead.  About  midway  in  their  course  to  the  pelvis  both 
ducts  are  crossed  in  front,  at  a  very  acute  angle,  by  the  spermatic  (or  ovarian)  ves- 
sels and  behind  and  obliquely  by  the  genito-crural  nerve.     The  right  ureter  passes 


'^'h- 


1896 


HUMAN  ANATOMY. 


behind  the  descending  part  of  the  duodenum,  lies  to  the  right  of  the  inferior  vena 
cava,  which  it  approaches  and  even  touches  in  its  descent,  and  is  covered  by  the 
attachment  of  the  mesentery.  Above  the  left  ureter  may  be  covered  by  the  pancreas 
when  that  organ  is  unusually  broad,  and  below  it  is  crossed  by  the  attachment  of  the 
sigmoid  flexure. 

The  pelvic  portion  (pars  pdvina) — from  12-13  "«•  (5  in.)  in  length — lies 
against  the  lateral  wall  of  the  pelvis,  close  benjath  the  serous  membrane  embedded 
within  the  subperitoneal  tissue,  and  curves  downward  and  foiward  to  about  the  level 
of  the  ischial  spine,  where  it  turns  inward  upi^n  the  visceral  layer  of  the  pelvic  fascia 
to  reach  the  dorsal  wall  of  the  bladder  (Fig.  1019).  In  its  descent  it  lies  in  front  of 
the  internal  iliac  artery  as  far  as  the  greater  sciatic  notch  (Merkel),  crosses  the  ob- 
literated hypogastric  artery  and  the  obturator  nerve  and  vessels  to  their  inner  side, 
and,  as  it  traverses  the  pelvic  floor,  is  surrounded  by  the  tributaries  from  the  vesica! 
plexus  to  the  internal  iliac  vein  and  may  lie  upon  the  middle  and  inferior  vesical 

arteries.     The  ureter  is  crossed 
Fio.  1615.  on  its  inner  side  by  the  vas  defer- 

ens, and  pierces  the  bladder-wall 
immediately  in  front,  or  under 
cover  of  the  anterior  part,  of  the 
seminal  vesicle  or  of  the  ampulla 
(  Fraenkel ' ) .  The  space  between 
the  ureter  and  the  seminal  vesi- 
cle, which  when  the  bladder  is 
empty  may  be  considerable,  is 
filled  by  areolar  tissue  containing 
veins  and  fat.  The  relations  of 
the  ureter  to  the  bladder  are  pe- 
culiar, since,  in  addition  to  pene- 
trating the  latter  so  obliquely  that 
the  last  18  mm.  (^  in.)  of  the 
renal  duct  are  embedded  within 
the  vesical  wall,  the  muscular  tis- 
sue of  the  latter  is  seemingly  pro- 
longed (page  1897)  over  the  ure- 
ter outside  the  bladder  for  some 
5  mm.  as  a  distinct  sheath  (Wal- 
deyer).  The  ureteral  orifices  on 
the  inner  surface  of  the  vesical 
wall  are  slit-like  and  valvular  in 
form  and,  in  the  contracted  condi- 
tion of  the  bladder,  about  3. 5  cm. 
apart,  thisdistance  being  increased 
twofold  or  even  more  when  that 
organ  becomes  distended. 
The  female  ureter  (Fig.  1622)  calls  for  specifd  description  on  account  of  the 
relations  of  its  pelvic  portion  to  the  generative  organs.  On  gaining  the  lateral  wall 
of  the  pelvis,  the  ureter  descends  in  close  proximity  to  the  unattached  border  of  the 
ovary  and  constitutes  the  postero-inferior  boundary  of  the  ovarian  fossa  (page  1986). 
On  the  pelvic  floor  the  ureter  entci-s  the  base  of  the  broad  ligament,  within  which 
duplicature  it  is  crossed  by  the  uterine  artery,  passes  between  the  veins  of  the  vesico- 
vaginal plexus,  and  contmues  downward  and  forward  in  the  vicinity  of  the  uterine 
cervix  to  the  vagina;  its  terminal  segment  lies  embedded  within  the  connective  tissue 
between  the  cervix  and  bladder,  close  to  the  anterior  vaginal  wall  for  a  distance  of 
from  1-1.5  cm.,  where,  bending  somewhat  inward,  it  reaches  the  posterior  vesical 
wall,  which  it  pierces  obliquely  in  the  manner  above  described. 

Structure. — The  wall  of  all  parts  of  the  renal  duct  is  the  same  in  its  general 
construction  and  includes  three  layers,  (i)  the  mucous  membrane,  (2;  the  mus- 
cular tunic,  and  (3)  the  outer  fibrous  coat;  the  mucosa  and  the  muscular  layer  are 
>  Die  Samenbtasen  der  Menschen,  Berlin,  1901. 


Ureter 


Sagittal  Mction  through  sinus  of  child's  kidney,  showing  lower 
part  of  pelvis  and  commencement  of  ureter,    X  lo. 


THE  RENAL  DUCTS. 


1897 


more  or  less  blendeu,  a  distinct  submucosa  being  wanting.  The  mucous  membrane 
is  clothed  with  "transitional"  epithelium  consisting  of  several  strata  of  cells,  the  su- 
perficial elements  being  plate-like  and  the  deepest  ones  irregularly  columnar.  The 
tunica  propria  constitutes  a  subepithelial  layer  of  fibro-elastic  tissue  which  blends  with 
the  subjacent  muscular  tunic.  Within  the  ureter  the  mucous  membrane  is  usually 
thrown  into  longitudinal  folds,  and  in  consequence  in  transverse  section  the  lumen 
of  the  canal  appears  stellate.  Neither  well-marked  papillae  nor  true  glands  are  pres- 
ent, although  in  places  the  subepithelial  tissue  invades  the  epithelium  and  subdivides 
the  latter  into  nest-like  groups  of  cells.  Occasional  aggregations  of  lymphoid  cells 
occur,  which  in  the  vicmity  of  the  calyces  sometimes  form  distinct  minute  lymph- 
nodules  with  I  the  mucosa  (Toldt).  On  the  papilla  the  epithelium  lining  the  renal 
duct  passes  uninterrupted  into  that  of  the  papillury  canals,  while  the  underlying  tunica 
propria  becomes  continuous  with  the  intertubular  renal  stroma.  The  muscular  tunic 
consists  of  bundles  of  the  involuntary  variety  disposed  as  a  thin  inner  longitudinal 
and  a  chief  external  circular  !iyer.  Within  the  renal  pelvis  and  its  larger  subdivisions 
both  layers  are  well  represented,  but  are  reduced  on  the  calyces  ;  at  the  junction  of 
the  latter  with  the  kidney  the  circular  muscle  increases  and  surrounds  the  papilla 
with  a  minute  sphincter-like  bundle  (Henle).     Except  in  the  upper  part  of  the  renal 

F10.  1616. 


Epithetium 

Macon  coat,  thrown  _      ^ : 
into  longitudinal  (olds 


Outer  lonKitudiiial 
muscular  bundles 


Inner  longitudinal  '^ 
muscular  bundles 


Circalar  muscular  bundles 


Transverse  section  of  ureter,    y  15. 


duct,  an  additional  imperfect  outer  longitudinal  layer  of  muscle  is  represented  by 
irregularly  scattered  bundles.  The  fibrous  coat,  or  tunica  adventitia,  composed  of 
bundles  of  fibrous  and  elastic  tissue,  invests  the  renal  duct  as  its  outer  tunic  and  con- 
nects it  with  the  surrounding  areolar  tissue.  At  the  kidney  the  outer  coat  of  the 
renal  duct  blends  with  the  tunica  fibrosa  that  invests  the  renal  substance  between  the 
calyces.  beginning  several  centimetres  above  the  bladder,  the  adventitia  of  the 
ureter  is  strengthened  and  thickened  by  robust  longitudinal  bundles  of  involuntary 
muscle  that  follow  the  duct  to  its  vesical  orifice  and,  in  conjunction  with  the  fibrous 
tissue  in  which  they  are  embedded,  form  the  ureteral  sheath  (Waldeyer).  Accord- 
ing to  Disse,  this  muscle  belongs  to  the  wall  of  the  ureter  and  is  distinct  from  the 
musculature  of  the  bladder. 

Vessels. — The  arteries  supplying  the  different  segments  of  the  renal  duct  are 
derived  from  several  .sources.  Those  distributed  to  the  pelvis  and  the  adjoining  part 
of  the  ureter  are  small  branches  from  the  renal  artery,  the  abdominal  portion  of  the 
canal  being  additionally  supplied  by  twigs  given  off  from  the  spermatic  (ovarian)  artery 
as  the  latter  crosses  the  duct  and  by  a  special  vessel  (a  tiretcrica)  prnceefli  ig  from 
the  internal  or  common  iliac  artery  or  from  the  aorta  (Krause).  The  pelvic  portion 
receives  branches  from  the  middle  hemorrhoidal  or  the  inferior  vesical  arteries.     The 


1898 


HUMAN  ANATOMY. 


vessels  from  these  several  sources  anastomose  and  produce  a  net-work  that  encloses 
the  canal  and  sends  twigs  that  break  up  into  capillaries  that  supply  the  coats  com- 
posing its  wall.  The  veins  begin  within  the  mucosa,  beneath  which  they  form  an  in- 
ternal plexus  that  communicates  with  a  wider-meshed  outer  plexus  withm  the  fibrous 
coat,  from  which  tributaries  pass  to  the  internal  or  common  iliac  and  the  spermatic 
veins.  The  lymphatics  withm  the  mucous  membrane  and  submucosa,  according  to 
Sakata,'  are  not  demonstrable  as  distinct  net-works,  but  as  such  are  seen  within  the 
muscular  tissue  and  on  the  surface.  The  lymph-trunks  from  the  middle  third  of  the 
ureter,  which  are  the  most  numerous,  pass  to  the  lumbar  nodes  ;  those  from  the  lower 
segment  are  tributary  to  the  internal  iliac  nodes  or  communicate  with  the  lymphatics 
of  the  bladder  ;  while  those  of  the  upper  part  either  empty  into  the  aortic  nodes  or 
join  the  renal  lymphatics. 

The  nerves  of  the  renal  duct,  derived  from  the  sympathetic  system,  accompany 
the  arteries  and  come  from  the  renal,  spermatic,  and  hypogastric  plexuses.  Within 
the  adventitia  they  form  a  plexus  containing  numerous  microscopic  ganglia,  the  largest 
of  which  are  at  the  upper  and  lower  ends  of  the  duct.  In  addition  to  the  fibres  sup- 
plying the  blood-vessels,  both  meduUated  and  non-meduUated  fibres  pass  to  the  mus- 
cular and  mucous  coats. 

Vaiiationa. — These  consist  most  often  in  more  or  less  complete  doubling  of  the  canal  on 
one  or  both  sides.  While  subdivision  of  the  pelvis  into  an  unusual  number  «  tubular  calyces 
is  rare,  its  cleavaf!^  into  two  separate  compartments,  either  alone  or  in  correspondence  with 
doubling  of  the  ureter,  is  relatively  common.  The  division  may  be  so  complete  that  the  two 
resulting;  ducts  open  into  the  bladder  by  separate  orifices.  The  termination  of  the  ureter  in 
the  semmal  vesicle — a  malformalion  occasionally  encountered — depends  upon  the  close  embryo- 
logical  relations  (page  2039)  which  exist  between  the  two  structures.  While  congenital  absence 
of  the  kidney  is  not  necessarily  associated  with  entire  absence  of  the  ureter,  faihire  of  the 
latter  to  develop  implies  incompleteness  or  absence  of  the  kidney,  since  a  part  of  the  duct- 
system  of  the  latter  is  derived  from  the  primitive  ureter  (page  1937). 


PRACTICAL  CONSIDERATIONS:    THE  URETERS. 

The  ureters  may  be  multiple  from  a  fused  kidney,  or  two  or  more  ureters  may 
spring  from  the  pelvis  of  a  single  kidney,  indicating  a  defect  in  the  development  of 
the  primary  foetal  ureter.  The  separate  ureters  may  unite  at  any  point  between  the 
kidney  and  the  bladder  or  may  remain  distinct  throughout. 

Marked  obliquity  of  insertion  of  the  ureter  into  the  pelvis  (page  1896)  may 
leave  on  a  lower  level  than  the  ureteral  origin  a  pouch  of  the  pelvis — corresponding 
to  the  lowest  of  its  original  subdivisions — which,  when  it  fills  with  urine,  compresses 
the  upper  end  of  the  ureter,  narrows  its  lumen,  and  favors  the  production  of  hydro- 
nephrosis. This  condition  may  also  occur  in  either  the  second  or  third  of  the  fol- 
lowing variations  in  the  upper  end  of  the  ureter  thus  described  by  Hyrtl  :  (a)  there 
is  no  pelvis,  but  the  ureter  divides  into  two  branches  without  dilatation  at  the  point 
of  division,  each  branch  having  a  calibre  a  little  larger  than  that  of  the  ureter  ;  (*) 
there  is  a  pelvis, — that  is,  a  funnel-shapeil  dilatation  at  the  point  of  division  ;  the 
upper  portion  is  the  smaller,  and  terminates  in  three  short  calyces  ;  the  lower  and 
more  voluminous  portion  terminates  in  four  or  five  calyces  ;  (<■)  there  is  only  half  a 
pelvis, — that  is,  the  lower  branch  divides  and  is  funnel-shaped,  forming  a  narrow 
pelvis,  which  terminates  in  one,  two,  or  three  short  calyces;  while  the  upper  is  not 
dilated,  and  extends  to  the  upper  portion  of  the  kidney  as  a  continuation  of  the 
ureter  (Fenger). 

The  lower  end  of  the  ureter  may  in  the  male,  as  a  rare  anomaly,  open  within 
the  boundaries  of  the  sphincter  vesicae,  or  into  the  prostatic  urethra,  or  into  the 
seminal  vesicle,  ejaculatory  duct,  or  vas  deferens. 

As  the  opening  is  never  anterior  to  the  compressor  urethra,  incontinence  of 
urine  does  not  result,  but  interference  with  its  free  exit  causes  ureteral  dilatation  and 
hydronephrosis. 

In  the  female  the  ureter  may  open  into  the  urethra,  v:igina,  or  vestibule. 
There  may  be  incontinence  of  urine,  or  again  such  obstruction  as  to  cause  uretero- 
renal  dilatation. 

'  Archiv  f.  Anat.  u.  Kntwick.,  1903. 


PRACTICAL  CONSIDERATIONS :    THE   URETERS. 

These  anomalies  are  readily  understood  by  reference  to  the  embryology  of  thie 
ureter  (page  1937). 

Ureteral  calculus  is  most  often  arrested  (tf.)  at  a  pomt  from  4-6.5  cm.  (i>4- 
2ji  in.)  from  the  renal  pelvis  ;  (*)  at  the  point  where  the  ureter  crosses  the  iliac 
artery;  (V)  at  the  junction  of  the  pelvic  and  vesical  portions;  (d)  at  its  vesical 
orifice.  At  these  places  normal  narrowings  are  found  in  the  majority  of  subjects. 
The  symptoms  of  calculus  impacted  in  the  ureter  are  difficult  of  distinction  from  those 
of  stone  occupying  or  engaging  in  the  pelvis  of  the  kidney,  but  it  may  be  said  that 
if.  after  the  usual  phenomena  erf  renal  colic,  vesical  symptoms  are  marked  and  per- 
sistent, and  especially  if  they  are  associated  with  slight  hsematuria  and  no  calculus 
is  detected  in  the  bladder,  the  existence  of  stone  in  the  ureter  should  be  strongly 
suspected.  The  bladder-symptoms— irritability,  frequent  urination,  tenesmus— will 
be  more  marked  the  nearer  the  situation  of  the  stone  to  the  lower  end  of  the  ureter. 
The  relations  of  thf  nerve-supply  of  the  ureter  with  that  of  the  bladder  and  the  geni- 
ulia  and  with  the  great  intra-abdominal  plexuses  sufficiently  explain  the  chief  sub- 
jective symptoms  of  calculus. 

Complete  and  sudden  blocking  of  the  ureter  by  a  calculus  often  produces  an 
acute  hydronephrosis,  the  symptoms  of  which  may  overshadow  those  direcriy  referri- 
ble  to  the  region  of  impaction.  The  muscular  walb  of  the  ureter  are  capable  of 
strong  contraction,  and,  indeed,  the  painful  "colicky"  symptoms  attending  the 
passage  of  a  stone  along  the  ureter  would  better  be  described  as  "  ureteral"  rather 

than  "renal."  ..,,..  .  j      -.u 

At  present  the  diagnosis  of  ureteral  stone  and  its  localization  are  to  be  made  with 

much  ceruinty  by  the  X-rays. 

In  an  effort  to  find  tenderness  which,  in  the  presence  of  the  above  symptoms, 
might  locate  a  stone,  or  might  determine  the  region  of  rupture  or  other  ureteral 
injury,  or  might  confirm  a  diagnosis  of  ureteritis  or  of  tuberculous  infiltration  {jas,  a 
result  of  ascending  or  descending  infection),  it  should  be  noted  that  the  beginning 
of  the  ureter,  the  lower  extremity  of  the  kidney,  and  the  level  of  origin  of  the 
spermatic  or  ovarian  artery  are  all  approximately  defined  byToumeur's  point,  which 
is  situated  at  the  intersection  of  a  transverse  line  between  the  tips  of  the  twelfth  ribs, 
with  a  vertical  line  drawn  upward  from  the  junction  of  the  inner  and  middle  thirds  of 
Poupart's  ligament ;  the  course  of  the  abdominal  portion  of  the  ureter  corresponds 
to  the  same  vertical  line.  Toumeur  considers  its  direction  vertical  from  the  border 
of  the  kidney  down  to  the  pelvic  brim,  over  which  it  passes  4j4  cm.  (2  in.)  from 
the  median  line.  The  exact  location  of  this  point  is  'he  intersection  of  a  horizontal 
line  drawn  between  the  anterior  superior  iliac  spinc;^  and  a  vertical  line  passing 
through  the  pubic  spine.  Morris  thinks  that  this  point  would  usually  be  too  low 
and  too  far  inward,  and  that  the  junction  of  the  upper  and  middle  thirds  f-f  the  line 
for  the  iliac  arteries  (page  819)  better  indicates  the  point  of  crossing  of  the  ureter 
over  the  artery.  At  this  point,  under  favorable  circumstances,  a  dilated  or  tender 
ureter  may  be  felt  by  gende,  steady  pressure  backward  upon  the  abdominal  wall  until 
the  resistant  brim  of  the  pelvis  is  reached.  The  vesical  portion  of  the  ureter  can  be 
palpated  in  man  through  the  rectum.  Guyon  has  caU«l  attention  to  the  exquisite 
sensitiveness  of  this  portion  of  the  ureter  upon  rectal  exploration  in  cases  of  stone, 
even  when  the  calculus  is  located  high  up.  In  woman  vaginal  examination  permits 
the  palpation  of  the  ureter  to  an  extent  of  two  or  even  three  inches,  as  it  runs  beneath 
the  broad  ligament  in  close  relation  to  the  antero-lateral  wall  of  the  vagina  (Cabot, 
Fenger). 

Morris  gives  the  following  directions  for  palpating  the  lower  extremity  of  the 

ureter :  .       ,  , 

(rt)  Vaginal  Palpation. — The  part  of  the  ureter  which  is  capable  of  being  felt 
through  the  vaginal  wall  is  about  three  inches  or  a  little  less,  or,  roughly  speaking, 
about  a  quarter  of  the  whole  length  of  the  duct.  It  is  that  part  which  extends  from 
the  vesical  orifice  of  the  ureter  backward,  outward,  and  upward  to  the  base  of  the 
iH-oad  ligament  .-ind  towards  the  lateral  wall  of  the  true  pelvis. 

It  is  in  the  superior  third  of  the  anterior  and  lateral  wall  of  the  vagina  that  the 
examination  must  be  made,  and  it  is  at  the  part  fietween  the  level  of  the  internal 
orifice  of  the  urethra  and  the  anterior  fornix,  where  the  tissues  are  very  lax,  that  the 


I90O 


HUMAN  ANATOMY. 


ureter  will  be  most  readily  felt.  The  examination  should  be  made  very  gently,  and 
the  finger  should  be  pa^ed  comparatively  lightly  over,  not  pressed  firmly  against, 
the  vaginal  surface.  The  ureter  courses  about  midway  between  the  cervix  uteri  and 
the  wall  of  the  pelvis,  and  by  hard  pressure  the  ureter  is  displaced  before  the  finger 
in  a  direction  towards  the  pelvic  wsdl.  The  uterine  artery  or  the  muscular  fibres  of 
the  obturator  intemus  or  levator  ani  (Sanger)  should  not  be  mistaken  for  the  ureter. 

{6)  RecUil  Palpation. — ^The  lower  extremity  of  the  ureter,  when  occupied  by  a 
foreign  body  or  in  a  state  of  disease,  can  be  felt  through  the  rectum  in  the  male,  but 
less  readily  than  through  the  vagina  in  the  female.  A  calculus  impacted  in  the  lower 
end  of  the  ureter  has  ^n  located  and  removed  through  the  rectum.  It  is  through 
the  antero-lateral  wall  of  the  bowel  and  a  little  higher  than  the  level  of  the  base  of  the 
vesicula  seminalis  that  we  feel  for  the  ureter.  The  pulp  of  the  finger  should  be 
directed  towards  the  back  of  the  bladder  and  pushed  as  far  as  possible  beyond  the 
upper  edge  of  the  prostate  ;  afterwards  the  finger-pulp  should  be  turned  towards  the 
lateral  wall  of  the  pelvis,  and  whilst  still  pushed  as  Sas  as  possible,  it  should  traverse 
the  wall  of  the  rectum  forward  and  backward.  The  examination  is  difficult,  and  if 
the  prostate  is  much  enlarged  the  detection  of  the  ureter  is  impossible.  The  normal 
ureter  b  not  likely  to  be  distinguished,  even  if  the  perineum  be  thin  and  the  prostate 
normal. 

(f )  Vesical  palpation — through  the  dilated  urethra  of  the  female — may  disclose, 
dilatation,  oedema,  prolapse,  or  infiltration,  inflammatory  or  tuberctilous,  of  the 
vesical  end  or  orifice  of  the  ureter,  or  may  reveal  the  presence  of  an  impacted 
calculus. 

Wounds  or  subparietal  injuries  of  the  ureter,  unassociated  with  other  intra- 
abdominal lesions,  are  rarer  than  similar  injuries  of  the  kidney,  decrease  in  frequency 
from  above  downward,  and,  on  account  of  the  bony  protection  afforded  it,  are  very 
uncommon  in  the  pelvic  portion  of  the  ureter. 

The  upper  portion  may  be  crushed  against  the  transverse  process  of  the  first 
lumbar  vertebra  (Tuffier),  or  so  stretched  as  to  tear  or  sevei  't  (Fenger). 

Unless  the  escape  of  urine  from  an  external  wound  occurs,  the  symptoms  are 
merely  those  of  ureteral  irritation,  usually  with  slight  transient  haematuria  and  the 
evidence  of  slow  urinary  extravasation  superadded. 

After  extraperitoneal  rupture  or  wound  the  swelling  due  to  extravasated  urine 
and  subsequent  cellulitis  might  be  recognized  in  the  loin  or  detected  by  rectal  or 
vaginal  examination  in  the  pelvis.  Longitudinal  wounds  gape  less  (and  therefore 
h^  more  readily)  than  transverse  \\  unds,  on  account  of  the  longitudinal  disposition 
of  the  thicker  internal  layer  of  muscular  fibres. 

Tumors  of  the  ureters  are  almost  unknown  as  primary  conditions,  but  consider- 
ation of  the  relations  of  the  ureter  (page  1895)  will  show  that  it  may  be  pressed  upon 
by  growths  or  involved  in  inflammatory  processes  originating  in  the  caecum  or  in  the 
ascending  or  descending  colon.  Its  pelvic  portion  is  more  exfxjsed  to  pressure  than 
is  the  abdominal  on  account  of  the  counter-resistance  of  the  pelvic  walls,  and  here  it 
may  be  compressed  by  fecal  masses  in  the  sigmoid  or  rectum,  by  iliac  aneurism,  or 
by  growths  of  the  uterus,  ovary,  or  Fallopian  tube,  or  may  become  involved  in  dis- 
ease of  the  appendix  when  it  occupies  a  pelvic  position,  or  of  the  bladder  or  seminal 
vesicles. 

The  tough,  resistant  character  of  the  walls  of  the  tube,  the  laxity  of  the  con- 
nective tissue  in  which  it  lies,  the  layer  of  loose  fat  that,  in  part  of  its  course, 
surrounds  and  protects  it  in  well-nourished  individuals  (Luschka),  and  its  rich  vas- 
cular supply  (from  the  renal,  spermatic  or  ovarian,  and  vesical  arteries)  enable  it  to 
resist  or  avoid  injury  or  to  undergo  speedy  repair.  It  is  thus  possible  to  separate  it 
extensively  from  surrounding  structures  during  operations  with  little  or  no  risk  of 
necrosis. 

The  oblique  course  of  the  ureter  through  the  vesical  wall  subjects  it  to  pressure 
when  the  bladder  contracts,  or  when  it  becomes  rigid  from  arterio-sclerotic  disease. 
Frequency  of  urination  alone  has  been  thought  competent — by  the  constandy  recur- 
ring obstruction  to  the  entrance  of  urine  into  the  bladder — to  produce  ureteral  dila- 
tation and  hydronephrosis.  As  its  obliquity  leaves  it  on  the  inner  asftect  covered  by 
mucous  membrane  only,  and  as  the  outer  aspect  is  covered  by  the  muscular  layer  of 


THE  BLADDER. 


1901 


the  bladder- wall,  it  can  be  understood  that  incision  of  the  mucosa  over  the  intra- 
parieul  part  of  the  ureter,  for  the  purpose  of  extracting  a  calculus,  involves  little 
risk  of  pelvic  cellulitis  from  extravasation  of  urine.  It  cannot  be  said  that  there  is 
no  risk,  as  in  one  case  a  peritoneal  fistula  and  death  resultetl  (Thornton). 

(^rations  upon  the  ureter  are  frequent  for  the  extraction  of  a  calculus  (uretero- 
lithotomy); or  the  extirpation  (ureterectomy)  of  an  infected  ureter  ( tuljerculous  or 
pyogenic)  either  at  the  same  time  with  its  kidney  (nephro-uretcrectomy )  or  at  a  later 
period;  or  f.r  the  closure  of  wounds  or  iistul^e,  or  the  relief  of  stricture,  or  the 
implantation  of  the  distal  end  of  the  ureter — after  removal  of  a  diseased,  injured,  or 
obliterated  portion — into  the  bladder,  rectum,  or  elsewhere. 

The  anatomical  factors  relating  to  these  operations  cannot  here  be  described, 
but  it  may  be  said  generally  that  whenever  it  is  possible  the  extraperitoneal  route  is 
selected  to  lessen  the  danger  of  peritonitis,  and  that  the  oblique  lumbar  incision 
employed  to  reach  the  kidney  (page  1893)  will,  if  prolonged  downward  and  forward 
parallel  to  Poupart's  ligament  and  to  the  outer  edge  of  the  rectus,  give  access  to 
the  whole  abdominal  ureter  and  to  the  upper  part  of  its  pelvic  portion.  Cabot  has 
shown  that  the  ureter  is  bound  to  the  external— or  under — surface  of  the  peritoneum 
by  fibrous  bands,  and  that  wh6n  that  membrane  is  stripped  up  from  the  posterior 
abdominal  wall  the  ureter  accompanies  it.  He  found  that  the  relation  of  the  ureter 
to  that  part  of  the  peritoneum  which  becomes  adherent  to  the  spine  is,  within  a  slight 
range  of  variation,  feurly  constant,  the  ureter  lying  just  outside  the  line  of  adhesion. 
Hence,  if  the  sui^eon  has  stripped  up  the  peritoneum  and  has  come  down  to  that 
point  where  it  refuses  to  separate  readily  from  the  spinal  column,  he  will  find  the 
ureter  upon  the  slripped-up  peritoneum  at  a  short  distance  outside  of  this  point. 
On  the  left  side  the  distance  from  the  adherent  point  to  the  ureter  is  from  one-half 
an  inch  to  an  inch,  while  on  the  right  side  it  is  somewhat  greater,  owing  to  the 
ureter  being  displaced  to  the  outside  by  the  interposition  of  the  vena  cava  between 
it  and  the  spine.  It  should  be  remembered  that  the  peritoneum  adherent  to  the 
abdominal  portion  of  the  ureter  is  very  thin  and  may  be  torn  in  an  attempt  to 
separate  it 

Aft':r  the  ureter  dips  down  into  the  true  pelvis  it  is  less  easily  located  because 
it  has  no  tixed  relation  to  a  bony  landmark.  Cabot  has  suggested  that  osteoplastic 
resection  of  the  sacrum  would  give  access  to  this  lower  pelvic  portion  of  the  ureter. 
In  women  it  can  often  be  reached  through  the  vagina.  The  ureter  is,  of  course, 
accessible  transperitoneally  through  its  whole  route. 


THE   BLADDER. 

The  bladder  (vesica  urinaria) — ^the  reservoir  in  which  the  urine  is  received  from 
the  renal  ducts  and  retained  until  discharged  through  the  urethra — is  a  muscular  sac, 
lined  with  mucous  membrane,  situated  in  the  anterior  part  of  the  pelvic  cavity  imme- 
diately behind  the  symphysis  pubis.  Its  form  and  size,  and  likewise  to  a  considerable 
extent  its  relations,  vary  with  the  degree  of  distention,  so  that  in  describing  the 
organ  the  condition  of  expansion  must  be  taken  into  account.  When  containing  little 
fluid  and  hardened  in  situ,  the  general  shape  of  the  bladder  is  pyriform,  presenting  a 
free,  slightly  convex  superior  surjuce,  covered  with  peritoneum  and  projecting  into 
the  [)elvic  cavity,  and  a  distinctly  convex  non-peritoneal  inferior  surface,  attached 
I'y  areolar  tissue  to  the  pubic  symphysis  and  the  pelvic  floor  upon  which  it  rests. 
The  urethra,  surrounded  by  the  prostate,  emerges  from  the  most  dependent  portion 
of  the  lower  surface,  behind  which  point  the  latter  ascends  to  join  the  upper  surface 
along  the  indistinct  posterior  border.  The  part  of  the  bladder  between  the  urethra 
and  the  posterior  border  constitutes  the  fundus  or  base  (fundus  vesicae),  which  in  the 
male  is  in  relation  with  the  seminal  ducts  and  vesicles  and  the  recto-vesical  pouch 
and  is  directed  towards  the  rectum,  and  in  the  female  is  attached  to  the  anterior 
vaginal  wall.  In  the  empty  oiyan  the  superior  and  inferior  surfaces  blend  along  the 
sides  in  the  convex  lateral  borders ;  anterioriy  these  meet  at  the  apex  or  summit  (vertex 
vesicae),  from  which  a  median  fibrous  band  (lixamentam  umbllicale  medium)  that  rep- 
resents the  urachus — the  obliterated  segment  of  the  intra-embryonic  part  of  the  allan- 
toi»— extends  to  the  umbilicus  along  the  abdominal  wall.     The  body  (corpus  vesicae) 


I903 


HUMAN  ANATOMY. 


mpulla 

Seminal  ve*  .Ic 

Uriurv  bladder,  slightly  dlatended  and  hardened  n  ii/k, 
■  Irom  formalin  subject ;  viewed  from  above. 


includes  the  uncertain  part  of  the  bladder  between  the  apex  and  the  fundus.  The 
term  neck  is  sometimes  applied  to  the  region  immediately  surrounding  the  urethral 
orifice,  although  a  distinct  neck  in  the  usual  sense  does  not  exist.     The  intersections 

of  the  lateral  and  posterior  bor- 
Fio.  1617.  ders   mark    approximately    the 

points  at  which  the  ureters  enter 
the  vesical  wall.  As  pointed  out 
by  Dixon,'  the  attachments  of 
the  ureters  correspond  to  the  lat- 
eral angles  of  the  trigonal  figure 
that  the  empty  bladder  resembles 
when  viewed  from  above,  the 
apex  being  the  anterior  angle. 

The  cavity  of  the  strongly  con- 
tracted bladder,  as  seen  in  sagittal 
sections  iA  organs  hardened  in  situ, 
is  little  more  than  a  cleft  bounded 
above  and  below  by  the  thick  vesi- 
cal walls  and  below  continuous  with 
the  urethra ;  in  the  vicinity  of  the 
ureteral  orifices,  however,  the  lumen 
broadens  Into  the  lateral  recesses 
which  are  never  entirely  effaced 
(Luschka).  Themodificatkinsof  the 
lumen  sometimes  seen,  more  frequently  in  women  and  especially  in  organs  not  hardened  in  situ, 
in  which  the  superior  surface  is  more  or  less  sunken  and  in  consequence  the  vesical  cavity  is 
crescentic  or  V-shaped  in  mesial  section,  are  to  be  rejjarded  as  the  result  of  post-mortem  change 
and  not  as  representing  conditions  existing  during  life,  since  normal  contractions  of  the  muscular 
vesical  sac  are  little  calculated  to  produce  such  forms.  The  empty  bladder  measures  in  length 
from  5-6  cm.  (1-2%  in.),  in  breadth  from  4-5  cm.  (i)i-jin.),  and  in  thickness  from  a-a.scm. 
(?^-i  in.)  (Waldeyer). 

In  the  distended  bladder  the  demarcation  between  the  surfaces  above  described  is  gradually 
effaced  urtil,  in  extreme  expansion,  the  organ  assumes  a  general  ovoid  form  in  which  the  supe- 
rior and  inferior  surfaces  and  the  fundus  are  uninterruptedly  continuous  and  all  indication  of 
the  borders  is  completely  obliterated.  Such  extreme  changes,  however,  accompany  only  exces- 
sive and  unusual  distention,  the  alterations  taking  place  under  normal  conditions,  with  a  prob- 
able maximum  capacity  of   from  250-300 

cc.  (7)i-9ft.  oz.   ,  Ijeing  much  less  radical.  "O.  x6x8. 

When  the  bladtl.  '  begins  to  fill,  the  region 
first  to  be  affectetl  is  the  posterior  and  lower 
lateral  portions  of  the  organ,  expansion  oc- 
curring more  rapidly  in  the  transverse  than 
in  the  longitudinal  axis  (Delbet),  which  for 
•  a  time  ret.iins  a  g^  aerally  horizontal  direc- 
tion. Willi  increasing  distention  the  blad- 
der invades  the  paravesical  fossae  at  its  sides, 
behind  is  prts.sed  against  the  seminal  vesi- 
cles, which  in  the  empty  condition  of  the 
bladder  extend  laterally  as  transverse  wings 
and  tou"h  the  vesical  wall  only  with  their 
inner  ends,  anil  encroaches  upon  the  recto- 
vesical pouch  and  the  rectum.  The  con- 
dition of  the  latter  also  influences  the  direc- 
tion of  the  vesical  expansion,  since  the  filled 
rectum  decreases  the  available  space  behind 
and  forces  the  bladder  upward  and  forward. 
Not  until  the  distention  has  progres.sed  to  a 
cnnKiderahle  ilpgree  does  the  antero-inferior 

segment  lengthen  and  undergo  upward  displacem-nt  and  the  apex  rise  much  above  the  pubic 
symphysis  ;  and  only  after  the  distention  greatly  . v-eeds  physiological  limits  and  becomes  very 
excessive  does  the  bladder  altogether  lose  its  pyriform  contour  and  become  symmetrically  ovoid. 
The  highest  point  of  the  greatly  enlarged  organ  no  longer  corresponds  with  the  attachment  of 
■   '  Anatom.  Anzeiger,  Bd.  xv.,  iS<>o 


Vaia  defemitia 

Superior  surface 

Apex 


Cut  edge  of 
peritoneum 
Lalero-inlerior 
surface 


Prostate  gland,  lateral  surface 

PrecedinK  preparation  viewed  from  side,  showinK  relations 
of  Madder,  auociated  ducts,  and  proetate. 


THE   BLADDER. 


»90i 


tha  urachiw,  but  lies  farther  abovt-  and  behind,  since  the  antero-infcrior  wall  always  remains 
•horter  than  the  postero-superior.  The  condition  of  the  rectum  ami  tlie  pressure  exerted  by 
the  abdominal  viscera  influence  in  no  sliRht  degree  the  form  and  (MMition  of  the  distended 
bladder,  since,  when  these  factors  are  both  unfavorable  to  unham|>eretl  expansion,  the  inferior 
surface  and  fundus  are  depressed  to  a  jfreater  degree  than  when  the  Ixjwcl  is  empty  and  the 
superior  surface  is  little  impressed  by  the  ovetlyinK  organs,  the  entire  bladder  aHsummg  a  more 
vertical  position  and  the  ovoid  form  being  modified  { Merkel ).  I'nder  pathological  conditions 
the  bladder  may  suffer  such  enormous  expansion  that  it  reaches  as  high  as  or  even  above  the 
umbilictLS  and  occupies  a  large  part  of  the  abdominal  cavity.  Owing  to  its  intimate  attachment, 
the  part  of  the  inferior  surface  united  to  the  prostote  and  the  pelvic  floor  undergoes  least  change 
both  as  to  form  and  relations. 

Pio    1A19. 


External  iliac 
artery 

Extemml  iHac- 
vein 
Deep  epig*itric. 
•rtery 
Spennatic  vcMels 


Internal  abdominal  - 
Tins 


OMiti 
h^'pogauric  artery 

Urachu*. 


Suspemory 
ligament  of  pcni 

Internal  urethral  orii 


Ureter,  enlerint 
bladder 


Fatty  tiasi 
containing  veint 


Pectinate  se|iti 


Spongy  urcthi 


Navicalar 


Seminal  vrsicle 
Rectum 

EJaculatury  duct 

Proiitatic  urethra 
and  utiide 

ProMate 
Membranous  urethra 
Bulb  o(  cavernous  body 

Balbouf  urethn 


Scrotum 
Dlaaection  of  sagitially  cut  pelvis,  showing  relations  of  organs  after  fixation  by  formalin  injection. 


The  capacity  of  the  bladder  during  life  so  obviously  depends  upon  individual 
peculiarities  and  habit  that  it  is  impossible  to  more  than  indicate  approximately  the 
quantity  of  fluid  that  ordinarily  induces  a  desire  for  the  evacuation  of  the  vesical 
contents.  This  quantity — the  physiological  capacity  of  the  bladder — may  perhaps  be 
said  to  vary  from  175-^50  cc.  (6-9  fl.  oz. ),  700  cc.  (24  fl.  oz. )  representing  the 
maximum  for  the  normal  organ  (Disse).  Under  pathological  conditions,  as  in 
paralysis  of  the  vesical  wall,  the  bladder  may  contain  from  3-4  litres  without  rupture. 
As  a  means  of  determining  its  capacity  during  life,  estimates  based  upon  artificial 
distention  of  the  bladder  after  death  are  worthless,  since  the  maximum  resistance 


1904 


HUMAN  ANATOMY. 


without  rupture  of  the  dead  vesical  wall  is  much  less  than  *hr.'  of  the  living  organ. 
The  bladder  in  the  female  has  d  smaller  capacity  than  in  the  malt . 

The  interior  of  the  bladder  varies  in  i^piiearancc  according  to  the  condition 
of  the  mucous  membrane.  The  latter  is  Ijxwely  attached  to  the  muscular  tunic 
by  iiiibniucous  areolar  tissue,  and  hence  in  the  contracted  state  of  the  organ  is  thrown 
into  conspicuous,  mostly  longitudinal  plications  ;  when  the  bladder  is  Ailed  these 
folds  are  efiaced  and  the  inner  surface  appears  smooth.  With  e.xcesslve  distention, 
the  interlacing  bundles  of  the  muscular  wall  may  be  stretched  so  far  apart  that  the 
submucous  tissue  and  the  mucosa  may  occupy  the  interstices  so  formed,  an  irregular 
pitting  or  pouching  of  the  mucous  linmg  resulting.  A  triangular  area,  the  trigonum 
rtsiitf,  included  between  the  urethral  orihce  in  ironi  and  the  ureteral  oixnings  ^hind, 
is  distinguished  by  its  smoothness  under  all  decrees  of  contraction,  even  in  the 
empty  Madder  bemg  only  indistinctly  wrinkletl.  Over  the  trigone  (Fig.  1620) 
the  .>iubmucosa  is  absent  and  the  mucous  membrane  rests  directly  upon  a  compact 
muscular  stratum  in  which  the  closely  plac««l  transverse  bundles  of  the  vesical  wall  are 
reinforced  by  radiating  fibres  continued  from  the  ureteral  sheath  (page  1897).  ^}** 
slighdy  cur>-ed  posterior  border  or  base  of  the  trigonum  ii>  marked  by  a  bond-like 
elevation,  the  p/ica  ureterica,  or  torus  urelefiau  of  Waldeyer,  that  unites  the  open- 
ings of  the  renal  ducts.  This  ridge,  best  marked  at  its  outer  ends,  is  less  evident 
and  often  interrupted  near  the  mid-line,  and  is  subject  to  much  individual  variati(Mi. 

Its  production  depends  upon  the  eleva- 
Pio.  t6to.  tion  of  the  mucosa  and  muscular  tissue 

in  consequence  of  the  oblique  path  of 
the  ureters  through  the  vesicsu  wall. 
The  margins  of  the  trigonum — lateral 
as  well  as  posterior — are  raised  and  its 
central  area  is  somewhat  depressed 
towards  the  urethral  opening.  The  lat- 
ter (orlfidna  urcthrac  internum)  occu- 
pies the  apex  of  the  trigonum,  and  is 
usually  not  circular,  but  crescentic, 
owing  to  the  projection  of  its  posterior 
border  as  a  small  median  elevation,  the 
vesical  crest  (uvula  vesicae),  that  ex- 
tends from  the  apical  end  of  the  trigone 
into  the  urethra  to  become  continuous 
with  the  urethral  crest  in  the  prostatic 
part  of  the  canal.  The  vesical  crest 
consists  of  a  thickening  of  the  mucous  membrane  enclosing  bundles  of  muscular 
tissue.  When  hypertrophied,  as  it  not  infrequently  is  in  aged  subjects,  this  fold 
may  form  a  valvular  mass  that  occludes  the  urethral  orifice.  The  anterior  wall  of 
the  latter  is  commonly  marked  by  low  converging  folds  continuous  with  the  longi- 
tudinal plications  of  the  urethral  mucous  membrane. 

The  ureteral  orifices  are  usually  slit-like  in  form  (4-5  mm.  long),  obliquely  trans- 
verse in  direction,  but  may  be  oval,  round,  or  punctiform  (Disse).  The  lateral  bor- 
der of  the  opening  is  guarded  by  a  valve-like  projection  (valvuia  ureteris)  that  forms 
part  of  the  nodular  elevation  that  is  produced  by  the  wall  of  the  ureter.  The  median 
margin  of  the  opening  is  embedded  in  the  interureteral  plica.  The  urethral  and  the 
two  ureteral  openings  mark  the  angles  of  an  approximately  equilateral  triangle,  the 
sides  of  which,  in  the  contracted  condition  of  the  bladder,  measure  from  2-2.5  ""•; 
when  the  organ  is  expanded,  this  distance  increases  to  from  3. 5-5  cm.  or  even  more. 
The  urethral  orifice  lies  from  1.75-2.2  cm.  in  front  of  the  base  of  the  trigone  when  the 
latter  is  contracted.  Immediately  behind  the  vesical  triangle  the  posterior  bladder- 
wall  presents  a  slight  depre»ion,  the  retrotrigonal  fossa  or  fovea  retroureterica 
(Waldeyer),  that  corresponds  to  the  "bas-fond"  of  the  French  writers.  When 
abnormally  enlarged  and  pouch-like,  as  it  often  is  in  advanced  life  when  associated 
with  an  enlarged  prostate,  this  fossa  becomes  of  practical  importance  (page  1981). 

Peritoneal  Relations.— -The  superior  surface  of  the  empty  or  but  slightly 
filled  bladder  is  completely  covered  by  peritoneum  as  far  as  the  lateral  and  posterior 


Opcningm 
of  untcra 


bimdder, 


'aecmcnt 
',  viewed 


fnwi  above  and  behind. 


bwdera.  On  each  iide  the  »er.m»  commmm  ip— iwrtunm  tfce  orfan  lo  JMC  the  p«a- 
vesical  ioMa,  the  »ickle-ahape<l  Jepmwi— <i*  jupwiLj  th.  art«rart«*»!  bladder  lr<^ 
the  adjacent  pelvic  wall.  In  irwnt  thM»  ade  toMn.  *r  /.rtfra/  yaAr  hgMmenis,  mr^ 
at  the  vesMal  apex,  where  they  awer  *e  iBtouuH  bantlxfi  the  urachus  mm  are  reflect*^ 
onto  the  anterior  abdomiaal  w Jl  jm  tht  mmvw/a/)w  Ju-ameu/  { litawtw  umbHicale 
■cdlan).  An  uncertain  told,  the  piiea  e^taHs  trmnsversa  ajien  croaiKrs  the  other- 
wise smooth  upper  surface  of  the  fabdrirr  Thw  lieritoiwal  r»«i|{e.  aumetunM  repre- 
sented by  two  or  more  low  wnnkles.  ejWJWto  lat*^allv  te»  be  »««  »ither  <>it  the  |)elvic 
wall  or,  passing  over  the  pelvi<:  tiriirt,  tiMnuids  th«?  ini«mu»l  alMti«minal  nnj>.  Dixon ' 
found  the  fold  well  represented  in  the  nwte  tortus,  awl  inclines  to  tli«-  view  tlwt  iu 
production  is  connected  w«h  a  drag  on  t»»e  jKiritoneuin  iwident  to  th*-  formation  oi 
the  ii^uinal  pouches.  Behind  the  peritoseiwi  passe*  front  the  posit.-rtor  b«»rder  ol 
the  emotv  bladder  over  the  upper  end  of  tb.  wsminal  v.-^iicl*-^  and  the  vasu*  de^erentia, 
to  form  ..  horiiontal  crescentic  shelf-like  loki  pUca  nctotcsicaliK )  fruin  1-1.5  cm. 
wide,  that  extends  from  the  bladder  backward,  embracing  tb*-  rectum  and  ending  at 
the  !s.'crum  on  either  side  of  the  gut  <V'z  1619). 


Sin      this  dupiicature  includes  pw . 
ham*  hav.   suggested  for  Its  lateral  aim. 
iifiUry  muscle  (ol  rtettvetilcalU)  atladMv 
ia.  ro-genital folds,  and  pointed  out  that  c 
(page  3007).    The  median  part  of  the 
but  more  or  less  obliterated  on  the  t"* 


<f  tiK  SI  »«nt  ducts  and  veiKles.  Dixon  and  Birmtnir- 

:\\*'-\v\  extcn  kms.  whirti  contain  Inindles  oJ  invol- 

••   -...trim    and  rectam.  the  appropriatt  name, 

I «jn»*?n<'      >  the  ut«frc>-!iacral  folds  in  the  (emoie 

f,,!"  :•.  r-i'jpicuous  behind  the  empW'  bladder, 

-  ,;•.   .>■,»   cuHiKS  the  lowest  part  of  the  jwritoneal 

receairdie  rtcto-vesital  fossa,  tliat  inter*'  .aa  ;i«ii.cec  t«e  rectum  and  the  seminal  vesrcles  and 
ainpullz  of  the  vasa  deferentia,  and  towards  whkh  the  fundw)  of  the  bladder  is  directed.  In 
recoicnition  of  these  relations,  the  anterior  wall  o*  this  recess  beinK  i.i  direct  relation  with  the 
seminal  tract-,  the  authors  last  mentioned  propose  to  call  this  deprcs,sion  the  rectfy^rnual  fossa. 
—a  term  alike  applicable  to  both  sexes,  since  the  relations  of  the  rectwm  to  the  uterus  m  the 
pouch  of  Douglas  in  the  female  are  similar  All  other  parts  ot  the  bladder,  including  the 
postero-inferior  (fundus)  and  the  antert>-inferior  surfaces,  are  entirely  de%'oid  of  peritoneal 
coverinK-  In  the  female  the  serous  membrane  puses  from  the  posterior  border  of  the  bladder 
onto  the  anterior  uterine  wall,  the  shall<jw  utero-vtsicai fossa  imerveninjt.  Occasionally  a  corre- 
sponding depres.sion  exists  in  the  male  as  a  slight  indenUtion  between  the  posterior  vesical  wall 
and  the  semin  •!  vesicles  (Dixon). 

With  the  hanges  of  form  and  position  which  the  bladder  undergoes  when  it  becomes  dis- 
tended are  as.s<K:iated  alterations  in  its  peritoneal  relations.  These  include  tlte  gradual  obliter- 
ation of  the  upper  part  of  the  recti  >-vesical  fos.sa,  along  with  the  shelf-like  fold,  and  the  elevation 
of  the  line  of  peritoneal  .oflection  at  the  sides,  so  that  the  lateral  false  ligaments  no  longer  reach 
the  pelvic  Boor,  Iwt  pa-  •-  from  the  lateral  wall  of  the  pelvis  directly  to  the  superior  surf^ice  of  the 
bladder,  from  which  thtr  ,  lica  transversa  has  disappeared.  Anteriorly  the  relations  of  the  serous 
covering  are  also  affected,  since  with  the  rise  of  the  bladder  above  the  level  of  the  symphysis 
the  peritoneum  is  carried  upward  and  a  suprapubic  non-peritoneal  area  becomes  progressively 
more  extensive  until,  in  extreme  distention,  a  space  measuring  vertically  from  8-9  cm.,  or  about 
3V  in.,  may  be  uncovered. 

Fixation. — The  attachments  of  an  organ  so  subject  to  ».  .isiderable  alteratioiu 
in  size  and  form  as  is  the  bladder  must  obviously  provide  for  such  changes  as  well 
as  the  maintenance  of  a  more  or  less  definite  piosition.  The  ' '  ligaments ' '  of  the 
bladder  are  conventionally  described  as  true  and  false,  under  the  latter  being  included 
the  peritoneal  folds  Cabove  describi-d)  that  pass  from  the  organ  to  the  adjacent  ab- 
dominal and  pelvic  walb.  The  sacro-genital  folds  were  formerly  sometimes  called 
the  posterior  faise  ligaments.  From  the  manifest  instability  of  the  relations  and 
attachments  of  the  peritoneum  incident  to  distention  and  contraction,  it  is  evident  that 
such  peritoneal  folds  can  contribute  little  to  the  definite  support  or  fixation  of  the 
bladder  ;  hence  those  parts  of  the  organ  possessing  a  serous  covering  are  movable. 
The  inferior  surface,  on  the  contrary,  is  comparatively  fixed  on  account  of  its  close 
relations  to  the  pelvic  floor  ^and  in  the  male  to  the  prostate")  and  the  presence  of 
fascial  bands  or  true  ligaments.  The  latter  are  derived  from  the  pelvic  fascia,  which 
in  the  vicinity  ok  the  bladder  presents  a  stout,  glistening,  band-like  thickening  (arcns 
tendincns)  that  on  each  side  stretches  from  the  posterior  suriace  of  the  symphysis,  a 

'  Journal  of  Anatomy  and  Physiology,  vol.  xxxiv.,  190a 
'Journal  of  Anatomy  and  Physiology,  vol.  xxxvi.,  1903. 


l9o6 


HUMAN  ANATOMY. 


short  distance  above  its  lower  border,  backward  to  the  ischial  spine  (pi^e  1899). 
On  either  side  of  the  mid-line  the  anterior  ends  of  these  tendinous  arches  pass  aa 
strong  fascial  bands,  the  pubo-prosttUic  ligaments,  from  the  symphysis  to  the  prostate, 
blendtne  with  its  capsule,  and  thence  continue  to  the  inferior  surface  of  the  bladder, 
where  they  are  lost  m  the  outer  fibrous  coat  of  the  vesical  wall.  In  the  female  these 
fascial  bands  pas^  direcdy  to  the  bladder  as  the  atUerior  true  ligaments.  After  leaving 
the  symphysis,  the  tendinous  arches  send  expansions — the  lateral  true  ligaments — to 
Jie  side  of  the  bladder,  which  materially  assist  in  fixing  the  organ. 

The  cleft  left  between  the  medial  borders  of  the  two  levator  ani  muscles  is  occupied  in  the 
male  by  the  rectum  and  prostate  and  in  the  female  by  the  rectum,  vagina,  and  urethra,  over 
some  of  which  organs  (rectum,  vagina,  and  prostate)  the  pelvic  fascia  covering  the  upper  sur- 
face of  the  levator  ani  muscles  (foida  dUphragma  ptivli  mpcrivr)  sends  more  or  less  extensive 
investments  and  thus  binds  them  to  the  pelvic  floor. 

Additional  support  is  afforded  by  more  or  less  definite  processes  of  muscular  tissue  pro- 
longed from  the  bladder  to  adjacent  structures ;  those  passing  within  the  arcus  tendineus  to  be 
attached  on  either  side  to  the  back  of  the  symphysis  constitute  the  pMbo-vesical  muscles,  while 
Otliers,  the  rtcto-vesical  muscles,  extend  backward  to  blend  with  the  rectal  wall. 


Pubovesical  tpace.  cloned  out. 


Ftlvic  line. 


Arcns  tendtneu* 
faaciic  pelvis 

VthWc linf  ji 
fsrcus  tendineus  m 
Icvatorisani) 


Syiiiph>'sis  pubis 


Pubo-vesicsl  ligament 

Arcus  tendineus 
Levator  ani  muscle 
;urator  canal 

y.  Wbite  line 


Bladder,  partly  distended 

Anterior  part  of  pelvis  of  female,  viewed  from  above  and  behind,  showina  relations  of  bladder 
to  pelvic  fascia ;  bladder  has  been  partly  distended  and  pulled  Iwckward 


Between  the  lateral  pubo-prostatic  ligaments,  the  symphysis,  and  the  bladder  lies  a  deep 
recess  (fovea  pubovtsicalis),  traversed  by  the  dorsal  veir.  of  the  penis  and  filled  with  fatty  areolar 
tissue,  the  floor  of  which  is  formed  by  the  fusion  of  the  pelvic  fascia  with  the  transverse  ligament 
of  the  perineum.  Above  the  level  of  the  pubo-prostatit  ligaments  lies  the  prevesical  space,  or 
space  of  Retzius,  which  is  bounded  in  front  by  the  anterior  wall  of  the  pelvis  below  and  the 
transversali!!  fascia  above,  and  behind  by  a  thin  membranous  condensation  of  areolar  tissue,  the 
fascia  umbilico-veticaiis  (Farabeuf),  that  passes  from  the  pelvic  floor  over  the  prostate  and 
bladder  to  the  abdominal  wall,  to  fuse  with  the  transversalis  fascia  at  a  variable  distance  below 
the  UiTibillcus.  Laterally  the  boundaries  of  this  space,  filled  with  areolar  tis-siie  loaded  with  fat, 
are  uncertain,  since  when  distended,  as  when  the  seat  of  an  abscess,  It  may  embrace  the  sides  of 
the  bladder  below  and  extend  above  as  far  as  the  obliterated  h>'pog.xstric  arteries.  Under  usual 
conditions,  however,  the  space  may  be  regarded  as  confined  chiefly  between  the  antero-inferior 
surface  of  the  bladder  and  the  adjacent  anterior  pelvic  wall. 


» 


Relations. — When  empty,  or  containing  only  a  small  quantity  of  fluid,  the 
bladder  possesses  t^vo  general  surfaces,  a  superior  and  an  inferior.  The  anterior  two- 
thirds  of  the  the  latter  rests  upon  the  prostate  and  the  pelvic  floor,  and,  according  to 
Dixon.'  when  hardened  in  situ  presents  a  rounded  niedian  ridge  which,  together  with 
the  ureters,  outlines  two  forward,  upward,  and  outward  sloping  infero-lateral  areas. 
These  rest  upon  the  pehic  floor  and  the  posterior  surface  of  the  pubis,  separated 
'  Journal  of  Anatomy  and  Physiology,  vol.  xxxiv.,  1900. 


THE  BLADDER. 


19&7 


from  th»  latter  by  the  retropubic  pad  of  fat  from  .5-1  cm.  thick.  The  fundus — the 
posterior  part  of  the  inferior  surface  included  between  the  urciliral  opening  and  the 
posterior  border — is  in  contact  with  the  median  ends  of  the  seminal  vesicles  and  of 
the  ampullae  of  the  seminal  ducts,  by  which  structures  and  their  musculo-adipose 
bed  the  bladder  is  separated  from  the  anterior  wall  of  the  recto-vesical  fossa. 

The  internal  orifice  of  the  urethra  lies  immediately  above  the  prostate,  usually 
from  1.2-2.5  cm.(  J^i  in. )  above  the  plane  passing  through  the  lower  border  of  the 
symphysis  and  the  lower  end  of  the  sacrum  ;  the  distance  from  the  upper  border  of 
the  symphysis  to  the  orifice  measures  from  5-6  cm.  (2-2J4  in.)  ;  in  the  horizontal 

Clane  it  lies  from  2.5-3  cm.  behind  the  symphysis,  its  nearest  point  on  the  latter 
eing  about  2  cm.  (Disse).  These  measurements  are  influenced  by  changes  in  the 
position  of  the  inferior  surface,  being  shortest  when  the  empty  bladder  b  pushed 
upward. 

Fio.  163*. 


L'rrtCT- 

Suipenaory. 
ligament  ol  ovary 

Fallopian  tube- 


Kound  liKamcnt. 
Ovary, 


OhMteralirt. 
hypogastric  artery 


Symphyaia  putW' 


Uretlii 


External  urethral, 
orifice  in  veallbule 


Utcnvaacral  foM 
Rectum 
External  oa  uteil 


Bottom  of  recto- 
nterine  pouch 


.Vagina 


Perineal  body 
Sagitul  aection  of  female  pelvis  of  formalin  «nl>(ect. 

Laterally  the  paravesital  fosstg  intervene  between  the  empty  bladder  and  the 
sides  of  the  pelvis.  In  the  contracted  condition  the  superior  surface  usually  lies 
below  the  plane  of  the  pelvic  inlet,  the  entire  bladder  being  within  the  anterior  third 
of  the  pelvis  and  close  to  the  pelvic  floor.  This  upper  surface,  covered  with  peri- 
toneum, is  in  contact  with  coils  of  small  intestine  which,  when  the  rectum  is  empty, 
may  occupy  a  [lart  of  the  recto-vesical  fossa. 

In  the  diitcndcd  bladdn  the  relatinn<i  of  the  inferior  surf.tce  suffer  little  change  on  account 
of  the  intimate  attachment--  of  the  vesical  wall  to  the  prostate  and  to  the  fixation  to  the  puWs 
afforded  by  the  pubo -prostatic  (pulio-vesic.nl )  li;;aments  and  enclosed  muscle.  The  postero- 
inferior  surface,  expanding  backward  and  outward,  comes  into  more  extensive  and  closer  rela* 


i9o8 


HUMAN  ANATOMY. 


Rectum 


tions  with  the  seminal  vesicles  and  ducts.  The  condition  of  the  rectum  maricedly  influences  the 
degree  to  which  the  distending  bladder  rises  above  the  symphysis,  since,  when  the  bowel  is  empty, 
and  hence  more  intrapelvic  space  is  available,  the  bladder  gains  a  lower  suprapubic  level  thtui 
when  its  ascent  is  favored  by  a  distended  rectum.  With  the  elevation  of  the  vesical  apex  above 
the  level  of  the  symphysis,  the  bladder  acquires  a  temporary  relation  with  the  anterior  abdominal 
wall  in  front,  and  its  sides,  in  case  of  marked  distention,  may  come  nearly  or  actually  into  con- 
tact with  the  vasa  deferentia,  the  obliterated  hypogastric  arteries,  and  the  obturator  vessels  and 
nerves,  as  these  structures  lie  along  the  pelvic  wall  embedded  within  the  fat-laden  subperitoneal 
tissue. 

The  bladder  in  the  female  lies  lower  within  the  pelvis  than  in  the  male,  chiefly  in  conse- 
quence of  the  absence  of  the  prostate,  and  when  empty  never  quite  reaches  the  level  of  the  upper 
border  of  the  symphysis.  When  distended,  therefore,  it  less  often  rises  into  the  abdomen, 
since  the  capacity  df  the  normal  organ  in  the  female  is  somewhat  less  than  in  the  male.  The 
fundus,  or  postero-inferior  surface,  is  firmly  united  by  connective  tissue  with  the  anterior  vaginal 
wall  and  sometimes  the  lower  part  of  the  uterus.  Where  reflected  from  the  anterior  surface  of 
the  uterus  onto  the  bladder,  the  peritoneum  lines  the  shallow  utero-vesical  fossa  and  then  con- 
tinues over  the  superior  vesical  surface.  Upon  the  latter  rests  the  body  of  the  uterus,  rising  or 
falling  with  the  expansion  or  contraction  of  the  bladder-wall,  but  normally  remaining  in  contact, 

— a  relation  predisponing  to  the  production 
Fio .   1 6»  J.    _  of  the  concave  or  sunken  condition  of  the  su- 

perior surface  not  infrequently  seen  In  frozen 
sections  of  the  female  pelvis. 

The  infentil*  bbiddcr  differs  both  in  form 
and  position  from  the  adult  organ.  Since 
the  greater  part  of  the  bladder  represents  a 
persistent  and  dilated  portion  of  the  intra- 
embryonic  segment  of  the  allantois,  its  fcctal 
form  is  essentially  tubular.  In  the  new-born 
child  (Fig.  i6ai),  in  both  sexes  alike,  the 
bladder  is  spindle-shaped  and  extends  from 
about  midway  between  the  umbilicus  and 
the  symphysis  to  the  level  of  the  pelvic  brim, 
its  anterior  surface  being  in  contact  with  the 
abdominal  wall.  Only  the  lower  pole  of  the 
in'.\ntile  bladder,  corresponding  to  the  ure- 
thral orifice,  lies  slightly  below  the  upper 
border  of  the  symphysis,  the  body  lying 
entirely  within  the  abdomen,  lateral  and 
posterior  surfaces  being  undifferentiated. 
Leaving  the  anterior  abdominal  wall,  the 
peritoneum  completely  invests  the  posterior 
surface  of  the  bladder,  as  well  as  the  semi- 
nal vesicles  and  the  ampullae  of  the  seminal 
ducts,  before  passing  onto  the  rectum.  The 
bottom  of  the  recto-vesical  fos.sa  lies  often  bek>w  the  level  of  the  urethral  orifice,  which  does  not 
come  into  relation  with  the  pelvic  floor.  In  the  new-bom  female  child  the  uterus  is  situated  rela- 
tively high  and  comes  into  contact  with  the  bladder,  while  the  vagina  does  not,  only  touching 
the  urethra.  The  reflection  <rf  the  peritoneum  to  form  the  utero-vesical  fr>.<sa  varies  in  position, 
and  when  high,  as  it  often  is,  may  l^ave  a  part  of  the  young  bladder  unprovided  with  a  serous 
co\  ering.  Coincident  with  the  descent  of  the  bladder,  as.sociated  with  the  growth  and  expaasion 
of  the  pelvis,  its  posterior  wall  increases  more  rapidly  than  the  anterior,  this  inetjuality  resulting 
in  the  production  of  a  fundus  that  gradually  approaches  the  pelvic  floor.  According  to  Disse,' 
thf  descent  of  the  young  bladder  is  rapid  during  the  first  three  years,  slower  fmm  the  fourth 
to  the  ninth  year,  between  which  and  puberty  little  change  ocriirs.  Succeeding  this  period  of 
rest  the  bladder  renews  its  descent,  and  by  the  twenty-first  year  has  gained  its  definite  position 
nn  the  pelvic  floor.  Hefore  the  third  year  the  empty  bladder  alway-s  remnins  above  the  symphy- 
sis ;  by  the  ninth  year  it  has  sunken  below  that  level,  but  when  distendeil  the  apex  ri.ses  within 
the  alKlomen.  During  descent  the  non-peritoneal  area  on  the  posterior  surface  progres.sively 
increases,  the  serous  investment  in  genenn"  extending  farther  downward  in  the  male  than  in  the 
female  child.    Persistence  nf  infantile  relations  often  accounts  for  variations  ol)ser\'ed  in  the  adult. 


S)'inph>iis  pubii 
Urethra 


Sagillal  wrtion  throiirh  pelrii  of  nrw-bom  female  child, 

hardened  in  fomulin,  showing  infantile  fonn 

and  (uprapubic  position  of  bladder. 


Stinicture. — The  hlaiJder  consists  esscntialiy  of  a  muscular  sac  lined  with  mucous 
mcmbi.inc  and  covered  cin  its  upper  surface  with  peritoneum,  a  layer  f>f  connective  tis- 
sue l«x»sely  uniting  the  ntticoiis  and  muscular  coats.     From  within  outward,  four  coats 

'  Anatomisrhe  Hefte,  Ud.  i.,  1891. 


iaffnaiiiiii 


mm 


THE  BLADDER. 


1909 


Epithcliunt 


are  distinguishable.— the  mucous,  the  submucous,  the  muscular,  and  the  incomolete 

**'**  T"he  mueous  coat  varies  in  thickness  with  both  location  and  the  d^ee  of  con- 
traction Over  the  vesical  trigone,  where  always  comparatively  smooth,  it  is  thin, 
nLsuring  only  about .  i  mm. ;  where  strongly  wrinkletl  by  contracuon  it  may  attain 
a  thicknL  of  over  2  mm.  The  mucosa  '««»"«, /^'^^'X^'^'^S^'^SX^^^^  ^l^^ 
consisting  of  a  fibro-elastic  tunica  propria  covered  with  transitional  epithelium.  The 
latter  includes  several  strata  of  cells,  the  deepest  of  which  are  columnar,  the  middle 
^Sularly  polygonal  or  club-shaped,  and  the  inner  pU»te-hke,  their  deeper  surface 
fitUSg  over  and'^between  the  underiying  elements.  Although  glands  may  be  con- 
sider^ as  absent,  tubular  depressions  are  occasionally  found  m  |he  vicinity  of  the 
ttigone  which  are  regarded  by  some  (Kalischer.  Brunn)  as  true  glands.  Waldeyer 
S  suggested  thatTese  structures  may  be  interpreted  as  representing  in  a  sense 

urethrd  glands  displaced  during  the  development  of  the  vesical  trigone.        

Th^ submucous  coat,  loose  and  elastic,  perr.uts  free  gliding  of  the  mucous  over 
the  muscular  tunic  when  readjustment  becomes  necessary  during  contracuon.  Com- 
S«ed  of  bundles  of  fibrous  tissue  interwoven  with  elastic  fibr«,  it  supports  the 
blood-vessels  and  nerve-plexuses,  and  contains  numerous  bundles  of  involuntary 
muscle.    It  is  not 

sharply     defined  _  Fio.  ««»4- 

from  the  adjoin- 
ing coats,  but 
blends  with  the 
stroma  of  the  mu- 
cosa on  the  one 
side  and  extends 
between  the 
tracts  of  the  mus- 
cular coat  on  the 
other.  Beneath 
the  trigonum  a 
distinct  submu- 
cous layer  is 
wanting  or  re- 
placed by  a  sheet 
of  muscular  tis- 
sue. 

The  muscu- 
lar coat,  thicker 
than  the  mucosa 
and  compara- 
tively robust,  va- 

[£  Stion  o?the  bladder,  being  thin  during  distention  and  verv  thick  in  strong 
contSn  when  it  may  measure  :«  much  as  1.5  cm.  The  bundfes  of  mvoluntary 
muile  are  arranged  in  two  fairiy  distinct  chief  layers.-a  thin  outer  longitudinal  and 
rS  inner  circular.  Inside  the  latter,  an||  virtually  within  the  submucosa,  hes  an 
Incomplete  additional  layer.  The  longitudinal  bundles,  best  developed  on  the  upper 
a"id  Wr  surfaces,  do  not  constitute  a  continuous  sheet,  hut  interface,  leaving  inter- 
h.scicuTar  intervals  which  are  occupied  by  connective  tissue.  In  the  vicin.  v  of  he 
pTSe  extensions  <,f  the  outer  layer  are  attached  to  the  antenor  pelvic  waH  as  he 
Sute  vesical  muscles  ;  others  pass  Kickward  to  blend  with  the  intestinal  wall  as  the 
K-  •«  cal  muscles,  while  from  the  apex  bundles  are  prolonged  into  the  urachus 
The  circular  layer,  although  more  robust  and  uniform  than  the  ou  er.  js  «'e..k  and 
imlrfect  over  the  trigond  region,  and  in  both  sexes  is  well  developed  only  aft^r 
Sing  the  level  of  the  internal  ureteral  orifices  (DisseV  T.  vards  tiie  apex  of  rf,e 
b  adder^he  bundles  of  the  circular  layer  .ssume  an  obli.,ue  and  >««,;;^'»»  ^^  3: 
sition.  The  innermost  laver-that  within  the  submucosa-.s  represented  by  .so  ated 
and  indefinite  muscular  bundles  that  are  blended  with  the  connective  tissue.     « >ver 


'Og// 


Section  o(  wall  oJ  bl«dd«r,  under  very  low  maicnification, 
showinn  itenenil  duponitlon  of  roats.    K  i>. 


I9IO 


HUMAN  ANATOMY. 


I  i 


the  vesical  trigone,  however,  this  layer  becomes  condensed  and  forms  a  compact 
transverse  muscular  sheet  that  is  closely  united  to  the  overlying  mucous  membnme 
and,  m  conjunction  with  the  muscular  tissue  of  the  urethra,  surrounds  the  beginninir 
of  that  canal  with  a  constrictor-like  tract  the  interned  vesical  sphincter. 

The  outer  ^brous  coat  of  the  vesical  wall  is  strongest  over  the  inferior  surface 
where  it  ro  cives  reflections  from  the  pelvic  fascia;  towards  the  apex  and  beneath  the 
peritonei-  it  is  less  definite  and  often  intermingled  with  adipose  tissue.  Over  the 
postero-inierior  surface  in  the  male  it  is  fused  with  the  fibrous  tissue  surrounding  the 
seminal  vesicles  and  ducts,  and  in  the  female  is  blended  with  the  anterior  vaginal  wall 
.  ,  VesMls.— The  arteries  supplying  the  bladder  are  chiefly  the  superior  and 
mfenor  vesical,  from  the  anterior  division  of  the  internal  iliac  ;  these  ar^  reinforced 
by  branches  from  the  middle  hemorrhoidal,  as  well  as  by  small  twigs  from  the  internal 
pudic  and  the  obturator  arteries.  The  superior  vesical  supplies  the  upper  segment 
of  the  bladder  and  sends  small  branches  along  the  urachus.  The  inferior  vesical 
divides  into  two  or  more  branches  which  are  distributed  to  the  infero-Iateral  and 
postero-inferior  surfaces.  In  addition  to  twigs  to  the  region  of  the  trigone,  others 
pass  to  the  prostate,  seminal  vesicles,  and  ducts.  On  gaining  the  bladder,  the  vesical 
branches  anastomose  and  enclose  that  oi^an  in  an  arterial  net-work  from  which 
twigs  enter  the  muscular  coat  and  break  up  into  capillaries  for  its  supply.  Others 
penetrate  the  muscular  tunic  and  within  the  submucosa  form  a  net-work  from  which 
arterioles  pass  inward  for  the  supply  of  the  mucous  membrane. 

The  veins  do  not  accompany  the  arteries,  but  form  a  submucous  plexus  that 
drains  the  mucous  membrane  and  empties  into  a  muscular  plexus  which,  in  turn,  is 
received  by  an  external  subperitoneal  plexus.  From  the  latter  the  blood  from  the 
entire  oi^n  passes  into  the  large  prostatico-vesical  plexus  at  the  sides  of  the  bladder 
and  thence  into  the  tributaries  of  the  internal  iliac  veins.  With  the  exception  of  the 
smaller  ones  on  the  inferior  surface,  all  the  vesical  veins  possess  valves  (Fenwick). 

The  lymphatics  of  the  bladder  begin  as  a  dose-meshed  net-work  within  the  mus- 
cular coat,  according  to  Geroto,'  being  absent  within  the  mucous  membrane.  Out- 
side the  muscular  coat  they  form  a  wide-meshed  subperitoneal  plexus,  those  from  the 
apex  and  body  coursing  downward  and  laterally  and  those  from  the  fundus  upward 
Leaving  the  sides  of  the  bladder,  the  efferent  channeb,  chiefly  in  company  with  the 
arteries,  pass  to  the  internal  iliac  lymph-nodes  and  to  those  situated  at  the  bifurca- 

'l*^"!-?'  J  j^  ^""^  ^'*'"^  ****  P*^**  °'  '•"  lymphatics  on  the  antero-inferior  surface  of 
the  bladder  Gerota  describes  one  or  two  very  small  nodes  as  usually  present. 

The  nerves  of  the  bladder  include  both  sympathetic  and  spinal  fibres.  The 
former,  distributed  chiefly  to  the  muscular  tissue,  are  from  the  vesical  plexuses,  which 
as  subordinate  divisions  of  the  pelvic  plexuses,  lie  at  the  sides  of  the  bladder 
The  sympathetic  fibres  accompany  the  arteries  and  are  joined  by  the  vesical  branches 
from  the  sacral  plexus  derived  from  the  third  and  fourth,  possibly  also  the  second, 
sacral  spinal  ner\'es.  The  principal  trunks  reach  the  bladder  in  the  vicinity  of  the 
ureters,  the  trigonal  region  receiving  the  most  generous  nerve-supply  and  the  apical 
segment  the  fewest  fibres.  Within  the  outer  fibrous  coat  the  larger  nen'es  divide 
into  smaller  branches  that  are  connected  with  ganglia,  especially  in  the  neighborhood 
of  the  ureters,  from  which  twigs  enter  the  muscular  tunic  and'break  up  into  smaller 
ones  bearing  terminal  microscopic  ganglia  before  ending  in  the  muscle.  Other 
branches  penetrate  the  submucosa,  where  they  form  plexiform  enlargements  contain- 
ing numerous  minute  ganglia,  from  which  fine  twigs  proceed  to  the  mucosa  to  end, 
according  to  Retzius,  between  the  epithelial  cells.  In  general  the  sensibility  of  the 
normal  bladder  is  comparatively  slight,  the  trigonal  region,  especially  at  the  ureteral 
openings,  being  its  most  sensitive  area. 

PRACTICAL  CONSIDERATIONS:    THE  BLADDER. 

Absence  of  the  bladder  is  a  very  rare  abnormality,  but  in  more  than  one  case 
has  proved  to  be  consistent  with  prolonged  life,  the  dilated  ureters— opening  into  the 
urethra— having  acted  as  reser\'oirs  for  the  urine  and  the  muscle-fibres  at  their  con- 
stricted orifices  having  taken  on  sphincteric  action  and  prevented  urinary  incon- 
'  Anatom.  Anzeifcer,  Bd.  xii.,  i8q6. 


PRACTICAL  CONSIDERATIONS:    THE  BLADDER. 


191 1 


tinence.  In  other  less  fortunate  cases  in  which  the  ureteral  openings  were  on  the 
surface  of  the  body,  implantation  of  the  ureters  into  the  intestinal  tract  (page  1901; 
has  been  done  with  varying  degrees  of  success. 

Extroversion  (exstrophy)  of  the  bladder,  the  most  frequent  congenital  ab- 
normality of  this  organ,  is  associated  with  failure  of  the  ventral  plates  formmg  the 
abdominal  wall  to  unite  in  the  mid-line.  In  this  condition,  which  occurs  m  males  »•> 
from  80  to  90  per  cent,  of  cases,  the  symphysis  pubis  and  the  anterior  wall  of  the 
bladder  frequently  are  also  lacking,  and  the  posterior  vesical  wall— protruded  by 
intra-abdominal  pressure— forms  a  rounded  prominence,  deep  red  m  color,  from 
chronic  congestion.  The  ureteral  orifices  are  often  plainly  visible.  Cryptorchism, 
bifid  scrotum,  inguinal  hernia,  and  epispadias  are  frequently  present.  Although  the 
opinions  regarding  the  causes  and  factors  leatling  to  these  malformations  are  various 
and  conflicting,  it  is  certain  that  these  defects  depend  upon  faulty  development  at  a 
very  early  period  of  foetal  life,  probably  in  connection  with  abnormalities  of  the 
allantois  and  of  the  cloacal  region  of  the  embryo,  and  that  the  suggested  explana- 
tions  on  a  mechanical  basis,  as  over-distention  of  the  allantois  or  unusual  shortness  or 
location  of  the  umbilical  cord,  are  entirely  inadequate  to  account  for  malformations 
which  often  so  profoundly  affect  the  entire  lower  segment  of  the  anterior  body-wall 
and  the  associated  organs.  •  u      .u 

Occasionally  a  vesico-abdominal  fissure  occurs  without  extroversion,  when  the 
posterior  wall  of  the  bladder  will  be  concave  instead  of  convex  and  partially  covered 
by  the  imperfect  abdominal  wall.  ... 

The  posterior  wall  of  the  bladder  and  the  anterior  wall  of  the  rectum  or  vagina 
may  be  defective  at  birth,  resulting  in  a  congenital  vesico-rectal  or  vesico-vaginal 

The  foetal  communication  between  the  extra-  and  intra-abdominal  portions  of 
the  aV..  ntoic  sac  may  remain  pervious,  so  that  the  urachus,  instead  of  becoming  a 
fibrous  cord  extending  from  the  umbilicus  to  the  summit  of  the  bladder,  is  patent 
and  constitutes  a  channel  by  means  of  which  urine  is  discharged  at  the  navel. 

Cysiocele.—K  portion  of  the  bladder  may  be  found  either  alone  or  together 
with  intestine  or  omentum  in  the  sac  of  an  inguinal  or  femoral  hernia,  or  more 
rarely  it  may  be  part  of  an  obturator  or  perineal  or  ventral  hernia. 

The  ordinary  causes  of  abdominal  hernia  (page  1759)  tavor  the  production  <A 
this  condition.  In  their  presence,  and  especially  if  there  is  also  present  an  intestinal 
hernia  of  long  standing,  a  thinned  and  dilated  bladder  may  readily  be  drawn  by 
gravity  into  one  of  the  hernial  orifices  by  the  connection  of  its  extraperitoneal 
portion  with  the  subperitoneal  fat  with  which  it  is  in  close  contact.  The  bladder 
"diverticulum,"  thus  formed,  is  a  result,  not  a  cause  of  the  hernia,  and  in  75  per 
cent,  of  cases  includes  only  the  extraperitoneal  bladder-wall.  As  vesical  dilatation 
and  atony  are  usually  the  result  of  obstructive  disease,— most  common  in  elderly 
males,— and  as  abdominal  hernia  is  frequent  during  late  middle  life  (page  1762;,  it 
will  be  understood  why  75  per  cent  of  cases  of  hernia  of  the  bladder  occur  in  men 
(irrespective  of  cases  of  vaginal  cystocele)  and  more  than  50  per  cent,  in  persons 
over  fifty  years  of  age.  In  old  hernia  there  has,  of  course,  been  an  opportunity 
for  the  stretching  and  elongation  of  the  bladder-wall  essential  for  the  production  of 
the  cystocele. 

The  laxity  of  the  attachments  of  the  bladder  to  surrounding  structures  necessi- 
tated by  its  changes  in  size  or  capacity  favors  the  production  of  hernia. 

Effects  of  Distention.  —The  cavity  of  the  normal  empty  bladder,  which  is  strongly 
contracted  during  life,  presents  little  more  than  a  narrow,  deft-like  lumen,  with  a 
gende  upward  curve,  continuous  with  that  of  the  urethra.  As  it  distends  the 
pyriform  bladder  becomes  oval  in  shape,  iu  summit  rises  from  the  pelvis  above  the 
symphysis  pubis,  its  anterior  wall  becomes  applied  to  the  inner  surface  of  the  ab- 
dominal wall  in  the  hypogastric  region,  and  the  wttole  organ  assumes  an  ovoid  shape 
or,  in  extreme  distention,  one  neariy  spherical.  Its  normal  capacity  in  the  adult  is 
about  one  pint,  but  the  looseness  of  the  submucosa  over  the  greater  part  of  «ts  sur- 
face, the  reticular  arrangement  of  its  muscle-fibres,  and  the  yielding  nature  of  the 
structures  by  which  it  is  surrounded  when  it  has  risen  from  the  pelvis  permit  of 
its  enormous  distention,  especially  as  a  result  of  slowly  increasing  obstructive  dis- 


I9I3 


HUMAN  ANATOMY. 


I! 


II 


ease.     Its  summit  may  then  oass  above  the  level  of  the  umbilicus  and  it  may  fill 
almost  the  whole  abdomen. 

Relentum  of  urint — inability  to  empty  the  bladder — may  be  due  (a)  to  obstruc- 
tion at  the  neck  of  the  bladder,  the  prostate,  or  the  urethra,  as  from  clots  in  bleeding 
from  the  kidneys,  ureters,  or  the  bladder  itself,  prostatic  hypertrophy,  stricture,  or 
rupture  of  the  urethra ;  {b)  to  affections  of  the  bladder  muscles,  as  paresis  or 
paralysis  of  the  detrusors  in  cerebral  or  spinal  injury  or  disease,  or  reflex  spasm  of  the 
sphincter  after  operations  on  the  anus  or  rectum  ;  or  incoordination,  as  in  hysteria, 
or  neurasthenia,  or  shock. 

The  distended  bladder  forms  a  rounded  fluctuating  tumor  in  the  hypogastric 
region,  which,  as  the  intestines  are  pushed  up  with  the  fold  of  peritoneum  txick  of 
the  urachus  (plica  vesico-umbilicalis),  is  always  dull  on  percussion.  If  the  disten- 
tion is  acute,  the  pressure  on  the  sensory  nerves  of  the  bladder  gives  rise  to  dis- 
tressing pain.  If  it  takes  place  slowly,  or  if  it  follows  cerebral  or  spinal  injury,  it 
may  be  quite  painless. 

After  a  time,  in  cases  of  great  distention,  the  sphincter  vesicae  and  compressor 
urethrae  yield  to  the  pressure  and  the  urine  overflows  the  bladder  more  or  Icsa  con- 
tinuously,— incontinence  of  retention, — a  condition  which  should  always  be  suspected 
to  exist  in  aged  male  patients  who  have  either  very  frequent  urination  or  constant  uri- 
nary dribbling.  Great  paresis  or  actual  paralysis  of  the  detrusors  may  result  from 
distention,  so  that  the  power  to  empty  the  bladder  is  temporarily  or  permanently  lost 
even  after  all  obstruction  has  been  removed. 

During  marked  distention  certain  changes  take  place  in  its  relations  that  are  of 
much  practical  impmrtance.  The  neck  of  the  bladder  is  so  firmly  fixed  in  position  by 
the  base  of  the  prostate,  with  its  dense  capsule  continuous  with  the  deep  layer  of  the 
triangular  ligament  (page  1977),  by  the  anterior  true  ligaments  of  the  bladder  itself , 
and  by  its  close  attachment  to  the  rectum  or  to  the  uterus  and  vagina,  that  it  does  not 
[tarticipate  in  the  upward  movement  of  the  summit  and  body,  but  if  the  rectum  is 
not  distended,  rather  sinks  slightly  in  the  pelvis.  The  looseness  of  the  fatty  con- 
nective tissue  occupying  the  space  of  Retzius  (page  1906)  and  separating  the  antero- 
lateral walls  of  the  bladder  below  the  peritoneal  reflection  from  the  pubes  and  the 
obturator  intemus  and  levator  ani  muscles  permits  the  elevation,  during  distention,  of 
all  the  remainder  of  the  bladder. 

The  anterior  peritoneal  fold,  which,  with  the  bladder  undistended,  reaches  to  the 
symphysis  pubis,  is  so  raised  that  if  the  summit  of  the  bladder  is  half-way  between 
the  pubes  and  the  umbilicus,  there  will  be  from  5-6.5  cm.  (2-2j4  in.)  of  the  non- 
peritoneal  portion  of  the  anterior  bladder-wall  in  close  apposition  with  a  similar  area 
of  the  inner  surface  of  the  abdominal  wall.  In  a  male  child  five  years  of  age  the 
space  between  the  upper  edge  of  the  symphysis  pubis  and  the  reflection  of  the  peri- 
toneum will  be  one  inch  when  the  bladder  contains  three  ounces  of  liquid.  The  close 
attachment  of  the  peritoneum  to  the  summit  of  the  bladder  and  its  very  loose  attach- 
ment to  the  parietes  ( neces.sitated  by  the  changes  in  size  and  position  of  the  bladder) 
permit  this  upward  displacement. 

Coincident  distention  of  the  rectum  by  a  rubber  bag  limits  the  backward  and 
downward  extension  of  the  distended  bladder,  adds  slightly  to  its  elevation  in  the 
abdomen,  keeps  it  in  close  contact  with  the  abdominal  parietes,  and  increases  the 
distance  between  the  recto-vesical  fold  and  the  anus  from  two  and  a  half  inches  to 
three  and  a  half  inches.  The  use  of  the  rectal  bag  has  practical  disadvantages  which 
have  led  to  its  abandonment  in  most  cases.  The  Trendelenburg  position  elevates 
the  partly  distended  bladder  and  carries  upward  the  peritoneal  folds  by  gravity. 
X'arious  operations  {vide  infra)  are  so  planned  as  to  take  advantage  of  this  uncover- 
ing of  the  bladder-wall,  which  permits  access  to  that  viscus  and  to  its  cavity  without 
danger  of  peritoneal  infection. 

Prevesical  inflammation  may  follow  infection  through  an  operation  or  otiier 
wound,  involving  the  pre\esical  space  of  Ketxius,  or  may  be  caused  by  extravasa- 
tion of  urine  into  that  space  :  and  as  the  connective  tissue  occupying  it  is  continuous 
superiorly  with  the  alxlominal  and  interiorly  with  the  pelvic  extraperitoneal  tissue,  a 
cellulitis  beginning  there  may  tie  widespread,  or  may  result  fatally.  Some  of  the 
relations  of  this  space  are  indicated  in  the  fact  that  such  infection  has  been  known  to 


i 


PRACTICAL  CONSIDERATIONS:    THE  BLADDER. 


1913 


follow  chronic  cystitis,  uterine  or  periuterine  inflammation,  postpartum  suppuration 
of  the  symphysis  pubis,  and  purulent  thrombosis  of  the  umbUical  vem  in  a  new-bom 
infant  (Thomdike).  ,     ,         ,     ,         .    . 

Collections  of  pus  have  opened  from  here  spontaneously  through  the  anterior 
abdominal  wall,  into  the  rectum,  the  bladder,  or  the  urethra,  and  mto  the  peritoneal 

'^'"^^jRufiture  of  the  bladder  rarely  follows  distention  alone,  but  is  not  uncommon  as 
a  result  of  trauma  expended  upon  the  pelvis  or  lower  abdomen  when  the  bladder  is  dis- 
tended The  cases  in  which  rupture  follows  over-distention  from  obstructive  disease, 
without  the  intervention  of  force,  are  usually  prostatic  in  ongin,  as  in  retention  from 
stricture  the  urethra  ordinarily  ulcerates  behind  the  constncuon  and  penurethral 
extravasation  of  urine  relieves  the  tension. 

The  liability  to  traumatic  rupture  is  direcUy  proportionate  to  the  degree  ot  dis- 
tention and  consequent  elevation  of  the  viscus,  and  if  that  condition  exists  in  a  blad- 
der the  subject  of  chronic  dilatation  and  atrophy,  or  m  one  rendered  unnaturally 
immobile  by  pericystitis  or  pelvic  cellulitis,  the  force  required  to  produce  rupture  is 
much  lessened.  Occasionally  in  the  presence  of  fracture  of  the  pelvis  it  is  difficult  to 
decide  whether  a  given  lesion  of  the  bladder  is  a  rupture  or  a  wound  from  a  fragment 

***  "^Bghty-five  per  cent,  of  ruptures  are  intrap^riloneaj,  bemuse,  («)  in  distention 
the  peritone.-^l  becomes  the  most  tense  of  the  coats  of  the  Wadder-wall ;  (b)  it  is  he 
«,st  dastic  ;  iO  it  covers  that  portion  of  the  bladder  which,  as  it  rises  into  the 
abdomen,  fii^t  loses  the  protection  afforded  by  the  pelvis  and  is  less  reinforced  by 
JrSure  from  surrounding  tissues;  (rf)  the  bladder-walls  are  thinnest  over  that 
area  •  (e)  tiie  region  is  exposed  to  counter-pressure  against  the  promontory  ot  the 
sacrum.     These  conditions  also  explain  the  usual  situation  of  intraperitoneal  ruptures 

in  the  upper  and  posterior  bladder-wall.  „       .        .    .      _• » 

Ext^ap^rilcUal  rupture  is  apt  to  be  in  the  anterior  wall,-/... ,  that  portion  most 
immediate^  in  contact  with  the  pelvic  bones,  which  in  these  cases  are  often  found 

*°  pSlogical  (spontaneous)  rupture  is  usually  in  the  extraperiton  al  portion  of 
the  bladder,  becaus«:  there  the  influence  of  gravity  is  most  potent  in  aiding  111  the 
production  of  the  protrusion  of  the  thinned  mucosa  between  the  often  hypertrophied 
Uds  of  nmscular  fibres.  The  eariy  stoge  of  this  condition---in  «!''«;,*' /hemuscie 
hypertrophy  is  the  prominent  change-constitutes  the  ^-cAX^  fasciculated  bladder . 
later,  when  the  pou-'hing  has  become  marked,  it  is  known  as  sacculated  bladder. 

In  children  nipture  of  the  bladder  is  rare  m  spite  of  its  thinness  and  of  the  fact 
that  in  them  it  is  an  abdominal  rather  than  a  pelvic  organ,  because  (a)  the  chief 
causes  of  distention  are  absent ;  (3)  the  greatw  sensibility  of  the  bladder  renders  its 
evacuation  more  frequent  or  less  likely  to  b»  neglected  ;  in  the  adult  incontinence  of 
urine  generally  means  distention,  in  the  child  irritation  rOwen);  (f)  owing  to  the 
undeveloped  condition  of  the  prostate  the  bladder  is  more  nKwable. 

Wounds  of  the  bladder  may  occur  from  within,— during  instrumentation,— or  the 
bladder  may  be  reached  by  weapons,  missiles,  or  vulnerating  bodies  of  any  w.rt, 
through  the  suprapubic  region,  the  rectum,  the  perineum,  the  f.I.iur.ttor  or  the 
sciatic  foramen.  They  often  result  from,  the  direct  laceration  of  the  blad''  .--wall  by 
a  bony  fragment  in  fracture  of  the  pelvis.  Like  ruptures,  tliey  m  ly  or  \\\  not  in- 
volve the  peritoneum.  .  ,    ,       .  ,  ^, 

The  symptoms  of  rupture  or  wound  will  obviously  v.try  with  t'l-  sit'i  itiri  )t  the 
lesion.  The  most  important  are  due  to  the  escape  of  urine  from  cbe  hi  idd.  r  either 
into  the  space  of  Retzius  or  into  the  peritoneal  c.ivity.  Tho  dettrmin:;vi(iri  of  the 
ireneral  character  of  the  injury— made  in  part  liy  catheterization,  which,  in  the 
presence  of  inability  to  urinate,  yet  fails  to  draw  more  than  a  little  bloody  urine,  and 
does  not  withdraw  all  <if  a  measured  quantity  of  injected  fluid— should  Iv  followed 
by  instant  operation,  whether  the  lesion  is  extra-  or  intraperitoneal  in  its  situation. 

Occasionall)',  after  a  small  stab  or  pistol  wound,  the  loose  mucosa  may  art  .-is  a 
plug  and,  aided  by  the  muscular  contraction  of  the  bladder-wall,  will  for  a  time 
prevent  extravasation,  and  tl,en  the  above-mentioned  signs  may  be  absent  or  may 
appear  later,  when  ulcerative  or  necrotic  processes  have  opened   the  way  for  the 


—I'M 


.--i.'ia.iii.j. 


1914 


HUMAN  ANATOMY. 


I 


escape  of  urine.  A  similar,  but  usually  pennanent  closure  of  the  wound — by  mus- 
cular contraction,  or  by  a  valvular  action  from  the  change  in  the  relation  of  the  coats 
of  the  vesical  wall  after  ter.  ''on  has  been  relieved — takes  place  when  the  bladder  has 
been  tapped  above  the  pubes  (^suprapubic  puncture). 

cystitis,  in  so  far  as  it  has  an  anatomical  bearing,  should  be  studied  with  regard 
to  the  possible  sources  of  the  essential  infection  and  of  the  almost  (.cjually  essential 
predisposing  condition  of  congestion.  No  explanation  is  required  of  the  influence 
of  (ii)  frequent  micturition,  however  caused;  (b)  trauma;  (e)  vesical  distention  ; 
(</)  acid  urine  ;  (c)  calculi  or  tumors  ;  ( /;  cold  and  wet ;  (^)  prolonged  sexual 
excitement;  (A)  cardiac  weakness,  in  bringing  about  a  congestion  of  the  vesical 
and  vcsico-prostatic  plexuses.  The  sudden  removal  of  pressure  when  an  habitually 
distended  bladder  is  emptied  may  be  followed  by  congestion  so  excessive  as  to  cause 
hematuria. 

Infection  may  occur  by  sprei  Jing  from  the  urethra  or  prostate,  by  instrumenta- 
tion, by  descent  from  the  kidneys,  by  extension  from  any  pericystic  focus  of  suppu- 
ration, or  by  direct  passage  of  the  microbic  cause  from  the  rectum.  The  great 
venous  plexus  at  the  base  of  the  bladder,  emptying  into  the  valveless  internal  iliac 
veins,  is  engorged  whenever  pressure  is  made  upon  the  latter,  as  by  fecal  masses  in  the 
sigmoid  flexure  or  rectum.  Constipation  is  thus  both  a  prediiiftosing  and — through 
the  migration  of  microbes  to  the  contiguous  bladder — an  excitir.g  cause  of  cystitis. 

The  mucosa  of  the  bladder,  supplied  by  the  hypogastric  plexus,  is  not  very 
sensitive  normally,  except  in  the  region  of  the  trigonum.  There  it  is  tightly  con- 
nected with  the  muscular  layer,  and  the  loose,  elastic,  submucous  connective  tissue 
found  in  the  remainder  of  the  bladder  is  absent.  The  difference  is  shown  by  the 
smooth  surface  of  the  trigonum  as  contrasted  with  the  rugae  of  the  lax  mucosa  seen 
over  the  rest  of  the  interior  of  the  empty  bladder.  The  laxity  in  the  superior  por- 
tions '.'  the  bladder  is  determined  by  the  necessity  for  great  changes  in  its  size.  At 
the  trigonum  a  similar  looseness  of  the  mucosa  would  encourage  its  prolapse,  and 
might  result  in  frequent  obstiiiction  of  the  ureteral  and  vesical  outlets.  This  close 
adlie-.,l.in  of  mucous  and  muscular  layers  prevents  free  swelling  when  inflammation 
occurs,  and,  in  conjunction  with  the  particularly  generous  vascular  and  nerve  supply 
to  the  trigonum  and  neck  of  the  bladder,  explains  the  pain  and  sensitiveness  of  that 
region  in  cystitis.  In  a  marked  case  the  whole  bladder  may  become  sensitive,  so 
that  hypog^:itric  pressure  is  painful. 

Frequent  micturition,  as  a  result  of  cystitis  or  of  other  conditions  in  which  vesical 
irritation  is  present,  is  due  tc  stimulus  of  the  sensorj.  nerves  supplied  by  the  third 
and  fourth  sacral  ner\'es  from  the  second,  third,  and  fourth  sacral  segments  of  the 
cord.  The  motor  impulse  reaches  the  bladder  from  the  eleventh  and  twelfth  dorsal 
and  first  lumbar  segments  through  the  hypogastric  and  pelvic  plexuses. 

The  skin  of  the  scrotum  and  of  the  penis  and  the  urethral  mucous  membrane 
are  supplied  with  sensation  from  the  same  spinal  segments  as  is  the  bladder,  and 
therefore  the  referred  pains  in  vesical  irritation  or  inflammation  are  often  felt  in  those 
regions  in  the  distribution  of  the  perinfal  branches  of  the  pudic  and  inferior  glutc.il 
ne  es.  As  the  inierior  hemorrhoidal  nerve — supplying  the  .skin  over  the  external 
sphincter  ani  and  about  the  and-; — is  often  derived  from  the  sacral  plexus,  itching  or 
tickling  in  that  region  or  painful  sp>asm  of  the  anal  sphincter  may  be  caused  by 
vesical  irritation. 

Other  referred  pains  in  vesical  disease  are  to  the  lumbo-sacral  region,  through 
the  communication  between  the  second,  third,  and  fourth  sacral  nerves  and  the  hypo- 
gastric plexus  ;  to  the  kidney,  by  the  junction  in  the  sf>ermatic  plexus  of  filaments 
frcm  the  vesical  and  renal  plexuses  ;  and  to  the  lower  limb,  occasionally  to  the  foot 
(pododynia),  through  the  sacral  nerves  which  enter  into  the  sacral  plexus  and  the 
lumbo-sacral  cord,  gi\'ing  off  the  great  sciatic  nerve,  and  also  mto  the  pelvic 
plexuses. 

The  important  muscular  element  in  the  vesical,  as  in  the  ureteral,  walls  gives 
the  "colicky"  chara^er  to  the  symptoms  of  irritation  and,  in  the  case  of  the  in- 
flamed bladder,  causes  the  violent  tenesmus  accor.  ,)anying  the  discharge  of  the  last 
drops  of  urine,  when  the  muscles  in  the  vicinity  of  the  sensitive  trigonum  contract 
si>asmodically. 


-^^CTTTT^TM 


PRACTICAL  CONSIDERATIONS:    MALIC   I'LRINEIM.  1915 

The  same  symptom*— frequent  micturition,  referred  |win!',  tenesmus— arc  caiwttj 
\w  a  vesical  eaiaui'smd  have  the  same  anatomical  basis.  They  are  most  marked 
if  the  atone  is  small,  rough,  and  movable,  so  that  in  the  erert  (Kisition  11  falls  ujion 
the  trigonal  surface.  Such  a  stone  may  roll  or  be  forced  by  the  stream  of  urine 
into  the  vesical  outlet  and  produce  sudden  interruption  of  micturition.  This 
symptom  is  seen  most  often  in  young  male  children,  in  whom  the  relatively  vertical 
MMition  of  the  bladder,  the  marked  tenesmus  caused  by  the  presciicu  of  the  stone, 
and  the  small  size  of  the  vesical  oriJice  favor  its  production.  The  tcmsmiis  in 
children  is  often  so  excessixe  as  to  result  in  prolapse  of  the  rectum,  which  is  aliected 
by  and  participates  in  the  straining  expulsive  efforts.  ,•..,•,. 

in  a  sacculated  bladder  a  very  lai^e  stone  may  he  in  a  pouch  with  but  little  ot 
its  surface  presenting  towards  the' bladder-cavity  (encystwl  stone)  and  give  nsc  to 
almost  no  subjective  symptoms.  ,    j.u. 

Perineal  lithotomy  is  much  less  frequently  done  than  formerly,  on  account  of  the 
application  of  Bigelow's  operation  of  lilholapaxy  to  the  great  majority  ..f  calculi,  and 
of  the  revival  of  suprapubic  lithotomy  and  its  use  in  a  considerable  propt>rtior.  ot  the 
remainder.  A  description  of  the  parts  involved  in  this  operation  ser\cs,  however, 
as  Treves  has  said,  to  give  a  proper  conception  of  their  important  anatomical  re- 
lationships. .         ,       1  •  I 

The  Male  Perineum.— This  region— a  fissure  when  the  thighs  are  approxi- 
mated—becomes  an  ample  lozenge-shaped  space  when  the  legs  and  thi^jhs  are  flc.x^d 


Pia.  i6t5. 


TnbcrlacliU- 


-TutwrUcbli 


-  Anns 


-MiU-m.  r.eout 
tihros  o(  sphinc- 
ter ani  extemtia 

.TipoC  coccy» 


DItMction  of  perineum ;  skin  lia»  been  removed,  leaving  nuperfirial  favia  undiaturbed 
Sound  has  been  paaaed  through  urethra  into  bladder  and  scrotum  drawn  forward. 

and  the  latter  are  strongly  abducted,— the  lithotomy  position.  It  corresponds  to 
the  outlet  of  the  pelvis.  On  the  surface  it  is  bounded  roughly  by  'he  scrotum 
anteriorly,  the  buttocks  posteriorly,  and  the  upper  limits  of  the  inner  as{>ects  of  the 
thighs  laterally.  More  deeply  the' boundaries  are  the  symphy.si.-.  pubis  and  subptibic 
ligament  anteriorly,  the  coccyx  posteriorly,  and  the  greater  sacro-sciatic  ligaments,  the 


I9i6 


HUMAN   ANATOMY. 


iidual  tubiTositiesand  rami,  and  the  pubic  rami  laterally  (Fig.  it-27).  It  is  divided 
into  two  lateral  Rymmetrical  halves  by  a  dense  cutaneous  ridge,  the  raphe,  across 
which,  as  it  represents  the  junction  ck  the  two  foetal  halves  of  the  perineum,  no  blood- 
vesseb  pass  from  one  side  to  the  other ;  and  into  two  unsvmmetncal  antero- posterior 
triangular  portions  by  an  imaginary  transverse  line  drawn  between  the  anterior 
borders  of  the  ischial  tuberosities  and  running  in  front  of  the  anus.  The  posterior 
of  these  two  divisions — the  portion  of  the  outlet  of  the  pelvis  which  contains  the 
rectum  and  anus — is  the  recUU  triangle  (anal  perineum).  Its  practical  relations  have 
been  sufficiently  dealt  with  in  the  article  on  the  rectum  and  anus  (page  1693). 

The  anterior  division,  the  Mro-genital  Mangle  (urethral  perineum),  has  for  its 
deep  boundaries  :  posteriorly  the  deep  layer  of  the  superficial  fascia  (fascia  of  Colles) 
as  it  passes  behind  the  transverse  perineal  muscles  to  become  continuous  with  the 
inferior  layer  of  the  triangular  ligament  (page  563);  laterally  the  rami  of  the  pubes 

Fif»    i6a6 


Internal  per- 
ineal nerve 
Inferior  - 

puflendal 

nerve 


Int.  itutlir  artrrv- 
I'udii  nerve- 
Anal  faKcia- 
Inferior  hcmc»r-|- 

rhulilul  at1er\  I 
Inferior  hrmnr  ) . 
rhoidal  nrrv-i'*  \ 


Colles'i  laacia 


Sphincter  ani 
extern  UK 
Tuber  iacliii 


Tip  o(  coco'X 


Disseclinn  of  peiineum,  shnwinK  luperfkial  an')  hemorrhoiilal  hranchea  of  internal  pudfc 
artery  and  uf  pudic  nerves  on  right  aide ;  CoUes's  faacia  exposed  on  left. 


and  ischia  :  anteriorly  the  pubic  arch.  Over  the  uro-genital  triangle  the  superficial 
fascia  is  separable  into  two  distinct  layers,  the  superficial  and  the  deep.  The  su|)<;r- 
ficial  layer  contains  a  considerable  an  >iint  of  fat,  and  is  continuous  with  the  corre- 
sponding l.-iyer  over  the  thighs  and  butuxks  and  with  the  masses  of  fatty  tis.sue  that 
fill  the  ischio-rtotal  fosike.  The  d«H"p  layer,  or  fascia  of  Colles,  is  membranous  and 
free  from  fat,  and  is  not  only  applied  closely  to  the  lower  edges  of  the  transveise 
erineal  muscles  and  attached  to  the  base  of  the  inferior  layer  of  the  triangular  lij;a- 
iiijnt,  but  is  also  attached  to  the  external  mar^'in  of  the  rami  of  the  pubis  and  ischium. 
Anteriorly  it  is  continuous  with  the  defep  layer  of  superficial  fa.scia  of  the  scrotum 
(dartos),  penis,  and  spermatic  cords,  and  with  the  f.iscia  of  Scaipa  (page  515) 
on  the  front  of  the  abdomen.  When  it  is  divided,  a  definite  space,  the  superficicl 
perineal  interspace,  is  opened,  which  is  bounded  below  by  CoUes's  fascia,  above  by 
the  inferior  layer  of  the  triangular  ligament,  laterally  by  the  attachments  of  the  fascia 


PRACTICAL  CONSIDERATIONS:    MALE  PERINEUM. 


1917 


• 

and  the  ligament  to  the  pubo-ischiatic  rami,  and  behind  by  the  union  ol  the  iasoa 

with  the  ba»e  of  the  ligament 

Thia  space  or  pouch  conuins  the  bulb  and  the  crura  of  the  penw  and  the 
muacles  covering  them,  the  superficial  transverse  perineal  muscles,  the  superficial 
perineal  nerves  and  vessels,  and  the  long  pudendal  nerves  ;  in  its  anterior  part  the 
mteriial  pudic  artery  divides  into  iu  terminal  branches,  the  dorsal  artery  ol  the  penis 
and  the  artery  to  the  corpus  cavernosum.  It  is  very  imporunt  in  its  relations  to 
wounds  and  ruptures  of  the  urethra  (y.r.). 

In  the  uro-genital  triangle,  hall-way  between  the  centre  ol  the  anus  and  the 
perineo-scroul  junction,  is  the  so-called  "  perineal  centre,"  where  the  bulbo-caver- 
nosus,  the  sphincter  ani,  and  the  superficial  transverse  perineal  muscles  meet,  and 
which  corresponds  to  the  middle  of  the  posterior  edge  of  the  fibrous  shelf  formed 
by  the  union  of  the  two  layers  of  the  triangular  ligament.  These  structures  are 
exposed  when  Colles's  iascia  is  turned  back,  and  on  either  side  a  triangular  »|)ace  is 

Fig.  1627. 


BuliMHomnMNt  auKla 


CrmpvBU 

ColtM'i  fMcU.  n^Ktfd  - 

Trianffula*  I'g..  inf.  U>«r  - 

Isi  hii)-caTCTmoftt»,  Mump* 

Tr»o«^t«.  periBtt  niu»tU~ 

Tut^TlwMl' 

Sphincter  a  il  citcti  M— 

l^v  alOT  anl  - 

rudlr  ncT^  t  - 

■  ■MffHAl  pudk  afMry  ' 

Gf«at«r  ucn-tclstk  llg.  - 

Clultus  ■uximitt 


llcMo.cat»nw«u*  mukh 

—  ln(«fiul  pvTtnMl  Mr*» 

-    ^^— E«lrfii*l  |i*Ho«l««f»« 
Supvrti.  ul  prriaekl  art«ry 


TraMvvnut  paftMl  nut. 

Aulb«l> 

— GfcalCff  urro^rUtk  llg. 
.  „|Bf .  licnia«Tlia4d«l  Bcrv* 
-  -I»». » 


■nucli  of  bwtk  ••.  nl 
■«r«« 

.Btu>hi<fNrtkM>j<l 


DitMction  ol  ucriiwuRi ;  CoHct'i  fucia  hM  been  cut  tnd  reflerterf  to  e xpoae  crura  gnd  bulb  oJ 
penli  covered  by  muKlei ;  on  rlchl  tide  ischio-recul  Inasa  ia  partly  cleaned  out, 

seen,  the  floor  of  which  is  constituted  by  tli--  inferior  layer  of  the  triangular  ligament. 
At  the  lateral,  median,  and  posterior  siden  *  the  triangle  lie  the  bulbo-cavemosus, 
ischio-cavprnosus,  and  superficial  transverse  perineal  muscles  respectively  (Fig.  1627 ). 
When  the  inferior  layer  of  the  triangular  ligament  is  divided,  the  space  (det-p 
perineal  interspace^  between  that  and  the  superior  layer  fas  this  portion  of  the  parie- 
tal layer  of  the  pelvic  fascia  is  called)  is  opened  and  is  found  to  be  broader  in- 
feriorly  and  behind,  the  two  layers  fusing  anteriorly  with  a  dense  band  {ligamenlum 
transversum  peMs)  stretching  from  one  pubic  bone  to  the  other,  and  ler.ving  only 
sufficient  space  above  it,  beneath  the  subpubic  ligament,  to  permit  the  passage  of 
the  dorsal  vein  of  the  penis.  The  space  between  the  two  layers  (F'ig.  1629)  is 
occupied  by  (a)  the  compressor  urethrx  muscle ;  (*)  the  membranous  urethra, 
about  half  an  inch  in  length;  (c)  Cowper's  glands  {glandulte  bulbo-vretkralfs^: 
(d)  the  beginning  of  the  artery  of  the  bulb;  (e)  the  continuation  of  the  internal 
pudje  artery,  which,  while  between  ?V,"  x--^-  layers  nf  the  triangular  lignmen!  and 


^     B 


I9i8 


HUMAN   ANATOMY. 


before  piercing  the  superficial  layer,  gives  of!  the  artery  to  the  bulb.  This  latter 
artery  may  come  ofi  from  the  accessory  pudic  when  that  vessel  is  present  (page  8i8), 
and  will  then  be  more  anterior,  and  less  exposed  to  division  in  lithotomy,  than 
usual  ;  or  it  may  come  off  from  the  internal  pudic  before  the  latter  has  penetrated 
the  superficial  layer  of  the  triangular  ligament,  and  will  then  be  behind  its  usual 
position  and  more  likely  to  be  wounded.  When  the  superior  or  deep  layer  of  the 
triangular  ligament  is  opened,  the  prostate — partly  covered  by  the  median  fibre*  of 
the  levator  ani — and  the  neck  of  the  bladder  are  exposed  (Fig.  1631).  this  deep  layer 
being  continuous  with  the  prostatic  sheath. 

It  will  be  seen  that  in  reaching  this  point  by  dissection  there  will  have  been 
exposed  certain  alternating  layers  of  fascial  and  muscular  structures  (Cunning- 
ham) as  follows  :  (a)  superficial  fascia  (superficial  and  deep  layers)  ;  {6)  super- 
ficial perineal  muscles  ;  (^)  inferior  or  superficial  layer  of  the  triangular  ligament 

Fig.  1628. 


TrUng.  hg»mtwt~- 
TuUtiKhll- 
Sphiocter  anI  - 
Levator  ani  ~ 
^.^eatersac^o— 
sciatic  lieaiticnl 

C<xcyji— - 
Gluteus  maximtu- 


[achio.cavtraa«utBiutclt, 
turned  aside 


■Cms  penis 

Dotsil  artery  of  penis, artery  of 
COH'US  cavernosum  to  tile  ri,;lll 
Bulb  of  i^enis 

—  Superf)  rial  perineal  artery 
^  Superficial  perineal  nerves 

— ^Tuber  Iscliii 

Dorsal  nerve  of  penis 

-—Perineal  division  of 


pudic  nerve 
'Internal  pudic  artery 


—  iBf.  hemorrhoidal  nerva 

—  lofrrior  hemorrhoidal 


Dissection  of  perineum,  ^hnwinj;  infen'or  la>'er  of  trianiniiar  iigam^t 
and  inner  wall  of  ischio-rertal  fossa  partially  ex(>osed. 


(fascia  trii;oni  urosenitalis  inferior)  ;  (d )  compressor  urethrse  muscle  ;  (e)  superior 
or  deep  layer  of  the  triangular  ligament  (fascia  trlKoni  urogenitalis  superior  (/) 
levator  ani  muscle  ;  (  j^)  prostatic  fascia  (sheath). 

Landmarks. — With  the  patient  in  the  lithotomy  position  :  ( i )  The  pubis, 
coccyx,  tuberosities,  ischio-pubic  rami,  and  greater  sacro-sciatic  ligaments  may  be 
felt.  (2)  The  transverse  diameter,  between  the  tuberosities,  is  9  cm.  (3J4  in.)  ; 
the  antero-posterior  diameter,  from  the  coccyx  to  the  pubis,  is  also  9  cm.  (^'/i  in.) 
on  the  skeleton,  10  cm.  (4  in.)  as  measured  on  the  living  person.  (3)  The  centre 
of  the  anus  is  about  4  cm.  ( i ';!  in. )  from  the  tip  of  the  coccyx,  and  is  on  a  line  drawn 
between  the  tips  of  the  ischial  tuberosities.  (4)  The  perineal  centre  is  approxi- 
mately 4  cm.  ( 1  li  in. )  in  front  of  the  anus.  (5)  The  bulb  (and  its  artery)  are  just 
anierior  to  this  ;  its  position  .may  be  indicated  by  a  slight  median  surface  elevation  : 
the  artery  passes  inward  between  the  layers  of  the  triangular  lisjament  about  a  half 


mMPP 


PRACTICAL   CONSIDERATIONS:    MALE    PERINEUM.  1919 

inch  above  the  base  of  the  latter,— />..  about  one  and  a  half  inches  from  the  anus. 
(6)  Measured  in  the  mid-line  from  the  symphysis  to  the  centre  of  its  base,  the  tri- 
angular ligament  extends  backward  about  one  and  a  half  inches.  (7J  The  mem- 
branous urethra,  lying  between  the  two  layers  of  the  triangular  ligament,  is  a  little 
below  the  middle  of  this  line,— />. ,  a  litde  less  than  an  inch  below  the  symphysis  and 
from  one-half  to  three-quarters  of  an  inch  above  the  anus.  It  measures  from  one- 
half  to  three-quarters  of  an  inch  in  length.  (8)  The  dorsal  vein  passes  above  the 
triangular  ligament  a  little  less  than  a  half  inch  below  the  lower  margin  of  the  sym- 
physis ;  the  pudic  artery  and  nerve  pierce  the  superficial  layer  of  the  triangular  hga- 
ment  a  litde  lower.  (9)  The  distance  from  the  surface  of  the  perineum  to  the  pelvic 
floor  is  about  one  inch  near  the  symphysis  and  from  two  tu  three  inches  posteriorly 
and  laterally.  ( 10)  The  vesical  orifice  is  on  a  horizontal  anteroposterior  line  drawn 
through  a  point  a  litde  below  the  middle  of  the  symphysis,  is  about  an  inch  to  an 
inch  and  a  quarter  behind  it,  and  is  from  two  and  a  half  to  three  inches  above  the 

Fig.  Z639, 


Corpus  spongtotun, 

cut 

I'rcthra 

Colics 's  hida^—- 

Crus  penii 

PoitfoB  of  bull^-    - 
Cowper's  ifUnd— -  - 

Posterior  edifc  ot-~- 
trian|£uUr  ligameDt 

Tuber  Ischil- 
lotenutl  pudic  artery— 


— ^Crw  penli 

— Dorsal  arfery  of  peals 
— Ischio-cavcrnosus  mutcle 
— lArterjf  of  corpus  i  avrrausum 
— Dorsal  nerve  of  p«nis 
--CoTn|)ressor  urethr.r  muscle 
-Artery  of  bulh 
Deep  transverse  perineal 
niuSi le 

Dorsal  nerve  t>f  i-enia 
—Internal  pudic  artery 

__SphincteT  ani 

Perineal  tttvtiion  of 
idk  nervr 
.^Lcvalur  ani 

^Greater  sacro-tciatlr: 
liicament 


"-:r:_.      .X 


Coccyx 


Dissection  of  perineum,  in  whicli  inferior  layer  of  trianicnlar  linament  and  corpus  spongiosum  have  been  par- 
tially removed,  exposing  uretlira  covered  by  compressor  uretiirte  muscle  and  Cowper's  gland. 


perineal  surface.  ( 1 1 )  The  prostate  is  about  three-quarters  of  an  inch  below  the 
symphysis.  (12)  The  pudic  artery,  as  it  lies  in  Alcock's  canal,  is  about  one  and  a 
half  inches  above  the  lower  inarjrin  of  the  ischial  tuberosity. 

These  measurements  are,  of  course,  approximate,  and  viry  with  the  size  of  the 
pelvis  and  its  outlet  and  the  amount  of  subcutaneous  fat,  which,  in  the  lithotomy 
position,  may  much  increase  the  normal  antero- posterior  convexity  of  the  perineal 
surface. 

Lateral  Lithotomy. — It  will  now  be  understood  that  in  openinfj  the  bladder 
through  one  side  of  the  perineum  the  incision  must  not  extend  too  far  forward,  as  it 
might  involve  the  artery  of  the  bulb,  which  lies  a  little  anterior  to  the  ' '  perineal 
centre"  (Fig.  1629) ;  or  too  much  externally,  as  the  pudic  might  be  wounded  where 
it  lies  on  the  ramus  of  the  ischium  ;  or  too  far  posteriorly,  as,  after  dividing  the 
layer  of  the  superficial  perineal  fascia  covering  the  rectal  triangle,  and  thus  opening  up 
the  ischio-rectal  space,  it  might  open  the  rectum  itself.  In  the  deeper  parts  of  the 
wound  it  will  be  seen  that  if  it  is  too  extensive,  or  carried  too  far  upward,  it  might 
pass  completely  through  the  left  lobe  of  the  prostate  and  divide  the  visceral  layer  of 


I920 


HUMAN  ANATOMY. 


t.ie  pelvic  fascia  (which  is  reflected  from  the  gland  near  its  upper  end),  favoring  the 
development  of  pelvic  cellulitis  from  urinary  infiltration  (page  1933) ;  or  it  might 
divide  the  neck  of  the  bladder  and  open  up  the  recto-vesical  fossa  with  the  same 
results  ;  or,  if  the  prostatic  incision  were  too  extensive  and  too  vertical,  it  might 
wound  the  ejaculatory  ducts  or  seminal  vesicles.  The  incision — which  is  made  after 
a  grooved  staff  has  been  introduced  into  the  bladder,  and  while  it  is  held  in  place  by 
an  assistant — accordingly  begins  at  a  point  a  little  to  the  left  of  the  raphe  and  a  litde 
posterior  to  the  perineal  centre — i.e.,  about  one  to  one  and  a  quarter  inches  in  front 
of  the  anus — and,  opening  the  left  ischio-rectal  fossa,  ends  at  the  junction  of  the 
outer  and  middle  thirds  of  a  line  drawn  between  the  posterior  margin  of  the  anus 
and  the  ischial  tuberosity.  This  incision  should  be  d^  epest  near  its  upper  end — not 
far,  at  its  upper  and  deepest  portion,  from  the  apex  ■  :  the  "  |>erineal  triangle" — and 
should  become  shallower  as  it  passes  into  the  iscb  >-rectal  space.     It  divides  skin, 


Fig.  163a 


Sectional  surface  of 
corpus  spongiosum 


CoTpiis  cav- 
ernosum,  cut 

Adductor  brevis 


Corpus  cavemosum, 

cut 
Urethn 

Subpubic  ligament 
i*rostatc 


Greater  sacro- 
sciatic  ligament' 

Coccygeus 

Gluteus- 
maximtts,  cut 


Tuber  ischii 

—  Obturator 
intemus 

Greater  sacro- 
sciatic  ligament 


Gluteus 
maximus 


Coccyx 


Deep  dissection  of  perineum.  In  which  root  of  penis  has  been  removed,  showing  urethra 
emerging  from  prostate,  which  is  partly  exposed  between  levatores  am. 


both  layers  of  superficial  fascia,  the  superficial  transverse  perineal  muscle,  artery,  and 
nerve,  the  lower  edge  of  the  superficial  layer  of  the  triangular  ligament,  and,  as  it 
crosses  the  ischio-rectal  fos.sa,  the  inferior  hemorrhoidal  vessels  and  nerves. 

The  left  forefinger  of  the  operator  now  guides  the  knife  into  the  groove  of  the 
staff,  and  the  incision  is  deepened  with  the  knife-blade  inclined  laterally  and  pushed 
onward  into  the  bladder,  dividing  the  compressor  urethrae  muscle,  the  membranous 
urethra,  the  superior  layer  of  the  triangular  ligament,  a  few  median  fibres  of  the  leva- 
tor ani,  the  prostatic  urethra,  and  a  portion  of  the  left  lobe  of  the  prostate. 

he  neck  of  the  bladder  should  be  dilated  with  the  finger  rather  than  incised, 
an  will,  without  serious  laceration,  permit  the  extraction  of  a  stone  of  the  diameter 
of  an  inch  to  a'  'nch  and  a  quarter. 

In  children  the  following  facts  should  be  borne  in  mind  :  (a)  the  relative  nar- 
rowness of  the  pelvis,  limiting  the  operative  space  ;  (^)  the  undeveloped  condition 


PRACTICAL  CONSIDERATIONS.    MALE   PERINEUM.  i92« 

of  the  prostate,  necessitating  the  division  of  more  of  the  vesical  neck  and  incrcMing 
the  risk  of  opening  up  the  pelvic  fascia  ;  (c)  the  greater  mobility  of  the  bladder 
(the  neck  of  which  in  the  adult  is  largely  fi.xed  by  its  connection  with  the  base  of 
the  prostate),  so  that  it  has  been  pushed  before  the  finger  and  torn  from  the  urethra  ; 
(d)the  situation  of  the  bladder  above  rather  than  in  the  pelvis,  the  neck,  therefore, 
being  relatively  higher  than  in  the  adult ;  (e)  the  looseness  and  delicacy  of  the 
recto-vesical  fascia,  permitting  the  easy  separation  of  the  bladder  and  rectum  and 
forming  a  cavity  which  the  linger  may  mistake  for  that  of  the  bladder ;  (/)  the 
relatively  low  level  of  the  recto- vesical  fold  of  peritoneum,  exposing  it  to  injury  if  the 
wound  is  unduly  prolonged  upward.  .... 

Median  lithotomy  involves  the  division,  through  the  median  raphe  of  the  jjeri- 
neum,  of  the  skin,  superficial  fascia,  sphincter  ani  and  portions  of  the  other  struc- 

Fio.  I 63 I. 


Cecpu*  fpongiofum,  cut 


Grcftter  tacio-tclatiC' 
IlKftnMBt 


Gluteus  mftxinus, 


Deep  dissection  of  perineuir.  in  which  pelvic  floor  has  heen  partly  removed.  enposinK  Madder, 
seminal  vesicles,  sp«.rmatic  ducts,  and  prostate ;  rectum  has  hcen  turned  baclc. 

tures  entering  into  the  "perineal  centre,"  the  lower  portion  of  the  superficial  layer 
of  the  triangular  ligament,  the  compressor  urethrae  muscle,  the  membranous  urethra, 
and  the  apex  of  the  prostate.  The  bladder  is  entered  by  dilating  with  the  finger  the 
prostatic  urethra  and  vesical  neck.  The  advantages  claimed  for  it  are  :_  (a)  dimin- 
ished hemorrhage  on  account  of  the  relatively  slight  vascularity  of  the  mid-line  :  {b') 
lessened  risk  of  opening  the  jjelvic  fascia  ;  (<•)  lessened  risk  of  wounding  the  ejacu- 
laiory  ducts  or  seminal  vesicles.  The  disadvantages  are  :  i  ij )  the  narrow  space 
between  the  rectum  and  the  deep  urethra,  exposing  the  bulb  and  its  artery  to 
danger  anteriorly  and  the  rectum  posteriorly  ;  (^)  the  lack  of  space  for  the  extrac- 
tion of  even  moderately  large  calculi  ;  (f)  the  increased  risk  of  pushing  the  bladder 
before  the  finger  and  tearing  it  from  the  urethra.  All  these  objections  are  much 
greater  in  the  case  of  children. 

Suprapubic  lithotomy  is  done  by  means  of  an  incisijn  in  the  mid-line,  imme- 
diately above  the  symphysis,  dividing   skin,  superficial  fascia,   transversalis  fascia 


1923 


HUMAN  ANATOMY. 


(there  is  no  distinct  linea  alba  at  this  point),  and  prevesical  fatty  connective  tissue 
in  the  space  of  Retzius.  Sometimes  this  fat  can  be  gently  pushed  or  sponged 
upward  and  carries  the  peritoneum  with  it.  The  method  of  securmg  a  non-peritoneal 
area  of  bladder  and  abdominal  wall  for  this  operation  (as  for  others  involving  a 
suprap  'lie  cystotomy;  has  been  sufficiently  described. 

TiK/ema/e  bladder  is  less  capacious  than  the  male  bladder.  Its  longest  diame- 
ter is  transverse,  as  posteriorly  the  pelvic  space  it  occupied  by  the  uterus  and 
vagina,  and  as  the  female  pelvis  is  relatively  wider  than  that  of  the  male. 

The  lesser  depth  of  the  pubic  symphysis  in  the  female  and  the  absence  of  the 
prostate  result  in  a  relatively  lower  vesical  oudet  and  a  short,  direct,  distensible 
urethra,  the  dilatability  of  which  (also  on  account  of  the  absence  of  the  prostate) 
extends  to  and  includes  the  vesical  neck. 

As  these  conditions  favor  easy  and  full  evacuation  of  the  bladder,  cystitis  and 
stone  are  comparatively  uncommon  ;  and  as  they  facilitate  intravesical  exploration 
or  operation  per  urethram,  cystotomy  in  the  female  is  rarely  called  for.  Foreign 
bodies  introduced  by  the  urethra  are  relatively  common  in  the  female  bladder. 

The  utero-vesical  jxjuch  of  peritoneum  does  not  descend  so  low  as  the  recto- 
vesical pouch  in  the  male.  Below  it  the  close  relations  between  the  bladder  and  the 
cervix  uteri  and  the  upper  h:ilf  of  the  vagina  lead  to  the  involvement  of  the  bladder 
in  many  of  the  diseases  originating  in  these  structures.  The  latter  relation  permits 
of  the  recognition  by  vaginal  touch  of  calculi  impacted  in  the  lower  ends  of  the 
ureters,  the  orifices  of  which  are  about  opposite  the  middle  of  the  vagina. 


THE  URETHRA. 

The  urethra — the  canal  conveying  the  urine  from  the  bladder  to  the  exterior  of 
th«  body — differs  in  the  two  sexes,  since  in  the  male,  in  addition  to  its  primary  com- 
mon function  of  conducting  the  urine,  it  serves  for  the  escape  of  the  secretions  of  the 
testicles,  seminal  vesicles,  prostate,  Cowper's  glands,  and  urethral  glands.  It  is  of 
interest  to  note  that  in  the  lowest  mammals,  the  monotremes,  in  which  the  urethra  and 
intestine  open  into  a  common  space,  the  cloaca,  the  seminal  duct  is  prolonged  to  the 
end  of  the  penis  as  a  separate  canal.  Embryologically  the  male  urethra  consists  of 
two  parts,  a  posterior  segment — homologous  with  the  canal  in  the  female — beginning 
at  the  bladder  and  ending  at  the  openings  of  the  ejaculatory  ducts,  and  an  anterior 
segment  including  the  remainder  of  the  canal.  With  regard  to  the  regions  of  the 
body  in  which  they  lie,  the  urethra  may  be  considered  as  being  composed  of  a  pel- 
vic, a  perineal,  and  a  penile  portion.  It  is  more  usual,  however,  to  describe  the 
male  urethra  as  consisting  of  the  prostatic,  membranous,  and  spongy  portions, — a 
division  based  upon  more  or  less  definite  anatomical  relations  of  structures  through 
which  it  passes. 

The  prostatic  portion  (par.  prostatica),  from  2-^  cm.  (H-1%  in.)  in  length, 
descends  with  a  slight  cur\-e,  but  almost  \'ertically,  from  the  internal  urethral  orifice 
of  the  urethra  to  the  superior  layer  of  the  triangular  ligament.  Beyond  the  vesical 
wall,  which  embraces  Its  commencement  (pars  intramuralis  o\  Waldeyer),  it  is  en- 
tirely surrounded  by  the  prostate,  which  it  pierces  from  base  to  apex  (Fig.  1619). 
Notwithstanding,  this  part  of  the  urethra  admits  of  considerable  dilatation,  althougli 
ordinarily  its  lumen  is  more  or  less  obliterated  by  the  apposition  of  the  anterior  and 
posterior  walls.  At  the  two  ends  of  this  division  the  lumen  is  narrower  than  in  the 
inten'ening  part,  although  this  spindle-form  dilatation  is  reduced  by  the  encroach- 
ment of  a  fusiform  elevation,  the  urethral  crest  (crista  urethralis)  or  venimontanum, 
that  extends  along  the  dorsal  wall  from  the  ridge  (uvula)  on  the  vesical  trigone  above 
to  the  membranous  urethra  below,  into  the  folds  of  which  it  fades,  usually  by  diverging 
ridges  (frenula  cristae  urethralis).  On  transverse  section  (Fig.  1681),  the  lumen  of 
this  part  of  the  urettra  appears  crescentic  in  outline  in  consequence  of  the  projection 
of  the  crest.  The  m  ^t  prominent  and  expanded  part  of  the  latter  (colliculns  semi- 
nalis)  is  occupied  by  le  slit-like  opening  of  the  prostatic  utricle  (utriculus  prostaticus) 
or  sinus  pocularis,  a  t  ibular  diverticulum,  usually  from  6-8  mm.  in  length,  but  some- 
times much  longer,  that  leads  upward  and  backward  into  the  substance  of  the  pros- 
tate and  represents  the  fused  lower  ends  of  the  Miillerian  ducts  of  the  embryo  ;  the 


IBPI! 


THE  URETHRA. 


1923 


sinus  is,  therefore,  regarded  as  the  morpholoRical  equivalent  of  the  vagina  and  uterus. 
On  the  lateral  lips  of  this  recess  lie  the  small  orifices  of  the  ejaculatory  ducts,  while 
those  of  the  prostatic  tubules  open  into  the  groove-like  depressions  on  either  side  of 
the  urethral  crest.  The  internal  urethral  orifice  lies  appro.ximately  on  a  horizontal 
plane  passing  through  the  middle  of  the  symphysis,  about  2. 5  cm.  ( i  in. )  behind 
the  latter  and  an  eqi^  distance  from  its  lower  border. 

The  membranous  portion  (parsmenbranacea)  curves  downward  and  forward 
from  the  apex  of  the  prostate  to  the  bulb  of  the  corpus  six>ngiosum,  which  it  enters 
somewliat  (about  i  cm.)  in  advance  of  its  posterior  extremity.  In  its  course  the 
membranous  urethra  pierces  both  layers  of  the  triangular  ligament  and  is  surrounded 
by  the  fibres  of  the  compressor  urethrjc  muscle  ;  behind  it,  on  either  side  of  the 
mid-line,  lie  the  glands  of  Cowper.  This  part  of  the  canal  measures  only  about  i  cm. 
in  length,  and  is  the  shortest,  narrowest,  and  least  distensible  of  the  segments. 
When  empty,  its  mucous  membrane  is  thrown  into  longitudinal  folds,  and  on  cross- 
section  its  lumen  is  stellate.     In 

consequence  of  its  curved  course,  pio.  163J. 

the  anterior  wall  is  shorter  than  the 
posterior,  which  ni»rks  the  most 
dependent  point  of  the  subpubic 
curve  that  lies  about  18  mm.  (3^ 
in.)  below  and  behind  the  lower 
border  and  in  the  plane  of  the  sym- 
physis. Since  almost  the  entire 
membranous  portion  lies  between 
the  layers  of  the  triangular  liga- 
ment, its  mobility  is  much  less 
than  that  of  the  other  parts  of  the 
urethra.  The  short  terminal  part 
of  the  membranous  urethra  that 
lies  below  the  triangular  ligament 
and  above  and  in  front  of  the  bulb 
as  it  enters  the  corpus  spongiosum 
(pars  praetrigonalls)  is,  however, 
not  only  wider  and  thin-walled, 
but  much  more  movable, — charac- 
teristics that  increase  the  difficulty 
of  guiding  instruments  into  the 
narrow  and  fixed  intratrigonal  seg- 
ment beyond. 

The  spongy  portion  (pars 
cavernosa)  includes  the  remainder 
of    the  canal    and    terminates  at 
the  external  urethral  orifice.     Its  ^ 
length   varies   with  the  size  and ' 

condition  of  the  penis,  but  averages  about  14  cm.  (s%  in.).  In  the  flaccid  condi- 
tion of  the  penis  it  presents  a  double  cur\'e  (Fig.  1619),  the  fixed  proximal  part  of 
which  continues  the  subpubic  cur\'e  forward  and  slightly  upward  through  the  peri- 
neum to  a  point  corresponding  aporoximately  with  the  attachment  of  the  suspensory 
ligament  to  the  dorsum  of  the  penis,  while  the  freely  movable  distal  part,  or  prepubic 
curve,  follows  the  pendent  penis.  Throughout  its  course  this  part  of  the  urethra  is 
surroundf  ^  by  the  corpus  spongiosum,  at  first  embedded  near  its  upper  border,  then 
about  in  the  middle,  and  at  the  termination  near  its  lower  margin  covered  by  the 
thick  cap  of  spongy  substance  forming  the  glans.  The  lumen  of  the  spongy  [xirtion 
is  variable  both  in  size  and  form  ;  at  its  two  ends,  where  surrounded  by  the  bulb  and 
the  glans,  it  presents  fusiform  dilatations,  the  intermediate  pirt  being  of  more  uniform 
calibre.  The  first  of  these  dilatations  (fossa  buibi)  occupies  the  bulb  of  the  corpus 
spongiosum  for  about  2  cm. ,  beginning  about  half  that  distance  in  front  of  its  posterior 
extremity.  Abruptly  narrowing  behind,  towards  the  pars  membranacea,  in  front  the 
fossa  gradually  diminishes  into  the  ordinary  lumen  of  the  canal.     The  ducts  of  Cow- 


Ejaculatory  duct 
Prostatic  dui'ts-^ 


Membranous  urethra 


Rulbus. 
sponKiosutn 


SpofiRV  urethra. 


Opening  vi  duct  ol 

Cowper's  gland 

— —Corpus 

cavcrnostim.  cut 
and  turned  out 


Part  o(  bladder  and  male  uielhra.  exposed  by  openinR  and 
tumhiK  aside  anterior  wall,  showinK  (Kjstenor  surface  of  prostatic, 
membranous,  and  beginning  of  spongy  portions  of  urethra. 


1934 


HUMAN  ANATOMY. 


per's  glands  open  by  slit-like  orifices  on  the  posterior  wall  or  floor  of  this  part  of  the 
urethra.  The  terminal  dilatation,  the  navicular  fossa  (foua  naTlcnlarls  nrcthrac), 
occurs  at  the  extreme  distal  end  of  the  canal  within  the  glans  and  opens  onto  the 
surface  by  a  vertical  slit-like  aperture,  the  external  urethral  orifice  (orifiduiii  nrctlirac 
eztcrnam)  or  meatus,  the  most  contracted  and  least  distensible  part  of  the  entire  pas- 
sage. Since  the  lateral  walls  of  the  navicular  fossa  are  in  apposition  except  during 
the  passage  of  fluid,  its  lumen  appears  as  a  vertical  slit  on  crosa-section  (  Fig.  1674) ; 
beyond  the  fossa,  however,  the  anterior  and  posterior  walls  come  into  contact,  and 
hence  the  lumen  is  here  represented  by  a  transverse  cleft  ( Fig.  1674, 6"),  which  in  the 
region  of  the  bulb  is  replaced'by  one  of  irregularly  stellate  outline. 

The  female  urethra — about  3.5  cm.  (i^  in. )  in  length — is  much  shorter  than 
the  canal  in  the  male  and  embryologically  corresponds  to  the  portion  of  the  latter  that 
lies  between  the  internal  urethral  orifice  and  the  openings  of  the  ejaculatory  ducts. 
Except  at  its  beginning,  the  canal  is  firmly  united  behind  with  the  anterior  vaginal 
wall,  the  downward  and  forward  curvr  of  which  it  closely  follows  until  near  its  termi- 
nation, where  it  turns  more  sharply  forward  (Fig.  1623).  In  consequence,  the  lower 
I>art  of  the  urethro-vaginal  septum  is  somewhat  thicker  below  than  above.  With  the 
exception  of  a  slight  spindle-form  dilatation  about  the  middle  of  its  course,  the  lumen 
of  the  female  urethra  a  fairly  uniform,  with  a  dian">ter  of  about  7.5  mm.  during 
physiological  distention  ;  except  during  the  passage  of  fluid,  however,  its  walls  are  in 
contact  and  the  mucous  membrane  is  thrown  into  slight  longitudinal  folds.  One  of 
these  on  the  upper  half  of  the  posterior  wall,  known  as  the  urethral  crest,  is  more 
conspicuous,  ineflaceable,  and  continuous  with  the  apex  of  the  vesical  trigone  ;  it  cor- 
responds, therefore,  with  the  similar  ridge  in  the  male  urethra.  The  position  of  its 
termination  below,  on  the  roof  of  the  vestibule,  is  marked  by  a  low,  corrugated,  coni- 
cal elevation  or  papilla  which  surrounds  the  external  urethral  orifice  and  lies  from 
1.5-3  cm.  below  the  subpubic  border.  The  urethral  orifice,  usually  a  small  sagittal 
slit  about  S  mm.  in  length,  is  subject  to  much  variation  in  size  and  shape,  being  at 
times  triangular,  crescentic,  cruciate,  or  stellate  in  form.  On  the  papilla,  on  either 
side  of  the  mid-line  and  close  to  the  posterior  margin  of  the  urethral  orifice,  lie  the 
minute  openings  of  the  paraurethral  ducts,  or  tubes  of  Skene,  from  i-a  cm.  long, 
which  are  the  excretory  passages  of  small  groups  of  tubular  glands  situated  without 
the  wall  of  the  urethra.  These  ducts,  regarded  as  the  homologues  of  the  prostatic 
ducts  that  open  into  the  grooves  at  the  sides  of  the  urethral  crest,  sometimes  open 
directly  onto  the  posterior  urethral  wall  just  within  the  orificium  externum. 

Structure. —  The  Male  Urethra. — The  wall  of  this  canal  consists  of  a  mucous 
membrane  containing  a  rich  venous  plexus  and  supplemented  in  the  prostatic  and 
membranous  portions  by  considerable  tracts  of  muscular  tissue.  The  mucous  mem- 
brane, which  [Kissesses  an  unusual  amount  of  fine  elastic  fibres,  is  clothed  with  an 
epithelium  that  varies  in  different  parts  of  the  canal.  Throughout  the  upper  two- 
thirds  of  the  prostatic  portion  it  resembles  that  of  the  bladder,  belonging  to  the 
transitional  vanety  ;  on  approaching  the  pars  membranacea  the  epithelium  becomes 
columnar  in  type,  usually  being  simple,  but  in  places  suggesting  a  stratified  arrange- 
ment on  account  of  the  presence  of  small  reserve  cells '  between  the  outer  ends  of  tht 
chief  epithelial  elements.  This  variety  is  continued  through  the  cavernous  portion  as 
far  as  the  navicular  fossa,  where  the  epithelium  becomes  stratified  squamous  in  type, 
and  at  the  external  orifice  is  directly  continuous  with  the  epidermis  covering  the  glans. 
The  deeper  parts  of  the  mucosa  contain  a  rich  venous  plexus,  and  in  places,  notably 
in  the  urethral  crest,  assume  the  character  of  erectile  tissue.  The  constriction  of  the 
external  orifice  is  due  to  a  ring  of  fibro-elastic  tissue  prolonged  from  the  envelope 
and  septa  of  the  cavernous  tissue  of  the  glans. 

The  muscular  tissue  associated  with  the  male  urethra  includes  intrinsic  and  ex- 
trinsic fibres,  the  former  being  involuntary  in  character  and  directly  incorporated 
with  the  wall  of  the  canal  and  the  latter  being  accessory  bands  of  striped  muscle  de- 
rived from  structures  surrounding  the  duct.  The  intrinsic  musculature  consists  of  an 
inner  longitudinal  and  an  outer  circular  layer,  of  which  the  former  is  thinner  but 
more  widely  distributed,  extending  from  the  internal  urethral  orifice  (where  it  is  con- 
tinuous with  the  superficial  layer  of  the  muscle  of  the  vesical  trigone)  as  far  forward  as 
'  Herzog:  Archiv  f.  mikro.  Anal.  u.  Entwick.,  Bd.  Ixiii.,  1904. 


THE  URETHRA. 


1935 


^Bvrlac*  cpittKlium 


Section  ol  mucoui  memhtane  ol  proMatIc  nrethra,  ibowinc 
(land-Uke  crypu  in  mucoM.    X  45- 


the  orifices  ol  the  ducts  ol  Cowper'  s  gUnds.  The  circular  fibres,  outside  the  longittidi- 
nal.  are  best  developed  at  the  internal  orifice,  where  they  form  a  layer  three  or  four 
times  as  thick  as  the  longitudinal,  which  they  accompany  as  a  dtstmct,  although  di- 
minishing, stratum  as  far 
forv  trd  as  the  termination 
ol  the  membranous  ure- 
thra, disappearing  first  on 
the  lower  and  last  on  the 
upper  wall  of  the  fossa 
bulbi.  Beyond  the  pos- 
terior third  ot  the  pars 
spongiosum  the  intrinsic 
musde  is  wanting,  the 
muscular  tissue  surround- 
ing the  remaining  parts 
belonging  to  the  erectile 
tissue  ol  the  corous  spon- 
giosum (Zuckerkandl). 

The  inter. 9I  vesical 
sphincter     .  .  the 

commence)  e- 

thra  is  d«  'i^ 

deeper  laj 

thlTmuS  o!  u.e  -^S^t  vesical  wall  does  not  direcdy  take  part  in  its  production 
(Kalischer).  ^^    ^^^^^  ^^^  ^^^^^^  .^  encircled  by  bundles  ol  striped  muscle 

known  as  thrextemal  vesical  sphincter.  Higher  up  th«e  bundles  he  entirely  in 
front  ol  the  urethra  in  close  relation  with  the  lower  border  ol  the  mvoluntary  sph'ncter, 
n  Iront  of  which  they  extend.  Below,  the  external  sphincter  ,s  continuous  with  the 
compressor  urethr*  muscle,  as  an  upward  prolongation  of  which  it  3  be  r^arded 
( Hoin  As  it  passes  between  the  two  layers  ol  the  tnangubr  ligament,  the  mem- 
viiuiiy-  f  branous  portion  of    the 

Fio.  1634.  urethra    is    enclosed   by 

stout  annular  bundles  of 
the  compressor  urethra 
muscle,  which  when  stim- 
ulated to  contraction,  as 
by  the  presence  of  an  in- 
strument in  the  canal, 
may  tightly  embrace  ihe 
urethra  and  embarrass 
the  passage  of  the  cathe- 
ter. These  fibres  are 
continued  forward  for 
some  distance  beyond  the 
lower  layer  of  the  trian- 
gular ligament. 

Since  they  affi  t  the 
canal,  although  not  in 
intimate  relation  with  its 
wall,  the  fibres  of  the 
bulbo-cavemosus  muscle 
may  also  be  included  in 
the    extrinsic    urethral 

Section  of  wall  of  urethra  in  sponfo'  portion,  showing  crypts  miis/'iilntiiri' 

in  mucosa  and  numerous  venous  spaces.    X  35.  iiiuM-umiuic 

,  The  urethral  glands, 

or  glands  of  Littri,  embrace  two  groups — those  within  the  mucous  membraiie  and 
those  within  the  submucous  tissue — the  ducts  of  which  are  seen  with  a  magnifying- 


Suiface  epithelium 


1926 


HUMAN  ANATOMY. 


glass  as  minute  openings  on  the  muams  membrane.  The  former,  the  intramuctms 
glands,  are  simple  in  structure,  consisting  usually  of  a  single  alveolus,  less  frequently 
of  two  or  three,  from  .070-.  100  mm.  in  diameter.  They  are  lined  with  cylindrical 
epithelium  and  occur  in  all  parts  of  the  urethra,  being  mi.st  numerous  in  the  sjxjngy 
portion  (Herzog).  The  submucous  glands,  although  small,  are  larger  than  those 
limitid  to  the  mucosa,  but  are  less  widely  distributed,  being  absent  in  the  distal  half 
of  the  pars  membranacea  and  the  proximal  third  of  the  spongy  portion.  They  are 
most  abundant  and  best  developed  on  the  upper  wall  of  the  spongy  poitioi..  anterior 
to  the  openings  of  the  ducts  of  Cowper's  glands  ( Herzogj.  Their  ducts  often  e.xtend 
several  millimetres  obliquely  backward,  more  or  less  pardlel  to  the  urethra,  and  divide 
into  two  or  more  slightly  e.\|>anded  terminal  tubules  which  are  lined  with  cylindrical 
epithelium.  Where  surrounded  by  the  corjjus  spongiosum,  the  submucous  glands  lie 
embedded  within  the  fibrous  tissue  of  the  albuginea  ;  in  the  pars  membranacea  the 
glands  are  surrounded  by  the  bundles  of  the  compressor  urethra  muscle. 

In  addition  to  the  foregoing  true,  although  small  glands,  the  urethral  mucous 
membrane  is  beset,  along  its  upper  wall  and  near  the  mid-line,  with  small  diverticula 
(lacunae  urctbralcs)  which  are  little  more  than  tubular  depressions  within  the  lining  of 
the  canal  and  cannot  be  regarded  as  glands,  although  they  often  receive  the  ducts  of 

submucous    glands  that 
Fio    1635.  open  into  them.     One  of 

exceptional  size  ( from  4- 
'  1 2  mm.  in  length  1  is  com- 
monly found  on  the  roof 
of  the  navicular  fossa,  its 
orifice  being  guarded  by 
a  fold  of  mucous  mem- 
brane (valvula  fossae  na- 
vicnlaris). 

The  Female  Urethra. 
— As  in  the  male,  the  wall 
of  this  canal  consists  es- 
sentially of  a  mucous 
membrane  supplemented 
by  an  outer  muscular  tu- 
nic. The  mucous  mem- 
brane, thrown  into  longi- 
tudinal folds  when  the 
canal  is  closed,  is  composed  of  a  tunica  propria,  rich  in  elastic  fibres,  covered  with 
stratified  squamous  epithelium  that  above  resembles  the  vesical  type  and  below  that 
of  the  vestibule.  In  the  female  the  urethral  glands  are  represented  by  small  groups 
of  tubular  alveoli  that  open  by  minute  orifices  on  the  mucous  surface  and  correspond 
to  Littr6's  glands  in  the  male.  They  are  most  plentiful  in  the  upper  part  of  the  ure- 
thra, and  often,  especially  in  aged  subjects,  contain  concretions  resembling  those 
found  in  the  prostatic  tubules  (Luschkai.  The  mucosa  is  also  beset  with  small  pit- 
like depressions,  similar  in  character  to  the  lacuns  in  the  male,  into  which  the  ducts 
of  the  glands  frequently  of)en. 

The  muscular  tissue  of  the  female  urethra  comprises  intrinsic  unstriped  fibres 
forming  part  of  the  wall  and  extrinsic  striated  tissue  outside  of  the  canal.  The 
former  aie  represented  by  an  inner  layer  of  longitudinally  disposed  fibres  and  an 
outer  one  of  circular  bundles,  the  two  being  separated  by  an  intervening  stratum  of 
areolar  tissue  on  which  a  rich  venous  plexus  confers  the  character  of  erectile  tissue. 
At  the  internal  orifice  the  circular  fibres,  in  conjunction  witli  those  from  the  trigone, 
form  the  internal  vesical  sphincter.  Between  the  layers  of  the  triangular  ligament  the 
canal  is  surrounded  by  bundles  of  the  compressor  ur..  .hrse,  fibres  of  which  are  pro- 
longed into  the  anterior  vaginal  wall.  The  lower  end  of  the  urethra  is  embraced  by 
the  anterior  fibres  of  the  sphincter  vaginae  muscle  (Lesshaft). 

Vessels.— The  arteries  supplying  the  urethra  are  from  several  sources,  since 
those  distributed  to  the  canal  are  usually  branches  derived  from  the  vessels  passing 
to  the  surrounding  organs.     The  pars  prostatica  receives  twigs  from  the  middle  hem- 


Circular 
muscle 


IxmgUudinal  section  of  wall  of  female  urethra,    x  50. 


PRACTICAL  CONSIDERATIONS:    MALE   URETHRA.  i<)27 

orrhoidal  and  the  interior  vesical  ;  the  membranous  jM.nion  from  the  inferior  hem- 
orrhoidal and  the  M.,K;rhcial  perineal:  md  the  spongy  portion  from  the  bulbar, 
cavernous,  and  dors.U  arteries  from  the  internal  pudic.  /«  thejanak  the  ure  hra  « 
supplied  by  branches  from  the  inferior  vesi.al.  the  uterine,  and  the  n.ternal  pudic  lor 
the  upi)er,  middle,  ai.d  lower  thirds  resi>ectively.  ,  ;..  .u. 

The  veins,  which  form  a  rich  plexus  beneath  the  mucous  membrane,  n.  the 
proximal  part  are  tributary  to  the  vesical  and  pr.«tatic  vcms,  and  n.  the  si>..ngy  |wr. 
rionTthl  dorsal  vein  of  the  penis  and  the  inter.u  pud.c  veins.  In  the  Jauak  tl  e 
veins  empty  into  the  vesico-vaginal  and  pudenda^  ple.xus  Below  hey  communicate 
with  the  venous  siwces  of  the  clitoris  and  the  bulbus  vestibuli  (,  W  aldc>  er ; . 

The  numerous  lymbhatus  within  the  mucous  n.  -nbrane  form  a  proximal  and  a 
distal  set  The  former  pass  backward  to  join  the  lymphatics  of  the  vesical  trigone, 
the  later  course  forward  and  unite  with  those  of  the  glans.  The  lymph-lracts  from 
the  sponiry  and  membranous  portions  of  the  urethra  communicate  with  the  internal 
or  pubic  group  of  inguinal  lymph-nodes  ;  those  from  the  prostatic  portion  are  aflcr- 
ents  to  the  internal  iliac  nodes.  In  the  femalt  the  lymphatics  from  the  upper  part  of 
the  canal  pass  to  the  internal  iliac  nodes  ;  below  they  empty  into  the  lymph-vessels 
of  the  labia  minora  and  communicate  with  the  inguinal  mxies. 

The  nerves  are  frjm  the  pudic,  which  conveys  sensory  fibres  to  the  mucous 
nembrane  and  motor  fibres  to  the  striped  muscle,  and  from  the  hypogastric  plexus 
of  the  sympathetic  by  -vay  of  the  prostatic  and  cavernous  plexuses. 

PRACTICAL  CONSIDERATIONS:    THE  MALE  I'RETHRA. 

Coneenital  abnormalities  of  the  urethra  are  not  common.  Absence  of  the  urethra 
usually  <auses  death  of  the  foetus  before  birth,  as  urine  is  secreted  and  enters  the 
bladder  during  intra-uterine  life,  the  vesical  distention  then  causing  pressure  upon 
the  umbilical  arteries  and  embarrassment  of  the  foetal  circulation.  Atresia  of  the 
urethra  may  be  found  at  birth  at  any  point  in  the  canal,  but  if  jjostenor  to  the  meatus 
is  apt  to  r«ult  in  death  of  the  foetus.  Occasionally  it  affects  only  the  meatus,  the 
mucous  membrane  of  the  glans  presenting  no  orifice,  but  either  yielding  sponune- 
ously  to  the  child's  efforts  to  urinate  or  being  readily  penetrated  by  a  probe. 

Contraction  of  the  meatus  so  t'  at  it  will  admit  only  the  finest  probe  is  a  not 
uncommon  congenital  condition,  is  ;en  associated  with  phimosis,  and  may  cause  a 
sufficient  degr^  of  urinary  obstruction  and  of  reflex  irritation  of  the  susceptible 
nerve-centres  of  an  infant  to  require  meatotomy  (y.f.).  „     ,  ,u    .,„tK„ 

Hvpospadias.—1\oA  is  a  congeniul  deficiency  in  the  lower  wall  of  the  urethra 
which  may  terminate  at  the  perineo-scrotal  junction  or  at  any  point  anterior  to  it. 
The  varieties  of  hypospadias  are  described  in  accordance  with  the  degree  of  arrest 
of  development  (page  2040)  which  has  occurred.  If  this  has  been  e.xtreme  the 
anterior  orifice  of  the  urethra  may  even  lie  in  the  perineum,  the  two  halves  of  the 
scrotum  remaining  ununited,  and  often  consisting  of  two  separate  pouches,  which  are 
empty  when  the  testicles  have  failed  to  descend,  and  which,  therefore,  resemble 
strongly  the  external  genitalia  of  the  female.  In  these  cases  the  penis  is  atrophied 
and  is  closely  applied  to  the  fissure  in  the  scrotum.  In  the  penoscrotal  yanety  the 
opening  is  at  the  junction  of  the  anterior  fold  of  the  scrotum  with  the  inferior  surface 
of  the  penis,  and  the  latter  is  apt  to  be  somewhat  better  developed,  although  still 
strongly  curved  downward,  owing  to  its  being  much  shorter  on  its  inferior  than  on 
its  upper  surface.  In  the  penile  variety  of  hypospadias  the  urethral  opening  may 
be  at  any  point  on  the  lower  surface  of  the  penis  between  the  peno-scrotal  junction 
and  the  corona  glandis.  In  the  so-called  balanic  hypospadias  the  opening  of  the 
urethra  is  situated  on  the  under  surface  of  the  glans  ;  the  frenum  is  absent.  There 
is  often  a  litrie  groove  at  the  anterior  extremity  of  the  glans  which  resemWes  the 
normal  meatus,  but  which  usuallv  ends  posterioriy  in  a  blind  pouch.  \V  hen  the 
urethral  orifice  is  situated  far  back,  the  patient  is  usually  sterile,  although  not  neces- 
sarily impotent  if  the  organ  is  well  developed.  Oftei,  however,  it  is^  •  rudimentary 
or  so  markedly  curved  upon  itself  that  intercourse  is  impossible.  Use  forms  ot  Hy- 
pospadias involving  the  glans  are  of  no  physiological  importance  and  requu-e  no 
treatment. 


193* 


HUMAN  ANATOMY. 


^itpadias  is  an  absence  oi  the  upper  wall  of  the  urethra  is  much  rarer  than 
hypospadias,  and  is  often  associated  with  exstrophy  of  the  bladder  (page  191 1).  It 
may  be  extensive,  in  which  case  the  opening  of  the  urethra  is  dose  to  the  pubes,  or 
there  may  be  congenital  absence  of  the  pubic  symphysis. 

In  relation  to  its  injuries  and  diseases  and  to  its  use  as  the  route  by  which  instru- 
ments are  introduced  into  the  bladder,  the  urethra  may  be  divided  into  various  por- 
tions, as  (a)  anterior aafl  posterior ;  {d)  Jixedniad  movable;  (c)  eurvedmd  straight; 
{a)  narrow  and  wide;  {e)  dilatable  and  noH-dUalable ;  {/)  erectile  and  muscular'; 
ig)  penile,  perineal,  and  prostatic. 

{a)  The  anterior  urethra  includes  all  the  spongy  portion  and  the  posterior  or 
deep  urethra  all  the  prosutic  portion.  They  are  separated,  especially  as  regards 
infectious  processes,  by  the  intervening  membranous  urethra, — that  portion  lying 
between  the  two  layers  of  the  triangular  ligament  and  surrounded  by  the  compressor 
urethrse  muscle.  The  contraction  of  that  muscle,  acting  on  the  narrowed  urethra 
of  this  region,  constitutes  a  natural  barrier  to  the  backward  progress  of  infection, 
and  is  doubtless  aided  in  thb  by  the  resistance  to  tumefaction  offered  by  the  un- 
yielding inferior  layer  of  the  triangular  ligament  (the  arbitrary  boundary  of  the 
"antmor"  urethra  posterioriy),  and  possibly,  in  the  ordinary  position  of  the  male 
organ,  by  |^vity,  as  the  movable  prepubic  downward  curve  of  the  urethra  (^vide 
infra)  begins  only  a  little  anterior  to  that  point.  The  division  is  a  practical  one, 
and  in  its  reladon  to  the  most  common  urethral  infection  (gonorrha>a)  affects  both 
prognosis  and  treatment  (page  1931). 

(^)  The ^x^rf  portion  of  the  urethra  includes  the  prostatic  and  the  membranous 
portions  and  a  little — from  one  to  one  and  a  half  inches — of  the  posterior  part  of 
the  spongy  portion.  It  may  be  said  to  extenu  from  the  neck  of  the  bladder  to  the 
posterior  margin  of  the  suspensory  ligament  of  the  penis,  about  two  and  a  half  inches 
anterior  to  the  inferior  layer  of  the  triangular  ligament  Of  this  relatively  fixed  portion 
the  membranous  urethra  is  the  only  part  that  has  practically  n..  mobility.  The  pros- 
tatic portion  may  be  moved  slightly  within  the  limits  alk.weU  ../  the  pubo-prostatic 
ligaments  and  by  the  connection  of  its  capule  with  the  .uperio;-  layer  of  the  triangular 
ligament  in  front  and  the  recto-vesical  fascia  and  rectum  beneath  and  above.  The 
posterior  part  of  the  spongy  urethra,  the  "bulbous"  portion,  has  even  more  motion 
both  laterally  and  inferiorly,  as  its  movement  in  those  directions  is  not  opposed  by 
any  strong  membranous  or  ligair  ^^ntous  structure.  Of  course,  anterior  to  the  suspen- 
sory ligament  the  spongy  urethra  moves  with  the  corresponding  portion  of  the  penis. 
This  division,  like  the  one  following,  is  of  great  practical  importance  in  urethral 
or  vesical  instrumentation. 

(f)  The  terms  curved  and  straight,  as  applied  to  the  urethra,  are  purely  rela- 
tive. With  the  penis  flaccid  and  pendent  there  is  almost  no  straight  portion,  and  the 
urethra  presents  a  reversed,  irregular,  S-shapcd  curve,  the  upper  segment  of  which 
begins  a  little  anterior  to  the  vesical  orifice  and  is  nearly  vertical,  with  its  concavity 
forward  in  the  erect  position  of  the  subject,  while  the  lower  and  longer  segment  is 
less  vertical,  is  convex  anteriorly,  and  ends  at  the  meatus.  The  whole  urethra  may 
be  divided,  as  to  its  cur\es,  into  ( i )  a  comparatively  fixed  subpubic  curve,  including 
most  of  the  prostatic  urethra,  all  of  the  membranous  urethra,  and  that  portion  of  the 
spongy  urethra  posterior  to  the  suspensory  ligament ;  and  (2)  a  prepubic  curve, 
including  the  remainder.  The  former,  or  fixed,  curve  is,  for  convenience,  described 
as  that  part  of  a  circle  of  three  and  one-quarter  inches  diameter  which  is  subtended  by 
a  cord  two  and  three-quarters  inches  long.  Practically  it  varies  greatly  from  this  stand- 
ard. It  maybe  flattened  out  by  downward  pressure  (the  patient  being  supine)  with 
a  finger  on  each  side  of  the  root  of  the  penis,  thus  elongating  somewhat  the  slightly 
elastic  suspensory  ligament  and  depressing  th^  anterior  limb  of  the  curve  ;  it  can 
temporarily  be  obliterated,  as  in  passing  *'  ^h  it  a  straight  instrument  or  the 
straight  shaft  of  an  instrument  •vith  a  tern,  ^i  curve.  The  two  ends  of  the  curve 
are  approximately  on  the  level  of  a  line  drawn  through  the  under  surface  of  the 
symphysis  at  right  angles  to  its  vertical  axis.  The  summit  of  the  curve — the  lowest 
point  with  the  subject  erect — is  on  a  line  prolonging  the  vertical  axis  of  the  sym- 
physis, and  is  at  the  centre  of  the  membranous  urethra  and  about  an  inch  behind 
and  below  the  subpubic  ligament. 


ice  of 
..lal  cali- 


PRACTICAL  CONSIDERATIONS :    MALE  URET     ^A.  1929 

The  prepubic  curve  can  be  ttraightencd  by  erecting  or  raisinR  up  the  penis  as 
is  done  during  the  uie  of  urethral  instruments.  «<«  of  which,  esjHrcially  wunds  and 
catheters,  are  made  u>  «  to  correspond  in  their  c-.  v«.  to  the  theoretical  hxed  curve 
above  deicribed.  The  catheters  employ  .•  -n  cer  «n  conditions,  esjH^cially  pr.«tatic 
hy^rtroThy.  are  elongated  and  given  a  I.,  ger  r  ve  to  correspond  with  tKc  elonga- 
tioroftfie  prostatic  urethra  and  the  greater  .urve  given  it  by  the  elevation  of  the 
vesicaUeck  (^p^e  .98^.).   ^^^^  ^^^  ^^^^^^^  ^^         p.^^^ 

instrumenu.  is  a  mere  valvular  slit,  the  walls  lying  m  contact,  it  has  to  be  stu.lied  as 
"owiM^narr^Hfss  by  various  methods  of  dilatation  during  life  and  of  injection 
rpTn  he  caXver.  The^esult  of  such  studies  demonstrates  that  the  narrow  and 
K  tSrt^ns  of  the  urethra  alternate  as  follow,  :  the  external  meatus  (the  nar- 
Tow^fr  thHowa  navicularis.  the  spongy  urethra,  the  bulbous  portion,  the  mem- 
branous  urethra,  the  prostatic  urethra,  the  vesical  onlit»>.  ... 

U)  a1  to  xs  dilatatility,-i.e.,  its  suscepHbiUly  todistfnl.cn  by  instruments  - 
the  m«.t«  is  the  least  distensible,  and  then,   in  order,  follow  t^e  membranous, 
sp^ngyr.  bulbous,  and  prostatic  portions,  the  latter  being  the  «"o?\*««tfn«»^''^:.       . 
•^  A  definite  n;tio  (nine  to  fouV)  has  been  thought  to  ex      ( Otis)  betwee     he  cir- 
cumference of  the  flaccid  penb  and  that  of  the  distended  uretn.a.     A  ceitai 
tionate  rel-Mionship  in  size  between  the  calibre  of  the  urethral  and  the  nrcum 
the  penU  does  undoubtedly  exist,  but  neither  is  it  so  dehnite  nor  is  the-  iiret. 
bre  so  laree  as  the  above  figures  would  indicate.  . 

f  n  At  the  point  at  which  the  prostatic  urethra  enters  th-  bladder  it  is  sur- 
rounded by  the  internal  vesical  sphincter,  a  muscle  mat!  u.  of  imstriii.  l  h^rcs  ;  antenor 
to  this  a  double  layer  of  unstriped  muscular  fibres  an.  >'■.  glandular  tructure  of  the 
prostate  surround  the  urethr  At  the  apex  ..f  the  pio.ute  lies  the  external  vesical 
sohincter,  made  up  chiefly  of  voluntary  muscular  fibres.  . 

The  discharge  of  urine  from  the  bladder  is  prevent«l  by  the  tonic  contrartion  of 
the  muscular  apparatus  of  the  membranous  and  prostatic  urethra.  As  the  bladder 
becomes  distended,  the  internal  vesical  sphincter  yields  and  the  unne  enters  the  pos- 
terior  part  of  the  prostatic  urethra,  causing  a  desire  to  urinate,  which  is  resiste.1  by  the 
artion  of  the  voluntary  fibres  of  the  external  vesical  sphincter  and  the  compressor 
urethne  On  passing  a  catheter  when  the  bladder  is  full,  the  urethra  seems  about  an 
inch  shorter  thknit  does  immediately  after  micturition  ;  this  is  owing  to  the  particir«- 
tion  of  the  posterior  portion  of  the  prostatic  urethra  in  the  retentive  hinction  of  the 

^'*'^  The  compressor  urethr*  muscle  is  readily  excited  to  reflex  spasm.  Ordinarily. 
on  the  passage  of  instruments,  a  moderate  degree  of  resistance  cr^n  be  detected  due 
to  the  contraction  of  this  muscle.  In  irritable  conditions  of  th-  mucous  membrane 
there  mav  be  excited  a  spasm  so  violent  that  it  will  be  impossible  to  introduce  a  soft 
instrument.  Such  spasm  may  also  be  excited  by  irritation  of  the  prostatic  urethra 
either  from  distention  of  the  bladder  or  from  any  other  cause.  Thus  it  is  often  found 
extremely  difficult  to  evacuate  the  bladder  when  the  desire  to  urinate  has  been  re- 
sisted for  many  hours,  and  acute  inflammation  of  the  posterior  urethra  not  infrequently 
reauires  the  use  of  catheters  to  overcome  the  tight  muscular  contraction  of  the  com- 
oressor  urethra  which  prevents  micturition.  Not  only  the  introduction  of  sounds,  hut 
even  the  injection  of  bland  liquids  will  cause  contraction  of  the  compres.sor  urethrje 
muscle  and  hence  prevent  such  injection  from  reaching  the  membranous  or  the  pros- 
tatic urethra.  Any  inflammation  in  these  portions  of  the  urethra  will  also  cause  the 
tonic  contraction  of  the  sphincter  muscles  to  be  accentuated.  Hence  inflammatory 
discharge  from  the  membranous  or  the  prostatic  urethra  wi»  ten-*  to  flow,  not  for- 
ward but  into  the  bladder,  and  injections  intended  to  reach  the  de.p  urethra  will,  it 
driven  in  at  the  meatus,  extend  no  farther  back  than  the  infenor  layer  of  the  trian- 

^"Thw^^s'^m  then,  to  be  good  grounds,  both  from  a  physiological  and  from  a 
clinical  stand-point,  for  dividing  the  urethra  into  an  anterior  erectile  part  and  a  pos- 
terior muscular  part.  •      .  .l  1: 

(£■■)  The  penile  urethra  terminates  at  the  antenor  margin  of  the  suspensor>- 1  ga- 
ment f  the/^r/wfl/  urethra  includes  the  bulbous  (with  the  so-called  pretngonal  or 


I930 


HUMAN   ANATOMY. 


prediaphragmatic  portion)  and  membranous  urethra ;  the  prostatic  ureihn,  of  course 
extends  thence  to  the  bladder.  All  of  these  terms  are  in  constant  use,  and  a  consid- 
eration of  the  urethra  from  the  stand-points  suggested  by  its  subdivisions  as  above 
described  cannot  fail  to  be  useful  in  relation  to  its  injuries  and  diseases. 

Subcutaneous  rupture  of  the  urethra  is  rarelv  seen  in  its  penile  portion  In  the 
great  majonty  of  cases  (92  per  cent. )  it  affects  t»>e  perineal  portion  (80  per  cent,  from 
falls  astnde,  12  per  cent,  from  perineal  blows),  and  in  the  majority  of  these  the  bul- 
bous urethra  sutlers  most  severely.  The  mechanism  of  rupture  varies  with  the  size 
and  shape  of  the  vulnerating  body,  but  the  urethra  is  usually  crushed  against  either 
•he  transverse  ligament  or  subpubic  arch,  the  anterior  face  of  the  pubis  (which  is 
placed  at  an  ang  e  of  only  30  degrees  with  the  horizon),  or  the  ischiatic  or  pubic 
rami.  In  cases  of  fracture  of  the  pelvis  or  temporary  or  permanent  disjunction  of  the 
pubic  symphysis,  the  membranous  urethra  may  be  lacerated  by  the  fragments  or  may 
be  torn  partly  or  completely  across  by  the  drag  upon  it  of  the  triangular  ligament. 

1  he  rupture  may  be  complete  or  incomplete,  the  former  being  more  common  in 
the  membranous  urethra  on  account  of  (a)  its  fi.xity  ;  (^Uhe  density  of  the  triangular 
ligament ;  (c)  its  proximity  to  the  pubes  and  ischium  ;  ( d)  the  relative  thinness  of  its 
walls  ;  and  (f )  the  absence  of  the  protection  afforded  by  erectile  tissue  which  is 
present  m  only  a  scanty  layer.  The  symptoms  are  hemorrhage  from  the  meatus  or 
into  the  bladder,  or  both  ;  difficult  or  painful  urination,  or  retention  of  urine  ;  swelling 
usually  in  the  penneum  or  at  the  perineo-scrotal  junction  ;  and  later  extravasation  of 
urine,  which  will  be  guided  in  certain  definite  directions  in  accordance  with  the  locality 
of  the  rupture  {vide  infra).  ' 

Urethritis,  almost  always  due  to  gonococcus  infection,  but  sometimes  caused  by 
the  ordinary  pyogenic  organisms  aided  by  congestion  from  trauma  (catheter  urethritis) 
may  from  the  anatomical  stand-point  best  be  divided  into  anterior  and  posterior 

Anlertor  urethritis  affects  that  portion  of  the  urethra  in  front  of  the  compressor 
urethrae  muscle  ;  the  following  characteristic  symptoms  and  complications  are  due  to 
Its  situation  :     (a)  free  discharge  from  the  meatus  ;  (b)  ardor  urinee,  due  partly  to 
the  mechanical  disturbance  of  the  flow  of  the  stream  of  urine  (converting  the  urethral 
sht  into  a  suitable  channel  and  separating  the  apposed  walls),  but  chiefly  to  the  con- 
tact of  the  acid  and  salme  urine  with  the  inflamed  mucosa  ;  {c)  frequent  and  painful 
erection  due  (1)  to  irritation  of  the  lumbar  centre,  causing  increased  blood-supply 
through  the  dorsal  arteries  and  the  arteries  to  the  bulb  and  corpora  cavem.isa     (2) 
to  the  compression  of  the  dorsal  vein  of  the  penis  by  clonic  contraction  of  the  com- 
pressor urethra?  and  bulbo-cavemosus  muscles,  and  to  the  compression  of  the  penis 
Itself  against  the  pubic  arch  by  similar  contraction  of  the   ischio-cavemosus   also 
obstructing  the  return  current ;  (3)  to  the  loss  of  elasticity  by  the  congested,  infil- 
trated mucous  membrane  and  submucous  connective  tissue,  which  are  not  able  to 
stretch  as  they  normally  do  when  the  cavernous  bodies  become  engorged  with  blood  • 
(d)  chordee,  a  cur\ation  of  the  penis  due  to  the  fact  that  the  inflammation  extends  to  the 
submi  cous  connective  tissue,  and  thence  to  the  trabecule  of  the  erectile  tissue  of  the 
sponp  body.     The  exudation  of  lymph  consequent  upon  this  fills  up  the  intertra- 
becular  spaces,   which    by  engorgement   ftirnish  the   ordinary   mechanical   element 
ot  normal  erection.     When  the  organ  becomes  erect  the  corpora  cavernosa  are  fully 
engorged  with  venous  blood.     The  infiltrated  portion  of  the  corpus  spongiosum  how- 
ever remains  ngid  and  undilatable,  the  blood  being  unable  to  find  its  way  into  the 
partially  obliterated  spaces.      If  the  inflammation  extends  to  the  corpora  cavernosa 
erections  will  be  equally  painful  :  but  in  this  case  the  cur^•e  will  be  upward.     If  only 
one  cavernous  body  is  involved,  the  cur\'e,  of  course,  will  be  towards  the  affected 
side  ;  (e)  follicular  or  peri-ttrelhral  abscess,  due  to  involvement  of  the  urethral  folli- 
cles and  to  occlusion  of  their  mouths  by  swelling  of  the  mucosa,  preventing  drainage 
into  the  urethra  ;  (/)  lymphangitis  and  bubo,  usually  associated  with  retention  of 
discharge  and  inflammation  between  the  prepuce  and  glans,  the  infection  extending 
by  the  superficial  lymphatics  and  reaching  one  of  the  superficial  nodes  lying  just  below 
Poupart  s  ligament,  embedded  in  the  subcutaneous  cellular  tissue  and  above  the  fascia 
lata.     The  lymphatics  more  directly  connected  with  the  urethra  itself  belong  to  the 
deeper  set.  and  run  beneath  the  pubic  arch  to  join  the  deep  pelvic  lymphatics  and  to 
terminate  in  the  lumbar  nodes. 


PRACTICAL  CONSIDERATIONS.    MALE   URETHRA. 


«93» 


A  rare  complication  {Cowperitis)  may  result  from  infection  of  the  bulbo- 
urethral glands  through  their  ducts  which  r.npty  into  the  bulbous  urethra.  The 
first  symptom  usually  developed  is  pain  ii'  the  perineum,  much  increasetl  by  press- 
ure, and  rendering  sitting  or  walking  markedly  painful.  Tiie  inrianunatory  swell- 
ing of  the  glands  is  resisted  by  the  two  layers  of  the  triangular  ligament  between 
which  they  arc  situated  and  by  the  deep  perineal  fascia,  and  this  resistance,  associ- 
ated with  the  determination  of  blood  to  the  part  by  gravitation,  imparts,  as  in  other 
inflammations  where  the  same  conditions  exist,  a  throbbing  element  to  the  pain 
which  renders  it  peculiarly  distressing. 

Posterior  Urethritis. — Although  it  is  true  that  the  compressor  urethra  muscle 
constitutes  a  sphincter  which,  by  its  tonic  contraction,  keeps  the  membranous  part 
of  the  canal  constantly  closed  against  injections  forced  through  the  meatus,  the 
gonococcus,  as  it  passes  backward  in  the  deeper  layers  of  the  epithelium,  is  not 
arrested  by  this  muscle,  but  with  few  exceptions  invades  the  posterior  urethra,  from 
which  region  it  can  readily  extend  to  the  prostatic  ducts,  the  seminal  vesicles,  the 
vas  and  epididymis,  and,  much  more  exceptionally,  to  Cowper's  glands  and  to  the 
bladder. 

To  some  or  all  of  the  above  symptoms  may  then  be  added  :  {a)  frequent  and  _ 
urgent  urination,  as  the  normal  slight  desire  to  urinate,  felt  when  the  bladder  is 
moderately  distended,  the  internal  vesical  sphincter  dilates,  and  the  urine  comes  in 
contact  with  the  prostatic  urethra,  is  transformed  into  an  uncontrollable  dc-sire  when 
the  prostatic  mucosa  is  inflamed  and  hypersensitive ;  (b)  tenesmus  from  spasm  of 
the  internal  sphincter  transmitted  to  the  detrusors  and  due  to  the  same  excitation 
in  the  neighborhood  of  the  vesical  neck  ;  (c)  cystitis  (page  1914)  may  follow  direct 
extension  of  the  infection  by  way  of  the  mucosa  ;  (d)  prostatitis  (page  igSo)  from 
its  spread  along  the  prostatic  ducts  or  into  the  prostatic  follicles  ;  (<■)  epididymitis 
(page  1952);  or  (/)  vesiculitis  (page  i960),  from  its  following  the  vas  deferens  or 
the  seminal  ducts. 

Chronic  urethritis  is  apt  to  follow  an  acute  attack  because  :  (a)  the  canal  affords 
periodical  passage  to  a  secretion,  the  urine,  which  is  liable,  by  reason  of  changes  in 
its  constitution,  to  become  an  actual  irritant;  (^)  it  is  exposed,  at  times  of  erection, 
to  intense  congestion  of  all  its  vessels,  and  the  converse  is  also  true,  a  congested  or 
irritated  spot  along  the  urethra  pretlisposing  to  erection  ;  (f )  gravitation,  the  propor- 
tionately excessive  supply  of  blood  to  the  region,  and  the  absence  of  extravascular 
resistance  due  to  the  loose  character  of  the  spongy  tissue,  all  favor  the  persistence 
of  any  congestion  left  after  a  first  attack  of  urethritis  ;  (</)  the  condition  of  approxi- 
mation of  mucous  surfaces,  as  of  the  urethral  walls  during  the  intervals  of  micturition, 
is  here,  as  elsewhere,  unfavorable  to  the  disappearance  of  granular  or  injected  areas 
or  other  traces  of  inflammation.  The  tendency  of  the  gonococcus  to  establish  itself 
in  the  deeper  layers  of  the  mucous  lining,  and  to  multiply  there  where  it  is  compara- 
tively inaccessible,  is  another  cause  of  the  frequent  occurrence  of  the  chronic  forms 
of  urethral  inflammation. 

Stricture  of  the  urethra  is  an  important  and  frequent  sequel  of  urethritis.  It 
consists  essentially  in  a  contracting  peri-urethral  deposit  of  fibrous  tissue  due  to  the 
organization  of  the  exudate  deposited  in  the  submucosa  during  the  existence  of  a 
urethritis.  The  situation  of  stricture  varies,  but  there  can  be  no  doubt  tluit  the  great 
majority  are  to  be  found  in  the  bulbo-membranous  region,  which  includes  a  space 
from  about  one  inch  in  front  of  the  anterior  layer  of  the  triangular  ligament  to  the 
prostato-membranous  junction.  The  next  most  frequent  seat  is  in  the  first  two  inches 
of  the  urethra.  The  frequency  of  strictures  in  these  regions  is  due  to  the  fact  that 
they  are  exceptionally  vascular  and  that  chronic  urethritis  is  especially  apt  to  become 
localized  at  those  points.  The  especial  abundance  of  follicles  in  the  bulbous  urethra 
favors  urine  leakage  and  submucous  exudate  there.  Gravitation  in  both  regions 
favors  chronic  congestion  and  may  possibly  of  itself  explain  the  clinical  facts  as  to 
frequency.  The  smallest  number  are  found  in  the  middle  of  the  spongy  urethra. 
These  remarks  apply  to  the  form  of  stricture  produced  by  urethritis.  Traumatic 
stricture  usually  affects  the  membranous  urethra.  Stricture  of  the  prostatic  urethra 
is  practically  unknown,  probably  because  in  that  region  the  submucous  connective 
tissue  is  relatively  scanty,  the  urethra  is  lined  with  vesical  or  transitional  instead  of 


1932 


HUMAN  ANATOMY. 


columnar  epithelium  and  is  supported  on  all  sides  by  the  firm  glandular  structure, 
thus  offering  greater  resistance  to  and  limiting  the  outward  passage  of  inflammatory 
exudate  or  of  urine. 

The  subjective  symptoms  of  stricture  are  due  to  the  interference  of  the  coarctation 
with  the  normal  passage  of  urine  through  the  urethral  canal  and  to  the  physical 
changes  in  the  urethra,  and  the  resulting  irritation  and  inflammation. 

The  urethra  behind  a  stricture  becomes  dilated  and  thinned,  the  walls  atrophy,  it 
is  deeply  congested,  the  increasing  pressure  produces  pouching  or  dilatation,  the 
retained  urine,  decomposing,  sets  up  a  superficial  inflammation,  the  mucosa  is  denuded 
of  its  epithelial  layer,  urine  escapes  into  the  spongy  tissue,  and  abscess  or  serious 
extravasation  may  follow. 

During  this  process  (which  may  not  pass  througl  all  these  stages)  the  most 
important  symptoms  having  a  definite  anatomical  basis  are  as  follows  : 

(a)  Frequency  of  urination  :  this  arises  first  from  the  change  in  relation  between 
the  expulsive  force  required  of  the  bladder  and  the  accustomed  demands  upon  it ;  then 
from  extension  of  inflammation  backward  by  continuity  until  the  vesical  neck  is 
involved ;  often  from  the  production  of  a  genuine  cystitis  ;  later  from  atony  with 
retention. 

(*)  Dribbling  after  urination  depends  upon  the  retention  behind  the  stricture 
of  some  drops  of  urine,  which  escape  by  gravity  after  the  act  of  micturition  is  com- 
plete. It  is  not  infrequently  a  very  early  symptom,  dependent  on  irregular  action  of 
the  circular  muscle-fibres  of  the  urethra.  The  dribbling,  which  is  called  the  "  incon- 
tinence of  retention," — the  overflow  from  a  distended  bladder, — is  a  very  late  symp- 
tom, following  retention  and  usually  associated  with  a  high  degree  of  atony.  The 
incontinence  of  stricture  is  to  be  diagnosticated  from  the  incontinence  of  prostatic 
hypertrophy  by  the  fact  that  it  is  at  first  worse  in  the  daytime,  and  only  becomes 
nocturnal  later.  The  reverse  is  the  case  in  prostatic  incontinence.  The  mechanism 
of  incontinence  of  urethral  origin  is  simple.  The  dilatation  of  the  urethra  behind  the 
stricture  having  extended  to  the  neck  of  the  bladder,  the  urinary  reservoir  becomes 
in  shape  a  funnel,  the  bladder  representing  the  base,  the  neck  situated  at  the  point  of 
stricture.  The  patient  being  in  the  erect  position,  the  weight  of  the  column  of  urine 
comes  direcdy  on  the  stricture,  which  permits  it  to  filter  through  drop  by  drop.  In 
dorsal  decubitus,  on  the  other  hand,  the  bladder  fills  up  and  retains  its  contents  until 
the  changes  in  it  and  in  the  urethra  are  very  far  advanced.  In  the  prostatic  patient 
it  is  possible  that  the  physiological  congestion  of  the  lumbar  cord  produced  by  the 
recumbent  posture  makes  urination  more  frequent  at  night  and  during  the  early 
morning  hours.  It  lessens  as  the  day  ^oes  on,  and  it  is  only  later  when  the  bladder 
becomes  confirmed  in  irritability  that  diurnal  frequency  follows. 

(<■)  Retenti'>n  of  urine  may  occur  early  and  suddenly  from  an  acute  increase  of 
the  congestion  ot  the  mucous  membrane  of  the  strictured  region,  or  it  may  be  a  late 
symptom  and  dependent  on  the  great  obstruction  offered  by  the  stricture. 

Ardor  urinae,  change  in  the  character  of  the  stream,  diminution  of  expulsive 
power,  vesical  tenesmus,  and  urethral  discharge  may  occur,  but  are  not  constant,  and 
require  no  explanation  from  an  anatomical  stand-point. 

(d)  Extravasation  of  urine  is  one  of  the  most  serious  of  the  late  results  of 
stricture.  The  localizing  symptoms — those  which  indicate  the  point  at  which  the 
urethra  has  given  way — depend  upon  the  course  taken  by  the  urine.  In  all  that  part 
from  the  meatus  to  the  scrotal  curve,  extravasation  is  accompanied  by  a  swelling  of 
the  penis,  greatest  in  the  immediate  neighborhood  of  the  point  of  escape.  In  the 
region  included  between  the  attachment  of  the  scrotum  and  the  posterior  part  of  the 
bulb  the  course  of  extravasated  urine  is  governed  by  the  attachments  of  the  deep 
layer  of  the  superficial  fascia,  or  the  fascia  of  Colles.  Extravasation  of  urine  occurring 
through  a  solution  of  continuity  in  this  region  of  the  urethra  will  first  follow  the  space 
enclosed  by  this  fascia  in  front  and  below  and  by  the  inferior  layer  of  the  triangular 
ligament  posteriorly,  and  as  it  cannot  reach  the  ischio-rectal  space  on  account  of  the 
attachment  of  the  fascia  to  the  base  of  the  ligament,  and  cannot  reach  the  thighs  on 
account  of  the  attachment  of  the  fascia  to  the  ischio-pubic  line,  it  is  directed  into  the 
scrotal  tissues,  and  thence  up  between  the  pubic  spine  and  symphysis  until  it  reaches 
the  abdomen. 


PRACTICAL  CONSIDERATIONS:    MALE  URETHRA. 


1933 


When  it  escapes  from  the  membranous  urethra,  extravasated  urine  is  confined 
to  the  region  included  between  the  layers  of  the  triangular  ligament,  and  only  gains 
access  to  the  other  parts  after  suppuration  and  sloughing  have  given  it  an  outlet,  the 
consecutive  symptoms  then  depending  upon  the  portion  of  the  aponeurotic  wall  which 
first  gave  way.  If  the  opening  is  situated  behind  the  superior  layer  of  the  triangular 
ligament, — i.e.,  in  the  prostatic  urethra, — the  urine  may  either  follow  the  course  of 
the  rectum,  making  its  appearance  in  the  anal  perineum,  or,  as  it  is  separated  from 
the  pelvis  only  by  the  thin  pelvic  fascia,  it  may  make  its  way  through  the  latter  near 
the  pubo-prostaUc  ligament,  and  may  spread  rapidly  through  the  subperitoneal  con- 
nective tissue.  .  ,      ,  ,, 

(ir)  The  bladder,  ureteral,  and  kidney  changes  are  similar  to  those  that  follow 
obstruction  from  any  other  cause,  and  cystitis,  sacculated  bladder,  ureteral  dilatation, 
and  pyonephritis  are  not  uncommonly  terminal  conditions  in  cases  of  stricture. 

Catheterism  is  one  of  the  most  important  of  the  minor  operations  of  surgery. 
For  its  proper  performance,  even  in  the  normal  urethra,  an  acquaintance  with  the 
differences  in  direction,  mobility,  dilatability,  and  contractility  of  that  canal  is  essen- 
tial (,vide  supra),  as  is  familiarity  with  its  relations  to  such  structures  and  o-gans  as 
the  triangular  ligament,  the  prostate,  and  the  rectum  {q.v.).  The  following  points 
are  worthy  of  mention  here  in  their  relation  to  the  anatomy  of  the  urethra,  (a) 
The  penis  is  gently  stretched,  the  dorsum  facing  the  abdominal  wall  to  avoid  folds  or 
twists  in  the  mobile  anterior  urethra.  (*)  In  persons  with  protuberant  bellies  the 
shaft  of  the  catheter  is  at  first  kept  parallel  with  the  line  of  the  groin  ;  if  this  is  not 
done,  the  point  of  the  instrument  may  be  made  to  catch  in  the  upper  wall,  at  the  tri- 
angular ligament,  owing  to  the  elevation  of  the  handle  necessitated  bjr  the  protrusion 
of  the  abdomen ;  the  handle  should,  in  any  event,  be  kept  low  until  the  tip  of  the 
instrument  is  about  to  enter  the  membranous  urethra,  (f )  The  penis  is  drawn  up 
with  the  left  hand  while  the  instrument  is  gradually  pushed  onward,  the  handle  being 
finally  swept  around  to  the  median  line,  the  shaft  being  kept  parallel  to  the  anterior 
plane  of  the  body  and  nearly  touchin^f  the  integument.  The  instrument  is  now 
pressed  downward  towards  the  feet,  while  the  left  hand  still  steadies  the  penis  and 
makes  slight  upward  traction.  After  four  or  five  inches  of  the  shaft  have  disappeared 
within  the  urethra,  it  will  be  found  that  the  downward  motion  of  the  instrument  is 
arrested,  (rf)  The  fingers  of  the  left  hand  are  then  shifted  to  the  perineum  and  used 
as  a  fulcrum,  while  the  handle  is  lifted*from  its  close  relation  with  the  anterior  abdomi- 
nal wall  and  swept  gendy  over  in  the  median  line,  describing  the  arc  of  a  circle,  {e) 
After  the  shaft  has  reached  and  passed  the  perpendicular,  the  handle  should  be  taken 
in  the  left  hand  and  the  index  and  middle  fingers  of  the  right  hand  should  be  placed 
one  on  either  side  of  the  root  of  the  penis,  making  downward  pressure  (to  straighten 
the  anterior  limb  of  the  subpubic  curve,  vide  supra),  while  the  left  hand,  depressing 
the  handle,  carries  the  point  of  the  instrument  through  the  membranous  and  prostatic 
urethra  into  the  bladder.  The  entrance  into  that  organ  will  be  recognized  by  the  free 
motion  that  can  be  given  the  tip  of  the  instrument  when  the  handle  is  rotated,  and  by 
the  latter  remaining  exactly  in  the  median  line  and  pointing  away  from  the  pubes 
when  the  hold  upon  it  is  relaxed. 

In  urethral  instrumentation  it  should  never  be  forgotten  that  the  elasticity  or 
extensibility  of  the  urethra  resides  for  the  most  part  in  the  spongy  portion,  as  is  clearly 
demonstrated  by  erection,  and  this  elasticity  belongs  in  the  greatest  degree  to  the 
inferior  wall,  which  permits  of  easy  distention  or  elongation,  and  changes  its  dimen- 
sions and  form  with  notable  facility  ;  while  the  superior  wall  yields  with  much  more 
reluctance,  and  offers  a  certain  resistance  to  all  agents  tending  to  depress  or  elongate 
it.     This  difference  increases  with  age,  and  obtains  especially  in  senile  urethra-. 

The  extensibility  of  the  inferior  wall  is  brought  into  play  even  by  a  moderate 
force,  and  the  surgeon  cannot  count  on  its  resistance.  It  glides  before  an  instrument, 
and  cannot  serve  to  guide  it  ;  it  cannot  be  incised  with  arty  accuracy  or  precision  :  it 
lacerates  or  ruptures  when  surprised  by  distention  ;  and  it  yields  rapidly  and  ea^  \- 
to  mechanical  pressure  testing  its  extensibility.  It  should  be  noted,  too,  that  this 
elongation  of  the  canal  is  chiefly  at  the  expense  of  the  anterior  urethra.  Again,  the 
sptong)'  portion  docs  not  yield  equally  in  all  its  parts,  since  it  has  been  shown  that  of 
the  different  regions  the  perineo-bulbar  is  the  most  distensible.     The  inferior  wall  of 


1934 


HUMAN   ANATOMY. 


the  urethra  can  then  be  considered  as  normally  longer  than  the  superior  surface.  The 
term  "surgical  wall,"  proposed  for  the  upper  wall  by  Guyon,  would  seem  to  be 
merited,  because  it  offers  the  shortest  route  to  the  bladder,  is  the  most  regular  and 
constant  as  to  form  and  direction,  presents  the  smoothest  and  firmest  surface,  is  the 
less  capable  of  gliding  before  an  instrument  or  being  modified  by  mechanical  pressure, 
offers  the  greatest  resistance  to  rupture  and  penetration,  is  less  intimately  connected 
with  important  structures,  and  is  the  less  vascular  of  the  two  walls.  As  to  the  calibre 
and  distensibility  of  the  urethra,  enough  has  already  been  said  ;  but  it  should  not  be 
forgotten  that  there  are  three  relatively  constricted  parts,  the  internal  or  vesical  mea- 
tus, the  external  meatus,  and  the  membranous  regions  ;  and  three  dilatations,  the 
fossa  navicularis,  the  bulbar  cul-de-sac,  and  the  prostatic  depression,  the  last  two  dila- 
tations presenting  numerous  individual  variations  ,  and  in  this  connection  it  is  impor- 
tant to  remark  that  all  three  of  these  dilatations  are  excavated  at  the  expense  of  the 
inferior  wall  of  the  canal.  The  urethral  curve  only  remaining  regular  in  the  superior 
wall,  it  results  that  the  more  pronounced  the  curve  the  more  accentuated  are  the  bul- 
bar and  prostatic  depressions  ;  and  as  a  certain  degree  of  lengthening  of  the  urethra 
always  corresponds  to  the  greatest  curve, — since  these  are  both  produced  by  bulbar 
and  prostatic  augmentation  of  volume,— one  can  reasonably  conclude  that  urethra  of 
the  greatest  curves  present  at  the  same  time  the  greatest  length.  With  a  knowledge 
of  these  facts,  the  instrumental  exploration  of  the  urethra  becomes  a  matter  of  much 
accuracy  and  precision  (Morrow). 

The  anatomy  of  the  various  forms  of  urethrotomy  and  other  operations  on  the 
urethra  is  sufficiently  dealt  with  in  the  foregoing  and  in  the  practical  considerations 
relative  to  the  bladder,  male  perineum,  and  prostate  {f.t:). 


DEVELOPMENT  OF  THE  URINARY  ORGANS. 

The  development  of  the  essential  parts  of  the  urinary  tract — the  kidney  and  its 
duct — is  so  intimately  related  with  the  foetal  excretory  organ,  the  Wolffian  body,  that 
a  brief  account  of  the  latter  and  of  the  f)rinciples  underlying  its  genesis  is  a  necessary 
introduction  to  the  intelligent  consideration  of  the  subject  here  to  be  presented.  The 
excretory  apparatus  of  amniotic  vertebrates,  even  in  the  highest  mammals  and  man, 
includes  three  structures  which,  although  a^  functionating  organs  existing  in  no 
single  animal,  stand  in  genealogical  sequence.  These  are  the  pronephros,  the  meso- 
nephros  or  Wolffian  body,  and  the  tnetanephros  or  definitive  kidney. 

The  Pronephroi. — The  first  of  these,  the  pronephros,  sometimes  called  the  "head-kidney" 
on  account  of  its  anterior  position  in  its  primary  condition,  in  all  higher  forms  is  at  best  a  rudi- 
mentary and  functionless  organ  ;  nevertheless,  it  is  of  extreme  interest  as  indicating  the  funda- 


FlG.   1636. 


Neural  tube 


IntermeHiale  mass 
Ectoblast 
Parietal  tneaobtast 


/      Body<avity 
Visceral  mesoblast 
:ntoblast 

Part  of  transverse  section  of  earlv  rabbit  em- 
brvo.  showing;  primar>'  division  of  mesoblast  into 
somite,  intermediate  mass,  and  parietal  and  vift* 
ceral  layers.    X  100. 


Fio.  1637, 


Neural  tube 


Somite 


'\nl3Ke  of  nephric  duct 
Parietal  mesoblast 


BodvKiavity 
Visceral  mesoblast 
Remains  of  intermediate  mass 

Section  of  sllKhtly  older  embryo,  show. 
ine  differentiation  of  duct-anlaj^  and  mass  in 
which  tubules  develop.    X  100, 


mental  plan  upon  which,  in  a  modified  form,  the  later  Wolffian  body  is  developed.  Although,  so 
far  as  known,  existing  as  a  permanent  organ  alone  in  the  hag  fishes  ( Ah.rinidtr),  as  a  temporary 
stnictiire  the  pronephros  attains  ron<:idcrahIc  developtnent  in  many  fishes  .ind  .-imphihi.-ms  ;  in 
the  higher  animals,  even  as  aii  embryonal  organ,  it  remains  very  rudimentary  and  transient. 
When  adequately  represented,  the  pronephros  consists  of  a  more  or  less  extensive  series  of 


DEVELOPMENT  OF  THE   URINARY   ORGANS.  1935 

sliehtly  transverse  Mmles  within  the  posterolateral  body-wall  that  intertjally  communicate 
with  the  body-cavity  or  calom.  the  openings  beinR  known  ius  nephrostomata,  and  externally 
join  a  common  canal,  \\\e  pronephric  duel,  wTiich  extends  caudally  and  empties  mto  the  dilated 
terminal  segment  of  the  intestinal  tube,  the  cloaca.  In  relation  with  the  inner  end  of  each 
tubule,  but  projecting  freely  into  the  body-cavity,  lies  a  group  of  convoluted  WcHKl-vessels.  the 
glomerulus,  supplied  by  branches  of  the  aorta.    These    liree  parts  of  the  pr     itive  excretory 


Fig.  jOji. 


Neural  tube. 
Somitic  cavity.  iw>1ated- 


Malpiffhlan  hody  of  mesonephros, 
Mesonephric  tubule 


Mooncphric  duct. 


Parieul  perJtoneuni- 

BoQy.cnvity^ 
Nephrostome'' 
Sexual  gland 
Suprarenal  body^ 


Integument 


Cavity  of  somite  continuous  with  cixlom 
Notochord 
Nephrostome 

Pronephric  tubule 


Gut-tube 


Pronephric  duct 
Mooblast  ul  body-wall 

,     BodyKavity  (coelom ) 
N^  Glomerului  of  pronephroa 
•v    Aorta 
Visceral  peritoneum 


Diagram  showing  fundamental  rrlations  ot  pronephros  (on  right  side)  and  of  roeaonephroa 
or  Wolffian  body  (on  left  side  of  figure).     {Uudersktim.) 


Fio.  1639. 


organ  provide  for  the  essential  requirements  of  the  most  elaborate  urinary  apparatus,— the  pro- 
duction of  the  watery  constituents,  the  excretion  of  the  wa.ste  products,  and  the  conveyance  of  the 
excretion  so  elaborated.  The  pronephros  is  fundamentally  a  segmental  organ,  the  tubules  being 
so  arranged  that  each  corresponds  to  a  single  body-segment  or  metamere,  although  by  no  means 
every  such  division  contains  a  tubule.  It  may  be  assumed  that  the  tubules  of  the  pronephros 
represent  the  segmental  ducts  which  in  ancestral  forms  extended  from  the  body-cavity  directly 
onto  the  external  surface  of  the  1  ody  and  thus  carried  off  the  fluids  accumulated  within  the 
ccelom.  In  consequence  of  the  closure  of  this  direct  communication  with  the  exterior,  which 
may  be  accepted  as  having  occurred  during  the  evolution  of  a  more  elaborate  excretory  system, 
the  necessity  for  a  new  path  of  exit  is  met  by  the  formation  of  the  common  pronephric  diict  into 
which  the  tubules  open,  and  which,  by  its  prolongation  to  and  termination  in  the  end-gut,  insures 
the  escape  of  the  excretions. 

The  development  of  the  pronephros  is  closely  associated  with  the  mesoblastic  somites.  A 
transverse  section  of  an  early  mammalian  embryo  ( Fig.  1636)  shows  the  paraxial  mesoblast,  be- 
tween the  neural  canal  and  the  cleavage  of  the  lateral 
mesoblast  into  the  somatic  and  visceral  plates,  to  comprise 
two  parts,  the  mesial  forming  the  somite  and  the  lateral  or 
inlennediate  cell-mass.  It  may  be  assumed  that  in  the 
higher  types  the  solid  somite  and  the  intermediate  cell- 
mass  have  arisen  by  fusion  of  the  primarily  distinct  dorsal 
and  ventral  mesoblastic  plates  (Fig.  163S).  The  inter- 
mediate cell-mass  soon  separates  into  a  small  duct-anlage, 
situated  dorsally  and  in  close  relation  with  the  ectoblast, 
and  a  larger  ventral  tract  comprising  the  remainder  of  the 
intermediate  cel'-mass.  Within  this  ventral  area  the  tu- 
bules shortly  appear,  and  later  the  glomeruli.  Although 
reaching  a  comparatively  hijfh  development  in  certain  fishes 
and  amphibians  (especially  in  Ichthyophis df'icribed  bv  Se- 
mon),  in  mammals  the  pronephros  consists  of  a  few  tuBules 
connected  with  the  duct,  and  even  as  an  organ  of  embryonic 
life  never  attains  more  than  a  feeble  and  transient  exist- 
ence. In  the  human  embry-o  of  3  mm.  length,  studied  by 
janosik,  it  was  represented  by  two  rudimentary  tubules  that 
extended  from  the  mesothelial  lining;  of  the  body<avity 
towards  the  pronephric  duct,  with  which  one  of  the  tubules 
still  communicated.  The  pronephros  of  the  amniotic  ver- 
tebrates, therefore,  must  be  regarded  as  a  rudimentarv- 
inherited  organ  which  appears  in  response  to  transmitted 
ancestral  tendencies. 

The  Mesonephros  or  Wolf  Body. — This  organ 
may  conveniently  be  regarded  as  con.prising  a  Liter  generation  of  excretory  hihules  opening  into 
a  common  canal,  the  Wolffian  duel,  wnirh  is  usually  l(X>ked  upon  as  the  continuation  .ind  mor- 
phological persistence  of  the  pronephric  duct.  In  tlieir  development  these  tubules  and  duct  bear 
a  similar  relation  to  the  intermediate  cell-ma.ss  as  do  those  of  the  pronephros,  onlv  the  body- 
segments  involved  lie  farther  tailward  and  the  strict  segmental  arrangement  of  the  tubules  is  lost 
owing  to  their  multiplication  and,  as  in  mammals,  precocious  development.     In  contrast  to  the 


Body^avity 


Lonf{itudin.il  section  of  \nunK  t mHr\-o, 
showing  early  stage  of  Wolffiaii  hody  ;  tu- 
bules are  joining  duct.     X  y> 


>936 


HUMAN  ANATOMY. 


— AotU 


nidimentary  character  of  the  pronephros,  the  Wolffian  body  not  only  serves  for  a  time  as  the 
chief  excretory  or^an  of  the  embrjo,  but  in  many  lower  vertebrates  continues  to  functionate 
during  life.  The  anlage  of  the  Wolffian  duct  first  appears  as  bud-like  outgrowths  from  the  dor- 
sal side  of  the  intermediate  cell-mass ;  these  fuse  into  a  strand  which,  separating  from  the  cell- 
mass,  lies  as  a  solid  cord  beneath 
Fir    1640.  the  ectoblast    The  latter  takes  no 

part  in  the  formation  of  the  duct, 
which  is  entirely  of  mesoblastic 
origin,  th*;  appearances  leading  to 
the  assumption  by  certain  authori- 
ties of  its  derivation  from  the  outer 
germ-layer  depending  upon  the 
temporary  apposition  or  attach- 
ment that  the  duct  effects  in  con- 
sequence, probably,  of  its  inher- 
ited inclination,  since  in  ancestral 
forms  the  tubules  opened  on  the 
free  ectoblastic  surface.  At  first 
solid,  the  Wolffian  duct  later  pos- 
sesses a  lumen  which  gradually 
follows  the  tailward  ^owth  of  the 
strand  until,  finally,  it  opens  into 
the  dilated  end-gut  or  cloaca. 

In  mammals  the  Wolffian 
tubules  are  developed  within  the 
ventral  division  of  the  intermedi- 
ate cell-mass  as  solid  cords  that 
later  acquire  a  lumen  and  an  at- 
tachment to  the  Wolffian  duct.  Although  in  the  lower  vertebrates  (fishes,  amphibians)  retain- 
ing a  communication  with  the  coelom  by  means  of  a  nephrostome,  in  mammals  this  connection 
is  Tost  and  the  expanded  inner  end  of  each  tubule  comes  in  close  relation  with  the  convoluted 
vascular  tuft,  the  glomerulus,  which  now,  however,  no  longer  projects  freely  into  the  body- 
cavity.  As  in  the  kidney,  the  glomerulus  is  supplied  by  an  afferent  twig  from  a  branch  of  the 
aorta,  and  is  drained  by  an  efferent  ves.sel  that  breaks  up  into  a  capillary  net-work  surrounding 
the  convoluted  tubule  and  eventually 

Fio.  1641. 


Wolffian  duct 

Mesot  helium' 
Wolffian 


Aortic 
branch  to 


glomerulus 

sloping  capsule 

Part  of  transverse  section  of  embr>'o,  showing  commencing  develop- 
ment of  Malpighian  corpuscle  in  Woifnan  body.    X  150. 


Capsule  of  Malpighian 
''  twdy 


becomes  tributary  to  the  cardinal  vein. 

The  first  apjiearance  of  the  Wolffian 
body  in  the  human  embryo  occurs  very 
early  (2.4  mm.  length)  and  at  a  time 
when  the  remains  of  the  pronephros  are 
still  present.  The  duct  precedes  the 
tubules  and  opens  into  the  cloaca  in  em- 
bryos of  4.2  mm.  length  (Keibel),  the 
tubules,  which  develop  independently, 
establishing  communication  with  the 
duct  shortly  before.  The  development 
of  the  glomeruli  is  relatively  tardy,  since 
these  bodies  are  not  found  until  the 
human  embryo  has  attained  a  length 
of  about  7  mm.  Their  formation  and 
growth  continue  during  the  first  and 
second  months  until  the  embryo  meas- 
ures 22  mm.  in  length,  when  their  great- 
est perfection  is  reached  (Nagel). 

When  fully  developed,  about  the 
end  of  the  second  month,  the  Wolffian 
body  appears  as  an  elongated  organ 
(Fig.  1720)  which  extends  along  almost 
the  entire  length  of  the  posterior  wall 
of  the  bodyovity,  on  either  side  of  the 
mid-line,  from  behind  the  lung-anlage  to 
the  lower  end  of  the  gut-tube.  Ah-  it 
the  eighth  week,  the  Wolffian  bo<l 
ters  upon  its  stage  of  regression  v  n, 
continuing  during  the  third  and  iuurth 
months  of  fietal  life,  results  in  the  grad- 
ual atrophy  of  the  organ  and  its  replace- 
ment as  the  functionating  excretory 
gland  by  the  kidnev  which  meanwhile 
has  been  formed.  This  atrophy  involves 
first  the  glomenili  of  the  .interior  portion  of  the  organ,  which,  together  with  many  of  the  tuhules, 
completely  degenerate,  the  retrogressive  process  extending  tailward  and  gradually  involving  the 
middle  and  posterior  segments.  Although  the  glomeruli  suffer  destruction,  some  of  the  tubules 
and  the  Wolffian  duct  for  a  time  remain  and  contribute  in  varying  degree,  according  to  the  sex 


Glomerulus 


Body-cavity 


Wolffian  duct 


Transverse  section  of  fully  developed  WolflSan  body, 
showing  also  indifferent  sexual  gland.    X  80. 


FlO.    lA4» 


DEVELOPMENT   OF   THE   URINARY   ORGANS.  1937 

of  the  foetus,  to  the  formation  of  certain  stnictures  and  pjirts  of  the  txcre»i>0'  canals  of  the 
sexual  Klands.  In  the  male  the  Wolffian  duct  and  tubules  jwr  st  chiefly  as  the  Vi>s  deferens  and 
the  epididymis ;  in  the  female,  in  whom  the 
atrophy  is  more  complete,  these  remains  are 
represented  principally  by  the  epoophoron  and 
Gartner's  duct.  In  both  sexes  certam  ad- 
ditional rudimentary-  organs— the  paradidy- 
mis in  the  male  and  the  paroophoron  in  the 
female— are  derived  from  the  tubules  of  the 
sexual  seKment  of  the  Wolffian  Ixxly.  A  more 
detailed  account  of  these  transformations  is 
given  in  connection  with  the  development  of 
the  reproductive  organs  (page  20,^7  and  Fig. 
1 719). 


■Stroma 


The  Metanephrca  or  Kidney.— 

The  development  of  the  definitive  kidney 
in  mammals  begins  as  a  i)ouch-like  out- 
growth from  the  posterior  wall  of  the 
Wolffian  duct,  a  Short  distance  alwve  its 
termination  into  the  cloaca.  In  man  the 
renal  diverticulum  makes  its  appearance 
during  the  fourth  week,  at  which  time 
the  embryo  measures  from  6-7  mm.  in 
length.  At  first  short  and  wide,  the  stalk 
of  the  pyriform  sac  soon  becomes  tubu- 
lar, growing  upward  and  backward  into 
the  mesoblast  of  the  posterior  body-wall. 
This  stalk  rapidly  elongates,  and  termi- 
nates above  in  a  blind  club-shaped  ex- 
tremity which  after  a  time  lies  behind  the 
upper  atrophic  segment  of  the  Wolffian 
body.      The  tubular  duct  becomes  the 

ureter  and  its  dilated  end-segment  the  renal  pelvis.     The  latter  is  surrounded  by  a 
sharplv  defined  oval  area  of  compact  mesoblast  that  is  intimately  concerned  in  the 

prcnluction  of  the  convo- 

Fio.  1643. 

Ampullarv  terminations  of 
prim.iry  collecting:  tubules 


.Primar>'  collrctinic 
tuhuleH  olH-ninK 
into  liubitivtaioiw 
of  pelvis 

Renal  pelvii 


Malpif;hian  txxly 


MalpiKfiian 
corpu-Hcle  of 
atrophJL- 
Wolffian 
body 


Lonxitudinal  section  throiiith  devflopine  kidney ;  por- 
tion of  atrophic  Wolffian  body  is  seen  below.     X  35. 


Devrloping 
Maipi^nian 
IxmIu's 


Primar>' 
collecting 
tube 


LatKC  col- 
lectiuK  duct 


Section  of  developing  kidney,  showing  formation  of  urinifer- 
ous  tubules  and  collectings  canals.    X  100. 


luted  kidney-tubules  (of 
which  as  yet  no  trace  is 
present),  and  hence  is 
termed  ^crenal blastema. 
From  the  \entral  and 
dorsal  walls  of  the  primi- 
tive pelvis,  which  is  com- 
prtssed  from  before  back- 
ward, a  number  of  hollow 
sprouts  grow  into  the 
surrounding  mesoblastic 
stroma.  Each  is  a  short 
cylinder  that  terminates 
in  a  slight  dilatation.  At 
first  few,  these  sprouts  in- 
cre.tse  rapidly  in  number 
as  well  as  in  length,  and 
by  repeated  dichotonious 
division  give  rise  to  a  sys- 
tem of  branching  canals 
that  later  are  represented 
by  the  straight  collecting 
tubules  of  the  kidney. 
Concerning  the  ori- 


gin of  the  remaining  portions  of  the  uriniferous  tubules  two  opposed  views  obtain. 
According  to  the  one,  all  parts  of  these  canals  develop  as  direct  continuations  of  the 


19.18 


HUMAN  ANATOMY. 


RiRht 

umbilu'ul  artery. 


Fio.  1644. 


Gut-tube 


outgrowths  from  the  primitive  renal  pelvis  ;  according  to  the  other,  the  convoluted 
tubules  (from  their  beginning  in  the  capsule  to  their  termination  ifr  the  collecting 
tubules  within  the  medullary  ray)  arise  inde{}endently  within  the  renal  blastema, 
and,  secondarily,  unite  with  the  duct-system  from  the  |x:lvis  to  complete  the  canals. 
The  careful  studies  and  reconstructions  of  Huber '  leave  little  doubt  as  to  the  cor- 
rectness of  the  latter  view,  which, 
moreover,  accords  with  the  prin- 
ciple observed  in  the  develop- 
ment of  the  pronephros  and  the 
Wolffian  bo<ly,  in  which  the  tu- 
bules and  the  duct  join  subse- 
quent to  an  independent  forma- 
tion. The  attenuated  proximal 
end  of  the  convoluted  tubule — for 
a  short  time  solid  and  in  close  rela- 
tion with  the  aniage  of  the  glom- 
erulus— soon  becomes  a  sickle-like 
process  which  gradually  incom- 
pletely surrounds  the  vascular  tuft 
and  later  expands  into  the  charac- 
teristic capsule.  With  the  con- 
tinued growth  of  the  tubules  their 
tortuosity  becomes  more  marked, 
the  loop  of  Henle  early  becoming 
a  conspicuous  feature  of  their  course.  By  the  third  month  the  formation  and  group- 
ing of  the  tubules  have  progressed  to  such  extent  that  the  surface  of  the  young 
kidney  exhibits  the  oudines  of  the  individual  lobes  composing  the  organ.  This  lobu- 
lation is  retained  until  some  months  after  birth.  In  addition  to  the  convoluted  tubules, 
the  vascular  and  supporting  tissues  are  derived  from  the  renal  blastema,  the  con- 
densed peripheral  part  of  which  becomes  the  fibrous  capsule  of  the  kidney.  As  the 
latter  assumes  the  r61e  of  active  excretory  organ,  the  Wolffian  body  undergoes  atrophy, 
with  the  exception  of  such  parts  as  are  concerned  in  the  development  of  the  sexual 
ducts. 

The  Bladder  and  the  Urethra. — The  details  of   the  development  of  the 
bladder  and  urethra  in  mammals  and  man  have  been  materially  advanced  by  the 


.Notochord 


End-gut 
Tail-bud' 

Reconstniction  of  caudal  portion  of  human  embryo  of  seven- 
teen days  u  mm.  greateat  length),  showing  cloaca  connected 
with  gut  and  allantoic  duct.  X  48.  ( Draumfrom  Keibtl  wmdel. ) 


Allantoic  duct 


Wolffian  duct 


Renal  bud 


Fig    1646 
Gm-tube 


Allantoic  duct 


Cloacal  membrai 


.Ventral  segment  of 
cloaca 

Dorsal  segment  of  cloaca 


Reconstruction  of  cloacal  region  of  human 
embr>-o  of  twenty-six  days  (6.5  mm.  length) ; 
Wolffian  duct  opens  into  ventral  segment  of 
cloaca.     X  75.     ( Drawn  from  Keibet  model. ) 


Cloacal  membrane 


Preceding  model  viewed  from  right  side,  show- 
ing beginning  division  of  cloaca  into  ventral  ( uro- 
genital) and  dorsal  (intestinal)  segment  by  longi- 
tudinal septal  fold.    (Drawn from  Keibet  modetTj 


investigations  of  Keibel,  Retterer,  and  Nagel,  upon  whose  conclusions  the  following 

account  is  based.       A  sagittal  section  through  the  r.iiidal  pole  of  an  f-arly  human 

embryo  of   6.5  mm.,  about  the  beginning  of  the  fourth  week  (Fig.  1645"),  exhibits 

'American  Journal  of  Anatomy,  vol.  iv..  Supplement,  1905. 


DEVELOPMENT  OF  THE  URINARY  ORGANS. 


»9.W 


Fig.  1647. 


N'ciia  luva 


Allmntotc 
iliict 


Brlty-italk- 


T»il .  ,         , 

Ureter    \         \         NotiKlionl 
Rixlum     Wolffian  duct     Krnal  (irlvis 
ReconMniction  of  cinaral  region  ol  human  embryo  of  thirty-lhre* 
davs  (MS  mm.  lent^h) ;  cloaia  now  incompleti'ly  wiiarated  mti>  uro- 
genital and  intestinal  aegmeiiU.     X  ly    {Drawn /ram  Kettel  modrl.) 


the  end-segment  of  the  gut  dilated  into  an  elongated  chamber,  the  cloaca,  from  the 
upper  end  of  which  the  allantois  passes  forward  and  on  the  sides  of  which  ojn-n  the 
Wolffian  ducts.  The  ventral  wall  of  this  space  is  thin,  and  consists  of  the  i>p|M)sed 
outer  and  inner  germ-layers  alone,  no  mesoblast  intervening.  This  crti>-entol>!astic 
septum  is  the  cloacal  mem- 
brane. During  the  fourth  week 
the  subdivision  of  the  cloaca 
into  a  ventral  and  a  dorsal 
compartment  begins  by  the  for- 
mation of  a  frontal  fold  that 
projects  downward  from  the 
angle  between  the  gut  and  the 
allantois.  Subsequently  this 
partition  is  supplemented  by 
two  lateral  folds  that  appear  on 
the  side  walls  of  the  cloaca  and 
are  continuous  above  with  the 
frontil  fold  (Fig.  1646).  By 
the  union  of  these  three  plicae, 
above  and  from  the  sides,  a 
septum  is  formed  that  gradu- 
ally grows  caudally  and  sub- 
divides the  cloaca  into  a  ventral  ...  ' 
allantoic  and  a  dorsal  intestinal  chamber.  This  partition,  however,  for  a  time  is  incom- 
plete below,  communication  between  the  two  spaces  being  thus  maintained. 

During  these  changes  the  short  canals  common  to  the  Wolffian  ducts  and  the 
primitive  ureters  are  drawn  into  the  ventral  chamber,  the  four  tubes  thereafter  open- 
ing independently,  but  in  close  proximity,  on  the  posterior  wall  of  the  ventral  cloaco- 
allantoic  space.  This  undergoes  further  differentiation  into  an  upper  (vesical)  and  a 
lower  (genital)  segment,  the  latter  gradually  narrowing  into  a  tubular  space,  closed 
below  by  the  fore  part  of  the  cloacal  membrane,  which  becomes  the  uro-genilal 
stmts  and,  after  rupture  of  the  membranous  floor,  communicates  with  the  exterior. 
For  a  time  the  orifices  of  the  Wolffian  ducts  and  the  ureters  are  closely  grouped, 

those  of  the  former,  how- 
Pio.  1648  ever,    lying  nearer  the 

mid-line  and  slightly 
higher  than  the  more 
widely  sef>arated  ureteral 
ojjenings. 

During  the  second 
month  an  important 
modification  of  these 
relations  occurs,  associ- 
ated with  elongation  and 
expansion  of  the  upper 
part  of  the  vesical  seg- 
ment, by  which  the  ure- 
ters are  drawn  upward 
and  the  Wolffian  ducts 
downward.  The  inter- 
vening tract  corresponds 
to  the  lower  segment  of 
a  spindle-shaped  sac  that 
extends  upward  and  is 
continued  towards  the 
umbilicus  by  the  allantois.  The  upper  part  of  this  sac,  which  is  the  dilated  allantois, 
forms  the  l)ody  and  summit  oi  the  bladder  and  the  urachus  ;  the  lower  part,  into 
which  the  ureters  open  (Fig.  1649")  and  which  is  derived  from  both  allantois  and 
cloaca,  differentiates  into  the  vesical  trigone  and  the  urethra  as  far  as  the  openings  (A 


Allantoic 
duct^ 


r.enital 
eminence 


>^- 


Epitl 
knc 


Notochord 


Wnlffian  duct 


T'reter 


Reconstruction  of  cloacal  reRJon  of  human  embno  of  thirty-seven  davs 
(14  mm.  lenxth);  ureter  now  opens  indei>endently  into  uro-Renital  siniis, 
which  above  contributes  lower  sefonent  of  bladder  and  below  is  now  almost 
separated  from  gut-tube.     X  17.    {Drawn/rom  Keibei  model.) 


«<MO 


HUMAN  ANATOMY. 


the  L-jaculatory  ducts, — the  permanent  representatives  d  the  Wolffian  ducts.  In  the 
female  the  tract  produce:*  the  entire  urethra,  since  the  orihce  of  the  sexual  canals 
upeas  into  the  uro-genital  sinus.     The  bladder,  therefore,  is  composite  in  origin,  its 


Broail  ligament 


Pia.  1649. 


Uvary 


Bladiirr 


Symphyii 


Spinal  col4 


Notochord 


I'liiorii 

(flauB 

Epilhclial  kiiuli._ 

Ann* 
t'r»tcnlul  (inui 

Rectum 


I'reltr 
Mtillerian  <tucts 


Wnlftian  dnct 


Keiunstructiui)  uf  huRuti  embn-o  of  nine  wcclu  (25  mm.  lenjcth ) ;  ureter  has  migrated  to 
bladder,  leaving  Wolffian  and  Miillerian  ducti  atuched  to  uro-geniial  >inui,  which  i>  com- 
pletely iiepanileil  from  intatine.    X  lo.    { Drawn  from  Keibtt  mmitl.) 

upper  part  being  from  the  allantois  alone,  while  in  the  formation  of  the  trigonal  region 
both  allantois  and  cloaca  take  part.  The  remaining  portions  of  the  urethra  in  the 
male  are  formed  by  the  extension  of  the  uro-genital  sinus  along  the  under  surface  of 
the  coqxira  cavernosa  of  the  developing  penis  (page  2044"). 


I 


THK  TKSTES. 


1941 


THE  MALE  REPRODUCTIVE  ORGANS. 

This  group  comprises  the  sexual  glands  (the  testes),  the  ducts  (^vasa  dt/frentia) 
and  their  appendages  (the  seminal  vesicles),  the  copulative  organ  (the  penis),  and 
certain  accessory  glands  (the  prostate  and  Cowper  s  glands).  Although  at  first 
situated  within  the  abdominal  cavity,  the  testes  migrate  through  the  inguinal  canal 
into  the  scrotum,  which  sac  they  usually  gain  shortly  btfore  birth.  In  their  descent 
they  are  accompanied  by  blood-vessels,  lymphatics,  nerves  and  their  ducts,  which 
structures,  with  the  supporting  and  investing  tissue,  constitute  the  spermatic  cord  that 
extends  from  the  internal  abdominal  ring  through  the  abdominal  wall  to  the  scrotum. 

THE  TESTES. 

As  often  employed,  the  term  "  testicle"  includes  two  essentially  different  larts, 
the  testis — the  true  sexual  gland — and  the  epididymis,  the  highly  convoluted  begin- 
ning of  the  spermatic  duct. 

The  testes,  or  testicles  proper,  the  glands  producing  the  seminal  elements,  are  two 
slightly  compressed  ellipsoidal  bodies  so  suspended  within  the  scrotum — the  left  lower 

Fio.  1650. 


Tunica  vaginalis 
communis,  cut 


Tunica  vaginalis 


l.ower  vihI  6k  spermatic  ci>nl,  with 

xtramls  of  crcmaster  mUMie" 


Tunica  vaginalis  communis- 


Diiptal. 
fossil 

Epididymii 


Reflection  i>l 
tunica  vaginali 
covering  scrotal 
lifcament 


Tunica  vagina 

lit  "^1 

I'dobuH  ma)or  of 

t^ididytnis 
Aftpendiii  epididymidix  " 

—     Appendix  tetlis 

^KjF  - 

Sac  u(  tunica 
vaKinalift 

Right  testis 

Serous  iao~^^^| 

Reflect  ioi 

of  s<.'nju.s 

A,  antero-lateral  view  of  right  testicle  after  enveloping  membranes  liave  been  cut  atul 
turnett  aside ;  B,  antero-median  view  of  same. 

than  the  right — that  their  long  axes  are  not  verticil,  but  directed  somewhat  forward 
and  outward.  Each  testis  measures  from  4-4.5  cm.  (I'/j-i^^  in. )  in  length,  .ibout 
2. 5  cm.  in  breadth,  and  2  cm.  in  thickness,  and  presents  a  lateral  and  a  medial  sur- 
face, separated  by  an  anterior  and  a  posterior  border,  and  an  upper  and  a  lower  pole. 
The  lateral  surface  looks  outward  and  backward,  and  the  flatter  medial  one  inward 
and  forward.  Both  surfaces,  as  well  as  the  anterior  border,  are  completely  covered 
with  serous  membrane  (the  visceral  layer  of  the  tunica  vaginalis)  and  are,  therefore, 
smooth.  The  rounded  anterior  border  is  free  and  most  convex,  the  much  less  arched 
posterior  border,  covered  by  the  epididymis  and  attached  to  the  sjjermatic  cord,  being 
devoid  of  serous  membrane  and  corresponding  to  the  hiluiu.  In  consequence  of  the 
obliquity  of  the  long  axis  of  the  organ,  the  upper  pole,  capped  by  the  head  of  the 
epididymis,  lies  farther  outward  and  forward  than  the  more  pointed  lower  one,  which 
is  related  to  the  tail  of  the  epididymis  and  attached  to  the  scrotal  ligament  ("page 


I 


1942 


HUMAN   ANATOMY. 


FlO. 


3043).     The  testis  is  of  a  whitish  color,  and,  although  readily  yiddinii;,  imparts  a 
characteristic  impression  {>f  resilience  when  compressetl  between  the  tinkers. 

Architecture  of  the  Teitit. — The  framework  of  the  testicle  pr(>|>er  consists 
of  a  .Htout  capsule,  the  luni:a  albuginta.  a  dense  libro-elastic  envelope  from  .4-.  6  mm. 
in  thickness,  that  (;ives  form  to  the  organ  and  protects  the  subjacent  soft  glundular 
tissue.  Along  the  posterior  border  of  the  testis  the  capsule  is  greatly  thickened 
and  projects  forward  as  the  mediastinum  testis  or  corpus  Highmori,  a  wedge-shaped 
body  (from  2.5-3  cm.  'i  length ),  from  which  radiate  a  number  of  membranous  septa 
that  piiss  to  the  inner  surface  of  the  tunica  albuginea.  In  this  manner  the  space 
within  the  capsule  is  subdivided  into  pyramidal  compartments,  the  bases  of  which  lie 
at  the  periphery  and  the  apices  at  the  mediastinum.  These  spaces  contain  from  150 
to  200  pynform  masses  of  glandular  tissue,  more  or  less  completely  separated  from 
one  another,  that  correspond  to  lobules  (lobnli  testis).  Each  of  the  latter  is  made  up 
of  from  one  to  three  greatly  convoluted  seminiferous  tubules,  held  together  by  delicate 
vascular  intertubular  connt  .-live  tissue. 

The  seminiferous  tubules — from  .15-.  25  mm.  in  diameter  and  from  25-70  cm. 
( 10-28  in. )  in  length — begin  as  blind  canals,  which  are  moderately  branched  and 

very  tortuous  ( tubuli contorti)  throughout  their 
course  until  they  converge  at  the  apex  of  the 
lobule,  where  they  pass  over,  either  directly 
or  after  junction  with  another  canal,  into  the 
narrow,  straight  tubules  (tubuli  recti)  that 
enter  the  mediastinum  and  unite  into  a  close 
net-work,  the  rete  testis.  The  latter  extends 
almost  the  entire  length  of  the  mediastinum, 
and  consists  of  a  system  of  irregular  inter- 
communicating channels,  the  cuboid  epithelial 
lining  of  which  rests  directly  uj)on  the  en- 
sheathing  fibrous  tissue  of  the  mediastinum. 
With  these  passages  the  canals  of  the  testicle 
proper  end,  the  immediate  continuation  of  the 
spermatic  tract  being  formed  by  from  fifteen 
to  twenty  tubules,  the  ductuli  efferentes,  that 
pierce  the  tunica  albuginea  along  the  posterior 
border  and  near  the  upjier  pole  of  the  testis 
and,  forming  the  coni  vasculosis  connect  the 
sexual  gland  with  the  tube  of  the  epididymis. 
Structure. — In  contrast  to  the  dense 
fibrf)-elastic  tissue  that  composes  the  frame- 
work of  the  testis, — ;'  e  capsule,  mediastinum,  and  interlobular  septa, — the  con- 
nective tissue  occupying  the  spaces  between  the  seminiferous  tubules  is  loose  in 
texture  and  arrangement,  consisting  of  delicace  bundles  of  white  fibrous  tissue  in 
which  elastic  fibres  are  few  or  absent.  In  addition  to  the  plate-like  cells,  leucocytes, 
and  eosinophiles  that  occur  in  varying  numbers  within  the  meshes  of  this  tissue  in 
conjunction  with  blood-vessels  and  nerves,  groups  or  cord-like  masses  of  peculiar 
polygonal  elements,  the  interstitial  cells,  also  occupy  the  intertubular  stroma,  especi- 
ally in  the  vicinity  of  the  mediastinum.  These  cells  (Fig.  1654),  from  .015-.020 
mm.  .'.-  diameter,  possess  relatively  small  round  or  oval  eccentrically  placed  nuclei 
and  a  finely  granular  protoplasm  that  usually  contains  numerous  brownish  droplets, 
pigment  particles,  and,  sometimes,  crystalloid  bodies  in  the  form  of  minute  needles 
or  rods.  In  some  animals,  notably  in  the  hog,  the  deeply  colored  interstitial  cellr 
form  conspicuous  tracts  that  impart  a  dark  tint  to  the  testicle  in  section.  Their 
significance  is  obscure,  but  they  are  probably  modified  connective-tissue  elements 
deriveti  from  the  niesoblast  of  the  germinal  ridge  (Allen,  Whitehead). 

The  wall  of  the  convoluted  seminiferous  tubules  consists  of  a  delicate  tunica 
propria,  composed  of  an  inner  elastic  lamella  strengthened  externally  by  circularly 
disposed  fibres,  within  which  are  several  layers  of  epithelial  cells.  The  latter  vary 
not  only  before  and  after  the  attainment  of  sexual  maturity,  but  subsequently  with 
functional  activity  or  rest  ;  in  man,  however,  the  variations  depending  upon  these 


1651. 

GU>bui  Rujor  of  epiilid)-r«b 
•Vi»  deferrn< 

Cntll 
VHM-'Ulosl 

Ductus 
epitlidymidi* 
-Ourluli 
effereiitn 
Tubulj  recti 

.Retr  testis  in 
mediastinum 
Tubuli 
conturti 

Vat  abeirans 

Durtus 
rpididymidis 
Globus  minor 


Septum       Tunica  albufinea 


Dtaftam  showing^  relaliuna  of  secretory- 
tubules  ana  system  oit  ducts. 


THE  TESTES. 


«943 


causes  are  much  less  marked  than  in  animalst,  in  which  sexual  activity  is  limited  to 
dehnitc  periods.  Seen  in  sections  of  the  mature  human  testicle  (Fiy;.  1656  ),  the  epi- 
thelium lining  the  seminiferous  tubules  includes  two  chief  kinds  of  cells,  the  support- 
ing and  the  sptrmatogenelic.  The  former— the  cells  of  Ar/o/i— take  no  active  piirt 
in  the  production  of  the  spermatozoa,  but  serve  chieHy  as  temporary  sup|)orts  for  the 
more  essential  elements  during  certain  stages  of  spermatogenesis.  1  hey  are  elongated 
elements  of  irregularly  pyramidal  form  that  rest  by  cxi>anclc«l  biises  «|K)n  the  nu-m- 
brana  propria,  and  project  towards  the  lumen  ol  the  tubule  between  the  layers  of  the 


Fio.  163*. 


BpldM)inli 


ConvolutioM  o(  duct  u<  cpMidymto  in  ilobiu  mi)ur 


(-'(Hii  vaKulonl 
icinivolutloiis  ol 
cfivrrnt  ducts  i 


DiKttll 
ScnHu  rartacc  oi  toll* 


T«tlt 


Interlobular  septum 
Tunica  albuginea 


Effcmu  ducts 

'Sections  f^  tluct  of 
cpitlHlvmis 

Blood' vnseli 


R*lc  leatit  in  mediastinum 


■Lx}bu1es  of  (land-tissue 


•Convolutions  of  duct  of 
epididymis  in  xlobus  minor 


Sagittal  section  of  testicle  of  child,  5howin(t  ceneral  arrangement  of  framework  and 
Kland-lissuc  and  of  canals  connectmg  epididymis  witli  testis,    v  lo. 

surrounding  spermatogenetic  cells.  The  large  oval  nuclei  of  the  Sertoli  cells  are  con- 
spicuously meagre  in  chromatin,  and  lie  towards  the  middle  of  the  cell  at  some  distance 
from  its  base.  Th«.  outer  part  of  the  protoplasm  contains  fat-droplets,  the  inner  zone 
being  granular  or  often  longitudinally  striated.  Where  the  tubuli  contorti  pass  into 
the  straight  tubules  the  supportini;  cells  bemme  reduced  in  height  and  form  a  layer 
of  simple  colu-nnar  cells  continuous  with  the  low  cuboidal  epithelium  lining  the  rete 

testis.  ,  .      ,        ,    •        , 

The  S}>    •*.  f'ogenetic  cells  include  three  forms  that  stand  in  the  relation  of  .suc- 
ceeding gent,      loiis  to  one  another,  those  representing  the  oldest  lying  nearest  the 


1944 


HUMAN  ANATOMY. 


membrana  propria,  and  the  youngest,  from  which  the  spermatic  filaments  are  directly 
derived,  next  the  lumen  of  the  tubule.  The  first  generation,  the  spermatogones,  lie 
at  the  periphery  between  the  cells  of  Sertoli,  and,  although  small  round  elements, 

Fio.  Z653. 


Seminiferous  tubule, 
cut  obliquely 

Tunicm  albu^ni 


Seminiferous  tubule,x^ 
cut  transversely        -■ 


'.'.roup  of  interstitial  cells 


Tunici.  vaginalis 


vesKi 


Blood'Vessel 


Portion  of  cross-section  of  testis,  showine  dense  fibrous  envelope 
and  adjacent  seminiferous  tubules,    X  y>, 

possess  nuclei  exceedingly  rich  in  chr  matin.  The  division  of  these  cells  results  in 
two  cells,  of  which  one  retains  the  position  of  the  parent  cell,  which  it  replaces  as  a 
new  spermatogone  destined  for  a  succeeding  division,  while  the  other  passes  inward, 
enlarges,  and  becomes  a  mother  cell  or  primary  spermatocyte  of  the  second  genera- 
tion. This  element,  conspicuous  by  reason  of  its  size  and  large  nucleus,  undergoes 
mitotic  division  and  gives  rise  to  daughter  cells  or  secondary  spermatocytes.  The 
latter  almost  immediately  divide  and  produce  smaller  cells,  the  spermatids,  by  the 
transformation  of  which  the  spermatic  filaments  are  directly  produced.  It  is  impor- 
tant to  note  that  the  spermatids 
Fio.  1654  contain  only  one-half  of  the  num- 

ber of  chromosomes  normal  for 
the  ordinary  (somatic)  cells,  a 
like  reduction  (pa^ji-  18}  occur- 
ring in  the  matured  ovum. 

Spermatogenesis.  —  The 
cytological  cycle  resulting  in  the 
production  of  the  spermatozoa 
from  the  epithelial  cells  lining  the 
seminiferous  tubules  comjirises 
four  principal  stages  :  (i )  divi- 
sion of  the  spermat{)gones  into 
spermatocytes  ;  ( 2 )  division  of 
the  latter  into  spermatids;  (3) 
transformation  of  spermatids  into 
.spermatozoa  ;  (4 )  completed  dif- 
ferentiation and  iilx;ration  of  sper- 
matozoa. The  changes  incident 
to  the  first  and  second  of  these 
stages  have  been  outlined  ;  a  brief  account  of  the  subsequent  changes  may  here  be 
•iddcd.  The  -spermatids,  at  first  small  cells  with  rouiul  nuclei,  elongate,  their  nuclei 
coincidendy  becoming  oval  and  smaller,  but  rich  in  chromatin,  and  shifdng  to  the 


;g|  L  Si  Intertuhular 
,vSi/^'  ton  nect  i  vc 
'  ■   "  tissue 


«T 


''©^ 


Tunica 
propria 
of  tuhule 


Group  of  interstitial  cells  lying  within  intertuhular  stroma.      X  .vk>. 


THE  TESTES. 


•945 


end  of  the  cell  most  removed 
from  the  lumen.   The  modified 
spermatids  now  become  closely 
related  with  a  Sertoli  cell,  with 
the  protoplasm  of  which  they 
fuse.      The   structure    thus 
formed,  known  as  the  sperma- 
toblast, consists  of  an  irrejijular 
nucleated    conical    protophis- 
mic    mass  (Fig.    1657,    27). 
with  the  inner  end  of  which  the 
radiating  clusters  of  partially 
fused  spermatids  are  blended. 
The   succeeding  changes    in- 
clude the  transformation  of  the 
elongated  nucleus  of  the  sper- 
matid into  the  head  and  of  its 
centrosome   into  the  middle- 
piece  of  the  spermatic  filament, 
while  from  the  protoplasm  of 
the  spermatid,  possibly  in  con- 
junction with  that  of  the  sper- 
matoblast, the  flagellate  tail- 
filament  is  derived.      As  the 
spermatozoa    become     more 
and  more  differentiated,  they 
appear  as  fan-shaped  groups 
in  which  the  heads  are  always 
buried   within  the   spermato- 
blast and  the  tails  directed  to- 
wards the  lumen  of  the  canal. 
After  separation,  which  subse- 
quently takes  place,  the  liber- 
ated spermatozoa  occupy  the 
centre  of  the  tubule  as  masses 
which  often  occlude  its  lumen 
and  in  which  the  seminal  fila- 
ments are  disposed  in  peculiar 
whorl-like  groups.  Their  com- 
plete development,  however, 
is  deferred   until   they  reach 
the  tube  of    the  epididymis, 
during  the   passage   through 
which   highly    tortuous   path 
they  attain  maturity  and  lose 
the   protoplasmic   remains  of 
the  spermatids  that  usually  for 
a  time  adhere  to  the  middle- 
piece.     The   spermatogenetic 
process  docs  not  involve  uni- 
formly all  parts  of  the  seminif- 
erous tubulo,  but  is  manifested 
with    wave -like    periodicity; 
consequently    sections   taken 
through  the  same  tubule  a  few 
millimetres  apart  exhibit  dif- 
ferent stages  of  the  cycle,  al- 
though the  cells  are  never  all 
of  one  phase. 


Fio.  1655. 


Dilatol  rtuct 


Bloo<!-vesseI 
Part  of  mediaBtinum.  showing  irregular  channels  of  rele  testis.     >  75. 

Fig.  1656. 

Tunica  propria 

Secondary  spermatocyte 
Spermatids 


Spermatitis  Iwiiiff 
transformetl  itito  spermatozoa  t^'\ 


SecoiKiary  spermattRV^e         -^Jv: 
Spermato/on 


InntT- 
lameDa  

Sertoli  cell  '  r~^~^^tS,\ 

Resting  si)ermat(>Ktnie 

Dividing  s|iermat<iKune  (primary  s|iernialin\te) 

Turlioii  I'f  »i-nilhiltr,iu.s  tut.uli .  cut  tr.in-.vcnicly,  -htmiiiK  'ii>ii>ii 
celU  in  various  stages  of  spermatogenesis.     X  350- 


1946 


HUMAN  ANATOMY. 


The  spermatic  filaments  or  spermatozoa,  the  essential  male  reproductive 
elements,  are,  hke  the  ova,  direct  derivations  of  epithelial  cells  that  ire  dracendants 

Flo.  1657. 


niaKiam  illiMtratinr  phaan  of  one  romplete  cycle  of  spermatogenesis.  Sequence  of  fieures  shows  in 
det.-i.l  Krowth  ( 1-6)  and  division  (7-S)  of  siKrSiatoKone ;  growth  and  .Tivision  ofprimary  spermat^vte  (^li^ 
1110  secmdary  sr*rmatoc>1es  ;  division  of  latter  ( 1.JI21 )  into  siK^rmati.ls  (22-24 1:  fusion  of  th\^  wrth^rtoircel 
to  (onn  siKrrmatoblast  (25-26);  digeremiation  (27-Ji  ( and  final  liberation  (32)  of  spermatc.zia(^/,rA'«i.,^) 

of  the  primary  indifferent  sexual  elements.     Unlike  the  ova,  however,  which  are  rela- 
tively large  and  often  absolutely  huge,  and,  apart  from  size  and  minor  distinctions, 
p  fairly  similar  in  all  vertebrates,  the  sper- 

5  matic  filaments  present  great  diversity 

in  form  and  detail  and  represent  a  high 
degree  of  specialization.  The  human 
spermatic  filament  is  small,  and  consists 
of  an  ovoid  Aead,  a  cylindrical  middle- 
piece  of  uncertain  extent,  and  a  gready 
attenuated  and  prolonged  tail, — the 
propelling  organ  of  the  flagellated  cell. 
The  mature  element  measures  about 
.050  mm.  in  its  entire  length,  of  which 
only  about  .005  mm.  is  contributed  by 
the  head,  prolxibly  about  the  same  by 
the  middle-piece,  and  from  .040-.045 
mm.  by  the  tail.  The  head,  somewhat 
flattened  in  front  and  hence  pyriform 
in  profile,  although  rich  in  chromatin, 
appears  homogeneous,  since  the  chro- 
matin is  uniformly  distributed  and  not 
Tt,„  „»„    »      1  u    •      t    ..  arranged   as   threads  or   mesh -works, 

structural  basis  .■    the  remaining  parts  of  th.'  spermatic  element  is  a  delicate 
axial  Jihre  that  extends  Ironi  the  head  to  the  tip  of  the  tail  (Fig.  12)  and  is  in- 


Human  spermatic  filaments  seen  from  the  hroad  sur- 
faif.  except  a.  which  is  in  profile.      •  hoo 


THE  EPIDIDYMIS. 


<947 


vested  by  a  delicate  envelope,  with  the  exception  of  the  last  .005-006  mm.  that  con- 
tinues uncovered  as  the  attenuated  end-piece.  In  front  a  mmute  spherical  thicken- 
ing the  end-knob,  marks  the  termination  of  the  axial  fibre,  where  it  joins,  but  does 
not  penetrate,  the  head,  and  probably  represents  the  centrosome  of  the  spermatid. 
Within  the  middle  uiece  the  envelope  surrounding  the  axial  hbre,  after  the  action 
of  certain  stains,  exhibits  markings  that  suggest  the  presence  of  a  spirally  arranged 
filament  of  great  '  elicacy. 

THE  EPIDIDYMIS. 

The  epididymis,  the  gready  convoluted  beginning  of  the  seminal  duct,  is  a 
crescentic  body,  triangular  in  section,  that  covers  the  entire  posterior  border  and  the 
adiacent  pait  of  the  outer  surface  of  the  testis.  Its  enlarged  upper  end  or  globus 
maior  (caput  epididymldis)  covers  the  superior  pole  of  the  sexual  gland  and  is  attached 
to  the  latter  not  only  by  connective  tissue  and  serous  membrane  (as  is  the  globus 
minor)  but  by  the  efferent  ducts  that  establish  communication  between  the  testis  and 
its  excretory  canal.  The  succeeding  part,  the  body,  gradually  tapers  as  it  descends  to 
the  lower  pole,  at  which  point  the  epididymis  presents  a  second  and  less  conspicuous 
enlargement,  the  globus  minor  (cauda  epididymidis),  that  bends  backward  to  liecome 
the  vas  deferens.    The  latter  passes 

upward  along  the  median  side  of  '''°-  '  so- 

the  posterior  border  of  the  epidid- 
ymis to  ascend  in  the  spermatic 
cord.  Where  attached  to  sur- 
rounding structures,  as  at  its  two 
ends  where  in  contact  with  the  tes- 
ticle and  along  its  posterior  border 
where  blended  with  the  spermatic 
cord,  the  epididymis  is  devoid  of 
serous  covering  ;  in  other  places 
it  is  completely  invested  by  the 
tunica  vaginalis,  a  deep  recess,  the 
digital  fossa  (s.nus  epididymidis) 
intervening  between  the  body  of 
the  epididymis  and  the  adjacent 
surface  of  the  testis.  The  bulk  of 
the  globus  major  depends  upon 
the  aggregation  of  from  twelve  to 
fifteen  conical  masses  (lobuli  epi- 
didymidis) formed  by  the  effenni 
ducts  and  their  tortuosities,  the 
coni  lasculosi,  that  pass  from  the 
upper  end  of  the  testis  and  connect 
the  rete  testis  with  the  canal  0/ 
the  epididymis. 

The  latter  (ductus  epididymi- 
dis)  bepi"^-  ing  in  the  globus  major,  receives  the  efferent  ducts  and  becomes  greatly 
convol'  ..,  the  extraordinary  windings  of  the  single  tube  contributing  the  chief  bulk 
of  the  body  and  the  tail  of  the  epididymis.  When  unravelled,  the  canal  measures 
from  5-5.5  m.  ( 18-20  ft. )  in  length,  its  remarkable  convolutions  sufficing  to  pack 
awav  this  long  duct  within  the  small  volume  of  the  epididymis. 

Structure.— The  conical  lobules  of  the  globus  major  are  enclosed  by  a  fibrous 
envelope  resembling  but  less  robust  than  the  tunica  altniginea  testis,  within  which  the 
convolutions  of  a  single  tubule  are  held  together  by  delicate  vascular  connective  tissue. 
The  transition  of  the  channels  of  the  rete  testis  into  the  efferent  ducts  is  marked  by 
an  abrupt  change  in  the  character  of  the  lining  epithelium,  the  low  cuboidal  cells  of 
the  former  giving  place  to  irregularly  ciliated  columnar  elements  within  the  latter. 
.e  tubules— from  .i-.5  mm.  in  diameter— present  .m  irregular  lumrn,  owing  to  the 
inconstant  thickness  and  pitted  surface  of  their  epithelium.     Just  before  terminating 


Kflerent  ducts 

•Rete  testis 


Glohu 
minor 


Pyramidal  lobules  of  gland-tissue  (seminiferous  tubules) 


Dissection  of  testicle  alter  tubules  have  been  filled  with  quick- 
silver; testis  has  been  separated  into  the  component  lobules. 


1948 


HUMAN  ANATOMY. 


Fibrous  envelope 


VaH  aberrans 


in  the  canal  of  the  epididymis,  the  tubules  become  narrowed  and  surrounded  by  a 
thin  layer  of  circularly  disposed  involuntary  muscle.  The  cana/  of  the  epididymis — 
from  .4-5  mm.  in  diameter — is  lined  throughout  by  a  double  layer  of  tall  and 
slender  columnar  cells,  the  free  ends  of  which  bear  groups  of  cilia  of  exceptional 
length  that  adhere  and  form  pointed  tufts  surmounting  the  cells.  A  noteworthy 
feature  of  the  wall  of  the  canal  is  the  layer  of  involuntary  muscle,  from  .01 5-.  030  mm. 
in  thickness,  that  encircles  the  membrana  propria  and,  especially  in  the  globus  minor, 

almost  entirely  replaces  the  stroma 
Fio.  1660.  „f  ti,g  mucous  membrane.     Exter- 

nally the  muscle  fades  into  the  con- 
nective tissue  holding  toj;  'ler  the 
convolutions  of  the  canal. 

Vessels  of  the  Testis  and 
Epididymis. — The  arteries  sup- 
plying these  organs  are  the  sper- 
matic and  the  deferential,  the  former 
being  distributed  especially  to  the 
testis  and  the  latter  to  the  epi- 
didymis. An  additional  source  is 
provided  by  anastomoses  with  the 
cremasteric  artery.  The  spermatic 
artery  (a.  testicularls)— a  slender 
branch  from  the  abdominal  aorta 
arising  a  short  distance  below  the 
renal — is  distinguished  by  its  long 
course  necessitated  by  the  migra- 
tion of  the  sexual  gland  from  the 
lumbar  region  into  the  scrotum. 
On  reaching  the  posterior  surface  of 
the  testicle,  it  divides  into  three  or 
four  branches  that  enter  the  medi- 
astinum and  break  up  into  super- 
ficial and  deep  twigs,  which  follow 
the  tunica  albuginea  and  the  septa 
respectively  and  form  the  rich  ca- 
pillary net-works  surrounding  the 
seminiferous  tubules.  One  or  more 
branches  pass  to  the  head  of  the 
epididymis  and  anastomose  with  the 
artery  of  the  vas.  The  latter  (a.  defercntialis),  from  the  inferior  or  superior  vesical, 
accompanies  the  spermatic  duct  and  supplies  chiefly  the  body  and  tail  o*  vhe  epididy- 
mis, by  its  connections  with  the  spermatic  artery  establishing  an  anastomosis  that 
may  become  of  importance  in  maintaining  the  nutrition  of  the  testicle. 

The  veins,  superficial  and  deep,  emerge  from  the  testis  and,  joining  with  thos^ 
from  the  globus  major,  form  several  stems  of  considerable  size  that  ascend  within  the 
spermatic  cord  in  front  of  the  vas  deferens,  while  those  from  the  body  and  tail  of 
the  epididymis  unite  into  a  smaller  (xjsterior  group  that  accompany  the  canal 
(page  i960). 

The  lymphatics  of  the  testicle,  beginning  in  the  walls  of  the  tubules  and  the  sur- 
rounding connective  tissue,  follow  in  general  the  coiirse  of  the  veins  as  a  superficial 
and  a  deep  set,  and  emerge  as  a  half-dozen  or  more  relativelv  large  trunks  to  which 
the  lymphatics  of  the  epididymis  are  tributary.  Within  the  spermatic  cord  they  ac- 
comp.-iny  the  groups  of  veins,  and  finally  empty  into  the  lumbar  lymph-nodes. 

The  nerves  of  the  testis  and  epididymis,  chiefly  sympathetic  fibres  destined 
for  the  walls  of  the  blood-vessels,  accompany  the  latter  as  the  spermatic  and  the 
deferential  plexuses  that  surround  the  corresponding  arteries.  Medullated  fibres, 
probably  conveying  sensor)'  impressions,  occur  among  the  inure  usual  pale  ones. 
The  relations  between  the  terminations  of  the  nerves  and  the  tubules  are  uncertain, 
Letzerich  and  .Sclavunos  describing  intercellular  filaments  within  the  canals  in  addition 


VaF  deferens 
Section  across  lower  part  of  epididymis, 


THE  APPENDAGES  OF  THE  TESTICLE. 


1949 


Epididymis 


ApiwiKlix  testis 


THE  APPENDAGES  OF  THE  TESTICLE. 

Under  this  heading  are  ...eluded  --J^'ti"S^::,Se:^i;j.ed\: 
variable  period,  some  throughout  Ufe  as  mor^  "J^'^^^Z  <"  ly  on  account  oC  their 
the  testis  or  to  the  epididymis    J'^^'^X  t  nee  they  may  become  the  seat   of 
.teresting   ^'''^trJicL  cKgl-s      Th^n  «riS^^^  the  appe.JJ.v 

I^X  S  Ta^^^^^t^'^:  (3!  the  parajJyn^s,  and  (4)  the  .asa  a^-r- 
''"""^u     o«n..ndix  testis    often  called  the  totsta.'Jked  or  scssi/e  hydatid,  is  a  small 

form  is  irregular.     Its  free  end  often  f.g.66.. 

presents  a  shallow,  funnel-hke  de- 
pression surrounded  by  a  denuted 
margi.1,  the  whole  suggest.ng  the 
fimbriated  end  of  the  oviduct  m  minia- 
ture, a  resemblance  supported  by  the 
embryological  significance  o!  the  ap- 
pendage as  the  remains  of  the  cranial 
end  of  the  Miillerian  duct  (page 
^o^8)  overgrown  and  enclosed  by 
connective  tissue.  In  structure  the 
appendage  consists  of  a  vascular  con- 
nective-tissue stroma  m  which  lies 
embedded  a  minute  canal,  of  variable 

size  and  extent,  lined  with  columnar 

epithelium.     Usually  the  canal  ends 

blindly,   but  in  exceptional  cases  it 

may  open  on  the  free  surface. 

Inconspicuous  additional  appen- 
dages of  the  rete  testis  have  been 

described  by  Roth  and   by  Poiner, 

which  consist  of  blind  tubules  that 

extend  from  the  testicle  into  the  lower 

end  of  the  globus  major,  either  lying 

SSI^tScW  "^         "SS^s  on  the  fVee  surface      Thev  probal.ly  represent 
tSremarns  oTw^lh  ales  that  faile-'    -.  retain  their  connection  with  the  canal  of 

the  f  .^''iy^li^^^jy^"''    idid^^  or  stalked  hydatid,  much  less  constant  than  the 

•i  ??^noI  cent   ace  -rdinsi  to  Toldt),  apt^ars  as  a  small  pyriiorm  »«dy  ( .n.m 

n  mnrin  iL'gth     ataXed  to'tLe  upper  polT  of  the  globus  major  <  Fig-   .650). 

'^"''■According  to  Toldt.  an  additional  minute  body  (louy  A':?''^:"'7'\^';'|S*ihe 
&'"'o'r":rrtly  ^disconSd      This   tube   is  frequently  the  seat  of  cysts  which,- 


SsKltUl  section  ot  appendix  testis.     V  as- 


I 


I950 


HUMAN   ANATOMY. 


when  the  canal  retains  its  connection  with  the  epididymis  or  testis,  may  contain 
spermatozoa. 

The  paradidymis,  or  organ  of  Giraldis,  consists  of  an  irregular  group  of  blind 
tubules  (from  5-6  mm.  in  extent)  that  lie  within  the  lower  end  of  the  spermatic  cord, 
above  but  close  to  the  globus  major  and  always  in  front  of  the  venous  plexus.  This 
organ  {upper  paradidymis  of  Toldt)  is  regarded  as  representing  a  partial  per- 
sistence of  the  rudimentary  tubules  of  the  Wolffian  body  (page  1936)  and  is,  there- 
fore, the  homologue  of  the  paroophoron.  It  is  essentially  a  fcEtal  structure,  usually 
entirely  disappearing  after  the  first  few  years  of  childhood.  The  tubules  (from  .  i-.  2 
mm.  in  diameter  and  lined  with   ciliated  epithelium)  rarely  give  rise  to  cysts. 

The  vasa  aberrantia  (ductuli  abcrrantes)  include  tubular  appendages — usually 
two,  but  sometimes  only  one — that  extend  for  a  variable  distance  within  the  epididymis 
and  end  blindly.  The  upper  and  shorter  one  is  attached  to  the  rete  testis  and  pur- 
sues a  downward  course  within  the  epididymis.  The  /ower  and  larger  one,  often 
,^0  cm.  (12  in. )  or  more  in  length,  passes  upward  from  the  lower  part  of  the  canal 
of  the  epididymis  and  consists  of  one  or  more  convoluted  tubes  of  considerable  size. 
Both  are  to  be  regarded  as  probably  originating  from  the  Wolffian  tubules. 


PRACTICAL  CONSIDERATIONS:    THE  TESTICLES. 

Monorchism — the  absence  of  one  testicle  (not  to  be  confounded  with  cryptor- 
chism,  vide  infra) — has  been  shown  at  autopsies  to  occur  occasionally.  It  is 
attended  by  no  symptoms. 

Anarchism — the  absence  of  both  testicles — may  be  inferred  when  the  scrotum 
is  also  absent  or  incompletely  developed,  and  there  is  a  rudimentary  condition  of 
the  external  genitalia  ;  impotence,  sterility,  and  the  physical  and  mental  attributes 
of  eunuchism  appear  later. 

Arrest  of  descent  of  one  or  both  testicles  (page  2040)  may  occur  at  any  point 
between  the  lower  border  of  the  kidney  and  the  bottom  of  the  scrotum.  The  chief 
forms  are:  (a)  Abdominal  Retention  (cryptorchism,  unilateral  or  bilateral)  :  the 
testicle  may  be  applied  to  the  posterior  abdominal  wall  in  close  relation  to  the  lower, 
outer  border  of  the  kidney  ;  it  may  be  provided  with  a  long  mesorchiiim,  allowing 
it  to  move  freely  in  the  abdominal  cavity,  or  it  may  lie  in  the  iliac  fossa  close  to  the 
internal  ring  ;  (^)  Inguinal  Retention  :  the  testicle  may  be  arrested  at  the  internal 
ring,  in  the  inguinal  canal,  or  at  the  external  ring.  It  is  usually  extremely  mobile 
until  subject  to  repeated  attacks  of  inflammation  and  fixed  by  adhesion,  (f)  Cruro- 
Scrotal  Retention  :  the  testicle  may  pass  through  the  external  abdominal  ring,  but 
fail  to  descend  completely,  lying  in  close  relation  to  the  ring  or  at  a  varying  distance 
bflow  it.  Of  these,  inguinal  retention  is  the  most  common.  Adhesions  from  prenatal 
peritonitis  in  a,  small  size  of  the  external  ring  in  i>.  and  undue  shortness  of  the  cord 
or  of  one  of  its  constituents  in  c  have  been  thought  to  explain  some  of  these  cases. 

Aberrant  descent  (ectopy),  in  which  the  testicle  leaves  its  normal  route,  may 
occur  in  one  of  several  forms,  (a)  \\\  peno-pubic  ectopy  the  testicle  is  found  beneath 
the  skin  of  the  abdomen  al)ove  the  root  of  the  penis,  (b)  In  perineal  ectopy  the 
testicle  is  felt  as  a  freely  movable,  ovoid  turr:<^r,  sensitive  to  pressure,  lying  on  one 
side  of  the  central  raphe,  and  placed  in  front  of  the  anus  ;  the  cord  can  often  be 
traced  from  the  tumor  to  the  external  abdominal  ring.  The  overlying  skin  some- 
times exhibits  ruga»,  and  the  corresponding  side  of  the  scrotum  is  often  atrophied. 
ic)  Femoral  ectopy  appears  as  a  movable  tumor  exhibiting  the  physical  character- 
istics of  the  testicle  and  the  peculiar  sensitiveness.  Its  position  is  that  of  complete 
femoral  hernia  or  of  the  inflammatory  swellings  which  so  commonly  affect  the  glands 
overlying  the  saphenous  opening. 

Of  these,  perineal  ectopv  is  the  usual  form.  Irregular  de\'elopment  of  the 
gubernaculum  may  explain  a  and  c,  as  certain  of  the  fibres  of  the  genito-inguinal 
ligament  run  to  the  pubic,  lower  inguinal,  and  inguino-femoral  regions,  and  their 
over-development  might  draw  the  testicle  in  front  of  the  pubes  or  into  the  femoral 
canal.  Exceptional  attachments  (which  have  been  shown  to  exist)  of  the  guber- 
jiaculum  below  to  the  tuber  ischii  or  sphincter  ani  may  account  for  at  least  some  of 
the  cases  included  in  b. 


PRACTICAL   CONSIDERATIONS:    THE  TESTICLES.  lysi 

In  its  bearing  on  the  development  and  course  of  hernia  and  inrtammatit)n  the 
relation  of  inisplacwl  testicle  to  the  peritoneal  pt.uch,  which  accompana-s  it,  is  of 
treat  imporfcince.  This  pouch  may  remain  oin-n.  conmunicatniK  freely  with  the  gen- 
eral peritoneal  cavity,  thus  enhancing  the  probability  of  the  formation  of  hernia  (.r  of 
the  extension  of  inflammation  ;  it  may  be  closed  above  but  oi>en  below  the  testicle, 
favoring  the  development  of  hydrocele  ;  it  may  be  obliterated.  Kxceptionally.  csi)e- 
ciallv  when  the  testicle  is  retained  but  the  vas  has  jxirtly  or  completely  descended, 
the  funicular  process  of  the  peritoneum  may  e.xtend  as  an  open  iM.uch  to  the  lK)ttoni 
of  the  scrotum,  thus  allowing  a  hernia  to  pass  far  lieyond  the  position  of  the  retained 

**^"  Occasionally  the  testicle  is  found  in  the  front  of  the  scrotum  (the  epididymis 
anterior  and  the  vas  deferens  in  front  of  the  other  constituents  of  the  cord  )  as  it  it 
had  made  a  semi-revolution  on  its  vertical  axis  {inversion  of  the  testicle  ).  1  he  pos- 
sibility of  the  existence  of  this  anomaly  emphasizes  the  propriety  o  deterimninK  by 
palpation  and  by  the  test  of  translucency  the  position  ot  the  twticle  before  tapping 
for  hydrocele  ;  or,  if  these  fail,  of  evacuating  the  fluid  by  incision  instead  of  with  a 

^'"^""'■hrsion  (axial  rotation)  of  the  testicle,  including  the  sperniatic  c'lrd,— also  on 
its  longitudinal  axis,— is  an  accident  which  usually  affects  imperfectly  descended  tes- 
ticles but  is  not  confined  to  them.  The  cause  is  probably  a  congenital  malformation^ 
since  as  Owen  has  pointed  out,  a  testis  property  placed  m  the  scrotum  and  possessed 
of  a  normal  mesorchium  cannot  be  twisted.  The  twist  may  be  in  either  direction,— 
to  the  right  or  to  the  left,— and  in  accordance  with  its  extent  and  the  degree  of  con- 
striction to  which  the  vessels  are  subject  the  symptoms  are  slight  or  severe.  In  slight 
cases  the  epididymis  alone  becomes  infiltrated.  In  severe  cases  the  entire  gland  with 
the  epididymis  becomes  gangrenous.  ....  i,    t    :,u,.r 

Orchitis— as  distinguished  from  epididymo-orchitis— is  rare  as  a  result  of  eithir 
trauma  or  infection,  owing  to  the  firm  support  the  gland  receives  fr.m  the  tunica  allni- 
irinea  and  to  the  free  movement  of  the  testicle,  not  only  within  its  serous  tunic,  but 
also  within  the  .crotum,  and,  on  the  other  hand,  to  the  fact  that  septic  organisms 
eaining  access  to  the  ejaculatory  duct,  or  brought  to  the  gland  in  the  general  circula- 
tion, are  in  either  case  arrested  and  given  the  opportunity  to  multiply  in  the  neigh- 
borhood of  the  epididymis.  .  ,  •  .   •  i  . 

The  intimate  investment  of  the  testicle  by  the  tunica  vaginalis,  which  is  complete 
except  at  the  point  of  entry  and  emergence  of  the  vessels  at  its  posterior  border,  but 
which  leaves  the  whole  hinder  aspect  of  the  epididymis  without  a  serous  covering, 
determines  the  frequency  with  which  serous  effusion  (acute  hydrocele)  occurs  in 
contusions  or  inflammations  of  the  testicle  proper  as  compared  with  those  of  the 

epi  '^y^'^^-^^.j^^  ^^^^  investment  of  the  former  by  the  tunica  albuginea  accounts  for 
the  relatively  greater  pain  and  slower  swelling  in  orchitis.  It  also  brings  about,  when 
by  ulceration  a  communication  with  the  cutaneous  surface  has  been  established,  the 
slow  protrusion  of  the  swollen  and  infected  testicular  substance,  known  as  hernia  tn 
fungus  testis,  analogous  to  hernia  or  fungus  cerebri,  the  physical  conditions--enclo- 
sure  of  peculiarly  soft  and  yielding  tissue  within  a  dense  and  resisting  membrane— 
being  similar  in  the  two  instances.  The  sickening  pain  following  contusion  of  the  tes- 
ticle or  often  associated  with  orchitis,  is  due  to  pressure  upon  or  irritation  of  testicu- 
lar nerves  which,  by  way  of  the  spermatic  plexus,  communicate  with  the  aortic  and 
solar  sympathetic  plexuses.  A  similar  communication  with  the  renal  plexus  explains 
the  testicular  pain  and  retraction  accompanying  the  passage  of  a  renal  calculus  1  he 
primary  development  of  the  testicle  in  the  vicinity  of  the  tenth  dorsal  vertebra  has 
determined  its  chief  inner%'ation  from  the  tenth  dorsal  segment  of  the  cord  (Head) 
and  thus  its  relation  to  the  posterior  divisions  of  the  lower  dorsal  and  the  lumbar 
nerves  which  causes  the  "  backache"  so  commonly  felt  in  orchitis,  in  the  presence  of 
a  solid  tumor  of  the  testicle,  or  after  injecting  the  sac  of  a  hydrocele.  The  epididy- 
mis derives  its  nerve-supply  chiefly  from  the  pelvic  plexus,  which  also  supplies  the 
vas  deferens  and  the  seminal  vesicles.  As  it  communicates  with  the  spermatic  plexus, 
the  same  symptoms  may  be  associated  with  an  epididymitis  ;  but  as  swdling  is  less 
resisted  and  pressure  is  therefore  less,  and  as  the  communication  with  the  great 


«952 


HUMAN   ANATOMY. 


abdominal  plexuses  is  more  indirect,  ' '  testicular  nausea' '  is  less  pronounced  and  is 
(if ten  absent 

^ididymo-orchitis  is  usually  of  infectious  origin,  the  gonococcus  and  the  bacillus 
tuberculosis  being  the  micro-organisms  most  often  found,  although  the  inflammation 
may  occur  in  the  course  of  any  infectious  disease,  as  scarlatina,  mumps,  or  typhoid 
fever. 

The  direct  channel  offered  by  the  vas  deferens  explains  the  localization  of  the 
gonorrhuL-al  infection  (page  1954);  the  division  of  the  spermatic  artery  at  the  epidid- 
ymis, and  the  fact  that  the  arteries  of  the  epididymis  are  smaller  and  more  tortuous 
than  those  of  the  vas  or  of  the  testicle,  and  the  consequent  slowing  up  of  the  blood- 
current  (favoring  bacterial  growth),  may  account  for  the  preference  shown  the  epidid- 
ymis by  the  general  infections.  Syphilis  more  often  affects  the  testicle  itself  because 
syphilitic  orchitis  is  usually  a  late  manifestation  ;  the  disease  at  this  stage  shows  its 
customary  predilection  for  fibrous  and  connective-tis.sue  structures,  and,  beginning,  as 
it  often  does,  as  a  cellular  infiltration  of  the  tunica  albuginea,  it  follows  the  trabecule 
into  the  interior  of  the  gland.  When  syphilis  affects  the  testicle  during  the  second- 
ary stage,  it  behaves  like  other  infections  and  is,  at  least  at  first,  Iodized  in  the 
epididymis. 

A  certain  numl)er  of  cases  of  epididymo-orchitis  follow  strain,  there  having 
been  no  known  infectious  cause  and  no  direct  trauma.  They  have  the  usual  symp- 
toms,— apt  to  be  slight  at  first, — and  occur  with  much  greater  frequency  on  the  left 
than  on  the  right  side.  Two  of  various  theories  as  to  their  production  are  inter- 
esting from  the  anatomical  stand-point.  («)  Violent  contraction  of  the  cremaster 
muscle,  which,  by  suddenly  jerking  the  testicle  against  the  pillars  of  the  external 
ring,  causes  bruising  of  the  gland-tissue  and  the  epididymis.  The  cremaster  is  cer- 
tainly capable  of  vigorous  contraction.  Thus  it  is  not  rarely  observed  that  direct 
trauma  of  the  testicle  is  followed  by  marked  retraction  of  the  organ,  so  that  it  may 
Ih;  drawn  into  the  inguinal  canal  or  even  into  the  abilominal  cavity.  Even  in  severe 
pain,  such  as  that  which  accompanies  renal  colic,  the  testicles  are  frequently  found 
in  close  apposition  to  the  external  ring,  while  any  one  can  observe  the  contraction 
of  the  cremaster  by  noticing  the  motion  of  one  or  both  testicles  during  the  passage 
of  a  catheter.  Certain  cases  of  chorea  of  the  testicle  are  at  times  observed  when 
this  organ  is  moved  by  the  cremaster  with  considerable  rapidity  and  violence. 
(<i)  Rupture  of  some  of  the  veins  of  the  spermatic  plexus,  which  are  peculiariy  under 
the  influence  of  intra-abdominal  pressure,  are  provided  with  but  few  and  imperfect 
\  alves,  are  feebly  supported  by  the  surrounding  tissues;  and  hence  are  especially 
subject  to  disease.  Thus  varicosity  of  these  veins  is  one  of  the  most  common  sur- 
gical affections,  and  the  effect  of  the  contraction  of  the  abdominal  parietes  and  the 
diaphragm  upon  the  dilated  veins  is  so  marked  that  siiccussion  on  coughing  or 
straining  in  anv  way  is  sufliciently  distinct  to  simulate  that  of  an  omental  hernia. 
Given,  then,  a  sudden  and  violent  increase  of  pressure  in  these  vessels,  it  is  perfectly 
possible  to  conceive  that  rupture  may  occur,  even  although  they  are  healthy  ;  this  is, 
of  course,  more  probable  if  they  are  weakened  and  dilated.  Such  a  rupture  would 
naturally  take  place  in  the  cord,  in  the  epididymis,  or  even  in  the  sul)stance  of  the 
testicle.  And,  if  the  theory  of  venous  rupture  from  pressure  is  correct,  we  should 
expect  the  left  testicle  to  be  more  frequently  in\  olved  ( as  the  veins  of  this  side  are 
more  frequently  varicose),  and  the  pain  to  be  slight  at  first  and  gradually  increase  as 
more  blood  was  effused  and  inflammatory  symptoms  developed. 

It  is  not  improbable  that  both  of  these  factors  are  concerned  in  the  production 
of  this  form  of  epididvmo-orchitis. 

The  various  tumors  of  the  testicle  have  no  especial  anatomical  significance  except 
as  to  the  routes  by  which  thev  involve  the  nearest  lymph-nodes  {^vide  infra). 

Castration,  unless  modified  by  extensive  malignant  disease,  is  usually  done  by 
means  of  an  incision  which  may  l^e  placed  over  or  just  beneath  the  external  abdomi- 
nal ring  or  even  lower,  and  extends  through  the  scrotal  tissues,  but  not  into  the 
tunica  vaginalis  The  gland  with  its  coverings  may.  if  normal,  easily  be  shelled  out 
and  the  cord  isolated,  transfixed,  ligated,  and  divided.  If  the  vascular  constituents 
of  the  cord  are  ligated  separately,  three  arteries — the  cremasteric,  the  spermatic,  and 
the  deferential — must  lie  tied.     The  deferential  artery  is  found  close  to  the  vas,  and 


THE  SPERMATIC   DUCTS. 


1953 


with  it  are  a  few  veins  ;  the  cremasteric  lies  to  the  outer  side  of  the  cord,  near  its 
surface  ;  the  spermatic  is  in  front  of  the  cord,  surrounded  by  the  anterior  group  ot 
veins,  and  can  scarcely  be  distinguished  from  them  Each  artery  should  have  a 
separate  ligature,  but  the  two  sets  of  veins  may  be  tied  en  masse;  the  divided  cord 
should  be  secured  with  artery  forceps  until  the  end  of  the  oi)eration. 

When  the  cord  is  extensively  involved,  the  incision  should  lie  cxtetided  up  along 
Pouoart's  ligament.  It  is  deepened  to  the  peritoneum,  which  is  stripped  up,  allowing 
acceM  to  the  lymph-nodes  of  the  pelvis.  When  the  lymphatic  involvement  extends 
upward  beyond  reach,  it  may  be  attacked  through  a  transperitoneal  opening.  1  he 
n^es  into  which  the  lymph-vessels  of  the  cord  ,«ss  completely  surround  the  aorta. 
There  is.  moreover,  one  lying  up<jn  the  external  iliac  artery  which  probably  will  be 

'"^°  HvdroceU—^n  efTusion  into  the  tunica  vaginalis— may  begin  in  the  acute  form 
(vide  supra),  may  result  from  disease  of  the  cord,  the  epididymis,  or— more  par- 
icularly--th;  testis,  or  may  appear  to  be  "idiopathic."-,...,  with  no  d«coverable 
preceding  pathological  condition  of  the  scrotal  contents.  In  the  majority  o  such 
cases  it  IS  thought  (Jacobson)  that  the  effusion  of  fluid  commences  passively  and 
without  any  irritation  or  inflammation  to  begin  with,  the  causes  predisposing  t<.  its 
production  being  the  pendent  position,  the  less  vigorous  condition  of  the  cremaster 
and  dartos,  feebler  cardiac  circulation,  deficiency  of  tone  in  the  scrotal  blood-vessels 
and  lymphatics,  together  with,  perhaps,  a  tendency  to  venous  congwtion  from 
hepatic  and  renal  d^enerati.<n.  All  these  conditions  which  combine  to  bring  about 
a  passive  effusion,  are  naturally  .,.<«t  active  in  middle  life,  this  being  the  age  when 
the  ordinary  hydrocele  of  the  tunica  vaginalis  is  most  frequently  met  with.  After  a 
while,  as  the  fluid  increases  in  bulk,  it  becomes,  from  exposure  to  friction  etc 
liable  to  irritation  and  to  inflammatory  changes,  which  show  themselves  in  both  the 
fluid  and  the  tunica  vaginalis  itself.  ...      •  .•  j      •     .1,    ^u.,. 

The  anatomical  relations  of  the  effusion  to  the  testicle  and  epididymis,  the  char- 
acteristic slow  increase  in  size  of  the  affected  side  of  the  scrotum,  the  effaccment  o 
the  rugs,  the  drag  upon  the  cord,  and  the  referred  pams  sometimes  caused  by  it 
have  been  s-ifficiently  explained  {vide  supra).  _  r      „  „ 

ComenHal  hydrocele  depends  for  its  existence  upon  the  maintenance  of  a  com- 
munication between  the  tunica  vaginalis  and  the  abdominal  cavity.  The  hinicular 
portion  of  the  tunic  does  not  become  obliterated.  The  fluid  may  come  from  he 
general  abdominal  cavity  or  may  be  exuded  from  the  vaginal  tunic.  It  may  develop 
in  eariy  infancy  or  not  until  later  in  life.  ,         ,  .u  u 

Infantile  hydrocele  is  an  effusion  into  a  sac  formed  by  more  or  less  of  the  unob- 
literate"d  funicular  portion  of  the  vaginal  tunic.  This  sac  is  closed  from  the  pentoneal 
cavity  above  and  communicates  with  the  tunica  vaginalis  testis  below 

Biloctdar  hydrocele  is  a  comparatively  rare  form  of  infantile  hydrocele.  1  he 
funicular  portion  of  the  tunica  vaginalis  is  commonly  obliterated  at  the  internal  ring. 
Below  this  the  whole  tunica  vaginalis  may  be  patulous,  or  it  may  be  closed  ]ust  above 
the  position  of  the  testis.  As  the  fluid  accumulates,  sacculation  develops,  the  tumor 
extending  either  backward  and  downward  into  the  pelvis  or  more  commonly  upward 
and  inward  between  the  abdominal  muscles  and  the  peritoneum. 

Encv'ted  hydrocele  of  the  cord,  or  funicular  hydrocele,  consist.s  of  an  accumula- 
tion of  fluid  within  an  uiiobliterated  portion  of  the  hinicular  portion  of  the  tunica 
vaginalis  This  accumulation  is  closed  from  the  peritoneal  cavity  atovo  and  trom  the 
tunica  vaginalis  testis  below.  The  hydrocele  may  be  unilocular,  bilocular  or  multi- 
locular  in  the  latter  case  forming  a  series  of  small  cysts  along  the  curse  of  the  cord 
These  cysts  may  be  placed  in  the  inguinal  canal,  and  are  more  common  on  the  nght 
side.     They  are  usually  oliserved  in  children,  and  may  be  complicated  by  hernia. 

THE  SPERMATIC  DUCTS. 

The  spermatic  ducts  arc  two  tortuous  canals,  one  on  either  side,  that  connect  the 
epididymi  with  the  urethra  and  thus  provide  channels  for  the  escape  of  the  products 
of  the  sexual  glands.  Each  duct  is  divisible  into  the  vas  deferens  and  its  ampulla 
and  the  ejacnlatorv  duct :  at  the  upper  end  of  the  latter  the  spermatic  duct  is  connected 

'2.5 


1954 


HUMAN  ANATOMY. 


with  the  seminal  vfsicle,  a  saccular  organ  representing  an  outgrowth  from  the  main 
canal. 

The  Vas  Deferens. — This  tube  (ductus  defercna)  extends  from  the  epididymis 
to  the  ejaculatory  duct  and  includes  almost  the  entire  length  of  the  spermatic  duct, 
with  a  diameter  of  from  2-3  mm.  Beginning  at  tne  globus  minor  as  the  direct  ain- 
tinuation  of  the  convoluted  canal  of  the  epididymis,  the  vas  deferens  is  at  first  also  very 
tortuous,  and  by  its  windings  forms  a  tapering  mas.s  (pars  testicularis)  about  3.5  cm. 
in  length.  From  the  latter  the  seminid  duct  is  prolonged  upward  along  the  inner 
sidt  of  the  epididymis  and  behind  the  testis,  becoming  progressively  less  wavy  and 

Fig.   1 66a. 


E>teni*l  iliac- 
artery 

External  il 
vein 
Deep  epiicaMrie 
artery 
Spermatic  vessels 

Internal  abdominal 
ring 


Obliterated 
hypogastric  artery 

Urachufl- 

Suspensory 
ligament  uf  peniS' 

Internal  urethral  orifice 

Fatty  tissi 
containing  veins 


Pectinate  septum- 


Spongv-  urethra- 


Navicular  fossa 


■Ureter,  entering 
bladder 


.Ejaculatory  duct 

'rostfttic  urethra 
anft  utricle 

restate 


-Membranous  ur  .hra 
Bulb  of  cavernous  body 

-Bulbous  urethra 


Scrotum 
Dissection  of  sagittally  cut  (>elvis,  showing;  ret.ttions  of  organs  after  fixation  by  formalin  infection. 

of  larger  and  more  uniform  size  (3  mm. )  .is  it  enters  the  sj)ermatic  cord.  Although 
the  apparent  entire  length  of  the  canal  is  about  30  cm.  (12  in.),  its  actual  extent  is 
some  45  cm.  C18  in.)  on  account  of  the  tortuosity  of  its  first  part. 

Within  the  spermatic  cord  (pars  funicularis),  accompanied  by  the  deferential 
artery  and  the  postrrinr  plexus  of  veins  (Fig.  i6S2\  the  vas  ncrnpies  .i  position 
behind  the  other  constituents  of  the  cord,  and  may  be  recognized  by  the  hard,  cord- 
like feel  imparted  by  its  thick  fibro-muscular  wall.  The  duct  ascends  almost  verti- 
cally to  the  pubic  spine,  and  on  gaining  the  abdominal  wall  pas.ses  through  the  external 
abdominal  ring,  traverses  the  inguinal  canal,  and  completes  its  passage  of  the  body- 


THE  SPERMATIC   DUCTS. 


1955 


^*^-^J«S^^^* 


Net- work  of 
rut  rtil|{t-H 

•Mucoux  coat 


.•  L  „„  ,Kr.,...,h  the  internal  abdominal  rin^-     Alter  emerging  Irom  the  laiur 

wall  by  KotnK  thjouRh   he  '"^'^^  »  ,     ^^^^^  „^„  ^^,^  ,.^i„„ai  and  ix«tcr...r 

it  parts  comi^iny  ^'J^ '^^^P^^^"*^  l'^^  obliquely  the  external  iliac  vessels  and 
suriace  of  the  *'«--*^l' .'^'>[f  *"if  S' "i™!  From  its  entrance  at  the  inter.wl  ri..>- 
t  I^^L'Sirtt'^XroJ/Jrue^-.n-li-'y  b^-neath  the  ..ntoneum.  through 
which  it  may  usually  be  traced.  ^     j  ,■  ^^t  xi^^  ^^^„^  the  lateral 

,  ••'"Tdl^Jt'StcWwa'^    nWhtly  i-rd  ^--^^'^  ^^^  ^^  f'"^-  ^"'=^-'"« 
pelvic  wall,  directed  nacKwaru  a..     .  ,P    /    .' ,^        ^^j^ic  artery,  the  obturator  nerve 

t.  their  inner  or  m^d^ms^yhe^^^^^^^^^^^  J^  .„  ^„  ^,^ 

and  vessels,  the  vesical  \^*?'  ■*""  ,harulv  downward  and  nward  and  traverses 
inner  side  of  the  ureter,  the  duct  "["^.  J;^  J^^^^^  ^*  ^h  the  vicinity  ol  the  seminal 
the  subperitoneal  "ri'^^iTTCter^uir  luri^e  if  the  bladder  and  the  rectum. 

rirlTi; -"^^^^^^^^^^^  mm'^^tn'itsVJst  ^idth.  that  p.^.  in 

front  and  then  along  p^^    ,^5^ 

the  median  side  of  the 
seminal  vesicle  in  its 
descent  to  the  pros- 
tate gland.  Thecott- 
tour  of  the  ampulla  is 
uneven  and  humpy, 
especially  alter  re- 
moval ol  the  invest- 
ing fibrous  tissue,  due 
to  the  sacculations 
and  tortuosity  ol  the 
canal  (Fig.  1666)  and 
the  short  diverticula 
that  pass  off  Irom  the 
main  duct  at  various 
angles,  thus  antici- 
patingin  simpler  lorm 
the  arrangement  seen 
in  the  seminal  vesicle. 
Just  before  reach- 
ing the  latter  t!     vas 

rrvt'dirfcre^'^l^cktard  and  outward  (Fig.  .469)  and  occupies  the  cresce"tic  rec^^ 
vcJcal  sacro-geniuil )  peritoneal  fold.  At  the  lower  end  of  the  ampu  la  the  v as  l<«,es 
ks  Scutadons  nd  again  becomes  a  narrow  tv.tn.  which,  joining  with  the  {.ass;ige 
m^the  sLm"nal  vesick.  ...ntinued  as  the  ejaculatory  duct  that  traverses  the  sub- 
mce  of  r  pros  a"e  gland  and  terminates  in  the  urethra  at  the  su  e  ol  he  pros- 
tik  utricle.  The  ampullar  ol  the  two  sides  converge  as  they  descend,  so  that  the  r 
g«er  ends  are  almost  in  contact  where  the  spermatic  duct  .ecen^es  th-  seminal  vesi- 
cle The  intimacy  of  the  relation  between  the  vasa  deferentia  and  the  bladder 
Ses  w  th  the  condition  of  the  latter  organ.  VVith  the  increased  volume  •ncuient  to 
Tte  dLtTntion.  the  posterior  surface  of  the  bladder  is  preyed  against  the  spermaUc 
|£cte    on  th;  otheVhand,  when  the  bladder  is  empty,  only  the  lower  parts  of  these 

structures  are  in  close  relation  with  the  vesical  wall.  .      r   ,i,„ 

strucmresae  ^^^^^  ejacnlatorius).   the  terminal    segment   of   the 

spermatL  canal  and  apparently  formed  by  the  imion  ol  the  duct  of  the  correspondmg 
seS  vesicle  and  the  vas  deferens,  is  really  the  morphological  continuation  ol  the 
,"™n;om  which  the  seminal  vesicle  is  developed  a.s  a  secondary  outgrowth.     Be- 

Snn  ng  wTth  a  dia.neter  of  from  1.5-2  mm.,  the  e  aculatory  'l""^^"^':^,"^  »^1'*="^^ 
ginning  *""  "  ,p.        .^.    defining  the  ower  limit  of  the  middle  lobe,  and 

XrrcouS^Cr,8^ro'mm.^Lut  H  i^)  in  length,  ends  in  the  urethra  by  a 

£ute  dlipTcaropening  situated  on  the  crest  at  the  side  of  the  orihce  ol  the  prostatic 


"^^.^O^ 


CFWM-settion  of  ampulla  of  spermatic  duct. 


Circular  muscle 


-Longitudinal 
muscle 


1956 


HUMAN  ANATOMY, 


Fihroiu  coat 


Lumen  ~^ 


Utricle  (Fig.  1634J.  In  rare  ca^t^  the  ductn  of  the  two  sides  may  juin  before  reucli- 
in^r  the  urethra  and  communicate  with  the  latter  by  a  common  aperture,  ur  they  may 
o|M*n  inde]K-ndently  into  the  prostatic  utricle.  In  the  desicent  of  the  duct  the  lumen 
of  iut  up|)er  and  middle  thirds  is  modiheil  by  a  series  of  four  or  live  diverticula  of  de- 
crea.sint;  size  (Felix).  At  such  levels  the  usual  oblique  oval  outline  of  the  canal  is 
amplified  by  the  irregular  dilatations. 

Structure  of  the  Spermatic  Duct. — The  tas  deftrem  is  distinguished  by  the 
conspicuous  thickness  of  its  wall  (from  1-1.5  mm.  )  that  encloses  a  relatively  narrow 
lumen  ( .  5-.  7  mm. )  and  confers  upon  the  canal  its  characteristic  hard,  cord-like  feel. 
The  wall  consists  c)f  three  coats,  the  mucous,  muscular,  and  fibrous  (  Fig.  1664).    The 

mucous  coat  is  clothed  with 
Kic.   1664.  epithelium  which  in  the  vi- 

cmity  of  the  testicle  and  for 
an  uncertain  disUtnce  lieyond 
resembles  that  lining  the  duct 
of  the  epididymis,  consist- 
ing of  an  imperfect  double 
layer  of  tall,  columnar  cili- 
ated  cells.  Throughout  the 
greater  part  of  the  duct,  how- 
ever, the  cells  are  lower  and 
without  cilia  and  contain 
numerous  particles  of  pijj- 
ment.  The  tunica  propria 
possesses  a  dense  felt-work 
of  elastic  fibres  intermingled 
with  bundlesof  fibrous  tissue. 
The  robust  muscular  coat 
(from  .8-1.2  mm.  in  thick- 
ness )  constitutes  approxi- 
mately four-fifths  of  the  en- 
tire wall,  and  consists  of  f>ale 
fibres  arranged  as  an  outer 
longitudinal,  a  middle  circu- 
lar, and  an  inner  longitudinal 
layer,  the  latter  being  less 
well  developed  than  the  outer  and  middle  strata.  The  external  fibrous  coat  that 
in\  ests  the  muscular  tunic  is  thin  and  serves  to  connect  the  spermatic  duct  with  the 
.surrounding  structures. 

In  its  general  structure  the  ampulla  corresponds  with  the  vas  deferens,  the  walls 
of  this  part  of  the  duct,  however,  possessing  a  much  thinner  mu.scular  coat,  in  which 
"le  inner  longitudinal  layer  is  wanting,  and  a  mucosii  modelled  by  numerous  ridges 
and  depressions  (Fig.  1663)  and  covered  with  a  single  layer  of  low,  columnar,  non- 
ciliated  epithelial  cells. 

The  ejaculaton'  duct  likewise  possesses  a  structure  es.sentially  the  same  as  in 
other  parts  of  the  spermatic  canal.  Its  walls,  however  are  thinner  than  those  of  the 
ampulla,  this  reduction  lx"ing  due  to  the  diminished  thickness  and  incompleteness  of 
the  muscular  coat,  which  on  nearing  the  urethra  fjecomes  attenuated  and  mingled  with 
fibrous  tissue.  In  some  places  the  epithelium  of  the  duct  consists  of  a  single  and  in 
others  of  a  double  laver  of  columnar  cells  until  within  a  short  distance  from  the  termi- 
nation of  the  canal, Where  it  assumes  the  transitional  character  of  the  epithelium 
lining  the  prostatic  urethra. 


Outst 

totiKitmlinal- 
muHclc 
Circular^ 
muitcle 
Inner 
lonKttiulinal' 
innsrlf 
Mucoiu 
mcmhranr 


rros»-!wrtton  of  v\%  deferens. 


THE  SEMINAL  VESICLES. 

The  seminal  vesicles  (  vesiculac  seminales  )  are  two  sacculated  appendages  of  the 
\asa  deferentia  that  lie  behind  the  bladder  and  in  front  of  the  rectum.  F"lattencd  from 
t)cfore  backward,  their  general  shape  is  pyriform,  with  the  larger  ends,  or  bases, 
directed  upward  and  outward,  the  long  axes  converging  towards  the  mid-line  as  the 


. 


THK  SEMINAL   VESICLES. 


|'>.S7 


Hadilrr,  loiiKi- 
-lutlinal  niu-Hlf 

Va*  ilrfctiiis 


I'rHri 

-  AmiiulU 
Seminal  vnitlv 


Rjaculatury  dui't 


Mcmbraiiouk  uiclhra 


Cf>wpcr'»  Klamli 


Ditarcllon  ahowinc  aemlnal  duiia  and  vt-Mcl«,  prortatc 
and  Cowpir^  gland»;  viewed  Irom  behiml. 


onrans  taper,  olten  abruptly,  at  their  lower  ends  to  join  the  spermatic  ducU.     Liwally 
fri!in  4-5  cm.  in  length,  sometimes  much  longer  ami  relatively  slender  and  at  others 
sh«)rt  and  broad,  the  seminal  vesicles  vary  Kri:M\y  in  size  and  in  the  detail  of  arranut 
nient  of  their  com|x>ncnt  jwrts  and  not  infrequently  are  markedly  icsyminetrical.  the 
right  one  bein^  often,  but  not  in- 
variably, the  lar^  r. 

Divested  of  the  tibro-muscular 
tissue  that  invests  the  or^an  as  its 
capsu/e  ani\  blends  its  divisions  into 
a  tuberculateti  common  mass,  each 
vesicle  may  be  resolved  into  a  c^if/ 
duel  and  diverticula.  The  former 
—from  IO-I2  cm.  (4-5  in.)  in 
length^^nds  blindly  after  a  more 
or  less  tortuous  course,  its  terminal 
part  often  describing  a  sharp  hook- 
like returninjj  curve  (  Fig.  1667). 
From  the  main  canal  an  unti-rtain 
number  (from  four  to  eight  or 
more ' )  of  blind  tubular  diverticula 
branch  at  varying  angles  and  in 
different  directions  and  by  their 
tortuosities  add  to  the  complexity 
of  outline.  The  lumen  of  the  chief 
duct,  as  seen  in  section,  is  irregu- 
lar, constrictions  and  dilatations 
foil  Jwing  one  another  with  little 
regularity.  The  opening  of  the 
duct  into  the  lateral  wall  of  the  vas  ,  1  u 

deferens  is  large  in  comparison  with  the  terminal  lumen  of  the  ejaculatory  duct,  thus 
favoring  the  entrance  of  the  secretions  temporarily  stored  within  the  ampulla  into  the 
sacculated  vesicle.  The  latter  contains  a  fluid  of  light  brownish  color  in  which  sjier- 
matozoa  are  nearly  always  found  during  the  period  of  sexual  activity. 

Relationa.— The  seminal  vesicles,  together  with  the  ampulla-,  lie  emlxKlded 
within  a  dense  fibro-muscular  layer,  so  that  their  position  remains  relatively  lixe<l. 
especially  below,  and  to  a  certain  degree  independent  of  the  changes  in  vclumeof  the 

bladder  and  the  rectum,  neither 
Fig.  1666.  of  which   they   directly  touch. 

Although  when  distendetl  tht-se 
organs  are  in  close  relation  with 
the  seminal  vesicles,  when  empty 
the  bases  of  the  latter  lie  laterally 
and  at  some  distance  from  lx>th 
the  vesical  and  rectal  wall,  sur- 
rounded by  numerous  veins  that 
continue  the  prostatic  and  vesi- 
cal plexuses.  The  lower  half 
of  the  seminal  vesicles  and  the 
ampulhe  lie  behind  the  fundus 
of  the  bladder,  their  axes  ap- 
proximately corresponding  with 
the  sides  of  the  vesical  trigone 
and  embracing  the  retrotireteric 
fossa,  which  part  of  the  bladder- 
wall,  when  distended,  m.ay  pro- 
ject between  and  even  displace  laterally  the  seminal  ducts  and  vesicles.  In  passing 
from  the  slightly  expanded  bladder  onto  the  rectum,  the  peritoneum  covers  the 
upjXT  fourth  of  the  seminal  vesicles  and  the  adjoining  part  of  the  ampullae.  I  he 
'  Pallin  :  .Archiv  f.  Anat.  u.  Entwick.,  190I. 


SeniitLiI  vesicle 


Ejaculatorv  ducts 


Cast  ol  anipulUe  and  seminal  vesicles,  shouitiK  wind- 
ings and  sacculations  of  lumen.    (Paiim.\ 


i  . 


1958 


HUMAN   ANATOMY. 


bWb 

DiaKram  showing  course  of  msin  canal  in  preceding  preparalio 
a,  ampulla;  r.  seminal  vesicle;  ^,  ejaculatory  duct,    {rallm.) 


extent  of  this  investment,  however,  varies  with  the  depth  of  the  recto-vesical  pouch, 
which  in  turn  dejjcnds  upon  the  degree  of  distention  of  the  Ixjunding  organs,  the 
bladder  and  the  rectum. 

Structure. — In  their  general  make-up  the  seminal  vesicles  closely  resemble  the 
ampulla,  possessing  a  robust  muscular  wall  composed  oi  an  inner  circular  and  an 

outer  longitudinal  layer  of  involun- 
FiG.   1 667.  tary  muscle.     The  mucous  mem- 

brane is  conspicuously  modelled 
by  numerous  ridges  and  pits,  so 
that  the  free  surface  appears 
honey-combed  (Fig.  1668).  The 
epithelial  covering  consists  of  a 
single  or  imperfect  double  layer 
of  low  columnar  cells,  many  of 
which  present  changes  indicating 
secretory  activity.  Although  true 
glands  are  wanting  within  the 
seminal  vesicles,  the  minute  di- 
verticula within  the  epithelium 
containing  goblet-cells  may  be  re- 
garded as  concerned  in  producing 
the  peculiar  fluid  found  within 
these  sacs,  which  is  of  importance  probably  not  only  in  diluting  the  secretion  of  the 
testicle  and  supplying  a  medium  favorable  for  the  motility  of  the  spermatic  fila- 
ments, but  also  in  completing  the  volume  of  fluid  necessary  for  efficient  ejaculation 
(VValdeyer). 

Vessels  of  the  Seminal  Ducts  and  Vesicles. — The  arteries  supplying  the 
spermatic  duct  are  derived  chiefly  from  the  deferential,  a  vessel  of  small  size  but  long 
ct)urse    that   arises  either   directly 

from  the  internal  iliac  or  from  its  Fio.   1668 

vesical  branches.  On  reaching  the 
duct,  just  above  the  ampulla,  the 
artery  divides  into  a  smaller  de- 
scending and  a  larger  ascending 
division.  The  former,  in  conjunc- 
tion with  accessory  twigs  from  the 
middle  hemorrhoidal  and  the  in- 
ferior vesical  arteries,  generously 
provides  for  the  ampulla,  and  the 
latter  accompanies  and  supplies  the 
vas  deferens  throughout  its  long 
course,  finally,  in  the  vicinity  of  the 
testicle,  anastomosing  with  branches 
from  the  spermatic, — a  communica- 
tion of  importance  for  collateral  cir- 
culation. The  twigs  passing  to  the 
spermatic  duct  enter  its  wall  and 
break  up  into  capillary  net-works 
within  the  mu.scular  and  mucous 
layers.  The  rich  arterial  supply  for 
the  seminal  vesicle  includes  anterior 
and  upper  and  lower  branches,  con- 
tributed by  the  deferential,  the  in 
ferior  vesical,  :>.ik1  the  superior  and 
middle  hemorrhoidal  ,\rteries.  The 
minute  (listribulion  is  effected  by  capillary  net-works  to  the  muscular  ind  mucous 
coats. 

The  I'-'iiii  fii.-.i  iullow  the  spermatic  duct  as  the  deferential  plexus^  and  within 
the  spermatic  cord   -ommunicate  with  the  pampiniform  plexus,  increase  in  size  and 


Muscular 
coat 


Pits  nf  ma- 
cous  coat 


Cross-section  of  seminal  \esic1e.  showing 
modelling  of  mucous  surface.     X  l6. 


Partition  st|  jratiiiK  adjacfiil  diverticula 


Epithelium 


PRACTICAL  CONSIDERi*r!(>NS  :    SEM'NAL  VESICLES.        i959 

number  as  they  approach  the  bladder  and  seminal  vesicle  ;  in  the  vicinity  of  the  latter 
thev  communicate  with  the  seminal  plexui  and  empty  with  the  trunks  ot  the  posterior 
bladder-wall  into  the  vesico-prostatic  plexus.  The  posterior  and  lateral  surfaces  ol 
the  seminal  vesicle  are  covered  with  a  net-work  of  large  veins  (plexus  vcnosus  scmi- 
aalis)  that  become  tributary  to  the  vesico-prostatic  plexus. 

The  lymthalks  of  the  seminal  ducts  anil  vesicles  are  numerous  and  arranKed  as 
deeper  and  superficial  sets  which  form  afferent  trunks  that  pass  to  the  internal  iliac 
lymph-nodes.  Those 

from  the  lower  part  F«o.  1669. 

of  the  seminal  vesi- 
cles join  the  vesical 
lymphatics. 

The  nerves  sup- 
plying the  spermatic 
duct  are  derived 
from  the  hypog;i.stric 
plexus  of  the  sympa- 
thetic and  consist 
chiefly  of  pale  fibres 
destined  for  Lhe  in- 
voluntary muscle, 
some  medullated 
fibres,  however,  be- 
ing present.  They 
accompany  the 
greater  part  of  the 
duct  as  the  deferen- 
tial plexus  and  have 
been  traced  into  the 
muscular  tissue  and 

the  mucosa.    Within  .,     ,  .     c-  1  1       i 

the  former  they  form  the  Atrnx  plexus  myospermatiais  described  by  Sclavunos,  anti 
are  fairly  plentiful  within  the  mucous  coat  (Timofeew  ')•  The  nervi>8  distributetl  to 
the  seminal  vesicles  are  very  numerous  and  are  derived  in  part  directly  from  the 
hypogastric  plexus  (Fraenkel'),  or  through  prolongations  of  the  latter  as  secondary 
plexuses  that  follow  the  vesical  and  middle  hemorrhoidal  arteries. 


■Mucous  cuflt 


■Fibrous  coat 


Portion  of  wall  ol  seminal  vesicle  in  lonRitudinal  section, 
showtiiK  piUiiiK  t>*  mucous  coal.     X  45- 


PRACTICAL   CONSIDERATIONS.    THE  SEMINAL  VESICLES. 

The  seminal  vesicles  are  rarely  injured.  The  two  forms  of  infection  that  are 
most  common  are  the  gonorrhccal  and  the  tuberculous,  although  vesiculitis  vcas  h^ 
due  to  the  ordinary  staphylococci  or  to  the  colon  bacillus.  The  channels  of  infection 
are  comparable  to  those  which  convey  disease  to  the  epididymis:  the  ejaculatory 
ducts  are  continuous  with  the  vas  deferens  and  the  vesicular  duct,  and  the  inferior 
vesical  and  middle  hemorrhoidal  arteries  replace  the  spermatic  artery.  The  tuber- 
culous disease  is,  however,  usually  secondary  to  similar  infection  of  the  prostate  or 

of  the  epididymis.  ...  /^n  .u 

The  anatomical  relations  of  the  vesicles  to  (a)  the  vesical  trigonum,  (*)  the 
prostate  and  prostatic  urethra,  and  (c)  the  rectum  sufficiently  explain  the  usual 
symptoms  of  acute  vesiculitis  :  (n)  frequent,  painful,  straining  urination,  hypogastric 
pain  •  (*)  priapism,  painful  emissions  of  blood-stained  semen,  occasionally  epididy- 
mitis as  a  complication  ;  (f)  painful  defecation,  rectal  tenesmus,  perineal  and  anal 

Rectal  exploration  (page  1692)  will  usually  establish  the  diagnosis,  as  it  will  n 
tuberculous  vesiculitis,  in  which  condition,  as  in  other  forms— acute  and  chronic— 
of  vesiculitis,  there  are  apt  to  be  pains  referred  to  the  loins,  the  hypogastrium,  the 

'  Anatom.  Anzeiger,  Bd.  ix.,  1894. 
'  Anatom.  Anzeieer.  Bd.  ix.,  1894- 
•  Zeitsch.  f.  Morph.  u.  Anthrop.,  Bd.  v.,  1903. 


i960 


HUMAN  ANATOMY. 


anus  and  perineum,  the  hip-joint  and  sacro-iliac  articulation  of  the  affected  side  and 
the  other  side  of  the  thigh,  due  to  the  association  of  the  vesical,  prostate,  and  pelvic 
plexuses  with  the  lumbar  and  sacral  nerves  and  their  plexuses. 

Vesiculitis  may  be  a  very  serious  condition,  as  it  may  result  in  abscess  with  per- 
foration into  the  bladder  within  the  limits  of  the  peritoneal  covering,  or  directly  into 
the  peritoneal  cavity  by  way  of  the  recto-vesical  cul-de-sac.  Cases  of  both  these  acci- 
dents have  been  reported.  Pyamia  has  also  been  known  to  follow  a  septic  phlebitis 
of  the  adjacent  venous  plexuses;  pelvic  cellulitis  with  diffuse  suppuration  has  resulted ; 
and  various  troublesome  abscesses  burrowing  between  the  bladder  and  rectum,  and 
leaving  fistulous  tracts  very  slow  to  heal,  have  had  their  origin  in  suppurative  vesicu- 
litis. The  chronic  form  may  be  associated  with  persistent  vesical  irritability,  with  some 
pain  on  emission  of  semen,  with  sexual  excitability  accompanied  by  premature  ejacu- 
lation, and  with  persistent  urethral  discharge  often  mistaken  for  an  ordinary  gleet. 

In  chronic  cases  "  massage"  through  the  rectum  has  been  advised  and  practised 
with  some  benefit  in  comparatively  rare  cases.  The  contents  of  the  vesicles  can 
sometimes  be  pressed  through  the  ejaculatory  ducts  into  the  prostatic  urethra  and  so 
evacuated.  A  similar  expression  of  the  normal  secretion  of  the  vesicles  by  fecal 
masses  at  stool  is  a  fertile  source  of  sexual  hypochondriasis  in  young  male  neuras- 
thenics, who,  in  consequence,  imagine  that  they  are  afflicted  with  ' '  spermatorrhoea. '  * 


Fio. 


THE  SPERMATIC  CORD. 

In  consequence  of  its  migration  from  the  abdominal  cavity  into  the  scrotal  sac, 
the  testicle  is  followed  by  its  duct,  vessels,  and  nerves  through  the  abdominal  wall 
into  the  scrotum.  These  structures,  held  together  by  connective  tissue  anil  invested 
by  certain  coverings  acquired  in  their  descent,  form  a  cylindrical  mass,  known  as  the 
spermatic  cord  (fuaicnlns  spennaticus),  that  extends  from  the  internal  abdominal  ring 
obliquely  along  the  inguinal  canal,  emerging  at  the  external  ring,  and  thence  descends 
vertically,  beneath  the  integument,  into  the  scrotum  to  end  at  the  posterior  border  of 
the  testicle.  Most  constant  within  the  inguinal  canal,  where  its  diameter  is  about 
15  mm.  Cfi  in.),  the  thickness  and  length  of  the  spermatic  cord  vary  with  the  con- 
traction of  the  cremasteric  muscular  fibres  that 
'  *70'  control  the  position  of  the  testicle. 

Poncrior  veins  The  Constituents  of  the  spermatic  cord 

are  numerous  and  fall  under  four  groups. 

f__^.     -^JKT  '  •  The  vas  deferens  with  its  accompanying 

jKgJ^^^^v,  deferential  artery  and  plexuses  of  veins,  lym- 

._  '?'JRB!faicik^>.  phatics,  and  nerves.     The  vas,  surrounded  by 

Its  artery  and  a  venous  plexus,  occupies  the 
posterior  part  of  the  spermatic  cord,  and  is 
readily  distinguished  as  a  hard,  round  cord, 
from  2-3  mm.  in  diameter,  by  virtue  of  its 
unusually  firm  walls. 

2.  The  spermatic  artery,  veins,  lymphatics, 
and  nerves  belonging  to  the  testicle  projjer. 
In  contrast  to  the  artery,  the  veins  are  particu- 
larly large  and  numerous  and  form  the  conspicuous  pampiniform  plexus  which  con- 
tributes in  no  small  measure  to  the  bulk  of  the  cord. 

3.  The  coverings  with  their  blood-vessels  and  nerves.  The  coverings  proper  of 
the  spermatic  cord,  contributed  by  the  layers  of  the  abdominal  wall,  correspond  to 
those  of  the  testicle,  with  the  exception  of  the  serous  coat,  which  is  wanting  after 
closure  of  the  processus  vaginalis.  From  within  outward  they  are  :  (a )  the  infundib- 
uliform  fascia  (tunica  vasinalis  cnmmunis),  a  distinct  layer  continued  from  the  trans- 
versalis  fascia  ;  (b)  the  cremasteric  fascia,  consisting  of  the  muscular  fibres  prolonged 
from  the  internal  oblique  and  transversalis,  blended  together  by  connective  tissue. 
The  muscular  fibres  descend  as  loops  along  the  spermatic  cord,  especially  on  the 
posterior  surface  as  far  as  the  testicle,  over  the  coverings  of  which  they  spread  out  in 
festoons  and  net-works  ;  and  (r)  the  intercolumnar  fascia,  a  delicate  sheet  derived 
from  the  aponeurosis  of  the  external  oblique  at  the  margin  of  the  external  alxiominal 


Veins  of  painpitij- 
form  plexus 

■S[)ennatic  arter> 

Tunica  vat^inalis 
C'lmmums 
trema-steric  fascia 

Section  across  left  spermatic  conl  hardcneH  in 
formatin,  showiuK  |K>sitiuti  of  vas  deferens. 


M 


THE  SCROTUM. 


196 1 


ring,  is  most  distinct  above,  becoming  thinner  as  it  descends,  until  over  the  testicle  it 
loses  its  identity  as  a  distinct  investment.  ^       ,.,      ,  ,    c  u:  «„  »u„ 

The  coverings  of  the  spermatic  cord  receive  their  blood-supply  from  chieHy  the 
cremasteric  branch  of  the  deep  epigastric  artery  ;  additional  cremasteric  tuigs  from 
the  spermatic  artery  are  distributed  to  the  upper  part  of  the  cord,  anastomosing  with 
those  from  the  first-named  source.  The  ner^'es  include  the  genital  branch  of  the 
genito-crural  and  usually  a  twig  along  the  front  of  the  cord  from  the  terminal  branch 

of  the  ilio-inguinal.  .        ,  ,  •     r     »u    „„,., 

4  The  rudimentary  structures,  the  remains  of  the  processus  vaginalis,  the  para- 
didymis, and  sometimes  the  vas  aberrans.  After  closure  of  the  communication  between 
the  serous  pouch  and  the  peritoneal  cavity,  the  processus  vaginalis  is  represented  by 
a  delicate  fibrous  band  (ligamentuni  vaginale)  that  may  be  traced,  under  favorable  con- 
ditions from  the  internal  abdominal  ring  above  through  the  spermatic  cord  as  tar  .a 
the  upper  margin  of  the  tunica  vaginalis  below.  The  paradidymis  (page  1950)  lies 
within  the  lower  end  of  the  spermatic  cord,  immediately  above  the  epididymis,  or 
behind  its  upper  pole,  and  in  front  of  the  venous  ple.xus.  Occasionally,  when  unusu- 
ally developed,  the  vas  aberrans  (page  1950)  may  also  extend  into  the  lower  end  of 

*  *P*      ■  ■■  •         '     •     '  >rings  proper,  the  spermatic  cord  is  enveloped 

>  -p  laver  of  the  superficial  fascia.     The  deep 
tinuous  above  with  thefascia  on  the  abdomen 
with  CoUes's  fascia  in  the  perineum. 


'e, 


In  addition  to  the  foregoi 
by  the  skin,  the  superficial  an 
layer  of  the  latter  is  important, 
and  below,  after  investing  the  tesi 

PRACTICAL   CONSIDERATIONS:    THE   SPERMATIC   CORD. 
The  most  frequent  pathological  condition  associated  with  the  cord  (and  not  else- 
where described)  is  varicocele,  an  enlargement— with  dilatation  and  lengthening— of 
the  veins  of  the  cord,  occurring  most  frequently  in  young  unmarried  adults  (fifteenth 
to  twenty-fifth  year)  and  on  the  left  side  (90  per  cent,  of  cases). 

The  veins  composing  the  spermatic  plexus  can  be  ranged  in  three  groups,  the 
most  anterior  of  which  has  in  its  midst  the  spermatic  artery,  the  middle  the  vas  def- 
erens and  the  posterior  is  compos-ed  of  those  veins  which  pass  upward  from  tlie  tail 
of  the  epididymis.  The  anterior  group  is  the  one  first  affected,  or.  if  the  dilatation 
affects  all  the  veins,  is  most  extensively  involved. 

It  is  thought  that  varicocele  often  depends  upon  a  congenital  predisposition 
but  many  anatomical  reasons  have  been  given  to  account  («)  for  its  occurrence  and 
(b)  for  its  greater  frequency  on  the  left  side,  (a)  i.  The  relative  length  and  the 
vertical  course  of  the  veins.  2.  The  lax  tissue  surrounding  them  so  that  (as  with 
the  long  saphenous  vein)  they  derive  littie  support  and  their  blood-current  receives 
no  aid  from  the  presence  or  contraction  of  surrounding  muscles.  3.  Their  large  size 
as  compared  with  the  corresponding  artery,  so  that  the  vis  a  tergo  mu.st  be  reduced  to 
a  minimum  (Treves).  4.  Their  tortuosity,  frequent  anastomosis,  and  few  anrt  imper- 
fect valves  5.  The  pressure  exerted  upon  them  as  they  pass  through  the  inguinal 
canal  not  altogether  unlike  that  experienced  by  the  hemorrhoidal  veins  m  their  passage 
through  the  walls  of  the  rectum,  (b)  i.  The  veins  in  the  left  cord  arc  much  larger 
than  those  in  the  right.  2.  The  left  tey'-'cle  hangs  lower  than  the  right,  so  that  the 
column  of  blood  in  the  left  veins  is  longer.  3-  The  left  spermatic  vein  empties  into 
the  left  renal  vein  at  a  right  angle,  whereas  the  right  spermatic  vein  empties  into  the 
vena  cava  at  an  acute  angle.  4-  The  left  spermatic  vein  running  behind  the  sigmoid 
flexure  of  the  colon  is  constantly  subjected  to  pressure  from  accumulation  of  fitces  in 

the  liowel.  ,    .  ...  ,  ^, 

In  the  operation  for  varicocele  by  excision  of  the  pampiniform  plexus  the  sper- 
matic artery  is  often  included,  but  gangrene  of  the  testicle  does  not  follow  because 
of  the  escape  of  the  deferential  arter>'  and  of  its  free  anastomosis  with  the  spermatic 
and  scrotal  vessels. 

THE  SCROTUM. 
The  scrotum,  the  more  or  less  pendulous  sac  of  integument  that  contains  the 
testicles  and  the  associated  structures  and  the  lower  part  of  the  spcrmatie  cords,  is 
attached  to  the  under  surface  of  the  penis  in  front  and  to  the  perineum  behind,     b  lat- 


•   If 


1963 


HUMAN   ANATOMY. 


tened  in  front  above,  where  atUched  to  the  penis  and  receiving  the  spermatic  cords, 
its  general  form  is  pear-shaped  and  somewhat  asymmetrical,  since  the  left  of  the  two 
oval  swellings  produced  by  the  enclosed  testicles  and  separated  by  a  shallow  longi- 
tudinal furrow  is  lower  than  the  right  owing  to  the  position  of  the  corresponding 
sexual  gland.  The  scrotum  vari'  ,,  however,  in  form  and  appearance,  even  in  the 
s;»me  individual,  with  the  condition  of  the  subcutaneous  muscular  tissue.  When  the 
latter  is  contracted,  as  after  the  influence  of  cold,  the  scrotum  is  drawn  up  and  com- 
pact and  its  surface  corrugated  by  numerous  transversely  cur\ed  folds  ;  when  relaxed, 
it  becomes  smooth,  flaccid,  and  penduloiw. 

Indications  of  its  formation  from  two  distinct  parts  are  seen  externally  in  the 
longitudinal  raphe,  which  marks  the  line  of  fusion  of  the  original  halves  and  extends 
longitudinally  from  the  urethral  surface  of  the  penis  over  the  scrotum  onto  the  peri- 

FiG.  1671. 


Ap<nieiirosis  of 
cxtcnt.-il  ohiique      ^H-^" 


Kxtcrnal  abdominal 
riiiK 

SusiKMisory  ligament 
01  penis 


Skin 

Superf.  hscU,  iuperf.  layer 

Deep  layer 

AfmneuroKis  of 
external  oblique 

Internal  oblique 


hitunflibuliform 
fascia 

AjHjneurosisof 
external  oblique,  cut 
and  reflected 


SiK-rmalic  cord 


Intercolumnar  fascia, 
reflected 


Oissection  nf  sjiermatir  cord  and  scrotum. 

neum.  Owing  to  the  greater  dependence  of  the  left  half  of  the  sac,  the  raphe  does 
not  occupy  a  strictly  median  position,  but  is  deflected  towards  the  left.  Internally 
evidence  of  the  union  of  the  scrotal  hahes  is  found  in  the  sagittal  partition  {septum 
scroti)  that  is  continued  inward  from  the  raphe  and  effectually  di\ides  the  scrotum 
into  a  right  and  a  left  pouch.  This  septum,  consisting  of  fibrous  tissue  rich  in  elastic 
fibres  and  the  prolongations  of  the  dartos  muscle,  is  attached  above  to  the  root  of  the 
penis  and  the  perineum,  blending  with  the  sheath  of  the  bulbo-cavernosus  muscle. 

Since  the  labio-scrotal  folds,  which  produce  the  scrotum  or  its  homologue,  the 
labia  majora,  according  to  sex,  are  developed  (page  2041)  independently  of  the  cov- 
erings of  the  spermatic  cord  and  the  testicle  derived  from  the  musculo-fascial  walls  of 
the  abdomen,  the  scrotum  contributes  additional  envelopes  for  :he  enclosed  structures. 
These  envelopes  are  the  skin,  which  is  here  thin,  delicate,  and  very  elastic,  unusually 
dark,  and  beset  with  scattered  crisp  hairs  and  numerous  sweat  and  sebaceous  glands  ; 


THE  SCROTUM. 


«9^? 


and  the///«/fa  dartos,  a  layer  of  modified  subcutaneous  ussue-the  superticial  fasiu- 
distinjfuished  bv  the  presence  of  numerous  longitudniaily  disiM.sitl  bundles  of  uu<»l- 
untary  muscle-fibres  and  much  elastic  tissue  and  by  the  entire  aUcnce  of  fat. 

The  muscular  tissue  (dartos  muscle),  where  best  developed,  as  m  the  anterior 
and  lateral  walls  of  the  scrotum,  is  sufficient  in  quantity  to  l>e  recounted  as  a  dis- 
tinct layer,  but  so  closely  att;iched  to  the  integument  as  to  lonu  practical  y  a  part  of 
t  At  Ihe  raphe,  while  ime  fibres  follow  the  skin  and  remain  superhcial.  the  majority 
enter  the  septum,  being  especially  well  vlevelo,K.-d  in  the  lower  part,  and  at  the  attached 
up4r  border  pals  over  into  the  dartos  of  the  penis  and  the  perineum.  The  numerous 
bundles  of  elastic  tissue  within  the  tunica  dartos.  m  the  upper  am  anterior  ,wrt  of  he 
scrotum  become  condensed  into  robust  bands  which  efhciently  aid  m  supp..rtin«  e 
scrotal  sac  since  they  are  continued  laterally  at  the  sides  of  the  penis  and  over  the 
spLrmauTcords  into  the  superficial  fascia  of  the  abdomen,  and  m  the  mid-iine  blend 
w^h  the  suspensory  ligament  of  the  penis.  Those  on  the  posterior  surface  are 
attached  over  the  pubic  and  ischial  rami.  .         _t  i 

Enumerated  from  without  inward,  the  layers  interposed  iK^tween  the  suriace  of 
the  scrotum  and  the  serous  cavity  surrounding  the  tc^stis  are  :  (  i )  the  skm  2  )  the 
modified  superficial  fascia  or  tunica  dartos,  ( 7, )  the  intercolumnar  fasca,  ( 4  •  the  crc^ 
masteric  fascii  (5)"  the  infundibuliform  fascia,  and  (6)  x\.^  tumcava^.nahs.  Of 
Tesf  he  first  two  alone,"  strictly  considered,  are  contributed  by  the  scrotum  the 
remaining  layers  being  derived  from  the  deeper  structures  o  the  abdominal  wall  and 
associated  wfth  the  descent  of  the  testicle.  The  connection  b^^w- V'^'i' 'd  bv\  Wse 
and  the  underlying  intercolumnar  fascia  is  by  no  means  firm,  being  eflected  b\  a  loose 
kyer  of  areolar  tissue,  devoid  of  fat.  that  penni^  a  ready  separation.  Part'ci'larly  m 
front,  between  the  external  scrotiil  envelope  and  the  coyerings  proper  of  the  teMis. 
Beneath  the  posterior  surface  of  the  scrotum  the  connection  is  firmer  (  Disse ).  I  his 
fep^ation.  h^ever.  is  arrested  at  the  lower  part  of  the  scrotum  owm,^  \°  l''U?Tower 
of  the  scrotal  liga,ne,it  (Fig.  1723).  a  mass  of  fibrous  tissue  that  anchors  the  lower 
end  of  the  tunica  vaginalis  and  the  testicle  to  the  external  envelopes. 

With  the  exception  of  the  serous  coat,  the  tunica  vaginalis,  these  con  erings  have 
been  considered  in  connection  with  the  spermatic  cord  (page  i960)  :  it  remains,  there- 
foTe  to  describe  more  fullv  the  serous  coat  to  which  incidental  reference  has  been  made 
rpa^'e  1041)  i"  its  relations  to  the  testis  and  the  epididymis.  ^  .  „  ,  , 
^  The  production  of  an  isolated,  closed  serous  sac  within  each  half  of  the  scro  urn 
results  from  partial  obliteration  of  the  serous  pouch,  the  processus  vaginalis,  that 
during  foetal  life  extends  from  the  general  peritoneal  cavity  into  the  scrotum  in  an- 
ticipation of  the  descent  of  the  sexual  gland.  _ 

The  tunica  vaginalis  (tunica  vaRinalis  propria  testis),  m  correspondence  with 
other  serous  membranes,  consists  of  a  parietal  and  a  visceral  portion,  the  latter  pro, 
V  ding  an  extensive  but  incomplete  investment  for  the  testis  and  the  ep-d'c  >"";•  a"d 
the  former  lining  the  serous  cavity  into  which  these  organs  thus  covered,  project. 
With  the  exception  of  small  spacer  caused  by  the  elevation  of  the  epididymis,  espe-- 
ciaSy  of  the  globus  major,  these  two  layers  are  practically  in  contact  and  separa  ed 
by  only  a  capUlary  cleft.     Whatever  space  exists  is  filled  by  a  clear  straw-colored 

'^''''TiSition  to  walling  the  c v  ity.  the  parietal  layerjny^t^  the  spermatic  cord  for 
abou  12  mm.  above  the  testicle  and  the  blood-vessels  behind,  and  then  '^  continued 
fnto  the  visceral  layer  along  the  line  of  reflection  th;it  passes  over  he  back  of  the 
tSs  to  i^'ower  pole  on  the  one  side  and  along  the  posterior  surface  of  the  epi- 
didymis on  the  other,  thus  leaving  an  intervening  uncovered  strip  as  a  passage-way 
for  the  duct,  vessels,  and  nerves.  .    .u    .    .: . 

From  the  line  of  reflection  the  thin  visceral  layer  completely  invests  the  testis 
and  the  epididymis,  adhering  intimately  with  the  tunica  albuginea,  a"<\dipping 
deeply  between  these  organs  to  form  the  digital  fossa  ( sinus  epididymidis)  This 
Set  (F  g  1650),  the  entrance  to  which  is  narrowed  by  two  transverse  folds  (liga- 
S^ntoepidiS-nidis  superior  rt  inferior),  may  be  so  deep  that  the  serous  membrane  at 
its  bottom  i/  in  contact  with  that  reflected  from  the  median  side  of  the  e.ticle.  Nu- 
merous bundles  of  involuntary  muscle-the  m.  cremaster  aUernus  oi  "^'"^'^-•^d'ate 
h^om  theTrotal  ligament  at  the  lower  part  of  the  scrotum  to  spread  out  between  the 


|,- 


1964 


HUMAN  ANATOMY. 


parietal  layer  of  the  tunica  vaginalis  and  the  infundibuliform  fascia,  extending  upward 
into  the  spermatic  cord. 

Vessels. — The  arteries  supplying  the  scrotum, — ^as  distinguished  from  those  des- 
tined for  the  sf>ermatic  cord  and  the  sexual  gland  and  associated  structures,  — although 
of  small  size,  are  derived  from  different  sources.  Those  distributed  to  the  front  and 
sides  are  the  anterior  scrotal  branches  from  the  deep  external  pudics,  supplemented 
above  by  twigs  from  the  superficial  external  pudirs.  The  back  of  the  scrotum  and  the 
septum  are  supplied  by  the  posterior  scrotal  arteries,  superficial  branches  from  the 
internal  pudics.  Free  communication  exists  not  only  between  the  vessels  of  the  two 
sides  across  the  mid-line,  but  also  between  the  anterior  and  posterior  branches  at  the 
sides.  The  scrotal  arteries  anastomose  with  twigs  from  the  obturator  and  internal 
circumflex,  as  well  as  with  those  from  the  cremasteric  artery. 

The  veins,  numerous  and  plexiform  in  arrangement,  form  tnmks  that  follow  the 
general  course  of  the  chief  arteries,  becoming  tributary  to  the  external  saphenous  or 
the  femoral  and  the  internal  pudic  veins.  They  anastomose  freely  with  the  adjoining 
venous  paths  of  the  penis,  jierineum,  and  pubic  region. 


Fio.  1672. 


Vdn 


Vas  deferens 

St)ermatir  %-eins 


'rmatic  arteries 


Blood-vesflels  -^-^ififflBmWM^'n  '^    I  S^S^ — MediaMiiiuni  te>tift 

♦.—- ^j — Visceral  tiiiiira  vaKitialis 

Parietal  tunica  vKxinalis 

Ltibules  of  left  testis 
Sac  of  tunica  vaginalis 

Tunica  vaijinalis'^  , '"  y"- 

Cremasteric  fasciu  | 

Skin  and  dartos  t  Septum  of  scrotum 

Obliquely  cut  vas  deferens 
Section  across  formalin-hardened  scrotum,  sliowinir  lower  end  of  spermatic  cords  and  testes  in  section. 


The  lymphatics  of  the  scrotum  are  very  numerous  and  form  a  superior  and  an 
inferior  group  of  vessels,  all  of  which  lead  to  the  median  group  of  superficial  inguinal 
lymph-nodes.  Frequent  communications  occur  with  those  of  the  penis  and  perineum, 
but  only  sparingly  with  the  deep  lymph-tracts  within  the  spermatic  cords. 

The  nerves  supplying  the  scrotum  are  derived  from  both  the  lumbar  and  sacral 
plexuses.  Those  from  the  foiner  source  are  distributed  to  the  front  and  sides  of  the 
scrotum  and  include  cutaneous  twigs  from  the  genital  branch  of  the  genito-crural 
nerve,  usually  reinforced  by  twigs  from  the  ilio-inguinal  that  end  in  the  integument  in 
the  vicinity  of  the  root  of  the  scrotum.  Those  from  the  sacral  plexus  supply  the 
posterior  surface  of  the  scrotum  and  are  from  the  perineal  or  inferior  pudendal 
branches  of  the  small  sciatic  nerves  and  the  anterior  or  external  superficial  perineal 
branches  of  the  pudic  nerves.  Sympathetic  fibres  accompany  the  cutaneous  ner\-es 
for  the  dartos  muscle. 


PRACTICAL   CONSIDERATIONS:    THE   SCROTUM. 

The  .scrotum,  from  a  practical  stand-point,  may  be  studied  as  if  composed  of 
two  layers,  an  external,  made  up  of  the  skin  and  dartos,  and  an  internal,  consisting 
of  the  three  coverings — fascial,  muscular,  and  afmneurotic — derived  from  the  abdomi- 
nal wall,  the  infundibuliform,  cremasteric,  and  intercolumnar. 

As  the  testes  are  safer  from  injury  in  a  loose  pouch,  in  which  they  can  readily 
glide  away  from  threatened  trauma,  the  scrotum  is  redundant  (more  so  on  the  left 


THE   PENIS. 


"965 


side  on  account  of  the  greater  length  of  the  left  spenvaiic  cord )  and  lax.  Advantage 
of  these  facts  is  taken  in  certain  operative  priKedure.,,  as  in  making  the  rtajw  in  Roux  s 
operation  for  vesical  exstrophy,  or  excising  a  ptjrtion  of  the  scrotum  ( to  secure  (inner 
support  for  the  vascular  structures  of  the  cord )  in  varicocele.  ,    ,      ,    , 

The  redundancy,  thinness,  and  elasticity  of  the  skin  and  the  laxity  of  the  falles.s 
areolar  tissue  connecting  the  internal  and  external  layers  combine  to  favor  :  ( <« )  marked 
discoloration  and  great  extravasation  of  bUxKl  in  cases  of  hemorrhage  from  the  ves-sels 
lietween  the  two  layers  ;  hence  in  orchitis  leeches  are  applied,  not  over  the  scrotum, 
but  in  the  line  of  the  cord  in  the  groin  ;  (d)  extreme  distention,  as  in  large  scrota 
hernia  in  hydrocele,  in  bulky  testicular  tumors;  (c)  extensive  o-dema  111  general 
anasarca  as  a  result  of  pelvic  venous  thrombosis,  or  accomiwnying  an  infectious  cellu- 
litis or  an  extravasation  of  urine,  which,  when  it  proceeds  from  a  s<jlution  of  aMitin- 
uity  anterior  to  the  triangular  ligament,  is  directed  by  CoUes's  fascia  into  this  cellular 
space  between  the  two  layers.  The  thinness  of  the  scrotal  skin,  increasetl  when  it 
is  distended,  makes  it,  in  spite  of  its  vascularity,  very  susceptible  to  gangrene  from 
pressure  as  in  "strapping"  an  intlametl  testicle,  or  from  underlying  cellulitis. 

The  longitudinal  contractile  fibres  of  the  dartos  draw  the  redundant  skin  into 
transverse  rug*  which,  by  retaining  extraneous  dirt  and  the  secretions  of  the  sweat- 
glands  and  sebaceous  follicles,  become  often  the  starting-jioint  of  eczema,  of  mucous 
iiatches,  or  even  (as  in  "  chinmey-sweep's  cancer"  )  of  epithelioma.  The  contractil- 
ity of  the  dartos  is  marked  in  young  and  robust  persons,  and  is  increa.sed  by  cold,  by 
sexual  excitement,  and  by  light  friction.  It  is  lessened  in  ok:  age,  by  debility,  or  by 
continued  warmth  and  moisture,  the  scrotum,  in  the  presence  of  those  conditions, 
becoming  smooth,  elongated,  and  pendulous.  It  is  useful  in  aiding  the  scrotum  to 
regain  its  normal  size  after  distention,  as  following  the  tapping  of  a  hydrocele  or  the 
removal  of  a  tumor.  On  the  other  hand,  the  dartos  tends  to  invert  the  edges  of  a 
scrotal  wound  (as  the  platysma  does  those  of  a  wound  of  the  neck),  and  warm  appli- 
cations may  therefore  be  useful  before  a  scrotal  incision  is  sutured. 

The  muscular  (cremasteric)  element  of  the  inner  layer  gives  it  contractility,  and 
the  intimate  connection  between  it,  the  deeper  ( infundibuliform )  plane  of  fascia,  and 
the  parietal  layer  of  the  tunica  vaginalis  enables  it  to  elevate  the  testicle  with  its 
coverings  when  it  is  excited  to  contraction.  This  may  be  done  (cremasterit  reflex) 
by  drawing  the  finger-nail  over  the  skin  of  the  thigh  a  little  below  Poupiirt's  liga- 
ment, the  sensory  impression  being  conveyeti  from  the  skin  through  the  crural  branch, 
and  to  the  cremaster  through  the  genital  branch,  of  the  genito-crural  nerve. 

The  inhmdibuliform  (internal  sjiermatic)  fascia,  by  its  close  relation  to  the  pos- 
tero-inferior  portion  of  the  testicle,  on  the  one  hand,  and  to  the  external  scrotal  layer, 
on  the  other,  assists  the  scrotal  ligament  (page  2042)  in  preventing  the  testicle  from 
lieing  floated  up  when  the  space  between  the  two  layers  &i  the  tunica  vaginalis  is 
fillet!  with  fluid  (hydrocele,  haematocele),  and  holds  it  in  the  lower  back  part  of  the 

scrotum.  ,     ,        ,       l  1         i  ■ 

In  exploratory  puncture,  or  in  the  tapping  of  hydrocele,  the  spot  selected  is 
therefore  on  the  a  iterior  surface  of  the  upper  two-thirds  of  the  scrotum,  care  being 
taken  to  avoid  the  large  superficial  veins. 

THE  PENl.S. 

The  penis,  the  organ  of  copulation  of  the  male,  consists  of  three  cylinders  of 
erectile  tissue — the  paired  corpora  cavernosa  and  the  single  corpus  spongiosum— 
united  with  one  another  and  in\ested  by  coverings  of  fascia  and  skin.  Since  the 
upper  or  proximal  portion  of  the  penis  ( pars  perinealis)  is  buried  l^neath  the  intcgu 
ment  and  fascia  of  the  perineum  aiul  the  scrotun.  only  the  free  pendulous  distal 
portion  of  the  organ  is  visible  in  the  undissected  subject. 

When  exposed  throughout  its  entire  extent,  the  fxjnis  presents  a  cylindncal  shaft 
or  bodv  (corpus  penis),  which  begins  above  in  a  three-pronged  root  (radix  penis) 
attached  to  the  pubic  arch  and  the  triangular  ligament  ami  terminates  below  in  a 
blunted  conical  end.  the  glatis penis.  The  anterior  or  upper  surface  (dorsum  penis) 
is  somewhat  flattened  and  formed  by  the  corpora  cavernosa.  The  posterior,  under, 
or  urethral  surface  <  facics  urethralis)  corresponds  to  the  corpus  spongiosum,  traversed 


1966 


HUMAN   ANATOMY. 


by  the  urethra,  and  is  marked  by  a  median  raphe,  which  is  continuous  with  that  of 
the  scrotum  and,  as  the  latter,  indicates  the  line  of  fusion  of  the  original  components 
of  the  spongy  body. 

The  conical  glans,  which  forms  the  distal  end  of  the  organ,  is  limited  along  its 
oblique  base  by  a  prominent  rounded  border,  the  corona  glandis,  that  runs  downward 
and  forward  from  the  dorsum  towards  the  under  surface  and  marks  a  groove  (sulcus 
retroKlandularls)  that  separates  the  glans  from  the  body  of  the  penis.  The  constricted 
zone  immediately  behind  the  glans  constitutes  the  neck  (collum  penis).  In  conse- 
quence of  the  obliquity  of  the  corona,  the 
Fig.  1 6731  dorsal  expansion  of  the  glans  measures 

about  twice  the  length  of  its  under  sur- 
face. 

The  skin  covering  the  pendulous 
portion  of  the  penis — very  thin,  delicate, 
and  elastic,  and  possessing  only  fine 
hair  (lanugo)  except  in  the  immediate 
vicinity  of  the  pubes — is  loosely  attached 
over  the  body  of  the  organ  by  subcu- 
taneous tissue,  devoid  of  fat,  that  permits 
of  ready  movement  of  the  integument. 
Along  the  under  surface  of  the  organ 
bundles  of  involuntary  muscle  closely 
adhere  to  the  integument  and  constitute 
a  stratum,  the  tunica  dartos  penis,  that 
resembles  the  similar  layer  of  the  scro- 
tum. Just  behind  the  corona  the  skin 
forms  a  free  duplicature,  the  prepuce  or 
foreskin  (praeputium  penis),  that  covers 
the  glans  to  a  variable  extent  ( in  children 
and  in  some  adults  completely)  and  is 
firmly  attached  by  its  inner  layer  to 
the  neck  of  the  penis  along  a  line  about 
3  mm.  above  the  corona.  From  this 
point  the  skin  is  prolonged  over  the 
glans,  to  which  it  is  intimately  applied, 
as  far  as  the  meatus,  where  the  mtegu- 
ment  becomes  continuous  with  the  ure- 
thral mucous  membrane.  The  lines  of 
reflection  of  the  prepuce  on  the  two  sides 
converge  and  finally  meet  along  the 
under  surface  of  the  glans  in  a  sharp 
median  fold,  the frcnum  (frenulum  prae- 
putii),  that  extends  as  far  as  the  pos- 
terior border  of  the  slit-like  urethral 
opening.  On  either  side  of  this  fold  a 
shallow  recess  ( fossa  frennli)  extends  the 
preputial  sac.  The  skin  lining  the  latter 
and  covering  the  glans  is  modified  so 
that  it  somewhat  resembles  a  mucous  membrane,  as  which  it  is  often  inaccurately 
described.  While  entirely  devoid  of  hairs,  small  sebaceous  glands  are  sparingly 
distributed  over  the  glans.  corona,  and  inner  layer  of  the  prepuce.  These,  formerly 
supposed  to  be  of  large  size  and  named  the  glands  of  Tyson  (glandulae  praeputiales), 
secrete  unctuous  material  which,  mixed  with  discarded  epithelial  cells,  may  collect 
in  the  groove  behind  the  corona  as  a  cheesy  substance,  the  smegma. 

The  corpora  cavernosa  (corpora  cavernosa  penis)  are  two  cylinders  of  erectile 
tissue,  when  relaxed  about  15  cm.  (6  in. )  in  length,  that  form  the  chief  bulk  of  the 
body  of  the  penis.  Each  is  enclosed  within  a  dense  fibro-elastic  envelope,  or  tunica 
albuginea,  which  internally  is  continuous  with  the  trabeculae  between  the  blood- 
spaces.     Beginning  above  at  the  root  of  the  penis  as  the  diverging  pointed  and  then 


j  Iiiferioi  layer 
I  of  tri.inKular 
I  ligament 
Attachment  of  bulb,  cut 

Dissection  of  fienis.  showinje  three  component  cylin- 
ders ;»f  erec  Jle  tissue ;  liislal  emi  nf  corpus  sponfifiosum. 
with  Klans,  has  been  freed  and  tumeil  asitle;  attachment 
of  urethral  bulb  has  Ijeen  cut  atui  bulb  drawn  aside. 


TH»:    I'KNIS. 


uK'7 


somewhat  expanded  crura  attached  to  the  inner  liorderot  the  pubic  arch,  the  cavern- 
ous bodies  are  at  first  separated  by  an  interval  occupied  by  the  bulb  of  the  corpus 

Flo.  1674. 


CrcMS-seilioiw  o(  formalin-hardened  penis  at  diHerent  leveh.  -^.throuffh  eUna,  near  Up;  /f,  al«.ut 
middle  o(  glans;  f,  thn.URh  corona;  />.  bodv.  distal  part;  /■:.  boily  proxmal  part,  rc^orpus  lawr- 
no.um;  rifcorpi.  suonxioSum  ;  rffl.  dorsal  artery  ;rfrf...  deep  dorsal  vein  ;  '•  fi^.^';"*. '■";^f  "Pf,  ,'' :  ""^'^ 
tissue  o(  i{Uns;/,frenum;//.  fibrous  tissue;  j,  fibrous  septum;  n/v,  auperficial  donal  vem;  i/,  super- 
ficial faacia ;  st,  skin ;  la,  tunica  albuginea ;  n,  urethra. 

spongiosum.  Farther  forward,  in  the  vicinity  of  the  penile  angle,  the  corixsra  caver- 
nosa press  against  each  other  with  their  median  surfaces,  the  opposed  flattened  cap- 
sules blending  to  form  a  median  partition  (septum  penis).  Lower  the  latter  becomes 
imperfect  and  replaced  by  a  series  of  vertical  bands,  and  hence  is  often  designated  the 
pediniform  septum,  the  intervening 


slit-like  apertures  permitting  commu 
nication  between  the  blood-spaces  of 
the  two  cavernous  bodies  as  well  ;is 
the  passage  of  anastomotic  branches 
of  their  arteries,  'n  certain  mammals, 
especially  the  rnivora  and  some 
marsupials,  a  bone  (os  penis)  is  de- 
veloped within  the  fibrous  septum. 
On  approaching  the  corona,  the  cor- 
pora cavernosa  again  become  discrete 
and  rapidly  taper  to  blunt-pointi  d 
ends  that  are  separated  externally  by  a 
slight  furrow  and  cappeU  by  the  over- 
lying glaas.  The  dorsal  and  under 
surfaces  common  to  the  closely  ap- 
plied cavernous  bodies  are  marked  by 
longitudinal  grooves  ;  that  along  the 
former  surface  lodges  ihe  dorsal  ves- 
sels of  the  penis,  while  the  under  fur- 
row is  filled  by  the  spongy  body. 

The  corpus  spongiosum  (cor- 
pus cavernosum  urethrat: ),  the  third  and 
much  smaller,  although  longer  (alx)ut 


Fig.  1675. 


Dorsal  vein, 
now  .iouble 


Pubic  bor 


Crus 

Deep  artery  ii 

corpus  cavenntsum 

r  ret  bra' 

lscbi»  wave!  nosus 
muscle 

Bulh 


Bulbo.ravemos  US- 
muscle 


Colles's  fascia 


Frontal  section  throunh  pubic  arch  and  root  ot  penis. 


l^  cm.  or  b%  in.),  cylinder  of  erectile  tis.sue,  occupies  the  groove  along  the  under 
surface  of  the  cavernous  bodies.     The  two  ends  of  this  cylinder  are  enlarged,  the 


1968 


HUMAN  ANATOMY. 


upper  expanding  into  a  pyriform  mass  of  erectile  tissue,  the  urethral  bulb  ( bulbvH 
nrethrae),  and  the  lower  broadening  into  a  conical  cap  of  erectile  tissue  that  covers  the 
ends  of  the  corpora  cavernosa  and  contributes  the  bulk  of  the  glans.  With  the 
exception  of  the  bulb,  the  major  jwrt  of  which  lies  behind  the  canal,  the  coq)us  spon- 
giosum is  traversetl  by  the  urethra,  the  cavernous  tissue  completely  surrounding  the 
urinary  tube.  The  bulb,  attached  by  its  upper  surface  to  the  inferior  layer  of  the 
triangular  ligament  and  covered  below  by  the  bulbo-Givemosus  muscle,  presents  a 
slight  median  furrow  (sulcus  bnibi)  that  suggests  a  division  into  the  so-called  hemi- 
spheres. Internally  an  imperfect  median  septum  bulbi  partially  subdivides  the  erectile 
tissue  below  and  behind. 

The  glans  penis  consists  almost  entirely  of  erectile  tissue  (corpus  cavernosum 
glandis)  directly  continuous  with  that  of  the  ;  -^  body.  Its  upper  surface  is 
holli>wed  out  to  receive  the  pointed  extreni'tie  the  corpora  cavernosa,  so  that  a 
section  across  the  upper  part  of  the  glans  shows  the  erectile  tissue  of  the  cavernous 
bodies  surrounded  by  an  overhanging  crescent  of  the  cavernous  tissue  of  the  glans 
(Fig.  1674,  C).  Along  the  frenum  the  fibrous  envelope  of  the  glans  is  prolonged 
inward  towards  the  urethra  as  a  fibro-elastic  band  ( ligamentnm  medianum  glandis) 
which,  in  conjunction  with  a  similar  band  connecting  the  ends  of  the  cavernous  bodies 
with  the  upper  urethral  wall,  forms  a  median  partition,  the  septum  glandis,  that  in- 
completely divides  the  erectile 
Fig.  1676. 

Krertilf  tiiwue  nf  corpus 
Turi'i'a  albuKUica     cavi-nMnutn  broken  u]> 


Prepuce 


by  ptxtttltfomi  septum 


l-^rectile  tissue 
of  Klans' 


Anterior 

I'Xtremityol 

corpus  lav- 

eriiosum 
External 
urethral 
orifice 

Navicular  lossa' 


Frenum         Erectile  I'relhni 

tisHUe  of  corpus  sjKiitKiosum 

Mesial  lonKittidinal  section  of  end  of  penis. 


tissue  of  the  glans  and  sur- 
rounds the  terminal  part  of  the 
urethra. 

The  penile  portion  of  the 
urethra  is  descnbed  with  the 
other  parts  of  the  urinary  tract 
in  the  male  (page  1923). 

Beneath  the  skin  and  sub- 
cutaneous tissue  the  cylinders 
of  erectile  tissue,  enclosed  and 
united  by  their  albuginea,  are 
enveloped  by  the  superficial 
fascia  (Fig.  1674,  E).  The 
latter,  directly  continuous  with 
that  of  the  perineum  (Colics' 
fascia )  behind  and  of  the  ab- 
domen (Scarpji's  fascia)  above,  invests  the  penis  as  far  as  the  neck,  where  it  becomes 
blended  with  the  prepuce.  This  fibro-elastic  sheath  is  often  called  the  faseia  penis. 

In  addition  to  the  attachment  of  the  crura  of  the  corpora  cavernosa  to  the  peri- 
osteum of  the  pubic  arch  and  of  the  bulb  of  the  spongy  body  to  the  triangular  liga- 
ment, the  penis  is  supported  by  fibrous  bands  that  extend  from  the  abdominal  wall 
and  pubes  to  the  dorsum  penis.  This  triangular  sheet,  the  suspensory  ligament,  in- 
cludes a  superficial  and  a  deeper  portion.  The  former  ( ligamentum  fundiforme  penis) 
begins  at  the  linea  alba,  from  4-5  cm.  (  i  J4-2  in. )  above  the  symphysis,  and  consists 
of  elastic  bundles  prolonged  from  the  deep  layer  of  the  superficial  fascia  downward  to 
the  dorsum  of  the  penis  (Fig.  1671)  at  the  so-called  angle,  where  it  divides  into  two 
arms  that  embrace  the  penis  and,  after  uniting  on  the  urethral  surface,  are  continued 
into  the  septum  scroti.  The  deeper  portion  ( liKameatum  suspensorium  penis)  contains 
compact  fibrous  bands  that  (mss  from  the  symphysis  to  the  corjxira  cavernosa,  just  in 
advance  of  their  separation  into  the  diverging  crura,  to  blend  with  the  dense  albuginea. 
Structure. — Each  of  the  component  cylinders  of  erectile  tissue  is  enclosed  in  a 
robust  sheath,  the  tunica  albuginea,  composed  of  dense  white  fibrous  tissue,  inter- 
mingled with  relatively  few  elastic  fibres  and  no  muscle.  The  sheath  surrounding  the 
corpora  cavernosa,  which  in  places  attains  a  thickness  of  2  mm.  and  is  much  stronger 
than  that  enclosing  the  ^^pongy  body,  is  imperfect  along  the  opposed  median  surfaces 
of  the  two  cylinders,  where  it  forms  the  pectiniform  septum. 

From  the  inner  surface  of  the  tunica  albuginea  septa  and  trabecule  are  given  off 
which  constitute  the  framework  supporting  the  vessels  and  nerves  and  enclosing  the 
characteristic  blood-spaces  of  the  erectile  tissue.      Numerous  bundles  of  involuntary 


THE   I'ENIS. 


1969 


Fio.  1677, 


Deep  domi  vein 


Snhcutanrou* 
tiMUe 


Skin- 


Septum^ 


■M 


Tunica  ilbiixinc* 


:mS'' 


l.M\'XiS\ 


UCorpu* 

1  cKverfKMum 


muscle,  rircularly,  lonRitudinally,  and  obliquely  disposed,  occupy  the  connective-tiMue 
trabecula-  and  plates  se|>aratin>{  the  venous  lacuna-,  aroun<l  which  they  k.rm  imperlect 
layers  of  contractile  tissue.  The  trabecular  muscle  is  most  developed  withm  the  cav- 
ernous and  spongy  bo<lies  and  least  so  within  the  ulans. 

The  arteries  conveying  blood  to  the  cylinders  of  erectile  tissue  are  of  two  kmds. 
— thiwe  nourishing  the  tissues  themselves  ( vasa  nulrilia  )  and  those  carryinK  bl.nxl  to 
the  venous  lacuna-.  The  latter  aie  connected  with  the  arteries  either  directly  by 
minute  channels  or  through  intervening  capillaries.  Within  the  traljecula;  of  the 
deeper  parts  of  the  erectile  mas.ses  the  deep  arteries  of  the  i>enis  give  of!  short,  tortuous 
branchw  {arterie  helicinte),  about  a  mm.  in  length,  that  project  into  the  blo<x  -spaces 
with  which  they  directlv  communicate  by  minute  ojienings  at  their  ends.  Notwith- 
sundinir  their  exceptional  development  in  man.  the  fact  that  the  hel.-ine  arteries  are 
wanting  in  many  mammals  showsth.it  they  are  not  essential,  although  advantageous, 
for  erection  The  arteries  of  the  erectile  tissue  are  distinguished  by  the  unusual  thick- 
ness of  the  circular  muscle  within  their  walls.  In  places  the  intima  ikewise  exhibits 
excessive  thickness.  Since  the  increase  is  not  uniform  but  local,  it  leads  to  the  pro- 
duction of  cushion- 
like elevations  that 
encroach  upon  and 
even  temporarily  oc- 
clude the  lumen  of  the 
arteries 

The  blood-spaces 
or  lacuna  that  occupy 
the  interstices  between 
the  trabecula  are  to 
be  regarded  as  venous 
net-works  which  com- 
municate with  the  ar- 
teries, on  the  one 
hand,  and  with  the 
radicles  forming  the 
veins,  on  the  other. 
Their  form  and  size  superficial' 
evidently  depend  '■"-'■- 
upon  the  degree  of 
distention,  when  con- 
taining little  blood  the 
spaces  being  often 
mere  slits  or  irregu- 
larly stellate  clefts, 
while  when  filled  they 

become  more   cvlin-  ... 

drical  in  form.  In  a  general  way  three  districts  may  be  disunguisned  :  (a)  a  narrow 
outer  peripheral  zone  of  .almost  capillary  spaces,  for  the  most  part  narrow  and  tnan- 
gular  in  outline  ;  ( *)  an  inner  peripheral  zone  of  larger  spaces  of  uncertain  form  and 
from  .  1 5-.  20  mm.  in  diameter  ;  and  {c)  a  central  zone  of  still  more  extensive  spaces, 
which  in  places  attain  a  diameter  of  one  or  more  millimetres  and  are  enclosed  by  rela- 
tively thin  intervening  lamell*  and  trabeculae.  Since  their  expansion  is  usually 
greater  in  one  direction,  the  general  form  of  the  larger  and  deeper  lacuna  is  often  ap- 
proximately cylindrical.  Within  the  corpus  spongiosum  in  the  immediate  \'icinity  of 
the  urethra  the  blood-spaces  are  somewhat  concentrically  disposed  owing  tt  •  the  fttble 
development  of  the  radial  lamellae  (Ebcrth).  The  spongy  body  is  further  distin- 
guished by  the  robustness  of  its  trabeculse  and  the  consequent  reduction  in  the  size  of 
the  blood-sp.-ices.  Beyond  the  single  layer  of  endothelial  plates,  the  lacuna-  do  not 
possess  a  distinct  wall  other  than  the  fibro-mii«riilar  tissue  of  the  surrounding  trab'-ulsp. 
The  deep  veins  draining  the  cylinders  of  erectile  tissue  do  not  directly  open  into 
the  blood-spaces,  but  are  formed  by  tributaries  of  various  size  that  begin  as  apertures 
in  the  walls  of  the  lacunae,  of  which  they  are  in  fact  extensions.    The  tributaries  of  the 

134 


UrcUm' 


Transverse  section  of  penis  of  child.    X  10. 


Corpus 

sponxiosum 


I970 


HUMAN   ANATOMY. 


more  superficially  situated  venous  trunks,  as  the  dorsal  vein,  arise  chiefly  from  the 
venous  net-works  of  the  peripheral  zone.  The  veins  possess  an  unusually  well- 
developed  muscular  coat,  and  m  places  exhibit  lc»cal  cashion-like  thickenings  of  their 
intima  similar  to  but  les.s  marked  than  those  seen  in  the  arteries. 

VetseU.— The  arteries  of  the  penis  constitute  a  superficial  and  a  deep  set,  the 
former  supplying  the  integument  and  as-sociated  envelopes,  while  the  latter  convey 
blood  to  the  masses  of  erectile  tissue.  The  suptrficial  arteries  include  twigs  from 
the  external  pudic  branches  of  the  femorals  to  the  lateral  and  under  surface  of  the 
penis,  from  the  dorsal  arteries  to  the  anterior  surface  and  the  prepuce,  and  from  the 
superficial  perineals  by  small  vessels  to  the  posterior  \\axX  of  the  urethral  surface. 
The  deep  arteries— a.11  branches  from  the  internal  pudics — supply  the  three  cylinders 
of  erectile  tissue,  including  the  glans.  The  corjjus  spongiosum  receives  the  arteries 
of  the  bulb,  their  continuations  (  sometimes  describetl  as  the  urethral  arteries)  accom- 
panying the  urinary  canal  as  far  as  the  glans,  where  they  anastomose  with  the  terminal 
branches  of  the  dorsal  arteries.  The  last-named  vessels  also  send  small  twigs  around 
the  corpora  cavernosa  to  the  sjH>ngy  body.  The  corpora  cavernosa  are  supplied 
chiefly  by  the  deep  arteries  of  the  penis,  supplemented  by  twigs  from  the  dorsal 

arteries  that  pierce  the  albu- 
Fio.   1678.  _        .       . 

Ceiilral  bluod-spactra       Inner  perlpbenil  ipaces 


Outrr  prriphcral  Bpacc* 


gmea.  Entering  the  cavern- 
ous bodies  about  where  the 
crura  unite,  the  deep  arteries 
of  the  penis  traverse  the  cyl- 
inders somewhat  eccentri- 
cally, to  the  median  side  of 
their  axes.  Communication 
between  the  vessels  of  the 
two  bodies  is  established  by 
anastomotic  twigs  that  i)ass 
through  the  apertures  in  the 
median  septum,  as  well  as 
by  the  terminal  loop.  The 
dorsal  arterii>.  the  longest 
branches  of  the  internal 
pudics.  pass  along  the  dor- 
sum between  the  fascia  and 
the  albuginea,  in  company 
with  the  dorsal  nerves  and 
vein,  and,  in  addition  to  the 
twigs  distributed  to  the  cov- 
erings, the  cavernous  Ixidies, 
and  the  corpus  sjwngiosum, 
supply  the  erectile  tissue  of 
the  glans.  The  anastomoses 
between  the  various  vessels 
supplying  the  penis  are  very  free,  not  only  between  the  corresponding  and  other 
branches  of  the  two  sides,  but  also  between  those  of  the  superficial  and  deep  sets. 

The  jeins  of  the  penis,  like  the  arteries,  constitute  a  superficial  and  a  deep 
group  which  freely  communicate  and  carry  off  the  blood  from  the  <  iv  .lopes  and  from 
the  erectile  tissue  respectively.  The  superficial  veins  for  the  most  p.in  .ire  tributary 
to  a  subcutaneous  trunk  f  v.  dorsalis  penis  superficialls )  that  passes  upward  along  the 
dorsum  beneath  the  skin  to  the  pubes  and  terminates  either  by  dividiiitr  i"t<.  I. ranches 
that  empty  into  the  internal  saphenous  or  the  femoral  veins  on  litlicr  side  or  by 
joining  the  deep  dorsiil  vein  ;  both  modes  of  ending,  however,  may  exist.  .A  number 
of  vessels  from  the  integument  covering  the  posterior  part  of  the  urethral  surface  are 
collected  by  the  anterior  scn^tal  veins. 

The  deep  vein^,  which  begin  by  tributaries  from  the  erectile  ssue  that  they 
drain,  to  a  large  extent  discharge  their  contents  into  the  deep  dorsal  vein  (v.  dorsalis 
penis  profunda )  that  lies  beneath  the  fascia  and  occupies  the  groove  on  the  dorsum 
as  far  as  the  suspensory  ligament,  between  the  superficial  and  deep  parts  of  which  it 


Trabecular 


Bundles  ot  muscle 


Denite  fibrous  ttiisue  r 
tunica  albUKtiiea 

Transverse  section  throuKh  peripher>'  of  corpus  cavernosum.     X  50. 


. 


THE  iKNIS. 


19"  < 


fr 


passes.     C.mtinuinK  betwtt-n  the  subpubic  a.,.t  tr.insverse  liKamonts  and  nierc »,«   he 

XxuH  IWinninK  aU.ve  the  corona  by  tho  union  of  two  stems  that  collet  brunches 
from  the  ulans  and  the  prepuce,  the  <ieep  dors;il  vein,  xs  it  courts  upwar.l.  r.H:e.ves 
trilnilarie^  fron.  all  thrcl  cjlimlers  of  erectile  tissue.  Th.«c-  from  the  cor.n.ra  n.ver- 
n,Ui  either  pierce  the  albuninea  as  short  branches  that  p;iss  directly  mto  tlj.  dors., 
vefn  o  emerRe  from  their  under  ^.  H.-e  aUmR  the  urethral  Kr-.w  and  «uu  around 
'hThodv  of  the  penis  to  reach  the  .  .lecting  trunk  on  the  dorsmn.  the  -"teru.r  of 
hese  clrrnm/lexrfins  Uk\n^  up  tribuuries  from  the  under  suriace  ot  the  ,;Uns. 
VVhhin  the  ,x.sterior  part  of ^he  cavernous  ».,dies  are  formed  the  deep  vems  o  the 
peni^  which  emerge  where  the  cn.ra  diverge  and,  alter  estabhshmK  commumcati.  s 
S^  h  the  prosutic  pUxus,  bc-con,e  im,K>rtant  tributaric-s  of  the  mternal  ,..k1.c  ve  ns 
St  acco,^p.my  th.-  corrc-spondin^  arteric-s.  The  corpus  s,K.n«..«um  .s  'Ir-u^-^^l'V 
anterior  brinchc-s  that  conXy  the  bUnxl  to  the  dorsal  ven.  by  jonunR  tj-  ' '^>^'  "f-'' 
or  other  veins  from  the  corp.racavern.««.  ami  by  ,K«.tenor  stems  (»v.  ufithrales)  hat 
pass  upward  and  backward' and  empty  i«rtly  into  the  prcmtat.c  plexus  and  partly  no 
The  intS  pudic  veins,  the  veins  from' the  urethral  bulbhavm^  a  sm.Uar  destuwt.o. . 
Numerous  aLtomoses  betwcH..n  the  cutaneous  veins  and  those  from  the  erect.le  tissue 
establish  free  communication  l)etween  the  suiK-rticial  and  deep  vessels. 

The  /v,nphalus  are  numerous  and  dispos-xl  .ns  su,>erfic.al  p.v-  -U.-p  vessels  The 
former  are  tnbutary  chiefly  to  a  su,>erficial  dors;il  stem  that  »c.on,.>an.es  the  t  r- 
T^'Jnl  x"in  and  begins  by  the'confluence  of  pkxiform  K  n  ;  .  aUcs  w.thm  the 
SuS  of  the  prepuce  and  frenum.  Duriujj  its  course  the  dor*il  trunk  recevc-s 
ynSics  from  thL  adjacent  territory  as  well  as  others  '^'^'he  under  surhice  that 
K^  the  dorsum  bv  following  the  circumflex  veins  around  the  b<xly  of  the  pen.s 
A  the  pubes  the  superficial  dorsal  lymph-trunk  p.-»sses  either  to  the  nght  o  left,  or 
when  double,  as  it  ^casionally  is.  to  both  or  even  opp.«,te  sides,  and  joins  he 
meXn  group  of  superficial  inguinal  lymph-n.Klc-s.  Direct  communications  with  the 
S  "ubinguin:U  nodes  sometimes  exist  (Kiittner).  The  dee,>er  lymph.-itics  are 
StkuSy  numerous  in  the  periphery  ..f  the  glans.  .around  the  meatus  commum- 
Sg  Sh  the  urethral  and  preputial  plexuses.  Trunks  are  formed  which  occupy 
the  retroglandular  sulcus  and  unite  into  a  deep  dorsal  lymph-stem,  sometime^  double, 
that  accompanies  the  corresponding  vein  beneath  the  fascia  and  terminatc>s.  when 
sinirle   in  the  median  inguinal  nodes  of  the  left  side  (Marchant). 

The  nerves  of  the  penis  include  both  spinal  and  sym,>athetic  fibres  the  former 
from  the  ilio-inguinal  and  the  pudic  nerxes.  and  the  latter  'f^l"  j'^^. ''>'P*'«''''\"^ 
plexus      The  integument  around  the  r.wt  of  the  penis  is  supplied  by  the  cuUmet, us 
Ranches  of  the  ilio' inguinal  and  the  inferior  P^^enclal  nerves   while  that  .J    h^  l,ody 
and  the  prepuce  is  provided  with  the  cutaneous  branches  of  the  dorsal  nerves.      I  he 
cv  nderTof'  cavernLs  tis.sue  also  receive  twigs  from  the  pud.c  -rv-.  the  bulba 
branches  of  which  pass  to  the  bulbus  urethra-  an.l  in  addition  supply  th^"  •"  ''""^ 
membrane  of  the  urethra.     Kach  corpus  cavem.jsum  rece.vc-s  a  deep  'l™";;'; '";^™ 
dorsal  nerve  which  is  given  off  as  the  latter  lies  between  the  layers  of  the  triangular 
Hgament.     The  sympathetic  fibres  destined  for  the  blcKH^-^  essels  and  muscle  o    the 
erecdle  tissue  are  continued  from  the  hypogastric  plexus  through  the  pn^tat.c  plexus 
U>  the  plexus  c-ivernosus,  where,  joining  the  don«.l  ner%es  of  the  penis   twigs  (  ncr^i 
«vern-i  ^nis  minores)  are  sent  to  the  posterior  part  and  the  crur:.  f  f^'"  corp-.ra 
cavernosa'^while  others  (nervi  cavernosi  penis  majores)  are  d.stnbv.te<l  to    he  low  r 
portions  of  the  erectile  masses,    st)me  fibres  terminating  wi  bin  the  sp^  ng>    bod> 
C  net-works  of  n.,n-m«lullated  fibres  have  been  traced  withm  the  bundles  o.inoN 
untarv  muscle  of  the  blo.Kl-ves.sels  and   tralKCul.T  of   the  erectile  tissue.      Certain 
cerebro-spinal  fibres  (nervi  eri«entes)  suppos.-d  to  Ix.  especially  "'""^^'J,;".,^^!.'    "" 
are  conveyed,  in  company  with  the  sym,«itlKt.c  fibres,  along  the  paths  of  the  cavernous 

^^^""in  addition  t.-.  n  gcnermw  ^-.i  .-nlv  of  the  more  nsnal  nerve-terminati.  ns  th--  skin 
of  the  glans  and  the  prepuce  is  provided  with  special  nerve-endings,  the  tactile 
^L  a  the  genital  corpuscles  o{  Krause  (p...   .0.7    'y"!.: -thm  th.  ^-e  and 

the  Pacinian  corpuscles  within  the  -'•     •'--'       n^tur       The  paths  of  >ens,.ry 

impressions  lie  within  the  dorsal 


. 


1972 


HUMAN   ANATOMY. 


VuiatioiM.— Apart  from  the  unimportant  individual  differences  due  to  age,  growth,  and 
sexual  activity,  the  variations  of  the  penis  are  for  the  most  part  referable  to  imperfect  develop- 
ment and  are  reccwnized  as  malformations  rather  than  as  anatomical  deviations.  The  explana- 
tion of  many  of  these  conditions  is  cupplied  by  the  developmental  history  of  the  structures 
mvulved  (p^  2044)  ■ 

PRACTICAL  CO>  ^DERATIONS :    THE  PENIS. 

The  size  of  the  penis  bears  less  constant  relation  to  general  physical  develop- 
ment than  does  any  other  organ  of  the  body.  The  normal  average  size  of  the  flaccid 
penis  of  the  adult  is  about  three  inches  in  circumference  and  from  three  and  a  half  to 
four  inches  in  length,  measured  from  the  suspensory  ligament.  When  erect,  this 
length  increases  to  about  six  and  a  half  inches  and  the  circumference  to  three  and  a 
half  or  more. 

Absence  of  the  penis  may  occur,  but  is  rare  unassociated  with  other  anomalies. 
Apparent  absence  (concealed  penis)  may  be  due  to  the  subcutaneous  situation  of  an 
atrophic  or  undeveloped  organ  which  may  be  palpated  through  the  skin  and  revealed 
by  an  incision. 

Micropenis  (infantile  penis)  is  not  uncommon,  and  varies  in  degree  from  a  mere 
failure  to  attain  quite  the  average  size  (annoying  chiefly  to  sexual  neurasthenics)  to  a 
retention  throughout  life  of  the  dimensions  and  development  normal  in  early  childhood 
or  infancy.  Occasionally  in  such  cases,  after  puberty  and  following  physiological 
activity  of  the  organ,  rapid  growth  takes  place  and  conditions  approximating  normal- 
ity may  result. 

Afegalopenis. — As  has  already  been  observed,  the  size  of  the  organ  bears  no 
constant  relation  to  the  size  or  strength  of  the  individual.  In  congenital  imbeciles  it 
is  often  of  unusual  size,  and  in  dwarfs  and  hunchbacks  it  is  not  uncommonly  devel- 
oped, not  only  out  of  proportion  to  the  other  parts  of  the  organism,  but  beyond  even 
the  average  for  individuals  of  normal  growth.  Hypertrophy  of  the  penis  is  at  times 
an  inconvenience,  and  may  even  be  a  source  of  danger,  since  an  excessive  develop- 
ment predisposes  to  abrasions  and  fissures  through  which  inoculation  with  venereal 
disea.ses  may  occur. 

Double  penis  has  been  recorded  in  a  few  instances,  in  at  least  two  of  which  each 
organ  was  functionally  perfect. 

The  skin  of  the  penis  is  thin  and  delicate  (to  maintain  the  sensitiveness  of  the 
organ),  and  is  lax  and  elastic  (to  permit  of  its  changes  in  size).  On  account  of  these 
qualities  abrasions  are  not  unusual,  and  through  them  syphilitic  infection  frequendy 
takes  place. 

The  loose,  plentiful  layer  of  subcutaneous  connective  tissue  permits  of  enormous 
oedematous  swelling  as  a  result  of  ordinary  staphylococcic  or  streptococcic  (pyogenic 
or  erysipelatous)  infection;  its  abundance  in  conjunction  with  the  elasticity  of  the  skin, 
accounts  for  the  disappearance  of  the  penis  in  cases  of  very  large  scrotal  hernia,  in 
hydroceles  of  similar  size,  and  in  elephantiasis  scroti. 

Anterior  to  the  corona  the  skin  is  modified  and  resembles  a  mucous  mem- 
brane, at  the  meatus  becoming  continuous  with  the  mucosa  oi  the  urethra.  The  line 
of  demarcation  between  the  ordinary  and  modified  cutaneous  surfaces  is  not,  however, 
so  distinct  as  on  the  lips  or  the  nostrils,  the  passage  of  one  surface  into  the  other  more 
closely  resembling  that  which  takes  place  at  the  margin  of  the  anus.  On  the  proxi- 
mal face  of  the  corona  the  subcutaneous  tissue  is  still  abundant.  Over  the  glans  it 
practically  disappears  and  the  modified  integument  closely  embraces  the  erectile  tissue 
of  the  expanded  anterior  extremity  of  the  corpus  spongiosum. 

Chancres  anterior  to  the  corona  (except  at  the  frenum)  are  apt  to  exhibit  the 
variety  of  induration  known  as  "laminated"  or  "parchment-like."  corresponding  to 
a  sclerosis  limited  to  the  papillary  layer  of  the  derma  and  to  the  vascular  net-work  of 
the  papill.-e.  At  the  frenum,  corona,  or  cerxix.  where  the  cellular  ti-ssue  is  abundant, 
"  nodular"  induration — a  sclerosis  of  the  whole  thickness  of  the  derma,  of  thesubder- 
moid  areolar  tissue,  and  of  the  a.ssociated  vascular  net-work,  which  is  much  larger 
than  the  superficial  or  papillary  supply — is  apt  to  occur,  and  is,  as  the  name  indicates, 
deeper,  thicker,  and  harder.  On  the  skin  of  the  penis  chancres  are  apt  to  be  exten: 
sive  in  area,  but  are  limited  in  depth  by  the  firm,  resistant  fascia  penis. 


PRACTICAL   CONSIDERATIONS:    THE   PENIS. 


•973 


At  birth  the  prepuce  is  normally  adherent  to  ihe  glans,  its  moderate  retraction 
barely  exposing  the  meatus.  Continued  retraction  everts  the  hps  of  the  meatus  and 
then  separates  the  epithelial  adhesions  between  glans  and  prepuce,  ultimately  exposmg 
a  congested  surface  and  causing  punctate  hemorrhages. 

This  separation  should  normally  take  place  during  mfancy  or  early  childhood, 
either  spontaneously  as  a  result  of  erections  and  of  the  growth  of  the  organ  or  because 
of  gradual  mechanical  retraction  by  nurse  or  mother.  When  it  fails  to  do  this,  the 
condition  of  i»A/»«t»«> -inability  to  retract  the  prepuce— follows,  and  is  due  partly  to  the 
persistent  adhesions  and  partly  to  a  frequently  associated  narrowing  of  the  preputial 

orifice.  .  ,  .     .    .•       ■ 

Both  these  factors  may  be  the  result  of  disease,  and  acquired  phimosis  may  occur 
at  any  time  of  life  and  follow  any  form  of  inflammation  of  the  skin  covenng  the  glans 
(balanitis),  of  the  inner  surface  and  cellular  tis.sue  of  the  prepuce  (poslAilis),  or  of 
both  (balano-posthUis),  the  last  named  being  the  most  common.  Following  phimosis 
there  may  be,  (a)  as  a  result  of  retention  of  secretion  and  of  urine  in  the  subpreputial 
space,  balanitic  or  herpetic  ulceration,  or  the  development  of  papillomata  (venereal 
warts)  •  (*)  as  a  result  of  obstruction  to  the  flow  of  urine  and  the  consequent  strain- 
ing vesical  irritability,  dilatation  of  the  bladder,  ureters,  and  kidneys,  hemorrhoids, 
and  hernia  (62  per  cent,  of  cases  of  congenital  phimosis)  (Kempe,  quoted  by  Jacob- 
son)  ;  (f)  as  a  result  of  nerve  irritation  (the  region  having  an  unusually  rich  nene- 
supply),  spastic  palsies,  reflex  joint  pains  and  muscular  spasm  (simulated  coxalgia), 
or  even  general  convulsions. 

These  complications  are  most  apt  to  occur  in  infants  and  very  young  children, 
and  their  frequency  has  been  exaggerated. 

As  a  result  of  phimosis,  even  when  the  preputial  orifice  is  ample,  there  may  be 
a  contracted  or  "pin-point"  meatus,  which  may  give  rise  to  the  same  train  of  symp- 
toms and  will  require  to  be  divided  (meaMomv)  by  a  linear  incision  directed  towards 
the  frenum,  and  kept  open  during  the  process  of  healing. 

Circumcision,  whether  done  for  phimosis  or  to  meet  other  indications,  requires 
for  its  successhil  performance  attention  to  the  following  anatomical  points  :  (a)  the 
laxity  of  the  skin,  permitting  it  easily  to  be  drawn  so  far  in  front  of  the  glans  that 
when  it  is  severed  at  that  point  so  much  may  be  removed  that  the  remainder  retracts 
quite  to  the  root  of  the  organ,  which  is  left  denuded  ;  {b)  the  close  attachment  of  the 
inner  or  mucous  layer  of  the  prepuce  to  the  corona,  so  that  the  length  of  the  portion 
of  that  layer  that  is  allowed  to  remain  will  determine  the  distance  of  the  operative 
scar  (at  the  muco-cutaneous  juncrion)  from  the  meatus  ;  if  this  stump  i.-i  not  exces- 
sive, it  will  thus  effectually  prevent  the  mortifying  but  not  infrequent  accident  of  re- 
formation of  a  phimosis  after  a  circumcision  ;  (r)  the  loose,  abundant  cellular  tissue 
and  rich  vascular  supply  in  the  frenal  region,  which,  together  with  the  dependent 
position  of  the  part,  may  determine  an  excess  of  exudate  that  will  result  in  an  objec- 
tionable fibrous  mass  in  that  region  if  full  hsemostasis  is  not  secured  or  if  any  redun- 
dant tissue  is  left  there. 

When  a  relatively  small  preputial  orifice  is  drawn  behind  the  corona  it  causes 
marked  constriction  at  that  point,  especially  if  it  is  not  only  small  but  also  inelastic  as 
a  result  of  chronic  inflammation.  If  the  constriction  remains  \mnY\e\eA,  paraphimo- 
sis results  ;  the  glans  becomes  distinctly  enlarged,  increa.sing  the  constriction,  purplish 
in  color,  and  glossy.  It  is  often  partially  concealed  by  a  thick  collar  of  shiny,  o-'dem- 
atous  skin,  behind  which  there  is  a  deep,  excoriated  sulcus,  and  back  of  this  sulcus 
there  is  usually  a  second  oedematous  band  less  marked  than  the  one  lying  immediately 
behind  the  coronary  sulcus.  The  penis  seems  to  have  a  distinct  upward  kink  or  bend 
just  behind  the  glans.  This  appearance  is  due  to  the  deep  notch  caused  by  the 
margin  of  the  retroverted  orifice  of  the  prepuce  and  to  the  oedematous  swelling 
which  is  particularly  marked  about  the  ptwition  of  the  frenum.  In  some  cases,  where 
the  tense,  inelastic  edge  of  the  orifice  exerts  a  more  than  usual  amount  of  constriction, 
circulation  is  markedly  interfered  with,  and  ulceration  and  even  sloughing  involving 
both  the  foreskin  and  the  head  of  the  penis  may  take  place.  This  complication  would 
undoubtedly  be  more  frequent  were  it  not  for  the  rich  blood-supply  to  the  glans 
and  the  anastomosis  between  its  vessels  .ind  those  of  the  corpora  cavernosa,  The 
ulceration  usually  involves  the  foreskin  only. 


«974 


HUMAN  ANATOMY. 


When  the  swelling  consequent  upon  paraphimosis  is  well  developed  there  is  en- 
countered first  a  furrow,  the  coronary  sulcus,  which  is  normally  found  behind  the 
corona  ;  in  these  cases  it  appears  deeper  because  it  is  intensified  by  the  cedematous 
swelling.  Covering  this  furrow,  and  even  overlapping  the  glans  somewhat,  is  the 
portion  of  the  prepuce  which  is  normally  in  contact  with  the  posterior  face  and  border 
of  the  corona.  Behind  this  swollen  fold  is  found  a  second  deep,  often  ulcerated  fur- 
row indicating  the  position  of  the  preputial  muco-cutaneous  margin ;  this  is  the  actual 
seat  of  constriction,  and  behind  it  is  placed  yet  another  ridge  of  swollen  integument. 

The /asda  penis  (page  1968)  gives  the  organ  some  of  its  most  im|x>rtant  physical 
characteristics.  The  tensile  strength  of  the  [>enis,  because  of  its  tough  fibrous  invest- 
ments, is  sufiicient  to  bear  the  entire  weight  of  the  body.  That  portion  of  this  fibrous 
investment  which  covers  the  blunt  extremities  of  the  two  cavernous  bodies  where  they 
are  capped  by  the  glans,  delays,  and  sometimes  prevents,  the  backward  extension  of 
inflammatory  or  infiltrating  processes,  particularly  cane- :  us  infiltration,  which  pri- 
marily involve  the  glans.  This  fibrous  sheath,  being  a  ci  iitinuation  of  the  deep  layer  of 
the  superficial  fascia,  also  limits  the  forward  extension  of  urinary  and  purulent  infiltra- 
tions beneath  this  fascia,  such  infiltrations  leaving  the  glans  untnvolved.  The  free 
blood-supply  to  the  penis  and  its  rich  innervation  insure  rapid  healing  in  case  of 
wounds,  and  justify  conservative  treatment  even  although  the  organ  has  been  nearly 
severed  or  extensively  crushed. 

Contusion  of  the  penis  is  often  followed — owing  to  the  laxity  of  the  skin — ^by 
such  rapid  and  pronounced  ecchymosis  and  oedema  as  to  simulate  gangrene. 

When  the  vessels  of  the  cavernous  bodies  are  involved  there  is  free  subcutaneous 
bleeding,  giving  rise  to  a  circumscribed  fluctuating  tumor,  most  prominent  during 
erection.  This  tumor  is  somewhat  slow  in  formmg,  and  occasionally  suppurates. 
Under  conservative  treatment  it  usually  disappears.  When  injury  has.  not  only  occa- 
sioned extensive  extravasation  of  blood,  but  has  lacerated  the  urethral  canal,  the 
inflammatory  phenomena  observed  after  rupture  of  the  urethra  quickly  develop. 
Moreover,  there  is  immediately  bleeding  from  the  meatus,  which  should  lead  to 
prompt  diagnosis  and  appropriate  treatment. 

Wounds,  if  involving  the  erectile  tissue,  bleed  freely,  and,  if  transverse  and  ex- 
tensive, may  be  followed  by  loss  of  erectile  power  in  the  region  anterior  to  the  wound. 
Fracture,  in  a  literal  sense,  is  possible  only  when  the  orijan  has  undergone  calcifica- 
tion or  ossification  (vide  infra),  but  the  term  is  applied  to  injuries  that  result  when, 
during  vigorous  erection,  the  penis  is  subjected  to  a  sudden  twist  or  bend.  The 
resulting  condition  is  not  unlike  that  caused  by  contusion,  but  the  subcutaneous 
effusion  is  apt  to  be  lacking.  The  chief  lesion  is  usually  in  the  corpora  cavernosa,  or 
in  one  of  them,  and  is  apt,  as  a  result  of  obliteration  of  erectile  spaces,  to  leave  a 
flail-''ke  organ,  erection  anterior  to  the  break  being  impossible. 

Chronic  induration  (ossification,  calcification,  chronic  inflammation)  of  the  sheath 
and  erectile  tissue,  especially  of  the  corpora  cavernosa,  is  marked  by  the  formation 
of  fibrous,  calcareous,  or  bt>ny  thickenings  or  plates,  which  fonn  usually  in  middle- 
aged  or  elderly  men  of  gouty  diathesis.  They  cause  but  little  pain,  are  easily  recog 
nized  by  palpatio",  and  are  accompanied  by  bending  of  the  pienis  to  the  affected  side 
during  erection,  which  is  incomplete  in  the  region  anterior  to  the  induration.  The 
condition  is  unknown  before  forty  or  forty-fi\'e,  and  is  probably  analogous  to  the 
thickening  ind  toughening  of  the  palmar  fascia,  which  goes  by  the  name  of  Dupuy- 
tren's  contnction,  and  which  we  recognize  as  partly  due  to  gout  and  partly  to  some 
constant  irritation.  Thus  they  may  he  met  with  in  both  the  penis  and  the  hands  of 
the  same  gouty  person  (Jacobson).  It  has  been  suggested  (Metchnikoff)  that  in 
their  osseous  form  they  represent  reversions  to  the  condition  existing  in  many  mam- 
mals and  e\en  in  the  anthropoid  apes,  in  whom  an  os penis  is  i>resent. 

Lymphangitis  may  follow  peripheral  inflammation  of  any  type,  but  is  usually  of 
venereal  origin. 

The  diagnosis  between  lymphangitis  and  phlebitis  of  the  dorsal  vein  is  based 
upon  the  much  smaller  size  of  the  lymphatic  \essels  as  compared  with  the  \ein  ;  upon 
the  fart  that  the  former  \psspIs  do  nnt  pass  vipward  in  the  middle  line,  but  are  directed 
into  the  groins  ;  and  finally  upon  the  ability  to  lift  the  indurated  vessel  up  from 
the  deeper  {larts,  this  not  being  possible  in  the  case  of  the  vein,  since  it  is  placed  in  a 


THE   PROSTATE  GLAND. 


1975 


furrow  between  the  two  cavernous  bodies.     Phlebitis  occasions  much  more  marked 

^"EMhelioma  of  the  penis  is  not  uncommon.     It  usually  follows  prolonged  subpre- 
putial  frritation.     It  involves  ultimately  bpth  the  inguinal  and  the  deep  pelvic  nodes. 

Amputation  of  the  entire  penis  may  be  required  for  the  relief  of  malignant  dis- 
ease The  following  description  (Treves)  should  be  studied  in  connccUon  with  the 
anatomy  of  the  penis  and  of  the  urethra.  The  patient  is  placed  in  the  lithotomy  pos._ 
tion  and  the  skin  of  the  scrotum  is  incised  along  the  whole  length  ot  the  raphe  VV  ith 
the  finKcr  and  the  handle  of  the  scalpel  the  halves  of  the  scrotum  are  separated  down 
to  the  corpus  spongiosum.  A  full-sized  metal  catheter  is  passed  as  far  as  the  tnan- 
Kular  liuament.  and  a  knife  is  inserted  transversely  between  the  corpora  r  ernosa  and 
the  corpus  spongiosum.  The  catheter  is  withdrawn,  the  urethra  is  cut  across,  and 
its  deep  end  is  detached  from  the  penis  back  to  the  triangular  hgament.  An  incision 
is  made  around  the  root  of  the  penis  continuous  with  that  in  the  median  line.  Ihe 
suspensory  ligament  is  divided  and  the  penis  is  separated,  except  at  the  attachment 
to  the  crus  The  knife  is  then  laid  aside,  and  with  a  stout  penosteal  elevator  or  rugine 
each  crus  is  detached  from  the  pubic  arch.  The  two  arteries  of  the  corijora  cavernosa 
and  the  two  dorsal  arteries  require  ligature.  The  urethra  and  corpus  spongiosum  are 
split  up  for  about  half  an  inch,  and  the  edges  of  the  cut  ?  stitched  to  the  back  part 
of  the  incision  in  the  scrotum.  The  scrotal  incision  is  closed  by  sutures,  and  if  drain- 
age is  used,  the  tube  is  m  placed  in  the  deep  part  of  the  wound  that  its  end  can  be 
brought  out  in  front  and  behind.     No  catheter  is  retained  in  the  urethra. 

THE   PROSTATE  GLAND. 

Altho-  ;  *•  developed  as  an  appendage  of  the  urinary  tract,  and  not  directly  as 
part  of  *^  'lal  apparatus,  the  prostate  is  functionally  so  closely  related  to  the  gen- 

erativ  ■.  ■  ^^        lat  it  may  appropriately  be  regarded  as  one  of  the  accessory  glands,  the 
others      ''\        .e  glands  of  Cowper.  ...         ^  •  i       i     j 

1   ^  ate  is  complex  in  both  its  make-up  and  relations,  being  partly  glandu- 

lar and     '.     ,  muscular  and  traversed  by  the  urethra  and  the  ejaculatory  ducts.     In 
general  form  it  resembles  an  inverted 

Spanish  chestnut,   having   the  base  Fic.    1679. 

applied  to  the  under  surface  of  the 
bladder  and  the  small  end,  or  apex, 
directed  downward.  Additional  an- 
terior, lateral,  and  posterior  surfaces 
are  recognized.  Grayish  red  in 
color  and  of  firm  consistence,  the 
adult  prosUte  varies  considerably 
within  physiological  limits  in  size 
and  weight.  The  former  includes  a 
length,  from  apex  to  base,  of  from 
2. 5-3. 5  cm.  ( I  to  I  ^  in. ) ,  a  breadth 
or  transverse  diameter  of  from  3. 5- 
4.5  cm.  {i%i-i}i  in.),  and  a  thick- 
ness of  from  2-2.5  cm.  (f-i  in.). 
Its  average  weight  is  about  22  gm. 
(3^  oz. ).  Marked  increase  in  size 
and  weight  is  common  in  elderly 
subjects. 

The   oblique   upper  surface  or  ,,,111 

base  (baste  prostatae.  fades  veslcallfi)  is  applied  to  the  under  surface  of  the  bladder, 
with  which  it  is  inseparably  blended  by  muscular  tissue  surrounding  the  urethral  ori- 
fice and  is  pierced  by  the  urethra  usually  slightiy  in  advance  of  the  middle.  Ihe 
base  is  outlined  by  free  rounded  borders,  so  that  its  limits  are  separate.1  from  the 
vesical  wall  by  a  groove.  The  posterior  surface  ( facics  posterior ),  directed  backward 
and  towards  the  rectum,  is  defined  literally  by  prominent  rouiuk-d  l>orders  that 
extend  from  the  base  to  the  apex  and  enclose  a  flattened  cordiform  or  triangular  area 


Blight  icroove  produced 
by  symphysiA 


Inferior  lurface 


St'miiial 
vehicle 


SliKhtlv  distendett  tilnddir.  liardeniKl  in  ji/k,  "ihiiw 
iiiK  prmlate,  wminal  vwiclea.and  seminal  ducts ;  viewid 
from  below  and  behind. 


tr-      *  ■ 


it      .il: 


1976 


HUMAN  ANATOMY. 


■Semiiial 
vesicle 


Ampnlla 


Inferior  wall 
of  bladder 

Intenial  urethral 
orifice 

I'rethfBl  crest 


Prostatic  urethra 


FrofiUte,  middle  icbe 
Ejaculatory  duct 


Portion  of  sagittal  section  showing  prostate  and  related  stmctum. 


that  ohen  presents  a  shallow  concavity.  The  junction  of  the  upper  and  posterior 
surfaces  is  marked  by  a  transverse  crescentic  slit  (incisiira  prostatae)  into  which  sink 
the  ejaculatory  ducts  in  their  course  to  the  urethra.     The  imperfecdy  defined  wedge- 

sttaped   mass   bounded   by 
Fio.  1680.  the  urethra  in  front,  the  ejac- 

ulatory ducts  at  the  sides 
and  behind,  constitutes  the 
so-called  middle  lobe  (lobus 
medius),  the  base  of  which 
lies  beneath  the  v.-isical  tri- 
gone. The  prominent  por- 
tions of  the  prostate  lying 
external  to  the  ejaculatory 
ducts  are  known  as  the  lat- 
eral lobes,  which,  however, 
superficially  are  not  dis- 
tinctly marked  off.  The 
prominent  convex  lateral 
surfaces,  dnected  outward, 
downward,  and  forward,  and 
behind,  limited  by  rounded 
borders,  in  front  pass  insen- 
sibly into  the  narrow  con- 
vex anterior  surface  (fades 
anterior)  that  is  approximately  vertical  and  faces  the  symphysis. 

The  urethra  traverses  the  prostate  with  a  vertically  placed  curve,  the  concavity 
looking  forward,  that  above  begins  slightly  in  advance  of  the  middle  of  the  base,  and 
below  ends  on  the  anterior  surface  just  in  front  and  above  the  apex.  The  posterior 
wall  of  the  prostatic  urethra  is  marked  by  a  longitudinal  median  nA%^.  the  urethral 
crest,  on  the  most  exjjanded  and  elevated  part  of  which  (colliculus  seminaiis)  are  situ- 
ated the  o()enings  of  the  pros- 
tatic utricle  (ntriculus  prostati-  Fio-  1681. 
cus)  and  of  the  ejaculatory 
ducts  fpage  1955).  In  the 
grooves  or  recesses  on  either 
side  of  the  crest,  open  the  mi- 
nute orifices  of  the  prostatic  tu- 
bules, some  twenty  in  number, 
that  discharge  the  products  of 
the  glandular  tissue. 

Owing  to  the  continuity 
of  the  muscular  tissue  with 
the  surrounding  structures  in 
front,  above,  and  below,  the 
outlines  of  the  prostate  in 
places  lack  definition.  Except 
over  its  base,  apex,  and  lower 
anterior  surface,  the  prostate 
is  enclosed  by  a  fibrous  envel- 
ope or  capsule,  the  extension 
of  the  visceral  layer  of  the  pel- 
vic fascia  in  conjunction  with 
the  investment  of  the  bladder 
and  the  seminal  vesicles.  The 
caps..',  is  best  oeveloped  on 
the  posterior  surface,  where  it  separates  the  prostate  from  the  rectum  and  constitutes 
a  part  of  the  recto-vcsiral  fascia  in  its  restricted  sense. 

Relatiotis. — Lodged  between  the  bladder  and  the  pelvic  floor,  the  prostate  is 
in   relation  'vith  a  number  of  important  structures.     Above,  its  base  is  intimately 


Folds  of 
mucous  membrane 


'Urethnl  mucous 
membrane 

Urethral  crest 
Prostatic 
utricle 


Ejaculatory  ducts 


Section  across  prostatic  urrihni  above  entrance  of  e)acala- 
lory  ducts,  showinK  crescentic  form  of  urethral  lumen  pro- 
duced by  encroacliment  of  urethral  crest.     Y  lo. 


THE   PROSTATE  (".LAND. 


1977 


attached  to  the  lower  surface  of  the  bladder,  lying  beneath  the  vesical  trigone. 
SL' Jts  apex  rests  upon  the  superior  layer  of  the  triansular  hgament.  surrounded 
by  fibes  of  the  com/lressor  ureVhr*  muscle  that  constitute  th-  external  v^l 
sphincter  (page  1925)  In  front,  the  rounded  anterior  surface  is  directed  touarc^ 
tLpubL  symphysis^  from  which  it  is  separates!  by  an  interveninK  w«lKe-sha,>ed 
space  occupied  by  loose  areolar  tissue  containing  p.rt  of  the  prostatic  plexus  of  veins 
aKt  The  pubo-prostatic  ligaments  (the  continuations  of  the  arcus  tendincus  of 
the  two  sides)  stretch  t .nween  the  symphysis  and  the  prostate  and  contain  muscular 
tissue  prolonged  from  the  latter  and  the  bladder.  At  the stdes,  the  prostate  ^-^^^^^ 
by  the  levator  ani  muscles,  the  prostatic  venous  plexuses,  '^'^Yl  .aIaV^. 
reflections  of  the  pelvic  fa.scia  that  here  constitute  the  capsule  of  the  gland  inter- 
venS  Behind,  ihe  prostate  is  in  relation  with  the  ampulla  of  the  vasa  deferent.a 
and  the  seminal  vesicte  above  and  with  the  lower  part  of  the  rectum  below,  separated 
from  the  latter  by  the  dense  capsule  and  the  overiying  layer  of  areolar  tis.ue^  The 
p^ition  of  the  prUate  is  not  constant,  since  it  is  affected  by  movements  of  the  vesi- 
S^wall,  with  which  the  prostate  is  intimately  united,  incident  to  marked  distention 
and   contraction  of  ^^^    i^g, 

the  bladder.   On  the 
other  hand,  the  at- 
tachments   of    the 
prostate  to  the  trian- 
gular ligament  and 
pelvic    fascia    indi- 
rectly confer  upon 
the  lower  segment  of 
the  bladder  its  most 
efficient    means    of 
fixation.    The  pros- 
tate is  further  influ- 
enced by  changes  in 
the  anterior  wall  of 
the  rectum,  under- 
going  compression 
and      displacement 
forward    when    the 
bowel  is  distended. 
Structure.  — 
The    prostate   is    a 
gland  of  the  tubo- 
alveolar  type  and  is 
made  up   of   three 


Tcnninal  duct  opening  into  alveoli 
Involuntmry  muscle. 


Alveoli 


Blood-vesael 


Portion  of  cross-section  of  prostate  Ktand.    X  75- 


chief  components,— the  connective-tissue  framework,  involuntary  muscle,  and  the  glan- 
dular tissue.  Of  these  the  latter  constitutes  usually  a  little  more  than  one-half  of  the 
entire  orc-in,  and  the  connective  tissue  and  muscle  each  somewhat  less  than  one-quarter. 

The  connective-tissue //-aw^ror/t  consists  of  an  external  investing  fibro-elastic  en- 
velope the  capsule  proper,  and  a  median  septum,  which  encloses  and  blonds  with  the 
wallsof  the  urethra.  Between  these  denser  lamellpe  numer-is  partitions  radiate  and 
subdivide  the  organ  into  from  thirty  to  forty  pyramidal  lobules  occupied  by  the  glandu- 
lar tissue  The  involuntary  muscle,  embedded  within  the  capsule  and  ramihcations 
of  the  connective-tissue  framework,  surrounds  the  gland-substance  as  a  superficial 
layer  from  which  a  median  septum,  about  2  mm.  in  width,  extends  ventro-dorsallv, 
enclosing  the  urethra  in  an  annular  thickening.  In  consequence,  the  interior  of  the 
prostate  is  occupied  by  a  dense  fibro-muscular  nucleus,  in  which  the  glandular  tissue 
IS  represented  by  only  the  narrow  prostatic  ducts  passing  towards  the  urethra.  The 
muscle  is  not  limited,  however,  to  the  foregoing  positions,  but  extends  also  between 
the  ultimate  divisions  of  the  gland-tissue,  the  interalveolar  septa  in  places  consisting 
largely  of  the  v.trionslv  disposed  muscle-bundles. 

The  glandular  tissue  consists  of  twenty  or  more  distinct  tube-systems,  each 
drained  by  an  independent  duct  that  opens  into  the  urethra  in  the  groove  on  either  side 


1978 


HUMAN  ANATOMY. 


Muiclc  cell 


ill  concrrtion 


of  the  colliculus.  Bej^nning  at  their  narrow  orifices,  these  excretory  tubules  (dnctnii 
prostatic! )  pass  outward  into  the  lobules,  and  after  a  course  of  about  i  cm.  divide  into 
tubules  that  repeatedly  branch  and  exfiand  into  the  terminal  alveoli.  Throughout  the 
greater  part  of  their  course  the  wavy  ducts  are  beset  with  saccular  and  tubular  diver- 
ticula, simple  or  com(x>und,  that  give  the  canal  an  irregular  lumen  and  constitute  what 
have  been  termed  the  duct  alveoli  as  distinguished  from  the  terminal  alveoli.  The 
latter  form  a  series  of  irregularly  branched  tubular  and  saccular  spaces  lined  with  a 
single  or  imperfect  double  layer  of  columnar  epithelial  cells, — the  secreting  elements  of 
the  gland.  In  places  the  alveoli  intercommunicate  and  form  net-works  of  spaces  of 
variable  lumen.  The  epithelium  in  the  ducts  and  their  diverticula  corresponds  with 
that  lining  the  more  deeply  situated  alveoli,  the  change  into  the  transitional  variety 
of  the  prostatic  urethra  not  talcing  place  until  very  near  the  termination  of  the  ducts. 
Peculiar  concretions  ( ' '  amyloid  bodies' '  or  "  prostatic  calculi' ' )  are  almost  con- 
stantly present  within  some  of  the  tubules  of  the  adult  organ,  especially  in  advanced 
life.  These  bodies  (Fig.  1683),  round  or  oval  in  outline  and  very  variable  in  size 
(from  .2-1  mm.  and  more  in  diameter),  usually  exhibit  a  faint  concentric  striation 

and  a  light  brownish  color. 
Their  nature  is  uncertain, 
but  they  probably  consist  of 
a  colloid  substance  giving 
the  reactions  of  albumen. 

The  secretion  of  the 
prostate  gland  {succus 
prostalicus)  is  milky  in  ap- 
pearance, thin  in  consist- 
ence, slightly  alkaline  in 
reaction,  and  possesses  a 
characteristic  odor  (Fiir- 
bringer  ) .  It  is  discharged 
into  the  urethra  and  min- 
gled with  the  fluid  enter- 
ing by  the  seminal  ducts 
during  ejaculation,  and 
probably  serves  an  impor- 
tant purpose  in  facilitating 
and  {>erhaps  stimulating 
the  motility  of  the  sper- 
matozoa. The  "sperm 
crystals"  formed  in  semen 
after  standing,  and  attributed  to  the  products  of  the  prostate,  are  not  found  in  the 
secretion  of  the  living  subject  (although  frequently  present  in  the  gland  after  death) 
until  after  the  addition  of  ammonium  sulphate  (Fiirbringer). 

Vessels. — The  arteries  supplying  the  prostate  are  small  branches  from  the 
inferior  vesical  and  middle  hemorrhoidal.  They  enter  the  periphery  of  the  gland  at 
various  points,  particularly  in  company  with  the  ejaculatory  ducts,  and  break  up  into 
capillary  net-works  that  surround  the  alveoli.  The  veins  are  exceedingly  numer- 
ous, forming  close  mesh-works  within  the  glandular  tissue  and  around  the  ducts. 
They  leave  the  organ  on  either  side  and  unite  into  a  plexus  within  the  capsule,  which, 
receiving  the  deep  dorsal  veins  of  the  penis  and  communicating  with  trunks  from  the 
bladder,  seminal  vesicles,  and  rectum,  is  continued  as  the  prostatico-vesical  plexus, 
tributary  to  the  internal  iliac  veins.  The  lymphatics  are  numerous  and  form  a  net- 
work on  the  lower  and  posterior  surface  of  the  organ  from  which  on  either  side  pass 
two  trunks,  a  superior  and  a  lateral.  The  upper  and  smaller  trunks  are  afferent  to 
the  obturator  lymph-nodes  of  the  pelvic  wall,  and  the  lateral  and  larger  terminate  in 
the  internal  iliac  nodes  (  Sappey). 

The  nerves  of  the  prostate  are  chiefly  sympathetic  fibres  derived  from  the 
hypogastric  plexus,  numerous  minute  ganglia  being  included  along  their  course. 
Peripherally  situated  Pacinian  corpuscles  are  said  to  be  connected  with  the  sensory 
fibres  (Griffiths). 


Blood-venel 


Portion  of  Mction  of  proatate  gland,  showing  details  of  alveoli.    X  rja. 


M.ir<^? 


PRACTICAL  CONSIDERATIONS  :  PROSTATE  GLAND.    '979 

Development.-At  about  the  third  month  of  fcetal  life  the  wall  of  the  primitive 
urethra  undergoes  thickening,  leading  to  the  1'^"^"*^"??/;'^'"  ^"""/'';;  "1?^^^  Xm 
blastic  tissue  that  surrounds  the  lower  ends  of  the  Wolffian  and  MuUerun  Uucts 
Ser  the  ejaculatory  ducts  and  the  prostatic  utricle  respectively)  and  subsequently 
Kmes  differentiated  largely  into  unstriped  muscle.  Into  this  penetrate  solid  epi- 
S^^urgrowTs,  from  the  lining  of  the  ut^ethra.  which  e.xpand  into  branched  cylinder 
Eliveriletothe  pro.static  glandular  tissue.  These  »"^«^7%\^'-V™«^^^^^ 
three  groups  (Pallin).  a  ventral,  an  upper  and  a  lower  dorsal  J»«-;'-\f  ^^^^^J^^^^^^ 
irives  rise  to  the  glandular  tissue  in  front  ok  the  urethra,  which  at  hrst  is  ri.lati\tly 
fbundLnt  but  sc^n  suffers  reduction,  and  in  the  adult  organ  is  often  almost  wanUng. 
The  S  «oups  produce  the  imporUnt  glands  of  the  median  and  lateral  lobes. 
For  a  Se'^he  btterarearranged'^as  two  separate  lobes,  but  afterward  beaje 
consoliS  by  the  capsule  and  broken  up  by  the  invasion  of  the  fibro-muscular 

^'''^t  birth  the  prostate  measures  about  '2  mm.  in  its  transverse  dimension  and 
remah^s  small  until  puberty,  when  it  begins  to  rapidly  enlarge,  acquiring  its  fuU  pro- 
[«rrions  with  the  esublishment  of  sexual  activity.  With  the  approach  of  old  age. 
[he  prosul;  usually  undergoes  increase  in  size.-an  augmenUUon  often  resulung  in 
pathological  conditions. 

V«i.tion..-Apart  from  abnormalities  in  size,  the  .pn»tote  U  subject  to  few  var^^ 
Amone  theUtter  have  been  persistence  of  the  original  independence  of  the  lateral  '"bes  ab- 
Among  tne  laiier  nave  uc^   i^  1^  I  j^      Variat  ons  m  the  relations  and  mode 

^endi  of  ™e$c2"a1o',?d?^tei^  imoasingle  canal  or  termination  in  the  PJ-tatic  utricle 
or  bv  a Tu^cial  caral  Wow  the  crest)  or  in  the  prostatic  utricle  (absence,  enlarged  size,  or  un- 
ZZ  oi^S)  aTprop^riy  referred  to  deviations  in  the  development  of  the  generative  tract 

PRACTICAL  CONSIDERATIONS:  THE  PROSTATE  GLAND. 
The  prostate  gland  is  a  portion  of  the  male  generative  system.  The  prostatic 
utricle,  or  sinus  pocularis,  is  the  homologue  of  the  sinus  genitalis  in  the  female,— the 
uterine  and  vaginal  cavities,— since  it  represents  the  persistent  part  of  the  fused  Mul- 
lerian  ducts  (page  2039).  Alhough  the  prostate  and  the  uterus  cannot  be  rtjgardetl 
as  homologous  organs,  they  are  similar  in  structure,  and  would  be  strikingly  alike 
if  the  tubular  glands  found  in  the  inner  walb  of  the  uterus  were  prolonged  into  its 
muscular  substance.  .  •       1 

During  infancy  and  childhood  the  prostate  is  still  immature  ;  at  puberty  it  enlarges 
coincidently  with  the  enlargement  of  the  testicles.  In  eunuchs  and  after  castration  in 
man  and  other  animals  it  is  atrophied.  The  seminal  vesicles  are  in  close  relation  to 
it  and  the  eiaculatory  ducts  penetrate  it  (page  1955).  Its  size  and  perfection  of  struc- 
ture in  animals  rise  and  fall  with  the  breeding  season  (Hunter,  Owen.  Grithths). 
These  facts  sufiiciendy  demonstrate  the  essential  relation  of  the  prostate  to  the  gen- 
erative system.  It.  however,  affords  passage  to  the  prostatic  urethra,  its  unstriped 
muscle-fibres  are  continuous  with  the  vesical  muscle  at  the  trigonum  and  with  the 
circular  fibres  of  the  bladder,  and  both  the  anatomical  and  subjective  effects  of  the 
more  common  pathological  changes  in  the  prostate  are  observed  in  relation  to  the 
urinary  system,  with  which,  therefore,  it  is  most  intimately  associated. 

Injuries  of  the  prostate  are  rare  on  account  of  its  protected  position,  and  usually 
involve  also  the  rectum  or  the  bladder.  Hemorrhage  from  the  prostato-vesical 
plexus  may  be  dangerous  in  amount ;  and  if  a  wound  extend  upward  into  the  neck 
of  the  bladder,  that  organ  may  become  distended  with  blood  and  form  a  tense,  globu- 
lar hypogastric  tumor.  Infihration  of  urine  following  a  prostatic  wound  may,  in 
accordance  with  the  situation  of  the  latter,  reach  the  hypogastrium  from  the  pre- 
vesical space,  the  ischio-recul  region  or  the  perineum  from  coincident  division  oi 
the  fascia  of  Colles,  or  the  recto-vesical  space  and  the  pelvis  from  similar  division  of 
the  recto-vesical  fascia.  _        ,  .         ,    .      j. 

Disease  of  the  prostate,  if  infectious,  is  usually  gonorrhceal  in  origin.  It  is  often 
due  tu  the  use  of  •  nclcan  urethral  or  vesic.nl  instruments.  It  tends  to  suppuration 
on  account  of  the  •.  dry  imperfect  drainage  of  the  products  of  inflammation  from  the 
numerous  follicles. 


.r 


m 


1980 


HUMAN   ANATOMY. 


Prostatitis  is  attended  by  (a)  much  swelling,  owing  to  the  vascularity  and 
spongy  structure  of  the  gland.  As  the  forward  enlargement  of  the  prostate  is  pre- 
vented by  the  resistance  of  the  dense  pubo-prostatic  ligaments,  the  subpubic  liga- 
ment, and  the  firm  superior  layer  of  the  triangular  ligament,  the  swelling  is  greatest 
in  the  posterior  two-thirds  of  the  gland.  Its  downward  extension  is  evidenced  by 
(*)  a  sense  of  weight  and  uneasiness  in  the  perineum  and  (c)  rectiil  irritation  and 
tenesmus.  Its  upward  and  backward  spread  is  shown  hy  id)  interference  with  mic- 
tuntion,  due  to  compression  of  the  prostadc  urethra  and  elevation  of  the  vesical  out- 
let. The  symptoms  of  (<•)  painful  and  ffequent  micturition  and  (/)  vesical  tenesmus 
are  due  in  part  to  the  mechanical  obstruction,  but  chiefly  to  the  extension  of  the 
inflammation  to  the  trigonal  region  and  to  the  obstruction  by  pressure  of  the  pros- 
tatic venous  plexus  into  which  the  vesical  plexus  empties,  causing  intense  conges- 
tion of  the  vesical  mucosa.  The  unyielding  character  of  the  prostatic  sheath  pro<luces 
(^)  the  heavy,  throbbing  pain  felt  in  the  infrapubic,  perineal,  and  rectal  regions,  and 
results  in  such  tension  that  (h)  referred  pains  are  very  common,  and,  on  account  of 
the  denvauon  of  the  nerve-supply  of  the  prostate  from  the  lower  three  dorsal  and 
upper  three  sacral  segments,  are  apt  to  be  widely  distributed,  as,  e.g.,  pain  over  the 
tip  of  the  last  rib  (tenth  dorsal  ner\e),  over  the  posterior  iliac  spine  (eleventh  dorsal 
nerve),  or  even  in  the  soles  of  the  feet  (third  sacral  nerve)  (Treves):  reflex  irrita- 
tion of  the  inferior  hemorrhoidal  ner\e  may  cause  intense  pruritus  ani, — sometimes 
a  very  annoying  symptom. 

Prostatic  abscess  usually  takes  the  direction  of  least  resistance  and  opens  into 
the  urethra.  Its  progress  towards  the  pelvis  is  resisted  by  the  dense  investment 
contnbuted  by  the  pelvic  fascia;  towards  the  perineum,  by  the  superior  layer  of  the 
triangular  ligament.  It  sometimes  points  towards  the  rectum,  from  which  it  is  sepa- 
rated by  a  thinner  and  less  resistant  layer  of  the  pelvic  fascia,  and  may  then  open 
directly  into  the  rectum,  or  be  guided  by  it  to  the  perineum. 

Hypertrophy  of  the  prostate  to  some  degree  occurs  in  about  one-third  of  all 
males  who  have  passed  middle  life,  and  in  about  one-tenth  of  all  males  over  fifty-five 
the  enlargement  becomes  of  pathological  importance.  Its  cause  is  unknown. 
Various  theories  having  a  more  or  less  direct  bearing  upon  its  anatomical  and  physio- 
logical characteristics  have  been  advanced  to  explain  its  occurrence,  but  none  has 
been  demonstrated.  It  has  been  attributed  to  (a)  the  general  arteriosclerosis  of  old 
age  (Guyon);  {b)  z.  primar>'  change  in  the  bladder  necessitating  a  compensatory 
hypertrophy  of  the  prostate  (Harrison);  (r)  a  growth  analogous  to  uterine  fibro- 
myoma  (Thompson) ;  (rf)  the  persistence,  in  an  adjunct  sexual  organ,  of  physiological 
activity  intended  for  the  control  and  determination  of  the  ma.sculine  characteristics 
after  the  need  for  such  activity  had  disappeared  (White);  (<■)  an  attempt  to  com- 
pensate quantitatively  for  a  qualitative  deterioration  in  the  prostatic  secretion,  whose 
function  (Purbringer)  is  to  facilitate  the  mobility  and  vitality  of  the  spermatozoa 
(Rovsmg);  and,  recently,  (/)  infecnon  (most  often  by  the  gonococcus),  aggravating 
a  senile  degenerative  process  (Crandon). 

The  enlargement  may  affect  chiefly  any  of  the  separate  components  of  the  pros- 
tate, and  may  thus  be  adenomatous,  myomatous,  or  fibrous  in  its  character,  although 
usually  the  glandular  element  predominates.  It  may  involve  particulariy  the  lateral 
obes,  or  may  affect  almost  exclusively  the  so-called  median  portion  placed  at  the 
lower  posterior  part  of  the  gland,  between  the  ejacislatory  ducts.  This  portion  is 
direcUy  beneath  the  vesical  neck. 

The  degree  of  hypertrophy  is  extremely  variable,  the  prostate  being  increased 
from  Its  normal  weight  of  between  four  and  six  drachms  to  a  weight  of  many  ounces, 
and,  of  course,  correspondingly  increased  in  size. 

It  is  not  possible  here  to  do  more  than  call  attention  to  these  varieties  of  hyper- 
trophy, but  Its  usual  and  general  effects  may  be  considered  with  reference  to  their 
anatomical  causation. 

I.  The  direction  of  greatest  resistance  to  enlargement  is  forward  (vide  supra) 
and  next  downward  (towards  the  rectum).  Hence  the  growth  usually  takes  place 
in  an  upward  and  t«ckward  direction,  although  the  resistance  offered  by  the  recto- 
vesical layer  of  fascia  does  not  prevent  marked  extension  in  that  direction  in  many 
cases.     As  a  direct  result  of  this  enlargement  there  follow  :  (o)  compression,  flatten- 


PRACTICAL  CONSIDERATIONS  :    PROSTATE  GLAND.         1981 

inij  and  elongation  of  the  prostatic  urethra,  or  lateral  deviation  of  that  canal  (if  one 
lobe  greatly  exceeds  the  other  in  size);  (*)  elevation  of  the  vesical  neck  and  outM 
which  are  carried  up  by  reason  of  their  intimate  connection  with  the  prostate, 
especially  with  iu  median  lobe,  the  base  of  the  bladder  remainmg  relaUvely  un- 
affected ;  (c)  the  formation  in  this  manner  of  a  pouch  or  pocket  (post-prostotic  pouch) 
in  the  bladder  at  a  lower  level  than  the  vesical  outlet. 

The  indirect  results  of  these  conditions  are  the  changes  in  the  bladder  occasioned 
by  (a)  the  mechanical  obstruction  which  the  enLvged  prostate  offers  to  the  ready 
and  complete  evacuation  of  its  contente,  (*)  the  circulatory  disturbance  incident  to 
pressure  on  the  prostatic  veins  into  which  the  blood  from  the  vesical  veins  passes, 
and  (f )  septic  infection.  .         .       ,        •         «  .l 

As  a  result  of  the  narrowing  or  deflecuon  of  the  urethra,  the  elevation  of  the 
vesical  outlet,  and  the  formation  of  the  post-prosutic  pouch,  the  bladder  is  not 
entirely  emptied  at  each  act  of  micturition,  a  certain  amount  of  residual  urine  remain- 
ing behind  This  may  gradually  increase  as  the  obstruction  becomes  more  marked, 
ultimately  causing  dilatation  0/  the  bladder,  with  atonv  consequent  on  partial  de- 
generation of  its  muscular  walls,  or,  in  consequence  of  the  more  vigorous  bladder 
contraction  required  to  empty  the  bladder,  the  trabeculae  may  become  enormously 
hypertrophied,  the  inner  layers  forming  pronounced  ridges.  These  by  their  con- 
traction exert  a  powerhil  pressure  upon  the  vesical  contents,  which,  escaping  very 
slowly,  transmit  the  pressure  in  all  directions  and  occasion  bulgmgs  or  sacculations 
in  such  weak  parts  of  the  bUdder-walls  as  are  not  supporlec.  by  muscular  bands  or 
by  strong  investing  fasd*.  The  hypertrophy  and  sacculation  are  hirther  encouraged 
by  the  vesical  irritability  incident  to  venous  congestion  at  the  neck  of  the  bladder, 
which,  as  the  prostatic  veins  become  more  obstructed,  keeps  up  a  condition  of  passive 
hyperiemia  and  erethism  more  potent  than  residual  urine  alone  to  occasion  the  fre- 
quenriy  recurring  desire  to  urinate  and  the  muscular  spasm  of  the  sphincter  at  the 
beginning  of  the  act,  which  calk  for  such  strong  and  repeated  efforts  on  the  part  of 
the  detrusor  muscles.  ... 

Septic  infection  of  a  healthy  mucous  membrane  by  the  pyogenic  microbes  caus- 
ing acute  or  chronic  cystitis  b  not  possible,  even  although  such  bacteria  are  present 
in  the  urine;  when,  however,  the  vesical  mucous  membrane  is  congested  in  conse- 
quence of  obstruction  to  venous  return,  and  of  distention  of  the  viscus  and  frequently 
recurring  contractions  of  the  detrusor  muscles,  it  offers  but  slight  resistance  to  the 
microbic  invasion.  The  pyogenic  microbes  are  generally  carried  to  the  bladder  by 
dirty  instruments,  or,  if  these  are  rendered  sterile,  through  failure  to  cleanse  the 
anterior  urethra  before  the  instrument  is  introduced  into  the  bladder.  Often  cystitis 
develops  independently  of  the  use  of  instruments,  probably  as  a  result  of  infection 
conveyed  by  way  of  the  urethral  mucous  membrane. 

2.  The  subjective  symptoms  brought  about  by  these  conditions  may  be  briefly 
summarized  and  will  be  readily  understood  by  reference  to  the  foregoing  and  to  the 
article  on  the  bladder,  (a)  Frequent  urination,  due  partly  to  the  inability  completely 
to  empty  the  bladder,  but  chiefly  to  the  venous  congestion  about  the  trigonum.  (b) 
Difficulty  in  starting  urination,  due  to  muscular  spasm  of  the  external  vesical  sphinc- 
ter, which,  excited  by  reflexes  from  the  hypersesthetic  prostatic  urethra  and  neck  of 
the  bladder,  is  not  fully  under  the  control  of  the  will.  A  temporary  reflex  inhibition 
of  the  detrusor  muscles  may  also  delay  the  act  of  urination,  {c)  Feeble  unnatton, 
due  to  the  weakness,  atony,  or  paresis  of  the  overstretched  detrusors,  (rf)  Inter- 
rupted urination,  due  usually  to  spasmodic  contraction  of  the  external  vesical  sphinc- 
ter and  compressor  urethra  muscles,  reflexly  excited  by  urethro-cystitis  ;  occasionally 
the  result  of  intermittent  contraction  of  the  detrusors,  often  (as  in  many  cases  of 
cardiac  palpitation)  a  sign  of  beginning  muscular  atony.  The  physiology  of  micturi- 
tion requires  continuous  contraction  of  the  detrusor  muscles  and  relaxation  of  the 
sphincter >r  a  brief  interval  only.  When  there  is  sufficient  obstruction  to  triple  or 
quadruple  the  time  normally  required  fully  to  empty  the  bladder,  the  detrusor  mus- 
cles, exhausted  by  their  effort,  may  relax,  whereupon  the  sphincter  miLscles,  relieved 
of  the  vis  a  tergo,  promptly  contract.  After  some  seconds  or  minutes  the  detrusors 
recover  sufficiendy  to  make  hirther  efforts  at  evacuation.  (*)  Incontinence  of  urine, 
which  may  always  be  taken  as  a  symptom  of  retention  with  overflow,  the  intravesical 


H 


ri 


19^3 


HUMAN  ANATOMY. 


tension  of  the  overfull  bladder  being  sufficient  to  overcome  the  resistance  offered  by 
the  tonic  contraction  of  the  sphincter  muscle  plus  that  due  to  the  prostatic  enlar);e 
ment.  (/*)  Complete  retention  of  urine,  due  either  to  an  aggravation  of  the  chronic 
congestion  of  the  urethro-vesical  mucosa  or  to  the  completion  of  an  atrophic  process 
which  has  finally  destroyed  all  power  of  contraction  in  the  bladder.  (^)  Referred 
pains,  similar  to  those  noted  as  occurring  in  acute  prostatic  swelling  (^vide  supra), 
(h)  Constitutional  disturbance,  due  to  septicsemia  or  urxmia,  or  both. 

Operationa. — Prostatotomy. — Incision  or  puncture  of  the  prostate  for  the  evac- 
uation of  an  abscess  may  be  made  through  the  rectum  or  by  a  median  perineal 
incision.  The  same  name  is  applied  to  an  o|)eration  which  consists  in  opening  the 
urethra  at  the  apex  of  the  prostate  by  a  median  perineal  incision,  and  dividing  the 
obstructing  portion  of  the  gland  by  means  of  a  probe-pointed  bistoury,  cutting  from 
within  outward.  The  channel  may  be  further  enlarged  by  divulsion  with  the  finger. 
The  anatomy  and  relations  of  the  parts  involved  have  already  been  described  (f>age 
1921). 

Of  the  various  operative  procedures  to  which  the  prostate  is  subjected,  prostatec- 
tomy is,  however,  by  far  the  most  important.  Under  this  name  operations  have  been 
described  which  consist  of  the  removal  of  the  enlarged  median  lobe,  or  of  portions  of 
one  or  both  lateral  lobes,  or  of  the  whole  prostate,  by  either  perineal  or  suprapubic 
routes. 

In  suprapubic  prostatectomy  the  prostate  is  approached  by  means  of  a  supra- 
pubic cystotomy  (page  1921).  The  mucous  membrane  over  the  most  prominent 
portion  of  the  intravesical  protuberance  is  scratched  through  and,  as  a  rule,  the 
growths  or  the  prostate  removed  by  enucleation  with  the  finger. 

The  possibility  of  total  removal  of  the  prostate,  and  especially  of  such  removal 
without  coincident  injury  or  removal  of  the  prostatic  urethra  and  ejaculatory  ducts, 
ha-,  been  vigorously  discussed.  It  has  been  complicated  by  confusion  as  to  the  struc- 
tures described  as  the  " capsule"  and  as  the  "sheath." 

The  views  of  Freyer  appear  at  present  to  explain  most  satisfactorily  the  actual 
anatomical  conditions  found  at  operation,  and  are  thus  summarized  by  him  :  The 
prostate  is  in  reality  composed  of  twin  organs,  which  in  some  of  the  lower  animals 
remain  distinct  and  separate  throughout  life,  as  they  exist  in  the  human  male  during 
the  first  four  months  of  foetal  existence.  After  tl  ■  period,  in  the  human  foetus,  they 
approach  each  other,  and  their  inner  aspects  bet  ..e  agglutinated,  except  along  the 
course  of  the  urethra,  which  they  envelop  in  their  embrace.  These  two  glandular 
organs,  which  constitute  the  lateral  lobes  of  the  prostate,  although  welded  together, 
as  it  were,  to  form  one  mass,  remain,  so  far  as  their  secreting  sutetance  and  functions 
are  concerned,  practically  as  distinct  as  the  testes,  their  respective  gland  ducts  open- 
ing into  the  urethra  in  the  depression  on  either  side  of  the  urethral  crest.  Elach  of 
these  two  glandular  bodies,  or  prostates,  is  enveloped  by  a  thin,  strong,  fibrous 
capsule  ;  and  it  is  these  capsules — less  those  portions  of  them  that  dip  inward,  cover- 
ing the  opposing  aspects  of  the  glandular  bodies  or  lobes,  and  thus  disappear  from 
view,  being  embedded  in  the  sulwtance  of  the  prostatic  mass — that  constitute  the 
trut  capsule  of  the  prostate  regarded  as  a  whole.  This  capsule  extends  over  the  entire 
organ  except  along  the  upper  and  lower  commissures,  or  bridges  of  tissue,  that  unite 
the  lateral  lobes  alxive  and  below  the  urethra,  thus  filling  in  the  gaps  between  them. 
This  true  capsule  is  intimately  connected  with  the  prostatic  mass  and  incapable  of 
being  removed  from  it  save  by  dissection. 

The  urethra,  accompanied  by  its  surrounding  structures, — viz.,  its  longitudinal 
and  circular  coats  of  muscles  continued  forward  from  the  liladder,  its  vessels  and 
nerves, — passes  forward  and  upward  between  the  inner  aspects  of  the  two  glands  or 
lobes  and  is  embraced  by  them.  The  ejaculatory  ducts  enter  the  prostatic  mass  close 
together,  in  an  interlobular  depression  at  the  lower  part  of  its  posterior  aspect,  each 
coursing  along  the  inner  surface  of  the  corresponding  lobe.  They  do  not  penetrate 
the  (-ipstilcs  of  the  lobes,  bnt  p.iss  forward  in  the  interlobular  ti.ssue,  to  open  into  the 
urethra. 

The  prostate,  thus  constituted  and  enveloped  by  its  true  capsule,  is  further 
encased  in  a  second  capsule  or  sheath,  formed  by  the  visceral  division  of  the  pelvic 
fascia,  numerous  connecting  bands  passing,  however,  between  the  two  (Thompson). 


PRACTICAL  CONSIDERATIONS  :    PROSTATE  GLAND.         1983 

Between  these  two  capsules,  or  rather  mainly  embedded  in  the  outer  one.  ««  the 
prostatic  plexus  of  veins,  most  marked  in  front  and  on  the  sides  of  the  prostate.  1  he 
larKer  arteries  also  lie  between  the  true  capsule  and  the  sheath  numerous  small 
branches  passing  from  them  through  the  true  cipsule  for  the  supply  of  the  prostatic 

substance.  ,  ,  •        i  a 

Freyer  illustrates  his  view  by  imagining  the  edible  portion  of  an  oninRe  comjioseU 
of  two  Kgments  only,  instead  of  several,  with  the  aeptum  between  them  placed 
vertically,  and  says  that  the  thin,  strong,  fibrous  tissue  which  covirs  the  segments  of 
the  orange,  and  which  is  intimately  connected  with  the  pulp  would  then  represent 
the  true  capsule  of  the  prostate,  the  two  segments  or  halves  of  the  orange  being  rep- 
resented by  the  two  lobes  of  the  prostate.  Further,  the  rind  of  the  orange  wou  d 
represent  the  outer  capsule  or  prostatic  sheath,  contributetl  by  the  jk^Ivic  fascia.  In 
the  method  of  suprapubic  prostatectomy  now  known  by  his  name,  it  is  the  true  cap- 
sule as  above  described  that  is  removed,  the  sheath  bemg  left  behind,  thus  pre- 
ventine  infiltration  of  i-rine  into  the  cellular  tissues  of  the  pelvis. 

In  most  cases  of  hypertrophy  of  the  prostate  the  overgrowth  is  adenomatous  in 
chara  .-r,  numerous  encapsuled  adenomatous  tumors  being  found  embedded  within 
the  substance  of  the  lobes  and  frequently  protruding  on  their  surfaces.  They  s..me- 
times  assume  the  form  of  polypoid  outgrowths,  which  however,  are  invariably  en- 
closed within  the  true  capsule,  which  is  pushed  before  them. 

As  the  lobes  enlarge  they  bulge  out  and  have  a  tendency,  each  enclcwed  within 
its  own  capsule,  to  become  more  defined  and  isolated,  thus  recalling  their  separate 
existence  in  early  foeul  life.  They  become  more  loosely  attached  along  their  com- 
missures (particularly  the  upper  one),  which  in  the  normal  prostate  unite  them 
above  and  below  the  urethra.  And  in  the  course  of  this  change  the  urethra,  with 
its  accompanying  structures,  is  loosenetl  from  its  close  attachment  to  the  inner  sur- 
faces of  the  lob«,  thus  facilitating  its  being  detached  and  left  behind  uninjured  in 
the  removal  of  the  prostate.  ...  .  •         u 

In  the  earlier  stages  of  the  adenomatous  overgrowth  the  enlargement  _  P'O''/'- 
blv  entirely  extravesical.  Its  expansion  in  this  position  is.  however,  limited  by  the 
pubic  arch  above,  the  triangular  ligament  in  front,  and  the  sacrum  below.  As  the 
enlareement  progresses,  it  advances  in  the  direction  of  least  resistance.— namely,  into 
the  bladder.  The  sheath,  which  at  the  posterior  aspect  of  the  prostate  is  least  de- 
finetl  becomes  gradually  thinner  as  the  enlargement  in  this  direction  pr.)gresses.  till 
eventually  the  prostate  has  burst  through  it,  and  is  then  merely  covered  by  the  mucous 
membraneof  the  bladder  (Freyer).  ,,.••...  , 

It  has  been  asserted  that  what  \^^&  here  been  called  capsule  is  in  the  normal 
prostate  reallv  only  a  thin  outer  nat:-glandular  portion— cortex— containing  both 
muscular  and  fibrous  tissue  (Shatt,  cl:),  and  that  the  envelope  formed  from  the  pros- 
tate by  the  expansion  of  adenomata  represents  more  than  the  "  cortex  and  contains 
glandular  tissue  derived  from  the  stretched  and  compressed  outer  portion  of  the 

prostate  (Wallace).  ...  ■    1    •  ..  t    .u 

However  this  question  may  ultimately  be  settled,  the  anatomical  views  set  forth 
above  explain  the  separability  of  the  mass  of  the  prostate  from  fa)  the  prostatic 
plexus  of  veins  (avoiding  hemorrhage),  (b)  the  under  surface  of  the  recto-vesical 
fascia  (avoiding  urinary  infiltration),  and  (f)  the  prostatic  urethra  .ind  cjaculatory 
ducts  (minimizing  interference  with  micturition  and  with  potency),  which  separa- 
bility has  been  shown  to  be  at  least  occasionally  possible  during  operation. 

Perineal  prostatectomy  is  done,  with  the  patient  in  the  lithotomy  position,  by 
means  of  a  semilunar  incision  in  front  of  the  anus  carried  down  through  the  successive 
structures  of  the  urethral  perineum  until  the  sheath  of  the  prostate  is  reached.  After 
division  of  the  sheath  on  either  side  in  a  direction  parallel  with  the  medial  ""jes  of 
the  levator  ani,  the  prostate  in  its  capsule— or  portions  of  it— may  be  enucleated  with 
the  finger  The  gland  mav  be  made  more  accessible  by  downward  pressure  tnfo'lB" 
the  space  of  Retzius  (by  means  of  a  suprapubic  incision)  or  through  the  bladder 
itself  (after  a  preliminary  suprapubic  cystotomy).  It  may  iie  reaLlitd  by  a  latr.a. 
incision  half  enrircling  the  anus.  It  should  be  remembered  that  it  is  separated  -i  nn 
the  ischio-rectal  fossa  only  by  the  levator  ani  muscle,  with  the  visceral  layer  of  the 
pelvic  fascia  on  its  upper  and  the  anal  fascia  on  its  lower  surface. 


I9M 


HL'MAN   ANATOMY 


THE  GLANDS  OF      (»VVPER. 

Cowper's  glands  (glaodulac  bulbeurcthraies  i  >'<-  tv.o  «,.i  u void  bodies  situated 
alon{f  the  under  surface  of  tf»e  membranous  porti"  n  erf  tht  vi  'hra  ( Fij;  1632),  one 
on  either  side  of  and  close  to  the  mid-line.  In  jjen'  al  forni  ,111  I  si/c  (frf>»n  5-8  mm. 
in  diameter)  they  resv  mWe  a  pea,  although  their  .-ont-jiir  is  ii  ftT^l  ir  and  ^rmiewhat 
knobl)e<l.  Their  color  Ls  reddish  yellow  and  their  consistence  tirm  They  lie  within 
the  deep  perineal  interspace  l>etween  the  two  layers  of  the  triangui.'ir  tii|[]iment  em- 
bedded within  the  fibres  of  the  compressor  urethr.i>  muscle. 

The  duf/s  of  the  glands — atxiut  1.5  mm.  in  diameter  and  In  n  3-4  cm.  in 
length — nm  forward  and  medially,  at  first  between  the  bulbus  spongiosum  and  the 
membranous  urethra,  then  within  the  bulb  itself,  and,  finally,  for  alxiut  2  cm.  be- 
neath the  urethral  mucous  membrane  to  opin  by  small  slit-like  orifices  on  the  lower 
wall  of  the  bulbus  urethra  near  the  mid-line.  The  position  of  these  inconspicuous 
openin^j-^  is  s<rfnetimes  masked  by  a  fold  of  mucous  membrane  or  a  slight  de- 
pression.    Quite  fretjuently  the  two  ducts  unite  and  open  by  a  common  >  Tifice. 

Structure. — These  glands  are  mucous  tubo-alveolar  in  tyj)e,  thi  r  terminal 
divisions  ending,  after  more  or  less  branching,  in  irreguLirly  sacculated  -  ompart- 
ments.  In  places  the  latter  communicate  by  means  of  a  retic\ilum  of  connecting 
canals  (Braus).  The  alveoli  are  lined  with  low  columnar  or  pyriform  epithelial 
cells,  among  which  mucus-secreting  cells  are  plentiful.  The  cuboida!  epithelium 
that  clothes  the  smaller  ducts  and  the  dilatations  connected  with  them  gives  place  to 
clear  columnar  cells  within  the  larger  excretory  canals.  The  divisions  of  the  gland 
arc  united  by  interlobular  connective  tis.sue  and  investetl  in  a  gener.il  filirous  en- 
velope in  which  a  consider  ;ble  quantity  of  unstriped  muscle  occurs.  The  secretion 
of  Cowper's  glands,  clear  and  viscid  and  of  alkaline  reaction,  is  probably  of  ser\ice 
in  maintaining  favorable  conditions  for  the  spermatozoa  by  neutralizing  acidity  of 
the  urethral  canal  due  to  pa.s.sage  of  urine  (  Eberth).  In  addition  to  their  recognized 
homology  with  the  glands  of  Bartholin  in  the  female,  the  observed  histological 
changes  incident  to  sexual  excitation  warrant  the  grouping  of  these  glands  as  acces- 
sory sexual  organs. 

Vessels. — The  arteries  supplying  Cowper's  glands  are  twigs  given  off  from 
the  arteries  of  the  bulb  as  they  course  between  the  two  lavers  of  the  triangular  liga- 
ment. The  veins  are  tributary  to  those  returning  the  blood  from  the  bulbus  sponvji- 
osum  which  empty  into  the  internal  pudic.  The  lymphatics  are  afHerents  to  the 
internal  iliac  lymph-nodes. 

The  nerves  are  derived  from  the  pudic. 

Development. — The  bulbo-urethral  glands  appear  about  the  end  of  the  tl  rd 
month  of  foetal  life  as  solid  outgrowths  from  the  entohlastic  lining  of  the  uro- 
genital sinus.  With  the  elongation  of  the  latter  incident  to  the  formation  of  the 
male  urethra  and  the  penis  (page  2044),  the  glands  issume  a  lower  position  ^m! 
their  ducts  are  correspondingly  lengthened.  During  first  ten  or  twelve  -  .-ais  the 
glands  undergo  only  small  increase  in  volume,  bvit  iietween  the  sixteenth  antl 
eighteenth  years  they  attain  their  full  size.  In  aged  subjects  they  atroph\  an"  are 
frequently  so  small  that  their  recognition  is  difficult 

Variations. — In  addition  to  abnormalities  in  size,  the  two  gl'tids  may  be  fused  into  .>  izle 

mass,  or  one  or  b<jth  may  Iw  wanting.     Sometimes  their  ahiseiice  is  only  apparent,  -    it  the 

organs  may  he  represented  by  rudimentary  glands  embedded  entirel\  within  the  subs  -e  of 
the  corpus  spongiosum. 


THE  OVARIES. 


I      i 


HE  FEMAl  E  REPRODi    mVF  ORGANS. 


if  the  fcmde  comi'      twi.        .ip*— tl' 
e  i>«lvis  and  abo-       iif  p'         :l(H>r,  . 

:    and  b*  1<>'    the  triuJigular  i,    irnent  a 
jones,  *;i      >.  and  inteuumvnt.     Thi 
,-s,  whith  \,  oduce      •  ova,  the  ovidu. 
^xual  ^ellh   the  Mi   us,  and  the  vagi 


Htemal  situ- 

;  the  exitmal, 

supported  by 

Ternal  organs 

or  Fallopinn 

the  passage 


vis,  eixbraces  the  !  >wer  end  of  the   uterus  above, 
Ixh         ithin  the  e   lernal  genital  cleft.     The  Fallo- 


The  reproductive  ortjans 
ated  for  the  most  part  w  iihin  ; 
embraced  by  the  subpubc  arc: 
attachmenu  to  the  surrout.dinj; 
are  the  sexual  gl  ds,  th«  ota, 
lubes,  the  canals  fivi-yinji  tlu 
which,  beffinninj    within  the  ji 

nierres  tht-  pelvii  rt(M)r,  aiv!  et>',    .ri „-  -  i     i      i 

pian  cubes  uterus,  and  v.«ma  repr.  o  the  excretory  canals  of  the-  sexual  glands 
which  in  ll.  .  mbryo,  as  tlu  .Mulleri.«a  ducts,  for  a  time  are  separate.  After  fusion 
of  their  lower  , -gments  tias  takvn  pla  .-.  the  unpaired  tube  thus  formed  b^omes  the 
vagina  and  the  ut.  .n-  tht-  latter  !-m.;  sperialized  for  the  recepUon  and  r  ention  o' 
the  fertilized  ovum  -     rmggesutii  Hi  ...  ,       ,     ^      ,  .    . 

The  e^ienwl  otj^tas,  oftei.  <.nm--l  colltH:tively  the  vulva  (pwlt     lum  muhcb! 
include  the  elUds,  the /«*/<!    ai>     the  enclosed  vesHMe  AnA  vagtHu.  Mfi,'      id 
glands  of  Bartholin,      in  a  -en,  i  .1  «ay  these  parts  represent  structures  ho     .log    . 
w    h  the  i)enis  and  scrotum,       i  .:    a  less  a   vanced  and  specialued  stage  of     f-vel   p- 
n    nt. 

THE   0\        lES. 
^  he  ovary  (ofanua),  ■•?»*  on  either  side  .  i  the  body,  is  the  sexual  gl. 
W!         and  f->m  whi.  h  ire  dev»  oped  and  liberated  the  mature  maternal 
tb    -  va      i    "  asohu  .lody,  rc^cm' img  in  forma  large  almond,  and 
lies  a^'atnst  or     ear  to  ^  'w  lateral  pelvic  wall  invested  by  peritonei  ^  co 
the     .«terior  suiiu-e  o    tS*  broir!  ligament  of  the  uterus      Ev.^        sei 
organ  pre-    "its  constdeni'-  •  indu  dual  \  mations  in  size,  its  averaj;      m. 
36  mm.  ( \      in. )  in  lenc       t8  m^'   (  ^  in. )  in  breadth,  and  i  a  mm. 
new.     \.. nations  in  ^\f      clud        length  of  from  2.5-5  cm.  (1-2 
from  I  vj   cm.   (H-«'«  ■*"J  »  thickness  of  from  .6-1.5  cr.  , 

according  to  German  auth.  =.i.e8.  The  right  ovary  is  frequently  somewhat  larger 
thar  the  left.  The  adult  organ  weighs  about  7  grm.  {%  oz.).  Acer  the  cesMtion 
di  n  ,.-4truation,  about  the  forty -fifth  year,  the  ovary  decreases  m  si?  ind  wtight.  m 
<^  u  Hnen  being  reduced  to  one-half  or  less  of  its  normal  proportio 

ibp  ovary  presents  two  turfaces— a  »m'</«i«  (fades  media  ted  mward, 

Afic  T     /rt-a/ (fades  lateralis),  looking  outward  and  in  more  '  i-i.<se  relation 

wifc     tie  pelvic  wall ;  two  margins  connecting  the  surfaces — an  ^r     »wr  (raargo  nieso- 
sricus),  which  is  thin,  straight,  and  attached  to  the  posterior  surface  of  the  broad 
^'araent  by  a  short  peritoneal  fold  or  mesovarium,  and  a  posterior  (marfo  libra), 
htch  is  thicker,  rounded,  convex,  and  unattached  ;  and  two  poles— an  upper  (ei- 
m»a»  tttbaria),  rounded,  embraced  by  the  oviduct  and  attached  to  the  susp«>soiy 
ament  of  the  ovary  and  usuaHy  to  the  fimbriated  extremity  of  the  Fallopian  t^^b*- 
id  a  lower  (extremltas  uterina),  pointed  and  attached  to  the  uterus  by  a  hbw. 
uscular  band,  the  utero-ovarian  ligament.     The  portion  of  fhe  .ittachrd  anten^ 
>rder  through  which  the  vessels  and  nerves  enter  and  emerge  is  knowi)  as  tbe 
:lum  (hllns  ovarii).     The  surfaces  of  the  mature  ovw'  »t*    '««  even,  as  in  eariy 
iife,  but  modelled  by  rounded  elevations  of  uncertair      Hnh«f  ^ae  and  W  irregu- 

lar pits  and  scars.     The  elevations  are  produced  H  \inrter  .i^  Graahaf  follicles 

in  different  stages  of  growth,  while  the  irregul )  ..  «'  was*  iadtcate  the^sitioti 
of  corpora  lutea  of  varying  age  and  develop  it.  «  'oelamd  the  attachment  of 
the  mesov-irium  and  parallel  to  the  hilnm.  the  M.Hac*  M  the  tw)^'-«ary  are  c-«^ 
by  a  narrow  stripe  of  lighter  color,  straight  or  <  urved  iw!  often  i%i*ii/  raised,  i  ms 
band,  the  while  line  of  Farre,  marks  the  tran»«>..n  n  the  usual  f#entoneal  endotb' 
lium  into  the  cylindrical  germinal  epithelium  thai  cfjvers  the  exterior  of  the  at^f' 
and  appears  dull  and  lacking  in  the  lustre  charactenstit  of  serous  surfaces. 

ii5 


^.cr 
cell^ 
adui 
I'd  from 
,    '.    the 
sioii-    -ew^ 
. )  in  ihick- 
a  width  of 
'4-5.i  in.), 


1986 


HUMAN  ANATOMY. 


Position  and  Fix  ation.— Although  subject  to  deviations  due  to  the  -nfluence 
of  other  organs,  especially  the  pull  of  the  uterus,  and  of  pregnancy,  the  long  axis  of 
the  normally  placed  ovary,  in  the  erect  pbsture,  is  approximately  vertical  (Fig.  1684). 
The  margin  attached  to  the  broad  ligament  of  the  uterus  is  directed  forward  and 
slighdy  outward  and  the  free  convex  tx>rder  backward  and  inward.  The  outer  sur- 
face usually  lies  in  contact  with  the  peritoneum  covering  the  lateral  pelvic  wall  within 
a  more  or  less  well-marked  depression,  the  ovarian  fossa  (fossa  ovarica).  This  recess, 
triangular  in  its  general  outline  and  variable  in  depth,  is  included  within  the  angle 
formed  by  the  diverging  peritoneal  folds  covering  the  external  and  internal  iliac  vessels. 
In  favorable  subjects,  in  which  the  amount  of  subperitonral  fat  is  small  and  the  em- 
bedded structures,  therefore,  not  masked,  the  ureter  and  the  uterine  artery  will  be 
seen  forming  the  immediate  boundary  of  the  ovarian  fossa  behind,  while  above  and 
in  front  extends  the  remains  of  the  obliterated  hypogastric  artery.     Below,  where  its 

Fig.  1684. 


Intenul  iliac  aitery 

Fimbriated  end  of  Fallopian 
tube,  pulled  fonnrd 


Suspensory 
ligament  of  ovary 

External  iliac 
vessels 

Round  ligament 

Deep  epigastric- 
artery 
Mesosalpinx 

Oblitersted 

h>-pogastric  artery 

Fallopian  tube 


Bladder 
Symphysis  pubis 


Itoaeum,  cat  cd(« 


Ureltr 


Right  ovary, 
median  surface 


Ligament  of  ovary 


.Utero-sacral 
ligament 


Rectum 
Recto-uterine  pouch 


~^Utems,  pulled  to  the  left 


Right  lateral  wall  of  pelvis,  showing  ovary  in  position  ;  Fallopian 
tube  has  been  pulled  forward  and  uterus  to  the  left. 


boundary  is  indistinct  and  uncertain,  it  fades  into  the  pelvic  floor,  often  without 
demarcation.  The  floor  of  the  fossa  is  obliquely  crossed  by  the  obturator  vessels 
and  nerve.  Within  this  depression  the  ovary  lies,  hidden  to  a  considerable  extent 
beneath  the  oviduct,  which  arches  over  the  upper  pole  and  largely  covers  the  median 
surface  with  its  expanded  fimbriated  end.  The  upper  or  tuba',  pole  reaches  almost 
to  the  level  of  the  external  iliac  vein  and  the  peUic  brim,  and  is  overhung  by  the 
inner  edge  of  the  psoas  muscle.  The  lower  pole  rests  upon  the  upper  ( posterior)  sur- 
face of  the  broad  ligament  and  nearly  touches  the  pelvic  floor — about  2  cm.  above 
and  in  front  of  the  upper  border  of  the  pyriformis  muscle  and  the  trunk  of  the  greater 
sciatic  nerve  (Rieffel). 

The  vertical  position  of  the  ovary  is  maintained  by  the  suspensory  ligament 
(liKamentum  suspensorium),  also  called  in/undibulo-pehic  li/fament,  which  is  a  trian- 
eiilar  band  of  ftbro-mtisculnr  tismip,  attached  to  the  upper  tubal  pole  of  the  ovary  and 
mvested  by  a  peritoneal  fold  continued  from  the  upper  and  outer  corner  of  the  broad 


THE  OVARIES. 


1987 


Fig.  1685. 


lieament.  It  passes  outward  across  the  external  Miac  vessete  in  front  of  the  sacro-iliac 
articulation  anri  is  lost  in  the  fascia  covering  the  psoas  muscle.  Embedded  w.thm 
the  enclosed  fibro-muscular  tissue  lie  the  ovarian  vessels  and  nerves,  which  thus  gam 
the  broad  ligament  in  their  passage  to  the  ovary.  •  .         i  .u- 

The  anterior  margin  of  the  ovary  is  attached  to  the  posterior  surface  of  the 
broad  ligament  by  a  short  but  broad  band— the  «i^f^..ar.««i— covered  on  both  sides 
by  peritoneum,  that  conveys  the  ovarian  vessels  proper  and  the  nerves  to  the  hilum 
through  which  they  enter  and  emerge  from  the  organ.  The  somewhat  pointed  lower 
end  0?  the  ovary  is  connected  with  the  posterior  border  of  the  uterus,  between  the 
oviduct  and  the  round  ligament,  by  a  cord-like  band.  \\i^uUro-ovartan  ligament  or 
ligament  of  the  ovary  (ligamentum  ovarii  proprlum).  This  band,  from  3-4  mm. 
thick,  lies  within  the  posterior  layer  of  the  broad  ligament  beneath  the  peritoneum, 

through  which  it  is  seen  as  a  distii-~t  cord.  ...  . .: 

Since  the  uterus  and  its  broau  Sigament  are  subject  to  continual  changes  of  posi- 
tion, the  attachment  of  the  ovary  to  these  structures  often  produces  deviaUons  from 
its  typical  location.     These  in- 
fluences  affect   particularly   the 
lower  pole,  the  upper  enjoying        s„rf,^. 
greater  fixation  from  the  support  epithelium  ' 
afforded  by  the  suspensory  liga- 
ment     Asymmetry  in  the  po- 
sition of  the  two  ovaries  is  usual, 
as  the  fundus  of  the  uterus  seldom 
lies  stricdy  in  the  mid-line,  and 
hence  the  lower  pole  of  the  ovary 
of  the  opposite  side  is  dragged 
medially.     The  long  axis  of  the 
ovary,  under  such  conditions,  is 
oblique  on  the  side  opposite  to 
that  towards  which  the  uterus  is 
deflected.      Conversely,    relaxa- 
tion of  the  ligaments  occurs  on 
the  side  towards  which  the  uterus 
tends  and  thus  favors  the  reten- 
tion of  the  vertical  position  of  the 
ovary.    Notwithstanding  the  lati- 
tude of  movement  possible,  the        „,„,„,„. 
position  of  the  normal  ovary  is  tranuimum  ■ 
fairly  constant,  the  close  relation 
of   the  oviduct   to   the    median 
surface,  aided  by  the  pressure 
exerted  by  other  organs  within 
the    pelvis,    materially  assisting 

in  retaining  the  ovary  within  its  . 

fossa.  The  stretching  and  subsequent  relaxation  of  the  suspensory  ligament  incident 
to  pregnancy  are  predisposing  causes  of  disnlacement  of  the  ovary  due  to  insufficient 
fixation. 

Structure. — The  ovary  consists  of  two  principal  parts,  the  cortex  (lona 
parenchymatosa) — ^a  narrow  superficial  Lone,  from  2-3  mm.  thick,  that  forms  the 
entire  periphery  of  the  organ  beyond  the  white  line  ;  and  the  medulla  ( zona  vascn- 
losa,)  that  embraces  the  deeper  and  more  central  remaining  portion  of  the  gland. 
The  cortex  alone  contains  the  characteristic  Graafian  follicles  and  the  ova,  while  the 
medulla  is  distinguished  by  the  number  at)d  size  of  the  blood-ves-sels.  especially 
the  veins. 

The  cortex,  as  seen  in  vertical  sections  of  the  functionally  active  organ,  con- 
sists chiefly  of  the  compact  ovarian  stroma  that  is  composed  of  peculiar  spindle- 
shaped  connective  tissue-cells,  from  .01 5-. 030  mm.  in  length  and  alwut  one-fifth  as 
mitrh  in  width,  and  fibrillar  intercellular  substance.  The  xtrotna-cells,  which  some- 
what resemble  the  elements  of  involuntary  muscle  in  appearance,  are  arranged  in 


Ovarian 
atroma 


Immatara 

primary 

follicle 


Follicle 
beginning 
to  grow 

Stnttura 


Theca 


Section  of  cortex  of  ovary  of  voung  woman,  nhowinn  primary 
and  growing  folliclea  within  ovarian  stroma,     a  I'jo. 


n 


1988 


HUMAN  ANATOMY. 


bundles  that  extend  in  all  directions  (chiefly,  however,  obliquely  vertical  to  the 
surface)  and  are  seen  cut  in  different  planes.  Immediately  beneath  the  germinal 
epithelium  covering  the  surface,  the  stroma-elements  are  disposed  with  greater  reg- 
ularity and  form  a  compact  superficial  stratum,  the  tunica  albuginea.  Embedded 
within  the  stroma  lie  the  most  characteristic  components  of  the  cortex,  the  egg-sacs 
or  Graafian  follicles.  These  are  seen  in  different  stages  of  development,  but  for  the 
most  part  are  small,  inconspicuous,  and  immature,  in  the  human  ovary  being  much 
fewer  and  less  prominent  than  in  many  other  mammals.  Corresponding  with  their 
stages  of  development  the  egg-sacs  may  be  divided  mXo  primary,  grcnving,  and  ma- 
turing follicles.     In  general,  the  youngest  lie  nearest  the  surface,  the  more  advanced 

deeper  and  towards  the 
Fig.  i68«.  medulla,  while  those  ap- 

proaching maturity  ap- 
pear as  huge  vesicles 
that  occupy  not  only 
the  entire  thickness  of 
the  cortex,  but  often 
produce  marked  eleva- 
tion of  the  free  surface. 
The  medulla,  the 
vascular  zone  of  the 
ovary,  consists  of  loosely 
disposed  bundles  of 
fibro-elastic  tissue  sup- 
porting the  blood-ves- 
sels, lymphatics,  and 
nerves.  In  the  mature 
organ,  with  the  excep- 
tion of  the  encroaching 
ripening  Graafian  folli- 
cles, egg-sacs  are  not 
found  within  the  me- 
dulla. The  larger  ves- 
seb  are  accompanied  by 
bundles  of  involuntar}' 
muscle  prolonged  from 


Blood-veucI 


Connective- 
tissue  stroma 


Muscle 


Section  of  medulla  of  ovary,  showinK  nnmeroin  blood- 
venaels  and  fibro-muscular  atroina.    x  7S. 


iiiu3\.ic  piuiuiigt^u  irom 

the  utero-ovarian  ligament  through  the  mesovarium  and  the  hilum  into  the  medulla. 
The  veins  are  particularly  large  and  appear  in  sections  as  huge  blood  spaces  of  irregu- 
lar outline  in  consequence  of  their  tortuosity  and  plexiform  arrangement. 

PoUidet  and  Ova.— The  aaxanXwK  primary  follicles  (folliculi  oopbori  primaril)  arc  micro- 
scopic in  size  (from  .04-.06  mm.  in  diameter)  and  var>-  greatly  in  number,  the  estimate  for  the 
two  ovaries  of  young  adults  being  placed  at  approximately  35,000  (Bonnet).  Each  follicle 
consists  of  the  centrally  situated  young  egg  (ovalam)  surrounded  by  a  single  layer  of  flat- 
tened epithelium  or  mantle  cells  (Fig.  1685).  Immediately  outside  the  latter  lies  the  stroma, 
in  the  interstices  of  which  the  young  <;gg-sacs  are  lodged.  The  primary  ova  are  approximately 
spherical  and  mea.sure  from  .035-.045  mm.  in  diameter  in  ordinary  sections,  but  a  third  more  in 
the  fresh  unshnmken  condition  (Nagel).  They  possess  a  finely  granular  cytoplasm,  a  centrally 
placed  spherical  nucleus,  about  .oiC  mm.  in  diameter,  and  a  nucleolus.  The  primary  ova  may 
remain  for  years,  sometimes  from  early  infancy  to  advanced  age,  practically  unchanged,  until 
they  undergo  either  atrophy,  as  do  most  of  them,  or  further  growth  leading,  under  favorable 
conditions,  to  the  development  of  the  mature  sexual  cell.  Of  the  thousands  of  primary  eggs 
contained  in  the  ovaries  just  before  puberty,  only  comparatively  few  attain  perfection.  Sooner 
or  later,  but  at  some  uncertain  time,  the  primary  follicles  enclosing  ova  destined  for  complete 
development  enter  upon  a  period  of  active  growth,  the  eartiest  indication  of  which  is  the  con- 
version of  the  flat  mantle  celts  of  the  egg-sac  into  a  single  layer  of  cuboid  epithelium. 

In  addition  to  increasing  size,  the  growing  follicles  are  distinguished  by  rapid  prolifera- 
tion of  the  cuboid  epithelium,  which  results  in  the  production  of  a  stratified  follicular  epUhe- 
Hum  that  surrounds  the  ovum.  Outside  these  polygonal  elements  the  stroma  becomes  con- 
densed into  a  connective-tissue  envelope  or  theea  (thcca  follinli).  Increasing  in  thickness,  the 
latter  is  subsequently  differentiated  into  two  layers,  an  outer  (taaica  txuna),  consisting  of  con- 


THF   OVARIES. 


1989 


centric,..,  '^r^r''^irn^Tr;^:fc:^i^i^  'usTr'^^i^c^'^^Lr:^ 

^'f^'t^^S":^^^^7^^^S^^     proceeding  unUorm.y  and  affecting 

parauvely  early  and   ong  ^'"j  '"V"  invested  with  a  protecting  envelope-,  the  zona 

5^S^er^^^£^^^ 

vac.o,r„':^r.iSk£=^''™ 

resulting  clefu  '.^"^  "^^^  »  XXth^^TsupJ.'^  Wrc^nri;:^Li%roil.eration.  vacuolation, 
accumulatmgflmd  the/w«^^/^'^^«^^»'^^  ,„„  ,he  surrounding  blood-vesseU. 

"i'^n^^C.'t^unTlo  ^Hch'L  extent  that  U  ««n  occupies  the  greater  part  o.  the 

and  rel^^  ^^T^^^^U^J^^^^^ 

li-hich  M  St^«  finTruptuC^atins  a  diameter  o.  .rem  .-.  cm.  ormore.  and  appears  on  the 


Fig.  1687. 


Surface  epitbeliimi— 


Prinuiry  lollicli 


Then  of  follicle 


Zona  pcllucida 


Ovum 


Section  of  ov»r>,  sliowinK  partially  dev«lof»l  Gnallan  follicle. 


Cavity  filletl  hy  liquor  folliculi 


free  surface  of  the  ovary  as  a  tense  rounded  elevation.  After  liberation  of  the  ovum,  the  folli- 
cle is  converted  into  the  conspicuous  corpus  lutetim  (page  1990).  r  „■  ,^  ^„„=i... 
Sin  section,  the  wall  of  the  ripe  follicle,  now  known  as  *e  (7r<»a;fa»>//.r/^,  cons.ste 
of  a  wenT^.qped  capsu.e  or  theca  (from  ..4-20  mm.  in  thickness)  of  which  the  outer  ayer 
UaUmXtedXous^mbrane,  and  the  inner  tunic  i''.  «>'"P««^  "' '°^.' 7"""^,  ^^  "3 
contaWng  numerous  peculiar  large  i-ells  which,  as  maturity  approaches,  exhibit  J^aniUar^d 
a  fSeflowish  color  Next  the  inntr  layer  of  the  caps.ite  lies  a  delicate  '"[^Xttl^; 
^ganst  theTnnersuriaceof  which  is  applied  the  stratum  granulosum,  composed  of  the  outer 
"E  of  the  follicular  epithelium  that  hound  externally  the  fhi.d-spa«  of  the  vesicle.  A  totve 
S  always  opposite  the  place  where  the  follicle  n.pt.,res  (stigma),  the  stratum  granulosum  is 
S«d  nto  r^uncurated  spherical  mass  of  epithelial  cells  that  projects  mto  the  cavrty 
SK  Uie  li^r  folliculi.  This  mass  (n.ulu.  -ph.™.)  contains  the  egg  and  m.  sect  on 
SiT as  a  nx^K  (discus proligerus)  that  encircles  the  zona  pelluc.da  and  the  enclosed  ovt^in 
an^co^sUts  of  Two  or  thrT^yers  of  epithelial  cells.  Those  next  the  .ona  are  elongate!  with 
?he  rends  directed  towards  the  ovum  pointed  and  prolonged  into  delicate  Processes  that  ai^ 
auS  toT^netrate  within  the  zona  pfllucida.  The  latter,  from  .007-J31 .  mm.  •"  thickness, 
fs  theWluct  of  the  surrounding  follicular  cells  and  does  not  form  a  part  of  the  ovum  pr^r. 
?te  radW  ^n°  tions  which  the  envelope  sometimes  exhibits  (hence  the  name,  z^«  r«<ft^Ar 
mvLr  which  it  is  often  described)  ate  probably  due  to  the  processes  of  the  epithelial  ce  Is  and 
StoAeexistence  of  minute  can..s  iCmicropyUs)  .een  in  the  eggs  of  many  lower  «,.mals. 


^::  '3 


1090 


HUMAN  ANATOMY. 


The  human  ovum  when  about  to  be  liberated  from  the  Graafian  follicle  pos- 
sesses a  dii>nieter  of  from  .16-.  20  mm.  Its  cytoplasm,  or  vitellui,  exhibits  differ- 
entiation into  a  peripheral  protoplasmic  and  a  central  deutoplasmic  zone.  According 
to  Nagel,  within  the  former  are  to  be  distinguished  a  narrow  slight  superficial 

marginal    layer,    apparently 
Fio.  1688.  homogeneous  and  free  from 

yoik-partides,  and  a  finely 
granular  zone  containing  mi- 
nut<>  and  scattered  deutoplas- 
mic granules.  The  dark  or 
central  deutoplasmic  zone  is 
conspicuous  on  account  of 
the  irregular  refraction  of  the 
enclosed  yolk-particles  that 
represent  the  important  nutri- 
tive materials  for  the  embryo 
contained  in  the  eggs  of  birds 
and  reptiles,  but  which  in  the 
mammalian  ovum,  especially 
in  that  of  man,  have  been  for 
the  most  part  lost  during  the 
evolution  of  the  higher  types. 
Beyond  a  slight  condensation 
of  the  surface,  the  presence 
of  a  distinct  cell-wall,  or  vi- 
telline membrane,  in  the  mam- 
malian ovum  is  doubtful.  In 
the  fresh  condition  the  egg- 
cytoplasm  is  usually  closely 
applied  to  the  zona  pellucida 
(Ebner),  the  narrow  inter- 
vening cleft  that  is  sometimes  seen  being  the  perivitelline  space.  Embedded  within  the 
deutoplasmic  zone,  and  always  eccentrically  placed,  lies  the  spherical  germinal  vesicle, 
as  the  egg-nucleus  is  termed.  The  vesicle  measures  from  .030-.045  mm.  in  diameter, 
is  bounded  by  a  sharply  defined  double-contoured  nuclear  membrane,  and  contains 
xhe  germinal  spot  or  nucleolus  (from  .004-.  008  mm.)  and  the  nuclear  reticulum. 

Corpus  LuteuRi. — The  causes  leading  to  the  final  rupture  of  the  Graafian 
follicle  are  still  uncertainly^  known,  although  in  the  light  of  later  researches  the  older 
view,  attributing  the  bursting  of  the  ripe  vesicle  to  mechan- 
ical overdistention  induced  by  accumulation  of  the  liquor 
folliculi,  is  inadequate.  According  to  Nagel,  when  the 
follicle  approaches  maturity  the  inner  layer  of  the  theca 
becomes  the  seat  of  great  activity.  The  blood-vessels  in- 
crease in  size  and  number  and  the  cells  undergo  not  only 
rapid  proliferation,  but  extraordinary  growth,  the  enlarged 
elements  becoming  filled  with  a  peculiar  yellowish  sub- 
stance and  transformed  into  lutein  cells. 

In  consequence  of  this  activity,  the  formerly  smooth 
theca  becomes  thickened  and  wavy  and  projects  into  the 
cavity  of  the  follicle  as  vascular  papilla  and  ridges.  The 
encroachment  thus  effected  gradually  forces  the  contents 
of  the  vesicle  towards  the  surface  and  that  part  of  the  dis- 
tended follicular  wall  possessing  least  vitality  and  resist- 
ance, until,  finally,  rupture  takes  place.  Coincidently  with 
the  proliferation  of  the  lutein  cells,  the  follicular  epithelium 

undergoes  fatty  change  which  results  in  the  breaking  down  of  the  cumulus  and  the 
setting  free  oi  the  ovum,  encircled  with  the  cells  of  the  discus  proligerus,  into  the 
cavity  of  the  ej^-sac.  When  rupture  of  the  follicle  occurs,  the  expulsion  of  the 
egg  and  the  epithelial  cells  immediately  surrounding  it  is  followed  by  hemorrhage 


Almost  mature  human  ovnm  taken  from  fresh  ovar\'.  Ovum,  with 
K«rmmal  vesicle  and  spot,  is  encircled  by  clear  xona  pellucida,  which  is 
surroundetl  by  cells  of  the  follicular  epithelium.    X  300.    ( WaUryer.) 


Fig.  1689. 


-Corpus 
luteum 


:ament 
ovary 


Ovary  has  been  laid  open  by 
lonaitudinat  incision,  exposlnx 
follicles  and  corpus  luteum. 


THE  OVARIES. 


1991 


.Central 
connective  tiuuc 


into  the  cavity  of  the  former  egg-sac,  which  now  becomes  converted  into  a  corpus 

The  latter  long  known  as  the  corpus  luteum  verum  when  associated  with  preg- 
nancy grows  to  huge  dimensions  and  forms  a  conspicuous  oval  mass  that  may 
approid  3  cm.  in  length  and  occupy  a  considerable  part  of  the  entire  cortex. 
When  impregnation  does  not  toke  place,  the  yellow  body  (now  called  the  ayrput 
luteum  s^rtum)  is  smaller,  seldom  exceeding  1.5-2  cm.  m  diameter.  The  classic 
distinction  of  "true"  and  "false,"  apart  from  difference  of  size,  has  no  anatomical 
basis  since  both  foiros  possess  identical  structure.  The  a.ssumption  that  the  presence 
of  a  'large  corpus  luteum  is  positive  proof  of  the  existence  of  pregnancy  must  be 
accepted  with  caution,    ince  yellow  bodies  of  unusual  size  are  sometimes  obser%ed  in 

°^*":^ortly"!§ter  the  rupture  of  the  follicle  and  the  replacement  of  its  contents  by 
blood,  the  opening  in  the  wall  of  the  egg-sac  is  closed.  The  rapid  proliferation  and 
growth  of  the  lutein  cells  pro- 

duces  an  irregularly  plicated  ^''G-  '<»9o. 

wall   of    increasing   thickness        z^JirMi 
that  encloses  the  remains  of  the 
degenerating  follicular  epithe- 
lium (granulosa)  and  invades 
the  hemorrhagic  mass.     The 
latter    is    gradually   absorbed 
until,  finally,  the  encroaching 
projections  of  lutein  ceUs  and 
connective  tissue  meet  and  the 
cavity  of  the  follicle  obliter- 
ated, its  former  position  being 
subsequently   indicated  by  a 
central  core  of  connective  tis- 
sue.    The  cells  of  the  stratum 
granulosum,  the  original  epi- 
thelial lining  of   the  egg-sac, 
entirely  disappear  and  take  no 
direct  part  in  the  formation 
of   the  corpus  luteum,    their 
function  during  the  develop- 
ment of   the  Graafian  follicle 
having  been  to  contribute  the 
liquor  foUiculi  (Schottlaender). 
Along   with  the  proliferating 
masses  of  lutein  cells,  strands 
of  connective  tissue   are  car- 
ried  inward   from  the  theca, 
whereby,  after  a  time,  the  yel 


Blood-vesKis 


Section  of  human  corpus  luteum.    X  To. 


wnereoy,  ;uier  a  iimc,  mc  yti-  ..  ,  ,  »  i  »!,«;.. 

low  body  becomes  broken  up  by  numerous  radially  disposed  vascular  septa  and  their 
prolongations.  With  the  production  of  a  solid  corpus  luteum  and  the  absorption  o! 
the  blood  (evidences  ot  which  latter  for  a  long  time  remain  as  hematoidin  crystals), 
the  active  rdU  of  the  lutein  cells  is  finished.  These  elements  now  lose  their  distinc- 
tive vellow  pigment  {lutein),  undergo  fatty  metamorphosis,  and  finally  entirely  tlis- 
appeai .  With  the  subsequent  shrinking  and  decrease  in  the  vascularity  of  the  corpus 
luteum,  the  connective  tissue,  which  now  constitutes  the  entire  mass  {corpus  fibro- 
sum),  undergoes  hyaline  change,  becoming  clear  and  non-fibrillar.  In  consequence 
the  ating  corpus  luteum  loses  its  former  appearance  and  is  transformed  into  an  irreg- 
ular body,  light  in  color  and  sinuous  in  outline,  sometimes  known  as  the  corpus 
albicans  (Fig.  I691).  This  gradually  suffers  absorption,  but  remains  for  a  consider- 
able time,  especially  when  associated  with  pregnancy,  as  a  conspicuous  hght  corru- 
galed  area  within  the  cortex,  the  last  traces  of  its  scar-like  tissue  hnally  disappearing 
in  the  ovarian  stroma.  The  greatly  increased  vascularity,  within  the  wall  o  the  ripe 
Graafian  follicle  and  later  around  the  corpus  luteum,  subsides  as  the  ye.low  .xiay 


if      "^ 


\\\\ 


1992 


HUMAN  ANATOMY. 


underg^oes  regression,  until  all  the  new  vessels  concerned  in  its  nutrition  have  disap- 
peared and  the  circulation  of  that  particular  part  of  the  ovary  is  permanently  reduced. 

The  function  usually  ascribed  to  the  corpus  luteum  is  that  of  filling  the  empty  follicles  and 
thus  restonng  the  eq^uilibnum  of  circulation  and  tension.  Clark '  regards  the  corpus  luteum  as 
a  preserver  of  the  circulation,  since,  when  performing  its  hinctions  most  perfectly  (durine  the 
eariier  years  of  menstrual  life),  it  effects  the  elimination  of  the  eflete  follicle  and  tl4  superifuous 
blood-vessels  without  leaving  dense  and  disturbing  scars.  Later  in  life,  however,  when  the 
oyanan  stroma  becomes  denser,  die  corpora  lutea  are  less  efficient  and  are  incompletely  absorbed, 
their  remains  impainng  the  circulation  until,  finally,  the  follicles  are  no  longer  matured  anJ 
ovulation  ceases. 

The  origin  of  the  lutein  celk  has  long  been  a  subject  of  discussion,  and  even  at  present 
two  opposed  views  ^re  the  support  of  eminent  anatomists.  According  to  the  older  theory, 
advanced  by  Baer,  diese  celU  are  modified  connective-tissue  elements,  derived  from  die  pro- 


Fic.  1691. 


Corpora  lutes 

^ 


of  corpora  lulca 


Sectiona  of  Fallopian  tube 


Cron-Mction  throuKh  ovary,  ovidact,  and  part  o»  broad  ligament.    X  6. 


hferation  of  die  cells  of  the  inner  layer  of  the  theca  folliculi.  The  other  view,  formulated  bv 
Bischoff,  rtwards  die  lutein  cells  as  modified  follicular  epithelium.  In  the  foregoine  sketch  0I 
the  corpus  liiteum,  the  lutein  cells  are  ascribed  to  die  dieca,  a  conclusion  based  up^n  the  con- 
vincing observations  of  Nagel,  RabI,  and  Clark,  and  confirmed  by  the  writer's  bwn  studies 
.sobotta,  on  the  odier  hand,  is  most  positive  in  his  support  of  the  follicular  origin  of  the  lutein 
ceMs,  oaseu  upon  an  exhaustive  investigation  on  the  ovaries  of  the  mouse  and  rabbit  The 
not  be  otS  chafl'"'"*^  corpora  lutea  in  the  earliest  stages  places  the  conclusions  as  to  man 

Vessels.— The  arteries  supplying  the  ovary  are  four  or  five  branches  that  arise 
from  the  anastomosis  of  the  ovarian  artery  with  the  ovarian  branch  of  the  uterine. 
The  trunks  {aa.  ovarica  propria)  given  dflf  from  this  anastomotic  arch  pass  to  the 
ovary  between  the  layers  of  the  mesovarium  and,  entering  through  the  hilum  as 
closely  grouped  tortuous  vessels,  reach  the  medulla.  According  to  Clark,'  whose 
descnption  is  here  followed  (Fig.  1692),  immediately  after  gainii^  the  medulla  each 
stem  divides  into  two  branches,  the  medullary  or  parallel  arteries,  that  proceed  in  a 
threct  course  towards  the  opposite  free  margin  of  the  organ,  lying  just  beneath  the 
corte.\,  to  which  they  distribute  cortical  branches  at  regular  inter\'als.  In  their  course 
to  the  periphery  the  cortical  branches,  losing  the  characteristic  corkscrew-like  twist- 
'"<^i,  1  parent  stems,  supply  hundreds  oi  follicular  twigs  to  the  e^-sacs,  each 
of  the  latter  being  provided  with  a  rich  vascular  net-work  anastomosing  with  irwo  or 
more  follicular  branches— an  arrangement  of  great  importance  in  assuring  an  adequate 
blood-supply  for  the  growth  of  the  follicle  (Clark).  At  the  penpherv,  the  cortical 
arterioles  pass  into  the  veins  through  an  intervening  capillary  net-work. 

.'.■^'^''i^'-  '^"**-  "•  Physlolog.,  Anat.  Abth.,  1898. 
'Welch  Anniversary  Contributions,  190a 


THE  OVARIES. 


1993 


Fig.  1691. 


Superficial 
•naMoffloM* 


The  vrins  follow  the  general  arrangement  of  the  arteries  within  the  cortex  and 
m«lulla  •  the  oairs  of  parallel  veins,  however,  do  not  unite  into  single  stems,  but 
Il"g^fmm  th^Sum  ^independent  tortuous  trunks  Within  the  nK-sovari«m  they 
a^  [nterwoven  with  the  bundles  of  involuntary  muscle,  and  when  distended  present 
a  conSuous  venous  complex  (bulbus  <rvarii).  The  veins  proceeding  from  the 
o^^^TvT^ari^^proprJ)\^o^^  tributary  to  both  the  uterine  and  the  ovarian 

(pam^inif^)  pl«cus^.^  in  the  cortex  as  net-works  within  the  thee*  -rroundijjg 
the  Graliian  follicles  a^  as  lymphatic  clefts  within  the  ovarian  stroma      From  th«* 
radiSrthelSgerand  irreglr^hannels  enter  the  medulla  where  they  form  con- 
^eS  steiShat  foUowX  blood-vesseb  and  leave  the  h.h.m  of  the  ovary  usu- 
allwine^rger  trunks  (Polano)  that  pass  upward  along  the  free  border  of  the 
susp^s^ry  ligament  and  empty  into  the  lumbar  lymph-nodes  surrounding  the  aorta. 
Occasionally,  but  by  no  means  constantly,  the 
ovarian  lymphatics  communicate    with   those 
from  the  fundus  of  the  uterus  and  the  oviduct. 
The  nerves  supplying  the  ovary  are  de- 
rived from  the  sympathetic  plexus  surrounding 
the  ovarian  artery  (plexus  arteriae  ovaricse), 
which,  in  turn,  is  formed  by  contributions  from 
the  renal  and  aortic  plexuses  and  corresponds 
to  the  spermatic  plexus  in   the   male.     The 
small   nerve-trunks,   composed  for  the  m<Mt 
part  of  non-meduUated  fibres,  accompany  the 
arteries  through  the  hilum   into  the  ovary, 
where  they  are  distributed  chiefly  to  the  walls 
of  the  blood-vessels,  around  the  larger  of  which 
terminal  plexuses  are  formed.    From  the  fairiy 
close  plexus  within  the  cortex,  additional  mi- 
nute twigs  pass  to  the  periphery,   to  end  in 
close  relation  with  the  suriace  (germinal)  epi- 
thelium, and  others  to  the  follicles.     The  ulti- 
mate relation  between  the  latter  and  the  sur-  .  ,  ■     . 
rounding  net-works  is  uncertain,  but  it  is  probable  that  the  nerve-fibnlte  end  in  the 
wa"b  of  the  follicular  blood-vessels  and  do  not  penetrate  beyond  the  '""er  tunic  of 
the  theca,  the  terminations  within  the  follicular  epithelium  descr     -.l  by  some  ob- 
se^erTn^eding  confirmatfon.     Sensory  fibres  are   probably  contained  «;thin  the 
^rtical  branches.     The  claimed  existence  of  minute,  true,  sympathetic  ganglia  within 

the  medulla,  has  not  been  established.  i„riiff»rent 

Development.— The  primary  development  proceeds  from  the  >nditterent 
germinal  ridge  which  is  early  formed  on  the  median  surface  of  '^e  Wolffian  b^^^^ 
(page  2038)  Whether,  as  usually  accepted,  the  ova  in  common  ^1*^ /^e  folhcular 
SeUum  are  direcdy  derived  from  the  modified  mesothelium  (germinal  epithelium) 
covering  the  sexual  ridge,  or  are  the  descendants  of  germ-cells  eariy  set  apart  from 
the  somatic  cells  for  the  special  r61e  of  reproduction,  remains  to  be  decided,  al- 
though evidence  in  support  of  this  latter  hypothesis— the  continuity  of  the  germ- 
cells— is  accumulating  from  obser\'ations  on  the  lower  animals,  in  which  the  origin  ol 
the  orimordial  sex-cells  is  less  obscured.  .     1    •  j 

Kiman  embryos  of  12  mm.  in  length,  among  the  cells  of  the  germinal  ridge 
certain  elements  are  already  distinguished  by  their  ««PV«"»';i!;t*"^;^!;«^' ^'X 
nuclei.  These  are  the  primary  sexual  cells,  ihi^prtmordtal  ova  ( F  g.  «7i7).  "dually 
regarded  as  originating  from  the  transformation  of  the  germinal  epithelium  At 
fiTthe  latter  and  the  subjacent  stroma  of  the  Wolffian  body  are  well  d««e.^n tiated 
from  each  other.  This  demarcation  is  soon  lost  in  consequence  of  the  a^^tive  inter- 
growth  which  takes  place  between  the  proliferating  germinal  epithelium  and  the  in- 
growing vascular  a.Lective  tissue  of  the  Wolflfon  body-the  two  chief  factors  in 

the  histogenesis  of  the  ovar) .  u    1       ,..,  K„  th^  mn- 

As  the  mass  of  epithelial  elements  increases,  it  becomes  broken  up  by  the  con 
nective-tissue  strands  into  large  tracts,  composed  of  the  primary  ova  surrounded  Dy 


Arteria  propfia 


Oiarian  artery 


Ovarian 
veins 


Diagram  iUuatraiinganangernentuf  blood- 
vcMelsof  ovar>-.    (Ciart.) 


I" 


1994 


HUMAN  ANATOMY. 


IT.  .7titudes  of  the  smaller  and  less  specialized  cells  of  the  germinal  epithelium.  The 
larger  tracts  are  subdivided  into  smaller  spherical  cell-segregations  (the  egg-balls 
of  Waldeyer)  by  the  continued  intergrowth  and  mutual  invasion  of  the  tissues,  and 
the  "  e^-balls,  '  in  turn,  are  broken  up  by  the  same  process  until  the  final  division 
results  m  the  isolation  of  the  ultimate  groups,  the  primary  follicles,  that  include  the 
primary  ova  surrounded  by  a  single  layer  of  flattened  germinal  epithelium.  In 
places  the  larger  compartments  are  cylindrical  and  attached  to  the  germinal  epithe- 
lium, appearing  as  solid  outgrowths  connected  with  the  surface  ;  to  them  Pfliiger 
gave  the  name  ' '  egg-tubes' '  and  attributed  an  aggressive  invasion.  Since  the  con- 
nective tissue  of  the  Wolffian  stroma  first  invades  the  deeper'stratum  of  the  germinal 

epithelium,  this  region,  the  fu- 
FiG.  1693.  ture   medulla  of  the  ovary,  is 

Gcimimi  epiuwiiom  subdivided    into  the   ultimate 

Mmordiaiovnm  groups  of  cells,  the  primary  fol- 

licles, earlier  than  the  more  su- 
perficial and  younger  layers, 
this  genetic  relation  being  seen 
in  the  fully  developed  ovary,  in 
which  the  youngest  and  least 
mature  follicles  always  occupy 
the  peripheral  zone.  The  most 
superficial  stratum  of  the  ger- 
minal ridge  remains  as  the  ger- 
minal epithelium  that  covers 
the  exterior  of  the  ovary  and 
replaces  the  usual  peritoneal 
mesothelium  plates. 

The  details  of  the  trans- 
formation of  the  prir,  ary  folli- 
cles, consisting  of  the  ovum  and 
the  investing  single  layer  of 
mantel-cells,  into  the  ripening 
Graafian  follicles  have  been  de- 
scribed (page  1988).  Of  the 
thousands  of  primary  follicles 
within  the  young  ovary  (over- 
estimated by  Waldeyer  at 
100,000  in  the  two  ovaries  of 
the  new-born  child)  very  few  reach  maturity, and  by  advanced  life  nearly  all  have 
disappeared.  This  reduction  begins  during  intrauterine  life  and  first  affects  the  fol- 
licles situated  within  the  deeper  parts  of  the  ovary  destined  to  become  the  medulla, 
from  which  the  ova  are  later  entirely  absent.  The  remains  of  these  early  follicles 
probably  account  for  certain  of  the  minute  epithelial  bodies  occasionally  seen  in  the 
medulla  of  young  adults. 


Section  of  developinif  ovaty  from  hummn  embo'Oj 
ersp-owth  netween  srerm  ■ 
stroma  tissue  Jerivetl  from  Wolntaii  bfKly 


siiowinfc  interernwth  I 


Tmmal  epithelium  and 


Numbers  of  follicles  within  the  cortex  also  are  continually  undergoing  destruction.  This 
affects  especially  thu  primary  follicles  while  they  lie  naked  within  the  stroma,  and  are  unpro- 
vided with  a  theca,  thi;  ovum  undergoing  hyaline  degeneration  and,  along  with  the  mantcl- 
cflls,  finally  entirely  disappearing  within  the  ovarian  stroma.  Beginning  in  the  young  ovary 
long  Ijefore  puberty,  as  well  as  throughout  the  period  of  sexual  maturity,  certain  egg-sacs  are 
continually  transformed,  moie  or  less  fully,  into  Graafian  follicles  that  develop  to  a  certain 
stage  .ind  are  then  arreste<l.  after  which  they  enter  upon  regression,  degenerate,  and  finally  may 
completely  disappear.  This  process,  known  as  atresia  of  the  follicles,  is  probably  closely 
related  to  alterations  in  their  blood-supply  (C'.ark). 

With  possibly  few  exceptions,  the  formation  of  new  follicles  cea.ses  during  the  first  few 
years  after  birth,  the  supply  developed  early  in  life  being  in  such  laWsh  excess  of  all  possible 
needs  that  ample  provision  is  made  against  dearth  of  reproductive  cells.  Infrequently 
follicles  are  encountered  in  which  two  or  more  ova  are  present.  This  condition  results  from 
the  inclusion  of  more  than  a  single  primary  egg  when  the  follicle  was  formed,  and  not  from 
division  of  an  ovum  already  enclosed,  since  after  the  mantel-cells  surround  the  o\Tim  it  is 


PRACTICAL  CONSIDERATIONS:    THE  OVARY.  I995 

occupying  the  common  sac  (Ebner.) 

Th*  rAfl«r«  in  form  and  ponHon  which  the  ovary  undergoes  during  life  are 
consSuous  IntheCT-bornSiild  the  organ  is  relatively  long  (from  .2- j8  mm  ) 
^Krnw  Vfrom T-^  mm  )  triangular  on  cross  section,  and  lies  entirely  above  the 
^JT^^^  i°v^  wu"^  lonS^axis  transversely  placed  and  its  inner  pole  dose  to 
TelJdS  ut^  I^ri^svKrst  two  vears.  owing  to  the  increasing  ca^^c.ty  o  the 
the  lunaiB  Y^^-^J^r^  pressure  and  its  attachments  to  the  uterus,  it  gradually 

S.«»!wS  "teiTrt."  o^  undergo^  sudde"  i»cio«  »"il  "«q»'"  «»  <"'*"'•« 

o  Ae  ?^  wSlLcomes  knobbed  and  scarred  and  contrasts  strongly  with  the 
ot  tne  sunace,  *'"J^ '  ^^  .^  .  -gggation  of  menstruation,  about  the  forty- 
fiZytrl^dl'^Jilt^Cinvo"  Sovary  follows,  until  the  organ  may  be 
r«iucS  io Tdense  fibrous  lidy  of  less  than  half  of  the  original  size. 

the  position  of  the  organ,  so  that  :t  may  retain  ite  ,9^'"?,'X>,e  Vound  iuament  (the  homoloRue 
upon  the  ,»oasma«nus muscle;  VX*^  e  wee^K  SL"pa%^^^^^^^^^  through  the 

ofthe  eenito-  ngumal  hgamen  u   the  "^KP»K^,=^>^S„Pf-S  rtie  aclult  are  commonly  a.^- 

||^Sib£S^eb^«%rch^ont?^-r^^^^^^^ 

PRACTICAL  CONSIDERATIONS:    THE  OVARY. 

Since  the  ovaries  project  below  the  Fallopian  tubes  from  the  V°^f^\  s"rf»<^^  ^ 
the  bSl  K^ments.  in  s^king  for  them  in  abdominal  operations  the  hand  should  be 
Jl^sed  outSlrom  the  posterior  surface  of  the  uterus  along  the  broad  ligament,  on 

*^'^i?Us  usual  position  the  long  axis  of  the  ovary  is  approximately  vertical  its 
externalTurface  lybg  against  the  pelvic  wall  close  to  the  obturator  vessels  and  nerve. 
TJiP  iiretfr  and  uterine  artery  lie  behind  and  below  it.  .,.,•£. 

SA  of    he  ovary  4urs  most  freq.  ■  .dy  as  the  result  of  subinvolution  after 

labor  tColution  is  in  any  way  arrest^  or  rendered  i-^^P''*-^' J^ofX  ^^^ 
favorable  f  ^r  prolapse  of  the  ovary  will  be  present. -increased  weight  of  the  ovary 
and  relaxac")n  and  lengthening  of  its  attachments.  ....  -,  „„...„,ii„ 

The  left  ovary  is  more  frequently  prolapsed  than  the  right,  because  .t  normally 
become!  more  enkrged  durinrpregnancy.  and  therefore  suffers  more  from  subinvolu- 
l^n  and  b<^ui  X  arrangement  of  the  veins  on  the  left  side  is  such  that  venous 
™donr"e^  liable  to^'occur  (Penrose).  An  analogous  anatomical  condition 
exEo  that  which,  in  the  male,  favors  left-sided  varicocele,  the  eft  ovarian  vem 
emptying  into  the  r^nal  vein  at  a  right  angle,  wi.^le  the  right  ov^nan  vein  empties 

'""  fn\rpi:«;roCrth"  :r^n  te'^ouglas^s  pouch  Het.v.en  the  rectum  and 
the  p^ten^?  vaginal  ^W.  There  is  apt  to  be  pain  on  walking,  because  the  ovarv  is 
SenCmpressed  between  the  cervix  and  the  sacrum,  and  on  coitus  or  defecation. 


1996 


HUMAN   ANATOMY. 


because  of  direct  trauma.     The  pain  is  often  nauseating  and  may  be  felt  in  the  breast 
on  the  same  side. 

In  spite  of  its  small  size  the  ovary  gives  origin  to  a  great  variety  of  tumors  and 
cysts  which  may  grow  to  enormous  proportions,  filling  and  distending  the  abdomen. 
As  they  grow  they  at  first  crowd  the  uterus  and  other  pelvic  structures  towards  the 
opposite  side  ;  later  they  ascend  into  the  abdomen,  drawing  the  attached  structures 
upward  with  them  in  their  pedicles.  The  pedicle  is  the  base  of  attachment,  and 
consists  of  the  same  anator<ical  structures  as  those  by  which  the  ovary  is  normally 
attached.  The  relations  of  the  structures  making  up  the  pedicle  to  one  another  will 
vary  greatly  according  to  the  manner  in  which  the  tumor  grows.  This  relationship 
should  be  studied  carefully  to  establish  a  correct  diagnosis  as  to  the  origin  of  the 
tumor.  The  anatomical  structures  involved  in  the  pedicle  are  the  mesovarium, 
mesosalpinx,  Fallopian  tube,  and  broad  ligament. 

THE   FALLOPIAN  TUBES. 

The  Fallopian  tube  (tuba  uterinae)  or  oi-idurt  is  in  principle  the  excretory  canal 
of  the  sexual  gland,  the  ovary,  since  it  conveys  the  ova  liberated  from  the  Graafian 
follicles  to  the  uterus,  into  which  it  opens.  The  relation  between  the  ovary  and  its 
duct,  however,  is  exceptional  in  that  these  organs  are  not  continuous,  but  only  in  ap- 
position, the  ova  liberated  from  the  ovary  finding  their  way  into  the  expanded  end  of 

Fic.  i6<)4. 


Sigmoid  aitery 


Intrmal  iliac- 

External  iliac  — 
vessels 
Ureter- 

SuspennoO' 

liKanicnt 

of  ov:in 

Rixht  uvar>' 


Sixinoid 
flexure 

-Rectum 


I'lero-sacral 
liKament 
-Left  ovary 

-Liltament  of 
ovary 

-Oviduct 

t 

-.Round 
IJKamenl 


-I'leru^. 
fundus 


Bladder'^ 


Pelvic  orpins  of  youni^  woman,  viewed  from  above  and  in  front;  hardened  in  situ  and  un<listurl)cd. 
Fimbriated  extremity  of  right  oviduct  lay  in  position  shown  and  not  in  relation  with  ovary. 


I 


the  oviduct.  This  canal,  one  on  each  side  of  the  body,  lies  within  the  free  margin  of 
the  upper  division  of  the  broad  ligament,  known  as  the  mesosalpinx,  and  extends 
from  the  uterus  medially  to  the  ovar>'  laterally,  in  relation  to  the  inner  surface  of 
which  it  ends  after  numerous  windings. 

The  entire  length  of  the  tube  is  about  11.5  cm.  ('4,'/^  in.),  although  variations 
from  6-20  cm.  (^2^-77/^  in.")  have  been  observed.  Emerging  from  the  lateral  angle 
of  the  fundus  uteri,  in  the  immediate  vicinity  and  just  above  the  uterine  attachments 
of  the  utero-ovarian  and  round  ligaments,  the  first  part  of  the  tube  is  narrow  and 


THE  FALLOPfAN   TUBES. 


1997 


comparatively  straieht  and  constitutes  the  hfimus  {Mhmm  tubaeuterinae),  about  .35 
cm  ( I  *i  in. )  in  length  and  from  3-4  mm.  in  diameter.     Throughout  the  succeeding 
8  cm   U^  in. )  of  the  tube,  known  as  the  ampu//a  (anpiilla  tubae  uteriaae),  the 
diameter  Kradually  increases  (from  6-H  mm. )  until  the  canal  suddenly  expands  mto 
the  terminal  trumpet-shaped  infundibulum.     The  margins  of  the  latter  are  prolonged 
and  slit  up  into  long,  irregular  processes.  the/tmM>,  from  10-15  mm.  m  length,  the 
resulting  fimbriated  extremitv  of  the  tube  resembling,  when  exammecl  m  fluid,  an  ex- 
panded sea-anemone  (Nagel).     One  of  the  fimbria:  ( fimbria  ovarica)  is  usually  longer 
than  the  others,  attached  to  the  free  border  of  the  mesosalpinx  and  stretches  towards 
the  ovary,  the  tubal  pole  of  which  it  often,  but  by  no  means  always,  reaches,     llie 
lumen  of  the  oviduct  varies  greatly  at  different  points.    Beginning  at  the  lateral  angle 
of  th-  uterine  cavity  as  a  minute,  inconspicuous  opening  (.ostium  uterinum  tubae), 
commonly  i>bscurcd  by  mucus  and  about  i  mm.  in  diameter   the  canal  traverses  the 
uterine  wall  fpars  uUrlna)  and  gains  in  size  and  longitudinal  folds   so  that  on  crosa. 
section  the  isthmus  presents  a  stellate  lumen.     Within  the  ampulla  the  plications  of 
the  mucous  membrane  become  progressively  more  markwl,  appearing  in  transverse 
sections  as  a  complex  figure  of  primary  and  secondary  folds  ( Hg.  1695)  »/'*»  Rf^")' 
encroach  upon  the  calibre  of  the  tube.     The  folds  are  continued  mto  the  infundibulum 
and  onto  the  inner  side  of  the  fimbria.     The  outer  or  ovanan  end  of  the  oviduct 
opens  direcUy  into  the  peritoneal  cavity  by  a  small  aperture  (ostium  abdomlnale 
tubae).  2  mm.  or  less  in  diameter,  that  lies  at  the  bottom  of  the  infundibulum  and  is 
produced  by  local  contraction  of  the  muscular  tissu  •  of  the  wall  of  the  tube,  a  special 
sphincter,  however,  not  being  demonstrable.     The  mucous  lining  of  the  oviduct  is 
continued  from  the  infundibulum  onto  the  fimbria,  the  line  of  transiUon  into  the  pen- 
toneum  following  the  bases  and  outer  sides  of  the  fringes.     The  excepUonal  relation 
of  the  tubal  lining  to  the  serous  membrane,  this  being  the  only  place  in  the  body 
where  a  mucous  tract  opening  onto  the  exterior  communicates  with  a  closed  serous 
sac,  b  referrible  to  the  similar  original  relation  of  the  embryonal  Mullenan  duct  from 
which  the  Fallopian  tube  is  directiy  derived  (page  2038). 

Course  aiid  Relation*.— Since  each  Fallopian  tube  occupies  the  free  border  ol 
the  broad  ligament,  changes  in  the  position  of  the  uterus  affect  the  course  of  the 
oviduct.     From  the  upper  angle  of  the  uterus  the  tube  may.  therefore,  first  pass  out- 
ward towards  the  ovary  in  a  strictly  transverse  direction,  or  describe  a  gentle  forward 
or  backward  curve,  depending  upon  the  position  of  the  fundus  uteri,  this  part  of  the 
tube,  however,  never  being  tortuous.     On  gaining  the  uterine  or  lower  pole  of  thie 
ovary,  it  there  bends  upward  and  winds  obliquely,  from  below  upward  and  backward, 
across  the  median  surface  of  the  ovary,  close  to  the  antenor  border  and  tub^  pole,  to 
the  convex  posterior  margin,  where  the  tube  bends  sharply  downward,  its  fimbriated 
end  being  in  relation  with  the  lower  and  back  part  of  the  median  surface.     When  in 
its  usual  position,  the  ovary  is,  thus,  partly  covered  not  only  by  the  tortuous  oviduct 
itself,  but  also  necessarily  by  the  mesos^pinx  in  which  the  tube  lies,  so  that  when 
viewed  from  above  the  ovary  is  often  entirely  hidden  by  the  Fallopian  t  ibe  and  the 
attached  portion  of  the  broad  ligament.     In  consequence  of  this  arrangement,  the 
ovary  is  partly  surrounded  by  a  hood  of  serous-membrane  and  lies  within  a  pocket, 
known  as  the  bursa  ovarii,  which  may  facilitate  the  entrance  of  the  hberatwi  ova  into 
the  FaUopian  tube.     In  its  course  from  the  uterus  to  the  ovary  the  oviduct  lies  in 
front  of  and  generally  parallel  with  the  utero-ovarian  ligament  and  is  overlaid  by  the 
coils  of  the  small  intestine.     As  the  tube  ascends  and  arches  over  the  ovary,  tlie 
intestinal  coils  cover  its  medial  surface,  the  sigmoid  colon  also  occasionally  being  m 
relation  on  the  left  side.     In  formalin-hardened  subjects,  with  otherwise  normal  pel 
vie  contente,  we  have  so  often  found  the  termination  of  the  Fallopian  tube  lying  away 
from  the  ovary,  that  Merkel's  suggestion,  that  the  assumed  constant  close  relation 
between  the  fimbriated  extremity  and  the  ovary  may  sometimes,  at  least  temporarily, 
be  wanting  during  life,  seems  well  founded. 

Structure— The  wall  proper  of  the  Fallopian  tube,  consisting  of  the  mucous 
and  muscular  coats,  lies  embedded  within  the  loose  connective  tissue  of  the  oroad 
ligament  {tunica  odvenHtia)  surrounded  by  the  peritoneum,  which  completely  invests 
the  tube  with  the  exception  of  the  narrow  interval  through  which  the  tubal  vessels 
and  nerves  pass.     The  wall  is  thickest  and  firmest  in  the  isthmus,  less  so  in  the 


i 


13 


199« 


HUMAN   ANATOMY. 


Epilbcliam 


ampulla,  and  thinnest  and  most  relaxed  in  the  infundibulum  and  fimbr!^.  The 
mucous  membrane  is  thrown  into  longitudinal  folds,  which  increase  from  5-15  low 
rid(res  in  the  commencement  of  the  isthmus  to  double  the  number  in  the  ampulla, 
where  they  attain  a  much  greater  height  as  well  an  complexity  of  arranf^ement,  the 
main  folds  bcin^  supplemented  by  secondary  and  tertiary  ones,  so  that  in  transverse 
section  the  lumen  ap|iears  almost  occluded  by  branching  villus-like  projections.  The 
surface  of  the  mucosa  is  covered  with  a  single  layer  of  columnar  epithelium  (from 
.015-.020  mm.  in  height;  provided  with  cilia  that  produce  a  current  directed  from 
the  infundibulum  towards  the  uterus,  and  thus,  while  facilitating  the  progress  of  the 
ova  -long  the  tul>e,  retard  the  ascent  of  the  spermatoroa.  Thf  elaborate  plications 
and  receswes  within  the  outer  jiart  of  the  ampulla  favor  the  temporary  retention  of  the 
sexual  cells  and  thereby  promote  the  chance  of  their  meeting,  fertilization  usually 
taking  place  within  this  part  of  the  tube.     The  vascular  connective-tissue  stroma  of 

the  folds,  which  in  the 
Fio.  1695.  chief     plications    may 

reach  a  thickness  of  .  3 
mm. ,  within  the  acces- 
sory folds  is  reduced 
to  a  narrow  interepi- 
thelial  layer  in  places 
measuring  less  than  the 
height  of  the  covering 
cells.  The  tunica  pro- 
pria of  the  mucosa  is 
directly  continuous 
with  the  intermuscular 
connective  tissue,  and, 
with  the  exception  of  a 
few  bundles  prolonged 
into  the  deepest  part 
of  the  mucous  mem- 
brane, does  not  contain 
muscular  tissue. 

The  muscular  coal, 
most  robust  towards 
the  uterus  and  thinnest 
at  the  infundibulum 
(therefore  the  reverse 
of  the  arrangement  of 
the  mucosa),  includes 
an  inner  circular  and  an  outer  longitudinal  layer  of  involuntary  muscle.  At  the 
isthmus,  where  the  firmness  of  the  tubal  wall  depends  chiefly  upon  the  muscular  coat, 
the  circular  layer  is  the  thicker  (from  .5-1  mm.)  and  the  hmgitudinal  one  repre- 
sented by  an  incomplete  stratum  of  mu.scle-bundles.  Towards  the  infundibulum,  on 
tiie  contrarj-,  the  longitudinal  layer  is  beiicr  developed,  the  circular-muscle  being 
reduced  to  .  2  mm.  or  less  in  thickness.  The  surrounding  fibrous  tissue,  sometimes 
retfarde<l  as  a  distinct  coat  of  the  tube  (lunica  adventitia),  and  the  outer  serous  in- 
vestment are  only  the  usual  connective  tissue  and  peritoneal  constituents  of  the  broad 
lijiament,  and,  therefore,  call  for  no  further  description  in  connection  with  the  oviduct. 
As  e\i<lencefl  in  patholojiical  conditions,  and  er-pecially  in  tubal  pregnancy,  the  wall 
of  the  o\iduct  is  capable  of  distention  to  a  remarkable  degree. 

Vessels. — The  arteries  supplying  the  o\iduct  are  derived  from  the  tubal 
branches  of  the  uterine  and  ovarian  vessels.  The  branch  from  the  uterine  artery 
(ramus  tubarius  a.  uterinte^  passes  in  front  of  the  utero-ovarian  ligament  to  the 
median  end  of  the  oviduct,  along  the  under  side  of  which  it  courses  outward  until  it 
meets  the  tulwl  branch  from  the  ovarian  artery.  The  latter  (ramus  lubarius  a. 
ovariae )  passes  within  the  mesosalpinx,  in  front  of  the  ovarian  fimbria,  towards  the 
outer  i)art  of  the  ampulla,  distributing  branches  to  the  fimbriated  extremity,  and 
mesially  joins  the  tubal  branch  from  the  uterine.     From  the  anastomotic  branch  so 


Cross-aection  r>f  oviduct  near  iiutrr  md  of  ampulla,     y  35 


PRACTICAL  CONSIDERATIONS.     FiiLi 


TIBES 


I9«W 


formed  numerous  twig»  are  Kiven  off  to  the  wall  of  tiw-  ull..,)ii«i  tuU-  *wd  to  iIh- 
mesosalpinx  Those  distributed  to  the  .ividuct  jiain  tb^  -.i^  aU.nn;  ii^  n..TOt>«nt«.i»eaf 
tract  between  the  iM.Titoneal  reflecti.>n  and.  piercing  the  *a»i  break  «p  iwt..  capiUary 
net-works  within  the  muscular  and  mucous  cf«it^  H.-  «»-  « lnc^  beRin  within  tne 
walla  ol  the  tube,  especially  between  the  mutcukr  layrrs  ..n»)  =*«  a  sul^^rous  net-wortc. 
follow  the  uteries  and  become  tribuUry  to  Ixrth  the  ui.-m:-   iml  ovanan  trunks. 

The  lymphatia,  alter  emerjnnK  frvmi  th.-  wall  ,  .Ik-    i-.nn  threr  „r  i.mr 

stems  that  accompany  the  blood-vessels  and  pa.*  in  i  r  tl.*  attaclH^  U««l.r  ..f 

the  ovary.  For  the  most  part  they  follow  th.-  n  ariar  ,-»»ph»i..H  thr..iiKh  ;.»•  sus- 
nensorv  Wament  to  become  finally  tribuUr%  to  the  lumwar  ivmph-.i.«i»  sun-^wiidii^ 
ihe  aorta  It  is  probable  that  !«>me  of  the  lymphatics  .irf  tl»-  tube  co«m«nicat«-  with 
those  of  the  fundus  uteri  (Poiricr,  Bruhns).  ,     ,     j  u 

The  nerves  supplying  the  Fallopian  tube,  numen  .«  ,\v\  chirtly  >vmpaThetic 
fibres  follow  the  arten  and.  therefore,  reach  the  oviduct  ir<«n  lx>th  the  .narian  and 
the  uterine  plexus.  Within  the  subserous  tissue  they  form  .i  pttntu^l  pu-xus  ivnm 
which  twigs  penetite  the  wall  of  thf  caiwl  antl  are  diwril»«ed  ,)nnci|«i«y  to  the 
~    '^_  .  ci ^  .„!.:„..  ..-.r*  ;« tlw  r  .       I.   •on  ol  a  subepUhelutl ptexui 


ill.  <Tiv>t  of  the  oviducw  is 
'11  c!i:'j>  (|K»ge  2o.^S),  the 
•  i:ir  III  !  ■!  abdominal  open- 
V  tic^Av  ..vity  or  ccelom  ^  is 
..e  fifth  foetal  month. 


muscular  tissue,  soi.  '■  filaments  uking  p;irt  in  the  j 
within  the  mucous  mt     Hrane  (Jacques). 

Development  aud  Change*.— The  earl) 
directly  associai-^d  with  that  of  the  embryonal   Mu 
unfused  portions  of  which  the  tubes  rei)reseni.     Thv 
ing  (the  persistent  original  evagination  from  the  p 

at  first  cushion-like,  but  soon  exhibits  indent;..ioBT  >   .-         ,  ^  ■     . 

develop  into  distinct  fimbria.  At  birth,  while  smal  er,  the  latter  possess  their  charac- 
teristic appearance  and  are  lined  by  ciliate<i  -olumnar  epithelium  that  covers  the 
plications  of  the  tube.  The  upper  ( outer )  sesrmenl  of  the  oviduct  participates  m  the 
migration  incident  to  the  descent  of  the  ov-ary,  lying  for  a  time  within  the  abd<Knen 
above  the  pelvic  brim.  In  contrast  to  the  ovary,  the  tube  eariy  acquires  Us  detmite 
form,  in  the  new-born  child  presenting  its  chief  characteristics,  although  it  is  im.re 
twisted  than  later  and  the  fimbrise  are  still  small  :  the  plication  of  the  mucosa,  how- 
ever is  almost  fully  developed.  During  childho-  k1,  beginning  at  the  uterine  end,  the 
tube  becomes  less  tortuou-  and  the  fimbriated  extremity  as.sumes  its  dehnitc  prop<.r- 
tions  In  advanced  age,  '■  e  oviduct  suffers  atrophy,  losing  its  fonner  tortuosity,  the 
infundibulum  becoming  fla  id  and  the  timhri;e  shrivelled.  Owing  to  the  atrophy  of 
the  muscle  its  wall  become-  thinner  ;  the  ciliated  columnar  epithelium  is  r.placed  by 
cuboidal  cells,  the  lumen  n.urows  and  in  places  may  disappear  in  consequence  of 
the  adhesion  of  the  mucous  fold 

Variations  —Apart  from  anomalous  situation  dependinjj  upon  malposition  of  tlie  utenis  and 
ovary  in  which  the  tube  of  neces.sitv  shares,  the  variations  ..f  the  oviduct  usually  cleixml  upon 
developmental  faults  traceable  U.  imiierf  rt  or  alxTi.int  tormatii>n  of  the  MiiHerian  ducts. 
Retention  of  the  fcetal  tortuosity,  stunted  lU  ,  elopment  .  r  entire  absence  ni.iy  affect  one  or  iM.tn 
tubes  Complete  doublinR  of  the  oviducts  m.n  <x-ciir  in  .-Lssociation  with  sui)erniimer;iry_ovaries. 
Occasionally  partial  duplication  of  the  tube  is  ,,liserv«l,  consi'^tinjc  of  a  short  c.inal  endinK  in  a 
diminutive  fimbriated  extremity  in  the  vicinity  o(  the  infundibulum.  Such  Mcessorylubrs  are 
to  be  referre<l  probably  to  a  repetition  of  llu-  liivaKination  that  normally  prmliiics  the  infundi- 
bulum (Najtel).  Quite  frequently  the  oviduct  is  Ixset  with  from  on.-  to  three  fringed  acces<.ory 
openings  that  may  lie  close  to  the  fimbriated  end.  or  at  i  distance  fr..m  the  latter  alom;  the  tube. 
The  explanation  of  these  apertures  is  i:ncertain,  although  it  seems  most  prohaMe  that  they  resiilt 
from  aberrant  development  of  the  Mullerian  duct,  rather  th.in  as  secondary  perforations  of  the 
tube  and  prolapse  of  its  mucosa,  as  held  by  Nagel  and  others. 

PRACTICAL   CONSIDF.RATIONS  :    THE   FALLOPIAN   TIBES. 

The  function  of  the  Fallopian  tube  is  to  transmit  the  ovum  from  the  o\ary  to 
the  uterus,  the  ciliated  epithelium  --f  thr  f.:(w  favnrif.vr  .v.nvement  in  that  dirertion. 
An  impregnated  ovum  may  adhere  to  the  wall  of  the  tub»>,  giving  rise  to  a.n,rt.>pic 
gestation  (tubal  pregnancy ).  Such  pregnancy  ma\  occur  in  the  ampulla,— th<-  most 
usual  place. — in  the  infundibulum  ( tubo-ovarian  pregnancy  \  or  in  the  intra-mural 
portion  of  the  tube, — i.e.,  that  part  traversing  the  wall  of  the  uterus. 


^1 


3000 


HUMAN  ANATOMY. 


The  chief  causes  of  tubal  pregnancy  are  pathological  or  abnormal  conditions  of 
the  tube.  The  more  important  of  these  are:  (a)  congenital,  such  as  exaggerated  con- 
volutions, diverticula,  and  atresias  ;  {6)  sagging  and  attachments  by  adhesions  dis- 
torting the  tube  ;  (c)  pressure  from  surrounding  structures  ;  (d  )  thickening  of  the 
tubal  walls,  interfering  with  peristalsis  ;  and  (e)  destruction  of  the  cilia  or  narrowing 
of  the  tube  following  salpingids.  Complete  occlusion  of  the  tubes  of  both  sides 
would  result  in  sterility. 

The  great  danger  of  ectopic  gestation  is  that  of  hemorrh^e  following  rupture 
of  the  tube  by  the  growing  fcetus.  This  will  occur  some  time  prior  to  the  fourth 
month,  and  may  be  intraperitoneal, — i.e.,  direcdy  into  the  pentoneal  cavity  ;  or 
extraperitoneal, — '  e.,  downward,  cleaving  the  layers  of  the  broad  ligament,  and 
finally  rupturing  the  tube  within  the  layers  of  the  ligament  ;  or,  in  case  the  pregnancy 
is  "mterstitial,"  the  rupture  may  be  intrauterine.  The  intraperitoneal  rupture 
usually  takes  place  before  the  seventh  week  ;  the  extraperitoned  usually  from  the 
seventh  to  the  twelfth  week.  If  the  foetus  should  survive  the  primary  rupture  in  the 
extraperitoneal  variety,  secondary  rupture  into  the  general  peritoneal  cavity  may 
occur  later,  and  the  ovum  may  go  on  to  full  term  within  the  abdominal  cavity. 

The  Fallopian  tube  offers  a  passagewav  in  the  opposite  direction  for  the  entrance 
of  infections,  especially  gonorrhoeal,  from  the  vap;ina  and  uterus  into  the  peritoneal 
cavity.  When  inflammation  involves  the  tube,  it  is  followed  soon  by  a  closure  of 
the  fimbriated  extremity,  the  fimbriae  adhering  to  each  other,  to  the  ovary,  or  to 
some  adjacent  peritoneal  surface.  Later  the  uterine  end  of  the  tube  also  closes,  and 
the  pus  which  results  from  the  infection  now  accumulates  within  the  tube  {pyo- 
salpinx)  and  may  gready  distend  it.  If  the  infection  is  gonorrhoeal,  such  a  pus-tube 
without  rupture  is  frequently  unaccompanied  by  acute  symptoms.  Slight  ruptures 
with  leakage  into  the  peritoneal  cavity  followed  by  sharp  attacks  of  localized  pelvic 
peritonitis  often  occur.  A  large  rupture  may  give  rise  to  a  diffuse  septic  peritonitis, 
although  the  danger  of  this  result  in  a  case  of  chronic  pyosalpinx,  even  if  of  enormous 
size,  is  far  less  than  after  acute  gangrene  of  the  appendix  with  escape  of  a  relatively 
minute  portion  of  its  contents.  In  the  former  case  a  certain  degree  of  immunity  has 
probably  been  esublished  during  the  slow  formation  of  the  pyoulpinx  (Binnie) ;  and 
moreover,  in  many  such  cases  (6i  per  cent,  Penrose)  the  contained  pus  has  become 
sterile. 

When  the  inflammation  's  of  a  mild  grade  the  accumulation  may  be  of  a  serous 
cliaracter  {hydrosalpinx),  and  may  become  so  large  as  to  reach  half-way  to  the 
umbilicus.     If  hemorrhage  occurs  mto  the  tube  it  is  called  an  hamalosalpinx. 

The  proximity  of  the  right  Fallopian  tube  to  the  appendix  should  be  recalled,  as 
salpingitis  on  that  side  has  not  infrequently  been  misUken  for  appendicitis,  and  rice 
t-ersa.  The  right  ovary  is  often  connected  with  the  meso-appendix  by  a  fold  of  peri- 
toneum,— the  appendiculo-ovarian  ligament ;  and  it  is  stated  that  the  fact  that  this 
fold  often  contams  a  small  artery  which  gives  an  additional  blood-supply  to  the  ap- 
pendix helps  to  account  for  the  relative  infrequency  of  appendicitis  in  females. 

RUDIMENTARY  ORGANS  REPRESENTING  FCETAL  REMAINS. 

The  development  of  the  reproductive  organs  (page  204J)  emphasizes  the  fact 
that  whereas,  in  the  male,  the  Wolffian  body  and  its  due;  play  a  very  imporUnt  r61e 
in  the  production  of  the  excretory  canals  for  the  sexual  gland,  and  the  Miiilerian  duct 
remains  rudimentary;  in  the  female,  the  converse  is  true,  the  Mullerian  ducts  forming 
the  excretory  can^s — the  tubes,  the  uterus,  and  the  vagina — while  the  Wolffian 
structures  arc  secondary  in  importance  and  give  rise  to  only  rudimentary  and  (unc- 
tionless  organs,  situated  chiefly  m  the  vicinity  of  the  ovary  and  Fallopian  tube  between 
the  layers  of  the  broad  ligament.  These  ffetal  remains  include  the  epoophoron, 
Gartner  s  duct,  \\\^  paroophoron,  and  the  vesicular  appendages,  which  may  be  appro- 
priately described  in  this  place. 

The  Epoophoron. — This  riidimentary  organ,  parovarium  or  or^an  of 
Kosenmiiller,  lies  tx-tween  the  layers  of  the  broad  ligantent  (mesosalpinx)  m  front 
of  the  ovarian  vessels,  in  the  aresi  bounded  by  the  ampulla  of  the  oviduct,  the 
ovarian   fimbria  and  the  tubal   pole  of  the  ovary.     It  is  quite  flat,  triangular,  or 


RUDIMENTARY  ORGANS. 


MOI 


tnoezoidal  in  outline,  and  measures  from  2-2.5  cm.  in  length  and  about  1.75  cm. 
STS      h  ^nsb^  of  from  8-20  narrow  wavy  canals,  which    beg.nn.ng  with 
d<^  Mid  diKhUy  expanded  ends,  diverge  from  the  vicnity  of  the  Tnlum  of  the 
nv^a^  ioin  dmostTrieht  angte,  a  common  chief  duct  that  lies  close  and  paraUel 
to  rfTeT^duSan'STriXe  sLuer  tubules  the  relation  of  the  backof  a  comb  to 
i^  t^    The  transverse  tubules  (ductali  transver^l).  the  remams  of  the  sexual 
mbSd  the  WoE  body,  may  extend  as  far  as  the  hilum.  or.  as  m  the  young 
SSd  evcn^netStVbto  the  medulla  of  the  ovary  and  be  continuous  with  the  rudi- 
Sk^meSX^  tubes  therein  found,  since  the  latter,  as  well  as  the  transve«e 
^n^them»dv«.  are  vestiges  of  the  same  embryonic  structures.     The  common 
onritud^SS^  (d^.epoo?hori  iongitudiiuiUs),  cfosed  at  both  ends.  «  a  pen«stent 
Sn  ofArK>l£nudr   From  iS  embryological  relations  it  «  evident  that  the 
KSpSi^on  U  homdious  with  the  epididymis  (the  transverse  tubules  corresponding 
n.e  durtuU  efieren^  and  the  coni  vasculosi.  '"^  »he  long.tud.^  *act  to  th^ 
^  of  the  epididymis),  since  both  are  direct  derivaUons  from  the  Wolffian  tubiUoi 
^dCct      iSe  ^rectVture,  when  in  its  normal  position  ^f"  .jJ'^r^PS 
the  longitudinal  duct  is  ^proximately  vertical  and  hes  paraUel  with  the  FaBopian 


Epoopborun    U«  Miu-t 
OMiam 
abdominmlc 


Licai 
uT  u 


Flu.  1696 

LtKament 
Cavity  of  olovao 

utcTUa 


Oviduct 
laid  open 


Epoophorun 


InluDdibiilum 


Hydatid  nf 
MoripiKn' 


Flmbrte 
Fimbi;!  ovaries 
R.Hind  liKamcM 

RiKht  o>.iry 


Rouiiil  liKam.ol 

Broad  linamcnt 


VaKin* 


tube,  while  the  transverse  tubules  are  horizontally  disposed.  The  chief  duct  may  be 
interrupted  and  connected  with  the  secondary  tubules  in  groups,  or  on  the  other 
hand,  it  may  be  prolonged  as  Gartner's  duct  (page  2043)  ^.r  beyond  its  usual  length 
In  the  child,  the  transverse  tubules,  from  .3-4  mm.  In  diameter,  usually  possess  a 
lumen  throughout  their  entire  lengtl,.  but  later  in  life  the  minute  canals  niay  undergo 
partial  or  complete  occlusion  and  may  be  the  seat  of  cystic  dilatations.  T»^*^  *^'*  ™ 
ihe  tubules  and  duct  consist  ot  :>.  fibrous  coat,  which  sometimes  contains  bundles 
of  involuntary  muscle,  lined  by  a  single  layer  of  epithelial  cells  ^jj^  /'»«>  1" '«"".  "^^^ 
low  cuboid  to  columnar,  and  in  places,  or  occasionally  in  the  adult  "^n^  frequently  in 
the  child,  bear  cilia.  The  epoophoron  is  most  satisfactorily  demonstrated  by  ho.ding 
tht  stretched  mesosalpinx  against  the  light  :  it  is  more  conspicuous  in  the  broad  li|^- 
nicnt  of  the  young  child  on  account  of  its  development  and  the  greater  transparency 
of  the  overlying  tissues.  In  common  with  the  sexual  organs,  the  epoophoron  'ncreasw 
during  the  years  leading  to  sexual  maturity  and  atrophies  in  advanced  age.  Uuring 
preenancy  It  is  said  to  lie  unusually  vascular  (Merkel). 

Oartner'8  duct  results  from  the  more  or  less  extensive  persistence  of  portions 
of  the  Wolffian  duct  that  usually  disappear  by  the  en.l  of  foetal  ife  and  is.  therefore, 
a  continuation,  direct  or  interrupted,  of  the  longitudinal  canal  of  the  epoopnoron. 
Although  by  no  means  consUnt  and  often  tepresented  by  only  a  short  atrophic 

126 


11 


I 


3003 


HUMAN  ANATOMY. 


segment,  the  duct  is  present  in  about  twenty  per  cent.  (Merkel)  of  adult  subjects,  in 
children  being  relatively  better  developed.  When  complete,  as  it  exceptionally  is, 
the  duct  continues  from  the  epoophoron  along  the  Fallopian  tube  to  the  hindus  of 
the  uterus,  then  descends  within  the  lateral  border  of  the  uterus,  between  the  vessels, 
and  sooner  or  later  (usually  in  the  lower  part  of  the  body)  enters  the  uterine  muscle. 
As  it  traverses  the  cenix,  the  duct  becomes  more  and  more  medially  placed  until,  in 
the  supravaginal  segment,  it  approaches  the  mucosa.  The  duct  then  assumes  a  more 
lateral  course,  and  in  the  vagina  descends  within  the  muscular  coat,  at  first  along  the 
side  and  lower  more  on  the  anterior  wall,  to  end  blindly  in  the  vicinity  of  the  hymen 
(R.  Meyer).  Such  complete  persistence  is,  however,  very  unusual,  Gartner's  duct 
being  most  frequently  represented  in  the  lower  part  of  the  body  and  the  upper  part 
of  the  cervix,  less  oftfen  in  the  cervical  segment  alone  (Maudach).  The  canal  is  lined 
by  a  single  layer  of  columnar  epithelium  and  beset  with  lateral  diverticula,  uncertain 
in  number  and  form,  which  in  the  lower  part  of  the  duct  are  often  short-branched 
tubules  that  resemble  glands.  Accumulations  of  secretion  within  the  tubules  or  the 
duct  may  lead  to  the  production  of  cysts. 

The  Paroophoron. — Under  this  name  Waldeyer  described  an  inconspicuous 
rudimentary  organ,  distinct  at  birth,  but  usually  disappearing,  and  only  exceptionally 
reUined  after  the  second  year,  that  lies  between  the  layers  of  the  mesosalpinx  medially 
to  the  epoophoron  and,  therefore,  nearer  the  uterus.  It  consists  of  a  small,  flat, 
irregularly  round  group  of  blind  canals,  which  represent  the  remains  of  Wolffian 
tubules.  The  accuracy  of  Waldeyer's  assumption  that  this  organ  is  homologous  with 
tiie  paradidymis  (page  1950)  has  been  challenged  by  later  mvestigators  (Aschoff, 
R.  Meyer),  who  have  discovered  similar  groups  of  rudimentary  tubules  within  the 
lateral  part  of  the  mesosalpinx  near  the  division  of  the  ovarian  artery,  in  a  position 
corresponding  to  that  of  the  paradidymis.  It  is  to  this  group,  therefore,  that  the 
term,  paroophoron,  may  be  applied  with  greater  propriety,  although  there  can  be 
little  doubt  that  both  sets  of  tubules  are  deviations  from  those  of  the  Wolffian  body. 
The  tubules  are  blind,  lined  with  columnar  epithelium,  and  in  places  resemble  the 
tortuous  canals  of  the  Wolffian  body.  Apart  from  their  interesting  morphological 
relations,  they  may  become  of  importance  as  the  seat  of  cysts. 

Vesicular  Appendages. — Under  this  heading  are  included  the  little  vesicles  or 
hydatids  (appendices  vesiculosi )  attached  to  the  broad  ligament  by  longer  or  shorter 
pedicle.;.  Tii»!se  structures  present  two  general  groups,  the  first  including  the  con- 
s;)icuGU..!i)n;f -stalked  hydatids  of  Morjjagni,  and  the  second  the  smaller  vesicles,  vary- 
ing in  f,)nr.  and  size,  conni  cted  by  short  steins.  The  hydatid  of  Morgagni,  present 
on  one  or  both  sides  in  tilty  \tcx  cent,  or  over  of  all  female  subjects,  is  a  spherical  or 
pyrifomi  thin-walled  sac,  that  contains  a  ciear  fluid,  and  usually  measures  from  4-8 
mm.  in  diameter,  but  sometimes  much  more,  and  is  attached  by  a  slender  stalk 
(from  1.5-4  cm.  '"  length)  to  the  anterior  surface  of  the  broad  ligament.  Traced 
towards  the  latter,  the  stalk  crosses  the  ovarian  or  other  fimbria-  without  being 
attached  and  sinks  into  the  mesosalpinx  about  i  cm.  from  its  free  border,  from  which 
point  it  may  be  followed  through  the  broad  ligament  to  the  upper  end  of  the  main  or 
longitiid-nal  duct  of  the  ejx)o|)horon,  as  the  continuation  of  which  it  may  be  identified 
(Watson).  In  structure  the  hydatid  consists  of  a  fibrous  coat,  lined  by  a  layer  of 
columnar  epithelium  and  c<- vered  extem.-illy  with  a  d.^licate  prolong.itioii  of  the  peri- 
toneum. The  smalli-r  vesicles,  present  in  aix)ut  twenty  |«.'r  cent.  ( Ros.s;i),  often  num- 
fier  two  or  thrci  on  each  side,  and  are  attached  to  the  anterior  surface  of  the  mesosal- 
pin.x,  usually  over  the  epoophoron.  They  are  fouml  at  birth  and  even  in  the  foetus, 
as  well  as  later  in  life,  in  advaucetl  age  undergoing  atrophy  The  origin  and  mor- 
phological si^ni(i<'ance  of  the  vesicular  afipendages  have  occasione<l  much  discussion, 
Init  it  may  Im'  acceptetl  as  established  tiiat  the  chief  hydatid  of  Morgagni  is  derived 
from  the  upper  end  of  the  Wolffian  f  pronephric)  duct,  nnd  is,  therefore,  the  equivalent 
of  thv  staikefl  appendage  of  the  cpididvmis  (page  1949).  The  sm.iller  vesicles  prob- 
.ably  owe  their  origin  to  the  'listrntimi  and  elongation  of  the  I'-:i. averse  canals  of  the 
epooj)horon  (Russ;i),  and,  hence,  are  deri\atives  (jf  the  Wolffian  tubules. 


THE  UTERUS. 


2003 


Fio.  1697. 


'Peritoneum 
(perimetrium) 

;.'avity  of 

body 


THE  UTERUS. 

tZ  ^:'l.Z^\Tu^tri^<i^So^r.U  a^d  from  which  the  r^tinj  fce^s 
Ts  expened  at  the  completion  oJ  pregnancy.  Its  lower  seKment  .s  '^"^t^ff^^^'t^"" 
The  iSvic  floor  between  the  bladder  and  the  rectum,  while  its  tipi^er  and  larger  end 
slr^and  i^v.-Ale  and  rests  upon  the  superior  surface  of  the  bladder  (Pig.  1700). 
£e  und^r^Sg  the  profound  changes  incident  to  pregnancy,  the  uterus,  pear- 
sluS  in  its  g'n^al  fonn.  measures  about  7  cm.  (2H  '"•).'"/'^"f»'' ."*  ^'""S  t- 
S^CT  2  ;  cm  T.^. )  constitutes  the  cylindrical  neck  or  cer-.v  (cervix  uteri  .and  the 

rideVthe  U  (corpus  «teri).     Its  greatest  »>'--«lf -/^^^.^irdr  '  1^^^ 
it.  thir-lcnpss  iboiit  2  ■;  cm    (I   n. ).      In  women  who  have  borne  chinir».n,  me  uierus 
Sdom'^quTe  rSHmsM  its  virgin  size,  but  shows  a  permanent  ""^^^  f,*^^"'^^,-- 
in  its  various  dimensions,  except  in  the  cervix,  which  is  relatively  shorter  than  before. 
The  convex  upper  extremity  of  the  organ,  above 
the  level  of  the  entrance  of  the  Fallopian  tubes, 
is  known  as  \.\ic  fundus  (fundus  uteri),  which  in 
front  and  behind  passes  into  the  anterior  and 
posterior  surfaces  and  at  the  sides  into  the  lat- 
eral borders  (margo  laterales).     Of  the  two  sur- 
faces, the  anterior  (fades  Ttaicalbi)  is  the  more 
flattened  and  less  convex  and  only  partially  cov- 
ered with  peritoneum,  while  the  more  rounded 
and  projecting  posterior  surface  (fades  intesti- 
nalls)  is  completely  invested  with  serous  mem- 
brane.   The  lower  end  of  the  cylindrical  cervi.x. 
flattened  somewhat  from  before  backward  and 
slighdy  tapering  downward,  is  divided  by  the 
attachment   of    the   sui rounding   vagin.il   wall, 
which  it  seemingly  pierces,  into  a  free  lower  seg- 
ment (portlo  vaginalis),  that  projects  into  the 
vault  of  the  vagina,  and  an  upper  one  above  the 
ring  of  attachment  (portio  supravaginaHs).     Be- 
low, the  vaginal  segment  of  the  cervix  termi- 
nates in  thick,  rounded,  and  prominent  lips  that 
bound  a  sunken  opening,  the  external  os  (ori- 
fidum  exteruum  uteri)  that  marks  the  lower  liinit 
of  the  cervical  canal  and  is  directed  towards  the 
posterior  vaginal  wall.     Owing  to  the  horizontal  position  °*  f^.*; "7^.-    '^^'^ .  m^^^^^ 
anterior  /,>>  (labium  anterius  cervids)  is  shorter  and  somewhat  lower  than  the  oxer 
hanging  posterior  lip  (labium  posterius  cervids ).  ,„-.mmes  ( 1  '^- 

The  weight  of  the  virgin  uterus  vanes  between  forty  and  fifty  gnimme^  ( 1   3 
i^i  oz. ).  that  of  the  organ  after  pregnancy  being  about  twenty  grammes  ( .7  oz.  ) 

""""The  ravitv  of  the  uterus  is  small  in  com,x..-ison  with  the  size  of  the  organ  and 
the  thickness  of  its  walls,  and  differs  i.i  form  according  to  the  pUtne  of  ''•'c Uo  v  In 
L'gi  tal  section,  it  is  little  more  than  a  narrow  cleft  separating  the  oppc>sed  .m  enor 
and  posterior  walls,  and  mea.s„res  atx>ut  6  cm.  (2-^  in. ).  "'j'^lf^  .^5  c  hr  n  out 
belongs  to  the  cervix.  In  frontal  section,  the  cavity  of  the  bodv  .s  ""^"^^  ""^  "^ '^^J. 
line  (Fig.  1A98),  the  apex  l^^ing  below,  where  the  up,>er  end  of  the  «* ^''V  ''  J;^^,^.^' 
vix  passes  into  that  of' the  ImkIv,  and  the  has.  above,  '-'t^^een  the  tubal  ..rihc^  which 
mark  the  iater.al  angles.  The  sid«  of  the  triangle  are  not  straight  »^"  ^''-^^^^^^'^J^^ 
to  the  itnvard  curve  of  the  thick  projecting  uterine  walls.  The  greatest  transNtrse 
width  ..f  the  cavity  of  the  b^Kly,  just  below  the  tubal  openings,  is  ^^^xnit  2  S  cm_ 

The  canal  of  the  cerx'ix  (canalis  cervids  uteri ),  as  the  lower  segment  o  t..^  uterine 
cavity  is  called,  is  fusiform  in  longitudinal  sections,  In^in^^  widest  mulwav  ^-tY,?,"  ^^ 
external  os  below  ami  the  somewhat  smaller  and  more  circular  '"t«;f"f'  ^, '""J^^^^^ 
internum  uteri)  above,  where  the  contracted  lumen  of  the  virgin  uterus  expands  into 


Vagina 


nerll*  lal.l  open  bv  raiciltal.Kecti.m.  nhowing 
r»vil>  ami  relation*  of  labia  to  vaitina. 


11 


'•  'J 
I'll 


l|ti 


3O04 


HUMAN  ANATOMY. 


Ovidnct 


the  cavity  of  the  body.  In  cross-section  the  canal  appears  as  a  markedly  compressed 
oval.  The  position  of  the  internal  os  corresponds  with  the  slight  external  constriction 
(iitfraiui  uteri)  that  uncertainly  marks  the  neck  from  the  body  of  the  utenis.  In 
contrast  to  the  smooth  mucous  surface  of  the  body,  that  of  the  anterior  and  posterior 
walls  of  the  cervical  canal  is  marked  by  conspicuous  ridges  (plicae  palmatae) — the 
arbor  vitie  tUerinte  of  the  (V  ivr  writers — consisting  of  a  chief  median  longitudinal  fold 
from  which  numerous  sec'   I'lary  rugae  divert  upward  and  outward  on  each  wall. 

Attachments  and  Peritoneal  Relations. — In  addition  to  the  Fallopian  tubes 
that  embryologically  are  direct  continuations  of  the  component  Miillerian  ducts  by 
the  fusion  of  which  the  uterus  is  formed,  the  uterus  is  connected  with  the  ovaries, 
the  abdominal  wall,  the  lateral  and  posterior  walls  and  the  floor  of  the  pelvis,  the 
vagina,  the  bladder,  and  the  rectum  by  fibro-elastic  tissue,  muscular  bands,  and  peri- 
toneal folds.  Most  of  these  attach- 
Fic.  1 698.  ments,  or  so-called  ligaments,  however, 

have  little  influence  m  supporting  the 
uterus,  but,  owing  to  the  intimate  con- 
nection of  the  cervix  with  the  vagina, 
and  thus  with  the  pelvic  floor,  and  with 
the  sacrum  by  fibro-muscular  bands, 
the  lower  segment  enjoys  a  relatively 
fixed  f>osition  ;  the  body,  on  the  con- 
trary, being  freely  movable. 

The  Broad  Ligament.— ^'nYi  the 
exception  of  a  narrow  strip  along  the 
sides  betAveen  the  layers  of  the  broad 
ligaments,  the  body  of  the  uterus  is 
completely  invested  by  peritoneum. 
The  cervix,  on  the  contrary,  possesses 
a  serous  covering  only  behind  and  at 
the  sides  above  the  attachment  of  the 
vagina.  From  each  lateral  border  of 
the  uterus  this  serous  investment  is 
reflected  to  the  pelvic  wall  and  floor 
as  a  conspicuous  transverse  duplicature 
of  peritoneum,  the  broad  ligament  {\i%% 
amcatum  latum),  that  passes  across  the  pelvis  and  encloses  between  its  layers  the  round 
and  ovarian  ligaments,  the  Fallopian  tube,  the  epoophoron  and  the  paroophoron, 
together  with  the  associated  vessels  and  ner\'es.  Although  enclosed  by  a  peritoneal 
duplicature  continued  from  its  posterior  surface,  the  ovary  is  attached  to,  rather  than 
lies  within,  the  broad  ligament.  When  detached  from  the  pelvic  wall  and  floor  and 
spread  out  (  Fig.  1699),  the  broad  ligament  is  wing-like  in  form  and  has  four  borders, 
of  which  the  median  or  uterine  is  vertical,  the  upper  or  tubal  is  horizontal,  longest, 
and  free,  the  lateral  short  and  approximately  vertical  to  correspond  with  the  plane 
of  the  pelvic  wall,  and  the  lower  sloping  downward  and  inward  in  agreement  with  the 
direction  of  the  pelvic  floor.  Within  the  body,  the  plane  of  the  median  portion  of 
the  fold  depends  upwn  the  position  of  the  uterus,  in  the  erect  posture  usually  extend- 
ing more  or  less  horizontally,  so  that  the  posterior  surface  presents  upward  and 
ba(  kward,  and  the  anterior  downward  and  forward  :  when  the  uterus  assumes  an 
upright  position,  the  fold  likewise  becomes  erect.  On  ncaring  its  lateral  attachment, 
the  upper  border  of  broad  ligament  becomes  not  f)nly  more  vertical,  but  also  parallel 
with  the  pelvic  wall  in  consequence  of  the  support  afforded  by  the  suspensory  liga- 
ment of  the  ovary.  From  their  attachment  to  the  pelvic  walls  and  floor  the  two 
serous  layers  of  the  broad  lijj.imeiit  pass  in  opposite  directions  and  are  continuous 
with  the  general  peritoneal  lining  of  the  pelvis.  Along  the  pelvic  floor  their 
diviTsiencc  leaves  a  non-pcritoiieal  interval  through  which  the  vessels  and  ncr\'es 
and  the  ureter  gain  the  si(le  of  tho  uterus. 

The  free  border  of  the  broad  ligament  is  occupied  by  the  Fallopian  tube,  the 
course  of  which  it  follows  as  far  as  the  outer  end  of  the  infundibulum,  and  thence 
passes  to  the  pelvic  wall  to  become  continuous  with  the  suspensory  ligament  of  the 


-55^ 


~^Exlrmal  uft 


Vagina 

rteru**  Imiil  open  by  (mntal  settton.  showing 
torm  of  iavilvof  body  and  i-trrvis. 


THE  UTERUS. 


2005 


««.rv      As  the  tube  crosses  the  medial  surface  of  the  latter  organ  the  broad  li^- 
r.^i,  d«in  over  it  sTthat  the  ovary  lies  partly  within  a  pentoneal  pocket   the 

!£.i;r  ikte^lir^^^^  ^^low.'Wmes  continuous  with  the  general  subserous  layer 

'^n^^touriJ  Lvam.ni.-ln  addition  to  the  Fallopian  tube  and  the  Uga^e";  °' 
the  or^,  a^ady  Lcribed  (page  .987).  a  third  band,  the  round  hgament  Hi,.. 

Fig.   1699. 


Fmllopiaii  Kibt,  ampulla    UKametit  ot  ovary 
w,..Jj^,       I        M«Ki«lpin«      I  hallopiai.  lube 


Alxlomiiial  u|>riiinK 
u(  Kallof>iaii  luht: 


K|ioophoroii 


Hy<la(i<l  "i  M-ituaniii 

Ovarian  fimbria 


Round  liicanwiit 

Me«imietrium 


Anterior  wall  tit  l>.u){las!'  iwuih- 


/ 


VaKina 

Uleru,  and  a,*e...l.«e,  «n  Iron,  "f  h'";!  ^  i™l|lSS  ""** 
oviduct  have  been  stretched  out  to  show  mewMalplna. 


mcfltniB 

structure 


This 
5  ^ni- 


um™.wSl"Xl..^ll>cKic  ,v,ll.«l.icl,  Ure»ch™  near  the  fl,»r     Thence  .1 
SI  in™™?o Viu:«  beneathV  pert™.,™  l™rf  »^^ 

r5:ih^,&:L^nireT,VL&s^^^^^^^^^^ 

he  iubic  sc^ne.  In  its  median  third  the  rotmd  liRament  contains  /"»'"«»  'f'^°' 
nvoCarV  muscle  prolonged  from  the  superficial  layers  of  the  uterus  but  LeNond 
tremuiuTar  tissue  disappears,  and  in  its  lower  part  the  ban.l  «-"f' ?.  ^^"^^ '>' ";1  ^^^^ 
ItetTcTssue.  During  its  passage  through  the  inguinal  canal,  the  l'R»"^5"t«'"  \^;« 
baccompaned.  along^ts  upper  border,  by  small,  short  bundles  of  striped  muscle 


if 


aoo6 


HUMAN   ANATOMY. 


derived  from  the  internal  oblique  and  transversrJis,  which  represent  a  feebly  developed 
cremaster  muscle.  Alter  gaining  the  pelvic  wall,  the  round  ligament  pursues  a  course 
very  similar  to  that  of  the  vas  deferens  ;  morphologically,  it  corresponds  to  the 
genito-inguinal  ligament  (p^e204o).  In  the  fcetus  the  round  ligament  is  preceded 
by  a  small  peritoneal  diverticulum  representing  the  larger  processus  vaginalis  peri- 
tonxi  in  the  male  ;  usually  this  disappears,  but  may  persist  as  a  distinct  serous  pouch, 
the  canal  of  Nuck,  that  accompanies  the  round  ligament  for  a  short  distance  within 
the  inguinal  canal.  In  exceptional  cases  it  may  extend  throughout  the  entire  length 
of  the  canal  into  the  labium  majiis. 

The  peritoneal  relations  of  the  two  surfaces  of  the  uterus  (P'ig.  1700;  are  dif- 
ferent, the  anterior  surface  being  covered  with  serous  mt  -nbrane  only  as  far  as  the 

Fio.  1700. 


Urn 


Suspensory, 
lixammt  ai  oviry 

Fallopian  tube. 


Round  IJKiinient 
Ovary. 

Ohlitciai^.'d. 
hypogastric  artery 

I'tcn 


Symphyan  pubii 


Urethra 


External  urethral 
orifice  in  vestibule 


.rtero-aacral  fold 
Kectum 
Eiiemal  o»  uteri 


Bottom  o(  recto- 
uterine |joucb 


.Vagina 


rerin*':»I  b<Kl> 


SaKittal  lection  of  pelvlH  of  female. 

junction  of  the  body  and  cervi.x,  from  which  line  the  peritoneum  pas-ses  on  to  the 
bladder  a.s  the  uteroveska/  fold  And  lines  the  shallow  utero-vesical  pouch  (ezcavatio 
vesicouterina  ).  Below  the  reflection  of  the  peritoneum  and  as  far  as  its  attachment  to 
the  vagina,  the  anterior  surface  of  the  cervi.x  is  connected  by  areolar  tissue  with  the 
adjacent  pt«terior  wall  of  the  bladder.  As  far  as  the  attachment  of  the  vaginal  wall, 
the  posterior  surface  of  the  vitenis  is  coveretl  with  peritoneiini,  which  then  -ontinues 
downward  for  about  2.5  cm.  over  the  tipper  part  of  the  back  wall  of  the  vagina  before 
being  reflected  onto  the  rectum  a.s  the  agino-rfctal  fold.  The  latter  forms  the  bot- 
tom of  the  ^w\iSf:\v,\\^  pouch  of  Douglas  ieicavatio  rcctouterina)  that  lies  between  the 
uterus  in  front  and  the  rectum  behind.  The  lateral  boundaries  of  the  opening  into 
this  pouch  are  formed  by  the  two  crescentic  utero- rectal  folds  (pliciie  rectoutcrina )  that 
curve  from  the  hind  surface  of  the  cervix  liackward  to  the  posterior  pelvic  wall  at  the 


THE  UTERUS. 


2007 


siden  of  the  rectum.  Between  the  layers  of  these  folds  robust  bundles  of  fibrous  and 
smooth  muscular  tissue  extend  from  the  uterus  to  be  insetted  partly  in  the  rectum, 
there  constituting  the  uUr^rectal  musek,  and  parJy  mto  the  front  of  the  sacrum  as 
the  utero-sacral  ligament.  The  latter  structure  contributes  eflicjent  aid  m  supporting 
the  cervical  segment  of  the  uterus,  which  is  thus  enabled  to  maintain  Us  powtion 
indeoendently,  to  a  certain  degree,  of  that  of  the  body.  •    ,      „       j 

l>08ition  and  Relations.— The  attachment  of  the  cervix  to  the  vaginal  walls  and 
utero-sacral  liRaments  give  to  the  lower  uterine  segment  a  more  definite  position  than 
that  enjoyed  by  the  body,  which,  being  little  restrained  by  Us  lateral  atuchments.  « 
e^eck^ly  affected  by  the  condition  of  the  bladder  and  rectum.     When  these  organs 
"rbTslighdy  distended,  the  uterus  normally,  in  the  erect  posture,  hes  tilted  for- 
ward  (anteverted).  with  the  body  resting  upon  the  upper  veJical  surface.     Since 
under  th«^  conditions,  the  cervi.x  is  comp^iratively  fixed  and  directed  backward  and 
the  tody^ore  or  less  bent  forward  (antiflexed).  the  uterine  axis  exhibits  a  marked 
flexure  at  the  beginning  of  the  cervical  segment.     This  angle  vanes  conUnually  with 
"he  posiUon  of  the  hindus,  which,  receiving  little  support  from  «ts  peritoneal  and 
otherattachments,  is  influenced  by  the  changing  condition  of  the  Madder.     When 
the  latter  is  contracted  and  the  uterus  strongly  anteflexed,  the  angle  »  !"«^«  F©- 
nounced  than  when  the  upper  vesical  wall,  and  consequenUv  the  fundus,  l'«  y  er 
With  increasing  distention  of   the  bladder  the  angle  gradually  disappears  and  the 
uterine  axis  becomes  straight :  in  exc.-ssive  vesical  expansion,  a.s.sociated  with  an 
empty  rectum,  the  entire  uterus  may  be  tilted  backward  (retroverted),  its  axis  then 
cor^iponding  with  that  of  the  vagina.     When  both  bladder  and  rectum  are  d  s- 
tendetl    the  entire  uterus  may  be  pushed  up  above  the  level  of  the  symphysis. 
UsualW  the  fundus  does  not  lie  strictly  in  the  mid-line  but  to  one  side,  pro.baWy 
more  frequently  to  the  left  (Waldeyer,  Merkel).     This  deflection  may  also  affect 
the  axis  of  the  ovary  of  the  opp*«ite  side,  which,  in  consequence  of  the  pull  thus 
exerted,  then  lies  more  obliciuely  than  on  the  side  on  which  the  utero-ovanan  li^^- 
ment  is  relaxed.     The  anterior  surface  of  the  uterus  following  the  changes  of  the 
upper  vesical  wall  upon  which  it  lies,  the  utero-vesical  fossa  very  seldom  co;^ains  in- 
t^tinal  coils,  which,  on   the    contrary,  frequently  occupy  the   i>ouch  o    Douglas. 
The  posterior  (upper)  surface  of  the  uterus  is  overlaid  by  coils  of  the  small  intestine, 
and  may  also  be  in  contact  with  the  i)elvic  and  sigmoid  colon.     Antenoriy.  below 
the  reflection  of  the  utero-vesical  fold,  the  lower  segment  of  the  uterus  is  connected 
with  the  posterior  bladder-wall  by  l.Kwe  connective  tissue  ;  posteriorly,  it  is  sepa- 
rated from  the  rectum  by  the  intervcninjj  peritoneal  pouch  of  po.igla.s  ;  laienUly  it  is 
crossed  bv  the  ureters,  which,  opposite  the  middle  of  the  cervix,  he  alxiut  2  cm  from 
the  uterine  wall.     In  the  erect  i)osition,  the  level  of  the  external  os  corresponds  ap- 
proximately with  that  of  die  upper  margin  of  th.-  symphysis,  and  m  »"?  antero- 
posterior axis  lies  slightly  behind  a  frontal  plane  paiwmg  *'ough  the  ischial  spines 

^Structure.— The  uterine  walls,  thickest  in  the  fundus  and  posterior  wall  of  the 
body  where  they  measure  fn.m  1-1.5  cm.,  and  somewhat  thinner  (fro.n  K-9  mm.) 
at  the  entrance  of  the  tulles  and  in  the  cer\'ix,  comprise  three  coats,  the  mucous, 
muscular,  and  serous.  The  mucous  coal,  or  endometrium,  of  a  light  red-lish  coU.r. 
soft,  and  friable,  and  from  .5-1  mm.  thick,  consists  of  a  connective-tissue  stroni;.^ 
loose  in  te.xture  but  rich  in  cells  and  resembling  the  ti.nica  propria  of  the  intcstmai 
mucous,  and  the  surface  epithelium.  The  latter  is  a  single  lay.-r  of  covunnar  i  ells. 
about  .028  mm.  high,  that  in  their  typical  cmdition  pos.sess  cih:i  l)y  <  li«:h  a  dovvn- 
ward  current  is  established  towards  the  external  os.  It  is  irobable.  h..«e'  er,  ihat 
the  cilia  are  neither  always  present,  nor  uniformly  distribut -d  since  'he.  u-  lost 
during  the  disturbances  incident  to  menstruation,  and  are  often  present  only  in 
patches  (Gage)  The  ulerine  glands  are  simple  tubular,  or  slightly  bifurcated, 
wavy  invaginations  of  the  mucosa,  said  to  be  lined  with  a  single  layer  of  ciliated  col- 
umnar cc'ls  resembling  those  covering  the  interior  of  the  uterus.  1  hey  are  dis- 
trit)uted  at  falrlv  regular  interxals  and  extend  the  entire  thickness  of  the  mucosa 
their  tortuous,  blind  extremities  in  many  cases  being  lodged  between  the  adjacent 
muscular  bun.iles,  since  a  distinct  submucom  is  wanting.  In  the  vicinity  of  the  orihces 
of  the  Fallopian  tubes,  the  uterine  mucos;>  becomes  thinner,  the  epitheUum  lower. 


If 


n 


3008 


HUMAN  ANATOMY. 


Gbnd 
opcuinx  on 
mucous  tur- 
tac«. 


and  the  elands  shorter  and  fewer,  until  they  finally  disappear,  glands  being  absent 
in  the  tubal  mucous  membrane. 

The  cen'ical  mucosa  differs  from  that  i;  ?ing  the  iiody  in  being  somewhat  denser, 
owing  to  the  greater  amount  of  fibrous  tissue  withm  its  stroma,  and  in  possessing  a 
taller  epithdium,  a  single  layer  of  columnar  cells  from  .040-.060  mm.  in  height, 
and  larger  mucous  glands.  The  latter  (glandulac  ccrvicales  uteri),  from  i-i.,j  mm. 
long  and  .5  mm.  wide,  are  branched  and  often  reach  with  their  blind  ends  between 
the  muscle  bimdies.  The  mucus  secreted  by  these  glands  is  peculiar,  being  clear 
and  exceeding  tenacious,  and  sometimes  is  .seen  as  a  plug  protruding  from  the 
external  os.     Not  infrequendy  the  orifices  of  the  cer\icaf  glands  become  blocked, 

which   condition    results  in 
Fic.   1701.  the  production  of  retention 

cysts  that  appear  as  minute 
vesicles  between  the  folds  of 
the  plicae  palmatx.  These 
bodies  were  formerly  de- 
scribed as  the  ovules  of  Na- 
both  i^ovula  Nabothi).  The 
transition  of  the  cylindrical 
epithelium  of  the  cervical 
canal  into  the  squamous  cells 
covering  the  vaginal  portion 
of  the  uterus  takes  place  ab- 
ruptly at  the  inner  border  of 
the  external  os.  At  the  inner 
OS,  where  the  cervical  mu- 
cosa passes  into  that  lining 
the  body,  the  change  is  so 
gradual  and  inconspicuous 
that  no  sharp  demarcation 
exists. 

The  muscular  coat,  or 
myometrium,  although  com- 
jjosed  cf  bundles  of  inv-olun- 
tary  muscle  arranged  with 
little  individual  regularity, 
may  be  resolved  into  a  robust 
inner  layer,  in  which  the 
bundles  possess  a  general 
circular  disposition,  and  a 
thin,  imperfect  outer  layer  in 
which  their  course  is  for  the 
most  part  longitudinal.  The 
longitudinal  musrie  bundles 
of  the  f«-eble  outer  layer,  which  is  present  only  over  the  fundus  and  body,  are  con- 
tinued beytjnd  the  uterus  onto  the  tubes  and  into  the  broad,  round,  ovarian  and 
utern-sacral  ligaments.  The  thick  inner  layer,  the  chief  compoi  ent  of  the  myome- 
trium, is  distinguished  by  the  number  and  size  of  the  blood-vessels  that  traverse  the 
intermuscular  connective  tissue  and,  hence,  is  known  as  the  stratum  vasculare  ( Kreit- 
zer).  The  bundles  of  this  layer  are  confined  to  the  uterus,  exrept  below,  where 
they  become  continuous  with  the  mu.scle  of  the  vaginal  walls.  At  the  three  angles 
i)f  the  body,  corrcspf>nding  to  the  two  tubal  orifices  and  the  internal  os,  the  dispo- 
sition of  the  bundles  surrounding  these  openings  suggests  the  existence  of  distinct 
sphincters.  Ir  other  places  the  innermost  bundles  are  less  regularly  disposed  and 
are  oblique  or  even  longitudinal  Within  the  cervix  the  outer  longitudinal  layer  is 
unrepresented,  the  musculature  of  this  segment  consisting  chieflv  of  circular  and 
oblique  bundles.  Intermingled  with  a  considerable  amount  of  dense  i.brous  and  elastic 
tissue  that  confer  upon  the  cer\'ix  greater  resistance  and  hardness.  The  component 
fibre-cells  of  the  uterine  muscle  vary  in  form,  being  in  some  places  short  and  broad 


Sfclion  of  endometrium,  fthowinic  utetiii«  glandi 
rut  in  varous  planes.     ^  40. 


THE  UTERUS. 


3009 


and  in  othus  long  and  spindle  form.     During  pregnancy  their  usual  length  (horn 
.O40-.o6t.  mm. )  may  increase  tfc>  old.  „         ,    .  ■.        1  :„,.„., 

The  serous  foot,  or  perimefrium,  continuous  laterally  with  the  peritoneal  invest- 
ment of  the  broad  ligament,  is  so  closely  adherent  to  the  utenne  nuisck  over  the 
Kus  and  adjacent  ^irts  of  the  anterior  and  posterior  surface  that  .t  '^",7;,"' 
with  d;ffic-.lty.  I-oweT  the  presence  of  the  mterxemng  loose  connective  tissue  {  />flr«- 
■««/«■«»»)  renders  the  attachment  less  intimate.  ■  u     u.   .^k 

VeMeU.-The  arteries  supplying  the  uterus  are  the  two  uterine,  each  a  branch 
of  the  interr.il  iliac  that  accompanies  the  ureter  along  tlie  |)elvic  wall.  Ix-hiPd  and 
Wow  the^^riai.  fossa,  to  the  a««ched  border  of  the  br.«d  ligament  iK-nea  ii  wh.rh 
U^Sm«  in  its  course  to  the  uterus.  On  gaining  a  point  about  a jm  from  the 
cei^nd  on  a  level  with  the  internal  os  (Merkel)  the  uterine  artery  bends  med.allv 
and  crosses  the  ureter  obliquely  and  in  front.  It  then  traverses  ilensc  •<.nnccU%e 
tteue^on  appiS^chhig^e  Uteral  wall  of  the  cervix  bends  sharply  "pward  ^. 
^^  b^een  °he  layers  of  the  broad  ligament  along  the  lateral  Ix.rders  of  the 
r^.  r^  as  the  lateral  angle.      Imm^iately  below  the  ovarian   ligament  the 


frll 


Fig.  170*. 
.Xntvrior  nurface 


Longitiuliiial  muscle 

^  Blood -vesaeU 


Attachment 
of  bnad     //•/«■ 
Hnment  en'  «^^ 
closinK  l«r* 
metrium 


Muco-m  (endomelriu.'n) 

Ixincitudlnal  mmclt 


-Circular  niUMie 


T^toneum  ((xrimflrium) 


Poitcrlor  raffece 
TraiMvcTK  section  ol  utenw  throngh  body.    X  »• 

uterine  artery  divides  into  if  terminal  branches  dirtrihuted  to  the  fundus^  Fallo- 
-jian  tube,  and  ovary.  In  addition  to  a  small  branch  lo  the  ureter  just  Ix tore 
bending  upward  it  gives  off  the  vaginal  artery  that  P^^*^  ,^"«-7;f;'' .;^":' .^T^e 
in  supplying  the  cervix  and  the  vagina.  As  it  ascends  along  the  sid.^  of  he 
uten,s^Vom%-.o  mm.  removed  and  surrounded  b>'  a  '^^"'"^  Pl""=; '^^  ^'^J^ 
very  tortuous  uterine  artery  sends  numerous  b«t  variable  branches  t"^^^  '^^'•\\Xe 
body,  as  well  as  to  the  broad  ligament,  those  distributed  to  t^e  pmtenor  surtace 
being  somewhat  larger  than  those  to  the  anterior  i Robinson)  1  "^^  !"^"^'"*'' ![-^^^^^ 
passing  to  the  fundus  framus  fundi)  is  especially  strong  and  freely  ^"^^^^'^^^  .'^ 
the  corresponding  vessel  from  the  opposite  arter>-.  thus  insuring  ""P^^jl'j^^^" 
larity  to  that  part  of  the  uterus  in  which  the  placenta  is  usually  •-\^t»'=»'«' 'jS^^L  of 
Twi^  also  accomptny  the  ovarian  and  round  ligaments.  After  the  establ^hmcnt  of 
the  Junction  bet^^een  the  ovarian  artery  and  its  ovanan  branch,  the  utenne  arter> 
plays  an  important  part  in  maintaining  the  nutrition  of  the  ov.-uy.  ""  ^^  ""? '"^ 
muLular  cc^t  the  ikrger  branches  divide  into  vessels  that  penetrate  he  o  U-Ma>  er 
of  the  myometrium  and  within  the  inner  muscular  ayer  break  "P  '"*"  "'"^If'"^^ 
minute  twigs  that  confer  upon  this  stratum  its  highly  vn-'ular  character.      Witnm 


90I0 


HUMAN  ANATOMY. 


the  mucosa  the  capillaries  s  >  ound  the  glands  and  form  a  superficial  net-work  beneath 
the  epithelium. 

The  vrtHs,  already  of  considerable  size  within  the  inner  muscular  layer,  emertje 
from  the  myometrium  and  form  a  dense  plexus  of  thin-walled  vessels  that  surround 
the  uterine  artery  at  the  sides  of  the  uterus  between  the  layers  of  the  broad  ligament. 
The  veins  are  arranged  as  an  upper,  middle,  and  lower  group.  The  first  of  these 
includes  the  veins  from  the  fundus  and  upper  part  of  the  body,  which  become  tribu- 
tary to  trunks  that  join  the  ovarian  veins  and  leave  the  pelvis  by  way  of  the  sus- 
pensory ligament.  The  middle  group  comprises  the  venous  radicles  from  the  lower 
half  of  the  body  and  upper  part  of  the  cervix  that  unite  into  one  or  two  main  stems 
that  accompany  the  uterine  artery.  The  lower  group  is  formed  by  the  veins  from 
the  most  dependent  part  of  the  uterus,  the  anterior  vaginal  wall,  and  the  posterior 
surface  of  the  bladder.  These  unite  into  robust  ascending  stems  that  become  tribu- 
tary to  the  trunks  following  the  uterine  artery.  The  middle  and  lower  groups  freely 
anastomose  with  the  vesical  plexus  and  also  communicate  with  the  hemorrhoidal 
plexus. 

The  lymphaHcs,  within  the  mucosa  not  demonstrable  as  definite  vessels  but  only 
as  uncertain  clefts,  constitute  an  intermuscular  net-work  of  which  the  larger  trunks 
follow  the  blood-vessels  and  establish  communication  between  the  cervical  lymphatics 
and  those  of  the  body.  On  emerging  from  the  myometrium  a  suj)erfici.-il  (subserous) 
jile.xus  is  formed,  especially  over  the  posterior  surface  in  the  vicinity  of  the  lateral 
.ingles  ;  large  trunks  also  accompany  the  blo«xl-vessels  along  the  sides  of  the  uterus. 
The  lymphatics  from  the  cervix,  usually  t^vo  or  thret  stems,  pass  to  th<  lytiiph-nodes 
occupying  the  angle  between  the  external  and  internal  iliac  arteries.  According  to 
Bruhns,'  those  from  the  remaining  parts  of  the  uterus  follow  different  paths  :  one 
set,  from  the  body,  goes  likewise  to  the  iliac  nodes  ;  another,  from  the  fundus, 
courses  towards  the  ovary,  and  in  company  with  the  trunks  from  the  latter  oi^jan 
follows  the  ovarian  artery  to  terminate  in  the  lumbar  nodes.  A  third  set,  also  from 
the  fundus,  eventually  gains  the  limibar  glands  after  joining  the  lymphatics  of  the 
Fallopian  tul)e,  while  a  fourth  jjroup  di\ergcs  from  the  fundus  along  the  round  liga- 
ment to  become  alferents  of  the  inguinal  lymph-nodes.  In  addition  to  free  anasto- 
mosis among  theniscKi-s,  the  uterine  lymphatics  communicate  with  those  of  the 
vairina,  n-ituni,  ovaries.  Fallopian  tubes,  and  broad  ligament. 

The  nerves  of  the  uterus,  being  ciiiefly  destined  for  the  involuntary  muscle, 
are  numerous  and  of  large  size  to  corrcspoiul  *ith  the  highly  developed  myome- 
tr  uni.  Thev  are  derived  not  only  fiom  the  sympathetic  system  from  the  utero- 
va.vnn.il  .sutwlivision  of  the  ikI,  ic  plexus  (the  continuation  from  ihe  liypogastric),  but 
also  (lir<itl>  from  tlie  second,  third,  and  fourth  sacra!  spinal  nerves.  According  to 
the  classic  description  of  FVankenhaiuser,  the  iitero-vag:nal  plexus  divides  into  two 
p;irts,  the  smaller  of  which  is  distributt*d  to  ihe  posterior  and  lattral  parts  of  the 
uterus,  while  the  larger  includes  a  chain  of  minute  ganglia  along  the  cervix  and 
vaginal  vault.  One  of  these,  the  cenical ganglion,  is  esj)ecially  large,  and  lies  behind 
the  upper  p.irt  of  the  vagin  i,  receiving,  in  addition  to  the  svmiwthetic,  spinal  fibres 
from  the  sacral  nerves  and  giving  off  twigs  to  the  uterus.  These  latter  pass  to  the 
titerine  walls  between  th-  Livers  of  the  br.ad  lig.iment,  p.irticularly  at  the  sides  in 
company  with  the  blood- .essek,  antl  penetrate  the  myometri'im,  to  the  fibre-cells  of 
which  the  ner\e-filamcnts  are  chiefly  distributed  ;  others  pass  mto  the  mucosa  to  end 
beneath  the  epithelium. 

Development  and  Cbange;;. — In  consequence  -f  the  medial  rotation  of  the 
ventral  border  of  the  Wolffian  hotly,  the  relations  of  tlie  Miillerian  to  the  Wolfl[ian 
duct  change.  Instead  of  lying  laterally  to  the  Wolffian  duct,  as  it  does  above,  the 
Miillerian  duct  gains  the  inner  side  of  that  tul)e  as  they  pass  into  the  urogenital  fold 
(page  2038)  wh..  h  prolongs  the  lower  end  of  the  Wolffian  body  into  a  median 
strand  known  as  the  genital  cord.  Within  the  latter,  formed  by  the  fusion  of  the 
plic.-e  urogenitales.  the  two  Miillerian  ducts  lie  next  the  mid-line,  side  by  side  and  in 
contact  with  the  Wolffian  duct  on  either  hand.  Beginning  about  the  eighth  w^ek, 
the  opposed  surfaces  become  imited,  the  intervening  septum  disappears  and  the  two 
Miillerian  ducts  are  converted  into  a  single  tube  from  which  the  uterus  is  derived. 

'  Archiv  f.  Anat.  u.  Phys.,  1898. 


THE  UTERUS. 


30II 


For  a  time  this  tube  ends  blindly  and  is  conUnued  to  the  urogenital  »in.».  with  which 
it  Jnttes  M  a  solid  cyUnder  of  Urgcr  cells  ;  thi=.  lumenless  seRment  r,f  the  fused 
MmSn  ductTrepSents  the  anV  «!  the  vapna.  The  extent  ^^  "h.ch  he 
Md  erian  ducts  undergo  fusion  is  early  indicated  by  a  sharp  inward  bend  of  t.*^ 
tubes  VuTt  below  the  lower  and  medial  ends  of  the  Wolffi;in  bodies,  the  flexure  on 
eaMe  co««,H,nd ing  to  the  atUchment  of  t.hrc-H  that  pass  to  the  antenor  aWom- 
fnal  wSl  an""ter  frcnn  the  round  ligament.  Ihe  portions  ..f  the  Mulleruin  duett 
Ltove  this  r^int  rem^un  se,«rate  and  ununite.1  and  become  the  ovducts.  th.«e  below 
undereo  fusion  and  produce  the  uterus  and  vi^tl^a.  i        „  /k„ 

Aher  the  vaginal  portion  of  the  united  Miillerian  ducts  acquires  a  lumen  (bv 
the  end  d  the  fourth  m^th),  the  uterine  and  vaginal  segments  of  the  tube  are  d.f- 
tenSat^  by  the  U,T  cylindrical  and  the  larger  o.boi.lal  epithelial  cells  that  line 
he  two^rtions  respectively.  The  transition  zone,  which  Incomes  progressively 
mL^red  c"  rr^Ss  to  the  position  where  later  the  cylindrical  utenne  epithe- 
hum  c^g^  into  the  s.,uamous  vig.nal  cells  at  the  '""" -''«7 ^ ^ nuTcal's 
Soon  the  distinction  between  the  uterine  and  vaginal  portions  of  t^egenit..!  canal  is 
addhionallv  emphasized  by  the  forward  curNe  of  the  onner  and  the  Mraightcr 
downS  ccuZ- .^  the  latter.  The  more  definite  division  of  the  utenis  from  the 
vaJinrTs  ef^S  by  the  appearance  of  crescentic  thickenings  of  the  anterior  and 
S  erio' w;Sk  oTthe  canal  wWh  mark  the  beginnings  of  the  corres,«nding  lips  of 
Ih^  cervix  Distinction  between  the  Ixxly  and  cervix  is  earlv  suggested  by  the 
'uterine  eJitheHum  the  cells  lining  the  lower  portion  being  talfer.  -o-j^jy^^d"-! 
aid  numerous  than  th.^e  of  the  bcxly  ^he  connectiveand  muacu  ar  ti^ue  of  he 
uterine  wall  are  differentiated  from  the  condensed  mesoderm  that  surrounds  tnt 
:  rdialtJb:  Distinct  muscle  is  not  distinguishable  before  the  .Jh  --th.  abou 
which  time  the  cervical  glands  also  make  their  appearance  '  Nagel).  thus  anticipa 
ting  bv  some  weeks  the  development  of  the  glands  in  the  corpus  lUeri 

At  birth  the  uterus  mciisiires  about  ^  cm.  in  length  of  which  the  c^rvi^  c  n 
tribu  es  more  than  half,  and  is  thicker  and  denser  than  the  thm-walled  and  riaccid 
3v  The  characteristic  arched  form  of  the  hmdus  is  lacking  and  the  lateral 
aSL  a  "prolonged  int>  the  tubc-s,  often  recalling  a  b.coniate  conditi.m.  The 
?r,SoA,!inaliss  inconspicuous  and  projects  to  only  a  slight  degree.  .Jthough  the 
K.«lnati  are^vcllde^^  limited,  ;is  they  later  are,  to  the  cervical 

£  'burSfend  through<,ut  the  uterine  cavity.     Since  at  this  time  the  "nternal  os  is 
Su   mmature.  the  division  of  the  uterine  cavity  into  an  upper  and  a  lower  segment 
U  onlv  sucir^teil.     The  general  position  of  the  utems  is  higher  than  later,  it, 
o«re£r  wfthX  bladder,  lying  al^ve  the  level  of  the  pelvic  hnm.  with  the  fundus 
oTposite    h 'u    the  fifth  lumLr  vertebra  (  Merkel).     With  the  increasing  capacity  of 
the^oelvis   th  ■  uterus  sinks,  so  that  by  the  end  of  the  sixth  year  the  external  .«  « 
inle'wgher   han  In  the  adult  (  SyminU)-     Ar«rt  from  the  Rradua^^devxlopment 
of  the  glands  and  the  disappearance  ..f  the  folds  of  the  mucosa  w  thin  the  U^> 
durine   childhood    the   uterus   grows   slowly  until   near   puberty,  «hen   the   body 
Sen.   leiKthens,   and  acquires  the  arched  c.ntours  of  its  mature  form.      In  its 
e  ative  V  long  cerv  x  and  slightly  prominent  fundus,  the  uterus  of  the  virgin  retains 
hecharuSt."of  early  childh^xl.     The  repeated  '  »^-«-  l^f "»  »V„,^  "^u"^ 
Itl^l  cycle,  produce  gradual  thickening  of  the  utenne  wall,  and  e">=»'-K^'"«"^,"' /l^^ 
lumen.^o  that,  even  independendy  of  pregnancy,  the  wtrus  increases  somewhat  in 
size  and  weight  during  the  years  of  se.xual  activity. 

After  the  cessation  of  menstruation,  between  the  forty-fifth  and  fiftieth  >ea,rs, 
the  uterus  suffers  gradual  atrophv  ( inx olution ).     This  first  affects  the  cer^•lx.  which 
£annc"  smaller  .tnd   more  sir.ul.r,    the  entire  organ  '" . -"X'-\.  ^J^^l 
more  pronounced  pyriform  outline.      The  general  reduction  in  the  size  and  prom 
nence  oT"he  vaginal  portion  is  accompanie<l  by  atrophy  of  the  pliae  palmata-  of  the 
cervkalcanll      The  walls  of  the  body  are  also  involved  and  l>ecome  thinner  an< 
lZsTes^"uJh  ..trophy  cl  tin-  n.Lular  tissue  and  decreased  vasculanty.  and 
hTnce^le^  color,  of  the  mucosal,      lor  a  time  the  uterine  cavity  is  enlarged,  but. 
later   sCng  in  the  general  atrophv  and  not  inconsiderable  dnn.nut.on  in  sMze  of    he 
organ,  the  lL..n  likewise  undergoes  reduction  and.  in  some  cases,  suffers  obliteration 
in  the  vi-ir,ity  -!  the  internal  os. 


w 


30I3 


HUMAN  ANATOMY. 


Cbanf  e«  during  Mcnttruation  and  Pregnancy — AlthouKh  liberation  of  a  mature  ovum 
may  occur  at  any  time,  such  independence  is  exceptional,  and  in  the  vast  majority  of  cases 
ovulation  and  menstruation  are  synchronous  processes,  the  uterine  changes  occurring  regularly, 
every  twenty-eight  days,  only  when  the  ovaries  are  functionally  active.  In  anticipation  of  the 
possible  reception  of  a  fertilized  ovum,  the  uterine  mucous  membrane  becomes  .swollen,  exces- 
sively vascular  and  hypertrophied,  with  conspicuous  enlargement  of  the  subepithelial  blood- 
vessels and  the  glands.  The  resulting  thickened  and  modified  mucosa,  now  from  3-6  mm. 
in  thickness,  offers  a  soft  velvety  surface  favorable  for  the  implantation  of  the  embr>o-sac. 
Should  this  purpose  be  realized,  the  hypertrophy  proceeds,  and  the  lining  of  the  uterus  is  con- 
verted into  the  decidua;  and  ukes  an  important  part  in  the  formation  of  the  placenta  and  at- 
tached membranes  (page  44).  If,  on  the  contrary,  fertilization  does  not  occur,  the  proliferative 
proces.ses  are  arrested  and  the  hypertrophied  mucosa  (now  called  the  decidua  meMs/rua/is) 
enters  upon  regression.  Incidental  to  the  latter  are  subepithelial  extravasation  and  rupture  and 
partial  dest.-uction  of  the  epithelium,  followed  by  the  characteristic  discharge  of  blood.  While 
usually  the  destruction  of  the  mucosa  is  limited  to  the  epithelium,  it  is  probable  that  at  times 
the  superficial  layer  of  the  subjacent  tissue  is  involved. 

During  pregnancy  the  most  conspicuous  changes  are  occasioned  by  the  growth  necessary 
to  accommodate  the  rapidly  augmenting  volume  of  the  uterine  contents,  by  the  provision  of  an 
adequate  source  of  nutrition  and  protection  for  the  foetus,  and  by  the  development  of  an  efficient 
contractile  apparatus  for  the  expulsion  of  the  same.  From  an  organ  ordinarily  weighing  about 
45  grams  (i^  oz.),  measuring  7  cm.  in  length  and  possessing  a  capacity  of  from  3-5  cc,  by  the 
close  of  pregnancy  the  uterus  has  expanded  into  a  rouiided  or  oval  sac  about  36  cm.  ( 14  in. )  in 
its  greatest  length,  from  900-1000  grm.  (about  2  lbs. )  in  weight  and  with  a  capacity  of  5000  cc. 
( 169  fi.  oz. )  or  more.  This  enormous  increa.se  depends  especially  upon  the  hypertrophy  of  the 
muscular  coat  of  the  organ,  which  during  the  first  half  of  pregnancy  becomes  greatly  thickened, 
but  later  thinner  and  membranous  owing  to  stretching.  The  increase  in  this  coat  results  from 
both  the  growth  of  the  previously  existing  muscle-cells  and,  during  the  first  half  of  pregnancy, 
the  development  of  new  muscle  elements.  The  individual  cells  may  increase  tenfold  in  length 
and  measure  between  .4-.5  mm.  Although  the  cervix  actually  almost  doubles  in  size,  its  growth 
is  overshadowed  by  that  of  the  body,  since  it  remains  relatively  passive.  During  the  first  five 
months,  the  mucous  membrane  of  the  body  of  the  uterus  also  becomes  greatly  hypertrophied, 
in  places  attaining  a  thickness  from  7-10  mm.  The  glands  and  blood-vessels,  particulariy  the 
arteries,  enlarge  and,  within  the  specialized  area,  are  concerned  in  the  formation  of  the  placenta 
(page  48).  The  cervical  mucosa  takes  no  direct  part  in  the  formation  of  the  decidus,  although 
it  thickens  and  is  the  seat  of  enlarged  glands  that  secrete  the  plug  of  mucus  that  for  a  time 
occludes  the  mouth  of  the  uterus. 

After  the  tennination  of  pregnancy,  the  uterus  enters  upon  a  (leriod  of  involution  and 
repair,  the  excessive  muscular  tissue  undergoing  degeneration  and  absorption  and  the  lacerated 
mucosa  regeneration,  the  latter  process  being  completed  in  from  five  to  six  weeks  ( Minot).  In 
sympathy  with  the  growth  of  the  myometrium,  the  round  ligaments  enlarge  and  also  show  marked 
augmentation  of  their  muscular  tis.sue.  The  peritoneal  relations  are  disturbed  by  the  excessive 
bulk  of  the  uterus,  so  that  at  the  sides  the  layers  of  the  broad  ligament  become  separated. 

Variations. — The  chief  anomalous  conditions  of  the  uterus  depend  upon  defective  devel- 
opment or  imperfect  fusion  of  the  Miillerian  ducts  by  the  union  of  which  the  normal  organ  is 
formed.  Arrested  development  of  the  lower  part  of  these  ftetal  canals  accounts  for  entire  ab- 
sence of  the  uterus  and  vagina.  Depending  upon  the  extent  to  w  hich  failure  of  fusion  occurs, 
all  degrees  of  doubling  are  produced.  In  the  most  pronourccd  cases,  in  which  the  Miillerian 
ducts  remain  separate  throughout  their  entire  length,  two  completely  distinct  uteri  and  vaginx 
may  result,  each  pair  being  capable  of  performing  the  functions  of  the  normal  organs.  (Jn  the 
other  hand,  slight  indentation  of  the  fundus  may  be  the  only  evidence  of  imperfect  union.  Be- 
tween these  extremes  all  gradations  occur ;  the  body  may  be  completely  cleft  (uterms  bicomis). 
with  or  without  divided  cervix  ;  or  the  duplicity  may  be  partial  and  limited  to  branching  of  the 
fundus  ;  or  the  faulty  fusion  may  he  manifested  by  only  a  partition,  more  or  less  complete,  that 
divides  the  uterine  cavity  into  two  compartments  (u/frus  septus),  although  the  external  form  of 
the  organ  is  almost  or  quite  normal.  When,  in  conjunction  with  any  of  the  foregoing  variations, 
one  of  the  component  Miillerian  ducts  fails  to  keep  pace  in  its  gi-owth,  all  degrees  of  asymmet- 
rical development  may  result,  from  complete  suppression  of  one  of  the  tuVies  in  a  bicomate  uterus 
to  merelv  unilateral  diminution  of  the  fimdus.  Subsequent  arrest  of  what  to  a  certain  stage  was 
a  normal  development  may  result  in  permanent  retention  of  the  foetal  or  infantile  type  of  uterus. 


PRACTICAL  CONSIDERATIONS  :   ITERUS  AND  ITS  ATTACHMENTS. 

In  the  female  the  pelvis  is  subdivided  into  two  compartments  by  a  fold  of  peri- 
toneum reflected  from  the  floor  and  sides  of  the  cavity.  This  fold  passes  from  one 
side  to  the  other  and  includes  between  its  layers  in  the  median  line  the  uterus.  On 
each  side  of  the  uterus  it  is  known  as  the  broad  ligament,  and  encloses  the  uterine 


PRACTICAL  CONSIDERATIONS:    THE  UTERUS. 


3013 


api>endages,  their  blood-vessels,  together  with  their  nerves  and  their  enveloping 
connective  tissue.  This  transverse  fold  of  peritoneum  is  analogous  to  the  mesentery 
of  the  small  intestine,  serving  the  same  purpose  for  the  uterus  and  its  appendages— 
/  e    to  hold  them  in  position  and  to  transmit  their  blood-vessels  and  nerves. 

'  The  posterior  compartment  of  the  pelvis,  the  recto-utertne,  is  the  larger  and 
deeper  of  the  two.  The  lower  portion  of  it,  included  between  the  two  recto-uterine 
folds  of  the  peritoneum,  is  the  pouch  of  Douglas,  or  recto-vaginal  pouch,  because  it 
lies  between  the  rectum  and  the  upper  fourth  of  the  vagina,  from  which  it  is  separated 
onlv  by  subperitoneal  connective  tissue.  The  rectum,  bulging  forward  the  ix>sterior 
wall  and  the  ovaries,  hanging  from  the  anterior  wall,  tend  to  till  this  compartment, 
the  remaining  space  being  occupied  by  small  intestine  and  a  portion  of  the  sigmoid 

Abnormally  it  may  be  encroached  upon  by  a  retroposed  uterus,  which  tends  to 
drag  downward  and  backward  its  appendages,  the  tubes  and  ovaries,  towards 
Douglas's  pouch,  where  they  may  be  palpated  by  the  fin^'  through  the  vagina. 
Because  of  the  greater  depth  of  the  posterior  compartment  .md  because  of  the  fact 
that  abscess  and  other  pelvic  operative  conditions  arc  usually  situated  in  it,  it  must 
almost  always  be  drained,  if  drain^e  is  necessary  after  operation  in  this  region. 

The  anterior  or  vesico-uterine  compartment  of  the  pelvis  extends  below  only 
to  the  isthmus  of  the  uterus.  The  remaining  supravaginal  portion  of  the  cervix 
is  in  close  relation  to  the  bladder,  but  the  loose  intervening  layer  of  subperitonea 
tissue  permits  a  ready  separation  of  the  two  in  the  operation  for  the  removal  of 
the  uterus  (hysterectomy).  Since  the  body  of  the  uterus  inclines  forward,  nor- 
mally, touching  the  bladder,  the  space  in  this  compartment  is  slight.  It  excep- 
tionally contains  a  few  coils  of  small  intestine,  and  may  lodge  also  a  part  of  the 
sigmoid  flexure.  .     •.• 

A  tumor  or  pregnant  uterus  filling  the  pelvis  may  press  upon  the  iliac  veins, 
producing  cedema  and  varicose  veins  of  the  lower  extremities,  of  the  vulva,  and  of 
the  rectum  (hemorrhoids)  ;  upon  the  lumbar  and  sacral  nerves,  causing  cramps, 
neuralgia,  or  paralysis  ;  upon  the  bladder,  with  resulting  vesical  irritability  and  pain  : 
upon  the  rectum,  inducing  constipation  and  hemorrhoids  ;  upon  the  ureters,  giving 
rise  to  hydronephrosis  ;  or  upon  the  renal  veins  and  kidney,  pro.lucing  albummuna 
and  piossiblv  uraemia.  . 

The  uterus  is  held  in  position  between  the  bladder  and  the  rectum  by  its  liga- 
ments, and  is  kept  from  dropping  to  a  lower  level  (prolapse)  mainly  by  the  support 
received  from  atmospheric  pressure  acting  through  the  floor  of  the  pelvis.  The  broad 
or  lateral  ligaments  attach  it  and  its  appendages— the  Fallopian  tubes  and  ovanes 

to  the  sides  of  the  pelvis.     The  round  ligaments  act  chiefly  in  tending  to  prevent 

retro-displacements.  The  musculo-fibrous  utero-sacral  ligaments  and  the  anterior  and 
posterior  reflections  of  peritoneum  materially  steady  the  cer^•ix,  which  is  also  fixed  by 
its  attachments  to  the  bladder  and  vagina.  Moreover,  the  intra-abdominal  pressure 
applied  through  the  intestinal  convolutions  that  are  normally  in  contact  with  its 
jjosterior  surface  aids  in  holding  it  in  position.  The  body  of  the  uterus  is  more 
freely  movable  than  the  cervix,  and  in  spite  of  its  supports  the  uterus,  as  a  whole,  is 
one  of  the  most  mobile  of  the  viscera.  The  cervix,  for  example,  may  easily  be  made, 
through  traction  by  means  of  a  tenaculum,  to  present  at  the  orifice  of  the  vagina,  in 
such  operations  as  amputation  of  the  cervix,  repair  of  lacerations,  or  dilatation  and 
:urettement.  On  account  of  its  mobility,  its  intrapelvic  situation,  and  the  elastic 
sui)port  received  from  the  bladder,  and  indirectly  from  the  levator  ani  muscles,  the 
uterus  is  very  rarely  injured  by  blows  on  the  abdomen.  If  upon  examination  it  is 
found  to  be  tixed.  or  not  easily  movable,  some  abnormal  cause  should  1k'  sought  for, 
such  as  pelvic  inflammations  or  tumors. 

The  essential  conditions  in  the  production  of  Vi  prolapsed  uterus  obtain  when  the 
uterus  is  the  seat  of  subinvolution  from  any  cause,  especially  a  puerperal  infection, 
and  the  pelvic  floor  is  relaxed  or  torn.  The  stretching  of  the  pelvic  lijjaments  has 
then  not  been  fully  overcome  by  later  contraction,  and  the  atmospheric  supjM)rt 
( dependent  upon  a'  tightly  closed  vaginal  outlet)  is  lacking  because  of  the  weak- 
ened jjcrineal  floor.  As  the  uterus  reaches  a  lower  level  its  ligaments  become  truly 
' '  suspensory" '  and  resist  its  further  downward  progress  as  soon  as  their  uterine  attach- 


30I4 


HUMAN   ANATOMY. 


ments  are  bel  w  their  pelvic  attachments.  Normally  their  insertions  and  origins  lie 
approximately  in  the  same  horizontal  plane  when  the  woman  is  erect  (Penrose). 

The  integrity  of  the  levator  ani  muscle,  ensuring  a  well-closed  vaginal  outlet,  b 
the  most  important  factor  in  supporting  the  uterus  within  the  pelvis.  It  keeps  the 
outlet  forward  under  the  pubic  arch  out  of  the  line  of  abdominal  pressure,  gives  it  the 
form  of  a  narrow  slit,  preventing  the  protrusion  of  the  pelvic  viscera,  and  directs  the 
axis  of  the  vaginal  canal  forward  instead  of  directly  downward,  so  that  the  intra- 
abdominal pressure  strikes  the  pelvic  floor  at  a  right  angle  ;  and  by  aiding  in  main- 
taining the  vagina  in  its  normal  condition  of  a  closed  slit  with  its  walls  in  contact,  it 
prevents  disturbance  of  the  forces  which  hold  the  uterus  in  place.  If  a  laceration  of 
the  perineum  converts  the  vagina  into  an  open  air-containing  tube,  the  equilibrium  of 
these  forces  is  destroyed  and  prolapse  often  follows.  In  severe  c  -es  of  prolapse  the 
ureters  are  so  stretched  that,  at  their  vesical  ends,  their  luri-  a  is  narrowed  and 
ureteral  dilatation  or  hydronephrosis  may  result. 

Anterior  and  posterior  jiexions  of  the  uterus  occur  at  thi  isthmus,  which  is  the 
weakest  point  and  is  the  junction  of  the  larger  and  more  movable  portion — the  body 
— with  the  smaller  and  more  fixed  portion — the  cervix. 

On  account  of  the  normal  anteflexion  of  the  uterus,  it  is  not  always  easy  to 
decide  in  a  given  case  whether  the  degree  of  anteflexion  is  normal  or  abnormal. 
When  it  is  abnormal  the  most  imfKtrtant  symptom  is  dysmenorrhcea,  from  obstruc- 
tion of  the  canal  by  the  flexion  ;  if  irritability  of  the  bladder  occurs,  it  is  probably 
reflex  in  its  origin. 

Anything  which  weakens  the  support  of  the  uterus,  or  increases  its  weight, 
tends  not  only  to  cause  prolapse,  but  also  to  the  production  of  retroflexion  or  retro- 
version of  the  uterus,  the  first  degree  of  prolapse  being  associated  with  some  retro- 
displacement.  The  uterus  then  loses  its  normal  anteversion,  and  the  intra-abdominal 
pressure  is  brought  to  bear  on  its  anterior  surface,  es()ecially  if  the  patient  is  either 
confined  too  long  in  the  supine  position  after  labor,  with  the  abdomen  too  tightly 
bandaged,  or  if  she  leaves  her  bed  too  soon  or  undertakes  any  physical  work. 

The  uterus  is  larger  and  heavier  than  normal,  as  a  result  of  imperfect  involution  ; 
the  uterine  ligaments  are  lax  ;  the  vagina  and  the  vaginal  orifice  are  relaxed,  and 
the  support  of  the  pelvic  floor  is  consequently  deficient  ;  the  abdominal  walls  are 
flabby  and  the  retentive  power  of  the  abdomen  is  diminished.  These  are  also  the 
causes  that  favor  prolapse  of  the  uterus  ;  in  fact,  a  slight  degree  of  uterine  prolapse 
usually  accompanies  such  cases  of  retrodisplacement.  A  certain  amount  of  retro- 
version must  always  exist  before  the  uterus  can  pass  along  the  vagina.  It  must  turn 
backward,  so  that  its  axis  becomes  parallel  to  the  axis  of  the  vagina  (Penrose). 

In  the  purely  retroverted  positions  the  uterus  revolves  on  the  isthmus  as  on  a 
pivot,  so  that  as  the  fundus  goes  in  one  direction  the  cervix  passes  in  the  other. 
Therefore,  as  the  cer\ix  is  turned  forward  against  the  base  of  the  bladder,  the  fundus 
presses  backward  on  the  rectum,  often  producing  reflex  symptoms. 

The  uterus  may  be  found  inclined  to  one  side — more  usually  the  fundus  to  the 
left,  and  the  cer\-ix,  on  account  of  the  presence  of  the  sigmoid  and  rectum  on  the  left 
side,  to  the  right.  Unless  extreme,  such  inclination  is  not  to  be  regarded  as  patho- 
logical. 

Between  the  layers  of  the  broad  ligaments  is  a  quantity  of  loose  adipose  cellu- 
lar tiissue,  the  parametrium,  separating  the  contained  structures — those  of  the  most 
importance  being  the  tubes  and  ovaries  with  their  vessels  and  ner\'es — from  one 
another  an<l  from  the  serous  membrane.  This  cellular  connective  tissue  is  continuous 
with  the  surrounding  subperitoneal  areolar  tissue  of  the  pelvis,  and  is  especially 
abundant  near  the  base  of  the  broad  ligaments. 

In  pfhic  crllulitis  there  is  infection  of  this  loose  cellular  tissue,  usually  through 
the  lymphatics  and  often  puerperal  in  origin.  It  may  follow  other  septic  intrapelvic 
conditioiis.  especially  salpingitis,  but  a  simple  cellulitis  unaccompanied  by  tubal 
inrtammition  is  ir  ,ic  vast  majority  of  cases  due  to  infection  through  the  uterus  from 
a  septic  endomt  ntis.  Because  of  the  laxity  of  the  tissue  it  may  spread  rapidly  and 
extensively  in  virulent  cases  It  may  extend  backward  alcng  the  iitero-sacral  liga- 
ments, then  upward  along  the  retroperitoneal  tissue,  as  far  as  the  kidnej's.  It  may 
pass  forward  and  upward  to  the  groin,  where,  should  an  abscess  form,  it  may  be 


PRACTICAL  CONSIDERATIONS:    THE  UTERUS. 


2015 


opened.     It  may  also  burrow  into  the  vagina  or  rectum.     Suppuration  tokes  place, 
however,  in  only  a  small  percentage  of  cases.  ,  .    ,        .  . 

The  condition  is  usually  recognized  by  the  rapid  swelhng  and  mduration  at  the 
sides  of  or  behind  the  uterus,  and  in  closer  relation  to  it  than  is  the  swelhng  of  a  pyo- 
salninx  or  of  an  ovarian  abscess.  Pelvic  collections  of  pus  of  this  nature  <nay.be 
e'T  cuated  through  the  vagina  by  an  incision  made  close  to  the  cervix,— to  avoid  the 
ureters  and  the  uterine  arteries  ;  but  it  should  be  remembered  that  this  procedure 
does  not  remove  the  focus  of  primary  infection,  such  as  a  diseased  Fallopian  tube. 

Blood  coUections  (hematoceles)  or  tumors  (intraligamentous)  may  abj  occur 
between  the  layers  of  the  broad  ligaments.  ,  ■     .       • 

The  narrow  lower  border  of  each  ligam  ^nt  lies  on  the  floor  of  the  pelvis,  but  is 
separated  from  it  by  a  thick  layer  of  subperitoneal  tissue,  in  which  tlie  utenne  artery 
with  its  veins  passes  neariy  transversely  inward  from  the  internal  iliac  artery  at  the 
side  of  the  pelvis  to  the  cervix  at  about  the  level  of  the  vault  of  the  vagina. 

The  ureter,  on  its  way  from  behind  forward  to  the  bladder,  passes  thrtmgh  this 
loose  ceUular  tissue  just  below  the  ba.se  of  the  broad  ligament.  It  lies  dcse  under 
the  uterine  artery  from  one-half  to  one  inch  from  the  side  of  the  cervix.  It  is  within 
this  short  distance  that  the  uterine  vessels  are  tied,  either  from  within  the  abdomen 
or  from  the  vagina,  according  to  the  method  of  operation,  in  the  removal  of  the 
utenis  (hysterectomy).  The  inclusion  of  the  ureter  within  the  ligature  is  one  of  the 
greatest  dangers  in  this  operation.  This  accident  is  more  likely  to  occur  if  the 
artery  is  crowded  closer  to  the  ureter  of  one  side,  by  a  tumor  or  other  mass,  m  the 
opposite  side  of  the  pelvis.  The  ureter  is  also  in  danger,  as  it  lies  along  the  side  and 
floor  of  the  posterior  compartment  of  the  pelvis.  It  may  there  be  injured  in  the 
removal  of  adherent  masses,  such  as  inflamed  tubes  and  ovaries,  or  of  retroperitoneal 
tumors  or  cysts.  Calculi  in  the  vesical  ends  of  the  ureters  may  be  removed  through 
the  vaginal  wall  (page  2020).  ,,..■.... 

The  free  upper  border  of  the  broad  ligament  between  the  fimbriated  extremity 
of  the  tube  and  ovary  and  the  side  of  the  pelvis— the  suspensory  ligament  of  the 
ovary  or  the  infundibulo-pelvic  ligament— is  of  practical  importance  because,  m 
addition  to  supporting  the  ovary,  it  contains  the  ovarian  vessels  where  they  we  usu- 
ally tied  in  the  operations  for  the  removal  of  the  uterus  or  its  append^es.  Kelly 
calls  attention  to  a  space  immediately  below  the  vessels  in  this  region,  where  the  two 
layers  of  the  peritoneum,  forming  the  broad  ligament,  come  close  together.  By  Pass- 
ing a  ligature  through  this  membranous  interval  and  tying  over  the  top  of  the  broad 
ligament,  all  the  ovarian  veins  and  the  artery  are  included.  If  the  uterine  vessels 
also  are  tied  by  a  separate  ligature,  at  the  comu  of  the  uterus,  there  should  be  no 
dan^f-r  of  hemorrhage  in  a  salpingo-oophorectomy ;  or,  if  the  uterine  vessels  are 
secured  at  the  sides  of  the  cervix,  in  the  floor  of  the  pelvis,  and  the  ovanan  vessels 
are  ligated,  as  above,  on  both  sides  of  the  pelvis,  the  hemorrh^e  will  be  controlled 
for  a  hysterectomy.  ...        ,    . 

The  round  ligaments,  passing  outward  and  forward  from  the  sides  of  the 
uterus  through  the  internal  ring  and  inguinal  canals  to  the  labia  majora,  tend  by  their 
direction  to  maintain  the  uterus  in  its  normal  anteflexed  position.  When  retrodis- 
placements  of  the  uterus  do  occur  these  ligaments  become  stretched  and  lengthened. 
They  have  frequentiy  been  shortened  by  operation  to  correct  such  displacements. 
This  may  be  done  bv  the  extra-abdominal  method  in  the  inguinal  canal  (Alexander's 
operation),  or  within  the  abdomen  (Palmer  Dudley  operation),  the  latter  method  per- 
mitting a  more  accurate  estimate  of  the  special  peculiarities  or  difficulties  of  a  given 
case. 

Occasionally  in  the  adult— always  in  the  foetus  and  in  20  per  cent,  of  cases  in 
children  (Zuckerkandl,  quoted  by  Woolsey) — a  patulous  process  of  peritoneum,  the 
canal  of  Nuck,  accompanies  the  round  ligament,  lying  above  and  in  front  of  it  for 
a  variable  distance  through  the  inguinal  canal.  It  is  analogous  to  the  vagina!  process 
of  peritoneum  which  descends  with  the  testicle,  and.  like  it.  predisposes  to  congenital 
inguinal  hernia  (page  1767)  and  to  hydrocele  (page  1953)-  Should  its  lumei  become 
constricted  at  some  |)oint,  the  portion  beyond  the  obstruction  may  secrete  t'lid  and 
give  rise  to  the  so-called  "cyst  of  the  canal  of  Nuck,"  which  is  analogous  to  an 
encysted  hydrocele  of  the  cord  in  the  male  (page  1953). 


30l6 


HUMAN  ANATOMY. 


Kici.  1703 


THE  VAGINA. 

The  vapiina  is  a  flattened  muscular  tube,  lined  with  mucous  membrane  and  about 
7.5  cm.  (3m.)  long,  that  extends  from  the  genital  cleft  enclosed  by  the  labia  minora 
below  to  Uie  uterus  a*~ove,  to  the  lower  segment  of  which  it  is  attached  a  short  dis- 
tance above  the  extes ..  1  os.  From  this  relation  and  the  direction,  downward  and 
backward,  of  the  portio  vi^inalis,  the  vagina  is  seemingly  pierced  obliquely  by  the 
uterus,  whose  external  os  looks  towards  the  posterior  vaginal  wall.  In  the  erect 
posture  the  long  axis  of  the  vagina  is  approximately  straight,  directed  from  below 
upward  and  backward,  and  corresponds  in  general  with  the  lower  part  of  the  pelvic 
axis.  With  the  horizontal  plane  it  forms  an  angle  of  about  70°,  and  with  the  axis 
of  the  cervix  one  that  is  usually  somewhat  more  than  a  right  angle. 

The  arched  upper  blind  end  of  the  vagina,  known  as  the  vault  (fornix  vui{inae), 
is  largely  occupied  by  the  obliquely  placed  portio  vaginalis  and  thereby  reduced  to 
an  annular  groove  that  surrounds  the  neck  of  the  uterus.     This  groove  is  deepest 

behind,  where  it  constitutes  the  posterior  fornix,  a 
narrow  pouch  from  1 . 5-3  cm.  in  length  lying  between 
the  cervix  and  the  adjacent  vaginal  wall.  The  recess 
in  front  of  the  cervix,  the  anterior  fornix,  is  shallow 
and  only  slightly  marked.  In  consequence,  the  length 
of  the  posterior  wall  of  the  vagina,  measured  from  the 
summit  of  the  posterior  fornix  to  the  vaginal  orifice,  is 
from  8.5-9  cm.  (3ji-3ji  in.),  that  of  the  anterior 
wall  being  about  7  cm.  (3^  in.),  or  from  1.5-2  cm. 
shorter. 

The  opening  at  the  lower  end  of  the  vagina  (ori> 
ficium  vaginae)  is  contracted,  and  in  the  virgin  is  still 
further  narrowed  by  a  duplicature  of  mucous  mem- 
brane, the  hymen,  of  variable  form  but  usually  cre- 
scentic  in  outline,  that  stretches  from  the  posterior 
wall  forward  and  occludes  more  or  less  the  vaginal 
entrance.  After  rupture  the  hymen  is  for  a  time 
represented  by  a  series  of  irregular  or  fimbriated  pro- 
jections that  become  the  caruncula  hymenales.  These 
surround  the  of>ening  of  the  vagina  and  undergo  re- 
duction and  partial  efl?rement  after  childbirth.  The 
anterior  and  posterior  walls  of  the  main  and  widest 
part  of  the  canal  (corpus  vaginae)  are  modelled  by 
median  elevations  (coluninae  rugarum),  from  which 
numerous  oblique  folds  diverge  laterally.  These 
markings,  most  r  onounced  in  the  lower  half  of  the 
vagina,  are  particularly  conspicuous  on  the  front  wall. 
Here  the  anterior  column  is  beset  with  close  V-like 
ridgf'  s  and  ends  below  in  a  crest-like  elevation — the 
carina  urethralis — that  lies  behind  the  urethral  orifice. 
Relations. — With  the  exception  of  the  triangular  area,  from  1.5-2  cm.  long, 
over  the  uppennost  part  of  the  posterior  wall,  where  the  bottom  of  the  recto-uterine 
pouch  reaches  the  canal,  the  vagina  is  devoid  of  peritoneum,  being  attached  to  the 
surroun<ling  organs  by  areolar  tissue.  In  front  its  upper  fourth  is  in  relation  with  a 
small  part  of  the  fundus  and  the  trigone  of  the  bladder,  being  attached  to  the  vesical 
wall  by  loose  connective  tissue.  Embedded  within  the  latter  and  surrounded  by  veins, 
course  the  converging  ureters,  which  reach  the  anterior  vaginal  wall  at  about  the 
level  of  the  lower  end  of  the  cervix.  Below  the  bladder,  the  anterior  wall  of  the 
vagina  and  the  urethra  are  intimately  connected  by  the  intervening  dense  fibrous 
tissue  (septum  urcihrovagina!is),  \v  !i  which  the  vaginal  wall  blends  without  sharp 
demarcation.  In  consequence  of  lie  forward  curve  of  the  urethra  this  partidon 
broadens  b<:low. 

Behind,  the  chief  relation  is  with  the  rectum,  v,-hich  is  separated  from  the  upper- 
most part  of  the  vagina,  for  a  short  distance  (from  1.5-2  cm.),  by  the  pouch  of 


Vajcina  of  vimti,  posterior  wall 
has  been  n*moven  exposifiK  rugous 
condition  of  anterior  wall. 


wnm 


THE  VAGINA. 


3017 


n«..«l«  Below  the  Utter,  as  far  as  the  levator  an.  muscles,  the  v^na  and  bowel 
Douglas.     Below  tne  uuer^  ^^  strengthened  by  the  mterxenmg 

are  connected  by  the  dcn^rectova^^^  p  ^  B^  ^^^^^  ^^^  backward, 
prolongation  of  the  pdv.ct^ia.runne  ^         i^^^  p^^Hca/  body,  which  on 

the  partition  broade.«  'TtiLde  with  th^base  below  in  the  perineum^Fig.  1700). 
«gittal  ?^"«"/PS  b  emC^cSCitS  unattached  lo.  the  median  (pubo- 
At  the  9.d^  '^yfK'"*^,^™^7'^J'i^,  which,  in  conjunction  with  the  pelvic  fascia, 
rectal)  jwrtionof  «»»*=  l*^*"^,""  T  ,^Oic  floor  the  vagina  gains  additional  fixation 
afford  efficient  support  ^^l^^^^^^^Lt'^^li^  whichU  is  ultimately  atUched.  In 
in  P?^'"g.  through  the  tnangjirligam^^^^^  7^^  Bartholin's 

^f rs"  "he  rianX  Tntervll  o'n  LTh side  litleen  the  levator  ani  and  Uie  pelvic 
S  and  fhVVa3  suSL  of  the  vagina,  is  occupied  by  the  veins  of  the  vesico- 


Fig.  1704. 


Pubo-vMiml  llgBBunt^ 


Pelvic  iascia  covering^ 
levator  ani 


Obturalor  memhratie. 


Visceral  exten- 
sion ol  pelvu- 
fascia 

Obturalor  (ascla- 
Fat  removed  ex 
posinupelvicBotr- 
Visceral  reflec- 
tion ot  pelvic 
fascia 

obturator 
intemus 
Levator  am 

Ischium,  cut 


Anal  tascla-^ 


Symphysis  puMt 
Pubic  bone,  cut 

.^,^Prevcsical  space, 
cleaned  out 


^Portion  f>f  «-all 
oi  bladder 


Urethra 


Veaico-vaginal 
venous  plexus 


Rectum 


Uchio-recUl  fossa 


vaginal  plexus  that  above  surrounds  the  ureter  and  the  vaginal  branches  of  the 
uterine  artwy^  vaginal  walls,  from  2-3  mm.  thick,  include  a  mucous  and  a 

muscular^coat,  supplemented  externally  by  an  indefinite  fibrous  tunic.  The  mucous 
Z^consSs  of  a  tunica  propria,  exceptionally  rich  in  elastic  fibres  and  veins,  he 
SrrS  of  which  is  teset  with  numerous  conical  papiU*  that  encroach  upon  the 
over  ying  epithelium,  but  do  not  model  the  free  surface.  The  epithelium  fom 
o  15^.  20  mm.  thick,  is  stratified  squamous  in  type  and  possesses  ^  superficial  stratum 
of  olate-like  cells  (.020-. 030  mm.  in  diameter)  that  resemble  the  epidermal  ele- 
ments of  the  skin  and  are  constantiy  undergoing  maceration  and  *b/=»«'°";„^^Jthou^h 
normally  moistened  bv  a  thin  mucous  secretion  of  acid  reaction,  the  vagina  is  devoid 
"rtme  gSand  probably  derives  its  lubricating  flui.i  for  the  most  part  from  the 
u teSe  glands,  the  laline  Lretion  becoming  modified^  Small  nodules  of  lymphoid 
dssue  a7e  scattered  within  the  mucosa,  especially  ...the  upper  P^rt  of  the  canaL 
The  duplicature  of  the  mucous  membrane  forming  the  hymen  corresponds  in  structure 
with  that  lin"ng  other  parts  of  the  canal.  The  muscular  coat,  which  directly  sup- 
norts  the  mucoia  without  the  intervention  of  a  submucous  tunic,  consists  of  bundles 
S^  involuntary  ...uscle  that  arc  arranged,  although  not  w.th  Prf^"''""-^'^  ^«"  '""^^^ 
circular  and  an  outer  longitudinal  layer.     The  Tatter  is  best  developed  over  the 

"7 


01 

Hi 


30l8 


HUMAN  ANATOMY. 


Fio. 


'70S. 


Tunica 

propria  of 

mucosa 


anterior  vaginal  wall,  from  which  bundles  of  muscular  tissue  are  continued  into  the 
urethro-vagmal  stptum ;  behind,  bundles  pass  into  the  recto-vaginal  partition.  Above, 
the  vaginal  muscle  is  directiy  continuous  with  that  of  the  uterus  and  below  penetrates 
the  perineal  body.  Within,  the  conspicuous  columme  rugarum,  the  muscular  coat, 
as  well  as  the  mucous,  is  thickened,  the  elevations  acquiring  the  character  of  erectile 

tissue  owing  to  the  great  num- 
ber of  veins  intermingled  with 
the  irregularly  disposed  mus- 
cle bundles.  After  piercing 
the  superior  layer  of  the  tri- 
angular ligament  and  in  the 
vicinity  of  the  orifice,  the  vagi- 
nal walls  receive  strands  of 
striated  fibres  derived  from 
the  middle  part  of  the  com- 
pressor uretnrae  (m.  urethro- 
vaginalis)  and  the  bulbo-cav- 
emosus  muscles. 

Vessels.— The  arteries 
supplying  the  vagina,  all  de- 
rived from  the  internal  iliac, 
reach  the  organ  by  various 
routes.  The  upper  part  of 
the  vagina  is  supplied  by  twigs 
continued  from  the  cervical 
branch  of  the  uterine  arteries, 
that  descend  along  the  sides 
of  the  canal  and  communicate 
with  the  branches  from  the 
middle  hemorrhoidal  and  vagi- 
nal (vesico- vaginal),  that  are 
distributed  to  the  middle  and 
lower  portions  of  the  vagina  respectively.  Those  from  the  vaginal,  of  the  two  sides, 
form  encircling  anastomoses  from  which  an  unpaired  ves.sel  (a.  azygos  vagina)  fre- 
quently is  given  off  on  the  posterior,  and  sometimes  anterior,  wall.  Additional 
branches  pass  to  the  lower  part  of  the  vagina  from  the  arteries  to  the  bulbus  vestibuli 
from  the  internal  pudics.  Free  anastomosis  exists  b'Ttween  the  vessels  derived  from 
these  various  sources.  The  veins,  numerous  and  large,  after  emerging  from  the  mus- 
cular tunic  unite  on  each  side  to  form  the  rich  vaginal  plexus  that  extends  along  the 
sides  of  the  genital  canal  and  communicates  with  the  vesical  and  uterine  plexuses. 
It  receives  tributaries  from  the  external  generative  organs  and  is  drained  by  a  trunk, 
the  vaginal  vein,  that  passes  from  its  upper  part  to  the  internal  iliac  vein. 

The  lymphatics  \\'\\\\\x\  the  mucous  membrane  form  a  close  net-work  that  commu- 
nicates with  the  lymph-vessels  of  the  muscular  coat.  The  collecting  trunks  pass 
from  the  upper  and  middle  thirds  of  the  vagina,  in  company  with  those  from  the 
cervix  uteri,  chiefly  to  the  lymph-notles  along  the  internal  iliac  artery.  Additional 
stems  from  the  posterior  vaginal  wall  encircle  the  bowel  and  terminate  either  in  the 
rectal  or  the  lumbar  nodes  (Bruhns).  The  lymphatics  from  the  vicinity  of  the  vagi- 
nal orifice  pass  chiefly  to 'the  ujiper  median  group  of  inguinal  nodes  ;  some,  however, 
join  the  lynij)h-paths  from  the  upper  segments. 

The  nerves  are  derived  from  the  hvpogastric  sympathetic  plexus,  through  the 
pelvic,  and  from  the  second,  third,  and  fourth  sacral  ner\'es.  The  immediate  source 
of  the  sympathetic  tihres  is  the  cervical  ganglion,  at  the  side  of  the  neck  of  the  uterus, 
from  which,  in  association  with  the  sacral  branches,  twigs  pass  to  form,  on  each  side, 
the  vaginal  plexus  that  embraces  the  vagina  and  provides  filaments  chiefly  for  the 
in\()luntary  muscle  of  its  walls  and  b!ood-\cssels.  The  sensorv-  fibres  supplying  the 
mucous  miMnhrane  i.f  the  iijijmt  p.irt  of  the  vagina  are  me.igre,  since,  under  norma! 
conditions,  this  part  of  the  canal  possesses  sensibility  in  only  very  moderate  degree. 
Towards  the  orifice  the  vagina  receives  fibres  from  the  pudic  nerves  which  endow 


Section  of  wall  o(  vagini.     X  So. 


PRACTICAL  CONSIDERATIONS:    THE  VAGINA. 


3019 


V ..  >„-  «f  th..  lower  third  with  treater  sensibility  and  send  motor  fila- 
':::rri^T£^^i^^VZnouM.Z  i^^.nu.n...     ScnLy  ncr^ccndings  o. 

of  th?MiuS  ducts  Alter  union  of  the  latter  with  the  iK.ster.or  wall  o  the  uro- 
s  1  in  r^nd  th.  iDoearance  of  a  lumen,  which  at  first  is  wanUng.  he  gcmlal 
genual  smus  f 'I.  ^V  ;  P^f  "^""p;rture  later  the  orificium  vagina;,  that  lies  between 
r/SruStS-^rthrWoCd'cts.  The  utter  sul^^uenUy  atrophy  a.ul 
ana  cioseiy  uimcu  «  „,:„„_i  na>u-i   iM>rs  st  to  a  ercater  or  less  extent  as  (.jart- 

disappear   but  may   .nex^^^^^^^^^^^^    i^Jr^'agina  is^early  guarded  by  an  annular 

E.TS.  ™^l.icb^e»  at  birth  i.  sliBMly  com.B.tcd.     In  con».-quejcc ..    I« 

the  fifth  month.  ^^j  j^^  ^^,5  j^,  comparatively 

At  birth,  the  vagma  .  -n^    r  .^       .^;  .      ^^^^  ^^^       ^^^^ 

'^'^b::u^Tu^"'''°^l^t  .      .dverdcal  but  after  the  tenth  year  grows 

liSlv  t^increSwidTh  ^...  :;eductionTn  the  rug*,  which  from  now  on  are 

s£i^Ss^t2ini=yea;js^c£^n^ 

ticity  and  undergoes  atrophy. 

V.ri.tion..-The  most  -PO"ft  variations  depend  up^^^^^^^ 

perfect  fusion  of  the  ^X^enV^e  tub^  M  tore^^h  ^he  ur^en"  ai  sinus,  the  v.nRina  en.ls 
anomalies  of  the  uterus.  When  these  tubes  }^";^^°  J^"^'^  ^e^y^nted,  the  vagina  (and  often 
blindly  above  the  vestibule  ;  or  when  their  lower  seRmentt  are  «^^^^  ^^ 

uterus')  maybe  ^"''^«'y  "^"""{^in.KucT'  The  doul^^rry'^not'exlend  tl'.roughout  the 
separate  or  imperfectly  fusedMullenan  ducts  ,„  imnerfect  and  partial  septum,  isolateil  tends, 
lelTgth  of  the  v»«ina  but  may  be  repj^esented  b>^^  ^^  ^^^     ^^^^ 

charges  occurs. 

PRACTICAL  CONSIDER.\TIONS :  THE  VAGINA. 
Congenital  malformations  of  the  vagina,  such  as  absence  of  the  vagina,  rudi- 
mentary vadna,  or  vaginal  septa,  are  usually  associated  with  corresponding  errors 
b  developr^rnt  of  the  uterus.  While  other  malformations  due  to  faulty  union  of  the 
\m  lerianTrts  occur,  the  more  common  is  a  uterus  bicornis,  or  a  double  "Jerus  and 
vSa  Tl  ev  are  not  incompatible  with  pregnancy,  labor  and  'l^^,  P^-'-P^""^  ^f^*^" 
pSg  w  thout  unusual  incident ;  indeed,  this  condition  is  usually  r«<^«K"'^!^J  y 
Sent,  since  no  external  evidence  is  seen.  Conception  may  occur  on  one  or  both 
"d^rsimultaneously.  A  vaginal  septum  >  ^ich  interfered  with  t^^  P-^^-f^"  ^^'^^^ 
head  should  be  divided.  From  imperfect  development  of  one  side  ,  !  ■''>'"'  "^^e 
uterus,  pregnancy  may  lead  to  great  danger  of  rupture  of  the  weak  utenne  wall,  or 

to  a  failure  to  expel  the  child.  .  ,     ,      ,.       .•        «  »u„  uuAA,.r  ivhpn  the 

While  varying  within  normal  limits  with  the  distention  of  the  bladder,  "henjhe 

latter  is  empty  the  axis  of  the  fundus  of  the  ulcus  lies  at  alKOUt  a  right  ^'"r!''  ^.th 

the  v4ina      The  inner  or  uterine  end  of  the  broad  ligament  is,  except  at  its  ba.e. 


ao2o 


HUMAN   ANATOMY. 


more  nearly  horizontal  than  vertical  in  direction.  As  a  result  oi  this  position  of  the 
uterus,  it  will  be  seen  that  the  lower  surface  of 'the  cervix  presents  aeainst  the  pos- 
terior vaginal  wall,  and  that,  therefore,  this  wall  of  the  vagina  must  he  longer  than 
the  anterior.  The  posterior  wall  is  usually  about  three  and  a  half  inches  long  ;  and 
the  anterior  about  two  and  a  half  to  three  inches.  The  length  of  the  ordinary  Anger 
is  about  three  inches  ;  it  can,  therefore,  reach  the  anterior  fornix  of  the  vagina  and 
anterior  lip  of  the  cer  'x.  To  explore  the  posterior  fornix  of  the  vagina  considerable 
pressure  is  required.  To  palpate  structures  in  Douglas's  cul-de-sac  the  bimanual 
method  of  examination  will  be  necessary,  and  a  relaxed  abdominal  wall,  to  obtain 
which  a  general  anaesthetic  may  exceptionally  be  required.  An  empty  bladder  facili- 
tates a  bimanual  examination.  In  the  knee-chest  posture  the  vagina  becomes  dis- 
tended with  air,  permitting  a  more  thorough  visual  examination  of  its  walls.  The 
rectum  posteriorly,  and  the  base  of  the  bladder  and  the  urethra  anteriorly,  are  within 
reach  of  the  finger  in  the  vagina.  Calculi,  either  in  the  lower  ends  of  the  ureters 
{vide  supra)  or  in  the  bladder,  can  be  removed  through  the  anterior  vaginal  wall 
(page  2015). 

The  intravaginal  portion  of  the  cervix  uteri  can,  with  little  or  no  pain,  be  grasped 
by  a  tenaculum  and  drawn  down  towards  the  vaginal  orifice  so  that  local  applications 
can  be  made.  It  is  so  insensitive  that  such  applications,  even  when  strong  and  irri- 
tating, do  not  necessitate  the  use  of  an  anaesthetic.  Since  it  is  the  part  of  the  cervix 
most  exposed  to  traumatism  and  infection,  it  is  the  most  frequent  seat  of  pathological 
lesions,  such  as  the  so-called  "erosions."  Persistent — i.e.,  unhealed — lacerations 
are  often  sources  of  irritation,  of  reflex  pains,  and  of  some  forms  of  dysmenorrhoea. 
Much  of  the  pelvic  pain,  associated  with  them,  is  probably  due  to  pelvic  lymphangitis 
or  lyn.phadenitis  (Penrose).  These  lacerations  seem  to  invite  the  development  of 
cancer.  Primary  involvement  of  the  body  of  the  uterus  is  comparatively  rare,  the 
great  majority  of  cancers  of  the  uterus  beginning  in  the  cervix.  As  a  result  of  the 
relations  and  contiguity  of  the  cervix  to  surrocnding  important  structures,  such  as  the 
bladder,  ureters,  and  rectum,  the  prognosis  of  cancer  of  the  cervix  is  less  favorable 
than  that  of  the  body  of  the  uterus,  where  infiltration  of  neighboring  stiactures  does 
not  occur  so  early.  As  a  rule,  dissemination  by  lymphatic  channels  from  carcinoma 
of  the  cervix,  affects  first  the  sacral  or  the  iliac  glands;  carcinoma  of  the  body  of  the 
uterus  is  more  likely  to  involve  the  lumbar  glands  surrounding  t'  .•  common  iliacs, 
the  aorta,  and  the  vena  cava.  Pressure  on  the  last-named  v  jel  may  result  in 
cedematous  swelling  of  the  lower  e.xtremities  or  in  ascites. 

An  hypertrophied  cer\'ix  shows  as  an  increased  projection  into  the  vagina  and  a 
deepening  of  the  vaginal  fomices.     This  condition  may  be  a  cause  of  sterility. 

The  vagina  is  most  roomy  in  its  upper  portion,  and  is  narrowest  at  its  lower 
end,  where  it  passes  through  the  triangular  ligament  and  is  surrounded  by  the  con- 
strictor vaginae  muscle.  This  favors  the  retention  of  blood-dots  within  the  vagina 
during  the  menstrual  period  and  after  labor.  Spasmodic  contraction  of  this  muscle 
(vaginismus)  is  described  as  being  sometimes  strong  enough  to  prevent  coitus  and 
to  call  for  surgical  treatment,  though  such  cases,  if  they  exist  at  all,  are  due  to  reflex 
irritation,  such  as  from  urethral  caruncle.  The  dilatation  of  the  vagina  seems  to  be 
limited  only  by  the  pelvic  wall.  In  nullipara  the  rugosity  of  its  mucous  membrane — 
necessitated  by  its  great  changes  in  diameter — is  marked.  The  transverse  folds 
favor  retention  of  secretions  and  of  discharges  resulting  from  infection  and  render 
sterilization  of  the  vagina  difficult.  Vaginitis  may  be  followed  by  endometritis,  as 
the  uterine  and  vaginal  mucoste  are  directly  continuous. 

The  hymen  rarely  may  have  no  opening,  when  it  will  require  incision  to  relieve 
the  obstructed  first  menstrual  flow.  The  exact  importance  to  be  attached  to  the 
presence  or  absence  of  the  hymen  in  medical  jurisprudence  is  still  undetermined. 
While  it  is  usually  broken  at  the  first  coitus,  it  may  remain  intact  until  the  first 
parturition.  Therefore  its  presence  does  not  prove  virginity.  Its  original  perfora- 
tion may  have  been  large  enough  to  leave  little  or  no  evidence  of  the  membrane, 
so  that  its  absence  does  not  prove  that  coitus  has  taken  place. 

Fislulte  between  the  bladder  and  vagina  (vesico- vaginal),  between  the  urethra 
and  vagina  (urethro-vaginal),  between  the  rectum  and  vagina  (recto-vaginal),  and 
between  the  cervical  canal  and  the  bladder  futero- vesical),  may  occur. 


THE  Labia  and  the  vestibule. 


302I 


openini!  into  .he  Wadte.     "  " '"^X.  to  a  ttoi  ottraditig  lotw.rd  through  the 
y„lt>-Mn^  li«.il«  '^.'?H,?"irf  1^  Jong  tte  ctvioJ  cnJ.     The 

S.^fe.'''KKr^n'T,£'r£.»rt:r.e  .K.n  h...  .  .;... 

ulero-vaginal  fistula.  ^  ,     e,  ^nd  of  the  vagiiw. 

^^'^--^-f' fi!t"S/;*irfr^^^^^  «t^nsion  of  an  epithelioma  o?  the 

1     V   FEMALE   EXTERNAL   GENITAL  ORGANS. 
The  external  gen«.tive  organs  oMheJ^^^ 
ductive  apparatus  that  he  below  ^^^^^  ^^^] *  J"^„  ^bove  and  the  urogen- 
pubic  arcli.     They  are  '^fJ^/J.^ZraTnymPha,  Ja  the  enclosed  vesHbuU,  the 
italcU/t  between  them.  *«  f^.*  *"!f C"  ^^He^AiW*  o/^  Bartholin  ;  within  the 
clitoris  and  the  bulbus  *f '*«'  '  ^!^^d  d  the  vS     Of  these  structures,  col- 

s^avTrubr»sr3,ftitotrvr^rirHhi„.^.-^»>««- 


THE  LABIA  AND  THE  VESTIBULE. 


The  Ubia  m.ior  (labia  major.  P-^-u^TTcr  HntS  Td" S  T^uZ 
folds,  the  homologueof  *e  scrotum  about  7-5  cm     ^m^^^^^^^ 
that  extend  backward  from  Je jnons  pub«  and  endo^^  beUveen  ^^^  ^^^^^^^^  ^  ^^,^. 
the  urogenital  cleft  (rinuumdeodi).    .Above^he*'  >nnf  ^        g  j^j^j^^ 

missura  labiorum  anterior)  «^,^^„  J^  '^^.^j^S^^^^  by  a  trans- 

where  their  upenng  ends  blend  with  the  P?'^*"'?;  "V^..  ^^  ^^^  sometimes 
verse  fold  (commissara  {f**'"™"  P^^^f^^J,!,^^^^^  Their  outer  surface  is 

wanting,  that  crossw  the  "ud-line  "'*^^  *"J  ^set  with  hairs,  in  varying  profusion, 
covered  with  thick,  dark-hued  mtegument  ^n**  .'^^  "^yj.^S,  and  may  extend  as 
that  encroach  for  a  limited  zone  on  the  '""^^^  »^^f  ^^^'^Ih^  arl  few  and'^  minute,  is 
far  as  the  anus.  The  med.al  ^"fXatP  textlre  thTt  at  the  bottom  of  the  nympho- 
clothed  with  skin  of  much  more  del«c^e Je'tture  that  «^»«^         j^j^j^^  ^^  ^^^  skin, 

labial  furrow  passes  onto  the  outer  «"£^!^°*  ^J^  f^f^fi^een  which  and  the  integu- 
each  labium  consists  of  » J.f  ^J  f^.«"*'"!,*^^nf  inVStT^  muscle  (tunica  darto- 
ment  in  the  posterior  l"*!'-*/*^'"  **™^""'°', '"L  perineum  and  represents  the 
labialis)  is  continued    «^-^^d  from  the  dlartos  of  the  pemeu  ^^  ^^^^  ^^P^^^  .^  ^^^ 

-ci;?^^7S;rS;:=^^^ 

IrStxX^'tr^^:^^  ^  :SL'Sin^r llbium  n,^^        sweat  .nd 
's^LrisglSaJe  numerous  within  '1- int^^^o  ,t^^^^^^^^^^  above  the 

^^^.^^:^:^^^^^^^ 

covered  with  hair.     The  subcutaneous  fatty  layer.  usuaii>  irom       •, 


i 


\\\ 


3033 


HUMAN   ANATOMY. 


Gtanl 
clitoridii 


PKpuiium 
clitoridii 
Frmulum 
clitoridii 


•omctinies  as  much  as  8  cm.  «>r  more,  »  supported  by  connective-tusue  septa  that 
pajw  from  the  underlying  peri.  ,teum  to  the  skm,  whereby  the  tension  of  the  L  ter  is 
maintained. 

,  ,.  '  ''*  ,'■*»'■  «n»nor«.  or  nymphs  (tabia  oiinora  padendi),  are  two  thin  folds  of 
delicate  skin  that,  for  the  most  part,  lie  concealed  between  the  larger  labia  unless 
the  latter  are  separated,  and  enckwe  the  vestibule.  Their  length  is  from  2.K--1  s  cm 
their  width  about  half  as  much,  and  their  thickness  from  3-5  mm.  Near  its  anterior 
end,  each  labium  divides  into  a  lateral  and  a  medial  limb  ;  the  lateral  divisions  of  the 
two  sides  unite  above  the  free  end  of  the  clitoris,  which  they  enclose  with  a  hood  the 
p-epu/tum  clitoridu,  while  the  medial  limbs  join  at  a.i  acute  angle  on  the  under  side 
of  the  ditoris  to  form  its/r<-«««  (freaulum  clitoridis).  Behind,  the  nympha  grad- 
ually  fade  away  by  joining  the  inner  surface  of  the  labia  m.ijora.  In  the  vifgin?  and 
when  well  developed,  the  medial  border  of  the  posterior  ends  of  the  nymphas  are  usu- 
ally connected  by  a  slight 
Fio  1706.  transverse   crescentic   fold, 

the  /tenum  or  fourchetlt 
(frtanlam  labionim  ptidendi) 
that  marks  the  posterior 
lx>undary  of  the  sliallow 
navicular  fossa  (Fig.  1706). 
Both  surfacesof  the  nymphae 
are  covered  with  delicate 
skin,  which,  on  account  of 
the  protection  afforded  by 
the  greater  labia  and  con- 
stan.  contact  with  the  vagi- 
nal secretions,  remains  moist 
and  soft  and  assumes  the 
color  and  appearance  of  a 
mucous  membtane.  The 
entire  absence  cf  mucous 
glands  and  the  presence  of 
numerous  sebaceous  folli- 
cles, on  the  inner  as  well 
as  on  the  outer  surface,  to- 
gether with  the  develop- 
ment of  the  nymphae  from 
the  margin  of  the  doacal 
fossa,  establish  their  cuta- 
neous character.  The  skin 
covering  the  nymphae  ex- 
ternally is  continuous  with 
that  of  the  labia  majora  at 

I  .1      ,     ,.        ,  the  bottom  of  the  interlabial 

turrow  ;  internally  the  line  of  transition  into  the  mucous  membrane  lining  the  vesti- 
bule follow.s  the  medial  attachment  of  the  folds  which  overlie  the  vestibular  bulb  In 
addition  to  the  two  cutaneous  layers,  the  nymphae  consist  of  an  intermediate  stratum 
of  loose  connective  tissue,  rich  in  blood-vessels,  and  containing  many  bundles  of  in- 
voluntary muscles  that  possess  the  character  of  erectile  tissue.  Hairs  and  fat  are 
entirely  wanting  in  the  labia  minora,  but  sebaceous  and  sweat  glands  are  present  the 
(WebstTr)  '^^'te''^  ^'U'  "lost  plentiful  in  the  anterior  part  and  in  the  prepuce 

The  vestibule  (vestibnium  vaginae)  is  the  elliptical  space  enclosed  between  the 
labia  minora,  extending  from  the  clitoris  in  front  to  the  cr  ntic  frenuin  behind 
When  the  nympha-  are  separated,  the  vestibule  resembles  i  .nond  in  outline  beine 
pointed  in  front  and  broader  behind.  In  the  roof  (as  usually  examined  the  9ioc^T^  of 
tins  space  arc  seen  the  urethral  and  vaginal  orifices  and  the  minute  openings  of  the 
paraurethral  ducts  and  of  the  canals  of  Bartholin's  glands.  The  urethral  orMce  occu- 
pies a  more  or  less  conspicuous  corrugated  elevation  (papilla  urethralis)  that  lies  about 


External  Kenital  organs  of  virgin :  lahia  haw  been  iwpinilcd  to  txtxKx 
vt-stibule  and  vaginal  orifice. 


mpp 


THE  LABIA  AND  THE  VESTIBULE. 


JOJ3 

papilla  to  the  frcnum  of  the  clitoris.  „,„,u„  ,-j  th^t  of    ...  vaeina  is  subject  to 

^^  The.vea  between  the  ont,ce..f  the  urehra  ana   hat  .^^^^^^^^^^^^         i„  the  extent 

considerable  inlividual  va"?*'""  '"^"^^fj'^i^^'^^rt^  encroaches 

to  which  the  lower  ^nd  of  the  «^tenor  v^irul^^^  ^^^  ^^     ^  ^„, 

upon  the  vestibule.  After  rupture  ot  ^^^/^^^  "^^^^,„^  that  turm  the  caruntu/o' 
is  surrounded  by  a  series  d  irregular  h^^"!^'^^.  'KsXuous  nodules.  InchuU-d 
kym.na/.s  which,  alter  l^^^^^' ^Xm^n  and  he  iTkwardly  directed  arching  fold 
^r  rich^r.^'tr/;rVa'«^^^^  r.'hl.low.  crescent^.  po.-Uet-,iWe  depres- 


Fio.  1707' 


CmtrmI  tol-body 


Labium  matus 


Labium  minut 


Ip-tr  ftiirfacc 


Sebaceous  glands  on  exi 
cutaneous  suriacea 


Intcrlabial  (roovc 


Section  acTOM  the  labia  oi  veiy  young  child. 


X  18. 


sion     This  recess  is  best  marked  in  the  virgin,  when  the  nymph*  are  well  developed. 

.„ais^usu^ly.^-dafjr^^^^^^^^^ 

posterior  labial  branches  '-m  the  external  and   in^^r^^^^^^  ^^^ 

^all  twig  from  the  »"?«'■««»  .^^^^^  Seen  ^ 

anterior  commissure  ;  several  ^^^'^.J^™/?  tuppS  by  the  posterior  labial  twigs 
half  of  the  labium,  while  the  posterior  haU  '*  *"P;P"7;,3i'^  di^^artery.  Additional 
from  the  superficial  Pe"«.^*l  branch  from  thy ntemapud^^^^^^ 

o  the  vestibule.     The  arteries  trom  tnese  varioy.      .  •       '{  tj,e  labia  ma  ora  in 

another  as  well  as  with  adjacent  vessels      Wh.le  the  ^^,«^^^^^^^^^  neighboring 

general  follow   the  con.esp»ndmg  arter.^^^^^^^^^  ,„„,!     ThI 

systems,  particularly  with  t]^?^"^;*'^^;"^ 'e  present  a  pkxiform  arrangement, 
;tX  tSl^ac^rtS^^^^^^^^^^  The  collecting  stems 


.■ 

(   i 


ma 

1 


1 


3034 


HUMAN  ANATOMY. 


join  those  of  the  labia  niajora,  as  well  as  communicate  with  the  veins  ol  the  clitoris 
and  bulb.  The  lymphatics  of  the  labia  are  very  numerous,  noubly  in  the  more 
superficial  parts  of  the  folds,  a  half  dozen  or  more  trunks  passing  to  the  upper  and 
medial  group  of  inguinal  lymph-nodes.  The  lymphatics  from  the  nympha,  also 
venr  numerous,  join  the  afierents  from  the  labia  majora  and  end  in  the  same  inguinal 
nodes.  Communications  sometimes  exist  with  the  nodes  of  the  opposite  sides 
(Bruhns). 

The  nerves  supplymg  the  anterior  half  of  the  labia  majora  are  derived  from 
the  ilio-inguinal  and  the  genital  branch  of  the  genito-crural,  while  the  posterior  part 
of  the  labia  receive  filaments  from  the  perineal  branches  of  the  pudic  and  the  small 
sciatic  trunks.  The  nymphse  are  highly  sensitive  and  receive  branches  from  the 
superficial  perineal  nerves  upon  which  special  sensory  endings  are  found  within  the 
subepithelial  tissue. 

THE  CLITORIS. 

The  clitoris,  the  homologue  of  the  penis,  repeats  in  reduced  size  and  modified 
form  the  chief  components  of  the  organ  of  the  male.  Morphologically  considered,  it 
consists  of  two  corpora  cavernosa,  united  in  front  into  the  body  and  separated  behind 
into  the  crura  attached  to  the  pubic  arch,  and  the  imperfectly  developed  and  cleft 
corpus  spongiosum— known  as  the  bulbus  vestibuli  and  usually  described  as  an  inde- 
pendent organ. 

The  clitoris  lies  so  buried  within  the  subcutaneous  tissue  and  beneath  the  labia 
that  only  its  small  conical  anterior  end,  called  the  glans  clitoridis,  and  the  low  verti- 

FiG.  1708. 


lorpus  clitoridit 
— Glans  clitoridit 


Pan  intermedia 
Urethral  orificC' 

Bulbui  vestibuli 
Vaginal  orifice 


Inferior  layer  ot- 
triansular  ligament 


■Cms  clitoridis  curved 
by  ischio<avemostta 
muscle 

-Cut  edge 


Compressor  buibi 


Tnnsvenus  pcrinei 


Disttction  of  urogenital  triangle  of  female,  showing  clitoris  and  bulbus  vestibuli. 

cal  ridge  of  integument  over  the  body  (torus  clitoridis)  appear  when  the  labia  are 
separated.  The  glans,  about  5  mm.  in  diameter,  is  partly  concealed  by  an  annular 
duplicature  of  skin,  the  prfputium  clitoridis,  that  is  free  in  front  and  at  the  sides,  but 
behind  is  attached  by  a  median  fold,  the  frenum,  continuous  with  the  nymphae. 
When  exposed  after  removal  of  the  labia  and  skin,  the  clitoris  (using  the  term  in  the 
more  restricted  and  conventional  sense)  is  seen  to  consist  of  the  small  unpaired  body 
(corpus  clitoridis),  from  2  to  2.5  cm.  long,  composed  of  tiie  fused  corpora  cavernosa, 
and  the  diverging  and  much  larger  crura,  from  3.5-4  cm.  in  length,  that  are  attached 
to  the  sides  of  the  subpubic  arch,  as  are  the  corresponding  parts  of  the  penis.  The 
crura  clitoridis  are.  however,  relatively  flat  and  blunt.  The  dependent  body  forms 
.-»  sharp  bend  with  the  diverging  crura,  being  fixed  to  the  lower  part  of  the  symphy- 
sis pubis  by  a  diminutive  suspei  sory  ligament.     Owing  to  its  attachments  to  the  in- 


THE  CLITORIS. 


J025 


change  even  in  the  turgescent  «''«^7"^' SeirJSuced  size  and  feebler  develop- 

the  corpora  cavernosa  chtc«id«  »Ifl'„'?'"i„Sng  cylinders  of  erectile  tjssue  en- 

ment,  correspond  with  *««=  "^Lo^"^  where  blendW  by  a  septum.     The  glans 
closed  by  a  tun.«^gine«  and  seated w^      ^^^  ^^^^^  ,.^^^  ^^^  ^,„„„„, 

however,  is  composed  chiefly  «  ,J^^by  the  urethra. 

rtructure:  it  i^^««  «=^"f;,^°i»^Th^  vestibular  bulb  consists  of  wo  converging 
The  Bulbus  Ve«tibuU.-l  Ije  ^««o"         separated  except  in  front,  where 
elongated  ™-ses«f  cavernous  ^««^^^^ompk»^^^^^  V  ^1!?*'^=''='=,  S'e 

they  are  connected  by  a  "'JT^^.i^'^^d  anteriorly  meet  the  under  surface  of  A^^ 
lower  end  of  the  vag..«  and  the  "«»»^I*;,^Vas  above  noted,  represents  the  bulbar 
cavernous  bodies  of  the  ditons.  The  ^^^'^,  ^j  j^  ^^e  component  parts  have 
TndTdjoin.n^  parts  of  the  corpus  »I«"P«um^*J^«:h^^  uro^nital  cleft  each 
remained  ununited  in  «>"«^Xof  he  un^T^  s-^ructure  in  the  male.  Each  bulb 
half  corresponding  to  a  semAm  b  of  ^^  ™  .  ^ody.  narrow  in  front  and  broad 
regarding  the  organ  as  paired,  is  »  rf^^^J?*^  ;„  length,  where  broadest  from 
a^  rounded  behind,  that  measures  from  3  4  cm.j^  ^^^  -^  ^ests  against  the 
,-,.5  cm.  in  width,  and  leM  »»»»"  '  ^m  'y^^^^T^^rgin,  somewhat  medially  di- 
inferior  layer  of  the  trmgular J^e^^^  Sb  um  ^jus  and  the  nympha.  Behind 
reeled,  being  covered  by  the  base  of  the 'aDwmmaj  ^  entrance,  and 

Ae  m^ial  surface  is  closely  /«»^»?2;«J^^ '^"g  Jthe  posterior  wall  of  the  vagina, 
when  well  developed  may  "^"^ Jf  ^.S^^urethra^nd  joU  the  under  surface  of  the 
In  front,  the  bulb  pa»«  at  ^e  s  de  of  the  uretnra  a      )  bulbo-cavemosus  mus- 

spongiosum,  although  1«8  ^«fi""* '" in^the'ditoris  and  vestibular  bulb  correspond 
^  Vessels.-The  arUrifs  supp  ymg  the  ciiioris  a  ^^^^^^  ^^^ 

withThose  dismbuted  to  the  homologous  ^^J^"*  J^^^^^j^e  (s  V  artery  of  the  bulb 
As  in  the  male,  the  fijf^t  branch  to  the^vemo  ^^^  ^^^  ^  ^  short  and 

(a.  bttlbl  VBitibuU).  winch  enters  that  PP^V  [^^J^  .  ^  ^^  the  bulb  from  the  deep 
J^mparatively  strong  vessel  and  ]o.n«wrAa<Wumaltw^^  ^^  ^^^  ^ 

artery  of  the  clitoris  (a.  pr"/-"*"' ^      g^^.i^^^av^no^^ 

artery  passing  to  the  pa«  '"^^^^famiSteS  backward!  traverses  the  cylinder  of 
that  enWs  the  cms  and  ^"^'"^  *  !™""^f  3  ^■,^^,  ^s  fellow  of  the  opposite  side 
erectile  tissue  towards  the  ^•''"^y^r^Ss  ^KteV     ^h^  '^"^^-  '^^  *^'™'"^'  ^"^ 

The  veins  follow  the  K^n^ralarrsmgement  observed  m  ^^^^  ^^^^^ 

carried  off  chiefly  by  the  dorsdjem  and^the^e^^^^^^^^       .^  ^^^  ^  , 

accompany  the  arteries.     The  most  »'"PO"r'u.v  that  lies  between  the  under  surface 
'';u:Tilrmedius  (Kobelt)   »  -nou^rnple-  thj^^^^^^^^^^  ^^^  ^,        i  ^ 

of  the  corpora  cavernosa,  jus   ^jbey  3"^\^bX   This  plexus  not  only  establishes 
anterior  ends  of  the  halves  of  the^lbusvestmun.  ^^;,,ernosa  and  the  bulbus 

connections  between  the  blcK^-'P*^?^  ° 'uf orS^e  and  frenum  of  the  clito 
vestibuli.  but  also  receives  tnbutar«  from  the  ^^^^^^^  ^^  ^^^  ^^^^^  that  join 

nympha.  and  the  adjacent  mrts  of  the  vestibule,     in  communicate  with  the 

the  Internal  pudic  veins,  tlie  cavem''"^^  J//,"''  in  consequence  of  the  connections 
S'je^n  ^!^:::'\r!:::^:S^^^'^^^^  -in  of  thl  clitoris,  the  latter  vc^se. 

nodes:  communications  exis.  however  «th  the  deep^^^^  correspondence  with 

The  nerves  o   the  chtons  are  derned  and  d.str  j^^i^  ^^e  sympa- 

S^tif s^^^S^'the  eXI  the'tLd^rparlndfrom  the  pudiC  nerves.     The 


n 


M' 


2026 


HUMAN  ANATOMY. 


_  Dorsal  nerve 

CorpuielitoridU  Dorial  artery,     /  Artery  of  balb 

GlaiM   clitoridia     \  /    /  /  ^         . 

.Cms  of 
clitorja 
pulled 
upward 


iiShr!I7  '"  relatively  large  and  supplies  the  integument  of  the  glans  and  prepuce 
with  fibres  connected  with  special  sensory  end-organs.  ^ 

THE  GLANDS  OF  BARTHOLIN. 

ro«,i!?r^«fSt  ?\^^^t^  fglandulae  vestibulares  majores),  the  homologues  of 
Cowper  s  glands  in  the  male,  are  a  pair  of  small  organs,  situated  one  on  either  side 

0  the  vaginal  onfice.  behind  the  bulbus  vestibuli  and  about  the  midXol  the  £ 

ll  tJTniTm'"!"  wiH^h'''  ""T  "^"^Z^  ''■'^'"  -'-5  ""•  i"  '^g"*  and  somew^ 
less  than  i  cm.  in  width  and  is  covered  on  its  anterolateml  aspect  by  the  bulbo- 
cavemosus  muscle  and,  often,  also  by  the  end  of  the  bulbus  vestibuli.  Ite  suSr 
surface  lies  against  the  inferior  layer  of  the  triangular  ligament,  and  ite  nSid  K 

1  cm.  external  to  the  vestibule,  from  which  it  if  sepailTed  b;  dense  fibrouTtSe 
From  the  anteromedial  border  of  the  gland  emerges  the  ductf  a  narrow  X  Sut 

waTllSr?£l'fr^  'fT  '-^-^  r-  '°"^'  ^•'«'  P^  ^'''•^"'^'y  inward  and  for! 

ward   beneath  the  base  of  the  nympha,  to  open  in  the  groove  between  the  latter  and 

the  hymen  about  opposite  the  posterior  third  of  the  kteral  boundary  of  die  yap^ 

P  nal  orifice.    The  minute 

■     '*^*        "— -• opening  of  the  duct,  from 

.5-.  6  mm.  wide,  is  often 
at  the  bottom  of  a  small 
depression  in  the  mu- 
cous membrane  of  the 
vestibule. 

In  structure  the 
gland  corresponds  to  the 
mucous  ;tubo  -  alveolar 
type,  the  small  compo- 
nent lobules,  however, 
being  separated  by  con- 
siderable tracts  of  fibro- 
mWular  tissue.  The  ter- 
minal compartments  are 
lined  with  columnar  epi- 
thelium containing  many 
goblet  cells.  The  lobular 
ducts  unite  to  form  the 
single  e-xcretory  canal, 
,  ,,.  ,         ^,  which  is  beset  with  mi- 

nute mucous  follicles.     The  main  iuct,  which  sometimes  exhibits  ampullary  enlarge- 
ments, IS  Clothed  with  columnar  epithelium  until  near  its  termination,  where  its  lining 
becomes  stratified  squamous  in  character,  to  correspond  with  that  of  the  vestibule 
I  he  secretion  of  the  gland  is  whitish  in  color  and  viscid. 

t,  iu^*if' **  l".^*^*^  arteries  supplying  the  gland  are  usually  twigs  given  off  from  the 
t)ulbar  branch  01  the  internal  pudic.  The  veins  are  tributary  chiefly  to  the  internal 
pudic  but  also  communicate  with  the  trunks  of  the  vestibular  bulb  and  of  the  vagina. 
The  lymthaiics  join  those  of  the  vagina  and  rectum  that  are  afferents  of  the  internal 
ihac  no<ii-s.  It  is  probable  that,  to  a  limited  extent,  communication  also  exists  with 
the  paths  ending  in  the  superficial  inguinal  nodes. 

The  nerves  are  very  numerous,  and  include  sympathetic  fibres  and  twies  from 
the  puoir.  *" 

Development.— The  glands  of  Bartholin  first  appear  in  embryos  from  4-5  cm. 
long,  ;is  solid  epithelial  outgrowths  from  the  lateral  walls  of  the  urogenital  sinus.  At 
first  simple  cylinders,  they  later  become  branched,  acquire  a  lumen  and,  in  embryos 
\i^  «^~'^  '^'""  '"  ''^"S:th,  begin  to  exhibit  alveoli  lined  with  mucus  secreting  cells 
(V  MuUer).  Although  fully  developed  at  birth,  the  glands  remain  small  until  near 
puberty,  when  they  enlarge,  acquiring  their  greatest  size  during  the  years  of  sexii.il 
activity.  After  the  cessiition  of  menstruation  they  gradually  diminish,  and  are 
atrophic  in  the  aged  subject. 


Ri^t  lobe 
of  b 


Inferior 
L-iyer  of 
triangular 
ligament 


tilaudaof  Bartholin 


Dissection  of  urogenital  trianfrie  of  female;  left  lobe  of 
vestibular  bulb  baa  been  removed. 


THE    MAMMARY   GLANDS. 


3027 


both  sides. 

PRACTICAL   CONSIDERATIONS  :    THE  EXTERNAL  GENITALS. 

Owing  to  the  Prot^ted  portion  «^  t::^l^^^:^^y'^^ 
tears  in  childbirth.  When  »f '«^^  *!,'''" /^%"^' J' bVo".s,  or  of  wound/ inflicted  by 
the  result  of  falls  astnde  h^^J^g-^'^f  ,J;'^^>  ^L  ^^^^  ihe  free  blood-supply  in  the 
horned  cattle.      Because  of  ^he  'axity  01  n  e  ^     ^^^^^^  vest.buli  «s 

labia  majora  >?r«e  h^rnatomata  ^^  t^^^'^J;,  7;:i^d\oose  tissue  in  this  region, 
opened.     Again.  heca"«e  of  the  free  "^^  JP  V        hemorrhage  is  free,  but  ord.- 
plastic  operations  are  ^o?^^"^^^'^  ere/t^  tissue  of  the  clitoris  or  its  continuations 
narily  stops  spontaneously  unlesa  tne  erecuie  i.» 
backward,  the  bulbus  vest.buh.  «  r'""^^^^  ^„  .^e  groin,  thus  explaining  the  en- 

The/j/«Ma/^^andr«»«oftheWva^^^^^  nguinal  nodes,  such  as 

ih-'S.  'a^Snls-  S-t^.  ;^Vlr;elf  '  About  L  oHfice  of  the 
vagina  is  a  zone  in  which  the  two  sete  '"J^'-^'^i^^^^^  .^^etion  within  the  glands 
Cysls  of  the  vulvaare  '^o"™'"^"  y,f "^  *? 5^'Hach SdeTthe  vaginal  orifice,  and 
of  Bartholin.  They  occupy  the  P«*7;°r,\^'"*  ""Jn^^fs^^^^^^  These  glands  are 
project  more  from  the  mucous  f^jT^^^  ST^hJ^orrhe^\M.c6ou.  The 
often  the  seat  of  abscess,  almost.  'J  "f  ^^  ^  '  j^^  if  is  nearest  to  the  vaginal 

female  urethra,  running  '^^^^^^'i^XiS  "c**  ^^'^'^'  '^'^"''^'^  '""''''  *''^^''' 
wall  in  its  upper  P<>rt'°"T«  T ^Jf^^:  bHttSrof  such  density-much  more 
and-as  it  is  not  surrounded  at  ''^  P^'^^^^y/^^^^^^^  j^,  shortness,  its  width,  the  direc- 
dilatable  than  the  male  urethra  '"  '=°"^"^'^f„„  ^^  serving  as  a  passage  for  urine, 
tion  of  its  course   and  the  l>™t*»'°"  "^ 'f„S  l^Veq^  andits  inflammation 

,t  is,  as  compared  with  the jna^e  uretfi^.  '"I^jf^^/;,^,^^     >o  treatment,  and  gives 
,s  associated  with  less  severe  ^y"?*"™^' JTiiLVre  for  example,  being  very  rare, 
rise  to  fewer  complications  a«dseguel^-^tnm^^^  ?     exploration 

As  a  result  of  its  d«latab.lity  it  may  be  u^  SlcuU  or  pedunculated  tumors,  if 

THE  MAMMARY  GLANDS. 


3038 


HUMAN   ANATOMY. 


and  separate  glands,  opening  by  independent  ducts,  that  collectively  constitute  the 
true  secreting  organ  (corpas  mammae),  as  distinguished  from  the  enveloping  layer  of 
tat  and  areolar  tissue. 

As  seen  in  the  young,  well-developed  subject,  before  the  occurrence  of  preg- 
nancy, the  mammae  form  two  hemispherical  projections  that  lie  upon  the  thoracic 
wall,  one  on  either  side  of  the  sternum,  extendmg  from  the  outer  margin  of  the  latter 
to  the  axillary  border  and  from  the  level  of  the  second  to  that  of  the  sixth  rib.  The 
oudine  of  the  organ  is  not  quite  circular  but  elliptical,  the  horizontal  diameter,  from 
IO-I2  cm.  (4-4^  in.),  being  about  one  centimetre  more  than  the  vertical.  The 
height  of  the  projection  measures  about  5.5  cm.  The  rounded  contour  of  the  breast 
depends  chiefly  upon  the  fat  that  forms  a  complete  envelope  for  the  glandular  tissue 


KiG. 


1710. 


Areolii 


Lohiile  oi  gland-tissue 


Fxrretory  duct 


Nipple 


Ampulla 
l.actiferous  duct 
Lift  mamma  drawn  from  living  subjct ;  ilucls  and  jclandular  tissue  have  lie.ii  drawn  (roni  ilisseilimi. 


except  beneath  the  nipple  and,  in  places,  on  the  deep  muscular  surface.  In  the  young 
subject,  in  whom  the  gland  has  ne\er  enlarged  in  consequence  of  pregnancy,  the  secre- 
ttiry  tissue  is  relatix  ely  small  in  amount  and  masked  by  the  fat  that  penetrates  between 
the  lobules.  The  approximate  summit  of  each  breast,  when  firm  and  non-pendulous 
as  in  young  women,  is  marked  by  the  conical  or  wart-like  >upp/e  (papilla  mammae), 
which  lies  opposite  the  lower  border  of  the  fourth  rib  and  is  pierced  by  the  excretory 
canals,  or  lactiferous  ducts,  from  the  lobes.  The  nipple,  about  1  cm.  high,  and 
marked  by  numerous  shallow  furrows,  is  surrounded  by  the  areola,  a  cutaneous  zone 
about  4. 5  cm.  in  diameter  that  is  modelled  bv  minute  low  elevations  produced  hv  the 
small  subcutaneous  areolar  glands,  or  glands  of  \fontgomery,  which  represent  isolated 
accessory  portions  of  secretory  tissue.     Although  varying  with  the  complexion,  the 


THE  MAMMARY   GLANDS. 


2039 


which  not 


Fig.  »;««• 


Siupen<or>'  faai 


PectonI  muK 


SSc,  the  oolor  ol  tl»«  part.  »  "f."^  C-m^  t,.  lJ~..   i"  varying  .hade,  ol 

isrjl;rrir;/,h?J-"  e'.Siy-'ss^.rs.  b„.w™»  te™,„™n, 

'"'■"Tt1,2X''.£nirr»i.hi„  .he  ...pcrtida.  la«U  o,  .he  ,«, 

only  forms  a  general  investment  for  the  or- 
gan, but  also  sends  into  it  septa  that  mate- 
&  aid  in  supporting  the  fat  and  glandular 
issue.  Local  Spheral  th.ckenmgs  of  he 
fascia  occur  above  and  below  and  assume  the 
character  of  suspensory  bands  those  above 
being  known  as  the  ItgofMnis  of  ^r^ 
Although  for  the  most  part  separated  fmrn 
the  underlying  muscle  by  a  layer  of  fascia  U«t 
permits  of  shifting  of  the  mamma.  «ts  deepest 
lobules  may  occupy  recesses  between  the  fas- 
ciculi of  the  pectoralis  major. 

Structure.— The  corpus  mammae  con- 
sists of  from  15-20  or  more  flj"e"ed  pyrami- 
dal lobes  (lobi  mammae),  each  of  which  ma 
distinct  gland  measuring  from  1.5-2  cm.     1  he 
lobes  are  radially  disposed,  the  groups  of  al- 
veoli or  lobules  lying  towards  the  periphery 
and  the  excretory  ducts  converging  towards 
the  nipple,  upon  which  they  open.     When 
enlarged,  as  during  lactation    the  lobes  pro- 
duce irregularities  in  the  outline  and  on  the 
surface  d  the  gland-mass  that  may  be  felt 
through  the  covering  of  adipose  tissue,     bach 
lobe  B  subdivided  by  connecUve  tissue  mto 
several  lobules  (lobuH  mammae),  which  in  turn 
are  made  up  of  the  ultimate  divisions  of  the 
s^reting  tissue   or  alveoli.      The  latter  are 
sacular  compartments,  the  walls  of  which  con- 
sist of  a  well-defined  membrana  propna,  or 
basement  membrane,  lined,  •"  the  resting  con- 
dition, by  a  double  layer  of  cells.      Those 
next  the  membrana  propna  are  probably  to 
be  regarded  as  muscular  in  nature  (Lacroix, 
Benda),  thus  emphasizing  the   resemblance 

^r^"  ^^uTTe'^rW  elfment^are  cuboid  or  low  columnar,   from  .005- 
i„,erveni,/con„ecti.e  feue  com»pond„,8ly  ■jf^u?  often  r^^U^.hi'^^rS 

ti'  ffin=rcoSsi,ThrSc"Sni  ss.  -;  £.|.<^^- °*  ^^e 

-  ^^^^XrJt^t-L  tSr  etSfTo  which  .he  aWeoU  open. 


never  borne  children  ;  hardene.1  in  lormalin. 


2030 


HUMAN  ANATOMY. 


'Excretoiyduct 


Involuntao' 
musck- 


Section  of  mammary  gland  before  lactation,    x  170. 


At  first  tiiey  are  small  and  much  like  the  terminal  compartments  of  the  eland  and 
imed  with  a  thm  stratum  of  longitudinally  disposed  involuntary  muscle,  upon  which 
reste  a  smgle  layer  of  cuboid  epithelial  cells.     The  latter  give  place  to  cells  of  col- 

umnar  type  within  the  lactiferous 
i-io.  i7it.  ^„^/j  jjjgj  g^p  formed   by  the 

junction  of  the  smaller  canals. 
On  approaching  the  base  of  the 
nipple,  beneath  the  areola,  each 
milk-duct  presents  a  spindle-form 
enhrgement  or  ampulla  (sinus 
lactiferus),  from  10-12  mm.  long 
and  about  half  as  wide,  that 
serves  as  a  temporary  reservoir 
for  the  secretion  of  the  gland. 
Beyond  the  ampulla  the  duct 
narrows  to  a  calibre  of  little  over 
2  mm.,  passes  into  the  nipple, 
and  ends,  after  traversing  the  lat- 
ter paiallel  with  the  other  ducts, 
in  a  minute  orifice  from  .5-.  7 
mm.  in  diameter,  at  the  summit 
of  the  papilla.  On  gaining  the 
last-named  point,  the  lining  epi- 
thelium of  the  duct  assumes  the 
stratilied  squamous  type  of  the 
adjacent  epidermis.  Embedded 
,..,.,  within  the  de'xate  but  more  or 

less  pigmented  skm  that  covers  their  exterior,  the  areola  and  nippl'  contain  well- 
marked  bundles  of  involuntary  muscle,  by  the  contraction  of  which  the  nipple  becomes 
erect  and  prominent,  as  after  the  application  of  mechanical  stimulus.  Within  the 
areola  this  contractile  tissue  forms  a  layer,  in  places  almost  2  mm.  thick,  that  encircles 
the  base  of  the  nipple  and  is  continued  into  its  substance  as  a  net-work  of  bundles, 
between  which  the  lactiferous  ducts  pass.  Deeper  longitudinal  strands  of  unstriped 
muscle  occupy  the  axial  portions  of  the  nipple. 

Over  both  areola  and  nipple  the  skin  is  provided  with  large  sebaceous  glands,  the 
secretion  of  which  is  increased 

during  lactation   and   designed  Fig.  1713. 

II  ir    protection   while    nursing.  . 

Sweat-glands  are  absent   over  -"^ '  "  "■ 

the  nipple,  but  large  and  modi- 
fied in  the  vicinity  of  the  perijih- 
ery  of  the  areola.  The  .surface  of 
the  latter  is  modelled,  esjiecially 
towariis  the  close  of  pregnancy, 
by  low  rounded  elevations  thiit 
indicate  the  positions  of  the  sub- 
cutaneous areolar  or  Montgom- 
ery s  glands.  The  latter  are 
rudimentary  accessory  masses  of 
glandular  tissue,  from  1-4  mm. 
in  diameter,  that  correspond  in 
their  general  structure  with  that 
of  the  mammary  glands.  Their 
ducts  open  by  minute  orifices 
on  the  surface  of  the  areola. 

Milk. —The  fully  estab- 
lished .secretion  of  the  mammary  gland  ( lac  fcmininum)  is  an  emulsion,  the  fattv  milk- 
globules  being  suspended  in  a  clear,  colorless,  and  waterv  plasma,  the  variations 
in  tint— from  bluish  to  yellowish-white— depending  upon  the  amount  of  fat.     The 


Section  of  mamman-  fland  durini^  lactation.  shnwinR  tlistendcd 
aJvpiiii  lintMl  with  fat-lK-arins  cells.      ■:  170. 


THE  MAMMARY   GLANDS. 


2031 


composition  of  human  n.uic  includes  over  86  per  c.nu  o«jate  .^^"'  \t*S  m^ 

subsmces,  5.3  of  fat.  5  of  sugar.  «^d J;^,;'^i"^Jj;^/S  d  Jpl^t?^  from  the 

phological  constituents  dm.lk  are  the  mMo^^^^^  ^^^     ^^.^^^ 

alveolar  cells),  that  vary  m  sixe  from  the  «"«•""*"";«  jP"*"  ^^j^^  ^  „uch.     Their 
diameter  of  from    ooj-.^os  mm^and    exc^P^^^^^^^^^  ^B^„,,^. 

r^jnroni;i^Str  1^^^^^^^  2^  •-.  the  ce..  already 

emulsiiie<l.  are  also  questions  undecided.  ^     j^^  termina- 

During  the  last  weeks  of  pre^cy  ^"^  JS  .^^^^''J^^^^  ,2strum,  that  differ, 

tion.  the  breasts  contain  a  c  ear  watery  ^"^J^'^X^^,  conspicuous  bodies-the 

from  milk  in  contaimng  '^^'^^^y^'^l^^^,^^   ThLe  bodies  aVc  usually  spherical. 
ca/ostrumcorpusc/es-<yi  uncauxnlormmjisxze^^  although  they 


Fig.   i7'4- 


■\ 


-03 

%. 


Humin  milk.    X  S». 


-N 


Colostrum,  showing  corpuKlel 
and  oil-drops.    ;■  500. 


for  months  or.  in  exceptional  cases,  for  even  years.  .„^..     j,    jhe  second,  third, 

A7.a>*U The  arteries  supplying  the  mamma  are  pnncipuuy  n^  . 

deeper  ones  surround  the  gtoups  ol  aheoU  as  =''»X„  ,h„  idn  the  tieh  sutareolar 

£f^"T&e^1,r^«=tfc*^^^^^ 

w»k.  that  drain  the  integument  covering  the  n.ppic  and  areola.     With  the  e«eept.o» 


'     11 


\{\ 


lllr, 


2032 


HUMAN  ANATOMY. 


of  a  few  trunks  that  follow  the  perforating  arteries  and  become  afierents  of  the  lymph- 
nodes  lying  along  the  internal  mammary  artery,  all  the  lymphatics  of  the  breast  join 
to  form  two  or  three  large  trunks  that  pass  from  the  lower  and  lateral  border  of  the 
organ  through  the  subcutaneous  tissue  towards  the  axilla  to  empty,  sometimes  united 
into  a  single  stem,  into  the  lymph-node  that  lies  upon  the  serratus  magnus  over  the 
third  rib. 

The  nerves  supplying  the  glandular  tissue  are  from  the  fourth,  fifth,  and  sixth 
intercostals,  the  accompanying  sympathetic  fibres  passing  by  way  of  the  rami  com- 
municantes  from  the  thoracic  portion  of  the  gangliated  cord.  Their  ultimate  distri- 
bution may  be  traced  to  the  plexuses  upon  the  t«sement  membrane  surrounding  the 
alveoli  and,  according  to  Arnstein,  even  between  the  secretory  cells.  The  cutaneous 
nerves  are  derived  from  both  the  supraclavicular  branches  of  the  cervical  plexus  and 
the  anterior  and  lateral  cutaneous  branches  of  the  second  to  the  fifth  intercostals. 

Development. — The  arrangement  of  the  several  pairs  of  mammarv  glands 
possessed  by  a  majority  of  the  lower  animals  in  two  longitudinal  rows  is  foreshadowed 
m  the  earliest  stage  of  the  development  of  these  organs,  so  characteristic  of  the  highest 
class  of  vertebrates  (mammalia).  A  linear  thickening  of  the  ectoblast,  known  as  the 
milk-ridge,  appears  as  a  low  elevation  that  extends  obliquely  from  the  base  of  the 
fore  to  the  inguinal  region.  Along  this  ridge  a  series  of  enlargements,  later  sepa- 
rated by  absorption  of  the  intervening  portions  of  the  ridge,  indicates  the  anlage  for 
a  corresponding  number  of  mammae.  The  occurrence  of  a  definite  milk-ridge  in 
the  human  embryo  is  uncertain,  although  its  presence  has  been  observed  (Kallius), 
and  the  {x>sition  of  supernumerary  mammse  suggests  its  influence. 

In  man  a  knob-like  thickening  of  the  ectoblast  appears  during  the  second  month 
n!  foetal  life.  This  thickening  sinks  into  the  underlying  mesoblastic  tissue,  which 
undergoes  proliferation  and  condensation  and  forms  an  mvestment  for  the  growing 
epithelial  mass.  From  this  envelope  the  fibrous  and  muscular  tissue  of  the  areola 
and  nipple  are  derived,  while  the  subjacent  mesoblast  produces  the  connective-tissue 
stroma.  The  ectoblastic  ingrowth  represents  a  sunken  area  of  integument  that  in 
principle  corresponds  to  the  marsupial  pouch  of  the  lowest  mammals  (.tnonotremes). 
Solid  epithelial  sprouts  grow  out  from  the  sides  of  the  coniral  or  flask-shaped 
epidermal  plug  and  are  the  first  anlages  of  the  true  mammary  gland,  later  becoming 
the  excretory  ducts.  Subsequently  the  central  part  of  the  ectoblastic  ingrowth 
undergoes  degeneration  and  destruction,  and  what  at  first  was  an  elevation  now 
becomes  a  depression  of  the  surface.  From  the  middle  of  this  depressed  area  there 
appears,  shortly  before  or  immediately  succeeding  (Basch)  birth,  an  elevation  that 
later  becomes  the  nipple.  Meanwhile,  the  epithelial  duct-outgrowths  penetrate  the 
surrounding  condensed  mesoblastic  stroma,  in(!rease  in  length,  subdivide,  and  acquire 
a  lumen  at  their  expanded  distal  ends,  thus  giving  rise  to  the  system  of  ducts  and 
the  lobules  of  imm^nre  gland-tissue.  With  the  further  development  of  the  latter, 
the  surrounding  m'  .oblastic  stroma  is  broken  up  into  the  interlobular  septa  and 
fibrous  framework  of  the  corpus  mammx. 

At  birth  the  gland  is  represented  by  the  lactiferous  ducts  with  their  ampullae,  the 
smaller  ducts,  and  the  immature  alveoli.  Quite  commonly  the  mammary  glands  in 
both  sexes  are  the  seat  of  temporary  activity  during  the  first  few  days  after  birth,  the 
breasts  yielding  a  secretion  resembling  colostrum,  popularly  known  as  "witch-milk." 

The  mammae  remain  rudimentary  during  childhood  until  the  approach  of  sexual 
maturity,  when  they  increase  in  size  and  rotundity  in  consequence  chiefly  of  the 
deposition  of  fat.  The  full  development  of  the  true  gland  is  deferred  until  the  occur- 
rence of  pregnancy,  when  active  proliferation  and  increase  in  the  gland-tissue  take 
place  in  pre[>aration  for  its  functional  activity  as  a  milk-producing  organ.  After  lacta- 
tion has  ended,  the  mammae  undergo  regression  or  involution,  the  glandular  tissue  being 
reduced  in  amount  and  returning  to  a  condition  resembling  that  existing  before 
pregnancy.  With  the  recurrence  of  the  latter,  the  gland  again  enters  upon  a  period 
of  renewed  growth  and  preparation,  to  be  followed  in  time  by  return  to  the  resting 
condition,  in  which  the  .imount  of  glandular  tissue  is  incon-spicuous.  After  cessation 
of  menstruation  the  mammary  gland  gradually  decreases  in  size,  and  in  advanced 
years  the  corpus  mammz  may  be  reduced  to  a  fibrous  disc  in  which  gland-tissue  is 
almost  entirely  wanting. 


PRACTICAL  CONSIDERATIONS:    MAMMARY   GLANDS. 

1     ^1 t..!*    Uai 


2033 


SSTof  DolvthelU  inJnen.  a*  •nn«»«4fi^.5fTte  o^Jlirrence  of  rudimentary  supe™""*'*! 

PRACTICAL   CONSIDERATIONS:    THE  MAMMARY  GLANDS. 
The  sUin  coveHn.  the  ^^^^'^ t^t^^t'^^^^'rft^^^^ 

mary  region.     The  frequent  °5f  "f^^^^e  .^^^o  tSrt  that  most  mothers,  being 
larger.  «  said  ( WiUi^™)  P'o^ably  to  t«  d^^^^  ^.^  ^^  ^  „„  ^„  ^^er- 

ri^t-handed.  sucVde  ?»"«f V /'^^t^'VitSe  pdvic  sexual  organs,  more  prone- 
a|e  heavier,  more  >«;t"»»»^L"?^  S  The  sSt  of  carcinoma  or  other  neoplasms, 
tf  hyP«^°P»'yu'"f  jrS^^lL  u^n  the^eath  of  the  pectoralb  major  muscle. 
The  greater  part  o  the  br«st  li«  "P°"  »  ;  ^^^^^^  tissue  being  extremely  ax. 
on  which  it  is  «r«  y  ™o^"fi  howevtf  extends  beyond  and  below  the  axillary 
About  one-third  of  the  gland.  •»°**=X'''  r,;!"  ;„  .u  '  axilla  with  the  serratus  mag- 
Sorderof  the  pectondis  nuj>r.  and  «  m  ^dat^n^^^^^^^  ^^l 

nus  and,  when  large,  *"V^  °"f "  ^' J^'S  miLle.  it  al*>  moves  slighdy  with 

the  normal  breast  "loyes  fr^Y  «ver  *«^?„«4  J^3:tio„  of  the  breast,  or  ^er 

it  when  the  muscle  «  «>nt^~;j  ^^mu^le  should  be  kept  at  rest  by  bmdmg 

operation  up«n  .t  or  ^r  tttremov^.  ^^^^^  ^^^^^^^  of  the  breast  to  the  pec- 

the  arm  to  the  side.     In  «'^"«£'bS^in  the  direction  of  the  fibres  of  the  pecto- 

Su  S'"  Wrf  rovrt'n.S:S^^lo  them,  it  may  carry  the  relaxed  muscle 

^t'hS  no  diminution  of  ability  wJlb^nuW^^^^  .,  ^^  ^ 

In  examining  for  PO*'*"  °*  Jr^'^J' w  and  may  be  mistaken  for  tumors. 

enlarged,  may  be  felt  ^ro^K^j^'t^^St^  wU^^^^^^^        hLd.  which  should  gently 

To  avoid  th.s,  the  gland  should  be  pa  pated  ^^^^^  ^^        p, 

comp  -ssit  agamst  *« ^^^'^^J'"^^  "J'"  resistant  and  more  promment  than  the 
may  i  recogn  zed,  <«  *7>*=^,'^^,tnhouW?^  thus  examined  at  the  same  time, 
normal  gland  t«sue.  .  J'^^  V^o^'^J^^g^tence,  or  sensitiveness  may  be  detected, 
so  that  any  difference  m  their  ?^^' "'""'^^^^^  j^  found  over  the  fourth  intercostal 
The  nipple  va  men  and  ^^y«"^^f  J.'JJ^^ers  of  an  inch  external  to  the  costo- 
space,  or  over  the  fifth  7^'  *^";  '  ;.f  o^itfon  is  not  constant,  and,  of  course,  it 
chondral  junction.  In  "^^l  ^X"emenriaxn^^  and  pendency  that  follow  preg- 
^  rd\£  a^r^cTmln  tntor^of-tn^pical  lands  and  in  negresses  and  women 
of  other  of  the  lower  ra<«s.  arrested  at  the  stage  when  the  central 

•  Anatom.  Anzeiner.  Bd.  vii.,  i^jt.  -^  Ergebrisse d.  Anat.  n.  Entwidc.. 

'  An  intetesung  review  of  the  suDjeci  is  given  uy 

Bd.  ii.,  189a.  „8 


w 


ao34 


HUMAN  ANATOMY. 


exists  towards  the  bottom  of  which  the  ducts  of  the  mamma  converge.  In  such 
casa  die  depression  persists  ;  in  others  the  areola  is  present,  but  the  nipple  absent 
In  both,  while  lacution  may  be  normal,  the  suckling  of  children  is  impossible.  The 
nipple  may  be  absent  or  defective  as  a  result  of  trauma  or  of  disease— wouiub,  burns, 
ulcers,  abscesses — during  uifancy. 

The  normal  nipples  of  virgins  or  nullipara:  may  be  almost  on  a  level  with  the 
areola,  whde  those  of  multipara  are  often  greatly  elongated  from  the  traction 
u[x>n  them.  Temporary  elongation  or  erecbon  of  the  nipple  may  be  caused  by 
reflex  stunulation  of  the  unstnped  muscular  tissue  of  the  skin  of  the  nipple  and 
areola.  "^"^ 

Infection  of  the  nipple  is  common,  because,  on  the  one  hand,  of  the  many  folds 
of  Its  delicate  cutaneous  covering,  containing  a  number  of  sebaceous  glands  and 
closely  connected  to  the  underlying  structures  ;  and,  on  the  other,  of  its  frequent 
exposure  during  suckling  to  irntotion  from  unhealthy  discharges  from  the  child's 
mouth,  leading  to  epidermic  maceration  and  to  painful  erosions,  fissures,  and  ulceis. 

Atrophy  of  the  mammary  glandular  elements  is  of  normal  occurrence  after  the 
menopause,  the  fibrous  and  fatty  structure  being  also  affected  in  many  instances  of 
noticeable  withenng  of  the  breasts.  In  early  life  this  condition  may  result  from 
disease,  or  from  removal  of  the  ovaries,  and  become  a  true  deformity. 

l[yP'^'^'^^y  o*  ^«  breast  consbts  in  an  overgrowth  of  both  the  glandular  and 
the  fibrous  elements,  the  latter  predominating,  an<]  tccurs  usually  between  14  and 
30  years  of  age— the  period  of  greatest  sexual  activity.  Amenorrhoea  and  pregnancy 
are  frequently  associated  with  it. 

•II  ^'*/'^*^  *•'  ***'  breast  is  usually  carried  through  either  the  lymphatics  or  the 
milk  ducts,  most  commonly  during  the  early  period  of  lactation  ;  more  rarely  it 
appears  during  the  other  notable  periods  of  mammary  physiological  excitement— 
f.r,  in  the  newly  bom— the  "witch-milk"  period  {vide  *i</ra)— and  at  puberty. 
In  the  nursing  woman  the  presence  of  fissures  or  abrasions  of  the  nipple  predisposes 
to  lymphatic  infection.  Lack  of  cleanliness,  with  fermentation  or  decomposition  of 
milk  and  of  cutaneous  secretions  in  the  folds  or  crevices  of  the  nipple,  favors  infec- 
bon  in  the  ampullae  of  the  ducts. 

If  the  superficial  lymphatics  are  the  channeb  of  infection,  suppuration  m  the 
cellulo-fatty  tissue  superficial  to  the  breast  may  result  (supramammary  abscess) 
and,  owing  to  the  lack  of  tension,  pointing  will  occur  early,  the  course  of  the  case 
will  be  rapid,  and  the  constitutional  symptoms  relatively  slight.  If  the  deeper  lym- 
phatics or  milk  ducts  convey  the  infection,  suppuration  occurs  within  the  lobules 
(intramammary  abscess)  and  spreads  slowly  from  one  to  another  through  the  inter- 
lobular connective  tissue.  As  the  pus  is  surrounded  by  the  unyielding  breast  tissue 
and  confined  by  the  capsule  of  subcutaneous  fascia  and  its  septa,  pain,  tenderness, 
fevur,  and  other  constitutional  symptoms  are  marked  and  the  progress  of  the  disease 
IS  slow.  Occasionally,  by  extension  from  an  intramammary  focus,  the  connective 
tissue  lying  between  the  breast  and  the  pectoral  sheath  is  involved  (retro,  infra,  or 
submammary  abscess),  but  suppuration  in  thb  region  is  more  apt  to  be  consecutive 
to  raries  of  a  rib  (usually  tuberculous).  The  constitutional  symptoms  are  less 
marked.  The  whole  breast  is  pushed  forward  and  made  more  prominent.  Point- 
ing—by reason  of  the  eflfect  of  gravity— is  apt  to  occur  somewhere  at  the  circum- 
ference of  the  breast,  usually  towards  the  inframaxillary  region.  Sometimes  these 
abscesses  ulcerate  directiy  through  the  breast  tissue  to  the  subcutaneous  area,  making 
two  cavities,  one  infra,  the  other  supramammary,  connected  by  a  narrow  channel, 
a  form  of  Velpeau's  "abcfis  de  bouton  en  chemise."  As  the  breast  is  thinnest 
along  a  line  drawn  from  the  stemo-clavicular  joint  to  the  nipple,  it  is  in  that  region 
that  such  perforation  of  the  gland  usually  occurs.  As  the  breast— glandular  and 
other  structures,  including  the  skin  covering  it— is  supplied  chiefly  by  the  lateral  cuta- 
neous branches  of  the  second  to  sixth  intercostal  nerves,  pain  in  inflammatory  or  sup- 
puraUve  affections,  or  in  the  case  of  new  growth,  may  be  felt  down  the  arm  (intercosto- 
humeral)  ;  over  the  shoulder-blade  (posterior  branches  of  the  thoracic  nerves)  ; 
down  the  side  or  along  the  posterior  parietes  of  the  thorax  (intercostab)  ;  01  up  the 
neck  (supraclavicular  from  the  cervical  plexus  anastomosing  with  the  second  inter- 
costal).    Incisions  for  the  evacuation  of  pus  should  be  made  on  lines  radiating  out- 


PRACTICAL  CONSIDERATIONS:  MAMMARY  GLANDS.  2035 
ward  from  the  nipple  «,  that  the  Urger  lactilerou.  ducU  converging  to  that  point 
may  not  be  mounded.  important  of  the  disease,  afiecling  rhat 

Carcinoma  ol  the  »"•»  »  IZ.oVa^,  inVolvinu  the  female  mamma  being  can- 
gland,  about  85  per  cent  of  J' "3^™^^^  bre^^  occur  in  the  female,  only 
cerous.  About  99  P*r  «"ii^^i"Tuw4.f  which  many  other  instance,  might 
I  per  cent,  m  the  male.      Uluwraung  ^"f  •*  .       ,.^    tendency  to  take  on 

b/dted-that  «unctionl«^°S:i*|«  TS -^-^^^n '" '»»^  ^'»''' ^«^^^^^ 
the  neoplastic  proc«s    [^^.'S^      "  e7^  but  not  uncommonly  in  the  columnar 
epithelium  of  the  ^''^'^^^^J^^'^x'  -ither  case  it  is  usually  at  first  a  dense 
epithelium  of  the  ducts-duct  can«rn  either  ca^u^u^      y 

thereby  produced,  arc  as  'o"°**  ■  ^.    ^.  (v  into  the  lymph  nodes  (pectoral 

,.  By  way  of  the  >r™P'S^^^'nf  th^  seSuVmagnus  ^arising  from  the  third 
or  anterior)  overlying  U»e  <Jig>tation  <M  »»«»?"'.  dissemination,  because  (a)  these 
rib.     This  is  the  most  frequent  form  °' Jy™Pj*'^^  f^^  ..'  (^j  the  nodes  first 

vessels  include  the  great  majonty  o«J*«  "'^^'^  Hymph  from\he  part  of  the 
involved  in  cancer  are  those  into  ^J*^**  »/?'P'S„„  oSates  most  frequenUy  in 
gland  afiected  by  the  pnmary  growth  ;  and(0  ^^J/''^*^";^  .^a^  „^^  ^  ^ort 
the  upper  and  outer  quadrant  °' /•^Jr^^lP^'ythrsdveoli  are  much  more 
exposed  to  minor  ^^T^^  °;  SSCTII  the  %t  the  majority  of  mam- 
numerous  in  the  penpheral  than  *e  central  ^01  i      »  ^tembryonal 

mary.  "-P'"™, ""-f^"  S: oT^^^^^^  abou^(Wiu4m,) 

activity  wW^^s.st.11^^^^^^  calls^ttention  to  the  fact  that  the 


— I.e. 


for  the  enlarged  gland.     By  P'^""g.XlTnf  the  axilla  and  moving  the  superficial 
S?St^;S«;dL«,in8  lymph  Iron,  the  «.pul.r  r.«,on,  .nd  often,  -hen  the 


i    \ 


2036 


HUMAN  ANATOMY. 


central  group  of  nodes  lies  on  the  deep  surface  of  the  axillary  fascia,  forming  one 
large  group  with  it.  Involvement  of  these  nodes  with  their  afferent  lymph  vessels 
probably  accounts  for  the  extensive  infiltration  of  the  structures  over  the  upper 
lateral  and  posterior  aspects  of  the  thoracic  parietes  occasionally  seen  in  advanced 
cases. 

3.  The  nodes  at  the  summit  of  the  axilla  may  be  involved  through  lymph  vessels 
passing  above  the  pectoralis  minor  and  through  Mohrenheim's  foaaa  without  entering 
the  pectoral  nodes. 

4.  Thfe  anterior  mediastinal  glands  mav  be  invaded— especially  if  the  inner 
segment  of  the  breast  is  affected — by  way  of  the  lymph  vessels  following  the  per- 
forating arteries  and  emptying  into  the  nodes  along  the  internal  mammary  artenr. 
In  this  manner,  as  well  as  by  direct  extension  through  the  inframammary  tissue,  the 
pectoral  fascia  and  muscles,  and  the  chcit  wall,  the  pleura  and  lung  may  become 
mvolved.  Ot  her  symptoms  due  to  mediastinal  growth  have  been  described  in  rela- 
tion to  that  region  ({>age  1833). 

5.  The  free  communication  in  the  sub.4reolar  plexus  between  the  glandular 
lymphatics,  deep  and  superficial,  (paramammary)  and  the  subcutaneous  and  thoracic 
lymphatics,  together  with  the  connection  established  between  the  periglandular 
tissue  below  and  the  skin  above  by  the  ligaments  of  Cooper  (suspensory  ligaments), 
explains  the  frequency  with  which  mammary  carcinoma  extends  to  the  overlying 
sicm.  As  a  result  of  its  infiltration  the  latter  bee  imes  dense,  inelastic,  brawny, 
dusky,  and  adherent.  It  cannot  be  picked  up  betw  :en  the  thumb  and  finger  in  a 
fold;  and  often  quite  early  and  before  it  has  become  adherent,  and  as  a  result  of  con- 
traction of  the  growth  pulling  on  the  fibrous  bands  uniting  it  to  the  deeper  parts,  it 
is  drawn  into  a  number  of  little  depressions  or  dimples  like  those  on  the  skin  of  an 
nrange.  When  such  infiltration  is  diffuse  and  spreads  largely  through  the  subcu- 
taneous net-work  of  lymph  vessels,  the  condition  known  as  cancer  en  cuiraste  is  pro- 
duced. In  the  later  stages  ulceration,  infection,  hemorrhage,  and  foul  discharge  are 
frequent  results  of  the  cutaneous  involvement. 

6.  If  the  growth  is  central  it  may  extend  to  the  lactiferous  ducts  or  to  the  peri- 
acinous  tissue  continuous  with  that  surrounding  the  ducts,  and  through  its  own  or 
their  cicatricial  contraction  it  may  depress  or  retract  the  nipple  or  puU  it  so  that  it 
deviates  from  its  normal  direction.  This  is  not  so  valuable  a  symptom  as  the  dim- 
pling of  the  skin  above  described,  as  it  may  be  caused  by  injury  or  by  chronic  disease, 
such  as  abscess,  tubercle,  or  mastitis.  Moreover,  it  may  not' be  present  if  the  growth 
is  peripheral. 

7.  The  carcinoma  may  extend  through  the  lymph  communications  between  the 
gland  and  the  underlying  connective  tissue  and  pectoral  fascia  and  muscle,  so  as  to 
become  fixed  to  or  incorporated  with  those  structures,  the  breast  losing  much  of  its 
mobility,  especially  in  a  direction  parallel  with  the  pectoralis  major  fibres.  It  may 
thence  continue  through  the  thoracic  wall  ^nd  invade  the  pleural  or  mediastinal  cavity 
directly. 

8.  Through  the  intercommunication  of  the  lymph  system  of  the  two  breasts 
through  the  subcutaneous  thoracic  lymphatics,  cancer  of  one  breast  may  extend  to  the 
other  (Moore),  or  to  the  glands  of  the  opposite  axilla  (Volkmann,  Stiles),  or  to  the 
glands  of  both  axillae  (Scarpa,  Cooper  ;  quoted  by  Williams). 

9.  General  dissemination  of  the  cancerous  disease  may  also  take  place  through 
detached  cells  or  particles  (emboli)  from  the  primary  growth  entering  the  blood 
stream.  The  liver  is  the  organ  most  frequently  affected  by  metastasis  in  cases  of 
breast  cancer.  The  bones,  the  lungs,  and  the  pleurae  come  next,  but  almost  no 
organ  or  structure  of  the  body  is  exempt. 

In  removal  of  the  breast  the  following  anatomical  points  should  be  borne  in  mind  : 
(o)  The  intimate  connection  between  the  skin  and  the  gland  itself  by  means  of  lymph- 
and  blood-vessels,  by  the  suspensory  ligaments,  and  by  glandular  processes  accom- 
panying or  contained  within  these  ligaments  (Stiles),  shows  the  necessity  for  free 
sacrifice  of  the  skin  overlying  the  breast. 

(b)  The  irregular  shape  of  the  breast,  which  has  two  extensions  that  frequently 
reach  into  the  axilla,  and  one  that  reaches  to  or  overlaps  the  border  of  the  sternum, 
and  not  uncommonly  similar  processes  that  spring  from  other  parts  of  the  surface  of 


DEVELOPMENT  OF  THE  REPRODUCTIVE  ORGANS.        »37 

eued  glandular  tiwue.  „trcMrlandutar  lattv  envelope.  brinninR  the  glandu- 

(f)  The  usual  detect  in  the  «\W™""'^^^  and  muscle  (  Hcidenham). 

,ar  lobile.  into  in^^X^^/^'K.  if  that  <^  -U^^^  a^lndicates  the  Iree  removal  ol 
laciliutes  extenwon  o«  the  disease  in  m-i 

the  pectoralis  major  in  most  <^^:  .   „^_,,  auBolies  the  same  indication  as  to 

V  )  The  lymphatic  distribution  [^^\J^^'^^  to  the  le«Ksr  pectoral  a^so. 
removal  o{  the  greater  P«^°r*>  f  ^IrJLnSorTh^Kh  cleaning  out  of  the  axilla. 
It.  of  cour...  poinu  -^"^^^ove  Uie  cS^ohJ^^^^^^  no<le»ipectoral.  centnd 
In  doing  this  it  a  well  to  remove  tne  *="»•"      ./t^^        ^  minimizes  the  risk  of 

deep,  subscapular,  etc.-m  °^'=P*^\^°\^Z6^(^<:yn'^).  but  because  if  the 
Sion  of  sUlthy  structure  dunng^hco^ra^^^^^^  ^.„^        i 

davi-pectoral  fasna  ^'^P^^J'^^^orJ^  minor  muscle  (on  account  of  the 
together  with  the  g^t^^.P^l  rLi  ^iS  Lscia),  are  removed  in  one  piece,  the 
continuity  of  its  sheath  *^»J  »»»«^^^'P^"SSd  in  them  will  be  removed  also 
groups  of  nodes  e«»»"««^»***  *'*''*  *"r,:!^^n  «  node  ol  the  subscapuUr  group 
(S.  To  this  there  »'lJ^'^ .''ZTr^^:^^^  i^^Xr^rnmot  and  rnfraspfnatus 
iometimes  projects  backward  and  "^^l^f^.^'^^J^^         ««  »«  ^^e  outer  side  of 

m«>«:les:  (a)  .«''"*  "^"AS  is  so  ^t^^^ 

the  axillary  vem.  and  when  this  is  so  m  inc       y^        7     s  ^^^  ^^^jj        ^e 

inner  side  these  glands  ^°"  ^  remau^hmd  .  UM         g^^;,,     .  j^j^  ^-ith  their 

rt'a::?ed'To^;  c:;*:^-  ^^^^^^^^  --»« ^^^''  ^  --^'^ '"'  -^^ 

removed  separately  (Leal).  dancer  during  the  operation  is  the 

(,)  The  most  '«'l^'^4"»,*'^e^^Lre^;^^^^ 
axillary  vein  (page  888),  '«.*''_f  ,?""^^^      .^-^j  ^nd  the  head  of  the  humerus  is  made 
and  the  brachial  P»«"*rf '^J^i^Tru^tC^r^^orm^^     lie  on  the  ..ter  waU  of  the 
to  pro  ect  into  the  «^;,T^f^_*""^;,  of  cancerous  tissue  as  to  be  difficult  of 
axilla,  but  may  be  so  «nbejf  ed jna  ^^    «'      j    ^j,^  subscapular  v-^ls  and  (in 
recognition.     On  the  P°?»*"°^  .^P^  °;  Se  long  subscapular  nerve  supplying  the 
close  proximity  to  the  '"b^fP"^' ^^      The  inner  (thoracic)  wall  of  the  axilla 
latissimus  doni{  mu^le  »^^^^^f^^  Jcondi^ted  with  the  greatest  freedom 
18  the  region  in  which  the  a»»«?tion  may  "^        .,    ^     ^^^d  in  close  contact  with 
the  posterior  thon^ac  "«-^~«J-^'  ^sf  LXch  it  is  distributed.     The 
the  outer  surface  of  *'.  r?^|"X  murse  of  the  operation  are  (1)  the  pectoral 
arteries  met  with  or  divided  in  the  "="""f  "^j'    thoracic;  (3)  the  long  thoracic 
branches  of  the  »"°'«'»».'i^'?"^^' u^' ^^^ 

(external  --2,> ,~he S^th^aS  f^^^^^^  intel^tal  arteries  :  and  (5) 
(4)  lateral  branches  from  tne  seco  ^^  artery,  emerging  at  the  second. 

some  during  operation. 

DEVELOPMENT  OF  THE  REPRODUCTIVE  ORGANS. 

and  temporary  stoj^eo^  the  p^u^oyh<^g^a  ^^^^  ^^  ^ 

'^^k^^S^tt^IcL^tn'^^^o^lA  two  additional^^canals-the  Miillenan 

•^-Vrences  to  the  ^^^.^^^  ^ ^Zftl^'^l^^^'^^^^'^^o 
t\:::^:^Z^LS:lT^:ttXr,  that  the  Wolfhan  tubules  comprise  an 
anterior  sexual  and  a  po?t,   ,  r  excretory  group. 


2038 


HUMAN  ANATOMY. 


'<?;<• 


Caidiiuil  vein 


.Mcsotheliuin 


Malpjgh:an  body 


Portion  of  cross-section  of  early  iiuman  embr 
ance  of  sexual  glands  wittiin  ^rminai 


Aniage  of  seyual  glands 
',  showing  first  appear- 
ridges.     X  60. 


During  the  development  of  the  Wolffian  body,  or  mesonephros,  a  second  tube, 
the  M'ullerian  duct,  is  formed  within  a  linear  thickening,  the  geniial  ridge,  that 
appears  upon  the  ventro-lateral  surface  of  the  Wolffian  body.  Near  the  cephalic  end 
of  the  latter,  an  evagination  of  the  lining  of  the  body-cavity  into  the  genital  ridge 

occurs,  by  the  contin- 
FiG.  1 716.  ued  prolOferation  and 

'A™<»  downward  growth  of 

the  cells  of  which  the 
evagination  is  con- 
verted into  a  tube — 
the  Miillerian  duct 
This  tube  communi- 
catesdirecdy  with  the 
body-cavity  by  means 
of  its  trumpet-shaped 
cephalic  extremity, 
extends  parallel  with 
and  closely  related  to 
the  Wolffian  duct 
and,  later,  below 
reaches  the  urogeni- 
tal sinus.  The  con- 
verging lower  seg- 
ments cif  the  two  Wolffian  and  the  two  Mullerian  ducts  are  embedded  within  a  median 
mesoblastic  band,  the  genital  cord,  that  represents  the  continuation  of  the  fused  geni- 
tal ridges  of  the  two  sides.  Within  the  genital  cord  the  Miillerian  ducts  lie  in  the 
middle,  closely  applied  to  each  other,  with  one  Wolffian  duct  on  each  side  (Fig.  1649). 
The  development  of  the  sexual  glands  begins  about  the  time  that  the  Miillerian 
ducts  are  forming,  as  a  linear  thickening  of  the  mesotheiiam  and  underlying  meso- 
blastic stroma,  situated,  however,  on  the  median  surface  of  the  Wolffian  body  (Fig. 
1716).  Over  this  raised  area,  the  germinal  ridge,  the  character  of  the  primary  peri- 
toneum changes,  its  cells  becoming  taller  and  undergoing  proliferation.  Very  early 
among  the  increasing  elements  appear  specialized  cells  distinguished  by  their  large 
size,  clear  protoplasm,  and  conspicuous  nucleus.  These  are  the  primary  germ-cells, 
which  later  become  the  primordial  ova  or  sperm-cells,  according  to  sex.  For  a  time 
this  cannot  be  determined,  since  in  this  indifferent  stage  of  the  sexual  gland  special- 
ization has  not  yet  progressed  sufficiendy  to  make  differentiation  possible.  The  dis- 
tinctive features  of 

both  sexes,  there-  Fio.  1717. 

fore,  are  acquired 
by  farther  devel- 
opment of  a  neutral 
sex-type  in  which 
the  indifferent  sex- 
ual glands,  the 
Wolffian  tubules, 
the  Wolffian  and 
the  Miillerian  ducts 
are  the  chief  com- 
ponents. Whethei- 
determination  of 
sex  is  dependent 
upon  nutrition, 
and,  therefore, 
more  or  less  acci- 
dental, or  is  established  early  and  r.ntedates  the  appearance  of  indifferent  organs, 
is  a  qviestinn  still  undecided. 

Differentiation  of  the  Male  Type — The  development  of  the  testis  from  the 
indifferent  sexual  gland  includes  the  invasion  of  the  proliferated  mesothelial  cells  of 


Primary  germ-cells 


Proliferating 
VVollBan  stroma 


Cross  section  of  germinal  ridge  of  young  human  embryo,  showing 
early  diKerentiation  of  primary  gem-cells,    y  500. 


DEVELOPMENT  OF  THE   REPRODUCTIVE  ORGANS.         :.o39 

•  1  ^^„-  w  the  underlvine  mesoblastic  stroma,  whereby  the  epithelial 
the  germinal  ndge  by  the  """^"^ly'-J^ J  ~~,  ....^ds  that  extend  into  the  subjacent 
mass'^becomes  broken  up  mto  <=y''"f "  .^"'^kindfof  elem^^^^^^  the  numerou^  chief 
stroma.  The  cell-cords  are  composed  «j  '*° '""J?  "^\7^e„dants  of  the  indiffer- 
epithelial  cells  and  the  ^^^gej.f -'tmbVace'  'Xtout'X  fifth  week  a  layer  of 
ent   primary  ?«""-«=«'?f  •   *'^JV  '  „  ^^^^^  and  deeper  portions  of  the  epi- 

mesoderm  msmuates  itself  between  '"«  f"^"""*'       ^his  inerowth  results  in  the 

thelial  mass,  thereby  ?fP^»'"&J„  f^"f/[^niera!bu Jnea,  around  the  entire  testis, 
formation  of  a  robust  fibrous  envelope   J^ J""\ca  a^bug m^^      ^^^^^^  ^^  ^^^ 

while  the  separated  mespthelial  l^y-^J  j»^'^[^"j'f^  mesoblastic  stroma  into  smaller 
cell-cords  become  subdivided  by  ^^e  ingrowth  of  the  mesooiasu 

spherical  masses,  which  «"bse^"^"t»yi„^;^,iruLX^^ 

^ti^'^^S^'S^tS^^-^^  grow  into  the  young  tct. 
from  the  adjacent  Wolffian  tub'ilM.    These 


inerowths  invade  the  attached  border  ot 
the  testicle  and  become  the  medullary 
cords,  which  are  so  disposed  that  each 
corner  into  relation  with  one  of  the  sphen- 
cal  epithelial  cell-masses.    Although  both 
the  latter  and  the  medullary  cords  are 
solid,  the  later  relation  of  the  secreting 
tubules  of  the  gland  to  the  excretory 
channels  is  thus  foreshadowed  since  from 
the  ingrowths  from  the  Wolffian  tubules 
are  derived  the  straight  tubules  and  those 
of  the  rete  testes.     The  farther  differen- 
tiation of  the  seminiferous  canals,  which, 
as  well  as  the  medullary  cords,  are  with- 
out lumen  untU  near  puberty,  pro^ee^ 
from  the  growth  and  branching  of  the  cell- 
masses,  the  cells  of  which  become  the  epi- 
thelium of  the  tubules.     The  latter  are 
enclosed  by  an  investment  of  condensed 
mesoblastic  stroma  continuous  witn  the 
supporting  tissue  and  framework  of  the 
gland.     At  the  approach  of  sexual  ma- 
turity the  primary  sperm-cells  within  the 
tubules  proliferate  and  become  the  sperma- 
togonia, while  from  other  epithelial  ele- 
ments are  derived  the  Sertoli  cells.     The 
roles  played  by  these  elements  in  the  pro- 
duction of  the  spermatozoa  are  descnbed 
under  Spermatogenesis  (page  i945)- 

Coincidently  with  the  growth  of  the 


Globus  major 


Fig.  1718. 


Rete  testis 


Duct  of 
epididymis 


Seminiferoui 
tubes 


Globus  minor 


Ligamentum  scrotal* 


Longitudinal  section  of  developing  testicle. 


X  so. 


S?Wolfli.n  wMe.  K.  develop^  the  com  -^^.fi^,?^Z  M^iS  " 
,h.  WoMBa.  due,  Biv«  ri»  .0  te  tub.  of  >^=  ^jaiX7"o»X^*  •""» 
a  secondary  outgrowth,  the  seminal  vesicle.     I  he  cauaai  group  oi  i"  i 

^rfrepr  Jnted^in  both  sexes  by  ^dime"^^^,^;,^"^  The  epidiiymiT.t  sUlkS 
paradidymis  and  the  vasa  aberrantia.     The  appendix  of  the  epiamym 
hydatid,  probably  also  owes  its  origin  to  the  NVolffian  duct 

^    Although,  L  is  evident  from  the  forgoing.  ^»>«.^°;5,Hn  the  m»»"   ^^^^^^^^^ 
largely  concerned  in  the  development  of  the  generative  '^act  m   he  male   the  M 

ierfan'^duct  is  not  without  representation,  ''•"-.f  ^^^^X^thf  tS  and  tSe 
upper  (after  migration  lower)  end  remains  as    he  a  pe^^^^^^  .^^^^ 

lower,  fused  with  its  fellow,  is  seen  as  the  Prostatic  titricie.wm^.     ^^   ^here  it 
ho.  .ologue  of  the  vagina  and.  possibly,  tiie  uterus.     In  exceptional  cases,  where 


3040 


HUMAN  ANATOMY. 


persists,  the  intervening  portion  of  the  Miillerian  duct  is  represented  by  Rathke's 
duct.  Since  the  prostate  gland  arises  as  an  outgrowth  from  the  urogenital  sini.s 
(page  1979),  it  has  no  genetic  relation  with  the  seminal  ducts. 

Descent  of  the  Testes. — ^The  development  of  the  sexual  glands,  in  both 
sexes,  is  attended  with  conspicuous  migration  from  their  original  position  on  either 
side  of  the  upper  two  lumbar  vertebrae,  opposite  the  lower  pole  of  the  kidney.  In 
the  case  of  the  testis,  this  migration  is  so  extensive  that  by  birth  the  organ  usually  has 
passed  through  the  abdominal  wall  and  entered  the  scrotum,  having  completed 
Its  so-called  descent. 

Certain  peritoneal  folds  (mesenteries)  and  fibro-muscular  bands  (ligaments)  merit 
brief  description,  since  they  are  more  or  less  concerned  in  the  migration  of  the  sexual 
glands.  The  Wolffian  body  is  enclosed  and  attached  to  the  posterior  body-wall 
by  a  fold  {mesonephridium),  of  which  the  upper  elongated  end  is  continued  to  the 


Fig.  1719, 


C  BG 


Diagrams  illustrating  differentiation  of  two  sexes  from  indifferent  type.  A.  Indifferent:  G.  sexual  Kland;  WD, 
Wolffian  duct;  WT.  WT.  groups  of  Wolffian  tubules;  MD,  Miillerian  duct;  RD,  renal  diverticulum ;  C.  cloaca; 
G,  gut;  A,  allantois.  *,  Male:  T.  testicle;  VE.  vasa  efferentia;  GM.  globus  major;  VD,  vas  deferens;  Pa,  para- 
didymis; VA,  vas  aberrans ;  SV,  seminal  vesicle  ;  AT.  appendix  testis ;  AE.  appendix  epididymidis ;  P,  bladder ;  PU, 
prosutic  utricle;  Pr.  prostate;  Ur,  urethra;  CG.  Cowper's  gland ;  CC,  coipus  cavemosum ;  R.  rectum;  RD,  rvnai 
duct;  K, kidney.  C  />»ni/^.- O,  ovar>- ;  Ov,  oviduct ;  F,  fimbria ;  U,  uterus ;  V,  vagina  ;  DEp,  duct  of  epoophoron ; 
TEp,  tubules  of  epoophoron ;  Po,  paroophoron  ;  HM,  hydatid  of  Morgagni ;  GD  Oirtner's  duct ;  BG,  Bartholin's 
gland;  C,  clitoris;  K,  kidney;  R,  rectum.     (Moiijied/rmm  Wiedershetm?) 


diaphragm  (plica  phrenico-mesonephricd)  and  the  lower  to  the  abdominal  wall  in 
the  inguinal  region  {plica  inguino-mesonephricci).  The  eariy  sexual  gland  is  also 
provided  with  a  mesentery  (mesorchium  or  mesovarium),  that  above  and  below  is 
continuous  with  folds  that  pass  from  the  upper  and  lower  poles  of  the  gland  to  the 
mesentery  of  the  mesonephros.  Within  the  inferior  plica,  of  the  two  much  the  better 
marked,  lies  a  (ibro-musciilar  strand  (the  ligament  of  the  testis  or  ovary),  that  below 
is  attached  at  first  to  both  the  Wolffian  and  Miillerian  ducts.  Later,  owing  to  the 
atrophy  of  the  one  or  the  other  of  these  ducts,  according  to  sex,  the  ligament  of  the 
testes  remains  connected  with  the  Wolffian  duct  and  the  ligament  of  the  ovary  with 
the  Miillerian  duct. 

A  second  band  of  muscular  tissue  appears  within  the  lower  part  of  the  inguino- 
mesonephric  fold,  and  has  its  upper  attachment  also  to  the  Wolffian  and  Miillerian 
ducts  at  a  pcint  about  \vhcrc  they  receive  the  insertion  of  the  ligament  of  the  testes  or 
ovary.  The  lower  end  of  the  band  blends  with  the  subperitoneal  tissue  of  the  anterior 
abdominal  wall  in  the  vicinity  of  the  future  abdominal  ring.     This  hand,  the  genito- 


Sexual 
gland 


DEVELOPMENT  OF  THE  REPRODUCTIVE  ORGANS.         2041 

sponding  to  the  origin  Pi^,   j^^^ 

of    the    vas    deferens 
from  the  epididymis. 

The  testicle  begins 
its  descent  during  the 
second  foetal    month, 
coincidendy  with  com- 
mencing atrophy  of  the 
Wolffian   body,    and, 
under  the  influence  and 
guidance  of  the  genito- 
inguinal  ligament,  by 
the  end  of   the  third 
month  reaches  the  an- 
terior abdominal  wall 
in  the  vicinity  of  the 
later  internal  abdomi- 
nal ring.  This  position 
it  retains  until  the  close 
of    the   sixth   month, 
when  it  enters  upon  its 
final  descent. 

Meanwhile,  the 
musculo-fascia  layers 


Plicm  phrenico- 
nKsonefihricm 

Sexual  glaiid 


Wolffian  btxly 


Mesentery  al_ 

(land 
Wolffian  dud 


Onilo-inguinal 
liKament 

I'lica  inguino-- 
niewnephnca  / 


LiKament  of  gland  ^ 

Umbilical  arteries>^ 


Allantnic  duct 
Umbilical  vein 

wolffian  bodie,  and  ^1  ^^^^Tl^tH::^  "'^'" 


ifltClll*»   •■■■"J        

musculo-fascia  layers  .^.^^nation   resulting  in  the  production  of  a  shallow 

of  the  abdomina  wall  unde  go  evagnation   r«u      g  v^^  processus  vapnafts 

pouch,  the  inguinal  bursa,  '"^o  ^-^l-- J^  genUo-inguinal  ligament.     The  mgumal 
^tends,  together  wuh  the  ck«elya^c.ated^^^^^^  ^g  independently  dev_el- 

bursa.  in  turn,  smks  mto  the  '•*'»'|°*J[/^f  j^Vbursa  conte^^^ 

master,  and  surround  feFem^-mgumal  ligament      ^^^^    ^  .light  elevation  appears 
Owing  to  the  thickenmg  «l  *^^ '"r^^^^in  ,     becomes  pushed  up  towards  the 
on  the  floor  of  the  bursa   which    l^us^eem^Y^^^  ^^^^^^^ 
testis  to  form  the  rudiment  «\„^^^^^'"Xrv,  remains  insignificant.     In  consequence 
tion,  the  c^us  inguabs,  but  in  man  »'*^y?^  "^^^^^  f^  displaced  upward  and  its 

of  these  changes,  during  the  fourth  month  the  testis  «^^^^^^   temporarily    inter- 

Fig.  i7»»- 

Epididymis 
Testis 

Vas  deferens 

Dttv  epigMtric  »«si€l» 


Peritoneal  cavity 

Im  obi.  ind  0»««™»  nii»cl«-^ 


Roi  tiis  muscle 


rupted.  .     .        , 

About  the  lieginmnj;  o 

the  seventh  month,  the  tinal 
descent  of  the  testicle  is  in- 
augurated with  dcepenmg 
of  the  bursa  and  downward 
extension  of  the  peritoneal 
pouch,  accompanied  by  the 
now  thickened  and  short- 
ened geiiito-inguinal  liga- 
ment. Although  shorten- 
ing of  the  latter,  together 
ij,.gT«n.  ~.w-...» .-..,  —  ^.\^\^  the  pull  exerted  by  the 

ing  from  the  ^       th  and  expansion  "«  th?Pf J'^  of  the  s^  otal  Ic  in  advance  of  the 
The  processus  vaginalis  reaches  the  bottom  ot  tne  scrui- 


ApoMurolU  of  eiMIMl  oHIque 

Pentoneun' 

Genito-inRuinal  ligamei.i  — 

Transversalls  fascia 

Cremasler  muscle 

Intercolumnar  fascia 

Integumenury  scroUl  pouch 


Processus  va(finalis 
\      AMmcbm«nl  of  llg«m«nt  to 
J  ihUkmed   Hoot  uf  liiiulosl 
-^  ^,^^   buna 

Diagram  showing  early  sUg.  in  descent  of  testicle.    (.-.//-  «'««-«) 


3042 


HUMAN  ANATOMY. 


Peritoneum 

y  Vas  deferens 


Deep  cpiKBStric  vessels 


Sac  of 

processus  vaginalis 

Peritoneum 

Tunica  vaginal 
communis 

Cremaster 

Intercolumnar 
fascia 
Skin  and  dartM 


Diagram  showing  relations  of  descended  testicle  to 

tcessus  vaginalis,  which    

peritoneal  sac  of  abdomen. 


processus  vaginalis,  which  still  freely  communicates  with 
(Aft"  WaUcyer.) 


testicle,  which,  drawn  from  its  mesentery  (mesorchium),  descends  outside  and  behind 
the  peritoneal  pouch  that  later  constitutes  its  partial  serous  investment,  the  tunica 
vaginalis.     After  the  descent  is  completed,  usually  shortiy  before  birth,  but  some- 
times not  until  afterward,  the  tubular 
Fig.  17a  a.  upper    segment    of  the    peritoneal    sac 

closes  normally  during  the  early  months 
of  childhood.  This  closure  takes  place 
first  in  the  vicinity  of  the  internal  ab- 
dominal ring  and  in  the  middle  of  the 
tube,  passing  upward  towards  the  ring 
and  downward  to  within  a  short  distance 
of  the  sexual  gland.  The  occluded 
portion  of  the  vaginal  process  is  later 
represented  by  a  small  fibrous  band  (lig- 
amentum  vagina/e)  that  extends  from  the 
internal  abdominal  ring  above,  through 
the  inguinal  canal  and  for  a  variable  dis- 
tance down  the  spermatic  cord,  some- 
times, although  not  commonly,  as  far  as 
the  tunica  vaginalis.  When  the  pro- 
cessus v^;inalis  fails  to  close,  as  it  oc- 
casionally does  in  man  and  always  in 
certain  animals,  as  the  rat,  in  which  de- 
scent and  retraction  of  the  testis  periodically  occur,  the  serous  sac  surrounding  the  tes- 
ticle communicates  throughout  life  with  the  peritoneal  cavity,  a  condition  favorable  to 
the  production  of  hernia.  With  the  obliteration  of  the  lumen  of  the  processus  vaginalis, 
an  inguinal  canal,  in  the  sense  of  a  distinct  tube,  disappears,  the  spermatic  duct  and 
associated  vessels  and  nerves,  that  necessarily  share  in  the  migration  of  the  sexual  gland 
into  the  scrotum,  passing  between  the  muscular  and  fascial  layers  of  the  abdominal  wall 
embedded  in  connective  tissue.  The  remains  of  the  shrunken  genito-inguinal  liga- 
ment, or  gubemaculum,  are  represented  by  a  fibro-muscular  band,  the  scrotal  liga- 
ment, that  connects  the  lower  end  of  the  epididymis  to  the  scrotal  wall  (Fig.  1687). 
Descent  of  the  testicle  may  be  imperfectly  accomplished,  so  that  the  gland,  failing 
to  reach  the  bottom  of  the  scrotal  sac,  may  be  arrested  within  the  inguinal  canal  or 
spermatic  cord,  or  permanently  retained  within  the  abdomen,  a  condition  known  as 
cryptorchism,  usually  leading  to  atrophy  of  the  gland.  Associated  with  faulty  descent 
may  be  anomalous  situation,  the  testis 
lying  beneath  the  integument  near  the 
external  abdominal  ring,  in  the  tliigh,  or 
in  the  perineum.  After  descent  the  axis 
of  the  testicle  may  be  abnormally  di- 
rected, the  gland  assuming  a  transverse, 
rotated,  or  even  inverted  position. 

Differentiation  of  the  Female 
Type. — Development  of  female  internal 
reproductive  organs  proceeds  along  the 
same  lines  as  in  the  male,  the  ovary  being 
differentiated  from  the  indifferent  sexual 
gland  and  the  genital  canals  from  the 
Miillerian  and  Wolffian  ducts. 

Differentiation  of  the  ovary  has  been 
described  in  connection  with  that  organ 
(page  1993).  That  of  the  Fallopian 
tubes,  uterus,  and  vagina  results  from 
further  growth,  fusion,  and  modification 
of  the  Miillerian  ducts.    Lower  segments 


Fig.  iraj. 
Peritoneum 

Vas  deferens 

Deep  epigastric  vessels 


Closed  portion  of, 
processus  vaginalis 


Cremaster 

loAindlbulifomi  bscU 

Sac  of  tunics  vs^sslla 

Visceml  layer- 

ParieUI  laver 

skin  and  dartoS' 


Diagram  showing  relations  of  testicle  to  serous  mem- 
brane after  upper  part  of  processusvaKinalis  has  closed,  its 
lower  part  |>ersisting  as  tunica  vaginalis. 


of  the  latter,  below  the  attachment  of  the  ligament  of  the  ovary  (p^e  2040),  undergo 
fusion  and  form  the  uterus  and  vagina.  Their  upper  segments  remain  uufused  and  be- 
come Fallopian  tubes.    Details  of  these  changes  are  given  under  the  respective  organs. 


DEVELOPMENT  OF    THE  REPRODUCTIVE  ORGANS.         »43 

I„  ,h.  ic^Je  the  Wolto  ...buta  and  due,  <''y'^^;'IT^^„:^;^'t^. 
,„  lorn  radimenHr,  organ.,  Ihe  •P<»Pl!»"",k"^rrt^.i;t»«  S^  S>0.  ^c 

t  --£SH£^s.r^d.c£°^'  S'.rK!  ill  ^^ 

cremaster  muscle.    The  gland 
fails  to  reach  the  internal 
abdominal  ring  and  remains 
until  birth  at  the  brim  of  the 
pelvis  in  consequence  of  the 
large   size   of    the   uterus   in 
relation   to  the  small  pelvis. 
When  the  growth  and  expan- 
sion of  the  latter  have  pro- 
vided additional  capacity,  as 
the  uterus  sinks  to  its  definite 
position,  the  ovaries,  attached 
by  their  ligaments  and  ovi- 
ducts, follow  into  the  pelvis. 
The  genito-inguinal  liga- 
ment becomes    the   round 
ligament  of  the    uterus,  the 
lower  end  of  which  is  attached 
to  the  subcutaneous  tissue  of 
the  labium  majus  at  the  exter- 
nal abdominal  ring.      These 
relations  are  foreshadowed  by 

the  close  association  of  the 

lower  end  of  the  fcetal  liga- 
ment to  the  bottom  of  the 

ing-jinal  bursa  and  the  wall  of 

the  processus  vaginalis.     The 

lumen  of   the  latter  usually 

disappears,  but  in  exceptional 

cases  may  persist  as  the  canal 

of  Nuck  (page  2015).     Asso- 

ciated  with  this  condition,  occasion.' 

of  the  testicle  by  passing  into  or  ever 


Suprarenft) 
body 


Kidney 


Ureter 

Oviduct 

Round 
ligament 

Bladder 


Suprarenal 
body 


Kidney 


.1  .,.»...  ol  female  talus  of  third  month .  showing  ovariea 
^*""  "i;!?!  undJ^nded  and  bicomate  uterus.     X  2. 

ovary  more  closely  imiutes  I'^e  descent 
gh  the  inguin-'  .-mal. 


DEVELOPMENT  OF  THE  EXTERNAL  ORGANS. 

The  external  genital  organs  d-lopj^m  an  ^^^^^^,;^^^^^ 

beginning  of  the  third  month  do  not  exhibU^ne  a«g^^^^^  .^  ^^^^^ 

=nui:r,s?n,fcrEsr'H^33E4s!or^^^ 

bordering  the  external  cloacal  fossa  m  '^?n;j™J^V°r:  ^  differentiates  into  adisul 
the  ;e-«..W  tui^cU.  The  latter  rapidly  ^creases  in  «'^^4"f/Xicji Vcomes  divided 
knob-like  end  and  a  bulbous  genual  expar^on  at  .t^^^^^^^  ^^^^^^      ^^^  ^.^ 

by  a  groove  that  ««"ds  along  Uieunde^^^^^^^^  g^^  ^.^^  ^j  ^^^  ^^^^^  i„t„ 

of  this  groove  elongate  into  the  genttai/oias  inai  nc 


!! 


iiij 


2044 


HUMAN  ANATOMY. 


Surface  nurkinf^a  of  cloacal  region  of  human  embn-o 
o<  seventeen  days  (Fi(.  1644)-  X  i>.  (Keibel.) 


Fig.  t7>6. 


Genital  tubercle 
Ctoacal  membrane 
Lower  limb 

Caudal  process 


the  urogenital  sinus  that  appears  when  the  cloacal  membrane  ruptures.  Somewhat 
later,  about  the  ninth  week,  a  pair  of  thick  crescentic  swellingrs,  the  outer  genital,  or 
!abio-scrotal  folds,  make  their  appearance  on  either  side  of  the  genital  tubercle. 

In  the  female,  in  which  the  original  relations  are  largely  retained,  the  genital 
tubercle  grows  slowly  and  is  converted  into  the  glans  and  body  of  the  clitoris,  while 
the  inner  genital  folds  become  the  nymphse  and  the  outer  ones  the  labia  majora. 
The  urogenital  sinus  remains  as  the  vestibule  and  its  opening  as  the  vulvar  deft. 
The  wedge  of  tissue  between  the  posterior  margin  of  the  latter  and  the  anus  becomet 
the  perineal  body. 

A  description  of  the  development  of  the  glands  of  Bartholin  is  given  in  connec- 
tion with  the  consideration  of  these  organs  (page  2036). 

In  the  male  the  modifications  lead- 
Fig.  i7»s-  ing   to  the    fully    differentiated  external 

f  organs  are   more   pronounced   in  conse- 

quence of  the  formation  of  the  urethra. 
The  genital  tubercle  rapidly  increases 
loacai  membrane  '"  *'^*'   ^comes   somewhat  conical  and 

differentiated  into  the  glans  and  shaft  of 
the  penis.  The  parts  of  the  outer  genital 
folds  behind  the  penis  soon  become  en- 
larged, rounded,  approach  each  other, 
and,  finally,  unite  along  a  line  afterward 
indicated  by  the  median  raphe,  so  that  in 
embryos  of  45  mm.  length  the  scrotum  is 
already  well  defined.  According  to  Her- 
20g,'  the  development  of  the  urethra  pro- 
ceeds from  an  epithelial  ridge  that  appears 
on  the  cloacal  membrane  and  extends  for- 
ward along  the  under  surface  of  the  geni- 
tal tubercle  towards  its  distal  end.  This 
ridge  sinks  into  the  mesoblastic  tissue  of 
the  elongating  genital  tubercle  as  a  nar- 
row longitudinal  strand  (urethral  septum), 
and  later  becomes  partially  divided  by  a 
superficial  furrow,  the  urethral  groove,  the 
lips  of  which  correspond  to  the  inner  geni- 
tal folds.  In  consequence  of  the  cleavage 
of  the  posterior  third  of  the  epithelial 
ridge,  the  cloacal  membrane  is  ruptured 
and  communication  established  with  the 
urogenital  sinus  by  means  of  a  small  canal 
that  opens  into  the  urethral  groove.  As 
the  latter  grows  farther  forward  towards 
the  glans,  approximation  and  fusion  of 
its  edges  occur  beh'nd,  whereby  the  groove 
is  gradually  converted  into  the  urethral 
canal.  In  this  manner  the  distal  opening 
of  the  urethra  is  carried  forward  until  its  definite  pt)sition  on  the  glans  is  reached. 
Arrested  development  or  fusion  of  the  edges  of  the  urethral  groove  results  in  defec- 
tive closure  of  the  canal,  a  condition  known  as  hypospadias  (page  1927 ■). 

The  formation  of  the  prepuce  begins  as  a  thickening  and  ingrowth  of  the  surface 
epithelium  at  the  bottom  of  an  annular  groove  that  separates  the  glans  from  the 
body  of  the  penis.  From  this  thickening  the  epithelium  grows  backward,  invading 
the  young  connective  tissue  as  a  narrow  wedge-shaped  mass  that  encircles  the  glans, 
except  below,  where  it  is  incomplete  and  the  frenum  later  appears.  In  this  manner 
an  annular  fold,  the  prepuce,  is  defined  around  the  base  of  the  glans  that  later,  just 
before  or  shortly  after  birth,  becomes  free  by  the  partial  solution  of  the  intervening 
solid  epithelial  stratum  and  its  conversion  into  the  preputial  sac. 
'Archivf.  mikros.  Anatom.,  Bd.  Ixiii.,  1904. 


External  genitals  of  human  embr>-o  of  about  twenty 
seven  days.    (AW/monm.) 


Fig.  17*7. 


Labio-scrotal 
folds 

ipenin^  of 
urogenital  sinus 

Anal  groove 

Coccygeal  eminence 
Indifferent  stage  of  external  genitals  of  human  embryo 
of  thirty-three  days  (Fig.  1647).    x  8.    (Keibfl.) 


DEVELOPMENT  OF  THE  REPRODUCTIVE  ORGANS. 


ao45 


Male. 


Fio.  i7»8. 


Fbmale. 


Gbuu 
Urethral  groove. 
Scroul  lolil — 
Anal  gnxiv- 

Coccyg«»l— 
eminence 


0  w 


.__GI«n»clUoridit 

kLmhium  maius 
t-Nymph« 
-UfogeniUl  slnuj 

Anu> 
-Coccygeal  eminence 


Seven  and  a  half  week..    («frw«^) 

Clans 
Urethral  groove  doling 

Raphe 
Scrotum- 


Nine  weeks.  {KtiM.) 


Clans  clitoridis 
•Nymph« 
Lahium  majus 

Vaginal  orifice 


Eleven  weelts.    (A5i.«»«<i"") 


Epithelial  knot. 

Urethral  groove, 
closed 


Clans  clitoridis 


Prepuce 
Urethra 
Nympha 
Vaginal  orifice 

Anus 


Fifteen  weeks. 


Slateen  weeks.    {Ktllmann.) 
(Hfrtog.) 
Development  of  external  generative  organs. 


Male 

COTi  vasculosi  and  ductuHeffer- 

entes 
Paradidymis 
Duct  of  epididymis 
Vas  aberrans 
Seminal  vesicle  . 

Appendix  of  epididymis 
Appendix  of  testis 

Prostatic  utricle 

PeWs  and   collecting  tubules 

of  kidney 
Bladder 

Prostatic  urethra 

Prostate  gland 

Cowper's  gland 

Penis 

Lips  of  urethral  groove 

Scrotum 


IndifTcrent  Typ« 

Sexual  gland 
Wolffian  tubules 
{sexual  group) 

Wolffian  duct 

(upper  end) 
Mullerian  duet 

Renal  oulgrojvth 
from  H'o/ffian  duct 

lower  segment  of  allantois 

and  part  of  cloaca 

Urogenital  sinus 

{outgrowths  from  wall) 

Genital  tubercle 

Genitalfolds 

.KaMo-scrotal  folds 


Female 

Ovary  . 

Short  tubules  of  epoophoron 

Paroophoron 

Main  tube  of  epoophoron 

G.^rtner•s  duct,  when  persisting 

Hydatid  of  Morgagni 

Oviduct 

Uterus 

Vagina 

Pewland  collecting  tubules  of 

kidney 
Bladder 

I'rethra  and  vestibule 
Paraurethral  tubes 
Bartholin's  gland 
Clitoris 
Labia  minora 
Labia  majora 


m 


3046 


HUMAN  ANATOMY. 


THE  FEMALE   PERINEUM. 

The  structures  closing  the  pelvic  outlet  in  the  female  correspond  with  those 
found  in  the  male,  modified,  however,  by  the  presence  of  the  urogenital  cleft  and  the 
small  size  of  the  clitoris. 

Owing  to  the  greater  divergence  of  the  bony  boundaries  of  the  subpubic  angle 
and  the  increased  disunce  between  the  ischial  tuberosities,  the  width  of  the  lozenge- 
shaped  perineal  space  (when  the  limbs  are  separated)  is  somewhat  greater  in  the 
female.  As  in  the  male  (page  19 16),  ihe  perineal  region  is  divisible  into  a  posterior 
recttU  and  an  anterior  urogenital  triangle  by  an  imaginary  transverse  line  drawn 
between  the  anterior  borders  of  the  ischial  tuberosities.  Distinction  must  be  made 
between  the  term  "perineum,"  as  above  used,  to  indicate  the  entire  region,  and 
when  applied  in  a  restricted  sense  to  the  bridge  separating  the  anal  and  vulvar  orifices. 
Reference  to  sagittol  sections  (  Fig.   1 700)  shows  that  this  superficial  bridge  forms  the 


Fig.  t7jg. 


Cut  cdKe  of  super- 
ficial layer  of  su- 
perficial fascia 

Prepuce  of  clitoris 
Glang  clitoridis 


Labia  niinora| 
Labia  majoia 

Superficial  fascia 


Superficial  layer 
of  superficial 
fascia  reflected 


Superficial  dissection  of  female  perineum ;  on  riitlit  side  skin  only  has  been  removed ; 
on  left,  superficial  layer   of  superficial  fascia  has  been  reflected. 

lower  part  of  a  triangular  fibro-muscular  mass,  t\\t  perineal  body,  that  divides  the 
vagina  from  the  rectum  and  anal  canal  and  contains  the  perineal  centre  with  the  con- 
verging fibres  of  the  external  sphincter,  transverse  perineal,  and  bulbo-cavernosus 
(sphincter  vaginae)  muscles. 

Apart  from  its  somewhat  jjreater  breadth  and  more  generous  layer  of  fat,  the 
rectal  triangle  presents  no  special  features  and  contains  the  same  structures  as  in  the 
male.  The  superficial  fascia,  prolonged  from  the  thighs  and  buttocks  and  usually 
laden  with  fat,  closes  in  the  ischio-rectal  fossae  and  is  directly  continuous  with  the 
fatty  areolar  tissue  filling  these  spaces.  The  internal  pudic  vessels  and  pudic  nerve 
occupy  the  fascial  (Alcock's)  canal  on  the  outer  wall  of  the  ischio-rectal  fossa  and 
give  off  the  inferior  hemorrhoidal  branches  distributed  to  the  skin  and  muscles  sur- 
rounding the  anal  canal. 

Over  the  urogenital  triangle  the  superficial  fascia  is  divisible  into  two  distinct 
layers,  a  superficial  and  a  deep.  The  former,  loaded  with  fat,  is  continuous  above 
and  at  the  sides  with  the  corresponding  stratum  on  the  abdomen  and  the  thighs,  and 
behind  with  the  superficial  fascia  covering  the  rectal  triangle.  The  deep  layer,  or 
Colles's  fascia,  is  devoid  of  fat  and  membranous  in  character.     Behind,  where  it  turns 


THE  FEMALE  PERINEUM. 


2047 


over  the  tr«»ver.  P-j-l-^^S,  "^ST^t  l!  SSX'^^^t'Z  ' 

angular  ligament  a^oj^  the  P^^^^''^" ',^1^^^^  majora  to  become  contmuou.  I 

&hr^:>^«inLl"i^ii  '^'»)  -r  the  abdomen. 


GlanB  ilitoridi* 

Suix:rfiii«l— — 
laKia 

Labia  minor*"" 
Vulvar  fiMure"^" 

Labia  majtif* 

CoUm's  fascia— 
EilKc  ol  cut  akin— • 


Ceccys — 


Interior 

pudcnilal  nerve 
— Faacia  laUk 
oi  thifh 

Inferior 

. pudendal  nerve 

-Tuber  iachii 

t  uttaMUl  l«ftBchM 

-..dnttnul*'"'!""'- 
Dsl  p«fi»e»l  ■«T»«* 

From  iiuemal 
(lerineal  ner>e 
— ur  b«inoffhot<ta'.  Mt. 
■Inf.  h«inotThotd*l 


.From  foufth 
•lacral  nerve 


-^  1.^  uro«niUl  triangle;  CoUea'.  faacia  and  cuttneou* 
Superacia.  tay«  C  .up«fidal  tacia  ha.  '5j;i^f^el3;  S^SSl      '""' 


Fig.  i73»- 

Do,-,  arury  of  cUUnta     Dor«l  "-^f  .—   „i„rt. 

Donal  velnd  clltoriav  /    /  y  Crua  clitoridia 

GteaacUtoridii.      ^ 


I 


Pubic  lamua- 


Crusclitoridis 

Bulbus  — 
vestibuli 


Triangular  7- 
liKament,  in-  _. 
lerior  layer 


Tuber  iachii 


Glands  of  Bartholin 


,l„u,.  «  tri.ng«l.r  pock«  l.™«»f,;^,"   ,Vuh  Cote's  lic».     In  addition  to  <he 
»  ^SlK.^'Sni,^S,S.ngpnd.nd.,n.,v»,the  t.»sv=™  p«.- 


4048 


HUMAN  ANATOMY. 


neal  muiclei,  and  the  inlands    f  Bartholin,  this  space  contains  the  crura  of  the  clitoris, 
the  vestibular  bulb  and  their  associated  muscles  (ischio-  and  bulboKavernoaus). 

KiG.   1731. 

Lcftdonal 
aftcry  <A  clitorit 


Colics'!  luiia 
reflect  wl 
Plini  intermedia - 
lKhio■ 
cavcniMaua' 
Bulbui  veatibuli 
Bmbo- 
cavrrnoMUi 
TriatiKVlar  Uxa- 
mctit,  inf.  layer 
Transveraua" 
perinei 

Superficial  fascia 

External 
sphincter 


.Glans  clltoridit 

Ischio* 
— ca\  einosus 
-Supcrflcial 

perineal  artery 

-  laf.  pudcadAl  serve 
_  AaC.  |)«Ha*«l  irterjr 
,  I^Mt.  IJCrincAj  serve 
— Tisu.  periaesl  wl. 

|B(.  IwliMikiitilsl 

sitarv 


serve 
Anal  fascia 


Anus 


-Coccya 


Deep  layer  oi  superficial  (aacia  (Colles's  laacia)  removed,  eaposing  ttructntcs  iHlhin  superficial  intenpace. 


Dorsal  artery  of  clitoria. 
Dorsal  vein  of  clitoria 


Fig.  X733- 

Glans  clitoridis 


Dorsal  artery  o(  clitorto 
Arteiy  of  corpus  cavemosus 


Dorsal  nerve  o(  clitoris 


Crua  clitoridi» 

Trian^lar 
ligament,  deep- 
layer 


Tuber  ischU 


Deep  trans- 
versus  perinei 


Levator  ani 


Internal  pndic 
artery 


Trf  angular 
Ugameiit 

—Artery  of  bulb 


Internal 
-pudic  artery 

-Perinealdiviskm 
of  pudIc  nerve 

-Inf.  hemorrhoidal  art 
—Pndic  nerve 
'Levator  ani 


—From  fourth 
sacral  ner\'e 

^Greater  sacro- 
^  sciatic  ligament 
^Gluteus 

maxim  us,  cut 


/  /  \  \ 

Gluteus  maximus  Coccyx  Inferior  hemorrhoidal  nerve         Coccygeus 

Deeper  dissection  01  iwrmtuni ;  inferior  layer  of  IrianKuJar  ligament  has  been  removed,  exposing  deep  perineal 
interspace;  ischio-rectal  fossa  partially  cleaned  out. 

Owing  to  the  diminutive  size  of  the  crura  clitoridis,  the  ischio-cavemosus  muscles  are 
correspondingly  small,  but  otherwise  agree  with  those  in  the  male. 


THE  FEMALE  PERINEUM. 


ao49 


band:)  that  encircle  the  vestibule.  ,pAiHfUr  vagina,  arises  from  the 

The  bulbo-cavernosus  [""^'fibres  of  the  exter^  sphincter  and  the  transverw; 
perineal  centre,  blending  .IJ^^'J^  J  '^n  and  a  Ut«al  portion  as  it  pas«»  forward, 
^rineal  muscles,  «.d  divides  \"»°  »J"^"  j^  thrvagU.  crosses  theTrus  to  |ain 
•rhe  lateral  and  more  '"g*:;^  *Xte"enSil  the^p^te  mu«:le.  by  blenSing 
the  dorsum  cHtorid». -"f  ^^J^j^^^^  ''^TSe  meSi^n  and  li^  portion  of  the  muscle 
with  the  hbrous  «h^f  °'  » Je  ditom    ^  ^^  g^^^^,,^  ^^  he  vesUbuUr 

ab;3Tf;oifui  :" h  S'Lrrespondin^g  strand  of  the  opposite  side  m  a 


Fio.  I7J4- 

Clltorii 


Clam  o(  cIMorto 


Vulvar  AnufC 
White  lliw  o4  wl- 
vic  taKia  illchtly 
displaced    toward 
midline 
Tuber  iKhii 


Levator  ani 

Aiitti 


-  -     CuccvKeua 


Greater 

■acro^ciatic 
ligament 

Gluteua 
maxima*  (rot) 


Coccya 


DeeJ.  direction' a.  perineum,  eapoain,  muacle.  of  pelvic  floor. 


delicate  tendinousexpansion  that  passesbeneath  the  body  Of  theditorisandisattached 

^''^'^^Be^^n  the  inferior  and       S^tTtht^tiSr^^^^^^^^ 

the  d»p  perineal  inUrspace       n  '^'^'M""  »° 'jl\^°^""  ^^  by  a  thin  and  imperfect 

iSsels  ai^  pudic  nerves.  »»>»  ^^^^J^J^  t  cCp^r  S^  '^^^  ^'''^°'  ^^ 
muscular  aheet  that  <:«":«P?"*^  ^''^h^^  Xri^«s.  into  the  deep  transverae 
of  this  sheet  is  differentiated.  ^'^'VX  ftiTtK)5ities.  pass  behind  the  vagina 
perineal  muscles  which,  ansing  fronri  the  ^^^  sheet,  collectively  much  le» 
to  the  perineal  centre.  The  "i^J"^'"'"^  ^^^  urShr^  in  the  male.  U  continued 
developed  than  the  sphincter-like  ~"?P''^' ,„ "{^closely  encircles  the  vagina. 
rC^arrfrom  the  perineal  centre  as  ^^^J'^/^f^^;  fr^^of  the  urethra  in  the 
and  in  front  either  surrounds  he  ^'^'l^\^^i  (Kalischer).  In  recognjuon 
LTtiriSr  totlhThe  T4S  SSri^canals.  ^this  muscular  sheet  has  been 
appropriately  called  the  urogenital  sphtncUr^ 


. 


INDEX. 


Abdomen,  examination  of.  •B«ton..-«l  rela- 
tiona.  S36 
faacia,  iuperficiftl  of.  515^      , 
Undmarlu  and  topography  of.  S3« 
lymphatici  of,  07  a 
iymph-nodea  of.  974 
muKleaof.  515 
pract.  coniiid..  5»6 
ventral  aponeuroM  of,  s»« 
Abdominal  cavity,  161$ 
aorta,  794 
regions,  1615 
hernia.  i7S9  , 

incisi'o' s  anatomy  of,  535 
ting,  exiemal,  514 
internal,  5*4 
walU.  lymphatics  of.  976 
poatenor  surface  of,  5»5 
Acervulus,  JUS 
Acetabulum,  336 
Acoustic  area,  1097 

strise.  laS"  , 

Acromio-clavicuUr  articulation,  a6a 

pract.  consid..  ao4 
Acromion  process,  a  50 
Adamantoblasts.  1561 

Adipose  tissue,  79         -  , 

chemical  composition  of,  83 

After-birth,  SS 

Sr^A  Kll'nd.  (Peyer's  patches),  .64. 

Air-cells,  ethmoidal,  i4a4 

pract.  consjd..  i4a9 
Air-sacs  of  lung,  1850 
Air-spaces,  accessory,  14?] 

pract.  consid.,  1436 
Ala  cinerea,  1097 
Albinism,  1461 
Alcock's  canal,  817 
Alimentary  canal,  1 538 

tract,  development  of.  1694 
Alis{>>ienoids,  .86 
Allatitois,  33 

arteries  of,  33 
human,  3  s 
stalk  of,  33 
veins  of,  33 
Alveoli  of  lung,  iSi'o 
Ameloblasts,  1561 
Amitosis,  14 
.\mnion.  30 
false,  31 
folds  of,  30 
human,  35 

cavity  of,  35 
fluid  of,  4> 
liquor  of.  31 
suture  of,  31 
Amniota,  30 
.\mphiarthrosis,  107 
Anal  canal,  it)73 
Analogue,  4 
Anamnia,  30 
Anaphases  of  mitosis,  13 
Anastomoses,  of  ophthalmic  veins,  880 

THIS  VOLUME    CONTA 


Angulus  Ludovici.  i6« 
Ankle,  landmarks  of,  67  a 

muscles  and  fasciae  of,  pract. .  onsid..  «>66 
Ankle-joint.  43* 

movements  of,  440 
prai.t.  consid  .  45" 
Annuli  tibroei,  of  heart,  698 
Annulus  ovalis,  695 
tymjpanicus,  1493 
of  Vieusaens,  695 
Anorchism,  «95o  .    .. 
Anthropology  of  skull.  asS 
Anthropotomy,  i 
Antihehx,  1484 
Antitragus,  1484 
Anlruin.  J27 

of  Highmore,  M^' 

pract.  consid.,  i4a» 
pylori.  1618 
of  superior  maxilla,  aoi 
Anus.  1673 

formation  of,  1095 
muscles  and  fasc^a^  of.  167  s 
pract.  consid.,  1689 
Aorta,  abdominal,  794         ^  .  .     .   . 

branches  of,  pract.  consid.,  »o6 
plan  of  branches,  796 
pract.  consid.,  796 
dorsal,  7a J 
pulmonary,  7aa 
segmental  arteries  of,  847 
systemic,  723 
thoracic.  791 

prac.  consid.,  730 
valves  of,  700 
ventral,  7a  1 
Aortic  arch,  ^l^ 

pract.  consid.,  7ao 
variations  of,  734 
bodies,  tSia 
bows,  847 
septum.  707 
Aponeurosis.  468 

abdominal,  ventral,  5a» 
epicranial,  48a 
(fascia)  plantar,  659 
i)almar,  606 
Appendages,vesicular,of  broad  ligament,aoo3 
Appendices  epiploic*.  1660 
Appendix  epididymidis,  1949 
testis,  1949 
vermiform,  1664 

blood-vessels  of,  1667 
development  and  growth  of, 
mesentery  of,  1665 
orifice  of,  1 66a 
peritoneal  relations  of,  1665 
pract.  consid.,  i68i 
Aquteductus  cochleae,  1514 

vestibuli,  15' a 
Aqueduct  of  Fallopius,  1496 

Sylvian,  1108 
Aqueous  humor,  1476 

chamber,  anterior  of. 


1668 


INS    PAGES   9»6   TO   THE 


1476 

J05.I 
END. 


2052 


INDEX. 


Aqueous  humor,  chamber,  pocterior  of,  147 

pract.  consid.,  1476 
Arachnoid,  of  brain,  1 203 

of  spinal  cord,  loaz 
Aranttus,  nodules  of,  700 
Archenteron,  aj 
Arches,  visceral,  59 

fifth  or  third  branchial,  61 
first  or  mandibular,  60 
fourth  or  second  branchial,  61 
second  or  hyoid,  60 
third  or  first  branchial,  61 
Arcuate  nerve-fibres,  107 1 
Area  acustica,  1097 
embryonic,  23 
parolfactory,  1 1 53 
pellucida,  35 
Areola,  aoaS 

Arm,  lymphatics,  deep,  of,  965 
superficial,  of,  963 
muscles  and  fascia  of,  pract.  consid.,  589 
Arnold's  ganglion,  1 346 
Arrectores  pilorum,  1394 
Arterial  system,  general  plan  of,  730 
Artery  or  arteries,  7 1  o 

aberrant,  of  brachial,  775 
allantoic,  33 
alveolar,  741 

of  internal  maxillary,  741 
anastomoses  around  the  elbow,  778 
anastomotica  magna,  of  brachial,  77S 

of  femoral,  831 
angular,  738 

of  facial,  738 
aorta,  systemic,  733 
articular,  of  popliteal,  833 
auditory,  internal,  759 
auricular,  anterior,  of  temporal,  745 
deep,  740 

of  internal  maxillary,  740 
of  occipital,  744 
posterior,  744 
axillary,  767 

pract.  consid.,  769 
azygos,  of  vaginal,  813 
basilar,  758 
brachial,  773 

pract.  consid.,  776 
brachialis  superficialis,  775 
bronchial,  793 
buccal,  741 

of  internal  maxillary,  741 
to  bulb  (bulbi  urethrx),  817 
calcaneal,  external,  838 
internal,  839 
of  external  plantar,  840 
calcarine,  760 
carotid,  common,  730 

pract.  consid.,  731 
external,  733 

pract.  consid.,  733 
internal,  746 

pract.  consid.,  747 
system,  anastomoses  of,  753 
carpal,  of  anterior  radial,  788 
of  anterior  ulnar,  783 
arch,  posterior,  789 
of  posterior  radial,  788 
of  posterior  ulnar,  783 
reta,  anterior,  791 
centralis  retinje.  749 
cerebellar,  inferior,  anterior,  755 
posterior,  759 


Artery  or  arteries,  cerebellar,  superior,  759 
cerebral,  anterior,  753 

middle,  753 

posterior,  760 
cervical,  ascending,  of  inferior  thyroid, 
766 
of  transverse  cervical,  767 

deep,  764 

superficial,  766 

transverse,  767 
choroid,  anterior,  751 
ciliary,  749 

anterior,  749 

posterior,  749 
circle  of  Willis,  760 
circumflex,  anterior,  773 

external,  of  deep  femoral,  838 

internal,  of  deep  femoral,  838 

posterior,  773 
circumpatellar  anastomosis,  834 
coccygeal,  of  sciatic,  815 
coeliac  axis,  797 
colic,  left,  803 

right,  803 
comes  nervi  ischiadici,  815 
communicating,  anterior,  753 

of  peroneal,  838 

posterior,  751 

of  posterior  tibial,  839 
coronary,  inferior,  738 
of  facial,  738 

left,  738 

right,  738 

superior,  738 

of  facial,  738 
of  corpus  cavemosum,  817 
cremasteric,  of  deep  epigastric,  830 

of  spermatic,  805 
crico-thyroid,  734 

of  superior  thyroid,  734 
cystic,  of  nepatic,  799 
dental,  anterior,  of  mtemal  maxillary, 
741 

inferior,  740 
development  of,  846 

of  lower  limb,  848 

of  upper  limb,  848 
digital,  collateral,  of  ulnar,  784 

of  ulnar,  784 
dorsal,  of  foot,  845 

of  penis  (clitoris),  817 
dorsalis  hallucis,  846 

indicis,  789 

pedis,  845 

pollicis,  789 
epigastric,  deep,  830 

superficial,  8a6 

superior,  763 
ethmoidal,  749 

anterior,  750 

posterior,  749 
facial,  737 

anastomoses  of,  738 

glandular  branches  of,  737 

pract.  consid.,  738 

transverse,  745 
femoral,  831 

anastomoses  of,  83 1 

deep,  838 

development  of,  833 

pract.  consid.,  834 
fibular,  supenor,  of  anterior  tibial,  844 
frontal,  of  ascending  middle  cerebral,  753 


TH!«  VOLUME    CONTAINS    PAGES    986    TO    THE    tND. 


INDEX. 


2053 


Artery  or  arterie..  frontal,  of  inferior  middle 
cerebral,  753 
internal,  anterior,  753 
middle,  753 
posterior,  753 
of  otmthalmic.  75°    .         ,   ,,„ 
GasserUr of  middle  menmgeal.  740 
gastric,  798  . 

short,  of  splenic,  800 
gastro-duodenal,  799 
gastro-epiploic,  left,  801 

right,  799 
glandular,  of  facial,  737 
gluteal,  811 

pract.  consid.,  014 
hemorrhoidal,  inferior,  817 
middle,  813 
superior,  803 
hepatic,  799 
hyaloidea,  i474 
hypogastric  axis,  808 
obliterated,  808 
ileo-colic,  80  a 
iliac,  circumflex,  deep,  8ai 
superficial,  826 
common,  807 

pract.  consid.,  807 
external,  8i8 

anastomoses  of,  8a  i 
pract.  consid..  819 
of  ilio-lumbar,  810 
internal,  808  ,  „  . 

anastomoses  of,  81 » 
pract  consid.,  810 
ilio-lumbar,  810 

infrahyoid,  of  superior  thyroid,  734 
infraorbital,  741 

of  internal  maxillary,  74' 
innominate,  729 

pract.  consid.,  729    .  , 

intercostal,  of  anterior  internal  mam- 
mary, 763 
aortic,  79a 

of  internal  mammary,  765 
superior,  764  .,       ^ 

internal  mammary,  pract.  consid.,  764 
interosseous,  anterior,  781 
common,  781 
dorsal,  846 

posterior,  78a  . 

intestinal,  of  superior  mesenteric,  80a 
labial,  inferior,  738 

of  facial,  738 
of  internal  maxillary,  74' 
lachrymal,  749. 
laryngeal,  inferior,  766 

superior,  of  superior  thyroid,  734 
lateral  cutaneous,  of  aortic  intercostals. 

lenticulo-striate,  of  middle  cerebral,  75a 
lingual,  735  ,       ^ 

anastomoses  of.  730 

dorsal,  736 

pra^t.  consid.,  736 
lumbar,  80  j 

of  ilio-lumbar,  810 
malleolar,  external,  844 

internal,  of  anterior  tibial,  844 
of  posterior  tibial,  839 
mammary,  of  aortic  intercostals,  793 

internal,  763 

lateral  interna],  764 
masseteric,  740 


Artery  or  arteries,  mi^sse.^.-  0,  of  facial,  738 
of  internal  maxillary,  740 
mastoid,  of  occipital.  744 
maxillary,  internal,  739, 

anastomoses  of.  74a 
development  of,  74a 
median.  781  , 

mediastinal,  of  internal  mammary,  703 

of  thoracic  aorta,  79a 
meningeal,  anterior,  748 

ofascending  pharyngeal,  743 

middle,  740 

of  internal  maxillary,  74© 
posterior,  of  otiipital,  744 

of  vertebral,  758 

small,  740 
mesenteric,  inferior,  80a 

superior,  801 
metacarpal,  dorsal.  789 
metatarsal,  of  foot,  84S 
middle,  colic,  80a 
musculo-phrenic,  763 
nasal,  lateral,  738 

of  facial,  738 
of  ophthalmic,  750 
naso-palatine,  of  internal  maxillary,  74a 
nutrient,  of  brachial.  774 
of  peroneal.  838 
of  posterior  tibial,  838 
of  ulnar,  781 
obturator,  813  . 

from  deep  epigastnc,  814 
occipital.  743 

pract.  consid.,  744 
cesophageal,  of  gastric,  798 
of  thoracic  aorta.  79a 
omphalomesenteric,  31 
ophthalmic,  748 

anastomoses  of,  7  50 
orbital,  of  middle  meningeal.  740 

of  temporal,  745 
ov.irian,  805 

of  uterine,  813 
palatine,  ascending.  737 
of  facial,  737 
descending,  741 

of  internal  maxillary,  74' 
palmar  arch,  deep,  785 
superficial,  784 
deep,  78a 
intero8S.TOus,  790 
palpebral,  of  internal  maxillary,  741 

of  ophthalmic,  7  50 
pancreatic,  of  splenic,  800 
pancreatico-duodenal,  inferior,  802 

superior.  799 
parietal,  of  middle  cerebral,  753 
parieto-occipital,  760 

temporal,  753 
parotid,  of  temporal,  74.S.  ,        __ 

perforating,  of  anterior  internal  mam- 
mary,  763 
of  deep  femoral,  828 
posterior,  of  external  planti.r,  840 
of  radial,  70' 
perineal,  superficial,  817 

transverse,  817 
peroneal,  anterior,  838 
posterior,  838 
of  posterior  tibial,  838 
petrosal,  of  middle  meningeal,  740 
pharyngeal,  ascending.  743 
I  of  ascending  pharyngeal,  743 


THIS  VOLUME    CONTAINS  PAGES  996  TO  THE    END. 


2054 


INDEX. 


Artety  or  arteries,  phrenic,  inferior,  804 

superior,  763 
plantar  arch,  840 

digital,  840 

external,  840 

internal,  839 

interosseous,  840 
popliteal,  831 

pract.  consid.,  833 
posterior  choroidal,  760 
ininceps  cervicis,  744 

hallucis,  841 

poUicis,  789 
profunda,  inferior,  777 

superior,  777 
prostatic,  81  a 
pterygoid,  740 

of  internal  maxillary,  740 
pterygo-palatine,  742 

of  internal  maxillary,  743 
pubic,  of  deep  epigastric,  810 

of  obturator,  813 
pudic,  external,  deep,  828 
superficial,  826 

internal,  815 

accessory,  8t8 
pulmonary,  723 

valves  of,  700 
pyloric,  of  hepatic,  799 
radial,  785 

development  of,  786 

pract.  consid.,  786 

recurrent,  787 
radialis  indicis.  790 

superficialis,  775 
ranine,  736 
recurrent,  of  palm,  791 

of  posterior  interosseous,  782 
renal,  804 
sacral,  lateral,  810 

middle,  806 
scapular,  dorsal,  773 

posterior,  767 
sciatic,  815 
septal,  of  nose,  738 
sigmoid,  803 
spermatic,  805 
spheno-palatine,  743 

of  internal  maxillary,  742 
spinal,  anterior,  of  vertebral,  759 

posterior,  of  vertebral,  758 
splenic,  800 

stemo-mastoid,  of  external  carotid,  743 
of  occipital,  744 
of  superior  thyroid,  734 
striate,  external,  of  middle  cerebral,  752 

internal,  of  middle  cerebral,  752 
structure  of,  675 
stylo-mastoid,  745 
subclavian,  753 

pract.  consid.,  756 
subcostal,  792 
sublingual,  736 
submental,  737 

of  facial,  737 
subscapular,  77a 
suprahyoid,  736 
supraorbital,  j\g 
suprarenal,  804 

inferior  .Hn.} 
suprascapular.  767 
tarsal,  external,  845 

internal,  845 


Artery   or  arteries,  temporal,  anterior,   ol 
vertebral,  760 
deep,  740 

of  internal  maxillary,  740 
middle,  74s 
posterior,  of  vertebral,  760 
superficial,  745 

pract.  consid.,  745 
thoracic,  acromial,  771 
alar,  773 
long,  772 
superior,  771 
thyroid  axis,  765 

pract.  consid.,  766 
inferior,  766 
superior,  734 

pract.  consid.,  735 
tibial,  anterior,  842 

anastomoses  of,  844 
pract.  consid.,  843 
posterior,  834 

anastomoses  of,  841 
development  of,  836 
pract.  consid.,  836 
recurrent,  anterior,  844 
posterior,  844 
tonsillar,  737 

of  facial,  737 
tubal,  of  ovarian,  805 

of  uterine,  813 
tympanic,  of  internal  carotid,  748 
of  internal  maxillary,  740 
of  middle  meningeal,  740 
ulnar,  778 

accessory,  776 
development  of,  779 
pract.  consid.,  780 
recurrent,  anterior,  781 
posterior,  781 
umbilical,  54 
ureteral,  of  ovarian,  805 
of  renal,  804 
of  spermatic,  805 
of  uterine,  813 
urethral,  817 
uterine,  813 
vaginal,  813 
vertebral,  758 

pract.  consid.,  761 
vesical,  inferior,  81 1 
middle.  811 
of  obturator,  813 
superior,  81 1 
vesiculo-deferential,  81  a 
Vidian,  742 
vitelline  33 
volar,  superficial,  788 
Arthrodia,  113 

Articulation  or  articulations,  acromio-clavio 
ular,  pract.  consid  ,  364 
carpo-metacarpal,  325 

movements  of,  336 
costo-vertebral,  160 
of  ethmoid,  194 
of  foot,  440 
of  frontal  bone,  197 
of  inferior  turbinate  bone,  308 
of  lachrymal  bone,  307 
of  malar  bone,  310 
metacarpo- phalangeal.  327 

movements  ot,  338 
of  nasal  bone,  309 
of  occipital  bone,  atlas,  and  axis,  135 


THIS  VOLUME    CONTAINS    PAGES   996   TO   THE    END. 


INDEX. 


2055 


ArUcutation  or  articulatioM.  of  palate  bone 
205 
of  parietal  bone,  199 
sacro-iliac,  338 
scapulo-clavicular,  aoj 
of  sphenoid  bone,  190 
stemo-clavicular,  a6i 

pract.  consid.,  263 
of  superior  maxilla,  »oi 
of  temporal  bone,  184 
temporo-mandibular,  214 
development  of,  215 
movements  of,  215 
thoracic  anterior,  1 58 
of  thorax,  IS7 
of  thumb,  3»6  ,    .  ^ 

tibio-fibular,  inferior,  390 

superior,  396 
of  vertebral  column,  132 
of  vomer,  206 
Arytenoid  cartilages,  1810 
Asterion,  228 
Astragalus,  4«3        , 

development  01,  4*5 
Astrocytes,  1003 
Atlas,  130 

development  of,  131 
variations  of,  120 
Atria  of  lung,  1850 
Auditory  canal,  external,  1407     „ 
blood-vessels  of,  1489 
nerves  of,  1490 
pract.  consid.,  1491 
internal,  1514 
ossicles,  1496 
path,  1258 
Auerbach,  plexus  of,  1643 
Auricle  or  auricles,  1484 
antihelix  of,  1484 
antitragus  of,  1484 
blood-vessels  of,  1480 
cartilage  of,  148  s 
concha  of,  1484 
of  heart,  693 
helix  of,  1484 
ligamenU  of,  i486 
lobule  of,  1484 
muscles  of,  i486 
nerves  of,  1487 
pract.  consid.,  1490 
structure  of,  1485 
tragus  of,  1484 
Auricular  canal,  70s  ,u  „^  ■,„, 

Auriculo- ventricular  bundle  of  heart,  701 

^"'muiJlU  and  fascia  of,  pract.  consid.,  579 

Axis,  121 

Axis-cylinder,  looi 
Axones,  of  neurones,  997 
Azygos  system  of  veins,  893 

Bartholki,  glands  of,  2026 
Basion,  228  , 

Bell,  external  respiratory  nerve  of,  1295 
Bertin,  bones  of,  191 

columns  of,  1876 
Bicuspid  teeth,  154S 
Bile-capillaries,  1715 
Bile-duct,  common,  1720 
opening  of,  1720 
pract.  consid.,  1731 

interlobular,  1717 

lymphatics  of,  981 


Biliary  apparatus,  17 18 
Bladder,  lymphatics  of,  985 
urinary,  1901 

capacity  of,  1903 
development  of,  1938 
in  female,  1908 
fixation  of,  1905 
infantile,  1908 
interior  of,  1904 
nerves  of,  191  o 
peritoneal  relations  of,  1904 
pract.  consid.,  1910 
relations  of,  1906 
structure  of,  i9°8 
trigone  of,  1904 
vessels  of,  19 10 
Blastoderm,  32 
bilaminar,  23 
trilaminar,  23 
Blastodermic  layers,  22 

derivatives  of,  24 
vesicle,  stage  of,  56 
Blastomeres,  21 
Blast  -    2S 

Bla. 
Blor 
Bio  jlored,  681 

.„c,   684 

development  of,  687 
Blood-crystals,  681 

lakes  of  dural  sinuses,  85* 
plaques,  685 
Blood-vascular  system,  673 
Blood-vessels  of  auricle,  i486 
of  bone,  93 
of  brain,  uo6 
capillary,  678 
of  cartilage,  81 
development  of,  686 
of  duodenum,  1649 
of  Eustachian  tube,  1 504 
of  external  auditory  canal,  1489 
of  eyelids,  1445 
of  glands,  1535 
of  hair-follicles,  1394 
of  kidney,  1884 
of  liver,  1 709 
lobular,  of  liver,  17 13 
of  lung,  1853      .  ^     .  ..       ,.. 
of  membranous  labynnth,  1522 
of  nasal  fossa,  1425   , 
of  non-striated  muscle,  456 
of  nose,  1407 
of  pericardium,  716 
of  pleura,  i860 
of  rectum,  1679 
of  retina,  1467 
of  sk=-     1387 
of  smaU  intestine,  1642 
of  spinal  cord,  1047 
of  stomach,  1627 
of  striated  muscle,  464 
structure  of,  673 
of  sweat  glands,  1400 
vasa  vasorum,  674 
Body-cavity,  differentiation  of,  1 700 
Body-form,  general  development  of,  56 
Body-stalk,  37 
Bone  or  bones,  84 
age  of,  106 
astragalus,  423 
of  Bertin,  191 
blood-vessels  of,  93 


THIS  VOLUME    CONTAINS    PAGES   996  TO  THE    END. 


2056 


INDEX. 


middle,  41; 
development  of,  94 


Bone  or  bones,  calcaneum,  4 1 9 
canaliculi  of,  86 
cancellated,  85 
carpus,  309 
cells  of,  89 

chemical  composition  of,  84 
clavicle,  257  • 

compact,  86 

development  of,  100 
cranium,  172 
cuboid,  423 
cuneiform,  310 

external,  428 

internal,  426 

of,  I 
endochondral,  94 
intramembranous,  98 

diaphysis  of,  104 

elasticity  of,  105 

ethmoid,  191 

femur,  352 

fibula,  390 

frontal,  194 

general  considerations  of,  1 04 

growth  01,  10 1 

Haversian  canals  of,  88 
system  of,  86 

humerus,  265 

hyoid,  216 

ihum,  332 

inferior  turbinate,  308 

innominate,  332 

intramembranous,  loi 

ischium,  336 

lachrymal,  207 

lacunx  of,  86 

lamells  of,  circumferential,  86 
Hav  rsian,  86 
int(   stitial,  86 

lymphatics  cf,  93 

malar,  209 

maxilla,  inferior,  211 
superior,  199 

mechanics  of,  105 

metacarpal,  314 

metatarsal,  428 

nasal,  209 

nerves  of,  94 

number  of,  107 

occipital,  172 

OS  magnum,  312 

palate,  204 

parietal,  197 

parts  of,  106 

patella,  398 

periosteum  of,  89 

phalanges  of  foot,  431 
of  nand,  317 

physical  properties  of,  85 

pisiform,  311 

pubes,  334 

radius,  287 

relation  of  to  figure,  107 

ribs,  149 

scaphoid,  309 
of  foot,  425 

scapula,  248 

semilunar,  310 

sesamoid.  104 

sex  of,  106 

shapes  of,  104 

Sharpey's  fibres  of,  87 


Bone  or  bones,  of  shoulder -girdle,  248 

skull,  17a 

sphenoid,  186 

sphenoidal,  turbinate,  191 

sternum,  155 

structure  of,  85 

subperiosteal,  98 

tarsal,  419 

temporal,  176 

of  thorax,  149 

tibia,  383 

trapezium,  311 

trapezoid,  311 

ulna,  281 

imciform,  312 

variations  of,  107 

Volkrnann's  canals  of,  89 

vomer,  205 
Bone-marrow,  90 

cells  of,  92 

giant  cells  of,  92 

nucleated  red  cells  of,  92 
erythroblasts,  93 
normoblasts,  93 

primary,  95 

red,  90 

yellow,  93  ' 

Bowman,  glands  of,  1415 

membrane  of,  1451 
Brachium,  inferior,  1107 

internal  structure  of,  mo 

superior,  1107 
Brain,  10S5 

blood-vessels  of,  1 206 

general  development  of,  lojS 

lymphatics  of,  948 

measurements  of,  1195 

membranes  of,  1197 

pract.  consid.,  1307 

weight  of,  1 196 
Brain-sand  (acervulus),  1135 
Brain-stem,  1056 
Brain- vesicles,  primary,  1059 

secondary,  1061 
Branchial  arches,  derivatives  of,  847 
Bregma,  328 
Bronchial  tree,  1847 

variations  of ,  1849 
Bronchus  or  bronchi,  1838 

homologies  of,  1848 

Sract.  consid.,  1840 
,  membrane  of,  1456 
Brunner,  glands  of,  1639 
Buccal  fat-pad,  489 
Bulb,  1063 

of  internal  jugular  vein,  8A1 

olfactory,  11 51 

urethral,  1968 
Bulbo-tecto-thalamic  strands,  11 16 
Bulbus  vestibuli,  2025 
Bulla,  of  ethmoid,  194 
Bums,  space  of,  543 
Bursa  or  burss,  1 1 1 

acromial,  $86 

around  ankle.  648 

bicipito-radial,  586 

iliopectineal,  623 

of  biceps  femoris,  636 

of  gluteal  region,  630 

of  knee-joint.  406 

of  m.  obturat.  int.,  630 

of  m.  pyriformis,  561 

olecranal,  586 


THIS  VOLUME    CONTAINS    PAGES    C96    TO    THE    END. 


INDEX. 


3057 


Bursa  or  bursa,  subdeltoid,  578 
subscapular,  57* 

Ca-vum,  1660 

blood-vessels  of,  io*7 
interior  of.  1661  .  ,(.. 

peritoneal  relations  of,  1665 
position  of.  1 66a 
pract.  consid.,  1680 
structure  of,  1663 

Calamus  scriptorius,  1096 

Calcaneum,  419 

Camper's  fascia,  Ji  5    ,,     .   . 

Canal  or  canate,  Alcock  s,  817 
alimentary,  1538 
anal,  1673 

auditory,  external,  i4»7 
auricular  of  heart,  705 

carotid,  184  

central,  of  spinal  cord,  1030 
of  Cloquet  (Stilling),  i474 
crural,  625  .     »   „. 

ethmoidal  (foramina),  19* 

facial,  184 
femoral,  6a S,^ 
Haversian,  of  bone,  »» 
Hunters,  6a8 
hyaloid,  147  4 
incisive,  I4'3 
inguinal,  523 
naso-lachrymal,  i479 
neural,  a6 
neurenteric,  as 
of  Nuck,  aoo6 
palatine,  anterior,  aoi 
posterior,  ao4 

of  Petit,  1476 
pterygo-palatine,  305 

reuniens,  1515 
of  Scarpa,  aoi 
of  Schlemm,  i45» 
semicircular  membranous,  151 5 

osseous,  151a 
structure  of,  1516 
of  Stenson,  aoi 
of  Stilling,  1474 
VidUn,  180 

Volkmann  s,  of  bone,  89 
Canaliculi,  of  bone,  86 

lachrymal,  1478 
Canine  teeth,  1 544 
Canthi  of  eye,  i44»  ,„ 

CapiteUum  of  humerus,  a68 
Capsule,  extemfil,  ii7» 
of  Glisson,  1708 
internal,  ii73    ^  ,     „ 
Suprarenal  (body),  1801 
of  Tenon,  504 
Caput  medusae,  534 
Cardiac  muscle,  46a 
Cardinal  system  of  veins,  854 
Carina  tracheae,  1837 
urethralis,  aoi 6 
Carotid  body  (gland),  1809 

chromaffine  cells  of,  1010 
sheath,  543 
Carpo-metacarpal  articulations,  335 
Carpus,  309 

pract.  consid.,  319 
Cartilage  or  cartilages,  80 


Cartilage  or  cartiUges,  articular,  81 
arytenoid,  1816 
of  auricle,  1485 
blood-vessels  of,  81 
capsule  of,  80 

chemical  composition  of,  83 
costel,  153 
cricoid,  181 3 

cuneiform  of  Wnsberg,  181 7 
development  of,  8a 
elastic,  81 
hbrous,  8  a 
hyaline,  80 
lacunae  of,  80 
lateral,  of  nose,  1405 
matrix  of,  80 
of  nasal  septum,  1405 
uf  nose,  1404 
perichondrium  of.  81 
of  Santorini,  181 7 
thyroid,  1814 

triangular,  of  nasal  septum,  aa4 
vomerine,  1406 
Cartilage-cells,  80 
CaruncuUe  hymenales,  aoi 6 

salivares,  1581 
Caruncle,  lachrymal,  1443  . 
Cauda  equina  of  spinal  cord,  loas 
Cavity,  abdominal,  161 5 
tiasal,  a  33 

pneumatic  accessory,  aa6 
segmentation,  aa 
synovial,  of  foot,  447 
tympanic,  I49» 
of  tympanum.  183 
Cell  or  cells,  animal,  6 
of  bone,  89 

of  connective  tissues,  73 
decidual,  47 
gustatory,  143 5 
mastoid,  1504 
of  Rauber,  33 
spermatogenetic,  1943 
tactile,  of  Merkel,  1016 
Cell-division,  10 
direct,  14 
indirect,  u 
reduction  division,  18 
Cell-mass,  inner,  33 

intermediate,  39 
Cementoblasts,  1563 
Cementum,  155a 

formation  of,  1 563 
Centrosome,  9 
Cephalic  flexure,  1061 
Cerei'sUar  peduncle,  fibre-tracts  of,  1093 
inferior,  1067 

inferior,  fibre-tracts  of,  1093 
middle,  fibre-tracts  of,  1094 
superior,  fibre-tracts  of,  1094 
Cerebellun.,  io8a 

architecture  of,  1088 
cortex  of,  ioqo 

histogenesis  of,  1 105 
development  of,  11 03 
flocculus  of,  1085 
hemispheres  of,  108  a 
lobus  cacumicis  of,  1085 
centralis  of,  1084 
divi  of,  1085 
culminis  of,  1084 
lineulx  of,  1084 
noduli  of,  1085 


THIS  VOLUME    CONTAINS    PAGES    996    TO    THE    END. 


iOjS 


INDEX. 


(-.';-' 


Cerebellam,  lobus  pyramidis  of,  1086 
tuberis  uf,  1087 
uvuls  of,  iod6 

medullary  substance  of,  1093 

nuclei,  internal  of,  108S 

nucleus,  dentate  of,  10S8 

einboliformis  (embolus)  of,  1089 
fastigii  of,  1089 
globosus  of,  1089 

Purkmje  cells  of,  1090 

tonsil  (a.mygd»la)  of,  1086 

worm  of,  108] 
Cerebral  commissures,  development  of,  1194 

convolutions  (gyri),  1135 

fissures  (sulci),  1135 

hemispheres,  1133 

architecture  of,  1155 
longitudinal  fiisure  of,  1133 

lobes,  1 135 

localization,  mo 

peduncles,  1107 
Cerebro-spinal  fluid,  1033 
Cerumen,  1489 
Cervical  flexure,  1063 
Cheeks,  1538 

lymphatics  of,  951 

pract.  consid.,  1594 
Choanse,  1413 

(bony),  334 

primitive,  1439 
Chorda  dorsalis,  37 
Chordae  tendines,  of  heart,  697 
Choriocapillaris,  1456 
Chorion,  33 

allantoic,  33 

epithelium  of,  49 

frondosum,  38 

human,  41 

laeve.  38 

primitive,  31 

syncytium  of,  49 

villi  of,  49 
Choroid,  1455 

development  of,  1483 

plexus  of  fourth  ventricle,  1 1 00 
of  third  ventricle,  1131 

pract.  consid.,  1459 

structure  of,  1456 
Chromaffine  cells  of  carotid  body,  1810 
Chromatin,  9 
Cilia,  70 
Ciliary  body,  1457 

ganglion,  1336 

muscle,  1458 

processes,  1457 

ring,  1457 
Circulation,  foetal,  939 

general  plan  of,  719 
Cistemu  magna,  1303 
Claustnim,  1 173 
Clava,  1066 
Clavicle,  357 

development  of,  358 

fracture  of,  359 

landmarks  of,  360 

pract.  consid.,  358 

sexual  differences,  358 

surface  anatomy  of,  358 
Clinoid  process,  anterior,  189 

processes,  middle,  186 
posterior,  186 
Qitoris,  3034 

glans  of,  3014 


Clitoris,  nerves  of,  2015 

prepuce  of,  3034 

vessels  of,  3035 
Cloaca,  1696 
Cloquet,  canal  of,  1474 

lymph-nodes  of,  993 
Coccygeal  body,  1810 
Coccyx,  137 

development  of,  131 
Cochlea,  membranous,  i5>7 
nerves  of,  1531 
or^an  of  Corti  of,  15 19 
Reissner's  membrane  of,  151 7 
structure  of,  15 18 

osseous,  1513 
Coeliac  plexus,  lymphatic,  973 
Coelom,  38 

pericardial,  1700 

pleural,  1700 
Cohnheim's  fields  of  striated  muscle-fibre,  4O1 
Collagen,  83 
Colles,  fascia  of,  563 

ligament  of,  533 
CoUiculi  inferiores,  1107 

superiores,  1107 
Colliculus,    inferior,    internal    structure    of, 

IIIO 

superior,  internal  structure  of,  mo 
Colon,  1668 

ascending.  1668 
blood- vessels  of,  1673 
descending,  1669 
flexure,  hepatic  of,  166S 

splenic  of,  1668 
lymphatics  of,  1673 
nerves  of,  1672 
peritoneal  relations  of,  1670 
pract.  consid.,  1685 
relations  of,  1668 
transverse,  i668 
Colostrum,  3031 

corpuscles,  3031 
Columnae  camese,  of  heart,  697 
Column,  spinal,  114 
Columns,  anterior,  of  spinal  cord,  1037 
lateral,  of  spinal  cord,  1037 
of  Morgagni,  1674 
posterior,  of  spinal  cord.  1037 
Commissura  habenulae,  1 1 34 
hippocampi,  1158 
hypothalamica,  11 28 
Commissure,  anterior,  1185 
of  Meynert,  1115 
middle,  11 19 
pnsterior,  1135 
Concha,  1484 
Condylarthrosis,  113 
Conjunctiva,  1441 
bulbar,  1445 
palpebral,  1445 
pract.  consid.,  1447 
Connective   substances,   chemical   composi- 
tion of,  83 
tissues,  73 

cells  of,  73 
fixed,  74 
typical,  74 
wandering,  74 
chemical  ccmposition  of,  83 
granule-cells  of  74 
^ound-substance  of,  7  5 
mtercellular    constituents  of,  74 
pigment-cells  of,  74 


1 


THIS  VOLUME   CONTAINS   PAGES   996   TO   THE   END. 


■  in 


INDEX. 


2059 


Construction,  general  plan  o^t 

Conus  meduUari.,  of  »P'"al  {^°[f  1, "" ' 
Convolutions  (gyn)  cerebral,  ii35 
Cooper,  Ugaments  of,  aoag 
Cord,  spermatic,  i960 
Corium,  1383 
Cornea,  1450 

pract.  consid.,  1453 

structure  of,  I45> 
ComiculiE  laryngjs,  1817 
Comua  sphenoidalia,  19' 
Corona  radiata,  it85 

Coronoid  process.  °f  "!"»•. '*'  .6 
Corpora  cavernosa  of  pems   1966 
SnammiUaria  (albicantia),  ii»S 

quadrigemina,  1106 
Corpus  albicans,  i99' 

Arantii,  7°° 

callosum,  1155 

ciliare,  I457 

dentatum,  1088 

tibrosum,  i99' 

Highmori,  i94» 

luteum,  1990  ,        .      ,., 

spongiosum,  of  penis,  196? 

striatum,  1169       ,     ,,, 
connections  of,  1172 
development  of ,  1193 
structure  of,  1 1 7 ' 
subthalamicum,  1128 
trapezoides,  1079 
Corpuscles,  corneal,  14  5» 
genital,  10 17 
of  Grandry,  1016 
of  Hassall,  I799 
of  Herbst,  1019 
of  Meissner,  1017 
of  Ruflfini,  1017 
Vater-Pacinian,  ioi» 
Cortex  of  cerebellum,  logo 

cerebral,  histogenesis  of ,  ..9. 
local  variations  in,  1180 
nerve-cells  of.  1176 
nerve-fibres  of,  "79 
structure  of,  11 75 
Corti,  ganglion  of,  "57 
membrane,  15*' 
organ  of,  I5'9 
Costal  cartilage,  153 
Cotyledons  of  placenta,  5° 
Cowper,  glands  of,  1984 
Cranial  capacity,  23° 
nerves,  1319 

abducent  (6th),  H49 
auditory  (8th),  1J56 
develooment  of,  1376 
facial  (7th),  i»5o 
Blosso-pharyngeal  (9th).  n6o 
Hypoglossal  (nth),  i»75 
oculomotor  (3rd),  uaS 
olfactory  (ist).  mo 
optic  (»nd),  1223 
pract.  consid.,  mo 
spinal-accessory  (nth), 
ineeminal  (5th),  1230 
trochlear  (4th),  m8 
vagus  (loth),  1265 
Cranio-cerebral  topography,  12 14 

Cranium,  172 

architecture  of,  220 
exterior  of,  218 
fossa,  anterior,  220 
middle  of,  220 


1274 


Cranium,  fossa,  posterior  of,  aao 
fractures  of,  238 

iSStdYascia.,  prac-..  consid..  489 
pract.  consid.,  235 
vault  of,  320 
Cretinism,  1794 
Cricoid  cartilage,  1813 
Crista  gain,  of  ethmoid.  191 
Crura  of  penis,  1967 
Crusta.  Ill 5 
Cuboid  bone.  422 
Cumulus  Oophorus.  1989 
Cuneate  nucleus,  1069 
tubercle,  1067 
Cuneiform  bone,  310 
extemal,  428 
internal,  426 
middle,  427 
Cuticle,  1385     ,   „ 
Cuvier.  duets  of,  854 
Cystic  duct,  1720 

pract.  consid.,  173' 
Cytoplasm,  structure  of,  7 

Dacrvon,  328 

Darwin,  tubercle  of,  1404 

Decidua,  44 

capsularis,  46 
I  cells  of,  47 

placentalis.  48 

retlexa,  45 

serotina,  48 

vera,  46  .  .         ,. 

Decussation  of  pyramids,  1064 

sensory,  1070 
Deiters.  cells  of ,  1521 

nucleus,  1076 
Demours,  membrane  of,  i45» 
Dendrites,  of  neurones,  997 
Dental  formula,  1 543 

papilla.  1558 
Dentine.  1550     , 

formation  of,  15  59      .        , 
Dentition,  first  and  second,  1 564 

Derma,  1383        ,  ,^,, 

Descemet  s  membrane,  1452 

S^^JlfimTntoUlimentary  tract,  .694 

of  atlas,  131 

of  auditory  nerves,  1535 

of  axis,  131 

of  bone,  94 

of  carpus,  3 1 3 

of  cartilage,  83 

of  cerebeUum,  1103 

of  clavicle,  358 

of  coccyx,  131 

of  cranial  nerves,  1376 

of  ear.  1523 

early,  IS 

of  elastic  tissue,  77 

of  ethmoid  bone,  194 

of  extemal  ear,  1526 

of  extemal  genital  organs,  2043 

of  eye.  1 480 

of  face,  62 

of  Fallopian  tube.  1999 

of  femur,  359 

of  fibrous  tissue,  76 

of  fibula,  393 

of  frontal  Done,  197 

of  ganglia.  1012 


THIS  VOLUME   CONTAINS    PAGES   996  TO   THE 


END. 


9o6o 


INDEX. 


Development,  general,  of  brain,  1058 
of  general  Dody-form,  56 
of  glands,  1537 
uf  hairs,  1401 
of  heart,  705 
of  humerus,  269 
of  hyoid  bone,  a  16 
of  inferior  turbinate  bone,  208 
of  innominate  bone,  337 
of  internal  ear,  1 523 
of  kidney,  1937 
of  liver,  1723 
of  lungs,  1 86 1 
of  lymphatic  vessels,  939 
of  lymph-nodes,  940 
of  malar  bone,  2 1  o 
of  mammaiy  glands,  2032 
of  maxilla,  inferior,  213 
of  maxilla,  superior,  202 
of  medulla  oblongata,  1 101 
of  mesencephalon,  1 1 1 7 
of  middle  ear,  1 52  s 
of  muscle,  non-striated,  457 
of  muscle,  striated,  465 
of  nails,  1403 
of  nasa!  bone,  209 
of  nerves,  1375 
of  nervous  tissues,  1009 
of  nose,  1429 
of  occipital  bone,  175 
ol  oral  cavity,  62 
glands,  1589 
of  ovary,  1 993 
of  palate  bone,  205 
of  pancreas,  1737 
of  parietal  tx>ne,  199 
of  patella,  400 
of  pelvis,  344 
of  peripheral  nerves,  loii 
of  peritoneum,  1 70^ 
of  pharynx,  1603 
of  pituitary  body,  1808 
of  pons  Varolii,  1 103 
of  prostate  gland,  1979 
of  radius,  293 

of  reproductive  organs,  2037 
of  respiratory  tract,  1861 
of  ribs,  1 53 
of  sacrum.  1 39 
of  scapula,  253 
of  skin,  1 400 
of  sphenoid  bone,  190 
of  spinal  cord,  1049 
of  spleen,  1787 
of  sternum,  157 
of  suprarenal  bodies,  1804 
of  sweat  glands,  1404 
of  sympathetic  system,  1013 
of  teeth,  1556 
of  temporal  bone,  184 
of  thymus  body,  1800 
of  thyroid  body,  1 793 
of  tibia,  387 
of  ulna,  385 
of  urethra,  1938 
of  urinary  bladder,  1938 

organs,  1934 
of  uterus.  2010 
of  vagina,  2019 
of  veins,  926 
of  vertebrae,  128 
of  vomer,  206 


Diaphragm,  ^56 

lymphatics  of,  970 

of  pelvis,  1676 
Diaphra^a  sella,  1 200 
Diaphysis,  of  bone,  104 
Diarthrosis,  107 
Diencephalon,  11 18 
Diverticulum  of  Meckel,  44 
Dorsum  selke,  1 86 
Douglas,  fold  of,  532 


JS'7 


pouch  of,  1741 
Duct  or  ducts,  cochlear, 

of  Bartholin,  1 585 

bile,  1730 

of  Cuvier,  854 

cystic,  1730 

eiaculatory,  1955 

Gartner's,  3001 

hepatic,  1718 

lactiferous,  3028 

lymphatic,  right,  945 

Mfllterian,  3031 

nasal  (naso-lachrymal)  1479 

pancreatic,  1736 

paraurethral,  1924 

parotid,  1583 

of  Rathke,  2040 

renal,  1894 

of  Rivinus,  1585 

of  Santorini,  1 736 

spermatic,  1953 

of  Stenson,  1583 

sublingual,  1585 

Submaxillary,  1584 

thoracic,  941 

thyro-glossal,  1793 

vitelline,  32 

of  Wharton,  1584 

of  Wirsung,  1736 

Wolffian.  1935 
Ductus  arteriosus  (Botalli),  733 

endolymphaticus,  15 14 

venosus  (Aarantii),  939 
Duodenal  glands,  1639 
Duodeno-hepatic  ligament.  1644 
Duodeno- jejunal  flexure,  1645 

fosss,  1647 
Duodenum,  1644 

interior  of,  1648 
Dupuytren's  contraction,  616 
Dura  mater  of  brain,  1198 

of  spinal  cord,  1033 

Ear,  1483 

development  of,  1 533 

e>:temal,  1484 

pract.  consid.,  1490 

internal,  1510 

membranous  labyrinth  of,  1514 
osseous  labyrinth  of,  1 5 1 1 
perilymph  of,  15 14 

lymphatics  of,  950 

middle,  1493 

antrum  of.  1508 
Eustachian  tube,  1501 
mastoid  cells,  1 504 
pract.  consid.,  1504 
suprameatal  triangle,  i5?o 
suprameatic  spine,  1 508 
tympanum  of,  1493 
Ear- point,  1484 
Ectoblast,  33 


THIS   VOLUME    CONTAINS    PAGES    S96    TO    THE    END. 


INDEX. 


3061 


\ 


EKK-nucleu»,  16 
lUstic  tiMue,  76 

development  of,  77 

Elastin,  83 
Elbow-joint,  301 

landmarks  of,  308 

movements  of,  303 

pract.  consid.,  305 
Embryo,  stage  of,  56. 
Emincntia  hypoglossi.  1098 

teres,  1097 
Enamel,  1548     ,       , 

formation  of,  1 50* 
Enamel-cells,  1561 
Enamel-cuticle,  1550 
Enamel-organ,  1560 
Enarthrosis,  1x3 
Encephalon,  lojS  , 

End-bulbs  of  Krause,  1016 
fiSd-knobs  of    free  «»nsory  nerve-endmgs, 

1015 
Endocardium,  702  »,.,,:„,»,    jua 

Endolymph  of  membranous  labyrinth.  i5«4 

Endometrium,  2007 
Endomysium,  45* 
Endoneurium,  1006 
Endothelium,  7« 

Enophthalmos,  i439     ^        _    .,« 
Ensilform  cartilage  of  sternum,  156 
Entoblast,  23 
Entoskeleton,  84 
Ependymal  cells,  1004 
Epicardium,  70* 
Epidermis,  1385 
Epididymis,  1947 

appendix  of,  1949 
canal  of,  1948 
digital  fossa  of,  1947 
globvis  major  of,  1947 

minor  of,  1947 
nerves  of,  1948 
structure  of,  1947 
vasa  abherrantia  of,  1950 
vessels  of,  194* 
Epiglottis,  1816 

ligaments  of.  181 7 
movements  of,  1817 
Epimysium,  458 
Epineurium,  1006 
Epiphysis.  iU4 

ossification  of,  98 
Epispadias,  1928 
Epithalamus,  1H3. 
Epithelium  of  chorion,  49 
columnar,  69 
glandular,  70 
modified,  70 
pigmented,  70 
specialized,  70 
squamous,  68 

stratified,  68 
transitional,  69 
Epitrichium,  1401 
Eponychium,  1403 
Epoophoron,  jooo 
Erythroblasts,  9» 
Ervthrocytes,  681 

development  of,  687 
Ethmoid  htme,  191 

articulations  of,  194 
bulla  of,  194 
cells  of,  192 
development  of,  194 


Ethmoid  tur<inate  bone,  middle  of.  «9.' 
superior  of,  193 
uncinate  procesa  of,  193 
Eustachian  tube.  1501 

blood-vessels  of,  1 504 
cartilaginous  portion,  1 502 
mucous   memorane  of,  1 503 
muscles  of,  1 503 
osseous  portion,  1 502 
pract.  consid.,  1507 
valve,  694 
Exocoelom,  32 
Exophthalmos,  1439 
Exoskeleton.  84 
Extremity,  lower,  332 

landmarks  of,  669 
lymphatics  of,  991 
upper,  landmarks  of,  ft  18 
lymphatics  of,  961 

Eye,  1436  ,       a 

development  of,  1400 
lymphatics  of,  949 
plica  semilunaris  of ,  1443 
pupil  of,  1459 
Eyeball,  1448 

aqueous  humor  of,  '47" 
chamber  anterior  of,  14  7' 

posterior  of,  147* 
choroid  of,  1455 
ciliary  body  of,  1457 

pro     >ses  of,  I457 
cornea  of,  14J0 
fovea  centralis  of,  1466 
iris  of,  1459 

lens,  crysUUine  of,  147 « 
macula  lutea  of,  1466 
movements  of,  505 
optic  nerve  of,  1469 
ora  serrata  of,  1467 
pract.  consid.,  1449 
retina  of,  1462 
sclera  of,  i449    , 
vascular  tunic  of.  14  54 
vitreous  body  of,  i473 
Eye-lashes.  i44> 
Eyelids,  1441     .      , 

blood-vessels  of,  144  5 
development  of,  1 483 
lymphatics  of,  1445 
nerves  of,  1446 
pract.  consid.,  i44<» 
structure  of,  i443 

Face,  222 

architecture  of,  228 
development  of,  62 
landmarks  of.  246 

muscles  and  fascia,  pract.  consid.,  49* 
pract.  consid.,  242 
FalcSorm  ligament,  i745 
Fallopian  tube.  1996 

changes  in,  1999 

course  of,  J997 

development  of.  1999 

fimbriae  of,  i997 

infundibulum  of,  1997 

isthmus  of,  1997 

lymphatics  of,  988 

nerves  of,  1999 

pract.  consid.,  1999 

relations  of,  1997 

structure  of,  199  7 

vessels  of,  1998 


THIS  VOLUME    CONTAINS   PAGES   996   TO   THE    END, 


3063 


INDEX. 


Fall  yi\u.  aatieduct  of,  iSi 
Falx  cerebelli,  iioo 

cerebri,  1199 
Faacia  or  fascitE,  470 

of  abdomen,  515 

anal,  1678 

of  ankle,  pract.  coniid.,  666 

antibrachial,  591 

of  anus,  1675 

of  arm,  pract.  consid.,  589 

of  axilla  and  shoulder,  pract.  consid.,  579 

axillary,  574 

(if  back,  508 

bicipital  (semilunar),  586 

brachial,  585 

bucco-pharyngeal,  488 

of  buttocks,  pract.  consid.,  641 

of  Camper,  5 1 5 

cervical.  543 

of  Colles,  56a 

of  cranium,  pract.  consid.,  489 

cremasteric,  i960 

cribriform,  635 

crural,  647 

dentata,  11 66 

of  face,  pract.  consid.,  49a 

of  foot,  pract.  consid.,  666 

of  hand,  606 

of  hip  and  thigh,  pract.  consid.,  643 

iliac,  634 

infundibuliform,  534 

intercolumnar  (external  spermatic),  534 

of  knee,  pract.  consid.,  645 

lata,  633 

of  leg,  pract.  consid.,  665 

obturator,  559 

of  orbit,  504 

palmar,  606 

palpebral,  1438 

parotido-masseteric,  474 

pectoral,  568 

pelvic,  S58 

perineal,  superficial,  56a 

plantar,  659 

prevertebral,  543 

rectal,  1678 

recto- vesical,  1678 

of  rectum,  1675 

of  scalp,  pract.  consid.,  489 

of  Scarpa,  5 1 5 

temporal,  475 

transversalis,  530 
Fasciculus,  auriculo- ventricular  of  heart,  701 

posterior  longitudinal,  11 16 

retroflexus,  1 134 

solitarius,  1074 
Fat,  orbital,  1437 
Fat-cells,  79 
Fauces,  isthmus  of,  1 569 

pillars  of.  1 569 
Femoral  canal,  635 

ring,  635 
Femur,  353 

development  of,  359 

landmarks  of,  366 

pract.  consid.,  361 

surface  anatomy,  360 

variations,  sexual  and  individual,  3  so 
Fertilization,  18 
Fibres,  intercolumnar,  534 
Fibrin,  canalized,  of  chorion,  49 
Fibro-cartilage,  83 
Fibrous  tissue,  74 


Fibrous  tissue,  development  of,  76 
Fibula,  300 

development  of,  393 
pract.  consid.,  393 
Fillet,  decussation  of,  1070 

median,  1 1 1 5 
Fimbria,  1 1 59 

hippocampi,  1165 
Fissure,  calcanne,  1 1 46 
calloso-marginal,  1 1 39 
central,  of  cerebrum,  1137 
collateral,  1 139 
ethmoidal,  1 4 1 1 
of  Glaser,  1 78 
palpebral,  1441 
paneto-occipital,  113.? 
portal,  of  liver,  1 708 
ptr  .yeo-maxillary,  jo.[ 
of  Rolando,  1137 
sphenoidal,  188 
Speno-maxillary,  33a 
(sulci)  cerebral,  1135 
of  Sylvius,  1 136 
Fistula,  cervical,  61 
Flexure,  cephalic,  58 

cervical,  of  embryo,  59 
dorsal,  of  embryo,  59 
sacral,  of  embryo,  59 
Flocculus,  1085 
1"  :.tus,  membranes  of,  30 
stage  of,  63 

eighth  month,  66 

week,  64 
fifth  month,  66 

week,  63 
fourth  month,  65 
ninth  month,  66 
seventh  month,  66 

week,  64 
sixth  month,  66 

week,  63 
third  month,  65 
Follicles,  Graafian,  1988 
Fontana,  spaces  of,  1453 
Fontanelles,  331 
Foot,  articulations  of,  440 
as  whole,  447 
bones  of,  41Q 

landmarks  of,  437 
pract.  consid.,  436 
joints  of,  landmarks  of,  453 
landmarks  of,  673 
muscles  of,  659 

and  fascise  of,  pract.  consid., 
surface  anatomy,  449 
synovial  cavities  of,  447 
Foramen  or  foramina,  csecum,  1574 
ethmoidal,  anterior,  193 

posterior,  193 
jugular,  330 
of  Luschka,  11 00 
of  Magendie,  1 1 00 
mastoid,  180 
of  Monro,  1131 
optic,  189 
ovale,  188 

of  heart,  695 
pterygo-spinosum,  190 
rotundum,  187 
sacro-sciatic,  great,  341 

lesser,  341 
sphenoidal,  187 
spheno-palatine,  304 


666 


THIS  VOLUME    CONTAINS   PAGES   996  TO  THE    END. 


INDEX. 


3063 


Foramen  or  (oramina.  tpinoaum.  iM 
»tyto-ma»toid,  i8> 
thvroid  (obturator),  337 
of -vena  cava,  of  diaphragm.  557 
of  Vesiiliui,  188 

Forearm,  381 

as  whole,  »QQ  , 

intrinsic  movements  01,  199 

motion  of  on  humerus.  303 

pract.  consid..  603 
Fore-brain,  105Q 
Formiitio  rcticulans.  1070 

reticularis  alba,  1076 

grisea.  1074 

Fornix.  11 58  .       ..,„ 

pillars  of ,  antenor,  i»S9 

posterior,  ii59 

Fossa  or  fossa,  ,      ,   . 

duodeno-jejunal.  J047 

glenoid,  178 
hyaloidea,  I473 
ileo-caecal.  1666 
infraspinous.  a  5° 
inguinal,  inner,  5'<> 

lateral.  i743 

median.  i74» 

outer,  5^6 
interpeduncjilar,  "07 
intersigmoid,  1671 
ischio-rectal,  1078 
jugular,  i8j 

nasal.  1409,        ., ._.. 

navicular  of  urethra.  19*4 

ovalis.  695 
ovarian.  1986 
pararectal.  i744 
paravesical.  i744 
perica^cal,  1666 
pineal,  no* 
pituitary,  186 
retro-colic.  1667 
of  Rosenmiiller,  1 59° 
spheno-maxillary,  a»7 
subscapular,  349 
supraspinous.  350 
supratonsillar,  1600 
supravesical.  536 
Sylvii,  "37 
temporal,  318 
zygomatic,  337 
Fourchetie,  3033 
Fourth  ventricle.  1096 

choroid  plexus  of.  i  too 
floor  of,  1096 
roof  of,  1099 
Fovea  centralis.  1466 

vagi.  1098  ,   . 

Frenulum  of  Giacommi.  11 66 
Frenum  of  prepuce.  1966 

of  tongue,  1 573 
Frontal  bone.  194  , 

articulations  of,  197 
development  of,  197 

lobe,  1 139         ^  _        , 

sinus,  1433.  326  (bony) 
Fuudamental  cmbryologjcal  proceMe«,  30 
Funiculus  cv.neatus,  1066 

gracilis,  1066 

of  Rolando,  1067 
Furrows,  visceral,  59 
external,  61 


Furrows,  inner.  61 

inner,  second,  6j 
innet,  third.  6a 

Galen,  vein  of,  856 
Gall-bladder,  17 '9 

cystic  duct  of,  i7'0 

fossa  of,  1708 

lymphatics  of,  981 

nerves  of,  1730 

pract.  consid.,  1739 

vessels  of,  1719 
Ganglion  or  ganglia,  1007 

Arnolds,  1346 

t«"iM.l  inferior  (sympathetic)    136* 
middle  (sympathetic),  1^63 
superior  (sympathetic),  1359 

^cygeal^mpar),  sympathetic,  1367 
development  of,  lois 
of  Froriep,  13*0 
Gasserian,  133a 
geniculate.  1353 
habenulae.  1133 
impar,  1367 
interpeduncular,  1134 
jugular,  of  glosso-pharyngeal.  1363 
of  vagus,  1 367 

lenticular.  1336 

Meckel's,  1340    . 

mesenteric,  inferior,  1373 
superior,  137  a 

nodosum  of  vagus,  i  a68 

ophthalmic.  1336 

™troiu*of  glosso-pharyngeal,  H64 

semilunar,  sympathetic,  1369 

spheno-palatine,  1340 

spinal,  1379 

spiral.  1357 

spiraleof  cochlea,  15a a 

splanchnic,  great,  sympathetic,  1365 

submaxillary.  1347 

sympathetic,  1009 

of  sympathetic  system.  1356 

vestibular,  1359 
Ganglion-crest,  1013 
Gartner's  duct.  3001 
Gasserian  gangUon.  133  a 
Gastric  glands,  1633 
Gastro-pulmonary  system.  iS»7 

Gastrula,  35 

Gelatin,  83 

Geniculate  bodies,  lateral,  H07 

"""^  Onteroal)  internal  structure  of, . .  10 
I  ganglion,  1353 

I  Genital  cord.  3038 

oiins^e^xtemal,  development  of,  304J 
female.  3031 

pract.  consid.,  2037 

ridge,  3038 

tubercle,  3043 
Genu  of  corpus  callosum,  H5S 
Germinal  spot.  i6 
Gestation,  ectopic,  199? 
Giacomini,  frenulum  of,  1106 
Gianuzzi.  crescents  oi.  iS34 
Gimbernat.  ligament  of,  533 
Ginglymus,  113    , 
Giraldes.  organ  of.  1950 
Glabella,  338 


external,  01  -..ur-    rtan 

THIS  VOLUME   CONTAINS   PAGES   996   TO   THE    END. 


ao64 


INDEX. 


'<>: 


GUdiolui  of  itemutn,  135 
Gland  or  sUnds,  1 511 

alveolar  (tacc-ular)  compound,  1535 
(saccular)  timpla,  1535 

anal,  1674 

areolar,  loaS 

of  Bartholin,  joi6 

of  Blandin,  1577 

blood-veuelt  of ,  153  s 

of  Bowman,  141 5 

of  Brunner,  1639 

cardiac  of  stomach,  1614 

carotid,  1809 

ceruminous,  1489 

ciliary,  1400 

circumanal,  1400 

ixiccygeal,  1810 

of  Cowper,  1984 

cutaneous,  1397 

gastric,  1623 

uf  Henle,  1445 

of  intestines,  1637 

of  Krause,  1445 

lachrymal,  1477 
aucts  of,  1477 

of  Lieberkuhn,  1637 

of  Luschka,  1810 

lymphatics  of,  1 536 

mammary,  1027 

Meibomian  (tarsal),  1444 

of  Moll,  1444 

of  Montgomer>-,  2028 

mucous,  1534 

nerves  of,  1536 

of  Nuhn,  1577 

parotid,  1582 

prostate.  1975 

pyloric,  1624 

salivary,  1582 

sebaceous,  1397 

serous,  1534 

sexual,  development  of,  2038 

sublingual,  1585 

submaxillary,  1583 

sweat,  1398 

duct  of,  1399 
structure  of,  1399 

of  tongue,  1575 

tubo-alveolar,  1533 

tubular,  compound,  153  a 
simple,  1532 

of  Tyson,  1966 

unicellular,  1531 

of  Zeiss,  1444 
Clans  of  clitoris,  3024 

penis,  1968 
Glaser,  fissure  of,  178 
Glisson's  capsule  of  liver.  1 708 
Globus  pallidus,  1 1 70 
Go'olet-cells,  70 

Golgi-Mazzoni  corpiiscles.  10 19 
Gonion,  228 
Graafian  follicle!:.  ig8S 
Grandry,  corput.  les  of,  1016 
Growth,  6 

of  bone,  loi 
Gudden,  inferior  commis-siire  of,  11 10 
Gums.  I  r.6y 

pract.  consid.,  1590 
Gustatory  cells,  1435 
Gyrus  or  gyri,  callosal  (fomicatus),  1 1 50 

(convolutions)  cerebral,  1 135 

dentate,  11 66 


Gyrus  or  gyri,  development  of,  1 190 
hippocampal,  11 51 

Hair-cells  (auditory)  inner,  1 510 

outer,  1520 
Hair-follicle,  1302 

blood-veaaels  of,  1394 

nerves  of,  1394 
Hairs,  1389 

arrangement  of,  1391 

development  of,  1401 

growth  of,  140a 

structure  of,  1391 

whorls  of,  1 39 1 
Hair-shaft,  1391 

Hamular  process  of  inner  pterygoid  plate,  1 89 
Hamulus  of  bony  cochlea.  1514 
Hand,  309 

deep  fascia  of,  606 

landmarks  of,  320 

lymphatics  of,  964 

muscles  of,  606 

pract.  consid.,  613 

surface  anatomy  of,  328 
Harelip,  1589 

Hassall,  corpuscles  of,  1 799 
Haversian  canals  of  bone,  88 

system  of  bone,  86 
Head,  movements  of,  14a 
Heart,  annuli  fibrosi  of,  698 

annulus  ovalis,  695 
of  Vieussens,  695 

architecture  of  walls,  700 

auricles  of,  693 

blood- vessels  of,  703 

canal  auricular  of,  705 

chambers  of,  693 

chordte  tendtnec  of,  697 

columns  cames  of,  697 

development  of,  705 

endocardium  of,  70a 

epicardium  of,  702 

faacicttlus  atiriculo-ventricular,  701 

foramen  ovale  of,  695 

foua  ovalis  of,  695 

feneral  description  of,  68n 
lis's  bundle,  701 
lymphatics,  703 
muscle  of,  462 
muscles,  pectinate  of,  695 
nerve-endings  in,  1015 
nerves  of,  704 
position  of,  693 
practical  considerations,  710 
relations  of,  693 
septum,  aortic,  707 

auricular  of,  694 

intermedium,  706 

interventricular  of,  696 

primum,  706 

secundum,  708 

spurium,  707 
Thebesian  veins  of,  694 
tubercle  of  Lower,  695 
valves.  Eustachian,  ^4 

auriculo-ventricular,  699 

mitral,  699 

position  of,  69  a 

structure  of,  703 

Thebesian,  695 

tricuspid,  699 
x-ein,  oblique  of,  695 
ventricles  of,  696 


THIS   VOLUME    CONTAINS    PAGES    996    TO    THE    END. 


INDEX. 


3065 


Het<lenbi^>*<  ifamilttiiM  o(.  1534 
Heltcotrama,  15M 

KliTuptait..  «oci.Uon  fibre,  of.  >.8. 
ofc««beUum.  io8j 


»«4 


lobMof,  IIJ9         ,    ...» 

proiaction  fibre*  of.  1 186 

whiU  centre  of .  h8j 
Henle,  gUnde  of.  i44S 

loop  of.  1881 
Henien.  node  of,  »S 
Herbal,  corpvactee  of,  1019 
Homiit,  abdominal.  17  59 

diaphragmatic,  «77» 

femoral,  17  73 

funicular,  17*8 

infantile,  1767 
inguinal,  1763 
direct,  «77o 

inte,iSa"o«t«-^««««"»    retroperito- 

««'>•  '",'     ». 
interpaneUl.  tyo» 

labial,  1769 
lumbar,  i777 
obturator,  i777 
perineal,  1778 
•ciatic,  1778 
■crotal,  1769 
umbilical,  i77S      . 
acquired,  1770 
congenital,  1775 
ventral,  177* 
Hesselbach,  ligament  of,  S»$ 

triangle  ot,  5'*^ 
Hiatus,  aortic,  of  diaphragm,  557 
Pallopii,  181 

ULi.  .phageal,  of  diaphragm,  557 
semilunaris,  of  nasal  cavity.  194 
of  nose.  14" 
Highmore.  antrum  of.  i4»» 
Hind-brain.  1061 

Hio.  landmarVM  of.  669  -a    a., 

^muscles  and  fasci«  of.  pract.  consid..  64a 
Hip-joint.  367 

movemcts  of.  373 
pract.  consid..  374 
synovial  membrane  of,  37' 
Hippocampis.  i«65 
His's  bundle,  of  heart,  70' 
Histogenesis  of  neuroglia,  loio 

of  neurones,  10 11 
Homologue.  4.      ,     „ 
Homer,  muscle  of,  484 
Howship,  lacuna  of,  97 
Humerus,  265 

development  of,  109 
pract.  consid.,  170 
sexual  differences,  269 
structure  of.  269 
surfacvi  anatomy,  270 
Humor,  aqueous.  1476 
Hunter's  canal,  628 
Hyaloid  canal.  1474 
Hyaloplasm,  8 
Hydatid  of  Morgagni,  200a 
Hydramnion.  4a 
Hymen,  aoi6 
Hyoid  bone,  216 

development  of,  216 
Hyomandibular  cleft,  61 

THIS  VOLUMe    CONTAINS 


Hypogastric  lymiihatic  pluxus. 
Hypophysis,  1806 
Hyiusiudias,  1917 
Hypothalamus,  1117 
Hypothonar  eminence.  607 

Ileo-cBcal  fossK,  1666 

valve,  1661 
llio-femoral  ligament,  369 
liio-pcctineal  line,  334 
llio-tibial  hand,  634 
Ihum,  3  j 
Implantatio...  35 
Impregnation.  18 
Incisor  teeth.  1 543 
Incus,  >497  .      .       .  ■ 

Inferior  caval  system  of  veins,  898 
Infundibulum,  1 1 29 

of  nasal  cavity,  nu 

of  nose,  I4>i 
Inguinal  canal,  523 

lymphatic  plexus,  991 
Inion,  228 


inion,  x<o 
Innominate  bone,  332 

structure  of,  337 

Insula,  1 1 49 
Intersigmoid  fosn.i.  1671 
Intervertebral  disks.  132 
Intestine    or  intestines,    developmei  .    .'"ct 
growth  of,  1671 
elands  of,  1637 
large,  1657 

appendices  epiploic*,  1060 
blood-vessels  of,  1 660 
glands  of  Lieberkuhn  of,  1657 
lymphatics  of,  1660 
lymphatic  tissue  of,  1658 
nerves  of,  1660 
peritoneum  of,  1670 
pract.  consid.,  i68o 
structure  of,  1657 
tenia  coli  of,  1660 
lymph-nodules  of,  1640 

small.  1633        ,      ,     , 
blood-vessels  of,  1642 
elands  of  Lieberkuhn  of,  1637 
lymphatics  of,  1643 
nerves  of,  1643 
Peyer's  patches  of,  1640 
pract.  consid.,  1652 
structure  of,  1634 
valvule  conniventes  of,  1 636 
villi  of,  1635 
solitary  nodules  of,  1640 
Involuntary  muscle,  1015 

Iris,  1459  ,        . 

pract.  consid.,  1401 

structure  of.  1460 
Irritability.  6 
Ischio-rectal  fossa,  1678 
Ischium,  336 
Islands  of  L^ngerhans.  173J 

of  Reil,  1 1 49 
Isthmus  of  fauces,  1 560 
rhombencephali,  lofn 

Jacobson's  nerve,  1264 
organ,  i4«7 

development  of,  143* 

Jeiunr.  Hcum,  :t-4v 

Vlood-ves-wls  of,  1652 
l<-mphatiis  of,  1652 
mesentery  of,  1650 

«30 


3066 


INDEX. 


Jejiino-ilaum,  nervea  of,  i6st 

topoKraphy  of,  1650 
Joint  or  joinU,  of  ankle,  438 

calcanco-astrajgaloid,  posterior,  445 

calcaneo-cuboid,  446 

calcaneo-tcapho-astragaloid,      anterior, 

capsule  of,  no 

of  carptis,  metacarpus  and  phalanges, 

pract.  consid.,  330 
costo-central,  160 
costo-stemal,  160 

motions  in,  t66 
costo-transverse,  160 
costo-vertebral,  motions  in,  165 
crico-arytenoid,  181 6 
crico-thyroid,  1815 
of  ear  ossicles,  1498 
elbow,  301 
fixed,  107 

general  considerations,  107 
half.  108 
of  hip,  367 
interchondral,  160 
interstemal,  159 
of  knee,  400 

limitation  of  motion,  iia 
metatarso-phalangeal,  447 
modes  of  fixation,  iia 
of  pelvis,  337 

of  pelvis,  pract.  consid,  350 
raoio-ulnar,  397 

inferior,  pract.  consid.,  308 
saddle,  113 

scapho-cubo-cuneiform,  446 
of  uioulder,  174 
synovial  memorane  of,  no 
tarso-metatarsal,  446 
of  tarsus,   metatarsus  and   phalanges, 

pract.  consid.,  45 
true,  108 

motion  in,  1 1  a 

structure  of,  109 

varieties  of,  113 
vessels  and  nerves  of,  in 
Jugular  ganglion,  of  glosso-pharyngeal,  1263 

of  vagus,  1367 
plexus,  lymphatics,  956 

Karyokinesis,  ti 

Karyosomes,  9 

Kidney  or  kidneys,  1869 

architecture  of.  1875 

blood-vessels  of ,  1884 

capsule  of,  1869 

cortex  of,  187C 

development  of,  1937 

ducts  of.  1894 

fixation  of,  1871 

glomeruli  of.  1876 

nilum  of.  1869 

labyrinth  of.  1876 

lobule  of.  1875 

loop  of  Henle  of.  1881 


lymphatics  of,  1885 
" of. 


1879 


1876 


Malpi^hian  body  01 
medulla  oi,  1876 
medullary  rays  of 
movable.  1888 
nerves  of.  1886 
papiils  of.  1875 
papillarv  ducts  of,  j88a 
pelvis  01,  1894 


Kidney  or  kidnevs,  position  of.  1870 

pract.  consio.,  1887 

pyramids  of,  1876 

ruationa  of,  1873 

sinus  of,  1874 

structure  of,  1877 

supporting  tissue  of,  1883 

surnces  of ,    '49 

tubule,  collecting  of,  i88a 
connecting  of,  1883 
distal  convoluted  of,  i88s 
proximal  convoluted  of,  1880 
spiral  of,  1880 
uriniferous  of.  1877 
Knee,  landmarks  of,  67 1 

muscles  and  fascic  of,  pract.  consid.,  645 
Knee-joint,  400 

bunae  of,  406 

capsiile  of,  400 

landmarks  of,  416 

movements  of,  408 

pract.  consid.,  409 

semilunar  cartilage  of,  40 

synovial  membrane  of,  405 
Krauae,  end-btilbs  of,  1016 

elands  of,  1445 
Kupner,  cells  of,  1717  > 

Labia  major,  30a  i 
minora,  ao33 
nerves  of,  3034 
vessels  of,  3033 
Labyrinth,  membranous,  1514 

blood-vessels  of ,  1533 

canalis  reuniens  of,  151 5 

cochlea  of,  1517 

ductus  endolymphaticus  of,  1514 

endolymph  m,  1514 

macuue  acusticc  of,  1516 

saccule  of,  1515 

semicircular  canals  of,  151 5 

utricle  of,  1 514 
osseous,  1511 

cochlea  of,  1513 

semicircular  canals  of.  151a 

vestibule  of,  151 1 
Lachrymal  apparatus.  1477 

pract.  consid.,  1479 
bone,  307 

articulations  of,  aoj 

development  of,  ao7 
canaliculi,  1478 
caruncle,  1443 

gland,  1477 
ike.  1443 

papiils,  1478 

puncta,  1478 

sac,  1478 
Lactation,  3039 
Lacteals,  1643 
Lacunae,  of  bone,  86 

of  cartila^.  80 

of  Howship.  97 
Lambda,  338 
Lamina  cinerea  (terminalis),  1130 

fusca,  1450 

suprachoroidea.  1456 
Landmarks,  of  abdomen,  53 1 

of  ankte  and  foot,  673 

of  bones  of  foot,  437 

of  buttocks  and  hip,  669 

of  clavicle,  260 

of  elbow-joint,  308 


THIS  VOLUME    CONTAINS  PAGES   996   TO   THE    END. 


INDEX. 


ao67 


I; 

14 


Landmarks,  of  face,  146 
of  femur,  366 
of  fibula,  396 
of  hand,  330 
of  ioints  of  foot,  453 
ofkmM,  671 
of  knee-joint,  416 
of  leg,  671 

of  lower  extremity,  669 
of  male  perineum,  1918 
of  neck,  554 
of  pelvis,  349 
of  radius,  296 
of  scapula,  35^ 
of  shoulder-joint,  a  80 
of  skull,  140 
of  spine,  146  . 
of  surface  of  thorax,  1868 
of  thigh,  670 
of  thorax,  1 70 
of  tibia,  390 
of  ulna,  387 

of  upper  extremity,  61S 
of  wnst-joint,  330 
Langerhans,  islands  of,  173s 
Lanugo,  66 

Laryngo-pharynx,  1598 
larynx,  1813  .     -  _ 

age  changes  of,  i8a8 
arytenoid  cartilages  of,  1816 
comicute  laryngis,  1817 
cricoid  cartilage  of,  18 13 
cuneiform  cartilages  of,  181 7 
development  of,  i86a 
elastic  sheath  of,  1817 
epiglottis,  1816 
form  of,  1818 
lymphatics  of.  958 
mucous  membrane  of,  1833 
muscles  of,  1824 
n-rves  of,  1827 
ossification  of,  1 81 8 
position  and  relations  of,  i8a8 
pract.  consid.,  i8a8 
region,  glottic  of,  i8ao 
infraglottic  of,  1823 
supraglottic  of,  1818 
sexual  differences  of,  t8a8 
thyroid  cartilage  of,  181 4 
ventricle  (sinus)  of,  i8aa 
vesseU  of,  i8a6 
vocal  cords,  false  of,  1820 
true  of,  1820 
ligaments  of,  181 8 
Leg,  bones  of,  as  one  apparatus,  397 
surface  anatomy,  397 
framework  of,  38a 
landmarks  of,  671 
lymphatics,  deep  of,  994 

superficial  of,  993 
muscles  and  fascite  of,  pract.  consid., 

Lens,  crystalline,  147 «   , 

development  of,  1481 . 
oract.  consid.,  1473 
suspensory  apparatiM  of,  1475 
Leptorhines,  1404 
Leucocytes,  684 

development  of,  688 
varieties  of,  685 
Lieberkuhn,  glands  of,  1637 
Lieno-phrenic  fold,  1785 
Ligament  or  ligaments,  iia 
alar,  of  knee-joint,  40$ 


665 


Ligament  or  ligaments,  anterior  annular,  of 
'  ankle,  647 

of  wrist,  335 
arcuate,  external,  557 

internal,  557 
atlanto-axial,  anterior,  137 
atlanto-axial,  posterior,  137 
of  auricle,  i486 
broad,  of  uterus,  3004 
broad,  vesicular  appendages  of,  aooa 
check,  of  orbit,  1438 
of  CoUes,  533  .        -   _;_ 

common  anterior  and  posterior,  of  spine, 

coraco-acromial,  256 
coraco-clavicular,  363 
conoid  part,  a6a 
trapezoid  part,  363 
coronary,  of  liver,  >7*'       . . 
costo-clavicular  or  rhomboid,  a6a 
cotyloid,  of  hip-joint,  367 
crucial,  of  knee-joint,  404 
cruciform,  of  axis,  136 
deltoid  (lat.  int.)  of  ankle-joint,  439 
denticulate,  of  spinal  cord,  1033 
dorsal,  of  foot,  443 
duodeno-hepatic,  1644 
of  epiglottis,  1817 
external  check,  of  eyeball.  505 
falciform,  1745 
gastro-phrenic,  1747 
of  Gimbemat,  533 
of  Hesselbach.  535 
•  ilio-femoral,  369 
ilio-lumbar,  339 
interarticular  of  ribs,  160 
interclavicular,  a  6a 
interosseous,  of  foot,  441 
interspinous,  134 
intertransverse,  135 
ischio-femoral,  370 

of  lamiiUE  and  processes  of  vertebrte,  133 
lieno-renal,  1747 
of  liver,  1731 

metacarpal,  superficial  transverse,  607 
nucr«,  134 

occipito-atlantal.  accessory,  137 
anterior,  137 
posterior,  137 
occi{nto-axial,  137 
odontoid,  or  check,  136 
orbicular,  of  radius,  397 
of  ovary,  1987 
palpebral,  1441 

internal,  484 
patellae,  4°° 
pectinate  of  iris,  145a 
of  pelvis,  J37 
of  pericardium,  716 
plantar,  444 
posterior  annular,  of  wrist,  335 


of  Poupart,  533 
pterygo-mandibular,  488 
radio-ulnar,  397 
round,  of  hip-joint,  370 

of  liver,  1731 

of  uterus,  3005 
sacro-iliac,  posterior,  338 
sacro-sdatic,  339 

Ct  or  posterior,  339 
T  or  anterior,  341 
of  scapula,  356 
of  shoulder-joint,  274 


THIS  VOLUME    CONTAINS    PAGES   996   TO   THE    END. 


2£: 


ao68 


INDEX. 


rtii)/ 


Ligament  or  UnmenU,  ipino-glenoid,  257 

stylo-manaibular,  475 

subflavs,  133 

suprascapular  or  transverse,  356 

supraspinous,  133 

suspensory,  of  lens,  1475 
of  orbit,  1438 
of  ovary,  1986 

thyro-arytenoid,  inferior,  t8i8 
superior,  181 7 

thyro-hyoid,  181 5 

transverse,  of  atlas,  136 

triangular,  of  liver,  1721 
of  perineum,  563 

of  verteoral  bodies,  133 

of  Winslow,  of  knee-joint,  401 

of  wrist  and  metacar,    s,  330 
Limb,  lower,  muscles  of,  633 
Limbic  lobe,  1 1 50 
Linea  alba,  533 

semilunaris,  of  abdomen,  533 

transversa,  of  abdomen,  533 
Linin,  g 
Lips,  1538 

lymphatics  of,  951 

muscles  of,  1 540 

nerves  of,  1543 

pract.  consid.,  1590 

vessels  of,  1543 
Liquor  amnii,  3 1 

pericardii,  714 
Littr^,  glands  of,  1925 
Liver,  1705 

bile-capillaries  of,  1 71 5 

biliary  apparatus,  17 18 

blood-vessels  of,  1709 

borders  of,  1707 

caudate  lobe  of,  1709 

cells  of  KupfTer,  1717 

common  bile-duct,  1730 

cystic  duct  of,  1730 

development  and  growth  of,  1733 

fissure  of  ductus  venosus  of.  1 707 

fossa  for  eall-bladder  of,  1 708 

gall-bladder  of,  1719 
rlisson's  capsule  of,  1708 
hepatic  artery  of,  171 1 

ducts  of,  1 7 18 

veins  of,  17 10 
impression,  oesophageal  of,  .  708 

renal  of,  1 709 
intralobular  connective  tissue  of,  1717 

bile-ducts  of,  1 7 1 7 

veins  of,  17 10 
ligaments  of,  1731 

coronary,  1731 

falciform,  1731 

round,  1731 

triangular,  1731 
lobes  of,  1706 

lobular  blood-vessels  of,  17 13 
lobules  of,  1713 
lymphatics  of,  17x1 
nerves  of,  1 7 1 1 
non-peritoneal  area  of,  1 707 
peritoneal  relations  of,  1731 
portal  (transverse)  fissure  of,  1 708 

vein  of,  1709 
position  of,  1733 
praot,  consid.,  1736 
quadrate  lobe  of,  1 709 
size  of,  1706 
Spigelian  lobe  of,  1707 


Liver,  structure  of,  1713 

sublobular  veins  of,  17 10 

surfaces  of,  1707 

tuber  omentale  of,  1 709 

umbilical  fissiue  of,  1 708 
notch  of,  1707 

weight  of,  1706 
Liver-cells,  1714 
Liobe  or  lobes,  cerebral,  1135 

frontal,  1139 

of  hemispheres,  1 139 

limbic,  1 1 50 

occipital,  1 145 

olfactory,  1151 

parietal,  11 43 

temporal,  1147 
Lobule  of  auricle,  1484 
Loin,  pract.  consid.,  530 
Lordosis,  144 

Liunbar  plexus,  lymphatic,  973 
Lumbo-sacral  coitl,  1331 
Lung  or  lungs,  1843 

air-sacs  of,  1850 

alveoli  of,  1850 

atria  of,  1 8  so 

blood-vessels  of,  1853 

borders  of,  1843 

development  of,  186 1 

external  appearance  of,  1846 

fissures  of,  1845 

ligament  broad  of,  1858 

l(»>es  of,  184$ 

lobule  of,  1849 

nerves  of ,  1855 

physical  characteristics  of,  184C1 

pract.  consid.,  1864 

relations  to  chest-walls,  changes  in,  1803 
to  thoracic  walls,  1855 

roots  of,  18^8 

dimensions  of,  1840 
nerves  of,  1839 
relations  of,  1840 

structure  of,  1851 

surfaces  of,  1843 

vessels  of,  1839 
Lunula,  of  nail,  1395 
Luschka,  foramina  of,  1 100 

^land  of,  1 810 
Lutein  cells,  1990 
Luys,  nucleus  of,  11 38 
Lymphatic  or  lymphatics,  of  abdomen,  97s 

of  abdominal  walls,  976 

of  arm,  deep,  965 
superficial,  963 

of  bile-duct,  981 

of  bladder,  985 

of  bone,  93 

of  brain,  948 

of  brain  and  meninges,  948 

broncho-mediastinal  trunk,  968 

capillaries,  933 

of  cervical  skin  and  muscles,  958 

of  cheeks,  951 

of  diaphragm,  970 

duct,  right,  945 

of  ear,  950 

of  eye  and  orbit,  949 

of  eyelids,  1445 

of  Fallopian  tubes,  988 

of  gall-bladder.  981 

of  glands,  1536 

of  gums,  9SI 

of  hand,  964 


THIS  VOLUME    CONTAINS    PAGES   996   TO   THE    END. 


INDEX. 


3069 


Lymphatic  or  lymphatics,  of  the  head,  045 
of  heart,  970 
hemolymph  nodes,  936 
intercostal,  969 
of  intestine,  large,  978 

small,  977 
jugular  trunk,  958 
of  Kidney,  982 
lacteals.  931 
of  lar^mx,  958 
of  leg,  deep,  994 

supernciai,  993 
of  lips,  951 
of  liver,  980 
of  lower  extremity,  991 
mammary  gland,  968 
of  meninges,  948 
of  muscle,  non-striated,  456 
of  nasal  fossa,  1416 

region,  951 
nodes,  935 
of  nose,  1 407 
of  oesophagus,  971 
of  palate,  954 
of  pancreas,  979 
of  pelvis,  083 
of  pericardium,  716 
of  perineum,  987 
of  pharynx,  954 
of  prostate  gland,  985 
of  rectum,  1 680 

of   reproductive    organs,    external, 
male,  987 
external,  male,  98 
internal,  femt' 
internal,  ma)        >: 
of  retina,  1468 
of  scalp,  948 
of  semmal  vesicles,  98t 
of  skin,  1388 
of  small  intestine,  1643 
of  spleen,  982 
of  stomach,  976 
of  striated  muscle,  464 
subclavian  trunk,  963 
of  suprarenal  body,  983 
system,  931 
of  teeth,  951 
of  testis,  987 
thoracic  duct.  941 

pract.  consid.,  944 
of  thorax,  966 

cutaneous,  968 
of  thyroid  gland,  959 
of  tongue,  95* 
of  tonsils,  954 
of  trachea,  958 
of  upper  extremity,  961 
of  ureter,  981 
of  urethra,  986 
of  uterus,  989 
of  vagina.  989 
of  vas  deferens,  988 
vessels,  development  of,  939 
Lymph-corpuscles,  031 
Lymph-nooes  of  abdomen,  pract.  consid. 
abdominal,  visceral,  974 
ano-rectal,  976 
ant"!rior  auricular,  946 
aj.,x:ndicular.  975 
of  arm,  pract.  consid.,  965 
of  axilla,  pract.  consid.,  965 
axillary,  961 


fe- 


Lymph-nodes,  brachial,  deep,  9*' 
superficial,  961 
bronchial,  967 
buccinator,  947 
cervical,  deep,  inferior,  958 

superior,  957 
of  Cloquet,  99a 
coeliac,  973 
delto-pectoral,  961 
development  of,  940 
epigastric,  973 
cpitrochlear,  961 
facial,  947 
gastric,  974 

of  head,  pract.  consid.,  955 
hepatic,  975 
hypogastric,  984 
iliac,  circumflex,  972 

internal,  984 
inguinal,  991 
intercostal.  966 
of  intestine,  1640 
jugular  plexus,  956 
of  leg,  piract.  consid.,  994 
lingual,  947 

mammary,  internal,  966 
mandibular,  947 
mastoid,  945 
maxillary,  947 
mediastinal,  anterior,  967 

posterior,  967 
mesenteric,  975 
mesocolic,  976 
of  neck,  956 

pract.  consid.,  950 
(Kciintal.  945 
pancreatico-splenic,  975 

parotid,  946 

pectoral,  962 

of  pelvis,  pract.  consid.,  990 

popliteal,  992 

posterior  auricular,  945 

retro-pharyngeal,  948 

of  RosenmttUer,  992 

sternal,  966 

structure  of,  937 

submaxillary,  94'> 

submental,  946 

subscapular,  962 

superficial  cervical,  056 

thorax,  pract.  consid.,  971 

tibial,  anterior,  993 

tracheal  nodes,  967 

umbilical,  972 
Lvmph-nodules,  936 
Lymphocytes.  031 

varieties  of,  685 
L>'mphotd  structures  of  pharynx,  1 599 

tissue,  structure  of,  936 
L>Tnph-space«,  931 
Lymph-vessels,  934 
Lyra,  11 58 


990 


Macula  lutea,  146* 
Maculte  acusticte,  1516 
Magendie,  foramen  of,  iioo 
Malar  bone,  20a 

articulations  of,  210 

Malleus,  i497  ,.       ,     ,  , 

Malpighian  bodies  of  spleen,  1 784 
Mammary  glands,  iai; 

development  of,  203* 

lymphatics,  968 


THIS  VOLUME   CONTAINS  PAGES  996   TO   THE    END- 


L 


aoffo 


INDEX. 


Mammary  glanda,  nerves  of,  2033 
pract.  consid.,  2033 
structure  of,  1029 
variations  of,  3033 
vessels  of,  2031 
Mandible,  11 1 

Manubrium  of  sternum,  155 
Marrow  of  bone,  go 
Mast-cells  of  connective  tissue,  74 
Mastoid  cells,  1 504 

pract.  consid.,  ijoS 
process,  pract.  consid.,  1508 
Maturation  of  ovum,  16 
Maxilla,  inferior,  211 

development  of,  213 
structure  of,  313 
superior,  199 

antrum  of,  301 
articulations  of,  202 
development  of,  303 
Maxillary  sinus,  1433 
Meatus,  auditory,  internal,  181 
inferior,  of  nose,  14 12 
middle,  of  nose,  141 1 
superior,  of  nose,  141 1 
Meckel,  divertic-'um  of,  44 
Mediastinum,  auverior,  1833 
middle,  1833 
posterior,  1833 
pract.  consid.,  1833 
superior,  1833 
Medulla  oblongata,  1063 

central  gray  matter  of,  1073 
development  of,  iioi 
internal  struct  tire  of,  1068 
Medullary  folds,  36  , 

groove,  26 
sheath,  looi 
velum,  inferior,  1099 
superior,  1099 
Medullated  fibres,  1003 
Megakaryocytes,  689 
Meux>mian  (tarsal)  glands,  1444 
Meissner,  corpuscles  of,  i  o  1 7 

plexus  01,  1643 
Membi^ne  or  membranes.  Bowman's, 
1451 
of  Bruch,  1456 
cloacal,  1939 
costo-coracoid,  568 
crico-thyroid,  1815 
of  Demours,  1452 
Descemet's,  1452 
fenestrated,  77 
foetal,  30 

human,  35 
hyaloid,  1474 

interosseous,  of  tibia  and  fibula,  396 
mucous,  1528 


obturator,  341 
olfactory  (Schneiderian), 
pharyngeal,  1694 
pleuro-pericardial,  1700 
pleuro-peritoneal,  1700 
of  Reissner.  1517 
of  Ruysch,  1456 
of  spinal  cord,  1022 
synovial,  of  joint,  no 
tectoria,  1521 
Ihyro-hyoid,  1815 
of  tympanum,  1494 
vitelline,  15 
vitrea,  1456 


1414 


Meninges  of  brain,  pract.  consid.,  1208 

lymphatics  of,  948 
Menstruation,  2013 
Merkel,  tactile  cells  of,  10 16 
Mesencephalon,  1105 

development  of,  1 1 1 7 

internal  structure  of,  1 109  . 
Mesenteries,  1741 
Mesenterium  commune,  1697 
Mesentery,  anterior,  1744 

of  appendix,  1665 

of  jejtmo-ileum,  1650 

of  large  intestine,  1670 

permanent,  1752 

posterirr,  pprt  1st,  1746 
pr.  t  3nd,  1751 
p.-,ii  3rd,  1753 

pmutive,  1697 
Meso-appendix,  1665 
Mesocolcn,  1670 

development  of,  1 704 
Mesoblast,  33 

lateral  ^tes  of,  39 

paraxial,  39 

parietal  layer,  29 

visceral  layer,  29  , 

Mesogastrium,  1697 
Mesognathism,  229 
Mesometrium,  2005 
Mesonephros,  1935 
Mesorarium,  2040 
Mtsorchium,  2040 
Mesorhines,  1404 
Mesosal]nnx,  1996 
Mesotendons,  471 
Mesothelium,  71 
Mesovarium,  1987 
Metabolism,  6 
Metacarpal  bones,  314 
Metacarpo-phalangeal  articulations,  327 
Metacarpus,  pract.  consid.,  319 
Metanephros  (kidney),  1937 
Metaphase  of  mitosis,  1 2 
Metaplasm,  8 
Metatarsal  bones,  428 
Metathalamus,  11 36 
Mevnert,  commissure  of,  1 1 1 5 
Mia -brain,  1061 
Milk,  2030 
Milk-ridge,  2033 
Mitosis,  II 

anaphases  of,  13 

metaphase  of,  13 

prophases  of,  1 3 

telophases  of,  13 
Molar  teeth,  1546 
Moll,  glands  of,  1444 
Monorchism,  1950 
Monroe,  foramen  of,  1131 
Mons  pubis,  2031 

veneris,  3021 
Montgomery,  glands  of,  2038 
Morgagni,  columns  of,  1674 

hydatid  of,  3002 

sinus  of,  497 

valves  of,  1674 
Morula,  22 
Mouth,  1538 

floor  of,  pract.  consid.,  1593 

formation  of,  1094 

pract.  consid.,  1589 

roof  of,  238 

pract.  consid.,  1593 


0 


THIS  VOLUME   CONTAINS    PAGES   996   TO   THE    END. 


INDEX. 


3071 


Mouth,  vestibule  of,  1 538 
Mucoid,  83 

Mucous  membranes,  1518 
structure  of,  ts>8 
MoUerian  duct,  1038 
Muscle  or  muscles,  abdominal.  515 
abductor  ballucis,  66 1 
minimi  digiti,  608 
minimi,  of  foot,  66s 
pollicis,  608 
adductor  brevii,  6a6 
hallucis,  663 
longus,  6a6 
magnus,  6a8 
polucis,  610 
anconeus,  589 
of  ankle,  pract.  consid.,  666 
antibrachial,  $91 

post-axial,  598  t 

pre-axial,  592 
of  anus,  1675 
appendicular,  566 
of  arm,  pract.  consid.,  589 
arytenoid,  i8a6 
of  auricle,  i486 
auricularis  anterior,  483 
posterior,  483 
superior,  483 
axial,  50a 
of   axilla  and  shoulder,  pract.  consid., 

azygos  uvuue,  496 
biceps,  586 

femoris,  636 
brachial,  58; 

post-axial,  588 
pre-axial,  586 
brachialis  anticus,  586 
brachio-radialis,  598 
branchiomeric,  474 
buccinator,  488 
bulbo-cavemosus,  565 
of  buttocks,  pract.  consid.,  641 
cardiac,  46a 
cervical,  54  a 
chondro-glossus,  1578 
ciliary,  145* 
coccygeus,  561,  1676 
compound  pinnate,  469 
compressor  urethne,  565 
constrictor  inferior  of  pharynx,  1606 
middle  of  pharynx,  1605 
pharyngis  inferior,  499 
medius,  498 
superior,  497 
superior  of  pharynx,  1604 
coraco-Drachialis,  575 
of  cranium,  pract.  consid.,  489 
cremaster,  519 
crico-arytenoid  lateral,  i8as 

posterior,  i8as 
crico-thyroid,  i8a4 
crural,  647 

post-axial,  6sS 
fffe-axial,  648 
crureus,  640 
dartos,  1963 
deltoideus,  578 
depressor  anguli  oris,  487 

labii  inferioris,  485 
diaphragma,  556 
digastricus,  477 
diuttor  pupilUe,  I4te 


Muscle  or  muscles,  dorsal,  of  trunk,  507 
of  Eustachian  tube,  1 503 
extensor  brevis  digitorum,  66$ 
pollicis,  60a 
carpi  radialis  brevior,  598 
longior,  598 
ulnaris,  601 
communis  digitorum,  599 
indicis,  603 
longus  digitorum,  655 
longus  biulucis,  656 

pollicis,  603 
minimi  digiti,  600 
ossis  metacar^x  pollicis,  60a 
of  face,  pract.  consid.,  49a 
facial,  479 
femoral,  633 

post-axial,  638 
pre-axial,  636 
flexor  accessorius,  654 

brevis  digitorum,  of  foot,  660 
hallucis,  66o_ 
minimi  digiti,  609 

digiti  of  foot,  664 
pollicis,  608 
carpi  radialis,  593 

radialis  brevis,  597 
ulnaris,  594 
'   longus  digitorum,  651 
hallucis,  651 
pollicis,  596 
profundus  digitorum,  595 
sublimis  digitorum,  595 
of  foot,  659 

post-axial,  665 
pract.  consid.,  666 
pre-axial,  659 
gastrocnemius,  649 
gemelli,  630 
genio-elossus,  1578 
genio-hyoid,  1578 
genio-hyoideus,  545 
gluteus  maximus,  630 
medius,  631 
minimus,  633 
gracilis,  616 
of  hand,  606 

pre-axial,  607 
of  hip  and  thigh,  pract.  c-wsmL,  64s 
hypoglossal,  506 
hyo-glossus,  1578 
hyoidean,  480 

variations  of,  480 
iliacus,  634 
ilio-costalis,  508 
infraspinatus,  576 
intercostales  extern!,  538 

intemi.  539 
interossei  dorsales  of  foot,  664 
of  hand,  613 
plantares,  663 
volares,  61  a 
interspinales,  513 
intertransversaWs,  S'S 
anteriores,  547 
laterales,  511 
intratympanic,  1499 
involuntary,  arrectores  pilorum,  1394 

nerve-endings  of,  1015 
ischio-cavemoeus,  564 
of  knee,  pract.  consid.,  645 
of  larynx,  1814 
latisstmus  dorsi,  574 


THI*^  VOLUME    CONTAINS    PAGES   996   TO   THE    Et  O. 


iHiM 


m 


3073 


INDEX. 


m 


Muide  or  luuKlet,  of  leg.  pract.   coniid., 
66s 
levator  anguli  orii,  487 
■capuUe,  571 
ani,  560,  167J 
labii  auperioni,  487 
labii  superiori*  alcqne  nasi,  485 
tnenti  (luperbiu),  485 
palati,  496,  1571 
palpebts  luperioris,  50a 
levatoret  coataruin,  540 
linguali*,  1579 
ofBpa,  1540 
longinimus,  510 
longua  colli,  548 
of  lower  limb,  613 
liunbricales,  of  hand,  610 

of  foot,  661 
masseter,  474 
of  mastication,  474 

variations  of,  477 
metameric,  503 
multifidus,  51a 
mylo-hyoideus,  477 
nasalis,  486 

non-striated,  blood-vessels  of,  456 
development  of,  457 
(involuntary),  454 
lymphatics  of,  456 
nerves  of,  456 
structure  of,  455 
obliquus  capitis  inferior,  514 
superior,  514 
extemus,  517 
.    inferior,  504 
intemus,  517 
superior,  504 
obturator  extemus,  619 

intemus,  629 
occipito-frontalis,  48a 
omo-hyoideus,  544 
opponens  minimi  digiti,  608 

pollicis,  608 
orbicularis  oris,  486 

palpebrarum,  484 
orbital,  502 

of  palate  and  pharynx,  495 
palato-glowus,  497,  1579 
palato-pharyngeus,  497,  1571 
palmans  brevis,  607 

longus,  593 
pectinate,  of  heart,  695 
pectineus,  63^ 
pectoralis  major,  569 

minor,  570 
pelvic,  559 
perineal,  c63 
peroneus  brevis,  658 
lon^,  657 
tertius,  656 
of  pharynx,  1604 
pinnate,  469 
plantaris,  A49 
platysma,  481 
popliteus,  655 
pronator  quadratus,  597 

radii  teres,  593 
psoas  magnus,  633 

parvus  (minor),  614 
pter^goideus  extemus,  476 

intemus,  476 
pyloric  sphincter,  1636 
pyramidalis,  517 


» 


Muscle  or  muaclet,  pyriformte,  s't 
quadratus  femoris,  639 

lumborum,  531 
quadriceps  femoris,  639 
of  rectum,  1675 
rectus  abdctmnis,  516 

capitis  anticus  major,  549 
capitis  anticus  minor,  550 
lateralis,  547 
posticus  major,  513 
posticus  minor,  514 
extemus,  503 
femoris,  639 
inferior,  503 
intemus,  503 
superior,  503 
rhomboide«u  major,  371 

minor,  573 
risorius,  487 
rotatores,  of  back,  513 
sacro-spinalis,  508 
lalpingo-pharyngeus,  1606 
iartoniis,  638 
scalene,  variations  of,  547 
scalenus  anticus,  546 
medius,  546 
posticus,  547 
of  scalp,  pract.  consid.,  489 
semimembranosus,  438 
semi-pinnate,  469 
semispinalis,  5 1 1 
semitendinusus,  638 
serratus  magnus,  (71 
posticus  inferior,  541 
posticus  superior,  541 
of  soft  palate,  1570 
soleus,  649 

sphincter  ani,  external,  1676 
extemus,  563 
internal,  1677 
pu|>ills,  1460 
vesical,  external,  1935 
internal,  1935 
spinalis,  511 
splenitis,  510 
stapedius,  480,  1499 
stemalis,  570 

stemo-cleido-mastoideus,  499 
stemo-hyoideus,  543 
stemo-thyroideus,  545 
striated,  attachments  of,  468 
blood-vessels  of,  464 
burse  of,  471 
classification  of,  471 
development  of,  465 
form  of,  469 

general  considerations  of,  468 
lymphatics  of,  464 
nerves  of,  464 
nerve-supply,  general,  473 
structure,  general  of,  458 
variations,  461 
(voluntary),  457 
stylo-glossus,  1579 
stylo-hyoideus,  480 
Etylo-pharyngeus,  495,  1606 
subclavius,  570 
subcostal,  539 
subcrureiw.  640 
submental,  477 
subscapularis,  578 
supinator,  601 
BUpraspinatus,  575 


THIS  VOLUME    CONTAINS    PAGES    996    TO   THE    END. 


4   *..\>*»-^  :",j 


INDEX. 


2073 


Ifuacle  or  muiclea.  temporalU,  475 
tensor  fasciz  laUe,  631 
palati,  479,  1570 
tympani,  479,  1499 
teres  major,  577 
minor,  576 
thoracic,  538 
thyro-arytenoid,  1815 
thyro-hyoideus,  545 
tibialis  anticus,  65  s 

posticus,  654 
of  tongue,  1 577 
trachealis.  1835 
transversalis,  510 
transverso-costaf  tract,  508 
transverso-spinal  tract,  511 
transvemus  perinei  profundus,  s^S 
superficialis,  564 
of  tongue,  1579 
trapezius,  500 
tn^ngularis  stemi,  540 
triceps,  588 
trigeminal,  474 
palatal,  479 
tympanic,  479 
of  tnmk,  J07 
of  upper  limb,  568 
vago-acct.*ory,  495 
vastus  externus,  640 

internus,  640 
ventral,  of  trunk,  515 
voluntary,  motor  nerve-endings  of,  10 14 
zygomaticus  major,  485 
minor,  485 
Muscle-fibre,  structure  of,  459 
Muscular  system,  454 

tissue,  general,  454 
Myelin,  looi 

Myelocytes,  of  bone-marrow,  q» 
Myeloplaxes,  of  bone-marrow,  9a 
Myometrium,  3008 
Myotome,  30 
Myxoedema,  1794 

Naboth,  ovules  of,  a  008 
Nail,  structure  of,  1395 
Nail-bed,  1396 
Nail-plate,  1395 
N«ils,  1394 

development  of,  1403 
Nares,  anterior,  1404 

posterior,  14 13 
Nasal  bone,  aoo 

articulations  of,  ao9 
development  of,  aog 
cavities,  pract.  consid.,  141 7 
cavity,  a 23 

hiatus  semilunaris  of,  194 
infundibulum  of,  194 
meatus  inferior  of,  aas 
middle  of,  aas 
superior  of,  aas 
chamber,  aa4 

fossa,  blood-vessels  of,  1425 
floor  of,  1413 
lymphatics  of,  1436 
nerves  of,  1436 
roof  of,  T4ia 
fosStP,  1409 
index,  1404 

mu(  JUS  membrane,  141 3 
septum,  333,  1410 
triangular  cartilage  of,  334 


Nasion,  338 

Nasmyth,  membrane  of,  1550 
Na£o-lachr>-mal  duct,  1479 
Naso-optic  groove,  63 
Naso-pnarynx,  1598 
Navel,  37 

Neck,  landmarks  of,  $54 
pract.  consid.,  550 
triangles  of,  547 
Nephrotome,  30 

Nerve  or  nerves,  abdominal,   of  vagus, 
137a 
abducent,  1349 

development  of,  1379 
aortic  (sympathetic),  1364 
auditory,  1356 

development  of,  1379 
of  auricle,  1487 
auricular,  ^;rea'      386 

posterior,  01  facial,  1354 
of  vag<is,  1368 
3uriculo-temporal,  of  mandibular,  1344 
of  bone,  94 

buccal,  of  mandibular,  1343 
culcanean,  internal,  1^44 
cervical,  anterior  divisions  of,   1385 
cardiac  inferior,  of  vagus,  1370 

superior,  of  va^us,  1370 
first,  posterior  division  of,  laSi 
posterior  divisions  of,  ia8i 
second,  posterior  division  of,  laSi 
superficial,  1387 

third,  posterior  division  of,  1381 
cervico-facial,  of  facial,  1354 
chorda  tympani,  of  facial,  1353 
ciliary,  long,  of  nasal,  1334 
circumflex,  1307 

piBct.  consid.,  1308 
of  clitoris,  3035 

coccygeal,  posterior  division  of,  1384 
of  cochlea,  membranous,  1531 
cochlear,  of  auditory,  1356 
of  cornea,  145a 
cranial,  13:9 

crural,  anterior  (femoral),  1337 
cutaneous  internal,  of  anterior  crural, 
1338 

middle,  of  ant^or  crural,  1337 
jwrforating,    of    pudendal    plexua, 

•347 
dental,  inferior,  of  mandibular.  1345 
superior     anterior,    of    maxillary, 

i»39 
middle,  of  maxillary,  1339 
posterior,  of  maxillary,  1338 
descendens  hypoglossi,  1377 
development  of,  1375 
digastric,  of  facial,  i  ^  54 
digital  of  median,  1301 
dorsal  of  clitoris,  13  51 

of  penis,  135 1 
of  epididymis,  1948 
of  external  auditory  canal,  1490 
external  cutaneoiu,  of  lumbar  plexus. 

13*4 
of  eyelids,  1446 
facial,  1350,  1331 

development  of,  1378 

genu  of,  1351 

pract.  consid.,  1355 
of  Fallopian  tube,  1999 
frontal,  1334 


(}< 


THIS  VOLUME    CONTAINS    PAGES    996   TO    THE    END. 


9074 


INDEX. 


Nerve  or  nenrea,  ganglionic,  of  naaal, 
"34 
gi-nito-crural,  ijai 
of  glands,  1 536 
gloMo- pharyngeal,  ia6o 

development  of,  1379 
gluteal,  inferior,  1333 

•uperior,  1333 
of  heart,  ^04 

hemorrhoidal,  inferior,  1350 
hypoglossal,  1375 

development  of,  1380 

pract.  conaid.,  1377 
ilio-hypogastric,  1330 
ilio-inguinal,  1331 
infratrochlear.  1335 
intercostal,  1314 
intercosto-humeral,  1317 
intermeditis  of  Wrisberg,  of  facial, 

1350 
internal  cutaneous,  1303 

cutaneous  lesser,  1303 
interosseous  anterior  of  median,  1300 
of  kidney,  1886 
of  labia,  3034 

labial,  superior,  of  maxillary,  1340 
lachrymal,  1333 

laryngeal,  external,  of  superior  laryn- 
geal, 1270 

interior  (recurrent)  of  vagus,  1370 

internal,  of  superior  laryngeal,  1 370 

superior,  of  vagus,  1370 
of  larynx,  1837 
lingual,  of  glosso-pharyngeal,  1364 

of  hypoglossal,  1377 

of  mandibular,  1344 
of  lips,  1543 
of  liver,  1 7 1 1 

lumbar,  posterior  divisions  of,  1383 
of  lungs,  1855 
of  mammary  glands,  30^3 
mandibular,  (maxillary  inferior),  1343 
masseteric,  of  mandibular,  1343 
maxillary  (superior),  1337 
median,  1398 

branches  of,  1300 

pract.  consid.,  1301 
meningeal,  of  hypoglossal,  1377 

of  vagus,  1368 
mental,  of  inferior  dental,  1346 
of  muscle,  non-striated,  456 
muscular  of  glosso-pharyngeal,  1364 
musculo-cutaneous,  of  arm,  1398 

of  leg,  1338 
musculo-spiral,  1308 

branches  of,  1309 

pract.  consid.,  13 14 
mylo-hyoid,  of  inferior  dental,  1345 
nasal,  1334,  1235 

anterior,  1335 

external,  1335 

fossa,  1436 

internal  (septal),  1335 

lateral,  of  maxillary,  1340 

septum,  1410 

superior  posterior,  of  spheno-pala* 

tine  ganglion,  1341 
naso-palatine,  of  spheno-palatine  gan- 
glion, 1341 
of  nose,  1407 
obturator,  1334 

accessory,  1336 
occipital,  small,  1386 


Nerve  or  nervea,  oculoinotor,  ists 

development  of,  1377 
oesophageal,  of  vagus,  137s 
of  ceiopnagus,  1613 
olfactory,  1330 

development  of,  1376 

pract.  consid.,  1333 
ophthalmic,  1333 
optic,  1333 

development  of,  1483 

pract.  consid.,  1470 
orbital,  of  spheno-palatine  ganglion,  1341 
of  ovary,  1993 
of  palate,  1J73 
palatine,  of  spheno-palatine  ganglion, 

1341 
palmar  cutaneous  of  median,  1301 
palpebral,  inferior,  of  maxillary,  1340 
of  pancreas,  1717 
of  parotid  gland,  1583 
of  penis,  1971 
pericardial  of  vagus,  1373 
of  pericardium,  716 
perineal,  1350 

peripheral,  development  of,  loii 
peroneal,  communicating,    of    external 

popliteal,  1335 
petrosal,  deep,  small,  1364 

superficial,   external,  of   facial, 

"S3 
great,  of  facial,  1353 
small,  1364 
pharyngeal  of  glosao-pharyngeol, 
1364 

of  vagus,  1369 
of  pharynx,  1606 
phrenic,  1390 
plantar  external,  1345 

internal,  1344 
of  pleune,  1861 
popliteal,  external  (peroneal),  1335 

internal  (tibial),  1339 
posterior  interosseous,  13 11 
of  prostate  gland,  1978 
pterygoid,  external,  of  mandibular, 
"43 

internal,  of  mandibular,  1343 
pterygo-palatine    (pharyngeal),    of 

spheno-palatine  ganglion,  1343 
pudic,  1349 
pulmonary,  anterior,  of  vagus,  137a 

posterior,  of  vagus,  1373 

(sympathetic),  1364 
radial,  1313 
of  rectum,  1680 
recurrent,  of  mandibular,  134s 

of  maxillary,  1337 
respiratory,  external  of  Bell,  1395 
sacral,  posterior  divisions  of,  1383 
sacro-coccygeal,  1353 

posterior,  1383 
saphenous,  internal   (long),  of  anterior 
crural,  1339 

short  (external),  1343 
scapular,  posterior,  1395 
sciatic,  great,  1335 

small,  1348 
of  scrotum,  1964 
of  skin,  1389 
of  small  intestine,  1643 
somatic,  13 18 
of  spermatic  ducts,  1959 
spheno-palatine,  of  maxillary,  1337 


THIS  VOLUME    CONTAINS    PAGES   9»6   TO   THE    END. 


INDEX. 


J075 


N«rve  or  nervM.  spinal.  1178 
•pina! -accessory,  1374 

pract.  consid.,  117} 
■pUnchnic,  (sympathetic),  1364 
of  spleen,  1787 
sUpedial,  of  facial,  is  S3 
of  stomach,  i6a8 
of  striated  muscle,  464 
•tylo-hyoid,  of  facial,  iaS4 
of  suUingual  gland,  i  $85 
of  submaxillary  gland,  1585 
subscapular,  1306 
supraorbital,  1234 
of  suprarenal  bodies,  1803 
suprascapular,  1295 
supratrochlear,  1234 
sural,  of  external  popliteal,  133  s 
of  sweat  glands,  1400 
of  taste-buds,  143S         ... 
temporal,  deep,  of  mandibular,  1243 
superficial,    of    auriculo-temporal, 

1244 
temporo-facial,  of  facial,  12J4 
temporo-malar  (orbital),  of  maxillary, 

1238 
of  testis,  1948 
thoracic,  13 14 

anterior,  external,  1297 
internal,  1303 

brandies  of,  13 17 

cardiac,  of  vagus,  127s 

first,  1315 

lower,  1315  .  .  ,       „ 

posterior  divisions  of,  128a 

posterior  (long).  1295 

pract.  consid.,  1 296 
pract.  consid.,  1318 
second,  1317 
third,  1317 

twelfth  (subcostal)  13 17 
upper,  13  IS 
of  thyroid  body,  1793 
of  thymus  body.  1800 
thyro-hyoid,  of  hypoglossal,  1277 
tibial,  anterior,  1336 

communicating,  134s 
posterior,  1342 
recurrent,  133s 
of  tongue,  1 580 

tonsillar  of  glosso-pharyngeal,  1264 
of  trachea,  1836 
trigeminal,  1230 

development  of,  1378 
divisions  of.  1232 
pract.  consid.,  1248 
trochlear,  1228 

development  of,  1377 
tympanic,  of  glosso-pharyngeal,  1264 
to  tympanic  plexus,  of  facial,  1252 
ulnar,  1303 

branches  of,  1305 
pract.  consid.,  1306 
of  ureter,  1898 
of  urethra,  1927 
of  urinary  bladder,  1910 
of  uterus,  2010 
of  vagina,  aoi8 

vagus,  1265  .      ,  . 

and  spinal  accessory,  development 

of,  1380 
ganglia  of,  1267 
pract.  consid.,  1272 
vestibular,  of  auditory,  1856 


Nerve  or  nerves,  visceral,  lait 
Nerve-cells,  998 
bipolar,  999 
multipolar,  1000 
unipolar,  999 
Nerve-endings,  motor,  1014 

of  cardiac  muscle,  101  s 
of  involuntary  muscle,  101 S 
of  voluntary  muscle,  1014 
sensory,  loij 

encapsulated,  1016 
free,  1013 

oenital  corpuscles,  1017 
Golgi-Massoni  corpuscles,  1019 
Krause's  end-bulb«,  1016 
Meissner's  corpuscles,  1017 
Merkel's  tactite  celts,  1016 
neuromuscular  endings,  1019 
neurotendinous  endings,  loao 
Ruffini's  corpuscles,  1017 
Vater-Paciman  corpuscles,  1018 
Nerve-fibres,  1000 
arcuate,  1071 
axis-cylinder  of,  loot 
cetebello-olivary,  107s 
cerebello-thalamic,  1114 
cortico-bulbar,  1115 
cortico-pontine,  1115 
cortico-spinal,  1115 
medullary  sheath  of,  toot 
medullated,  1003 
neurilemma  of,  looi 
nonmedullated,  1003 
rubro-thalamic,  11 14 
of  sympathetic  system,  1356 
Nerve-terminations,  1014 
Nerve-trunks,  1006 

endoneurium  of,  1006 
epineurium  of,  1006 
funiculi  of,  1006 
perineurium  of,  1006 
Nervous  system,  996 
central,  1021 
peripheral,  1218 
sympathetic,  1353 

development  of,  1013 
tissues,  997 

development  of,  1009 
Neurilemma,  looi 
Neuroblasts,  loio 
Neuro-epithelium,  70 
NeurogUa,  1003 

ependymal  layer  of,  1004 
glia-fibres  of,  1004 
of  gray  matter,  of  spinal  cord,  103s 
histogenesis  of,  loio 
spider  cells  of,  1004 
Neurokeratin,  looi 
Neuromuscular  endings,  1019 
Neurone  or  neurones,  996 
axones  of,  997 
dendrites  of,  997 
histogenesis  of,  101 1 
Neurotendinous  endings,  1020 
Nictitating  membrane,  1443 
Nipple,  2028 

Noaose,  ganglion  of  vagus,  1268 
Nodules  of  Arantius,  700 
Nonmedullated  fibres,  1003 
Normoblasts,  92 
Nose,  1404 

blood-vessels  of,  1407 
cartilages  of,  1404 


¥. 


m^ 


THIS  VOLUME   CONTAINS    PAGES  ©96   TO   THE    END. 


ao76 

Note,  developinent  of,  1419 
hiatus  leniilunarit  of ,  1411 


INDEX. 


inferior  maattw  of,  141a 
infundibulum  of,  141 1 
Ut«nU  cartilages  of,  1405 
lymphatics  of,  1407 
middle  meatus  of,  1411 
nerves  of,  1407 
olfactory  ragion  of,  1413 
pract.  connd.,  1407 
respiratory  region  of,  1415 
superior  meatus  of,  141 1 
vestibule  of,  1 409 
Nostrils,  1404 
Notochord,  J7 
Niick,  canal  of,  aoo6 
Nuclein,  9 
Nucleolus,  9 

Nucleus  or  nuclei,  abducent,  1249 
acoustic,  1*57 
ambiguus,  1074 
amygdaloid,  117a 
arcuate.  1076 
caudate,  1 1 69 
cuneate,  1069 
facial.  ia5i 

dentate,  of  cerebellum,  1088 
emboliformia  (embolus)  of  cerebellum 

1089 
facial,  laji 

fastigii,  of  cerebellum,  1089 
globosus,  of  cerebellum,  1089 
pracile,  1069 

mtemal,  of  cerebellum,  1088 
of  lateral  fillet,  1358 
lenticular,  11 69 
mammillaris,  1 1 29 
olivary,  107 1 
olivary,  superior.  1257 
red,  iti4 
structure  of,  8 
trapezoideus,  1357 
vago-glosso-pharyngeal.  1073 
vestibular,  of  reception,  1359 
Nuhn,  glands  of.  1577 
Nutrition,  accessory  organs  of,  1781 
Nymphae,  aoaa 

f)belion.  aa8 
Obex,  1096 
Occipital  bone,  17a 
lobe,  1145 

protuberance,  external,  1 74 
internal.  175 
Odontoblasts.  1558 
CEsophagus.  1609 

course  and  relations  of,  1609 

lymphatics  of.  971 

nerves  of.  1613 

pract.  consid..  1613 

structure  of.  161 1 

vessels  of,  161  a 
Olecranon,  of  tilna.  a8i 
Olfactory  bulb,  11 51 

cells,  1414 

hairs.  141 5 

lobe   1 1 51 

met,  orane,  1414 

pits,  6a 

region  of  nose,  1413 

strije,  1 1 53 

tract,  1 1 52 

trigone,  1 1 53 


Olivary  eminence,  loM 
nuclei,  1071 

•ccesiory,  107s 
nucleus,  inferior,  107* 
Omental  sac,  1 703 
Omentum,  dtioaeflo-hapatic,  1746 

gastro-colic,  1747 

gastro-hepatic  (leaaer),  174* 

gastro-stdenic,  1747 

greater,  1747 

greater,  structure  of,  1 749 
OOcjrte,  primary,  1 7 

secondary,  17 
Ooplasm,  15 
Opercula  insulte,  1137 
Ophryon,  aaS 
Opisthion,  aa8 
Optic  commissure,  iaa3 

entrance  or  papilla,  146a 

lecess,  113a 

thalami,  11 18 

tracts,  iaa3 
Ota  serrata,  1467 
Oral  cavity,  development  of,  6a 

glands,  development  of,  ic8« 
Orbit,  aaa 

axes  of,  aaa 

fasciae  of,  504 

lymphatics  of,  949 

pract.  consid.,  1438 
Organ  or  organs,    accessorv.   of   nutritioa 
1781 

of  Corti,  1 519 

genital,  external  female,  aoai 

Jacobson's,  1*17 

reproductive  female,  198$ 
male,  1941 

of  res{riration,  1813 

of  sense,  1381 

of  taste,  1433 
y,  1869 


urinary,  .„,^ 
Oro-pharynx,  1598 
Orthognathism,  339 
Os  intermetatarseum,  43* 

magntmi,  31a 
Osseous  tissue,  84 
Ossicles  auditory,  1496 

articulations  of,  1498 
incus,  1497 
malleus,  1497 
movements  of,  1 500 
stapes,  1498 
of  ear,  development  of,  1515 
Ossification,  centres  of,  94 

of  epiphyses,  98 
Osteoblasts,  95 
Ostium  maxiUare,  1423 
Otic  ganglion,  1346 
Ova  or  ovum,  1 5 

centrolecithal,  33 
fertilization  of,  18 
holoblastic,  33 
homolecithal,  ai 
human,  1990 
maturation  of,  16 
meroblastic,  33 
primordial,  1993 
segmentation  of,  31 
stage  of,  56 
telolecithal,  32 
zona  pellucida  of.  1989 
Ovary  or  ovaries,  1085 
cortex  of,  1987 

THIS  VOLUME    CONTAINS    PAGES   986   TO   THE    END. 


INDEX. 


2077 


f1 


Ovmry  or  ovariM,  deacent  of,  1043 

davelopnwnt  of,  1993 

fixation  of,  ig86 

Graafian  foUiclea  of,  1988    . 

hilum  of,  1985 

ligament  of,  1987 

meduUa  of,  1988 

nerve*  of,  1993 

poattion  of,  1986 

pract.  comid.,  1995 

■urfacea  of,  1985 

■uapenaory  ligament  of,  1986 

structure  of,  1987 

veaaels  of,  1991 
Oviduct,  1996 

Pacchionian  bodiea,  laos 

depreasions,  198 
Palate,  1567 
bone,  ao4 

articulationa  of,  105 
development  of,  m  , 
hard,  1567 
lymphatics  of,  934 
nerves  of,  1 573 
pr    ^  conitia.,  1591 
r  'i.  -.568 

.nuacles  of,  1570 
'  >iel*of,  i57» 
Pall  T.'.i,  developrnent  of,  1189 
Palti.  .r  aponeurosis,  606 

fascia,  606 
Pancreas,  1731 
body  of,  1733 
development  of,  1737 
ducts  of,  1736 
head  of,  1731 

interalvoolar  cell-areas  of ,  1735 
islands  of  Langerhans  of,  1735 
lymphatics  of,  979 
nerves  of,  1737 
pract.  consid.,  1738 
relations  to  peritoneum  of,  1736 
structure  of,  1734 
vessels  of,  1736 
Panniculus  adiposus,  1384 
Papilla  or  papillae,  circumvallate,  1575 
dental,  1558 
of  duodenum,  1720 
filiform,  1575 
fungiform,  1575 
lachrymal,  1478 
optic,  146a 
renal,  1875 
Paradidymis,  1950 
Parametrium,  jooj 
Parathyroid  bodies,  1795 

structure  of,  1795 
Parietal  bone,  197 

articulations  of,  199 
impressions,  199 
lobe,  1 1 43 
Paroophoron,  aooa 
Parotid  duct,  1 583 
gland,  1582 

nerves  of,  1 583 
relations  of,  1 583 
structure  of,  1 586 
vessels  of,  1 583 
Parovarium,  aooo 
Patella,  398 

development  of,  400 
movements  of,  409 


10A7 


350 


Patella,  pract.  consid.,  ^lA 
Peduncle,  cerebellar,  inferior, 

cerebral,  1107 
Pelvic  girdle,  33  a 
Pelvis,  33  a 

development  of,  344 

diameters  of,  34a 

diaphragm  of,  $$i) 

index  of,  343 

jointB  of,  337 

pract.  consid. 

of  kidnev.  1894 

landmarks  of,  349 

ligaments  of.  337 

lymphatics  of,  983 

position  of.  14a 

pract.  consid.,  345 

sexual  differences,  343 

surface  anatomy  of.  345 

white  lines  of,  559 

as  a  whole,  341 
Penis,  1965 

corpora  cavemtjsa  of,  1966 

corptis  spongiosum  of,  1967 

crura  of,  1967 

glans  of,  1968 

nerves  of,  197 1 

pract.  consid.,  1971 

prepuce  of,  1966 

structure  of,  1968 

vessels  of,  1970 
Pericecal  fosss,  1666 
Pericardium,  714 

blood- veaaels  of,  716 

ligaments  of,  716 

lymphatics  of .  716 

nerves  of,  716 

pract.  consid.. 
Perichondrium,  81 
Pericranium,  489 
Perilymph  of  internal  ear, 
Perimetrium,  aooy 
Perimysium,  458 
Perineal  body,  3046 
Perineum,  female,  3046 

lymphatics  of,  987 

male,  191s 

land,  narks  of,  i  g  1 8 

triangular  ligament  of,  563 
Perineurium.  i.>o6 
Periosteum.  89 

alveolar,  1553 
Peritoneum,  1740 

cavity,  lesser  of,  1749 

development  of,  170a 

of  large  intestine,  1670 

parietal,  anterior,  1743 
folds  of.  174a 
fosss  of,  1743 

pract.  consid.,  1754 
Perivascular  lymph-spaces,  931 
Pes  anserinus,  1  352 

hippocampi,  1165 
Petit,  triangle  of,  574 
Petro-mastoid    portion 

I7Q 
Petrous   ganglion,    of 
1364 
subdivision,   of    petro-mastoid 
181 
Peyer's  patches,  1641 
Phalanges  of  foot,  433 
of  nand,  317 


71ft 


'S"4 


of    temporal    lM)ne, 
glosso-pharyngeal, 
bone, 


n 


THIS  VOLUME    CONTAINS    PAGES   996    TO    THE    END. 


S078 


INDEX. 


PhalanfM  of  hand,  davalopamt  of,  jil 
peculMritiM,  318 
IKmct.  Gonaid.,  ji o 
VMiationtof,  J19 
Pharyiifval  pouchea,  1695 
Pharynx,  1596 

development  of,  i6oj 
growth  of,  160J 
urynso-,  1398 
lymi^Btict  of,  954 
lymphoid  atructures  01,  1599 
muaclea  of,  1604 
naao-,  1598 
nervea  of,  1606 
oro-,  1598 
pract.  conaid.,  1606 
primitive,    1694 
reUtiona  of,  1601 
ainua  pyriformia  of,  1598 
veaaela  of,  1606 
Philtrum  of  lipa,  1 540 
Pia  mater,  of  otain,  laoa 

of  aptnal  cord,  loaa 
Picment-cells  of  connective  tiiaue,  74 
Pillara  of  faucea,  1569 
Pineal  body,  1114 
Pinna,  1484 
Piaiform  bone,  311 

Pituitary  body,  anterior  lobe  of,  1806 
development  of,  1 808 
(hypophyaia),  1139 
Placenta,  49 

baaal  plate  of,  51 
cotyledona  of,  50 
diacoidal,  34 
foetal  portion,  50 
^ant  cella  of,  51 
mtervilloua  apacea  of,  51 
marginal  ainua  of,  53 
maternal  portion,  51 
multiple,  34 
aepta  of,  51 
vitelline,  31 
zonular,  33 
Placentalia,  34 
Plane,  frontal,  3 
aagittal,  3 
transverse,  3 
Plasma-cella  of  connective  tiaaue,  74 
Plaamosome,  9 
Plates,  tarsal,  1444 
Platyrhines,  1404 
Pleura  or  pleurse,  1858 
blood-vessels  of,  1 860 
nervea  of,  1861 
outlines  of,  1859 
pract.  consid.,  1864 
relations  to  chest-walls,  changes  in,  1863 

of  to  surface,  1859 
structure  of,  i860 
Plexus  or  plexuses,  aortic,  1373 
of  Auerbach,  1643 
brachial,  1293 

branches,  infraclavicular  of,  1297 

supraclavicular  of,  1295 
constitution  and  plan  of,  1193 
pract.  consid.,  1294 
cardiac,  13^7 

carotid  (sympathetic),  1360 
cavernous,  of  penis,  1374 
(sympathetic),  1361 
cervical,  1285 

branches  of,  1285 


Plexus  or  plnuMS,  cervical,  br      I.ea. 
communicating  O'    t    s^ 
daep,  of,  isSo 
.  deacanding  of,  1 28M 
muacular  uf,  1289 
auparficial  of,  1286 
aupraikcromial  of,  1 389 
aupraclavicular  of,  128b 
aupraatemal  uf,  ia8S 
pract.  ronaid  ,  129a 
coccygeal,  1352 
caliac,  1370 

lymphatic,  973 
coronary,  1368 
gaatric,  1370 
hemorrhoidal,  1374 
hepatic,  1370 
hypogaatnc,  1373 

lymphatic,  984 
iliac,  lymphatic,  983 
inguinal,  lymphJatic,  991 
lumbar,  1119 

lymphatic,  973 
muacular  branchea  of,  1310 
of  Meiaaner,  1 64 1 
meaenteric  infenor,  1373 

auperior,  1372  ' 

oeaophageal,  127* 
ovarian,  1371 
pampiniform,  i960 
parotid,  1252 
pelvic,  1374 
phreni'-.  1371 
pract.  consid.,  1330 
proatatic,  1374 
pudendal,  1345 

branch^,  muscular  of,  1346 
viaceral  of,  1346 
pulmonary,  anterior,  1272 

poatenor,  1272 
renal,  1371 
aacral.  133 1 

branchea,  articular  of,  1334 
collateral  of,  1332 
muacular  of ,  1333 
terminal  of,  1334 
lymphatic,  984 
poaterior,  1282 
pract.  consid.,  1352 
solar,  1368 
spermatic,  13  71 
aplenic,  1370 
suprarenal,  13  71 
of  sympathetic  nerves,  1367 
tympanic,  1264 
utero-vaginal,  1374 
vesical,  1374 
Plica  fimbriata,  1 573 

semilunaria,  of  eye,  1 443 
aubUngualis,  1573 
Polar  body,  first,  16 
aecond,  16 
Pona  Varolii,  1077 

development  of,  1103 
internal  atructure  of,  1078 
Pontine  flexure,  1063 

nucbus,  1078 
Portal  system  M  veins,  519 
Postaxial,  4 

Pouch  of  I>ouglas,  1743 
pharyngeal,  61 
recto-uterine  '1743 
recto- vesical,  1743 


THIS  VOLUME   CONTAINS  PAGES  996   TO  THE    END. 


I 


INDEX. 


ao79 


\i> 


PDapart,  iigktnent  o<,  j-ij 
Pl*«xial.  4 
Pragnai    v,  joia 
Prapui'c  of  jiriiU,  i<)66 
Primitivo  streak,  34 

»ignjti>an.  0  o(,  »i 
Proceu  of  prcK-esBw*.  ciliary,  1457 
fronto-nasai.  6a 
mandibular,  &a 
maxillary,  6a 
naaal,  mesial,  6a 

lateral,  6j 
styloid,  of  petrous  oone,  183 
uncinate  of  ethmoid,  193 
Processus  cochleariformis,  18a 

vaeinalis,  ao4i 
PriKtodieum,  1695 
Prognathism,  aa(; 
Pronephros,   19,^1 
Pronucleus,  femai     16 

mate,  ao 
Prophases  of  mitosU,  1 2 
Prosencephalon,  loscj 
Prostate  eland,  1975 

development  of .  kit} 
lymphatics  of,  uAs 
nerves  of,  1978 
pract.  consid.,  11179 
relations  of,  197' 
stnu-ture  of,  19    7 
vessfla  of    1978 
Proteins,  8 
Protoplasm.  7 
Protovertel>r»,  m 
Psalteritmi.  i '  '^ 
PseudostomHtJ    ?» 
Pterion.  ia8 

Pterygoid  plait-    inner,  iSg 
ou         iSq 
process..     jI'  -phenoid  l».ne,  t 

Fube«,  33 1  ,  „ 

Pulmonary  svs  em  of  veins,  35; 

Pulp  of  teeth,  i  =;54 

Pulvinar,  11 19 

Puncta,  lachryi         1478 

Pupil,  1459 

Purlcinje  cells  of      rebellur       dqo 

Putamen,  1 1 70 

Pyramid,  1065 

Pyramidal  trait    m  mt- 'iU''=         '5 

Pyramid?   dec  issition    1, 

renal    18-'' 
Pvronin,  • 


Radius,  a:  ; 

devefc  .pwe' 

landm. 

pract. I . 

structure 

iurUice  an. 
Rai  a  coinmunii 

•r,  nodes  01. 


<ymp«thetic  S5rstem, 


ftMr> 
iec 

Re-; 


•rils  of,  a3 
■  — ne  pouch 
a!  pouch. 
672 

'.t-ssels  of, 
hof,  1680 
phatics  of,  16S0 
iscles  and  fascite  of,  1675 
,;rves  of,  1680 
(jeritoneal  relations  of,  1679 


<43 
'743 

T679 


Kectiim,  pract.  consid.,  i68<,i 

»i  ructure  of,   ■  674 

V  .tlveaof.  167  i 
KeductKm  division    18 
Keil,  island  of,  1  M'i 

liti  'ting  sulcus  of,  iijij 
Keissm-    s  libre,  10 jo 

mc:   brane,  of  i ochlea,  1    1 7 
Kemak.    ibres  of,  1005 
Rtual  di     t,  I  894 
Ke)>rodu:    ion,  6 
KefTitdut     ve   or^."        develojm>ent  ol. 

.  .'ct«rTial,     K'     tie,    h      .jhatus 
of,   <)8 , 
male   lymphatics '      986 
1.  ->ials,  !  ::•-  ^ 
miemii    n  nale,  lymphiitics  of,  yU 

maid,  ivmtrfMtic*  of,  087 
mala,  it^i 
lUapiratiun,  otk^hh  uf.  1813 
Respiratory  res;-  "i  of  nose,  1415 
tract,  di         pment  of,  1861 
Kesttform  body,  1067 
Kete  Mal]nt!hi,  1  {86 
Retifiilar  t!««r,  75 
Ruticuhn.  »  ; 
Retina,  '46-' 

b|<     1-v.  -uieU  of,  .    iSy 
dev  .iopi'ient    (,  1      ' 
lym{*atics  ol.  14' 
pars  i.pti-  a  of,  14< 
fwact.  consid..  146; 
F-  'ucture  of.  1463 
Retru-coli    fossa.  1667 
K«txius.  t^evesiial  space  of,  sas 
space  uf ,  I  sio6 
veins  of.  934 
Rhi:   -ncepl'   loo,  i  '  ^! 

ieveUij  snent  <  ;    1 193 
R"!       beiK»»!.halon,  derivatives  of,  1 
Rib      149 

'fm,:      .  50 

i.      I'lg.  ISO 
praci    consid.,  109 
stem-il,  150 
variations  of,  1 53 
Right  lymphatic  duct,  945 
Rima  glottidis.  i8ao 
Ring,  abdominal,  external,  584 
I  internal,  524 

femoral  (cTural),  1773 
. !  Riolan,  muscle  of,  484 
i  Rivinus,  ducts  of.  1 585 
I  notch  of,  1493 

!  Rolando,  fissure  of,  1137 
i  funiculus  of.  1067 

I  Rosenmflller,  fossa  of,  1 598 
lymph-nodes  of,  992 
organ  of,  2000 
Rostrum,  of  corpus  callosum,  M56 

of  sphenoid  bone,  1S7 
Ruflfini.  corpuscles  of.  1017 
Ruysch,  membmne  of.  MS* 

Sac,  conjunctival,  1443 

lachrymal.  1478 

vitelline,  32 
Saccule,  is'S 

structure  of,  1 5 1  ft 
Sacral  lymphatic  plex»t«.  0X4 
Sacro-iliac  articulaticm.  338 


1063 


THIS  VOLUME    CONTAINS    PAGES    996    TO    THE    END. 


aoSo 


INDEX. 


■   ^\-": 


8acto-«ciatic  ligamenU,  339 
Sacrum,  134 

development  of,  lao 
sexual  difference*  01,  137 
variations  of,  137 
Salivary  glands,  1581 

structure  of,  1585 
Santorini,  cartilages  of,  1817 

duct  of,  1 7^6 
Saphenous  opening,  635 
Sarcolemma,  459 

Sarcous  (muscular)  substance,  459 
Scala  tympani,  15 14 

vestibuli,  1514 
Scalp,  lymphatics  of,  ^4$ 

muscles  and  fascue,  pract.  consid.,  489 
Scaphoid,  309 

bone  of  i.jOt,  435 

development  of,  436 
Scapula,  348 

development  of,  353 
landmarks  of,  355 
ligaments  of,  356 
pract.  consid.,  353 
sexual  differences,  353 
structure  of,  3  a 
Scapulo-clavicular  articulation,  36a 
Scarpa,  canals  of,  301 
fascia  of,  515 
ganglion  of,  1359 
triangle  of,  639 
Schlemm,' canal  of,  1453 
Schwann,  sheath  of,  looi 
Sclera,  1449 

develojxnent  of,  1483 
pract.  consid.,  1453 
structure  of,  1450 
Scleiotome,  30 
Scoliosis,  144 
Scrotum,  1961 

dart--  muscle  of,  1963 
nerves  of,  t<)64 
pract.  consid.,  1964 
raphe  of,  1963 
tunica  vaginalis  of,  1963 
vessels  of,  1964 
Segmentation,  31 

complete,  33  * 

eq'ial,  33 
partial,  33 
Sella  turcica,  1S6 
Semilunar  bone,  310 

cartilages  of  knee-jcint,  403 
valves,  700 
Seminal  vehicles,  1956 

lymphatics  of,  g88 
pract.  consid.,  1959 
relations  of,  1957 
structure  of,  1958 
vessels  of,  1958 
Seminiferous  tubules,  i>>43 
Sense,  organs  of,  1381 
Septum  or  septa,  aortic,  707 
auricular,  694 
crurale  (femorale),  635 
intermedium,  706 
intermuscular,  470 
interventricular,  696 
lucidum,  1 1 59 

median,  posterior,  of  spinal  cord,  1037 
nasal,  1410 

cartilage  of,  1405 
placental,  51 


Septuii  or  septa,  primum,  706 

aei;undum,  708 

spuiium,  707 

transversum,  1701 
Serosa,  31 

Sertoli,  cells  of,  1943  , 
Sesamoid  bones,  104 
of  foot,  433 
of  hand,  318 
Sharpey's  hbr^  of  bone,  8 


L 


Shoulder,    miucles    and    fascia    of,    pnct 

consid.,  ^79 
Shoulder-girale,  348 

surface  anatomy  of,  363 
Shoulder-joint,  374 
burste  of,  377 
dislocation  of,  583 
landmarks  of,  380 
ligaments  of,  374 
movements  of,  377 
pract.  consid.,  378 
Shrapnell's  membrane,  1494 
Sigmoid  cavity,  greater,  of  ulna,  sSi 
lesser,  of  ulna,  381 
flexure,  1669 

peritoneal  relations  of,  1671 
pract.  connd.,  1685      , 
Sinus  or  sinuses,  basilar,  874 
pract.  consid.,  874 
cavernous,  873 

prrxt.  consid.,  873 
circular,  873 
confluence  of,  868 
of  dura  mater,  867 
frontal,   1433;  336  (bony) 
development  of,  1433 
pract.  consid.,  1437 
intercavernous,  873 
lactiferus,  3030 
lateral,  867 

pract.  consid.,  869 
longitudinal,  inferior,  871 
superior,  870 

pract.  consid.,  870 
marginal,  873 

of  placenta,  53 
maxillary,  1433;  30  (bony) 
development  of,  1431 
pract.  consid.,  1438 
of  Morgagni,  497 
occipital,  873 
palatal,  1435 
petrosal,  inferior,  874 

superior,  874 
pocularis,  1933 
prjecervicalis.  61 
pyriformis  of  pharynx,  1598 
renal,  1874 
reuniens,  707 
sigmoid,  868 
sphenoidal,  143  j 

pract.  consid.,  1438 
spheno-parietal,  874 
straight,  873 
uro-genital,  1939 
of  Valsalva,  700 
venosus,  705 
Skeleton,  103 

appendicular,  104 
axial,  103 
Skene,  tubes  of,  1934 
Skin,  blood-vessels  of,  1387 
development  of,  1400 


THIS  VOLUME    CONTAINS  PAGES   S9«   TO   THE    END. 


mmta 


mik 


1^ 


INDEX. 


3081 


Skin,  end-bulbs  of  Krauio,  1389 
end-organs  of  Ruffini,  1389 
genital  corpuscles,  1389 
Golgi-mazzoni  corpuscles,  1389 
lymphatics  of,  1388 
Meissner's  corpuscles,  138') 
nerves  of,  1389 
pigmentation  of,  1387 
stratum  comeum.of,  1387 

germinativum  of,  1385 

granulosum  of,  1 386 

lucidumof,  1386 
8truct»ire  of,  1381 
Vater-Pacinian  corpuscles,  1389 

Skull,  i7»  .        ,       o 

alveolar  point  of,  a»» 
anthropology  of,  tiS 
asymmetry,  230 
auricular  point  of,  m8 
capacity  of,  iao 
changes  in  old  age,  233 
chordal  portion,  38 
dimensions  of,  329 
fontanelles  of ,  331 
glenoid  point  of,  »38 
growth  and  age  of,  330 
index,  cephalic  of,  329 
facial  of,  339 
of  height  of.  329 
nasal  of,  239 
orbiul  of,  339 
palatal  of,  339 
landmarks  of,  340 
malar  point  of,  328 
mental  point  of,  338 
occipital  point  of,  338 
pract.  consid.,  335 
prechordal  portion,  28 
sexual  differences,  234 
shape  of,  229 
■ubnasal  point  of,  339 
surface  anatomy,  334 
weight  of,  333 
M  whde,  216 
Smegma.  19M 
SoUUry  nodules  of  Intestme, 
Somatopleura,  29 
Somites,  29  ,  _ 

Space  or  space*,  of  Bums,  543 
of  Fontana,  1452 
perforated,  anterior,  J153 

posterior,  1107 
quadrangular,  of  w 

of  Retiius,  1906      .     ,      _,     „,, 
subarachnoid,  of  spinal  cord,  1022 
subdural,  of  sjrinal  cord,  1022 
sublingual,  ijSi 

of  Tenon,  1437  „- 

triangular,  ot  m.  teres  major,  578 

Spermatic  cord,  i960    , 

constituents  of ,  1060 
pampiniform  jdexus  of,  i960 
pract.  consid.,  1961 
ducts,  1953   . 

nerves  of,  19  59 
structure  of,  loS^ 
vessels  of,  195^ 
filaments,  1946 
Spermatids,  1944 
Spermatocytes,  primary 

secondary,  1944 
Spermatogenesis,  1944 
Spermatogones,  1944 


1411 


lOjC 


,  1640 


[  m.  teres  major. 


1944 


Spermatosoa,  1946 
Spemiatosoon,  16 
Sperm-nucleus,  30 
Spheno-ethmoidal  recess. 
Sphenoid  bone,  186 

articulations  of ,  190 
development  of,  190 
great  wings  of ,  187 
fesser  wings  of,  188 
pterygoid  procssae*  of.  189 
Sphenoidal  sinus,  1425 
Spheno-palatine  ganglion,  1240 
Spigelius,  lobe  of,  1707 
Spinal  column,  114 
Spinal  cord,  103 1 

anterior  horn,  nerve-cells  M, 
arachnoid  of,  1032 
blood-vessels  of,  1047 
Cauda  equina  of,  103$ 
central  canal  of,  1030 
columns  of,  1037 
anterior,  1037 
lateral,  1037 
posterior,  1027 
commissure,  gray  of,  io»8 

white,  anterior  of,  1038 
conus  meauUaris,  io3t 
denticulate  ligaments  of,  1023 
development  of,  1049 
dura  mater  of,  1033 
enlargement,  cervical,  of,  1036 

lumbar  of,  1036 
fibre-tracts  of  white  mattor,  1038 
fissure,  median  anterior  of,  1017 
form  of,  1036 
gray  matter  of,  1028 

nerve-fibres  of,  1036 
neuroglia  of,  1035 
ground-bundle,  anterior,  1046 

lateral,  104J 
horn,  anterior  of,  1029 
lateral  of,  1029 
posterior  of,  1029 
membranes  of,  1032 
microscopical  structure  of,  1030 
nerve-cells,  grow    ig  of,  1032 
pia  mater  of,  102* 
posterior  horn,  nerve-cells  of,  1033 
pract.  consid.,  1051 
root-line,  ventral  of,  1037 
segments  of,  1024 
septum,  median  posterior  of,  losT 
substantia  gelatmosa  Rotandi  ol, 

1029  ,    , 

sulcus  postero-lateral  of,  ]on 
tract,  anterior  pyranwdal  (direct), 
1046 
of  Burdach,  1039 
direct  cerebellar,  1044 
of  GoU,  1039 

of  Gower,  1044  .  . ,  ,. 

lateral     (crossed    pyramidal), 

1043 
of  Lissauer,  1042 
white  matter  of.  T036 
ganglia,  1279 
nerves,  1278 

constitution  of,  1278 

divisions,  primary,  anterior,  01, 1 204 

posterior,  of,  1279 
number  of,  1279 
sice  of,  1379 
typical.  1284 


I 


THIS 


VOLUME    CONTAINS  PAGES  996  TO  THE    END. 


A 


ifir^if 


alglfC 


3083 


INDEX. 


Spiiisi  nerves,  ventral  (motor)  root*  of,  1179 
Spine,  114 

articulations  of,  131 
aspect,  anterior  01,  138 
lateral  of,  138 
posterior  of,  138 
curves  of,  138 

dimensions  and  proportions  of,  141 
landmarks  of ,  146 
lateral  curvature  of,  144 
ligaments  of,  13  a 
movaments  of,  14a 
practical  considerations,  143 
sprains  of,  144 
as  whole,  138 
Sfdanchnopleura,  19 
Splanchnoskeleton,  84 
Spleen,  1781 

development  and  growth  of,  1787 
lymphatics  of,  98  a 
movable,  1788 
nerves  of,  178T 

nodules  (Malphighian  bodies)  of,  1784 
peritoneal  relations  of,  1785 
pract.  consid.,  1787 
pulp  of,  1783 
structure  of,  1 783 
surface  anatomy  of,  1787 
basal,  178a 
gastric,  178a 
phrenic,  1781 
renal,  1783 
suspensory  hgament  of,  1 786 
vessels  of,'  1 786 
Spleens,  accessoiy,  1 787 
S(denium,  of  corpus  callosum,  1 1 56 
Spongioblasts   10 10 
Spongioplasm,  8 
Sprains,  of  spine,  144 
Squamous  portion  of  temporal  bone,  177 
Stapes,  1498 
Stenson,  canals  of,  aoi 

duct,  1583 
Stephanion,  339 
Stemo-clavicular  articulation,  a6i 

pract.  consid.,  363 
Sternum,  155 

developmient  of,  157 
pract.  consid.,  168 
sexual  differences  of  1 56 
variations  of,  156 
Stigmata,  72 
Stilling,  canal  of,  1474 
Stomach,  161 7 

blood-vessels  of,  1637 
ctirvature  greater  of ,  1617 
curvature  lesser  of,  1617 
fundus  of,  1 61 8 
glands  of,  1633 
growth  of,  1639 
lymphatics  of,  976.  1638 
nerves  of,  1638 
peritoneal  relations  of,  1619 
position  and  relations  of,  i6ig 
pract.  consid.,  T639 
pylorus,  1 61 8 
shape  of,  1618 
structure  of,  i6ai 
variations  of,  1639 
weight  and  dimensions  of,  1619 
Stomata,  73 
Stomodeum,  1694 
Strabismus,  1440 


Stratum  sonale,  of  thalamus,  iisj 
Stria  medullsrif,  11 19 
Stris,  acoustic,  1096 
Structure,  elements  of,  5 
Styloid  process  of  ulna,  285 
Sublingual  ducts,  1585 
gland,  1585 

nerves  of,  1585 
structure  of,  1587 
vessels  of,  1 585 
space,  1 58 1 
Submaxillary  duct,  1 584 
ganglion,  1347 
gland,  1583 

nerves  of,  1385 
structure  of,  1 58/ 
vessels  of,  1 585 
Subpatellar  fat,  405 
Subperiocteal  bone,  98 
Sub-peritoneal  tissue,  174a 
Substantia  nigra,  itoq 
Sulci,  development  of,  1 190 
fissures,  cerebral,  1135 
Sulcus  hypothalamicus,  11 19 
Suprarenal  bodies,  1801 
accessory,  1805 
development  of,  1804  ^ 

growth  of,  1804 
nerves  of,  1803 
pract.  consid.,  1806 
relations  of,  1801 
structure  of,  t8o3 
vessels  of,  1803 
body,  lymphatics  cf,  983 
Suture  or  sutures,  107 
amniotic,  31 
coronal,  316 
cranial,  3t6 

dostuie  of,  333 
lambdoidal,  317 
sagittal,  a  16 
Sylvian  aqueduct,  1 108 
gray  matter,  11 09 
Sylvius,  fissure  of,  1136 
Sympathetic  ner\-es,  plexuses  of,  1367 
Sympathetic  system,  1353 
aortic  nerves,  1364 
association  cords  of,  1357 
constitution  of,  1355 
ganglia  of.  1356 
gangliated  cord  of,  1355 
gangliated     cord,    cervico-cephalic 
portion,  1358 

lumbar  portion,  1366 
sacral  portion,  1367 
thoracic  portion,  1364 
nerve-fibres  of,  1356 
plexus,  aortic,  1373 
cardiac,  1367 
carotid,  1360 
cavernous,  1361 
cavernous,  of  penis,  1374 
coeliac,  1370 
gastric,  1370 
nemorrhoioal,  1374 
hepatic,  1^70 
hypogastric,  1374 
mesenteric,  inferior,  1373 

superior,  1373 
ovarian,  137a 
pelvic,  1374 
phrenic,  1371 
prostatic,  1374 


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tg^m 


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I-  .^ 


/ 


INDEX. 


30S3 


.» 


Sympathetic  aystem,  plexiia,  renal,  1371 
•oUr,  1368 
•pennatic,  137  a 
■plenic,  1370 
•uprarema,  137 1 
utero-vaginal,  1374 
vesical,  1374 
plexuiet  of,  1356 
pract.  consid.,  1375 
pulmonary  nerves,  1364 
rami  communicantes  of,  1356 
•fdanchnic  afferent  fibres  of,  1357 
efferent  fibres  of,  1357 
nerves,  1364 
Symphvsis,  108 
pubis.  339 
Synarthrosis,  107 
Synchondrosis,  108 
Syncytium  of  chorion,  49 
Syndesmosis,  108 
System,  gastro-pulmonary,  1597 
muscular,  454 
nervous,  906 
uro-genital,  1869 


Tsnia  chorioidea,  1164 

coli,  1660 

fomicis,  1 1 63 

semicircularis,  ti6a 

thalami,  iiig 
Tapetum,  1157 
Tanal  bones,  419 

plates,  1444 
Tarsus,  419 
Taste,  organ  of,  1433 
Taste-buds,  1433 

development  of,  1436 

nerves  of,  1435 

structure  of,  1431 
Teeth,  154; 

alveolar  periosteum,  1553 

bicuspids  (premolars),  1545 

canines,  1544 
milk,  1545 

cementum  of,  1552 

dentine  of,  1550 

development  of,  1556 

enamel  of,  1 548 

homologies  of,  1 566 

implantation  and  relations  of, 

incisors,  1543 
milk,  1 544 

lymphatics  of,  951 

milk,  eruption  of,  1 564 


«S54 


(temporary),  154* 
molars,  1546 

milk,  1547 
neck  of,  154a 
permanent,  1541 

development  of.  1 564 
eruption  of,  1565 
relations  of,  1554 
pract.  consid.,  1591 
pulp  of,  1 554 
pulp-cavity  of,  1542 
temporary,  relations  of,  1556 
variations  of,  1 566 
Tegmen  tympani,  1496 
Tegmentum,  ma 
Tela  chorioidea,  1097 
subcutanea,  1384 
Telencephalon,  1131 
Tdophaaes  of  mitosis,  13 


Temporal  bone,  176 

articulations  of,  184 
cavities  and  passages,  1S3 
development  of,  184 
portion,  petro-mastoid,  179 
squamous,  177 
tympanic,  179 
lobe,  1 147 
Tempoto-mandibular  articulation,  a  14 
Tenoo  oculi,  484 
Tendon,  77,  468 

conjoined,  518 
Tendon-cells,  78 
Tendon-sheaths,  470 
Tenon,  capsule  of,  304 

space  of,  1437 
Tentorium  cerebeiU,  1199 
Terms,  descriptive,  3 
Testis  or  testes,  1941 
appendages  of,  1949 
architecture  of,  194a 
descent  of,  ao4o 
lymphatics  of,  087 
mediastinum  of,  194a 
nerves  of,  1948 
pract.  consid.,  1950 
structure  of,  194a 
tubules  seminiferous  of,  1949 
tunica  albuginea  of,  194a 
vessels  of,  1948 
Thalamic  radiation,  112a 
Thalamus,  it  18 

connections  of,  11  ai 
structure  of,  11 30 
Thebesian  valve,  695 

veins,  694 
Theca  foUiculi,  of  hair,  139a 
Thenar  eminence,  607 
Thigh,  landmarks  of,  670 

muscles  and   fascise  of,  pract.  consid. 
64  a 
Third  ventricle,  1131 

choroid  plexus  of,  113 1 
Thorax,  149 

artictUations  of,  i<;7 
in  infancy  and  childhood,  164 
landmarks  of.  170 
lymphatics  of,  966 
movements  of,  165 
pract.  consid.,  167 
sexual  differences,  104 
subdivisions  of,  1832 
surface  anatomy   166 

landmarks  of,  1868 
as  whole,  163 
Thumb,  articulation  of,  336 
Thymus  body,  1 796 

changes  of,  1797 
development  of,  tSoo 
nerves  of,  t8oo 
shape  and  relations  of,  1796 
structure  of,  1 798 
vessels  of,  17^9 
weight  of,  1797 
Thyroid  bodies,  accessory,  1793 
Thyroid  body,  1789 

development  of,  1793 
nerves  of,  1 793 
pract.  consid.,  1794 
shape  and  relations  of,  1789 
structure  of,  1791 
vessels  of,  179a 
cartilage,  181 4 


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9084 

Thyroid  t\rvilage,  development  of, 

vrowtn  of,  181 5 
gland,  lymphatics  of,  959 

TIblt.,  i»2 

development  of,  387 
landmarks  of,  390 
pract.  consid.,  387 
Ktnicture  of,  387 
variations  of,  383 
Tibio-fibular  articulation,  mfenor,  396 

superior,  396 
Tissue  or  tissues,  adipose,  79 
connective,  73 
elastic,  76 
elementary,  67 
epithelial,  67 
fibrous,  74 

muscular,  general,  454 
nervous,  997 
osseous,  84 
reticular,  75 
Tongue,  1573 

foramen  csecum  of,  1574 
frenum  of,  1573 
glands  of,  1575 
growth  and  changes  of,  1 580 
lymphatics  of,  952 
muscles  of,  1577 
nerves  of,  1 580 

papillse,  circumvallate  of,  157S 
filiform  of,  1575 
fungiform  of,  1575 
ptact.  consid.,  1 594 
vessels  of,  1 580 
Tonsil  or  tonsils  (amygdala),  of  cerebellum, 
1086 
faucial,  1600 
faucial,  relations  of,  1603 
lingual,  1575 
lymphatics  of,  054 
pharyngeal,  1601 
pract.  consid.,  1608 
tubal,  1503 
Tooth-sac,  156a 
Tooth-structure,  1548 
Topography,  of  abdomen,  531 

cranio-cerebral,  1114 
Trachea,  1834 

bifurcation  of,  1837 
carina  of,  1837 
growth  of,  1837 
lymphatics  of,  958 
nerves  of,  1836 
pract.  consid.,  1840 
relations  of,  1836 
structure  of,  1835 
vessels  of,  1836  , 

Tract  or  tracts,   (fibre)   nibro-spmal, 
1114 
habenulo-peduncular,  it»4 
mammillo-thalamic,  im 
of  mesial  fillet,  1076 
olfactory.  115* 
thalamocipetal,  lower,  ii»» 

Tragus,  1484 
Trapezium.  311 
Tra peloid  bone,  311 
Trerts,  muscle  of,  558 
Triangle  of  Hesselbach,  saft 

rectal,  191 6 

uro-genital,  191 6 
Triangles  of  neck,  547 


INDEX. 


Trigone  of  bladder,  urinary.  1904 
Trigonum  acustici,  1097 
habenuUe,  11 23 
hypoglossi,  1097 
lemnisci,  1108 
uro^nitale,  563 
vagi,  1097 
Trochanter,  greater,  of  femur,  35a 

lesser,  of  femur,  353 
Trochlea  of  humerus,  a  68 

of  orbit,  504 
Trochoides,  113 

Trophoblast,  46  .  , 

Truncus    bronchomediastmalis,    lympnatw 
968 
Eubclavius,  lymphatic,  963 
Tube,  Eustachian,  1501 
Tuber  cinereum,  1129 
Tubercle  of  Lower,  695 
Tuberculum  acusticum,  1097 

olfactoritmi,  11 53 
Tubes,  Fallopian,  1996 
Tunica  vaginalis  of  scrottmi,  1963 
Turbinate  bone,  inferior,  208 

articulations  of,  io8 
development  of,  308 
middle,  of  ethmoid,  193 
superior,  of  ethmoid,  193  ' 
Tympanic  portion  of  temporal  bone,  17Q 
Tympanum,  149a 
attic  of,  1 500 
cavity  of,  183 
contents  of,  1496 
membrane  of,  1404 

pract.  consid.,  ijos 
mucous  membrane  of,  1500 
oval  window  of,  149  5 
pract.  consid.,  1 504 
promonotory  of,  149S 
pyramid  of,  1496 
round  window  of,  149  5 
secondary  membrane  of,  1495 
tegmen  of,  1496 
Tyson,  glands  of,  1966 

Ulna,  a8i 

development  of,  a85 
landmarks  of,  a  87 
pract.  consid.,  a8s 
structure  of,  385 
surface  anatomy,  300 
Umbilical  cord,  53 . 

allantoic  duct  of,  $4 
amniotic  sheath  of,  54 
blood-vessels  of,  54 
furcate  insertion  of,  55 
jelly  of  Wharton  of,  54 
marginal  insertion  of,  5  s 
velamentous  insertion  of,  SS 
fissure  of  liver,  1708 
hernia,  1775 
notch  of  liver,  1707 
vesicle,  4» 
Umbilicus,  37 
Unciform  bone,  31a 
Uncus,  11S4  ,       ,     ,, 

Upper  limb,  muscles  of,  568 
Urachus,  535 
Ureter  or  ureters,  1895 
femals,  1896 
lymphatics  of,  983 
ner^'es  of,  1898 
pract.  consid.,  t»9» 


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ittmirii 


2o86 

Vein  or  vein*,  cervical,  deep,  859 
middle,  884 
chord*  WiUitei,  870 
choroid,  877 
ciUary.  antenor,  879 

posterior,  879 
circulation,  foetal,  9 '9 
circumflex,  iliac,  deep.  910 
superfitial,  917 
of  leg;,  9>4 
claMification  of,  851 
clitoris,  909 
colic,  middle,  981 


INDEX. 


right.  931 
condyloid,  antenor,  874 


863 


confluence  of  the  sinuses 
coronary,  of  {»"?••.** 5 

inferior,  of  facial,  865 

left,  85s 

right.  856 
of  corpus  callosum.  antenor,  87S 
posterior,  877 

cavemosum,  907 

striatum,  877 

^^th?pi2:'orsuperior  thyroid.  867 

d^p'^do^l  of  penis  (clitoris),  909 
of  forearm,  886 
of  hand,  886 
dental,  inferior.  883 

superior.  883 
development  of,  926 
diploic.  874 

anterior.  875 
occipital,  875 

pract.  consid..  875  | 

temporal,  antenor.  873  | 

posterior.  875  ] 

dorsal,  of  foot.  Qio  j 

interosseous,  886  I 

ductus  Arantii.  929  ! 

arteriosus,  930  ' 

Botalli.  930  ' 

venosus,  920  .  j-..^ 

emissaries  of  foramen  lacerum  medium, 

876 
emissary.  875 

condyloid,  antenor.  870 

posterior,  876 
of  foramen  ovale.  876 

of  Vesalius,  876 
mastoid,  876 
occipital.  876 
parietal.  876 
pract.  consid.,  876 
epigastric,  deep.  901) 
superficial,  qi  7 
superior,  of  internal  mammary,  860 

ethmoidal.  879 
facial.  864 

common.  864 

deep.  865 

pract.  consid..  fiCu 

transverse,  882 
fernoral.  deep.  01  i 

rrart.  consid.,  oiS 
circulation,  929 
of  foot.  deep,  qio 

superficial.  914 
foramen  lacerum  medium,  876 
frontal,  of  facial.  865 
of  Galen,  856 


Vein  or  vein*,  gMtrlc,  9»3 
short,  931 
gMtro-«piploic,  left,  9*1 

right,  921 
gluteal,  905 
hemiacygoa,  895 

acceuorv,  80s . 
hemorrhoidal,  infcnor,  907 
middle,  908 
plexus,  908 
superior,  9a* 
hepatic,  90* 

pract.  consid.,  904 
hepatica  communis,  900 
ileo-colic,  931 
iliac,  common,  905 

pract.  consid.,  917 
external,  909 

pract.  consid.,  918 
internal,  905 

pract.  consid.,  910 

ilio-lumbar,  906  

inferior  cava,  pract.  consid.,  900 

caval  system,  898 
innominate,  858 

development  of,  859 
pract.  consid.,  859 
intercapitular  of  hand,  889      > 
intercostal,  896  ^^„^   riso 

anterior,  of  internal  mammary.  8O0 
superior.  896  ; 

accessory  left,  896 
intervertebral,  898 
jugular,  anterior,  884 
external,  880 

posterior,  884 
pract.  consid..  88f 
internal,  861 

bult>»  of.  86 1 
prac.  consid.,  863 
labial,  inferior,  of  facial,  865 

superior,  865 
lacunae  of  dural  sinuses,  851 
laryngeal,  inferior.  861 

superior,  of  superior  thyroid,  867 

of  leg,  deep,  9".         , 
pract.  consid..  918 
of  limbs,  development  of,  939 
lingual,  deep,  of  facial,  867 

of  facial,  867 
lumbar,  901 

ascending,  901 
mammary,  external.  888 

internal.  860 
marginal,  right.  856 
marginalis  sinistra,  855 
of  Marshall,  856 
masseteric,  of  facial.  866 
mastoid  emissary,  869 
maxillary,  internal,  881  .  .   a^, 

internal,  antenor,  of  facial.  865 
median,  890 

deep,  886 
mediastinal,  anterior.  861 
meduUi-spinal.  898 
meningeal,  middle,  883 
mesenteric,  inferior,  qii 

superior.  931 
metacarpal,  dorsal.  889  , 

nasal,  lateral,  of  facial,  865 
oblique,  of  heart,  69s 

of  left  auricle,  856 
obturator.  907 


<i: 


^1 


-I 


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,.%.^ 


"sap-iw-w  "i 


INDEX. 


3067 


Vain  or  veins,  occipital,  859 

ojdtthalmic,  anastomoae*  of,  8S0 
inferior,  879 

pract.  consul.,  S80 
superior,  879 
ovati&n,  903 
palatine,  ascending,  of  faciai,  866 

inferior,  of  facial,  866 
palmar  arches,  886 
superficial,  890 
palpebral,  of  facial,  865 
pampiniform  plexus,  903 
pancreatic,  921 
pancreatico-duodenal,  931 
parotid,  anterior,  of  facial,  866 

posterior,  882 
parumbilical,  933 

perforating,  of  internal  mammary,  860 
pericardial,  861 
perineal,  superficial,  907 
peroneal,  911 
pharyngeal,  863 

plexus,  864 
phrenic,  inferior,  901 

superior,  861 
plantar,  910 

external,  910 
plexus,  alveolar,  883 

external,  spinal,  897 

hemorrhoidal,  venous,  908 

internal,  spinal,  897 

pterygoid,  883 

sacral,  905 

of  Santorini,  909 

venosus  mammilUe,  888 
popliteal,  911 

pract.  consid.,  918 
portal,  919 

accessory,  933 

collateral  circulation  of,  933 

development  of,  938 

of  liver,  1 709 

system,  919 

pract.  consid.,  925 
pterygoid,  plexus,  882 
pudendal  plexus,  909 
pudic,  external,  916 

internal,  907 
pulmonary,  852 

anastomoses  of,  853 
pyloric,  923 
radial,  886 

superficial,  891 
accessory,  891 
renal,  902 

pract.  consid.,  904 
of  Retzius,  924 
sacral,  anterior,  plexus,  905 

lateral,  906 

middle,  905 
sapMnous,  accessory,  916 

long,  916 

short,  915 
sciatic,  906 

of  septum  lucidum,  877 
sii^oid,  922 
sinus,  basilar,  874 

pract.  consid.,  S74 

cavernous,  872 

pract.  consid.,  873 

circular,  872 

coronary,  854 

of  dura  mater,  867 


Vein  or  veins,  sinus,  dural,  blood-lakes  of, 

structure  of,  851 
intercavernous,  87a 
lateral,  867 

pract.  consid.,  869 
longitudinal,  inferior,  871 
superior,  870 

pract.  consid.,  870 
marginal,  873  . 

occipital,  873 
petrosal,  inferior,  874 

superior,  874 
spheno-parietal,  874 
straight,  873 
small,  of  Ualen,  877 

intestine,  931 
spermatic,  903 

pract.  consid.,  904 
spheno-palatine,  883 
spinal,  897 
cord,  898 
pract.  consid.,  898 
splenic,  921 
stemo-mastold,   of  superior  thyroid. 

867 
structure  of,  677 
subclavian,  884 

pract.  consid.,  885 
subcostal,  896 
sublingual,  867 
submental,  of  facial,  866 
superficial  of  hand,  889 
superior  cavM  system,  857 
supraorbital,  of  facial,  865 
suprarenal,  middle,  903 

inferior,  902 
suprascapular,  884 
Sylvian,  deep,  878 
temporal,  deep,  883 
middle,  S82 
superficial,  882 
temporo-maxillary,  883 
testicular,  903 
Thebesian,  694 
thoracic,  acromial.  890 

long,  887 
thoraco-epigastric,  888 
thymic,  861 
thyroid,  inferior,  860 

pract.  consid.,  861 
midmc,  867 
plexus,  860 
superior,  867 
tibial,  anterior,  911 

posterior,  g  1 1 
torcular  Herophili,  86S 
tvmpanic,  of  temporal,  883 
lUnar,  886 

superficial,  890 
umbilical,  54 
of  upper  extremity,  886 

pract.  consid.,  891 
ureteric,  of  renal,  902 
of  spermatic,  903 
uterine,  908 

plexus,  908 
utero-vaginal  plexus,  go8 
vaginal,  908 

plexus,  908 
valves  of,  850,  851 
vena  cava  inferior,  899 

development  of.  927 


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min 


HMHIIiMliii 


iiiiiiiiiiiiiiifililllili^^ 


J 


1 1 


ao88  INDEX. 

Vein    -  vein«,  vena  cava  superior,  857 
devolopment  of,  927 
prtft.  contid.,  858 
cephalica  ^  ^iiicis,  889 
■alvutella,  889 
supraumbilicaiis,  933 
thyfeoidea  ima,  861 
veiue  cotnitcs,  851 
vorticosse,  879 
vertebral,  860 
vesical,  908 

vesico-prostatic  plexus,  909 
vesico-va^inal  plexus,  909 
vitelline  arculation.  929 
Velutn  interposituRi,  ii'i^ 
Ventricle  or  ventricles,  fifth,  11 60 
fourth,  1096 
of  heart,  696 
lateral,  11 60 

anterior  horn  of,  1 160 
body  of,  1 161 
choroid  plexus  of,  1162 
inferior  (descending)   horn  of, 

1 1 64 
posterior  horn  of,  1 168 
(sinus)  of  larynx,  1832 
third,  1 131 
Vermiform  appendix,  1664 
Vemix  caseosa,  66 
Vertebra  or  vertebrae,  114 
articular  surfaces  of,  116 
body  of,  115 
cervical,  116 
development  of,  118 
dimensions  of,  lai 
gradual  regional  changes  of,  122 
lamins  of,  115 
lumbar,  117 

mammillary  processes  of,  itS 
peculiar,  119 
pedicles  of,  115 
presacral,  128 
prominens,  12 1 
spinal  foramen  of,  115 
spinous  process  of,  115 
structure  of,  128 
thoracic,  115 

transverse  processes  of,  115 
variations  of,  131 
Verumontanum,  1922 
Vesalius,  foramen  of,  188 
Vesicle,  germinal,  1 5 

umbilical,  42 
Vesicles,  seminal,  1956 
Vessels  of  clitoris,  2025 
of  epididymis,  1948 
of  Fallopian  tube,  1998 
of  gall-bladder,  17 19 
of  labia,  2033 
of  larynx,  1826 
of  lips,  1542 

of  mammary  glands,  2031 
of  oesophagus,  161 2 
of  ovary,  1992 
of  palate,  1572 
of  pancreas,  1736 
of  parotid  gland,  1 583 
of  penis.  1970 
of  pharynx,  1606 
of  prostate  gland,  1978 
of  roots  of  lungs,  1839 
of  scrotum,  1964 


Vessel*  of  seminal  veaiclet,  1958 

of  spermatic  ducts,  1958 

of  spleen,  1786 

of  sublingual  gland,  1 585 

of  submaxillary  gland,  1 585 

of  suprarenal  bodies,  1803 

of  testis,  1948 

of  thymus  body,  1799 

of  thyroid  body,  1 79a 

of  tongue,  1 580 

of  trachea,  1836 

of  ureter,  1897 

of  urethra,  1936 

of  urinary  bladder,  191a 

of  uterus,  3009 

of  vagina,  3018 
Vestibule  of  mouth,  1538 

of  nose,  1409 

cf  osseous  labyrinth,  1511 

of  vagina,  3033 
Vicq  d'Azyr,  bundl"  of,  1131 
Vidian  canal,  189 
Villi  of  chorion,  49 

of  intestine,  1635 
lacteals  of,  1636 
Vincula  tendinum,  471 
Vital  manifestations,  6 
Vitelline  arteries,  33    ' 

duct,  32 

membrane,  15 

sac,  32 
Vitello-intestinal  duct,  37 
Vitellus,  IS 
Vitreous  body,  147.1 

pract.  consid.,  1474 
Vocal  cords,  false,  1820 

trtie,  1820 
Volkmann's  canals,  of  bone,  89 
Volvulus,  1687 
Vomer,  205 
Vulva,  2021 

Wharton,  duct  of,  1584 

jelly  of,  54   . 
White  lines  of  pelvis,  559 

of  anal  canal,  1673 
Winslow,  foramen  of,  1 7  ,•> 
Wirsung,  duct  of,  1736 
Wisdom-tooth,  1546 
Wolffian  body,  1935 

duct,  193  s 
Womb,  2003 

Worm  of  cerebellum,  1082 
Wrist,  anterior  annular  ligament,  607 

movements  of,  336 

pract.  consid.,  613 

surface  anatomy  of,  328 
Wrist-joint,  landmarks  of,  330 

pract.  consid.,  329 

Xiphoid  process  of  sternum,  156 

Volk-stalk,  37 

Zeiss,  glands  of.  1 444 
Zinn,  annulus  of,  503 

zonula  of,  147 5 
Zona  pellucida,  1 5 

radiata,  i  s 
Zonula  of  Zinn,  1475 
Zuckerkandl,  bodies  of,  1812 
Zygomatic  process  of  temporal  bone,  178 


THIS  VOLUME    CONTAINS    PAGES    996    TO    THE    END. 


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